Columbia HttttiprHttg i« t\}B (Eitg of Nfuj fork ffloUpg:? of Pliyairians anb ^urgronB ^AtUnna library Digitized by the Internet Archive in 2010 with funding from Open Knowledge Commons http://www.archive.org/details/hygienepublicheaOOpark HYGIENE AND PUBLIC HEALTH LOUIS C. PARKES, M.D., D.P.H. Univ. of Lond. CONSULTING SANITARY ADVISER TO H.M. OFFICE OF WORKS ; CIVILIAN SANITARY MEMBER OF THE ADVISORY BOARD FOR ARMY MEDICAL SERVICES ; MEDICAL OFFICER OF HEALTH OF THE METROPOLITAN BOROUGH OF CHELSEA ; EXAMINER IN rUBHC HEALTH TO THE ROYAL COLLEGES OF PHYSICIANS AND SURGEONS, LONDON ; FELLOW OF THE ROYAL ■ SANITARY INSTITUTE AND HENRY R. KENWOOD, M.B., F.R.S. Edin. D.P.H. Lond. CHADWICK PROFESSOR OF HYGIENE IN THE UNIVERSITY OF LONDON; MEDICAL OFFICER OK HEALTH AND PUBLIC ANALYST OF THE METROPOLITAN BOROUGH OF STOKE NEWINGTON ; EXAMINER IN PUBLIC HEALTH TO THE ROYAL COLLEGES OF PHYSICIANS AND SURGEONS, LONDON ; FELLOW OF THE ROYAL SANITARY INSTITUTE FOURTH EDITION, WITH ILLUSTRATIONS PHILADELPHIA BLAKISTON'S SON & CO. I0I2 WALNUT STREET igii Printed in England] [ r^ \^- llo^^^' 'KA4U -? xl 1 c. PREFACE This, the fourth edition under the conjoint authorship, of a work which had previously run through five editions, has been carefully revised, and new matter has been introduced, where necessary, to bring the work up to date since the last edition was issued in 1907. L. C. P. H. R. K. December, 1910. CONTENTS CHAPTER I. Water II. The Collection, Removal, ani^ Disposal of Excretal and OTHER Refuse . III. Air and Ventilation . IV. Warming and Lighting V. Soils and Building Sites VI. Climate and Meteorology VII. Exercise and Clothing VIII. Food, Beverages, and Condiments IX. The Contagia — Communicable Diseases and their Pre VENTioN — Hospitals . X. School Hygiene .... XL Disinfection .... XII. Statistics ..... XIII. Sanitary Law and Administration Index , , ... 68 1 66 240 259 272 299 309 394 526 563 594 624 683 LIST OF ILLUSTRATIONS I . Underground Water Curves ...... 3. Depression of Water in Shallow Well by Pumping . 3. Diagrammatic Section through London Basin . 4. Diagrammatic Representation of Strata, showing Shallow Deep, and Artesian Wells . 5. Suction Pump ..... 6. Single-acting Suction and Force Pump 7. Double-acting Suction and Force Pump 8. Centrifugal Pump .... 9. Hydrauhc Ram .... 10. Berkefeld Filter .... 11. Cesspool with House Drain Inlet and Overflow to Filter Bed 12. Privy constructed for Pail System ..... 13. Field's Annular Siphon Flush Tank for Flushing House Drains 14. Long Hopper Water-closet with Side-inlet for Flushing 15. Wash-down Water-closet ....... 16. Wash-out Water-closet ....... 17. Century Siphonic Closet ....... 18. Pan Closet with D trap, supplied from Drinking Water Cistern 19. Era Valve Closet ........ 20. S trap, with Water Seal ....... 21. P trap, with Water Seal ....... 22. Trough Water-closet ....... 23. New Form of Trough Closet or Latrine with Isolated Pans 24. Day's Waste-water Closet ..:... 25. Wiped Soldered Joint ....... 26. Joint made with a Copper Bit or Blowpipe 27. Soil Pipe and Ventilator, with Anti-siphonage Pipes from the W^ater-closet Branches 28. Section of Disconnecting Chamber . 29. Flushing Grease GuUey .... 30. Semi-detached Houses ; Plans of Drainage 31. Dean's Silt Gulley ..... 32. Sink with Double Trapped Waste Pipe I'AGE 22 25 29 32 34 34 34 35 36 58 75 77 82 85 85 85 87 89 90 92 92 94 95 96 99 99 lOI 106 no 112 1x6 121 LIST OF ILLUSTRATIONS FIG. 33. Diagrammatic Sketch of Various Provisions for Ventilation 34. Plenum System .... 35. Rifle-back Stove with Economizer 36. Euthermic Ventilating Gas Stove 37. Types of Radiators . 38. House Foundation with Damp-proof Course in Wall and Dry Area ...... 39. Synoptic Chart showing Cyclonic System 40. Synoptic Chart showing Anticyclonic Systi 41. Fortin's Standard Barometer . 42. Diagram of Barometer Scale and Vernier 43. Robinson's Anemometer 44. Daniell's Hygrometer 45. Regnault's Hygrometer 46. Wet and Dry Bulb Hygrometer 47. Rain Gauge 48. Six's Thermometer . 49. Solar Radiation Thermometer 50. Sunshine Recorder . 51. Cotton Fibres 52. Linen Fibres 53. Wool Fibres 54. Silk Fibres SS- Hemp Fibres 56. " Measly " Pork 57. Head of Taenia solium 58. Head of Taenia mediocanellata 59. Brood Capsule of an Echinococcus 60. Trichina Spiralis encysted in Muscle 61. One of Raineys Capsules 62. Distoma hepaticum . 63. Percentage Composition of Solids of Human and Cow's Milk 64. Aspergillus Glaucus . 65. Penicillium Glaucum 66. Mucor Mucedo . ^j. Puccinia Graminis 68. Smut Spores : Uredo segetum 69. Acarus faringe . 70. Vibriones tritici 71. Weevil .... 72. Section of Wheat Grain : Outer Coat T^. A, Ear of Rye with Ergot ; B, a Slice of Ergot Plates I. and II. Illustrating Starch Grains . . facing 74. Coffee : Cells of Testa and Cellular Structure .... LIST OF ILLUSTRATIONS XI FIG. PAGE 75. Chicory : Dotted Ducts and Cellular Structure .... 375 76. Tea Leaf ........... 376 "J J. Torula cerevisiae : Yeast Plant . . . . . . . 378 78. Fulham Small-pox Hospital. Special Area divided into Sec- tions, showing Number of Houses invaded by Small-pox . 409 79. Chart showing Average Death-rates in different Infectious Diseases in Corresponding Weeks of a Period of Years. . 413 80. Small-pox Epidemics, 1871, 1881 ; Mortality per cent, in Fever Hospitals (London) . . . . . . . .417 8 1 . Hospital Slop-sink with Flushing Rim and Bed-pan and Slipper Douches . . . . . . . . . .qi9 82. Borough Hospital, Croydon. First-floor Plan . . . .522 83. Isolation Hospital Block (as recommended by the Local Govern- ment Board) ......... 522 84. (a) Disinfecting Station. Infected Side . . . . -573 84. (&) Disinfecting Station. Non-infected Side . . . -574 85. Graphic Expression of Male Population : Number Living or Lives at Risk ......... 616 86. A Sanitary Cowshed. Double Byre with Central Feeding Passage .......... 649 HYGIENE AND PUBLIC HEALTH CHAPTER I WATER Water is a prime necessity of life. Without it, terrestrial animal and vegetable life must cease to exist. The earliest settlements in all countries were, therefore, made in the neigh- bourhood of water. Towns and villages sprang up on the banks ol streams and rivers, on the shores of lakes and in the neigh- bourhood of springs ; or water was obtained from the soil around these early settlements by shallow excavations or wells. In modern times, sites for dwellings are not necessarily limited to a small area around a natural source of water. Our engineering knowledge enables us, on the one hand, to obtain water by means of wells and borings from great depths beneath the surface of the earth, and on the other, to convey water from a distance bv means of conduits to the places where it is required. This latter method was well known to the ancient Romans, manj^ of whose aqueducts and reservoirs are, after the lapse of many centuries, still standing and serving their original pur- pose. In Rome the total supply per head was certainly not less than 300 gallons daily for a population of about 1,000,000 people, the greater portion of this vast supply of water being required for public baths and fountains. London is an instance of a settlement founded originally on the banks of a river, and subsequently spreading away from the neighbourhood of the river only in those directions where a water-bearing gravel overlaid the impermeable London clay. The bed of gravel being of but slight thickness— 10 to 30 feet — water was easily reached by shallow excavations or wells ; whilst at some places springs flowed out where the gravel I 2 HYGIENE AND PUBLIC HEALTH terminated; as at Bagnigge Holywell, and Clerkenwell. Eighty years ago, parts of London where the clay came to the surface, and which are now densely populated owing to the introduction, of a public water supply, were quite uninhabited. Sources of Water— Collection and Storage. The natural sources of water are the rain and snow which fall on the surface of the earth. When the rain has reached the surface of the ground, it is disposed of in the following ways : a portion {a) is evaporated ; another portion (6) flows off in the direction of the inclination of the surface ; whilst a third portion {c) sinks into or percolates through the interstices of the soil. The amount of rain that evaporates depends upon the tem- perature of the air. The higher the temperature, the greater the evaporation. If the inclination of the surface is nil, or only very slight, and the soil is of some depth and of a porous nature, the larger portion sinks into the soil or percolates. If, however, the inclination of the surface is great and the soil is not porous, but more or less impermeable to water, the greater portion of the unevaporated rain flows down the incline. It is this portion which forms or helps to swell the brooks, streams, and rivers, which are the natural drainage channels of the locality. In very porous soils, such as pure sand or coarse gravel, the rain so rapidly sinks into the interstices of the soil that the evaporation, even in summer, is but slight. In nearly all other soils, however, the amount of rain evaporated greatly exceeds the percolation, even in winter. The portion that percolates, after a certain deduction that must be made for the moisture absorbed by the roots of vege- tables and grasses growing on the surface, and which is subse- quently evaporated from their leaves, helps to form and renew the underground sources of water. These are made available to man by natural outlets as springs, or by artificial tappings in their subterranean depths through wells. In its passage through the soil, the water absorbs carbonic acid from the ground air, which is very much richer in this gas than ordinary atmospheric air. This water holding carbonic acid gas in solution is capable of dissolving some of the mineral constituents of the rocks through which it passes. WATER 3 Rainfall. The rain that falls on the roofs of houses can be collected and made available as a means of water supply. To calculate the amount of water supply per head from this source, we must know the amount of roof space per individual (the slope of the roof must not be taken into account, but merely the area of horizontal surface covered by the roof), the average amount of yearly rainfall, and the average amount of evaporation of the rainfall. The amount of yearly rainfall varies considerably in different parts of England. In the Eastern Counties the average is less than 25 inches per annum. Throughout the remainder of England the average is from 30 to 40 inches per annum, with very much larger amounts in the mountainous and hilly districts of Devon- shire. Wales, Cumberland and Westmorland (60 to 200 inches per annum). The expression " an inch of rainfall " signifies that one cubic inch of rain-water has fallen upon each square inch of horizontal surface. (For description of rain gauge see Chap. VI ) During the past 15 years the least annual rainfall, ■ measured at Greenwich, has been 18-85 inches (1898), and the greatest 35-54 inches (1903). In the latter year (1903) ex- ceptionally heavy falls of rain occurred ; thus on July 23, 2-47 inches feU in 24 hours, and on numerous occasions over an inch fen in the same period. During the 13 years 1890-1902, the annual rainfall at Greenwich had been below the average (24-53 inches) in 11 years, and only twice slightly exceeded the average, namely in 1891 and in 1894. Rain is also sometimes collected from prepared surfaces of ground, which, together with the storage reservoir or tank, should always be railed off to keep live stock away. The surface of a certain area of land in an exposed situation is rendered impermeable by a covermg of slates, asphalte, or cement, and sloped towards an outlet pipe or pipes leading to a tank or reservoir. In estimating the amount of water that can be obtained from such a surface calculations may be facilitated by remembering that one inch of rain delivers 4-673 gallons on every square yard, or 22 617 gallons (loi tons) on each acre. The amount of evaporation from the surfaces of roofs may be taken as averaging throughout the year 20 per cent, of the rainfall. There is more evaporation from tiled than from slated 4 HYGIENE AND PUBLIC HEALTH roofs, and from roofs of low than of steep pitch. The evapora- tion is greatest where the rainfall is least, and vice versa. If the amount of roof space per head is 60 square feet, and the rainfall 30 inches in the year, deducting one-fifth for evaporation, 120 cubic feet or 748 gallons is the amount available for each person in a year, which is equal to about two gallons daily. This is the amount available from the rainfall — 30 inches — of an average year. It has been found from a great number of records of rainfall extending over a long series of years in different places, that the rainfall in the driest year is usually one-third less than the average fall, whilst in the wettest year it is one- third greater than the average. So that in a very dry year, in the example given above, the amount of water available may be only i| gallons daily per head, whilst in a very wet year it maj^ be 2f gallons. Rain, as it leaves the clouds, is water pure and simple, free from all foreign ingredients. In its passage through the air to the earth it may collect various impurities, gaseous and suspended. The rain falling in towns is found to have absorbed sulphurous and sulphuric acids, which are always present in the air of towns from combustion of coal and coal gas, and to contain numerous sooty particles. It also appears that the rain washes out of the air countless bacterial and fungoid organisms and their spores. The rain which first falls after a period of dry weather contains far larger numbers of bacteria than that which falls later in a storm ; 200,000 germs per litre is not an unusual quantity under such circumstances. During the warm months of the year, the number of bacteria in the rain exceed those found in the rain of winter and early spring The greater number of the organisms in rain are micrococci. Besides bacteria pollen of grasses and flowers, microscopic plants, such as Protococcus phivialis and spores of fungi, are occasionally found in rain, the latter being on rare occasions in sufficient quantity to cause a localized fall of what is kno\vn as " coloured rain "; but dust,, possibly of volcanic origin, or derived from vast sand deserts, is sometimes responsible for falls of coloured rain. Rain is thus seen to be a great purifier of air, for it washes out of it gaseous and solid impurities , organic and inorganic. For this reason the rain which falls in the impure smoke and soot-laden atmosphere of large towns is unfit to drink. WATER 5 When roofs are used as collecting surfaces for rain-water, the first portion of rain which falls and descends from the roof should be rejected, as it is liable to be much polluted with soot, vegetable matter (leaves), and animal matter (excrement of birds, etc.) washed off from the slates or tiles. After the first washing the remainder of the water may be collected and stored. Robert's Rain-water Separator, which can be fixed on the downward course of the rain-water pipe, effects this purpose by allowing the first portion of water that passes through the apparatus to run to waste. After a certain time, a part of the apparatus which is balanced on a pivot cants over, owing to its centre of gravity being altered as one of its compartments fills with water, and the water escapes into another pipe, which conducts it to a storage cistern. Rain-water should always be stored in as pure a condition as possible, otherwise the storage receptacle becomes coated with foul matters, which contaminate the water. The advantage of underground storage is that the water does not get frozen in the winter or unpleasantly hot in the summer. But, on the other hand, the tanks are often difficult of access. Underground tanks must be built of sound masonry or brickwork and lined with hydraulic cement. They should rest upon a bed of concrete and be covered over with arches of masonry or brickwork ; and if there is a special danger of polluting material gaining access to the tank, they should be surrounded with at least a foot of well-puddled clay. Rain-water is especially useful for cooking and washing on account of its softness — -that is to say, its freedom from the salts of lime or magnesia in solution. When these salts are dissolved in a water they render it hard. Hardness is usually reckoned as equivalent to so many grains of chalk (or carbonate of calcium) per gallon of water. A water containing more than 10 grains of chalk or its equivalent in other salts (sulphate of lime or magnesia, carbonate of magnesia, etc.) to the gallon is said to be hard. Hardness due to the presence of carbonate of calcium, held in solution by carbonic acid, is said to be temporary ; for when the water boils, the carbonic acid is driven off, and the chalk, no longer able to remain in solution, is precipitated. It is this deposit of chalk which causes the fur on the bottom and sides of boilers and kettles. When meat or vegetables are cooked by boiling in hard water, a certain amount of the hard b HYGIENE AND PUBLIC HEALTH material is deposited on their surfaces, which either hinders the proper penetration of the heat into the interior, or prevents solution of the soluble materials when this is desired. The fur lining is also a non-conducting material, and impedes the passage of heat from the fire to the contents of the boiler or kettle, thus causing a waste of fuel. This fur lining is one of the causes of the boiler explosions from which loss of life not infrequently results. To reduce the possibilitj^ of such explosions the follow- ing precautions are desirable : — The boilers should be of wrought iron, properly tested ; they should be periodically inspected and cleaned ; pipes connected with them should not be carried up externa] walls where the}' ma}' be affected by frost, and the cisterns should also be in well-protected positions ; the safety valve should be accessible, easily adjusted, and sensitive to variations of pressure. Great waste of soap, too, is caused by the use of hard water in washing. When the water is hard, the lime or magnesia combines with the fatty acid of the soap, forming a curdy pre- cipitate ; and all the lime or magnesia of the water must be so combined before a lather can be formed. Consequently a certain amount of soap is wasted. One grain of chalk wastes about eight grains of soap. The hardness of rain-water is generally less than half a degree ; that is to say, there is less than half a grain of chalk or its equiva- lent salts to the gallon of water ; hence its value for domestic purposes. Rain-water should never be allowed to run to waste where the water derived from other sources is hard. There is one great disad\'antage possessed by rain and other soft waters, namely, their liability to dissolve lead, iron, or zinc if left in contact with these metals. Consequently cisterns of lead, iron, zinc and even galvanized iron in some cases should not be used to store soft water ; and such water when collected from lead roofs, should not be used for drinking. Upland Surface Waters. In hilly districts, the water which flows off the hiUs in the form of rivulets or streamlets can be collected and stored by building an earth and masonry dam or barrier across the outlet of the valley to which the streams converge. By this method of collecting in " impounding reser\'Oirs," large artificial lakes may be formed — capable of holding a supply sufficient for WATER 7 several months — at suitable elevations above the towns which they supply with water. A certain amount of " compensation " water (usually estimated at one-third the amount impounded) must be allowed to pass down to any mill-owners on the streams from which the waters have been diverted. Large storage reservoirs for such waters are made by exca- vating or embanking the soil, and then lining the floor and sides with concrete or well-puddled clay ; common mortar must not be used, as the water takes up the lime. Their position should be such that a jet reaching 20 feet above the highest house to be supplied is assured by gravitation alone, otherwise the water has to be pumped to a higher elevation. Means are generally taken for diverting the tributary streams from the storage reservoir when these get foul in times of flood, by means of a by-wash. The size of a storage reservoir for a catchment area will depend upon the numbers of the community requiring the water, and upon the mean rainfall of the district. Hawksley's formula is of value in estimating the number of days' supply (x) which must be stored when a community is dependent on a rain- 1000 water supply. In this formula x = ; where y = the mean rainfall during the three driest consecutive years — which is usually about one-fifth less than the average. In this country from 120 to 130 days' supply have to be stored. The average annual amount of evaporation from an exposed body of water reduces the depth by some 30 inches over the whole surface ; therefore there is an advantage in diminishing the exposed area of the water by constructing deep reservoirs, rather than shallow ones. The probable daily yield (in gallons) of a catchment area {x) may be arrived at by Dr. Pole's formula, in which ;c=62 A^iRm-E ■5 In this formula A=the area of the gathering ground in acres j Rm=the estimated average rainfaU of the three driest con- secutive years ; and E = the loss of rainfall by evaporation, percolation, and unavoidable waste. The value of E may be as little as 10 inches, and may even exceed 20. Peaty matter is very frequently present in the upland surface 8 HYGIENE AND PUBLIC HEALTH waters of mountainous districts, often imparting a decidedly yellow or brownish hue to the water. It may be removed by filtering the water through beds of fine, sharp sand, as is done at Yaxtry (Dublin). Under the headmg of Upland Surface Waters may also be considered the waters derived from natural lakes in mountainous districts, of which Glasgow furnishes a good example. Glasgow is supplied with water from Loch Katrine, 34 miles north of the City. This beautifully soft and pure lake-water, which replaced in 1859 the grossly-polluted supply drawn from the Clyde, has been of inestimable advantage to Glasgow, not only by raising the standard of health of its inhabitants, but also by effecting an enormous saving in manufacturing and industrial pursuits, from the fact of the hardness being equivalent to only one grain of chalk per gallon of the water. Upland surface and lake waters, in their comparative free- dom from mineral matters, approach more nearly to the composition of rain-water than water derived from any other source. Many of the manufacturing towns in Lancashire and Yorkshire are supplied with upland surface waters. Manchester has lately obtained a new source of supply from Thirlmere, 90 miles from the City. By the construction of a dam, the level of the lake has been much raised, and its storage capacity increased. Liverpool, by immense engineering works, has impounded the waters of the Vyrnwy, in Wales, by a massive masonry wall built across a narrow part of the valley, creating an artificial reservoir 4f mxiles in length and conveying the water a distance of 68 miles ; and Birmingham is now engaged in the task of bringing water from the upper sources of the Wye. Occasionally the water of lakes and open reservoirs becomes contaminated by the growth and subsequent decay of algae and other microscopic organisms. In some instances so abundant is the growth of the organism that the water becomes coloured red or green-blue, according to the nature of the organisms, and is also turbid and evil-smelling. Beyond the unpleasantness arising from the odour and turbidity of the water, and the disturbance of the sand filter-beds when the reservoir water is subjected to filtration, it does not appear that this contamination induces any injurious effect upon the health of the consumer. The quantity of water that can be collected and stored in an impounding reservoir amongst hills can be calculated with some WATER 9 approach to accuracy if the area of the catchment basin, the average rainfall, and the average amount of percolation, evapora- tion, and flow of the rainfall off the surface, are known. Records of the rainfall, percolation, etc., extending over a long series of years are necessary for this purpose. The loss from evapora- tion in open reservoirs may reach to ^ of an inch per day in summer, the average throughout the year varying from ^V to iV of an inch daily. The area of the catchment basin or gathering ground can be ascertained from a 6-inch ordnance map. It is in many cases a district enclosed by a ridge line, which is continuous except where the water finds exit ; or if the ridge line is complete and the water does not find an exit, a lake or natural reservoir is formed. The main ridge line may give off branches, and thus produce subsidiary or secondary catchment basins. In 6-inch ordnance maps, contour lines, which are lines of equal altitude, are drawn at every 25 feet of elevation. Ridge lines, or watershed lines, indicate where the ground is higher than that immediately adjacent on each side, the land sloping from them on both sides. On the ordnance map will also be found the Bench Mark figures, which indicate in feet the height of the particular spot above ordnance datum. If the place noted by any of these figures be visited, there will be found a B. M. or broad arrow marked on some object, such as a milestone, church- wall, rock, etc. The maps of the Ordnance Survey of the United Kingdom are published in the following scales : (i) |- inch to the mile, or .rWiiir the actual measure- ments of the ground. This map shows a considerable area of country in one sheet. (2) One inch to the mile, or -5-75 ^utj the actual measurements of the ground. This is the general road map of the country. The out- line edition shows contours at 100 feet intervals up to 1,000 feet, and above that height at 250 feet intervals, and numerous spot levels along the roads. (3) Six inches to the mile, or i-iri^xr the actual measurements of the ground. This map shows houses and fields and boundary lines. Altitudes are shown as on the 2 5 -inch map, and contours are shown at 50 ft., 100 ft., and at 100 ft. intervals up to 1,000 ft. above sea level. (4) Twenty-five inches to the mile, or -rr-^iru the actual measurements of the ground. This map shows the details of buildings, and the boundaries and areas of fields, etc. It shows levels of bench marks along the roads to one place of decimals, but does not show contours. (5) Town maps, with the exception of London, Dublin, Belfast, and some smaller towns, are on the scale of 10-56 feet to the mile, or ,. i^ the actual measurements of the ground, for all towns which at the time of the survey had 4,000 inhabitants and upwards. The scale is large enough to show doorsteps, the thickness of walls, and the divisions between buildings. It also shows all objects con- nected with water-supply, lighting, and drainage, such as hydrants, lamp- posts, sewer-manholes, and gratings. Levels are shown along many of the 10 HYGIENE AND PUBLIC HEALTH streets, and bench marks showdng to two places of decimals the altitude above mean sea level. Areas are not sho^^^l on town plans, nor are con- tours. In London, Dublin, and Belfast the scale adopted is 5 feet to the mile, or yuVu the actual measurements of the ground. The altitudes on the maps are those above ordnance datum or mean sea-level at Liverpool, which is 0-65 feet below the mean level of the sea round the coast. Trinity high water mark at the entrance of the London Docks is 1 2 '48 feet above ordnance datum. Surface levels are shown in feet along the roads on the 6-inch maps thus 4- : on lo-feet town plans one decimal is given. Levels are shown thus " ^ B. M. S7'4-" ^- ^^ means the Bench Mark cut on buildings, walls, etc., and at this spot the Bench Mark is 57/4 feet above ordnance datum. Waters collected from upland surfaces are liable to pollution from shepherds' huts and the droppings of animals allowed to feed upon the collecting area. The water collected upon these areas ought alwa3^s to be carefully protected from such pollutions. Streams and Rivers. Streams near their sources, and passing through uncultivated land on hills and moorlands devoid of human habitations, are good sources of water-supply ; they form, in fact, those upland surface waters which have already been considered. Streams and rivers in their course through cultivated valleys, with towns and villages on their banks, furnish water which must always be regarded as undesirable, and in many cases as dangerous for drinking purposes. The composition of river water, as regards its mineral in- gredients, is most variable. Fed from a variety of sources, by springs and streams in the uplands, by surface drainage, by springs in their beds, and by other streams and rivers through- out the whole of their course, rivers are a combination of spring and surface waters, and present sometimes mainly the char- acteristics of the one and sometimes those of the other. All rivers, as being the natural drainage channels of the sur- rounding land, must be subject to pollutions of animal origin. The surface and subsoil drainage from manured land under culti- vation, the sewage effluents from isolated houses, the slop waters and the sewage of villages and sometimes even of towns, and the waste products of industries on their banks frequently flow into the river. Towns, as a rule, draw their supply of water from a river above the spot at which the sewage of the town is dis- charged. But the intake of the next lower town on the banks of that river must necessarily be from a stream already polluted with sewage ; and the question arises, can a ri\''er once polluted WATER ir with sewage, and with all the possibilities of specific disease contamination thereby introduced, ever be a safe source of supply below the point of pollution ? When sewage or other polluting liquids are discharged into rivers, they are more or less diluted with the river water, the amount of dilution depending on the comparative volumes of sewage and river water which are thus mixed together. II the river into which the sewage is discharged consists of clean and hitherto unpolluted water, the oxygen dissolved in it will, to a certain extent, oxidize the organic matters of the sewage, this destruction being very largely effected through the agency of aerobic or oxygen-requiring bacteria. If, too, the dilution of the sewage with clean water is considerable, plant life is not interfered with but continues to give off oxygen, reoxygenating the water, and enabling the process of purification by oxidation to continue. No doubt, also, as the oxygen dissolved in the water is used up, fresh oxygen is absorbed from the air. Besides water plants, minute animals (infusoria, anguillulidae or water worms, entomostraca or water fleas, etc.) aid the process of purification by feeding on the organic impurities of sewage. These organisms are found in countless numbers in the polluted reaches of rivers. Fish, too, if the pollution is not sufficiently great to cause serious diminution of dissolved oxygen in the water, feed on some of the elements of sewage, and aid in the process of purification ; and when the current is sluggish, or in the deep and quiet pools of a rapid stream, the suspended matters of the sewage will be largely deposited. Delepine has shown that this sedimentation, which occurs when the flow is sluggish, is a very important factor in promoting bacterial purification in river water. The result of all these processes is that, under certain con- ditions and within certain limits, streams and rivers which have been polluted are capable of undergoing a certain amount of self-purification by natural means. The Rivers Pollution Commissioners (Sixth Report) came to the conclusion, as the result of their experiments, that " the oxidation of the organic matter in sewage proceeds with extreme slowness, even when the sewage is mixed with a large volume of unpolluted water, and that it is impossible to say how far such water must flow before the sewage matter becomes thoroughly oxidized. It will be safe to infer, however, from the above results, that there 12 HYGIENE AND PUBLIC HEALTH is no river in the United Kingdom long enough to effect the destruction of sewage by oxidation." The truth of the matter then appears to be, that under favour- able conditions, when the dilution of the sewage with clean water is very considerable and the oxidation and purification exerted by aquatic animal and vegetable life can have free play, a stream or river, especially if it undergoes agitation and exposure to the air by flowing over rapids or by falling over weirs, is capable of being so far purified that, although it may never quite regain its original purity, it becomes at least very much improved. The oxidation of the organic matters in sewage is not, how- ever, the only process with which the self-purification of rivers is concerned. Of more importance is the destruction or elimination of the bacterial organisms introduced into the water by the polluting agents, more especially of those of " intestinal type," e.g.. Bacillus coli, Bacillus enteritidis sporogenes, Bacillus enteri- tidis (Gaertner), and streptococci, with which are occasionally associated the Bacillus typhosus and other pathogenic organisms. It is probable that organisms of this type may persist in a polluted water which has freed itself from all other evidence of sewage contamination, and be present in such numbers as to indicate recent contamination with animal matter with all its attendant dangers. There is evidence that organisms of the intestinal type, after obtaining admission to water, undergo after a time changes ol a degeneiative nature, probably accom- panied by loss of virulence, so that they no longer comply with all the tests characteristic of the types they represent. When the river into which sewage is discharged is already much polluted, or if the dilution is not sufficiently great, oxidation and purification are brought to a standstill. The dissolved oxygen is then greatly diminished in amount ; many forms of animal and vegetable aquatic life are injuriously affected or destroyed ; decomposition or fermentation of organic matters is started, with the production of foul gases ; the bed of the river becomes silted up with decaying matters, which, buoyed up by gases, occasionally rise to the surface and sink again, and a most serious nuisance results. The process is one eventually tending to purification by resolution of complex organic bodies into their simpler elements, but in the meantime the effects of the process are most offensive. WATER 13 A considerable rise of temperature will produce a like result on rivers which are having their purifjdng powers tested to the height of their capacity. Purification goes on so long as the weather is cool, but with a rise in temperature, certain forms of bacterial growth are stimulated and decomposition sets in, replacing the oxidizing processes. Sewage in drinking water is chiefly dangerous from the fact of its being liable to contain the specific poisons of disease. Cholera and enteric fever, diarrhoea and dysentery, we know to be sometimes spread by means of infected and polluted water. A considerable mass of evidence, based largely on laboratory experiments, was submitted to the Royal Commission on Metro- politan Water Supply (1893), as to the behaviour in water of the bacilli of typhoid fever and cholera. The statements of the bacteriological witnesses before the Commission, therefore, represent knowledge obtained under artificial conditions of disease organisms cultivated under such conditions, and are consequently only inferentiaily applicable to similar microbes in a state of nature and subjected to a natural, as opposed to an artificial, environment. With this reservation, the general results of the bacteriological evidence may be summed up as follows : The bacilli of typhoid fever and cholera tend to lose their vitality, and ultimately to disappear, when placed in water. In water which is sterile, or devoid of other organisms, these bacilli may retain some kind of vitality for several weeks or months if the water contains organic pabulum. But in water containing actively growing non- pathogenic organisms, such as ordinary river water, the destruc- tion of the pathogenic organisms is effected much more rapidly. This statement helps to throw light on certain outbreaks of enteric fever due to specific contamination of deep well-water. Pure deep weU-waters contain relatively few bacteria ; conse- quently the typhoid bacillus when introduced into such a water (as occuired in the Caterham outbreak) may possibly retain its vitality and virulence sufficiently long to render large volumes of water infective. It appears possible, also, that under such conditions, deep underground, with an absence of light, the typhoid bacillus for a space of two or three days might increase in numbers, thus enabling a relatively small amount of polluting ingredient to contaminate large volumes of water. The process of sedimentation which occurs in the deep and 14 HYGIENE AND PUBLIC HEALTH sluggish reaches of a river tends to the ehmination of bacteria, the suspended matters in their subsidence entangling them and carrjang them down. The effect of aeration and of flow are less apparent qua bacterial destruction ; whilst as regards the undoubted powerful germicidal action of bright sunlight, in the case of a river like the Thames, with an average depth of over six feet, it is doubtful what effect the water has in cutting off the actinic light, and, therefore, what is the precise germi- cidal action of sunlight or dajdight at different depths from the surface, and under different conditions of clearness or turbidity of the water. Dr. Houston has sho\\Ti that if sufficient storage capacity is provided in the reservoirs for the crude river water from the intakes, it is possible to eliminate from the water all but a very small percentage of disease-producing organisms. In eighteen experiments with unfiltered water, infected with enormous numbers of the bacilli of enteric fever, it was found that over 99 per cent, of these organisms died as the result of simple storage of the water for four weeks. The final and complete disappearance of t3^phoid bacilli from an artificially infected raw river water may not take place until nine weeks after inoculation. The process of storage and purification of Thames water pursued by the Metropolitan Water Board, on the efficiency of which the health and freedom from disease of so large a population depends, is as follows : — The water taken from the river is passed into a storage reser- voir, capable of holding several days' supply. It is important that the capacity of this reser\^oir should be sufficiently great, both to obviate the necessity of drawing water from the river when it is in flood (and therefore very turbid), and to allow time for the clarification of the water by the deposition of suspended matter. The Tondon storage reservoirs are of an aggregate capacity of over 8,000,000,000 gallons, and the average daily supply of water exceeds 220,000,000 gallons. From the storage reservoirs the water is conducted to the surface 01 the filter beds, which consist of layers of fine sand (average thickness 3 feet) lying upon layers of gravel, fine above but coarse below, and of a total depth varying from 3 to 8 feet. The average filtering area per million gallons of daily supply is 079 acre. In the coarse gravel or rough stones are the open mouths of the outlet pipes, WATER 15 which convey the filtered water from the filter beds to a central filtered-water well, from whence it is pumped through iron mains to the Metropolis, or to a high-level reservoir near London. Vents run up from the deeper layers of the filters to above the water level to permit of the escape of displaced air when the bed is being filled with water. The large reservoirs for the storage of filtered water in or near towns should be covered ; they are not infrequently made to feed supplementary reservoirs, especially where the demand in one part of the district greatly exceeds the average for the district generally. The depth of water on the filter beds is never more than 2 feet, the average rate of filtration per square foot of filter bed being i^ gallons per hour, or 1,568,160 gallons per acre in 24 hours. The upper layers of fine sand must be occasionally renewed, as they become choked with sediment. The old sand is washed with water jetted from a hose under high pressure, before being used agam in the filter beds. Houston has shown that in fresh, healthy, human faces 85 per cent, of the organisms known as Bacilli coli commvmis are typical B. coli, answering to all the known tests for this organism, the remaining 15 per cent, being atypical, in the sense that they do not respond to all the tests. In sewage and sewage effluents the percentage of typical B. coli is slightly reduced, and in sewage polluted waters there is a further reduction. In filtered waters derived from polluted sources, such as the water of the Thames at Hampton, the percentage of typical bacilli is reduced as low as 38 after storage and sand filtration, such as is practised by the Metropolitan Water Board, in addi- tion to the 98 per cent, reduction in total number of organisms as compared with the unfiltered crude river water. Dr. Houston is of opinion that the smaller proportion of typical B. coli in the stored and filtered water is evidence of elimination from the water of bacilli which are specially characteristic of faecal matter ; and therefore of purification by change of type of bacilli, apart from reduction in numbers. The disappearance of the typical bacilli is relative and not absolute, as 30 per cent, of the samples of filtered water analyzed contained typical B. coli either in 100 c.c. (15 per cent.), 10 c.c. (11 per cent.) or i c.c. (14 per cent.) of the water. In the latter case only, however {B. coli present inji c.c), would the water be considered decidedly unsatisfactory. l6 HYGIENE AND PUBLIC HEALTH Sand acts almost entirely as a mechanical filter, but a small amount of purification by oxidation takes place. This purifi- cation results mainly from the condensation of oxygen, which takes place upon the upper surface of the sand. Dr. Percy Frankland has shown that the micro-organisms (harmless) present in unfiltered Thames water at Hampton are reduced in number on the average 977 per cent, by the sedimentation and filtration which the water undergoes at the hands of the Water Board, and that this reduction is largest in the case of those installations which have the largest storage capacity for unfiltered water, and the slowest rate of filtration, these being factors of much influence on the chemical, as we]] as on the biological, characteristics of the water. All the witnesses before the Royal Commission on the Metro- politan Water Supply (1893) were agreed that the efficiency of the sand filter beds in intercepting bacteria is due to the forma- tion of a superficial gelatinous deposit on the top of the sand. Green and blue algge interweave their filaments into one felted sheet ; diatoms, with their siliceous frustules and gelatinous envelopes, fill up the meshes ; zooglea adhere to every particle ; and innumerable bacteria dot the whole mass (Thresh). The bacteria become attached to and entangled in the colloidal mass, and are consequently prevented from passing down into the deeper beds of sand and gravel. This fi]tration has been likened to the dialysis through a fine jelly, which is capable of inter- cepting the very smallest bacteria, if there is no rupture or loss of continuity in the material. This gelatinous film which forms on the top layer of sand consists therefore very largely of intercepted organic matter and bacteria. It appears to be sufficiently^ well formed to be effective in intercepting bacteria within two or three days after the filter-bed has been in use, subsequent to renewal of the top layer of sand. It follows, therefore, that the filter-bed does not attain its normal efficiency in the inter- ception of bacteria until it has been in use at least two days after the periodical renewal. On the other hand, there is no evidence of the efficiency of the sand filter-beds, qua bacterial interception, being reduced by prolonged use, even for so ex- tended a period as sixty-eight days. It would seem that the organisms tend to grow down deeper and deeper into the beds, and might possibly in time grow quite through the interstices of the filter, and so reappear in the filtered water. But owing WATER 17 to the thickness of sand this process must occupy a very long time. The reason why the top layers of sand should be removed and renewed periodically is to prevent other filter-beds being overtaxed, because the filtration becomes slow in old beds, owing to the thickness of the gelatinous coating, and consequent clogging of the top layers. If certain filter-beds are working too slowly, others have to be pressed, possibly resulting in inefficient filtration, in order to make up the volume of filtered water necessary for the daily supply. The result of the Massachusetts experiments on the purifica- tion of water by filtration may be briefly summarized as follows : — [a) By reducing the rapidity of filtration, and employing the finer sands, increased efficiency is obtained. (&) With moderate rapidity of filtration (2,000,000 gallons per acre per diem) i foot of sand appears to be as effective as 5. (c) The scraping off of the upper layer of clogged sand enables more organisms to pass through the filter ; and it is not, as a rule, until three days after scraping that the filters regain their highest efficiency. [d) Fifty-five per cent, of the organisms removed were found in the upper J inch of sand, and 80 per cent, in the upper inch. {e) Much less water at 32° F. passes through a filter than when the water is at 70° F., owing to the increased viscosity of the colder water. (/) Shallow filters require more frequent scraping than the deeper ones, due to the greater head available in the deeper filters. (g) Filters used continuously require less frequent scraping than when used intermittently. The connection between the cholera outbreak in Hamburg in 1892 and its water supply, and the value of sand filtration are clearly demonstrated by the following facts : — Hamburg,; Altona, and Wandsbeck are three towns which are contiguous to each other, and really form a single community, not differing from each other except in so far that each has a separate and different kind of water supply. Wandsbeck obtained filtered water fiom a lake which is hardly at all exposed to contamination with faecal matter ; Hamburg obtained its water unfiltered from the tidal Elbe above the town ; whilst Altona drew its water from l8 HYGIENE AND PUBLIC HEALTH the Elbe, but below Hamburg, after the river had received the sewage of 800,000 people. The water so taken, however, was subjected to careful sand filtration, before being supplied to the people of Altona. \Vhereas Hamburg in 1892 was severety visited by cholera, nearly 17,000 attacks and 8,600 deaths occurring in the autumn of 1892, Wandsbeck and Altona were nearly free from the disease. About 500 cases of cholera occurred in Altona, but at least 400 of these were infected in Hamburg. The water supplied to Hamburg was taken from the Elbe above the sewage outfalls into the river, but was nevertheless contaminated at times by the tidal action carrying sewage back above the outfalls. This water, supplied in an unfiltered condition to the population, was the cause of the cholera epidemic. Careful sand filtration of the Elbe water, in a much more grossty sewage-polluted condition, saved Altona from the disastrous epidemic which raged in Hamburg. Professor Koch lays stress upon the following three points as . to the efficacy of sand filtration : (i) That a proper thin layer of mud or slime should be formed on the top of the filter-bed ; that it should not be disturbed during the process of filtration, and that when the deposit becomes too thick and impermeable it should be removed ; (2) that the thickness of sand should never be less than 30 cm. (ii-8 inches) ; (3) that the downward movement of the water through the sand layer must not exceed 100 mm. (3-94 inches) in the hour, or a little over 2,000,000 gallons per acre per diem. He recommends that, after a filter has been scraped, the slimy deposit should first be allowed to form before the water is conducted to the filtered-water well or reservoir ; that each separate filter should be bacteriologicaUy investigated daity, and water containing more than 100 germs, capable of development in a cubic centimetre, should not be allowed to reach the pure water reservoir. The majoritj^ of the bacteria in adequately filtered water are attributable to post- filtration sources, the filter-beds below the slime layer, the channels, collecting drains, culverts, and wells being, of course, not sterile. The slightest disturbance, however, m the process of filtration, as, for instance, the quickening of the pace of filtra- tion to over 100 mm. per hour, or the disturbance of the sHmy covering, as in periods of frost or immediately after a filter is cleaned, tends to create an immediate increase of germs in the filtered water. WATER 19 The mechanica] filtration of water under pressure provides a rapid means of filtering large volumes of water. In the pressure filter the water is forced uDder pressure through several feet ,of fine sand or quartz, the cleaning of the filters being effected by means of a reversed current of water. Other materials are sometimes used, such as a black, porous, magnetic oxide of iron, called Polarite. These filters can be used with or without coagulant, but in the former case a satis- factory bacterial standard of purity cannot be obtained. The coagulant most commonly used is the sulphate of alumina, from I to 2 grains per gallon ; and the object of its employment is to form a gelatinous cover on the surface of the mechanical hlter which will take the place of the bacterial scum which forms on ordinary sand filters. These filters, employed in conjunction with a coagulant, are very serviceable when dealing with raw river waters. The conclusion that we may come to, then, in the case of the London water supply from the Thames, is, that as long as it is efficiently filtered and not taken from the river when in flood, it is fairly pure and reasonably wholesome ; but that the Thames is not really a safe source of supply, for should the filtering arrange- ments break down at a period of epidemic prevalence in the upper reaches of the river, disease would in all probability arise amongst the consumers of the water in London. The same may be said of any other polluted river used as a source of drinking water ; and all attempts to purify by filtration organically polluted water, whether it be on a public or a domestic scale, ought to be deprecated. The yield of a small stream, or water-course, may be approxi- mately ascertained by observing the average width and depth of the stream over a portion of the channel where it is fairly '^miform. The yield is found by multiplying the area thus obtained by four-fifths of the surface velocity in this portion of the channel. Current meters may also be employed ; or, if the whole stream is dammed up and made to pass through a trough oi known area and length, through a sluice of known size, or over a weir in which a rectangular notch of known area is cut, the discharge of water can be very accurately estimated. It is only necessary to multiply the sectional area (in square feet) of the trough or sluice by the velocity of the water (also in feet), to ascertain the number of cubic feet of water being discharged. 20 HYGIENE AND PUBLIC HEALTH WTien water is taken from the head of a stream for municipal purposes, a " compensation reservoir " is often provided to impound storm waters, which can be led into the river for trade purposes to augment the drj^-weather flow. Sometimes river water is obtained from deep trenches dug in the proximity of a river, and it is assumed that the water under- goes purification in its passage through the soil. Although more or less ground water is generaUj^ collected in these trenches, water of great purity has often thereby been obtained.. Springs. The advantages of underground water supplies over surface- collected suppHes are that large reservoirs are not required, less land is wanted, filtration is unnecessary, and there is less liability to pollution. In some springs, derived from under- ground waters at great depths below the surface of the earth, the mineral constituents of the water are so excessive in amount as to render it quite unfit for drinking, but valuable for medicinal purposes. There can be little doubt that the water forming these springs is, in many cases, forced out of the earth by the pressure of confined gases ; but the origin of most of the springs which afford a pure and wholesome water for ordinary use is explained in a different manner. The rain which percolates the porous strata (sand, gravel, hssured chalk, sandstone, etc.), at the surface of the earth, sinks through these strata by the force of gravity untH it reaches — as it usually does at a greater or less depth — an impermeable stratum. This underground water does not always stand at the same level. It is constantly rising and sinking, and in most years these variations of level are fairly regular, both as to amount and as to the season of the year at which they occur. The highest level is usually reached in this country in February or ]March, whilst the lowest occurs in October or November, The cause of these variations must be looked for in the cir- cumstances attending the rainfall. In districts having an average rainfall (25 to 30 inches per annum), the amounts of rain that fall in summer and in wintei are very nearty equal. But in the summer months (April to September) the amount of rain that percolates is generally very small ; it is only one-seventh of the summer rainfall in chalky soU. Nearlv all the rain that falls in an average summer is evaporated WATER .21 from the surface of the soil or from the leaves of plants. The consequence is that the underground water is not replenished from the surface, and its level sinks. In the winter months (October to March) considerably more than half the rainfall percolates in most chalky soils, the remainder being lost bj^' evaporation. The underground water begins to rise usually in November, if percolation has commenced in October, and con- tinues to rise until it attains its maximum in March. Occasionally it happens, as in 1879 and in 1903 when the summers were very wet, that the^nderground water rises ]during the summer months. But such years are exceptional. The underground water is not only constantly changing its level, but it is also always moving slowly towards its natural outlet. The water tends to find its own level according to the laws of gi^avitation ; not rapidly, but slowly, owing to the friction and capillarity which obstruct its passage through the interstices of the rocks or soil. The outlet may be into the sea or into a river, or by springs. It has been found by observation on shallow wells that the underground water has a curved surface from its highest level to its outlet. The curve rises steeply from the outlet, but gradually becomes more nearly horizontal as the distance from the outlet increases (fig. i). The variations in level between high and low underground water are small near the outlet, whilst they gradually increase as the distance from the outlet increases. When the level of the underground water is highest, the fall to the outlet is greatest, and, consequently, the volume of water discharged at the outlet is at its maximum. Springs are usually divided into " main or deep " and " land " , springs. Land springs are formed by the " cropping out " on the surface of the earth of the impermeable stratum which holds the underground water up, i.e. prevents it from sinking further into the earth. Such springs are the outlets of limited collections of under- ground water, formed in superficial beds of sand or gravel over- lying an impermeable stratum. They are often intermittent, ceasing altogether to flow during the summer, when the under- ground water is exhausted, and beginning again in the autumn, very""soon after percolation commences. Intermittent springs are also formed where a valley cuts across the highest levels of a large volume of underground water, so that the spring flows 22 HYGIENE AND PUBLIC HEALTH only for a short period of every year — usually in Februar}^ or March — when the highest water line of the underground water is tapped by the depression of the valley (fig. i). ^ w Main springs are the deep-seated springs issuing through a fault or fissure from regular geological formations, such as chalk, oolite, sandstone. They are usually perennial, flowing all the year round, but often exhibit well marked seasonal variations, their volume increasing in winter, when the underground water level stands highest {see fig. i). Springs afford good sources of water supply for small com- munities, such as villages. Main springs are better than land springs, both because, as before stated, they yield water through- 1 out the entire year, and because they are less liable to accidental pollutions, the great thickness of strata through which the water percolates from the surface effectually dealing with any organic Fig. t. — Underground Water Curves. A, high level; B, low level; C, inter- mittent land spring ; D, constant land spring at sea level. impurities it may contain. Such spring water is usually clear and sparkling, well aerated, and of nearly constant temperature throughout the year. It generally contains more or less of the salts producing hardness, and is, therefore, though palatable and wholesome for drinking, less well suited for washing, cooking, , and manufacturing purposes than the softer waters. To guard against pollution, the surface of the soil around the point of delivery of the spring should be walled in, and the water conducted to the surface by a short pipe. In some cases it may be necessary to collect the water issuing from a spring, and to store it in a reservoir before distribution to the houses of the consumers. The yield of a spring may be estimated by observing how long it takes to fill a vessel of known capacity. It is well to know the average flow throughout the year. In chalk and sandstone districts springs generally occur at points much below the level of the surrounding country, as these permeable rocks themselves form vast reservoirs. In the oolite, owing to the frequent alternation of porous and retentive strata. WATER 23 springs are common. In limestone regions main springs are often fed by subterranean reservoirs caused by the solution of the limestone by water charged with COo. The most constant and abundant springs in this countrj^ are generally in the chalk, oolite, new red sandstone, the millstone grits, and mountain limestones ; and the most invariably good water is obtained from the lower chalk immediately above the greensand. Springs may be made to su])ply water to houses situated above the level of their delivery if the flow is sufficient to work a ram, turbine, or other similar form of pumping engine, so that the water can be pumped up to the cistern or reservoir. Sometimes the spring water issuing from a great depth is warm or even hot. This is due to the fact that, below the level at which varia- tions due to atmospheric alternations of temperature cease to be recognizable, the temperature of the earth increases with its depth, and the water temperature rises about 1° F. for every 50 to 60 feet of depth, on an average. Wells. ^ It is usually said that there are three kinds of wells, shallow, deep, and artesian ; but the last is merely a variety of a deep weU. Shallow wells are those which are sunk into superficial porous beds of sand or gravel overlying an impermeable stratum of clay or other dense rock. They tap the underground water held up by an impermeable stratum, and ^deld a water identical in composition with that flowing from the land springs in the neighbourhood. The depth of the well must, of course, vary with the vertical distance of the impermeable stratum from the surface of the earth ; as a rule, this distance is not great, and, in fact, it is often said that shallow wells are those which are less than 50 feet deep ; but it is better to keep to the definition here given. The rural population of this country derives its water almost exclusively from shallow wells. Formerly shallow wells were also the usual sources of supply in towns ; but these, in nearly all instances, have now been abolished in favour of a public supply from better sources. The Rivers Pollution Commissioners (Sixth Report) stated that in their experience shallow wells were almost always horribly polluted by sewage and by animal matters of the most disgusting origin. 24 HYGIENE AND PUBLIC HEALTH Where the level of the underground water is but a few feet from the surface, it is obvious that the surface water, which may contain impurities, has but little chance of being purified in its passage through the soil to the well. But the grosser pollutions that shallow well waters suffer from, come, not from the surface, but from leaking drains and cesspools in the vicinity. Cesspools are but rarely made watertight, as they would then require to be frequently emptied. When sunk in a porous soil and merely lined with bricks without mortar or cement, the contents soak away, and the cesspool can be closed over and need not be opened for many years. The liquid sewage percolates through the soil and joins the underground water below. As the underground water is — as before explained — slowly but steadily moving along in the direction of its natural outlet, the position of the well in regard to the cesspool is all- important. Should the well be above the cesspool, the under- ground water flowing from the well to the cesspool, the risk of pollution is greatly diminished, so long as but little water is drawn from the well. If the well is below the cesspool, and in the line of flow of the underground water, it must infallibly be polluted with the cesspool soakage. The direction of flow of the underground water can usually be determined from the contour of the surrounding country ; and this evidence can be confirmed by observations on the height of the underground water at different places, as determined by the height of the water above ordnance datum in different wells or trial holes ; for the level of the underground water falls as it approaches its outlet in springs, lakes, streams, or rivers, giving rise to a curve which has been already considered [see p. 21). When, however, the amount of water abstracted is sufQcientl}/ great to cause a considerable depression of the water in the well, the well then drains an area all round it in the form of a circle ; and in such a case it would not matter what position the well had to the cesspool if the cesspool was included within the area drained by the well, for pollution must inevitabl}/' occur. The distance within which a well draws water to itself, when its own water-level has been depressed by pumping, depends on the amount of the depression and on the nature of the soil. The surface of the underground water in the area of the circle drained by a well depressed by pumping has the form of a cur- WATER 25 vilinear cone, with steep gradient near the well, but becoming more nearly horizontal as the distance from the well increases (fig- 2). We have thus seen that the conditions which favour the con- tamination of a shallow well from cesspool or other forms of pollution are : (i) Its position as to cesspools or other sources of pollution, with regard to the flow of underground water ; (2) the amount of depression of water-level in the well which may be produced at any time by pumping ; (3) the nature of the soil in which the well is sunk, as regards porosity and the easy passage of water. It is quite possible, if these conditions are attended to, to sink a well that shall be uncontaminable Fig. 2. -Depression of Water in Shallow Well by Pumping. A, well ; B, cess pool; C, underground water curve. (After Field and Peggs.) in or near a village, in which the shallow wells are generally polluted with cesspool soakage. The well must be sunk in such a position as regards possible sources of pollution that the underground water flows from the well to the sources of pollution. The distance of the well from such possible polluting sources should be from 100 to 160 times the depression of the water in the well that is ever likely to be produced by pumping, this distance varying with the nature of the soil. The mouth of the well should be closed over, and the water raised by an iron pump ; draw wells, where the water is raised by a windlass, chain, and bucket through an open mouth, are liable to accidental contamination from refuse being thrown in, or animals falling in. To prevent contamination from impure surface washings, the mouth of the well should be protected by a coping carried up to about a foot 26 HYGIENE AND PUBLIC HEALTH above the surface of the ground, and the drainage water from the pump should be conducted away to a safe distance. It is very desirable to make the walls of a shallow well im- pervious. When the porous stratum in which the well is sunk is of considerable depth, the sides of the well for about 20 feet should be imperviously steined with brickwork set in and lined with hydraulic cement ; or cast or wrought iron cylinders may be employed for lining the upper portion. If this is done, water percolating from the surface must pass through about 20 feet of soil before entering the well, and, in its passage through the soil, the organic impurities in the water will be, to a certain extent, removed. The less the fluctuation in level of the subsoil water, the more likely is the supply to be permanent, and the less the liability to contamination. It is a noteworthy circumstance in regard to the grossly polluted waters of many shallow wells^ that they are, as a rule, clear, sparkling, and very palatable./ The organic filth from cesspools and drains, in its passage through even a few feet of porous soil, is filtered and deprived of suspended matters, but does not lose its dangerous properties. The shallow well into which the filth percolates is found to furnish a water loaded with ammonia and chlorides— evidences of sewage (urine) con- tamination — with organic matter in solution, and with nitrates and nitrites, the oxidized residues of organic matters ; but yet, from its containing abundance of carbonic acid gas, the water is sparkling and palatable. Such wells, however, after a heavy rainfall, are sometimes liable to furnish a turbid and foul-smelling water which nobody would think of drinking. The heavy rain washes foul substances in the soil, derived by soakage from manure-heaps, middens, privies, leaky drains, or cesspools, direct into the well, no time being allowed for that filtering and partial purification which does so much to give the well water at ordinary times its pure and deceptive appearance. Where suspicion is entertained that a well water is polluted, the method by which the polluting material reaches the well may sometimes be ascertained by the use of solutions, which either by reason of their colour, taste, or chemical properties, can be easily identified, even when largely diluted. For this purpose strong solutions of common salt, lithia salts, an alkaline solution of fluorescein, paraffin oil, or an emulsion of Bacillm WATER 27 prodigiosits have been employed. When introduced into the drain, cesspool, or other supposed source of the mischief, such solutions will within a few days, if the supposition is correct, be found in the well water. For most purposes fluorescein, along with a simDar quantity of sodic hydrate, is preferable to the other substances, as it is very soluble, has great colorific power, is easily identified, and is harmless in small traces. One grain imparts a visible green fluorescence to over 500 gallons of water. Emulsions of Bacillus pvodigiosus are of use where leakage into a well from the surrounding soil is suspected, and it is desired to ascertain if the filtering power of the soil is sufficient to arrest the passage of bacterial organisms contained in sewage or other polluting liquids. i,^^lxi making an examination of a well, the cover should be taken off, and the sides of the well should be carefully examined for evidence of liquids finding their way through the brickwork, or for the discoloration of the sides due to past leakages. The position of the pump and the rising main should be noted, and the point at which the latter leaves the well should be examined. The depth of the water in the well, the distance of the water-level from the ground surface, and the depression of water-level caused by pumping should be ascertained, also the time that elapses before the original water-level is restored after pumping ceases. The surroundings of the well should be noted, the distances from possible -sources of pollution, and the porous or impervious nature of the soil and subsoil. The condition of the ground around the well, and the method of disposal of the waste water from the pump should also receive attention. If samples of the water are taken, it is often desirable that a sample should be taken from near the surface of the water, as well as from near the bottom, as polluting materials may be very unequally distributed in stagnant water undisturbed by any currents. Polluted shallow well waters are usually hard, and therefore unsuited for domestic purposes. The hardness is sometimes due to the polluting liquids which find their way into the well, but little being caused by the mineral salts present in the strata through which the well is sunk. Another source of pollution of shallow weUs is the vicinity of graveyards, especially when the subsoil water is liable to rise up to the level of the coffins. Tube wells are contrivances for obtaining water from super- 28 HYGIENE AND PUBLIC HEALTH ficial porous strata by means of borings. They were largely used during the Abyssinian campaign, where the occupation of any piece of ground was necessarily temporary, the tube being quickly sunk and as quickly withdrawn. An iron tube with a steel nozzle and perforations at its lower end for the passage of water is driven into the ground by a driving weight or " monkey "; before it has altogether disappeared into the ground another length of tube is screwed on, and this is then driven in. Successive lengths of tube are attached until a depth of 20 to 28 feet is reached,, when a hand - pump is screwed on the top and the water pumped out. Difficulty is often experienced from sand blocking the lower part of the tube and the perforations. The sand must be dislodged by a clearing tool, or pumped out until a space free from sand is formed around the nozzle, and the water issues clear and bright. These tube wells are most suitable where the distance of the water from the surface of the ground is not more than a few feet, and it is sometimes advantageous to drive one from the bottom of an ordinary well to increase its yield. They can be used in gravel, coarse sand, or chalk, but their use in clay soils, maris, or, fine sand is not satisfactory. V Deep wells are those which are sunk to considerable depths in search of water through regular geological strata such as chalk, oolite, and sandstone. Those also are known as deep wells which pass through a superficial porous bed and an under- lying impermeable stratum to reach water-bearing strata below, though often at no great distance from the surface. In sinking a deep well, as soon as the water-bearing strata are reached the water often rises rapidly, and may even overflow at the surface. If the sides of a deep well of this nature are properly steined with brickwork set in cement as far down as the impermeable stratum, surface waters and underground water resting on this stratum are entirely excluded, and the well is freed from those sources of pollution which so often contaminate shallow-well waters. In hard chalk, new red sandstone, oolite, and limestone, the wells require no lining, but in clays, marls, and in all free and broken strata they should be steined. The water collected from deep wells has usually travelled a long distance since it fell as rain on the surface of the earth ; for the outcrop of the water-bearing strata on the surface, which WATER 29 are the catchment areas for the rain, may be many miles from the spot at which the well is sunk, as is the case with the deep wells in the chalk sunk into the London basin. The London basin is interesting as an example of a geological formation with water-bearing strata in different rocks at varying depths from the earth's surface (fig. 3). Most superficially are the subterranean waters in the beds of gravel or alluvium of but slight thickness (10 to 30 feet) upheld by the London clay. These waters supplied the shallow wells which formerly formed so large a part of the water supply of London. After boring through the London clay (100 to 400 feet in the neighbourhood of London) water is again reached — or was before these strata were exhausted— in the Lower London Tertiaries, beds of sand, gravel, and clay of variable thickness (20 to 100 feet), with limited outcrops beyond the edge of the London clay, and more or less surrounding it as they rise from the margin of the basin. Having such a limited outcrop exposed to rainfall, the water which accumulated in the deep strata of these beds under the London clay was soon exhausted, when numerous wells were sunk into them. Beneath the Lower London Tertiaries comes the chalk, with its outcrop in the chalk hills and downs, north, south, and west of the Thames and many miles from its centre. The outcrop a very extensive catchment area for rain, which, percolating through the joints and fissures of the chalk, gives rise to vast reservoirs of subterranean water in the underground basin forms 30 HYGIENE AND PUBLIC HEALTH extension of this rock beneath the tertiary beds of the London basin. As the London basin is hollowed into the form of a shallow trough, the sides of the trough being the outcrop of the chalk in hills and downs, it follows that the water in the chalk is also trough-shaped, and that when wells or borings are sunk into it near the centre of the London basin, the water tends to rise in the boring, and ma^^ even overflow at the surface, forming true Artesian wells. In consequence of the number of borings drawing water from the chalk near London, the water-level has been lowered ; and borings have now to be made deeper than formerly. Owing to the joints and fissures in the chalk allowing a free passage for water, the distance which a well or boring drains, when its water-level is depressed by pumping, is very great ; and thus borings at considerable distances from one another are mutually affected by continued pumping in any one of them. If a boring in the chalk should not happen to open up any fissures or cracks, it may supply but a limited quantity of water, or none at all. Beneath the chalk is the upper greensand in thin beds (lo to 30 feet), with a very limited outcrop around the edge of the chalk ; and beneath this again is the gault, a bluish clay with an average thickness of 130 to 200 feet. Under the gault lies the lower greensand in very thin beds, often completely thinned out, and therefore absent. Although the greensands are rocks permeable to water, neither the upper nor lower beds have yielded water in any quantity to deep borings in the neighbourhood of London. Their outcrop is very limited, with but a small ex- posure of catchment area for rain ; and these formations appear also to thin out considerably in their underground extensions towards the centre of the basin. Near their outcrops in many places the greensands furnish abundant supplies of water, which are, however, very frequently due to percolation from the overlying chalk. Several borings made in or near London have passed through aU the strata above mentioned into the primary rocks beneath. In making these borings it is usual to excavate a wide well -hole for some depth, from the bottom of which a bore tube of small diameter (6 to 15 inches) is sunk. The water should rise through the bore tube in sufficient volume to form a reservoir in the lower part of the well-hole, from which it can be pumped to the surface from considerable depths. Boring tools of large diameter WATER 31 • have been recently introduced, and these are found less costly, whilst the borings are more easily made. At some new works in the chalk at Southampton, the bore tubes are 6 feet in diameter. It has been in many cases found that the driving of headings (" galleries ") and adits horizontally below the water- level is more effective in increasing the yield of wells than deepening them, as the area of collection of water is thereby increased, and there is a greater likelihood of striking the fissures through which the largest volumes of water are moving. Artesian wells, so called from the province of Artois in France, where they have long been in use, are formed when a boring taps a subterranean reservoir confined in a permeable stratum by impermeable strata above and below, the permeable stratum having its outcrops on the surface at considerably higher levels than the surface of the ground where the boring is sunk. The subterranean reservoir is consequently basin-shaped ; and the water, when tapped at the lower part of the basin, strives to regain its level by flowing up the boring and spouting out at its mouth. The waters which feed these wells often come from a great distance, the outcrops of the permeable strata on each side of the basin being sometimes 60 or 70 miles from the well in a straight line. The best Artesian wells are found in the chalk. ^^ The water supplied by deep wells is generally remarkably free from organic impurities, even when sunk in the midst of large cities. Nitrogen, as nitrates and nitrites, is usually present in deep well waters ; the other mineral constituents of the well water depend chiefly on the strata through which the water has percolated, and on the solubility of the component elements of these strata by water charged with carbonic acid. I In the near neighbourhood of the sea there is a danger of the infiltration of sea water into deep wells, especially when sunk in chalk formations. ") Such infiltration is recognized by an increase in the amount of chl^ine in the well water, and is probably due in some cases to excessive pumping causing considerable depres- sion in the water-level of the well. It has happened that the brackishness so caused has rendered a town water supply quite unusable for domestic purposes, and has given rise to diarrhoea and other evidence of gastro-intestinal disturbance among some of those drinking it. The yield of water from a well can only be ascertained by HYGIENE AND PUBLIC HEALTH Shallow Well Artesian Welh pumping down to a certain level, and observing the length of time required for the water to regain its original level. In this country the largest supplies of deep well water are obtained from the chalk, the oolite, and the new red sandstone. WATER 33 Although deep wells, when protected from surface drainage in their upper parts, are but rarely polluted, even when situated in the centre of towns, it does occasionally happen that liquid soakage from sewers or cesspools finds its way into fissures^ in chalk or sandstone, which conduct it to the water of the well, unfiltered and therefore unpurified, and pregnant with danger to the consumers. Deep wells in Liverpool and other places have been closed for this reason. ' The following facts will be found of value in seeking for water. In comparatively flat districts, trials should be made by Norton's tube wells at the lowest sites on the survey. The part most covered by herbage is probably the site where the water reaches nearest to the surface. The same fact is sometimes denoted by localized early morning mists or swarms of insects. The nearer the sea, the more likely is water to be found, but if too near the sea the water may be brackish. In hilly country a search should be made in the deepest valleys, especially the side of the valley towards the highest hill, and at the junction of two long valleys. If there is any evidence of an original watercourse at this point, water is often found at no great depth. A knowledge of the dip^ of the strata in the district, and the situation and area of their outcrop, is of the greatest value in such an investigation. Pumps. Suction Pump. — Fig. 5 shows a section of a common suction pump, which works by the exhaustion of air inside a cyhnder, by means of the upward stroke of a piston ; the atmospheric pressure on the surface of the water forcing the water up through the suction pipe into the cyUnder. The downward stroke of the piston forces the water through the piston valve, and the next upward stroke dehvers it through the spout of the pump. Where water has to be delivered at a height above the pump, the spout is replaced by a pipe (the rising main) with a valve at the point of attachment to the cylinder, which permits water to enter the rising main, but prevents its reflux into the cylinder. In this class of pump the lift of water is effected by the upward stroke of the piston, and the delivery is in consequence intermittent. At each up-stroke of the piston the suction or clack valve C is opened and the piston valve B is closed ; at each down-stroke the action of the valves is reversed. The height of the clack 1 Faults, fissures, joints or dislocations, are defects which are due to the excessive strain of contraction when drying or to movements of the earth's crust. 2 The term " dip " refers to the inclination of the strata to the horizon : an originally horizontal deposit dips from movements of the earth's crust. A " strike " is a line drawn at right angles to the direction of the dip. 3 34 HYGIENE AND PUBLIC HEALTH valve C above the lowest level of the water to be raised must not be more than 25 feet. Although theoretically atmospheric pressure is capable of supporting a column of water 33-9 feet in height, practically the most perfect vacuum obtainable in a suction pump is only equivalent to 25 feet of head, and these pumps work best with heights of less than 15 feet. Force Pumps. — Sections of force pumps are shown in figs. 6-7. These pumps are used where water has to be raised to a height exceeding 25 feet. i^ii = =3& -3^ f to Fig. 6. Single-Acting Suction Force Pump. V, V-^, valves. and Fig. 5. — Suction Pump. A, piston ; B, piston valve ; C, suction or clack valve ; D, suction pipe ; E, water ; F, spout. Fig. 7. Double-Acting Suction and Force Pump. V, V^ V2, V^, valves. as from deep wells. In each case the water is raised by suction into the pump, but whilst in the single acting pump (fig. 6) the delivery is inter- mittent, in the double-acting pump (fig. 7) the flow of water is continuous. Semi-rotary Pumps. — These are suction and lift pumps, in which the water is raised by the suction induced in a small disc-shaped cylinder by means of metal valves rotating in a half-circle at a considerable speed. WATER 35 where large quantities Fig. 8. Centrifugal Pump. These pumps are small, occupy little space, and are easily worked by a lever with vertical action. Centrifugal Pumps. — These are used (see fig. of water or sewage have to be raised through a moderate lift, not exceeding 25 feet. The apparatus is simple and compact, consisting of revolving fans, which by their rapid revolu- tion cause a vacuum, and draw water through a suction pipe into the centre of the rotary wheel. The centrifugal action set up by the fans causes the water to be ejected through the delivery pipe. The wheel is made to revolve by belting passing round the fly-wheel of a steam, gas, or oil engine. Chain Pumps. — In this pump, water is raised by means of a series of small buckets attached at equal distances to an endless chain, which passes round a vertical wheel above and dips into the water below. Instead of the buckets, the endless chain may be enclosed in a tube, and carry a number of equidistant dia- phragms provided ■\\'ith leather washers just large enough to work up and down inside the tube. The vertical wheel is made to revolve, and the little buckets, or the diaphragms, in their ascent lift the water, and discharge it into a spout at the top of the apparatus. These pumps axe especially suitable for raising sewage or other water containing suspended matter, which is apt to clog and derange the action of ordinary pump valves. Pulsometers. — These are mostly used for temporary pumping purposes. The pump consists of two vessels with a ball valve at the top, steam from a boiler being admitted alternately into each vessel. The steam forces the water out of the vessel into the rising main or delivery pipe ; and the condensation of the steam, by contact with the cold sides of the vessel, causes a vacuum, the pump thus having a suction effect on the water over which it is suspended, which rises through a suction tube and suction valve into the pulsometer. Thus alternate condensation and discharge takes place in each of the two vessels composing the pulsometer, and there is a continuous discharge of water so long as steam is supphed. Water-wheels. — By the use of water-wheels the motive power of a running stream can be utilized in raising water to a height. Vertical water-wheels are of three kinds : (i) Overshot, when the water is delivered on the top of the wheel ; (2) Breast, when the water is delivered near the centre of the wheel ; and (3) Undershot, when the wheel is driven from the bottom by the impact of a strong current. For overshot and breast wheels the stream must be dammed, as seen in the common mill dam and w-heel. By suitable gearing the circular motion of the wheel is transformed into the reciprocating motion of the piston rod of the pump used to lift the water of the well or reservoir. Hydraulic Ram. — When water flowing rapidly in a pipe is suddenly checked, there is an increase of pressure on the interior of the pipe. This increase of pressure is known as ramming, and is used to force a certain proportion of the water flowing down the pipe to a height above the point at which ramming takes place. The apparatus is shown diagrammatically in fig. 9. Water descends with considerable velocity down the supply pipe S from a stream or reservoir, and runs to waste through an opening at V, which is guarded by a valve. But the momentum of the water in its flow is suf&cient to overcome the weight of the valve, which is raised and closes the orifice. The flow of water thus momentarily checked causes an increase of internal pressure in the apparatus, and the ball valve^O is opened, allowing water to pass into the air-chamber A, where the cushion of compressed air drives the water steadily up the pipe E to the^storage 36 HYGIENE AND PUBLIC HEALTH tank. As soon as the pressure is reduced by the opening of the ball valve O the discharge valve falls, and water again escapes at V, until the velocity of flow reaches the point at which the discharge valve is again raised, and Fig. g. — Hydraulic Ram. V, self-acting pulsating discharge valve ; A, air vessel ; O, ball valve ; S, supply pipe ; E, delivery pipe. the cycle of events is reproduced. A fall of lo feet from a stream or reservoir to the ram is sufficient to raise water to a height 150 feet above the ram. Composition of Water from Various Sources. The nature and amount of the organic pollution to which water from various sources is liable, is such a variable quantity that it is useless and misleading to attempt any classification under this head ; for it is local circumstances that will determine whether a shallow well water is polluted or a deep well water is pure. Generally speaking, however, the purest waters are derived from deep springs and wells and upland surfaces, while the waters from the subsoil, from cultivated surfaces, and from rivers are especially liable to be organically polluted. But the character of the soil and subsoil from which the water is collected influences its composition to an extent which, though variable, may be approximately defined by chemical analysis. I. Surface Waters. — Those waters collected from the hard sur- faces of the practically impervious rocks which support little animal or vegetable life are very pure. They commonly contain less than 10 parts of total solids, 5 of total hardness, i of chlorine, and o-i of nitrogen as nitrates, in 100,000 parts of water. The mineral solids consist mainly of sodium carbonate and chloride, and a trace of lime or magnesia. The variable amount of organic matter, which is often exclusively of vegetable origin (peat), yields practically no free ammonia ; but the organic ammonia figure and that of the oxygen absorbed by organic matter may be high, in which case the water is often highly-coloured and acid in WATER 37 reaction. Such characters are presented by the waters collected from the surfaces of the igneous metamorphic (quartz, mica, granite, etc.), Cambrian, Silurian, and Devonian rocks. The waters from the surface of the non-calcareous carboniferous rocks (Yoredale rocks, millstone grits, and coal measures) are very similar ; but those which have flowed over the surface of the calcareous carboniferous rocks — the mountain limestone and limestone shales — differ from the former in possessing a moderate degree of hardness., higher total solids, and a neutral or faintly alkaline reaction. The mineral solids consist chiefly of sulphate and carbonate of calcium and magnesium. Surface waters from the lias, new red sandstone, magnesian limestone, and oolite may vary considerably in their composition. The total solids are generally between lo and 20 parts per 100,000, the total hardness between 10 and 15 parts, the chlorine is below 2 parts per 100,000, and the nitrogen as nitrates below 0-2 of a part. Clay waters are, as a rule, opaque, from a variable quantity of suspended matter, but generally there are few dissolved solids, and the water is fairly soft. They vary, however, greatly in their composition. The waters collected from cultivated land present great variations in composition, and the total hardness may range from 5 to 20 parts per 100,000, according as to whether the soil is non-calcareous or calcareous. Alluvium is generally a mixture of sand, clay, and organic matter ; and w^aters from such a source generally contain high mineral solids (50 to 100 parts), consisting of calcium and magnesium salts, sodium chloride, iron, and silica, and also excess of organic matters. 2. Waters from a Depth. — Those collected from the chalk > are generally clear, bright, and well charged with carbonic acid. The total solids are generally from 25 to 50 parts per 100,000, and the total hardness from 15 to 30 parts ; the hardness is mostly temporary, and calcium carbonate may vary from 10 to 30 parts. The chlorine is commonly from 2 to 3 parts, but it may reach a higher figure in some pure chalk waters. The nitrogen as nitrates is below 0-5 part per 100,000, and is commonly about 0-3. Sulphates are present in small quantity, and there is often a trace of phosphates and of iron. Although the carbonic acid present is often sufficient to turn blue litmus red, when this is driven off an alkaline reaction is invariably obtained. 38 HYGIENE AND PUBLIC HEALTH Some waters derived from the chalk are very soft and contain sodium carbonate. They are only found where the chalk lies buried beneath a thick mass of London clay (Thresh). Waters from the oolite present characters very similar to those from the chalk. Those derived from limestone and magnesian limestone formations only differ from the chalk waters in generally con- taining more total solids, far more calcium or magnesium sulphate (which may reach nearly 20 parts per 100,000), and less calcium or magnesium carbonate, and by consequence the hardness is generally higher and to a greater degree permanent. In dolomite districts the mineral solids contain much mag- nesium carbonate and sulphate, and a large proportion of the total hardness is permanent, dolomite being a double carbonate of lime and magnesia. The greensands are porous strata containing a reducing salt of iron, which by reducing oxidized nitrogen to ammonia often furnishes to the water a very high figure of free ammonia. The total solids vary considerably, but they sometimes approach 100 parts per 100,000 where the water is collected at great depths from greensand underlying the chalk ; the chlorine may reach a figure of from 4 to 14 parts ; the total hardness (much of which is permanent) is very variable — from a low to a high figure ; and the nitrogen as nitrates is generally from about 0-3 to 0-6 part per 100,000. "Waters from red sandstone strata vary considerably in their composition, according as the deposit is pure or impure, soft or hard. The total solids and total hardness are both some- times high, and the former may reach 100 parts per 100,000 ; the latter is mainly of a permanent nature, but the water may sometimes be soft and possess a total hardness figure not exceed- ing 10 parts per 100,000. The chlorine may vary from 2 to 6 parts per 100,000 ; and traces of phosphates are always to be detected in the mineral solids, which mainly consist of sodium chloride, carbonate and sulphate, calcium and magnesium carbonates and sulphates, and a trace of iron. Waters from selenitic deposits are often harmful to drink, on account of the large proportion of calcium sulphate (10 to 30, or more, parts per 100,000), which is taken up from the deposit — -this consisting of calcium sulphate in clear cr3^stals. Waters collected from loose sands are of variable composition. WATER 39 Some are soft, with total solids of from only 6 to 12 parts per 100,000, and others are rather hard (permanent) with mineral solids amounting to even 100 parts per 100,000 The chlorine figure is generally rather high, and may amount to a high figure in some cases. The mineral solids consist of sodium chloride, carbonate and sulphate, calcium and magnesium salts, and traces of iron and silica. Those from gravel are generally soft, but some are hard, with high total solids. Waters coming from a depth in the lias clays have generally very high mineral solids (often consisting largely of calcium and magnesium sulphate). There is, as a rule, considerable opacity, and the physical characters generally are not favourable to the water. The hardness, which is almost entirely permanent, is generally over 20, and the mineral solids may reach 300 parts per 100,000. Quantity. The water supplied to a community must be good in quality and abundant in quantity. Impure waters are liable to cause injury to the health of those who drink them ; whilst deficiency of water means want of cleanliness, with its ensuing discomforts and dangers. Water is required for the following purposes, the under- mentioned quantities representing average requirements : — Household Fluids as drink . Cooking Personal ablution Utensil and house washing Clothes washing (laundry) Water closets Trade and Manufacturing [ Cleansing streets . A-Iunicinal Public baths and fountains Flushing and cleansing sewers Extinguishing fires Gallons per head daily. 0-33 075 5 -GO 3-00 3-00 5-00 S'OO Total 27- The quantities of water given above as required for the house- hold are those which are necessary to maintain a good condition of cleanliness. The 5 gallons for personal ablutions would allow a daily sponge bath for each person. If each person has also a weekly general bath of from 30 to 40 gallons, 5 gallons extra per head daily must be added. 40 HYGIENE AND PUBLIC HEALTH In towTLS, 5 gallons per head daily is found to be ordinarily sufficient for municipal purposes ; and the same amount is required, on the average, for mianuiacturing and trade purposes. M'ater is also required for animals — drinking, washing, and cleansing of stables. About i6 gallons dail}^ for each horse, and 10 gallons for every cow, are average requirements. On the whole, it may be said that not less than 30 gallons per head of the population should be supplied to every town daily. There will ahvays be some waste in households from leaky taps and fittings, and this must be provided for. The greater part of the waste, however, ver}^ often takes place from the mains, before the water reaches the consumer. In some towns it has been found that as much as one-half or two-thirds of the total water suppl}^ has leaked out of the mains into the soil. The supplies per head in the various to\vns in this country vary greatty. The amount of water actuallj^ utilized in the houses of a town varies enormously. In the houses of the poor it may be only 2 or 3 gallons per head daily ; whereas it should amount to at least 15. The adult human being consumes daily about 2j pints of water as drink, and about another 2 pints in his solid food. Distribution. The system adopted by the ancient Romans for conducting the water collected at the gathering grounds into their cities was the construction of masonry aqueducts built on arches, with a gentle incline to allow of a steady flow of water from its source to its outflow in the city. The aqueducts usually crossed the valleys on raised arches, but the Romans also knew how to construct inverted siphons of lead piping for the passage of the water across valleys. The remains of the reservoirs with which the inverted siphons were connected on either side of a valley are still to be seen in the neighbourhood of Lyons. The water supplied by public companies to towns in this country is now usually distributed from their reservoirs through iron pipes laid underground. These cast-iron mains are subject to much rusting and corrosion, especially when the water is soft. Many of these pipes have been found much weakened by corro- sion at some places, and nearly blocked with accumulated rust at others, the water also having deteriorated in quality. It WATER 41 is now usual to coat these pipes with some material which is unacted on by water, such as Angus Smith's solution/ or with a vitreous_glaze. The magneticjDxide of iron produced on the surface of the metal by Barjff's process is also occasionally used. In this process the iron pipes are heated to a white heat, and then exposed to superheated steam for several hours. The practice of caulking the joints of iron pipes with tow or gaskin next the interior of the pipe, and then running the joint with molten lead, was strongly condemned by the Rivers -Pollution Commissioners, as the water absorbs impurities from the tow and hemp. They recommended that the pipes should have turned and bored joints, or, in the case of mains large enough for a man to enter, that the inside of the joint should be pointed with Portland cement. The mains should have scouring valves at their dead ends, and should be placed at a minimum depth of 3 feet, so as to be protected from frost and sun. All the service pipes of the house must also be protected from extremes of temperature, but they should always be left accessible ; and if concealment is necessary, it should only be by a removable wooden casing. On freezing, water expands, and the pipe may burst ; but as the fracture is not discovered until the thaw sets in, there is a popular impression that the thaw is the cause of the pipe bursting. An enormous amount of leakage formerly took place from water mains in many towns, from slight settling of the ground after laying, or from the vibration of heavy traffic causing fracture of the pipes and joints. It has been estimated that in London at one time 15 gallons out of the 35 supplied per head daily ran to waste in the soil. The loss is especially great where the supply is constant and the mains always kept under pressure. If the spots at which leakage occurs could be known, the pipes could be easily taken up and repaired, but the difficulty is to find where the leaks are. This difficulty has been over- come by Mr. Deacon, who has invented a meter which can be used as a waste detecter. One of these meters is placed on each district main ; it registers the flow of water by day and night and therefore the waste, for the water flowing through the main during the dead of night is not used by the consumers, but is 1 Angus Smith's process consists in heating the pipes to a high tempera- ture and then dipping them into a hot varnish consisting of coal-tar pitch, resin, and linseed oil. 42 HYGIENE AND PUBLIC HEALTH running to waste. Having localized the waste to the district supplied by a district main, the exact spots where the leakg^es are taking place can be determined by the vibrations thereby produced in the nearest house communication pipes, which can be distinctly heard on app]^ng a stethoscope to the pipe. By this system, to take one example only, the Lambeth Water Company has reduced its consumption from 34 gallons per head per day to 20 gallons, the quantity available to the consumer remaining the same. The temperature of the water in the underground mains of a town varies considerably with the season of the year. In Chelsea, where the temperature of the water in the mains has been tested daily since 1897, a minimum temperature of from 37° F. to 40° F. is usually recorded in January or February, whilst a maximum of from 68° F. to 74° F. is usually attained in July or August. The water temperature follows the mean air temperature, but the changes are of course far less in volume, and are effected more gradually. It would seem probable that the temperature of the water in cisterns exposed to the sun and atmosphere is likely to be considerably in excess of that drawn from the mains during the warm months of the year, so that temperatures of 80° F. are probably not unusual under such conditions. The house communication pipes in nearly all towns are of lead, connected with the main by a brass screwed ferrule. Lead house service pipes are employed, because the ductile metal can be easily bent as occasion may require in carrying the pipes through a house, and they are easily jointed and rustless. If wr ought-iron pipes are used, double screw joints should be provided at convenient points to admit of the clearing away of the rust, which often chokes an unprotected iron service pipe. Lead pipes may be acted on by water, especially soft water with an acid reaction, and in this way there may be danger to the consumers. Such has not been found generally to be the case, for although new lead pipes are undoubtedly acted on by soft water, an oxide of lead being formed which rapidly dis- solves again in the presence of faint acidity, the action is often very slight. The Loch Katrine water acts most powerfully on lead, and yet no symptoms of lead-poisoning have ever been observed amongst the population of Glasgow. It is now recog- nized that the degree of plumbo-solvency of a water is chiefly WATER 43 determined by the amount of its acidity, and that this acidity is mainly due to acid-producing bacteria in peat. A distinction must be made between plumbo-solvency and the " erosion " of lead surfaces which sometimes takes place ; the latter depends on the presence of dissolved oxygen, and shows itself by the formation of a relatively insoluble powder (the oxy-hydrate of lead), which may tend to fall away from the surface, and so permit of progressive action. The hard waters, which contain salts of lime and magnesia, either have very little solvent action on lead, or they quickly coat the metal with the basic carbonate or sulphate of lead, which prevent further action. The soft, highly oxygenated waters containing organic matters, peaty acids, nitrites, nitrates, and chlorides, are those which have the most powerful action on lead, the oxide of lead which forms upon the surface of the metal being constantly dissolved and carried away in the water. Where lead-poisoning is feared, a block-tin pipe or a cast or wrought-iron pipe protected by a coating of Angus Smith's solution should be substituted for the lead pipe. Block-tin pipes enclosed in lead pipes are occasionally used ; it is important that there should be no crack or fracture of the tin lining, otherwise galvanic action will be set up when the pipe is full of water and large quantities of lead will be dissolved. Great care, moreover, is necessary in making the joints on this kind of piping, as the heat necessary for making a joint in the lead pipe is liable to melt the tin. To obviate this a layer of asbestos is sometimes introduced between the lead and tin, this serving to keep the metals apart. Polluted shallow well waters have sometimes been known to have a very powerful and persistent solvent action on lead, probably from their containing excess of carbonic acid, which tends to dissolve the coating of carbonate of lead formed in the pipe or cistern. It has been suggested that the varying powers of corroding lead, exhibited by soft waters of apparently identical chemical composition, are influenced by the presence or absence of silica in the water. When silica is present, even in the proportion of only half a grain per gallon, the action on lead is said to be very slight. There must be no excess of alkali in the water, or this inhibitive action of silica is not displayed. By passing distilled waters and other soft waters known to have a corrosive action on lead through a filter formed of layers of sand, and 44 HYGIENE AND PUBLIC HEALTH broken limestone, enough silica is taken up to reduce the lead- corrosive power very considerably. Recent experiment, how- ever, seems to show that the alkaline carbonate, which may be taken up from the limestone, may be an even more important factor than the silica. The waters of several large towns, which have a considerable effect on new lead, have been rendered nearly inactive by neutralizing the acid present by a solution of sodium carbonate or by slaked lime. The solvent properties of these waters are believed to be mainly due to the presence of peaty acids (humic, ulmic, etc.), and if the acidity is thus neutralized the plumbo-solvent action of the water is much reduced. After the prolonged drought of 1887, the waters in the Sheffield reservoirs ran very low, the peat}" acids — derived from the gathering-grounds — were not diluted to the usual extent, and a severe outbreak of lead-poisoning occurred in the town. In rare cases the acidity which gives the water its lead-dissolving powers may be due to the presence of free sulphuric acid formed by oxidation of iron pjnites, when the water drains off rocks rich in that substance. It has been suggested by Mr. Power, in a report to the Local Government Board, that the biological characteristics of a water — the presence or absence of bacterial organisms — may exercise an influence over its " plumbo- solvent " properties ; but this is probably true only in so far as the production of acidity in peaty matter is the result of micro- organic life. Having regard to the importance of acidity as affecting plumbo-solvency, on some gathering-grounds measures are taken to divert the most acid feeders of the general upland surface supply, and so avoid the inclusion of the more plumbo-solvent waters in the general supply. There is also some evidence to show that leaden pipes are much more rapidly corroded when the mains are intermittently charged, than when kept under constant high pressure. Water companies supply water to their customers either on the constant or the intermittent system. Under the former, the aim is to keep the mains constanth^ charged with water under pressure, so that the house pipes being also always charged, no storage of water on the premises of the consumer is required. The only cisterns which should be required in a house supplied with a constant service of water are small cisterns or water-waste preventers for flushing water-closets, and a small cistern to WATER 45 supply water to the kitchen boiler. Under the intermittent system, the flow of water in the mains is stopped, except for a short period of every day, by the turncock. The house pipes are only charged when the water is flowing in the main, and consequently water must be stored for use on the premises when the pipes are empty. The great fault of the intermittent service is that water must be stored on the premises of the consumer. Water stored in small receptacles, even under the most favourable circumstances, deteriorates ; it loses its aerated character, may become flat and insipid, and collects impurities from the air. In the houses of the poor, water is often stored in the most filthy receptacles — wooden butts and tubs, rotten and decayed within, or cisterns exposed to the air, which are the receptacles of all sorts of filth and rubbish. The situations in which cisterns are often found on such property are the immediate vicinity of the w.c, and beneath landing floors, staircases, or even bedroom floors. Even in the better-class houses cisterns are sometimes placed in the most improper places, as under stairs or floors, where dust and dirt fall into them, or inside water-closets, where the air is at times charged with foul gases. Another disadvantage of the intermittent service is that the capacity of the cistern is often utterly inadequate — especially in tenement houses, occupied by numerous poor families — for the wants of the people who depend upon it as their only source of supply. Moreover, the intermittent charging favours corrosion of the service pipes. The same cistern is far too frequently used to flush water- closets as well as to supply the drinking water, which may become polluted in this way {see Chapter II). Another method by which drinking water in cisterns becomes liable to pollution, is the practice — now, fortunately, but seldom seen — of connecting the " standing waste " or overflow pipe of a cistern with a drain or soil pipe of the house, or with a D trap under a water-closet. It may be that the overflow pipe has a \j~ bend on it before its junction with the drain, but as the water in such a trap quickly evaporates when not renewed — and the water in this trap can only be renewed if the ball-cock of the cistern leaks — little obstacle is presented to the passage of foul air from drain, soil pipe, or D trap, up the overflow pipe, where it escapes over the water of the cistern 46 HYGIENE AND PUBLIC HEALTH {see Chapter II). The overflow pipe from the cistern should discharge in the open air as a warning pipe — at some point where it is not exposed to polluted air. Besides the danger of pollution of water in cisterns by sewer air, dust, soot, and accidental contaminations such as dead mice, birds, or cockroaches, the material of which the cistern is composed is an important factor as regards the purity of the water stored in it. Iron cisterns rust and discolour the water ; zinc is occasionally dissolved in smah quantities by water ; lead is dissolved at first when the cistern is new, but rapidly becomes coated with carbonate or sulphate of lead when the water is hard. The deposit forms a lining which protects the surface of the metal from further action, and it is for this reason that the inside of a leaden cistern should never be scraped when the cistern is being cleaned out. A lead cistern may be pro- tected against the action of soft water by coating it with lime from time to time. Galvanized iron is largely used for cisterns ; it is light, cheap, and durable, and generally perfectly safe, but has been known to give up a trace of zinc to the Water. In galvanizing iron, the metal is first washed in a weak solution of vitriol and cleansed and dried ; it is then placed in a vessel containing molten zinc, which adheres to it and forms a coating. Wrought-iron cisterns covered with a vitreous enamel may also be safely used. Slate, though heavy, is a good material for cisterns, but the cemented joints of the five slabs must not be repaired with red lead when they leak, as they often do ; for both white lead (a mixture of carbonate and oxide) and red lead (an oxide) are soluble in water. Glazed or vitrified stone- ware and fireclay cisterns, though heavy, are very valuable, as they give up nothing to water, and no joints are necessary. In selecting them, however, care should be taken that the enamelling or glazing is not rough or fractured. Enamelled iron, glass lined iron, and tinned copper cisterns have been made. Water should never be left in contact with wood, as wood, when constantly wet, rapidly rots, and forms a breeding place /or minute worms and other animal organisms and fungi. To indicate briefly the conditions under which water may be safely stored in houses : — (a)^The cistern should be of stone- ware, slate, or galvanized'iron'; (6) it should be placed in a light and well ventilated position, and should be properly covered ; (c) it must not be used to flush water-closets, but may supply WATER 47 the " intercepting " or waste-preventing cisterns which should be used for this purpose ; (d) the overflow pipe must be carried out into the open air to terminate as a warning pipe ; (e) the cistern should be cleaned out at least once in every three months, and should be reasonably accessible for this purpose. Cisterns are occasionally used to supply water-closets which have regulator valves on the supply pipes near to the closet basin. Although there is but little danger by this arrangement of foul air finding its way into the drinking water of the cistern, as the supply pipe is always full of water unless the cistern is empty, still, it is better to break the connection altogether between drinking water cisterns and water-closets. The advantages of an intermittent over a constant service are that there is less waste inside houses, and that the service of pipes, taps and fittings, need not be so strong as for a con- stant service. This latter point has been disputed, as regards the pipes, on the ground that there is a greater strain on the pipes where the water is suddenly turned on or off with a common stop-cock, than where it is slowly turned on or off by the screw- down tap used with a constant service ; but it must be remem- bered that with a constant service the water in the house pipes is under a much higher pressure than where the pipes are con- nected with a cistern in the house. There is less danger, also, with an intermittent service, of the higher parts of the town being without water on account of great waste in the low-lying parts, as sometimes occurs with a constant service. A merit often claimed for the constant service is that no storage is required on the premises of the consumer. The water drawn from the taps on the house pipes is clear, cool, and sparkling, in the same condition as it leaves the street mains, and the supply is — or should be — abundant and never-failing. But ex- perience has shown that it is generally desirable to retain or provide some means of storing water on the premises, to meet requirements when the supply is cut off on account of repairs to the main or by frost. In houses supplied by a constant service it' is a good plan to obtain a direct supply for drinking purposes from a draw-off tap fixed on the service pipe on its way to the cistern, when the latter is retained as a means of storage. It has been suggested that the shape of the cistern in common use should be modified to that of a cylinder, ending below in 48 HYGIENE AND PUBLIC HEALTH an inverted cone, with a draw-off pipe at its bottom to admit of the flushing away of any deposit which accumulates ; the service pipe from the cistern to be soldered into the side like the present overflow pipe, but of course lower down, and the lid to be tightly fitting. In actual practice in many cases, the advantages of a constant service have been somewhat mitigated by errors on the part of both consumers and water companies. Unless constant inspec- tion is exercised and the taps and fittings in houses frequently supervised, there is great waste. This occurs especially in cases where an intermittent service has been changed to a constant service, and the old pipes and fittings have been retained. Not only this, but where water-closets are flushed by a pipe and tap direct from the house main, without the intervention of a cistern or water-waste preventer — a not unusual occurrence in poor neighbourhoods — there is great danger of foul air, or even liquid filth, being sucked up into the empty pipe when the tap is left unscrewed, and so finding its way into the water main of a district. The suction is due to a partial vacuum being created in the water mains when the water is turned off, owing to the water finding its way through leaky joints into the soil, or from the mains being emptied by taps on house pipes at a lower level. Such occurrences are believed to have given rise to out- breaks of enteric fever at Croydon, Cambridge (Caius College), Sherborne, and other places. They demonstrate the absolute necessity of breaking the connection between water-closets and water mains by the interposition of a small cistern or water waste- preventer. In some cases of constant service, water companies try to economize by insisting on the insertion of a throttle of very small diameter (^ to yV inch) into the house communication pipe, with the result that water merely dribbles out of the house taps when they are full on. In any case, screw-down taps must be substituted for common taps, and a screw-cock must be placed on the house pipe, where it enters the premises, to shut off the water in case of a pipe bursting. A drip-tap should also be placed on a pipe at the lowest part of the system, by which it may be emptied during frost. All the leaden service pipes of a house should be strong (12 pounds per lineal yard for i-inch pipes, and 6 pounds per lineal yard for |-inch pipes), in order to withstand the constant pressure to which they are WATER 4(5 subjected. If pressure is maintained in the mains by pumping, and not by storage in a high-level reservoir, greater power must be used in the morning of every day, this being the time when the largest quantities of water are drawn for domestic use. The waste of water can be overcome by the use of Deacon's waste-water meter on the district mains, and by frequent super- vision of house taps and fittings. The supply of water by meter would tend greatly to check waste, but is not advisable in the case of poor populations, as the inevitable stinting of water that would follow would have great sanitary disadvantages. For trade purposes it is the most just and reasonable method. Water meters are either " positive," and indicate the amount of water supplied by the number of times a cylinder of known capacity is filled, as shown on a dial ; or they are " inferential," when the amount of water which has passed through them is inferred from the velocity of the flow, as registered on a dial. There is one danger to which water mains are subject, which has not yet been alluded to. If water mains and sewers or house drains are laid in the same trench, there is a possibility of foul matters, which have escaped into the soil from leaky drains or sewers, being sucked into the water mains, if these are in any way defective, during intermissions in the service. Such intermissions are the daily occurrences of an intermittent service, and are often unavoidable with a constant service for executing necessary repairs to the pipes. In a similar manner, too, water mains may suck in from the surrounding soil coal gas which has escaped from leaky gas pipes and mams. It is not only, however, during intermissions in the service that such accidents may occur, for experiments prove that there is a partial vacuum inside water pipes in the immediate neighbour- hood of defective joints, whenever the water is flowing in the pipes. The water and sewerage systems must be kept as far apart as possible. Rats have been known to burrow from a drain or sewer to an underground water supply in search of water, lead water pipes being frequently found gnawed, and sometimes perforated. With a constant service the mains are always charged in case of fire ; with an intermittent service much valuable time is often lost in finding the turncock. 50 hygiene and public health Purification of Water. It is highly desirable that the water supph'^ of a community should, as far as possible, be kept free from all foreign and polluting ingredients. Nearly all waters derived from natural sources contain such ingredients, and the various processes of purification aim at their elimination. The foreign ingredients may be divided broadly into mineral and organic matters. The removal of the salts producing hardness and the production of softer^water is eminentl}^ desirable for economic purposes, and occasionally to improve the potability and wholesomeness of the water when the salts are in great excess. The removal of the organic matters, suspended or dissolved in water, is another and still more important object in any process aiming at com- plete purification. We shall now proceed, first, to the con- sideration of those processes which are, or could be, undertaken on a large scale for the purification of water before its distribution to the consumers ; and, secondly, to such processes of domestic purification as may be undertaken on his own premises b}^ the consumer. What should be aimed at, however, is to procure at its source a water sufficiently good to require no artificial purification ; but failing this, the water should be efficientlj^ purified before its distribution to the consumers. It is certainly not wise to leave the purification to individual initiative. Purification on a Large Scale. — There are several processes (Clark's, Porter-Clark's, Maignen's, Howatson's, etc.) which aim at the removal of the mineral matters (the salts of lime and magnesia) from a water. The fundamental basis of them aU is the addition of lime water. \\Tien a certain quantity of Jime w^ater is thoroughl}^ mixed with a hard water, it combines with the carbonic acid holding the chalk in solution, with the result that the new carbonate thus formed is precipitated, together with the original chalk. In this way chalk weU \^-aters of 20° of hardness, and Thames water (i6°), may be reduced to 4° or 5°. The hardness thus got rid of is due to the pre- cipitation of chalk, and chalk alone ; it is temporary hardness, and the same effect would be produced on the water by sufficient boiling. The working of the process (Clark's) may be described shortlj^ as foUows :— One ounce of quicklime to every 700 gallons of WATER 51 water is used for each degree of temporary hardness. The lime in the form of quicklime is first slaked with water in a tank, into which the water to be softened is gradually allowed to flow ; thorough mixing must be insured by wooden paddles or other mechanical means. The water becomes milky in appearance from precipitation of the chalk, and must then be allowed to settle for twelve hours, the supernatant clear water being subsequently drawn off. Besides chalk, a certain amount of colouring and organic matters are removed from the water by this process. It is important that uncombined lime should not. pass out with the purified water, as would be the case if lime were added in excess of that required to combine with all the. carbonic acid holding the chalk in solution. .To detect uncombined lime, it is only necessary to add a few drops of a solution of nitrate of silver to the treated water in a shallow white dish, when a brownish colour is produced if uncombined lime is present, but only a white precipitate of chloride of silver if there is none present. Lime is also used as the precipitating agent in Porter-Clark's process ; but the suspended particles of chalk are removed, not by settlement, but by filtration through a series of linen cloths in a filter press under high pressure. The plant includes two vertical cylinders and a filter press. In the first cylinder there is a continuous preparation of lime water, which is mixed in the second cylinder with the hard "^water. ;_ The ^ precipitant formed is then separated by the press. The process is expe- ditious, and very effective in removing lime and suspended matters from the water. It is one of the best means of softening water on a large scale. In Atkins's process, which is somewhat similar, arrangements are made for cleansing the cloth filters by means of revolving brushes which play on the surface of the discs. The Stanhope Water Softener aims at reducing both the temporary and permanent hardness, lime and soda being used. The caustic soda somewhat reduces the permanent hardness by converting some of the calcic or magnesic sulphates into sulphate of soda. Clarification is effected by subsidence in high tanks containing numerous funnel-like shelves, one above the other, which coUect the deposit and direct it to the bottom of a tank. Howatson's process is very similar. In this process the 52 HYGIENE AND PUBLIC HEALTH deposit is removed by opening valves in the hopper bottoms of the tanks. In the Maignen Automatic Softener a small motor is worked by the water, and this regulates the amount of anticalcaire, which mixes with the water in a small tank. Sedimentation takes place in a second small tank, in which provision is made for flushing out the deposited chalk ; and finall}^ the water passes through a filtre rapide into a storage tank. The precipitating agent, anticalcaire, contains lime, sodium carbonate, and alum. A smaU plant suitable for use in a dwelling house is also made. The Lawrence process of softening and steiilizing water is ingenious and effective. In this apparatus the water is boiled, and therefore softened and sterilized ; the steam is condensed bj^ the cold water entering the boiler, which takes up the heat from the steam, and thereby an important economy is effected in the heat required. \^T\ie process of filtration through' sand or gravel on a large scale, as carried out by the Metropolitan Water Board, has already been described [see p. 14). Suspended matters, both mineral and organic, are very effectuall}^ removed by sand filtration. i^Spongy iron, which is porous metallic iron, obtained by roasting haematite iron ore, has a very similar action on dissolved organic matters in water to that exerted by magnetic carbide of iron ; and, like magnetic carbide also, it jdelds nothing to water except a little iron, which may be removed by subsequent filtration through sand. Spongy iron retains its properties for a long period, but requires periodical renewal, especially when used, as it generally is, as a mechanical filter for separating suspended matters from water, as well as a chemical purifier. Spongy iron separates lead from water, but has no effect on other mineral matters. The property possessed b}' spongy iron and the magnetic carbide and oxide of iron of yielding nothing to water — no phosphates or other germ nutrients — is a valuable one ; for the water after filtration can be stored for a time without any great deterioration from growth of microscopic organisms. The especial fitness of the magnetic carbide of iron or of polarite for filtering a town water suppl}^ on a large scale lies in the fact that, when once the beds of these materials are in sitn, the\^ need not be disturbed or renewed, and thus an enormous amount of WATER 53 labour and expense is avoided. The aeration by intermittent filtration, which is essential for magnetic carbide of iron if it is to retain its oxidizing properties, must not be practised with spongy iron, as the latter cakes on exposure to the air. At Antwerp and other places on the Continent scrap iron (Anderson's process) is now being used for filtering water on a large scale. The scraps of iron are placed on a cylinder, which is caused to revolve on its long axis. The inner circumference of the cylinder is provided with short curved shelves reaching from end to end, which, when the cylinder is revolving, serve to direct a shower of iron through the water as it passes through the apparatus. The water is then exposed to the air by flowing along a trough, so as to cause a precipitate (as ferric oxide) of the iron taken up in the revolving cylinder, and this precipitate as it settles carries down organic matter with it. The precipitate is subsequently removed by filtration through sand. Domestic Purification.-^Distillation effects a more complete purification of water than any other method which is practised. If the first portions of the distillate, containing volatile sub- stances present in the water to be distilled, are rejected, a water free from all foreign ingredients is obtained. Its aeration, how- ever, is deficient ; but this aerated quality can easily be furnished by allowing the water to flow out of fine holes in the bottom of a receptacle and to pass through the air in finely divided streams. The distillation of sea water is now largely carried out on board the ships of H.M. Navy and in the large steamships of the mer- cantile marine. As long as there is fuel on board, a most whole- some water can be obtained. Distilled water acts very readily on metals such as copper, zinc, iron, and lead ; so it is important that the several parts of the distillation or condensing apparatus should not expose these metals to the action of the water. Silver- lined or block-tin vessels and pipes may be used. There are now several makes of small domestic stills upon the market. -"^By boiling water, carbonic acid is driven off with other volatile gases dissolved in the water, and chalk (temporary hardness) is deposited at the bottom of the vessel. The water is therefore softened. We have the strongest reason for believing that distillation and boiling — raising the temperature of the water to 212° F. — render innocuous all organized living matter in the water. There can be little doubt but that the germs of cholera, enteric fever, and of other diseases, occasionally propagated by 54 HYGIENE AND PUBLIC HEALTH means of impure drinking \\-ater, are effectually destroyed by even a few minutes' boiling. The spores that resist the tem- perature of boiling water are, seemingly, not disease germs, but mereh- the immature forms of harmless species ; for experience has sho\^-n that water, and other fluids mixed with water, such as milk, in which the existence of germs capable of producing enteric fever, cholera, scarlet fever, or diphtheria, was almost un- doubted, have been rendered harmless b}^ a few minutes' boiling. But to sterilize completely water or an}^ other fluid, it is necessarj' to boil it, or merely raise the fluid to a temperature of 212° F. \\dthout actual ebullition, for a short period (half an hour) on three or four successive days. In this way the spores, which escape destruction by the first boiling, have time to develop into adult bacteria, which are destro^^ed by the next boiling, and so on, until all the successive crops are disposed of. Boiled water is flat and insipid, and should be aerated before being drunk. The ^^'aterhouse-Forbes is perhaps the simplest form of port- able apparatus for boiling drinking \\'ater, such as is required for the use of armies in the field. "S^arious schemes have been suggested for purifying water by chemical means. If such a method were easily practicable, it would be of great value for military- purposes to meet the require- ments of troops on the march, or in the field, when the adequate filtration or sterilization of sufficient water for drinking purposes is a matter of great difiiculty. Schumberg's bromine process consists in adding o-o6 grain of free lbromine,^dissolved in potassium bromide, to every litre of water, and then after 5 to 10 minutes removing the excess of bromine and making palatable by sodium sulpnite and carbonate. The addition of calcium peroxide, of ozone, and of potassium permanganate, have been suggested bj^ other authorities, but have been little em- ployed. Chlorine in the form of a hj^pochlorite is also serviceable for the above-mentioned purposes. In a fairlj'' clean water, from I to 2 parts of chlorine per 1,000,000 parts of water have been found to suffice for practical sterilization ; and bj^ subse- quent treatment ^^'ith bisulphite of soda the residual chlorine can be removed and the palatabilit}^ of the water completely restored. During the epidemic of enteric at Lincoln, in 1905, sodium hypo- chlorite was added to the water prior to filtration. At first a strength of i in 10,000 was employed, but later this was reduced WATER 55 to I in 50,000. Bleaching powder has also been employed for the purpose of sterilizing water. When this powder is added to water the hypochlorite of calcium which is liberated is acted upon by carbonic acid, and splits up into carbonate of calcium and hypochlorous acid, the latter being a powerful oxidizing agent. The use of acid sodium bisulphate has been recommended by Parkes and Rideal in the proportion of one gramme of the salt to a pint of water, experiment having shown that in this strength, if contact is permitted for fifteen minutes, bacillus typhosus infection in broth culture medium is destroyed. In Nesfield's method a 2-grain tablet of iodide-iodate of soda and a similar amount of citric acid are added to 4 gallons of water, the effect being to kill in a few minutes any typhoid and cholera organisms that are present. Subsequently the free iodine may be eliminated by a tablet of sodium h3^posulphite. The poisonous effect of copper upon the lower forms of life has led to its advocacy and adoption for the purpose of removing certain growths which form odour in stagnant water, and also specific micro-organisms. There is, for instance, testimony to the fact that the addition of 10 pounds of sulphate of copper to 1,000,000 gallons of water was suffi- cient to remove a fishy odour which was previously in the water. There is also evidence that the addition of sulphate of copper, in the proportion of i part to 100,000 parts of water, will destroy the typhoid bacillus ; but there is conflict of opinion as to whether this is always effective in 24 hours. Strips of copper foil im- mersed in water for 12 hours will generally destroy the typhoid bacillus ; and this is also true of the storage of water in copper vessels. In many waters most of the copper is deposited in an insoluble form ; but before this method of treating water can be safely advocated it is necessary to study the further effects of very small quantities of this metal upon the more susceptible human beings. Aluferis sometimes employed as a purifying agent. It is much used in China, where the turbid waters of the large rivers are extensively drunk after the addition of a little alum. When added to water containing chalk in solution, it forms^ a bulky precipitate of aluminium hydrate, which falls to the bottom, carr5^ng with it suspended and floating matters. It has little or no effect on organic matters in solution in the water. About 6 grains of alum to the gallon of water is the proportion generally required. 56 HYGIENE AND PUBLIC HEALTH Filters. — Domestic filters are probably more often a source of pollution of the water than other\vise. It is usually considered that a filter requires no attention ; it is consequently but rarely cleaned ; the filtering material is seldom renewed, and its pores become clogged with putrescible organic matters, which form a suitable nidus for the growth and development of living organisms which contaminate the filtered water. It is not unusual, under such circumstances, to find a considerably larger proportion of organic matter in the filtered water than was present before filtration. ^ This is especially the case when animal charcoal is used as the filtering material. This substance is prepared by calcining crushed bones in closed vessels ; it is extremely porous, and exerts considerable oxidizing action on dissolved organic matters in water, and bleaches colouring matters in solution. These properties, however, are evanescent, and rapidly disappear if the charcoal is not cleaned or renewed, especially if the water filtered through it is somewhat impure. Not only this, but the charcoal yields to water phosphate of lime, of which it is largely composed. The phosphate favours the growth of living organisms, so that water must neither be kept too long in the filter, nor should it be stored for use after filtration. Animal charcoal does not prevent the passage of living disease germs through its sub- stance. For these reasons filters composed of animal charcoal, whether in loose fragments or in compressed blocks, are not at all suited for domestic use. They require more care and atten- tion than any domestic filter is likely to meet with. Charcoal block filters have the power of removing lead from water if their surfaces are kept constantly clean by frequent scrubbings ; this is probably due to the lead forming a phosphate in the filter. Silicated carbon and manganous carbon block filters are fre- quently used. They consist of animal charcoal compressed into blocks by admixture with silica or manganese. They do not yield so much phosphate of lime to water as the pure animal charcoal filters, but they tend to become coated with a layer of organic matter which clogs the pores. The block should be brushed occasionally to remove the thin film coating it ; and every three months, at least, it should be purified by subjecting it to a red heat, or by boUing it in a solution of Condy's fluid and sul- phuric acid. Maignen's Filtre Rapide consists of a strainer of asbestos cloth spread over a perforated porcelain cone. Powdered WATER 57 animal chaixoal, or other filtering medium, is laid over the strainer. The delivery of water through this filter is very rapid, and the asbestos and powder can be easily renewed at a very small cost. Domestic filters are also made of spongy iron, magnetic carbide of iron, polarite, and car feral, this latter substance being a mixture of iron, charcoal, and clay. It has good oxidizing properties, and yields nothing to water which is favourable to organic life ; but its lasting powers are inferior to spongy iron and magnetic oxide and carbide. In Bischoff' s spongy iron filter the iron ore rests upon a layer of pyrolusite (a crude oxide of manganese) above, and a layer of fine sand below. The pyrolusite acts as an oxidizer, and helps with the sand to remove the iron taken up by the water. The outlet to the filtered water receptacle is generally protected by a layer of asbestos cloth. With regard to filters of the kind alluded to above, which afford no protection against the infection of water-borne disease, Drs. Woodhead and Wood point out that they may materially increase the risk to the consumer of acquiring such infective diseases, inasmuch as the specific organisms of these diseases become arrested in the filtering materials, and may then be washed through in great numbers into the filtered water for many days subsequent to the introduction of infected water into the filter. If, for instance, the water supply of a house received a chance contamination, which rendered it dangerous for one day only, the consumption of the water involves the risk of specific in- fection on that day only ; but should the polluted water be passed through a domestic filter of the kind indicated, the arrest of the specific microbes in the filter, and their subsequent passage into the filtrate, would render the water passed through the filter liable to convey infection for several days after the initial introduction of the pollution. The consequent multiplication of the oppor- tunities of infection necessarily greatly increases the risk of such an occurrence. The wrong and misleading statements set forth so prominently by the makers of such filters, as to their capacity to render any water, however polluted, harmless and innocuous, gave rise to a false sense of security in the minds of the public, and are an evil which should be""strenuously combated. In the PastSur^hamberland filter the water, under pressure, is passed through hollow cylinders of a specially prepared form 58 HYGIENE AND PUBLIC HEALTH of porous porcelain. The filtered water is entirely free from all suspended matters, including all kinds of organisms and their spores. The water is therefore sterilized ; but, the filter acting merely mechanically, there is no alteration in the chemical com- position of the dissolved constituents of the water. This filter is emploj^ed to sterilize pure waters for laboratory purposes, and may with advantage be so used for domestic purposes. The bottom of the filter is connected with a main under pressure, the water issuing from the top. These filters require periodical cleaning at short intervals by a hard brush, to remove slimj^ deposits on the surface of the porcelain ; if this is not done, the deliver}:' of water becomes very much reduced, and separ- ated organisms may in time grow through the cylinders. The Berkefeld filter is similar in principle to the above, but the hoUow cylinder, through which the water is filtered, is composed of a compressed siliceous or diatomaceous earth called Kiesselguhr (fig. lo). It permits of more perfect cleansing, and is very much more rapid in its deliver}-, but is more fragile than the Pasteur- Chamberland filter. The experiments of Drs. Woodhead and Wood show that the Berkefeld table filter completely arrests specific disease organisms, but that, like the Pasteur-Chamberland, the Slack and Brownlow, and the Porcelaine D'Amiante to a lesser degree, it allows water organisms usualh^ present in water to grow through the filtering material, with the result that they appear in the filtrate on the third day after introduction. It does not, therefore, continuoushT-Xsterilize. The Porcelaine D'Amiante filter, in which the clay is mixed with finely Fig. 10. — Berkefeld Filter. AA, screws for joint to open filter case for removing filtering cylinder for cleaning, etc. ; E, outlet for filtered water, which can either be fixed or simpl)' placed on the protruding metal end of the cylinder ; CC, filtering cylinder ; D, tap union to attach to water service ; F, flushing tap to wash out filter or to supply unfiltered water. WATER 59 powdered asbestos, is the best sterilizer, but in it the rate of filtration is so slow that it is unfitted for domestic purposes. The experiments conducted by Dr. Horrocks at Netley in 1901 show, (i) that typhoid bacilli are not able to grow through the walls of the Pasteur-Chamberland candle ; and the filter ought to give complete protection from waterborne enteric fever. (2) Typhoid bacilli can grow through the walls of the Berkefeld candles, probably owing to the larger size of the lacunar spaces, and the consequently diminished immobilizing and devitalizing influences. The time required for the typhoid bacilli to traverse a candle varies between 4 and 11 days, and appears to be largely dependent on the nutriment supplied to the organisms by the medium in which they exist. In order to obtain complete pro- tection from waterborne enteric fever, when employing Berke- feld filters, it is necessary to sterilize the candles in boiling water every third day. It is obvious that the matters of which this class of filters are composed must be quite free from flaws, otherwise a direct passage of micro-organisms will take place. There is also a certain amount of liability to failure owing to hidden defects in the con- nection made between the sterilizing candle and the delivery pipe. Sometimes the only water available for drinking, in addition to the risk of its being specifically infected, also contains much sus- pended matter. It is useless to attempt to filter such a water through porcelain, as the filtering'material soon becomes clogged. The Brownlow germ filter, in which the water is first passed through charcoal, and then through porous porcelain, is specially advantageous in such cases ; or the porcelain may be covered with a strainer of fine linen cloth, which can easily be renewed. Filters should never be placed inside cisterns. In such posi- tions they are neglected, their very existence being sometimes forgotten, with the result that they become excessively foul and pollute the water they are intended to purify. From what has already been said, it will be seen that the essentials of a good filter are — that every part should be easily accessible for cleansing purposes ; that there should be nothing in the construction of the filter which is capable of yielding metallic or other impurities to the water ; that the filtering medium sliould be efacient for the work in hand, and its purifying power reasonably lasting ; and that the delivery of filtered water should be reasonably rapid. 60 HYGIENE AND PUBLIC HEALTH Diseases produced by Impure Water. Dyspepsia and Diarrhoea. — Waters with permanent hardness exceeding 8° or 9° sometimes cause dyspeptic symptoms and diarrhoea, especially amongst those who are not used to them. Similar symptoms are generally produced by drinking brackish water drawn from wells near the sea coast. The injurious salts ' are especially the sulphates of magnesium, calcium and sodium, and the chloride of magnesium. Particles of suspended clay, mica, or vegetable matter may also cause diarrhoea. Waters containing calcium carbonate in solution, the tem- porarily hard waters, are not in any way injurious to health. At the same time there is no reason to believe that the chalk waters are at all superior to soft waters for drinking. The idea once entertained, that the salts in hard water aided the growth and nutrition of the bones in children, has been abandoned as untenable. Diarrhoea, often of a severe choleraic type with violent purging, vomiting and cramps, is occasionally produced by drinking water contaminated with sewage. But here, again, it is princi- pally amongst those who are unaccustomed to the water that these severe symptoms occur ; or v/hen the water, previously fairly pure, becomes temporarily polluted, and especially in the summer months. Instances have been known where people have gone on drinking filthily polluted shallow-well water for years with no apparent bad effects. It seems, indeed, certain that by long habitude the system becomes tolerant of man}^ substances in water which exert a marked effect on those who drink them for the first time. Whether the choleraic diarrhoea is due to the presence of a living germ in the water, to faecal organic matter in solution or suspension, or to alkaloidal poisons, the products of the growth of bacterial organisms, is not yet certain. Vegetable matter, such as peat in water, is generally harmless. Large excess of such matters, especially when decaying, may produce unpleasant symptoms. Infantile diarrhoea, which is so prevalent and fatal in the large towns of this country in the warmer summer months, appears to be due to water pollution in some cases. The same conditions of drinking water which produce diarrhoea in this country often give rise to dysentery in hot climates. WATER 61 Dysentery may certainly be spread by the evacuations of patients suffering from this disease contaminating the water used for drinking. Enteric Fever is often spread by the medium of water. There is considerable evidence of the possibility of the discharges of a single patient infecting large volumes of water [see Chapter IX). Asiatic Cholera is a specific disease, spread by a specific virus contained in the evacuations of a person ill of the disease. There is now abundant evidence that cholera is often propagated by means of drinking water to which the specific disease poison has had access. This is not the only mode of spread of the disease, any more than it is of enteric fever ; but the evidence which is constantly accumulating points strongly to the conclusion that as for enteric fever, so for cholera — specifically infected drinking water is one of the most frequent methods of its propagation. In India, the filthy habits of the natives cause a gross and per- sistent pollution with f^cal matters of the drinking water in the wells and tanks, from which so large a population obtain their entire supply. The evacuations of cholera, like those of enteric fever, are probably not possessed of any high degree of infective- ness at the moment of discharge. The virus requires to grow in contact with air before its higher powers of infectiveness can be developed. Yellow Fever was formerly believed to be due to drinking water polluted with the discharges of people ill of the disease ; but the part plaj^ed by mosquitoes in the transmission of the disease was then unknown. Diphtheria is not usually propagated through the medium of drinking water, but cases favouring such a view have been recorded. Urinary calculi were at one time supposed to arise from the use of hard water, but this view is now generally abandoned from want of any definite proof. Rickets has been ascribed to the use of soft water, but the contention is not warranted by facts. Goitre appears to be due, in many instances, to the water used for drinking, but the impurities in the water which appear to favour hypertrophy of the thyroid gland in some districts are not those found in the water of other goitrous districts. For instance, the carbonates and sulphates of lime and magnesia, 62 HYGIENE AND PUBLIC HEALTH which are present in the waters of some districts, and have been credited with being the cause of goitre, are not found in the waters of other districts where goitre prevails. The presence of sulphides of iron or copper in water has been regarded by some observers as the cause of goitre, but not apparently with much reason. On the whole, then, we shaU be justified in concluding that the quality of the drinking water, in districts where goitre and its allied disease, cretinism, exist, is only one — and perhaps not the most potent — factor out of many which, in com- bination, are productive of the disease. Further researches are required to elucidate this question, which is one of great interest. Entozoa. — -The embryos or eggs of the following parasites have been found in water, and may be taken into the stomach of man when such water is used for drinking. They are : Tcenia solium, Tcenia echinococcus, Bothriocephalus latus, Ascavis lumbficoides (round worms) , Oxyuris vermicularis (thread worms) , Filar ia sanguinis hominis (tropical endemic chyluria) — the embryos of which are sucked from the blood of infected persons by mosquitoes, and, after developing in the body of that insect, are then transferred to water by means of the larvae — Bilharzia hcBmatobia, Tricocephalus dispar, and Distoma hepaticum (liver fluke of sheep). Bilharzia hcBmatohia causes endemic haematuria in Egypt, Abyssinia, the Cape, etc. The ova are passed with the urine, find their way into water, and hatch into ciliated embryos. Anchylostoma duodenale causes ansemia, internal haemorrhages, etc., and occasions great mortality in Brazil, West Indies, and Egypt, where it is thought to be sometimes due to infected water. The embryo guinea worm, Filaria dracunculus, is aquatic and finds its way into the human body through the alimentary canal by means of drinking water, the adult worm being subsequently found in most cases in the sub- cutaneous tissue of the feet and legs of affected persons. Aquatic leeches may be swallowed in the act of drinking, and fixing them- selves in the pharynx may cause much haemorrhage. Anthrax, hog-cholera, and glanders may all be communicated to cattle through the agency of impure water ; and drinking water appears to be the principal medium by which the entozoa generally pass from one animal to another. Metallic poisoning may be caused by pollution of drinking water with refuse from trades and drainage from metalliferous WATER 63 mines, or from absorption by water of the metals used in the construction of distributing pipes, tanks, and cisterns. The amounts of copper, zinc, or arsenic, which must be present in the water to give rise to symptoms of poisoning have not been definitely ascertained ; as regards lead, as little as ^V grain per gallon may produce plumbism in predisposed persons. In the case of the poisoning of Louis Philippe's family at Claremont, -/o grain of lead was found in each gallon of water. The Collection of Samples of Water. The water should be sent to the analyst in a stoppered Winchester bottle of white or pale green glass. The bottles should be reserved for water samples, and should be cleansed with strong acid, and subsequently well washed with clean water, before use. The bottle should be rinsed out twice with some of the water to be examined, and should not be entirely filled with the sample, a small amount of air being left in it. The bottle should then be stoppered and capped with clean wash- leather or linen, and dated and labelled to enable subsequent identification. MTiere the sample must be taken by immersing the bottle, as in ponds, reservoirs, rivers, and open wells, the bottle invented bj^ Dr. Thresh, which contains a contrivance whereby water can be made to enter the bottle at any required depth from the surface, finds a useful application. The Opinion upon a Water Sample. Where the water is considerably polluted, no difficulty is experienced in detecting the pollution by chemical analysis ; but, generally speaking, the slighter degrees of pollution are detected only with difficulty. The most a chemical analysis of a water can tell us is whether the figures of the analysis indicate little or much organic im- purity as judged from certain arbitrary standards. Whether the slight contamination which is practically always discovered is harmful, or whether the particular water has recently received slight (but significant and maybe dangerous) pollution, can only be told with certaintj^ by several analyses of the water at short intervals of time, and a careful comparison of the results obtained ; or by a comparison between the sample of water 64 HYGIENE AND PUBLIC HEALTH and others in the immediate neighbourhood, collected from similar sources from the same geological area, and which are kno^^'n to be above suspicion. A chemical analysis, in short, cannot always guarantee absolute purity and safety, but it \'ery frequentl}" serves to reveal impurity and danger. Nitrates and Nitrites. — These are the oxidized residues of organic matters, almost always derived from an animal source (sewage). Their determination is, therefore, a point of the greatest importance, for they indicate either a. pollution of the water at some remote period with possibly dangerous ingredients, or the contamination of the water at the present time with partialh' or completely purified sewage. They are found, often in considerable quantities, in deep wells or spring waters, and in this case merely indicate the complete purification which the water has undergone in its passage from the surface to the subterranean reservoirs. In the case of shallow-well waters, nitrates and nitrites, if found in association with excess of chlorine and ammonia, indicate soakage of sewage or animal refuse into the well, more or less purified by its passage through the intervening layers of earth. At any time, however, the purifying power of the filtering earth may be exceeded or overcome, and then the liquid filth may pass into the well with its dangerous ingredients unchanged or unpurified. Nitrates and nitrites are not present in raw sewage, but they are found in polluted streams and watercourses, where a certain amount of oxidation is always in progress, and in the effluent subsoil waters from manured or sewaged land. Ammonia. — The urea of the urine, by a process of fermenta- tive decomposition, rapidly becomes carbonate of ammonia in sewage. Ammonia will therefore be found in all sewage-polluted waters, unless the sewage has been filtered through a sufficient thickness of soil to enable the bacteria to convert the ammonia by oxidation into nitrates and nitrites. A few pure deep- well waters from the greensand are found to contain excess of ammonia owing to the presence of a reducing salt of iron, which con- verts oxidized nitrogen into ammonia ; but these waters are remarkably free from organic matters. On the other hand, sewage polluted shallow-well waters, which contain excess of ammonia, often contain also an excessive amount of organic matters. i ^ Organic matters derived from an animal source are dangerous WATER 65 as well as disgusting ; the slightest trace of such matters in a water should suffice to condemn it. Organic matters derived from the vegetable world, though often quite harmless, as when they exist in the form of peat, should not be disregarded ; and their presence in considerable quantity should insure the rejection of the water for drinking purposes. The distinction between animal and vegetable organic matters in a water is often only made with difficulty, if at aU. Generally it may be said that, when excess of organic matter in a water co-exists with excessive chlorine, oxidized nitrogen, and am- monia, the source of pollution is animal filth or sewage. \'\Tien, on the other hand, excessive organic matter is not accompanied by excessive chlorine, oxidized nitrogen, and ammonia, the source of pollution is probably vegetable ; and this diagnosis may be confirmed by the results of physical examination of the water, and by microscopic examination of the suspended matters and sediment. Inasmuch as the chemical methods of analysis can only determine the presence and amount of organic matters in water, and cannot determine their quality, nor separate living and possibly actively dangerous organisms from dead and inactive matter, it has been thought by many that a bacterioscopic examination would afford conclusive evidence of the possibly dangerous qualities of a water, and might come in time to super- sede chemical analysis altogether. But the characteristic micro-organisms of cholera and typhoid lever are only with great difficulty isolated and separated from the crowds of harmless species which are found in greater or less abundance in all natural waters. The finding of a greater or less number of non-pathogenic bacteria or fungi in a water gives evidence of the presence of a larger or smaller amount of organic pollution, which forms a suitable pabulum for bacteria ; for pure waters are found to contain very few bacteria or fungi, whilst impure waters often swarm with them. They increase in numbers if water is stored for any length of time. The detection of bacteria of intestinal type, which have their usual habitat in the intestines of man and animals, throws considerable light on the nature of the pollution, and if they are present in such amount as to point to recent contamination, should serve to secure the condemnation of the water. The 66 HYGIENE AND PUBLIC HEALTH more important of these intestinal organisms, for which the tests have been most fully elaborated, are Bacillus coli communis and its congeners, Bacillus enteritidis sporogenes, and streptococci. A water which gives no indications of the presence of typical B. coli communis in lo c.c. of the water examined, nor of strepto- cocci in 50 c.c. (?), nor of the spores of B. enteritidis sporogenes in 500 c.c. is, at the time of the examination, so free from sewage pollution that it may be certified as safe for all domestic purposes providing its source is satisfactory (Thresh). By the typical B. coli communis is meant the organism found in animal excrement and in fresh sewage. It would appear that in water to which this organism has obtained access, the typical B. coli undergo after a time changes of a degenerative character, so that they no longer fulfil all the tests which are characteristic of the typical organism. There are also other organisms of intestinal type, such as B. acidi lactici and B. enteritidis (Gaertner), which give most of the reactions of B. coli, but not all. It is doubtful, at present, as to what is the precise significance of the presence of such organisms in water. Their presence certainly should lead to suspicion and to further investigation, as they may indicate a recent previous sewage contamination, a contamination which may also be a recurring one. The mere presence of typical B. coli communis and of B. enteritidis sporogenes in a water would not justify, on this ground alone, the condemnation of the water ; for they do not necessarU}^ mdicate human contamination. It is only when the B. coli is appreciably present in i c.c. of the water that, in the opinion of vaoxiy, the water should be regarded as definitely unsafe. The Bacillus typhosus is exceedingly difficult to detect in sewage-polluted waters. It is very doubtful if this organism has ever been isolated from a natural water, even although such a water has been credited with the causation of enteric fever. In addition to a chemical and biological examination of a water sample, it is of great advantage to possess the fullest information as to the risks of pollution to which the water has been subjected, and this can only be obtained from a painstaking local investigation. WATER 67 Analytical Results of Certain Waters (Parts per 100,000). New River Company (Filtered,!. Polluted Well Water. Peaty Surface Water. lo-o 7-0 3-0 Spring Water from Chalk, 33-0 lo-o 23-0 26-0 20-0 6-0 Rain Water. A Sus- picious Water. Total solids (a) Volatile . (b) Non-volatile Total hardness . {a) Temporary (b) Permanent 31-2 9-8 21-4 6o-o 25-0 3S-0 3-0 1*5 40 -o I5-0 25*0 25 '0 14-5 IO-5 21-5 13-0 8-5 30-0 15-0 15-0 5-0 i-o 4-0 o-o Chlorine 1-8 7-0 07 o-oi O-OOI o-oiS 0'200 2-5 0-30 0-25 4-0 0-50 Oxidized nitrogen 0-18 0-80 0-030 0-015 O'OI 0-015 o-ooo Free and saline NH3 . Organic NH3 c-ooi 0-003 O-OOI 0-003 0-030 o-oo6 0'0I2 Oxygen absorbed in two hours at 80° F. 0-030 o-i6o 0-015 0'120 CHAPTER II THE COLLECTION, REMOVAL, AND DISPOSAL OF EXCRETAL AND OTHER REFUSE In any community of persons, arrangements must be made for the collection and removal of their excretal refuse (faeces and urine), of the waste waters from houses, and of the dry refuse (ashes, dust, and refuse food). The solid and liquid refuse matters from stables, cowsheds and slaughter houses, street sweepings, and the waste waters from works and manufartoiies, must also be removed. In all towns the collection and removal of dung, ashes, dust, refuse food, and street sweepings, is performed by mechanical labour, the various processes above mentioned being included in the term scavenging ; whilst in some, human fasces and a certain amount of urine are also removed by this method, after being deposited in privies, cesspools or dry closets, on what is known as the conservancy system. In a large majority of the towns of this country, at the present time, human excrement is removed with the liquid refuse of dwellings on what is known as the water-carriage system — a system of drains and sewers for the passage of the refuse in a liquid condition to some spot outside the town. The public health largely depends on the efficiency with which refuse matters, and especially human excretal refuse, are re- moved from towns ; for the health of towns in this country and abroad has very much improved, and the death rates have been permanently lowered, as the result of works of sewerage. Removal of Domestic Dry Refuse. Domestic dry refuse consists partly of mineral matters, but to a considerable extent of organic substances derived from the waste scraps of food. These latter, being prone to undergo 68 DISPOSAL OF REFUSE 69 decomposition when stored in dust-bins or other receptacles, are very liable to become a source of nuisance. It is, therefore, very desirable that the quantity of organic refuse to be temporarily stored on the house premises should be reduced as far as possible ; and this may be accomplished by burning the more easUy destructible matters, such as potato peelings and other food scraps, in the kitchen fire at the end of every day. The old-fashioned brick dust-bin is now being largely replaced by galvanized iron receptacles, with well-fitting metallic covers, to insure dryness of the contents and their protection from rain. This is an important point, as the presence of moisture hastens putrefaction and the formation of offensive gases in the refuse. The non-absorbent walls of iron pails, and the ease with which they can be moved and carried out to the dust-carts, constitute very great advantages over the brick dust-bins, of which the walls become saturated with decaying matters and the contents are often incompletely removed at each visit of the scavengers. The contents of the dust-bins or pails should be removed at least twice a week ; in summer a more frequent removal is desirable, but is not usually practicable. Specialh^ constructed carts provided with covers should be employed to convey household refuse through the streets. There is an obvious advantage in keeping the refuse as dry as possible, and if such vans are not jjrovided with sliding metal covers or covers of tarpaulin, the escape of dust in windy weather creates a great nuisance. Motor dust vehicles are to be recommended as effecting a great saving of time. Horse manure must also be frequently removed from stables, and the removal in urban districts is often attended with considerable nuisance, especially where peat moss litter is used as a bedding tor the horses. The nuisance mainly arises at the time of loading the cart, in which the manure is removed, from the receptacle, the disturbance of the contents of the receptacle giving rise to very offensive gases ; and the recently disturbed manure is often highly offensive as it is carted along public thoroughfares. It is found in practice that the best remedy for the nuisance is to store the manure in the same cart in which it is to be removed. The disposal of house refuse has hitherto been mainly effected by depositing it on waste ground, the site being commonly called a " shoot." These refuse heaps frequently constitute a JO HYGIENE AND PUBLIC HEALTH serious nuisance in the neighbourhood. Offensive gases are given off from the fermentation of the organic matters, and the liquids draining from the heap are of the most noxious character, and occasionally cause serious pollution of neighbouring water- courses. In windy weather dust and the lighter particles are scattered around, whilst in summer the rotting refuse attracts large numbers of flies, which invade surrounding houses and settle on food exposed to the air. Rats, too, burrow in the heap in search of food, and are generally much complained of. The practice of shooting or tipping refuse cannot be defended, and it is slowly giving way to a more sanitary method, i.e., the destruction of refuse by fire. As the area of a town increases, these muck-heaps often become the sites for buildings long before natural agencies have succeeded in purifying the " made- soil "; and, moreover, the difhculty of acquiring sites sufficiently near the area to be scavenged is growing greater year by year in our larger towns, and makes the adoption of some other method of house refuse disposal imperative. The refuse, when deposited at the " shoot," is sometimes submitted to the process of hand-sorting. The paper and rags are removed for paper-making, the tins and iron for scrap, the bones for manure, the unbroken bottles for re-use, and the broken glass for re-melting. This sorting process is a degrading occupation ; the workers are of necessity in a filthy condition, and the air they breathe is constantly polluted with fine dust and foul odours. The best method of getting rid of dust-bin refuse is to burn it in a destructor furnace ; and offensive market refuse, fish offal, and even diseased carcases can also be disposed of by this method without creating a nuisance. The proportion of cinders in the refuse is always sufficient to insure complete combustion in a well constructed furnace. A small commercial value attaches to the residual clinker, either for making mortar, or mixed with granite chippings and cement to make paving slabs or concrete bricks. The temperature attained in the furnace, while destro3dng the refuse, can be utilized to generate steam for electric power, to pump water or sewage, or to drive mortar mills. The calorific value of the screened house refuse varies from yV to i that of coal. In summer the heat value of the refuse is less, owing to the smaller proportion of cinders and ashes and the greater quantity of garden refuse and vegetable matter. DISPOSAL OF REFUSE 7I There are various types of refuse destructors, most of which possess the following features in common : — The furnaces or cells are strongly built of brick with fire-brick lining, and the general building is also of brick. The destructor is approached by an inclined roadway to the top or tipping platform, which is well above the ground level. In the centre of this platform is a series of feeding holes or hoppers into which the refuse is shot, and allowed to fall into the cells below. The stokers rake the refuse forward on to the fire ; and after burning, the refuse is re- duced to about one-third or one-fourtli of its original weight, the residue consisting of fine ash, hard clinker, etc. By means of forced draught produced by a steam jet or fans, the combustion can be made so complete that temperatures of 1,500 to 2,000° F. are attainable merely from the burning of the refuse. Some destructors are known as " slow combustion " or " low temperature " destructors, and in these " fume cremators " should be provided at the foot of the chimney. In the fume cremator (which is a coke furnace) incompletely burned vapours and fine dust particles, which are liable to escape into the air from the destructor furnace, are completely burned up before they can enter the chimney- flue. In the " high temperature " destructors such cremators are unnecessary, and the expense of burning the coke or coke-breeze in the fume cremator is saved. The advantages of the " low temperature " destructors consist in the diminished wear and tear on the fire-brick sides of the cells, and the consequent saving in upkeep. On the other hand, the disadvantages are that both the inlet for refuse and , the outlet for gases are, as a rule, at the rear of the cell, and therefore the empyreumatic and noxious vapours and fumes given off during the drying of the refuse, and before it is in active com- bustion, escape before being burnt, and a cremator is necessary. Further, more cells are required, because a smaller quantity of refuse per cell (from 6 to 8 tons) is burnt per day than with " high temperature " destructors. In the " high temperature " destructors (such as the Horsfall or the Beaman and Deas) the outlet for gases is at the front of the cell, and the vapours given off during the process of burning and drying pass over the hottest part of the fire to reach the exit. As the cell is raised to a very high temperature by forced draught (steam blast or fans) , such gases are destroyed within the cell itself ; a larger quantity of refuse is burnt per day per cell {i.e., from lo to i6 tons), and 72 HYGIENE AND PUBLIC HEALTH fewer cells are therefore required. On the other hand, they cost more for maintenance. The site on which the destructor is placed should be a central one for the district to be served, or the cost for cartage may considerably exceed that for burning ; and in some cases it would appear advisable to construct two destructors in different parts of a large town. The number of cells required will of course depend on the nature and amount of the refuse to be destroyed, and also upon the type of cell adopted. If a " high temperature " destructor is selected, about ten cells are necessary for a population of 100,000. These cells can be erected in a single row or " back to back." The cost of erection may be taken as about ;£5oo per cell, including enclosing building ; and the burning will cost from ()d. to 2s. 6d. per ton, according to the greater or less completeness of combustion required, and the number of tons to be burnt per cell per day. Human Excreta. An adult male, living on a mixed diet of animal and vegetable food, passes daily 4 ounces, by weight, of solid, and 50 fluid ounces of liquid excreta. The solid excreta of children under twelve years of age are in amount considerably less, probably on an average not much more than one-half the above quantities. If all ages and both sexes are considered, the daily amount of excreta per head of a mixed population may be taken at 2| ounces of faeces, and 40 fluid ounces of urine. Fresh faeces contain on the average 23-4 per cent, of dry solids, and fresh urine contains 4-2 per cent, (of which 54 per cent, is urea). The quantity of nitrogen voided per head daily in the excreta of a mixed population is 189 grains in the urine and about 40 grains in the faeces,- making a total of about 230 grains. The other valuable constituents of the excreta are phosphates and potash. A given weight of faces is more valuable than the same weight of urine, in the proportion of about ten to six ; but the weight of urine passed daily (in a mixed population) is about sixteen times as great as that of the faeces, consequently the total urine is worth about ten times as much as the total fasces. The estimated or theoretical money value, then, of the excretal refuse of an individual of a mixed population for one year may be taken as bein^ 6s. Sd. to ys. It is very evident that it must DISPOSAL OF REFUSE 73 be impossible to realize practically any such value, because it is impossible to collect the whole of the urine and faeces free from admixture with other substances, which greatly detract from the value because they are agriculturally worthless. Faeces and urine, especially when mixed, as in cesspools, privies, and sewers, rapidly undergo putrefactive changes, giving rise to the formation of foetid gases (organic vapours, sulphur- etted hydrogen, ammonium sulphide, etc.). The urea — CO(NH2)2 — of the urine decomposes, giving rise to carbonate of ammonia — CO(NH2)2+2H20= (NH4)2C03 — and so rapid is the change that it is probable that, even in the best sewered town, all the urea of the urine in the sewage has been converted into ammonia before the arrival of the sewage at the outfall. House Waste Waters. In these are included the waste waters from kitchens, which are highly charged with decomposable organic matters and grease, and slop waters containing urine, soap, and the dirt from the surface of the body and from clothes. These waste waters, when mixed with the liquid refuse or drainage of stables, cow- sheds, and slaughter houses, with the washings from the street surfaces, with the urine from public urinals, and the waste liquors from manufactories, form the sewage of the non- water- closeted or midden owns. The drainage from stables is very rich in urine' (one horse excretes about fifteen times as much urine as an adult man) , and the waste liquors from manufactories are often excessively foul. It is not surprising, then, to find that such sewage is often quite as foul as that of some water-closet towns, which contains the solid human excreta as well. The Rivers Pollution Com- missioners stated in their First Report that, " for agricultural purposes, lo tons of average water-closet sewage may, in round numbers, be taken to be equal to 12 tons of average privy sewage " — i.e., sewage of privy towns, where human faecal matters are kept out of the sewers. Such being the case, it is necessary to bear in mind that, in towns where there are middens or some form of dry closet for the collection of f^cal matters, there is also a liquid sewage to be conveyed away from houses by drains and from the towns by sewers, which is too impure to be admitted into a stream and which must therefore be purified before being discharged. 74 hygiene and public health Conservancy Systems. The Privy or Midden System. — The system which formerly prevailed in many towns in this country — where there was any system at all — was that of privies, midden pits, and cesspools, often open to the air and unprotected from rain, and situated in the yards and areas about houses. These receptacles were generally mere holes dug in the ground, and their contents over- flowed, saturating the air with noxious effluvia, or percolated into the soil around and under the houses and poisoned the water in the neighbouring wells. At the present time, in those towns which still retain con- servancy systems, the middens are required to be constructed according to certain definite rules. The model bye-laws of the Local Government Board with regard to the construction of privies and middens for new buildings require that the privy must be at least 6 feet away from any dwelling, and 40 or 50 feet away from any well, spring, or stream ; means of access must be provided for the scavenger, so that the filth need not be carried through a dwelling ; the privy must be roofed to keep out rain, and provided with ventilating openings as near the top as practicable ; that part of the floor of the privy which is not under the seat must not be less than 6 inches above the level of the adjoining ground, must be flagged or paved with hard tiles, and must have an inclination towards the door' of the privy of ^ inch to the foot ; the capacity of the receptacle under the seat of the privy must not exceed 8 cubic feet — a weekly removal is then necessary ; the floor of this receptacle must be in every part at least 3 inches above the level of the adjoining ground ; the sides and floors of this receptacle must be constructed of impermeable material — they may be flagged or asphalted, or constructed of 9-inch brickwork rendered in cement ; the seat may be hinged, or other means of access to the contents of the privy must be provided ; and the receptacle must not communi- cate with any drain or sewer. With privies constructed and managed according to these rules, there would be no danger of percolation of liquid filth into the soil around houses and in the neighbourhood of wells ; and there would not be much pollution of the air from the excreta — except during removal — if dryness were insured by the proper application to them of ashes and cinders. The success of DISPOSAL OF REFUSE 75 the system depends to a large extent on efficient inspection by the sanitary inspector, and on proper scavenging arrangements. Cesspools. — These receptacles for filth are so evidently un- desirable in the neighbourhood of houses that it is the practice now in nearly all towns to fill them in, and provide more suitable means for the collection of excreta. When, in the year 1847, it became compulsory to carr}^ house drains into sewers, many cesspools with which house drains were connected were filled up, or otherwise abolished ; but some of them escaped observation, and to the present day occasionally one or more cesspools are Fig. II. — Cesspool with House Drain Inlet and Overflow to Filter Bed. discovered in the basements of town houses, of the existence of which the owners or occupiers are ignorant. In country districts where there are no sewers, cesspools are still largely used for the reception of human excreta and waste waters. When dug in a porous soil, such as gravel or chalk, they are too frequently constructed to allow all the liquid filth to percolate through their walls into the soil, with the certain danger of polluting wells, springs, and other sources of under- ground water-supply. When the liquids escape thus easily, the cesspool but very rarely requires emptying, and this fact con- stitutes the raison d'etre of the porous cesspool. The model bye-laws of the Local Government Board for new 76 HYGIENE AND PUBLIC HEALTH buildings require that a cesspool must be at least 50 feet away from a dwelling, and 60 to 80 feet distant from a well, spring, or stream. It must have no communication wdth a sewer (in sewered districts) ; its walls and floor must be constructed of good brickwork in cement, rendered inside with cement, and with a backing of at least 9 inches of weU puddled claj^ around and beneath the brickwork. The top of the cesspool must be arched over and means of ventilation provided. Constructed in accordance with these rules, and with the house drain dis- connected from the cesspool in the same manner as it is dis- connected from a sewer, the possible dangers of cesspools are reduced to a minimum. In this country cesspools are generaUy emptied b}^ hand labour — a disgusting and dangerous task — or by pumping into a night soil cart. On the Continent, and especiall}" in Paris — where so many houses have a fosse permanente in the courtj^ard ■ — the cesspools are emptied b}^ pneumatic pressure. A flexible tube, connected with a tub or tonneau exhausted of air by an air- pump, is thrust down to the bottom of the cesspool. On turning a valve, the pressure of the atmosphere forces the contents up into the tonneau. This method is said not to give rise to any nuisance comparable with that from emptjdng the cesspools b}^ hand labour. Whenever a cesspool or privy pit ceases to be used, it should be completely emptied and the contaminated brickwork, earth, etc., removed ; or, after emptjdng, its walls should be well limed, and the interior filled up to the ground level with good concrete or with suitable dry, clean earth or brick rubble. The Pail System. — In this system the excreta are received into movable receptacles, such as pails and tubs. Removal is thereby greatly facilitated and there is no pollution of the air from disturbance of contents, as there always must be when the contents of middens are taken awa}^ In some towns iron paiJs are used, in others tarred oak pails. The capacity of the pail should not be greater than 2 cubic feet. Both kinds should be provided with a close fitting lid, to be adjusted before removal of the pail by the scavenger. The structure of the privy (fig. 12) need only be very simple ; it should be well roofed and louvred for ventilation, its floor being raised above the level of the ground adjoining and flagged, and the pail placed under the seat. The seat may be hinged to DISPOSAL OF REFUSE 77 /\ insure a more complete covering of the excreta with cinders and ashes, when these are used, and to allow of the removal of the pail ; or the back wall of the closet may be provided with a door to facilitate the latter purpose. The pail should be removed at no longer intervals than once a week and a clean one substituted. It is very important, from a sanitary point of view, that the pail contents should be kept as dry as possible ; and for this object the house ashes and cinders should be thrown into the pail, either by a scoop after each use of the closet, or by a mechanical arrangement (to be described under earth- closets) above the pail, which sifts the cinders and deposits the fine ash auto- matically on the pail con- tents, as in Morell's closet. It is perhaps convenient for sanitary authorities to re- move all house refuse in one receptacle ; but if it is intended to create a saleable manure from the excreta! refuse, all garbage and kitchen refuse, and even all but the very finest ash (for this detracts from the value of the manure), should be kept out of the pails and removed separately. In such cases the pail contents can no longer be kept dry, and sanitary considerations are, to a certain extent, sacrificed to insure commercial ends. All slops should be kept out of the pails, and should be carried away from the houses in drains with the other waste waters. In some cases separation of the urine from the faeces has been attempted. Besides introducing a complication into a system whose chief merit, perhaps, is simplicity, this plan is open to the great objection of abstracting the most valuable fertilizing con- stituents of the manure in posse. In the Goux system an attempt is made to dry the excreta by 3" Fig. 12. Privy constructed for Pail System. 7^ HYGIENE AND PUBLIC HEALTH lining a wooden tub with a layer of refuse sawdust, shoddy, tan, or other absorbent material, to which is added a little soot, charcoal, gj^psum, or other cheap deodorizer. This system was in use in Halifax, and on the whole has worked weU. Wood charcoal and charcoal obtained from seaweed (Stanford's patent) have been used instead of ashes to aid in drying the pail contents. Thej^ act as absorbents, and to a certain extent as deodorizers. Manufacture of Manure. — In to\vns situated in agricultural districts, where there is a demand for the coarser sorts of manure, the pail contents need merely be mixed with a certain portion of fine ash. But in some of the large towns, where the pail systems are in vogue, it is now the practice to convert the pail contents into a dry manure of a more imperishable character, which can be packed and sold at a distance. The heat required for this purpose is generated by the combustion of house cinders and refuse in a destructor furnace, the invention of Mr. Fryer. The pail contents — urine and faeces without ashes — are mixed wdth a small portion of sulphuric acid, to fix the ammonia, in an air-tight store tank, where the thicker portion of the material settles at the bottom. The more fluid portion of the contents of the tank is drawn off into evaporators, which are tall cast- iron cylinders each containing near its lower end a drum-shaped heater, precisely resembling a multitubular steam boiler. These cylinders are partially filled, and the heating drums are covered \\-ith the thin liquid ; steam is then introduced within the heating drums, and the liquid becomes partially concentrated. \\'lien the contents of these cylinders have lost by evaporation the greater portion of their water, they are drawn off into a Firman's Dryer, into which the thick portion of the patl con- tents, which settled in the store tank, has also been admitted. This machine consists of a steam- jacketed horizontal cjdinder, traversed by a steam-heated axis with steam-heated revolving arms, and furnished with scrapers to keep the inner surface of the cylinder free from accumulations of dried excreta. The pail contents are admitted into the dryer at a consistency of thin mud ; after treatment they emerge as a dry powder — poudrette — resembling guano in appearance and qualit\^ The odorous gases given off during the process are all passed through the destructor fire and burnt. From the time the liquid material enters the store tank until the end of the process when it emerges DISPOSAL OF REFUSE 79 as a dry powder, no odorous gases should be permitted to escape into the outer air, and no nuisance ought to result. The Dry Earth System. — This system is the invention of the late Rev. Henry Moule, and consists in the application to the excreta, deposited in a pail or tub, of a certain quantity of dried and sifted earth. One and a half pounds of dry earth applied in detail, i.e., each particular stool being covered at once with this quantity, is found to be sufficient to remove odour and to form a compost which remains inoffensive as long as it is dry. A certain action takes place in the mixture of earth and excrement, which resrdts in the complete disintegration of the faecal matters and paper, which after a time are found to have completely disappeared and are no longer recognizable. The compost after further drying may be used over again, and has the same action as the original dry earth. The best kinds of earth are loamy surface soils, and vegetable mould. Sand, gravel, and chalk are unsuitable and inefficient. The closet generally used with this system is almost identical with the cinder-sifting ash-closet previously mentioned. There is a hopper or metallic receptacle above and behind the seat, and the proper amount of dry earth is shot into the pail by a simple mechanical contrivance connected with a handle, or self-acting seat arrangement. The contents of the pail must be kept as dry as possible, or fermentation results, with the disengagement of foul gases ; consequently slops must on no account be thrown into them, and even chamber urine must be kept out of them, unless a considerable extra quantity of dry earth is used. The earth must be dried before use, and then sifted by means of a sieve, the finer portions only being used. There can be but little doubt that the compost or manure produced by the passage of the earth even five or six times through the closet has but little agricultural value. The late Dr. Voelcker estimated its value as only ys. 6d. per ton. It is probable that there is some escape or evolution of nitrogen in a free state from the manure when kept ; and this may partly account for its deficiency in fertilizing properties. But when we reflect on the large amount of valueless earth with which the compost is diluted, and the absence from it of a large pro- portion of the daily urine of each individual, the reasons for its low value are not far to seek. 80 hygiene and public health The Disposal of Slop Waters. We have already seen that the conservancy systems do not provide for the removal of the liquid refuse, domestic or muni- cipal ; and we have seen, too, that in the so-called midden towns this liquid refuse or sewage may be quite as impure as the ordinary sewage of some water-closet towns. In these towns, too, there is always a certain percentage of houses provided with water-closets, so that the crude matter . passing into the sewers is inadmissible into a river or stream, and requires to be purified. A system of drains and sewers is necessary for its removal from the to-wn ; and the principles on which such drains .and sewers must be constructed do not differ from those which would be necessary if they were intended to carry water-closet sewage as well. In small villages and isolated houses provided with middens or some form of dry closet, the slop waters are usually carried by a drain from a sink or yard gully into " sumpt " holes in the garden, into an open ditch, into a cesspool, or into a stream ; if into a " sumpt " hole or open ditch, there to stagnate and generate offensive gases ; if into a cesspool, often to percolate through its porous walls and pollute the neighbouring wells ; and if into a stream, to foul it nearly as much as if they contained the solid excreta also. The slop waters may be retained in cesspools which are rendered impermeable by brickwork set in cement and well puddled with clay outside ; and they can then be utilized on garden ground by means of a pump and hose and jet. They may also be passed through a small coke or ash filter, which should be prepared on a specially selected area well away from the house ; or they may be disposed of by irrigation upon grass fields. \\Tierever the nature of the soil and the slope of the land will permit of it, recourse may be had to sub-irrigation to purify the dirty water and utilize it to the best advantage. A very small piece of ground is required for this purpose. The late Mr. Rogers Field considered 4 perches of land sufficient for an ordinarj^ cottage. The drain conveying the slop waters from the house should be connected by a few lengths of impermeable piping with a system of 2-inch agricultural porous earthenware pipes, with- out joints, laid laterally about 5 or 6 feet apart, at a depth of about 8 to 12 inches in the soil, the whole having a slight fall or DISPOSAL OF REFUSE 8l inclination, away from the house, of 6 or 8 inches in lOO feet. The ends of the pipes should rest upon cradles formed of larger half-pipes, and similar covers should be placed above, so as to prevent earth getting into the pipes, whilst allowing the water to escape. The lower end of the main outlet pipe should turn up into the air to allow air to escape. This is especially necessary when the slop waters are discharged into the sub-irrigation drains by a flush tank. If the soil is very porous, no under-drainage is needed ; other- wise, porous drain pipes must be laid at a depth of about 3 feet from the surface, with an outlet into a stream or ditch. The slop waters escape through the open joints of the sub-irrigation pipes into the soil, where some of their fertilizing ingredients are absorbed by the roots of the grasses and vegetables grown on the plot, and the rest is purified by percolation through the soil ; so that the effluent water passes away in a purified condition into a stream or ditch, or helps to swell the volume of the subsoil water. The chief difficulty in connection with this method is that the flow of slop waters from a single house is so small that the liquid penetrates but a short way along the sub-irrigation pipes, which become in time choked with deposit ; and that portion of the sub-irrigation plot nearest the house receives an unduly large share of the irrigating liquid, and its cleansing properties are speedily overtaxed. This difficulty, where the gradients admit of the necessary loss of head, has been overcome by providing a flush tank which will discharge at intervals into the head of the system. The tank now in most general use for this purpose is fitted with the annular siphon arrangement invented b}^ Mr. Rogers Field. In the annular siphon tank (fig. 13) the ascending arm of an ordinary siphon is represented by a short wide cylindrical pipe, closed at the top, which is placed over and encloses the descend- ing arm, a longer pipe of smaller diameter. The upper end of the descending arm is open, and in Field's tank is provided with a lip projecting inwards and downwards, which serves to direct the water, as it overflows, into the centre of the pipe. The lower end of the descending arm opens over a discharging trough below the body of the tank, and is trapped by the water which stands in this trough to the level of the top of a weir, over which the water flows into a pipe connected with the head of the sub-irriga- tion system. 6 82 HYGIENE AND PUBLIC HEALTH fi \ oS€3€3£?€^:^^^~-£> :^^g^ '^^^^^^- i s Fig. 13. Onh^ a very small dribble of water into the tank is necessary to put the siphon into action. This takes place as follows : As the tank fills, the water ascends between the inner and outer pipes constituting the siphon, until it reaches the level of the top of the inner pipe, the air displaced finding an exit through this pipe into the discharging trough below. The water then trickles over the top of the inner pipe, and, thrown into its centre by the lip, falls clear of the sides, entangling and carry- ing air with it which cannot pass back, owing to the lower end of the pipe being trapped. This con- tinues until the siphon is sufficiently exhausted of air to be brought ■"'^or musSStot^DSs'''"'* i"to action, when the whole con- tents are discharged by siphonage. It is not necessarj^ to strain the slop waters before they enter the tank, as they contain but few of the coarser suspended matters and solid particles found in water-closet sewage. The sub-irrigation drains require to be taken out of the ground, and the deposit removed before they are relaid, every few years, according to circumstances. Comparison of Methods. There can be no doubt that all conservancy systems proceed on a wrong principle, viz., that of keeping excremental matters mthin or near dwellings longer than is desirable from the point of view of health. In towns the expense of scavenging is directly proportional to the frequency of removal, so that there is always an inducement to the local authority to economize at the risk of the health of the inhabitants. The costs of this kind of scavenging are high, and nowhere does the sale of the refuse cover the expense. Movable receptacles are far better than fixed ones foi the collection of excremental matters. The pail system is un- doubtedly the best lor towns which wiU not enforce the adopcion of water-closets. In the case of Nottingham, where middens, pails, and water-closets are in use in different parts of the town. Dr. Boobbyer has shown that the greatest prevalence of enteric DISPOSAL OF REFUSE 83 fever is to be found in the houses with middens, and the least in the water-closeted houses, those with pails occupying an intermediate position. However suitable the earth-closet system may be for country houses and villages in this country, and for villages and stations in India, and in cold countries, where the water supply is small and liable to interruptions, and where earth of suitable quality is easily procured and dried, and the compost can be distributed over gardens and fields in the immediate vicinity, it is quite inapplicable to towns of any size, on account of the enormous quantities of earth that would have to be dried and brought into the town, the difficulties of storing the earth on the premises of houses and keeping it dry, and the still larger quantity of nearly worthless manure to be removed out of the town and finally disposed of. The Water-Carriage System. In this system the solid excreta together with all liquid refuse are conveyed away — borne along by flowing water — in drains and sewers from the neighbourhood of houses and towns. In many towns, before any general introduction of water-closets, sewers existed for conveying away house waste waters, stable drainage, surface and storm waters, and in some cases waste liquors from manufactories. These sewers, which were made of brick, oval or circular in section, acted also as land drains ; for not being constructed of impermeable materials, they admitted subsoil water and had considerable effect in drying the soil. It became at one time also the practice to drain off the liquid contents of privies and middens, or to carry overflow pipes from cesspools into these sewers, which in consequence speedily became choked with sediment. This sediment rapidly putrefied, and the offensive gases given off created an abominable nuisance. It then became necessary for the sewers to be regularly cleansed, and the deposit had to be removed at great expense by hand labour. The drainage of privies and middens entered the sewers in a most foul and offensive condition, owing to the putrid state of the contents of these receptacles. Another result was that the streams and rivers into which this sewage was permitted to pass became highly polluted. In many towns these brick sewers still exist, and perform the double function of removing sewage and rain-water, and draining the subsoil ; whilst in others they are 84 HYGIENE AND PUBLIC HEALTH only permitted to perform their original function of carrying off rain and surface water and of draining the subsoil, impermeable sewers being laid to remove the sewage of the town on what is known as the separate system. House Drainage Arrangements. Water-closets. — A water-closet may be defined as an apparatus for the reception of excrement, which is connected with a sewer by a pipe, and in which water must be used to carry away the excrement deposited in it. It is therefore seen at once to differ in all essentials from a privy, which ought not to be connected in any way with a sewer, and in which water cannot properly be used. Water-closets may be classified under two heads : {a) those in which there is no movable apparatus for retaining water in the basin ; (5) those in which there is such a movable apparatus. Under the first head are included the various types of hopper closets ; under the second head, pan, valve, and plug closets. The hopper closet consists of an inverted stoneware cone, connected below with an LO or lj--shaped pipe, which retains sufficient water to prevent the free passage of air, and is known as a trap. The old form of hopper closet, called the long hopper, from the length (about i8 inches) of the cone (fig. 14), is liable to fouling of the basin, and is difficult to flush, especially where the water is admitted by a side inlet, which has the effect of causing the water to whirl round and round, whereby the trap is not flushed out and excreta are left, behind. A short hopper or imsh-down (fig. 15) is constructed with a shorter (8 to 9 inches) cone of china or stoneware ; the back of the cone should be made nearly vertical, so that the excrement drops into the water of the trap, and not upon the sides of the basin. The short hopper, especially when constructed with a " flushing rim," by which the sides of the basin are well washed, is found, under proper management, to be easily kept clean. It is a form of closet which is now largely used, for it is simple in construction, inexpensive, has no confined air space where foul air could accumulate, and conveys slop waters away at once, /no overflow pipe being necessary. For the out-door water-closets of the houses of the working classes the short hopper closet, made in stout glazed stoneware or fireclay, is far the best. The floor of the closet should not be DISPOSAL OF REFUSE 85 of wood, but of cement-concrete sloped towards the door of the closet. The siphon trap under the closet basin should be fixed upon the cement floor by embedding it in cement so as to form a pedestal, thus rendering it and the basin very strong and perfectly secure. There should be no vertical wooden casing, and the seat should be hinged, so that every corner around the Fig. 14. — Long Hopper Water- closet with Side-inlet for Flushing. Fig. 15. Wash-down Water-closet. space beneath the seat can be got at for cleansing. The trap of the closet should be joined at the back of the basin to a 4-inch stoneware drain pipe by a cemented joint. A closet fixed after Fig. 16. — Wash-out Water-closet. this manner will stand a great deal of rough usage without getting broken or out of order. Nearly all closets of the wash-down type are now made in pedestal form, that is 10 say, with a hinged, lifting seat, and with- out wooden casing or riser. The closet is then well adapted for use as a urinal and for the discharge of chamber slops. The space under the closet should be cemented or tiled, or lined with lead finished with a beaded border. In the bracket form of closets, the basin and trap are supported by galvanized cantilever 86 HYGIENE AND PUBLIC HEALTH brackets let into the wall, and do not rest on the floor, conse- quently aU the space beneath the closet apparatus can be readily cleansed. Bracket closets are much used in hospitals. The wash-out closet (fig. i6) is constructed of stoneware or china, with the basin so shaped that a small quantity of water remains in it to receive the excreta, which are flushed out over the edge of the basin into a siphon trap below. This form of closet is difficult to flush with only 2 gallons of water, for the rush of the water from the flushing cistern is broken by the force necessary to clear out the contents of the basin ; and then the water falls into the trap, but often without sufflcient impetus to propel the excreta through it. The basin, too, is very apt to become soiled by solid matters near the outlet. The basin — as in the case of every closet basin — should be provided with a flushing rim. These disadvantages have led to the disuse of wash-out closets. Various " siphonic " closets are now made by English manu- facturers, in which the contents of the basin are not only forced out by the water-flush, but are also sucked out b}^ means of a temporarily induced siphonage in the trap. Not aU of these closets are reliable, as in some cases it has been found that foul water returns to the basin after flushing ; also in some forms of this closet, to prevent the siphon becoming " air bound," air- escape pipes have to be inserted — an undesirable complication of what should be a simple apparatus. Water-waste preventing cisterns should be used with each of these three forms of closet, both for economy of water and to break the connection between the house cistern, used for drink- ing water, and the water-closet basin. Where there is no house cistern, the water being supplied by constant service, the water- waste preventer is especially necessary. Numerous outbreaks of enteric fever have been attributed to the ascent of foul air and liquid filth from water-closet basins up the supply pipes into the water mains, with which they were directly connected. One of the simplest forms of water-waste preventer merely has a spindle valve in the cistern on the supply pipe of the closet, which can be raised by pulling a chain attached to a lever, when the water — 2 or 2| gallons — is discharged. When the lever is de- pressed by the chain, the baU valve is raised, and no more water can enter the waste preventer as long as the chain is held. The chain must be held until the waste preventer is empty. The best form of water-waste preventer is that with a siphon DISPOSAL OF REFUSE 87 action. A very short pull of the chain will put the siphon in action, when the whole contents of the cistern are discharged through the flush pipe of ij to if inches in diameter. No more water can then escape until the cistern is refilled and the chain again pulled. There are numerous forms of siphon water-waste preventer. The especial advantage of the siphon action is that the cistern is emptied by a verj^ short pull of the chain — an important factor in the proper flushing of closets used by careless persons. These cisterns should be fixed at a height of not less than Fig. 17. — Century Siphonic Closet. 4 feet above the closet basin. If this " head " is not obtainable, a good flush can be secured, as in the " combination " closets, by using a cistern, fixed at the seat level, with a comparatively large outlet pipe, which is only narrowed just before it joins the basin. The joint between the china or stoneware trap and lead soil pipe is difficult to make perfectly secure with red lead as a joint- ing material. Therefore it is better for these closets, where they must be connected to a lead soU pipe, to have lead traps, as a wiped joint can be easily made between the closet trap and the soil pipe. The disadvantage of the lead trap is that it cannot be S8 HYGIENE AND PUBLIC HEALTH enamelled internally, and enamel paints soon wear off, giving a dirty appearance to the bottom of the closet. In most cases a good joint is made by wiping a brass collar on to the lead soil pipe, when the joint between the china trap and brass collar is made with Portland cement, a little asbestos packing being employed to prevent the cement finding its way into the interior of the pipe. Under the head oi closets with a movable apparatus for retain- ing water in the basin, we have the pan, the valve, and the plug closets. The pan closet (fig. 18) has been, up to 30 years ago, more largely in use than any other form in the better class of houses ; and it is undoubtedly a very badlj^ contrived closet, and one which is often productive of nuisance. The pan closet consists of a china basin, shaped like an in- verted cone, with its outlet guarded by a movable metal pan, which retains water in the basin ; and for this purpose the pan must be of considerable size. On raising the handle of the closet, the pan is swung back into a large rounded cast iron receptacle called the " container," into which the excreta and water fall. From the bottom of the container a short pipe leads to a trap — usually a D trap — designed to prevent the passage of foul air from the soil pipe into the closet. The interior of the container becomes much splashed and soiled by the excreta ; and the deposit thus formed putrefies, giving rise to foul gases which escape into the air of the closet apartment as soon as the pan is swung back. The D trap — so called from its resemblance to the letter placed sideways (Q) is made of lead, and quickly becomes coated with a deposit of foul matter, for there are parts of the trap which cannot be flushed by the water passing through. This deposit, like that in the container, gives rise to the forma- tion of foul gases. The walls of old D traps and containers are not uncommonly found perforated in places, owing to the chemical action of the deposited matter. Pan closets and D traps, wherever found, should be replaced hy one of those forms of closet which are capable of being flushed in such a manner that no deposit of filth can take place in any part of the apparatus. The valve closet (fig. 19), which is now largely in use, consists of a hemispherical basin of china or stoneware, with a circular DISPOSAL OF REFUSE 89 outlet at its lowest part, 3 inches in diameter. This outlet is closed by a circular water-tight clack valve, hinged at one side, Fig. 18. — Pan closet with D trap, supplied from driaking water cistern. Standing waste pipe directly connected with unventilated soil pipe. Waste pipe of safe tray enters the D trap. where it is connected with the handle of the closet. On raising the handle, the free edge of the valve is depressed into a metal 90 HYGIENE AND PUBLIC HEALTH valve box, just large enough to allow the valve to assume a perpendicular position. The valve box is connected at its lower part with a trap — preferably a siphon trap, or an anti-D trap formed of 4-inch lead pipe — and the outlet of this trap is con- nected with the soil pipe. The valve closet should be flushed from a small cistern holding 6 or 8 gallons of water, and not from a water- waste preventer, as it is necessary to provide a considerable " after-flush " — that is to say, to allow a supply of water to enter the basin after the handle is released and the valve closed. To secure an after- flush, some form of " regulator " valve in Fig. 19. — Era Valve Closet. the supply pipe from the cistern to the closet basin must be used. The " bellows regulator," which is commonly used, con- sists of a piston working in a cylinder, and connected with the handle of the closet and with the valve in the supply pipe. The cylinder is provided with an escape pipe for air, on which is a tap to regulate the speed with which the air escapes and the piston falls. When the handle is raised, the valve in the supply pipe is opened, and the piston also is raised ; but on letting go the handle — the clack valve to the closet basin being then closed — the valve on the supply pipe is kept open, admitting water to the basin, until the piston has completely fallen and thereby closed it. The amount of after- flush, which is directly pro- portional to the slowness with which the piston sinks in the DISPOSAL OF REFUSE 9I cylinder, can be regulated to a nicety by the tap on the air- escape pipe. As the outlet to the closet basin is guarded by a water-tight valve, the basin may overflow from too much after-flush, or from the throwing in of slops. It is necessary, therefore, to provide an overflow pipe to the basin ; this is usually carried from near the top of the basin into the valve box below, after forming an LT) bend, which, by holding water, prevents the ascent of foul air from the valve box. But it is found in practice that foul matters may find their way into or accumulate in the overflow pipe, and that the water in the bend is liable to be evaporated or drawn out by siphonage when the contents of the basin are discharged through the valve box. Two precautions are adopted to obviate this difficulty. The first is to carry the overflow pipe into that side of the valve box where its open end will be protected by the depressed valve ; and the second, which is most necessary, is to recharge the water in the overflow at each use of the closet. The basin of the closet should be provided with a flushing rim. Occasionally a ven- tilating or " puff " pipe is attached to the valve box, and carried up and out into the open air, being left with an open end away from any windows. When the contents of the basin are being discharged, the foul air in the valve box then escapes into the open air, instead of into the closet compartment. There is very little risk of the deposition of filth in any part of the apparatus, as the large volume of water which the basin can contain effectually flushes the small valve box and trap beneath. Occasionally the valve box is enamelled inside to prevent corrosion. The chief disadvantage of the closet is that the clack valve may become in time leaky, allowing the water in the basin to escape, and possibly foul air to ascend into the general air of the closet. "WTierever a valve closet is used as a urinal or for the reception of chamber slops, a white ware slop-top should be fitted, and the seat should be hinged for lifting. Valve closets are also now made in pedestal form, so as to obviate the wooden casing and riser. An advantage possessed by valve closets over the wash- down closets is that the flushing is comparatively noiseless ; and this fact accounts for their popularity in the best class of resi- dential property. In the anti-D trap the calibre of the pipe is diminished in the 92 HYGIENE AND PUBLIC HEALTH bent portion which holds the trapping water, and the bend of the pipe beyond the trap instead of being circular is squared. These properties cause some resistance to the passage of water through the trap, and tend to prevent both si-phonage by suction — i.e., the drawing of the water in the trap by the passage of water down the soil pipe from a higher level — and siphonage by momentum, which may occur in plain siphon traps by the water discharged from the water-closet sweeping through the trap, insufficient remaining behind to form the water-seal. The depth of the water-seal in water-closet traps should not be less than I inch, and not greater than i| inches. If the depth of the water- seal is too small, there is a liability for the trap to be unsealed ; if the seal is too great, the trap and the closet above it are not self-cleansing with an ordinary flush of water. These remarks apply more especially to " wash-down " closets (short hoppers) with water-waste preventers. The Water-seal of Traps. — The water-seal of a trap is the vertical distance between the level at which water stands when the trap is fixed in position, and the lowest point of the bend of the upper surface of the trap. Thus in figs. 20 and 2 1 , which are diagrammatic sections of a S trap and a P trap, in each case the water-seal is the same, namely the vertical distance AB in the case of the S trap, and the vertical distance A'B' in the case of the P trap. Fig. 20. — S trap, with Water-seal. Fig. 21. — P trap, with Water-seal. The water-seal is, in fact, the depth of water that opposes the passage of air or gases from one side of the trap to the other, from outlet to inlet or from inlet to outlet. In the figures, the upper dotted line represents the water- level in each trap, and the lower dotted line is parallel with the upper dotted line, and is tangential to the apices of the bends. In the plug closet the basin and trap are usually cast in one piece of china or stoneware, the basin above being shut off from ■the trap (siphon) below by a solid plug or plunger, by which water is retained in the basin. The cistern and flushing arrange- ments may be the same as those for the valve closet, an after- flush being necessary for both alike. The plug, which is con- nected directly with the handle, is usually perforated by a channel bent on itself so as to form a trap, and thus provides an overflow to the basin, permitting water to pass through the DISPOSAL OF REFUSE 93 plug to the trap beneath. Sometimes these closets are used without the trap beneath, but in both plug and valve closets a siphon trap is necessary to prevent the passage of foul air from the soil pipe when the closet is discharging its contents. The plug or plunger is liable to become much soiled, and, being out of sight, escapes cleaning. When this is so, it may happen that excremental filth is forced up on the handle when the plug is suddenly plunged. This constitutes a great disadvantage in use, and has led to the practical abandonment of plug closets. The valve and plug closets are under the disadvantage of having a space between the water in the basin and the water in the trap, from which air— possibly foul — escapes into the general air of the closet when the contents of the basin are being discharged. But they have this advantage over those of the first class, that the larger quantity of water in the basin renders them more cleanly in use. On the floor beneath the closet basin is usually placed a lead safe-tray, to catch any overflow. This tray should be provided with a waste pipe, which must be carried through the wall into the outer air, its end being covered by a brass flapper to prevent cold currents of air passing into the house. It was formerly the custom to connect this waste pipe with the D trap {see fig. i8) under the closet basin, thereby permitting foul air to enter the house at aU times. Water-closets should be placed against the outside wall of a building, in which is a window with an area of at least 2 square feet, made to open, and reaching to the ceiling. Where possible they should be separated from the house by a well-ventilated lobby ; for it is important that air from the closet should find an easy exit to the outer air, and not pass into the house, as so often happens when water-closets are placed in dark, unventi- lated corners. The water-closet must not open directly into anj^ living-room, factory, workshop or compartment in which food is stored. The division wall between the water-closet and a dwelling-room, or a factory, or workshop, or food store, should " always be of brick, and not a porous lath and plaster structure. The trough closet is used in large establishments, as hospitals, schools, workhouses, and asylums. One apparatus serves for the use of several people at the same time, and the flushing can be rendered automatic. The old form of closet (fig. 22) con- sists of an open trough, usually of stoneware, with rounded 94 HYGIENE AND PUBLIC HEALTH bottom, of varying length according to the number of compart- ments desired. The trough has a slight incline towards the drain ; and by means of a weir at its lower end it is able to retain sufficient water to cover the bottom for its whole length. It terminates in a siphon trap protected by a grid, to keep back articles improperly thrown in, before joining the drain. Each seat over the trough should be in a separate compartment. The closet may be flushed by means of a Field's annular siphon flush tank {see fig. 13) of capacity proportional to the length of the trough to be flushed. The more modern and approved type of trough w.c. or latrine is a great improvement upon the old form. In this (fig. 23) the trough is retained, but each closet is cut off from its neighbours by a separate basin, the outlet from which dips into the water in Fig. 22. — Trough Water-closet. the trough. The trough, moreover, is kept filled with water, which also rises up for a few inches into each w.c. basin ; this is effected by doing away with the weir and substituting a high siphon trap at the outlet to the trough. Each separate basin is flushed through its flushing rim every time the automatic flush tank discharges, this discharge causing the emptying of the basins and trough by siphonic action. On the whole, trough closets have not been found to be verj^ satisfactory in practice, and in schools and institutions they are now being replaced by separate pedestal wash-down closets. Waste-water closets, in which the excreta are carried away by means of the house waste-waters, and in which flushing cisterns with separate water supply are not used, were originally intro- duced by Dr. Alfred Hill, and are now to be seen in many working- class houses in Midland towns. DISPOSAL OF REFUSE 95 The annexed figure (fig, 24) shows a section through Day's waste-water closet. In this pattern the excreta fall into a stoneware tipper, which also receives the waste water. This tipper is so balanced on its bearings that when full it automati- calty tips over and discharges its contents (fseces, urine, paper, and waste water) into the siphon trap below, which leads to the Fig. 23. — New form of Trough Closet or Latrine with isolated pans. drain. The entrance to the siphon trap is considerably narrowed transversely, so as to prevent bulky articles improperly intro- duced finding their way into and obstructing the drain. The upper part of the closet is so constructed as to prevent, as far as possible, fouling of the sides above the tipping basin ; and this upper part can be taken down easily and removed for cleaning. 96 HYGIENE AND PUBLIC HEALTH In another pattern of waste-water closet the tipper is not placed under the seat, but in some position between the closet and the guUey into which the house waste water empties itself. The discharge of water from the tipper flushes the drain in which the excreta are deposited direct from the closet. The advantages of this system of waste-water closets are that clean water is not required for flushing, a head of water is not necessary, there is no delicate apparatus to be damaged and get out of order by rough usage, and both the primary cost and the outlay in keeping in repair are small. On the other hand, the economy of clean water and the absence of dilution cause the Fig. 24. — Day's Waste-water Closet. sewage passing from districts supplied with these forms of closets to be very strong and foul; and the difficulty of satisfactory treat- ment of the sewage at the outfall is much enhanced. Economy of water is purchased at the'^expense of difficulties in the purifica- tion of the sewage. Moreover, waste-water closets are liable to get foul and to block up, for in the poorer class houses with no bathrooms the slop-waters may not be adequate to provide suffi- cient flushing. It should be stated that waste-water closets should only be fitted up outside dwelling houses. In the Mid- lands these closets are not" now regarded with favour, and the system is not being extended. DISPOSAL OF REFUSE 97 Urinals should be made of non-corrosive materials, such as fireclay, slate, and stoneware ; all metal apparatus is liable to corrosion, and should not be used. The floor should be cemented, and should slope towards a channel which discharges into a siphon trap connected with a drain. Urinal basins may be made of china or stoneware, constructed so as to retain water, and their waste pipes should discharge over the channel in the floor. The best kind of flush is that from siphon-action flush tanks which discharge automatically at regular intervals. Unless urinals are regularly and freely flushed with water, there will be a deposit of urates in the attached lead waste pipe, soil pipe, or drain, which by continual accretion and hardening eventually leads to obstruction. Where urinals are not supplied with water, there is usually a nuisance from smell, but this can be largely obviated by brushing the backs and sides daily with paraffin. Slop sinks should be used only where it is objectionable to discharge slops from bedrooms through the water-closets. They are usually short hopper china basins with a siphon trap below, protected by a grid to keep back the larger foreign bodies which might obstruct the pipes. The trap should be connected with the soil pipe like a water-closet. They should be provided with a flushing rim, and flushed from a water-waste preventer. Soil pipes are used to receive the contents of water-closets, urinals, and slop sinks, which are above the basement or ground level. They should be circular in section, and 3| or 4 inches in diameter, these being the most convenient sizes for ordinary use. They should be of drawn, milled, or roUed lead, 8 pounds to the square foot, or 9 pounds to the square foot for very high buildings, without any longitudinal seam, and should be fixed outside the house, with wiped (soldered) joints between the different lengths of pipe, each pipe being 10 feet in length. Lead T pieces are used to receive the branches from the water-closets. The London County Council Byelaws require 3^-inch lead soil pipes to weigh not less than 65 lb. per 10 feet length, and 4-inch pipes not less than 74 lb. per 10 feet length. The thickness of metal of 3 |-inch and 4-inch iron soil pipes must be not less than -f^ inch ; and the weight of 4-inch iron pipes per 6 feet length (including socket and headed spigot or flanges, the socket not to be less than ^- inch thick) must be not less than 54 lb. Soil pipes outside the house are often made of light cast iron or galvanized iron. The}^ are inferior to lead pipes, as the 7 98 PIYGIENE AND PUBLIC HEALTH internal surface of iron pipes is much rougher than that of lead, and the joints as usually made with red lead putty are insecure. Heavy cast-iron socketted soil pipes are in some cases insisted on by local drainage byelaws, especial precautions being laid down for the construction of the joints between the different lengths. To prevent oxidation and the formation of rust, iron soil pipes should be coated inside and outside with the magnetic oxide of iron (Barff's process), with hot coal-tar pitch, or with Angus Smith's solution. All cast-iron pipes must be free from holes or other defects, and properl}- tested, and of a uniform thickness of not less than y^- inch. The joints between the different lengths must be caulked-*- with lead ; and the joints between the iron pipe and the lead T pieces from the closets should be made with a brass ferrule, caulked in with lead, the lead pipe being attached to the ferrule b}^ a wiped joint. Heavy iron soil pipes are heavier than lead pipes in the proportion of about 9 to 7-4. Joints of Pipes. — In making a wiped soldered joint on lead pipes, the upper end of the lower pipe is opened out about J inch. The lower end of the upper or male pipe is next rasped so as to make it fit into the opened-out end of the female pipe. The ends of the pipes which are to be covered with solder are next shaved with a shave hook, so as to take the dulness off the lead and allow the solder to readily tin upon them. Above and below the soldered line (fig. 25) the pipes are then soiled round with plumber's soil (a mixture of lampblack and size) to prevent the solder adhering. It is weU also to soil the insides of the pipes to prevent the solder adhering here and causing projections. The male end is next fixed into the female end, and a coUar placed round the bottom of the joint to catch the solder as it falls off. The heated solder (a mixture of two parts of soft lead to one of tin) is then poured over the shaved ends of the pipes, and gradually worked into the right shape. A hot moleskin cloth is now taken and wiped round the joint, so as to leave it of the shape shown in fig. 25. As the pipes become heated b\^ the solder splashed over them, the solder penetrates 1 A caulked lead joint is a joint made by firmly packing lead strips into the socket of the iron pipe by means of a caulking tool (which is in the form of a blunt chisel) and a hammei. The lead is kno\\Ti in the trade as " ribbon " lead. It should be quite free from oxide, and therefore must onl}' be used when fresh. This process has now largely superseded the older method of caulking with oakum and filling in with molten lead. DISPOSAL OF REFUSE 99 between the ends of the pipes and readily adheres to all the shaved bright surfaces exposed, leaving when cool a homogeneous mass of metal. Fig. 26 shows a joint made with a copper bit or blow- pipe. The ends of the pipe are heated either with a copper bit or blowpipe, and, when hot, the solder is poured around the point of junction and penetrates between the cut ends. A very good joint is thus obtained with little trouble, but inferior in strength to the wiped joint with its strengthening band of solder. A new method of jointing pipes has lately been introduced, which is intended to supersede the old - fashioned soldering methods. For jointing lead pipes a cutting tool is used, the ends of the pipe being shaped into a coned joint, and the surfaces left in perfect apposition. A substance called " Amalgaline " is then inserted between the cut ends, and the exterior of the joint is heated with a flame. Amalgaline consists of a metallic ribbon. Fig. 25. Fig. 26. 0-05 millimetre thick, coated with a composition to prevent oxidation. On the application of heat, the ribbon melts at a lower temperature than the metals to be acted upon, and causes an amalgamation of the metals at a considerably lower temperature than their normal melting-point. The joints between iron pipes can only be caulked with lead when the pipes are of sufficient substance and strength to stand it. The joints of the light iron pipes commonly used are made with spun yarn and red lead, or occasionally with Portland cement. If lead soil pipes are used where much hot water is discharged through water-closets or slop sinks connected with them, owing to the expansion of the metal of the rigid pipe, twisting and con- tortion takes place (the pipes are said to " buckle "), and such pipes readily wear out. Under such circumstances, either iron soil pipes should be used, or the lead pipes, if outside the house 100 HYGIENE AND PUBLIC HEALTH and not near windows, should have sHp joints or rubber expan- sion joints. ■"■ For this reason, also, south and west aspects, involving rniich exposure to the sun, should be avoided for lead soil pipes. With the precautions noted above, and under skilled work- manship, cast-iron soil pipes may be used outside a house. Stoneware, zinc, or wrought iron should never be used for soil pipes ; for stoneware is too heavy, and zinc is thin and liable, like iron, to erosions. The proper fixing of a. lead soil pipe by means of cast lead ears or tacks to the walls of the house at intervals of 3-4 feet, to insure its being perfectly rigid, is a point of importance ; if not securely fixed, there will he, strain on some or all of the joints, with the result of their becoming insecure. Outside soil pipes should be connected with the house drain by a plain stoneware bend below the ground level, a thimble or ferrule of rough brass casting being wiped on to the lead pipe and a Portland cement joint being made between the brass and stone- ware. An iron soil pipe should be connected with the stoneware drain by receiving the spigot end of the iron soil pipe into the socket end of the stoneware drain, and making the joint with Portland cement. When a branch lead soil pipe has to be con- nected to a heavy iron main soil pipe a brass ferrule or thimble is soldered to the lower end of the lead pipe, and the ferrule is then jointed with the socket of the iron pipe by means of hemp and molten lead, or the " ribbon " lead previously alluded to. All soil pipes, whether inside or outside the house, should be carried up full bore above the entrance of the branch from the highest water-closet to the top of the house (fig. 27) above the ridge of the roof, clear of all windows and chimneys, their ends being left open or covered merely with a wire-gauze dome to prevent birds from building in them. Cowls should not be placed on the tops of soil pipe ventilators. They are useless as aids to extraction of air ; and they very frequently lead to obstruction of the outlet, besides being perishable. Where one soil pipe receives the discharges of several water- closets on different floors, the passage of the contents of one of the upper closets down the soil pipe may cause the water in the trap of one of the lower closets to be drawn off, owing to the i A slip joint is made by slipping the end of one pipe into the slightly expanded end of another pipe, so that the one fits more or less firmly into the other, but allowing a certain amount of play for expansion. DISPOSAL OF REFUSE lOI ? suctional force of the downward current of air caused by the descent of the liquid in the soil pipe. To prevent this siphonage l>y suction taking place, a 2-inch or 2|-inch lead ventilating pipe should be carried up from every branch soil pipe, a few inches beyond the trap (on its soil pipe side) , and these anti-siphonage pipes should join with one another on their way up outside the house, the common pipe being carried up separately or connected with the ventilator to the soil pipe (fig. 27). By this means the water-closet traps will not be disturbed by the passage of liquid down the soil pipe, for air will be sucked down these anti-siphonage pipes to restore the disturbed equilibrium. Siphonage is most likely to occur in 3|-inch lead soil pipes where the branch pipes from the water-closet traps to the soil pipe are long and curved. If they are short and straight, there is less likeli- hood of siphonage occurring. The long arms or branches from water-closets thus ventilated are relieved of foul air which otherwise accumulates in them, and eventually leads to erosion and perforation of the metal of which the pipes are made. A trap at the foot of the soil pipe immensely intensifies siphonage by suction. Rain-water pipes from the roof should not be used cLS soil pipes and ventilators, for during heavy rain, when it may be most necessary to give a safe exit for displaced drain air, they will be useless as ventilators, and foul air from unventilated drains may be forced through water-closet traps into the houses. Moreover, the joints of rain-water pipes are frequently found to be defective ; and if the pipe passed near to windows there would be a risk of drain gases finding an entrance into the house. House drains are usually constructed of circular glazed stone- ware socketed pipes, 2 feet in length, with cemented joints (Port- land cement) . The pipes are also connected by Stanford's patent joints or Doulton's modification (which makes the pipes adjust- i: Fig. 27. — Soil pipe and venti- lator, with anti- siphonage pipes from the water- closet branches. 102 HYGIENE AND PUBLIC HEALTH able in any position), in which the spigot and socket ends of each pipe are provided with a mould of smooth plastic materia], causing them to fit accurately into each other when in position ; a very perfect joint being formed by greasing the prepared ends with a Httle rosin and melted tallow. These patent joints, how- ever, are inferior to cement, as they are hable to erosion and decay, and are usually found not to be watertight some years after laying. Stoneware pipes are less porous and more durable than earthen- ware pipes ; the former may be distinguished from the latter by their colour (generally pale buff), the ringing note which they give out on being struck with a hammer, and their comparatively slight increase in weight after twenty-four hours' immersion in water. Portland cement is a mixture of chalk and clay burnt at a high temperature and subsequently ground very fine. It is stronger and capable of bearing greater tensile strains than other cements (Roman and Medina), but does not set so rapidly. When cemented joints are made, neat Portland cement only should be used, and care must be taken to remove any cement projecting from the interior of the joint into the drain, which when hardened would lorm an obstruction to the flow of sewage through the drain. Portland cement should be spread out and exposed to the air for some time before it is used, otherwise the joints, when made, are apt to " blow," and the collars become fractured. Socketted cast-iron pipes coated inside and outside with some preservative material such as the magnetic oxide of iron (Barff process) or Angus Smith's solution, to prevent oxida- tion, are used when the drain is required to be of extra strength to withstand constant vibration, as when laid under roads or paths on which there is heavy traf&c, and also in soft, swampy ground. The joints of an iron drain must be caulked with molten lead and gasket or hemp (old method), or with " ribbon " lead (new method). Iron pipes have advantages over stoneware as they are made in g-feet and 12-feet lengths, and consequently fewer joints are required ; the pipes are stronger, and the caulked lead joints more durable, and they are capable of resisting strains that would fracture stoneware pipes ; on the other hand, the interiors of even the best protected iron drains are liable to rusting and erosion in course of time, a defect which the less costly stoneware drains are free from. DISPOSAL OF REFUSE IO3 When it is necessary to connect a lead to a heavy iron pipe, a strong brass ferrule or thimble should be joined to the lead pipe by means of a wiped soldered joint ; the brass ferrule is then received into the socket of the iron pipe and the joint made with hemp and molten lead, or " ribbon " lead. For small and medium-sized houses a drain 4 inches in diameter is the proper size ; for large houses a 6-inch drain may be used, and for large institutions or establishments consisting of several buildings a 9-inch drain may rarely be required. The smaller the drain, the better the flushing and removal of deposit ; but the drain must in all cases be large enough to guard against blockage and to carry off at all times all the rainfall over the area drained, as well as the maximum flow of sewage proper of the house. A volume of water sufficient to make a 4-inch pipe run full causes a 6-inch pipe to run less than half-full, and a 9-inch pipe only about a quarter full, when all three are laid at the same inclination, since the sectional areas of the three pipes are in the ratio of about i, 2, and 5. Stoneware drains are made in 3-inch, 4-inch, 6-inch, 9-inch, 12-inch, 15-inch, and 18-inch sizes. Iron drains are made in these sizes, and in addition 5 inches in diameter — a size which is very frequently employed. The London County Council Byelaws require stoneware drains (4 -inch and 6-inch) to be not less than f inch in thickness ; the depth of the socket to be 1 1 inches for 4-inch, and 2 inches for 6 inch pipes ; and the annular space for the cement to be not less than ^^^ inch for both 4-inch and 6-inch drains. For iron drains (4-inch, 5 -inch, and 6-inch) the thickness of metal must not be less than | inch : and the weight per 9 feet length (including socket and beaded spigot or flanges, the socket not to be less than | inch thick) must be not less than 160 lb. for 4-inch drains, 190 lb. for 5 -inch drains, and 230 lb. for 6-inch drains. The pipes must be laid (with the socket end pointing upwards towards the head or commencement of the drain) on a perfectly smooth incline of hard ground, or where passing under the basement of a house, on a bed of 6 inches of cement concrete, the drain being embedded to the extent of half its diameter. In London it is the practice in addition to cover stoneware drains with 6 inches of cement concrete all round, the concrete projecting on each side of the drain to an extent equal to the external diameter of the drain. Concrete should be made of clean sharp sand, 2 parts ; clean ballast (gravel, or hard brick broken small), 6 parts ; Portland cement, i part. Each pipe 104 HYGIENE AND PUBLIC HEALTH should rest upon the concrete for its whole length, so that the drain ma}^ be truly laid, the lumen of each pipe being concentric with the next. The concrete should be hollowed out where the collar of the pipe rests, and the cement must be introduced all round the joint, below as well as above ; and the joint should be finished with the trowel. It is sometimes the practice to introduce a strand of spun yam into the interior of the joint to prevent the cement passing into the drain, and to insure the thickness of cement being the same all round. It is often the custom now to lay the drain on bricks at the bottom of the trench, and when the joints have been made with cement, to fill in with concrete beneath the pipes. If this is done, a brick should be used to support each end of every pipe, so that the drain may be truly laid. Iron drains should be laid on 6 inches of concrete, where passing under a building, as above described for stoneware drains, but need not be embedded in concrete. The gradient of a 4-inch drain should, if possible, be not less than I in 40, of a 6-inch drain i in 60, and of a 9-inch drain i in 90 ; this will give in each case a velocity of flow of between 3 and 4 feet per second. The drain should not, wherever it can be avoided, be carried under the basement of a house. WHiere, however, this is unavoidable, the special precautions noticed above must be taken, and at the point where the drain leaves the premises the waU should be supported by a relieving arch to prevent settlement and fracture of the pipes. Drains should be laid as far as possible in straight lines. It a bend is necessary, it should be effected by means of a special pipe curved to the proper degree, and the radius of any curve should not be less than ten times the cross-sectional diameter of the drain or sewer. The bends most commonly used are known as ], I, and j-^ bends, implying that if 4, 8, or 16 respec- tively of these pipes are placed together they will form a complete circle. A branch drain should be made to join the main drain by means of a V junction pipe, so that the branch current may be flowing nearly in the direction of the main current, thus causing no obstniction at the point of union. In large houses it is very often impossible to carry the drain in a straight line for its whole length. It is advisable in these cases, at every change of direction, to provide means of inspection by manhole chambers, the drain being continued through the floor of the chamber by a suitably curved channel pipe, i.e., a pipe divided longitudinally DISPOSAL OF REFUSE I05 in half. Into these inspection-chambers the branch drains also should be made to discharge by means of short curved channel pipes emptying over the main channel. Winser's curved channel pipes, from which about a quarter section only of the circum- ference has been removed, should be used when connected with a high soil pipe, so as to avoid splashing of solid fsecal matters over the floor of the chamber ; and where the drains are joined in a manhole, the invert or bottom of the smaller drain should be higher than that of the main by so much as the difference between the diameters of the two, so as to prevent the liquid flowing in the large or main drain from backing up into the smaller. By this system of manhole or inspection-chambers, the drain — which runs in a straight line from manhole to manhole — can be inspected, and cleared by rods of deposit or obstructions, without breaking into it. Where it is necessary to connect a small pipe with a larger pipe, the junction should always be effected by means of a taper or diminishing pipe. The disconnectiun of the house drain from the public sewer is generally provided for, although it is not now generally held that sewer air is more specially harmful than drain air. Siphon disconnecting traps, however, prevent the passage of sewer rats up the house drains ; and unless such traps are fixed, it would be impossible to provide for the ventilation of house drains by fresh air inlets as now practised. Disconnection is effected by interposing a siphon trap between the house drain and the sewer, and on the house side of the trap a means of inlet for fresh air into the house drain is provided. The point usually chosen for disconnection is immediately before the house drain leaves the premises in its course to the street sewer. If the house drain is provided with a ventilating pipe at the further end, air, admitted on the house side of the disconnecting trap, will gene- rally travel continuously from the lower opening to the higher, and a circulation will thus be established in the drain and soil pipe, preventing any accumulation of foul air. The simplest form of disconnecting apparatus consists of a siphon trap with fresh air inlet formed of stoneware pipes on the house side of the water seal. There are several varieties of this sort of trap sold, under the names of " sewer air intercepter," " sewer air trap," etc. The points to be observed in choosing a trap of this description are : (i) Where the drain is a 6-inch or a 9-inch pipe, the siphon should be a size smaller than the drain ; io6 HYGIENE AND PUBLIC HEALTH (2) there should be a fall of 2 inches or more from the level of the discharging end of the house drain to the surface of the trapping water ; (3) the siphon should provide an adequate seal of 2 or 3 inches of water ; (4) the inlet to the siphon should be nearlj^ vertical, whilst the outlet rises at an angle of not more than 45°. These qualities, except (3), are necessary to insure sufficient flushing of the trap ; and, to further attain this end, the drain should be laid with a slightly greater fall before its junction with the trap. The fresh air inlet to the siphon is continued up by a Fig. 28. — Section of Disconnecting Chamber. A, junction 45° (4") ; B, junction 90° (4") ; C, junction 30° (4") ; D, main channel (4") ; E, intercepting trap (4" to 6") ; jp, clearing eye ; G, drain to sewer (6") ; //, drain (4") ; I, fresh air inlet ; K, galvanized terminal ; L, air-tight cover ; M, condensing dome ; N, york stone ; O, glazed bricks, or preferably brickwork rendered in Portland cement ; P, concrete ; Q, cement ramps ; R, cap to clearing eye ; S, water joint automatically sealed by condensation ; T, ordinary joint, taUow or soft soap. vertical pipe to a little above the surface of the ground, and there covered by an open iron grating, which may be guarded by a mica flap valve to prevent any escape of foul air. There is no doubt that the odour of drain and sewer gases plays an important part in determining injurious effects upon health, for rapid and profounti constitutional disturbances are often induced by foul odours, the effect of which often lasts for some time, and may render the individual specially prone to certain infections. Doubtless the short length of house drain, with its greater fall, generally leads to that pipe keeping cleaner than DISPOSAL OF REFUSE I07 the long common pipe or sewer into which it discharges ; and since the offensive sewage gases are produced in proportion to the time during which the sewage remains in the pipe, the atmo- sphere of sewers is, generally speaking, fouler than that of drains. Another circumstance favouring the retention of the disconnect- ing trap between the house drain and the sewer is that the faulty condition of stoneware drains, so frequently discovered, is re- sponsible for the fact that a considerable number of house drains are always under repair, and for this purpose may be laid open for several days ; the dangers to the occupants would be increased if during these occasions the drains were ventilating the sewer. It is claimed that without using intercepting traps the gases from the sewer would be distributed by escaping through the drain and soil pipe of each house ; but no such equable distribution of escaping gases would occur in a district of varying levels, with houses which varied a great deal in their size, height, and proximity to the sewer, and in which the sewers were not uniformly sound and of equal gradient. In a comparatively flat district with a recent and well-laid system of sewerage, or in newly-developed districts in which iron drainage is provided for the dwellings, there would be little advantage derived by intercepting the house drains ; but if the intercepters are properly fixed, of a good type, and always cleared before the drainage is covered up, they very rarely give rise to any trouble. In larger houses it is now usual to provide a disconnecting manhole chamber (fig. 28), instead of the simple trap above described. The chamber walls are buHt of brickwork rendered in cement, and the floor is made of concrete. Walls lined with glazed brick are not so good as rendered waUs, as the joints in the brickwork are apt to become defective, and then the chamber is no longer water-tight. The drain is continued through the floor of the manhole in the form of a glazed channel pipe, from which the floor — made of cement — slopes up (ramps or bench- ings) at an angle of 30° to the brick walls of the manhole. The branch drains, in the form of suitably curved (J or |) glazed channel pipes, are made to discharge over the main channel, which itself discharges into a trap. The siphon trap should be provided with a " raking " arm or clearing eye, one end of which opens into the manhole, the other end being connected with the drain beyond the trap. This arm is to permit of obstruc- tions being removed from the drain between the siphon trap and I08 HYGIENE AND PUBLIC HEALTH the sewer ; when not in use, the manhole end should be closed with a patent stopper or a tUe or piece of slate set in cement. The manhole chamber may be closed above by an air-tight iron cover ; and the fresh air should then be admitted into the chamber by a 6-inch pipe, the manhole end of the pipe being opposite the entrance of the drain, whUst the end open to the air is covered by an iron grating and provided with mica flaps, which permit air to pass in but prevent the reflux of foul air. The double seal condensing cover (fig. 28) is frequently used where the manhole chamber must be built inside the walls of a house. Where the disconnecting chamber is some distance from the house and away from footpaths, fresh air may be admitted by perforations in the iron cover. The chief advantage of the manhole chamber is the readiness with which the drain can be inspected and cleansed. Wherever possible, the plan of drainage should be so designed as to provide for all manhole chambers being situated in yards or open areas, and not actually within the walls of the house ; for there is generally some danger of escape of drain air through covers which are not perfectly air-tight. It is important also that the interiors of manholes should be rendered in cement, so as to be water-tight, as, if the disconnecting trap becomes choked, the chamber may become filled with sewage. For house drains with insufficient gradient, in which deposit is liable to occur, it is advisable to provide an automatic flush tank to discharge into a guUey at the head of the drain ; by this means the dangers arising from insufficient fall may be to a great extent obviated. Automatic flush tanks should be fed with clean water and not with bath or other dirty waste waters. Flush tanks fed with dirty waste waters invariably become a nuisance. The frequency of discharge of the tank can be regulated by adjusting the tap through which the water enters ; the merest dribble is usually quite sufficient. These tanks in practice should work without " dribbling " or " continuous action," which can be secured by fixing them on a perfectly level surface with the discharge pipe quite plumb. Flush tanks are now usually fitted with a " reversed " ball- valve. When the ball is depressed in the tank very little water passes through the valve ; but when the tank is very nearly full the valve is fully opened, a rush of water enters the tank, and siphonage at once DISPOSAL OF REFUSE lOQ takes place. Dribbling and continuous action, which are some- times due to smallness of flow into the tank, are thus a\'oided. whilst the time of filling the tank can still be regulated as desired. All waste pipes from baths, lavatories, sinks, and safe-trays under water-closets or baths must be disconnected from the drain or soil pipe by being made to discharge into the open air. The waste pipes from baths, la\'atories, and sinks should be of a large diameter (i^ or 2 inches) to insure rapid empt^ang of the baths, sinks, etc., and as short as possible, for they tend to become coated internally with a deposit of dirt and soap, which decomposes and may be productive of nuisance. To prevent foul air from these pipes entering the house, a cast- lead siphon trap should be fixed under ever}' bath, lavatory-, and sink ; and in the case of kitchen sinks this siphon trap should be provided at its lowest point with a screw cap, capable of removal, in order to clear the trap of sediment and grease. The waste pipes from the upper floors are often carried through the external waUs to discharge into the open head of a rain-water pipe divided, if necessary, into lengths for this purpose ; but this is not a very good plan if the open heads are anywhere near windows, for the iron pipes become in course of time much fouled from soap and dirt, and then are apt to smeU offensive!}'. In such cases the 2-inch lead waste pipe should be continued down to the guUey at the ground level, its upper end being carried up to the roof and left open ; anti-siphonage pipes will usually be required in the case of bath and lavatory wash-hand basin waste pipes, to prevent siphonage of traps, especially where several waste pipes on different floors discharge into a main waste pipe. Every rain-water or waste pipe must be disconnected from the drain at its foot by opening over or under the iron grating over a stoneware siphon yard gulley. The basement waste pipes may discharge into yard gulleys by side inlets. When it is impossible to avoid having a long waste pipe, this must be ventilated by a pipe of its own diameter carried up outside the house to a convenient point. Whenever it is necessary to place waste or other pipes within partitions or recesses in walls, they should never be covered, except \\-ith woodwork, which should always be made readily removable. The surface water from yards and areas should, where possible, be carried off by those siphon gulleys which receive the waste waters from the house, because these gulleys are always efiiciently no HYGIENE AND PUBLIC HEALTH trapped in dry weather. Yard gulleys used for surface water only become untrapped in dry weather, owing to the evaporation of the water in them. These gulleys for waste and surface water are connected with branch drains which join the main drain SINK >'<- DRAIN Fig. 29. — Flushing Grease Gulley. in the inspection or manhole chambers before referred to ; they require to be cleansed periodically of sand and dirt, which collect at the bottom of the trap. In large houses it is found that the sand and grease discharged through the kitchen or scullery sink are apt to lodge in the drain DISPOSAL OF REFUSE III from the gradual solidification of the grease as the water cools, and so form an obstruction. It is usual in such cases to cause the waste pipe (2-inch pipe, trapped under the sink) to discharge into a grease gulley instead of into a 3'ard gulle^^ This grease giilley is made of stoneware, and may with advantage be con- nected with an automatic siphon flush tank (fig. 29). The hot water from the sink is cooled on entering a large volume of cold water in the trap, the grease solidifies and rises to the top, whilst the sand sinks to the bottom of the trap. When the flush tank discharges, the grease is thoroughly broken up by the sudden inrush of the large volume of water, and is then carried along through the drain without any opportunity being given to it to deposit on the sides or floors of the pipes. The grease gulley should be covered above by a grating, and sunk a little beneath the surface of the adjoining ground to confine all splashings to the trap. To carry off the water used for washing down laundries, sculleries, and dairies, the floors should slope to a channel leading to a 3'ard guile}" outside the house. \^ — ^he house drainage arrangements described above have for their object : (i) The speediest possible removal from the house to the public sewer of excretal and other refuse by means of water ; (2) the prevention of deposit of foul matter in any part of the drainage system, and of percolation into the soil of polluting liquids ; (3) the establishment of a current of air through every part of the soil drains and pipes, in order to disperse any foul gases that may form, and allow them to escape with safety into the open air ; (4) the prevention of any entry of gases from soil pipes, drains, and waste pipes, into the house ; (5) the exclusion of the air of the common sewer from the house drain and the house. Objects (4) and (5) are to a great extent attained, as we have seen, by means of traps or water seals, and the question arises, " How far do such traps carry out the objects for which they are designed ?" Siphon traps are the most cleanly of all traps, because they present no corners or angles where deposit can accumulate, and are most easily flushed clean. Their liability to siphonage we have considered, and we have endeavoured to show that it can be obviated by a sufficient depth of siphon, providing an efficient seal of water, and by adequate ventilation. There is, however, another disadvantage common to all water 112 HYGIENE AND PUBLIC HEALTH traps, which is that the water may absorb gases on one side of the trap, and give them off on the other, so that foul air from the R>VP B Fig. 30. — Semi-detached houses. A, modern drainage ; B, old drainage system ; D.C., disconnecting chamber ; F.A.I., fresh air inlet ; I.C, inspec- tion chamber ; S.P., soil pipe ; G., gulley ; S., sink ; R.W.P., rain-water pipe ; W.C., water-closet. drain or sewer may be given off — onty, however, to an inconsider- able extent — into a house, notwithstanding the presence of the DISPOSAL OF KEFUSi; IIJ trap. The only remedy for such a state of things is tlie pre- vention of foul air accumulations by adequate ventilation. The proper ventilation of drains and soil pipes can only be effected where there is an inlet for fresh air at one end of the system, and an outlet for foul air at the other end. Where there is an outlet but no inlet, the pipes must be always full of foul air, though not under pressure, for there can be then no renewal of the air in them by the passage of fresh air currents. The Testing of Drains and Soil Pipes and their Branches. Tests are employed for new sanitary work, during the progress of the work, to ascertain that it is being properly constructed, and also for sanitary works that have been in existence for some time, to ascertain if the work is still sound. The principal tests are the water or hydraulic test, the smoke test, the pneumatic or air test, and the chemical test. The Water Test. — This test is now almost invariably employed for new drainage work, and is applied after the drains are laid and jointed, but before they are embedded in concrete, or before the drain trenches are filled in. The lower end of the drain, as it enters the disconnecting cham- ber, is plugged by means of an expanding screw plug with rubber rim of the size appropriate to the drain, or by means of a strong canvas bag, which can be filled with air under pressure by means of an air force-pump. As soon as the drain is secnrely plugged, and a cord has been attached to the plug to prevent its being carried away when the water is released, water is allowed to flow into the upper portion of the system until it has risen to the top of an inspection chamber or guUey at the head of the drain. If, after stopping the flow, the water-level remains stationary for some minutes, the drainage system under test is sound ; but should the water-level fall, there is a defect at some point, and the joints of the drain should be carefully examined for evidence of leakage. It is important to remember that in thus applying the test to a system of drains, air will be imprisoned in the branch drains leading from guUeys or water-closets, if the latter are charged with water. This air is hable to become slowly absorbed by the water, when compressed, and thus lead to a fall in the general level of the water, although the drains may be sound. The imprisoned air should be allowed to escape by passing a bent pipe through the water of the trap that retains the air. In drains of considerable length with steep gradients the head of water pressure in the lowest section of the drain may be considerable ; but in testing house drains, at any rate, nothing approaching a bursting strain for well made and well jointed stoneware drains is liable to be reached. In testing the drains of very large establishments, however, the system should be tested in sections, and any general test which would place undue strains upon the pipes and joints should be avoided. In applying the water test to existing drainage, the same methods are applicable ; but should a general test show leakage, it will be necessary to test in sections until the leak is sectionally located. There is no dififi- culty in carrying this out, if there are the proper proportion of inspection chambers, as branch drains can be plugged in the inspection chambers to which they are connected at one end, and tested with water up to the levels of the tops of the guUeys or water-closets with which they are connected at the other. Inspection chambers, which are very often found to be leaky from defective rendering with cement, can be tested separately by filling with water, after all drains entering or lea\'ing them have been 114 HYGIENE AND PUBLIC HEALTH securely plugged. It sometimes happens that an old drain is found to be in a very dirty condition, but water-tight on testing. After the drain has been rodded and cleansed, on further testing, it may be found to be no longer water-tight, owing to the grease and filth which sealed the interiors of defective joints being washed away in the process of cleansing. In old drainage systems without any inspection chambers the water test cannot be applied unless the drain is exposed at some point (usually at or near its lower end), and a pipe removed in order that the plug may be inserted. Old drains of this description are very seldom found to be water-tight ; and it has been said that the application of the water test to an 'Old drain is liable to damage it and open up the joints. It is very doubtful, however, if the water test carefully applied ever does anjr injury of this sort even to an old drain. Any soil drain passing under or quite near to a house should be sufficiently sound to pass a water test. Vertical soil pipes and their water-closet branches may be tested with water, before the w.c.'s are connected, by soldering over the apertures where the closet apparatus is connected, and then filling with water, after plugging the lower end of the soil pipe, or the branch drain from the soil pipe in the nearest inspection chamber. This is a severe test, if there is a great head of water, and one but rarely applied, yet it is withstood by a good lead soil pipe with strong wiped joints. The Ball Test. — This is applied to new drainage work, before the drains are covered in, to ascertain that there are no projections of cement from the joints into the interior of the drain, by passing a spherical wooden ball, ^ inch less in diameter than the drain, through the pipes from the upper to the lower end. The Smoke Test,- — This test is applied either by means of a smoke rocket or by a smoke machine. The test is usually applied to both underground drains and vertical soil pipes, or drain ventilating pipes, at the same time. The disconnecting chamber, or inspection chamber at the lowest point of the drain, is uncovered, and the smoke rocket after ignition is inserted into the drain delivering into the chamber. The rush of smoke from the rocket forces the air upwards through the drain, and where there is a good upward draught, the smoke will shortly be observed issuing from the top of the soil pipe or the drain ventilator. As soon as the smoke issues freely from the outlet, this should be closed by means of a plug or by a wet cloth, and at the same time the drain should be plugged where the rocket is inserted, or the cover to the inspection chamber should be replaced to prevent reflux of smoke at this point. In this way the whole length of drain and soil pipe and soil-pipe ventilator can be charged with smoke confined under very slight pressure. If there are any defects in the pipes or in their joint- ing, smoke will escape at such points, and will generally make itself evident either to sight or smell, according as to whether the defect is exposed to view or concealed beneath the ground or in walls and casings. In carrying out the smoke test, particular care is necessary to ensure that all traps connected with the drain or soil pipe under test are properly charged with water, and that doors and windows facing the spot at which the test is being applied are carefully closed. In the smoke machine, air is forced by means of a bellows through a metal compartment containing smouldering paper or cotton waste well saturated with oil, and a flexible pipe from the machine leads the smoke into the drain or soil pipe. The machine is rather cumbersome to carry about, but has the advantage over smoke rockets that the test may be applied under a definite pressure of about i to 2 inches of water, and that the flexible pipe can be passed through gulleys or traps on the line of a drain, where inspection chambers do not exist, or the test can be applied from the top of the soil pipe ventilator in the reverse manner to that usually employed with rockets, where this method is more convenient. The test with the smoke machine DISPOSAL OF REFUSE II5 is carried out in the same way as previously described for rockets. In either case, when there is no disconnecting chamber to the drain, the water seal in the gulley trap which is nearest to the outlet of the drain is generally removed, and the smoke rocket, or the tube of the smoke machine, is inserted into the bend of the trap. In doing so, however, there is always a possibility that the smoke will pass directly into the sewer, and not traverse the house drain, owing to the absence of a disconnecting trap. The smoke test is better evidence of defects in vertical soil pipes and ventilating pipes than of defects in underground drains ; as, in the case of the latter, although defects may exist, the issuing smoke may not reach the surface of the ground or find its way to any point at which it could be detected either by sight or smell. Escapes from vertical pipes are usually readily detected. The Pneumatic or Aiv Test. — This is very similar to the smoke test as applied by a smoke machine, air being forced by means of an air pump into the drain or soil pipe after the top of the soil pipe or other drain ventilating pipes have been securely plugged. A water gauge attached to the pneu- matic machine shows the pressure in inches of water ; and if this pressure is maintained for a few minutes, it is evident that the system under test is air-tight. The nozzle of the machine passes through an expanding screw plug or pneumatic bag, which makes an air-tight joint with the drain or pipe into which the nozzle is inserted. The test is a severe one, as the very smallest pin-hole defect will present an aperture for the escape of air, sufficient to prevent a pressure of an inch of water being maintained with the pipes under test. It suffers also from the drawback that there is nothing to indicate the exact position of the defect, since the escaping air is both colourless and odourless. The Chemical Test. — This is usually applied by means of grenades or small glass capsules containing a composition of phosphorus and asafoetida. When the containing glass is broken and the composition comes into contact with water, a slight explosion takes place, and dense white fumes having the characteristic smell of asafoetida are evolved. These fumes escape through defects in the drain or pipes, and so give evidence of leakages, which are recognized by the sense of smell. In testing underground drains by this method a certain time (15 to 30 minutes) should be allowed to elapse before deciding that there is no evidence of defects, as the odour may take a considerable period to travel from the defective drain to any point at which its presence could be appreciable. In using the grenades, one or two may be wrapped up in blotting paper, broken by a sharp tap, and then thrown into the w.c. basin on the highest floor, the basin being immediately flushed, so as to carry the broken capsules to the drain side of the w.c. trap ; or the same result may be attained in Kempe's apparatus, the grenade or capsule being floated through the trap of the w.c, and then broken by a sharp pull on a string which releases a spring. There is a method of repairing leaky drains, in situ, without opening the ground, which may be applied in suitable cases. The drain is first cleansed, and then a small apparatus containing Portland cement under pressure is passed several times through the drain. As the apparatus passes any leaky point in the drain, the liquid cement escapes at this point and fills the leaky joint, etc. Time is then allowed for the cement to partially set, when a swab is drawn through the drain to remove any projecting pieces of cement. The drain is thus treated in sections, which are temporarily disconnected, and finally a water test is applied to the whole .For old and defective drains from which there has been much leakage it is more sanitary, and often more economical, to remove the old pipes and the contaminated earth surrounding them, and to replace with sound pipes and clean earth. IID HYGIENE AND PUBLIC HEALTH Stables. The proper paving and drainage of stables is important, as dampness and foul air are very injurious to the health of horses. The floors of stables should be paved with a small hard brick, such as that known as adamantine clinker, with chamfered edges set in cement, such bricks being imper\dous to water and small enough to give a foothold to the animals. The floor should have a gentle slope of about i inch in lo feet, from the heads of the stalls to\A-ards a cement drainage channel constructed to convey liquids outside the stable to a gullej:^ in the stable yard. These channels should be covered with iron gratings flush with the floor, easi]}' detachable for the purpose of cleansing. If horse and mare pots are considered pre- ferable to channels, the}^ should be connected to drains, which are led outside the stable to discharge into the back or side inlet of a deep gulley. Inasmuch as a good deal of straw or other material used for litter is apt to pass away with the stable drainage, the gulley receiving those hquids should be a Dean's silt gulley with removable bucket for collecting solid particles {vide fig. 31). For storing stable manure, whilst awaiting removal, the best receptacle is an open wire cage, which allows the free play of air over the surface of the refuse, and thus prevents heating and fermentation in the interior. Sunken dung pits are generall}* a nuisance, as the\^ favour fermentative changes ; they should be abohshed in favour ol open wire cages resting on a cemented surface in the stable yard. Peat moss, dried and compressed, is now largel}^ used as litter instead oi straw, especiall}' in cab and omnibus j'ards. It is more absorbent than straw, and consequently keeps the stables where it is in use very dry. If used too long, it becomes highly impregnated with urine, and gives off most offensive effluvia. In cab and omnibus yards the peat moss manure is generally \'ery rank and stale before it is removed from the stable, and Fig. 31. — Dean's Silt Gulley. A, cast-iron receptacle to lift in and out. DISPOSAL OF REFUSE II7 when stacked in heaps and subsequently thrown up into carts, the nuisance is very great. It is in these cases especially that carts or vans should be used to receive the manure directly as it issues from the stalls of the stables, so that when the van is filled it can be drawn away without further disturbance. Mines. Although many conditions are imposed which aim at safe- guarding the miners of this country from accidents, and although much has been done in recent years to diminish the incidence of pulmonary complaints among miners by reducing dust and noxious gases arising from drilling and blasting operations, com- paratively little has been done in reference to those other sanitary precautions which are necessary in order to guard against the risks of spread of enteric fever and ankylostomiasis. That the danger which the miner runs of infection of enteric fever is real, and at times leads to outbreaks of disease in this country, is testified by certain reports of medical inspectors of the Local Government Board. The reports upon ankylostomiasis in Westphalia and elsewhere provide almost a voluminous literature on the prevalence of this disease in hot, damp mines ; and among the most valuable of these reports, and one which has also a topical interest, is Dr. Hal- dane's Report to the Home Secretary on an outbreak of the disease in a Cornish mine, -where ankylostomiasis, though abated, still exists. The sanitary conditions underground have often been demon- strated to favour the spread of both of these diseases, and it is alike in the interests of mine owners and miners that more precautions should be taken to guard against them. The capital expenditure involved would return a satisfactory^ rate of interest by maintaining a higher level of production. A mine that would satisfy the full demands of hygiene in respect of the danger associated with miners' excreta should have sufficient and suitable provision in the workings for the collection, removal, and disposal of all dejecta. It should be remarked here, however, that in the case of coal mines, where the bed is approximately horizontal, there is little objection to the use of the " goaves " or " wastes." Miners should realize the import- ance of taking suitable precautions underground with reference to their dejecta ; they should also endeavour to acquire the Il8 HYGIENE AND PUBLIC HEALTH habit of defsecating morning or evening before descending, so far as possible, and should only defsecate below when really neces- sary ; and in order to promote this practice privies or water- closets should be provided near the pit mouth. Miners should be informed of the necessity of being careful with reference to the food consumed underground ; this should be kept covered in tin cans or paper and only handled through paper, and the hands should be kept out of contact with the mouth. The men should wash and change clothes before partaking of food upon their return home after work, and to promote tliis practice spray baths and dressing-rooms should be provided near the pit mouth. Miners very rareh' drink am^ mine water (except in some excep- tional circumstances abroad) ; thej^ take their drink down into the mine with them ; but the men should realize that imder no circumstance is it safe to drink mine water, and that if such water is used for rinsing the hands it can never sufficiently cleanse them. Stagnant water in the workings should be reduced to a mini- mum ; and where there is running water the channels should be kept clear and the water not allowed to '' pond " in places through waste matter blocking up the channels. No new hand should be employed without previous medical inspection, and a careful inquiry into his previous infectious disease history. If he has recentl}^ had enteric fever, or if there is a possibilitj" that he may be harbouring the ankylostoma, his dejecta should be first examined bacteriologically ; and all cases of illness should be promptly reported to the manager or agent. Provision should be made at the nearest bacteriological labora- tory for samples of dejecta to be examined. The special rules relating to the dejecta which have been made under The Metalliferous Mines Regulation Acts, 1872 and 1875, are to the following effect : — (5) The o^vner, agent, or manager shall cause a sufi&cient number of suitable sanitarj' conveniences to be provided above and below ground in convenient places for the use of the persons employed, and to be constantly kept in a cleanly and sanitary condition, and no person shall relieve his bowels below ground elsewhere than in those conveniences. No person shall soil or render unfit for use in any waj' an)^ convenience or sanitarj' utensil or appliance provided- for the use of the persons employed. Pump cisterns, sumps, and water accumulations in the mine shall not be in- directly used for the purpose of a sanitarj^ convenience. (6) It shall be the duty of the o^^^ler, agent, or manager to see that plant, material, and other things necessarj^ to enable the above rule to be carried out are provided and maintained in working order, and to appoint sufficient competent officials to enforce the requirements of the rules, and for this purpose to assign to each his respective duties. disposal of refuse iiq Defective Sanitary Arrangements in Houses. In examining houses, all sorts of appliances and arrangements will be found departing more or less from the sound principles we have laid down, and we will now briefly describe a few of the sanitar}' defects still to be found in houses. Drains, rectangular, barrel, or oval in shape, constructed of bricks set in mortar without any cement, and of large size (i8 inches or more in diameter), are not unusually found under the basements of houses, and are sometimes connected with brick cesspools in these positions. These brick drains, although originally intended only to cany off surface and house waters, will sometimes be found to receive the water-closet discharges as well. They invariably leak, for the mortar becomes loosened from the bricks, and water finds its way out through these open spaces ; in some cases all the liquid leaks out of the drain to saturate the surrounding soil, whilst the solids accumulate in the drain until it is completely blocked. As the brick drain communicates directly with the sewer, rats find their way into it, and, pushing through the loosened bricks, form runs under the house and sometimes into the larder, which become passages for foul air. To ascertain if a brick drain exists under a house, the ground must be taken up ; or the sewer can be entered, if large enough, and the drain examined where it joins the sewer. Pipe drains are always preferable to leaky brick drains, but all sorts of mistakes are made in laying pipe drains, and the resulting evils are similar to those arising from brick drains. In the first place, the pipes may be of improper material, such as unglazed porous earthenware, and without proper sockets. If glazed stoneware socketed pipes are used, the drain may be laid for the whole or part of its length with insufficient fall, or with a fall the wrong way. Again, the pipes used ma}^ be, and often are, much too large — g-inch pipes where 4-inch would be suffi- cient ; or the pipes may be laid the wrong way with the socket end downwards or towards the sewer. The pipes are sometimes laid dry, i.e., without any luting material in the joint, or the luting material used may be clay, which is soon washed out of the joints. Even where the joints are luted with cement, if the drain is laid on uneven ground settlement takes place and the cement joints become cracked and leaky. 120 HYGIENE AND PUBLIC HEALTH Bends in drains are often made by fitting straight pipes into one another, the result being an open joint on the side with the greater curvature. The junctions of branch drains are some- times made by knocking a hole in one side of the main drain sufficient^ large to receive the end of the branch, which projects more or less and constitutes an obstruction, the hole being filled in with clay or cement. Even where proper junction pipes are used, the junction may be made the reverse way, so that sewage from the branch enters the main drain in a direction opposed to the flow of sewage in it. WTiere a small pipe joins a larger pipe, the junction is often effected %vithout a diminishing pipe by placing the socket end of the small pipe into the socket of the larger pipe, and the joint that results is most defective. In this case also, the smaller pipes ^^dll be all laid the wrong wsiy (with the socket end do'WTi- wards), and junctions ^^^ll be wrongty connected in a direction opposed to the flow of sewage. The e\als arising from such defects in drains are leakages of foul liquid into the soil, escape of foul air, and formation of foul deposits in the drains, leading eventually to complete obstruction. House drains were, and are stUl, commonly connected directh^ with the common sewer, an iron flap trap only being placed over the opening of the drain into the sewer. This flap trap affords no protection against the passage of foul air or rats from the sewer into the drain. It was formerty the custom to place a difstone trap (fig. 32) on the course of the drain to prevent the passage of foul air up it. It consisted of a brick chamber of some depth retaining liquid, into which dipped a stone fixed in the roof of the trap. This trap not being self-cleansing, because the upper part of the trap, though soiled with splashings, is never flushed, becomes choked with deposit, which putrefies and causes a most offensive nuisance. ^Vhere disconnection is prac- tised, it is not uncommon to find siphons too large, or of improper construction, and incapable of complete flushing ; in some cases the siphon is so constructed that the outlet is higher than the inlet, with the result that the sewage is backed up in the drain. One of the worst forms is that in which a vertical access pipe rises from the dip of the trap, for in this pipe solid matters are bound to accumulate. Soil pipes are very commonly found fixed inside the house. ]i of lead, the pipe maj^ be longitudinally seamed for its whole DISPOSAL OF REFUSE 121 length, with perforations in the seam of solder, and the joints may be formed by slipping one length of pipe inside the other. Cast-iron pipes with loose packed joints occasionally do duty as soil pipes, and may perhaps take rain-water as well. Zinc is sometimes used for soil-pipes ; where it has been long in use, it is sure to have numerous perforations. In old houses the soil pipe is almost invariably unventilated ; that is to say, it is not open, but closed at its highest point. The foul air in un- ventilated pipes acts on the lead (or zinc) walls, and gradually, by erosion, forms holes through which foul air or liquids escape. But such closed soil pipes are often in reality— though not so intended — ventilated into improper places, for the foul air in the drain and soil pipes is sure to find some way out. Where the waste pipes of baths, sinks, or lavatories are con- nected directly with the D trap under a water-closet, with the soil pipe, or with the drain, foul air will find its way out through these waste pipes, or through bell traps into the house. An- other ready means of exit of foul gases is the waste pipe to the safe-tray under a bath or water-closet, when this is connected with the soil pipe or drain. Another sanitary defect sometimes found is the direct connec- tion of the overflow or standing waste pipe of a drinking water cistern with the drain or soil pipe (fig. i8). Other means by which foul air can escape from unventilated drains are bell traps (fig. 32) in the basement of the house (kitchen or scullery), or in yards and areas, and rain-water pipes directly connected with the drains. In this last case also, foul air will escape through any loose or open joints of these pipes, which may be in close proximity to bedroom windows. With an unventilated drain, water traps — even the best designed — as we have already seen, are not effectual safeguards against foul air entering the house. Bell traps, which present Fig. 32. Sink with Double Trapped Waste Pipe. A, bell trap ; B, dipstone trap. 122 HYGIENE AND PUBLIC HEALTH SO small a seal of water and which are usuallj^ choked with rubbish, are often incapable of preventing the passage of foul air. It is very usual, too, to find the bell removed and the trap consequentl}' useless, because the obstruction to the flow of water through the trap is so great. The aspirating effect of fires inside a house must not be lost sight of ; the draught up the chimney tends to draw air towards it, from any opening, into the room ; and thus it often happens that drain or sewer air is drawn into the living rooms. \'VTiere some attempt has been made to ventilate the soil pipe, it is often either inadequate, as when a i-inch pipe is carried up as ventilator to a 4-inch soU pipe, or it is improperly carried out, as when a rain-water pipe is led into a soil pipe and also acts as a ventilator. Besides the danger of foul air escaping into windows, especially attic windows under which the rain- water pipe often commences, it is obvious that during a storm of rain, when it is most necessary to provide a safe means of exit for displaced drain air, the ventilator may be running full of water and will be useless. The pan closet and D trap were perhaps the most common of all insanitary appliances, but of recent years it has become rarer to find examples of these defective contrivances. They should, wherever found, be replaced by improved forms of closet and trap. The pan closet is usually supplied with water from the same cistern that supplies drinking water, the supply pipe being connected with a small service box at the bottom of the cistern {vide fig. 18). Water is admitted into the service box by a spindle valve guarding an opening in the top of the box, this valve being connected with the handle of the water-closet by wires and cranks, and an air escape pipe rises from the service box to give exit to displaced air. When the handle of the closet is pulled up, the spindle valve is raised from its seat, water enters the service box, and air is forced up the escape pipe to be discharged over the surface of the water in the cistern. . Now the supply pipe and service box are always full of air, which, ascending from the closet basin, is often befouled, and it is this air which escapes over the water of the cistern and may cause pollution. Hopper water-closets are often found to be supplied with water direct from the house main. During an intermission of the water service the tap may be left open, and foul air or liquid DISPOSAL OF REFl^'SE 123 filth may at such times be sucked up from the closet basin into the water pipes. Several outbreaks of enteric fever ha\'e been attributed to this cause. Sewers. Sewers are underground channels designed to receive and convej'' away by gravitation the rainfall and waste waters of the town, and, where the water-carriage system has been adopted, excretal refuse as well. In former times, and in some towns at the present day, if a river or stream passed through or near a town, the sewers took the shortest available course to the banks of the stream, and there discharged — each sewer by its own out- fall. When it became no longer possible for towns to discharge their crude sewage into streams in this manner, intercepting sewers of large size had to be constructed to receive the sewage of the tributary sewers and conduct it outside the town. As we have already seen, brick sewers, as originally con- structed, perfomi a double function ; they are land drains as well as sewers. By permanently lowering the level of the subsoil water in towns, these sewers have had an important effect in improving the health of the inhabitants. But the beneficial influence of sewers acting as drains has an undoubted drawback, viz., that drain sewers will readily permit of foul liquids percolating out of them, through their walls, to pollute the surrounding soil and contaminate ground water and ground aii- in the neighbourhood. That such escape of foul water does take place is plainly shown by the fact that in London with its drain sewers, all shallow well waters have been found to be polluted with sewage, and the wells have in consequence been closed. It is now the practice of all engineers to construct sewers as far as possible water-tight, and to provide other means for draining the soil. The Combined System. — In this system the sewers are designed to receive the rain — or such part of it as does not evaporate or is not retained by the soil — falling over the area covered by the town, as well as the sewage proper. The amount of evaporation depends largely on the temperature of the air ; but even in summer it is found in towns, where a large part of the surface exposed to rainfall consists of roofs and paved surfaces of yards, courts, and streets (especially also where there are steep gradients), that from one-half to three-quarters of the rain falling 124 HYGIENE AND PUBLIC HEALTH reaches the sewers. It is therefore necessary to construct the sewers of sufficient si^e to take a large part of the rain falling during heavy storms, such as | inch of rain in one hour in towns, and i to J inch in the suburbs ; otherwise, if no storm overflows are provided, the sewers in low-lying districts are overcharged, and cellars and basements are flooded. In London the inter- cepting sewers were constructed to receive J inch of rain over the whole area sewered in twenty-four hours (including subsoil water) ; but storm overflows direct into the Thames relieve these sewers during heavy storms. When a storm occurs after a time of drought, the sewers are flushed of accumulated deposit, and the sewage which first escapes by the storm overflows is often very strong and foul, and productive of nuisance in the river. At high-water, too, the storm overflows are tide locked, and then low-lying districts may be flooded. This principle of the interception of sewage is also commonly practised in seaside towns where the original sewers have been given a direct course to the sea, and the escaping sewage gave rise to offence. The intercepting sewer running along the sea- shore picks up the original sewers, and conveys the sewage to its outlet some distance away from the town. Such a main outfall sewer discharging into the sea should terminate below the water-level, even at low tide, and should have the outlet protected by a flap valve. To prevent deposits, sewers should be rendered self-cleansing by being constructed with a sufficient gradient, and of a size suitable to the volume of sewage which they will ordinarily be required to carry. According to Mr. Baldwin Latham, sewers of from 12 to 24 inches diameter should have a gradient sufficient to produce a velocity of not less than 2J feet per second, and in sewers of larger dimensions in no case should the velocity , be less than 2 feet per second. For large sewers a less gradient is required than for small sewers to produce the same velocity ; but the volume of the sewage to be conveyed must be very much greater for the large than for the small sewer. A sewer 10 feet in diameter having a fall of 2 feet per mile ; a sewer 5 feet in diameter having a fall of 4 feet per mile ; a sewer 2 feet in diameter having a fall of 10 feet per mile ; and a sewer i foot in diameter with a fall of 20 feet per mUe, will all have the same velocity of flow, but the volume of sewage in the lo-foot sewer must be 100 times, in the 5-foot sewer 25 times, and in the DISPOSAL OF REFUSE 125 2-foot sewer 4 times, the volume of sewage in the i-foot sewer. To calculate the discharge from sewers, the following formula is generally used ; — Let V=velocity of flow in feet per minute. ,, D= hydraulic mean depth. ,, F— fall in feet per mile. Then ¥ = 55 ^/Dx 2F. If A = sectional area of current of fluid, Vx A = discharge in cubic feet per minute. The hydraulic mean depth is the sec- tional area of the current of fluids the wetted perimeter [i.e., that part of the circumference of the sewer wetted by the fluid flo\Aang through it) ; in circular sewers running full or half full it is one-fourth the diameter. The term, when applied to a sewer, implies the depth of a rectangular channel whose sectional area equals that of the curvilinear channel under consideration, and whose width is equal to the entire wetted peruneter of the latter. In modern systems of sewerage, the sewers are laid in straight lines with manholes at every point of change of direction. The inspection and cleansing of the sewers is much facilitated by such an arrangement. The best form of sewer in all cases in which the volume of sewage undergoes fluctuation is the egg- shaped, the small end of the egg being downwards. In this form there is a greater depth of sewage and less contact with the walls of the sewer (and consequently less friction) than in any other form. For outfall sewers, in which the volume of sewage to be conveyed is large and uniform, Mr. Baldwin Latham advises the circular form, as it is cheaper and stronger when constructed. Up to 18 inches internal diameter, sewers should be circular in section ; and for these small sizes, stoneware, cement, or concrete pipes are better than sewers constructed of brick. Iron pipes and patent joints in stoneware pipes are often used in damp sites. No public sewer should be less than 9 inches in diameter, owing to the risk of smaller pipes becoming obstructed and stopped up b}- articles improperly introduced into the house drains. Sewers of unequal sectional area should not join wdth level inverts ; but the bottom of the lesser sewer should have a fall into the main at least equal to the difference between the diameters of the tributary and the main sewer. 126 HYGIENE AND PUBLIC HEALTH Well burnt, tough, impervious bricks, or glazed firebricks, should be used in the construction of sewers, especially in the construction of the lowest segment or invert of the sewer, which is the part most liable to wear and erosion from the passage of stones and grit in the sewage over it. For the smaller sewers suitably curved bricks only should be used. Sew^ers under 3 feet in diameter, when laid in good ground, may be constructed of 4J-inch brickwork. When laid in bad shifting ground, or for larger sewers, g-inch brickwork should be used. Suitably curved stoneware blocks are sometimes used for the inverts of sewers ; their smooth hard upper faces forming an excellent floor for the sewer. When these blocks are made hollow, they provide a means of draining off the subsoil water during the construction of the sewer ; but engineers do not now advise their use, as the hollow block is apt to split from the weight of the sewer built over it ; and in sandy soils sand in the subsoil water passes into the hollow blocks and may cause settlement of the sewer. The mortar used in jointing the bricks should be made of the best Portland cement and fine sharp sand. The Separate System. — Where it is intended to convey away sewage proper onty, storm, surface, and subsoil waters being separated, the sewers need be only of small size. Under such circumstances glazed stoneware pipes, jointed with Portland cement, are generally used to form the tributaries, whilst the outfall sewer is constructed of brickwork. Cement or silicated concrete pipes have been used, especially in Germany, instead of stoneware pipes. They are said to be less brittle, to withstand extremes of climate, and to resist the chemical action of the sewage better than stoneware pipes. Under the separate system, the sewers, of whatever material, must receive water- closet sewage and waste waters only ; all rain-water from yards, or areas, must be conveyed by separate pipes into surface channels at the sides of the streets, when the gradients are sufficient, or into underground channels constituting a system of drains quite distinct from the sewers. At convenient points the surface channels or underground drains should discharge into the stream or river which forms the natural drainage bed of the locality. The drainage of the subsoil should be effected by agricultural tile drains laid in the same trench, but above the sewers, and diverted into the watercourses at all suitable points. DISPOSAL or REFUSE I 27 The advantages of the separate system are : (i) The volume of sewage to be conveyed outside the town is small as compared with that to be dealt with by the combined system ; its daily or seasonal fluctuations, and the total quantities to be dealt with, can be calculated approximately from the population and water supply (points of great importance where the sewage has to be pumped to the outfall, or to be purified before being discharged) ; (2) the sewage is uniform in composition because protected from dilution with storm waters, and its purification and utilization day by day are therefore undertaken with much less difficulty than is the case with sewage which is sometimes strong and at others very weak from admixture with rain and subsoil w^aters ; (3) the sewers, being small and having smooth walls, are more frequently flushed, and there is less tendency to deposit, with formation of foul gases, than in the case of the larger brick sewers. The disadvantages are : (i) That every house must have two drains or two sets of pipes — one for sewage and the other for rain-water ; and this gives rise to mistakes on the part of builders, who occasionally connect the pipes with the wrong system ; (2) that the surface water from yards and streets is often too foul to admit into a stream, especially when a storm succeeds a period of drought, unless the yards and streets are constantly cleansed and well scavenged ; (3) that the flushing effect on the sewers of storm waters is lost. It is, however, sufficiently obvious that these disad\-antages in no way counterbalance the undoubted advantages of the separate system. Inspection, Flushing, and Ventilation of Sewers. In any system of sewerage it is necessary to provide means of access to the sewers for their cleansing and for the removal of accumulations of deposit. Manholes are shafts sunk from the surface of the road to the sewer, by which the sewer-men can descend. They are constnicted of brickwork, and pro- vided with a locked iron door at the street level. In streets where there is much traffic, the shaft is sunk from the footway perpendicularly for a short distance, and then carried down by means of steps to the side of the sewer. In other cases the manholes are sunk from the middle of the road to the crowm of the sewer. They have also a variety of other uses ; they are used as points of junction between tributary pipe sewers and 12a HYGIENE AND PUBLIC HEALTH the main sewer, curved channels being constructed in the floor of the manhole ; and they are also the points at which flushing gates may most advantageously be fixed in brick sewers. Flushing gates are sluices made to fit the whole or part of the sectional area of a sewer. When in position they dam back the sewage in the sewer above, and on being raised, or liberated, the sewage so stored rushes forwards and effectually flushes the sewer below. Self-acting gates are often used for this purpose. The gate being hinged below its centre, the pressure of the sewage on that portion of the gate which is below the hinge fixes it in position. As the sewage rises, the upper portion of the gate is likewise exposed to the pressure of the sewage, and presenting a larger area than the part below the hinge, a point is at length reached when the gate tilts, assuming a hori- zontal position, and the sewage escapes. Flushing gates are not used for flushing the upper ends of brick sewers, nor are they used for flushing pipe sewers. For these purposes, automaticaUy discharging siphon flush tanks find a most useful application. They should be supplied with water from a tap connected with the town water mains, and regulated to discharge at intervals as required. It might be thought that the pipe sewers used with the separate system do not require artificial flushing. But experience has taught otherwise, and it must be remembered also that under this system the sewers are not flushed by storm waters. There can. be no doubt that heavy rainfall is very effectual in flushing sewers ; but besides introducing a quantity of grit and sand from the roads, rainfall cannot be depended upon in this climate to occur at properly recurring intervals, and is often absent for long periods in summer, when sewer deposits are most abundant and offensive. The ventilation of sewers is a matter of importance, as the health of a sewered district probably depends to some extent on the efficiency of the sewer ventilation. The most offensive gases are given off from sewers in which deposit forms, such as the old-fashioned brick conduits with flat bottoms, or oval sewers in which a portion of the invert has sunk below its proper level, or sewers which are too large for the volume of sewage they ordinarily convej^ and in which the deposits and slime, formed on their floors and sides, are not removed by flushing. Outfall sewers in which sewage is, for DISPOSAL OF REFUSE 1 29 any reason, backed up and stagnant during a portion of the day are also liable to become sewers of deposit. The deposit rapidly putrefies, giving off offensive gases, which escape through the nearest ventilator ; or should the sewer be insufficiently ventilated, the foul gases find an exit through house drains and traps into the interior of houses. In all sewers, owing to the constant variation of the flow of sewage through them, some deposit forms on their sides, which, being alternately wet and dr\^ rapidly putrefies and parts with its putrefactive ferments to the sewage flowing b}'. In pipe sewers there is less tendenc}' to deposit than in brick sewers of larger diameter, owing to the smooth interna] surfaces of the pipes, and to the greater frequency with which they are washed, as pipe sewers are more often running full or nearly full than brick sewers. Natural ventilation of sewers, b}^ which movements of air in them are produced, is due to a variety of causes, the most important of which are : — (i) Where there is a strong and rapid stream, a current of air is produced which is in the same direc- tion as the sewage stream, and of proportional velocity. Most of the openings into the sewers will be inlets for fresh air (drawn in by the current of air beneath), which finally escapes through the outfall sewer. (2) During the cold months of the year, the temperature inside a sewer is, owing to the warmth of the sewage, higher (average about 7"^ F.) than that of the external atmosphere, consequently the warmer sewer air tends to rise and to be replaced by the cold external air. During the warm months of the year the temperature of the sewer is by day often considerably cooler than the external air. In spring and autumn the temperatures inside and outside are more nearly equal. (3) The air of sewers is generally saturated with moisture, and therefore lighter as a rule than the general atmosphere outside, both in summer and winter. For this reason sewer air generally tends to rise up from any openings into the sewer. (4) The passage of hot liquids from houses and from factory boilers causes a rise in the temperature of the sewage and ex- pansion of the sewer air. Blowing off steam from boilers into sewers causes a great rise of pressure, and unless ample ventila- tion is provided house traps will be forced. (5) During the early part of the day, the volume of sewage in the sewers increases rapidly to a maximum, and air is consequently slowly expelled, 9 130 HYGIENE AND PUBLIC HEALTH to be replaced by inflowing air as the level of the sewage falls. The rising of the tide in an outfall sewer, not protected b}' a tidal valve, will also displace air, but the displacement is so gradual as to be almost inappreciable. \'\Tiere storm waters are admitted into the sewers, sudden heavy rainfalls exert a marked influence in expelling air, which is somewhat counter- balanced by the aspirating effect produced b}-^ the flow of air in the direction of the current. (6) Sudden falls of barometrical pressure cause air and gases dissolved in the sewage to be given off. (7) Sudden variations in temperature of the external air produce variations in pressure of the sewer air. A high tempera- ture favours decomposition of the sewage and evolution of gases. Openings into the crowns of sewers from the surface of the roadway should be made at distances of not more than 100 yards apart. Some of these will act as inlets, and others as outlets, and the pressure of air in the sewer will at no time be able to rise sufficiently to force the traps on house pipes and drains. There are objections which apply to the method of ventilating sewers by means of the soil pipe ventilators of houses, as when this method is carried out there must be no disconnecting traps to the house drains and fresh-air inlets to the drains cannot be fixed. Sewer air escaping in large voliunes near dormer windows might also cause a serious nuisance. MTiere a dis- connecting trap is fixed on the house drain, a 4-inch pipe may be carried up to the ridge of the roof from the drain on the sewer side of the trap, its end being left open ; and it will be found useful as an exit for sewer air when used in combination with road ventilators. But it is needful to bear in mind that where rain-water is admitted to the sewers, during heavy rainfall when ventilation is most required for affording a safe exit for suddenly displaced sewer air, house drains, or any part of them, are often useless for this purpose, as their openings into the sewer may be sealed by the height at which the sewage is flowing in the sewer. The best form of street ventilator is the shaft sunk from the middle of the roadwa}^ to the crown of the sewer. Beneath the grating at the surface of the street should be placed a dirt box to catch gravel and mud, which would otherwise fall into the sewer, a space being left around the box for the passage of air. The dirt box should be capable of removal from the surface of the road. Ventilators may also be constructed in connection DISPOSAL OF REFUSE I3I with manholes. A shaft is sunk for a short distance by the side of the manhole, openings being made between them for the passage of air. Mud and gravel fall to the bottom of this shaft, from which a pipe conducts the water to the sewer beneath. The air which escapes from the sewers by these street ventilators is rapidly diluted with fresh air ; and, from their position in the centre of the roadway, there is the least chance of offence to foot passengers or of foul air gaining entrance to houses. In narrow courts and streets, especially at the upper or dead ends of sewers, the surface ventilators should be replaced by shafts carried up from the crown of the sewer to above the tops of houses ; for it is desirable to avoid any risk of foul sewer air collecting in stagnant courts and streets surrounded by buildings, in which rapid dilution of the sewer exhalations with fresh air might not always take place. Street gulleys should be effectually trapped, both to prevent mud and sand entering the sewer, and to avoid an escape of sewer air close to the footways and the fronts of houses. Iron wire baskets containing small wood charcoal were at one time extensively used to sweeten the air escaping through the ventilators. When dry they exercise considerable influence in oxidizing and deodorizing organic vapours. But they rapidly become wet from rain and watery vapour, and then they are not only useless as deodorizers, but the pores are so clogged as to obstruct all passage of air through them. For these reasons their use has been nearly everywhere discontinued. Various processes (such as Reeves') have from time to time been patented for deodorizing the sewer air escaping from street ventilators by bringing it in contact with gases, generated by the automatic and gradual mixing of different chemical solu- tions. • More recently a method of cremating the sewer air, by passing it over or through a gas flame placed in a chamber at the top of the ventilator, has been tried. By this method the escaping sewer air is heated, possibly even to the point of steriliza- tion, whUst the combustion of the gas tends to create an artificial draught up the sewer ventilator. There can be no question that any general adoption of such systems is undesirable. If the sewers are well laid and self- cleansing, they are not required. Should the sewers be so old and dilapidated as to be generally offensive throughout a district, it would prove more satisfactory and far more beneficial to the public health, to reconstruct them 132 HYGIENE AND PUBLIC HEALTH on modern principles than to inaugurate a system of concealing the effects without attacking the cause. Where sewers are laid with steep gradients, it is found that the current of air tends to pass in the reverse direction to the flow of the sewage from the low to the high levels. To prevent the escape of large volumes of foul air at the upper parts of a sewered district, it is therefore necessary to construct at various points a tumbling bay — with manhole and ventilator opening above at the street level. Then the sewer air in its course upwards meets a flap valve, hung from the crown of the sewer immediately over the tumbling bay, and is forced to escape into the outer air through the ventilator. It was at one time thought that by connecting sewers, by means of shafts, with a furnace chimney, a powerful extractive force, useful in ventilating a large portion of the system, would be put in operation. By this method, however, a great draught for a short distance only is produced, as air rushes in from all openings in the neighbourhood to supply the place of that extracted by the furnace. Beyond a very short distance no effect is produced, and there is besides considerable risk of traps in houses being drawn. If any such method is adopted, the chimney selected should be one in connection with a furnace which is kept going day and night throughout the entire year, and all untrapped openings into the sewers in the neighbourhood of the furnace must be carefully closed. At the same time the connections of house drains to the sewers should be examined, to make certain that such an intercepting siphon trap exists on every drain as will not become unsealed. The method is really only applicable to large main sewers which do not receive house drains, but intercept the sewage from tributary sewers. Outfall Sewers. — In some cases it may be necessary to carry the sewage of a town across a river or a valley. This may sometimes be done by bridging ; but usually the outfall sewer is at too low a level to permit of it. In such cases the sewer should be carried across by means of an inverted siphon, formed of wrought-iron pipes with riveted flange joints, laid in the bed of the river or valley. Arrangements must be made for pre- venting the accumulation of solid matters at the lowest point of the siphon, resulting eventually in a stoppage, to which there is a tendency unless the current through is of sufficient velocity to carry all solid matters with it. With this view the sewage DISPOSAL OF REFUSE I33 ma3^ be strained before passing through the siphon, or the siphon must be periodically flushed. To give exit to air under pressure in the siphon, which might prevent its proper action, a ventilating pipe should be attached to the descending arm. The Disposal of Sewage. The disposal of the sewage of a town or district is often a most difficult problem to solve. Since the Rivers Pollution Prevention Act became law in 1876, it has been illegal to discharge crude sewage into a stream — this term including rivers, streams, canals, lakes, and watercourses, other than watercourses mainly used as sewers, and also the sea to such extent, and tidal waters to such point, as may after local inquiry, or on sanitary grounds, be determined b}^ the Local Government Board. It is greatly to be regretted that this Act has in many parts of the country entirely failed to prevent the continued pollution of streams, from which the community has already so largely suffered. X^Tiere sewage is discharged into fresh running water and at once largely diluted, it becomes in course of time to a great extent purified. Distributed through a large volume of river water, the organic matters are oxidized (through the aid of nitri- fying bacteria) by the oxygen dissolved in the water and by that given out by minute water plants (algge, diatoms, and desmids), and are also assimilated by minute animals (infusoria, rhizopoda, entomostraca, anguillulae, etc.). They are thus purified, or got rid of, without the occurrence of putrefaction and the formation of offensive gases, which must occur when the sewage is not sufficiently diluted with fresh water and the temperature of the air and water is high— the growth of fermentative bacterial organisms then taking place to such an extent as to cause putre- faction. Putrefactive bacteria will no doubt in time break up complex organic matters into their constituent parts, and thus purify sewage ; but the process is one productive of nuisance and injury until the ultimate effect is attained. In the case of tidal sewage-polluted rivers, the Reports of the Royal Commission on Metropolitan Sewage Discharge show that the only true sources of dilution of the sewage are the land water entering from above, and the sea water from the mouth of the river. During dr^^ weather, when the quantity of land water is slight, the displacement of the sewage towards the sea is very slow (about a quarter of a mile daily in the case of the 134 HYGIENE AND PUBLIC HEALTH Metropolitan sewage) ; so that the sewage discharged on any particular day oscillates up and down the river with the tide, and is continually receiving fresh increments. The sewage, too, that is discharged after high water on an ebbing tide wUl be carried up by the flowing tide above the outfall ; and when neap tides are giving place to spring tides, the whole volume of dis- charged sewage is carried up higher and higher above the outfalls every day as the spring tides increase. The consequence is that at such times the sewage may be carried in the river up to or above the town so discharging its sewage. The effect, too, of the sea salts in estuary water is to cause a precipitation of organic matters and a deposit of mud, whilst the oxidation and purification processes are delayed by their presence. If the volume of sewage discharged is relatively small to the volume of water in the river, the sewage will in time be purified ; but such water can under no circumstances be a proper source of supply for drinking water. Under certain circumstances crude sewage may be discharged directly into the sea without risk of nuisance and offence. If the sewage can at all times be borne away from the shore out to sea, it becomes mixed with an immense volume of water and rendered harmless. The danger is that sewage may be cast up by the tide on the foreshore, or borne along by currents the whole length of the sea front of a town. To avoid such an event, the outfall must be chosen at such a spot that the sewage, at whatever state of the tide it may be discharged, shall be carried by currents, where such exist, straight out to sea, or at least in a direction away from the town. The direction of the currents may be ascertained by means of float experiments. The outfall sewer must open below the level of the water at all states of the tide, and its mouth should be protected by a tidal valve to prevent sea water entering it. The prevailing winds should also be studied, to prevent the possibility of floating fseca] matters being blown back on to the beach. If the town lies at a low level, so that its sewers are tide locked for several hours of each tide, tanks must be constructed to retain the sewage which accumulates at such periods ; or a certain length of large oval tank sewer must be built to serve the same purpose. Tank sewers, however, are very generally productive of nuisance. The tide-locked sewage stagnates in them, and a DISPOSAL OF REFUSE 135 copious deposit of sediment takes place which gives rise to the formation of foul gases. In such cases no amount of ventilation suffices to obviate the nuisance. It is better to have recourse to steam pumping at the outfall, or to use Shone's Pneumatic Sewage Ejectors to relieve the sewers of their accumulated sewage. Shone's sj^'stem is now in operation at several towns lying on low flat ground, and has been found very beneficial in preventing the evils which result from absence of proper sewer gradients. The motive povv^er is compressed air, which is conveyed from a central station by wrought-iron pipes to the cylindrical reser- voirs or " ejectors," which are situated in ch ambers beneath the streets at different parts of the town, and receive the sewage from the street sewers. When the ejectors are full, a valve opens and compressed air is admitted by means of a float acting on a counterpoise lever, and the sewage is thereby forced out into a gravitating sewer at a higher level. A ball valve in the pipe sewer entering the " ejector " prevents the sewage from being forced backwards by the compressed air ; and as the sewage is discharged and its level sinks in the " ejector," the sinking of the float closes the valve of the compressed air tube, and a fresh charge of sewage can then enter. The great advantage of the system is that good gradients can be given to the sewers, for the ejectors are placed at sufficient depths below the surface of the ground to permit of house drains and street sewers, with which they are connected, having a good fall ; and the sewage can thus be carried away and forced out of the town in a fresh con- dition. In addition, no storage is required as in ordinary pump- ing, for the rate of working of the ejectors varies with the rate of flow of the sewage into them, although the air compression machinery at the central station works nearly uniformly. Liernur's pneumatic system of sewage removal and treat- ment is carried out at Amsterdam and Trouville. It is claimed to be especially applicable in towns where the water supply is limited, and where the ground is too flat to admit of good sewer gradients. There is an air-tight system of sewers, the contents of which are drawn into closed chambers fixed in different parts of the town, by means of a powerful air pump at a central station. From these chambers the sewage is sucked into a steam concen- trator at the central station, and is there heated to about ioo° C, after the ammonia has been fixed by the addition of bulphuric 136 HYGIENE AND PUBLIC HEALTH acid. The dried sludge (" poudrette ") finds a ready market as manure. It appears that the pipes tend to get clogged, but otherwise the system works well. The Purification and Utilization of Sewage. It can safely be said that in this country no stream or river should ever receive crude sewage ; for so numerous are the towns on the banks of nearly every stream, that, although the sewage of one town might be purified alter a certain run, it would be quite impossible for any stream to purify the successive sewage discharges from every town on its banks. As the sewage must be purified before discharge, the question arises whether the manurial matters contained in it can be utilized, and made to pay the whole or part of the expenses incurred in its purifica- tion. It becomes necessary, then, to consider the amount and value of the manurial ingredients contained in ordinary town sewage. In the first place as to the chemical composition of sewage. The Rivers Pollution Commissioners give as the average in water- closeted towns, in 100,000 parts, 72-2 of total solid matters in solution, in which there are 6703 of ammonia ; total combined nitrogen, 7728 ; chlorine, 10 -66 ; and an inappreciable quantity of nitrogen as nitrates and nitrites. In 100,000 parts there are, besides, 44-69 of suspended matters, of which 20-51 are organic, and 2418 mineral matters. This is an average from a large number of analyses ; but it must be borne in mind that the sewage of different towns varies greatly in character, and that the sewage of the same town varies in strength from day to day and from hour to hour. To obtain an exact knowledge of the average strength of a day's sewage in any town, samples must be taken frequently — at least every hour — and to form a sample for analysis they must be mixed in such proportions as are indicated by gauging the flow of sewage at the time each sample was taken. In this way only can the average composition of the sewage be arrived at with anything like exactitude. The strength of the sewage depends on the number of water- closets in the town (proportion of water-closets to middens), the amount of water supply per head of the population, the amount of waste liquors discharged into the sewers from manu- factories, and, in the case of combined sewers, the amount of rain that has fallen and of subsoil water that has found its way DISPOSAL OF REFUSE I37 into them. During the early part of the day (in dry weather) the sewage of any town is strongest and the flow greatest, whilst at night the sewers may be discharging nothing but subsoil water. The chief valuable ingredients of sewage are the different forms of combined nitrogen, the phosphates, and salts of potash. The money value of these constituents in loo tons of the sewage of the strength noted above is 17s., the dissolved matters being worth 15s., the suspended 2s. This gives a value to the sewage of about 2d. per ton. We have already seen that the yearly excretal refuse of an individual of a mixed population is worth from 6s. 8^. to ys. {see p. 72), and this refuse, if diluted with water to form 40 tons of sewage (an average dilution of 24 gallons per head per day), will also give a value to the sewage of 2d. per ton. This dilution is about that of the London sewage during dry weather. It may further be stated that 855 tons of the sewage of the composition given by the Rivers Pollution Com- missioners contain i ton of solid matters (in solution and in suspension), estimated to be worth £y 5s. ^d. From such data as these calculations might be made of the total yearly value of the sewage of any town. But such theoretical calculations are very far from representing the real values available for agricultural purposes. The composition of sewage from midden towns {see p. 72) does not differ very materially from that of water-closeted towns. The Rivers Pollution Commissioners gave as the average com- position of midden town sewage in 100,000 parts : Total solids in solution, 82-4; organic nitrogen, 1-975 ; ammonia, 5-435 ; total combined nitrogen, 6-451 ; total solids in suspension, 39-11, of which 21-30 are organic matters, and 17-81 mineral matters. Sttbsidence, Straining, and Precipitation. By allowing sewage to settle in tanks, a portion of the sus- pended matters subsides to the bottom and a more or less clarified liquid can be decanted from the top. By straining crude sewage through beds of ashes or charcoal, the suspended matters are removed ; but the filters speedily become clogged, and require frequent renewal at great expense. Certain chemical substances, when mixed with sewage, cause a more rapid and copious precipitation of the suspended matters than can be effected by subsidence alone. The number of 138 HYGIENE AND PUBLIC HEALTH chemicals that have been used or advocated for this purpose is enormous, as may be seen on inspection of the specifications of patents taken out to protect the inventors of such processes. Lime — as lime water or milk of lime — sulphate of alumina, and protosulphate of iron, are the substances now most commonly used as precipitation agents. Lime is the most frequently employed — either alone or in combination with sulphate of alumina or iron. The precipitating effect of lime on sewage is due partly to its combination with carbonic acid, forming an insoluble carbonate of lime, and partly to its combination with some of the organic bases of sewage. These substances subside, carrying with them most of the suspended matters in the sewage, and sink to the bottom of the tank, forming the sludge ; whilst a more or less clear liquid remains above. If too much lime is added, the sludge and supernatant liquid, being strongly alkaline, tend soon to undergo decomposition. The proportion of lime usually added to sewage of average strength is about 12 grains to the gallon of sewage. The precipitating effect of sulphate of alumina on sewage is due to combination of the sulphuric acid with iime and other bases in the sewage, whilst the alumina hydrate is precipitated in a flocculent condition, entangling and carrying down in its course most of the suspended organic matters. The crude sulphate of alumina used as a precipitant is acid, and reduces somewhat the alkalinity of the lime when this material is em- ployed in combination with it. For treating sewage of medium strength the quantities need not exceed 5 grains of lime and 5 grains of sulphate of alumina per gallon of sewage. When protosulphate of iron is added to alkaline sewage or to sewage which has been already treated with lime, a highly floc- culent hydrated protoxide of iron is formed, which falls to the bottom of the tank, carrying suspended organic matters with it. The iron salt is also a powerful antiseptic, checking further putre- faction of the sludge and effluent, when used in sufficient quantity. But its use is attended with the disadvantage that the mud banks of the stream, into which the effluent is discharged, are blackened by the formation of sulphide of iron. When used with lime, protosulphate of iron should be added in the proportion of from 2 to 5 grains per gallon of average sewage. The London sewage is thus treated, the lime and iron being added in the DISPOSAL OF REFUSE 139 proportion of 5 and 2 grains, respectively, to the gallon of sewage. The combination of iron with alumina is also effective as a precipitating agent, and both enter into the composition of two well-known sewage precipitants — Ferr ozone and Aluminoferric. These three precipitating agents — lime, sulphate of alumina, and protosulphate of iron — cause a more or less complete deposi- tion of the suspended matters in sewage, and also remove the grosser sewage odour from the effluent ; but they have very little effect in removing from the sewage the organic matters in solution. Sulphate of alumina is said to have the effect of removing 5 per cent, of the dissolved organic matters of sewage, but lime and iron remove practically none. The matters pre- cipitated from sewage, which form the sludge at the bottom of the tanks, are comparatively worthless, whilst the bulk of the ^'aluable manurial ingredients remains in the effluent. ■ To insure the most complete clarification of the sewage liquid by chemical precipitants, the follo\Adng conditions must be satisfied : The sewage must be fresh and undecomposed, and the larger solid bodies should be strained from it before the admixture of the chemical precipitants. The chemicals must be added to the sewage immediatety before it arrives at the tanks, and must be well stirred and mixed up with it by means of rota- tory mixers. There must be sufficient tank accommodation. The Local Government Board requires that the tanks must be capable of holding the dry weather flow for 24 hours. The tanks are often arranged in series, so that the sewage maj^ pass slowlj^ but continuously through two, three, or four tanks before the supernatant liquid escapes into the effluent channel, which should be kept scrupulously clean. The tanks must be at least 4 feet deep, and the effluent passing out of a tank should flow over a weir not more than ^ inch below the surface into the next tank of the series, or into the effluent channel. After a certain period of continuous working, the flow of sewage through the series must be discontinued, and the sludge allowed to settle, the clear liquid above being drawn oft" through float valves into the effluent channel. Sometimes the chemically treated sewage is not allowed to pass slowdj" from tank to tank in series, but each tank is filled separatety. When fuU the flow is stopped and the sewage is kept at rest for from 2 to 4 hours (according to its strength) so that it may deposit its sludge. The clarified super- 140 HYGIEXE AXD PUBLIC HEALTH natant liquid is then drawn off. There should be a double set of tanks, in order that the treatment of the sewage may continue whilst the sludge is being removed. The sludge must be frequently removed or it \\iU putref}^ and black masses \vill be disengaged, which, rising to the surface, give off foul gases. The tanks, when emptied, must be thoroughly cleansed before being refilled. The form of precipitation tank with a conical bottom (the Dortmund tank) has the advantage over the old-fashioned flat- bottomed tank in so far that it permits the sludge, which falls to the apex of the cone, to be remo^•ed without first drawing off the supernatant effluent. Occasionally substances which act as deodorants or antiseptics are added to the sewage as well as the chemical precipitants. The addition of manganate of soda and sulphuric acid to chemi- call}^ treated sewage has been recommended by ]\Ir. Dibdin in order to promote oxidation. Another deodorizing method is that kno\^-n as the Amines process. The sewage is treated with milk of lime and %^ith a small quantitj^ of herring brine, which contains a certain percentage of the compound ammonia termed methylamine. This substance acts as a deodorant and antiseptic, so that the effluent undergoes no secondarj^ fermentation ; whilst the sludge is so far deodorized that it can be dried in pits exposed to the air, or on the floor of a drying kiln, without gi^dng rise to noxious efflu\da. It is now generally recognized that the use of deodorants, as auxiliaries to precipitation pro- cesses, is advantageous if they do not interfere \\dth the natural agencies of purification. In the Hermite system sewage is treated \\dth partially electrolyzed sea water. The electric current, generated by a djmamo, is passed through sea water contained in a galvanized iron tank, between electrodes of zinc and platinum. In doing so, magnesium chloride is probably decomposed, forming a disinfecting fluid of a strength equal to 075 gram of chlorine per htre. The active principle of the fluid may be an oxygenated compound of chlorine, hypochlorous acid, or hypochlorite of magnesia. The solution has the smeU of a weak solution of bleaching powder. It contains no free chlorine. It is claimed for the process by its inventor that the solution produces an instantaneous decomposition of faecal matter in sewage, and effectually sterihzes the sewage, but the experiments conducted at Worthing do not bear out these assertions. A solution of DISPOSAL OF REFUSE I4I bleaching powder in water would probably be equally effectual, and much cheaper. In the oxychloride process sea water or water containing 10 per cent, of common salt is electrically decomposed in an electrolyzer having a large superficial area of electrical surface, which permits the use of a high density current at a low voltage. The resulting liquid contains o-2 per cent, of available chlorine. From Dr. Rideal's experiments at the Guildford Sewage works it appears that when mixed with appropriate volumes of sewage effluents the oxychloride solution very largely reduces the total number of organisms present in the effluent, and practically eliminates Bacillus coli communis. Thus 3^ gallons of oxychloride per 1,000 gallons of secondary effluent, i.e., effluent from septic tank treatment, contact beds, and streaming filters, is sufficient after one hour's treatment to reduce the Bacillus coli from 100,000 per c.c. of untreated effluent, so that none could be found in i c.c. It is claimed for this process that whilst a sewage effluent cannot be actually sterilized by its means, yet organisms of intestinal origin can be so far eliminated as to render the effluent admissible into a stream supplying potable water, or into waters containing oyster layings or water-cress beds. Oxychloride solution itself is non-poisonous. In the ABC process, alum, blood, clay, and animal and vegetable charcoal are added to the sewage. The blood is said to act as a refiner, but in the small quantity used its action is probably nil ; the clay acts as a weighting material, carrying down the precipitated matters ; whilst the charcoal acts to a certain extent as a deodorant. A highly clarified effluent is pro- duced by this process on a small area of ground, and the dried sludge (" poudrette " or " native guano ") can be sold as manure. The suspended matters, or sludge, of sewage being deposited at the bottom of the settling tanks, the questions arise : What is to be done with the clarified sewage ? and, How is the sludge to be got rid of ? No nuisance will result if the effluent is dis- charged into a quickly running stream or river, whose volume is at least ten times greater than that of the effluent, and which is not used below the point of discharge as a source of supply of drinking water. The danger is that during drought in summer the volume of fresh water might considerably diminish ; and then, the effluent sewage not being sufficiently diluted, would putrefy and become turbid, forming foul deposits in the bed 142 HYGIENE AND PUBLIC HEALTH of the stream, and giving rise to offensive exhalations. This would be especially likely to happen if, at the same time, the temperature of the air was high. By this m.ethod, too, all the valuable manurial ingredients of sewage run to waste. The only satisfactory mode of purifying the effluent sewage is to carry it over land by irrigation, or through specially constructed filter-beds. Where it is not possible to obtain suitable land for this pur- pose, the partial purification of the effluent from the tanks may be effected by passing through specially constructed filters, consisting of burnt ballast, coke, coke-breeze, coal, or gravel ; or the filters may be composed of coarse sand laid upon magnetic oxide and carbide of iron (polarite). The nitrifying organisms in the pores of the filter exert a powerful oxidizing effect on the organic matters dissolved in the effluent, by which these are converted into nitrates and nitrites, etc. The slower the filtra- tion, i.e., the longer the effluent liquid is in contact with the particles composing the filter-bed, the greater is the purification. The filtration must be intermittent to allow of aeration of the filter. The sludge left at the bottom of the tanks is generally con- ducted into a well, and thence pumped out in a semi-liquid condition. It then contains from 90 to 95 per cent, of water. It may be got rid of by allowing it to flow, or by forcing it up, in this liquid condition, along raised carriers on to land, into which it is subsequently dug, thereby eventually becoming incorporated with the soil. This was the method pursued at Birmingham, the sewage being treated with lime, and the effluent from the tanks being purified by irrigation over the soil of the sewage farm. If the semi-liquid sludge is allowed to dry by exposure to the air in pits, it generally causes a nuisance, so that it is the usual practice to press part of the moisture out of the sludge by hydraulic filter presses, by which a solid cake, con- taining from 50 to 60 per cent, of moisture, is produced. The pressed sludge can be stored up without causing any nuisance, and sold or given away according to the demand for such sewage manure. It may be further dried by heating in drying machines, and then ground into a granular condition, when it generally contains some 20 per cent, of moisture. In this condition the manure is far more suitable for application to land than in the form of the coherent masses which issue from the filter presses. DISPOSAL OF REFUSE I43 Although the theoretical value of a ton of pressed sludge cake is calculated at 17s., the actual price obtained from the sale of this sludge cake varies in different towns ; in some there is no demand for it, and it is either burnt in a destructor furnace, used for raising low-lying grounds, or even a small premium is paid to farmers for removing it. Owing to the large amount of lime it contains its actual manurial value is but slight. Calculation. — State approximately the amount of moist sludge containing 90 per cent, of moisture that can be precipitated daily from the sewage of a population of 10,000, with a water-supply of 20 gallons per head per day. The sewage may be taken as equivalent to the water supply, viz., 20 x 2,000,000 10,000 = 200,000 gallons per day ; or lox 200,000 lb. by weight = — V^mE~ =892-86 tons. We will suppose that in every 100,000 parts cf the sewage 40 parts of suspended matter can be precipitated by chemical reagents. 40 Then the dry solids precipitated from the sewage amount to x J t- f D 100,000 892-86 tons =0-357 ton, and the moist sludge containing 90 per cent, of moisture will be lox o-357 = 3-57 tons. The Biological Purification of Sewage. The chief natural agencies concerned in the purification of organic matter are micro-organisms. It is almost entirely due to such organisms that organic matter — whether it be faeces deposited on the surface of soil, or an animal body buried within it — eventually becomes resolved into invisible and harmless gases and mineral ash, for sterilized organic matter remains undecomposed for indefinite periods, so long as sterility is maintained. Ever since cesspools were employed for the reception of the sewage of a house, it has been noted that the material which is periodically emptied out of the cesspool, or which overflows from it, is a liquid containing very little suspended solid matter. Solid matters in bulk are only encountered near the floor of the cesspool. How is it that a comparatively small cesspool, with an overflow discharging nothing but liquid material for a year or more, does not become filled with the large amount of solid faecal matter daily entering it ? The answer is that micro- organisms in countless myriads are constantly feeding upon this solid matter, and converting it into products which ultimately become dissolved in the liquid part of the sewage. The organisms which effect this change are of many forms, and may be broadly classified into three groups. 144 HYGIENE AND PUBLIC HEALTH 1. Those which work m the absence of oxygen (anaerobes). 2. Those which work in the presence of oxygen (aerobes). 3. Those which are capable of working either in the presence or absence of oxygen (facultative aerobes). Our knowledge of the last named group is not sufficient to enable us to speak with certainty as to the part they play in sewage purification, but it is certain that both the aerobes and anaerobes are concerned in the resolution of organic matter. With regard to these two classes of organisms, there are reasons for belie\dng that the anaerobes are the most efficacious in causing the liquefaction of the solid matter contained in sewage. Prior to attack by these liquefying organisms, the solid organic matter is in a more or less stable condition ; but as the result of their life action the complex organic molecule is split up into by- products, which are largely soluble and unstable, and considerable quantities of gases (CH4, NH3, CO2, and SH2) are evolved. This first stage of purification of sewage is closely analogous to the process of gastric digestion, whereby the organic matter is spht up and liquefied ; the gelatinous and albuminoid material undergoing a peptonizing process, and the non-nitrogenous substances being reduced, and finally converted into CO2 and H2O. As in digestion, also, the element of time is essential. The organisms must not, therefore, be asked to do their work in too short a time, or their activity will be unavailing. The second stage of purification is doubtless largely performed by the aerobes, and, in consequence, every effort should be made to set them their work under conditions favouring an abundant supply of available oxygen. The more or less stable solid organic matters having been broken up, rendered less stable, and thro^^^l into solution in the first stage, are in the second stage converted into the ultimate products CO2, NH3, HgO, and traces of SH2 ; nothing ultimately remaining but a trivial quantity of mineral matter, rich in nitrates, chlorides, and sulphates. It is only in recent j^ears that these natural agencies of puri- fication have been scientifically utihzed in the disposal of sewage in bulk, but we have already arrived at such a stage of know- ledge that some remarkable results have been achieved. The Royal Commission on Sewage Disposal, appointed in 1898, issued an Interim Report in 1901. In this Report they state that "It is practicable to produce by artificial processes alone, as opposed to land treatment, either from sewage or from certain DISPOSAL OF REl'USE I45 mixtures of sewage and trade refuse, effluents vvlucli will not putrefy, whicli would be classed as good according to ordinary chemical standards, and which might be discharged into a stream without fear of creating a nuisance." The advantages often gained over the older, or what may be termed the chemico- biological method (in which the sewage solids are first precipi- tated by chemicals, the comparatively clear effluent being then exposed to biological agencies in filter beds or in land), are obvious. The almost useless sludge which resulted from the chemical treatment, the collection and ultimate disposal of which entails considerable labour and expense, is reduced to a relatively small bulk (in the septic tank quite | of the suspended matters entering the tank are destroyed), and the cost of the chemicals and of their application is also saved. But the greatest gain is doubtless often in the direction of greater efficiency of treatment, which results in a purer and sweeter effluent — one more readily susceptible to the agencies of ultimate purification, and more valuable to vegetable life. We may now review the various means which have been adopted for utilizing these natural agencies in sewage purifica- tion. The first practical attempt to solve the problem was commenced by the Massachusetts Board of Health in 1888. The extensive experiments since made by that Board have established the fact that intermittent downward filtration through prepared filters of suitable material will, by reproducing the most favourable conditions of land filtration, achieve all the good results of the latter on a much smaller area. The experi- ment showed that the beds need not be of a greater depth than 4 to 5 feet, in order to treat satisfactorily 100,000 gallons of sewage to the acre per diem. In such beds, after a week of two of sewage treatment, the particles of filtering material become covered with thin films (" colonies ") of micro- organisms. Mr. Scott-Moncrieff was the first (1891) to suggest a mode of treatment whereby the preliminary liquefaction of solid matters could be brought about in a separate apparatus, and the purification of the matter in solution could be subsequently effected. This mode of treatment of sewage by separating the stages of its purification is doubtless advantageous, seeing that the classes of organisms concerned in the preliminary lique- faction are distinct from those concerned in the subsequent 146 HYGIENE AND PUBLIC HEALTH purification, and each class exerts its powers most effectually • when kept apart from the other. There is, moreover, evidence that the second stage of purification itself comprises many subsidiar}^ stages, and that special classes of organisms are concerned in these several stages. Almost all the installations at present in use embod}^ the principle of dividing, to a greater or less degree, the whole pro- cess of sewage purification by natural means into these two stages : Stage I. providing essentially for liquefaction of solids, and Stage II. for subsequent purification of the unstable and liquid products of Stage I. The installation adopted by Mr. Scott- Moncrieff consisted of two or more tanks (" cultivation tanks ") filled with large stones below and smaller ones above. The sew^age is allowed to flow slowly and continuously into a false bottom on the floor of the tanks and to escape at the top. In its upward passage over the stones the solid matters of the sewage are to a large extent retained, and the stones become coated with anaerobic liquefying organisms obtained from the sewage. Under the influence of these organisms the solids of the sewage become liquefied to such an extent that the effluent escaping from the top of the tank contains but very little suspended matter. In Stage II. of purification the aim is to bring the sewage under the most favourable aerobic conditions obtainable. To this end the tank effluent is conducted into a series of channels (" nitrification channels ") freely exposed to the air and filled with large stones, which serve the double purpose of breaking up the current of liquid (and thereby helping to thorouglily aerate it), and also of affording surfaces on which the aerobic organisms can plant themselves in great numbers. More recently Mr. Scott-Moncrieff designed means of securing an even more complete aeration of the effluent from the tank b}^ the use of a series of perforated trays containing filtering media, placed at intervals of a few inches one above another, so that the liquefied sewage delivered over the surface of the top tray trickles slowly from tray to tray to the ultimate outfall in the effluent collecting channel. It is probable, as claimed by the inventor, that the organisms in the different trays, having to deal with sewage in different stages of purification, become differentiated, and therefore work to the best advantage. DISPOSAL OF REFUSE I47 He also advocates, where possible, the addition to the effluent from the trays of a certain volume of well-oxygenated water. Kenwood and Butler found from an extensive series of experiments performed upon an installation of a modified Scott- Moncrieff anaerobic tank at Finchley, that there was a continuous reduction of the more stable organic matter to unstable organic compounds, and subsequent production of the ultimate products of anaerobic organic decomposition. A microscopical examination of the small amount of matter retained in the tank disclosed the presence of fine granular debris which was rich m iron, particles of silica and carbon, algoid growths (some with chlorophyll and others without), a few live protozoa and rotifers, vegetable hairs, bundles of vegetable fibres, large numbers of vegetable spiral vessels, zoogloea, an ovum of taenia, a few striated muscle fibres, cotton fibres, and human hairs. By experiments on a septic tank, or hollow chamber, on a small scale, they found that the same changes which occurred in Scott- Moncrieff' s anaerobic filter tank took place in a hollow septic tank, only somewhat more slowly. Extensive experiments by Mr. Dibdin from 1891 to 1895 with the Metropolitan sewage led to his advocacy of what is known as the Sutton system of biological purification. The sewage is first strained of large particles by means of fine metal strainers introduced at the sewer outfall, where the sewage enters the works ; it is then exposed to dowmward filtration through coarse beds. It is in these coarse beds that liquefaction should take place. They are 4 feet deep, and made of coarse burnt ballast of particles of such a size that they will pass through a 2-inch ring, but are rejected by a J-inch mesh ; the object of using such coarse material being to admit the soHd particles of crude sewage into the body of the bed, and also to favour thorough aeration when the liquid sewage is drawn off. The coarse material, moreover, does not get so readily clogged. The effluent from the coarse bed is then conveyed on to the surface of a fine fflter 4 feet deep, constructed of particles which will pass a J-inch mesh, but which are rejected by one of xV inch. The sewage is aUowed to fiU these beds almost to their top surfaces, and then to rest in them for a period of two hours (hence they are known as contact beds). Then the beds are slowly emptied and aUowed to remain at rest for several hours, 148 HYGIENE AND PUBLIC HEALTH SO that several of such filters are necessary in even a small installation, f Each filter-bed is filled up thrice daily. This inter- mittent application of the sewage insures also a certain amount of aeration of the beds. One drawback to the use of the coarse or " roughing " filter is the fact that the upper stratum of the filtering material becomes clogged at intervals with a black deposit of solid matter. The surface of such filters, therefore, requires occasional raking or ploughing. The practice of applying the crude sewage by a single carrier to a coarse continuous bed would have the effect of overtaxing the bed on either side of the trough, for the material there will collect more than its share of suspended matter whilst the bed is filling ; such a filter, therefore, is not given the best chance of carrying on its work. Kenwood and Butler found that in installations upon Dibdin's principle with coarse and fine contact beds, a greater area of coarse filter than of fine filter should be provided, and that the sewage should be locked up for longer periods (4 hours) in the coarse beds, and shorter periods (2 hours) in the fine beds. It is in the coarse beds that the liquefaction of the solid matter takes place, and the stability of the organic matter in solution is shaken, and time is the all-important element in bringing about these changes. Their experiments also demonstrated the fact that, for the second stage of purification, the transference of the sewage from one bed to another in a series of two or three beds brought about a higher degree of purification in a shorter time than prolonged treatment in one bed alone. The " septic tank" method was devised by Mr. Cameron of Exeter at about the same time that Mr. Dibdin'^ experiments were in progress. The method, like that of Mr. Scott- Moncrieff, provides for a well-defined line of demarcation between the stages of lique- faction and of subsequent purification. Provision is made for hquefaction under strictly anaerobic conditions in a large covered receptacle provided with an inlet for the sewage and an outlet for the tank effluent. The sewage travels so slowly through the tank that every particle takes some twenty-four hours in passing through it. This period of time is sufficient for such a complete sedimentation and liquefaction of solids to be effected that the tank effluent should contain but a few grains per gallon of fine suspended matter. The black deposit which DISPOSAL OF REFUSE I49 settles in the bottom of the tank was found after fifteen months' working to be under 2 feet in depth. This deposit consists of indigestible material, and includes mineral matter, cellulose, vegetable and elastic fibres, cartilage cells, etc. The gases given off from the tanks are not offensive, but are highly inflammable. The mixture of gases contains (Rideal) CO2 = o-6, methane = 24-4, hydrogen = 36-4, nitrogen = 38-6, in 100 parts. The second stage of purification is effected by passing the dark coloured tank effluent through an " aerator " — a long trough over the edges of which the liquid falls in thin films, thereby mechanically entangling a certain quantity of air ; and from thence on to a series of coke-breeze filters 4-I feet deep. These filters are filled, rested while full, slowly emptied, and rested for several hours while empty, in the manner advocated by Mr. Dibdin. The effluent from the tank is applied to the filters in rotation by an ingenious automatic arrangement, which removes the necessity for continuous manual attention. The practice at Exeter leads to about six hours being consumed m the filling of each filter, which then remains full for six hours ; the filter is then emptied in half an hour, and is allowed to remain at rest for the remainder of the twenty- four hours (i.e., eleven and a half hours). The Local Government Board has since sanctioned a scheme for the treatment of the whole of the Exeter sewage on similar lines. When sewage is allowed to flow slowly through an open tank, a thick spongy scum gradually covers the surface. The effluents furnished by similar sewage from an open "scum" tank and a closed septic tank are very similar to each other. The scum . provides a cheap roof which preserves the heat in the sewage and thereby promotes bacteriolysis, and also tends to prevent the dissemination of smell from the tanks. One may broadly sum- marize the advantages of anaerobic tanks as foUows : They pro- mote uniformity of effluent ; they permit of the digestion of from 30 to 40 per cent, of the suspended solids of sewage, with the result that such solids in the tank effluent rarely exceed 15 to 20 parts per 100,000 ; the stability of most of the organic solids is rapidly reduced by a short sojourn in a tank, and subsequent purification thereby much facilitated. The difficulties often arising from the treatment of the highly offensive effluent from a septic tank led Dibdin to advocate the preliminary treatment of crude sewage in slate beds, in which 150 HYGIENE AND PUBLIC HEALTH it is onl}^ retained for two hours, so that it emerges in a fresh condition. The slates, which are the refuse of slate quarries, are laid horizontally in layers about 2^ inches apart, in a bed about 4 feet deep. The slates are supported on small slate slabs of the required thickness. These beds are filled from the top, and emptied from the bottom, the sewage remaining at rest for two hours, and the beds being left empty for a like period. This process is now at work at Devizes, where the crude sewage is very strong, and is mixed with the refuse from breweries. The effluent from the slate beds is clear and inodorous, and is in a condition very suitable for application to the contact beds of fine clinker, in which the process of purification is completed. A certain amount of silt from the sewage is deposited on the slates, but the amount so collected is not large, and it has not been found necessary to wash out the silt more frequentty than once or twice a year. The deposited sUt soon loses any sewage odour, and has the character of rich mould when taken from the slates, with a strong earthy smeU. In Colonel Ducat's method the stages of liquefaction and subsequent purification go on continuously side by side in the same apparatus. A filter some 8 feet in depth, and varying in area with the amount of sewage it is required to treat, is built up from the ground level with walls composed of agricultural drain pipes, arranged so that their long axes are directed {with a slight fall) towards the interior of the filter. By this arrange- ment the wind, from whatever direction, can blow into the bod}^ of the filter, whereas the slope of the pipes prevents the sewage from flowing out of them. The bodj^ of the filter is formed of layers of coke, large at the top and small below, each layer, which is about 18 inches deep, being separated from its neigh- bours by an aerating la5/er of big stones and of pipes. Dis- tributing troughs appl}^ the sewage e\'enly over the top of the filter, through which it sloMdj/ passes, the effluent finaUy coUecting in a channel which surrounds the bottom of the filter. Colonel Ducat also devised means of warming his filter in the winter, thus pro\dding against the effects of frost, and also insuring a constant temperature speciaU^^ favourable to the work of the micro-organisms. This process has furnished satisfactory results in practice ; but it is difficult to believe that this would generally be the case, seeing that, the process being one of continuous action, the DISPOSAL OF REFUSE I5I essential and all-important element of time is not sufficiently pro\'-ided for the " digestion " which by other methods forms the preliminary state of sewage treatment. When an installation is provided for the natural purification of sewage, the organisms concerned in the process are planted on the filters, etc., by the sewage itself ; but it is not until after the sewage has been applied to the installation for many days that the organisms have become sufficiently developed and differentiated to produce their best effects. In installations of the " septic tank," or the Scott- Moncrieff tank, the provision made must be sufficient to hold at least one day's sewage flow. The matter is, however, complicated by the necessity of makmg provision for some at least of the storm water, which may at times swell the dry weather flow, for during rain}^ periods the volume of sewage is often more than quad- rupled. The Local Government Board requires that storm water amounting to thrice the dry weather flow of sewage must be treated in every respect as the sewage, while any additional quantity of storm water up to six times the dry weather flow must receive special treatment, either by means of an artificial filter or by land used for no other purpose. The storm water over and above six times the dry weather flow may be discharged into a stream. Local authorities must therefore make provision for the treatment of six times the dry weather flow. Special storm water filters of burnt ballast, etc., will deal satisfactorily with 500 gallons of dilute sewage to each superficial yard of filter area (2,420,000 gallons per acre) per diem. Aerating filter-beds must be constructed of fine grain material. The nature of this material, given that it is hard and durable, does not appear to be a matter of prime importance. It may be of coal, cinders, coke, clinker, saggars (refuse pottery), burnt ballast, gravel, or ffint, and local circumstances may be left to determine which to select. Coke is generally scarce and ex- pensive, coal is expensive, and, like burnt baUast, gravel, and flint, can often only be obtained by the payment of heavy charges for carriage. Sand and gravel do not appear to be so satisfactory as filters of clinker, coke, coal, and burnt baUast. Iii order to secure good and uniform results, the filters should never be made to deal with more than a million gallons of average sewage per acre per diem (about 200 gallons per superficial yard) . The water capacitv of these fine .grain beds diminishes somewhat with use 152 HYGIENE AND PUBLIC HEALTH owing to the retention of solid sediment, until as a rule a stage of equilibrium is reached, when the liquid capacity of the bed generally averages about 33 per cent, of the total cubic capacity. Contact beds of coarse coke-breeze or burnt ballast, used to receive crude sewage, separate a large proportion of the sus- pended matter of the sewage ; hence their capacity for liquid generally settles dov\Ti to a smaller proportion, represented commonly by an average figure of 25 per cent. The eight hours cycle of treatment of these filter-beds meets with the approval of the Local Government Board, the time being allotted as follows : I hour to fill, 2 hours to rest full, i hour to empty, and 4 hours to rest empty. It has now been proved that such contact beds can be worked at the rate of 1,000,000 gallons per acre per diem, if the eight hours cycle is strictly maintained. In all natural processes of sewage purification the sewage must first of all be passed through a grit or detritus chamber in order to retain large mineral particles, which would otherwise find their way into the installation and accumulate there, organisms being of course quite incapable of attacking them. What is essential in the working of a natural process is for the superintendent of the works to fully appreciate that he has countless colonies of living, working units under his control. Their work must always be regulated according to their powers, and sufficient and periodical intervals of rest must be allowed them between the regular periods of work. Then, and then only, will they attune their powers to the work they are called upon to perform, and so establish that equilibrium between intake and output which is so easy to maintain, and so difficult to regain when once lost. It is an interesting matter to note that the total nitrogen in organic combination in the sewage which enters any of these installations is not nearly accounted for in the NH3, nitrates, nitrites, and the organic nitrogen still remaining in the final effluent. The loss is doubtless due to the fact that free nitrogen passes away from the beds, possibly also oxides of nitrogen, and a considerable amount of ammonia. On the ground that the micro-organisms concerned in oxida- tion and nitrification of organic matters are so dependent on oxygen, that they will even reduce chemical compounds in order to use their available oxygen, Adeney advocates the addition to tlie sewage of small quantities of an agent contain- DISPOSAL OF REFUSE I53 ing available oxygen, such as nitrate of soda or the manganate of soda. With the same object Lowcock has devised a filter of sand and gravel which is kept aerated by pumping air into it,. and which can be used continuously with good results. The intermediate flushing of the filter-beds with water has been advocated by Lomain, Barwise, and others, and where prac- ticable there is every reason to believe that a gain would result. Bostock Hill advocates the use of coal as a filtering material (Garfield's filter), the particles of coal being about the size of ^-inch cubes at the bottom of the filter, and becoming smaller towards the top. When certain trade effluents, especially waste acids, are passed into town sewage, experiment alone can decide whether it will be necessar}^ to employ a preliminary chemical (lime) treatment prior to bacterial treatment in filter-beds. It is certain that the natural agencies of purification are for the most part capable of dealing with such quantities of the trade effluents as more usually find their way into sewage. It would, however, ■ be advantageous if manufacturers could be made to distribute the discharge of trade wastes more equally over the twenty- four hours ; and in some cases the waste products should undergo some purification or treatment before they are permitted to leave the premises on which they are produced. The introduction of brewery waste into sewage is often pro- ductive of nuisance in the subsequent processes of treatment, more especially in the case of small tov^ois, where the brewery waste forms a considerable proportion of the total volume of liquid carried to the outfaU sewer. The brewery waste has an aromatic odour, which is penetrating and disagreeable, and is sometimes perceptible at a considerable distance from the sewage works. In such cases it may be desirable to have the septic tanks covered over, and not to employ sprinklers to distribute the tank effluent over the streaming filters, as the wind passing through the effluent issuing from the sprinklers may convey smeU to a distance. If the sewage works are in the neighbourhood of dwellings, primary and secondary contact beds are less likely to be productive of nuisance than sprinkler beds ; and if streaming filters are to be used, fixed distributors \viU be preferable to revolving sprinkling arms. Sewage rich in fatty and soapy matters, as in districts where certain manufactories and laundries are numerous, is very 154 HYGIENE AND PUBLIC HEALTH retractable to purification by biological agencies. The fat is especiall}^ resistant and tends to coat the particles of which the aerating beds are composed, thereby reducing their biological efficiency, and presenting obstacles to the passage of the sewage through a fine filter. Kenwood and Butler found that a filter soon acquires a state of equilibrium, as regards powers of purification, which tends to adjust itself to the average strength of the poUuting material with which it is day by day being supplied. It is for this reason that the necessity for multiple filters is so great where strong, or alternating weak and strong, sewages have to be dealt with ; for a filter will effect only a certain percentage reduction of the polluting ingredients of the sewage it receives, even when it has reached its maximum biological efficiency. The point alwaj^s to be borne in mind is that what has to take place is not merely the reduction of unstable matter to ultimate products, but the reduction of the more stable organic matter to the unstable. The reduction of the unstable to the ultimate appears to be best effected by change of filters, that of stable to unstable by rest in a filter. Drs. Clowes and Houston advocate the use of coke for contact filters in pieces of about the size of walnuts, as the larger pieces enable the bed to hold a larger volume of sewage and to be more rapidlj^ filled and emptied, as well as more effectively emptied and aerated. They find that in a bed 13 feet in depth the purification approximates to that in one 4 feet deep. A bacterial filter of coke will cost from £2,000 to £4,000 per acre, and each acre will treat from 500,000 to 1,000,000 gallons daily, according to the nature of the sewage. The amount of purification exerted by a filter or installation may be expressed as a percentage calculated upon the reduction in the albuminoid ammonia and oxygen absorbed figures of the liquids before and after treatment. In many installations such purifica- tion amounts to over 80 per cent, of the original pollution. If the aeration beds (commonly known as " streaming " filters) are treated intermittently, with the outlet pipe kept constantly open (and excellent results can be got by this method), then the sewage must be applied evenl}^ and equally over the whole area of the filter. It is difficult to effect this with ordinary fixed trough distributors ; but it can be provided for bj^ means of re- volving sprinkling arms, such as Candy's, or the Fiddian Rotary DISPOSAL OF REFUSE I55 Distributor, which automatic ahy revolve horizontally over a circular bed, the motive power being loss of head (about i foot) by the passage of the sewage on its way to the sprinkling arms. Stoddart's distributor consists of a galvanized iron channel furrowed with numerous narrow gutters in close parallel rows. Along the under surface of each gutter is a series of small per- forations terminating in vertical points. The clarified sewage, entering these gutters, forms drops upon each of the vertical points which drip steadily on to the filter-bed immediately below. Streaming filters are more expensive to construct and maintain than contact beds, and are more often a nuisance from flies. The chief source of the white-winged fly, so common on many coarse percolating filters, is the accumulation of undigested suspended and colloidal matter with gelatinous growths, which occur immediately below the surface of percolating filters. The methods of distribution of tank effluent over filter-beds by means of elongated water-wheels, which, pivoted at the centre, roll bodily over the surface of a filter on circular rail-tracks laid around the circumference of the filter, or by travelling distri- butors, in which the water-wheels pass backwards and forwards over rectangular beds, are far preferable, from the point of view both of even and regular distribution of the effluent over the filter, and also of lessened likelihood of nuisance, to the revolving sprinklers and fixed nozzle distributors. In the water-wheel distributor, the effluent falls in thin sheets, and has but little depth of air to traverse, the water-wheel being close down upon the bed, unlike the fountain sprays of the sprinkler and nozzle distributors. Consequently there is less risk of effluvia being conveyed by winds to considerable distances. In Messrs. Whittaker and Bryant's installation, as the sewage passes to the sprinkler a jet of steam is blown through it, which raises its temperature, the bacterial bed being thereby kept at an equable temperature very favourable to the activity of bac- teria. It is also claimed that the application of the warm sewage to the surface of the bed causes an expansion of the air between the filtering particles ; and, as a consequence, fresh air is drawn through the drain pipes at the bottom of the filter, and made to traverse the body of the bed, a high degree of aera- tion being thus assured. It is said that such a bed can deal with 600 gallons of sewage per square yard in twenty-four hours ( 2,904,000 gallons per acre). 156 HYGIENE AND PUBLIC HEALTH The artificial warming of bacterial beds, though it increases bacterial activity, is not necessary ; for even in the coldest winter months the temperature of the body of the beds rarely falls below 50° F., though the temperature of the atmosphere may be below 40° F. It may be taken for granted that circumstances favouring high oxygenation promote the ultimate changes of purification and the production of an effluent with good physical characters — incapable of putrefaction and of developing odour. Efficient oxygenation is aimed at in the system of emptying and filling fine bacterial beds in Dibdin's method, in the aerating channels and beds of the " septic tank " method, in the nitrifying channels and trays of Scott-Moncrieff, in the Ducat filter, Stoddart's distributor, Lowcock's filter, Adeney and Parry's suggestions for the addition of small quantities of an oxidizing agent in the effluent, and in the use of sprinklers. Contact beds do not secure oxygenation of the effluent so well as some of the other methods in practice, and observations go to show that the best results are to be obtained by an intermittent application of the previously sedimented sewage upon a bed, the outlet pipe of which is constantly open (streaming filters). '^ With the evidence at present available, it is extremely difficult to decide as to the respective merits of all of the installations which have been advocated. Sewage varies so much in its characters, and in the relative proportions of its different con- stituents, that experiments performed on different sewages afford no precise information on which can be based a safe and scientific comparison. Any opinion expressed must, therefore, be accepted with reservation, but probably every one of the methods referred to may be made to give satisfactory results. Questions of economy of plant and of time, of working and maintenance, and of the relative applicability of the process to local wants and conditions, must and will ultimately determine the choice. There is no evidence of the elimination of the micro-organisms characteristic of sewage by any process of filtration in bacterial filter-beds. It is evident, then, that such processes can in no sense be regarded as effectual in preventing danger, where filter effluents are discharged into streams used for water supply, into .water where water-cress is grown, or into estuaries where oysters are laid. DISPOS.\L OF REFUSE 157 The Royal Commission on Sewage Disposal appointed in i8g8 reported at the end of 1903 that they were satisfied that the consumption of shell-fish specificall}^ polluted by sewage maj^ cause enteric fever and other illnesses, and that bacteriology at present cannot be relied upon to determine whether or not sheU-fish are so polluted. It is, however, a fact that a very- much smaUer number of Bacilli coli or coli-hke microbes are found in 03'Sters stored in pure water than in those stored in polluted waters. In the opinion of the Royal Commission tidal waters should be placed under the jurisdiction of some competent authority, whose duty it would be to see that where shell-fish are collected, fattened, or stored, there is no risk of dangerous contamination. They further recommend that in respect of imported sheU-fiish similar precautions should be demanded as a condition of their importation to this country ; and, in default, aU imported sheU-fish should be deposited in registered layings for at least six weeks antecedent to their disposal on the market. The same Royal Commission reported in 1901, that while in the case of sewage effluents from land which is of a kind suitable for the purification of sewage, there are fewer micro-organisms of intestinal origm than in the effluents from most artificial processes, yet any sewage effluent must be regarded as potentiaUy dangerous. In conclusion they say that the general protection of our rivers is a matter of such grave concern as to demand the creation of a separate Commission, or a new department of the Local Government Board, which shaU be a Supreme Rivers Authority, dealing with matters relating to rivers and their purification, and which, when appeal is made to them, shall have power to take action m cases where the Local Authorities have failed to do so. A fair sewage effluent would have the foUowing composition m 100,000 parts : Saline and free ammonia Organic ammonia Oxygen absorbed in 4 hours at Oxidized nitrogen Chlorine Suspended matter Solids in solution [a) Volatile (6) Non-volatile 80° F. I -SO 0-I2 I '40 r-oo lo-oo 1-50 86-15 3 5 -OS 51-10 In an experimental instaUation at Hanley, the sewage being subjected to septic tank treatment and subsequent filtration I5S HYGIEXE AND PUBLIC HEALTH through a streaming filter 4^ feet deep formed of broken saggars (a waste material which is plentiful in the pottery towns), and composed as to the lower 9 inches of particles from 2^ to i| inches in diameter, and as to the upper 3 ft. 9 in. of particles J to J inch in diameter, Dr. Reid found that the septic tank effected a purification of 64 per cent, and 62 per cent, in the organic ammonia and oxj'gen absorbed figures, respectively, as compared \\-ith the crude sewage, whilst as regards the filter effluent the percentage purification was 97 per cent, and 94 per cent., the amount of nitric nitrogen in the effluent being 1-62 parts per 100,000. A satisfactory sewage effluent must be without fsecal odour and marked deposit. In the opinion of many, the organic ammonia figure is the best criterion of a satisfactory effluent. It is held b\- some authorities that this figure should not exceed o-i part per 100,000, while others advocate a limit of 0-15, or even 0-2. The oxygen absorbed by oxidizable organic matter in four hours at 80^ F. does not exceed 1-5 parts per 100,000 in good effluents. The chlorine and free and sahne ammonia figures are unimportant, since these are ultimate products ; the chlorine in the effluent of a sewage of average strength is about 10 parts per 100,000. There should be practically no soUds in suspension ; the Rivers PoUution Commissioners' standard required that the suspended matter should not exceed 3 parts of dry mineral matter per 100,000, nor I part of dry organic matter per 100,000. Above aU, the final effluent must not be Hable to putrefaction or secondary decomposition. The presence of oxidized nitrogen in an effluent must not be regarded as a sure index of purity, although if nitrates are found to persist in an inoffensive effluent for a few days after its collection, the effluent is not likely to become offensive. Nitrates are a measure not of that pollution which ma}" be oxidized, but of that which has been oxidized, and their presence gives no indication of what remains to be purified. Xo general standard applicable to aU cases is possible or desirable. The best possible results must alwaj^s be aimed at, having due regard to the nature of the sewage, and to the conditions, volume, and uses of the stream which is ultimately to receive it. The maximum impurity permissible will in certain cases be \evy slight indeed, while in others a greater latitude may be conceded. But certainl}' aU effluents should conform DISPOSAL OF REFUSE I59 to the following requirements : they should contain but very little suspended matter (certainly not more than 3 parts per 100,000) ; they should possess no odour of sulphuretted hydrogen ; and there should be no physical evidence of putre- faction when they are incubated for a week in a closed vessel at 80° F. Intermittent Downward Filtration. When sewage percolates through porous soil, it is purified to a greater or less extent. This purification is partly due to the soil acting as a mechanical filter, separating out and retain- ing the suspended matters in the sewage ; but greatly more to the. destruction by organisms of the organic matters in the sewage. This purification is chiefly effected by the bacterial organisms which exist in the upper layers (extending to 3 or 4 feet from the surface) of all soils, but chiefly in those rich loamy soils which contain much organic matter. The nitrifying organisms feed on the organic matters of sewage, causing their oxidation. They require air and oxygen for their growth and life, which are supplied to them when the soil is being aerated during its periods of rest. The soil or the sewage should also be rich in lime or other alkali ; for the nitric and nitrous acids formed by the nitrifying organisms must be able to combine with bases, or the nitrifying action ceases. A very large volume of sewage can be purified on a small area of land, if the soil is of a porous and rich loamy character. Sandy soils are not efhcient purifiers — at any rate at first. Clay, and other retentive soils, must be well broken up and mixed with ashes. The surface of the land must be levelled, and under- drained with porous tile drains, laid at a distance of about 10 to 30 feet apart, according to the nature of the soil, and at a depth of 4 or 5 feet from the surface. The area should be laid out in plots ; and no plot should receive sewage for more than six hours, so that it may have eighteen hours' rest out of the twenty-four ; to this end the screened, filtered, or precipitated sewage is distributed over each plot of ground intermittently by means of branching carriers. If it is intended to apply the sewage of more than 1,000 people to an acre, the sewage should be treated chemically, or passed through a septic tank, to remove the suspended matters, and the clarified sewage only should be applied to the land. IbO HYGIENE AND PUBLIC HEALTH When crude sewage is applied in large volumes to a small area of land, the pores of the soil become clogged with the slimy suspended matters, and a kind of coating is formed over the surface, which prevents the percolation of the sewage and the penetration of air into the interstices of the soil. When the sewage of considerably less than i,ooo people is to be applied per acre, the screened sewage may be applied in its crude state ; for it is much cheaper to allow the suspended matters to reach the soil by gravitation in the liquid sewage, than to separate them bjr precipitation and then, as is sometimes necessarj/, to pump the liquid sludge on to the land. It is generally the practice to lay out the filter areas in ridges and furrows, the sewage being allowed to flow down the furrows, whilst vegetables are grown on the ridges. The roots of the vegetables assimilate organic products, and thus help to purify the sewage, whilst the leaves and stalks, being above the sewage, are not contaminated by floating matters. The suspended matters deposited from the crude sewage in the furrows must be dug into the soil from time to time, before they have time to form an impenetrable coating. '~By intermittent downward infiltration through specially pre- pared filter-beds, the clarified sewage of even 5,ooo people can be applied to each acre of filter ; but it is not really safe to allow less than i acre to each i,ooo of population (20,000 to . 30,000 gaUons daily of dry weather sewage flow), when the inter- mittent downward filtration is through soil, however suitable the soil may be. Under favourable circumstances, the effluent water issuing from the drains will be found very free from organic matter. The nitrogen of the sewage exists in the effluent water, but in the innocuous forms of ammonia, nitrates, and nitrites. The sewage, therefore, by this process is effectually purified ; but all its manurial ingredients are wasted, except in those cases where the sale of vegetables, grown on ridges, covers part of the cost of the distribution. But the area of land being so limited, the crops, and the income derived from their sale, must necessarily be very small. Irrigation. In the words of the Royal Commission on Metropolitan Sewage Discharge, broad irrigation means " the distribution of sewage over a large surface of ordinary agricultural ground, having in view a maximum growth of vegetation (consistently with due DISPOSAL OF REFUSE 161 purification) for the amount of sewage supplied." Filtration means " the concentration of sewage at short intervals, on an area of specially chosen porous ground, as small as will absorb and cleanse it ; not excluding vegetation, but making the produce of secondary importance. The intermittency of application is a sine qud non even in suitably constituted soils, wherever complete success is aimed at." It becomes necessary to inquire what are the conditions under which the crude sewage of a town may be applied to land by broad irrigation. Experience has taught that no great profit should be looked for from a sewage farm. Unfortunately local authorities have found great difficulty in acquiring sufficient land at a low rental for purifying sewage. In the first place, the land chosen should be so situated in relation to the town that the sewage may flow to it by gravita- tion ; pumping is costly and greatly reduces any profits that may arise. The rent to be given for the land ought not to exceed £2 los. per acre (Bailey Denton). The extent of land that should be acquired varies under different circumstances ; on an average, I acre to every loo to 200 persons of the population is sufficient. The best kind of soil is a friable loam ; but clayey, gravelly, or sandy soils are all capable of purifying and utilizing sewage when properly managed. " Peat and stiff clay soils are generally unsuitable for the purification of sewage " (Interim Report of the Royal Commission on Sewage Disposal, 1901). The land must be levelled, and, unless very porous, underdrained, to allow the sewage to percolate and prevent its stagnation on the surface. With very dense clay soils filtration is impossible, and in such cases surface flow must be entirely relied upon. This is capable of giving a fairly pure effluent if the sewage has been freed of suspended matters by a preliminary precipitation, and if the area of the land is sufficient. In these cases underdrainage should not be attempted, as in dry summer weather the stiff clay soil cracks, and the sewage may pass away directly through the fissures into the underdrains, and so reach the watercourses unpurified. The main carriers for the distribution of the sewage on the farm should be masonry, concrete, or stoneware channels, which can be easily flushed and cleansed. Great care must be exercised where sewage is allowed to irrigate land of a chalky nature, or where a top layer of clayey soil of but little thickness covers a thick stratum of chalk. In certain l62 HYGIENE AND PUBLIC HEALTH chalk formations, what are known as " swallow holes " exist — that is, extensive fissures in the chalk reaching up to the sur- face. In such cases it sometimes may happen that unpurified sewage flowing over the surface may disappear into one of these fissures or swallow holes and pollute the underground water, which at no great distance away may be pumped out of a deep well in the chalk to supply houses, villages, or towns. Such an occurrence is believed to have occurred at the East Riding Lunatic Asylum, near Beverley, Yorkshire. The top layer of clay became extensively cracked in dry summer weather, per- mitting unpurified sewage to pass through to the chalk beneath, where it was conducted by fissures to the deep well, about half a mile distant, which supplied Beverley with water. As the water in this well is sometimes depressed by pumping to the extent of 17 feet, the area of the circle drained by the well must be very extensive. In the immediate neighbourhood, a stream much polluted b}' the sewage of a village on its banks disappeared into one of these swallow holes, where the chalk rises up into the bed of the stream. The method most capable of general application for applying the sewage from the main carriers to the surface of the farm is that known as the ridge and furrow system. The surface is laid out in ridges — 30 to 60 feet broad — running parallel to each other, and at right angles to the main carrier, with a slight fall from it. Between every two ridges is a furrow formed by the slope (a fall of several inches) of the two ridges towards each other. The sewage is made to pass down a grip in the centre of the ridge, and thence to flow over the sides towards the furrow. When the central grip becomes clogged with the suspended matters of the sewage, it should be filled in, and a fresh one made in its place. The underdrains of porous earthenware should be laid at a depth of about 5 feet in the soil, and from 20 to 100 feet apart, according to the porosity of the soil. What is known as the " catch water system " of irrigation can be adopted where the areas for sewage treatment have sufficient gradients. By this method a series of furrows or trenches are dug in lines one below the other. The sewage is conducted to the topmost trench, over which it passes to find its way into the next lower trench, and so downwards to the bottom of the slope, where the subsoil effluent is collected and carried into a stream. DISPOSAL OF REFUSE 163 The best crops for a sewage farm are Italian rye grass, roots (mangold wurzel), and cabbages. Italian rye grass absorbs a large volume of sewage, and bears from five to as many as seven cuttings in the year. After two or three years, the plot of rye grass should be ploughed up, and the land sown with cabbages or roots (mangolds). These may be sewaged when growing, but they should not be sewaged when they arrive at maturity. They help to exhaust the soil of the sewage products retained in it, which have not been absorbed by the rye grass. Pulse, cereals, and all other vegetables should not be sewaged when in growth, except in times of great drought. The land, when fallow, may be enriched by the application of sewage ; for some of the manurial ingredients of sewage are doubtless retained in it, ready for use on a future occasion. Market gardening may be undertaken, and made very profitable on farms where the area of land is more than sufficient to deal with all the sewage ; but, where this is not the case, market gardening does not answer, because the area so cultivated cannot deal with the whole volume of sewage. The amount of capital required to stock and work a sewage farm is very great, probably five times the amount required for an ordinary farm. The crops that have to be taken off the land are enormous, and a large amount of labour is required to keep it clean and free from weeds. The crops of Italian rye grass, being so large, may — and often do — exceed the demands of the local markets. If not sold at once, the grass is wasted ; for it will not keep, and will not bear long carriage. In dry summers it may be made into hay, and at other times it may be converted into ensilage. It has been found, however, that, to reap the greatest profits from a sewage farm, the produce should be converted into milk and meat. In other words, a dairy farm should be established, and stock should be reared and fattened for market. The idea that sewage-grown vegetable produce is dropsical and prone to decompose has been long exploded. The milk and meat, also, from animals fed on such produce in no way differs from milk and meat produced on ordinary farms. From experiments extended over five years (1871-76), the British Association Sewage Committee found that the average amount of nitrogen recovered in the crops of a sewage farm was 32-88 per cent, of that applied in the sewage. About 11 per cent, of the nitrogen in the sewage escapes in the effluent water, 164 HYGIENE AND PUBLIC HEALTH almost entirely as nitrates and nitrites, whilst a portion of the unaccounted-for nitrogen is stored up in, and enriches, the soil of the farm. The amount of evaporation of water from the surface of a sewage farm is enormous. The above committee found that, on an average of over a year's observations, only 47-3 per cent, of the sewage pumped on to the land was discharged through the deep drains as effluent water. This fact must be reckoned with on making analyses of effluent water from sewage farms, which are to be compared with samples of crude sewage flowing on to the farm. Although the evaporation of water is so great, the committee found that there was no loss of ammonia from the sewage by evaporation in its passage along the open grips and carriers on the farm. One of the great drawbacks to the utilization of sewage by irrigation is the fact that the sewage must be applied to the land as it comes, by night as well as by day ; on Sundays as well as on week days. There may be times when it may not be desirable to apply sewage to the general surface of the farm, especially during wet weather, when enormous volumes of dilute sewage arrive at the farm. This difficulty may be got over by la^dng out a portion of the farm as a filter-bed closely drained. The extent of this filtration area should be sufficient to purify the whole of the sewage when not required on the general surface of the farm. The land may be left fallow, or laid out in ridges and furrows and cropped. When the sewage is much diluted \vith storm water, it may, in other cases, be carried over a specially prepared filtering area planted with osier beds, or over meadow lands, before being discharged into a stream. It would be of great advantage if storm and subsoil waters could always be excluded from the sewers ; the problem of satisfactory disposal of the sewage would be thereby greatly facilitated. During the most severe frosts irrigation may continue uninter- ruptedlj^ A coating of ice is formed over the surface of the farm, but the sewage, which always has a temperature well above the freezing-point, flows underneath this coating and sinks into the soil, which remains unfrozen and open. As the weather moderates, the sewage rapidly melts the ice above it. Even in America, where the frosts are most intense, no trouble has arisen from this cause on any of the sewage farms. Are sewage farms productive of nuisance and injury to health ? DISPOSAL OF REFUSE 165 There can be no doubt that badly managed farms — where more sewage is appHed than the land can absorb and cleanse, or where, from the sewage bemg applied too continuously, the surface becomes sodden, and ponded sewage stagnates on it — may be a nuisance. When properly conducted, and the sewage is distributed over the land in as fresh a state as possible, and not after prolonged sojourn in a lengthy main or outfall sewer, sewage irrigation is not found to be productive of any nuisance. That sewage farming is no more unhealthy than ordinary farming is shown from the returns of the nine sewage farms which were in competition for the Royal Agricultural Society's prizes. The rate of mortality amongst the labourers and their families, on an average of the number of years these farms had been in operation, did not exceed 3 per 1,000 per annum. No facts, either, have ever been brought forward in favour of the view that entozoic diseases are spread by the agency of sewage farms. It is probable that alkaline sewage destroys organisms like the ova of tapeworms, whose natural habitat is the acid secretion of the human intestines. If so, they are destroyed before they arrive at the farm. On one farm, too, it was found that there was a remarkable absence of those moUuscan and insect forms of life which frequently play the part of intermediary bearers to entozoal larvae, and without which the cycle of their existence cannot be completed. Even where cattle have been allowed to feed upon land to which sewage is being applied, it has not been found that they are in any way affected with parasitic diseases. Generally speaking, land is becoming too valuable to be put to purposes of sewage purification, hence the modern endeavour to reproduce all the most favourable conditions of land and to concentrate them in a small area known as a bacterial bed ; but where land, suitable in nature and quantity, can be procured, equally good results are obtainable. CHAPTER III AIR AND VENTILATION Pure atmospheric air. freed from aqueous ^'apour, has tlie following volumetric composition :— Oxygen ..... 20-94 Nitrogen ..... 78-09 Argon ..... 0-94 Carbonic acid .... 0-03 100-00 The amount of aqueous vapour present in air is variable, the average in this country being i'4 per cent. Traces of organic matter, ozone, mineral salts, ammonia, nitric acid, neon, helium, krypton, xenon, hydrogen, and carburetted hydrogen are found in air ; and in towns sulphurous acid and sulphuretted hydrogen. This composition is, as regards the four gases which compose almost the entire bulk of ordinary air, remarkabh' uniform in ever\^ part of the world. Even in the midst of large cities, where the atmosphere is being polluted in many ways, the air of open spaces differs but very slightly in the proportions of its constituent gases from the air on the open plains, mountains, or seas, which is far removed from such sources of contamination. This is not to be wondered at when the immense power and universality of the forces which promote purification of the atmosphere are considered. Such are : — The wind, which dilutes and sweeps away impurities, bringing pure air in their place ; the rain, which washes the air, carrying down in its fall dis- solved gases and suspended impurities ; the chemical effects of the oxygen and ozone in the air on the oxidizable matters in it ; and. lastly, the power possessed by the green parts of plants, in sunlight, of absorbing carbonic acid, fixing the carbon, and setting free the oxj'gen. The latter process is, however, reversed 166 AIR AND VENTILATION 167 during the hours of night, CO2 being evolved ; but the balance is decidedly in favour of purification. Ozone, which is oxygen in an allotropic and highly active condition, is generally absent from town air, even in open squares and parks. Confining our attention for the present to the outer air — the air outside buildings — it has been found in large cities that when the atmosphere is stagnant, and no wind is blowing, especially during fogs, the air of open spaces may contain only some 20-8o per cent, of oxygen, or even less, and the carbonic acid may exceed o-o6 per cent., with a considerable increase likewise in organic matters. Such observations have been made in London and Manchester. In the narrow closed courts or streets, surrounded by high buildings, which constitute so large a portion of the densely populated parts of these cities, the air has been found considerably more impure than the samples above given, which were taken from open spaces. The air of such places is stagnant and confined, as in a well ; there is no circulation to effect a proper renewal of fresh air and dispersion of accumulated impurities, and the sun rarely penetrates. Yet such is the only air supply attainable in thousands of the dwellings of the poorer classes. We thus see that although in towns much may be done by constructing wide and airy streets, by preventing the undue aggregation, of dwellings and their back to back construction, and by suitable restrictions as to their height, to provide for proper ventilation and purification of the atmosphere, yet its purity is liable to variations, which do not occur in the air of the open country. These variations may be only very slight in amount, but they are not unimportant. Their bearing on the health and vitality of the populations exposed to their influence is probably considerable. Amongst suspended matters usually present in the air, to a greater or less extent, are minute particles of mineral matter (including common salt, especially near the sea), soot, dust of various kinds — -in towns consisting largely of organic matters from horse droppings — textile fibres, vegetable debris, pollen of grasses and flowers in the early summer, the spores of various fungi and moulds, diatoms, bacteria and their spores, monads and amoebifomi organisms — dead and living. The purest air, such as exists at considerable elevations on mountains and l68 HYGIENE AND PUBLIC HEALTH over the sea, contains but very little suspended matter. In tov\Tis, especially manufacturing towns, the air is often loaded \\dth soot and dust of mineral origin. The dust in the atmo- sphere provides innumerable nuclei for the condensation of moisture or water vapour. In to\\Tis, the amount of organic and mineral dust in the air will depend greatly on the efficiency of the scavenging and watering of the streets. The wind raises minute particles from the surface of the ground, and carries them often great distances before they are deposited. In this way infectious particles from domestic dust heaps and dried excreta may be caught up and carried into the air. Air is vitiated by respiration of men and animals ; by com- bustion of coal, gas, oil, etc. ; by fermentation and putrefaction of animal and vegetable organic matters ; by various trade and manufacturing processes. Vitiation by Respiration. An adult individual at rest breathes at the rate of about seventeen respirations a minute, kt each respiration about 500 c.c. (30-5 cubic inches) of air pass in and out of his lungs. The air in the lungs loses 4 per cent, of oxygen, which is absorbed by the blood in the pulmonary capillaries, and gains carbonic acid from the venous blood to the extent of 3-5 to 4 per cent. The nitrogen remains unchanged. In addition, the expired air is raised in temperature to nearly that of the blood, 98-4° F. ; it contains 5 per cent, of aqueous vapour, and a larger proportion of putrefiable organic matters than the air which is inspired. The amount of carbonic acid which is given off by an adult male person at rest can be calculated from the above figures,^ and will be found to be 0*72 cubic foot in one hour. From actual experiment it has been determined that an average adult gives off 0*9 of a cubic foot of COg during gentle exertion, and possibly as much as 1*8 during hard work. The adult female gives off about one-fifth less of each of these quantities under similar circumstances, and an infant is said to give off about 0-5 cubic foot of CO2 per hour. In a mixed assembly at rest, ^ 1 7 X 30 X 60 = lyr, cub. feet breathed per hour. 1728 ^ ■■ ^ A per cent, of 17S -0*72 cub. foot per hour of CO,, AIR AND VENTILATION 169 including male and female adults and children, the COo given off per head is therefore taken as 0*6 of a cubic foot. The repeated inhalation of air fouled by human beings tends to the production of a lowered state of health and promotes the onset of disease. Recent experiments have demonstrated that the physical changes in impure air are mainly responsible for the usual sjmiptoms complained of in overcrowded rooms. These experiments included a number of tests made in a speciall}^ constructed glass chamber in which the physical and chemical qualities of the air could be rigorously controlled. It was found that with a respiratory impurity of carbonic acid exceeding oxvy recorded up to that time as having been found in the air of a crowded room — e.g., from i-o to 1-5 or even 1*7 per cent.- — no injurious property of the air could be demon- strated so long as the temperature and humiditj^ were kept low ; and that under these circumstances the absence of any dis- turbance was so complete that the power of co-ordination remained intact — as was proved by the ease and normal manner in which certain arithmetical calculations given by way of test were carried out. Parallel results have been obtained in the case of schoolrooms crowded with children, but in which the temperature was kept low. On the other hand, as soon as the temperature and humidity N\ere increased to bej^'ond certain limits, there appeared, both in normal and in diseased persons who were submitted to experi- ment, the usual s^nnptoms that occur when people are crowded together in one room — i.e., feelings of drowsiness and headache, oppression, lassitude, giddiness, nausea, etc. These symptoms, however, could be relieved at once simpl\^ by reducing the temperature and humidity of the air to normal, and they may be attributable to heat retention. Increase of Carbon-dioxide Gas. — In the air of an inhabited room the amount of COg is always increased, as compared with pure air ; and this increase is directly proportional to the number of persons present, and inversely proportional to the volume of fresh air introduced by ventilation. But the increase of CO2, even in crowded and badly ventilated rooms, is compara- tively speaking a small matter. The amount of CO2 by volume in pure air being from 3 to 4 parts per 10,000, in inhabited rooms, the proportion of CO2, even where there is excessive lyO HYGIENE AND PUBLIC HEALTH crowding and very defective ^-entilation, as in some elementary schools, seldom rises above 50 volumes per 10.000, and it requires about six times as much (300 volumes per 10,000) to produce an immediately perceptible effect on the respiration, as sho^\•n b\' increased depth and frequency of breathing (Haldane) ; whilst no poisonous effects appear to be produced until the proportion of CO2 rises to 500 volumes per 10,000, or 10 times the amount ever likely to be found in inhabited rooms. There is always about 6 per cent, of CO2 in the residual air of the pul- monary alveoli (Haldane and Priestley). An increase of CO2 in the respired air stimulates the respiratory centre to induce increased pulmonary action, so that the percentage of CO2 in the alveolar air remains constant. The alteration in the breath- ing induced by respiring air containing 50 volumes of CO2 per 10. 000 is quite inappreciable. A slight muscular exertion, such as that of walking at the rate of 3 miles an hour, would pro- duce 30 times as much effect on the breathing. From these facts it msLj be inferred that the increased CO2 in the air of inhabited rooms is not of itself productive of injury to health. Diminution of Oxygen. — The diminution of oxygen in air vitiated by respiration has been the subject of experiment, but in no case has the reduction been found to be more than trifling. The normal amount of oxygen in pure air being 20*94 per cent, by volume, instances have been recorded where the oxygen has been reduced to 20*65 ; but it can hardly be supposed that such a reduction can exert any influence on health, having regard to the fact that many mountain climates are notorioush^ healthy at altitudes where the diminution of atmospheric pressure cor- responds with a very much greater reduction in the percentage of oxygen. Ozone. — Formerly considerable importance was attributed to the alleged absence of ozone from the air of inhabited places. But owing to the unreliability of the methods for ascertaining the presence of this gas, doubt has arisen as to whether this supposed allotropic form of oxygen exists in the general atmo- sphere at all. and whether the supposed characteristics of ozone are not realh^ due to the presence of nitrous acid. Organic Matter. — For many years it was believed that the injurious effects due to the breathing of air vitiated by human respiration were attributable to organic matters contained in gXpired air. It was supposed that these organic matters were AIR AND VENTILATION I7I partly suspended in the air, consisting of small particles of epi- thelium and fatty matters from the mouth, and in part were in the form of an organic vapour from the lungs and air-passages, which was held to be nitrogenous in character and poisonous when re-breathed. The experiments, however, of Berger, Weir Mitchell, and Billings in the United States, and of Haldane and Lorrain Smith in this country, tend to show that there is no volatile organic poison in expired air ; whilst there is no definite proof that the tests for the presence of organic matter in air vitiated bj^ respiration are any indications that the source of such matters is the air expelled from the lungs. The reducing action of vitiated air upon permanganate of potash may be due to other constituents of such air than organic matters ; and the fact that the washings of such air with distilled water yield, on distillation, ammonia and albuminoid ammonia in excess of that present in pure air, does not necessarily mean that the organic matters, of which these ammonias may be taken as evidence, are invariably derived from the lungs. They may, in fact, be due to volatile products given off from the teeth and gimis, from dirty skins, and from excretions adhering to foul clothing. More exact research is required to ascertain the organic constituents (if any) of expired air, and to differentiate them from the volatile products of decomposition arising from the general surface and other parts of the body. Personal Emanations. — ^These emanations are undoubtedly ver}' largely responsible for the unpleasant odours which are perceptible on passing from the outer air into a crowded, unven- tilated room, more particularly when the occupants are persons of uncleanty habit. No sufficient experiments have been made, nor are there perhaps any satisfactory tests known which could determine the nature and quantity of the volatile matters to which these odours are due. It is possible that the deleterious action of air vitiated by the presence of human beings is to some extent due to the presence of these odoriferous volatile substances, minute in amount though they be. The long con- tinued action of such substances on the olfactory nerves may ultimately induce through the central nervous system alterations in respiration, circulation and nutrition, which are inconsistent with the maintenance of good health. Heat and Moisture. — It is probable that the heightened tem- perature and the larger amount of watery vapour present in 172 HYGIENE AND PUBLIC HEALTH the air of places much vitiated by the presence .of human beings are auxiliary factors of some importance in producing loss of health. The debilitating effects produced by respiring impure air are undoubtedly augmented when such air is much raised in temperature, and the tendency to an increased output of foul-smelling volatile products from the bodies of the occupants of a room is materially increased by a high temperature and an atmosphere approaching saturation from the presence of mois- ture given off in the breath. Unless the vitiation, however, is extreme, it is but seldom that the temperature of the air or its relative humidity are sufficiently raised by the presence of the occupants of a room to exert any noticeable effects, apart from the much greater effects produced in the same direction by the combustion of fires and gas. Micro-organisms. — It is now known that during ordinary quiet breathing micro-organisms are not given off from the air-pas- sages to the expired air ; but that the respiratory efforts associated with laboured respiration, such as coughing, sneezing, and loud talking, are characterized by the spraying of microbes present on the mucous membranes of the air-passages into the air. Most of the microbes so given off are harmless and incapable of affect- ing the health of those who breathe such air ; but at times the infective organisms of nasal and laryngeal catarrhs, of influenza, diphtheria, tuberculosis, and other diseases, are thus ejected from the air-passages, and may be the means of propagating these diseases. Apart, however, from the occasional presence of definite pathogenic bacteria, the number of harmless organisms in the air we breathe does not appear to be very material. A small number of germs per litre of air is more an indication of cleanliness of the apartment and the absence of dust, than of efficient ventilation and the avoidance of respiratory impurity. The number of microbes present in air vitiated by respiration seems to bear no very definite relation to the amount of COg gas present. This is not to be wondered at when we know that the greatest numbers of microbes are found in the air which contains the largest amount of dust, and that the air of inhabited places may be stagnant and therefore comparatively free from dust, although much polluted by respiration. It appears also that the microbes and dust particles in the air we breathe do not as a rule reach the lungs, but adhere to the moist membranes lining the mouth, nose, and throat, and are got rid of by the AIR AND VENTILATION I73 mucous excretions of these membranes. The air reaching tlae lungs is consequently, as a rule, sterile ; and the expired air in gentle breathing is also devoid of organisms. It is probable that the infective organisms present occasionally in the air are absorbed into the system, after being deposited on the mucous surfaces of the nose, tonsils, or palate, and only occasionally reach the air cells or bronchi of the lungs. On the whole, then, it would appear that there is some con- stituent of air vitiated by human respiration and transpiration, which is responsible for the injurious action of such air upon health, but that this constituent has not yet been certainly identified. Whether this unknown substance is present in the air from the lungs, or whether it is given off from other parts of the body, is uncertain. It hardly seems probable that excess of CO2, deficiency of oxygen, absence of ozone, a raised tem- perature, excess of moisture, or the presence in the air of non- pathogenic micro-organisms from the air-passages, taken either singly or in combination, would be able to give rise to those far- reaching effects that the continued respiration of foul atmospheres is known to produce. It may, however, be the fact that whilst nothing of any importance is given off to the air by human respiration and transpiration, yet the air by such means is deprived of some vital element, with which we are unacquainted, and without which the highest state of bodily health and efficiency cannot be maintained. The purity of the air in dwelling rooms depends upon the amount of cubic space for each individual and the facilities afforded for the entrance of fresh and the exit of foul air. Where these points are properly attended to, the air, although rather more impure than the external atmosphere, will not be pro- ductive of injury to health. In those extreme cases where many people are crowded together and the ventilation is totally in- adequate, the air often becomes sufQciently impure to cause headache, lassitude, nausea, and fainting. In a schoolroom crowded with seventy girls Pettenkofer found the carbonic acid to exist in the air to the extent of 0*723 per cent., or about twenty times the amount normally present in air ; whilst the organic matter, measured as albuminoid ammonia (usually present in pure air to the extent of 0*08 milligramme per cubic metre) has been found in the ward of a hospital to reach 1*3 milligrammes per cubic metre. 174 HYGIENE AND PUBLIC HEALTH The above figures represent in each case excessively foul atmospheres ; all intermediate conditions of air, varying accord- ing to circumstance, may be found in the different kinds of inhabited rooms and dwellings. The long-continued breathing of even much less vitiated air than the above sample is, probably, one of the causes of rickets in children, and tends to produce a lowered state of vitality, characterized by anaemia, dyspepsia, and lassitude, in older people. People in this lowered condition of health, which is very common amongst those who spend the greater portion of every day indoors, in ofhces, schools, work- rooms and factories, offer much less resistance to attacks of acute disease than do people who live out-of-door lives ; and they are greatly more subject to all chronic and wasting diseases. Dr. Ogle's researches have shown that, of all the industrial classes, those which are the healthiest and have the lowest death rates are the gardeners, farmers, agricultural labourers, and fishermen — those, namely, whose occupations are carried on in the open air. The death rate from phthisis in these classes is only half that of the male community generally, and they enjoy about the same amount of freedom from diseases of the respiratory organs. Differences in food or housing accommo- dation cannot account for the comparative freedom of these classes from pulmonary disease. The causal relation subsisting between foul air, produced by overcrowding and insufficient ventilation, and phthisis is now generally recognized. The most convincing proofs of such a relation are to be found in the comparative immunity enjoyed by soldiers, sailors, and prisoners at the present time from this disease. Formerly, owing to the very limited amount of cubic space allotted per head, and the disregard paid to ventilation, phthisis was considerably more prevalent among soldiers. Royal Navy sailors and marines, and prisoners in His Majesty's gaols than amongst the males of the same age in the classes from which they were derived. At the present time, other conditions, such as food, exercise, etc., remaining much the same, but more air-space and better ventilation having since been provided, the death rate from phthisis is considerably less amongst these servants and prisoners of the State than amongst the civil population. The theory of the contagiousness of phthisis has received the strongest confirmation from the discovery by Koch of the AIR AND VENTILATION I75 tubercle bacillus, an organism invariably present in tubercular deposits, but not found in any other disease. The tubercle bacillus is present in the sputa, and may be thus transferred through the air, as dust from dried sputa, to the lungs of the healthy, under conditions of too close crowding and failure to observe other necessary precautions. The excessive incidence of disease on the inmates of back-to- back houses, in which there can be no through ventilation and circulation of air, has been well established. Acute diseases of the air-passages, especially catarrhs, bron- chitis, and pneumonia, are very prevalent amongst those who live in heated, overcrowded rooms. The zymotic diseases generally are more prevalent amongst overcrowded populations than amongst those who are better lodged ; but this may be accounted for by the ease with which contagion can pass from the sick to the healthy ; for air vitiated by the ordinary products of respiration of a healthy person may induce illness, but cannot be productive of a specific disease. There is, however, evidence that insufficient air-space and defective ventilation of school dormitories and classrooms tend to produce inflammatory conditions of the throat (follicular and ulcerative tonsillitis), which in some instances, as the outbreak progresses, may be indirectly responsible for attacks of true diphtheria. The defective ventilation induces the unhealthy throat conditions ; and the subsequent appearance of diphtheria may, as Thorne supposed, be due to progressive development in type of the throat organisms, or, as is more probable, it may merely be due to the accidental introduction of the true Bacillus diphthericB, which at once assumes virulence under the defective sanitary conditions prevailing. In the air of ill-ventilated sick-rooms and hospital wards the debris of dried epithelial scales and pus cells may often be found floating. These matters are especially frequent in wards where many of the patients have purulent discharges from suppurating wounds or copious expectoration from the lungs, and are usually accompanied by an abundance of spores of fungi and bacteria, and large excess of organic matters generally in the air. In many persons the breathing of such polluted air produces an immediate effect on the throat and tonsils, passing sometimes into acute tonsilitis or hospital sore throat. Its effect in increasing the severity of, and in retarding recovery and convalescence I/b HYGIENE AND PUBLIC HEALTH from acute disease, is now generally recognized. Patients suffering from erysipelas, ophthalmia, pysemia, septicaemia, and hospital gangrene, are undoubtedly infectious to those who have open wounds. The contagious particles (pyogenic micro- organisms of various kinds) — contained in dried epitheUal scales and pus cells — may be transferred through the air from patient to patient ; and often no measure short of emptjdng the ward appears to be of any avail to stop an epidemic once begun. In times not very far distant, these diseases were, in the surgical wards of many hospitals and infirmaries, almost con- stantly present. Freer ventilation, improved sanitary arrange- ments, and the aseptic treatment of wounds and injuries, have almost eradicated such calamities from modern hospital practice. It is possible that parasitic skui diseases may spread through the air, for sporules and mycelia of Tricophyton tonsurans and Achorion Schonleinn have been found floating in the atmosphere of wards occupied by patients suffering from diseases of the skin. Vitiation by Combustion. There are three kinds of mineral coal — lignite, anthracite or smokeless coal, and bituminous coal. Lignite is a deposit intermediate in its characters between peat and coal. In some parts of Germany, considerable deposits occur ; and it is there often used both for domestic and manufacturing purposes. It is a poor fuel compared with coal. Bituminous coal is used exclusively in the manufacture of illuminating gas. Anthracite is a sort of natural coke, most of its gases having been driven off during the process of formation. Bituminous coal is generallj^ used for domestic fireplaces, although anthracite, being smoke- less (no soot), when used in properly constructed stoves, would be far preferable. Bituminous coal when burnt in an open fireplace gives off nearly three times its weight of carbonic acid, small quantities of carbonic oxide, sulphurous acid, bisul- phide of carbon, sulphuretted hj^drogen, and steam. About I per cent, is given off as fine particles of carbon or soot and tarry matters. One pound of coal requires 240 cubic feet of air for complete combustion. Illuminating gas is obtained b}^ the destructive distillation of. coal in closed retorts, wdthout access of air. The gas is subsequently purified b};' condensation to remo\-e tar and ^^"ater, AIR AND VENTILATION I77 and its temperature is reduced to about 60° F. If the tempera- ture of the gas is lowered below 58° F., naphthaline and other valuable illuminants are deposited, and the gas is impoverished. The crude gas is then passed through coke scrubbers, which are large chambers so arranged as to offer an extended surface, constantly sprayed with water, to the gas. The water absorbs from the gas nearly the whole of the ammonia and the remain- ing tarry matters, whilst a certain quantity of the ammoniacal and sulphur compounds are removed. This water impregnated with ammonia and its compounds forms the " gas liquor " or crude ammoniacal liquor of commerce, which is conducted to the tar well. The gas is then led on to the purifiers, formed of lime or sesquioxide of iron, or both, and here the carbonic acid, sulphuretted hydrogen, bisulphide of carbon, sulphocyanides, and other offensive sulphur compounds, are removed, or at least reduced in the gas to a practically unimportant quantity. The purified gas is stored in gasometers, which are sunk in the earth to a considerable depth, water being used as a seal to prevent the escape of the gas. The standard adopted by the Metropolitan Gas Referees requires all gas to be quite free from sulphuretted hydrogen ; the maximum of sulphur (in compounds other than H2S) must not exceed 17 grains per 100 cubic feet, nor the ammonia 4 grains per 100 cubic feet. When purified, coal gas contains, on an average : hydrogen, 47 per cent. ; marsh gas, 35 per cent. ; carbonic oxide, 6 per cent. ; illuminants (ethylene, acetylene), 6 per cent.; carbonic acid, i per cent.; nitrogen, sulphurous acid, etc., 5 per cent. The products of combustion of coal gas are carbonic acid, 50 to 60 per cent. ; water, 16 per cent. ; variable traces of carbonic oxide — least when combustion is most perfect — sulphurous acid and ammonia. One cubic foot of average gas combines with the oxygen of from 5 to 8 cubic feet of air, and produces when burnt about ^ cubic foot of CO2, and from 0*2 to 0*5 grain of SO2 ; and it is able to raise the temperature of 31,290 cubic feet of air 1° F. A common gas burner consumes on an average about 4 cubic feet of gas per hour, and furnishes, therefore, about 2 cubic feet of CO2 in that time. If this CO2 is to be brought down to 0'6 per mille, 10,000 cubic feet of fresh air would have to be supplied per hour for each such burner. But this is not necessary, and indeed, when adequate measures are adopted for purifying coal gas, its products of combustion contain but little impurity 178 HYGIENE AND PUBLIC HEALTH besides CO2. It is therefore generally considered that about 1,200 cubic feet of fresh air supply is amply sufficient for every cubic foot of gas consumed. A " standard " sperm candle (six to the pound), and burning 120 grains per hour, gives off about 0*4 cubic foot of CO2 per hour ; and one cubic foot of CO2 is produced bj/ the combustion of about 300 grains of oil in a lamp. The sulphurous acid in the air of towns, where coal is largely consumed, may cause the rain to be acid, and has a ver^^ destructive effect on vegetation, mortar, and the softer kinds of building stone. The products of combustion of coal gas usually escape into the air of the rooms where the gas is burnt, and serve to intensify the ill-effects on health of air already vitiated by respiration. Carbonic acid when present in the air, even to the extent of 2 per cent., if unmixed with other impurities, appears to have little, if any, effect upon health ; but above this quantity it may produce headache and nausea, and if present to the extent of 10 per cent., or even less, it may produce rapidly fatal results. Carbonic oxide, on the other hand, is very poisonous. As little as G'4 per cent, in the air may cause death from asphyxia, the gas uniting with the hsemoglobin of the red corpuscles and displacing the oxygen, so that the red corpuscles can no longer act as carriers of oxygen to the tissues, and failure of the chief nervous centres results. It therefore acts as a powerful narcotic, and exerts its effects in a most insidious manner ; for being destitute of odour and not causing any irritation of the air- passages when inhaled, it may be breathed unconsciously by the victim, who quickly experiences a loss of the power of move- ment, and even of any desire to make an effort to escape from the poisoned atmosphere. The sulphurous acid and soot in the general air of towns like Manchester, Liverpool, and London, appear to have no very marked effect on healthy people ; but they are undoubtedly injurious to many asthmatics and to people suffering from bronchitis. During dense fogs the mortality from lung diseases always increases. Yellow town fogs are due to the suspended particles of moisture in the air (which constitute a mist) be- coming enveloped in a greasy coat of mixed carbon and hydro- carbons. The mist is thus rendered yeUow and opaque, the light of the sun cannot penetrate, whilst the sulphurous products contained in the fog are extremely irritating to the respiratory mucous membranes. AIR AND VENTILATION I79 Corfield has called attention to cases of relaxed and ulcerated sore throat caused by slight escapes of coal gas into houses by defective pipes and burners. Coal gas also occasionally finds its way into houses from leaky or fractured mains in the street. The gas passes through the soil and escapes under the base- ment floor, or even finds its way up the walls behind panelling. When the escape is large in amount, the effects produced on persons inhaling the gas are of an asphyxial type due to the contained carbonic oxide ; but when the escape is small, but long continued, the sulphur compounds, and especially the bisulphide of carbon, appear to be the injurious factors affecting the throat. These effects of escape of gas would probably be most intense where the gas is insufficiently purified after manufacture. The method usually adopted for testing the soundness of gas pipes and fittings is to subject them to air pressure by means of a force pump. A pressure gauge is attached to one of the burners, and air is forced into some other connected pipe until a pressure of 5 or 6 inches of water is registered on the gauge, when the stopcock on the force pump is closed. If the pressure gauge reading is not maintained during a few minutes, the pipes or fittings are unsound. Foul-smelh ig sulphur compounds may also gain access to the atmosphere of occupied rooms from defective chimney flues. In testing a chimney flue, the outlet should be sealed from the roof, and one or more smoke rockets discharged from the fire- place opening, which must be sealed with a large piece of gummed paper immediately after the lighted rockets have been placed up the chimney ; the smoke will then escape at any defective parts of the flue. Vitiation of Air from Decomposition of Organic Matters. Animal and vegetable organic matters in cesspools and in badly constructed sewers and drains ferment and putrefy, disengaging gases, some of which are foetid and highly complex bodies, probably carbo-ammoniacal and aUied in chemical constitution to the compound ammonias (methylamine and ethylamine), whilst others are the simple gases, carbonic acid, sulphuretted hydrogen, ammonium sulphide, carbon bisulphide, carburetted hydrogen, nitrogen, etc. Recent research tends to show that the organic vapours arising from decomposition of l8o HYGIENE AND PUBLIC HEALTH animal substances may contain traces of the animal alkaloidal substances — ptomaines and leucomaines — which are contained in the faecal and urinary excretions of the animal body, and which exert a directly poisonous action on the system. The carbo- ammoniacal vapours have a strongly offensive odour, and are found in the air of cesspools and sewers where fermentative pro- cesses are in action. The suspended particles in cesspool or sewer air are dead organic debris and living organisms (bacteria, moulds and fungi, and their spores). The micro-organisms — the bacteria and fungi — are constituents of sewer air to which attention has been lately most directed. The net result of these observations goes to show that, contrary to what might have been expected, sewer air is under ordinary conditions remarkably free from the microbes which are capable of cultivation on solid nutrient media at ordinary temperatures. By ordinary conditions are meant sewers of modern construction, well laid with good gradients, and therefore comparatively free from deposits. Several observers have shown that sewer air generally possesses a relatively less number of microbes, capable of forming colonies on cultivation, than the atmospheric air outside ; and Mr. Parry Laws' investigations tend to prove that the microbes in sewer air are derived from the organisms usually present in atmospheric air, and are not identical with those found in sewage. The microbes in sewer air are chiefly moulds, whilst those in sewage belong to the class of bacilli. The explanation appears to be that the internal walls of sewers are more or less wet or moist, and it is assumed, probably with reason, that the microbes in the sewer air adhere to the damp surfaces, and are thus prevented from floating in the air. This reasoning is strengthened by, what is already known of the presence of microbes in atmospheric air generally ; for in dry dusty weather they are found in far larger numbers than in damp weather or after rainfall. In well-made sewers the sewage is borne away from the houses in a fresh and undecomposed condition ; but in old and defective sewers, and even in moderately good ones~when the temperature of the air is high, and the amount of diluting water is small — as during hot and dry summers — putrefactive bacteria undergo enormous multiplication, fer- mentative changes are set up in the sewage, and gases are formed which bubble up and break upon the surface of the liquid. AIR AND VENTILATION l8l It was demonstrated as long ago as 1871 by Professor Frank- land, that liquids flowing smoothly in channels give off no solid particles to the air, and that even considerable agitation re- sulting in frothing may not cause any perceptible increase of the solid particles in the superincumbent air, but that the bursting of bubbles of gas in a liquid had a marked effect in disseminating solid particles. The experiments of Haldane and Carnelly, which have been more recently made, also show that splashing in a sewer, which may be caused by branch drains entering near the crown of the sewer, is productive of dissemina- tion of micro-organisms in the air. The earlier investigations of Mr. Parry Laws and Dr. Andrewes on the micro-organisms of sewage and sewer air tended to show that sewer air has no power of taking up bacteria from the sewage with which it is in contact. The authors concluded that the possibility of the existence of the bacillus of typhoid in the air of our sewers is infinitely remote. They also experimented on the vitality of the bacillus of typhoid in sewage. They concluded, as the result of their investigations, that sewage does not form a medium in which much, if any, growth of the bacilli is possible under natural conditions. The death of the bacilli in sewage is probably only a matter of a few days, or at most one or two weeks. But this degree of resistance may, nevertheless, be sufficient to allow of their being carried in sewage to remote distances, and of their being able to produce disastrous results should they gain access to any water supply. Horrocks found that Bacillus prodigiosus added to sewage may be recovered from the air of drains and sewers, even when the sewage is flowing smoothly and without splashing. In one experiment the B. typhosus was found in the air of a drain through which the stools of an enteric fever patient had been slowly passed. He also recovered B. coll from the air of one of the main sewers of the town, about 10 feet above the flowing sewage. The experimental results obtained by Horrocks will tend to revive the opinion, formerly held, that sewer and drain air may be the means of spreading infective diseases, such as enteric fever, and diarrhoea. They also showed that the disconnecting trap on a house drain prevents the passage of bacteria present in sewer air into the house drains. Horrocks concludes that specific bacteria present in sewage ma}^ be ejected into the air and carried by air currents through l82 HYGIENE AND PUBLIC HEALTH drains, sewers, and ventilation pipes by (a) the bursting of bubbles at the surface of the sewage, (&) the separation of dried particles from the walls of the sewers and pipes, and probably (c) by the ejection of minute droplets from lowing sewage. The more recent work of Andrewes confirms that of Horrocks, for he has shown that under many ordinary circumstances characteristic sewage bacteria are to be found intermittently in the air of drains and sewers. The streptococci of drain air correspond with those of sewage, and only to a slight extent with those found in the outer atmosphere. Similarly the bacilli of the colon group obtained from drain air correspond with those present in sewage ; fresh air contains practically no bacilli of this character. The bacteria derived from sewage probably form but a small proportion of the total bacterial flora present in sewer air, unless there is much splashing or agitation of the sewage in the vicinity. Still, they are liable to be present, even although their numbers are relatively small. Andrewes is of opinion that the failure to identify these organisms in sewer air in former experiments w^as due to the fact that the special selective media, which are now available for the cultivation of various classes of micro-organisms, were then unknown. Chemical examination shows that sewer air is subject to wide variations. A sample of air taken from a choked sewer in Paris was found by Parent Duchatelet to contain only 13*79 P^^ cent, of oxygen, and as much as 2-99 per cent, of sulphuretted hydrogen. The air of closed cesspools in Paris must often have been very polluted to have caused those symptoms of partial asphyxia from which the workmen employed to empty them occasionally suffered. Where the quantity of sulphuretted hydrogen has been re- latively great, sudden death has in some instances resulted amongst those who have opened cesspools. The same results have followed when men have entered foul sewers. Uncon- sciousness may be produced when there is as little as 0*2 per cent, of HgS in the air. Whenever it is necessary to enter an old or foul sewer (or cesspool) the following precautions should be taken : Open the lids of the two adjacent manholes and leave open for some time, so as to obtain free ventilation and dilution of the gas ; then cautiously lower a lighted candle into the sewer, which must not be entered unless the candle burns brightly. If there is a likelihood of explosive gases being AIR AND VENTILATION 183 present in the sewer, a miner's safety lamp should be lowered, or a mouse in a cage ; in the latter case, if the mouse is lively after ten minutes in the sewer, it will be safe for a man to enter it. Whenever circumstances appear to warrant it, the man should have a strong rope tied around his shoulders, so that he could be extricated by a comrade, who should always be in readiness ; and if he should have to crawl along the sewer, a rope should also be securely tied to his ankles, so that he may be drawn back if overpowered by gas. For men overpowered by sewer gas the best remedy is artificial respiration, or oxygen inhalation, if available. Liquor strychniae should be injected subcutaneously, and artificial warmth applied to the extremities. In the London sewers the air is generally fairly pure. The most impure sample taken by Dr. Russell from the Paddington sewers was found to contain 0*51 vols. CO2, 20*7 vols. O, and 78*79 vols. N in 100 vols. The breathing of drain or sewer air undoubtedly at times produces injury to health. This is especially the case w^hen people are exposed to escapes of drain or sewer air into houses for a long period. The dose of the poison may not be sufficiently great at any one time to cause the acute symptoms above described ; but the long-continued inhalation of diluted sewer air, as in houses with defective drainage, tends to produce a general loss of health (especially in children), which is shown in various ways, as by anaemia, loss of appetite, prostration, diarrhoea, fever, headache, vomiting, or sore throat ; or it may be that only a condition of depressed vitality is produced, which offers but slight resistance to attacks of acute disease. Occasionally a severe form of tonsillitis attacks the occupants of a badly drained house. This form of tonsillitis, which is now generally recognized as " sewer air throat," is marked by great inflammatory swelling of the tonsils, very foul tongue and gastric derangement, accompanied by severe headache ■and intense depression. The temperature of the body is often not much raised, certainly not to a height proportionate to the severe symptoms ; and this low temperature, together with the intense prostration, are characteristic of many illnesses resulting from septic infection of the system. Symptoms of blood-poisoning, as shown by boils and carbuncles, petechial rashes, glandular enlargements, lymphangitis, phlebitis, albu- minuria, and fever, have been noted by some observers, and 184 HYGIENE AND PUBLIC HEALTH attributed to long-continued exposure to drain or sewer air escapes into houses. To what particular constituents of sewer air we are to attribute these and allied illnesses, it is difficult to determine. The attacks of tonsillitis, diarrhoea, etc., are not protective from future attacks ; and although there is some evidence of the " sewer air throat " being contagious and directly transmissible from person to person, it is equally likely that examples of apparently direct contagion are really due to exposure to a common cause. Probably on account of the violent splashing in soil pipes, etc., there are more possibilities of conveyance of infection through the drainage system of a building than through the air of a sewer. Inquiries have from time to time been made into the health of sewer men, who are constantly engaged in flushing and re- moving deposits from sewers. The results of such investigations lead rather to the belief that the constant breathing of sewer air is not injurious to health and life. But it must be remembered that these are picked men in the prime of life, who, now at any rate, generally work in well-ventilated sewers, where the air is not abnormally foul, and that these inquiries have not been very exhaustive. It appears, however, that they suffer somewhat from ophthalmia, and that the occupation tends greatly to aggravate venereal disease. The work is certainly unsuited to some constitutions, as many men are obliged to give it up after a short trial. It seems only fair to assume now, in the light of our present knowledge, that the men engaged in this occupation undergo a species of acclimatization, so to speak, to the influences to which they are exposed. The long- continued inhalation or ingestion of tainted air may be considered as conferring im- munity upon the individual so occupied from diseases bred by sewer air, which would readily attack one whose system had not been exposed to the acclimatizing process. Diarrhoea and dysenteric diarrhoea are sometimes caused by breathing air contaminated with excretal emanations. This is one of the many causes of the summer diarrhoea which is so common in a hot and dry season in the badly drained districts of large towns. There is now being accumulated a very considerable body of evidence to show that puerperal fever may be produced by sewer or drain emanations finding their way into the chamber of a lying-in woman ; whilst under similar conditions septic peri- AIR AND VENTILATION 185 tonitis may ensue after a miscarriage. Erysipelas, pysemia, septi- caemia, and hospital gangrene, if not caused by such emanations, are certainly favoured by conditions of excretally polluted air. The exact relationship subsisting between attacks of enteric fever or diphtheria and the previous exposure of the patient to the inhalation of emanations from sewers, cesspools, or drains has not yet been fully elucidated. The theory which is now usually accepted is that exposure to drain or sewer emanations predisposes the person so exposed to an attack of either disease, both by depressing the powers of resistance of the system and by inducing morbid conditions in the throat or alimentary canal that favour the growth and virulence of the specific organism should it happen to obtain access. It is now recognized, so far at least as regards diphtheria, that the specific organism may be present in the throats of apparently healthy persons, but unpossessed of virulent properties. Exposure to defective sanitary condi- tions may restore virulence to the organism either by offering it a suitable nidus for its growth, or by exciting the activity of other organisms (streptococci) which favour the renewal of virulence of the diphtheria bacilli (symbiosis). When excretal or other offensive emanations are given off into the open air, they are much less liable to cause disease or injury to health than when they find their way into confined spaces, such as narrow courts or the interiors of houses. In the open air of the country they are rapidly diluted and oxidized, and rendered practically harmless. In this way we can account for the excellent health enjoyed by the workmen on sewage farms and by those who live in the neighbourhood, as well as by the men engaged at sewage works ; but the process of habituation may also perhaps be partly responsible for such good results. There is some evidence that since the introduction of the septic tank system of sewage treatment, and the discharge of the putrid or septic effluent upon artificial filters (sprinkler beds) or upon land, the near neighbourhood of town sewage works has in some cases been depreciated by effluvia which are stated to be injurious to the health of the residents in the affected zone. Such effluvia may be carried at times a considerable distance by the wind ; but only those residing within a short distance of the works are likely to be affected in health. Grossly polluted rivers, which give rise during hot weather to most offensive emanations, may at times cause injury to health. l86 HYGIENE AND PUBLIC HEALTH The same may be said of effluvia from manure manufactories, soap works, tallow works, and other offensive trades, and also of the effluvia from putrefying animal bodies, given off into the open air ; it being a matter of experience, that occasional attacks of sickness and diarrhoea and chronic distaste for food may be produced by offensive emanations, even when discharged at a height from lofty chimneys. The air of crowded graveyards and vaults may contain excess of CO2 and organic vapours (carbo- ammoniacal) ; if such polluted air rises from the soil and escapes into buildings, it may cause serious sickness among the occu- pants ; but when the vapours escape into the open air, even in the midst of towns, no marked injurious effects appear to arise. The air over marshes is impure from the large amount of decaying vegetation in the water and soil. Carbonic acid, sul- phuretted hydrogen, and carburetted hydrogen (marsh gas), are generally present in some excess, together with decaying organic matter, both in the form of vapour and of suspended matter. The suspended matters in marsh air consist of vege- table debris, diatoms, algse, fungi, bacteria, and other micro- organisms. In some marshes the air is very rich in H2S, and the symptoms of anaemia and prostration have been held to be due to this fact. Vitiation of Air in Industrial Occupations. Two kinds of occupation have long been recognized as hurtful, viz., (i) those that give rise to mechanical or chemical irritation of the lungs by trade dusts or vapours ; and (2) those in which the workers are exposed to great variations of temperature. Although in some trade processes injurious gases are evolved and escape into the air that must be respired by the workmen engaged in the trade, yet the vast majority of industrial occu- pations are injurious, or otherwise, according to the amount and nature of the dust which is produced. As subsidiary factors of high importance must be considered the conditions under which the dust-producing work is carried on, whether in the open air, in well-ventilated workshops or factories, or in overcrowded close rooms at a high temperature and with the air saturated with moisture. The long-continued inhalation of dust tends to produce disease of the lungs, especially bronchitis, emphysema, and interstitial pneumonia, and it predisposes to fibroid phthisis. The source of the dust, whether vegetable or mineral, is not so AIR AND VENTILATION 187 important as the character of the particles which compose it. The most injurious kinds are those whose particles are hard, sharp, and angular, which become impacted in the walls of the bronchioles or air cells of the lungs, are not easily expectorated, and set up irritation and chronic inflammation of the tissues around. The soft or rounded particles are not capable of doing nearty so much mischief. Coal-miners' lungs are often after death found to be black (anthracosis) from the impaction of fine particles of coal dust in the puhnonary alveoli, without the m- dividual having manifested any puhnonary sj^mptoms during life. The following table gives the comparative mortality figures for males in different dust-inhaling occupations, the mortality figure from all causes amongst males in England and Wales being taken at 1,000. It is important to note that the column under phthisis represents the tubercular form of this disease, but undoubtedly includes many cases of fibroid phthisis as well. Comparative Mortality of Males, Twenty-five to Sixty-five Years OF AGE, in certain DUST-INHALING OCCUPATIONS FROM PHTHISIS AND Diseases of the Respiratory Organs. ^ Diseases Phthisis and ; of the Diseases of the Phthisis. Respiratory Respiratory Organs. Organs. Coal miner .... 126 202 328 Carpenter, joiner 204 133 337 Baiier, confectioner . 212 186 398 Plumber, painter, glazier . i 246 18S 431 Mason, builder, bricklayer 252 201 453 Wool manufacturer . 257 205 462 Cotton manufacturer 272 271 543 Quarryman (stone, slate) . 308 274 S82 Cutler ....'. ZT^ 389 760 File maker .... 433 350 783 Earthenware manufacturer 473 - 645 1,118 Cornish miner .... All males (England and Wales) . 690 4S8 1,148 220 182 402 Fishermen .... 108 90 198 More recently Dr. Tatham has furnished a valuable contribu- tion^ on the varying rates of mortality among men engaged in 1 Dr. Ogle's Report, Supplement to the 4Sth Annual Report of the Registrar-General. 2 Supplement to the 55th Annual Report of the Registrar-General. lOb HYGIENE AND PUBLIC HEALTH different occupations, the main conclusions being based upon the deaths that occurred during the three years 1890-92 among males between twenty-five and sixty-five years of age — the period during which the effect of occupation is assumed to be most marked, and in which the proportion of occupied males is largest. Taking 1,000 to represent the mortality of all males at these ages in England and Wales, the comparative mortality figure for all occupied males was 953, and while it was 687 in agricultural districts, it reached to 1,248 in industrial districts. The com- parative mortality figures of males from twenty-five to sixty-five years of age was low for clergymen (533), gardeners (553), farmers (563), school teachers (604), farm labourers (632), and lawyers (821) ; for medical men it was 966 ; and it was high among brewers (1,427), general labourers in industrial districts (1,509), publicans (1,642), costermongers (1,652), and hotel servants (1,725). The excessive mortality of cutlers, file makers, scissor makers, and nail makers, noted in previous periods of observation, , was still higher m 1890-92 ; and slaters, tilers, wool, silk, and cotton dyers, potters, glass manufacturers, tin miners, coal heavers and chimney sweepers again showed marked excess of mortality. In Dr. Tatham's report the figures bearing upon the fatal effects of breathing dust-laden air, or air fouled in other ways, have acquired increased value from the careful elimination of the disturbing influence of the varying age proportions of persons engaged in different occupations. Taking 100 to represent the combined mortality from phthisis and diseases of the respiratory organs among those engaged in agricultural occupations, the comparative figures from these diseases among those engaged in occupations which cause dust of various kinds reaches 373 for file makers, 407 for cutlers and scissor makers, and 453 for potters and earthenware manufacturers. That coal miners should stand at the head of Ogle's list, as re- gards freedom from lung diseases, is somewhat surprising, con- sidering that the air in the underground passages in which they work, even in the best ventilated mines, is vitiated by respiration, combustion of lights, and blasting agents, which throw into the air much CO2 CO, H2S, etc. In addition, CO2 and CH4 are often evolved in considerable volumes from the strata cut through by the shafts and borings, and the air in the workings is always thick with coal dust. Dr. Ogle explains the comparative in- AIR AND VENTILATION l8g nocuity of coal dust in causing lung disease by the microscopical character of its particles, which are comparatively free from sharp points and corners. He is also inclined to attribute to coal dust a special property of hindering the development and arresting the progress of tuberculosis — a disease, it is to be remembered, which might be expected to be very fatal to coal miners, from the fact of their working in a heated vitiated atmosphere, and being liable to sudden alterations of temperature in going to and leaving off work. Where there is a considerable proportion of stony particles in the coal, lung diseases appear to be favoured ; and this no doubt accounts for the fact that the incidence of miners' phthisis in different collieries is unequal. Experiments upon the lower animals indicate that carboniferous particles arrested in the nasal and pharyngeal passages, and after- wards swallowed, may pass through the intestinal epithelium and through the lymphatic system, finding their way into the thoracic duct and thence into the venous circulation, to be ultimately arrested in the capillaries of the lung. These experiments also demonstrated that in young animals the carbon particles do not readily get beyond the mesenteric glands. In animals and men the lungs soon rid themselves of such particles when the broncho- tracheal glands are healthy ; but when these latter have become injured, as in the case of miners, definite anthracosis supervenes. The workers in coal mines are liable to a condition of the eye- sight which has been termed " miners' nystagmus." This is essentially a disease of the collier, but is unknown among the younger miners ; it was first described at the time when the illumination in collieries was considerably reduced by the intro- duction of the Davey safety lamp. The evidence collected points to the conclusion that the condition is not caused by awkward positions of the body nor by feeble illumination alone ; and with an improvement in the ventilation and lighting, and shorter hours of work in mines, the incidence of the disease shows a tendency to diminish. The comparative immunity of coal miners from tubercle is not displayed by the Cornish or tin miners, who come at the bottom of the list. Their mortality from lung diseases constitutes nearly two- thirds of their total mortality, and is nearly three times as great as that of Cornish males generally. They work under conditions of heated and vitiated air like the coal miners, but they inhale a sharp, angular, and most irritant stone dust, instead of the com- igO HYGIENE AND PUBLIC HEALTH paratively smooth coal dust. All metalliferous miners working in hard stone are exposed to dust-inhalation ; but those who- are most exposed are those who employ drilling or boring machines acting by percussion (compressed air). A jet or spray of water directed upon the rock, when the drill is at work, is a valuable means, which has been largely adopted, of keeping down this dust. Gold miners also are short-lived, and suffer largely from phthisis. The other occupations in which the workers are ex- posed to the inhalations of stone dust are masons, builders, and bricklayers, who carry on their work chiefly in the open air, and have a lung disease figure of 453 ; stone and slate quarrymen, who also work mainly in the open air (582) ; and the earthenware, china, and pottery manufacturers, who suffer enormously from pneumonia, bronchitis and emphysema (potters' asthma), and phthisis. Among these latter the lung disease mortality is nearly the same as that of the tin miners. They carry on their trade in close and heated factories, and, besides the fine irritating dust, are exposed to great vicissitudes of temperature. The chinaware is baked with flint dust, and this is subsequently brushed off by women, the process being known as " china scouring." This process is especially dangerous, the silicious constituents of the dust being the chief cause of mischief. Cutlers and file makers, needle, pin, and tool makers are exposed to metallic dust and stone dust given off from the grindstones, and they suffer largely from phthisis, bronchitis, and pneumonia. File makers are in addition liable to lead poisoning, from their using a cushion of lead on which to strike their file. In these trade processes the dust should be collected, so far as possible, by hoods placed immediately over the benches which lead into a common outlet shaft, the draught in which is maintained by a revolving fan. Or, where hoods are inconvenient, perforated metal plates may be let into the benches and hopper expansions of the outlet shafts fitted immediately below these plates ; the fan then pulls air, and with it the dust, through the perforations of the metal plates. The dust from the common outlet shaft may be aUowed to settle in a dust chamber, or be arrested by filtering the air through canvas screens, or by a water surface or spray. The workers should be made to wear respirators in the more dusty rooms ; and in steel grinding, magnetic shields are useful for attracting and collecting the steel dust. In the grinding trades the grindstone may be enclosed in a hood or AIR AND VENTILATION I9I casing connected to a powerful exhaust fan. This is especially desirable in dry grinding ; and, where necessary, glass may be let into the hood to permit light to pass to the grinding surface. Dr. Harold Scurfield has recently shown (1908) that the death- rate of grinders from phthisis is more than six times that from respiratory diseases, and nearly three times that of the average male in Sheffield ; also that in the case of cutlers the death-rate from phthisis is nearly three times that from respiratory diseases, and four times that of the average male in Sheffield. The first direct result of this form of dust-inhalation is an irritation of the mucous membrane of the nasal passages, often with erosion and ulceration, followed by atrophy and loss of smell. This atrophy facilitates the entrance of dust into the lungs, and fibrotic inflammatory masses form, which ultimately break down, leaving cavities which frequently become inoculated with the tubercle bacilli. Hence those who contract this pneumoconiosis are very liable to die from a superimposed tubercle infection. In brass foundries the workers (more especially the turners, polishers, and filers) inhale a metallic dust which is productive of a disease formerly called " brass founders' ague." The sjonptoms which caused Dr. Greenhow to designate the disease brass workers' ague are shown to be due to the ingestion of a quantity of the irritant metallic dust sufficiently large to cause vomiting with its attendant depression. Brass is an alloy of copper and zinc, in the proportion of about three to one. Prob- ably the zinc is the offending ingredient, although possibly the copper may have some additional influence. The s5nnptoms are described as tightness and oppression of the chest, with indefinite nervous sensations followed by shivering and profuse sweating. The illness only occurs in those who are new to the work, or who resume work after an absence of a few wee~ks. The men who suffer in this way drink freely of milk and promote vomiting, the best treatment that could be devised for copper or zinc poisoning. Chronic copper poisoning is also common amongst brass workers, and bronchitis from inhalation of the irritant dust. The leading symptoms of chronic copper poisoning are : Anaemia, nausea and vomiting, colic, wasting, headache and nervous symptoms, and a green line (due to copper) is seen at the bases of the teeth. The patient also suffers from profuse sweatings which stain the underlinen a greenish colour, itching, skin erup- 192 HYGIENE AND PUBLIC HEALTH tions, chronic bronchial catarrh, and later, pulmonary fibrosis. For the prevention of brass founders' ague " special rules " are enforced b}^ the Chief Inspector of Factories. These rules apply only to the casting and mixing shops, and require that adequate means be provided for the escape of noxious fumes and dust, that the shops be cleaned down and limewashed every year, that the workpeople have every facility for personal cleanliness, and are prohibited from eating during the process of casting. The operatives in cotton factories work in a heated atmosphere saturated with moisture by steam, and laden with filamentous particles of cotton and mineral substances used for sizing. A standard of purity of the air is now enforced, by which the CO2 may not exceed 0*09 per cent, in the artificial^ moistened sheds. In order to avoid the consequences of heavy steaming, Haldane has suggested that a fine spray of cold water should be employed instead of hot steam. In woollen factories the heat is not so great, and there is less dust owing to the wool being treated with oil ; but wool sorters are liable to contract anthrax from infected fleeces. In silk mills, dust and high temperature are injurious to the material, and are consequently avoided. Millers and bakers are liable to inhale flour dust, but as this substance is probably arrested in the mouth and nose, and does not reach the lungs, it can hardly be regarded as productive of lung disease. Carpenters, joiners, and cabinet makers are exposed to wood dust. The dust from the harder kinds of wood is prob- ably more injurious than that from the softer kinds. Dr. Birmingham has drawn attention to the great mortality among those engaged in the " ganister " industry. Ganister is a very hard silicious stone, with a very high fire-resisting capacity, and it is used for lining the bottoms of crucibles, etc. Formerly a very large proportion of the workers died from fibroid phthisis. Millstone masons also suffer largely, the phthisis death-rate of these workers being nearly ten times as great as that among the general male population of corresponding ages. Occupational deafness is most in evidence among persons employed as boiler makers, owing to the loud hammering which is maintained. Where the noises are very great and continuous, workmen are recommended to plug the ears with plasticine worked into cotton. From brickfields, organic vapours and CO2, CO, H2S, and SO2 gases are evolved. Bricks are made of clay mixed with a small AIR AND VENTILATION I9J proportion of ashes. When bricks are arranged in the clanii)s in layers, alternating with the breeze or combustible material, the emanations from the burning material are very penetrating ; and when dust-bin refuse is used to burn the bricks, the partially burnt organic vapours are highly disagreeable, and are perceptible at considerable distances from the brickfields. When bricks are burnt in kilns provided with flues, there is far less liability to nuisance, as the products of combustion are more perfectly con- sumed. Kiln burning should be insisted upon in the case of all brickfields situated in the close vicinity of inhabited houses. The Alkali Works, etc., Regulation Act of 1881 provides that 95 per cent, of the hydrochloric acid gases and vapours produced in alkali works must be condensed ; and in each cubic foot of air, gas, or smoke escaping into the atmosphere there may be only i grain of HCl. Each cubic foot of air, gas, or smoke issuing from sulphuric acid works must not contain acidity amounting to more than 4 grains of sulphuric acid (SO3). The keeping apart of acid drainage and alkali waste is strictly enforced, and all waste substances must be got rid of without nuisance. Other works to which this Act applies are salt works, cement works, chemical manure works, nitric acid works, sulphate and chloride of ammonia works, chlorine works, bleaching works, and gas Uquor works. In the manufacture of alkali the chief nuisance arises from the improper storage and disposal of the " tank waste," which con- tains compounds of sulphur. In the process, common salt is decomposed by sulphuric acid, and the crude sodium sulphate (" salt cake ") is mixed with chalk and coal and heated ; sodium carbonate is thus formed, and the unburnt carbon and calcium sulphide darkens the mass, which is known as " black ash." The sodium carbonate is dissolved out by water, and the residue constitutes the " tank waste." The workers suffer from diseases of the lungs, bad teeth, and dyspepsia, mainly arising from the acid fumes of the salt cake ; but the hydrochloric acid fumes are so diluted as to generally produce but little effect on the workers, though they injure surrounding vegetation. The process of the manufacture of coal gas varies somewhat in different manufactories. The waste gas lime gives rise to serious offence, and its removal from the tank causes consider- able irritation to those engaged in the work. To prevent dust, the lime should be watered a little before being dug out from 13 194 HYGIENE AND PUBLIC HEALTH the purifiers, and removed as often as necessary. During removal it should be covered over with sacking. Nuisance may result in the neighbourhood of gas-works by (i) smoke given off during the charging and drawing of retorts ; (2) the generation of water-gas and steam when the red hot coke is quenched with water, the steam being especially offensive when the coal used in the manufacture of the gas is of a sulphurous nature ; (3) the escape of crude gas from the mouthpieces of the retorts ; (4) the smoke given off from imperfectly carbonized charges when withdrawn ; (5) the offensive lime refuse from the purifiers, where lime alone is used for the absorption both of carbonic acid and sulphur compounds. When exposed to the air, sulphuretted hydrogen and bisulphide of carbon are released from the sulphides and sulpho-carbonates of lime by the action of the oxygen and carbonic acid in the air, and a most offensive nuisance is created. When, however, sesquioxide of iron is used for removing the sulphur compounds, and the lime is used only for absorbing carbonic acid after the sulphur compounds are with- dra^^•n. the nuisance is reduced to a minimum. Offensive Trades. The noxious or oijensive trades specified in the Public Health Act, 1875, are those of a blood boiler, a bone boiler, a tripe boiler, a soap boiler, a tallow melter, and a fellmonger. Bye-laws may be made regulating these trades " or any other noxious or offensive trade." The model bye-laws of the Local Government Board also specify the trades of a blood dryer, a leather dresser, a tanner, a fat melter or fat extractor, a glue and size maker, and a gut scraper. As to what will constitute " a noxious or offensive trade " other than those specified, it is held that the business, in addition to being proved noxious, must be ejusdem generis with those specified, and deal with animal matters in some form. Thus, brick making has been held not to be an " offensive trade," whereas the business of a rag and bone merchant is so. A BLOOD BOILER OR BLOOD DRYER deals with the fresh blood collected at slaughter houses, in order to procure (i) blood albumin, by desiccating the serum which is drained off from the clots ; (2) turkey-red pigment ; and he may also (3) prepare blood for sugar refiners, etc. The blood clot is often mixed Math sulphuric acid, desiccated, and mixed mth super- phosphate to form manure. The chief sources of nuisance are : (i) Unsuitability of premises for carrjdng on the process, thus rendering it difficult to conduct the business without nuisance ; (2) the improper conveyance and storage of the blood ; (3) offensive vapours given off during the process of blood boiling or drying, or manure making (which is often can-fed on on the same premises) ; (4) effluvia from the storage of exhausted clots prior to the manufacture of manure or their removal from the premises. A BONE BOILER deals with fresh bones in order to procure gelatine, glue, and fat. The bones are boiled along ^dth the hoofs, trimmings of hide, etc., procured from the slaughter houses. The boiled bones are subsequently AIR AND VENTILATION I95 used for liaiulles to knives and forks, tooth brushes, etc., or are crushed, and superphosphate manure manufactured from them by adding sulphuric acid. The chief sources of nuisance arise from ; (i) Unsuitabihty of premises ; (2) improper conveyance and storage of old bones and scraps ; (3) offensive vapours given off during the process, especially where steam jacketed cylinders are not used for the boiling ; (4) the debris in the boihng cyhnder, called " the scratch," is a fruitful source of nuisance, as is also the piling up of the recently boiled and steaming bones. A TRIPE BOILER is One who boils the first stomach (" the paunch ") of oxen and sheep for sale as food. The chief nuisances result from : (i) Filthiness and unsuitability of premises ; (2) improper storage of material on premises ; (3) the vapours escaping during the process of boiling ; (4) the vapours arising from the steaming tripe after its removal from the boiler. A FAT OR TALLOW MELTER (and SOAP BOILER) is One who melts kitchen fat and butcher's waste fat in pans for the purposes of manufacturing candles, soaps, leather dressings, and preparations for greasing machinery. In soap boihng the fat is boiled with soda lye for " hard soaps," and with potash lye for " soft soaps." I'he chief nuisances result from : (i) Filthiness and unsuitability of premises ; (2) improper conveyance and storage of material ; (3) the vapours escaping during the process of melting or boiling, and ladling out ; (4) the improper storage of waste residue (" the greaves "). The greatest nuisance during melting arises when old and offensive materials are used. A FELLMONGER is One who prepares either recent or old foreign skins for the leather dresser. The fresh skins are first trimmed of adherent flesh and then freed from dirt by beating them with sticks. They are then soaked in water. Lime is next worked into the fleshy side of the skin, and the skin is then hung up until the wool or hair is easily detachable by the hand. The old foreign skins are prepared by first soaking in water, and then they are kept until decomposition has so loosened the wool or hair that it is easily detached ; this is known as " the tainting process." By either method the skin thus prepared is known as " a pelt," and these are cast into a pit containing milk of lime, after which they are dried and sent to the leather dresser. 1 ...■ The chief mdsances arise from : (i) Filthiness and unsuitability ^of premises ; (2) improper conveyance and storage of skins ; (3) offence arising from the " tainting " process ; (4) the failure to satisfactorily dispose of the dirt and flesh removed from the skins. A LEATHER DRESSER and TANNER couvert the skins, after treatment as above described, into various kinds of leather. The tanning agent (oak bark, etc.) brings the putrescible hide into a non-putrescible condition : and the leather dresser, by appropriate treatment with fatty and other matters, completes the conversion to leathers of various sorts. Pigeons' manure and dogs' dung are used in the " soaks " for softening the skins prior to tanning. The chief nuisances arise from : (i) Filthiness and unsuitabihty of premises ; (2) improper storage of skins ; (3) the failure to satisfactorily dispose of the waste water or spent liquor, etc. A GUT SCRAPER is One who scrapes the small intestines of swine and sheep for the purpose of making sausage skins, catgut, etc. The gut is first cleansed, and soaked in salt and water for a few days, and then allowed to remain in plain cold water until sufficiently softened to admit of the easy removal (by means of a wedge-shaped piece of wood) of everything but the peritoneal and a httle of the external muscular coat of the intestine. The chief nuisances arise from : (i) Filthiness and unsuitabihty of premises ; (2) the failure to promptly remove all refuse and waste material ; 196 HYGIENE AND PUBLIC HEALTH (3) improper and too prolonged storage of the intestines prior to their utilization. A GLUE AND SIZE MAKER extracts the gelatine by boiling almost every kind of waste animal tissue, but more especially bones, hoofs, horns, and skin trimmings. The raw material is first limed, and then washed and well boiled for some hours. After the glue has been allowed to cool and set, it is cut into slices and dried. The chief sources of nuisance are / (i) Unsuitability and general filthiness of premises ; (2) the storage of material, especially when old and foul ; (3) vapours arising from the conduct of the process, which are especially offensive when old material is used ; (4) the accumulation and improper storage of the residue (" scrutch "). The fat is usually skimmed off the surface of the hot water, and the " scrutch " is used for manure making. The various nuisances in the trades above referred to may be prevented or abated by the adoption and enforcement of suf&cient bye-laws. Such bye-laws should secure : — 1. Free access to the premises by any officer of the sanitary authority. 2. The restriction of such trades to suitable premises. Gut scraping, for instance, cannot be carried on, as it sometimes is, in small houses, without giving rise to offence. 3. The maintenance in good order of the drainage, lighting, and ventila- tion of such premises, and the proper cleansing of them. The floors or pavements should be kept in good repair so as to prevent absorption of any liquid filth, and should be swept or washed at the close of every day, and all splashings should be removed. The walls and ceilings should be hot limewashed twice a year at specified periods (say the first weeks of April and October) , after all splashings have been wiped off ; and the walls must be rendered non-absorbent of any liquid filth or refuse to at least the height to which such splashings may reach. 4. The proper conveyance to the premises, and storage on the premises of the material used, so as to prevent the escape of noxious and offensive emanations. In soine cases the material should be brought to the premises in non-absorbent covered receptacles, and stored in special closed compart- ments ventilated into a tall chimney flue, by means of an air shaft provided, if necessary, with a gas jet or fan. Sometimes the materials to be stored should be dried, or treated with milk of lime, or even sprinkled with a little carbolic acid solution (i in 40). Stored fat should be dried and laid out on racks in a cool room ; and the materials used for glue making should be stored as dry as practicable, or treated with a sufficient quantity of milk of lime and closely stacked. 5 . The best practical means of rendering inert the vapours emitted during the carrying on of the process. Where melting and boiling is performed, this should be done in steam jacketed pans, so as to guard against the higher temperatures which burn the fat, etc., and give rise to the formation of most offensive empyreumatic odours. Large hoods communicating by pipes with the furnace flue should be used to collect the vapours given off from the contents of the pans during the boiling ; and the chimney by which these fumes escape should either be carried up to a considerable height, or the vapours should be condensed in a suitable condensing apparatus, 1 or conducted into the furnace fire and cremated, This cremation may also be effected by means of a small " cremator " placed in the chimney. 1 A cheap and satisfactory condenser can be made by taking ordinary drain pipes and packing them with pieces of coke, over which water is allowed to trickle in a constant stream ; or the vapours may be absorbed in a water spray, or by being brought in contact with trays of water, as in a " scrubber." AIR AND VENTILATION I97 The fumes arising from steaming bones, meat, etc., can be prevented by applying cold water, directly after their removal from the boiler. 6. All filth and refuse matter to be collected in a sufficient number of non-absorbent vessels with close-fitting covers, and removed from the premises forthwith. Fellmongers and others must not keep uselessly decomposed skins, etc., on the premises. 7. All water used for soaking skins, etc., to be renewed sufficiently often (at least once a day) to prevent effluvia arising therefrom, and all pits used for holding such water to be rendered water-tight. This bye-law will apply to the trades of a fellmonger, gut scraper, and leather dresser. 8. All waste hme to be removed with reasonable dispatch in covered receptacles, as also all other waste or useless material. 9. All implements and receptacles to be kept sweet and clean. The floors and receptacles in some cases to be sprinkled or washed with some deodorant, as in gut scraping. 10. Penalties for offending. The discharge of waste liquor into drains at a temperature exceeding 110° F. has often given rise to great offence from the sewer ventilators adjoining the premises on which some of the above trades are conducted. This is now provided for by statute (The Public Health Act Amendment Act, 1890), and all hot liquid refuse must be allowed to cool before it is discharged into a drain. It will be well to next consider a few of the more common trade nuisances. Fish frying. — Nuisances arise from the neglect to adopt proper meanej of collecting the effluvia and dealing efficiently with them. The effluvia are increased by (i) the prolonged use of the same oil for cooking purposes, (2) the burning of the oil and consequent production of empyreumatic odours, when the heating is done over an open fire. These nuisances are best prevented by using the best dripping instead of oil, and by supplying a large deep hood to collect the effluvia arising from the frying. The hood should lead by a shaft into a fairly high chimney, and it is often necessary to provide a gas jet at the mouth of the shaft leading from the hood, so as to promote draught. To obviate the burning of the oil, the frying should be done in a deep vessel containing from 6 to 10 inches in depth of oil, or preferably steam jacketed cylinders should be employed. It is rarely, if ever, necessary to cremate the effluvia in the fire, or to absorb them in the water of a " washer " or condenser. Knackeries. — A knacker is properly a horse slaughterer, but he also slaughters other old and diseased animals, and receives the carcases of those which have died of disease or accident. Nuisances arise from the cries of the animals prior to their slaughter, for they are commonly kept several days ; the filthy way in which they are sometimes kept ; the undue and improper storage of material on the premises ; the general unsuitability and filthiness of the premises ; and the processes of bone boiling, flesh boiling (for cats' meat or fat extraction), or gut scraping, etc., which are sometimes carried on in the same premises. Pig keeping. — This trade may become a nuisance from the improper storage of sour, malodorous food, with which the pigs are frequently fed, and from the effluvia from the sties. The sties should always be placed at a considerable distance from houses — at least 100 feet in urban districts. They should be floored with hard, impervious, and jointless material (e.g., concrete), laid to a good fall towards a channel leading to a gulley which discharges into a drain or covered cesspool. The feeding material should be kept in impervious vessels Avith close fitting lids, and the sties should be swept out and cleansed daily. Artificial manure making. — The materials used are : (i) All animal waste materials from the offensive trades above referred to ; (2) mineral matter, e.g., sulphate of ammonia, nitrate of soda, gypsum, etc. 19^ HYGIENE AND PUBLIC HEALTH " Superphosphate " is made from a mixture of mineral phosphate and ground bones, treated with sulphuric acid. The whole process is more or less offensive from the presence of the organic materials, and the fumes given off during the manufacture and the subsequent drying. " Poudrette " is generally manufactured from privy or pail contents, fish offal, etc., by treatment with sulphuric acid ; it consists of a brown dry powder. The process must be conducted under very special conditions, or a grave nuisance results. Paper making. — Cotton and linen rags, wood pulp, hemp, straw, waste paper, etc., and esparto grass are employed in this business. The rags are " dusted," and then placed in boilers to which caustic soda is added. After the rags have been well boiled, the liquid should be run into settling tanks, and subsequently filtered through earth and ashes, before it is permitted to enter a stream, so as to obviate serious pollution and nuisance. When the rags are removed from the boilers they are washed, and bleached. Esparto grass is reduced to pulp by boiling with caustic alkali and by subsequent treatment by machinery. The vapours given off during the boiling of the grass, and from the hot liquor after removal from the boilers, have an offensive senna-like odour, but the recovery of the soda from the waste liquor is the most offensive part of the process. Industrial Poisonings. Lead poisoning may result from direct absorption of the metal through the skin or mucous membranes, or by inhalation of the vapours or powder of lead compounds. The trades most liable to suffer are : painters, plumbers, pottery workers, gilders, file cutteis, type founders, calico printers, glass grindeis, bronzers, enamellers, and the manufacturers cf white lead and lead paints and colours. Carbonate of lead, or white lead, is very extensively used as a paint, and many coloured paints contain the metal. Both the acetate and the nitrate of lead are used in calico printing and cotton dyeing to produce orange and yellow colours. Sulphide of lead is used mainly for glazing pottery, bricks, etc., and oxide of lead is used in enamels. File makers are liable to lead poisoning from their using a cushion of lead on which to rest the file while the rough surface is being prepared by means of a blunt chisel struck with a hammer. The glass grinders may be poisoned from the constant contact with the putty powders (rich in lead) which are used for polishing the glass ; and the type founders and type setters from the constant handling of the type metal — an alloy of lead, tin, and antimony. At piesent the most common causes of lead poisoning are the working with lead glazes, and the manufacture of white lead. " The proportion of severe cases among file cutters and those engaged in coach painting, in ship building, and in other industries where paint is used, exceeds that of those engaged in industries where the danger is primarily from the dust of salts of lead " (T. M. Legge, H.M. Medical Inspector of Factories). Plumbers inhale volatilized oxide of lead and painters the dust of white lead ; but lead is also taken into the system when meals are taken with dirty hands. Sanitary Piecautio-ns. — i. All fumes and dust should be collected as rapidly and completely as possible as they are formed, and conducted, by means of a powerful exhaust, to condensing chambers or washers ; so that the air of the work places may be kept as pure as possible, and the external atmosphere around the works also saved from pollution. 2. The handling of the metal, or of substances containing lead, should be reduced to a minimum. 3. Every facility and encouragement should be given to the workers AIR AND VENTILATION I99 to practise personal cleanliness. Mouth washes and tooth and nail brushes should be used before partaking of a meal. Strict rules should be enforced for the washing of hands. A basin, tap, and towels must be supplied for at most every five persons. 4. In the more dusty rooms overalls, close fitting round the neck and wrists, and respirators are desirable, in addition to exhaust fans to remove dust and insure abundance of fresh air. 5. Meals should not be permitted to be taken in any of the workrooms. 6. There should be periodical medical inspections of the workers. Those who are more especially susceptible to the poisonous effects of the metal should at least be excluded from the more dangerous rooms. This \vill apply to all women and children. All those with cuts or sores should be excluded from the works. 7. Sulphuric acid lemonade is recommended as a drink for the work- people, as it favours the formation of an insoluble sulphate of lead ; the free drinking of milk is also recommended. 8. The workrooms must be kept clean, well ventilated, and as free from dust as possible. The immediate removal of the dust is the essential preventive measure in china and earthenware factories, in places where processes connected with white and red lead are carried on, in paint and colour factories, in all workrooms in which operations of litho-transfer are conducted, and wherever iron plates are enamelled. By the adoption of preventive measures on these lines, cases of industrial lead poisoning in this country have been reduced some 50 per cent, during the past few years. The beautiful glaze on chinaware and its colouring have hitherto been mostty obtained bv the use of carbonate of lead, and the workers in these processes suffer considerably from lead poisoning. The use of " fritted " lead — ^that is, lead fused into a kind of glass (a silicate) which is ground down and mixed with water — is attended with far less danger to the workers. It is stated that it is even safer to employ a double silicate of lead, which is more insoluble than the silicate. It appears, moreover, that the use of leadless glazes gives equally satisfactory results in ordinary white and cream-coloured ware ; and experts have expressed the view that for seven-tenths of the total output leadless glazes can be used. No glaze can now be used which yields to a dilute solution of hydrochloric acid (o"25 per cent, of acid, the same acidity as that of human gastric juice) more than 5 per cent, of its dry weight of soluble lead, calculated as lead mon- oxide. Higher percentages of lead are allowed on condition that the employer adopts a scheme of compensation for those of his workpeople who suffer from lead poisoning, such workpeople being aware of the risks they run, and agreeing to face such risks. Phosphorus poisoning is experienced anaong match makers. Makers of phosphor-bronze and the old-time vermin killer have also suffered. The phosphorus is obtained from bone ash, and serious nuisance and harm to the workers will result unless every proper precaution is taken. During the distillation of the impure phosphorus, dangerous gases are evolved. The red or amorphous phosphorus is largely used in the manufacture of safety matches, the phosphorus mixed with glue being contained in the rubbing surface on the box. The igniting material is composed of chlorate of potash, iron pyrites, peroxide of manganese, powdered glass, sulphide of antimony, and an adhesive agent — generally glue. Sanitary Precautions. — i. The discontinuance of the use of the dangerous yellow phosphorus, which is volatile at ordinary temperatures, and the employment of the red phosphorus for safety matches only. A harmless " strike everywhere " match can now be made from the sesquisulphide of phosphorus. 2. Frequent medical inspection, especially of the teeth. It is found that 200 HYGIENE AND PUBLIC HEALTH workers with sound teeth are practically exempt, but workers with carious teeth are specially prone to poisoning by phosphorus and to the onset of " phossy jaw " (caries of the jaw bones). 3. The selection of the Avorkers. 4. Every facility for the practice of extreme personal cleanliness. Alkaline mouth washes should be used. 5. Large, specially well ventilated workrooms, and when possible the work should be performed in the open air. This precaution greatly reduces the amount of phosphorus poisoning. All fumes should be drawn awaj?- from the Avorker by means of efficient extraction fans. 6. No food or drink to be taken in the workrooms. 7. Short shifts of work, especially of those employed in the more dan- gerous rooms. Charcoal respirators should be worn by those engaged in the worst rooms ; i.e., where the dipping of the wooden heads of tlie matches in the phosphorus paste is performed. 8. The emplo5mient of machinery for dipping, drying, and boxing matches, as now installed in some manufactories. The most dangerous factor in the whole process is the escape of fumes of the lower oxide of phosphorus (P^Og) from the moist heated paste. The oxidizing effect of the vapour of turpentine is recomnaended as advantageous. The atmosphere may be impregnated with these vapours by exposing turpentine in saucers about the room, or on sponges hung round the necks of the workers, so that the vapours rise up into the ail as it is respired. The phosphorus should always be stored carefully in glass or earthenware vessels surrounded by water, and away from the workrooms. The sulphur employed must not be overheated, or there is danger of ignition and the development of large quantities of SOg. The pans in which the sulphuring is done should be covered, and the fumes conducted to a tall chimney. Owing to the adoption of greater sanitary precautions, only one case of phosphorus necrosis has been reported for several years. The symptoms of chronic phosphorus poisoning are angemia, anorexia, headache, emaciation, cutaneous and muscular hypertesthesia, muscular pains and weakness. In those exposed to fumes, there may occur pain and swelling of the gums, followed by abscess and, later, necrosis of the jaw bone (" phossy jaw "). Persons exposed to phosphorus fumes are said to be liable to bronchitis and to spontaneous fracture of the long bones. As to the causation of chronic phosphorus poisoning the most probable theory (Lorinser) appears to be that the blood becomes surcharged with phosphorus, which in turn has a special affinity for bone, and as a conse- quence weakens the resistance of that tissue to local iujury — this local injury in the case of the jaw bone being supplied through the medium of a carious tooth. Such necroses occur only after the worker has been for some years engaged in the work, and the necessary constitutional changes have been induced. By an order of the Secretary of State in 1899, cases of phosphorus poisoning must be notified under the Factory and Workshop Act, 1895. Mercurial poisoning. — Those exposed to the poisonous effects of the vapours are mainly the makers and users of vermilion pigment from cinnabar and of imitation bronzing, barometer and thermometer makers, and the gilders working with mercurial gold amalgam. The former great source of industrial mercurial poisoning — the silvering of mirrors by means of an amalgam of mercury and tin — has ceased, the process having been superseded in this country by the nitrate of silver and ammonia process. The workers in factories where calomel, corrosive sublimate, and the red oxide of mercury are prepared, hatters, furriers, and the makers of electric meters and electric lamps, also suffer. AIR AND VENTILATION 201 The symptoms of mercurial poisoning are insidious in their onset. They are anaemia, tender gums, often saUvation, diarrhoea, tremors of the face, arms, and hands ; the teeth frequently fall out. Mercurial poisoning appears to predispose to phthisis. The sanitary precautions necessary are similar to those already indicated where poisonous fumes and dust occur ; but it is important to observe that the mercury should be kept covered over as much as possible, so as to limit the diffusion of the vapours, especially in hot workshops. The diffusion of the vapours of ammonia throughout the workshops, when these are temporarily vacated, is highly spoken of. The floor of the workshop should be such as to admit of a thorough collection of all spilt mercury at the end of each working day. A very important preventive measure is care of the mouth and teeth, and the removal or filling of carious teeth. All cases of mercurial poisoning must be notified to the Chief Inspector of Factories. Arsenic poisoning may result from the use of arsenical wall papers, carpets, and curtains, in which the arsenic is used as a colouring agent. In the following trades the workers are liable to arsenic poisoning : The makers of articles coloured with arsenical dyes (carpets, dresses, artificial flowers, etc.) ; those who prepare skins of animals for stuffing ; and the makers of arsenical paints and dyes, such as " emerald green." This salt is also used for the destruction of the insect pests which destroy fruit trees and potatoes. The sanitary precautions necessary are very similar to those which should be practised against lead poisoning. Arsenical colours and dyes are unnecessary, and their use should be prohibited. No water from the works containing waste arsenic should be allowed to enter a stream. Chromium poisoning. — Chrome colours are largely used by dyers, chiefly as yellow, orange, and red colouring agents, but aniline dyes are now taking their place. The chief symptoms of poisoning (from swallowing chromium) closely resemble those of Asiatic cholera. The effect of the chromates of potash on the skin and mucous membranes exposed to their action is to cause destructive ulceration, the nasal mucous membrane being especially liable to suffer from the lodgment of the fine dust resulting from the giinding of the chromates. The sanitary precautions which are necessary can be gathered from what has already been said with reference to lead. Various forms of eczema and ulceration may be set up by irritants used in the technical arts and crafts. Of these, bichromates, aniline, arsenic, materials used by potters and laundresses, flax, strong alkalies, acids, and other chemicals, are the most important. Often the lesions in the mucous membranes are more distressing than those of the skin. Under special rules issued by the Home Office, periodical medical examination of workers in dangerous processes, either by the certifying factory surgeon or other medical practitioner, is required in the following industries : White lead works, china and earthenware works, the manu- facture of litho-transfers, enamelling of iron plates, electrical accumulator works, the manufacture of explosives in which dinitro-benzol is used, and bichromate factories ; in lucifer match factories where yellow phosphorus is used periodical examination of the teeth of the persons in certain specified processes is enjoined. Further, in paint and colour factories, in chemical works where pharmaceutical mercurial preparations are made, in hatters- furriers' processes where mercury nitrate is used, etc., similar voluntary periodical examination is in some cases provided. Sulphurous acid may find its way into the atmosphere from a large number of industries : The manufacture of sulphuric acid, alum, and glass, the tinning of iron, bleaching works of certain kinds (wool, cotton. 202 HYGIENE AND PUBLIC HEALTH silk, straw, etc.), the preparation of hops, and the burning of coal rich in pyrites, etc. The gas may give rise to bronchitis and anaemia. Chlorine may gain access to the atmosphere from bleaching and dyeing works. It causes acute catarrh, acute pneumonia, conjunctivitis, pyrosis, and indigestion. Respirators kept moist with alcohol are recommended as a protection. Bisulphide of carbon gets into the atmosphere of vulcanized india- rubber works, the liquid being used as a solvent of gutta-percha. In the manufacture of Portland Cement traces of compounds of cyanogen are given off during the process of burning. Carbonic acid is given off in large quantities from hme burning, and is often present in excess in the air of aerated water manufactories. It causes debility, loss of appetite, drowsiness, and nervous derange- ments, and when present in great quantities causes dyspnoea, muscular debility, and coma ; and, if death resiilts, the heart and lungs are filled ^vith dark blood. Well sinkers are occasionally asphyxiated by the large amount of this gas which collects in deep shafts. In carbonic oxide poisoning, on the other hand, there is no dyspnoea, coma is slight or absent, there is drowsiness followed by loss of conscious- ness, convulsions may occur, and the blood is bright, -with a bluish tint. Less than 0*3 per cent, of CO in the atmosphere may cause unpleasant if not serious sjonptoms. The symptoms of chronic poisoning are not very definite. There may be headache, sickness, diarrhoea, impaired digestion, a dry throat, physical and mental depression, and anaemia. Those most liable to CO poisoning are the workers at coke ovens and brick-kilns, limestone workers and cement workers, coal miners after explosions of fire-damp, coal gas makers (from escapes of gas), distillers of coal tar, lamp-black makers and iron smelters. CO is also liable to be present in the air of laundries where the irons are heated over flueless gas stoves. Several fatal accidents have resulted from the carrying of ferro-silicon as a cargo on ships and barges. This material is used in the manufacture of certain grades of steel, and is an alloy of iron and silicon. The low grade variety, containing not more than 15 per cent, of silicon, is made in blast furnaces in this country ; while the high grade classes, containing from 25 to 95 per cent, of silicon, can only be made in the electric furnace, and are largely imported from the Continent. Ferro-silicon of grades under 30 and over 70 per cent, would appear to be innocuous (Copeman), but grades between 30 and 70 per cent, give off poisonous emanations, the chief poisonous gas being phosphoretted hydrogen, along with a small quantity of arseniuretted hydrogen. In a report of the Local Govern- ment Board on ferro-silicon (1908-09), it is recommended that only the non-injurious grades should be used in steel manufacture, but that if the injurious grades are used, they should be exposed to the air, but under cover, for at least a month before transit ; that no passenger boats should be used to convey them ; and that storage places at docks or works should have free provision for access of air, and should not be near work- rooms 'or offices. Household Dust. Besides vitiation by products of respiration and combustion, one great cause of impurity of air in liouses is the presence of floating particles of dust. This dust is the debris arising from the wear and tear of articles in domestic use, mingled with the soot and ashes from fire-places, lamps and gas burners. As soon AIR AND VENTILATION 203 as the air is still, it tends to settle upon walls, floors and articles of furniture, to be again caught up and wafted into the air, when this is in brisk movement. Under the microscope this dust resolves itself into soot, mineral particles (silica, oxide of iron, crystals of sodium chloride), cotton fibres, spores of fungi or bacteria, starch grains, pulverized straw, epithelial and epidermic debris from the skin. It is thus seen to consist largely of organic refuse, sometimes more or less putrescent, and its presence in the air assists in the production of the low state of health so common to the occupants of dirty overcrowded houses. In all houses dust must be produced by the wear and tear of domestic life ; but in towns this strictly domestic dust is much augmented by that which finds its way in through doors and windows from the outer atmosphere. We cannot hope, then, to materially limit its production ; but much may be done to get rid of it, and to prevent its undue accumulation, by thorough and regular house cleaning. House cleaning can only be efficient where the structural con- ditions of walls, floors, and ceilings permit of easy access for the broom and duster into every part of the room, and where furniture and fittings are so arranged as to prevent dust being deposited in inaccessible places. As generally arranged, nearly every part of a room is a dust trap. Cornices and projections on ceilings and above doors ; rough or flock wall papers ; floors with crevices between the boards into which dust drops, to gradually accumulate between the floor and the ceiling below ; carpets accurately fitting every corner of the room ; cumbersome articles of furniture, as wardrobes, sideboards, and bookcases, which collect dust above, and are too heavy to be moved to allow dust to be swept out below ; heavy curtains with canopies, draperies, etc. — all these tend to the collection of dust, which, being unseen, is forgotten and not removed. It is especially in bedrooms, which are occupied for so many hours without any thorough renewal of the air, that these dust accumulators tend to do so much harm, by contaminating an atmosphere already vitiated. The following rules, therefore, although to be recommended in every room of a house, are more especially applicable to bedrooms. The floors, if old and warped, should be accuratety fitted with thin oak parqueterie, kept well polished with oil and beeswax ; 204 HYGIENE AND PUBLIC HEALTH or the spaces between the boards may be filleted — i.e., filled in with strips of wood, so as to leave no chinks — and the whole either stained or varnished, or coated with three or four good coats of paint and varnished. This flooring can be kept clean with a damp duster. Carpets should be abolished in favour of mats or Indian matting for bedrooms, which is very little retentive of dust and easily cleaned. The mats can be frequently shaken and beaten in the open air, whereas fixed carpets are usually beaten once a year, and in the interval accumulate much dust (especially the thick pile carpets). The use of linoleum and oilcloth should be avoided, as it hinders the ventilation of the boards, and tends to cause dry-rot. Heavy curtains, canopies, and draperies should be replaced by light muslin fabrics in bedrooms, which can be washed and cleaned at frequent intervals. Bedroom furniture should be light and easily moved. It would be a great improvement, if, when houses are built, the bedroom walls were planned with recesses, which could be converted into cupboards, shelves, and drawers ; and thus the actual furniture of a bedroom could be reduced to the bed, washstand, dressing table, and chairs, and there would be no surface on which dust could lie concealed. Cornices and projections from walls and ceilings should be avoided, as likely to collect dust. The wall coverings should be smooth and gloss}-. Rough wall- papers, especially flock paper, can hold enormous quantities of dust. For bedrooms and nurseries distemper colouring is perhaps better than wall-papers, as the surface can be renewed at a trifling cost and at frequent intervals. In distempering, common whiting is used as a basis for the colouring, and not white lead or zinc white, as is almost invariably the case in painting. Newh^ painted surfaces give off traces of lead, volatilized or in powder, to the air in drying ; and symptoms of lead poisoning have fre- quently been observed in the occupants of a freshly painted room. Painting, then, is not to be recommended for wall surfaces, unless the paints are warranted free from lead. Sometimes the paints themselves contain no lead, but the " dryers " with which they are mixed before use are found to be full of lead. Varnished wall-papers are coming more largely into use. They have a smooth non-absorbent surface, and are easil}/ cleaned with a damp cloth. In papering a room it is important to see that the old paper is all peeled off, and the plaster underneath well washed. AIR AND VENTILATION 205 before the new paper is applied. Tiie size and paste used should be perfectly fresh. A paper should never be put on a wall unless it is guaranteed free from arsenic ; and it is even advisable to test a piece with Marsh's apparatus to make perfectly certain. The general suppo- sition is that wall-papers are not likely to contain arsenic unless the}' are coloured some shade of green. But arsenic has been found in various coloured papers — reds, mauves, browns, and greys. The arsenite of copper (Scheele's green) and the aceto- arsenite of copper are principally used in the manufacture of green papers. The amount of arsenic present has been found to vary in different cases from a grain, or less, per square yard up to 50 or 60 grains. The injurious effects of arsenical wall-papers appear to be due to the dissemination of volatile arsenical compounds, or of solid particles of arsenious acid or even metallic arsenic, as dust, into the air of the apartment. In flock papers, coloured with arsenic, it is probably diffused as dust ; whilst in the smoother papers, arseniuretted hydrogen or other volatile compounds are formed by the decomposition of the size and paste on a damp wall acting chemically on the arsenical salt. The long continued inhalation into the lungs or swallowing of the arsenical dust and vapours derived from wall-papers tends to produce a chronic form of poisoning, characterized by one or more of the following symptoms, arranged more or less in the order of their appearance, viz., conjunctivitis and lacrymation, cough, nausea, sickness and diarrhoea, cohc pains, cramps, dry- ness of the mouth and throat with much thirst, headache and gradually increasing debility, with actual paralysis of the extremities, terminating in convulsions and death. As a rule, the symptoms do not go beyond conjunctivitis, cough, nausea, and diarrhoea, with much debility. But these cases of illness often last for a long period, until, indeed, the source of the poisoning is discovered. The artificial fruit and flower makers suffer from arsenic poisoning in its worst forms. Ventilation. Ventilation is a term which has a somewhat extensive meaning. Generally it may be said to imply the removal and dispersion of foreign gases or suspended matters, which have accumulated in the atmosphere as the result of the vitiating processes already 206 HYGIENE AND PUBLIC HEALTH described. We speak of the ventilation of streets and buildings, the ventilation of inhabited rooms, factories, and mines, and the ventilation of drains and sewers. In each case the same object is aimed at, but the means by which it can be attained are different. The ventilation of streets and buildings is dependent upon the width of the street, and the height of adjoining or opposite buildings — -in fact, upon the amount of free air space around the buildings, and the facilities afforded for the entrance of light and air. This may be called external ventilation. To ventilate dwelling houses, factories, or mines, fresh air from out- side must be introduced within these more or less closed places by natural or artificial means, and adequate exit must be provided for used or vitiated air. It is the same for drains and sewers, with this addition, that the escaping air must be aUowed exit at points where it is least likely to be productive of nuisance or danger. In addition to the natural forces of rain, \'vind, sun, and vegetation, which promote the purification of the atmosphere on the large scale, natural ventilation as applied to circumscribed localities may be said to depend upon (i) diffusion of gas,es ; (2) the action of the winds ; (3) the difference in weight of masses of air of iineqital temperature. 1. Gases diffuse inversely as the square roots of their densities ; and this diffusion can take place through porous substances such as dry bricks. The process is necessarily a slow one, and inade- quate to produce complete renovation of vitiated air. 2. Winds are very powerful ventilating agents. Thej'- act chiefly by perflation, i.e., b}^ setting masses of air in motion, driving them onward by propulsion . They have also an aspirating effect on air which is shielded from the direct or perflating action. For when wind passes horizontally over chimneys, or tubes placed at right angles to its course, it causes a diminution of pressure within them, thus creating a current of air up the chimney. The air in these tubes being partially aspirated or sucked out by the action of the wind, to restore the temporary vacuum so made, air from below rushes up to take its place, a continuous current in a perpendicular direction being thus set up. 3. When air is heated it expands. The expansion is equal to ilx of its volume for ever}^ degree Fahrenheit, or Tri^ for every degree Centigrade. A volume of hot air is consequently lighter, bulk for bulk, than the same volume of colder air. The warm air rises, and equilibrium is restored by colder air rushing in to AIR AND VENTILATION 20/ occupy its place. The winds themselves are caused in this manner by the unequal heating of the air over different parts of the earth's surface. External Ventilation {Streets, Buildings, etc.). The health of a town largely depends on the width of its streets, the general height of the buildings, and the amount of yard space at the rear of each building which separates it from its opposite neighbour. Contrast the health and vitality of the occupants of houses in wide open streets with those who live in narrow courts closed at one or both ends, the courts themselves being surrounded by higher buildings, or built back to back, or with the smallest possible intervening space. In such places the air is almost always necessarily stagnant, as the passage of the wind is ob- structed by the surrounding buildings. The sun's light — the most powerful of germicides — ^for many months in the year cannot penetrate, vAi\i the result that the ground is never thoroughly dried, and the air in contact \^ath it remains continuous!}' damp. Impure gases and exhalations, evolved from the inhabited dwell- ings, are not at once swept away by the wind, and consequently accumulate in the air of the court and its surroundings. Sus- pended organic matters tend to accumulate in the still air, which, being thus both damp and impure, produces that state of low \itality and predisposition to disease which characterize the inhabitants of such places. Z^-motic diseases — especiaUj' typhus — when once introduced, spread rapidly through the vitiated air, the enfeebled constitu- tions of the inhabitants presenting but slight resistance to their onset. Absence of sunlight appears to have a specially mjurious effect on child life, which, hke plants, becomes blanched and weakl\- when reared in semi- darkness. When it is added that in many of these courts and alleys the houses ha^-e no through venti- lation, the windows being only in front of the house, it is not to be wondered at that the general death-rate is sometimes double, or even treble, that of the healthy parts of the town, and that the mortality' amongst infants and young children is appalling. AU investigations into the effect of back-to-back houses upon the health of the inmates show an increased incidence of disease and mortality from all causes, phthisis, diseases of the respiratory organs, diarrhoea, and z3Tiiotic diseases generally ; and in dis- tricts where such houses form about 50 per cent, of the total, the 208 HYGIENE AND PUBLIC HEALTPI death-rates from the above mentioned causes are nearly half as much agam as the rates generally prevailing for the whole of England and Wales. Back-to-back houses are built in double rows with only one side exposed to the open air, except in the case of those houses at the ends of the blocks, which have two sides open to the external air. Through ventilation is impossible in such houses, and the rooms are generally dark and dirty as a consequence. To show what is the minimum amount of external air-space which should be allotted to every building in a town, we may quote from the model bye-laws of the Local Government Board, which refer to new streets and buildings. The width of every street intended for use as a carriage road must not be less than 36 feet ; if not to be used as a carriage road it must be at least 24 feet wide, and open at one end. Twenty- four feet is the least width allowed before the frontage of any new building ; and the aggregate amount of yard space at the back of such a building, and belonging to it, must not be less than 150 square feet, and, whilst extending the entire width of the building, it must not in any case be less than 10 feet wide, and must be wider when the height of the building exceeds 15 feet. It is important to note that the model bye-laws insist on the yard space at the back of a house being increased with the height of the house up to 35 feet, but not so the frontage area. The higher the buildings, of course the greater the obstruction to the passage of air and light, and the amount of space compulsorily left unoccupied (both in front and back) should have been correspondingly increased. The erection in London and some large provincial towns of huge blocks of industrial dwellings, whilst affording vastly superior accommodation to the working classes over the old insanitary tenements, has not always secured efhcient external ventilation for certain of the tenements. Lofty blocks are too often built in such a way as to enclose a narrow and well-like court, in which the atmosphere is always sunless and stagnant, and from which the rooms facing on to it derive all their light and air. Cottage buildings with sufficient space in front and rear are far preferable to lofty blocks placed in rows ; but as they do not house the same number of people for the space occupied, in crowded districts, where the land is of such enormous value, the rents must necessarily be higher. AIR AND VENTILATION 2O9 The London Building Act, 1894, Part V., provides for open spaces about buildings and the height of buildings. Section 41 applies to domestic buildings erected after the commencement of the Act and abutting upon a street formed or laid out after the commencement of the Ace, and requires t^^ be provided in the rear of every such building an open space exclusively belonging to it of an aggregate extent of not less than 150 square feet, the open space to extend throughout the entire width tc a depth of at least 10 feet from the building. The height of the building is regulated as follows : An imaginary horizontal line is drawn at the level of the pavement from the roadway, and at right angles to it through the centre of the face of the building, and prolonged to intersect the boundary of the open space at the rear. An imaginary diagonal line is then drawn in the direction of the building above, and in the same vertical plane with the horizontal line, and inclined thereto at an angle of 63*5°, meeting the horizontal line where it intersects the boundary of the open space at the rear. No part of the building will then be allowed to extend above the diagonal line, except chimneys, dormers, gables, turrets, or other archi- tectural ornaments. Exception is made in the case of new buildings abutting at the back upon a street or open space dedicated to the public. With respect to new domestic buildings abutting upon a street formed or laid out before the commencement of the Act, the horizontal line may be drawn at a level of 16 feet above the level of the adjoining pavement, and the open space of 150 square feet may also be provided above the level of the ceiling of the ground story, or 16 feet above the level of the adjoining pavement. Section 42 enacts that the sanction of the London County Council must be obtained to the plans of dwellings for the working classes to be erected after the commencement of the Act, which do not abut upon a street. Section 45 prohibits the construction of habitable rooms lighted and ventilated entirely from enclosed courtyards, or from courtyards open on one side, but of which the depth, measured from the open side, exceeds tmce the width, unless the width of the court measured from the window of the room to the opposite wall is equal to half the height measured from the sill of the window to the eaves or top of the parapet of the opposite wall. Section 43 enables new domestic buildings, which are not artisans' dwelhngs, to be erected on the same sites as existing buildings, if abutting upon a street, and to cover the same extent of land, but no more than was occupied by the previously existing domestic building. Section 47 enacts that a building (not being a church or chapel) shall not be erected of or be subsequently increased to a greater height than 80 feet (exclusive of two stories in the roof, and of ornamental towers, turrets, or other architectural features) without the consent of the Council ; provided that where any existing buildings forming part of a continuous block or row of buildings exceed 80 feet in height, any other building in the same block belonging to the same owner at the date of the passing of the Act may be carried to a height equal to, but not exceeding, that of the existing buildings. Section 49 requires that no existing building (other than a church or chapel) on the side of a street formed or laid out after August 7, 1862, and of a less ^\'idth than 50 feet, shall be raised, nor shall any building be erected so that the height of the building exceeds the width of the street, Avithout the consent of the Council. Section 69 provides for the ventilation of staircases both in artisans' dwelhngs and in ordinary dwelling houses constructed after the Act. Section 70 requires that every habitable room in a new building, except rooms wholly or partly in the roof, shall be in every part at least 8 feet 6 inches in height from floor to ceiHng. Rooms wholly or partly in the roof must be at least 8 feet in height throughout not less than one-half their 14 210 HYGIENE AND PUBLIC HEALTH area. Every habitable room with an external wall, which is not in the roof ^ must have a window opening into the external air, or into a conservatory, with a total superficies clear of the sash frames, free from any obstruction to the light, equal to at least one tenth of the floor area of the room, and so constructed that at least one half of such window can be opened, the opening to extend to at least 7 feet above the floor level. Smoke Prevention. In London the smoky atmosphere of the winter months is almost entirely due to the unconsumed smoke from private dwelling houses, whilst in the Northern towns it is the manu- factory smoke that pollutes the air, a fact at once evident from the very striking contrast between the air on Sundays and the dense smoke cloud that overhangs the town on the working week- days. To deal with the whole smoke question in London is to attack a problem of unexampled magnitude and difficulty ; all that can be hoped for is that coal gas may in time be so far cheapened as to replace with economy the common use of coal for domestic heating and cooking purposes. A smoke-laden atmo- sphere is impure ; it reduces daylight, and therefore leads to an increased employment of artificial light ; it renders it difficult and sometimes impossible to keep public buildings and private dwell- ings clean, and it doubtless promotes ill-health in some people. In the Lancashire and Yorkshire towns the abatement of smoke is a far easier task to accomplish, and already a good deal has been done in this direction by the adoption of smoke preventing appliances in connection with factory furnaces. The smoke nuisance is chiefly due to the fireman allowing too long intervals between the firings. This leads to too much coal being put on at one firing, and the issue of black smoke ; but a deficient air draught — often due to a small cramped flue in a low chimney — is frequently a cause. ( The best method of smoke prevention is to secure frequent and light firing, and the admittance to the furnace of the necessary air to provide complete combustion of the carbon particles after each fresh charge of fuel.} Many devices are em- ployed to secure these objects independently of the fireman. Of these appliances, perhaps the most commonly used are the mechanical stokers, which may conveniently be divided into two classes : {a) Those that throw small quantities of fuel evenly over the fi.re, and thus obviate the dense black smoke produced, under the ordinary conditions of stoking, when the fire door is opened and fresh fuel is cast by a fireman on the fire. It is evident that AIR AND VENTILATION 211 with stokers of this class (" sprinklers ") the fire bars must be made to move by appropriate mechanical arrangements, and so keep the fire level and free from aggregations of imperfectly coked fuel at certain parts of the furnace. The second kind of mechanical stokers (6) are those of the coking class. By these the fresh fuel is dehvered from a hopper to the front of the fire, where it gets coked ; it is then graduallv worked backwards on the fire bars, until the clinker falls over the back of the grate into the ashpit. By these contrivances the furnace is continuously taking in the raw fuel at the front, burning this smokelessly (because the black smoke arising at the front of the furnace is " killed " by passing over the white hot fuel at the back), and dropping the ashes over the other end of the bar. " Side firing " is said to give good results. By this method the fuel is delivered at each side of the fire alternately, and the smoke from the side which is being fed curls towards the incandescent fire on the other side, and gets burned. These coking mechanical stokers give far better results than the sprinkhng class. As smoke arises from a furnace when the supply of air admitted is inadequate to secure complete combustion of the fuel, a great number of contrivances have been invented for supplying air either heated by passing through special pipes laid in the flues, or cold, to various parts of the furnace or main flue. Grids or circulars which can be opened and shut by hand are sometimes placed in the door to admit air to the furnace, and panels and louvres in the furnace door are now made to open and shut auto- matically. These can be regulated to admit the desired quantity of air. " Forced draughts " are often utilized to increase the draught in the furnace, and thus to favour combustion, and for this purpose jets of steam are generally admitted through the frame of the furnace just above the door. Again, spUt bridges or hollow fire bars of various kinds are made to admit ak. The " bridge " is the metal or brickwork projection at the back of the fire bars, over which the flames and products of combustion pass on their way to the flue. There is a door underneath the split bridge, which can be opened, when firing is taking place, to lei the air pass up through the bridge to ignite the gases passing over it and further complete combustion. SpHt bridges may be made to work automatically, and many are in use ; but if left continu- ally open, they^tend to destroy the draught in the front part of the furnace, and they soon get filled with ashes. 212 HYGIENE AND PUBLIC HEALTH Revolving cast-iron chain grates are now being used in certain classes of furnace in connection with mechanical stokers. The revolving grate carries the incandescent fuel slowly from the front to the back of the furnace, where the spent fuel falls into the ashpit. These grates are intended for consuming soft coal, and not Welsh steam coal, the excessive heat from the latter being too speedily destructive of the cast-iron chains. Amongst less effective appliances may be mentioned the use of fans to force the smoke again through the furnace, and the washing of the smoke by passing it through shafts in which sprays of water are descending. There is a considerable advantage to the manufacturers in the use of mechanical stokers, inasmuch as they can by their means burn an inferior slack coal (cheaper fuel), and less labour is required. If spht bridges only are used, great care is required on the part of the fireman, and fuel of fair quality must be used, or smoke is emitted ; whilst the mechanical stokers do away ^^dth these sources of expense. In conclusion, it may be said that the quality of the coal used has an important bearing on the subject of smoke prevention, and that coke and anthracite are practically smokeless. The ordinary or bituminous coal is much cheaper, weight for weight, than anthracite, but on account of the greater heat obtained from the latter it is said to be almost as cheap in use. Coal dust firing is held by a recent Prussian Commission to possess the following advantages : It allows of uniform distribution ; it permits of perfect combustion without smoke ; and secures the greatest calorific efficiency. Section 91 of the Public Health Act, 1875, defines as a nuisance " any fire-place or furnace which does not as far as practicable consume the smoke arising from the combustible used therein, . . . and which is used in any manufacturing or trade process whatsoever." The same section provides that the court shall dismiss the complaint if it is satisfied that such furnace is con- structed in such a manner as to consume its smoke as far as practicable. It should be noted that, according to the same section, when any chimney (not being the chimney of a private dweUing house) is sending forth black smoke in such quantity as to be a nuisance, it is not necessary to prove, in order to secure a conviction, that the furnace is improperly constructed or in- efficiently tended. A notice " to abate " must precede a AIR AND VENTILATION 213 summons, as in the case of other nuisances ; and a conviction must follow the proof of the emission of " black smoke in such quantity as to be a nuisance." The London County Council is of opinion that the escape of black smoke for five minutes from the lighting of the furnace might be permitted, but that afterwards a discharge of one minute or more should be the subject of legal procedure. The allowance varies from two to fifteen minutes in other large towns. In Sheffield the following working limits must not be ex- ceeded : — 1 boiler . . 2 minutes of black smoke in the hour. 2 boilers . . 3 3 ,. . . 4 4 ,, and more 6 ,, „ ,, ,, ' Ventilation oj Inhabited Rooms. In providing for the ventilation of inhabited rooms by the replacement of vitiated air by fresh air, it has been found neces- sary to adopt a certain standard of impurity above which no increase should be allowed. It is only out of doors, then, that we can be constantly breathing air of normal purity, as indicated by the amount of CO, (0-4 per 1,000). Pettenkofer proposed as a standard for inhabited rooms I volume of CO2 per 1,000 of aii\ CarneUy, Anderson, and Haldane proposed 1*3 per 1,000 for elementary schools during the daytime, and i per 1,000 for dormitories at night. The only legal maximum standard at present in force is that fixed by the Home Office in respect of cotton-cloth factories, where the air requires to be humidified by the addition of steam, namely 0*9 vols, of CO2 per 1,000. It was found by the late Professor de Chaumont, by chemical examination of a large number of samples of the air of inhabited rooms, that — the amount of CO2 in the outer air being 0*04 per cent., or 0*4 per 1,000 — no close or disagreeable smell is perceived in the air of a room until the CO2 from human respira- tion reaches o*6 per 1,000, or exceeds by 0*2 per 1,000 that present in outer air, the close smell being always due to the foul organic matter in the impure air, which increases fari passu with, and is therefore estimated by, the amount of CO2 present. When the CO2 in an inhabited room reaches i*3 per 1,000, the limit of 214 HYGIENE AND PUBLIC HEALTH differentiation by the sense of smell, when a person first enters such a room from the outer ak, is reached. Any greater impurity than this cannot be distinguished by the unaided senses. It was assumed b}^ De Chaumont that air vitiated to the extent of 0*2 per i,ooo — air which is still fresh and does not differ sensibly to smell from the outer atmosphere — can be breathed ^^dth impunit}^, but that no greater vitiation ought to be allowed. Ideal ventilation may be said to be the supply of • sufficient pure air to a room to prevent the respiratory CO2 increasing bej^ond 0*2 part per 1,000. The permissible limit of respiratory impurity is therefore generalty held to be 0*2 per 1,000 (which is the same thing as 0*0002 cubic foot of CO2 per I cubic foot of air). E By the equation = 7 — where E = amount of COg exhaled, Y = respirator}^ impurity per cubic foot of air, and D = the delivery, or the amount of fresh air available in cubic feet — if E and r are kno^^1l we can find D, or if D and E are kno\\Ti we can find r. If E = o*6, and ;' = 0*0002, then D= =3,000. 0*0002 That is to say, each individual requires 3,000 cubic feet of fresh ail- per hour in order that the respiratory impuritj^ may not exceed 0*2 per 1,000, 01 — what is the same thing — the total impurity 0*6 per 1,000. In a similar way it can be shown that when the adult male is doing gentle work (and giving off 0*9 cubic foot of CO2 in the hour) he theoretically requires 4,500 cubic feet of fresh air per hour ; and if he is engaged in ver}^ hard work (and giving off, may- be, 1*8 cubic foot of CO2 per hour) he needs as much as g,ooo. Example. — If a room of 1,000 cubic feet is occupied for four hours by 10 persons, each giving off the average amount of CO2, what v/iil be the total amount of CO2 per 1,000 volumes at the end of the time, supposing 10,000 cubic feet of fresh air per hour have been supplied ? In this problem D and E are given, and we have to find r. The total amount of air available for breathing by the 10 persons in the four hours is 1,000 cubic feet (the cubic space of the room) + 10,000 x 4 (the amount in cubic feet supplied in four hours) =41,000 cubic feet=D. The amount of CO2 expired by 10 persons in 4 hours =0'6x lox 4 = 24 cubic feet=E. E E 24 D= — or j' = Tf^= =0'00058 per unit ; r D 41,000 ^ i.e., r, or the respiratory impurity, is 0*58 part per 1,000. The total amount of CO2 in the air -will be o-58 + o*4=o-98 part per 1,000. Example. — The air of a room occupied by 6 persons, and containing AIR AND VENTILATION 215 5,ouu cubic leet ol space, yields 7-5 parts of COg per 10,000 parts. How much air is being supplied per person per hour ? Here E and r are given, and we have to find D. E=o'6x 6 = 3-6 cubic feet CO2 exhaled in i honr. r — j-c, -4 = 3-5 per 10,000, or 0-35 per 1,000, or 0*00035 part of CO2 per cubic foot. 3-6 D=— ^^ =10,285. 0-00035 5 But the room contains 5,000 cubic feet of space ; therefore in the first hour 5,285 cubic feet of fresh air were supplied, or 880 cubic feet per head. After the first hour, to maintain the same amount of CO2 in the air, the full 10,285 cubic feet of fresh air will have to be supplied, or 1,714 cubic feet of fresh air per head per hour. During exertion a man gives off more respiratory impurities (CO2, organic matters, etc.) than when at rest. For this reason, and also because the air is generally further vitiated by the trade process, the amount of air supphed to factories or work- rooms should be considerably in excess — double, or even treble, according to the nature of the work — of that required in an ordinary living or sleeping apartment. Some allowance, too, must be made for lights, especially gaslights, when the products of combustion are allowed to escape into the air of the room. The amount of cubic space allotted to each person in a room is a matter of great importance, not because cubic space, how- ever large in amount (as met with under ordinary conditions of inhabited dwelhngs) , can take the place of a regular supply of fresh air from outside, but because the larger the cubic space, the easier it is to supply the proper amount of air without creating a draught. For instance, suppose in a dormitory occupied by ten persons the amount of space per head is only 300 cubic feet, to supply 3,000 cubic feet of fresh air per head per hour 30,000 cubic feet must be admitted in this period, and the air of the room will have to be completely changed ten times — a proceeding which would cause in cold weather, unless the entering air was warmed, a most disagreeable draught. But if the cubic space per head be 1,000 cubic feet, then the air of the dormitory need be changed only three times per hour ; and if such renewal is effected steadily and gradually, the cold entering air is broken up, and, mixing with the warmer air of the apartment, creates no draught. A certain amount of superficial or floor space is necessary for each individual, for if the height of the room is much over 12 feet, excess in this direction does not compensate for deficiency in the other dimensions, although the total cubic space may be the same ; thus, it would not be the same thing to allow a man 2l6 HYGIENE AND PUBLIC HEALTH 50 square feet of floor space in a room 20 feet high as to provide 100 square feet in a room 10 feet high, although the cubic space would be identical. The reason is that the products of respira- tion are not readily diffused throughout the air of an apartment, but tend to accumulate in the lower strata, consequently excessive height does not, in their case, mean a corresponding dilution. Haldane and Osborn in their examination of the air of factories and workshops found that some of the rooms, where there was the largest amount of cubic space per head, contained the foulest atmospheres, there being no proper means of ventilation, the air being never thoroughly renewed, even when the rooms were empty. The cubic and superficial space allotted under various statutes, bye-laws and regulations are as follows :■ — - 1 Minimum Space per Head in Cubic Feet. Authority. Common lodging houses (sleeping ' rooms) Registered lodging houses — Rooms occupied by day and night Rooms occupied by night only . Non-textile workrooms . Non-textile workrooms during over- time ..... Underground Bakehouses Above ground bakehouses where night work is car- ried on by artificial light other than electric light Army barracks .... Army hospital wards Public elementary schools ' London County Council Schools Canal boats (persons over 12 years) Canal boats (persons under 1 2 years) Seamen's cabins .... Cows in cowsheds .... 3or; 400 300 250 400 500 400 eft. between 9 p.m. and 6 a.m. 600 1,200 Sol 1302 6o3 4o3 120 800 Local Government Board (Model Bye-laws). Ditto Ditto Ditto Ditto Factory Act, 1901. Order under Factory Act, 1901. Order under Factory Act, 1901. British Army Regulations. Ditto Ditto Education Department. London County Council. ("Local Government Board -j Regulations under the [ Canal Boats Act, 1877, Merchant Shipping Act, 1906. Local Government Board. Model Regulations under the Dairies, Cowsheds, and Milkshops Order. i Minimum floor space 8 square feet. 2 Minimum floor space 10 square feet. 3 An after-cabin must not be less than iSo cubic feet in capacity nor a fore-cabin less than 80. AIR AND VENTILATION 2I7 In the large public schools of this country the amount of super- ficial area and cubic space varies according to the ages of the boys and other circumstances. Average requirements for boys of 12-18 jT'ears of age are 70-80 square feet of floor space and 700 to goo cubic feet of air space ; but, as previously pointed out, ample floor and cubic space will not compensate for defective ventilation. Unhealthy conditions of atmosphere are sometimes found to prevail in large and lofty dormitories, where defective ventilation leads to stagnation of air. Natutal Ventilation. — During the colder months of the year in this country three complete changes per hour of the air in an inhabited room is all that can be borne when the entering air is not artificially warmed. Hence the importance of an allowance for each individual of cubic space not much less than 1,000 cubic feet. The area of the inlet opening should be sufficiently large to allow the required volume of air (3,000 cubic feet) to enter at no greater speed than 5 feet per second. This speed could be attained where the inlet opening for each individual was 24 square inches. During cold weather this velocity could not be borne ; and it may be said generally that efficient ventilation is difficult to procure in cold weather, unless the entering air is artificially warmed. A velocity of the entering air of 2 to 3 feet per second is far more agreeable to the senses than a velocity of 5 feet. If the entering air is artificially warmed, the size of the inlet opening may even be increased up to 70 or 80 square inches per head, and the amount of cubic space may be diminished, for it would be possible then to change the air of the apartment more frequently than three times per hour without creating a draught. Of the forces which act in natural ventilation, diffusion causes the gaseous impurities of respired air to mix with the fresh air in a room until homogeneity is estabhshed. Diffusion, however, does not affect the suspended matters, which tend to fall towards the earth in a still atmosphere. The perflating action of the wind may be utihzed by opening windows facing the wind, and the action is increased when windows, or a window and door on opposite sides of a room, are left open. The room is rapidly and continuously flushed with air, an enormous effect being produced, for it is possible to renew the air of a room in this manner over a hundred times an hour, even when the movement of the wind outside is only 3 feet per 2l8 HYGIENE AND PUBLIC HEALTH second, equivalent to a very gentle breeze. Such a method is of unquestionable utility for rapidly changing the air of an unoccu- pied room — especially school and work rooms — and may be generall}^ put in operation in inhabited rooms in summer when the temperatures outside and inside the house approximate. In any system of ventilation, however, that depends entirely on the ^\dnd, there is always the difficulty of regulating the velocity of the current, and during complete cahns the action is of course nil. The wind, too, often impedes ventilation by obstructing the passage of' vitiated air from an exit shaft into whose mouth it blows ; and this is not to be wondered at, for when blowing at the rate of lo miles an hour the pressure of the wind is | pound on each square foot of surface. For ventilating the holds and cabins of ships at sea, the wind may be most advantageously utihzed, because the ships' motion is almost always producing a breeze. A large cowl, placed so as to face the wind, conducts the air below by means of a pipe, whilst another cowl, reversed so as to back to the wind, allows the used air to escape. By this exit shaft the aspirating force of the wind is utihzed. Sylvester's system of house ventilation proceeds on these principles. A large cowl facing the wind is placed outside the house, and conducts the air to an under- ground chambei , where it can be warmed if necessar}- by passing over hot water or steam pipes ; it is then conducted to the rooms above by means of tubes, and finally escapes above the roof through tubes surmounted by cowls backed to the wind. The aspirating action of the wind is constantly being used to ventilate rooms by means of the chimne}'. With a fire burning in the grate, the draught up the chimney is increased bj-^ the aspiration of the wind when the top of the chimney is above surrounding buildings. Even when there is no fire in the grate, it will usuall}^ be found that there is a current setting up the chimney. Should the top of the chimney be lower than sur- rounding structures, the wind striking these and then descending will often cause a back-draught and a smok}" chimney. The remedy is evidenth^ to carry up the chimney to at least the height of the surrounding buildings. A suitable cowl surmounting the chimney may prevent or mitigate back-draught. From experi- ments carried out by the Ro3^al Sanitary Institute it appears that certain forms of cowls or terminals have the effect of increasing the up draught in air shafts, but that some 30 per cent, of those AIR AND VENTILATION 219 forms experimented with were valueless for that purpose. It is e\-iclent that on duU days, when the atmosphere is still, ventila- tion is most required, and that then such air shafts surmounted b\' cowls or terminals are of little value. Another cause of smok}-' chimneys is an insufficient supply of air to the room. To feed the fire, air is drawai down the chimney, and coming down in puffs, it causes an escape of smoke. The remedy is obtained by making a suitable inlet for fresh air into the apartment. Sometimes it is found that the smoke escaping from one chimney is drawn down another opening close by and on the same level. In such a case one of the chimneys should be raised. The movement produced by inequality in density or weight of contiguous masses of air at different temperatures is the natural force chiefly relied on for ventilating the interior of houses in this climate. This force is naturally chiefly called into action in cold weather, when the difference between the internal and external temperature is considerable, and is more or less in abey- ance in summer, when the temperature outside is often equal to, or even greater than, that of the house. The greater this difference of temperature and the difference of level between the aperture for the entrance of cold air and the aperture for the exit of heated air, the greater will be the velocity of the entering air. We are enabled to calculate the theoretical velocity by means of Montgolfier's formula, which is founded on the dyna- mical law that the velocity in feet per second of falling bodies is equal to eight times the square root of the height through which they have fallen. In this case the height fallen is repre- sented by the difference in pressure of the air inside and outside the house, which is equal to the difference of level between the apertures of entrance and exit multiplied by the expansion of air caused by the difference in temperature inside and outside. „. o /{h-h') {t-t') ^ "^ V = velocitv in feet per second, 491 where A = height in feet of aperture of exit from ground; ,, h'= ,, ,, entrance from ground ; ,, t= temperature of air inside in degrees Fahr. ; t'= ., ,, outside in degrees Fahr. In practice an allowance for friction of J or J must often be made. As it is impossible to tell, with any degree of accuracj', what allowance must be made for friction in any given instance, 220 HYGIENE AND PUBLIC HEALTH the formula is little employed in actual practice, and the anemo- meter {v. page 228) is preferred. If the area of the inlet opening is known, the amount of air entering the room in a minute or an hour can easily be calculated by multiplying the velocity of the entering air by the area of the inlet expressed as square feet, the result being the number of cubic feet entering. In a room as usually constructed with sash windows and with a tire-place and chimney, but without any special means of venti- lation, when a fire is burning in the grate the fresh air entering the room gets warmed as it approaches the fire, and part ascends the chimney flue while part rises to the ceiling. Cold air from outside will then enter — if the windows are closed — ^under the door, under the skirting boards, between the sashes of the window, and through any other chinks or apertures due to loose fittings. The bricks and plaster of the walls are also porous to a certain extent, and if uncovered by paint or wall-paper will admit a small quantity of air. Thus a large volume of air may be entering a room in cold weather when the fire is burning, although there are no visible inlets ; and the amount of air thus supphed may be sufficient for the needs of two or three persons if it were pro- perty distributed. But such is not the case. The cold air, which enters chiefly near the floor, takes as straight a course as possible to the fire-place, often producing a disagreeable draught to the feet of the occupants, whilst the heated and vitiated air near the ceiling is left undisturbed. In this country, to prevent draughts and to insure a thorough distribution, fresh air not previously warmed should be admitted into the room slightly above the heads of the occupants, an upward direction being given to it so that it may rise a little towards the ceiling, mix with and be warmed by the heated air in this situation, fall gently into all parts of the room, and be gradually removed by means of the chimney flue, or other outlet — which should preferably be at the highest part of the room. Amongst simple contrivances for windows by which these objects may be attained may be mentioned Hinckes-Bird's method (fig. 33), now so well known, of placing a solid block of wood under the entire length of the lower sash frame of a window, so as to raise the top rail of the lower sash above the bottom rail of the upper sash. By this means the air is admitted between the two sashes above the heads of the occupants of the room, and is given an upward direction towards the ceiling. The same AIR AND VENTILATION 221 result may be more conveniently obtained by the use of a deep beaded sill, which permits the lower sash to be raised without any passage of air under it, at the same time allo\ving air to enter between the two sashes. Holes bored in a perpendicular direction in the bottom rail of the upper sash, louvred panes to replace one of the squares of glass, an arrangement for allowing one of the squares of glass, provided with side checks;, to fall inwards upon its lower border, or a double pane of glass in one square, open at the bottom outside and at the top inside, Fig. 33. — Diagrammatic sketch of various pro^dsions for ventilation. A, Sash window with Hinckes-Bird's arrangement. B, Hopper sash-light falling inwards. C, Louvred outlets. D, Mackinnel's ventilator. E, Shering- ham's Valve. F, Tobin's Tube (showing valve open). G, Ellison's Conical Bricks. H and I, Grid ventilators below floor joists. all effect the same purpose and are simple and inexpensive contrivances. Cooper's ventilator, which consists of a series of apertures in the glass of a window pane, arranged in a circle and capable of being more or less completely closed by a circular glass disc, also with apertures, and movable on a central pivot, does not admit the air in an upward direction, but breaks it up into a number of divided currents, and thus lessens the 222 HYGIENE AND PUBLIC HEALTH tendency to draught. The same object can be obtained by placing wire gauze or musHn over any inlet opening. The most generally used wall inlet ventilators are Sheringham's valve, Tobin's tube, and Ellison's conical bricks. In the Sheringham valve (fig. 33) air passes through the wall by means of a perforated iron plate, and is then directed upwards by a valved plate with side checks, which projects into the room, and, being hinged at its lower border, is capable of being more or less completely closed by a balance weight. The usual size of the inlet opening in these ventilators is 9 inches by 3, giving an area of 27 square inches. In Tobin's tube (fig. 33) air is introduced from the outside at the floor level through a perforated plate, and then passes up a vertical tube to a height of from 4 to 6 feet above the floor. After escaping from the tube, the current of air ascends more or less vertically for a short distance, before it begins to spread out and mix with the air of the room. In these two contrivances (Tobin's tube and the Sheringham valve) the entering air may be filtered through muslin or cotton wool, or made to impinge upon a tray containing water, and so deposit its sooty particles — a procedure often advisable in smoky towns. Tobin's tubes and other inlet and outlet ventilators should be made accessible in all their parts for cleansing, as they quickly become lined internally with dirt and adherent filth. Tobin's tubes should be made detachable from the external wall opening for this purpose. Ellison's bricks (fig. 33) are pierced with conical holes, the small opening, i inch in diameter, being placed outside the building, whilst the larger opening, ij inches in diameter, is placed inside. The thickness of the brick is 4 J inches. The air passing through these conical apertures becomes distributed over a gradually increasing area, and in this way its slow entrance is rendered im- perceptible and unproductive of draught. These bricks are mostly used for ventilating drill halls, gymnasia, stables, and cowsheds. All the inlet ventilators described are intended to utilize the movements produced by contiguous masses of air at unequal tem- peratures. For this reason they should be protected as far as possible from the perflating action of the wind. This cannot, however, always be done ; and when a strong cold wind is blowing into a ventilator, even of the most approved sort, a most un- AIR AND VENTILATION 223 bearable draught may be the resuh. To obviate this, there should be some means of controlling the amount of entering air by partially closing the ventilator, and in many cases the venti- lator must be closed altogether. Sheringham's valve, Tobin's tube, and louvred inlets, fulfil these requirements very satis- factorily. It is often found that inlet ventilators are acting as outlets for the escape of air, when fresh air is entering a room from other sources. This cannot be obviated, nor, indeed, is it neces- sary. All that can be done is to place the inlets in the best possible position for distributing the entering air throughout the apartment without causing a draught, and to close up all such sources of entering air as are productive of draughts. The usual outlet for the vitiated air of a room is the chimney flue ; and this, for an ordinary medium sized sitting-room, with a fire burning in the grate, is sufficient for three or four people provided no gas is alight, or the gas lamp has its o\\ti special ventilating arrangement. With an ordinary fire, from 10,000 to 15,000 cubic feet of air are dra^vn up the chimney in an hour, the current being generally from 3 to 6 feet per second ; but a large lire will often induce a current of 8 or g feet per second. Heated air rises to the top of a room ; therefore the proper place to admit of the vitiated air escaping is in or near the ceiling. Neil Arnott's or Boyle's valves, in which a metal frame supports small talc plates, which open into the chimney flue near the ceiling, are sometimes used as outlets for foul air. They permit air to pass from the room into the flue, but the.talc plates prevent its return; the objections to their use are that they occasionally permit the reflux of smoke into the room, and the movements of the plates produce a slight clicking noise. If exit shafts other than the chimney flue are provided, they should be short and straight, and capable of being readily cleansed ; otherwise friction, and loss of heat by passage of the air through an exposed tube, will stop the current ahogether, or reverse it, causing a back-draught. The escaping air must have its temperature kept up, or it cannot escape. One of the best methods of attaining this object, which might be put into practice in all new buildings, is to construct a shaft at one side of or surrounding the chimney flue, with an inlet near the ceiling of the room, and the outlet at the level of the chimney top. The air escaping from the room wnll then have its temperature kept up by contact \vith the chimney flue, thus 224 HYGIENE AND PUBLIC HEALTH aiding the up draught, whilst the risk of reflux of smoke will be avoided. The air flues may be moulded in the same piece of fire clay as the smoke flue ; but those from different rooms should not be connected in any way, or foul air from one room might pass into another. The combustion of gas may be made a very effective means of getting rid of foul air. It has been found by experiment that the combustion of i cubic foot of coal gas causes the discharge of 1,000 cubic feet of air. An extraction shaft may be placed over a gas lamp or chandelier ; and by means of a Benham's ventilating globe hght, or a Mackinnel's ventilator, slightly warmed fresh air may be admitted at the same time as foul air is extracted. Mackinnel's ventilator (fig. 33) is very useful for a room which has no other apartment over it. Two tubes, one inside the other, are carried through the ceiling or roof of the building. The inner one, which is for the extraction of foul heated air, projects outside above the outer, and inside also below it. At its lower end a broad circular horizontal rim is attached to the inner tube which deflects the air entering by the outer tube, and causes it to pass for a short distance parallel to the ceihng before falling intb the room, as otherwise the fresh air would be drawn round into the inner or exit shaft. The gas burners or lamps used to light the room are placed immediately under the inner tube of this ventilator. The inner or extraction tube should have its top protected by a cover or cowl, to prevent the wind blo^^^ng down and the entrance of rain, which by evaporation might so cool the escaping air as to cause it to be heavier than the air of the apartment. The entering air will be sKghtly warmed by its passage over the heated extraction shaft. The area of the outer tube for the passage of fresh air should be equal to, or slightly larger (for there is more friction to overcome) than the area of the inner tube for exit of foul air. Mackinnel's ventilator is well adapted for large buildings, as schools, churches, halls, etc. , which have no upper floors or stories. Benham's ventilating globe light, as its name expresses, combines ventilation and lighting ; slightly warmed fresh air is admitted, and foul air is extracted along with the products of combustion. In theatres sunlight burners are largely used ; they aid the extraction of foul air, but do not admit fresh air. In Pott's method of ventilation a hollow metallic perforated cornice is divided into an upper and lower half by means of a AIR AND VENTILATION 225 horizontal plate. Pure air enters the room through the lower hall , which communicates with the outside air, and foul air is extracted through the upper half, which opens into the chimney. Extraction shafts, like inlet openings, are liable to have their action reversed under certain circumstances. When the wind is blowing down upon them, when rain gets in, when the escaping air is subject to much cooling in an exposed shaft, or when there are more outlets than one in a room, one predominating over the others, down draughts are likely to occur. This most frequently happens when the draught up the chimney is very great from there being a large fire burning ; then there is a tendency for every other opening into a room to become an inlet. Also, when the wind is blowing down an exit shaft or chimney flue, the windows or inlet ventilators may become outlets. These matters can, however, generally be regulated by attention to the facts and principles which have been akeady laid down as a guide to proper ventilation. It will be convenient to mention in this place some facts with regard to loss of velocity in air shafts by friction. The actual loss can in some cases be determined by calculating the theoretical velocity in an air shaft by Montgolfier's formula, and then ascer- taining practically by means of a current meter or anemometer the actual rate at which the air is issuing or escaping. The differ- ence represents the loss due to friction ; but allowance must of course be made for disturbing forces, such as the perflating or aspi- rating action of the wind. Contrasting two similar tubes of equal sectional area, the loss by friction will be directly as the length of the tube. If the two similar tubes are of unequal size, the loss by friction is inversely as the diameter of the cross section in each. When two tubes are dissimilar in shape, the loss by friction is inversely as the square roots of the sectional areas. A circle is a figure which includes the greatest area within the smallest periphery ; thus, if there are two tubes, one of which is circular in section and the other square, but having the same area (i square foot), the loss by friction is directly as the periphery, and in this case is as — , the periphery of the square being 4 feet and 4 of the ciicle 3^ feet. Every right angle in a bent shaft dimmishes the velocity of the current one-half. It will thus be seen that air shafts should preferably be circular in section, short and straight, so as to diminish the loss by friction as far as possible. 15 226 HYGIENE AND PUBLIC HEALTH The absurdity of ventilating soil pipes and drains by narrow pipes, I or 2 inches in diameter, of great length, and bent on themselves often to a right angle, is apparent from the above statements. The ventilation of drains is always difficult to establish ; carried out by such methods it becomes an impossi- bility. Ventilating appliances whose object is the supply of artificially warmed air will be considered separately in the chapter on Heating and Warming. Artificial Ventilation. — Under this heading are usually described m.ethods of extraction of air from inhabited buildings by means of heat, steam, or fans ; and methods of propulsion of air into buildings by mechanical means. It has been found convenient to describe under natural ventilation of rooms the ventilating effects produced by fires and chimneys in ordinary rooms ; and the extractive properties of gas lights have also been alluded to, although, properly speaking, fires and gas are artificial means of ventilation. The fire and chimney of an ordinary sitting-room are types of the methods used on a larger scale for extraction by heat. The principle is the same in all, and depends on the heating of a column of air in an extraction shaft, which being thus made lighter ascends ; as long as the heat is applied, a continuous current of air towards the shaft is produced, which, in its turn being heated, ascends and escapes, to be replaced by more from below. It is in this way that some mines are ventilated. The under- ground workings and galleries of the mine are connected with two large shafts — an upcast shaft and a downcast shaft, usually from 8 to 12 feet in diameter, leading to the open air — when air is made to pass down the do\\Ticast or intake shaft, it has to travel through all the workings of the mine before it can escape by the upcast or return shaft. The power which produces this continued movement of air may safely be supplied in some mines by a furnace at the bottom of the upcast shaft exerting an extractive force by the heated column of air, as previously described. But in most mines the extractive force is exerted by means of a powerful rotatory exhaust fan placed at the top of the upcast shaft ; such fans can be made to propel some 12,000 cubic feet of air per minute. Numerous doors and partitions are necessary in the galleries AIR AND VENTILATION 227 and workings in order to make the air traverse the whole length of these, and prevent it taking short cuts. An enormous volume of fresh air must be passed through a mine in the course of every hour in order to supply the quantity necessary for the respiration of the men and ponies employed underground, and to withdraw the products of combustion of lights (lamps and candles) and agents used for blasting, and to replace these injurious gases by pure air. Where fire damp (CH4) is evolved from the strata cut through, the ventilation must be exceptionally good, in order to dilute this gas sufficiently to prevent its forming an explosive mixture with atmospheric oxygen. The same may be said with regard to the evolution of carbonic acid from the rocks underground, which so frequently takes place. This gas must not be allowed to form much over i per cent, of the underground air, or its asphyxiating properties will be exerted on all animal life within its influence. The injurious effects produced by gunpowder blast- ing are no longer necessary evils in the life of the collier or coal miner since the introduction of cartridges made of quicklime, which swell up from slaking when water is run over them, and exert their action without producing any gas at all. By the use of such cartridges there is, besides, no risk of explosion from ignition of fire damp or of coal dust. Other substitutes for explosives in fire damp collieries are plugs of dry wood, which swell when wetted, wedges worked by hydraulic pressure, and cartridges containing compressed air at extremely high pressures. Dynamite is now largely used instead of gunpowder, as it is more powerful, may be used under water, and requires no hard tamping. It is a mixture of nitro-glycerine C3H53(N03) and infusorial earth or kieselguhr. Carbonic oxide is not one of the products of its explosion under pressure ; and hence its superiority to gunpowder, in which carbonic oxide forms 7I per cent, of the explosive gases. There is besides no forma- tion of sulphuretted hydrogen and marsh gas when dynamite is exploded, whereas these gases form respectively about 2 per cent, of the total gases resulting from gunpowder explosion. Carbonic acid and nitrogen form nearly the entire bulk of the gases result- ing from nitro-glycerine explosion in closed vessels. Nitrated gun-cotton and blasting gelatine (nitro-cotton and nitro-glycerine) are also superior to gunpowder for the same reasons, carbonic 228 HYGIENE AND PUBLIC HEALTH acid and nitrogen forming almost the entire bulk of the gases generated when these substances are exploded under pressure. ■'- Notwithstanding the importance of an abundant supply of pure air to all the workings of a mine, it has been found impos- sible by the Government inspectors to insist even-on so low a standard of purity as that indicated by 0-25 per cent, of CO2 in the air. It is maintained that in every mine at least 6,000 cubic feet of fresh air per hour should be supplied for every man employed below, for if this quantity is much reduced there is a serious diminution in the amount of work performed by the men, so that even commercially it pays employers to have adequate ventilation. In mines where fire damp or choke damp is evolved, the amount of fresh air supplied should exceed this figure. The furnace at the bottom of the upcast shaft, or the speed at which the fan is driven, must be regulated according to the number of men employed and the amount of work that is going on at any time below ground. Public haUs, hospitals, and other large buildings, are some- times ventilated on the extraction principle. Shafts for the escape of vitiated air lead from the different rooms and open into the chimney just over the furnace. The air from these shafts should not be used to supply the fire or furnace, but should always open into the flue just above it, where the draught is greatest. The column of air in an extraction shaft may be heated by steam or hot water pipes, instead of by a fire. This is the plan adopted at the Hopital Lariboisiere in Paris. The extraction shaft is heated throughout the greater part of its length by spiral hot water pipes coming from a boiler in the basement. These hot water pipes are also carried into the wards, where they are coiled so as to warm the fresh air entering from with- out ; they then return to the boiler, and thus complete the circuit. The tubes from the wards for the escape of foul air open into the bottom of the extraction shaft. In summer the circulation of hot water in the pipes in the wards is stopped, the circuit being completed by return pipes from the top of the extraction shaft, so that the ventilation continues, but the air entering the wards is not artificially warmed. The column of air in an extraction shaft may be heated by gas instead of by fire ; but this method is more suitable for the 1 Encyclopaedia Briiannica, article on " Mining," by C. Le Neve Foster, D.Sc, F.R.S. AIR AND VENTILATION 229 smaller tubes used as exit shafts in ordinary sized dwelling-rooms. Foul ail- may also be extracted by passing a steam jet into a chimney or upcast shaft. The shafts for the escape of foul air must open into the extraction shaft below the steam jet. The cone of steam emitted from a boiler is said to set in motion and drive before it a body of air equal to 217 times its own bulk. On board steamships and men-of-war it has been found that very effective ventilation can be obtained by causing the furnaces to extract the air from all parts of the ship through special shafts. By this means also, if the boilers and steam apparatus are enclosed in iron casings, as far as possible, within which the air shafts open, the temperature of the stokehole is greatly reduced. Some of the chief objections to the method of extraction by heat are : (i) Where the heat is produced by a furnace, it is most difficult to keep this at a constant temperature, conse- quently the draught is often very irregular. This difficulty is not encountered where the extraction shaft is heated by steam, gas, or hot water pipes, or where the air in it is forced upwards by steam. (2) In all cases where a number of air conduits from rooms at different distances open into an extraction shaft, there is a great tendency to create powerful currents from rooms that are near, 'and have short conduits leading from them ; whilst from the distant apartments with long and perhaps much curved con- duits the current may be very slight, or even nil. This difficulty may to a certain extent be overcome by increasing the diameter of the longer pipes so as to reduce the friction, and by bending the shorter pipes so as to increase it ; but in practice it is a rather serious drawback. (3) When air is drawn out of a room it is somewhat difficult to control the entrance of fresh air to supply its place, especially with regard to its point of entry and its exclusion from places such as water-closets, from which it is most desirable that no air should be taken. In the ventilation of factories, steam may often be economically and usefulty applied as the extraction force, but extraction by fans has also been largely used, and presents considerable advan- tages, as the amount of draught can be nicely regulated by altering the speed (the number of revolutions per minute) at which the fan is driven. It is especially in the textile trades — in the cotton, woollen, silk, worsted, and flax factories — that ventilation is most urgently needed. In many of the processes of these manufactures the work is not only carried on in clouds 230 HYGIENE AND PUBLIC HEALTH of dust, but also in greatly heated atmospheres which are satur- ated \vith moisture, this being necessary in some instances to the proper performance of the work. To carry off the floating particles of dust it is necessary to induce a powerful current in the exit shaft, so that the air may be drawn in as if to a vortex. In some cases the opening into the exit shaft may be in the centre of the room ; but it is more often advisable to carr}^ the dust away as soon as it originates, and before it can mix with the general air of the apartment. Thus, in the wool sorting trade, each bench on which the wool is sorted has an opening leading by means of a pipe into the extraction shaft, at the extremity of which the exhaust fan is working. When the wool is being shaken, the dust, amongst which may be the spores of Bacillus anthracis, is drawn into the tube, and does not mix with the air which is inhaled by the workmen. The dust is then driven into settling chambers, where it is damped by steam jets, and so deposited can be col- lected and burnt. In silk dressing processes, air tubes are placed above the machinery \vith dependent hooded openings, which cover the area of dust production and quickly remove the dust ; such flues either lead into the chimney flue, or have a powerful draught created in them by means of fans placed towards the end of the shaft which leads from them to the outside air. In the dry grinding processes of the metal trades, the air tubes are placed level with the grindstones and have openings opposite each stone, in such positions as to catch the dust, as it is driven off, and carry it away at once. The best material for the exit shafts and tubes is galvanized sheet iron, as it can be made into smooth circular pipes. Arrangements must be made to provide that the draught from the benches, or the workrooms nearest the fan, is not so great as to prevent the shafts at a dis- tance from working properly. A very convenient form of fan is that known as the Blackman Air Propeller ; it can be used for exhaustion (vacuum ventilation) or for propulsion (plenum ventilation), and is very powerful in its action, its vanes being large and curved. Another good form of fan, which is noiseless in its working, is that kno"v\Ti as the Sturtevant " blower." They can be driven by a gas or steam engine, by water or electricity, and are employed for removing dust, foul air, or fumes and steam. When used for propelling air into a building, the rate of movement in the main conduit AIR AND VENTILATION 23 1 should not exceed 5 feet per second, and, where dehvered into the rooms, not more than i| or 2 feet per second. The sectional area of the air shafts should be at least equal to that of the fan, so as to reduce resistance by friction. The warmed fresh air should be delivered by the pipes into the rooms. Special exit shafts are not always necessary, and those existing near the ceiling should be closed. The air finds its way out through fire-places, doors, windows, or the innumerable minute apertures by which every room communicates with the exterior. In the "plenum " system, windows, etc., are kept closed, so that the air being constantly driven into the rooms is under a slight pressure which causes it to escape through the exit opening or openings communicating with special exit shafts. These exit openings should be low down in the rooms or workshops, and principally on the same side of the room as the inlets, so as to cause the incoming air to circulate thoroughly before it escapes. Mechanical ventilation by means of fans is now much used in public halls and restaurants, and is advocated for school class- rooms. The objections to the propulsion or " plenum " system of ventilating buildings is that experience shows that air which has travelled through lengthy shafts and special air chambers has lost its freshness and is liable to cause lassitude and a feeling of depression amongst those who habitually come under its influ- ence. Chemical and bacterioscopic examination may demon- strate the purity of such air, but none the less there is reason to believe that in such air the vitalizing principle characteristic of really fresh air is diminished. The essential distinction be- tween town and country air is likewise probably due to a diminu- tion or deterioration of the unknown vitalizing principle present in a purely natural atmosphere. The very artificiality of the plenum system, which permits of the air supply being regulated with great nicety as to volume, temperature, moisture, etc., robs it at the same time of the refreshing qualities so important for the maintenance of a good standard of health. Open windows and direct ventilation through the external walls of a building may cause draughts and irregularities of temperature, but such methods appear to be more healthful for hospitals and buildings of the factory and domestic class, which are more or less con- tinuously occupied, than the artificial systems of ventilation. For theatres, churches, concert halls, etc., where large numbers 232 HYGIENE AND PUBLIC HEALTH are collected for limited periods only, artificial systems of ventila- tion find their best application ; but in the plenum system the permanently closed ^^dndows constitute a very bad object-lesson to scholars at school. PI eraanz Sy3rerT^ Fig. 34 But ventilation by propulsion (plenum method) presents several advantages. The amount of air deHvered and the rate of movement can be regulated mth nicety, and the entering air can be taken from the most desirable point, can be warmed or cooled by a spray of water, and filtered in special chambers through cocoa-nut fibre screens, kept moist by M^ater, or, what is better, through a very fine meshwork of copper wire continu- ously sprayed by water ; and all this can be done at one spot for a nmnber of rooms or buildings. A more frequent air renewal can be provided hy this than by any other method, and less dirt is introduced from ^vithout. In the Houses of Parliament at Westminster a combined method of ventilation bj' propulsion and extraction by heat is in operation. Air is propelled by rotary fans along conduits to the basement, where it is filtered through cotton- wool and AIR AND VENTILATION 233 warmed in winter by passing over steam pipes, and then passes upward through shafts into the space beneath the grated floor of the House. The heat can be regulated by covering the steam pipes with woollen cloths, and in summer the entering air can be sprayed with water or cooled by passing over ice. The vitiated air in the House passes through a perforated glass ceiling in the roof, and is then conducted by a shaft to the basement of the clock tower, where it passes into a flue from which the air is extracted by a rotary fan. What is known as the " balance " system — a combination of plenum and vacuum — is specially applicable for the ventilation of large halls and rooms with extensive seating capacity. In the large Examination Hall of the University of Cambridge this system has been successfully applied. Warm fresh air is intro- duced on opposite sides of the hall, about 7 feet above the floor, by means of a fan, and is extracted by another fan from apertures in the ceiling leading to an extraction shaft. The building is warmed prior to use by hot- water radiators ranged along the four walls — it being far more economical to warm a building in this way than to attempt to warm it by the heat conveyed in the warmed fresh air used for ventilation. The windows of the hall are double glazed, the air space between the two sheets of glass forming a non-conducting layer, which not only prevents loss of heat by radiation from the interior of the building, but also tends to minimize the interference with the proper direction of the ventilating currents, which is caused by chilling of the air in the neighbourhood of the windows. In this "balance" system, when the inlet and outlet fans are properly adjusted, there is neither excess nor vacuum pressure within the building ventilated. There is, therefore, no tendency, on the one hand, for air to escape, nor, on the other, for air to enter, except at the proper inlets and outlets, and the distribution of the air is kept under very perfect control. In Verity's system, air is set in motion by a spray of water from a number of very fine jets. The rate of motion can be regu- lated by the tap which supplies the jet. The method is useful for houses where it is not desired to go to the expense of fans driven by machinery. In addition to hot water pipes, the incoming, air may be warmed by passing it into firebrick chambers, or through air ducts, placed behind and at the sides of a fire grate or stove ; 234 HYGIENE AND PUBLIC HEALTH or the air may be warmed by conducting it through a tube which passes through the centre of a gas stove (George's Calorigen and Bond's Euthermic (fig. 36). The Manchester stove is largely used for schools, hospitals, etc. In this stove the cold air is carried along a shaft placed between the joists of the flooring, and enters a firebrick chamber built into the back of the grate. It then passes through tubes leading from the top of this chamber, and, travelling round the hottest part of the smoke flue, enters the room through openings at the top of the stove. The smoke flue is bent back and carried down the back of the stove, passing under the flooring to the outside, where it is carried up as a chimney. In all systems of ventilation it is important to remember that air ducts of all kinds should be made easily accessible for cleaning. This principle has been too often neglected in the past, with the result that air fouled by contact with dirt is very fre- quently used to supply buildings, whilst outlet pipes and shafts are found choked with accumulations and practically valueless. Ozonization of Air. — This has been recommended for the deodorization of foul atmospheres and for the destruction of the organic matters and living microbes that may be present in such air. The amount of ozone in the air, which is produced by the use of the apparatus of the Ozonair Company, is ordinarily from I to 5 parts per million, the limit for comfortable respiration being about 10 parts per million ; above this amount the irritating effect on the mucous membranes of nose, eye, and throat begins to get very marked. In the Ozonair Company's apparatus, ozone is produced by the action of an alternating electric current of high frequency on the oxygen of the air, through the medium of a non-sparking or silent (condenser) discharge, no oxide com- pounds of nitrogen being formed by this form of discharge. The machine, when at work, emits a continuous stream of ozonized air, which for ventilating purposes is mixed with ordinary atmospheric air, the resulting mixture having the composition above mentioned (i to 5 parts per million of ozone). The characteristic smell of electrically produced ozone is noticeable in air containing these small amounts of the gas, but it is not disagreeable, nor are there any irritating effects of the mucous membranes of the eye, nose, or throat, probably because of the absence of oxides of nitrogen. Air ozonized to the extent that is compatible with comfort AIR AND VENTILATION 235 is a safe and valuable deodorant. Whether volatile organic matters in the air are actually oxidized and destroyed by these very weak dilutions of ozone, or are merely masked and rendered inappreciable by the penetrating odour of the gas, is a matter of uncertainty. What, however, is certain is that, in the very weak dilutions that can be inhaled ^vith safety, ozone has no sterilizing or disinfectant action on air-borne micro-organisms. To destroy the Bacillus typhosus in dry air there must be present 0*3 per cent, of ozone in the air (3,000 volumes per million), and the bacilli must be allowed to remain in contact with the ozonized air for one hour, otherwise disinfection is incomplete. The bacilli of tubercle, influenza, diphtheria, and nasal catarrh are probably not less, but more, resistant than the B. typhosus, so that it is evident that an atmosphere containing 10 parts per 1,000,000, of ozone — the limit for respirability — has only Tj^th part of the amount of ozone requisite to destroy patho- genic organisms, which must be left in contact with it for an hour at least. Practical Examination of the Ventilation of Inhabited Rooms. In the first place it is necessary to determine the amount of cubic space. In rooms of regular shape this may be done by multiplying together the three dimensions of height, length, and breadth. If the room is irregular in form, containing recesses and projections, or mth a raised ceiling, it is usually most con- venient to divide it up into a number of simpler parts, whose cubic contents can be determined by some one or more of the following rules : Area of circle = square of diameter (Dg) x 0*7854. Circumference of circle = D x 3'i4i6. Area of ellipse = the product of the two diameters x 0'7854. Circumference of ellipse = half the sum of the two diameters X 3-1416. Area of square = square of one of the. sides. Area of rectangle = the product of two adjacent sides. Ai^ea of triangle = base x \ height. Area of a parallelogram = divide into two triangles by a diagonal, and take the sum of the areas of the two triangles. Area of trapezoid = half the sum of the parallel sides x the perpendicular distance between them. A trapezoid 236 HYGIENE AND PUBLIC HEALTH is a plane four-sided figure having two of its opposite sides parallel. Area of segment of circle = (Ch x H x f ) + —7;^ (Ch= chord, H= height). Cubic capacitj^ of cube or solid rectangle = length x height x breadth. Cubic capacity of solid triangle = area of triangle x height. Cubic capacity of cylinder = area of base (circle) x height. Cubic capacity of cone or pyramid = area of base (circle) X ^ height. Cubic capacity of dome= area of base (circle) x f height. Cubic capacity of sphere = D^ x 0'5236. Thus, supposing it was required to determine the cubic capacity of a circular hospital ward 30 feet in diameter, with walls 10 feet high, and a dome-shaped roof 5 feet high. The area of the base or floor space is 706*86 square feet. The cubic capacity of the cyhnder below the dome is 706*86 x 10= 7,068*6 cubic feet, to which must be added the cubic capacitj^ of the dome =2,356*2 cubic feet. So that the cubic capacity of the ward is 9,424*8 cubic feet. Having determined the gross cubic space, the next point is to determine the available cubic space, i.e., the gross cubic space less the space occupied by solid objects in the room. Any bulk}^ furniture must of course be measured, and it is usual to deduct 3 cubic feet as the space occupied by each individual, and 10 cubic feet for each bed and occupant. Having made these deductions, the available space for ventilation is arrived at. Next, the various openings acting as inlets and outlets respect- i vely must be determined, and thus the area of inlet and outlet provision per head can be ascertained. To distinguish inlets from outlets, observe the direction given to the smoke evolved from smouldering brown paper or cotton velvet, when held close to the apertures, some of which \vill be found to act as inlets and others as outlets. The rate of movement of air through these apertures may be approximate^ ascertained by placing in them an anemometer, which is an instrument consisting of four little revolving sails driven by the wind or current of air. The sails turn an axis with an endless screw running on small toothed wheels, which, by means of a plate and dial, indicate the number of revolutions of the axis and the space traversed by the sails. / AIR AND VENTILATION 237 By experiment with air moving at a known rate of speed, the anemometer may be graduated. It appears, however, that even tested anemometers are subject to variations, and too much rehance must not be placed on their indications. When the instrument is placed in a ventilating shaft or opening, it should be at about two-fifths of the distance from the centre to the margin of the opening, that being the situation where the mean velocity is obtained with the greatest degree of approximation, A modification of the water manometer, or pressure gauge, is occasionally used. The current of air impinges on the surfaces of the water in one arm of a bent tube, and in proportion to its strength drives the water up the other arm, which is inclined at a certain angle. The records obtained in this manner can be compared with the theoretical velocities arrived at by the use of Montgolfier's formula, allowances being of course made for friction and wind. When the wind is at all strong and is blowing directly into inlet ventilators, or is exerting a powerful aspirating action on chimneys or exit shafts, calculation is useless. As air enters a room by every crack and crevice, and may even do so through the brickwork of the wall, it is practically impossible to gauge the amount of the incoming air. The best plan is to deduce it from the amount which is leaving the room, as the out- going air will only leave the room by well-defined channels or out- lets. In an ordinary room practically the whole of such air tends to escape by the fire-place, the entrance to the flue of which has generally a transverse section of about 126 square inches. If the rate at which the air is travelling up the chimney is ascertained by an anemometer, the amount of air leaving the room is easily cal- culated. Thus, assuming the velocity to be 7 feet per second, then the quantity of air escaping will equal this velocity x the sectional 126 area of the opening (in feet) = 7 x = 6-1 cubic feet per second, or 21,960 cubic feet per hour. If samples of the air are to be taken for an estimation of the CO2, any gas burners, lamps, etc., which may be alight at the time must be carefully noted, together with the temperature at the time the sample is taken. : In any scheme of ventilation, regard must be had to the follow- ing practical points :— 1. When air is heated it expands and tends to rise ; when air is cooled it contracts and tends to fall. 2. Cold air tends to enter a room and to move about very 238 HYGIENE AND PUBLIC HEALTH much as water would ; and this holds true so long as the tempera- ture of the fresh air remains lower than that in the room. 3. The extent of inlet provision for fresh air is not quite of the same importance as that for the exit of foul air ; for if foul air is extracted in sufficient quantities, fresh air will enter somehow to replace it, as by skirtings, crevices in doors and windows, or even through the brickwork of the walls. 4. The inlet provision for fresh air should average 24 square inches for each individual ; the provision of inlet areas somewhat larger than those of exit tends to minimize draughts. 5. Inlets should generally be as low in the room as possible, viz. , just above the floor (so as not to raise the dust) if the outside air is warm or has been warmed prior to entry, but at a height of about 5 feet if the outside air is cold ; otherwise unpleasant draughts are experienced. As a further protection against unpleasant draughts when cold air is admitted, the incoming air should be directed upwards ; while hot air, since it tends to rise, should be directed downwards. 6. Outlets should in every case be as high as possible, and preferably close to or in the ceiling ; and they should have their extractive powers maintained by means of heat or an exhaust fan, or they are liable to act as inlets. 7. Where practicable, an effort should be made to so place out- lets that the vitiated air is drawn towards them before mixing with the general air of the apartment. 8. There is a tendency for fresh air to take a direct course to the outlets, and this must be counterbalanced by a judicious selection of the relative positions of inlets and outlets. 9. Methods of ventilation devised to ventilate crowded premises are generally inefficient, unless the incoming air can be warmed in winter to about 60° F. ; for then efficient ventilation by cold air cannot be tolerated, and there is a great tendency among workers to close all ventilating inlets. 10. With less than 250 cubic feet of space per head, no ventila- tion can be satisfactory which is not aided by mechanical force. 11. The source of the incoming air should be considered. It should not be borrowed from adjoining rooms, but taken direct from the outside. One great advantage of the more expensive mechanical system of plenum ventilation is the fact that sufficient air can always be obtained from a source which is known and selected. AIK AND VENTILATION 239 12. Ventilation dependent on the extraction of foul air is often more convenient than that in which propulsion is mainly relied upon ; but the purity of the air is not so easily provided for or guaranteed. 13. If warmed air is forced into a room, it should only be raised to a temperature sufficient to prevent a feeling of cold (about 60° F.). More highly heated air is often felt to be overdry and unpleasant. 14. The heating of the room should be effected by fires, stoves, or pipes in the room itself, and should not be made to depend upon the warmth of the incoming air. 15. It is difficult and expensive to apply methods of mechanical ventilation to old premises. CHAPTER IV WARMING AND LIGHTING Warming. Individual susceptibilities to heat and cold are various, depend- ing as they do upon age, robustness of constitution, and previous habitude. It may, however, be stated that, as a general rule, the temperature of a sitting-room or workroom should be about 60° F. to 65° F. Radiation. In this country houses are generally warmed by radiant heat from open fire-places. By radiation is meant the direct passage of heat from warm bodies to colder ones, the rays of heat passing through the intervening air. This form of heat is no doubt the most healthy, for whilst objects within the range of the fire are warmed, no impurities are added to the air of the room. Moreover, the column of air in the chimney flue is heated, and, becoming lighter, escapes at the roof of the house, to be replaced by colder and denser air from below, and thus an open fire-place is a great factor in ventilation. It is, however, extremely wasteful, for the greater part of the heat escapes up the chimney. The intensity of radiant heat is inversely as the square of the distance of the heated object from the source of heat. Thus, if there are two objects, i foot and 3 feet distant (respectively) from an open fire-place, the more distant object only receives one-ninth the amount of heat received by the nearer object. This fact shows the impossibility of warming equally all parts of a room, when the source of heat is an open fire-place. Of late much has been done to improve open fire-places by securing the greatest amount of heating effect with the least consumption of fuel. Some of these improvements have been 240 WARMING AND LIGHTING 241 made at the suggestion of Mr. Pridgin Teale. They may be thus summarized : The width of the grate at the back should be about one-third the width in front facing the room, the sides of the grate being splayed out at the necessary angle. The back and sides of the grate should be formed of fireclay, and the back, instead of rising perpendicularly, should be " rifle-backed," i.e., curved forward so that the flames may play upon it (fig. 35). The curved portion becomes heated by some of the upward rays, which would otherwise be lost up the chimney, and radiates this heat into the room. Vertical fire bars are said to allow more heat to radiate into the room than horizontal bars. The floor of the grate should be formed of a solid slab of fire- clay as in slow combustion grates ; or if the lower fire bars are retained, a shield should be placed on the hearth, rising as high as the bottom bar of the grate, so as to form a hot air chamber under the grate com- pletely cutting off the air of the room (fig. 35) ; or an iron plate may be laid upon the bars form- ing the bottom of the grate. The object of this arrangement is to prevent a draught under a fire which hastens combustion and wastes fuel. The whole fire-place should be brought well forward into the room, the grate being placed low down near the floor ; and to reduce draught the chimney throat should be narrowed as much as possible. A movable hinged canopy, to regulate the draught up the chimney, is a desirable arrangement. Open grates of this description create much smoke, as the combustion of the fuel is bj'- no means complete. Attempts have been made to construct a smokeless open grate ; and the plan which has been found on the whole to answer the best is 16 Fig. 35.- Economizer. B, flue. Rifle-back Stove with A , hot air chamber; 242 HYGIENE AND PUBLIC HEALTH to " underfeed " the fire, by which is meant that the supply of fresh fuel is introduced beneath the incandescent coal which forms the top of the fire, and through which the smoke arising from the fresh coal must pass, thus securing complete combustion. In one of the best of these smokeless fire-places a curved ledge projects from the bottom of the grate. The fresh fuel is placed on this ledge and forced under the blazing coal above by means of a special kind of shovel. These " underfed " grates are found to be very efficient heaters for the amount of coal con- sumed, and they continuously expose a clear fire free from smoke, but they require more care in stoking and management than ordinary grates. Wherever possible, fire-places and chimney flues should be built in one of the inner walls of a house. The waste heat of the flue will then help to warm the upper rooms. It is evident that, as open fire-places act as ventilators for extraction of air, to carry on this function the column of air in the flue must be kept continuously heated ; otherwise the chimney will not " draw," and back currents of smoke enter the room. In an ideal stove, the heat escaping up the chimney should be not more than sufficient to maintain a good draught, the rest being radiated into the room. There are several forms of " slow combustion " grates now upon the market, the principle of which is to reduce the draught through the fire to its smallest possible dimensions. One of these, the " Well Fire," consists of a fireclay trough, inside which is placed a cast-iron grate whereon the first rests. The space between the iron and the fireclay constitutes a hot air chamber to which a continuous current of air at a raised temperature is admitted by side tubes. With a reduction in the price of coal gas, open gas fires have come more largely into use. As usually constructed, the flames from a row of Bunsen burners play upon asbestos, in lumps or fibre, which is heated to a red heat. A gas fire consumes from 10 to 20 or more cubic feet of gas per hour. Until gas is supplied at IS. or IS. 6d. per 1,000 cubic feet, which could easily be done if it were freed from illuminants, or until a public supply of water gas is made safe and available, gas fires must be more expensive than coal. But they have the advantage of being very cleanly — there is no soot in the chimney flue and no dust or ashes — very convenient, and of causing no trouble. As regards the prevention WARMING AND LIGHTING 243 of smoke, the more extended use in our large towTis of coal gas for heating and cooking would undoubtedly tend to free the air from much of the soot and smoke that now pollute it. Fogs, which depend so largely upon climate and site, would be just as frequent, though less sooty and yellow. They would also be less sulphurous, for the sulphur compounds produced by gas combustion are less than those produced by coal. It is probable that water gas would come largely into use for heating and illuminating purposes — for gas fires and gas cooking stoves, and for incandescent burners — were it not dangerous, from containing such a large percentage of carbonic oxide. Water gas is produced by blowing steam through incandescent coke or other carbonaceous matter, raised to a high temperature in a " generator " furnace by the aid of an air blast. The in- candescent coke gives off what is known as " producer gas," and this is led away from the generator before the steam is introduced. The introduction of the steam is only continued for about four minutes, after which time it is necessary to turn on the air blast again to reheat the coke. The " producer gas," consisting largely of carbonic oxide, is used for heating the boilers which generate the steam. It will thus be seen that the process consists of alternately blowing the generator hot (for ten minutes), when producer gas is formed and led away, and of making water gas by introducing steam over the hot fuel (for four minutes) . In this way the water is split up into hydro- gen and oxygen ; the hydrogen remains free, and the oxygen with most of the carbon forms carbon monoxide, the mixture being " water gas." The water gas, as formed, is passed over scrubbers and purified over oxide of iron, in much the same way as coal gas, before being stored in gas holders ; it then consists of hydrogen gas (about 35 per cent.) and of carbonic oxide (25 ■to 35 per cent.), marsh gas 20 per cent., and 10 per cent, of ethylene, etc. In heating power water gas is far superior to coal gas ; and as the only products of combustion are H2O vapour and CO2, the sulphur products of combustion of coal gas are avoided. Water gas, too, can be produced very cheaply, viz., at about 4^. per 1,000 cubic feet. But the large quantity of CO in water gas causes it to act as a powerful poison, and yet, from being odourless, escapes, if they occur, are not at once detected. For lighting purposes the gas is " carburetted " — that is, enriched by hydrocarbons derived from oil. This car- 244 HYGIENE AND PUBLIC HEALTH buretted water gas smells much like coal gas ; its candle power is greater, and it is, on the whole, cheaper to make. It has been adopted for lighting purposes in many towns in America, and it is often used, mixed with coal gas, in this country. A recent Departmental Committee recommended a statutory limit of 12 per cent, of CO in any illuminating gas ; for an escape leading to the presence of 0*4 per cent, of CO in the general atmosphere may prove fatal. It is perhaps needless to point out that plumbers should never be allowed to fix a gas fire, or, in fact, any gas consuming appliance (such as a bath heater or "geyser"), which burns more than 12 feet of gas per hour, without providing a chimney flue to carry off the products of combustion to the outer air. Ventilating grates may be combined with open fireplaces. The usual method is to construct a chamber lined with fireclay at the back and sides of the fireplace, and extending up around the lower part of the chimney flue. An opening below admits fresh air from outside the house into the chamber, where it is warmed and escapes by an opening into the room above the chimney-piece. Galton's Grate and the Manchester School Grate act upon this principle. Conduction and Convection. By conduction heat passes from one molecule of air to another in contact with it ; but, as air is a very bad conductor of heat, the process is very slow. The conveyance of heat by means of the movements of masses of heated air (convection) is the most effectual agent for heating. Air when heated expands and becomes lighter bulk for bulk than colder air, so it rises upwards, its place being taken by the colder, denser air. Houses may be heated by means of stoves in which coal, coke, gas, or oil is burnt, by hot water and steam pipes, or by " radiators," which are radiators only in name, their heating effect being due to convection. The air coming in contact with the heated surfaces is warmed, and therefore expands and rises, and is replaced by colder air. In this way currents of air are maintained which circulating about a room tend to heat every part of it. The most satisfactory way of uniformly heating the whole house is by warming the air of the entrance hall by means of hot water pipes, a hot water radiator connected with the kitchen boiler, or a ventilating stove placed in the hall. The WARMING AND LIGHTING 245 I A warm air which ascends can then be admitted to all the rooms above the ground floor by openings over the doors, which openings may be fitted with valves. The great distinction between stoves and open fire-places is that, whilst in the latter the heated air escapes up the chimney, in the former the heated air circulates through the room. There is a great variety of heating stoves, but they may all be classified as either close or ventilating stoves. In the former kind no arrangement exists for providing fresh warmed air ; whilst in the latter fresh air from outside the house is made to circulate through the stove, with- out coming into contact wdth the products of com- bustion, and is, when warmed, allowed to enter the room. Bond's Eu- thermic Stove is one of the best forms of venti- lating stove. In this the fresh air from the out- side is conveyed to and warmed in a central up- right tube, which com- municates with the room at the top of the stove. The space between this tube and the outer case of the stove is open below, where a circle of gas jets burn, and above it communicates with a flue. Thus, not only is warmed fresh air suppUed to the room, but also foul air is removed along with the products of combustion between the inner tube and the outer case. From an inquirj^ undertaken by the Lancet into the general efficiency of gas stoves, the following facts emerged : A properly constructed gas stove with a suitable flue, while more costly than a coal fire, does not vitiate the air of a room nor produce any abnormal drjang effect upon it ; more heat is lost in the flue gases in coal fires than in gas fires ; coal fires take longer to warm a room than gas fires ; as gas fires are so easily regulated, the ^ J Fig. 36. — Euthermic Veatilating Gas Stove. A, fresh air chamber ; B, ring of Bunseii gas burners ; C, to foul air flue. 246 m'GIENE AXD PUBLIC HEALTH temperature of the room can be controlled in a manner which is not possible with coal fires, and a more equable temperature is maintained A\dth a gas fire with an absence of dust and smoke ; no carbon monoxide was detected in the hot air and gases coming from these stoves, except in one instance where the stove was faulty. In all stoves economy of fuel is aimed at, by providing doors and dampers to shut off the draught and make the combustion as slo\\- as possible ; and the flues are sometimes carried horizontal!}^ for some distance, in order that extra heat may be obtained. It is e\-ident that the slower the combustion and the more complete the utilization of the heat of the burning fuel in warming the room, the less does a close stove act as an exhaust ventilator ; and economy of fuel and utilization of heat may be procured at the expense of healthiness. The ventilating stoves which introduce a supply of fresh warmed air are decidedlj' more healthy ; but there are certain disadvantages which require consideration in the use of stoves of aU kinds. In the lirst place, they are apt to render the air of a room too dry, and therefore unpleasant to the nose, eyes, and skin. There may be the same amount of moisture in a cubic foot of heated air as in a similar bulk of cold air before it is warmed ; but the relative humidity of the air when heated \^ould be greatly diminished, as hot air is capable of holding more moisture, before saturation is reached, than cold air ; and it is upon relative himaidit}" to some extent that health and comfort depend. This drawback may, to a certain extent, be overcome by placing vessels of water in the room or on the stove. Secondl}-, if the stove becomes overheated, the organic matters in the air become charred bj" contact \^ith the heated surface, and a disagreeable close smell is perceived. Lastty, the presence of carbonic oxide has been detected in the air of stove-heated rooms when the stove is of cast iron. Either this gas passes out of the furnace through in\-isible hssures in the cast iron, or it traverses the walls of the stove when at a red heat. Others suppose that the gas may be formed by incomplete combustion of particles of carbon or organic matter floating in the air, when brought into contact %^dth the hot metal. Cast-iron stoves are very liable to become overheated, as, WARMING AND LIGHTING 247 being good conductors, they rapidly heat and cool. In such stoves, therefore, the heating surface should be increased by vertical flanges projecting from the top and sides, by which means the heat, being conveyed to a larger surface, is less intense, because cooling is more rapid. It is safer not to use cast-iron stoves at all, unless lined inside with fireclay ; this, being a good non-conductor, prevents the over rapid heating of the iron walls, and the warming of the room is altogether more equable. There are many ornamental stoves now made entirely of fireclay and china, with arrangements for the supply of warmed fresh air at an agreeable temperature of about 65° to 70° F. They are especially valuable for heating halls and public buildings. No ill effects appear to follow upon the use of oil stoves in living room.s, if the combustion of the oil is complete and there is efficient air renewal in the room, despite the general absence of flues to convey away the products of combustion. Steam pipes are largely used for heating factories and work- shops and public buildings where steam power and waste steam are at hand. Systems of Heating by Hot Water or Steam. The impossibility of adequately warming large rooms, halls, theatres, and other public buildings by open fireplaces or stoves has led to the adoption of various systems of hot water or steam heating, of which the principal varieties in use are : High Pressure Gravity Hot Water. — The pipes are of welded wrought iron of small diameter (| inch internal diameter). There is no boiler, the water being heated by a coil of the piping, of about one-sixth the total length, passing through a brick furnace. An expansion tank is connected to the highest point of the system, in which is fixed a combined " blow off " and " suction " valve. As the water expands on heating, the valve lifts off its seat, and the surplus water escapes into the expansion tank, until the proper working pressure is reached. When the furnace is drawn or not replenished, the water in the pipes cools, contracts, and creates a vacuum. The suction valve then comes into action, and water passes from the tank into the pipes. The water, being under pressure, can be heated to 300° or 350° F- ; but although this renders the system efficient as a heat producer, the high temperature of the heating surface causes an unpleasant, 248 HYGIENE AND PUBLIC ,HEALTH stuffy atmosphere— probably from charring of organic matter in the air. Such atmospheres are often productive of headache, lassitude, and dry sensations in the throat, the latter being due to overdrying of the air (low relative humidity). Types O^ F^QdiaVo'TS witiz fre.st2LQ'y lyzJglS Radigfor otz. hracMaX f, Clear §pacg andcr ^r cXgoru^ ^ideElevalioire yronT BevolTorz. Wards Fig. 37- Zoze" Pressure Gravity Hot Water — (i) Heating by Hot Water Pipes. — In this system 2 or 3 inch cast-iron pipes are connected with a boiler at the base of the system, so as to provide a com- plete circulation. The water is heated in the boiler, circulates through the pipes, parting with some of its heat to the air in- contact with them, and on cooling returns to the boiler, the circulation being due to the difference between the specific WARMING AND LIGHTING 249 gravities of the water in the flow and return pipes. An expan- sion tank is connected to the highest point of the system to allow for increase in volume of the water when heated, and the tank is supplied with water from the house supply by a ball valve. At the highest point of the system, or at any place where aii- is likely to collect, a small air escape pipe should be carried to the outer air. (2) Heating by Radiators. — In this system the circulating pipes are of small diameter (about an inch or less), and the heating effect is produced by radiators fixed at convenient points, the radiators being vertical pipe coils of ornamental pattern. Each radiator is controlled by a valve to entirely or partially cut off the flow of water through it, and thus the temperature can be regulated to some degree of nicet}-. An air-cock is also provided to allow air to escape when the radiator is filling. The great advantage of these two systems is that the heating surfaces are maintained at a comparatively low temperature, seldom rising above i8o° F., and there is, in consequence, very much less tendency for the air to become stuff}' from over- heating and overdrying. The system is simple, is inexpensive to install and maintain, and the boiler only requires stoking at long intervals. On the other hand, in buildings of irregular shape and height there may be some difficulty in maintaining a regular and even flow of water through all parts of the system, and air- locks often give rise to trouble. Low Pressure Hot Water, with Assisted Circulation. — To over- come the difficulties arising from irregular flow, when the force of gravity alone is depended upon, the use of steam to assist the flow has been successfully applied. In Barker's " cable " sj^stem, steam is led from a boiler into an apparatus consisting of two chambers side by side. In the first chamber, the water to be heated comes in contact with the hve steam by falhng in drops through a perforated tray. On reaching a certain height in the chamber, the heated water opens a valve, and passes into the second chamber. When this chamber is full, a valve is opened which admits steam, and the heated water is forced by steam pressure into an expansion tank above the apparatus, from whence it passes into the main flow pipe leading to the radiators, and thence by a return main to the first chamber. In this chamber the condensation of the steam, as it heats the incoming water, causes a partial vacuum, which very materially aids the 250 HYGIENE AND PUBLIC HEALTH return flow of water. The whole work of the apparatus is auto- matic, and requires no attention. It will be seen that the hot water is forced to travel through the system by steam pressure and gravity, and is aided in its return by the suction induced by steam condensation. It is due to this that very small pipes only are required for the mains and branches, and considerable obstacles in the way of dips can be overcome, as the motive forces render the system very largely independent of friction. The temperature of the circulating water can be regulated to anything between ioo° F. and 200° F., the temperature usually employed being 150° F. or 160° F., so as not to overheat or over dry the air. There are various systems of Low and High Pressure Steam Heating, but the most useful is the Vacuum System, as in this the temperature of the steam does not rise above 212° F. Steam is led from a boiler to the radiators, which are similar to those on hot- water systems. The steam, however, is reduced to atmo- spheric pressure by a reducing valve after leaving the boilers, and is condensed in the radiators, the condensed water passing through the exhaust pipe to a vacuum chamber worked by a vacuum pump, where a vacuum of 10 or 12 pounds is main- tained. The radiators are fitted with valves to shut off the steam when required. The steam system of heating overcomes all the difficulties connected with the distribution of heat in large and irregular shaped buildings, and very uniform tem- peratures can be attained in all parts of such buildings. On the other hand, the heating surfaces are usually over a tem- perature of 200° F., and there is more tendency to the creation of overheated and stuffy atmospheres than with low pressure hot water systems. The exact cause of the stuffiness of atmosphere created when air is heated by contact with surfaces of over 200° F. has not been determined. It is not altogether a question of relative humidity, as the air of rooms warmed by open fire-places or by hot water radiators is often found to be of low relative humidity (less than 50), whilst it is fairly fresh to the sense of smell, and has no " stuffy " characteristic. Whether the air of a stuffy room has had something added to it by contact with a heated surface, or has been deprived by such contact of some con- stituent essential to " freshness," is so far only a matter of con- jecture. The sensation of freshness, however, would appear to WARMING AND LIGHTING 25I be due to three more or less co-existing conditions — namely, (i) Absence of any odour due to organic matters ; (2) an air temperature not exceeding 65° F., when the external tempera- ture is below the internal (room) ; and (3) slow movements of masses of air — i.e., non-stagnation. Wherever the low pressure hot water system is installed, radiators should be located under the windows, with a fresh air inlet behind the radiators, so that incoming air may be warmed. It is a good practice to construct radiators without feet, but carried on cast-iron brackets built into the wall ; this facilitates cleaning. In the forced hot water circulation system the water is pumped through the pipes. This method of heating scattered blocks of buildings from a central plant is of special application to public institutions, such as hospitals, lunatic asylums, etc. The system must, however, be very carefully designed, so as to maintain the resistance in each circuit approximately the same. The low pressure steam is specially suitable in high buildings, and where the apparatus is not in use the fact that the pipes are empty removes the risk of damage by frost. Ventilating heat radiators are now largely used. They are fixed against an outer wall, so that fresh air can be conducted into the base of the radiator, and thence pass over the heating surface to escape into the room through a grating at the top of the radiator. By means of a valve, the communication with the outer air can be closed if desired. Electric radiators possess the advantages of yielding no products of combustion, and the heat is available immediately the current is turned on, but the cost of heating by this method is high at ordinary rates for current. Soft water is far preferable to hard water for use in boilers and hot water pipes. The deposit of lime salts from hard water gradually narrows the calibre of the pipes, which in time may become completely blocked. In boilers, the deposit forms a non-conducting lining, which obstructs the passage of heat to the water. When the fur lining is thick it may lead to an explosion, for the iron boiler plates become red hot from the heat of the fire. Should a crack in the fur suddenly form, the water, coming in contact with the red hot metal, is converted into steam with explosive violence. Another cause of explosion in kitchen boilers which are not connected with a hot water cistern, or are 252 HYGIENE AND PUBLIC HEALTH unprovided with a steam escape pipe, is the blocking of the pipe which supphes cold water to the boiler. This occasionally happens after a hard frost, if the pipe is unprotected. In adopting a scheme for heating purposes it is necessary to consider the heat required to raise and maintain the temperature of the air, and in addition to this the further quantity necessary to replace the heat lost through windows, etc. Lighting. The illumination of a room is a matter greatly affecting the comfort and, indirectly, the health of the occupants, and is of especial importance to eyesight in the case of factories, work- shops and schools, where the eyes are concentrated on small objects for many hours at a time. Artificial Lighting. The most commonly employed method of obtaining an artificial illumination is the combustion of inflammable material pro- ducing a flame. Coal gas, petroleum and colza oils, and candles, are well known examples of this form of illumination. In the electric light, on the other hand, there is no combustion, or only to a trifling extent ; but light is emitted from a substance raised to a high temperature and a state of incandescence by the passage through it of an electric current. The inflammable gases and vapours are chiefly compounds of carbon and hydrogen. When these inflammable vapours are heated to a sufficient temperature, the h3^drogen combines with oxygen to form water vapour, and an intensely hot flame with- out luminosity is produced ; the carbon particles, which are lioerated in a state of very fine subdivision, are rendered incan- descent by the heat of the hydrogen flame, and they combine with oxygen to form CO2 and traces of CO. The luminosity, which is situated in the outer portion of the flame, is due to the incandescent carbon, whilst the inner portion — the hydrogen flame — is very hot, but almost non-luminous. The products of combustion are chiefly water vapour and carbonic acid. The light is very deficient in the blue and violet rays of the solar spectrum, and has therefore a yellow or orange colour. Hence the true colours of objects illuminated by a flame are not perceptible. WARMING AND LIGHTING 253 Coal Gas. — The principal illuminant of coal gas is heav}' carburetted hydrogen or olefiant gas (C2H4). There are also present other hydro-carbons — i.e., benzene, propylene, naphtha- lene — which are illuminants. The heavy hydro-carbons, if burned by themselves, would yield a smoky flame ; but these are suitably diluted in coal gas by hydrogen, marsh gas or methane, and carbonic oxide, which together form some go per cent, of the coal gas. Wlien the gas is burnt, the hydrogen or hydro- carbons are almost destroyed, and the products are approxi- mately : Nitrogen, 67 per cent. ; water, 16 per cent. ; carbonic acid, 7 per cent. ; carbon monoxide, variable (traces), and traces of sulphurous acid and ammonia. Coal gas illumination was a great advance on the candle illumination of a former period, but it has certain drawbacks. There is the danger of escape of gas in the houses from mains and pipes, forming, if the escape is large, explosive mixtures with the oxygen of the air ; or if small, causing a serious pollu- tion of the atmosphere. The products of combustion are injurious to health, and the sulphurous acid from the sulphur compounds in coal gas is destructive to books, furniture, and pictures. The combustion also heats the air and dries it ; for although watery vapour is one of the products, the relative humidity of the air at the higher temperature is lowered. Finally, when the supply of gas and air is not regulated during combustion, the gas is wasted, the Hght is lessened, and un- consumed particles of carbon are given off \^^ich deposit as soot on adjacent cold surfaces. The burners in common use are : (i) The fish tail or union jet, which has a flat steatite top, sHghtly depressed in the centre, through which two small holes are bored in directions inclining towards^ one another from below upwards. The two streams of gas meet and produce the flat flame usually seen. (2) The hatimng has a hemispherical steatite top, through which a vertical slit is cut for the gas to issue. The flame is flat and semicir- cular. The flames from these two burners require no chimnej^s, but are usually enclosed in globes to soften the hght. (3) The Argand burner is a small ring or double- walled cylinder, pierced at the top with fine holes for the issue of the gas. The flame thus forms a hollow cylinder, and the air has free access both to its interior and exterior. The flame must be enclosed in a chimney, in order that the supph- of air to it may be regulated. 254 HYGIENE AND PUBLIC HEALTH The Argand burner has been improved b}- Silber, Sugg, and other manufacturers. These improvements are directed, first, to cause the issue of the gas at the lowest possible velocitv, and, secondly, to divide and regulate the air suppty both to the outside and inside of the flame, and to direct a part of it to the higher portions of the flame, where perfect oxidation of the carbon is most required. These unproved Ai-gands give a far better and steadier light for the same consumption of gas than the flat flame burners. There are several ventilating turners in which the products of combustion of the flame are conducted through a flue to the external air, the heated and \'itiated air from the top of the room or hall being also removed by ducts surrounding the flue. The sunlight burners used in theatres and the globe hght are examples of these. The Welsbach incandescent gas burner now has a ^■ery ex- tended use. It consists of a Bunsen biu"ner, \vith a cap (mantle) of asbestos gauze material (rendered non-inflammable by chemical treatment A\ith sulphate of zirconium) suspended in the non- luminous flame ; the gauze mantle becomes incandescent and gives a brilHant Hght, far w^hiter and steadier than the ordinarj^ gas flame. The flame should be enclosed in a chimney. The illuminating power is verj' high for the amount of gas consumed, and the heat given off is far less than wdth an ordinary gas flame. If such burners came into general use, a cheap form of gas containing no illmninants could be supphed ; for heat and not Hght is required in the flame. The cheap gas would also lead to a more general adoption of gas-heating and gas-cooking, and thus to the partial solution of the smoke question. The Welsbach incandescent gas burner is, hygienicaUy, by far the best form of Ughting b}' coal gas. In the alho-carhon Hght, the vapour of naphthalene is burnt in the coal gas, and a brilHant ^^'hite Hght is produced. The naphthalene, which is soHd at ordinar}- temperatures, is placed in a reser\'oir connected vath. the gas burner, and this reservoir must be heated by a smaU gas jet or bj'' strips of metal extending from the flame. The vapour of naphthalene must not be allowed to escape into the air, as its odour is most offensive. One cause of waste and imperfect combustion ^^ith flat flame burners is the constant alterations of pressure in the gas pipes and mains. At one period of the da}- the pressure may be less WARMING AND LIGHTING 255 than one inch of water, whilst at another it may be 3 inches or more. Consequently the flat flame, which is steadily burning under the low pressure, at the high pressure is flaring and singing ; more gas is issuing from the burner than can be perfectly burnt, and unconsumed carbon is given off from the flame to pollute the air and blacken everything around. To control these varia- tions in pressure, gas governors or regulators are employed. In the larger form, the governor is fixed close to the meter, and controls the pressure throughout the house pipes ; whilst a small form is made as part of each individual burner. The best kind of governor acts automatically ; by the action of valves an increased pressure narrows the lumen of the channel through which gas passes, and a diminished pressure widens it. Single burner governors are also found to answer fairly well. Acetylene gas (CaH,), generated by the action of carbide of calcium on water (CaC2+H2 0= CaO + CsHa), furnishes a powerful white light ; but its use is not unattended with danger, unless great care is exercised. Petroleum Oils. — By the distillation of crude petroleum oil an oil suitable for burning in lamps— commonly called crystal oil or kerosene — is obtained. In the distillation, a volatile spirit (benzoline) and heavy oils, some of which are sohd from containing parafiin, are also obtained, and are separated from the lamp oil. Lamp oil contains the hydro-carbons previously mentioned, and gives off an inflammable vapour which at a certain tempera- ture takes fire. This temperature varies for different specimens of oil, and is called the " flashing point." A select Conmiittee appointed by Parhament attributed the chief danger from lamp explosions to cheap lamps of defective design, and they recommended that the flash point (Abel close test) should be raised from 73° F. (the limit defined by the Petroleum Act, 1879) to 100° F. ; that statutory powers should be created to enable the Secretary of State to issue orders affect- ing the manufacture and sale of lamps ; and that information should be spread among the public as to the nature of petroleum and the management of lamps. In the suggestions issued by the London County Council, it is pointed out that the flashing point of ordinary petroleum oil is a little above 73° F., that the oil in the reservoirs of lamps is rarely heated above 100'' F.. 256 HYGIENE AND PUBLIC HEALTH and that the best safeguard against accident is therefore never to burn oil which has a flashing point of less than 100° F. , which oil should be sold as cheaply as low flash oil. Lamps, too, should be strongly made, and kept thoroughly clean ; especially should the reservoir and burner be strong ; the latter should screw into the collar, and the base of the lamp should be broad and heavy. The Avick should be soft, and should reach to the bottom of the reservoir, and just fill the wick tube ; it should be frequently renewed, and before being put into a lamp it should be dried at a fire, and immediately soaked with oil. The reservoir should be filled with oil before the lamp is lit, and the burner made clean before lighting ; the wick when lit should be partially turned down, and then gradually raised ; the wick should not, however, be left turned down ; lamps that have no extinguishing apparatus should be put out by turning down the wick until there is only a small flickering flame, and a flat piece of metal should then be placed on the top of the chimney, so as to close it entirely ; finally, cans or bottles used for oil should be free from water and dirt, and kept closed. Owing to improvements in lamps, and to the prohibition of the sale of highly inflammable oils, the danger of explosion is now slight. Lamp explosions may occur when, from any cause, the vapour over the oil in the reservoir comes in contact with the flame of the lamp, as through defects in the lamp or by blowing down the chimney past an ill-fitting wick, etc. But the best duplex lamps (the Defries and other safety lamps) are now sold with extinguishers, and with an ingenious arrange- ment by which, if the lamp is overturned, the flame is immedi- ately extinguished. Lamp accidents generalty appear to arise from the use of cheap lamps of defective design, leading to a leakage of oil through imperfect connections and fittings. The oil may thus become ignited. Sometimes the lamp is upset from its instability, or broken owing to the fragile character of the reservoirs. The " Petrolite " lamp is a safe lamp of high candle-power. In this lamp the petrol is absorbed by a block of highly ab- sorbent stone, and the petrol vapour, being made to mix with air, furnishes a hot flame, which, playing upon a mantle, pro- duces a brilliant incandescent light. In the event of the lamp being upset the flame is immediately extinguished. The Kitson light has been used successfully for the purpose WARMING AND LIGHTING 257 of public street lighting. This light is obtained by the auto- matic vaporization of petroleum oil, the mixture of air with this oil by injection, and the impingement of the flame upon a specially made mantle. The diffusive power of this light exceeds both the electric arc hght and the incandescent gashght, it is cheaper than either, and the roads have not to be taken up — as when electric light or gaslight are employed. Colza oil does not give off any inflammable vapour, but it is much dearer than kerosene, and the illuminating power is less. Colza oil lamps require more care in trimming than kerosene lamps. Kerosene, like coal gas, gives off sulphurous acid when burned, but colza oil does not. Candles, especially the cheaper kinds, give off much uncon- sumed carbon, by reason of their low melting point admitting of volatile products being given off before the fats reach the flame and are properly consumed. Electric Light. — The electric Hght presents the following advantages over coal gas, oil, and candles. There is no con- sumption of oxygen, there are no products of combustion to pollute the air, and the heat produced is relatively slight. The light of the arc light is not yellow, but white. It precisely resembles solar light in being rich in the violet and the ultra violet rays. Plants grow and flower, and fruit ripens, when exposed to this light, just as they do in the sunhght ; whilst photographs can be taken as easily by the arc electric Hght as by daylight. The electric current can be produced by batteries, accumu- lators and dynamo machines, and is conveyed in copper wires to the spots where illumination is required. In the arc Hght, which is suitable for lighting streets, squares, and large halls and buildings, the iUumination is produced by the passage of the current through two carbon rods brought into close apposition. The resistance offered to the passage of the current across the space intervening between the points of the carbon rods creates sufi&cient heat to cause the carbon points to become brilHantly incandescent. The light is ex- tremely dazzHng, and is productive of injurious effects on the eyes of those who are much exposed to its influence. The incandescent lamps are best suited for domestic use.. In these the current is passed through a loop of filamentous carbon enclosed in a small glass globe exhausted of air, or fiUed 17 258 HYGIENE AND PUBLIC HEALTH with some gas (such as nitrogen) which does not support com- bustion. The resistance offered by the carbon to the passage of the current raises it to a white heat. Metallic filaments are now largely used instead of carbon. These metallic filament lamps give a far more powerful and whiter light with less current than do the carbon lamps. The extent to which different modes of lighting affect the atmosphere may be thus represented : — Amount Consumed. Candle Power. Oxygen Removed. CO2 Pro- duced, Heat ' Calories Produced. Tallow candles 2,200 grs. 16 IO'7 C. ft. 7'3 1,400 Sperm candles 1,740 „ 16 9-6 „ 6-S 1. 137 Paraffin oil lamp 992 „ 16 6-2 „ 4-S 1,030 Kerosene oil lamp . 909 „ 16 5-9 „ 4-1 1,030 Coal gas, No. 5 bat- wing burner S-S c. ft. 16 6-S „ 2-8 1,194 Electric incandescent 16 o-o „ 0-0 37 CHAPTER V SOILS AND BUILDING SITES The health of a locahty is often influenced by the nature of the soil on which the houses are built ; and it has been truly said that, if the site is unhealthy, the dwelling cannot be made healthy. It is generally believed that the most porous soils — the gravels and sands — are the healthiest, because they are the driest, and this view is in the main correct ; but owing to their porosity they are readily polluted by leaky drains and cesspools. The porous or permeable soils — the loose sands and gravels and the sandstones — are capable of holding considerable volumes of air or water. Even the impermeable rocks — the granites and metamorphic rocks, the dense clays and hard limestones and dolomite — are not wholly unabsorbent, but comparatively speaking they may be looked upon as impermeable. Between these and the porous sands and gravels are all stages of gradation. The surface soils which usually lie upon the denser kinds of rocks, of which they are to a considerable extent the weathered frag- ments, are always more or less porous. The interstices or interspaces between the particles of the porous soils are neces- sarily occupied by air (ground air) , or at a varying depth by water (ground water). When there is air as well as water between the interstices, the water is nothing more than " ground moisture," but when the interstices are completely filled with water, then the " ground water " has been reached. The ground water is derived from the rain which percolates the soil until it reaches an impervious stratum which prevents it penetrating any fruther. Above the level of this subterranean water the in- terstices of the soil are mainly filled with air. The depth at which the ground water will be reached in any soil depends on a varietj^ of circumstances — the elevation of the district and its surroundings, the depth of the impeimeable 259 260 HYGIENE AND PUBLIC HEALTH stratum from the surface, and tlie ease with which the under- ground water reaches its natural outlet in spring, river, or sea. In the low-lying plains and valleys the underground water is not, as a rule, far from the surface of the earth. Its level is not constant, as we have seen in the chapter on Water (p. 21), but is always changing. After heavy rainfall the level may rise ; and there is usually a periodic rise, commencing in the late autumn, due as explained before to the increased percolation of rain-water through the autumn and winter, and its diminution through the drier spring and summer months. The lateral movement of the ground water is generally towards the nearest watercourses, the sea, wells, fissures in rocks, shafts of coal- mines, etc. The rise and fall of the ground water cause corresponding movements in the ground air which lies above it. As the ground water rises, it occupies the space formerly occupied by the ground air, and the latter is slowly expelled from the surface of the earth : as the ground water sinks, air is sucked in to occupy its place, to be again expelled when the water rises. There are other factors influencing the movements of the ground air which have no effect on those of the ground water. The principal of these are alterations in barometrical pressure, sudden varia- tions in temperature, and the perflating action of the wind. It is thus seen that the porous surface-layers of the earth act as a sort of lung, slowly taking air in and slowly expelhng it again. This action is no doubt greatly increased on the small surface of ground covered by a house. In winter, when the adjacent surface of ground may become ice-locked, the heat of the building and the aspirating action of fires must tend to draw air in large volumes through the soil beneath the dwelling, unless the site is covered with an impenetrable layer of asphalt or cement concrete. The ground air is generally moist and always impure. The amount of moisture depends on the proximity of the ground water to the surface of the soil ; if this is but a few feet from the surface, the ground air is saturated with moisture ; if at great depths, the moisture is not excessive. But the ground near the surface of the earth in most parts of the world is damp, even after a prolonged drought, owing to capillary at- traction and evaporation from the surface of the ground water. The impurity of the ground air is due to the decomposition of SOILS AND BUILDING SITES 261 the various organic matters which are washed into the soil by the rain, or which are naturally present in some marshy soils. These latter are usually of vegetable origin. The impurity of the ground air even in virgin or natural soils is shown by a great diminution in oxygen and an enormous increase in carbonic acid. In the neighbourhood of houses, however, the foulness of the ground air is often due to animal contaminations, and these may be of the most dangerous description. Leaking cesspools, sewers and drains allow animal filth, and possibly infected ex- cretions, to pollute the water and air in the soil ; graveyards and cemeteries permit decomposing animal bodies to exercise a similar pollution ; whilst the organic effluvia arising from made soils — soils formed of old deposits of house refuse and dry rubbish — seriously imperil the health of the inmates of the houses built over them. The organic matters, whether of vegetable or animal origin, are decomposed in the soil by micro-organisms. These organisms grow in the presence of such food material, breaking it up into simpler combinations — carbonic acid, ammonia, and water — and thus by the processes of fermentation and putrefaction exert a purifying action, and at the same time convert the complex organic bodies into products best fitted to be assimilated by the growing vegetation. The presence of oxygen, warmth, and moisture is essential to the proper carrying out of these pro- cesses. The oxygen is present in the ground air, the moisture is derived from the ground water, and the temperature of the soil is usually suitable, except during long frosts or in very cold climates. It is thus seen that surface soil acts as a vast natural laboratory for the purification and utilization of effete animal and vegetable matters. The draining of damp soils, so as to permanently lower the level of the subsoil water, is a measure much needed in the interests of health. In the first place, it is desirable to avoid great fluctuations in the level of the ground water ; and this can, to a certain extent, be accomplished by subsoil drainage, which at once carries off the water when it rises to the level at which the drains are laid. When the subsoil water rises, it forces the ground air before it and out of the soil ; not only this, but it causes, when it arrives within a few feet of the surface, a damp- ness of the atmospheric air and, by evaporation, a cooling of the air. The moisture ascends by capillar}^ attraction into the 262 HYGIENE AND PUBLIC HEALTH walls of houses, to be subsequent^ evaporated from the surfaces of the internal walls ; in this evaporation heat is absorbed from surrounding objects, and the air of a house \^dth damp walls is not only moist, but cold. This condition of dampness in the'site and air of a' house is one credited by universal experience ^^'ith the production of rheumatism, catarrh, neuralgia, and affections of a bronchial and pulmonary nature, and is probably a strong predisposing factor to diphtheria, measles and whooping-cough. The researches of Dr. Bowditch, of Boston, U.S.A., and of Dr. Buchanan in this countrj-, have conclusively sho\Mi that there is an intimate connection between moisture of soil and phthisis. Such diseases were sho\Mi by Dr. Buchanan to be much less fatal in certain Enghsh to^^•ns after they had been sewered and the soil consequently drained, than they had been previouslv to the construction of the sewer works, ^^^lere the dr\dng of the subsoil was considerable, the deaths from phthisis were reduced to two-thirds, or even one-half, of what they had previously been. Professor Pettenkofer has shown a relation between the height of the ground water and epidemic outbreaks of enteric fever in Munich ; and he demonstrated that when the water in the wells was at its lo\^^est level, especially after a rapid fall succeeding an unusuallj^ high level, the disease was most preva- lent in that city. ]\Iunich is built on a porous sandy soil, at that time riddled \^dth cesspools, of which the contents rapidly soaked into the surrounding soil ; so that it is conceivable that, after heav}'' rainfall, Uquid cesspool filth ^^ould be carried into the wells, and an outbreak of enteric iever might result two or three weeks after the specific pollution of the drinking water, and when the level of the ground water had fallen. In this country, however, no invariable relation has been found to exist between the onset of enteric fe-\'er epidemics and low level of ground water. But in considering this subject, it must not be forgotten that there are other factors, such as temperature, condition of the soil as regards moisture and pollution, etc., which may have a more direct bearing on health conditions than the level of the ground water. The right view appears to be that fluctua- tions of level are of but Httle consequence in themselves, but that bj' favouring pollution of water in wells, or bj' forcing SOILS AND BUILDING SITES 263 impure ground air into houses, they may exercise a most con- siderable influence on health. Pettenkofer has also recorded the occasional coincidence of cholera outbreaks with a low state of the ground water. Epidemic diarrhoea occurring in summer and autumn has also been shown to be related to certain soil conditions, and the prevalence of yellow fever is also generally held to be influenced by soil, which being retentive of surface moisture favours the breeding of mosquitoes. But connection between malaria and damp marshy soils capable of holding stagnant water — the breeding grounds of the mosquito [Anopheles]— is more firmly established. In many instances malarious districts have been rendered healthy by subsoil drainage or by tree planting. In hot climates, trees and vegetation abstract large quantities of water from the soil, and this is evaporated from their green leaves. It has been cal- culated that an oak-tree evaporates eight and a half times the rainfall over the area it covers, whilst the Eucalyptus globulus absorbs and evaporates eleven times this amount. The latter tree has been extensively planted in many malarious districts, with the effect of rendering them more healthy ; for the soil has been dried by permanently lowering the level of the subsoil water, and the moisture factor being withdrawn, the mosquitoes are no longer provided with an environment favourable to their propagation. It must be remembered also that moisture favours decomposition of putrefiable material ; therefore a dry soil is cleaner, and the ground air is purer than in the case of a damp one. In verj^ damp, marshy districts it is advisable that houses should be raised above the ground on arches open to the air ; or, in the case of wooden houses, on piles. Moist ground immediately around the site of the house should even then be drained and filled in, and the surface covered with grass kept closely cut. Excessive vegetation should be cleared away and burnt. Low-lying alluvial tracts are not desirable sites for residences, for the ground water is either very near the surface, or the ground is water-logged for many months of the year ; and the site is damp, subject to fogs, and affords an unreliable foundation for buildings. When an alluvial site is on the borders of a river, it is liable to flooding, and it becomes extremely difQcult to secure dry basements. There is, moreover, great difficulty in 264 HYGIENE AND PUBLIC HEALTH providing efficient drainage for the sewage of the house, especially where houses have basements. ( From the above remarks it follows that for the choice of a site for a house, a dry, fairly open and sunny situation, and a pure, dry and porous soil are desirable, in an elevated position ■ and on a gentle slope favouring natural drainage both on the surface and in the subsoil. Valleys tying in the direction of the prevalent winds are drier and therefore more healthy than those lying in other directions. In cold and temperate climates, sands and gravels, if of considerable depth, and not water- logged by reason of a low situation or underlying clay per- mitting ground water to rest upon it, are the healthiest, because the warmest (most absorbent of heat) and the driest. Gravel in patches has sometimes a clayey or loamy matrix, and may thus be itself retentive of water. Clayey soils are cold, because little absorbent of heat ; they are also damp from the retention of moisture, and therefore not so healthy as the more permeable soils. The disadvantages of living on clay are materially reduced by elevation with sufficient surface falls to favour good surface drainage. Chalk is usually dry, but, being little absorbent of heat, is cold. Generally speaking, soils may be classified, as follows, in the order of their healthiness i — Gravel, sand, sandstone, chalk, rocks (granite, clay-slate, limestone), loam and stiff clay, alluvial land (low-lying), made soil. In hot climates sands are excessively hot, unless covered with herbage, which protects from the sun's rays and cools the air by evapora- tion of moisture. Trees by favouring the stagnation of air tend to check evaporation from the ground, and thus favour damp- ness. They may be utilized, at a sufficient distance from the house, for sheltering from the north and east ^^dnds. In towns, made soils- — which result from the filling in ^^^th household refuse and other rubbish of low-lying sites or excava- tions made for the purpose of removing the virgin gravel, etc, — should be avoided. If the soil is damp, the entire site below the foundations should be drained, by laying unglazed agricultural pipes in trenches filled in above with pebbly gravel. This aUows free percolation of water into the pipes, through the porous material of which they are constructed and between their ends, which are laid in apposition but not jointed. The subsoil drains sliould not be connected with any soil drain, sewer, or cesspool^ SOILS AND BUILDING SITES 265 but should discharge, if possible, into a ditch or stream. WTiere this is not possible, the subsoil drain may be connected with a house drain or sewer after proper disconnection has been practised, as for house drains {see page 105). In open soils, such as sands, a single drain will lower the level of the ground water over a considerable area, whereas in stiff close soils numerous drains are necessary. The ground water should preferably not reach to within 10 feet of the surface of any site on which a dwelling is to be erected. To prevent the entrance of ground air and moisture, the entire site of the house, within the external walls, should be covered with a layer of cement concrete, 6 inches thick, rammed solid ; and the surface thus formed should be grouted over with cement. In large town houses with basement floors below the street level, the cemented surface when asphalted, tiled, or paved with soHd wood-block flooring may conveniently form the finished flooring ; being free from cracks and crevices, it can afford no lodgment for cockroaches or other vermin, which so frequently infest the lower stories. In houses without cellars, more especially where the site is not concreted over, the lower floors should be raised 2 feet above the surface of the ground, and the intervening space should be well ventilated through air grids or air bricks in the external walls. Great care must be taken that the excavations for the house foundations are protected from the access of water by proper drainage where necessary, otherwdse they serve to store moisture and occasion serious dampness in basements. If the building is on sloping ground, it should be well protected from moisture on the side towards which the surface waters flow. The building should be erected on a uniform bed — not partly on gravel and partly on clay, for instance, as there would then be unequal resistance to the superincumbent pressure. A chalk foundation should be first well tested, as cavities or pipes therein may lead to subsidence. Clay slopes are undesirable sites, because the clay may shrink and crack after a prolonged drought, or swell and soften after much rain, and thus injure the building. A wall built of ordinary building bricks and mortar is very porous, and capable of absorbing large quantities of water. Each brick can hold about 16 ounces of water. To obviate damp from the ground rising in the brick walls, 266 m'GIENE AND PUBLIC HEALTH a horizontal damp-proof course of slates bedded in cement, a |-inch IsLver of asphalt, or slabs of perforated glazed stoneware, should be inserted in the wall, slighth^ above the level of the ground adjoining. The stoneware slabs answer a double pur- pose ; they are not only damp-proof, but the perforations afford an air passage through the wall, and ventilate the space under the flooring — a ver^- necessary' precaution to prevent dry rot in timbers and joists. Damp-proof courses ma^^ even be inserted in the walls of old buildings, by remo%dng a course of bricks piecemeal, after under- pinning the Avails, and then inserting air bricks in sections. XONCRETE Fig. 38. — House Foundation with Damp-proof Course in Wall and Dry Area. The external house walls, when these pass below the surface of the ground, must be separated from the moist earth b}'^ an " open " area extending upwards from the footings or founda- tion. \ATLere space Avill not admit of an open area, a " dr^^ " area should be formed (fig. 38). This is merely an area a few inches v^dde, to prevent the moist earth coming in contact A^ith the wall, which is carried up well above the surface of the ground, and is covered at the top ; or a double (cavity) wall may be formed below the ground level so as to enclose a narrow vertical air space. This arrangement necessitates two damp-proof courses — the lower just above the footings, and the upper across the outer portion of the cavit}^ wall slighth^ aboA^'e the ground level. These provisions are necessary- to prevent damp cellars and basements, SOILS AND BUILDING SITES 267 In very exposed situations the outer walls of houses are liable to become damp from driving rain. The usual remedies consist in covering the walls with slates or glazed tiles, set in cement, or coating the brickwork with Portland cement, which, being impervious to moisture, answer extremely well. House walls constructed of soft porous bricks jointed with bad mortar are especially liable to become damp from driving rain. If both bricks and mortar are soft and rotten, the wall should be coated \\ith cement ; if the bricks are sound, but the mortar decayed, the wall should be repointed with good cement. Good lime mortar should contain one part of recently burnt lime to three parts of sand. Cement mortar consists of one part of cement to four of sand. Sometimes in new houses the wall-papers are stained from temporary dampness, which is due to the evaporation of the water in the new bricks and mortar (" building water "). Another common cause of damp walls is defective gutters to the roof, or broken or otherwise damaged rain-water pipes. In both these cases water drips down the outer walls, and, soaking through the bricks and mortar, causes a serious dampness. In most towns the local authorities now compel house owners to pave the ground immediately around dwellings. The best material for yard-paving is cement-concrete, the Portland cement being first well dried and then thoroughly mixed with clean sharp sand. Asphalt also makes a good paving. Other materials used are blue glazed Staffordshire bricks and York flagstones, but in these cases a good hard and sm.ooth bottom of concrete should first be laid. There is probably some relation existing between the sanitary condition of streets in urban districts and the prevalence of summer diarrhoea. The desirability, from a public health stand- point, of perfectly sanitary roads is now recognized. The sanitar}- condition of streets depends not merely upon the use made of them, but also upon the materials of which they are constructed, and the manner in which they are kept, as regards the frequent removal of slop and dust. A perfectly good road should have a firm dry foundation, with a hard, tough, and compact surface, the latter being neither too flat to allow water to stand, nor too convex to inconvenience traffic. The substitution of mechanical power for horse traction would 205 HYGIENE AND PUBLIC HEALTH be a great sanitar}- advancement, and in the matter of street cleansing would effect a great saving of expense. The usual method of bringing trade refuse out into the streets, and the general littering which results, is a practice which ought not to be allowed. In large urban communities a considerable propor- tion of the population spend the major part of the day in the streets, and their houses practically abut upon them. The necessity, therefore, of keeping the streets as wholesome as possible b}^ guarding them from all a^^oidable animal and vegetable pollution b}^ frequent scavenging is ob\aous, and makes itself speciallj:^ felt in the hot weather, when the odours given off from badly scavenged streets are most marked, and the suspended dust (consisting of powdered horse-dung, etc.) is highly unpleasant and UTitating to the ej^es and throat. Frequent flushing by water- vans or by hose has possibly some effect in reducing the preva- lence of summer diarrhoea. The chief kinds of road paving are macadam, granite setts, wood, and asphalt. Macadam creates bj- far the most mud and dirt, and is therefore expensive to maintain and cleanse ; it is noisj^ and ven,- absorbent. Constant watering in drj- weather, and cleansing of the surface at all times, are absolutety necessary to maintain macadam roads in good condition. Granite setts furnish a most enduring pavement, easily and cheaply repaired and cleansed, and practically non- absorbent. The great objection to this form of pavement is the noise arising from the wheels of the vehicles and the iron shoes of the horses striking upon it. The noise can be diminished by running the joints ^^dth asphaltic composition instead of the ordinary Portland Qement grouting. Wood paving is the most expensive, but possesses the follo^^dng advantages : — It is comparativety noiseless ; it is clean, and creates no mud of itself until it is worn ; cleansing is eas}', when not much worn ; and, though slippery at times, a fall does not hurt a horse like a fall on an asphalt or macadam road. The dis- advantage is its capacit}' for absorption, A\ith the giving off of offensive odours during the hot, dr}- season ; but this is in some measure obviated b}- the use of hard woods, creosoted under pressure and jointed with impervious material. Asphalt is the most sanitary paving, being smooth, imper- meable, jointless and most durable. It is cleansed, swept, and flushed more easily than any other kind of paving, and is ad- SOILS AND BUILDING SITES 269 rairably adapted for all classes of town roads and streets which are level, or have only very slight gradients. Its chief dis- advantage is that it is slippery when first damped with rain, and that horses fall very heavily on it. It is doubtful, however, if it is more slippery than wood under similar circumstances. For motor traffic and for pedestrians asphalt forms an ideal paving material. For the surface treatment of roads for the purpose of dust laying, the methods which are employed are watering, tarring, oil tarring, and treatment with certain trade preparations con- taining tar oils, etc., and calcium chloride. It is generally accepted that coal tar should be appHed hot, and the treated surface covered at once with fine grit. Oil-tar is the by-product of the manufacture of gas from oil, and it is necessary to apply about four dressings during the six summer months. It may be applied by means of the ordinary water-cart, manual labour being utiUzed to work it into the road. A solution of calcium chloride may be apphed by means of the ordinary water-cart, the calcium chloride, by taking up moisture from the atmosphere, tending to keep the road surface slightly moist. The Dwelling — General Considerations. With regard to aspect in this country, north and north-eastern aspects are cold, whilst southern are warm ; north-western and south-western are exposed to boisterous winds, and the latter generally to driving rains ; the south-easterly aspect is generally dry and mild, and it is well to select this for the living rooms of a house. Sunshine should be capable of entering every living room at some time of the day. The provision of bay windows will help to secure this desideratum. The sufficient lighting of every room is most important. Gwilt's rule that there should be I square foot of glass to every 100 cubic feet of room-space is piobably rather an under-estimate of the requirement in towns ; on the other hand, excessive window provision makes a room very warm in summer and cold in winter. All staircases, passages, and corridors should be well lighted and ventilated direct from the outside air. Bedrooms should have, where practicable, an east or south- east aspect, so as to get the morning sun ; they should have plenty of window area and an open fire-place. 270 HYGIENE AND PUBLIC HEALTH Too little attention is often given to the situation of the larder, and it is frequently found in a most undesirable position — badly lighted, badly ventilated, the window opening just above the dust bin, and one lath and plaster wall separating it from a water- closet. The larder should face north for coolness, and have provision for a through current of fresh, pure air ; the window should be protected with perforated zinc to exclude insects. All chimneys should be kept as much as possible together, and protected from cold so as to favour upward draught. The most sanitary wall covering for water-closets, bathrooms and sculleries is glazed tiles, or the walls may be cemented and painted ; in either case they can be easily and frequently cleansed. For bedrooms distempering is to be preferred to wall- paper. If in the sitting-rooms wall-paper is employed, one with a smooth varnished surface should be chosen in preference to an uncleanly, absorbent flock paper. As to the floors, the ordinary floor boarding supported on floor joists, placed i foot apart, and leaving an open space some inches in depth between the floor surface and the concrete founda- tion or the ceiling of the room below, has httle to recommend it. The space beneath the floor becomes a receptacle for dirt, which gets through the cracks between the floor boards. Whenever such a floor is laid down it should be made with grooved and tongued, or ploughed and tongued boarding, so as to insure the boards being tight-fitting. But it is far preferable that " solid floors " should be constructed by laying the floor joists side by side and nailing the floor boarding to the solid upper surface of the joists. For large buildings fire-proof flooring formed of coke-breeze and cement laid on steel joists is most desirabl . The floor boards should be nailed to the fire-proof material. Glazed tiles and bricks form satisfactory floors for water-closets, lavatories, bathrooms, sculleries, and larders. The best floor covering for the rest of the house is hard wood, such as oak well fitted, beeswaxed, and polished ; or hard, well seasoned deal, stained and well varnished. Parquet flooring insures a uniform and impervious surface. For roofing, some non-absorbent material is to be preferred. Roofs of thatch and wood are liable to be damp and to harbour insects, and their inflammability is a source of danger. Slates and tiles are good materials ; the former are light, but, being SOILS AND BUILDING SITES 27I good conductors of heat, are cold in winter and hot in summer, whereas the latter, though heavy, are warmer in winter and cooler in summer. Lead, zinc, and copper have all been used for roofing ; like slates, they are good conductors of heat, and impervious. In house furnishing, woolly and fluffy articles of decoration, heavy draperies, fittings, and ornaments, which will harbour dust and render it difficult of removal, should be avoided ; and carpets should not be made to cover the whole floor and be nailed to it, but should be laid down as squares which admit of easy removal for cleansing purposes. Walls are generally built of brick, stone, timber, or concrete. The materials used in building should be as compact and as im- permeable as possible ; all bricks should be hard and as little absorbent of moisture as practicable, all wood well seasoned, and the plaster impermeable. " Light construction " materials are now being extensively used for certain classes of building, and especially for structures designed for temporary occupation. The weight of the building is carried on steel piers and steel framing, the interspaces being filled with hollow slabs of stoneware material, which form a wall at once impervious to moisture and highly non-conductive. The cost of such a structure is considerably less than if it was brick-built. Buildings constructed of " reinforced concrete " — i.e., concrete strengthened by steel rods and ties introduced in its substance — are also strong and cheap. A notable example of this form of construction may be seen in the new General Post-office at St. Martin's-le-Grand, London. CHAPTER VI CLIMATE AND METEOROLOGY Climate. The human body possesses marvellous powers of adaptability to the varying external conditions occasioned by changes of climate and season, and the transition from cold to heat, dryness to humidity, and vice versa. The normal temperature of the body is sustained, and the bodily functions are properly per- formed, under all the varying conditions of climate and season to be met with in the habitable globe. In hot climates, where the temperature of the air approaches, or even exceeds at times, the temperature of the blood, there is little call made upon the heat-producing powers of the body. As less food is required, metabolism is decreased ; the urea of the urine and the respiratory carbonic acid are lessened in amount ; the digestive and assimilative powers are lessened ; and oxygena- tion of the blood is diminished, because the number of respira- tions is decreased and the heated air contains less oxygen in a cubic foot than cold air. At the same time great heat, although compatible with health, is enervating ; for the perfection of bodily activity can only be obtained when tissue changes are rapid. In hot climates the skin is extremely active, and the secretion of sweat enormously increased. This means great evaporation from the surface and cooling of the blood, with the result that the body temperature is maintained at its normal level. At high atmospheric temperatures the body loses little or no heat by radiation, while the loss by evaporation is considerable ; whereas at low atmospheric temperatures, while the heat loss by radiation is considerable, that lost by evaporation is very small indeed. The effects of cold are exactly the reverse to those of heat. 272 CLIMATE AND METEOROLOGY 273 To maintain the temperature of the body, tissue metamorphosis must be rapid ; food, and especially carbonaceous food, must be taken in large quantities ; oxygenation of the blood and elimination of COg are increased ; the skin functions are reduced to a minimum, while the excretion of urine increases, and but little blood reaching the surface, surface cooling is obviated ; whilst the rapid tissue changes permit of great bodily and mental activity being shown. Great humiditj^ of the air causes lessened evaporation from the lungs and skin. For the air, being saturated, or nearly so, with moisture, has little drying power, and the moisture from the skin and lungs is with difficulty evaporated. The evapora- tion of moisture, by which much heat is rendered latent, is one of the chief means of cooling the body. Consequently, when the air is hot and very moist, the humidity tends to increase the effects of the heat ; the blood is with difficulty kept at its proper temperature ; and all the disagreeable results of the high tempera- ture are intensified. Moreover, the humidity of the air affects the climate of a place by hindering the terrestrial radiation of heat. For healthy people in temperate climates, the pleasantest degree of humidity is about 75 per cent, of saturation. This figure is a climatic average for the year. The relative humidity of the outer air varies greatly from season to season, from day to day, and even from hour to hour, and there is no evidence that atmospheres of high or low relative humidity are per se unhealthy. At night and during rain the relative humidity is high, the atmosphere being often nearly or quite saturated with watery vapour, whilst a warm sun and a dry wind will cause a drop in the relative humidity from 90 to 40, and that within the space of an hour or two. It is evident that, in Nature, the changes in relative humidity are extensive and rapid ; and it seems prob- able that the human body, under normal conditions of health, is capable of adapting itself as readily to these hygrometric changes as it is to the varying temperatures of an uncertain and variable climate. Some of the more rapid fluctuations of rela- tive humidity are probably attributable to passing intervals of sunshine. The effect of movement of air (winds) on evaporation is very great. In cold weather a chilly wind, if dry, increases the evaporation, and also lowers the temperature of the body by 274 HYGIENE AND PUBLIC HEALTH the impact of its cold particles, which absorb the heat of the bod}^ and then pass away to be replaced by more cold air. The skin becomes dry and chapped, and the lungs are irritated. In hot cUmates a dry, hot wind increases the evaporation enor- mously. The warm and moist south-west ^dnds in the British Isles are mild and relaxing, while the drier and colder east and north Minds are bracing. At high altitudes the air is rarefied, and the pressure of the atmosphere is diminished. The other conditions met with in mountain climates, as contrasted with those of plains, are : (i) Greater movement of air — strong winds are very prevalent ; (2) lessened humidity ; (3) increased sunlight ; (4) great freedom of the air from suspended matter — mineral and organic ; (5) a larger amount of ozone in the air ; (6) a lowered temperature generally ; but as the soil is rapidly heated by the sun, the days in summer may be warm, whilst the rapid radiation of heat, as soon as the sun sets, causes sudden cooling and a very low temperature at night. Temperature decreases with altitude to the extent of about 1° F. to every 300 feet of ascent. Although the weight of oxygen in a cubic foot of air is decreased at high altitudes,^ the oxygenation of the blood is increased, for the respirations are more frequent and have greater depth ; and after a period of residence the capacity of the chest is found to be increased in all its measurements, together with increased power of expansion and contraction. The action of the heart is also increased, and tissue change is stimulated by the low tem- perature and the dryness of the air, leading to improved digestion, assimilation and excretion, ^vith increased bodily activity. These effects of residence at a high altitude, together with the freedom of the air from dust and germs, and its impregnation with ozone, have led to the treatment of cases of phthisis at mountain resorts, with often the most beneficial results. The cases most benefited are those in an early stage without much congestion or bronchitis, which might be aggravated by the cold dry air. It is advisable that spots should be chosen which are sheltered from cold winds ; and those popular resorts, where I The weight of oxygen in a cubic foot of air is diminished in proportion to the diminution of pressure ; thus, if the barometer stands at 20 inches, the i30'4 grains of oxygen present in a cubic foot of dry air at 30 inches of mercury and 32° F., is reduced to *^ of 130-4 =86*9 gi-ains only. CLIMATE AND METEOROLOGY 275 many phthisical persons are crowded together in hotels and boarding houses without proper precautions being taken, should be avoided. As much time as possible should be spent in the open air. A mountainous district in proximity to the sea is liable to excessive rainfall. The moist currents of air blowing in from the sea are chilled by striking against the mountain chain ; clouds are formed, and some of the moisture, no longer able to be held as invisible vapour at the lower temperature, is deposited as rain, snow, or sleet, according to the temperature and season of the year. If the mountains are in the centre of a continent far removed from the sea, the rainfall may not be great. The excess of moisture in the ocean currents will already have been deposited before reaching the hills ; and in these situations a mountain climate without the drawback of excessive rainfall may be obtained, suitable for the requirements of consumptives and invalids. The westerly winds which blow over the Rocky Mountains deposit most of their moisture on the western sides of the range, and on the eastern slopes the climate is comparatively dry and cold. Increased pressure of the atmosphere produces effects very much of an opposite nature to those just considered. It is found, however, that the system quickly accustoms itself to increased atmospheric pressure, and that men can work vigor- ously in diving bells, and in the very deepest mines. In the compressed air chambers necessary to lay the founda- tions of bridges and aqueducts under water, the painful effects of exposure to very high atmospheric pressures are generally referred to as " caisson disease." A caisson is a cylinder of iron plates rivetted together, which is sunk on the bed of a river so as to form a shaft. Into this, when closed at the top, air is pumped under sufficient pressure to force the water out of the lower part of the shaft, and to keep it out while men excavate the bed of the river, for the purpose of obtaining a suitable foundation for the piers of bridges. There is at the top part of the cyHnder, near to the closing diaphragm, a chamber or " air lock," in which the pressure of the air can be gradually increased or diminished. By this means the men, before entering the compressed air in the shaft, are subjected to a pressure which is gradually increased, until it equals that within the shaft. Similarly, on leaving the shaft the men 276 HYGIENE AND PUBLIC HEALTH are gradually " decompressed " in this lock before emerging into the outside air. The workers are liable to suffer from the altered conditions of atmospheric pressure to which they are daily subjected, and they are affected far more by the consequences of decompression and returning to the outside air, than from compression and con- tinuance of exposure to the high pressure in the caisson. The leading symptoms of caisson disease are : (i) Unpleasant sensations or severe pains in the ears, doubtless the result of the t5nTipanum being driven in by the compressed air. The drum of the ear is said to have been even ruptured, and sometimes deafness results. These ear sjnnptoms are materially aggravated if the person happens to be suffering from a cold in the head or sore throat, when pain in the forehead is often marked. (2) Neuro-muscular pains. (3) A feeling of giddiness, with a tendency to fall. (4) Loss of power in the legs, amounting at times to paralysis. (5) Slight to severe pains in legs, arms, and shoulders. (6) Epistaxis. (7) Itching of skin. (8) Haemoptysis. (9) Epigastric pain, and sometimes nausea and vomiting. (10) Occasionally unconsciousness. There is, of course, a physiological rise in the blood pressure. Three theories have been adduced to explain compressed air illness. It has been held to be due to CO2 poisoning ; to the mechanical congestion of internal organs ; and to increased solution bj' the blood of the nitrogen in the compressed air, and the liberation of this gas (probably forming gas emboli) during decompression. The last theory is most generally accepted. If the first were correct, the illness should occur while the men are in the caisson, and not after they emerge from it. In support of the second theory, it may be said that in several necropsies the membranes of the brain, etc., have been found deeply congested. The symptoms mostly yield to recompression, followed by slow decompression lasting some forty-five minutes. The favouring causes are : Too long stay in the compressed air ; insufficient ventilation of the compressed air space — the amount of illness varies inversely with the extent of the provision for ventilation (Snell) ; too rapid decompression ; fulness of habit ; advancing age ; over-indulgence in alcohol ; and organic disease. New hands suffer more than the old. The preventive measures to be adopted include : Working during short shifts — if the pressure exceeds 35 pounds, the shifts CLIMATE AND METEOROLOGY 277 should probably not exceed four hours, and if the pressure reaches 50 pounds, two hours ; an abundant supply of fresh air ; electric lighting to be employed, so as to insure the continued purity of the air ; the rate of decompression certainly not to exceed one minute to every 5 pounds of pressure ; the systematic examination of all hands', and the selection of those who are physically sound ; advice to be given as to how to inflate the middle ear by swallow- ing air when uneasiness first appears ; as to the importance of rest for a short period after leaving the compressed air ; and as to the necessity for extreme temperance with alcohol. It is desirable to temporarily exclude those with a cold in the head or sore throat. The climate of small islands and of places on the seashore differs from that of the interior of continents chiefly in its greater equability. The variations in temperature between day ard night and between summer and winter are much less marked, whilst the winds blowing in from the sea bring a moist but pure air, comparatively rich in ozone and free from dust and germs. The specific heat of water is far greater than that of land ; hence water heats slowly, and parts with its heat slowly. The land heats quickly and radiates quickly ; but on the land it is the surface alone which is affected by the change of seasons. At Greenwich the variations between summer and winter tempera- tures at a depth of 25 feet are only about 2° F. In winter the ocean acts as a storehouse for the heat absorbed from the summer sun, and slowly parts with it to warm the superincumbent air. In summer the land is heated by the sun more rapidly than the water ; consequently, the air over the land is heated and rises, and a cool breeze blows in from the sea during the day. During the night the earth is rapidly cooled by radiation, if the sky is clear ; the air over the sea is then warmer than the air over the land, it rises, and a land breeze sets out to sea. On a summer's da}^ at the seashore the air is constantly in motion, and is cool and moist, whilst in the interior it may be insufferably hot, close and dry. Marshes, by the evaporation from the shallow water, help to lower the summer temperature ; but the influence of large lakes, as in North America, is to bring about an almost insular climate in summer, and a continental one in winter, for the frozen lakes then exert a similar influence to land. Ocean climates are of the greatest benefit to certain cases of lung disease, where a pure air, free from dust, but moist and of 278 HYGIENE AND PUBLIC HEALTH equable temperature is desired ; but ocean voyages should be recommended with extreme caution to phthisical patients. The confinement and over-crowding in cabins and state rooms, the want of exercise, and the costive habit thus produced (tending to excite hemoptysis), are all grave disadvantages, and may counteract any benefit to be derived from the sea air. The effect of vegetation on climate must not be lost sight of. In cold climates trees and shrubs obstruct the passage of the sun's rays to the soil, which is therefore liable to be cold and moist ; on the other hand, they may protect against cold winds. In hot climates the evaporation of water from the leaves tends to dry the soil and to lower the temperature, and the ground is sheltered from the direct rays of the sun and kept cool. Thus, the heat of summer is lowered and the cold of winter tempered by the presence of trees, and, having a lower temperature than the neighbouring earth's surface, high forests increase the rain- fall. In very dense forests the air is generally stagnant. Prob- ably in all climates a due admixture of herbage, shrubs and trees, without dense undergrowth, but admitting the passage of free currents of air in every direction, is the most conducive to health. Large tracts of country destitute of trees and vegeta- tion are in hot climates unbearably warm and dry, and in cold climates are exposed to every chilling wind. In such districts, too, rainfall is often absent or very slight in amount, the influence exerted by trees upon water-charged clouds being wanting. For these reasons the desert of Sahara gives to the south of Europe a much higher temperature than would otherwise be the case. The mean temperature of the air of any place is dependent on the latitude, the altitude, the relative proportions of land and water, the aspect, and the nature of the soil ; and the extent of the diurnal variations in temperature is largely determined by the proximity to the coast and the height above sea level. The " amplitude of the yearly fluctuations " in temperature is not more than about 4° F. in some tropical places at sea level, while it maj^ be as much as 110° F., or even more, in the heart of large continents situated near the poles. The principal factors, therefore, which determine the climate of a district are : (i) Distance from the equator ; (2) distance from the sea ; (3) altitude ; and (4) prevailing winds. Of the many separate elements that go to make up the climate of a place, temperature is the most important, and the mean CLIMAlIi AND METEOROLOGY 279 annual temperature depends primarily upon the amount of radiant heat received from the sun. The heat received from the sun, however, in one place may be carried by winds and ocean currents to another. The mean temperature of the tropics is about 80° F., and that of the arctic circle in latitude 60° is 25° F., the difference of some 55° F. being due to the fact that the heat received from the sun is concentrated upon a small surface when the sun's rays fall near the equator, and is spread over a large surface when they fall nccir the poles. The differ- ence would be far greater were it not for the heat carried away from the tropics to the temperate and arctic regions by ocean currents, and to a less extent by winds. The difference between summer and winter temperatures is . also important, but Httle variation being sho\vn in places within the tropics, or on islands in the middle of large oceans, either in tropical or temperate latitudes. The heating of the air in the tropics, the cooling around the poles, and the deflective action of the earth's rotation, produce all the prevailing winds of the globe. The colder air of the northern and southern regions of the globe is constantly flowing towards the warmer and more rarefied air over the open seas on both sides of the equator. The result of the earth's rotation on the flow of the warm water from the equator towards the poles in the North Atlantic Ocean is the large circular swirl, the northern and eastern sides of which produce the well-known current of the Gulf Stream. This current, together with the circumstance that the prevaiUng winds have a westerly direction, accounts for the British Isles possessing such a mild climate ; whilst countries with the same latitude as England — such as Labrador and Eastern Asia, in which the prevailing winds are from the land instead of from the sea — have a mean winter temperature below zero. Weather Observations. Under the modern system, a number of barometrical readings taken at the same time over an extended area, such as the greater part of Western Europe, are telegraphed to a central station, where they are laid down upon a map. On this map Hnes are drawn connecting the places showing equal barometrical pressure; these lines are termed "isobars." This weather map will show the cylonic or anticylonic systems, as the case may 28o HYGIENE AND PUBLIC HEALTH be, their position, and their extent. A cyclonic system is a system having at its centre the lowest barometrical pressure, and surrounded by isobars of gradually increasing pressure. The isobars will be near or far apart according to the amount of depression in the centre. If this depression is great, then the isobars are generally close together, and the " gradients " are said to be " steep." If, on the other hand, the depression in the centre is shallow, the isobars are further apart, and the gradients are " shallow." An anticyclonic system is the reverse of this, for its centre is the highest barometrical reading, and it is surrounded by isobars of gradually decreasing pressure. In order to restore atmospheric equilibrium, the air tends to move from a region where the barometer is high and pressure greatest, towards one where it is low and the pressure is least. Consequently, currents of air set in from all sides towards the centre of a cyclonic system, and flow out in all directions from the centre of an anticyclonic system. These currents of air do not, however, as a matter of fact, flow straight to or from the centre, but have a gyratory movement imparted to them, owing to the rotation of the earth on its own axis. The equatorial circumference of the earth being 24,900 mileSj and the earth rotating on its axis once in twenty-four hours, it follows that a point on the earth's crust at the equator must be carried round at the rate of 1,040 miles an hour. In latitude 30°, however, the point would only move at the rate of 900 miles an hour, owing to the lesser circumference of the earth at this distance from the equator. In latitude 60° the rate will be only 520 miles an hour, and at the poles it will be nil. Now, the atmosphere is carried round, from west to east, at the same rate as the earth's crust ; consequently winds or currents of air travelling from the equator towards the poles, or from low lati- tudes into high, tend to keep the higher rate of rotatory motion imparted to them when nearer the equator, and become westerly — that is, come from the south-west (in the northern hemi- sphere) as they progress towards high latitudes. In the same way, winds travelling from high latitudes to low ones meet an atmosphere which is rotating at a greater rate than they are, and consequently appear^ to come out of the north-east (in the 1 As when a steamship is rapidly passing through the air from west to east a wind coming from the north appears to come from the north-east. Climate and meteorology 281 northern hemisphere). This is the reason why the trade winds which blow towards the equator appear as north-east winds in the northern hemisphere, and south-east winds in the southern hemisphere. This direction of the trade wnds is constant over all open seas to about 30° north and south of the equator, but land changes their course. The position of the sun has an in- fluence on the strength and direction of these trade winds ; when the sun is near the Tropic of Cancer the south-east wind is more southerly and strong, and the north- east wind is weaker and more easterly ; and the reverse happens when the sun ap- proaches the Tropic of Capricorn. The same forces apply to the currents of air moving towards the centre of a cyclonic system, or away from the centre of an anti- cyclonic system. In the case of a cyclonic system (in the northern hemisphere), a current setting towards its centre from the north appears to come from north-east. A current setting towards the centre from the south of the system is deflected to the east, or comes from south-west. In this way a gyratory or spiral movement is imparted, which causes the wind to travel round the centre of a cyclonic depression, in a direction against the hands of a watch ; or supposing a person to be travelling with his face towards the direction the wind is taking, he wiU always keep the centre of the system, i.e., the point of lowest pressure, on his left hand side. Fig. 39. — Sjmoptic Chart showing Cyclonic System. The arrows show the direction of the wind. The figures show the barometric pressure of the isobars. 282 HYGIENE AND PUBLIC HEALTH The central space of the cyclone is occupied by a vast ascending current, which after rising to a considerable height flows away as upper currents into surrounding regions. The direction of the -wind round an anticyclonic centre is exactly the reverse. The air flows away from the centre of greatest pressure in all directions. The current flowing south- wards is deflected to the west, and appears to come from north- east. The current flowing northward is deflected to the east, and comes from south- west. Consequently the currents revolve with the hands of a watch, and the person travelUng with the wind keeps the centre of the system — the point of highest pres- sure — always on the right hand. From this it follows that having a weather (synoptic) chart before us, and knowing the distribution of pressure over the area included in the chart, we can generally tell the direc- tion of the wind at any particular spot ; and if we know what course the system is taking, i.e., the direction in which it is travelhng, we can predict what changes will subsequentl}^ take place in that direction, so long as it remains included in the system. Cyclonic systems are never stationary. They move over the earth's surface, usualty from west to east in European latitudes ; but in the case of the British Isles, coming from off the Atlantic, their approach is difficult to forecast. In these depressions the isobars lie close together and the winds are strong. The greater the depression in the centre and the steeper the gradient, the Fig. 40.- -Synoptic Chart showing Anticyclonic System. CLIMATE AND METEOROLOGY 283 more violent is the wind ; but, according to Scott, no simple relation between the force of the wind and the steepness of the gradient has yet been determined. In this country the arrival of cyclonic systems off our coasts heralds the approach of cloudy skies, wind, rain, and damp air. These conditions imply warmth in winter, and cold weather in summer. The centre of the c^'clonic depression usually lies to the north of the British Isles ; consequently, these islands lying in the track of the southern portion of the system, the wind is first experienced from the south-east, it then shifts through south to south-west, and blows harder the more rapidly the mercury drops. When the barometer has reached its lowest point the wind flies round to west or west- north-west ; the barometer then begins to rise, the rain ceases, the temperature falls, and as the wind becomes north the sky clears, and fine weather is again experienced (Scott). Anticyclones, on the contrary, are generally more or less stationary, or move very slowly. The isobars lie far apart, and the winds are light. They are accompanied by fine weather, a dry atmosphere, a sky generally clear of clouds, though fogs are very likely to prevail at places. These conditions produce cold, frost, or fog in winter, and heat in summer. The synoptic charts (figs. 39, 40) show that the wind in both cyclonic and anticyclonic systems has a direction more or less parallel to the isobars, but still, on the whole, tending to cross the isobars very obliquely, so as to blow spirally towards the centre of the cyclone, and spirally away from the centre of the anticyclone. A col is a neck of relatively low pressure connecting two anticyclones. It is comparable to the col which forms a pass between two adjacent mountain peaks. Meteorological Instruments. The Barometer. — The pressure of the atmosphere is expressed by means of a barometer in terms of the perpendicular height of a column of mercury, glycerine, or water, which it is capable of supporting. The weight of the atmosphere at the sea level supports a column of mercury of 29*992 inches, or 760 milli- metres, in height, a column of glycerine about 324 inches, and one of water 34 feet, in height. The water barometer is accordingly the most sensitive, but it is inconvenient in use. 284 HYGIENE AND PUBLIC HEALTH The simplest form of mercurial barometer is a graduated U-tube, ^^dth one end closed. The closed arm is about 32 inches in height, and the open arm about 8 or 9 inches. The mercury placed in the U-tube is made to completely occupy the closed arm, so that all the air is displaced from it ; then, when the tube is brought to its proper upright position, and the mercury falls, there is a complete vacuum left above it in the closed arm. The varying pressure of the atmosphere on the surface of the mercury exposed in the open (short) arm causes the level of the mercury to rise and fall in the long (closed) arm ; and the difference between the levels in the two arms represents the height of the column of mercury supported by the atmosphere. In a standard mercurial barometer, a vertical tube 33 inches long rises from a cistern of mercury, the tube above the level of the mercury being in a state of perfect vacuum. In Fortin's standard instrument (fig. 41) the smaU cistern has a leathern bottom, which by means of a thumb-screw {a) can be tightened or relaxed so as to raise or lower the level of the mercury in the cistern. The scale for reading the height of the column of mercur}^ is divided into inches, tenths, and half-tenths (2V) of inches ; and to obtain more accurate readings than the scale alone allows, a sUding scale or vernier (5) is attached, which serves to indicate the amount of space occupied by the mercurj^ between the half-tenth lines. The vernier scale is divided into twenty-live equal parts, which correspond to twentj^-four half- tenth divisions on the barometer scale. Consequently each division on the vernier is -J^ less than a half-tenth division on the barometer scale, and is therefore ttV of ^ inch (= -ghj or 0-002 inch). In order to take an accurate observation, the eye, the zero edge of the vernier, and the top of the mercury, should all be in the same horizontal plane ; hence the necessitj^ of fixing the barometer at a height convenient to the observer. The tem- perature of the attached thermometer (c) is first noted ; then the level of the mercury in the cistern is so adjusted that the ivory point (d) projecting downward from the roof of the cistern just touches the surface of the mercuI3^ This little ivory point indicates the zero of the scale ; and since the level of the mercurial surface in the cistern varies with every change of atmospheric pressure, the level of the mercury must be adjusted CLIMATE AND METEOROLOGY 285 prior to each observation, to the zero of the scale. Next read off on the barometer scale the division immediately below the Jiiil Fig. 41. — Fortin's standard barometer. Fig. 42. — Diagram of barometer scale and vernier. A , scale ; B, vernier. top of the column of mercmy. Then adjust the vernier (fig. 42) so that its lowest hne is level with the top of the column of mer- cury, and the Hght is just excluded between the lower end of the 286 HYGIENE AND PUBLIC HEALTH vernier and the top of the mercury, and count the number .of divisions on the vernier from below upwards, until a line on the vernier is exactly continuous with one on the barometer scale. Multiply the number of the divisions on the vernier so obtained by 0*002, and add the result to the already observed height on the barometer scale.-"- Corrections, by Glaisher's tables, must then be made for temperature above 32° F. — for mercury, like all other metals, expands with a rise of temperature. The mercury falls about toW inch for every foot ascent above sea- level, and allowance must be made for this if the observation is made at an altitude. The barometer must always be carefully and truly fixed by means of a plumb line, in a good light and protected from sun- shine, rain, and winds. Before fixing, it should always be ascer- tained if the vacuum above the mercury is true. To do this, unscrew the bottom of the cistern until the mercury is 2 or 3 inches from the top, and then rather suddenly incline the instrument. If the vacuum is true, the mercury strikes against the top of the tube \\dth a sharp click, but a dull sound results if air is present. In the latter case, screw up the bottom tightly, turn the instru- ment upside down, and tap the side forcibly until a bubble of air is seen to pass through the mercury column into the cistern. Barometric observations are always expressed to the third place of decimals ; and isobarometric lines, as shown on charts, in- dicate areas over which the barometric pressures are identical. If the isobars, which are drawn for each yV inch, are close together, the " barometric gradient " is said to be steep, and the wind velocity will be high. The aneroid barometer is a small watch-shaped metal box from which the air has been exhausted, and in which the two flat surfaces of the box are kept apart by a powerful but sensitive spring. The atmospheric pressure acts upon the spring, and is recorded on a dial. This instrument is chiefly used for taking altitudes. The practice is to read the aneroid to the nearest ywo inch both at the commencement and at the termination of an ascent, and then to subtract one reading from the other (ignoring decimal points), and multiply 1 For instance, in fig. 42 the mercury is shown to reach to a Uttle above 29-55 inches on the barometric scale ; taking the seventh line on the vernier as the line Avhich is exactly continuous with one of the barometric scale, then 7 x '002 = '014; and the barometric reading is 29*55 + '014 = 29 '5 64 inches of mercury. CLIMATE AND METEOROLOGY 287 the difference by g, this giving the height of the ascent in in feet. Example. — Reading at start = 30"00 inches. Reading at end = 29*00 100 9 900 feet ascended. The weight of a cubic foot of dry air at 32° F. and 30 inches of mercury is 566'85 grains. As air expands xttt of its volume for every degree rise Fahrenheit, the volume at 60° F., for instance, is i+tvt x (60 — 32) = 1*057 cubic feet. The weight is inversely as volume ; consequently the weight of a cubic 566-85 foot of dry air at 60° F. = = 536*28 grains. •^ 1*057 " The weight of a cubic foot of water vapour at 60° F. is 5*77 grains. Therefore, the added weights of a cubic foot of dry air at 60° and of a cubic foot of vapour at 60° are 536*28 + 5*77 = 542*05 grains. But dry air expands on taking up moisture, and the actual weight of a cubic foot of saturated air at 60° is 532*84 grains, or 3*44 grains less than the weight of an equal volume of dry air at that temperature, because the cubic foot of originally dry air is now more than a cubic foot. This fact ex-- plains the fall of the barometer when the moisture in the air is increasing and a fall of rain is imminent. R oh i ns n's Wind Anemometer is an in- strument which records the velocity of the wind. The figure (43) sufficiently explains the construction of the instru- ment. The revolving cups set in action a train of clockwork, and the velocity of the wind i? -ecorded on a series of dials. Robinson's Anemometer. 288 HYGIENE AND PUBLIC HEALTH The cups travel at a rate equal to only one-thii-d that of the \^ind, and allowance is made for this fact in graduating the instrument. The square of the velocity in miles per hour, multiplied b\' 0*005, gives the wind pressure in pounds per square foot ; and on the other hand, the square root of 200 times the ^^dnd's pressure gives the velocit}^ The instrument must be kept clean and well oiled, and should be fixed at least 20 feet from the ground, and away from buildings. The average velocity of the ^vind is from six to eight miles per hour. On the Beaufort scale, in a " light wind," the air travels at a rate of 13 miles per hour ; in a " moderate breeze," 23 ; in a " strong breeze," 34 ; and in a " gale," 65. All ^^'ind direction observations b}^ vanes, etc., should be recorded to the nearest point of the compass. The instruments which register the moisture in the atmosphere are kno^vn as hygrometers. Of these there are two distinct classes, i.e., those which indicate the dew point directly, and those from which the dew point is indirectly determined. In the former class the air is cooled until the moisture is deposited on a bright surface to which a thermometer is attached, the latter indicating the temperature of the dew point. In Daniell's hjrgrometer (fig. 44) ether is placed in the lower bulb, and the other bulb (which contains nothing but ether vapour) is covered mth musHn moistened ^^ith ether. This ether on the muslin evaporates into the air, and the loss of heat so occasioned condenses the ether vapour inside the bulb, causing evaporation from the ether inside the other (lower bulb). The lower bulb thus becomes gradually colder, and chills the air sur- rounding it, until a temperature is reached at which the air is compelled to part \vith some of its moisture, which condenses upon the bright metal band surrounding the bulb. Directly this takes place the temperature of the dew point is read off from the attached thermometer. The temperature at which the dew disappears is next observed, and the mean between these two temperatures is taken as the dew point. In Regnault's instru- FiG. 44. DanieU's Hygrometer. CLIMATE AND METEOROLOGY 289 ment (fig. 45) one cylinder is half filled with ether, and the other is left empty, thermometers being inserted in both cylinders. An aspirator communicates, by means of the hollow upright, with both cylinders, and when this is put in action air is drawn through them. The passage of the air through the evaporating ether soon cools it down to the dew point, and then the bright metal surface surrounding the lower part of the cylinder becomes dulled with moisture. The temperature recorded at that instant by the thermometer in the ether is the temperature of the dew point, the second thermometer simply showing the temperature Fig. 45. — Regnault's Hygrometer. of the air at the time of observation. In Dines' instrument a vessel which holds ice- water has a bright metal plate with an attached thermometer in its roof. As the cold water is made to flow under the plate, the outside air in contact with it becomes chilled ; and when the dew point, as shown by the deposition of dew, is reached, it can be read off from the attached ther- mometer. Wet and Dry Bulb Hygrometer. — This instrument consists of two absolutely identical thermometers mounted on a stand. In the wet bulb thermometer the bulb is kept moist by being covered with muslin, one end of which dips into a small vessel of 19 290 HYGIENE AND PUBLIC HEALTH distilled or rain water, so that moisture ascends by capillary attraction. The evaporation of moisture from the wet bulb, which takes place so long as the surrounding air is not saturated, causes loss of heat, and the wet bulb reads lower than the dry bulb. Both the vessel containing water and the wet bulb must be sufficiently far from the dry bulb to insure that the readings of the latter are not affected by the evaporation. The instrument must be exposed in the shade and protected from air currents and direct sunshine, both of which, by increasing evaporation, would cause the wet bulb thermometer to indicate a temperature not strictly due to the hygrometric state of the atmosphere. If the muslin becomes frozen in the winter, the two thermometers will read the same ; then the wet bulb should be brushed over with cold water, and the evaporation which will go on from the frozen surface will enable a proper reading to be taken. From the readings of the dry and wet bulbs can be ascertained — the relative humidity of the air, i.e., the amount of moisture present in air, expressed as a percentage of the amount just necessary to cause saturation ; the dew point, i.e., the tempera- ture at which the amount of moisture actually present in the and the weight of vapour in a cubic foot of Fig. 46. Wet and Dry Bulb Hygrometer. air causes saturation air, from which can be deduced the additional weight of vapour necessary to cause saturation, or the drying power of the air. The relative humidity is found from tables. The greater the difference between the dry and wet bulbs, the lower is the relative humidity. If the dry and wet bulbs record the same temperature, the air is completely saturated with moisture. The dew point can be determined by the equation : Dew point _ T'^ — F (Xjj — T^^,) ; where T^ is the dry bulb temperature, T^ is CLIMATE AND METEOROLOGY 29I the wet bulb temperature, and F the factor opposite the dty bulb temperature found in Glaisher's tables. In De Saussure's instrument [the hair hygrometer) , a hair freed from fat by ether is fixed at one end, and this hair contracts with lesser and expands with higher degrees of humidity. The hair is kept stretched by a small weight, the connecting cord of which is led round a pulley ; and an index needle attached to the pulley indicates the relative humidity on an empirically graduated scale of relative humidities. The instrument is standardized by first wetting the hair and noting whether it accuratel}^ registers saturation on the scale (i.e., 100) ; but it is necessary to frequently verify the readings by other methods. The " elastic force of vapour," or " the tension of aqueous vapour," is the amount of the barometric pressure which is due to the aqueous vapour in the atmosphere. If the temperature of the air is lowered, and with it the tension of aqueous vapour, a temperature mil sooner or later be reached at which the air is saturated with moisture ; and then the slightest further reduction in temperature will cause a deposition of dew (" dew point "). The tension of aqueous vapour is ascertained from tables or by formula. The relative humidity can be calculated by dividing the elastic force of aqueous vapour at the temperature of the dew point by the elastic force of the aqueous vapour at the temperature of the air, and then multiplying by lOO. Example. — The dry bulb temperature is 62° F., and that of the wet bulb is 56° F. The dew point is therefore 62- ■{ (62-s6)x 1-86 ^ = 50-84° F. The aqueous tension at 62° F. is (from Glaisher's tables) 0*5 $6 of an inch of mercury, and that at 50'84° F. is 0-372 of an inch. The relative O' ^72 humidity is, therefore, —~ X ioo=66-9 per cent, of saturation. 0-556 If the relative humidity at 61° F. is 70, the amount of vapour in a cubic foot is 70 per cent, of saturation, or ^wo of 6 = 42 grains ; and the drying power of a cubic foot of the air is 6 — 4*2 = 1*8 grains. Atmometers, for determining the amount and rate of evapora- tion, have been devised. In these instruments a kno\vn volume and weight of water is exposed in a receptacle, so as to present a known surface area to the atmosphere ; and the evaporation in a given time is determined by the loss either in volume or in weight of the original water. The weight of .moisture which a cubic foot of dry air can take 292 HYGIENE AND PUBLIC HEALTH up, before it is saturated, varies with the temperature. The higher the temperature, the larger is the amount of vapour which can be held, as the following table shows : — Grains of Vapour to saturate a Cubic Foot of Dry Air (Approximate). 30° F. 2 grains 66° F. 7 grains 80° F. 1 1 grains 41° F. 3 ,. 70° F. 8 ,, 83° F. 12 „ 49° F. 4 ,. 74'' F. 9 „ 86° F. 13 „ 56° F. s „ 77° F. 10 „ •88° F. 14 „ 61° F. 6 „ Hence, when waimer air, already moisture laden, is chilled, the moisture representing the difference between what it originally held and what it is capable of holding at the reduced temperature is deposited in the form of dew or rain. Rain Gauge. — This instrument consists of a vessel supporting at its top a circular funnel which collects the rainfall. The vessel must be sunk in level ground, away from shrubs and build- ings, to such a depth that the collecting surface is one foot from the ground. A measuring glass graduated according to the area of the funnel, so as to indicate the fall of rain as decimals of an inch, is required. The area of the top of the circular funnel (the receiv- ing surface for the rain) is usually 50 square inches. To graduate the measuring glass for a funnel of this area, 50 cubic inches of water are poured into it, and a mark placed at the level the fluid stands at. Then if the rainfall collected on 50 square inches should measure the 50 cubic inches, each square inch of surface has collected one Fig. 47. — Rain Gauge. i,- • i, r x j ^.i cubic mch of water, and the rainfall is " one inch." But the glass below the mark is divided into 100 equal parts, so that each division indicates a fall of y\x5 or O'Oi inch of rain. The readings are generally taken daily at 9 a.m. In time of snow, the collected snow should be melted by adding CLIMATE AND METEOROLOGY 293 a measured quantity of warm water to it, the extra water derived from the snow being recorded as rain-water. The average depth of the adjacent snow should also be noted. In Crosley's self-registering rain gauge every xoo inch of rain- fall is recorded on a dial. The rainfall collected gradually fills one compartment of a small bucket divided into two compart- ments, and balanced on a pivot. When one compartment is full, the bucket tips and causes an index to record, and the second compartment then commences to fill. Aqueous vapour requires free surfaces for its condensation. When air is filtered, no cloud of condensed vapour can be formed. " Wet fogs " result when the particles of suspended matter are relatively few and the condensed moisture excessive, whereas " dry fogs " occur when the smoke and dust are relatively abundant. When the films of moisture are discoloured by the products of coal combustion, a yellow or " pea soup " fog will result. The death-rate generally increases as a result of town fogs, and the increase is ascribed to the irritating effects of the im- j:urities in the atmosphere upon the lungs, and to the sudden fall of temperature which takes place on the occurrence of the fog. Fogs lead to a considerable loss of that important element, sunshine, in our great towns : for, as a rule, when the town is enveloped in fog there is a cloudless sky above. Clouds consist of collections of condensed aqueous vapour. The principal forms which they assume are : (i) The cirrus, con- sisting of separate fine feathery formations, generally white in colour ; (2) the stratus, consisting of a smooth horizontal stratum of cloud ; (3) the nimbus, constituting the raining clouds, of dark coloured, irregular forms ; and (4) the cumulus, or heavy, thick, well defined clouds, generally rounded off in shape. Two or more of these four principal forms may be mixed together, giving rise to appearances which are defined as " cirro-stratus," " cirro- cumulus," " strato-cumulus," " cumulo-nimbus," etc. Thermometers measure the temperature from the amounts of expansion and contraction of certain bodies when these are exposed to varying degrees of heat and cold. Mercury is com- monly employed, because of its very low freezing point ( - 38° F.) and its high boiling point (675° F.) ; but alcohol is preferred when very low temperatures may have to be recorded, because it does not freeze at the greatest known degree of cold. 294 HYGIENE AND PUBLIC HEALTH The instruments are graduated from the fixed points of freezing and boiling water, b}^ plunging them into melting ice and boiling water, respective!}^, at the standard pressure. On the Centigrade scale the freezing and boiling points are o"^ and ioo° respectivety, while on the Fahrenheit scale the freezing point is 32° and the boihng point 212° ; therefore, to convert Centigrade to Fahren- heit, multiply the former figure by t and add 32, while to convert Fahrenheit to Centigrade subtract 32 and then multiply bj?' f . Maximum thermometers are instruments designed to register the highest temperature reached during the period of exposure of the instrument ; in these the temperature is registered b}' mercurj^ The registration is effected by either breaking the column of mercury b}^ an air bubble, or by a shght narrowing of the tube near the bulb. In either case the natural cohesion of the metal when contracting is overcome, and the mercury always remains at the highest point reached. Another method is to insert a small piece of solid glass enamel in the bend near the bulb ; this, acting as a valve, allows the mercur}?' to pass on one side of it as it expands, but does not allow it to return on cooling. In hanging a maximum thermometer, it is necessarj?- to see that the end of the tube furthest from the bulb is shghtty inclined downwards, to assist in preventing the return of any portion of the column of mercurj^ into the bulb on a decrease of temperature. Before reading the instrument, the end furthest from the bulb should be gently elevated to an angle of about 45°. Minimum thermometers record the lowest temperature reached. They are alcohol instruments, ^vith an index in the alcohol (Rutherford's) which moves mth the spirit on contraction by cold, owing to capillar}^ attraction, but not on expansion, and is therefore left registering the lowest temperature. The end of the index furthest from the bulb indicates the minimum tem- perature. Occasionally air bubbles appear in the alcohol and fix the index. They can be removed b}^ holding the thermometer with the bulb do\^Tiwards, and s^^dnging it round rapidty at arm's length. These instruments should be hung so that the bulb end is I inch lower than the other end, because then the index is less likely to be affected by a rise in temperature. The so-called " earth " thermometer is a maximum thermometer which is suspended by a chain in a stout iron tube, 5 feet long, which is provided with a pointed metal cap. By this means the temperature of the earth at depths up to nearty 5 feet can be CLIMATE AND METEOROLOGY 295 ascertained. In taking an observation the thermometer must be quickly drawn up and read. In Six's thermometer (fig. 48) there is a U-tube, the middle part of which is occupied by mercury. The bulb {a) and both tubes above the mercur}^ contain alcohol, in which are two steel indices, which are brought, by means of a magnet, to rest upon either column of mercurj- ; and (6) is a small chamber containing air. On a rise of temperatm^e, the alcohol, expanding in the bulb (a), depresses the mercury level in one arm, and therefore raises it in the other, the maximum temperature being indicated by the position reached by the lower end of the index. Conversely, as the temperature falls the alcohol in the bulb con- tracts, and the pressure of the air in the chamber {b) depresses the mercury level in the arm im- mediately beneath, and therefore raises the mercury level in the other arm, in which the index then registers the lowest temperature experienced. Thus, in the arm (c) maximum temperatures are registered, and in the arm (d) minimum temperatures. A barograph and a thermograph are instru- ments which furnish a record of the barometric pressure and of the temperature for the whole twenty-four hours of the day and night. The records are traced on slowly revolving drums worked by clockwork. The instruments require repeated standardizing. In the recording aneroid barometer the fluctuations of atmos- pheric pressure act upon a series of aneroid vacuum chambers, a sensitive index attached to the latter recording the results. In one form of thermo- graph the record is continuously marked by an index attached to a deUcate metal spring, the expansion and contraction of which is dependent on the atmospheric temperature. Isochimenal lines are lines di'awn through districts, as shown on a chart or map, having the same winter temperature ; and isothermal lines similarly indicate districts ^^dth the same mean annual temperatures. Shade maximum and minimum thermometers should be placed horizontallv in the shade, or in a Stevenson's louvred box, 4 feet Fig. 48. — Six's Thermometer. 296 HYGIENE AND PUBLIC HEALTH above the ground and at least 20 feet awa}- from buildings or other sources of radiation. The vacutim solar radiation thermometer (fig. 49) is a mercurial maximum self-registering instrument, ^^•ith a blackened bulb, which absorbs the sun's rays. It is placed in a glass case from which air is exhausted ; thus protecting the bulb from loss of heat, which would ensue if the bulb were exposed, owing to atmospheric currents and the absorption of heat by aqueous and other vapours. This instrument is placed 4 feet above the ground, and is directly exposed to the sun's rays. The bulb should point south- east in this country. The difference between the maxima in the sun and in the shade is a measure of solar radiation, or of the power of the sun's rays. Other instruments which may be found useful are : A terrestrial radiation thermometer, which is merely a minimum shade thermometer placed close to the ground, the bulb resting on grass — the difference between this minimum temperature and the air minimum in the shade being taken as the amount of terrestrial radia- tion ; a sunshine recorder (Campbell-Stokes', fig. 50), a little instrument by which the rays of the sun are concentrated on to a strip of millboard stretched in a frame at the proper focal distance from a large spherical lens. When the sun shines, a charred line is burnt in the millboard, and when hidden by clouds the record ceases. Results are best expressed as a percentage of the possible sunshine ; i.e., if the sun is above the horizon ten hours, and the record is but one hour, the sunshine equals 10 per cent, of the possible amount. Jordan's instrument is a sunlight rather than a sunshine re- corder. By this instrument a straight line of sunlight is recorded on sensitive c5^anot3rpe paper placed in two semicircular dark chambers. The sunlight, being admitted through small apertures in the sides, travels over the sensitive paper or chart by reason of the earth's rotation, and leaves behind a record of the duration Fig. 49. Solar Radiation Thermometer. CLIMATE AND METEOROLOGY 297 of sunlight and the relative degrees of its intensity. The in- strument must be carefully adjusted to the meridian and to the latitude of the place. To this end the base plate of the instrument must be inclined until the index points to the divisions on the arc corresponding to the latitude of the station ; then turn the instrument until it faces due south, taking care that the base is perfectly level. When the sun is on the meridian, the sunshine passing through the apertures should fall on the chart line indicating twelve o'clock. One box takes the records for the forenoon, and the other for the afternoon, thus enabling the charts to be changed without interfering with a continuous record. Atmospheric Electricity. The atmosphere is charged with electricity, which is chiefly positive in fine weather and negative in wet. The sources of this electricity are : (i) Vegetation, (2) evaporation from waters con- taining salts in solution, (3) the unequal distribution of heat, leading to atmospheric friction, and (4) combustion at the earth's surface (giving off positive electricity). Vegetation furnishes electricity by the evaporation of moisture, and by the giving off of CO2 and O charged with positive electricity. When clouds charged with different electricities (positive and negative) approach each other, a thunderstorm results. The 298 HYGIENE AND PUBLIC HEALTH heat generated along the track of the electric discharge causes the " Hghtning," and the thunder probably results from the sudden expansion of the air consequent upon the lightning, and the subsequent inrush of air to restore the resulting partial vacuum. Lightning rods are generally of iron, of about i inch in diameter, and pointed wnih copper. They are carefulty insulated, one end being buried in the ground. They must be fixed at a dis- tance from any of the metal pipes of a building. CHAPTER VII EXERCISE AND CLOTHING Exercise. The effects of exercise on the body are as follows : — I. Increased force and frequency of the heart's action, and by consequence the increased circulation of the blood through all parts of the body. 2. The pulmonary circulation being quickened, more carbonic acid and moisture are eliminated. The amount of air inspired and expired is largely increased. 3. The action of the skin is heightened, and perspiration becomes marked. The dilatation of the cutaneous blood vessels, and the evaporation of the sweat from the surface of the body, regulate the temperature and prevent any rise above the normal. 4. The water and salt of the urine are decreased owing to the large cutaneous secretion, but the nitrogen eliminated (in the form of urea, uric acid, and extractives) remains about the same. In the period of rest following excessive exercise, the nitrogen elimination may be slightly increased. 5. The voluntary muscles are brought into active play ; the circulation of the blood through them is accelerated ; waste products are rapidly carried away for excretion ; whilst the material to replace waste is brought to them. It is thus seen that exercise, which means muscular action, involves more rapid combustion, as shown by the increased elimination of carbonic acid and water. Thirst and appetite are created, and water and carbonaceous foods are required to supply the waste ; whilst an increased amount of nitrogenous food, during or after periods of exercise, is necessary to replace the waste caused by the nitrogenous tissues performing their function of regulating oxidation. Regular exercise in the open air is most essential to brain 299 308 HYGIENE AND PUBLIC HEALTH With reference to boots, these should fit the foot, and at the same time admit of free movement. Tight or badly fitting boots may give rise to flat foot, ingrowing toe nails, corns, bunions, and even to permanent lameness. The soles should be flexible and the heels kept low. High heels cause the foot to press forward in the boot, tiring the walker and causing a feeling of discomfort. They also give rise to an uncertain and unbecoming gait. In conclusion, it may be said that clothing should not be changed according to calendar, but according to weather ; and that clothing worn in successive layers is warmer than when a similar weight of material is applied in a single layer. CHAPTER VIII FOOD, BEVERAGES, AND CONDIMENTS Food. The purposes fulfilled bj^ food may be defined to be as follows : 1. To form new tissues in the process of growth. 2. To repair and renew the wasted tissues — solid and fluid — of the body. 3. To provide the material which serves as fuel to the body, and which, by its combination with oxygen, is reduced to the simpler forms of urea, carbonic acid, and water, thus supplying the sources of the animal heat and the manifestations of energy which are essential for the maintenance of life. All the various food substances and proximate constituents of food may be classified broadly under two heads— as nitrogenous and non-nitrogenous. The proteids, which are substances ahied in chemical constitu- tion to albumin, form a large proportion of the nitrogenous food substances, whilst the non-nitrogenous substances consist of the fats, the carbo-hydrates, the vegetable acids, the mineral salts, and water. Proteids. — The average composition of albuminoids may be taken as being approximately as follows : In 100 parts — nitro- gen, 16 ; carbon, 54 ; oxygen, 22 ; hydrogen, 7 ; sulphur, i. The proportion of nitrogen to carbon is nearly in the ratio of 2 to 7. In the group headed by gelatine (see table) the N is about 18 per cent., and the proportion of nitrogen to carbon is greater than in albuminoids : these substances are much less nutritious than the albuminoids proper. In the process of digestion albuminoids are converted into albumoses and soluble peptones, which are highly diffusible and capable of passing through the inner coats of the alimentary tract into the blood and lymph streams. A part of the peptones is further transformed into leucin and tyrosin, but the final products derived from proteid food are carbonic acid, water, and urea. Peptones differ from common 309 302 HYGIENE AND PUBLIC HEALTH Clothing. The ordinary garments of civilized life are made either of one, or a mixtm^e of two or more, of the following materials : — Cotton and linen from the vegetable kingdom ; wool and silk from the animal kingdom. Cotton materials have a smooth, fine texture, but not equal in Fig. 51. — Cotton Fibres ( x about 200 these respects to linen. Under the microscope cotton is seen to consist of flattened fibres with well-marked twists in their course. There are no joints or nodes, and no branching fibres (fig. 51). Cotton garments are durable, and do not shrink in washing. Fig. 52. — Linen Fibres ( x about 200). They are non-absorbent, and rapidly conduct away heat ; hence cotton is the wrong material for undergarments, for it soaks up the perspiration and becomes wet, and the moisture is re-evapor- ated, causing a chill to the surface of the body. The heat of the body is not retained by cotton, but is rapidly dissipated. A EXERCISE AND CLOTHING 303 material called " cellular " cotton cloth obviates the last defect. In this material the fibres are so woven as to form cellular air interspaces in the texture. Air being a bad conductor of heat, the cellular cloth is much warmer than ordinary cotton clothing. Cotton materials are preferable to woollen for the outer clothing of sick and hospital nurses, as organic matters in the air cling far less easilj' to cotton than to wool, and the former is more readily cleaned. Linen materials have a very fine, smooth, and close texture. Under the microscope the fibres of linen are seen to be cylindrical and jointed, with minute branching filaments at intervals (fig. 52). These latter are the elementary fibres of which the main fibre is composed. Linen is, like cotton, a good conductor of heat and a bad absorbent and retainer of moisture, and is an unsuitable material for underclothing. Wool forms a valuable material for clothing. Under the "micro- scope the fibres (fig. 53) are seen to be rounded, colourless (unless d3'ed), with fine cross-markings and indentations in the border at the site of the cross-markings. There is a central longitudinal canal, but it is generally obliterated. The cross-markings and reticulations are best seen in new wool, as when the fibres are old and worn they are not so distinct. Wool is an extremely bad conductor of heat, and is very absorbent and retentive of water and moisture, hence its value as a material for underclothing. Being a non-conductor, wool is warm by preventing the dissipation of the bodily heat. Its non- conducting properties are partly due to the wool fibres themselves, which contain an animal oil in their substance, and partly to the air entangled in their interspaces. After exercise causing perspiration, the moisture is absorbed and retained by the wool, and the vapour is condensed, thus giving back to the body the heat rendered latent by evaporation from the surface of the skin. A woollen garment after exercise is therefore warm and dry, and prevents the chilling of the surface from the lowering of the temperature by evaporation, which is so dangerous. In hot Fig. 53. Wool Fibres ( x about !oo;. 304 HYGIENE AND PUBLIC HEALTH climates especially, wool should be worn next the skin to ward off those chills which are often the forerunners of dysentery, diarrhoea, and ague. The disadvantages of wool are the hardening and shrinkage the fibres undergo when frequently washed (especially where soda and strong soaps are used), and the loss of absorbency resulting therefrom. The wool fibres, being hygroscopic, readily absorb organic vapours and dirt from the body, so that woollen under- garments require frequent but careful washing. They should be washed in soft, cold or tepid, water, with mild soap without soda, and should not be much wrung out. Flannel, which is a woollen material, is also often found to be too irritating to be worn next to a delicate skin. The addition of a little kerosene or paraffin to the soap used for washing clothes facilitates the removal of dirt, as less rubbing and wringing of the clothes are then required ; but the clothes must be well rinsed after the washing and aired out of doors, or a slight odour of kerosene (when kerosene soap is used) is retained in the fabrics. The paraffin soaps are free from this defect. The grease and dirt cannot be removed from clothes (any more than from the skin, owing to the fatty secretion from the sebaceous glands at the roots of the hair follicles) by merely washing in water without the use of soap. The alkali of the soap combines with the grease and emulsifies it, whereby it is easily washed off ; whilst the fatty acid pre- vents the too great removal of the oil from the wool fibres, and the deterioration of the fabric. Cheap soaps, containing an excess of alkali, are I? bad for the skin, for it is rendered over- dry and loses supple- ness by excessive removal of sebaceous secretion ; and they are also injurious to woollen fabrics by carrying away the animal oil contained in the fibres. In merino, wool and cotton are mixed in varying proportions. " Shoddy " is old, used and worked up, wool and cloth. Fig. 54. — Silk Fibres ( x about 200). EXERCISE AND CLOTHING 305 Sitk (fig. 54) is a bad conductor of heat, but is less absorbent than wool. It presents some advantages for underclothing, as it is more cleanly and shrinks less than wool, and is less irritating to the skin ; but it cannot hold perspiration like wool. It is expensive, and is less durable than cotton or merino. Leather and Waterproof Material. — These are invaluable for exposure to very cold bleak winds and rain. Leather is the more suitable for very cold climates. Being imperme- ^^^s!^|^|s/;^ss^,S!=I5i^^-a3» able, they are extremely ^--=i^;=^^=::~^:r_-— ~:~:r_7r' ~ :tj|? warm, but this imper- cL-_____:^:__x__- ^— ____i2=l meability prevents the l:-^'-^-::::^: ^■^~"^^^^^-'"-'— T'^^^=^7^3~r:^r=?, ventilation and renewal of ^ssMi^iiis--^ — --^ — ---is~2:E2ii*Sl:!z^? the layers of air confined fig. 55.— Hemp Fibres ( x about 200). under the clothing near the skin. The discomfort that arises from the wearing of water- proofs in warm weather is weU known. In hot climates the outer garments should be white or grey in colour to protect from the direct rays of the sun. At the two extremes of life — in childhood and old age- —warmth of covering is most essential. Children lose heat rapidly and are liable to chill, partly because the circulation being rapid, more blood is carried in a given time to the superficial vessels, and more heat is thus radiated from the surface than in an adult ; but mainly because in children the surface of the body is larger in proportion to its bulk or contents than is the case in adults. Children should be clothed in woollen materials ; and the legs, arms, neck, and chest should be equally protected with the other parts of the body. In old age the circulation is often feeble and languid, and the functions of heat-production and regulation are less efficiently performed than before senile decay commenced. Consequently, if the body is chilled, the restoration to the normal heat is slow, and the vital functions are dangerously depressed. Aniline dyes are now largely used for colouring various dress materials and undergarments, such as stockings. As a rule the dyes used are free from arsenic ; but it has occasionally happened that eczematous sores have been produced on the feet and legs by wearing dyed stockings, and there can be but little doubt that the sores were due to the action of arsenic on the skin when the feet were hot and damp. 306 HYGIENE AND PUBLIC HEALTH A good material for clothing purposes must meet the following requirements : — 1. It must afford proper protection to the body against cold and heat, so as to assist in preserving it at a proper uniform temperature in winter and summer alike. 2. It should interfere as little as possible with the natural functions of the skin. 3. It must exert no irritating or poisonous effects upon the skin. It has been seen that clothing is warm in proportion to its capacity for retaining the natural heat of the body, and, therefore, the materials which are the worst conductors are the warmest. Arranged in the order of their warmth, the materials in common use are : Wool, fur and down, silk, cotton, and linen. But it must be borne in mind that the warmth of an article of clothing also depends upon certain other subsidiary circumstances. Thus the colour of the most external clothing is important, black absorbing more of the heat from external sources than any other colour,' and white the least of aU. The order in which the dif- ferent colours absorb heat is as follows : — Black, dark blue, light blue, dark green, turkey red, light green, dark yellow, pale straw, and white. The degree of porosity of the article also affects its warmth, for the smaU spaces are occupied by air, which is a bad conductor of heat ; flannel is the most porous article of clothing, and silk is the least porous. Again, the textile fabrics with rough surfaces are generally warmer than those which are smooth, the rougher surfaces stimulating the skin and favouring the capillary circulation. The hygroscopic properties of the material determine its warmth to a considerable degree, for this property of absorbing moisture enables the fabric to absorb the perspiration from the skin ; and the chilling effect of the evaporation of this natural moisture is thereby trans- ferred from the skin to the article covering it. The following is the order in which the various articles of clothing must be placed, so as to indicate their relative hygroscopic properties : — Wool, fur, eider-down, silk, linen, cotton. The same order will indicate the facility with which each material absorbs odours. A few general remarks may next be made upon the require- ments of suitable and healthy clothing. The clothing of the body should be designed for the following purposes : — (i) For pre- serving the whole of the body at a uniform temperature. Doubt- EXERCISE AND CLOTHING 307 less the dress of women and children offends chiefly against this requirement. Women's dress encourages a very unequal distri- bution of warmth ; the upper part of the chest and the legs are unduly exposed, whereas the trunk below the upper part of the chest is, by comparison, clothed very warmly. The dangerous habit of exposing the bare legs and arms of infants to the vicissi- tudes of our winter climate, and swaddling the rest of their bodies with many layers of warm clothing, should be obvious to all. (2) Clothing must interfere with no natural function or move- ment, so as to lead to injury of the part of the body to which it is applied. The head covering should be light, porous (so as to admit air), and with no tight rim to press upon the scalp and interfere with the circulation of its blood supply, which is a cause of baldness. No tight-fitting article should be worn round the neck, as im- portant vessels are specially liable to be pressed upon in that situation. The trunk and extremities have probably suffered most from the adoption of bad principles in clothing ; and the dress of women in many respects still defeats the main objects of clothing. Petticoats and dresses are often heavy ; they impede movement and accumulate dirt, and they exert a dragging weight from the waist and hips. They should either be, like the male trousers, suspended by braces, or hung from a bodice by means of buttons. The effects of tight lacing are to deform the body and to dis- place important viscera. The diaphragm is pushed up, the lung space diminished, and the lungs and heart often suffer in con- sequence. Constriction and displacement of the liver are pro- duced, and the resulting pressure on other important abdominal organs causes them to suffer also. Those who lace tightly are frequently, therefore, the victims of dyspepsia, malnutrition, gastralgia, vomiting, shortness of breath, palpitation and faint- ness. Tight, rigid corsets give rise to muscular flabbiness, which conduces to spinal curvature, round shoulders, and a stooping carriage. The waist of the average woman should be from 26 to 27 inches in circumference. Tight sleeves should also be avoided. Suspenders should always be preferred to garters ; and the lower extremities of women should be protected by thicker stockings in the winter. The substitution of warm " bloomers " for the petticoat is a practice to be commended. 308 HYGIENE AND PUBLIC HEALTH With reference to boots, these should fit the foot, and at the same time admit of free movement. Tight or badly fitting boots may give rise to flat foot, ingrowing toe nails, corns, bunions, and even to permanent lameness. The soles should be flexible and the heels kept low. High heels cause the foot to press forward in the boot, tiring the walker and causing a feeling of discomfort. They also give rise to an uncertain and unbecoming gait. In conclusion, it may be said that clothing should not be changed according to calendar, but according to weather ; and that clothing worn in successive layers is warmer than when a similar weight of material is applied in a single layer. CHAPTER VIII FOOD, BEVERAGES, AND CONDIMENTS Food. The purposes fulfilled by food may be defined to be as follows : 1. To form new tissues in the process of growth. 2. To repair and renew the wasted tissues — solid and fluid — of the body. 3. To provide the material which serves as fuel to the body, and which, by its combination with oxygen, is reduced to the simpler forms of urea, carbonic acid, and water, thus supplying the sources of the animal heat and the manifestations of energy which are essential for the maintenance of life. All the various food substances and proximate constituents of food may be classified broadly under two heads— as nitrogenous and non-nitrogenous. The proteids, which are substances allied in chemical constitu- tion to albumin, form a large proportion of the nitrogenous food substances, whilst the non-nitrogenous substances consist of the fats, the carbo-hydrates, the vegetable acids, the mineral salts, and water. Proteids.— T\i% average composition of albuminoids may be taken as being approximately as follows : In 100 parts — nitro- gen, 16 ; carbon, 54 ; oxygen, 22 ; hydrogen, 7 ; sulphur, i. The proportion of nitrogen to carbon is nearly in the ratio of 2 to 7. In the group headed by gelatine (see table) the N is about 18 per cent., and the proportion of nitrogen to carbon is greater than in albuminoids : these substances are much less nutritious than the albuminoids proper. In the process of digestion albuminoids are converted into albumoses and soluble peptones, which are highly diffusible and capable of passing through the inner coats of the alimentary tract into the blood and lymph streams. A part of the peptones is further transformed into leucin and tyrosin, but the final products derived from proteid food are carbonic acid, water, and urea. Peptones differ from common 309 310 HYGIENE AND PUBLIC HEALTH albumins in being soluble, uncoagulable by heat, acid^ or spirit, and in being dialy sable. Nitrogenous. NOX-NITROGENOUS. Fats. Carbo- . vi Hydrates. ^^^ Salts. •§ > '1-1 r Albumin Fibrin S^Titonin Myosin Globulin Casein Olem Stearin Palmitin Margarin But\Trin Starch Dextrine Cane sugar Grape sugar Lactose or Milk sugar Oxalic Tartaric Citric :^IaUc Acetic Lactic Sodium chloride Potassium chloride Calcium phosphate Magnesium phosphate Iron, etc. ■1' a, /'Gelatine ^ rS ' Ossein ^ H 1 Chondrin .^ I^Keratine 11 /Gluten ^ ~ y Legumin .^ 'Kreatine Kreatin- ^"^ ine K amine Xanthine Nitrogenous foods are essential for the maintenance of animal life. All organized animal structures contain nitrogen, and there can be no chemical change and no manifestation of energy in any animal tissue from which nitrogen is absent. Consequently nitrogenous foods are required for the formation of new and the repair and renewal of old tissues, and for the formation of the digestive and other fluids of the body. The nitrogenous tissues of the body are also the regulators of the absorption and utiliza- tion of oxygen, by which energ\^ is manifested ; therefore the proteid foods, which make and repair the tissues, also participate in this regulation of oxidation and energ}'. They are also sup- posed to have another function under certain special conditions, viz., the formation of fat and the yielding of energy ; but of this little is known, and doubtless the main source of energy is the oxidation of non -nitrogenous substances. Under a diet from which nitrogen is withheld the body languishes ; the fimctions are carried on at the expense of the existing tissues and structures, and these undergoing no renewal, death must eventually result. FOOD 311 The albuminoids proper are of nearly equal nutritive value, and are therefore mutually replaceable in a diet. This applies to the different members forming the animal albuminoid class and to the vegetable and animal albuminoids taken as two separate classes. The only advantage — if, indeed, it be one at all — in favour of animal nitrogenous food as opposed to vegetable is tliat the former is more rapidly and completely digested, and therefore more quickly replaces wasted tissue. But against this must be set the fact that proteid substances are split up in the processes of healthy digestion, either in part or whole, into the poisonous alkaloids ptomaines and leucomaines. These bodies are, no doubt, under conditions of normal health and activity, disposed of in the system without detrnnent to its vital functions ; but if they are produced in excess, or more rapidly than they can be destroyed or eliminated, as may happen after a meal of meat excessive in amount, they tend to accumulate in the system, and may be the cause of that heaviness and languor so frequently experienced by large meat eaters, especially by those of a dyspeptic habit. Whilst there is not sufficient evidence to prove that vege- tarianism, so-called, is more conducive to health or longevity than a mixed diet, there can be but little doubt that the wealthier classes eat too largely and too frequently of meat. Excess of nitrogenous food causes not only an abnormal production of the poisonous alkaloids, of whose potentialities for evil but little is at present known ; but an excess of nitrogenous waste accumu- lates in the blood, oxidation is interfered with, the liver, the kidneys, and the other excretory organs are overtaxed in their work of eliminating waste substances, which are also insufficiently elaborated, and gout, or liver and kidney disease result. As gelatine, ossein, etc., are not the nutritive equals of the other albuminoids, they cannot replace them. Gelatine is easily oxidized in the body, and appears to be of value in cases of acute disease, when given in the form of jellies, in preventing excessive tissue waste. In such cases the albuminoids, if given, may not be digested or assimilated. Gelatine probably cannot form nitro- genous tissues, but it can take the place of part of the nitrogenous substances in the blood which undergo oxidation. The extractives, such as those contained in the juice of flesh, can neither build up tissue, nor serve as fuel, but they appear to ?i,ct as regulators and stimulants of digestion and assimilation, 312 HYGIENE AND PUBLIC HEALTH especially when gelatine and allied bodies are comprised in the diet. Hence the use of beef-tea, which, as usually made, contains little beyond extractives,,dn the dietary ^of sickness. Hydrocarbons or Fats. — These bodies are compounds of glycerine with the fatty acids — oleic, stearic, palmitic, etc. They contain no nitrogen, but are made up of carbon, hydrogen, and oxygen, the proportion of oxygen being less than sufficient to form water with the hydrogen present. The fats are unacted upon by the saliva and by the gastric juice, and pass through the stomach unchanged ; but in the small intestine they are emulsified by the pancreatic juice and bile, and rendered capable of absorption by the lacteal vessels, whilst a small portion is saponified — i.e., split up into glycerine and fatty acids, the latter uniting with alkalies to form alkaline palmitates, oleates, and stearates (soaps), which are directly absorbed into the blood or lacteals. The chief function of the fatty foods is to repair and renew the fatty tissues, and to yield energy and keep up the animal heat by oxidation into carbonic acid and water. The presence of the fats in food promotes the flow of the pancreatic juice and bile ; they thus help in the proper assimilation of other foods, and assist the excretory functions of the intestine, which are badly performed if bile and the other digestive fluids are not secreted in sufficient quantit5^ The animal fats are more easily digested and absorbed than the vegetable. If there is excess of fat in a diet^ it passes out unchanged in the faeces. Carbo-hydrates.- — These substances are made up of carbon, hydrogen, and oxygen, the oxygen being present in the exact proportion necessary to form water with the hydrogen present. In the process of digestion starch, cane sugar, dextrine, and milk sugar are converted into grape sugar. This change is commenced in the mouth, during the process of mastication of the food, by the action of the saliva ; it is not carried any further in the stomach, but is completed in the small intestine by means of the pancreatic juice. The starch (CgHioOg) takes up a molecule of water to become grape sugar (CgHigOe), which is taken up by the blood and carried by the portal vein to the liver, where it is deposited as glycogen or liver starch. The liver acts as a store- house for the deposition and accumulation of these converted starchy foods, which are subsequently supplied to the system as the needs of the economy demand, there to undergo oxidation FOOD 313 for the manifestation of heat and energy, and to be used for the building up of the fatty tissues of the body. The functions of the starchy foods are thus seen to be the pro- duction of animal heat and energy by oxidation, and the formation of ne^v fatty tissues. The latter property has been demonstrated by Lawes and Gilbert by experiments in the fattening of pigs. The fat given in the food was not sufficient to account for all the fat stored up in the pigs. Most of the excess must have been derived from the conversion of the carbo-hydrates, but a portion may have been due to the metaboUsm of nitrogenous substances. The fattening caused by a diet rich in starch and sugar may partially be due to the oxidation of these substances sa^-ing the fatty tissues from destruction, and allowing the fat in the diet to form new fatty tissues. Although the functions of the fats and carbo-hydrates in the economy are very much the same, they are not mutually replace- able under ordinary conditions, if health and vigour are to be maintained at their maximum. Where men are much exposed to very cold temperatures and undergo great fatigue in the open air— as during Arctic expeditions — a diet of albuminoids, fats, salts, and water (without carbo-hydrates) may maintain them for a time in good health ; but the deprivation of fat from the diet under any circumstances is not well borne and leads rapidly to loss of health and vigour. Moreover fat m the diet stimulates the flow of bile, increases intestinal movements, and promotes the passage of chyme through the intestinal mucous membrane. The absence of fat in a diet leads to a state of malnutrition, possibly predisposing to such diseases as tubercle, especially in children and young persons. The deprivation of starches can be borne for a long time if fat is given ; but httle is known as to the ultimate effects of such deprivation, for wherever food can be obtained at all, the starchy constituents, so widespread and abundant in Nature, are sure to be largely represented. It also appears that the carbo-hydrates are concerned with the maintenance of the proper reactions of the various body fluids (blood, lymph, gastric juice, urine, etc.). They give rise to lactic and other similar acids in the body, which act upon the alkaline phosphates, chlorides, etc., and elaborate the various acid juices characteristic of the different bodily secretions and excretions. Starches and sugars have much the same dietetic value. Cellu- lose is only to a shght extent converted into sugar by the human 314 HYGIENE AND PUBLIC HEALTH digestive processes, consequently much passes out unchanged in the faeces. It is evident, therefore, that a diet which is to maintain proper bodily health must contain all the three substances — albuminoids, fats, and carbo-hydrates. The albuminoids are the most indis- pensable, as without them vital action must cease for want of a supply of nitrogen. But a diet of albuminoids, salts, and water, alone, is rapidly destructive of healthy action. As before ex- plained, the excessive waste resulting from the metabolism of so much nitrogenous food, necessary to maintain animal heat and energy, overtaxes the system, and imperfectly oxidized sub- stances accumulate in it, which pervert healthy action and eventually set up diseased conditions. Organic Acids. — These exist in fresh vegetables and fruit, probably also in fresh meat and milk, in combination chiefly with alkalies as alkaline salts. These acids form carbonates in the system, and preserve the alkalinity of the blood and other fluids. This is their chief function, but they may also furnish a small amount of energy and animal heat by oxidation. If these sub- stances are absent in a diet, the blood becomes impoverished, and scurvy results. There is evidence, however, that fresh vegetables or lime juice are not alone sufficient for the preven- tion or the cure of scurvy, and that the disease is essentially due to poisoning by the ptomaines of tainted animal food, or by bodies of unknown composition present at times in tinned or preserved animal foods, which are apparently in good condition and free from putrefactive taint. During the recent voyage of The Discovery in the Antarctic regions, symptoms of scurvy appeared when the crew were receiving tinned preserved foods as rations, even although fresh meat was occasionally eaten ; but all symptoms of scurvy dis- appeared when the use of tinned meats was abandoned, and freshly killed meat was substituted. Scurvy, although formerly very fatal to crews of ships on long voyages, and to populations on shore during times of want and famine, can hardly now be called a disease of modern life, when fresh meat, vegetables and fruit are within the reach of all classes. Such is the case at least with adults ; but infants, fed for long periods exclusively upon condensed milk or preserved foods, have been shown to sometimes suffer from a form of scurvy. The haemorrhages characteristic of scurvy take place FOOD 315 under the periosteum of the long bones. The disease is often associated with rickets (hence known as " Scurvy Rickets "), and is generally rapidlj'' cured by the administration of fresh milk and fresh food. The mineral salts are essential for the growth and repair of all the tissues of the body. The phosphates of lime, potash, and magnesia contribute largely to the formation of bone ; whilst iron for the red blood corpuscles and colouring matters, chlorine for the gastric juice, potash for the blood cells and solid tissues, and soda for the intercellular fluids, are all indispensable. Mineral salts are required in diets for all ages, but more especially for infants and children, when not only has waste to be made good, but new material for the growth of the body has to be supplied. Water is a component part of all the so-called sohd foods, and is likewise taken separately, the amount of water contained in the solid foods of an average diet being insufficient for the needs of the body. The water contained in different food stuffs varies within very wide limits ; in some articles it amounts to not more than 12 per cent, by weight, while in others it may exceed 90 per cent. Water is necessary to make up the losses occasioned by its excretion in the breath, sweat, urine, and fseces, and to renew all the various fluids and solid organs of the body, into whose constitution water largely enters. Water also serves as a vehicle for the solution and dilution of the solid foods, whereby they are more easHy digested and assimilated, and it is essential for the elimination of many waste products. The Digestibility of Food. — Not verj^ much is known of the digestibility of different kinds of food under varying conditions, but the following facts have been ascertained : — -The protein of the ordinary table meats, fish, and milk is very readily and completely digested. The protein of vegetable foods is much less completely digested than that of animal foods. As much as a third of the protein of beans, for instance, may escape digestion, and thus be useless for nourishment. Much of the fats of animal food at times fails to be digested. The carbo- hj^drates of vegetable food, with the exception of cellulose, are in general very digestible. Diet. From physiological experiment and actual experience, dietaries of different kinds, suitable for an adult under varying conditions, have been constructed ; but there is considerable discrepancy 3i6 HYGIENE AND PUBLIC HEALTH among physiologists regarding the quaUtative and quantitative composition of these diets. Thus, there is a subsistence diet, calculated as sufficient for the internal mechanical work of the body alone ; a diet for ordinary work (entailing the expenditure of energ}^ equivalent to 300 foot-tons per diem) ; and a diet for laborious work (450 to 500 foot-tons daily) — all suitable for a man of average size and weight (150 pounds). The follo^^dng table is compiled from the researches of Playfair, Moleschott, Pettenkofer, Voit, and Ranke. j Subsistence. 1 Ordinary Work. Laborious Work. Oz. av. Grammes. Oz. av. Grammes. Oz. av. Grammes. 1 Albuminoids . 2-0 57 4-5 127 6-5 184 Fats 0-5 14 1 3-5 99 4-0 113 Carbo-hydrates I2-0 300 1 14-0 397 17-0 482 Salts O-S 14 I-O 28 1-3 ^7 : Total water-free food 15-0 38s 23-0 651 28-8 816 i The above quantities represent dry food. Ordinary solid food contains on an average 50 or 60 per cent, of water, so that the above quantities must be rather more than doubled in actual practice. About 50 to 80 ounces of water are in addition taken into the system daily in a liquid form, the quantity depending upon the amount of exertion undergone and the temperature and humidity of the air. Thus, for subsistence a man requires about xV ounce of water-free food for each pound of body weight, and for ordinary work about 7 ounce. By the following table, which shows the approximate percentage composition of some of the more ordinarj^ articles of food, it is ' possible to calculate a diet consisting of some of these common foods. In 100 Parts. Albuminoids. F-s. 1 hjdttts. ; Salts. ' Raw meat Hen's eggs Cow's milk 1 Butter Cheese Bread Potatoes Oatmeal 20-5 13-5 4-0 28-0 8-0 2-0 12-6 8-5 II-5 3-5 83-5 23-0 o-s o-i 5*5 — 1-5 — 1 I-o 4-5 1 0-7 I-o ' 1-5 I-o j 7-0 1 50-0 1 1-5 2I-0 1 1-0 63-0 3-0 i DIET 317 Supposing a diet of meat, bread, and butter is required for a body of men in ordinary work. Let ;(r = amount of meat required in ounces per laead, per diem. y=amount of bread ^^ = amount of butter ,, ,, Then — - x + — y + — - ^ provides 4'^ oz. (albuminoids). 100 100 100 ^ ->■ J . — - X + —- y + — — z provides 3-5 oz. (fats). 100 100 100 ^ J J V I — V + — ^^ provides 14 oz. (carbo-hydrates). 100 ■ 100 *^ t \ J I These equations, when solved, give the required amount of meat as I0'8 ounces, the bread as 28 ounces, and the butter as about 3 ounces. The amount of nitrogen in the diet for ordinary work is 315 grains (20-4 grammes), and the amount of carbon 4,790 grains (310-4 grammes). One-tenth of the total nitrogen eliminated leaves the body in the faeces ; the kidneys eliminate the remainder chiefly in the form of urea ; the skin and lungs give off only a trace in the form of ammonia. Albumin contains 16 per cent, by weight of nitrogen and 48-4 per cent, of carbon. Fat contains 76-8 per cent, of carbon, and carbo-hydrates about 43 per cent, of carbon. In the best diets tfie proportion of nitrogen to carbon should be about as i to 15. The energy obtainable from the chfferent articles of food is expressed as so many foot-tons per ounce consumed. It is the amount which would be produced theoretically, if the constituents of the food were completely oxidized to carbonic acid and water ; and the energy derivable on this hypothesis from different food stuffs can be calculated from the heat — as measured in a calori- meter — required for their complete combustion. It is evident, however, that such theoretical expressions may have little bearing upon dietetic value, which depends so largely upon the digestibility and capability of assimilation of different food products ; and that the whole of the potential energy thus calculated is therefore not available. In the case of albuminoids also, a portion passes out of the animal system incompletely oxidized in the form of urea. The figures usually given are : One ounce of dry albuminoid yields 173 foot-tons of potential energy. One ounce of fat yields 378 foot-tons of potential energy. 3l8 HYGIENE AND PUBLIC HEALTH One ounce of dr}^ carbo-hydrate yields 135 foot-tons of potential energy. According to these figures, the average daily diet for ordinary work would yield 3,977-5 foot-tons, or in round numbers close upon 4,000 foot-tons ; but a large proportion of this total energy, viz., about 2,500 foot-tons, is devoted to the maintenance of the body temperature, and to the performance of the various bodily functions, when the bodj^ is in a state of rest. In a state of rest, a man of 150 pounds weight gives off about r6 cubic feet of CO2 gas in twenty-four hours. The production of I cubic foot of CO2 by combustion is equivalent to 160 foot- tons of energ}^ Therefore 16x160=2,560 foot-tons of energy are consumed in the production of the 16 cubic feet of CO2 daily. Again, if the average temperature of the air is taken as 50° F., the difference between the temperature of the human body (98° F.) and that of the air is 48° F. If, then, we consider the human body as absorbing and losing heat like water, the energy required to support a temperature of 98° F. in a man of 150 pounds weight is 150 X 48 X 775 2,240 = 2,490 foot-tons. The number 775 is Joule's equivalent, i.e., the number of foot- pounds of energy necessary to raise i pound of water 1° F. These two methods of estimating the amount of energy neces- sary to sustain human life are seen to produce very similar results, viz., 2,560 foot-tons in one case, and 2,496 foot-tons in the other- The subsistence diet given in the table (p. 316) yields 2,155 foot- tons of theoretical energy. Playfair's subsistence diet (2-5 oz. alb., I oz. fat, 12 oz. carb.-hyd.), however, yields 2,430 foot-tons of theoretical energy, which is nearly identical with the results of the two methods just described. The average diet, as before said, yields nearly 4,000 foot-tons of theoretical energy. If 300 foot-tons is taken as the energy consumed in actual physical labour, then 4,000 — 300 = 3,700 foot-tons are consumed in supplying energy for the functions of the body in a state of physical activity. This would mean that during ordinary work the production of CO^ is raised from 16 cubic feet to an average of 23 cubic feet in the 24 hours ; or supposing the man works for 8 hours and rests for 16 hours, DIET 319 then the CO2 produced iii the 8 hours of work is 11 -8 cubic feet (1-47 cubic feet per hour), and in the 16 hours of rest ii-2 cubic feet (0-7 cubic foot per hour). In the same way the diet for hard (laborious) work produces 4,930 foot-tons of energy : subtracting 500 for actual visible work, there is left 4,430 foot- tons for the work of the body, equivalent to the production of 27-6 cubic feet of COg in 24 hours, or i-6 cubic feet per hour for 12 hours of work, and 0-7 per hour for 12 hours of rest. The theoretical amounts of heat produced by the metabohsm of various foods within the body have been calculated, and are stated in terms of calories — a calorie being the amount of heat required to raise a kilo (or i litre) of water 1° C, or, which is the same thing, i pound of water 4° F. In these calculations allow- ance is made for incompletely oxidized products. The heat value, or amount of energy set free in combining with oxygen, of i ounce of each of the three chief nutritive constituents of food, when metabolized within the body, is as follows : — - Proteid Carbo-hydrates . Fat 116 calories. 116 263 According to this table, the diet for ordinary work yields the following : — - Oz. av. Calones. Albuminoids .... Fats Carbo-hydrates 4-5 3'5 14-0 ^22 921 1,624 22'0 3,067 In applying the calorie standard to any particular kind of food, it Js merely necessary to multiply the percentage (in grammes) of proteid or carbo-hydrate which it contains by 4-1, and the percentage of fat by 9-3, to obtain the total calories yielded by 100 grammes of the food. Professor Chittenden of Yale Universit}^ in his work on Physio- logical Economy in Nutrition with Special Reference to the Minimal Proteid Requirements oj the Healthy Man, has shown that health and vigour without loss of body weight, when equilibrium has once been established, can be maintained on a 320 HYGIENE AND PUBLIC HEALTH diet containing only from one-third to one-half of the proteid stated to be necessary in the standard dietary scales of Voit. Ranke, Moleschott, and other authorities, which have received almost universal acceptance, and this without any increase and, even in some cases, with a diminution in the non -nitrogenous elements of the diet. The experimental diets (Chittenden's) were " mixed," and not purely vegetarian, but meat was only sparingly taken. Chittenden's experiments were conducted over a period lasting some months with 3 classes of men, namely {A) brain-workers, consisting of 5 professional men ; {B) a detail of 13 U.S.A. soldiers, representative of men undergoing moderate physical work ; and (C) a group of 8 University students, all being thoroughly trained athletes, and engaged daily in arduous physical exercises. Voit's standard diet for ordinary work for an adult man of average body weight (70-75 kilos. = 154-165 lbs.) requires daily 118 grammes ( = 4-16 oz.) of proteid or albuminous food, of which 105 grammes should be absorbable, 56 grammes ( = 1-98 oz.) of fat, and 500 grammes ( = 17' 65 oz.) of carbo-hydrate, with a total fuel value of over 3,000 calories, in order to maintain the body in equilibrium. This diet contains the equivalent of at least 16 grammes of nitrogen. Chittenden's experiments with class A show that during periods ranging from 6 to 18 months, these men maintained their body weight (in some cases there was an initial loss), estabhshed nitrogen equilibrium, kept in good health, and pur- sued their ordinary avocations with an average daily metabolism of from 5-4 to 8-9 grammes of nitrogen ; that is to say, with diets containing only from 34 to 56 per cent, of the proteids considered essential by Voit, whilst the total fuel values of their diets varied from 2,000 to 2,500 calories, as against the 3,000 of Voit's scale. The soldiers in class B during a period of 5 months were on diets containing only from 44 to 50 per cent, of the proteids in Voit's diet, and with total fuel values of 2,500 to 2,800 calories. These men maintained their body weights, and established con- ditions of nitrogenous equilibrium, whilst their physical condi- tion was markedly improved during the period of the experi- ment, which also coincided with a period of physical training and g5niinastic work. DIET 321 With the athletes in class C the same i-esults were obtained, the average amount of proteid in their diets being about 55 per cent, of Voit's scale, and the fuel values varying between 2,000 and 3,000 calories. All these men well maintained for the whole period of experiment their physical condition, and were just as " fit " as prior to commencing their reduced dietaries, when there was an average daily metabolism of over 120 grammes of proteid, these athletes having been firm believers in the necessity for an abundance of proteid food (meat) when training. Professor Chittenden's work not only raises the question as to the necessity for a revision of the accepted dietary scales, which serve as standards for computing the daily necessary food for soldiers, sailors, prisoners, and the inmates of many different kinds of institutions, but is suggestive of the hygienic possibilities of the diet of reduced proteid value as a matter of general application. If the amount of proteid food needed daily for the actual physiological wants of the body is not more than one-third to one-half that ordinarily consumed by the average individual, as Professor Chittenden's experiments appear to demonstrate, not only is there waste and loss of energy from the vital forces being engaged in the metabolism of matter which is not required, and is of no service to the body, but there is also the danger of the accumulation in, and imperfect removal of such waste products from the system ; and even if, for a time, these waste matters are properly removed, excessive meta- bolism implies greater efforts on the part of the excretory organs than would be needed under a diet suited to the exact physio- logical needs of the body. Overaction of the liver, kidneys, and other excretory organs, persisting with little variation over long periods of time, and the resulting retention of partly elaborated and toxic waste matters in the blood, when the excretory organs are unequal to the strain put upon them, furnish the conditions which are known to be causative of degenerative changes in the tissues, and which lead in middle life to many chronic diseases of important organs, and to death at an age when impairment of functional activity should hardly have commenced. Professor Chittenden's conclusions have been by no means universally accepted by physiologists and others interested in the construction of dietary scales, as they seem opposed to the 21 322 HYGIENE AND PUBLIC HEALTH general experience of civilized nations ; and however interesting as indications of the adaptabihty of the human frame and frmctions to alterations in nutrition for comparatively short periods, the experiments were hardly of sufficiently long dura- tion to warrant conclusions applicable to the life of a community for long periods. There are some also who think that a diet somewhat in excess of actual corporeal needs supplies a reserve of energy, which maj' be useful to prevent invasion of the system by the agents of infection, and to aid the restorative powers of the body in the case of actual sickness. The whole question of the adequacy of Chittenden's dietary scales under the many varying cii'cumstances of mental and physical acti\dty must, therefore, be still considered as sub judice. When food is taken in large excess of the requirements of the system, a considerable portion remains undigested ; fermenta- tive and putrefactive changes are set up in the undigested mass as a result of the acti\'ity of the bacterial organisms always present in the intestinal canal, foetid gases containing sulphur and carbon are formed, and dyspepsia and charrhcea are pro- voked. Some of the products of putrefaction — possibh' the alkaloids already referred to, the ptomaines and leucomaines — are absorbed into the blood, and cause fever, torpor, headache, and foetid breath. Excess of fats and starches tend to produce acidity and flatulence ; whilst taken habitually in excess they may cause excessive formation of fatty tissues and obesity. In cases of over-eating and faulty digestion, undigested muscular fibres, fat, and starch cells may be found b\^ microscopical ex- amination in the feeces to an unusual extent, and occasionally albumin and sugar ^^•ill be found in the urine. Deficiency in all the constituents of a diet tends to produce loss of weight, debility, prostration and anaemia. If carried to the point of starvation, low fever and gastric disturbances are often excited, ending eventually in death. It appears, however, that some constitutions can withstand long periods of fasting (thirty to forty days), if plenty of water is taken ; apparent health being maintained the whole time, although \\-ith gradual]}' increasing emaciation and debility. The elimination of urea is always markedly diminished. The considerations which will influence the selection of a diet are many. They may be briefly summarized as follows : (i) Age. It is generally held that a child of ten requires half as much FEEDING OF INFANTS 323 and a child of fourteen quite as much, as a woman. An average diet for a child between eight and fourteen years of age should contain about 6 ounces of meat, 14 ounces of bread, 6 ounces of potatoes, 9 ounces of milk, and small quantities of butter, fresh vegetables, tea or coffee. A generous diet for a working man would contain 9 ounces of meat, 18 ounces of bread, 16 ounces of potatoes, 16 ounces of milk, 2 ounces of butter or dripping, and 3 ounces of oatmeal. Old people should be given somewhat less proteid (about 15 per cent, less) and carbo- hydrates, and slightly more fat, than those in middle life. (2) Sex. Women require on an average one-eighth less food than men. (3) Selection of food. In making the selection, the local ma'ket will have to be studied ; and it is essential to furnish a sufificient variety of food. The digestibility of various articles of foods must also be taken into account. On an average, about 5 to 10 per cent, of all the common food stuffs is indigestible. (4) What is of prime importance is to see that the dietary allotted to each day contains the proper amounts and relative proportions of albuminoids, fats and carbo-hydrates ; what- ever the food selected, the salts will always be in sufficient quantity. In distributing meat rations it must be borne in mind that 20 per cent, of the gross weight must be deducted for bone. As to (5) meals, it is the usual practice to provide four meals daily : breakfast, dinner, tea, and supper — at intervals of about four hours, although three meals a day are sufficient for an adult. The Feeding of Infants. Until the child is at least seven months old nothing but milk should be given, for it is unable to digest starch and other foods. The following instructions may be advantageously followed, at the earlier ages, in cases where the mother is unable to suckle her infant, and at the later ages in all cases : — ^ (a) During the first six weeks after birth the child should be fed every two hours throughout the day, reckoned as between 4 a.m. and 10 p.m., and once between these hours in the night. Its food should consist of one part of fresh cow's milk and two parts of water, mixed and (if there is any doubt as to the quality of the milk) boiled, and then sweetened with a teaspoonful of brown sugar to each pint of the mixture. Barley water may sometimes with advantage be used instead of plain water, but lime- water is better avoided. The mixture should be kept in a clean, covered vessel, and in a clean, cool place, between meals. The temperature of the food given to a young child should be about that of the human hand. Three or four tablespoonfuls should be given to a child each time it is fed. (&) From the age of six weeks to three months the child should be fed ^ For the preparation of humanized milk from cow's milk, see page 351. 324 HYGIENE AND PUBLIC HEALTH with a mixture of equal quantities of cow's milk an,d water, with sugar as above ; but two teaspoonfuls of cream may now be advantageously added to each meal. The quantity given at each meal should be about eight table- spoonfuls. The intervals between meals should now be gradually lengthened. (c) From the age of three months to seven months the child should have a mixture of two parts of cow's milk to one of water. About eight table ■ spoonfuls should at first be given at each meal, but the intervals between meals being still lengthened, a larger quantity than this will soon be required. The quantity of cream given with each meal may now be increased from two to three or four tablespoonfuls. The infant should only be fed during the night if it happens to awake. "The following is a useful working rule for the feeding of a child during the period in which liquids should be exclusively given : — Begin with about thirty -two tablespoonfuls a day, as above (a), and increase this by the addition of two to four tablespoonfuls a week up to the end of the seventh month. (d) From the age of seven months to twelve months, the child should be fed every three hours, between 6 or 7 a.m. and 9 or 10 p.m. Each meal should consist at the first of about ten to twelve tablespoonfuls of undiluted cow's milk, with cream as above (c) : but three of the meals may also each contain about a teaspoonful or more of baked flour or arroAvroot, or of some infant's food, well boiled and stirred up with the milk. (e) From the age of twelve months to eighteen months the child should still be fed about every three hours, between early morning and night. The amount of milk should be about twice as great as that given under {d) and porridge, bread and milk, bread and gravy, bread and butter, and a lightly boiled egg occasionally, may be given with advantage, or in place of some of the milk, as time goes on. When nine or ten months old, the child should, as a rule, be gradually weaned, but it is well not to commence in very hot weather, owing to the risk of summer diarrhoea. Feeding bottles should be boat-shaped, preferably with an opening at each end. They should be fitted with a short rubber teat, capable of being easily turned inside out for cleaning. The long feeding tube usually found in use very quickly becomes foul, and should not be employed. Any milk left in a feeding bottle after a meal should be at once emptied away. Two bottles should be us.ed alternately, each bottle being boiled and rinsed immediately after use, and placed neck downwards to drain in a cool, clean place, so that no dust may get into it. Condensed milk is never so good for infants as fresh milk ; if used at all, it should be condensed " whole " milk. Condensed milk should never be given to an infant from a tin which has the words " hand skimmed " or ' machine skimmed " upon the label, for such milk has been robbed of a very important nutriment, and a child cannot thrive on it, however much is taken. It is harmful to give children tea, beer, spirits, or cheese, for they inter- fere with the power of digestion ; and teething powders or soothing S5'-rups are dangerous because they often contain opium. When an infant is fretful or suffering from indigestion or diarrhoea, it will often be found that it is having too much or too strong food, and is fed too frequently. By diminishing its diet or diluting the milk with a little extra water, and carefully attending to the proper feeding times, the child will often get well. If, in spite of every care, it continues so to suffer, proper medical advice should always be sought. Relatively too much starchy food along with too little fat is ascribed as a caiise of rickets in young children. FEEDING OF INFANTS 325 Dr. Reid has demonstrated statistically the evil that results from the prevailing practice in many manufacturing towns of mothers leaving their homes during the day to work in factories. Children are as a consequence deprived of their natural food and of the care of their natural guardians. An inquiry instituted by a Parliamentar}^ Bills Committee tended to show that the amount of infant mortality attributable to the practice of married women engaging in factory work, may amount to 21 per cent, of the total. Two remedies are suggested in the report, one being the extension of the period of compulsory absence from work after confinement, required by the Factory Act, 1901, from one month to three ; and the other, the establishment of day nurseries or creches by local authorities, for which a small payment should be exacted from the parents. Under the conditions of modern urban life many women of the poorer classes must be engaged in other than domestic labour, and absent from their homes for many hours ; and the wage earned by these expectant and young mothers is doubtless of considerable value to the health of both mother and child in the food which it provides ; and the disadvantages of such work at such times is therefore to some extent compensated for. This circumstance has to be borne in mind in connection with the suggestion of the prohibition of the employment of women within four weeks of confinement. For such women a cheap and well-administered creche is a great boon ;. and it has been suggested that such institutions might be utilized by the elder school girls for training purposes in the management of infants. The advantages of a creche are that it affords a health}^ abode for the infants during the absence of their parents from home, skilled feeding for the infants, and facilities for detecting the onset of illnesses when the creche is under skilled supervision. The obvious drawbacks are that the child is exposed to cold while bringing it to the creche and taking it away at night, and the risk of the spread of communicable diseases among the children. Homes for the reception of pregnant working women have been for some years in existence in France. The experience of these homes shows that cessation from labour for a fortnight or a month preceding confinement, renders the pregnancy more likely to proceed to the normal term, and the infants in consequence are stronger and more fully developed at birth. 326 HYGIENE AND PUBLIC HEALTH The " Consultations des Nourrissons " were founded by the late Professor Budin, and are now to be seen in France in con- siderable numbers. The scheme included advice, and in some cases assistance, to pregnant women, and advice and assistance to mothers with reference to the feeding of the infant. The mother is always encouraged to suckle the child for the full period ; but those who are dependent partially or entirely upon artificial feeding are provided with sterilized milk, and the infants' weight is weekly registered. These mothers' clinics have been aptly called " Ecoles des Meres." A somewhat similar provision first founded at Fecamp in 1894 was termed the " Goiit de Lait." Dr. J. F. J. Sykes and others have drawn attention to the increased immaturity of infants at birth during recent years, and to the fact that this diminished viability cannot be due to artificial feeding, but to the ante-natal condition of the mother ; and, as Dr. Sykes points out, the fundamental idea of the home for mothers provided in the Borough of St. Pancras, London, is, that the pre-natal conditions of the mother are of primary concern, and of the post-natal conditions the mother should receive the first consideration ; that mothers must, where- ever it is possible, be prevailed upon to suckle their infants ; and that in order to make the provision really effective, the co-operation of medical practitioners, medical attendants at provident dispensaries, the medical staffs of hospitals, midwives, nurses, district visitors, and the philanthropic public, must be invited to co-operate. Meat. Meat contains a large quantity of nitrogenous material, some fat, and salts — chiefly the chlorides and phosphates of potash. It is rapidly digested and easily assimilated, and hastens tissue metamorphosis. The albuminoids form about 20 per cent, of raw meat (beef), of which about 15-5 parts are digestible albumins, peptones, and extractives, the remaining 4-5 parts being indigestible. Bones contain a large amount of nourishing material, viz., albuminoids (gelatine), 24 per cent. ; fat, 11 per cent. ; ash or mineral salts, 48 per cent. A most nourishing soup can be pre- pared by boiling bones. In inspecting meat, the muscles should be found firm and elastic, of a deep red colour (neither purple nor pale, flabby nor MliAT J27 sodden), and marbled with fat, in well-conditioned animals. There should be no excess of moisture, no pus or fluids in the intermuscular cellular tissue, and no lividity on cutting the muscle across. The flesh must be quite free from deposits (tumours). The odour should be fresh and not unpleasant, without a suspicion of putridity or smell of physic. Meat which has commenced to putrefy is pale and soft ; the reaction of the juices is no longer acid ; and later the meat becomes greenish. If the odour of putrefaction is not otherwise apparent, a knife or a new wooden skewer should be thrust into the meat and then held to the nose ; or a little of the meat may be chopped up and soaked in hot water, when the steam arising may be found offensive. The fat should be firm and of a pale yellow colour, and free from haemorrhagic points. The lymphatic glands afford an excellent clue to the existence of chsease if they are enlarged, congested, or show deposits. In bovines the chief lymphatic glands are to be looked for immediately in front of the spinal column (thoracic and lumbar glands), between the two lungs (medias- tinal), and on both sides of the trachea or wind- pipe near to its bifurcation (bronchial). In health these lymphatic glands are about the size of a pea. Any lymphatic glands attached should be firm, slightly moist, and of a pale greyish-yellow colour on section ; and the marrow of the bones should be light red. The lungs should be examined for inflammation or abscesses, tuber- culosis, or actinomycosis ; the liver for distoma or liver-fluke, tuberculosis, or hydatid tumours ; and the spleen for enlargement or nodules. The Important Parasites of Flesh. CYSTiCERCi.^The cysticercus, or " bladder- worm," causes the condition known as " measles " in the pig, ox, and sheep. When measly flesh is consumed by man, the " bladder- worm " undergoes a series of changes which terminate in its conversion into a tape-worm. In the flesh of the pig, and much „ , ,,.,,,, , ^ °' Fig. 56. — Measly pork, more rarely in that of dogs, showing (diagrammatically) its monkeys, or man, a number of appearance to the naked eye. small oval or round cysts are seen, occupying a position between the muscle fibres, and commonly varying in size from a pea to a cherry — though they have been found as small as ^V inch, and as 32« HYGIENE AND PUBLIC HEALTH large as f inch in diameter. These cj^sts are the Cysticerci cellulosce — the bladder worms which form a stage in the development of TcBnia solium. The cj^sticerci are surrounded by a pale milky looking fluid, and the cyst wall shows a white spot (generally central) upon its surface. The affected flesh is pale, soft, unduly moist, and flabby, and it has a smooth slipper}^ feel. Sometimes there is some degree of calcification of the capsule, the result being that, when sections are cut, a grating sensation is experienced. The bladders should be incised with a sharp knife, and the worm examined by a powerful hand lens, when at one extremity will be found the blunt square head provided with a sucker at each " angle," and a fringe of booklets placed more centrally. These booklets are very characteristic, and must always be found before a definite diagnosis is ventured on. Those cysts that are dried up and indistiact can be made \isible by soaking in weak acetic acid. Ostertag attaches great diagnostic importance to the rounded or oval calcareous cor- puscles, which are so generally embedded in the tissue of the head, but which disappear on the addition of acetic acid. Young pigs are more especially liable to be attacked ; and Fig. 57. Head of Taenia solium. (Obj. I inch.) Fig. 58. — Head of Taenia mediocanellata. (Obj. I inch.) Fig. 59. — Brood capsule of an echinococcus. during life the earliest evidence of the parasites is afforded by the presence of one or more small cj^sts in the conjunctiva, or in the loose tissue of the fraenum linguae. After death the hver and the muscles of the shoulders, intercostals, and loins, are .seen to be chieflv affected. MEAT 329 The Cysticercus of the Ox. — Cysticercm bovis, or " beef-measles," which chiefly affects the calf, possesses a flat head armed with nt) hooklets, but simply with suckers, around which there is fre quently a considerable deposit of pigment ; and on the surface of the head there is a pit-like depression (" frontal suction cup "). It develops in man into the adult tapeworm called Tcsnia medio- canellata, which is longer than T. solium, and appears to be more prevalent in this country. Bolhriocephalus latits, a tapeworm which is almost limited to certain parts of the Continent of Europe, is even larger than T. mediocanellata. It has a club-shaped head, not armed with hooklets, but possessing two deeply grooved longitudinal suckers, one on each side. TcBuia echinococcus is the small tapeworm, of three or four segments, which is commonly found in the dog. The encysted form (" hydatids ") is generally found in the lungs and liver of oxen, sheep, and swine, and (more especially in Iceland) in man. The hydatids consist of thin pale vesicles floating in a clear liquid, the whole being encysted in a tough capsule. The inner lining of the capsule consists of ciliated epithelium ; and from the inside of the cyst wall there generally arise many so-called " brood capsules " (fig. 59). The condition is diagnosed with certainty by the microscope either b}^ the discovery of the characteristic heads or of detached hooklets in the clear iJtsi' !#y^ttf liquid of the cyst. Valuable corroborative evidence is furnished by the fact that the liquid is quite free from albumin, and, in consequence, does not coagulate on boiling. Trichina Spiralis. — This parasite has been found in the flesh of many different animals (pigs, pigeons, eels, etc.), but most commonly, by far, in that of pigs. Oxen and | v_^j sheep do not suffer from attack by these ' // nematodes. Fig. 60. — Trichina The shape of the minute worms is nearly spiralis encysted m ■^ . muscle (X about 40 that of a typical nematode, i.e., a diameters). slender rounded body tapering gradually at either end. The extremity which constitutes the head, proceeds to a long slender point having a small central orifice — 330 HYGIENE AND PUBLIC HEALTH the mouth ; the other extremit}^ the tail, ends more bluntly. The worms possess a distinct ahmentary canal, and even rudi- mentary sexual organs are present. In the female a uterus is discernible, which wUl frequentlj^ be seen to be fuU of minute free embryos curved upon themselves ; these latter have been observed to become extruded from the vagma, and subsequenth* to move sluggishly about the field of the microscope. The male worm is much smaller than the female, and is only about yV inch long when mature : the female reaches to ^ inch. The long slender head and blunt tail are two characteristics which serve to dis- tinguish these worms from parasites which other^^ise resemble them, such as Draciincnliis and Filaria sanguinis hominis. The small worms are mostly coiled up in cysts, so disposed that their longest diameter is in a line ^^ith the muscular fibres ; and a drop of acid will stimulate them to transient movements if the\' are alive. These cysts lie between the muscle fibrillae, and their walls are sometimes partiallj' or complete^ calcified, so as to give a grating sensation when the ^ finger is passed over a section of the flesh. ^^ , . , ; This calcareous deposit serves to shield the Pj^ g^ parasites from the destructive consequences One of Rainey's capsules, of Salting, and to a shght extent also from ■^ ^ ^ heat when the flesh is being cooked. There ma}- be fiom one to three trichinEe in a cyst. Frequently 25 per cent, of these parasites are enc5'sted in the diaphragm of the host ; and therefore, w^hen possible, a piece of tliis muscle should be procured. The back muscles, on the other hand, are the least attacked. Either a section ma}- be made of the muscle, or it may be teased out \\dth needles ; and preferably, in the case of a long muscle, a point near its insertion should be selected for teasing — since this is a fa\-ourite site for encystment. The affected muscle is seen to be pale and oedematous ; and. if the worms are encapsuled, small, rounded (or, more truly, lemon-shaped), whitish specks, averaging about the size of a ver}^ small pin's head, are visible to the naked eye. These can be made very distinct by means of a hand lens ; but a low power of the microscope should be em- ployed in every case. The most characteristic appearance \\all be got by making a thin longitudinal section of the affected muscle, and immersing this in potassic h}-drate solution of medium strength MEAT 331 — which serves to make the muscle fibres transparent, and leaves the worm exposed in its coiled condition \vithin the capsule. The soaking should not be prolonged beyond a minute or two, or the worm itself will also be cleared up. Glycerine is a good mounting medium when a permanent specimen is desired. Sometimes, owing to a considerable calcareous deposit in and around the walls of the capsule, a view of the worm is obscured ; in these cases a drop of dilute hydrochloric acid, run under the cover-glass, will dissolve this deposit ; or if, as is sometimes the case, one or more oil globules partially obscure the worm, a drop of ether, apphed in a similar manner to the acid, will clear away the fat. There are generally oil globules at the poles of the capsule. The parts of the body which are most hkely to be affected will easily be remembered if it be borne in mind that the worms migrate to their settlements from the gastro-intestinal tract, and chiefly from the commencement of the small intestine. The diaphragm, the liver, the intercostal and abdominal muscles, are necessarily the first encountered, and therefore suffer most ; but in later stages of the infection there is hardly a muscle which may not be affected. It is also a common practice to make an effort to diagnose the presence of the parasites in the hving animal, by examining the eyes and the under surface of the tongue, both of which will frequently show the small pinhead deposits. The dangerous and often fatal disorder created b\^ these worms, as they traverse the gastro-intestinal walls and travel to their encj^stment in the various organs of the body, is most prevalent in those countries where the uncooked or imperfectly cooked flesh of the pig is consumed, as in the form of sausages, ham, etc. Hot smoking and efficient cooking destroy these parasites, but in the latter case the meat must be " done through " — ^i.e., thoroughly cooked through the centre — or some of the parasites, especially when shielded by calcareous walls, may escape the temperature necessary to destroy them — that of 150° F. There are certain small semi-transparent bodies, called " psoro- spermia," or " Rainey's capsules." which somewhat closely re- semble trichinae, presenting as they do small dark oval or elliptical bodies, of greater lengths, however, than encysted trichiuce. They are made up of a thick membrane, formed by smaU hairlike fibres arranged in lines, which encloses small oval or kidney- shaped granular cells, closely adherent together ; and the whole 332 HYGIENE AND PUBLIC HEALTH lies embedded in the muscle substance itself, i.e., the sarcolemma. They are extremely common, and may exist in the flesh of most of the animals used for human consumption, and apparently when eaten they do no harm. Several more obscure bodies, the nature and significance of which we are still more ignorant of, may exist in flesh, such as bodies somewhat resembling pus cells, and others forming minute concretions or tiny hard nodules. Interesting as these are pathologically, they are rare, and when present even in consider- able numbers do not appear to affect the wholesomeness of the meat to any degree. Actinomycosis. — The " ray-fungus " (actinomycosis), one of the " fission fungi," is now becoming recognized as a parasite of commoner occurrence in the ox than was once suspected. The difficulties which stood in the way of an earlier appreciation of this fact arose from the circumstance that both the ante- and post-mortem appearances of the disease closely simulate those of tuberculosis. It has not yet been proved that the disease can be com- munica;ted by the flesh of animals (bovines) suffering from an attack, for the vitality of the fungus when exposed to heat is very shght. The subject is of such interest and importance, however, that a few additional facts are appended. The parasites almost entirely affect the tongue, the jaws (especially the lower one), and the lungs, where they may be detected, by the naked eye, as small dirty white specks commonly about the size of a very small pea, but varying from the tiniest speck up to ^ inch in diameter. The parasites assume, when encysted, a peculiar symmetrical appearance, due to the fact that they consist of small linear elements, thicker at one extremity than at the other, and so arranged that their smaller extremities are all directed towards a central point ; the stellate or rayed appearance thus created Fig 62 ^^ sometimes remarkably regular and uniform. The Distoma tongue when affected is hard and swollen, and (natural size), presents the flattened nodules chiefly upon its dorsal aspect. Distoma Hepaticum. — To examine for these parasitic trema- todes the liver should be taken, and the bile ducts carefully exposed. The parasites will be found as small organisms of a MEAT 333 pale brown colour, in shape like little soles, and provided at their broad extremit}^ with a sucker for attachment to the walls of the bile ducts. Their surfaces are beset with many little warty points, and they average in size from i to i| inches in length, and about | inch in width. They generally attach themselves to the bihary ducts, but they may be found also in the parench yma of the liver. The Life-histories of the Animal Parasites of Man. Tcenia solium. — Portions of the ripe proglottides of the fully matured tapeworm are swallowed by pigs, or more rarely by dogs, monkeys, or man. Very commonly the ova they contain escape and become scattered — some into water, others upon grass or vegetables, where they may certainly survive for some days. If the eggs are ingested, on reaching the stomach the shell becomes dissolved by the gastric juice, and the embryo (a globular body armed with three pairs of booklets) bores its way through the stomach or intestinal walls, and finally comes to rest in some part of the body. It then grows in size, loses its six booklets, and after a time develops a head provided with four suckers, and armed with a circle of minute booklets (" bladder- worm," or Cysticerctis cellulosce). The head grows out from the inside of the bladder, to the wall of which it is attached by a constricted part known as the neck or pedicle. The parasite may remain in this condition for long periods, or may shrive] up and die, for it is incapable of further development until it is ingested by a carnivorous animal. When this occurs, on reaching the alimen- tary canal, it projects its head and neck (by invagination), the bladder part is dissolved by the gastric juice, and very shortly transverse lines appear on the neck, which increase in size and so separate from each other, until after a few weeks a jointed adult tapeworm results, with proglottides charged with ova ready to commence a fresh cycle. The life-histories of Tcenia mediocanellata and Bothriocephalus latus are similar to that of T. solium ; but the bladder-worm of the Bothriocephalus latus is supposed to inhabit some species of fish (perch, pike, and salmon trout ?). or possibly a freshwater mollusc. Distoma hepaticum.— The ova develop, in water, into ciliated embryos, and these undergo in small water snails {Limnceus truncatulus) a further development into larvae. These larvae 334 HYGIENE AXD PUBLIC HEALTH ultimateh' become little organisms resembling tadpoles {cercaria), which either remain encj'sted in water snails, or Jeave them and become attached to grass. They are generally taken up by grazing sheep, but very rarety man also becomes a host. TcBiiia echinococcus. — Of the three or four segments of this tapeworm the last one only contains sexual organs. The ova are discharged \^dth the faeces (commonty of .dogs), and thej' probablv infect cattle, s^^^ne. and man through the medium of water or raw vegetables. On entering the stomach the gastric juice dissolves the shells of the ova, and liberates the embryos, which possess six booklets in two rows ; b}' means of these hook- lets the embryo bores its wa}^ through the waUs of the intestine and develops, chiefly ^^ithul the liver, into so-called " h5^datid cysts " ; i.e.. the booklets are lost, and the formerlj^ solid embrj'O swells out into a vesicle. GeneraU}' a number of protrusions (" daughter cj^sts ") gr-jw from the interior of the vesicle, which itself forms a cyst (" mother cj^st "). To the mother cyst the daughter cj'sts are attached by a pedicle, which ultimately becomes detached. Each " daughter cyst " may develop " grand- daughter cysts," and thus the original echinococcus maj'' become fuU of smaU cysts of varying sizes (" piU-box hydatids ") . Final!}? the httle buds develop into " brood capsules," i.e.. thin walled sacs which remain attached by a pedicle, each sac developing a number of heads, ^vith four suckers and a row of booklets apiece. Thus the encysted form of these parasites possesses the distin- guishing feature of being able to give rise to a large number of scolices, most of which are capable of developing into the adult worm when they enter another host. Rarely the hydatid throws out protusions externally. Ascaris lumhricoides (the round- worm). — The ova of the females are discharged ^^dth the faeces of the host, and then they become capable of furnishing embryos, a power not hitherto possessed. The embryos probabty have an independent existence (possibty in water or in some intermediate host — such as worms or insects) before again entering the human body, and completing their development. The parasites inhabit the small intestine, are of a bro^vnish-yeIlow colour, and are most commonly met wth in people who hve amid dirty surroundings. Oxyuris vermicularis. — These fine, white, thread-like parasites MEAT 335 occupy the large intestine. The ova, unlike those of A. lumbri- coides, contain embryos prior to their discharge ; but probabl}^ these are incapable of further development until they have passed with the faeces, when they may reinfect the same individual or others occupying the same bed, etc., or may pass into water, or become deposited upon vegetables and fruit, and thus again become ingested. The life-histories of Tricocephalus dispar (whip-worm) and Sclerostomum duodenale (common in Egypt and Brazil) have not yet been definitely ascertained. It is not yet certain by what vehicle the ova of the females (which develop in man) infect their host, or whether in either case there is an intermediary stage of development of the parasite. Bilharzia hcematohia. — The male is a white flattened worm, |- inch in length ; posteriorly the sides of the parasite curve to- wards each other, and meet to form a channel, in which the long slender female (| inch in length) lies during fecundation. The ova possess a beak, which generally projects from one end, but sometimes laterally. These ova may be hatched before the parasite leaves the tissues of the original host, but the embryos are not born until afterwards. If the ova find their way into water, their walls swell up and rupture, and the minute embryos escape, armed with cilia, which serve to project them through the water. Probably the embryo becomes attached to some freshwater mollusc (or possibly some fish), and, developing into a cercaria form, is ingested as such by man, and then completes its cycle of development. Trichina spiralis. — When trichinous meat is consumed, the trichina embryos (averaging a little over o-i mm. in length), which resemble small filarise, bore their way through the intes- tines and reach the tissues. They always become encysted in muscle fibres, where they increase in size (up to 0-6 to i mm. in length), and acquire an alimentary canal and sexual organs. The encysted worms remain quiescent for long periods, and may ultimately die ; but if trichinous flesh is eaten they give origin, through their embryos, to a fresh cycle of existence. Horseflesh. By the Horseflesh Act (1889) powers are given to the Officers of the Local Sanitary Authority, for the inspection, examina- tion, and seizure of horseflesh sold for human food, from any 336 HYGIENE AND PUBLIC HEALTH shop or stall not conspicuously labelled " Horseflesh is sold here." It becomes necessary, therefore, in order to check fraud, to be familiar with the chief differences which exist between the meat of the ox and that of the horse. In horseflesh the meat is of a darker red, and sometimes brownish in hue ; it is coarser — the muscular fasciculi being broader — than in oxflesh ; the odour of the fresh meat is different, and after the lapse of a day or two, as the flesh dries, it develops a peculiar faint odour and imparts a soapy feeling to the fingers. The fat is more yellow and soft, and possesses a sickly taste, and, in consequence, it is sometimes removed and replaced by ox fat, which is skewered on the meat. If the bones have not been removed, they will afford an additional clue, inasmuch as they are larger, and their extremities (tuber- osities, etc., for the attachment of muscles and ligaments) are larger and more marked, these signs being additional to some anatomical differences in the construction of the horse's skeleton. For instance, the horse has eighteen ribs, fixed by long unions with the cartilages, and a keel-shaped sternum ; whereas the ox has thirteen ribs, jointed to the cartilages, and a flat and broad sternum. For these reasons horseflesh is usually boned before it is offered for sale as beef. The tongue, kidney, and the liver of the horse, together with some other organs, are also occasionally placed on sale as the corresponding organs in the ox. The tongue of the horse is, however, broad and rounded at its free end, instead of pointed, as in the ox ; and if the hyoid bone is attached, it is found to be made up of five parts, whereas that of the ox consists of nine. Moreover the base of the horse's tongue is smooth on its dorsal aspect, whereas that of the ox is rough from very prominent papillae. The epiglottis is smaller and more pointed in the horse. The Hver, whether of the ox or sheep, consists of one very large lobe and another relatively small one ; in the horse there are three large and distinct lobes, and a fourth re- latively smaller one, and there is no gall bladder. The kidney of the horse is more heart-shaped and cannot be mistaken for the long lobulated kidney of the ox. The heart of the horse differs from that of the ox in being less conical, darker, softer, and with less fat at its base ; and without the bone that is found in the heart of the ox. MEAT 337 Cooking. The cooking of meat preserves it from putrefactive changes by heat sterilization, increases its digestibihty, and produces that palatabihty which a civilized taste demands. By cooking, the connective tissue binding together the - muscular fasciculi tends to become disintegrated. The con- nective tissue is changed into more or less soluble gelatin, the meat is made tender and easier to chew, and the proteids and fats are more perfectly exposed to the solvent action of the digestive juices. The flavour induced by cooking stimulates the secretion of the digestive juices. In all cooking processes meat loses weight, usually from 20 to 30 per cent. In boiling a joint, the meat should be plunged into boiling water for five minutes to coagulate the outside albumin and retain the salts, extractives and soluble substances in the interior. The remainder of the boiling should be con- ducted at a temperature below 170° F. — which is the temperature at which most of the albuminoids coagulate — in order that the meat may not become tough, dry, and indigestible. On the other hand, in making broth the meat should be cut into small pieces, and placed in cold water, which is gradually warmed to 150° F. ; in this way the salts and extractive matters pass out of the meat into the broth, together with a certain proportion of the more soluble albuminoids. In baking and roasting, the joint of meat should first be sub- jected to an intense heat, in order to coagulate the outside albumin and retain the soluble juices. After a few minutes the temperature should be lowered and the roasting or baking com- pleted at 180° F. to 200° F. Aromatic products are foimed in roasting and baking which are volatilized ; some of the fat is melted and flows out of the jokit together with gelatine and extractives to form the gravy. The gas cooking ovens, which have now come so largely into use, present several advantages over kitchen ranges heated by coal. They are very cleanly ; the temperature of the oven can be adjusted with great nicety by regulating the consumption of gas ; there is the convenience of the oven being ready for use in a few minutes after the gas is lighted ; and as soon as the cooking is finished the gas can be turned out. It is very difficult to distinguish between a joint of meat baked in a gas oven and 22 338 HYGIENE AND PUBLIC HEALTH one roasted before an open fire, if the gas oven is properly ventilated and a flue is provided to carry off the products of combustion. If the ventilation is insufficient either in a gas oven or ordinary close range oven, the meat becomes sodden in its o\\ii vapours, and in the case of the gas o"\'en also with the gas products, which give it a disagreeable taste and odour. Gas cooking stoves should be pro\nded with Bunsen burners, arranged round the side of the oven at the bottom ; and the oven walls should be double, the space between the plates being well packed with slag wool to prevent loss of heat. No soot is formed in gas cooking, and there are no dust, ashes, and dirt, as in a coal cooking range. i\Ieat can be -preserved b^^ drying in strips in the sun, caUed jerking ; by salting ; by canning, i.e., by heating and thereby sterilizing the meat in tins, which are hermetically sealed b}^ solder at a high temperature ; and by refrigeration in the raw state — a process now very largely used, the refrigeration chambers on board ship permitting of the importation into this country of meat from South America and the Australian colonies. The last process is by far the best, as the freshness and nutritive value of the meat remain unaltered. It is not easy to distinguish a New Zealand joint of mutton from the home product — if it is properly thawed before being cooked. The low temperature of the ice house (not less than 6° F. below freezing point) does not destroy aU bacteria, but prevents the development of the organisms of putrefaction. The preser\'ation, for man}' ages, of the Siberian mammoth in its icy casing is a notable example of the antiseptic properties of great cold. Frozen meat can generally be disting"uished b}' the uniform and darker colour of the meat, even the fat being stained by the exuded juices from the lean parts. It is also softer to the touch. The external surface of the meat is duller and browner than that of fresh meat, and the joints are not usuall}^ so well dressed as in the case of home killed meat. American killed carcases can generally be told by the bruises about the legs, hy which the animals are hoisted prior to slaughter. Effects of Diseased or Unsound Meat. It was formerly believed that thoroughly cooked meat is not likely to produce any injurious effects, even when derived from a diseased animal, or after putrefactive changes ha^'e commenced in it ; but recent research tends to show that meat which is MEAT 339 derived from a diseased animal, or vvliich has become tainted by the presence of putrefactive bacteria, may possibly be cooked sufticiently to destroy the microbes themselves, whilst the poisonous products of the microbes are unaffected by cooking. Tainted meat, eaten hot, is sometimes harmless, but when taken cold may produce symptoms of poisoning, the bacterial ferments having had time to act upon the albuminous sub- stances of the meat. Where the meat is only partially cooked, and underdone in the centre, danger is still more likely to arise ; and in such cases sjmiptoms of poisoning, occasionally ending fatally, have been observed in those who have partaken of decomposing food. A large number of instances of meat poison- ing have been connected with the consumption of sausages, pies, and hams (Welbeck, Nottingham, etc.). The symptoms, which in most cases supervene in from six to eight hours, are those of violent irritation of the alimentary tract, and are characterized by acute vomiting, diarrhoea and colic, increased mucous secre- tions, cramps in the extremities, and failure of the heart's action. The symptoms are produced by either putrefactive bacteria or special bacilli in the food, or the products of their action upon albuminous substances — the poisonous alkaloids, ptomaines, or albumoses. Where the poisoning is due to*putrefactive products it is termed " ptomaine poisoning." The organisms most generally concerned are Bacillus froteus and coli. These are killed in ordinary cooking, and the toxin of B. proteus is also destroyed. Where the illness commences within twelve hours after par- taking of the food, the probability is that the poisonous condition of the food was due to already formed toxins ; but where a period of twelve to forty-eight hours or longer supervenes between the consumption of the food and the illness, the action of bacteria is indicated, requiring, as they do, time for their growth and development, and for the production within the body of the toxins, the absorption of which gives rise to the symptoms of poisoning. In some instances the symptoms of ptomaine (food) poisoning have borne a strong resemblance to those indicative of poisoning by the alkaloid muscarine. Besides a muscarine-like poison, there appears to be another poison formed in decomposing flesh, which produces symptoms analogous to those of atropine, viz., quickened pulse, paralysis ■of the muscles of the eyeball, diihculty of swallowing, dryness of 340 HYGIENE AND PUBLIC HEALTH the mouth and throat, constipation, and diminished secretion from the mucous membranes. This poison exerts an antagon- istic effect upon the muscarine-hke poison ; and in different cases one of these poisons may predominate over the other, and produce its characteristic symptoms more or less modified. Tlie group of symptoms similar to those occurring in atropine poisoning give rise to the condition known as " botulism," from the circum- stance that they have been most frequently observed as the I'esult of eating bad sausages {botulus — a sausage). The toxin of " botulism " is produced by the anaerobic Bacillus botulimis, and symptoms generally appear in from twenty-four to thirty-six hours. This condition is to be distinguished from allied condi- tions which are characterized almost exclusively by gastro- intestinal symptoms, and are due to the Bacillus enteritidis of Gaertner, or the paratyphoid organisms, the agents most com- monly found to be causative of meat-poisoning. The animal prior to death had probably suffered from disease of the gastro- intestinal tract, or some form of septic infection, and the out- breaks are most frequent in summer. The toxin is very resistant to heat ; and the mortality of outbreaks varies from 2 to 5 per cent, of those attacked. The diagnosis of this form of poisoning is based upon the isolation of the bacilli from the stools, or (after death) the organs of the body, the feeding of mice, etc., upon the cultures, and the agglutination test with the patient's serum upon known cultures of the various organisms. The presence of alkaloidal substances may possibly account for the ill effects produced by eating oysters, mussels, and some kinds of fish, such as mackerel, when out of season, and pork in hot climates. It is maintained by some that scurvy is a form of toxic poison- ing from food. There is also some evidence that acute diarrhoeal attacks maj^ be due to the ingestion of sound, wholesome food, which has been accidentally inoculated with the Bacillus enteritidis of Gaertner after cooking. A recent investigation by one of the authors into an outbreak of acute febrile diarrhoea attacking a very consider- able proportion of those who had partaken of a certain meal, showed that the cook had suffered from an acute diarrhoea whilst engaged in preparing the food on the day previous to the meal. The food so prepared was stored during the night (warm weather prevailing at the time), and was eaten cold on the MEAT 341 following day. All the food was sound when 1 eceived for cooking, and no particular article of food was especially indicated as the source of the mischief. In a great majority of the attacks of diarrhoea there was an incubation period of thirty-six to forty- eight hours. The evidence pointed strongly to contamination of the prepared food by the dirty hands of the cook whilst suffering from an acute diarrhoea, the probability being that Gaertner's bacillus was directly inoculated into the food by this means. In investigating a case of food poisoning, it is best to enter on a paper every article that has been consumed in the affected household or households, and then by a process of exclusion to determine the article or articles that have been eaten in common by the sufferers. The suspected article must then be traced and secured, and the correctness of the conclusion confirmed by feeding experiments on one of the lower animals and a bacteriological investigation. There are certain diseases of animals which are kno^vn to be, or beheved, on good grounds, to be transmissible to man. These are anthrax and malignant pustule, tubercle, foot and mouth disease, rabies, glanders and farcy in horses, Cysticercus cellulosce and bovis in the pig and ox, respectively, and Trichina spiralis in the pig. With the exception of cysticercus and trichina these diseases are far more frequently transmitted to man by other means than by the consumption of diseased flesh. But it must be remembered that such transmission is possible in respect of several diseases, and would probably be much more frequent than it is, were it not for the precautions taken to prevent the sale of unsound meat, and for the safeguard of cooking. In some diseases it is generally held to be sufficient to condemn the affected parts, if the rest of the carcase appears healthy. The Report of the Royal Commission (1895) appointed to inquii'e into the effect of food derived from tuberculous animals on human health, is worthy of careful study. As regards the prevalence of tuberculosis in food animals the records of the Copenhagen and Berlin slaughter houses show that from 15 to 18 per cent, of the oxen and cows slaughtered are tuberculous, of calves only from o-i to 0-2 per cent, are tuberculous, of sheep only 0-0003 to 0-0004 P^i" cent., and of swine r'55 to 15-3 per cent., the latter figure applying to the Copenhagen and 342 HYGIENE AND PUBLIC HEALTH the former to the Berlin swine. For milch cows there are no figures available on a large scale ; but of 300 milch cows which were slaughtered in Edinburgh in 1S90. on account of the appear- ance of epidemic pleuro-pneumonia there, 120, or 40 per cent.,, were found to be tuberculous on post-mortem examination. There is no doubt that milch cows suffer far more frequentty than oxen, heifers, or bulls, and that tuberculosis is more fre- quently found in the carcases of cows than in any other animal slaughtered for sale. From the experiments made for the Commission b}' Sidnej^ ]\Iartin, it appears that tuberculous deposits are but seldom found in the meat substance — ^the muscular tissue — of the carcase of an affected animal. They are principally found in the organs, membranes, and glands. In cases of mild, moderate, and locahzed tuberculosis, if the affected organs are discarded, and if great care is exercised to prevent smearing and contamination of the meat hy caseous or other tuberculous material adhering to the butcher's hands, knives, and cloths, there is no reason why the rest of the meat should not be used for human consumption. As at present practised, howe^"er, in this country, the slaughtering of a tuberculous animal almost necessarity involves the contamination of the surfaces of the joints of meat \\dth infective tubercular material. In cases of generalized tuberculosis, not only is the risk of con- tamination of the meat in dressing the carcase greatest, but there is also no certainty that tubercular material may not be present in the muscular substance, or in glands in the connective tissue between the muscles, and consequently the carcases of animals so affected should be condemned and destroyed. The necessity for skilled and weU trained meat inspectors is dwelt upon by the Commissioners, who were of opinion that the following principles should be observed in the inspection and condemnation of tuberculous carcases of cattle : — - " (a) When there is miliary tuberculosis of both lungs ..... (fe) %\Tien tuberculous lesions are present on the pleura and peritoneum (c) When tuberculous lesions are present in the muscular s5-stem or in the lymphatic glands embedded in or betu"een the muscles (d) When tuberculous lesions exist in any part of an emaciated carcase . The entire carcase and aU the organs may be seized. MEAT 343 The carcase, if otherwise healthy, shall not be tuberculous lesions shall be seized. " (a) When the lesions are confined to the \ lungs and the thoracic lymphatic glands ..... (b) When the lesions are confined to the liver ' condemned ; but every (c) When the I'esions are confined to the ^ part of it containing pharyngeal lymphatic glands (d) When the lesions are confined to any combination of the foregoing, but are collectively small in extent " In view of the greater tendency to generalization of tuberculosis in the pig, we consider that the presence of tubercular deposit in any degree should involve seizure of the whole carcase and of the organs. " In respect of foreign dead meat, seizure shall ensue in every case where the pleurae have been ' stripped.' " As regards cow's milk, the Commissioners found that there was no evidence of danger to the consumer, even when the milk is derived from a tuberculous animal, so long as there is no disease of the udder. But the affection of the udder may be present in a cow not otherwise markedly affected with tuber- culosis ; and the infection once implanted in the udder may spread with alarming rapidity. The milk of cows with tuber- culosis of the udder possesses a high degree of virulence ; and appears to be virulent even when no tubercle bacilli can be demonstrated in it. The Commissioners held that all udder diseases should be notified, and that any one selling milk from a cow with diseased mammary glands should be liable to a heavy penalty ; they advocate systematic inspection of cows by veterinarians as a means to this end. This recommendation was given effect to by the Dairies, Cowsheds, and Milkshops Order of 1899, by which Article 15 of the Order of 1885 is amended, so that the expressions in the article which refer to " disease " shall include, in the case of a cow, such disease of the udder as shall be certi- fied by a veterinary surgeon to be tubercular. Such tubercular disease ought to be suspected when a painless hard lump, slowly enlarging, can be detected in one or more of the quarters of the udder. Further recommendations of the Commissioners were to the effect that stock owners should be encouraged to test animals by the gratuitous supply of tuberculin, and the offer of the services, free of charge, of a veterinary surgeon ; that better sanitary conditions should be enforced in cowsheds ; that the closing of private slaughter houses, and the enforced use of public slaughter houses should be brought about, to ensure a uniform 344 HYGIENE AND PUBLIC HEALTH and equitable system of meat inspection ; and that foreign meat should be required to bear a mark of inspection and approval stamped upon it at the time of killing. They do not recommend compensation to the owners of condemned carcases. The influence of cooking upon tuberculous meat and milk was investigated by Sims Woodhead, who arrived at the follow- ing conclusions : "In the boiling and roasting experiments, as ordinarily carried out in the kitchen, the temperature, however high it may be near the surface, seldom reaches 140° F. in the centre of a joint, except in the case of joints under 6 pounds in weight. Ordinary cooking is quite sufficient to destroy any smeared (infective) material that remains on the outer surface of the meat, but it cannot be relied upon in the slightest degree to render innocuous the same smeared material when in the centre of a roll." Rolled meat, the central parts of which had become smeared by tubercular matter, were not sterilized by any process of cooking, unless the roll was less than 4 pounds in weight. The least reliable method of cooking, qua sterilization, is roasting before the fire, next comes roasting in an oven, and then boiling. Probably tuberculosis is not conveyed through the consump- tion of the flesh of tuberculous animals to any great extent. This view is supported by the fact that the reduction in the mortality from tuberculosis has been very marked during the age-periods in which meat is most largely consumed ; and the great reduction in mortality, between 1851 and 1910, has been coincident in point of time with a large increase in the amount of meat consumed in this country. As regards the sterilization of tuberculous milk, it would appear that absolute safety is only to be attained by raising the milk actually to the boiling point. The Commissioners were of opinion that the innocence of tubercular milk treated in this manner was not entirely demonstrated to their satisfaction. When the tuberculous material in milk is raised to temperatures insufficient for the actual destruction of the virus, it is possible to obtain from the most deadly tuberculous material a weaker sort of tuberculous matter, so tardy in its operation upon test animals as to simulate the slower forms of consumption seen in the human subject, or when used to feed pigs — animals having some specialities of throat (tonsillar) structure like that of man — giving rise to chronic enlargements of the cervical glands, MEAT 345 resembling the scrofulous glands so common in children. These observations, the Commissioners think, are suggestive of the possibilitj'' of widety prevalent forms of human tuberculosis having an origin in milk. Bovine and porcine cysticerci, which develop Tcenia medio- canellata and Tcenia solium respectively in man, are probably little affected by salting and smoking. There is, however, good ground for believing that exposure for some minutes to a tempera- ture above 150° F. destroys them. The same may be said for the Trichina spiralis ; only the temperature must be somewhat higher, as the worm is surrounded by a dense capsule which retards the passage of heat. The most common condition which renders flesh unfit for human consumption is putrefaction. The whole carcase should be condemned in marked emaciation from disease (but not mere leanness), in glanders, anthrax, generalized tuberculosis, measles and trichinosis. Localized inflammatory conditions or suppuration, early actinomycosis, localized tuberculosis, liver-fluke and echinococci, do not justify the condemnation of the whole carcass, if the rest of the flesh is firm and of a good colour. The meat of animals which have been slaughtered in the early stages of acute inflammatory disease, foot and mouth disease, and epidemic pleuro-pneumonia is probably quite wholesome if well cooked, unless the animals have been drugged with medicines before killing. The evidence as regards the possible bad effects from the use of meat taken from animals which have suffered from rinderpest or cattle plague, swine fever, braxy or splenic apoplexy (sheep), and smallpox (sheep), is conflicting. A certain amount of the meat condemned in public slaughter houses may be used for human food under the following circum- stances : (i) It may be dealt with in public kitchens under pre- cautions which will ensure a thorough cooking, and the cooked meat or soup made therefrom may be sold at a small charge — as in the Freibanks in Germany, or (2) the meat can be sterilized by steam under pressure, and then sold. If, however, it is unfit for human food under any circumstances, it should be either made into manure under supervision, or, failing this supervision, it should be saturated with petroleum, carbolic acid, or mineral acids, before it is allowed to be removed, in order to ensure that it will not be sold as food. 34^ HYGIENE AND PUBLIC HEALTH The arguments in favour of public abattoirs may be sum- marized as follows : They constitute the only possible means of proper and systematic inspection at the time of slaughter, such inspection being necessary to prevent the sale for human food of diseased meat. The consumer would have a guarantee that home killed meat was good and wholesome, and this would prob- abl}'' increase the demand for it. The better provisions for slaugh- tering and cooling the meat, and the diminished handling, would favour its good appearance when exposed for sale. If public slaughter houses are constructed near railway stations, the driving of cattle through crowded streets is avoided. On the other hand, butchers as a body do not favour these establish- ments ; and slaughtering is likely to be done elsewhere, unless private slaughter houses are at the same time abolished, and only stamped meat allowed to be sold. Butchers argue that the hand- ling and carting, entailed by the removal of the meat from the abattoir, tend to destroy the characters of home killed meat, but this argum.ent does not apply if suitable carts are used in which the meat is suspended by hooks from the roof. The buildings of a public abattoir should include lairs for animals about to be slaughtered, separate places for such as are unsound, separate slaughter houses for the different kinds of animals, cold storage for meat, buildings for the treatment and disposal of the offal and diseased parts, stables and sheds for horses and vehicles and the drivers' dogs, and a market room with restaurant. There must be an ample water supply, and the means of making ice should be provided. Fish. Though many parasites attack fish, the encysted form of the tapeworm called Bothriocephalus latus, which is sometimes found in the pike or turbot, is the only one which is known to be harmful. Oysters and mussels have been known to produce poisonous symptoms, and nettlerash is an occasional consequence of the con- sumption of the latter. The common symptoms of poisoning are nausea, vomiting, dyspnoea and muscular weakness. The toxic substance of poisonous mussels is an alkaloid'called mytilotoxin ; but, as in the case'^of oysters,' the S5miptoms of poisoning may be due to infection or intoxication from the Gaertner, paratyphoid, or even the botulinus, bacilli. Such mussels generally appear MEAT 347 to be unhealthy, with large livers. Both mussels and oysters, fed in sewage polluted water, have conveyed the infection of enteric fever. There are few points so easy to detect as commencing putridit\' in fish ; this is fortunate, inasmuch as decomposition sets in rapidly, and appears to be more generally productive of poisonous s3Tiiptoms than decomposing meat — the sjnnptoms produced being very similar in both cases. The bright gills, the prominent eyes, the elastic resistance of the firmly adherent flesh, and the absence of any but the characteristic odour, are all evidence of freshness. The soft inelastic feel of the fish, and the unpleasant odour, furnish the chief clue — and the most reliable — to com- mencing decomposition ; since it is possible to revive the gills bj'- artificial colouring agents, and to keep the eyes prominent by a small piece of stick, fixed transversely in the head, so that it presses the eye outwards on either side. Meat Extracts. Many meat extracts are now upon the market, the tendency being for the public to over-estimate their food value. They consist of the extractives of meat, and not of the meat itself ; and they act as stimulants and regulators of digestion rather than as true foods capable of providing the necessary amount of nitrogenous material for the needs of the body. A meat extract should consist of a golden-brown sticky sub- stance with a pleasant meaty odour. It should never be hard, and should attract moisture strongly from the air. The reaction should be slightly acid. The usual method of preparation consists in heating raw meat, which has been finely divided, with a little water under pressure. The extract thus made is filtered and evaporated in vacuo in the open. It is essential that a temperature below 75° C. be employed if all gelatine is to be excluded (Beveridge). The extract thus made contains the flesh bases or extractives and mineral matters of the meat, but is free from albumin, meat fibre, gelatine, and fat ; but in some of the meat extracts on the market these substances and also vegetables are subsequently added in order to give the extract a certain food value. A meat essence is a more liquid extract, containing more water, but has the same colour, odour, and reaction. Meat juices are prepared in the cold by subjecting finely divided meat to strong pressure and ultimately concen- 348 HYGIENE AND PUBLIC HEALTH trating by evaporation tn vacuo. They contain the soluble proteins of meat. These substances, prepared as above, are only to a very limited extent foods or tissue-builders ; and produce neither heat nor energy. They are chiefly valuable in sickness or fatigue as adjuvants to other foods, as they excite the flow of gastric juice, aid digestion, and increase appetite. Beveridge gives the anatysis of a well-known meat extract as follows : Water, 37-2 per cent. ; mineral matter, 22-2 per cent. ; fat, 1-07 per cent. ; total nitrogen, 7-1 per cent.; equivalent flesh bases, 18-62 per cent. Milk. Milk is the natural food of all animals belonging to the Mam- malia for a longer or shorter period following their birth. It therefore contains all the constituents of the standard diet, and these in the proportions most favourable for the growth and development of the young animal. The varying proportions of the different solid constituents of milk as secreted by the human female, the cow, the ewe, the goat, and the mare, are shown in the following table. The presump- AvERAGE Percent A (iE Composition by Weight. Constituents. Cow. Mare. Goat. Ewe. Woman. Specific gravity 1032-50 1036-12 1032-70 1039-30 1032-00 iFat . 376 1-76 5-80 11-28 3-14 Caseinogen, albumin, ! etc. 3-50 3-S8 4-20 8-83 2-53 Sugar 4-75 r87 4-94 3-S8 6-26 Ash . . . . 0-72 0-39 i-oo 1-09 0-32 Water 87-27 88-40 84-06 1 75-22 lOO-OO 8775 Total ] 00-00 lOO-OO lOO-OO 100-00 tion is that the natural milk of one young animal is not suited for the nutrition of another animal of a different species. This is cer- tainly true of the human infant, which thrives far better on human milk than on cow's milk. In cow's milk the caseinogen is in much too large a proportion as compared with human milk ; the fat and salts are also in excess, whilst the milk sugar is ver}^ deficient. Two-thirds of the proteid of human milk consists of lactal- bumin, which is a soluble form of albumin not curdled by acids, MILK 349 and coagulating at 165" F. The other third part of the proteid of human milk is caseinogen, which is an insoluble form of albumin, ■"■ and forms a dense curd with rennin and acids ; it is not coagulated by heat. In cow's milk, on the other hand, only about one-tenth part of the proteid is in the form of lactalbumin, the remainder being caseinogen (see p. 350). In the process of digestion, milk is curdled by the gastric juice ; the caseinogen and fat separate as curd, whilst the sugar, the soluble albumins, and the salts remain dissolved in the water as whey. Owing to the small proportion of caseinogen in human milk, the curd formed in the stomach is a loose flocculent mass, easy of digestion and assimilation ; whilst cow's milk, owing to the abundance of caseinogen, clots in putty-like or wet cheese- like masses. The cow's milk curd is far less easily digested ; it may give rise to dyspepsia, flatulence, and diarrhoea, and some of it may be passed unaltered in the faeces. Ass's and mare's milk approximate much more closely in composition to human milk, and give a loose, flocculent, and easily digestible curd. Goat's milk is too rich in fat and proteids, but it also forms the proper kind of curd in the human stomach, and the circumstances that her excrement is solid and her tail short, tend to favour the cleanliness of the milk. For hand-fed infants under nine months of age, if cow's milk is used, it should be given diluted with water, and milk sugar should be added. The dense clotting may be, to a certain extent, prevented by the addition of some mucilaginous substance to the milk, such as pearl barley water well boiled and strained, which has the mechanical effect of preventing the particles of casein coming too close together ; and the curd thus formed is looser and more easily attacked by the digestive juices. Wright and Poynton have shown that the dense clotting of cow's milk with rennet, as occurs in human digestion, may be prevented by partial removal of the lime salts in the milk. By adding 2 or 3 grains of citrate of soda to each ounce of milk, citrate of lime is precipitated, and the clot which rennet produces is then much lighter and more flocculent, resembling the clot formed with human milk. Humanized cow's milk is now very largely used in the feeding of infants. The principle to be observed in the humanizing pro- ^ Caseinogen probably exists in milk in combination with phosphate of lime, which helps to keep it in solution. 350 HYGIENE AXD PUBLIC HEALTH cess is to prepare a fluid which shall have, as far as practicable, the composition of human milk so far as the chief constituents are concerned, and which shall also be devoid of organic life. To effect this, the insoluble caseinogen of cow's milk must be reduced to the proportion present in human milk, the lactose must be increased to the right proportion, and the resulting mixture must be Pasteurized, i.e., heated to a temperature of 70° C. (about 160° F.) for twentv minutes. Pasteurization ensures the destruc- Humaa Milk. Cow's Milk. Satts 03Z ctalbiunen 35 SalisOJZ Total Solids, i2'27. Total Solids, 12*73. Fig. 63. — Percentage Composition of Solids of Human and Cow's Milk. tion of most pathogenic organisms, but does not sterilize (destroy all organic life). Sterilization may be necessary, if the milk has to be preserved for any length of time, but the high temperature to which the milk has to be submitted (over 170° F.) causes coagu- lation of the lactalbumin, with the result that the milk is clotted, and loses in appearance and digestibility. The taste of the milk also is altered, the fine emulsification of the fat is partlj' destroyed, and the caseinogen is rendered less easy of digestion. MILK ;',5i The whey cream mixture is probably the simplest and most satisfactory form of humanized cow's milk. The method of preparing this mixture is as follows : A pint of milk is allowed to stand in a cool place for three hours. The cream which has risen to the top is then separated by skimming. The skimmed milk is then divided into two equal parts. A small piece of rennet is then added to one part, and the curds, when formed, are strained off, leaving the whey. This whey is heated to 150° F. to destroy the rennet ferment remaining in it, and the other half of the skimmed milk and the cream are added to it. Add 175 grains (3 drachms) of milk sugar (lactose) to the mixture, and sufficient lime water to render very faintly alkaline. Then heat to 158° F. for twenty minutes. The advantages of the whey cream mixture are (i) that the excess of caseinogen in the cow's milk is removed, whilst the soluble and easily digested lactalbumin is retained. (2) The whey makes a better emulsion with the fat (cream) than water would, and yields a finer curd. Koumiss is a fermented drink prepared from mare's milk in Russia and Tartary ; in this country it is now largely made from cow's milk. It is very easily digested and absorbed, and is a valuable food for invalids. All the solid constituents of milk are dissolved in the water of the milk, with the exception of the fat, which exists as innu- merable minute globules floating freely in the fluid. Cow's Milk. The average milk secretion of a healthy cow may be taken as 20 to 25 pints daily ; but the quantity of milk and its richness in solid constituents depend largely upon breed in different cows, and in the same cow upon its age, the age of the calf, and the season of the year as influencing its food. As a general rule, it may be stated that cow's milk should have not less than 12-5 per cent, of total solids, of which 3-5 per cent, is fat, and 0-7 per cent, is salts ; the specific gravity of the milk being 1031 or 1032, and the percentage of cream by volume not less than 10 per cent. To make up the standard diet for an adult man, of 23 ounces of water-free food, about 9 pints of milk must be consumed ; but in such a diet, the albuminoids, the fat, and the water would be far in excess of the requirements of the system. A prolonged course of milk diet — no other food being given — has been found 352 HYGIENE AND PUBLIC HEALTH exceedingly useful in certain forms of kidney disease. In some cases skimmed milk only should be taken, and a portion of the casein should be separated by rennet, (a preparation from the gastric mucous membrane of the calf). By this means the diet is deprived of much of its fat and albuminoids ; and the other constituents, being very assimilable, give the kidneys little work to do in elimination, whilst the water clears away disease products from the uriniferous tubules and promotes and restores healthy function. Many persons, from constitutional idiosyncrasy or weak digestion, cannot digest milk. If the milk is first curdled by the addition of a few drops of acetic acid or a little rennet, and the curds and whey thus formed beaten up altogether, and a little salt and pepper added, a most digestible dish is prepared, by reason of the stomach being saved the operation of curdling, which is the cause of the disagreement. When milk is allowed to stand, some 70 per cent, of the cream rises to the top of the vessel in about eight hours. A centrifugal apparatus is now largely used for the separation of cream ; quite 95 per cent, of the fat being removed by this method. Skimmed milk generally contains about i per cent, of fat ; whereas separated milk generally contains less than 0-3 per cent. Slightly more fat might be obtained by skimming if a longer period were allowed for the milk to stand ; but after a time, depending upon the temperature, milk undergoes the lactic fermentation, and becomes markedly acid, the sugar being converted into lactic acid by the agency of a special bacterium, which grows and multi- plies in the milk. The milk becomes curdled, and the whey separates from the curd. At a later stage the lactic acid is con- verted into butyric acid by means of another bacterium or bacillus ; the milk at the same time becomes turbid, and putre- factive changes set in from the growth of Bacterium termo and other saprophytic organisms. Sour milk has now come largely into use for the treatment of intestinal dyspepsia. The organisms which break down lactose into lactic acid appear to be chiefly of two kinds — the baciUus of Massol, or the Bulgarian bacillus (Youghourt), and the Strepto- coccus lactidis. The milk is first sterilized by heat, and then inoculated with a pure culture of the lactic acid bacilli, the milk being incubated at 37° C. for several hours, until sufficient lactic acid is formed. In the intestine the lactic acid baciUi appear MILK 353 to have the property of restraining the growth of the organisms which cause fermentation and putrefaction, whilst they them- selves are harmless. After a time a growth of the lactic acid bacilli is established in the intestine, as shown by the appearance of these organisms in the faeces. Care must be taken to thoroughly sterilize the milk in the first place, and subsequently to add nothing except a pure culture of lactic acid organisms, otherwise undesirable fermentations may be induced causing the formation of toxic products. Milk may be sterilized, and thus preserved from fermentation and decomposition, by keeping it at a temperature of 212° F. for five minutes in sterilized vessels. The milk is then raised to a boiling temperature and hermetically sealed. A closed vessel should be used, because in an open vessel a skin forms on the surface of the milk, and then the vitality of the organisms is not so readily destroyed. Although the term " pasteurization " is a term applied to denote a procedure the details of which may vary considerably, it may be defined as the exposure of milk (previously cleansed by filtration or centrifugalization) to a temperature not exceeding 70° C. for a short period ; and then rapidly cooling it to a tem- perature as much below 16° C. as possible. Under such con- ditions it is possible {a) to reduce the micro-organisms which are capable of being cultivated on artificial media to less than 5 per cent, of those which can be cultivated from the original milk ; to thereby destroy or inhibit the fermentation bacteria so as to delay the natural souring of the milk some twelve to twenty-four hours, the milk meanwhile keeping perfectly whole- some ; (b) to destroy the specific organisms of tuberculosis, diphtheria, enteric fever, cholera, and dysentery, and doubtless also, in large measure, those organisms that are causal of zymotic diarrhoea ; (c) to do away with the necessity for drugging the milk with harmful chemical preservatives. It is, therefore, a valuable measure of protection against the recurrence of those milk-borne epidemics which have figured largely in the epidemio- logical records of this country ; it is a useful means of reducing the grave risks of the infection of tuberculosis in milk ; and the evidence is overwhelming that it reduces the suffering and mortality among infants who are artificially fed in the summer months. For trade pasteurization, which has for its object the improve- 23 354 HVGmN£ AND i>UBLlC HEALTH merit in the keeping qualities of the milk, a temperature of about 70° C. is usually maintained for only about a minute or so. Milk is also preserved in a desiccated form as a powder, the wat€r being expelled by evaporation ; or it is highly concentrated, mixed with sugar, and then sold as " condensed " milk. Many of the so-called condensed milks on the market are condensed skimmed or separated milks, i.e., milk from which most of the fat has been abstracted prior to condensation. Such^prepara- tions are quite unsuited for infant feeding, and they have been well styled " starvation brands." It has lately become the custom, especially in the summer months, to add a little formalin, or boracic acid and borax to the milk as a preservative against fermentative changes. What- ever antiseptic is used, it is consumed with the milk by the customer, and adds another danger to the already long catalogue attributable to milk. This employment of agents, termed antiseptics, which will prevent the development of micro- organisms in food, is extensively practised. The antiseptics most commonly employed in different kinds of food are : Borax and boracic acid, salicylates, benzoates, formic aldehyde (used as " formalin," a 40 per cent, solution of formic aldehyde), sodium chloride, and vinegar ; but saltpetre, chloride of ammonium, sulphate of calcium, alum, spirits of wine, sulphurous acid, bisulphite of lime, and sulphate of copper, have all been employed. There is no doubt that the unrestricted use of these agents should be condemned ; for although in the case of those most commonly employed their use has not been proved to cause any direct harm to consumers, it is a reasonable belief that the ignorant employment, even of such a substance as boric acid, may effect slight and indirect injury to health, and is capable of seriously interfering with digestion. Dr. H. W. Wiley, of the United States Department of Agriculture, demonstrated in 1905-7, from feeding experiments upon twelve healthy young men, that formic aldehyde, boric acid and salicylic acid are substances which when added to food, even in small quantities, may exercise a harmful effect on digestion and health. Few of these agents enter normally into the constitution of the human body ; and at least they must be regarded as foreign bodies whose ingestion works no possible good, and which, not being foods, do not in any way make amends for the additional work of elimination MILK 355 which their presence demands. Moreover, they enable vendors or manufacturers to deal with stale or badly prepared food, to the prejudice of the more honest tradesman. If the adultera- tion is permitted, the vendor should at least be compelled to state the nature and amount of preservative employed. Opinion is somewhat divided as to the actual harm which results from the use of very small quantities of preservatives in food ;■*• but the use of such agents is unnecessary ; and it is certain that even so rapidly decomposable a food as milk, when collected and stored with proper regard to cleanliness, and quickly chilled, can be sufficiently preserved, even in the hottest weather, to meet all the requirements of its distribution and use. Food purveyors have very little knowledge as to the amount of preservative it is necessary to add, and there is nothing to prevent such an article as milk from being dosed more than once ; moreover an injurious quantity of preservative may easily be consumed in a meal which includes a number of foods, in each of which there is only a small quantity of preservative. The practice of using preservatives in food also leads to uncleanly treatment, and is often the means employed to render unwholesome food saleable. In several countries preservatives are expressly forbidden by law, and successful results are obtained by pasteurization, sterilization, refrigeration or chilling. The Departmental Committee ap- pointed to inquire into the use of preservatives and colouring matters in food in the year 1899, recommended the prohibition of the use of formic aldehyde, and that salicylic acid should not be used in greater proportion than i grain per pint in liquid food, and I grain per pound in solid food. The use of any preservative and colouring agents in milk was condemned. Certain boron compounds might be used in cream and butter when they do not exceed 0-25 per cent, and 0-5 per cent, of boric acid in cream and butter respectively. They found that no preservatives should be used in any invalid or infant food, and that copper salts should not be used for greening preserved fruits and vegetables. Experiments have shown that boric acid in the proportion of 20 grains to the pound prevents objective decomposition, such as is detected by smell, without affecting the growth of coli ^ It is possible that the " epidemic eczema or dermatitis " which has been observed of recent years in various metropolitan poor law infirmaries, and which, attacking principally inmates of advanced age, caused in some outbreaks the deaths of 10 per cent, of those attacked, is due to the con- sumption of milk containing formalin, and possibly other preservatives. 356 HYGIENE AND PUBLIC HEALTH organisms or Gaertner's bacillus. Its emplojTiient may there- fore cloak the use of stale meat in sausages \Adthout removing or reducing the possibly harmful results of its consumption. The Budde process for the preservation of milk, the invention of a Danish engineer, has been favourably reported on by Professor Hewlett in this country. In this process peroxide of hydrogen, in the proportion of about 15 c.c. of a 3 per cent, solution per litre of milk, is added to the milk, and the mixture is heated to 52° C. for at least three hours. A temperature below 48^ C. is not sufficient, and one above 55° C. should be avoided, as this may induce changes in the physical qualities of the niilk. When the milk is thus heated, the peroxide of hydrogen is decomposed into water and oxygen by an enzyme (catalase) present in the milk, and the oxygen being Uberated in a nascent condition acts as a germicide. At the end of the three hours heating the whole of the peroxide of hydrogen should have been decomposed, provided the right proportion has been added to the milk, so that no antiseptic remains behind in the milk, but only a very small addition of water. The heated milk should be immediately bottled ; it i? unaltered in appearance and flavour, and all ordinary non-sporing germs having been destroyed by the nascent oxygen, it will keep fresh and sweet oven for eight to ten days in hot weather. There is at the present time a very copious literature dealing \\ith the diseases and injurious effects attributable to the use Fig. 64. — Aspergillus Glaucus (X about 150 diameters). Fig. 65. — Penicilliuni Glaucum (X about 200 diameters). of cow's milk. Forming, as it does, so large a proportion of the daily food of infants, young children, and invalids of all ages, and consumed, as it generallj^ is, by all ages and all classes, in an uncooked state, the importance of the inquiries that have been made and of the facts that have been elicited can hardly be over- estimated. The following considerations will be found of use in arriving at a proper understanding of the subject. Milk has a remarkable power of absorbing gases and vapours, organic and inorganic. It is, besides, a fluid which, while possess- ing all the essential constituents of food, forms a most suitable cultivating medium for low forms of life, fungoid or bacterial. So that it is not too much to assume that specific disease germs, MILK 357 which have gained access to the milk, may so grow and multiply as greatly to increase its power of infection. The chief sources of the infection of milk are dirt and water — dirt finding its way into the milk during and after milking, and the water through the washing of the cans, or by wilful addition to the milk with the object of increasing its bulk. More cleanly methods in connection with the collection, transit, and storage of milk are urgently demanded. It has been demonstrated that the dirt in milk chiefly gains access at the farm, and to a less extent during transit and during storage in the home. It has not yet been found practicable to establish a dirt standard ; but successful prosecutions have been taken under the sections of the Public Health Act which deal with unwhole- some food, where the dirt in milk has been found to be very considerable. In order to reduce the amount of dirt in milk it is necessary that the milker should have clean hands and clean overalls at the time of milking, and that the cow should have a clean udder. The daily grooming of cows is now undertaken by some of the best dairy farmers ; the clipping of the hairs on the flanks, round the udders, the hind quarters, and the tip of the tail also aids in protecting the milk from dirt. Clean bedding in the sheds is also necessary. Immediately after collection the milk should be strained through a fine metal gauze, filtered through a layer of cotton, and then cooled to 55° F., or as much below this as possible. It follows that all utensils must be scrupulously clean. For cleansing purposes steam or boiling water is essential. In railway transit the milk should be con- veyed in sealed dust-proof cans, in proper refrigerating vans; and in the home it should always be stored in clean receptacles kept covered, and thus protected from the access of dust and flies. There is danger in the promiscuous mixing of the milk from different farms, as practised by large milk dealers ; any infection in the milk is thus conveyed to a wider area of consumers than would be the case if this practice were abandoned. One advan- tage of a municipal milk depot is the opportunity which it affords to the sanitary authority of presenting an object-lesson to the local milk sellers of a model dairy ; for even if the farm supplying the milk is not a municipal one, the local authority can usually impose what conditions it deems necessary upon the milk vendor who obtains the contract. Milk, as being derived from the living animal, must be also, 3D^ HYGIENE AND PUBLIC HEALTH to a great extent, a reflection of the animal's state of health. But we can go further than this, and say that milk is, for a certain period, derived from an animal in the puerperal condition conse- quent on parturition — a condition kno^vn to be liable to certain disorders, chiefly inflammatory, and particularly prone to take the infection of contagious disease. Milk which has become acid from lactic and coincidental fermentations is liable to cause sick- ness and diarrhoea in children ; and if O'idium albicans is present in the milk, it may attack the mouth and digestive tract of infants, causing thrush. Other fungi and moulds — penicillium, aspergillus, mucor, etc. (see pp. 356, 358) — ^when pres- ent, may cause severe gastric irritation. Similar symptoms have been produced by pus and ^^^QyA'^'W'S^i^-^ll W " "o " fluids from inflamed udders and « // \f^\i^fl/J ' udder abscesses contaminating the milk. In 1881 Mr. Ernest Hart com- piled tables with particulars of 50 epidemics of enteric fever, 15 of scarlet fever, and 6 of diph- theria— 4,800 cases of infectious disease in all — which had been traced to an infective or a supposed infective quality of the milk supplies ; and since that date there have been numerous other milk epidemics recorded. In the case of enteric fever, the most usual means by which milk obtains its specifically infectious quality is the washing of the milk cans, etc., or the intentional dilution of the milk, with water polluted by typhoid dejecta. In other cases the infection has been attributed to the storage of milk in rooms or dairies the air of which was subject to drain or sewer emanations. There is no evidence that enteric fever is a disease of cattle communi- cable to man through the milk secretion, or by means of pollution of the milk by the alvine discharges through careless milking. In those epidemics of scarlet fever which have been traced to milk, it has been usual to find that the milk was infected through human agencj^ by a previous case of the disease at farm or dairy. The cows were milked b}' a person who was attending on a Fig. 66. — Mucor Mucedo ( x about 80 diameters). MILK 359 scarlet fever patient, who had the disease amongst his family — possibly in an unrecognized form, as sore throat without rash — or who was himself suffering from it in a mild or disguised form. Occasionally the milk appears to have derived its infective quality from being kept in a room in which clothes or refuse matters from the sick were lying. But besides such easily understood methods, the history of the Hendon, Wimbledon, and Wiltshire (1909) outbreaks ap- peared to show that cows are liable to a disease identical with or very closely resembling human scarlet fever, and that the milk from animals so suffering might prove to be the cause of epidemic outbursts of the disease amongst those who consumed it. Dr. Klein isolated an organism — a streptococcus — from the udder lesions (ulcers) on the Hendon cows, which he believed to be the true pathogenic organism. A streptococcus has also been found in the diseased 01 gans and tissues of human scarlatinal cases. Subcultures of this organism obtained from human scarlatinal cases, when inoculated into recently calved cows, are said to produce the characteristic ulcers on the teats, along with other manifestations of the Hendon cow disease ; and calves fed on these subcultures obtain the same disease. This matter has been, however, and still is, the subject of much controversy. The opponents (including nearly all the members of the veterinary profession) of the views of Dr. Klein and of Mr. Power, who investigated the Hendon outbreak, hold that a possible human source of the disease at Hendon was not absolutely excluded, and assert that other cows suffering from the Hendon disease have not given rise to any scarlet fever outbreak. The weight of opinion is opposed to the view that cows are capable of imparting the infection of scarlet fever to their milk. In the most recent instance of a scarlet fever epidemic being apparently due to a cow disease, in which parts of London and its south-western suburbs were extensively invaded in June, 1909, it was not possible definitely to exclude a human source of infection ; but the Hendon disease was undoubtedly present in several of the cows on the Wiltshire farm which supplied the milk, just anterior to the onset of the first cases. In a large percentage of the milk epidemics of diphtheria, it has not been possible to trace the source from which the milk derived, its infective quality. This is not to be wondered at; for 360 HYGIENE AND PUBLIC HEALTH slight cases of diphtheria are very difficult to trace, the diph- theritic character of a sore throat not being always recognizable even to a medical attendant. There is practically no evidence to show that diphtheria may be a cow disease transmissible to human beings, although calves have been known to suffer from a throat affection presenting post-mortem appearances very similar to those found in human diphtheria. The question as to whether garget or mammitis in cows is capable of producing diphtheria in the consumers of milk taken from gargety udders may be answered in the negative, but there is considerable evi- dence to show that it may be responsible for outbreaks of septic sore throat. Recent experiments of Savage, however (L. G. B. Report, 1908-9), tend to show that the common organism of mastitis in cows — the Streptococcus mastitidis — is not a cause of human sore throat or other human illness. Stall-fed dairy cows in towns are very susceptible to tubercle. Veterinary authorities have stated that at least 25 per cent, of all dairy cows kept in cowsheds are the subjects of this malady. These animals are stalled day and night in stables often uncleanly and badly ventilated, and they are perpetually being drained of large quantities of milk. Prolonged lactation in the human female is well known to be a frequent precursor of phthisis ; and it is not wonderful that under such circumstances, and with the additional factors of confinement, want of exercise and bad air, cows should succumb to a malady to which they are in a high degree susceptible. It often happens that the best bred animals, which are usually the best milkers, are those which are most affected. In the early stages the symptoms of the disease are ill defined, the health of the animal is not much interfered with, and the milk secretion is as abundant as ever. Nutrition is not interfered with until the disease is well advanced, and even then the amount of milk yielded, although poor in quality, may not be diminished, and the dairy farmer continues to keep the animal in stock. From the Third Report of the Royal Commission on Tubercu- losis it appears that the milk of cows ohviously suffering from tuberculosis frequently contains tubercle bacilli, even although no disease is present in the udders. By " obviously suffering " is meant the display of clinical symptoms of disease, not merely a reaction to tuberculin. It is^ however^ generally jrgcognized MILK 361 that the liability of the milk to contain tubercle bacilli is far the greatest when one or more quarters of the udder have become tubercular. Tuberculosis of the udder may be suspected when, as a result of inspection and palpation of the udder (empty of milk), certain of its parts are found to be hard or enlarged. The healthy udder, when empty of milk, feels uniformly soft, and shows no asjTnmetrical enlargements. To confirm the diagnosis, it will be necessary to draw off (with aseptic precautions) some of the milk from each of the four teats, and submit each sample to bacteriological examination. The milk of tubercular cows which have no udder affection may become contaminated from the alvine discharges, when the cows are not kept clean in their stalls or are carelessly milked, as it has been ascertained that in cows presenting clinical symp- toms of the disease the faces often contain large numbers of living and virulent tubercle bacilli. In every dairy farm of any size, where no special precautions are taken to control the spread of tuberculosis, there will prob- abl}^ be tuberculous cows, some of them most likely with tuberculous udders ; and as it is the common custom of dairy- men to mix together the milk yielded by different cows, it is not too much to assume that tubercle bacilli may be widely dis- tributed in the milk supplj^ As a matter of fact, the bacilli have been found bj^ many observers in from 10 to 20 per cent, of the dairy samples examined by them. The bacilli of bovine tuberculosis are practically identical — according to all bacteriological methods at present known — with those found in tubercular formations in the human organs, although the disease presents anatomical differences in man and cattle. But these differences are probabty due to differences of soil in the human and bovine tissues, the bacilli engrafting them- selves in those tissues which present conditions most favourable to their growth and development. The human bacillus differs from the bovine bacillus in that it is longer, thinner, and grows more luxuriantly ; it is also of relatively lower virulence. There are, however, connecting forms which clearly indicate that these two types belong to the same species, and that these differences are merely modifications of their characters. The bovine bacillus produces by feeding or inoculation the typical tuberculosis lesion in many animals 362 HYGIENE AND PUBLIC HEALTH other tha.n the bovine ; this is true even of monkeys and anthro- poid apes. The human bacillus produces the typical tuberculosis lesion in several animals — e.g., the guinea-pig and monkeys. It can infect bo vines, though usually in a limited retrogressive foim. In a certain proportion of the cases of human tuberculosis the bacillus is the bacillus of bovine tuberculosis, in all respects identical and indistinguishable from those bacilli taken from a pure bovine source. There is some confirmation of the view that bovine tuberculosis is transmissible, at least to young children, from the fact that whilst the death-rate from pulmonary tuberculosis has undergone a steady diminution during the past fifty years, the mortality from tabes mesenterica in infants and children under five years is still maintained at a high rate. On the other hand it is well known that tabes mesenterica is a somewhat indefinite term, and is often employed for the registration of deaths occurring in 3^oung children where the evidence of tubercular abdominal mischief is of the slightest character. The autopsies of young children also show that primary tubercular intestinal ulceration of the intestines is very rare, whilst pulmonary lesions, even in the case of very young children, are markedly more common than abdominal ; and even where there are tubercular deposits in the abdominal glands, the probability of these being the primar}^ lesions cannot always be definitely affirmed. It is, however, quite possible that in children tubercle bacilli may pass through the intestinal mucosa and the mesenteric glands, and thence invade the bronchial glands and the lungs, leaving little or no trace of their passage in the intestines 01 abdominal glands. A^Tiat appears, then, to be a primary deposit in the chest may in reality have been due to an infection introduced into the alimentary canal by means of food. Again, it may be stated that whilst the children of the poor are the most notable sufferers from tabes mesenterica, they are not nearly such large consumers of milk as the children of those higher in the social scale, who suffer much less from this and other complaints suggestive of abdominal tuberculosis. It is quite possible that any excess of abdominal tubercle amongst the children of the poor, if there is such an excess, is due to infection from human sources, the children contracting tubercle from being allowed to crawl about dirty, dust}^ rooms, infecting their mouths from their fingers and from dirty rubber bottle teats. MILK 363 On the other hand some observers are of opinion that all forms of tuberculosis in children (scrofulous glands and joints as well as abdominal tuberculosis) are due to infection with bacilli of bovine origin, whilst the phthisis of adults is solely due to bacilli of human origin. Evidence obtained by Delepine shows that bovine tuberculosis is, on an average, more prevalent in districts where shippons are generally in a bad state, small, or badly ventilated and dirty ; and where also it is the usual practice to retain many aged cows on the farms. In order to deal with the dangers arising from the consump- tion of the milk of tuberculous cows, the following are measures which have been suggested and in some cases adopted : 1. A quarterly veterinary inspection of all cows the milk of which is being sold or offered for sale for human consumption. 2. The isolation from other milch cows of those showing clinical symptoms of tuberculosis ; and the prohibition by law of the sale of milk of such cows for human consumption, or for the feeding of other animals unless effectively sterilized. 3. The making of tuberculosis a notifiable disease in the case of milch cows. 4. The compulsory notification of all forms of udder disease in milch cows, and the prohibition of the sale of milk in these cases, except on a veterinary certificate to the effect that the disease is not of a character likely to affect the wholesomeness of the milk. In order to eradicate bovine tuberculosis the following sug- gestions have been favoured : 1. The provision of open-air sheds. It has already been demonstrated by actual experiment that the cows are in a decidedly better condition by being kept more in the open, and that their coats become thicker, while the milk does not decrease in amount. 2. The slaughter of all infected bovines. This is impracticable. All are not agreed as to the desirability of the sanitary authority giving compensation to the owner, and most authorities are opposed to compensation, in respect of advanced cases. A system of mutual assurance amongst farmers is preferred bj^ manj^ 3. Good results appear" to have been obtained from efforts to render bovines immune to the disease, as by Behring's vac- cination. 364 HYGIENE AND PUBLIC HEALTH 4. The system of eradication recommended by Professor Bang includes a testing of herds in the spring and autumn of each year wnth tuberculin ; the segregation of those which react ; and the selection of the tuberculosis-free cow for calf-rearing. 5. By Ostertag's scheme only cases of open tuberculosis — namely, those bovines discharging tubercle bacilli — are segregated and slaughtered. Foot and month disease, or epizootic eczema, is a contagious disease, characterized, in cows, by an eruption of small vesicles on the lining membrane of the mouth and the interdigital spaces of the feet ; not infrequently the vesicles appear on the udders and teats. In the majority of cases the milk secretion is dimin- ished as the disease progresses, and may become entirely sus- pended. The fever runs its course in from eight to fifteen days. The contagium exists in its most concentrated form in the lymph or serum of the vesicles (those on the teats are liable to be rup- tured in milking) and in the saliva, and it possesses considerable vitality. Numerous outbreaks among human beings of a peculiar illness have been traced to the use of milk from cows with this disease. The sjnnptoms were slight fever, vesicular eruptions on the throat and lips, swelling of the tonguC; salivation, nausea, foetor of breath, pain in limbs, and marked swelling of the lymphatic glands of the neck. It is probable that the transmission of the disease is most certain in those cases where there are vesicles on the cow's teats, which are sure to be ruptured in milking, the virus thus obtaining direct access to the milk. Goat's milk has been shown to be one of the channels of the infection of Malta fever. In the case of cows suffering from cattle plague and anthrax, the milk secretion is suspended at a very early stage. In cow-pox the milk secretion is said to be rapidly diminished or suppressed, A milk epidemic is characterized by the suddenness with which it makes its appearance, the sufferers being for the most part attacked about the same time. The infected houses will be found to have been supplied, with a few exceptions, by the par- ticular milk vendor whose supply is at fault. Where infected houses are discovered to which milk has been supplied from different vendors, this circumstance is often due to the fact that the vendors on their rcunds very commonl}^ buy small quantities of milk from each other. MILK 365 The cases are, of course, localized to the area of distribu- tion of the infected milk supply ; women and children in the better class houses are mostly attacked, and the drinkers of raw milk are often picked out. Generally speaking, incubation periods are shortened, attacks are mild, the mortality rate is lower than usual, and the epidemic often ends rapidly. Sometimes valuable corroborative testimony implicating the milk is forthcoming in the circumstance that some of those in the infected households, who have consumed no unboiled milk, have escaped ; and that households supplied from the implicated dairy, but in which no unboiled milk is consumed at all, have entirely escaped. Until cowsheds and dairies are placed under rigorous sanitary control, and until cow diseases are better understood and recog- nized, the only safeguard against the spread of disease through milk is to sterilize it. Exposure to the heat of boiling water for five minutes destroys the life and action of every variety of specific disease virus, and practically sterilizes the milk. This steriliza- tion — the destruction of all living organisms — is of especial importance where infants are fed on cow's milk. Under natural conditions the mother's milk, as sucked in by the infant, is free from all organic life ; but where cow's milk is substituted, im- mense numbers of living germs are introduced into the stomach, which may at this tender age be unable to cope with them, and ill-health and disease ensue. The act of boiling undoubtedly produces some slight alteration in the nutritive properties of the milk (the fat emulsion is injured, the lactalbumin is coagulated and digestion of the caseinogen is delayed), but its value as a food is scarcely affected thereby ; but against this disadvantage must be set the removal of any risk of infection, which under existing circumstances cannot be disregarded. The question of the production of infantile scurvy by the prolonged use of sterilized milk has received much attention. The matter must be regarded as still sub judice. In several towns in England and on the Continent municipal depots have been established for the distribution of humanized (sterilized) milk ; and it is claimed that these have had a beneficial effect in reducing infantile mortality. Good cow's milk is diluted and cream and sugar added. The humanized milk is then placed in small stoppered bottles of some five ounces capacity and placed in the sterilizer. The bottles are kept 366 HYGIENE AND PUBLIC HEALTH exposed to a temperature of 102° C. in a steam sterilizer for about 45 minutes, and the}^ are then taken out and placed in baskets. The quantity of the milk is adjusted according to the age of the child, and before use each bottle should be placed in a little hot water, the stopper removed, and a teat fitted to the bottle direct. The parents are generally charged is. 6d. per week ; but this does not meet all the expenses in connection \vith the depot. Dried milk as a food for infants has been favourably spoken of by Dr. Millard, Medical Officer of Health of Leicester. In the process of manufacture fresh milk is fed in a continuous stream on to revolving heated cylinders on which it forms thin films. The cylinders are heated by steam at about 40 pounds pressure (250° F.), and the moisture of the milk is thus evaporated. The dried films are automatically detached from the cylinders by knife-edges, and subsequently sieved and pulverized. The result is a coarse, granular powder, practically sterile, which in air- tight packages will keep good for a long period. For use, the milk powder is mixed with an equivalent quantity of water. The fluid thus formed is found to be digestible by infants, probably owing to the fact that the curd formed in the stomach is not dense, like the ordinary cow's milk curd. To prevent scurvy the routine administration of fresh fruit- juice is advised. At the present time at the Leicester Infants' Milk Depot dried milk has almost entirely superseded the " humanized " milk, as it is found less costly than the latter system, where so much labour is spent on bottling the " separate " feeds and cleansing the bottles, and equally satisfactory from the health aspect. Fl About 10 per cent, of the milk retailed in London has either had some of its cream separated, or water has been added. Annatto , turmeric, and j^eUow coal tar colours are sometimes employed to give a rich yellow colour to a naturally poor or watered milk. The Board of Agriculture has fixed certain low limits (standards) with reference to the composition of milk. The fat must be not less than 3 per cent., the non-fatty solids must reach 8-5 per cent., and the total solids of skimmed milk must amount to 9-0 per cent. Butter. \Mien the cream of milk is churned-^e.g., violently agitated in a suitable apparatus — the fat globules coalesce, entangling in their meshes some casein and serum. The butter so formed is then pressed to squeeze out some of the moisture, and salt added to BUTTER 367 preserve it. The percentage proportions of the constituents of butter are approximately as follows : Fat 83-5 Curd . . . . . . . . . i*o Ash . . 1*5 Milk-sugar . . . . . . . . I'o Water i3'o The amount of water in a sample of butter should never be more than 16 per cent, by weight, and the fat should constitute at least 80 per cent. The fat of butter consists^of a mixture of the glycerides of the fatty acids — palmitic, stearic, and oleic — not soluble in water ; and also of the glycerides of certain soluble and volatile fatty acids, principally but5n:ic. Margarine, oleo-margarine, or hutterine, is manufactured from animal fats (lard, beef, and mutton fats), and vegetable oils (cotton seed, sesame, earth nut, etc.). When made from beef fat, this is first finely minced and heated in tanks to about 39° C. The fat then melts, and the water and debris sink to the bottom. The melted fat is run off as a clear yellow oil, and kept at a tem- perature of about 30° C. The stearin to a certain extent solidifies at this temperature, whilst the oleo-margarine is separated as a liquid, from which much of the stearin has been removed ; for oleo-margarine solidifies at a much lower temperature than stearin. The oleo-margarine is then filtered, pressed, churned up with milk to give it the flavour of butter, coloured with annatto, and cooled with ice, when it is ready for sale. The great distinction between butter fat and margarine fat lies in the fact that the butter fat contains nearly 8 per cent, of the volatile fats, whilst the margarine fat has rarely more than J per cent. In the analysis of these substances this difference is made use of. The same antiseptic and colouring agents are employed in butter as in milk. Margarine is but little inferior in nutritive qualities to butter ; it constitutes a good article of diet — but it must not be sold as butter. It is somewhat less digestible than butter, and much more generally contains colouring agents and preservatives. Cheese. Cheese is an easily digested and most nutritious article of diet- In the manufacture of cheese, casein and most of the milk fat are precipitated from milk by rennet at a suitable tempera- 368 HYGIENE AND PUBLIC HEALTH ture. The curds are then pressed, to squeeze out the whey and reduce the mass to a proper shape. In the process of decay the fat increases at the expense of the casein, and numerous alkaloidal substances, extractives, and aromatic acids are pro- duced, which give a decayed cheese its aroma. These bodies are harmless, but rarely a poisonous ptomaine called " tyro- toxicon " is produced. This substance has also been discovered in cream, butter, and cheap ice-creams, and in milk stored during hot weather. The symptoms produced by tyrotoxicon are allied to those of atropine poisoning ; they include vertigo, nausea, vomiting, diarrhoea, collapse, muscular cramps and rigors. Tyrotoxicon is diazo-benzene-butyrate, and its effects have been chiefly observed in America. Various kinds of parasites grow in decaying cheeses, but they do not seem ordinarily to produce any harmful effects. The more common are : Aspergillus glaucus (causing blue or green mould), Sporen- donema casei (causing red mould), and the cheese maggots {Pio~ phila casei). Wheat Flour and Bread, Wheat flour contains about 15 per cent, of water, 8 to 12 per cent, of gluten (vegetable albumin), and about 70 per cent, of starch, sugar, and dextrine. It is very deficient in salts and fat. In the finest flour nearly all the outer envelopes of the wheat grain are separated. This separation of the bran, whilst it renders the flour fine in texture and white in colour, deprives it of much nutritious matter, for bran contains 15 per cent, of nitrogenous substances, 3-5 per cent, of fat, and 57 per cent, of salts. On the other hand, most of this nutritious matter is in a form difficult of digestion and irritating to the bowels, for the outer envelopes of the wheat grain are hard and silicious ; but bread made from wholemeal flour is favoured by many. Where it can be tolerated its use may be advantageous, as it promotes evacuation of the bowels, and is more nutritious than ordinary white bread. It is certainly deserving of trial by the working classes, whose diet is often deficient in fat and nitrogen ; and with the modern methods of very fine grinding its irritant properties are reduced to a minimum. Bread is made by mixing water, yeast, and a little salt with wheat flour until a consistent dough is formed, which is allowed to rise before a hot fire and then placed in a baking oven. By the action of the yeast at a suitable temperature, some of the WHEAT FLOUR AND BREAD 369 starch is changed into sugar, and the sugar splits up into alcohol and carbonic acid gas. The coherent nature of the gluten pre- vents the escape of the carbonic acid, which forms for itself little cells in the substance of the loaf, and causes the spongy structure characteristic of well-made bread. The alcohol escapes into the air. It is important not to let the fermentative process go too far, or lactic and butyric acids may be formed, which cause the bread to be sour. Alum has the property of arresting this change, and of imparting a fine white colour to bread. Hence its frequent use in baking powders. The loaf when " risen " is put into the oven and baked. It appears, from ex periments conducted by Drs. Waldo and Walsh, that the tem- perature of the interior of a loaf in a baker's oven is not sufficiently high to destroy all microbes. The process of baking, therefore, does not sterilize the loaf. Fig. 67. — Puccinia Graminis ( X about 200) Aerated bread is now extensively used. In this system CO2 gas is prepared and forced through the dough under pressure. Its great advantage lies in the fact that there is no fermentation as in ordinary bread-making, and no danger of sourness and acidity being produced. There is besides no loss of starch, and no yeast is left in the bread to cause fermentative changes in the stomach, giving rise to acidity, heartburn, and flatulence. On the other hand, the yeast fermentation is supposed to render the bread more easily attacked by the digestive juices — in other words, more digestible. Baking powders are occasionally used to disengage CO2 gas, and cause dough to rise. They usually consist of sodium carbonate and some acid such as citric or tartaric, the acid and alkali being brought together for use. Baking powders are also sold in which the acid constituent is furnished by acid phosphate, and in other cases by the sulphuric acid contained in some form of alum salt. 24 Z1^ HYGIENE AND PUBLIC HEALTH Under the microscope wheat flour is seen to consist of round or oval starch grains, of very various sizes. The smallest are mere points, whilst the larger ones may reach to io\)o inch in diameter or more. Intermediate sizes are very often absent. The hilum and concentric lines of the starch grains are barely visible, if at all. Portions of the outer envelopes Co oO Oo a o° °o ° O o Fig. 68. — Smut spores : Uredo segetum (X about 200), Fig. 69. — Acarus farinEe ( X about 40). of the wheat grain may be detected in the coarser and more branny flours. WHieat grains are subject to attack by certain parasites, viz. (figs. 67 to 71), " smut " {Uredo segetum) and " bunt " {Uredo joetida), the latter being the commonest ; ," rust " or Puccinia graminis, which attacks the stem and leaf ; and ergot {O'idium abortifaciens) (fig. 73), which, however, is more often a disease of Fig. 70. — Vibriones tritici (X about 40). Fig. 71. — Weevil (X about 40). rye. Amongst the nimierous animal destroyers of wheat are : Vibrio tritici, or ear cockle, which destroys the grain and fills it \vith a cotton-like substance ; Acanis farincB ; and the weevil, or Calandra gr anuria (fig. 71), a little insect— visible to the naked eye— which eats the core out of the grain, leaving only the shell. Lolium temulentum, or darnel seeds, occasionally find their way into flour, and have given rise to symptoms of narcotic poisoning WHEAT FLOUR AND BREAD 371 among some of those who consumed the bread made from such flour. Other fungi may likewise be recognized by means of the microscope in the flour made from blighted and diseased corn ; and flour and bread, when badly stored and allowed to become damp, become the seat of growth of moulds and fungi such as Mucor mucedo, Penicillium, and Aspergillus (see pp. 356, 358). All these growths are apt to produce dyspepsia and diarrhoea, whilst the prolonged consumption of ergoted bread may give rise to the sjmiptoms of ergotism, viz., painful cramps in the limbs and gangrene of the extremities. Ergot may also be detected by the herring-like smell of propylamine which is produced when liquor potassse is 'added to ergoted flour. Fig. 72. — Section of wheat grain : outer coat, a. Girdle cells ; b, cerealin cells ( X about 50). Fig. 73. — A, ear of rye with ergot — the latter shown as germinating and producing Claviceps purpurea; B, a slice of ergot (x about 250). With wheat at its present low price, adulteration is very little practised. Alumina is normally present to a very slight extent in flour and bread (equivalent to 6 to 10 grains of alum in a 4 pound loaf). When alum is added in any quantity, its presence may be detected by pouring a fresh infusion of logwood, made with distilled water, over the flour or bread. The colour of the logwood changes to a lavender or violet-grey in the presence of alum. There can be little doubt that alumed bread tends to produce dyspepsia and constipation, and it permits of an inferior flour being sold as a good one, but it is now only added in small quantities in certain baking powders. The adulteration of wheat flour with other grains, such as barley, potato, beans, peas, maize, oats, rye, and rice, is now but little resorted to. 372 HYGIENE AND PUBLIC HEALTH The nitrogenous substances in these grains have little or no adhesive properties like wheat gluten, so that bread of an inferior quality can only be made from them. The nutritive values of some of these cereals will be seen from the following table : Wheat ! (winter- Barley. Oats. Maize. Rye. Rice. sown). Starch! . 63VI 63-51 49-78 64-66 61-87 7r^6 Nitrogenous matter (i.e., albumin, ce- realin, etc.) i5'53 11-46 14-67 14-27 14-87 9*34 Cellulose 3-03 7-28 13-53 1-86 3'23 traces •. Sugar^ . 2-57 1-34 2-36 1-94 4-30 G-38 Fat . . . 1-48 1-03 5-14 3-58 i'43 G-19 Mineral matter I -60 2-32 2-66 i"35 1-85 0-28 Moisture I2-08 13-06 11-86 12-34 12-45 12-15 Total . loo-oo lOO-QO I GO-GO IGG-OO loo-oo IGG-OO It will be seen that barley is — compared with wheat — poor in nitrogenous matter and sugar, but rich in cellulose and mineral matter ; that oats are exceptionally rich in cellulose and fat, possess a high amount of mineral matter, but are relatively poor in starch ; that maize possesses a high amount of fat, but the cellulose is low ; that rye is exceptionally rich in sugar, and in other respects closely approximates to wheat ; and that rice is rich in starch, but poor in everything else. 1 Barleymeal, oatmeal, peas, lentils, and maize or Indian corn, are all most nutritious and fattening, and very cheap. They are easily made into most nourishing porridges, soups, or pud- dings, with a little milk, and form very valuable — though greatlj^ neglected — foods for people of small incomes. Starchy foods must be carefully cooked to render them digestible. By boiling or otherwise cooking, the cellulose coats of the starch granule are ruptured, and the saliva and pancreatic juice then have ready access to the granulose — the inner contents of the granule. Barley. — The starch grains are almost indistinguishable from wheat. Barley is very nutritious, and the ash is rich in iron and phosphates. Rye. — The starch grains are like those of wheat, but many ! The starch includes from i to 1-5 per cent, of dextrine, and, together with cellulose and sugar, comprises the carbo-hydrates of the cereals. " The saccharine body is alUed to cane sugar in its reactions. PLATE I ARROWROOT STARCH GRANULES, (x 250.) E. C. Botcsfield, photo. To face page 3^2. PLATE II Fi5;'jAiJCfc>f>'Ov 7 • ^ J -"- ^ ::A. (-A WHEAT c^■o ^O ,.w . ,^^ . -^ ^ b "^^J o ^ tO .< TAPIOCA STARCH GRANULES, (x 250.) £. C. Bozisfield, photo. To face page 3J2. WHEAT FLOUR AND BREAD 373 have a peculiar rayed hilum. Rye can be made into bread, which is very acid and dark coloured, and liable to produce diarrhoea in those unaccustomed to it. Oatmeal. — ^The starch grains are small and angular, and tend to cohere into rounded masses. It is most nutritious and somewhat laxative. When badly prepared, oatmeal may contain hairs and husks, which are liable to form intestinal concretions. Maize. — The starch grains are small, compressed, and faceted. Pellagra, or Elephantiasis Italica, is a constitutional disease operating destructively on the integument. It is most prev- alent among those living under the adverse conditions of dirt and poverty so rife in Italy. That the consumption of diseased maize, to the exclusion of other diet, is probably the main factor in producing epidemics of the disease is supported by the circum- stance that in the Lombardo- Venetian territory, where this is the chief food of the agricultural labourer, the disease is most in evidence, and also by the fact that pellagra-like symptoms have been produced by feeding lower animals with the diseased maize. Peas and Beans. — Pea starch grains are more or less oval, and many of them have a central longitudinal cleft extending nearly the whole length of the grain. Bean starch ceUs are somewhat larger and more flattened, and the longitudinal cleft is crossed by transverse fissures. Peas and beans contain a large amount of proteid substance called legumin (hence the name of Leguminosge applied to this natural order of plant), also sulphur and phosphorus. They are highly nutritious, but somewhat indigestible, and are apt to give rise to flatus from the formation of sulphuretted hydrogen. Rice. — ^The starch grains are very minute, angular, and faceted ; in shape like maize starch cells, but very much smaller. Rice is poor in everything but starch, which is, however, ex- tremely digestible when cooked. It has been held to give rise to Beri-beri, when it has been too exclusively used for human food. Arrowroot. — ^There are many different kinds of arrowroot, obtained from various countries. As a rule, the starch grains are oval or pyriform in shape, of large size, and with the hilum as a slight cleft or cross at the larger end of the grain. The concentric lines are very well marked. Sago and Tapioca. — The starch grains of sago are large, irregular in shape, with ill-ddined concentric lines. Those of tapioca resemble sago, but are considerably smaller. 374 HYGIENE AND PUBLIC HEALTH Potato. — The starch grains of potato are very characteristic. Man}/ of them are large and pyriform in shape, the hilum being at the smaller end, and the concentric lines are very well marked. Potatoes are very deficient in proteids and fats, but the starch is most digestible when properly cooked ; and they are valuable antiscorbutics, for they contain large quantities of the salts of the vegetable acids — malates, tartrates, and citrates. The juice of the potato is acid. Potatoes are better cooked by steaming in their skins than by boiling when peeled ; for by the first method there is no loss of the salts to the water used for boiling, as occurs in the second method. In the case of all vegetables, and, in fact, in all cooking pro- cesses, soft water is far better than hard water. The consumption of potatoes has been responsible for the occurrence of symptoms of solanin poisoning. BEVERAGES. Coffee. Coffee berries contain fat, legumin, sugar, dextrine, vegetable acids, and mineral salts ; also an aromatic oil, an alkaloid — caffein (about o-8 per cent.) — and an astringent— caffeo-tannic acid. When the berry is roasted, it swells from the formation of gases, the sugar is changed into caramel, and the aroma is developed. The roasted coffee is made into a beverage by infusion with nearly boiling water. If the water is used at a boil- ing temperature some of the aroma is lost. The coffee infusion acts as a stimulus to the nervous system ; it increases the fre- quency of the heart's ac- tion, the urinary excretion, and the action of the skin, and is said to increase the carbonic acid given off from the lungs. It has considerable effect in removing the sensation of fatigue. It is valuable as a beverage for men undergoing exertion both in hot and cold climates, from its stimulant and invigorating qualities. The Fig. 74. -Coffee : Cells of Testa and Cellular Structure (X about 200). fiEVERAGES 37^ heat of the infusion is useful in cold climates, whilst the increased action of the skin produces a cooling effect in hot climates. The principal adulterant of coffee is chicory. Under the microscope, diligent search should be made for the long oval cells of the testa of the berry, wdth their irregular cross-markings (fig. 74) ; and fragments of the internal structure of the berry may be seen, consisting of an irregular network of fibres forming a cellular structure, in which are contained dark angular masses and oil globules. All these structures are better seen /^ ^ ^^^ \V_ before the berry is roasted rM^M/ ^■^f0]l^^( and ground. Chicory is re- vealed by the presence of frag- ments of much coarser areolar tissue, and by the long dotted J , 1 . 1 -,1 Fig. 75. — Chicory: Dotted Ducts and ducts, which are quite charac- cellular structure (x about 200). teristic (fig. 75). Roasted coffee floats for a considerable time in water, owing to the gases that are developed in roasting, and to the quantity of fat it contains ; whilst roasted chicory rapidly sinks. Unlike coffee, chicory contains no aromatic oil nor caffein, but it has much sugar in its composition. When mixed with coffee it serves to sweeten it, and causes a darker coloured infusion than pure coffee ; but the stimulating effect of the mixture is less than that of pure coffee. Rare adulterants of coffee are other starches (such as potato and sago) , and caramel or burnt sugar. Tea. Dried tea leaves contain albumin, extractives, dextrine, and mineral salts, also tannin (about 13 per cent.), an aromatic oil, and an alkaloid — thein (3 per cent.). Green tea contains more tannic acid and ethereal oils than black tea, and is pre- pared from younger leaves, but the thein appears to be generally less in amount. The difference between black and green teas is entirely due to their mode of preparation ; they are both derived from the same plant. Formerly tea was exported almost exclusively from China, but now Indian and Ceylon teas have come largely into the market. Tea should be made with boiling water, but it should not be allowed to stand for more th^n five minutes, the infusion being then poured into another vessel. If this is not done, so much 37^ Hygiene and t>uBLtc i4ealtii tannin is extracted as to cause the infusion to be bitt6i and astringent, and most unwholesome. If soft water is used, a smaller quantity of tea is necessary than with hard water, as the soft water extracts more from the leaves than hard. Dextrine^ glucose, tannin, thein, the volatile oil, and a small quantity of the albumin pass into the infusion. Tea should not be taken with or shortly after meals, as the tannin tends to coagulate the albumins of the food undergoing the process of digestion. The action of tea on the system is similar to that of coffee. It is, therefore, valuable as a nervous stimulant and restorative in fatigued conditions of the body. The abuse of tea leads to weakened digestion, constipation from the astringent properties of the tannin, and nervous depression leading to insomnia and trembling — the effects of the volatile oil and thein. The structure of the tea leaf is characteristic, and is best seen when the leaf is young and green. It is oval in shape (fig. 76), with a serrated border, each serration being spine mounted, and the serrations terminating a little before the point of attachment of the stalk ; the primary veins run out alter- nately from the midrib, and turn towards the point of the leaf, but without reaching the border, the venation being looped ; the apex of the leaf is notched. Adulteration with foreign leaves is now little practised ; but used leaves may be dried, mixed with gum and rolled, and sold as sound tea. Green tea used to be coloured or faced with indigo, Prussian blue, and other mineral substances. Fig. 76. — Tea Leaf. Cocoa. Cocoa is a food as well as a beverage, and is much less astringent than tea or coffee. Cocoa nibs contain nearly 50 per cent, of oil (cocoa butter), proteids about 15 per cent., and theobromin — • allied to thein and caffein — 0*5 to 17 per cent. The ash is rich in phosphate of potash. For people of weak digestion, some of the fat of the cocoa should be removed by heat and pressure. Cocoa is generally adulterated with sugar and the cheaper BEVERAGES 377 starches, in order to disguise the large amount of fat and to render it more palatable. The starch grains of cocoa are very- small, and are often seen massed in the intercellular spaces of the structure of the nib. Mineral Waters. These are either derived from natural springs, the water of which contains gases (usually CO2) or mineral salts in solution (salts of potassium, sodium, magnesium or lithium), or they are manufactured by impregnating ordinary river, spring, or well water with CO2 gas, and dissolving in it small quantities of the mineral salts usually found in natural waters. Both kinds of water have come very largely into use in recent years. Besides the stimulant effect upon the digestive organs of the contained COo and the dietetic or aperient value of the mineral salts, these waters serve a useful purpose in providing a pure beverage for consumption in cases where there may be hesitation to drink the ordinary water provided for domestic purposes, on the ground of its impurit5^ Care should be taken, however, to choose a mineral water which does not contain an excess of common salt, producing thirst, or an excess of alkaline salts, which act as depressants on the nervous system. Travellers both at home and abroad usually show a wise discretion in their preference for mineral waters to the ordinary water of the establishments in which they are staj'ing or seeking refreshment. Too much reliance, however, should not be placed on the purity of all artificial waters, as in more than one instance it has come to our knowledge that certain manufacturers have obtained their waters from grossl}^ polluted sources. There is one other danger in the use of the artificially aerated waters that requires mention. They often exhibit traces, and sometimes very decided traces, of lead. This metal is dissolved from lead pipes or leaden apparatus used in the manufacture of the CO2, and the water charged with this gas holds the lead in solution. Another possible source of the metal is the silicate of lead which enters into the composition of the glass bottles in which such waters are stored. The habitual use of these waters containing traces of lead might in time lead to the development of s;viiiptoms of lead poisoning, the source of which would in all probability be overlooked. 378 hygiene and public health Fermented Liquors. A solution of grape sugar when subjected to the action of the yeast plant {Saccharomyces cerevisics) at a temperature of from 20° C. to 30° C, is mainly split up into alcohol and carbonic acid. CgHiaOe - 2C2H6O + 2CO2. The 5^east plant is composed of minute organized cells, oval in shape, and with granular protoplasm (fig. yy). In the presence of saccharine fluids at a suitable tempera- (5<^^Q .^ i,g> o ture, the cells undergo enormous multi- i^S^^^^^'^^^^^^^ plication by the process of budding, and ^^fv o ° (^ ^ "^ eA the alcoholic fermentation ensues. Under ^^^^^e.^y^i"^ the microscope, the cells which are bud- ei © © ^ ding may be seen as one large cell united ^'^•7pr'^,T?\''T'^T -to one or two smaller cells, end to end; Yeast Plant ( x about 200). ' ' or groups of several budding cells are attached together. The CO2 escapes as gas from the fermenting liquor, whilst the alcohol remains dissolved in the solution. The fermented drinks may be considered under the heads of spirits, wines, and beers. Spirits. — Brandy is spirit derived from the grape. It contains about 50 per cent, of alcohol, the remainder of the liquor being water, in which are held various secondary products, including acids, aldehydes, ethers, furfural and higher alcohols. Its specific gravity is generalty from 0-930 to 0-940 at 62° F. Rum is dis- tilled from fermented molasses. ^VhiskJ^ is made by distillation of malted grain. When new, it contains amylic alcohol or fusel oil, a substance which, when present in any quantit}' , produces rapid intoxication, followed by intense headache and depression. The percentage of alcohol in whisky is much the same as in brand}^ Gin is weaker in alcohol ; it contains oil of juniper, and is sweetened mth various aromatic substances. Absinthe is a liqueur flavoured with various essential oils, and contains oil of wormwood, a powerful poison to the nervous system. Brandy, as sold commercially, is now veiy largely blended with varying amounts of spirit obtained from the distillation of com grain spirit, etc. The dietetic and medicinal values of these sophisticated articles are probabty inferior to those of the genuine wine spirit ; and recent legal decisions show that the BEVERAGES 379 sale of blended spirits, when brandy is demanded, is an infringe- ment of the Sale of Food and Drugs Acts. Analysis differen- tiates between a pot still and a patent still spirit, because the secondary products are practically absent in the latter owing to the spirit being more highly rectified by means of the patent oi fractionating still. A therapeutic value has been ascribed to these secondary products, but the evidence is not conclusive. The secondary products in whisky are small in amount ; it con- tains relativel}^ more higher alcohols but less compound ethers than brandy ; it further contains traces of empyreumatic or tarry substances derived from the malting process. Wines. — What are known as the lighter wines — the Bordeaux, Burgundies, Rhine wines. Champagnes, and Moselles — contain usually less than lo or 15 per cent, of alcohol by volume. The stronger wines — port, sherry, and madeira — contain from 15 to 25 per cent, of spirit. Besides alcohol, wines contain various aromatic compound ethers which impart the bouquet, albuminous and colouring matters, sugar, free organic acids, and the acid salts of the vegetable acid series, including tannic acid (which is largest in amount in new port wines) and mineral salts, chieiiy those of potassium. Wines are manufactured from the fermented juice of the grape. Cheap wines are largely made from other fruits, and even grape juice wine is subject to various fortifications and adulterations to fit it for different markets. Home-made wines and cider are occasionall}^ manufactured or stored in earthenware vessels, coated inside with a litharge glaze, which readily gives up large quantities of lead to such acid liquids, and may be thus produc- tive of lead poisoning. If earthenware vessels are used, they should be coated with a hard salt glaze. When wine is kept long in cask or bottle, there is a deposit of the colouring matter and tannic acid, and some of the sugar disappears. If air is not absolutely excluded, the acetous fermentation is liable to be set up from the entrance of the ferment [Mycoderma aceti), which transforms alcohol into acetic acid (C2H6O becomes C2H4O2), and the wine is soured. The more common adulterants used are sugar, various ethers, logwood and other colouring agents, alum, and sulphate of lime. The latter improves the colour of cheap wines, and the addition is known as the " plastering " of wine. The practice is injurious, and by giving rise to the formation of potassium sulphate it induces a purgative effect upon consumers. 380 HYGIENE AND PUBLIC HEALTH Beers. — These beverages were formerly made from malt and hops only ; now they can be legally made from starch and sugar and various vegetable bitters. Pure beer is the fermented liquor obtained from the germinating grain of barley. The grains are made to partially germinate by being first moistened and then kept warm until they begin to sprout. A small quantity of the ferment " diastase " is thus produced. Further germination is then prevented by heating the barley in kilns and thus converting it into " malt." The malt is next subjected to " mashing " by mixing ^^dth water at 180° F. and well crushing and stirring for about two hours. During this process the diastase acts upon the starch and largely converts it into the sugar — " maltose/' which is easily ferment- able. After clarifying, the infusion is boiled with hops, and then the cooled liquor or " wort " is transferred to vats to ferment (yeast being added). When this alcoholic fermentation has pro- ceeded far enough the yeast is removed and the beer is run into casks. In recent years glucoses and invert sugars have been largely substituted for the malt, and these sugars have been obtained from rice and other starches which are not fermentable until they are converted into " invert sugar " by the action of dilute sulphuric acid. The commercial sulphuric acid is liable to con- tain a considerable amount of arsenic (derived from the iron pyrites used in its manufacture) ; and this circumstance was responsible for a considerable outbreak of arsenical poisoning among beer consumers, chiefly in the north-western part of England, in the winter of igoo-1901. Amounts of arsenic varying from -^ to i grain per gallon of beer were found by analysis, and some invert sugars were found to contain arsenic equivalent to 2-04 grains of arsenious oxide per pound. It may be stated that traces of arsenic have been found in jams, sweets, lemonade, liqueurs, sugar, and treacle — all now largely manufactured from glucose — and also in several chemical substances — such as sulphate of soda, phosphate of soda, car- bonate of soda and potash, caustic soda, sulphurous acid, sul- phites, borax, oxide of iron (used for colouring confectionery), etc. It has also been pointed out that the coke used for kilning the barley gives off traces of arsenic when burned. The percentage of alcohol in beer varies from 3 per cent, in the lighter to 6 or 7 per cent, in the heavy beers. There are also BEVERAGES 381 contained in beer, malt extract, 4 to 15 per cent., free organic acids, traces of albuminous matters, and salts. Considered as articles of diet, wine and beer will produce effects which may be partly ascribed to the action of alcohol on the system, and partly to the other constituents of which they are composed. Leaving out of consideration for the moment the effects of the alcohol, it will be seen that wine and beer possess some of the properties of a food. They contain sugar and starchy matters, mineral salts rich in potash and phosphates, and a considerable amount of the vegetable acids and their salts which are so valu- able as antiscorbutics. The compound aromatic ethers in wine may also act as aids to digestion, by promoting the flow of the pancreatic and intestinal juices ; and the bitters of beer act as stomachic tonics and appetizers. Little can be said against the use of beer and wine in strict moderation ; but taken habitually in excess, they lead to the storage up of superfluous fat in the tissues, and they interfere with the proper elimination of effete matters ; imperfect oxidation leads to an excessive formation of uric acid, and a plethoric and gouty habit are produced, eventually tending to palpable disease. These effects are, doubtless, in part due to the excess of alcohol taken into the system, but not entirely. Lessened metamorphosis has a considerable share in their pro- duction. Effects of Alcohol. Alcohol when taken into the body is rapidly absorbed unchanged into the blood. Taken in excess, it speedily commences to pass out of the body in an unaltered condition. The principal channel of elimination is the lungs and breath, but small portions are got rid of by the skin, the urine, and the bowels. The greater portion, however, of the alcohol (98 per cent.) is destroyed in the body. In fact, when taken in small (not excessive) quantities, alcohol acts as a food, supplying heat and energy by its oxidation in a similai manner to the fats and carbo-hydrates. After full doses of alcohol given to a healthy man or animal, the following effects have been noted : i. The vessels of the stomach are dilated, and the flow of gastric juice augmented. 2. The force and frequency of action of the heart are increased. 3. There is partial paralysis of the vaso-motor nerves to the superficial vessels, which dilate, causing flushing of the skin of the face and other parts. 4. The brain is partially anaesthetized ; 382 HYGIENE AND PUBLIC HEALTH the rapidity of external impressions, the power of concentrated thought, and the discrimination of the senses, are all lessened, as is also sustained voluntary muscular power. 5. The temperature of the body is slightly depressed ; but although there may be a decreased elimination of CO2 by the lungs, there is no delay or diminution in the metamorphosis of tissue, for the excretion of urea in the urine is not affected. 6. The acidity and water of the urine are somewhat increased. The long continued immoderate use of alcohol leads to degenera- tive changes, primarily in the stomach and liver, and at a later period in the kidneys, lungs, brain and bloodvessels. The de- generation is characterized by increased growth of interstitial fibrous tissue, which in course of time shrinks and causes atrophy of gland cells and loss of function. Chronic catarrh and cirrhosis of the stomach ^vith cirrhosis of the liver, followed by dropsy and haemorrhage, are the well-recognized results of alcoholic intemperance. The effect of such intemperance in shortening life is now uni- versally recognized. Statistics bear overwhelming evidence on this point. It may be stated generally that the mortality of the intemperate is from four to five times greater than that of the strictly temperate of the same age and in the same class of life. ^\^len the mortality of all occupied males in 1890-2, at ages ranging from twenty-five to sixty-five years, from alcoholism and diseases of the liver, is expressed as 100, and the mortality in each separate industry is expressed as a figure proportional to that standard, the follo\^ing results are obtained bj^ Dr. Tatham (Supplement to the 55th Report of the Registrar-General) : — Deaths from Alcohol and Diseases of the Liver (1890-2). All occupied males 100 Dock labourer • 195 Coachman, cabman • 153 Chimney sweeper . . 200 Costermonger . 163 Butcher . 228 Coal heaver . . 165 Brewer . 250 Fishmonger . . 168 Inn servant . . 420 Musician . 168 Inn keeper • 7ZZ Hairdresser . • 175 Dr. Tatham points out that the mortality from alcoholism is often registered as due to other causes that are known to be fre- quently associated ^^ith alcoholic excess, and this is often pur- posely done out of regard to the feelings of relatives. Experience proves that the liver is the organ which, more than any other, is affected prejudicially by intemperance. BEVERAGES 383 Those engaged in the brewing and licensed victualling trades are notably an intemperate class ; but, naturally, if the temperate men in these trades could be excluded, the figures indicating special disease of organs would be very much magnified. AU evidence points to the fact that alcohol, except in strict moderation, is injurious to men who are exposed to extremes of climate (great heat and great cold), or who have to undergo great bodily or mental labour. Its effect on the circulation is distinctly injurious to those engaged in hard bodily work, for it causes the heart to do more work without conferring any counterbalancing advantage. In strictly moderate doses alcohol has not been proved to do any harm ; and, taken in the form of beer or wine, many of the inhabitants of our large towns find it a useful aid to digestion and assimilation. But it must be remembered that there are idiosyncrasies as regards alcohol, and that what is harmless to one individual may be injurious to another. For thoroughly healthy people, alcohol in any form presents no advantages, and for children and young people it is decidedly injurious. The comparative immunity enjoyed by drunken persons from the usual effects of accidents is due to the paralysis of those nervous centres through which a shock would be produced in a condition of sobriety. The Report of the Departmental Committee, which was appointed to report upon Physical Deterioration, brought out the following facts : — 1. That the abuse of alcoholic stimulants, whether in the form of spirits, wine, or beer, is largely responsible for physical deterioration, and that it leads to disease in most tissues and organs of the body. 2. That alcoholic excess reduces the natural power of resistance to disease possessed by healthy individuals, rendering them especially liable to many inflammatory disorders, causing them to suffer much more severely from any illness they may contract, and making their recovery slow. 3. That intemperance predisposes to consumption. 4. That children of intemperate parents are seriously affected ; they frequently suffer from paralysis, epilepsy, and idiocy, which lead, if not to death, to their permanent disablement. From statistics obtained, it was found that the mortality among children of intemperate parents was many times greater than among children of sober parents of the same class. 5. That the increase in lunacy is largely due to intemperance, and that there is also an increase in the number of cases of general paralysis from the same cause. The Swedish (Gothenburg) system seeks to diminish the abuse of alcoholic stimulants, to acquire public-houses, and to devote 384 HYGIENE AND PUBLIC HEALTH the profits accruing from the sale of alcoholic drinks to public purposes. There is strict local option as to the provision of public-houses, and conditions are imposed upon the sale of 'S'idnes and spirits, but not of beer. CONDIMENTS. Vinegar is prepared by acetous fermentation from white wine or malt. Vinegars made chiefly from unmalted barley, maize, rice and other grains, and from sugar 01 molasses, are some- times sold as malt vinegar. Its acidity should amount to from about 3 to 5 per cent, of glacial acetic acid. It is largely adul- terated with sulphuric acid, which is injurious from its tendency to form insoluble sulphate of lime in the body. Acetic acid is neutralized in the system, and ultimately becomes transformed into an alkaline carbonate. In cases where vinegar has been added to " tinned articles," such as pickles, fish, etc., the liquid should be tested, where necessary, for lead, zinc, copper, or tin, since the vinegar adds materially to the solvent action of the juices, etc., upon the vessels containing them. Lemon and lime juice contain vegetable acids, chiefly citric, about 30 grains in a fluid ounce. They are frequently mixed ^^dth water, and sometimes -with other acids, such as sulphuric and tartaric acids. Lime juice has generally a little less acid than lemon juice. They are most valuable antiscorbutics. These vegetable acids and their salts are also largely contained in all kinds of fresh fruit ; but perhaps the chief advantage of fruit in a diet — when taken early in the day (before breakfast) — is its tendency to promote evacuation of the bowels. Mustard is generally adulterated with wheat flour and turmeric, for the pure seed possesses too acrid a taste to be palatable ; pepper with rice and minerals. Added mineral matter in pepper can be mostly separated by shaking up thoroughly with chloroform — when foreign mineral matters settle. Pickles are now generally coloured with chlorophyll and vegetable colouring matters. Formerly copper was much used for this purpose. Sweetmeats and confectionery are now almost invariably sold free from an}- injurious colouring matter.% The coloration is imparted by careful heating of the sugar, bj^ which a variety of TINNED OR CANNfiD l^oODS 3^5 shades of j^ellow and brown may be obtained, or by the use of such harmless organic matters as saffron, turmeric, annatto (yellow), cochineal (red) , logwood (violet), and chlorophyll (green). The use of the mineral and metallic salts for colouring purposes — those containing iron, lead, copper, arsenic, chromium, and zinc — is now hardly practised at all. An easy and rapid test for the separation of poisonous from harmless colouring matters may be applied as follows : Dissolve some of the sweetmeat in distilled water. If the colouring matter is soluble and is bleached on adding solution of sodium hypo- chlorite, it is organic and probably harmless. If the colouring matter is insoluble, or is soluble and is not bleached by sodium hypochlorite, it is probably mineral and possibly poisonous. The aniline dyes are but little used for colouring sweetmeats. They are soluble in alcohol and mostly innocuous, if quite free from arsenic, which is usually the case. Picric acid (trinitro phenol), a yellow dye, is injurious ; and the same may be said of the yellow colouring matter derived from gamboge, and a few aniline dyes, viz. : — Naphthol green, aniline yellow, Martins' yellow, Bismarck brown, methylene blue, and gentian violet. Tinned or Canned Foods. The amount of tinned or canned food-stuffs upon the market is very considerable, and it constitutes an increasing part of the food supply of large communities. The canning of food has the effect of preserving a large amount of material which would not otherwise be available for food, and it is thus a pro- vision which cheapens the cost of living ; moreover for the pur- poses of our Colonies, of the Army and Navy, or for expeditions to parts of the world where food is scarce, canned food is essential. There is no doubt that when meat preserved in this way has to be consumed for long periods, the consumer suffers less than when salted meat is exclusively eaten ; but experience has shown that health cannot be maintained for several months on these canned foods unless a certain amount of fresh animal or vegetable food is introduced into the diet. It is, of course, of prime importance that the material to be canned should be in a wholesome condition at the time of canning, but it is also very important that the cans in which the material is placed should be of good quality and sound. . The coating of the can with tin should be properly done, so that no flaws are 25 386 HYGIENE AND JPUBLIC HEALTH perceptible with the magnifying glass, as otherwise the iroil beneath will rust through ; the tin used for coating should not contain more than i per cent, of lead ; and " terne-plate/' which consists of 2 parts of tin to one of lead, should be prohibited ; the solder emploj^ed in the tins should not contain more than 10 per cent, of lead, and should be kept entirely on the outside of the tin ; and those tins which are to contain much acid juice (namely, vinegar, plum, and asparagus juice) should be lacquered inside. It is very desirable that the date of the canning should be required to be stamped on each can. The usual process of canning is briefly as follows : — The food is placed in the tin and the lid is soldered on. The small " blow-hole," which is generally in the centre of the lid, is next sealed by solder. The sealed tin is then placed in either a steam retort at 115° C. for from one to two hours, or in a boiling solution of calcium chloride for the same period, or in ordinary boiling water for about four hours. The tin is then removed from the retort or boiling solution, and the solder seal is quickly melted off, by means of a red-hot instrument, when the expanded gases escape ; the small blow-hole is again sealed ^dth solder, and the tin and its contents are again placed in the steam retort for another hour. The finished tin has then tM^o concave surfaces and emits a hard sound on percussion. Should, however, there be any flaw in the " tins," or the solder seal be imperfectly applied, or should the heating process be ineffectually performed, then the contents may go bad. In this event, owing to the accumulation of the gases of putrefaction, the tops and bottoms of the " tins " become quite fiat, and later on convex outwards, and the tin when struck gives out a hollow or drum -like sound. It is not difficult, therefore, in the majority of cases, to detect, before opening them, those " tins " in which the contents are bad. Sometimes, however, " blown tins " have been punctured to allow the accumulated gases to escape, and the small opening has been subsequentlj^ closed by solder. The presence of two solder points on a tin might therefore justify a suspicion that this practice had been resorted to, but as a rule the solder upon the original blow-hole would be melted and resoldered. The two solder points do not necessaril}- indicate fraud, because it is sometimes found more expeditious and convenient to make a second blow-hole to let out the expanded gases rather than TINNED OR CANNED FOODS 387 to unseal the original one. Again, what appears to be a second solder point may sometimes be nothing more than a splash of solder accidentally deposited. Beveridge has shown that the " blowing " of tins is due to the spores of Bacillus sporogenes of Klein, which are extremely re- sistant to heat. This organism is present in the colon, and contaminates all meat. It may not be destroyed by the so- called sterilization ; may remain inert for long periods if the tins are stored at a low temperature ; but may develop if the tem- perature reaches 37*^ C. or thereabouts. It is non-pathogenic to animals, but decomposes the meat, and renders it unfit for human consumption. These facts explain the circumstance that tins of meat which have passed the makers' tests, and have kept good for months, suddenty become blown and unfit for use. It was recognized that this occurrence was not due to injury of the tin through rust and entrance of air organisms ; for if so, the gas produced by putrefaction would have escaped, and no blowing would have resulted. The recommendation is accordingly made that the tempera- ture of sterilization should be raised to 120° C. (240° F.), and that this temperature should be maintained for one hour. The bulging of tins results from : — (i) The formation of gas by putrefaction of the contents of the tin ; (2) the displacement of the contents from rough handling and rough usage so as to make the ends bulge ; (3) the freezing of the contents of tins of liquid or semi-liquid foods, as when kept in cold storage, this sometimes making the ends bulge for the same reason that frost bursts water-pipes. It may be stated that the bulging of tins of condensed milk is not necessarily due to any of the above causes ; it may be produced by gas formed by electrolytic action between the metal of which the cans are composed and the acids generated by the growth of bacteria in the milk before the latter was condensed. The vinegar in which certain vegetables are conserved may produce gases in the same way. The dangers to health in the consumption of tinned or canned foods arise (i) from changes in the food itself (which may either be of a definite putrefactive nature or due to the development of non-putrefactive ptomaines or toxins) ; (2) from the use of antiseptics ; (3) from the addition of colouring agents ; or (4) from impurities yielded by the tins. Putrefactive changes J5h HYGIENE AND PUBLIC HEALTH cause the generation of gas within the tin, which leads to a blowing or bulging, and when the bulged end is tapped the sound is muffled or drum -like. On opening the tin a discolora- tion of the inside of the tin is often observable ; the contents are often discoloured and soft (fish, for instance, is often yellowish, soft and friable) ; and, lastly, the odour of putrefaction may be perceptible. Viry states that putrefactive changes in canned foods may take place without the formation of any gas ; and it is certain that the evil consequences which have sometimes been traced to the consumption of canned food were due to ptomaines which were foimed in partly decomposed material prior to canning. The development of ptomaines and toxins in food, and the use of colouring agents and antiseptics, are dealt with elsewhere. But a word must be said with reference to the impurities yielded by the tins. Metallic tin may be dissolved by acids or by oil (as in the case of canned pieces of pine, lobster, condensed milk, and sardines) ; and this metal is the most frequent metallic impurity found in the juices of preserved food, especially of fruit. Lead may be dissolved from the solder, or from the varnishes and enamels which have sometimes been used in connection with the tins. It is most important, therefore, that any solder used should be beyond the possibility of contact with the tinned material. Very rarely have traces of arsenic, copper and zinc been obtained from the juices of preserved foods. In cases where the tin is attacked by the contained juices, etc., a slaty-blue discoloration is often to be seen. In conclusion some advice may be offered with reference to the examination and selection of tinned articles. It is desirable to avoid cheap brands, and more especially those which do not bear the name of the maker. A very good idea of the nature of the contents can generally be obtained from an examina- tion of the tins. Poor quality tins commonly contain poor quality material. Of all tinned articles of food preserved fruits are the most likely to contain metallic impurities ; it is well, therefore, only to purchase these when they are bottled. Any canned meat or fish, which is not of good colour and firm re- sistance, should be avoided ; and any indication of marked loss of colour, of softness, and of friability, is highly suggestive of unwholesome material. Furthermore, it is very desirable that the contents of the can should be eaten during the day on which TOBACCO 389 it was opened, for there have been recorded instances where those who have eaten the material fresh from the can have escaped, whilst others, partaking of the same material the next day, have suffered from poisoning. Tobacco. The effects produced bj^ the excessive smoking of tobacco have often been discussed. Of all the components of tobacco smoke, nicotine is by far the most important ; the other com- ponents, including pyridine, are of little moment. Smoking raises the blood-pressure by vaso-constriction, accelerates the heart and respiration, and increases intestinal movements. Fimctional disorders of digestion and gastric catarrh, irritation of the pharynx, defective vision, nervous tremors, and dilatation of the heart, are all ascribed to excessive tobacco-smoking ; and it is maintained by some that serious circulatory disorders, including arterio-sclerosis, may be produced. It is, of course, towards the end of a pipe, cigarette, or cigar, that most of the nicotine is taken into the system. 390 HYGIENE AND PUBLIC HEALTH Q O O O tn ft 'A < < H in Q W H P^ O P ^ P < ^ f^ O O >H :pq fl o 2 m ^ Ph.2 c« j5 iO rt n3 v^ V. 03 S '^ O C ■pi Xi O "U en O -e O O 03 U O ;^_| 03 5^3 2 073 ON «^ S 00 Ph o ^ •■S^a ' s a o 03 m £ •H a •S c o Is C g -M _r 03 03 03 ^, O rj d X 03 O^j g 43 fX" ^ . -^ "^ S ?, -■a s ^^ • ^ en S-^ ^ ^ ■^^ ^^ o3 03 1-1 -fl &,03 a^ u-i en -p p.a p^ o3 •- a'S ^sa 03 St? 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P Q c8 o ■+J bo d ce O o o en 43 CO ■u ^ « O tn j- 03 rt en P en 4; > Ph p en o "o -M c -. i O c o 03 T) -^ « rt J^ S '^ 5 OJ JH o "-1 o " nS 5 - be H m S o bo o3 be _C 'C P _o "o o tn _o '-P P. 'o 03 o % o "cS en 3 -4-J 03 & 43 en 43 U Ph en 03 'G o 03 o '2 'o o3 o ■>, _o en 03 o I 1 > T3 " ^ a; o o +-> o X) en d 4; s o o CO fi| _cn o 'o _o 'o o "cS -d p o3 1 cd 53 tn 43 u a -3 JJ J3 S n3 1 o s 1 Jj be a N P 'en en o3 P^ pq fl^ H S w <; O W pq : en O .'S > d 43 d -(-1 0) en i ,p p" o i U m p en" CJ 03 o -1-1 O ■n 43 /3 tC "rt o o TJ O p 03 13 en" 4J 1^ p en a en P ^ o3 o u < o3 O 'p cti 1—1 03 CD o.t: 03 C/J o 43 p n ctf -tj Vn Vh rO 43 !_i X) P P 4)" P p -1-1 o 01 +J p p o IT) 43 -f-" o rP ;.< AO frt o3 jj 43 OX O P O 4-> rn 4J 43 en 3-cJ P o (T^ •^ p O ? '? T) r^ P P V. 4) o en Vh '-' 03 rj 43rP O ",P "3 !rt 'x 4J P +J p ,_^ 9 ^'3 .5 ^ " 43 O 4; P O O cR 75 ,Q O .P 43^ TO ^^ S MH O 03 °^ be >>S3.2 TO -p QJ 43 42-2 O O 1^ ■-n ^T en IS >~t < w cifnrru" + + + + + I I I 1 I I any such conditions. It is probable that during epidemic periods small-pox is very frequently spread by the number of mild and not easily recognizable cases of the modified disease in vaccinated persons, and the failure to distinguish chicken-pox from this 414 HYGIENE AND PUBLIC HEALTH type. The virus from such mild forms is capable of imparting a very virulent form to un vaccinated persons, and the same holds true of nearly all infectious diseases. Pre\'ious to the discovery b}^ Jenner, towards the end of the eighteenth centurj^ of the protection afforded by the inoculation of co^^•-pox IjTnph against attacks of small-pox, small-pox was a disease from which few escaped. From 1750 to 1800, small- pox caused nearly one-tenth of the total number of deaths (96 out of ever}'" 1,000 deaths from all causes), and in epidemic years — 1796, for example — this fatalit}^ was occasionally nearty doubled. So universal was the disease, and so frightful its dis- figuring effects and the risk of loss of sight, that the practice of inoculation, introduced originally from Constantinople by Lad}^ Mary Montagu, became ver}^ general during the latter half of the eighteenth century. The fatality of the disease so imparted was found to be much less than that of natural small-pox, 2 or 3 per cent, of the cases ending fatally instead of 20 or 30 per cent. ; but the infection was thereby enormously multiplied all over the country, and the epidemics became more frequent than ever. Mean Annual Death-rates from Small-pox at Successive Life Periods per Million living, at each such Life Period. All 45 and age.s. 0-5. 5-10. 10-15. 15-25- 25-45. upwards. I. Vaccination op- tional (1847-53) 305 1617 337 94 109 66 22 II. Vaccination ob- Hgatorj^, but not efficiently enforced (18 54- 71) ... . 223 817 243 88 163 131 52 III. Vaccination bet- ter enforced by vaccination officers (1872- 91) ... . 89 177 95 54 97 86 38 IV. 1 891 -1 900 . . . 13 29 10 3 8 17 10 Jenner published the result of his researches in 1798, and since that time vaccination has made steady progress through all classes of the population, with the result of gradually diminishing the frequency of epidemics, the severity of the disease, its incidence on the population, and its death-rate. In 1838 gratuitous vacci- nation was provided, and in 1854 vaccination became compulsory for all infants above the age of three months ; but it was not until COMMUNICABLE DISEASES 4I5 1871 that Boards of Guardians were obliged to appoint public vaccinators for their districts. From 1838 to 1853 the annual death-rate from small-pox in England and Wales averaged 0-42 per 1,000 persons living ; but during the past twenty years the average is below 0-02 per 1,000. At the same time the proportion of small-pox deaths to deaths from all causes has fallen gradually from nearly 100 per 1,000 (or yt>) in the eighteenth century to an average of about 10 per 1,000 (or t^^) from the year of com- pulsory vaccination to the present time. The average death- rate from small-pox in the eighteenth century was probably not less than 3 or 4 per 1,000. During the ten years 1891-igoo the average death-rate in England was only 0-013 per 1,000, notwithstanding the increased facilities for the spread of the disease resulting from the greater crowding on area of the population during recent years. Compulsory vaccination in infancy has saved the lives of an enormous number of children, who formerly died of small-pox, whilst the death-rate from small-pox at all ages has of recent years greatly diminished. The mortality from small-pox amongst infants under one year of age is largely due to deaths of infants from this disease before vaccination has been performed. After the age of fifteen the protective influence of the primary vacci- nation has to a large extent disappeared ; and unprotected adults form a larger proportion of the population than in the earlier periods, when an attack of small-pox in childhood was far more common and, as a rule, gave immunity from the disease for the rest of life. It was at first thought that one vaccination afforded indefinite protection to the individual against small-pox. This is now known not to be the case— with regard to infantile vaccination, at least. In the first place, the efficacy of vaccination depends largely upon the efficiency of the operation and the number and character of the resulting scars. Secondly, the protective influence wears away with the lapse of time, and revaccination at or before the age of puberty is a measure the necessity of which is beyond question. Calf lymph, and that from a vaccine vesicle of the eighth day from a healthy infant, if used perfectly fresh, are probably capable of giving equally good results, as regards protection. The protective effects of vaccination have been studied chiefly in relation to the fatality and severity of the disease in the 4l6 HYGIENE AND PUBLIC HEALTH vaccinated and unvaccinated. But this, it must be lemembered, is only one side of the question, and the relative incidence of the disease on these two classes is deserving of study. The exact proportion of unvaccinated to vaccinated in the com- munity is not definitely known, but taking it at its highest figure, the unvaccinated probably do not form more than lo per cent, of the total population. On the other hand, the unvacci- nated certainly form not less than 30 per cent, of the cases treated in small-pox hospitals, and the proportion of severe and heemorrhagic cases is far larger amongst the unvaccinated than the vaccinated. The fatality of the disease in the two classes is illustrated in the diagram, founded on figures supplied by Dr. Collie (for the two epidemic years of 1871 and 1881), of cases treated in London small-pox hospitals (fig. 80). Under fifteen years of age and over fifteen years the mortality per cent, of cases in the unvaccinated is nearly identical, viz., 37 or 38 per cent. ; whilst under fifteen the influence of the number and character of the scars in the vaccinated is seen to be of not nearly so much importance as over fifteen. The evanescence of the protective influence of primary vaccination after the age of fifteen is thus well exhibited : for whereas one or more bad marks reduce the mortality to 4 per cent, under fifteen, over fifteen the mortality of cases with one or more bad marks is 10 per cent. Taking nearly 7,000 cases observed in recent years, the Royal Com- mission on Small-pox and Vaccination found that the small- pox fatality rate in persons with one mark was 6-2 per cent. ; with two marks, 5-8 per cent. ; with three marks, 3-7 per cent. ; and with four marks, 2-2 per cent. Revaccination at puberty, if properly performed, confers a very high degree of immunity from small-pox for the remainder of life ; and if by any chance a revaccinated person should acquire small-pox, the disease generally assumes its mildest type. In Prussia since the year 1874, when vaccination and revaccina- tion became compulsory, the death-rate from small-pox has been reduced to one-tenth of its former rate, viz., from 0-24 per 1,000 to 0-02 per 1,000 ; and it is stated that in the Prussian Army there has not been a single death from small-pox from 1874 to the present time. In Germany, with a population of over 50,000,000, surrounded on three sides by badly vaccinated countries, small-pox has been COMMUNICABLE DISEASES 417 almost stamped out, and during the ten years 1885-95, 79 per cent, of the few cases which occurred were resident on the frontiers ; whereas in Austria and Belgium, where vaccination is not compulsory, the death-rates from small-pox are more than Under 15 Years. 10- 3] Over 15 Years. 5S A B G n E A. B C n E Fig. 80. — Small-pox Epidemics, 1871, 1881 ; Mortality per cent, in Fever Hospitals (London). -15 -I-15 (386) (174) A = = unvaccinated. (222) (483) B = = one or more bad marlv (76) (141) C = = one good mark. (44) (151) D = = two good marks. (70) (100) E:: = three good marks. twenty-fold as great. The great immunity which Germany enjoys is due to the fact that in that country vaccination and revaccination are compulsory, and, as a consequence, in Berlin, with a population of 2,000,000, 12 hospital beds reserved for small-pox have been found for many years to suffice for all requirements. The compulsory vaccination age is the second year of life, and it is significant to note that in 1886-90 more than two-fifths of the few deaths that occurred from small-pox were under two years of age. Revaccination is performed in Germany at the end of the period of compulsory school attend- ance, and every recruit is revaccinated on joining the army. In France primary vaccination must be performed between three and twelve months of age, and revaccination between ten and eleven years of age, and again between twenty and twenty-one. Dr. Barry found from the facts of the Sheffield epidemic of 1887-8 that un vaccinated children under ten years are twenty times more liable to attack than the vaccinated, and unvaccinated persons over ten are five times more liable ; and in unvaccinated 27 41 8 HYGIENE AND PUBLIC HEALTH children under ten the attack is twenty-two times more likely to be fatal than among the vaccinated, while in unvaccinated persons over ten the risk of an attack proving fatal is eleven times as great. Therefore, during small-pox prevalence, an unvaccinated child under ten is 440 times more liable to die than a vaccinated one, and an unvaccinated person over ten is fifty-five times more likely to die than a vaccinated one. Moreover, 17-2 per cent, of the attacks were severe among those vaccinated, while among the unvaccinated 81 per cent, were severe ; and in children under ten years 9 per cent, of the attacks were severe among those vaccinated, and 78 per cent, among those unvaccinated. In houses invaded by small-pox, in the course of an outbreak, not nearly so many of the vaccinated inmates are attacked as of the unvaccinated, in proportion to their numbers. Taking children under ten in invaded houses, in Dewsbury, io-2 per cent, of the vaccinated were attacked, and 50-8 per cent, of the unvaccinated ; in Leicester, 2-5 per cent, of the vaccinated, and 35 per cent, of the unvaccinated ; and in Gloucester, 8-8 per cent, of the vaccinated, and 46-3 per cent, of the unvaccinated. It is the custom for antivaccinators to attribute the reduction in small-pox incidence to improved sanitation ; but improved sanitation will not account for — (i) The fact that small-pox mortality has been transferred from childhood to the later periods of life since vaccination has been introduced ; whereas in Germany, where vaccination is not compulsory till the second year of age, over 40 per cent, of all the small-pox mortality occurs under two years of age. (2) The immunity enjoyed by revacci- nated postmen and nurses. The re vaccinated nurses at the Leicester Small-pox Hospital escaped, while those who refused revaccination were attacked. (3) That the disease passes by the vaccinated children, but attacks the unvaccinated living in the same house, as in Dewsbury, Leicester, and Gloucester. (4) The lessened fatality among the vaccinated if attacked. (5) That those with three or four vaccination marks are less liable to a fatal attack than those with one or two. (6) The great immunity which Germany enjoys, even as compared with Great Britain. Finally, the disease has never been shown to be caused, directly or indirectly, by any insanitary condition. The isolation of small-pox cases in hospitals is a useful auxiliary to vaccination, but it is not a sufficient substitute for it, owing COMMUNICABLE DISEASES 419 to the inevitable failure to secure isolation, in all cases, with the necessary thoroughness and promptness. Such failure results from parents not observing the early symptoms of the illness, the neglect to call in a doctor, the difficulties of diagnosis, the delays in removal, the probable inadequacy of the hospital accommoda- tion during an epidemic, and the possible inefficiency of the disinfection of infected articles. The operation of vaccination, if properly performed with clear fresh lymph, does not impart any other disease but vaccinia. But among the maladies which have been attributed to vaccination are : syphilis, erysipelas, diarrhoea, tabes mesen- terica and scrofula, bronchitis, cancer, leprosy, and many forms of skin disease. Vaccino -syphilis has, however, in the past happened so rarely as to constitute it a clinical curiosity. With the general intro- duction of calf lymph it will disappear altogether, as calves are not subject to syphilis. Vaccino-syphilis has often been confounded with a congenital syphilis, latent until lighted up by vaccination. The acquired syphilitic rash, however, appears at the earliest from fifty to ninety days after vaccination, and in every case a chancre forms at the site of vaccination. The syphilitic chancre is limited to one or two points of inoculation, inflammation is slight, loss of substance is superficial, and the parchment in- duration is typical (Fournier). That the increase in infantile syphilis is due to vaccination, as asserted by the antivaccinators, is disproved by the fact that whereas in England and Wales, with vaccination generally enforced, the increase in the infant mortality from syphilis between the two periods, 1863-7 ^^^ 1883-7, was 24-7 per cent., in Leicester, where vaccination has been neglected, the increase was no less than 69-3 per cent. As to vaccino-erysipelaSjthis disease has doubtless often resulted from vaccination, either directly from the failure to take due precautions as regards cleanliness at the time of the operation, or, indirectly, from exposure to dirt and insanitary conditions in the home of the recently vaccinated infant. The frequency of occurrence of vaccino-erysipelas is, however, greatly exagger- ated by the antivaccinators. In the two periods already men- tioned the infant mortality from erysipelas in England and Wales decreased by 16-7 per cent., whilst in Leicester, with neglected vaccination, there was an increase of 41-5 per cent. Similarly, diarrhoea and bronchitis have increased among the unvaccinated 420 HYGIENE AND PUBLIC HEALTH infants of Leicester more than in England and Wales as a whole, a fact which proves the fallacy of attributing any increase to vaccination. With regard to cancer, the Royal Commission on Vaccination concluded : — " There is not a shadow of evidence to connect the increase with the practice of vaccination, whilst there is . . . evidence pointing the other way." The same remarks are applic- able to the alleged spread of leprosy by vaccination. There is no evidence, moreover, that tuberculosis has ever been in- oculated by vaccination, and attempts to thus inoculate the skin of guinea pigs with lymph from tuberculous patients have uniformly failed. That the disease may be transmitted through the medium of animal (calf) lymph is a groundless fear, which has been encouraged by antivaccinators. Such a case has hever yet been reported, although animal vaccine has been in use for many years, more especially on the Continent. Certain rashes have doubtless been produced, and not infre- quently, by vaccination. Even when vaccine quite pure and free from other virus is inoculated, eruptions of urticaria, erythema, lichen, purpura, and later, as sequelae of vaccination, eczema, psoriasis, and pemphigus, have been observed. When, however, the vaccine has not been pure, impetigo contagiosa, S5^philis (very rare), erysipelas, cellulitis, pyaemia, or local gangrene have occasionally resulted from the inoculation of the lymph. It is the intention of the Government to limit vaccination and revaccination in the future, so far as is possible, to vaccination with glycerinated or chloroformed calf-lymph. The object is to reduce the risks of conveying " vaccinal " diseases, which were sometimes incidental to " arm-to-arm " vaccir^ation. The glycerine or chloroform serves to preserve the lymph, without in any way interfering with its activity, and it destroys extraneous organisms (even, in time, the Bacillus tuberculosis). The presence of a little blood in the Ijnnph is quite harmless, and the danger of imparting disease appears to be absolutely avoided by the use of such lymph. The calves used are carefully watched, their past history is enquired into, they are slaughtered after use, and a post-mortem examination is made, whilst in some countries the calf is tested with tuberculin before inoculation with vaccine lymph. These precautions are taken notwithstanding the great rarity of tuber- culosis in young bo vines. The age of the calf, its general health COMMUNICABLE- DISEASES 421 and nutrition, and even the season of the year, affect the quality of the lymph collected. In Paris the lymph is diluted with an equal bulk of glycerine •; in Brussels twice the bulk of glycerine is added ; in England five to eight times its bulk of 40 or 50 per cent, pure glycerine in distilled water is added ; and in Berlin a solution of equal parts of glycerine and boiled water is added to the epithelial pulp scraped from the vaccine vesicles, in the proportion of 14 parts of the solution to i of the pulp. In the process of chloroforming, a mixture of chloroform vapour and air is passed through the vaccine emulsion. The vaccine so treated can be issued for vaccination purposes after an interval of seventeen days, which is a shorter period than is required in the case of glycerinated lymph. It is probable that if vaccination is performed on a person who has already contracted small-pox, within forty-eight hours of the exposure to contagion, vaccinia ensues and small-pox is avoided. But if performed at a later date small-pox is contracted, modified if within three days, but unmodified if later, with vaccinia possibly running its own course at the same time. Considerable evidence has now been accumulated in support of the view that cow-pox is human variola modified by its occur- rence in the cow. Klein has shown that when lymph from the vesicles of a human small-pox case is inoculated into a calf, very little local result is produced, but that if material from the local lesion is taken on the filth day, and inoculated into another calf, and this process is continued until four calves have been inoculated, the material from the fourth calf (four removes from the small-pox patient) might with safety be transferred to the human subject, with the production of typical vaccinia. The lymph from the vaccine vesicles, so produced in the human subject, caused, alike on inoculation into the bovine or the human subject, typical vaccinia. ■ . Whatever the original cause of cow-pox in the bovine species, it seems certain that the disease is now tra^smitted directly from animal to animal, and that its origin from human small- pox is an event of very rare occurrence, if it ever happens. Small-pox may be confounded with measles and scarlet fever, owing to scarlatiniform or morbilliform rashes occasionally preceding the true variolous eruption ; and the latter may be 422 HYGIENE AND PUBLIC HEALTH mistaken for chicken-pox, acne, impetigo, eczema, syphilis, and typhus. A failure to recognize the true nature of the disease is often responsible for subsequent spread in epidemic form. The chief preventive measures to be taken on the occurrence of a case of small-pox are : — (i) The removal of the patient to an isolation hospital ; (2) the disinfection of infected rooms and clothing ; (3) the revaccination of the other inmates of the house ; (4) either the quarantining of those contacts for fourteen days who have had personal communication with the patient during his illness ; or a daily medical inspection with the object of promptly isolating them on the appearance of the initial symptoms ; (5) the notification of schools attended by children in the house. Having regard to the fact that in the event of an outbreak of small-pox the Sanitary Authority has to direct all the other administrative measures taken to stamp out the disease, it is an anomaly that the important measure of vaccination and revac- cination should not also be under its direct control. It is, moreover, desirable that legislation should empower the infliction of a penalty for withholding the fullest information, or for giving false information, when sanitary officials are en- deavouring to trace the origin of, 01 to otherwise deal with, the infection. With reference to the quarantining of contacts the Local Government Board, in a circular issued in 1902, advised as follows : — If, on a dwelling becoming invaded by small-pox, the actual patients are at once removed to hospital, the dwelling and all articles in it that have been exposed to infection, including the clothes worn by the other inmates, are properly disinfected, and the other inmates of the house are immediately revaccinated or vaccinated (as the case may be), there is no material advantage to be gained by keeping these other inmates at home. They are not likely to infect other people unless they themselves develop small-pox ; and all that is required is to keep such persons under medical observation for a fortnight, and particularly to examine them carefully day by da}'- towards the end of the second week from their exposure to infection, in order to ascertain whether any of them are developing small-pox. If none of them do so by the beginning of the third week from exposure, the revaccination (or vaccination) to which they were at once submitted on the occurrence of the first case in the invaded house should secure them from attack by the disease. The Board consider that in ordinary circumstances the course of action indicated above is the correct one. Occasions, however, may arise in which additional precautions may be necessary ; as, for example, when laundries are in question, or where the business or habits of the inmates of an invaded house are such as to make it difficult for proper medical observation of them to be maintained. In exceptional cases of this kind, in which a Borough COMMUNICABLE DISEASES 423 Council are advised by their Medical Officer of Health that in the special circumstances it is essential that the inmates should remain in their own houses, the Board would be prepared to sanction a reasonable expenditure in securing such a result. Many outbreaks of small-pox have been traced to tramps — a class of people who are practically exempt from any sort of sanitary supervision. To obviate this danger, the local authority should be empowered to require a medical examina- tion of all persons entering common lodging-houses and casual wards, and to enforce the temporary detention of all small-pox " contacts " of the vagrant class. Scarlet Fever. This is a specific infectious disease like small-pox, its propaga- tion being dependent upon a specific contagium derived from a previous case of the disease. The incubation period vaiies from a few hours to eight days, and is usually from twenty-four to seventy- two hours. Infection is given off in the throat secre- tions and from the skin of the patient during the whole period of illness, but the acute stage of the fever, when the sore throat and rash are most highly developed, is doubtless the most infectious, and not the desquamative stage, as once generally supposed. The contagion clings with great pertinacity to the clothes, bedding, and furniture of the sick-room, but is not capable of diffusion and dissemination through the air without loss of virulence, like the small-pox contagium appears to be. Schools play an important part in disseminating infection, and many milk-borne outbreaks of this disease have been recorded. The usual duration of infectiveness in scarlet fever is from six to eight weeks, lasting throughout convalescence, and possibly prolonged by the occurrence of nasal or oral discharges, etc. In large towns scarlet fever epidemics tend to recur every few years, as a fresh series of susceptible children accumulates in the community. Scarlet fever is more especially a disease of childhood, the incidence being greatest at five and six years of age. The influence of age and sex upon the incidence and fatality of the disease may be thus summarized :■ — The mortality from scarlet fever is greatest in the fourth year of life, and after this diminishes with age, at first slowly and afterwards rapidly, owing to the diminishing risk in successive age periods of an attack, should it occur, proving fatal. The 424 HYGIENE AND PUBLIC HEALTH liability to attack is small in the first year of life, increases to a maximum in the fourth or fifth year, and then becomes rapidly smaller and smaller with the advance of years. The female sex throughout life is more liable to scarlet fever than the male sex ; but the attacks in males, though fewer, are more likely to ter- minate fatally. The proportion of fatal cases to attacks of scarlet fever cannot be accurately stated, owing to the large number of unrecognized cases of very mild type, often without skin eruption, and with very little desquamation. The case mortality (proportion of deaths to attacks) is not greater than from 2 to 3 per ceiit. The very mild and unrecognized cases are, doubtless, the most frequent sources of dissemination of infection, and the fact of their being true scarlet fever cannot be doubted. The mortality of well-marked cases, such as those admitted into the Metro- politan fever hospitals, is now between 3 and 4 per cent. (3-2 per cent.), whilst the mortality of notified cases in London is 2*6 per cent. For the five years 1901-5, the death-rate from scarlet fever per 1,000 living at all ages in England and Wales was 0'i3. In 1908 it was only o*o8. During the ten years 1871-80, the average death-rate in England and Wales from scarlet fever was 07 per 1,000 living at all ages. The lower mortality from scarlet fever of recent years is due, not to a lesser prevalence of the disease, but to a milder type. The proportion of deaths to attacks is now only about a half of what prevailed thirty years ago. Scarlet fever is a disease from which very many people alto- gether escape. The importance of saving young children from attacks of scarlet fever has been well expressed by Dr. White- legge :— " In shielding a child against infection during the first few years of life there is a double gain ; every year of escape from scarlet fever renders him less and less susceptible, until finally he becomes almost insusceptible ; and, secondly, even if he should ultimately take the disease, every year that the attack is deferred reduces the danger to life which it brings. In other words attacks of scarlet fever become both less severe and less frequent with every year of age after the fifth. Up to the fifth year the liability is less (than in the fifth year), but the risk of life in case of attack is very great." COMMUNICABLE DISEASES 425 The same reasoning applies with almost equal force to measles, whooping cough, and the other infectious complaints of child- hood. Overcrowding and insanitary conditions in houses tend to aggravate the severity of scarlet fever attacks, and to aid in their dissemination, but can have no influence per se in originating an outbreak. Scarlet fever is most prevalent and most fatal in the months of October and November. Two curves may be formed, one expressing the deaths as percentages of the average mortality throughout the year (fig. 79), the other expressing the number of cases as percentages of the average of cases throughout the year. These curves correspond very closely, but Dr. Whitelegge has noted that the mortality curve rises less and falls less above and below the mean than the case curve, which would imply that when most prevalent scarlet fever is least fatal, and vice versa. There is a strong probability in favour of this view, as the number of mild cases is usually greatest when scarlet fever is most prevalent. It sometimes happens that a patient discharged from hospital, apparently free from infection, is the means of communicating the disease to another member of the family on his return home. These " return cases," which, however, in most large communities form less than 3 per cent, of the total cases treated in hospital, have been explained in many ways. Doubtless they are some- times examples of mere coincidence ; at others they may result from : (i) the non-disinfection of articles of clothing, books, or toys, which have been used by the patient prior to removal to hospital, and produced again on the patient's return home ; (2) carelessness on the part of hospital officials in prematurely discharging patients with unhealthy throats, nose and ear dis- charges, etc., or in not sufficiently bathing the patients and shampooing the head prior to discharge ; (3) the reappearance of desquamation (?), or infectious discharges after dismissal of the patient from hospital in an apparently healthy condition ; (4) the conveyance of the infection in the lungs of recently discharged patients (?). The entire prevention of such " return cases," even by the exercise of every possible care, seems impossible in practice ; but their number would doubtless be reduced if parents could ;and would observe the precaution of keeping the child apart 426 HYGIENE AND PUBLIC HEALTH from other children for at least one week after returning home from hospital. The provision of special convalescent wards, of smaller ^^•ards invohdng less aggregation of the patients, and the greater development of bacteriological assistance, are further measures that are recommended. The value of the hospital isolation of scarlet fever has been called in question, as those to^^^ls where the largest proportion of cases are thus isolated cannot be sho^^^l, statistically, to have suffered less from scarlet fever than others where little or no such isolation has been provided. This is largely due to the fact that the value of the hospital isolation of this disease has been discounted by the frequent failure to recognize cases of infection in a sufficiently early stage — more especially during the recent years of attenuated virulence of the disease. But hos- pitals are onlj' one of the factors which determine the prevalence of infectious diseases, and the other factors concerned may con- ceivabl}^ favour those to^^^ls where hospital isolation has been comparatively little practised ; besides, we have no means of kno^^dng what would have happened in those towns where a large proportion of cases are isolated, if no hospital isolation provision had existed. Moreover, the different wave lengths of epidemics, the variable intervals between local epidemics, and the different proportions of those comprised within the sus- ceptible age periods in the towns compared, may make the comparison a misleading one. Certainl}^ scarlet fever is now a very mild disease, and a large amount of money is spent upon its isolation to the possible prejudice of other far more fatal diseases ; and these facts warrant some discrimination in the selection of the cases which should be admitted to hospital — the cases selected being limited to those who cannot possibty be isolated at home owing to special circumstances, including interference \\ith the wage-earning or educational needs of the other members of the household. It is only reasonable to maintain that hospital isolation of the disease must have done something to reduce the number of those who would otherwise have been attacked, and that skilled hospital treatment must have been beneficial to the sufferers ; but there is little to be said for the indiscriminate isolation practised in London and elsewhere. In conclusion it must be borne in mind that the experience of the past shows that the infection of scarlet fever has exhibited secular periods of attenuation and renewed COMMUNICABLE DISEASES 427 vdrulence ; and the disease may possibly in a few years again assume the severer type, which demands an extensive provision of hospital isolation. Measles. A specific infectious fever, with an incubation period generally of nine to twelve days, but which may be as short as four days and as long as fourteen. The contagion is given off from the secretions of the nose, throat, lungs, and possibly from the skin of the patient during the whole period of illness. The catarrhal stage preceding eruption is especially infectious, and at this stage it is impossible to diagnose the complaint with certainty. It is for this reason that epidemics of measles are so difficult to control. The infection is not widely diffusible in the air, but clings to clothes and garments. Measles is a disease of infancy and early childhood, and is very fatal to young children, frequently owing to pulmonary complications and sequelae. Adults unprotected by a previous attack are also susceptible, but the disease is so universal in this country that few children escape from it. The mortality from measles is greatest under three years of age ; the highest death-rate is reached in the second year of life ; after five years of age the mortality is enormously diminished. Over 90 per cent. of the total deaths are among children under five. During the five years 1901-5, the death-rate at all ages in England and Wales from measles was 0*33 per 1,000 living at all ages ; and in 1906-8, it was 0-29. In the ten years 1871-80, the average death-rate in England from measles was 0-38 per 1,000 living at all ages ; and in the decennium 1861-70 it was 0-44. Both sexes are equally liable to attack, and the case mortality is about the same for both. In this disease the case mortality is greatly affected by overcrowding and insanitary conditions generally. In the over- crowded houses of the poor, amongst badly nurtured children, the proportion of deaths to attacks may be as much as 20 or 30 per cent., and is, no doubt, intensified by the neglect of the parents to provide suitable warmth and nourishment for the sufferers from a disease which they think of little moment. In healthy houses, well-nourished children almost invariably make a good recovery. Measles is most prevalent and most fatal in the winter months of November, December, and January ; but it also tends to 428 HYGIENE AND PUBLIC HEALTH become somewhat intensified in the late spring (May and June) (fig- 79)- Measles epidemics tend to recur in large to\^^lS about ever}^ two or three 3^ears, \dth the accumulation of a batch of susceptible children ; and since the disease is pre-eminently fatal in the first, second, and third years of life, it follows that if it can be so far discouraged by preventive measures as to acquire epidemicity onh' everj' fourth year, a large number of children Mdll have passed the age at which the disease is most fatal, and many lives \^ill be saved. Some people advocate the compulsor}' notification of measles, and the arguments that have been adduced in favour of this measure are as follows : — It is claimed that compulsory notification furnishes early information of the first cases, and that notification is the best means of obtaining this information. This information would enable the follo^^'ing measures to be carried out : (i) the visiting of parents and guardians, and advising as to isolation and removal to hospital (where hospital provision exists) ; (2) the control of school attendances ; and (3) the prompt detection (to be followed by closure) of schools which are acting as foci for the dissemination of infection. It has also been asserted that the notification of measles, and the measures resulting therefrom, would cause the public to regard the disease ^^^th more seriousness, and that it would encourage amongst the poor a more general medical attendance upon the sufferers. Those who do not favour the compulsory notification of the disease maintain that, on account of the exceedingly infectious pre-emptive stage of measles, the notification certificate would arrive too late to be of much value in the adoption of the measures necessar\^ to protect others in the infected household. In most cases four daj^s elapse (during which the infection is at its highest) before the characteristic rash makes its appearance, and another day at least would follow before the notification is received and acted upon. Prior to the rash the disease cannot be diagnosed, and aU those who are susceptible have probably been full\:' exposed to the infection. This is the intrinsic difficulty which has to be faced in measures dealing with this complaint. Further, there is a great tendenc}' among the poor to regard the disease as inevitable and trivial, and in consequence they do not recognize COMMUNICABLE DISEASES 429 the desirability of isolation, nor do they consult a medical man in a large percentage of cases, unless grave symptoms supervene. In country districts the majority of the cases are not medically attended. Obviously, then, those cases which, occurring in small houses often crowded with other children, are the most potent for harm, would not be notified ; and the notification of cases among the better classes, who have already called in a medical man and received the benefit of his advice, would form the bulk of the notifications received. Efficient home isolation of infant sufferers from measles in the dwellings of the poorer classes is generally impracticable ; and without the means of offering hospital isolation, the com- pulsory notification of measles would be premature. But even if such hospital provision were made — and it would have to be on a very large scale to deal with a fair proportion of the cases occurring in an epidemic — there would still be much difficulty found in inducing the parents to accede to the removal from home of children of such tender years as those who form the bulk of the sufferers from measles. Certainly, if notification is to prove of service, every possible use must be made of the information it provides. Every infected household must be promptly visited ; the source of infection traced ; the existence of unnotified cases discovered, if possible, from the clues afforded by the notified cases ; schools, libraries, etc. , must be communicated with ; premises must be disinfected ; and suitable isolation at home insisted upon (where possible). Now, all this would entail a large staff, which could scarcely be appointed temporarily with advantage ; and if, therefore, notifica- tion proved a failure, it would be a very costly one. During past years a few (under i per cent.) of the sanitary authorities in England and Wales have included measles in the list of notifiable diseases ; and in the majority of cases the Medical Officers of Health either acknowledge that they have reaped no advantage, or they express their doubts as to the utility of the measure. It is both interesting and significant to note that, up to the commencement of the year 1899, the Infectious Diseases Notifi- cation Act had been extended to measles in no cases, to rotheln in seven, to whooping cough in tweijty-six, and to chicken-pox in eight (on account of the frequency with which it is confused with modified small-pox) . But in over forty of these cases the 430 HYGIENE AND PUBLIC HEALTH sanitary authorities have subsequently revoked the addition of measles, in one that of rotheln, in seven that of whooping cough, and in four that of chicken-pox, while in one case the Act was extended to measles only for a limited period, which has now expired. It may be useful to bring measles under the Notification Act in rural districts and in small isolated communities, if in these cases every advantage is taken of the information thus obtained to detect unnotified cases, and the means of hospital isolation are provided ; but in larger communities, especially when not adopted in neighbouring districts, the measure is not to be recommended. What has to be faced is a largely preventable mortality due to ignorance — a mortality which is very high among the poor, and very low among the better classes ; and the most successful scheme for reducing measles mortality appears to be one which will take advantage of all the means which elementary schools offer of {a) educating the future parents to take a more serious view of the disease, and to treat children affected on proper lines, and of (6) gaining early information, and checking the spread of infection. The greatest checks to the spread of the disease would be the exclusion from school of the younger children from infected houses, the sending home of suspicious scholars, the visitation of absentees, the prompt notification to the sanitary authority of infected households by school attendance officers, and the occasional prompt closure of schools (infants' departments) during epidemic periods. Occasionally measles is responsible for considerable loss of school attendance. To reduce this to a minimum it is now advocated that a " measles history " of the school children attending each class should be kept ; and when a child is suspected to be suffering, and the record shows that he has not had the complaint, and is therefore susceptible, he should be sent home. If, when the disease- is rife, the class contains a large proportion of such susceptibles, it should be promptly closed. Dr. Thomas found (i) that in London, except in the better class districts, 75 per cent, of the scholars above five years of age are protected b}^ a previous attack, and therefore at present the disease can spread but little in classes of scholars above that age ; (2) that a class of over 30 per cent, of susceptibles is one COMMUNICABLE DISEASES 43I in which the disease tends to spread ; and (3) that, if children under five were excluded, school closure for measles would be unnecessary in London. When school closure is resorted to, it must take place before the " first crop " of cases occurs, if any useful purpose is to be effected. It is highly desirable that measles should be definitely brought within the scope of the expression " infectious disease " as used in the Public Health Acts of 1875 and 1891 (London), in so far as relates to wilful exposure of sufferers. Rotheln, Rubella, or German Measles. — This is a specific infec- tious fever, propagated by a specific contagium ; and not a hybrid between measles and scarlet fever, from neither of which diseases is it protective. It has a usual incubation period of fourteen to eighteen days, but this may vary from one to three weeks, and the patient is infectious during the whole course of illness (seven to fourteen days). It is not a disease of common occur- rence, and the illness produced is almost invariably very mild. Children and young adults are most susceptible. Whooping Cough. This is a specific infectious disease, the infection being given off in the secretions from the lungs. The specific organism has not yet been determined. It is probably not carried far in the air, but clings pertinaciously to articles of clothing. The period of incubation may last from one to three weeks, and the period of infectiveness is usually not less than six weeks from the onset of cough, and may be longer. Infants and young children are especially susceptible, and comparatively few escape attack. The younger the child, the greater is the likelihood of the attack proving fatal ; 40 per cent. of the mortality from whooping cough occurs in the first year, 30 per cent, in the second, 15 per cent, in the third, and 6 per cent, in the fourth. Girls suffer more from severe attacks which end fatally than boys, and their liability to contract the disease is also probably greater. In the first two years of life the pro- portion of deaths to attacks cannot be less than 10 per cent., and is probably . higher. After the third year this proportion is not more than 2 per cent. Adults seldom suffer, as they are so generally protected by an attack in childhood ; but if unpro- tected they are equally liable with children. Whooping cough is now, next to measles, the most fatal of all 432 HYGIENE AND PUBLIC HEALTH the infectious complaints of childhood under the age of five years ; the deaths being due in most cases to pulmonary complications (broncho-pneumonia). For the period 1891-1900, the death-rate was 3-1 per 1,000 under five years of age (measles being 3-2) ; and the death-rate for all ages was 0-38 per 1,000. Between 1871 and 1880 the death-rate for all ages averaged 0-5 per 1,000. Whooping cough recurs in regularly recurring epidemics every few years, but it has an exceptional prevalence and fatality in the spring. The seasonal curve attains its maximum late in March or early in April, and from that point rapidly declines {see fig. 79). Outbreaks of whooping cough and measles frequently occur at the same time, and the preventive measures in both diseases are similar. Varicella. Varicella, or chicken-pox, is often mistaken for mild or modified attacks of small-pox ; but the two diseases are quite distinct. It is a mild disease, but rarely fatal when uncom- plicated with other disease, and children are mainly attacked. The incubation period varies from thirteen to nineteen days, and is commonly about fourteen days. The infection of varicella is very considerable from the first, and may remain active for some time in fomites. The patient should be isolated until the last scab has fallen off. ■ Mumps. Often in cold and wet weather an epidemic of this disease breaks out, the infection spreading with great rapidity, but giving rise to little, if any, mortality. Outbreaks are sometimes associated with an epidemic of measles. Nothing is known of the etiology of the disease, but it is probably microbic in origin, the organism entering the gland from the mouth by way of Stenson's duct. One attack generally confers immunity from others. The disease attacks chiefly the early age-periods of life, and the incubation period is generally three weeks, but may vary from fourteen to twenty-five days. The swellings of the parotid and submaxillary glands, which are the most prominent symptoms, generally remain for about a fortnight. Occasionally epidemics occur among young adults ; and then serious complications are by no means uncommon, and deaf- ness, etc., may result. COMMUNICABLE DISEASES 433 Typhus. A specific contagious disease, but almost invariably found to be associated with conditions of filth, privation and over- crowding in large towns amongst poor working-class populations. The usual period of incubation is about one to two weeks. The infection appears to exist in the exhalations from the lungs and skin, and to be transmitted through the air from the sick to the healthy ; but it is rapidly destroyed by dilution with fresh air, and does not cling to articles of clothing, so that in a well-ventilated house typhus rarely spreads from the original case. It is probable that the disease may be conveyed by the bite of insects. The female sex and the age-period of ten to twenty-five years appear to be the most susceptible. The disease is liable to be mistaken for enteric fever, pneu- monia, meningitis, and even scarlet fever and measles. Ill- defined illness often precedes attacks, and these are characterized by their sudden onset and the late appearance of the rash. Being so closely associated with overcrowding, typhus increases in intensity during cold weather, when there is an inducement for many people to huddle together to keep warm. In some of our large to\vns, epidemics have recurred in certain poverty- stricken quarters with considerable regularity, as fresh susceptible individuals accumulate. The mortality from typhus has undergone an enormous diminution in this country during the last twenty years. Before 1869, typhus, enteric fever, and simple continued fever were included in the Registrar-General's returns under the generic heading of " Fever " ; but since that date mortality returns of these three diseases have been presented separately. In 1869 the death-rate from typhus in England was 0-193 per 1,000 living at all ages ; but for the ten years ending 1907 the average annual rate has been only o-ooii._ Simple Continued Fever. This is, probably, in a large majority of cases, a convenient term for the registration of deaths from undiagnosed and obscure cases of fever, such as may occur in typhus, general tuberculosis, septicaemia, pneumonia, and intermittent fever. Dr. Longstaff is of opinion that only a very small proportion of these deaths, if any, are due to enteric fever. Simple continued fever as a 28 434 HYGIENE AND PUBLIC HEALTH cause of death exhibits a decrease in the last twent\^ years closely analogous to that of typhus (in 1867 the death-rate was 0-24 per 1,000 ; in 1907 the death-rate was o-ooi). This decrease is, no doubt, largely due to greater precision in diagnosis, but ma}- to a certain extent be due to the diminishing prevalence of a definite disease. Diphtheria. The etiolog}^ of this disease is still to a certain extent veiled in obscurity. AA^ilst on the one hand it cannot be doubted that the contagion is transmitted from the sick to the healthy, on the other hand diphtheria outbreaks in rural districts at times appear to originate independently of the infection of a pre-existing case. But probably the diphtheria contagion has the power, under certain conditions, of lying latent for long periods of time, ^^ith the capacity of renewing its virulence under special circumstances ; and, as in the case of enteric fever, mild and unrecognized forms of the disease and " chronic carriers " may account for much obscurity of origin. In many instances of such occurrences the explanation may be that the organism of diphtheria, the Klebs-LoefSer bacillus, is sometimes present in a non-virulent form in the mouths of healthy persons ; and if a slight sore throat or tonsillitis occurs in such a person, then the bacilli maj^ become \drulent, and give rise to true diphtheria. A bacillus, kno^vn as the pseudo-diphtheria bacillus (Hoffmann) , has been described by many observers in the throats of apparently healthy children, as well as in those of patients convalescent from diphtheria. This pseudo-diphtheria bacillus is morphologically and culturall}'' allied to the Klebs-Loeffler bacillus, but is usuallj^ non-pathogenic to animals.. The relation between the two organisms has not yet been conclusively sho^^•n. Most authorities agree that Hoffmann's bacillus does not necessitate the preven- tive measures undertaken for coping against diphtheria. The diphtheritic contagion is given off from the body in the secretions from the mouth, nose, and throat ; and, although probably not far diffusible in the air, clings ^^ith gi-eat pertinacity to infected articles of clothing and bedding. As is the case \\ath some other infectious maladies, there appears to be in certain individuals a peculiar hereditary or fpmil}' susceptibility to attacks of diphtheria. Season has a marked influence on the manifestation, and, COMMUNICABLE DISEASES 435 above all, on the mortality from diphtheria. Epidemic preva- lences of the disease commonly commence in September, reach their highest point during October and November, and then subside slowly during the following two months — the smallest amount of mortality being witnessed from May to July. There is some excess of diphtheria mortality in females as compared with males. It is probably due, at all periods of life to greater exposure of females to infection in nursing (Thorne Thorne). The incubation period is usually under four days' duration, rarely, if ever, less than two or more than seven days. Diphtheria occurs endemically in certain localities, localized epidemic extensions taking place from time to time. It has been a matter of observation that certain districts, in which the surface soil is cold and humid, and where damp houses and privy and drainage nuisances abound, or where the aspect involves much exposure to cold and wet winds, suffer from an exceptional incidence. The broad geological features of a district — the permeability or otherwise of the surface strata — have not, as such, any observed influence on the development and diffusion of the disease ; but such topographical relations as facilitate the retention of moisture and organic refuse in the surface soil, or involve bleakness of site or exposure to cold and wet winds, appear to be of importance. According to Newsholme diphtheria tends to become widely epidemic in years of deficient rainfall, the epidemic wave becom- ing most marked when three or more years of deficient rainfall follow each other. Until lately diphtheria was regarded as being to a far greater extent a rural than an urban disease, but during the last thirty years diphtheria mortality has progressively increased very greatly in London and some other large cities. Thus, in 1881 in London the death-rate from diphtheria was 0-17 per 1,000, the average of the ten years 1871-80 being 0-12 per 1,000. The average of the decennium 1881-90, however, was 0-26 per 1,000 ; and of the decennium 1891-1900 050 per 1,000. Since 1899 there has, however, in London, been a steady decline in diphtheria mortality, the death-rate for 1908 being only 0-15 per 1,000. The same progressive increase and subsequent decrease has been witnessed in some of the other large cities and towns. -The incidence of the disease is most marked in children between the ages of two and twelve years, and subsequently decreases 436 HYGIENE AND PUBLIC HEALTH with every year of advancing age. As a rule, the younger the child, the greater the chance of an attack proving fatal. The average mortality of cases notified in London (average of 1890-4) was 23-8 per cent., and is now 9-1 per cent, (average of 1904-8), antitoxin having been in regular use since the end of the year 1894. The case mortality in the Metropolitan Asylums Board hospitals was, in the pre-antitoxin days, 30-3 per cent, (average of 1888-94), and is now under 10 per cent., the case mortality among those treated with antitoxin on the first day of the disease being only about 3 per cent. School attendance is now acknowledged to be a very potent factor in the spread of diphtheria, as in scarlet fever and measles. Infection is spread by the attendance at school of mild or un- recognized cases, and this is especially likely to occur in the public elementary schools, where the class-rooms are often overcrowded and badly ventilated, and the children are brought into very close contact at the most susceptible age-periods. Sir Shirley Murphy has shown that in London the increased incidence of diphtheria among children from three to ten years of age (school age) first became conspicuous in the year 1871 — the year, that is, in which the Elementary Education Act first became operative ; that there is a marked decline in incidence during the holidays, and a sub- sequent rise with the re-opening of the schools (due allowance being made for the incubation period and for some delay in notification). Although during the summer holidays there is also a decline in incidence among persons over ten years of age, it is never so great as the decline among children of the school age (three to fourteen). Prevalences of recognized diphtheria are very commonly associated in their beginnings, during their continuance, and after their apparent cessation, with a large amount of ill-defined throat illness. Vincent's angina is a disease allied to diphtheria, which spreads from direct or indirect contact. While the patient's symptoms in some cases simulate those of diphtheria, they more commonly take the form of deep ulcerations on the tonsils, palate, etc. The disease is most frequent amongst children from eight to ten years of age. Diphtheria epidemics are occasionally inextricably mixed up with outbreaks of scarlet fever and measles. There is no reason to believe that diphtheria is in any way interchangeable with scarlet fever or measles, in the sense that the infection of the one disease may produce the COMMUNICABLE DISEASES 437 other ; but it would seem that the morbid condition of the throat left after scarlet fever or measles predisposes the sufferer to become receptive of the diphtheria contagion, which may at the same time be present. Faulty sanitary surroundings (drainage and filth nuisances) tend to the production of diphtheria in the same way, namely, by engendering a morbid condition of the tonsils favourable to the growth of the diphtheria contagion if implanted thereon. The virus of diphtheria attenuated as to its virulence by exposure to atmospheric conditions is, no doubt, at times widely distributed among populous communities. The attenuated bacilli very readily regain their virulence when they become implanted on human fauces weakened by the attacks of other organisms, especially streptococci, and the organisms associated with measles, scarlet fever, and rotheln, as well as of those occa- sionally present in drain and sewer emanations (drain throat). Patients convalescing from scarlet fever are not infrequently attacked with diphtheria (" post-scarlatinal diphtheria "), the infection of which is probably introduced into the scarlet fever wards by an unrecognized case of diphtheria. The prevention of post-scarlatinal diphtheria is a matter' of great difficulty. A bacteriological examination of the throats of all cases on ad- mission would prevent the introduction into the fever wards of cases of diphtheria running concurrently with scarlet fever, but would not necessarily lead to the isolation of patients in the incubation stage of diphtheria. An affection of the throat, in many respects similar to human diphtheria, has been noticed as occurring in pigeons, fowls, and other birds, during periods of epidemic prevalence of this disease. According to Klein, a very similar disease can be produced in cats by subcutaneous inoculation of cultures of the Bacillus diphthericB, giving rise at first to a tumour at the seat of inocula- tion, subsequently followed by broncho-pneumonia and kidney degeneration. But the bacillus is only recoverable from the tumour, and is not found in the blood or affected organs, pointing to the visceral disease being a result, as in man, of the action of a chemical poison — an albumose (toxin) — produced by the bacillus at the seat of inoculation and absorbed from thence into the system. The disease called diphtheria in pigeons, calves, and other animals is due to a different organism, and appears not to be communicable to man ; but Cobbett has recorded a case of natural 43-8 HYGIENE AND PUBLIC HEALTH diphtheria in a pony, from which a child contracted the disease ; and the diphtheria bacillus has been isolated by Dr. Tew from the apparently healthy throat of a cat. There is abundant evidence to show that diphtheria has often been conveyed through the medium of milk, and this infectivity of the milk has been ascribed on some occasions to some morbid condition of the cow or cows. Klein has shown that cows and calves, when subcutaneously inoculated with cultures of the Bacillus diphthericB, develop a disease similar to that observed in cats, and usually proving fatal in the course of two or three weeks, the chief post-mortem signs being intense broncho-pneumonia and necrotic patches in the liver. There is little or no evidence pointing to the spread of the disease by drinking contaminated water. Klein has stated that the Bacillus diphtherice is killed when kept for a few days in pure water, on account of its not finding sufficient nutriment. The specific bacillus may persist in the mouth for a considerable time after the false membrane has disappeared. Dr. Hennann Biggs (New York Health Department) has subjected 405 cases of true diphtheria to repeated bacteriological examinations during the course of the disease, and during convalescence. In 245 cases (60-5 per cent.) the Klebs-Loeffler bacillus disappeared within three days of the complete separation of the false mem- brane ; in 103 cases (25-4 per cent.) the bacilli persisted for seven days ; in 34 cases (8-4 per cent.) for twelve days ; in 16 cases (4 per cent.) for fifteen days ; in 4 cases (i per cent.) for three weeks; and in 3 cases (075 per cent.) for five weeks, after the time when the exudation had completely disappeared from the upper air-passages.^ In many of these cases the patients were appar- ently well many days before the infectious agent had disappeared from the throat. Such results as the above are suggestive of a method of dissemination of the disease by the mixing of con- 1 Sternberg in the 1901 edition of his book quotes the following : " Park and Beebe (1894) in an extended research, made for the purpose of deter- mining the persistence of the diphtheria bacillus in the throats of convales- cents (2,566 cultures made) found that, in 304 out of 605 consecutive cases, the bacillus disappeared within three days after the disappearance of the exudate (that is, in 50-25 per cent.) ; in 176 cases (29-1 per cent.) it per- sisted for seven days ; in 64 cases (io*6 per cent.) for twelve days ; in 36 cases (5'9 per cent.) for fifteen days ; in 12 cases (2 per cent.) for three weeks ; in 4 cases (0-66 per cent.) for four weeks ; and in 2 cases (0*33 per cent.) for nine weeks." COMMUNICABLE DISEASES 439 valescents with healthy people, whilst their throat secretions still contain specific bacilli. It is never safe to allow recovered patients to mix with healthy people until at least fourteen days have elapsed since the disappearance of all membrane. During the whole of this time the mouth and throat should be repeatedly washed with disinfectant lotions ; and as the bacilli are frequently present in the nasal discharges, an antiseptic nasal douche should also be used, especially if much discharge from the nasal cavities was present during the acute stage of the disease. Outside the body the diphtheritic virus may possibly retain its active properties for long periods (many months), when protected from light and air currents. The action of light and air and alternating moisture and dryness destroy the virus with considerable rapidity. The bacilli can resist a dry heat of 98° C. for one hour, but a moist temperature of 58° C, acting for ten minutes, is sufficient to kill them, so that boiling water or disinfection in a steam chamber is always efhcacious in destroying their vitality. Klein has shown experimentally that the virulence of B. diph- thericB can be increased by placing it under symbiotic condi- tions with Streptococcus pyogenes : that is to say, it may be inferred from his experiments that a mixed infection of these organisms is liable to produce an especially virulent type of diphtheria. It is probable that the Klebs-Loeflfler bacillus may be much more widely distributed in the throat secretions of children than at one time was considered possible. In large towns, when diphtheria was endemic, it would appear from recent statistics that from 5 to 10 per cent, of the children of the working classes have the bacillus in their throats ; and in the majority of these cases there is no evidence of any unhealthy condition of the fauces. These " carrier cases " are of importance when an out- break of diphtheria occurs in a school. The examination of the throats of all the children and of the nasal discharges of those with " running noses," may reveal in some the presence of the specific bacillus. The isolation of such children should prove effective in limiting the spread of the disease. During the prevalence of the disease at schools a prompt bacteriological examination of suspects often prevents a needless loss of school attendance. In the London County Council's Schools it has been found safe to ignore the presence of the 44'0 ilYGlENE mT> tUfeLiC HEALtfi pseudo-diphtheria bacillus among scholars ; but, when this 'organism is found during the prevalence of diphtheria in viru- lent form, it is wise to isolate those scholars who are harbofiiir- ing it. pi. The presence of nasal diphtheria must not be overlooked, as the nasal passages have been found to be more commonly affected than was at one time suspected. An antitoxin serum has recently been introduced through the observations of Behring, Kitasato, and others, which not only has the power of conferring immunity upon animals, but also of arresting the disease after it has commenced in the human subject. The serum is obtained as follows :— The virulent Klebs-Loeffler bacillus is grown in broth for seven to twelve days 3-t 35° C., when a maximum quantity of toxin will be furnished in the liquid by the metabolism of the bacilli. The culture liquid is then filtered through a porcelain filter, to arrest all microbes, and the clear liquid resulting is injected subcutaneously into a horse. Gradually, by repeated injections of this toxin over a period of two or three months, the horse is brought into a condition in which its serum possesses very high antitoxic properties. The animal is then bled, and the serum obtained from the drawn blood is mixed with a little weak antiseptic, usually 0-2 per cent, carbolic acid, filtered through a porcelain filter, and after standardization, is stored ready for use {see p. 404)- That the lessened case mortality from diphtheria which has resulted from the use of antitoxin is not attributable to any natural attenuation of the virus, or to a change in the conditions of environment, is proved from the fact that in parts of Germany and elsewhere on the Continent, whilst the local incidence of the disease has remained unchanged among people in the same com- munity and influenced by similar sanitary environments, there is a reduction in the case mortality only among those who have been treated with antitoxin. In order to facilitate an early application of the remedy, some local authorities keep a stock of antitoxin at their public offices, and supply it to practitioners at cost price, or gratuitously in the case of poor patients. The provision is a useful, one, for experience has shown the high importance of an early applica- tion of a large initial dose, ranging from 6,000 to 8,oOo units, according to the gravity of the symptoms. COMMUNICABLE DISEASES 44I Diphtheria antitoxin also possesses valuable prophylactic properties, and may be used with advantage in doses of at least 1,000 units for the protection of children who are or have been exposed to the risks of infection. Enteric Fever. Typhoid or enteric fever is a specific disease dependent for its propagation upon a specific virus. It is not always possible to establish the dependence of an outbreak on a pre-existing case ; but it is not necessary for this reason to assume that the disease can originate independently — from organic filth apart from the infection of a previous case — seeing that the contagion may undoubtedly survive in polluted soil for considerable periods. Besides this, enteric fever is sometimes a mild disease and unrecognized even by the patient himself, who goes about his oidinary avocations unaware that he may be spreading con- tagion broadcast ; and the proof now forthcoming as to the existence of " chronic carriers " is of especial importance in this connection. The period of incubation is usually a long one, from ten to fourteen days. The limits of its maximum duration are not accurately known, but in rare cases it may be prolonged to twenty-one days, or even to twenty-three. Infection is transmissible {a) by those who are actually suffer- ing from a recognizable attack, typhoid bacilli being especially numerous in the stools during the second and third weeks of the illness ; (&) by those who are suffering from an " ambulatory " type of the disease — the type that is mild, obscure, or unrecog- nizable clinically ; (c) by those who are " contacts " — i.e., those who have been infected, and who for a time pass Bacillus typhosus in their excreta, but are apparently not in any way affected in health thereby ; {d) by those who are convalescent from the disease, but whose urine contains the specific bacilli, often in pure culture ; and {e) by those probably very exceptional cases (about 3 per cent, of the total) known as " chronic carrier " cases, in which an attack of enteric fever (mostly in women, about 75 per cent, of these cases being females) is succeeded by an indefinite period of latent infectivity lasting sometimes for many years, and due apparently to the discharge from time to time of virulent typhoid bacilli in the faeces for certain periods, such periods alternating with others when the discharges are 442 m^GIENE AND PUBLIC HEALTH free from infective organisms. The habitat of the typhoid bacilli in the body in these cases appears to be the gall-bladder ; and Dr. Davies of Bristol has noted that in the cases investigated by him the months of May and June were those in which the bowel discharges of the " chronic carrier " resumed kifectivity. Carrier cases who are engaged in the constant handling of food (such as cooks) have in several recorded instances been responsible for an outbreak of enteric fever. Special mention deserves to be made of the now famous Strassburg case, described by Kayser in igo6. It was observed that almost every new employe in a bakery, kept by a woman who had suffered from typhoid fever ten years previously, became seriously ill, with intestinal symptoms resembling those of tj^phoid fever. At length the faeces of the woman were examined, and were found to contain the specific bacilli in large numbers. It is important to realize that in enteric fever the urine in the later stages of the illness and in convalescence may be more potent for mischief than the faces, as in a certain proportion of cases of this disease, which, according to the recorded observa- tions, may amount to some 20 per cent, of the total, the urine contains enormous numbers of Bacilli typhosi. Inasmuch as the soiling of body- and bed-linen and of water- closet seats and chamber utensils is much more readily effected by the urine than by the faeces, it is easy to understand how the hands of healthy persons may become infected by the handling of such objects ; and, in consequence, how easy would be the transmission of infection in this manner, whilst the source of the mischief would in many instances be quite unrecognized. A disease so closely simulating enteric fever as to be clinically indistinguishable from it is ascribed to a micro-organism, or rather to a class of micro-organisms, which have been named Bacilli paratyphosi. The latter can be distinguished culturally from the true B. typJwsus, and have, in fact, cultural character- istics which seem to place them generically between the true B. typhosus and the B. coli communis, the whole group of colon organisms presenting certain common features which seem to indicate a family relationship. The disease due to paratyphoid organisms is only, perhaps, occasionally seen in Europe and temperate countries, and appears to be even less frequent in India, but in South Africa it is relatively more often met with. COMMUNICABLE DISEASES 443 Thus, in the Report oj the Army Medical Department for 1907 it is stated that in India, out of a very large number of examina- tions of blood, faeces, and urine from typhoid cases made at the Central Research Institute, in only six were paratyphoid bacilli found. Of these, four were B. paratyphosus " A " (Brion-Kayer), and two were B. paratyphosus " B " (Schotmiiller) . This pro- portion differs from what has been found in Europe, where the paratyphoid organism is far more common ; but it tends to indicate that the great majority of typhoid infections in British troops in India are due to the B. typhosus. In South Africa, on the other hand, amongst the British troops stationed there in 1907, it would appear that about 20 per cent, of the typhoid cases might be due to organisms of the typhoid colon group (paratyphoid, colon bacillus, and unclassified forms) other than the true B. typhosus. It is possibly due to the presence of a relatively large number of these atypical and mild cases that the proportion of deaths to attacks of enteric fever in South Africa is comparatively low. According to Forster and Kayser, the serum of those who merely harbour the B. typhosus as a saprophyte in the intestine, without having actually suffered from typhoid (" acute carriers "), has generally no agglutinative power. To add to our difficulties in the campaign against this disease, we are unable, in the present state of our knowledge, to free from bacilli those carriers who have been detected ; and measures suggested to minimize the risks of infection— e.g., thorough cleaning and disinfection of hands and anus after defaecation, and continuous disinfection of dejecta — are not likely to be carried out by most " carriers," who are under no sort of control. The bacilli have been shown by Conradi to be present in the blood during the incubation period, and even before the bacilli can be found the presence of anti-bodies may be demonstrated by the precipitin test, as was shown by Fornet ; whereas, it is only during the first and second weeks of the disease that the bacilli appear in the fseces. With the aid of the Drigalski-Conradi medium and the agglu- tination test, strong evidence of the presence of B. typhosus may be obtained in the course of twenty-four hours, and within forty- eight hours this evidence may be confirmed sufficiently to warrant the undertaking of special preventive measures. It is obvious that methods of this kind must be more generally adopted if we 444 HYGIENE AND PUBLIC HEALTH are to obtain full information with regard to the secondary in- fections, and especially of the incubating and mild or abortive cases which contribute such a large proportion to extensive epidemics. The virus, which is almost certainly the Bacillus typhosus isolated by Eberth and Gaffky, is transmitted from the sick to the healthy, chiefly, in this country, by means of drinking water, but occasionally through fomites and other channels. In enteric fever, as in cholera, it would appear probable that at the moment of leaving the body the specific contagion is not possessed of any high degree of virulence, for the reason that the mode of existence of these organisms in the intestine must be from the first practi- cally an anaerobiotic one. Many people who are exposed to the infection of both enteric fever and cholera escape, owing to the virus being destroyed on swallowing by the aid of the gastric juice. But those who are out of health, or who are suffering from diarrhoea, may offer much less resistance to the invasion of the contagion. Klein has shown by experiments on animals that the virulence of B. typhosus, and to a less extent of the Vibrio cholerce, may be enhanced, by association (symbiosis) with certain strains of B. coli, with the Bacillus of Gaertner and with B. enteritidis sporogenes and B. carnis, all these organisms being capable of setting up gastro-enteritis, when they happen to be ingested with the specific typhoid or cholera organisms. Of those who drank the infected water in the outbreaks at Maidstone and Worthing about 6 per cent, were attacked with the disease. But this figure is obtained from the notification returns, and doubtless many cases of mild infection are never notified ; so that the incidence of infection in these outbreaks probably exceeded lo per cent. Apparent insusceptibility may sometimes be explained by the possibility that the disease may have been contracted in childhood, when it is often mild and unrecognizable, for, as a rule, one attack confers immunity for the remainder of life. No age and neither sex is free from risk of attack, but those from fifteen to twenty-five years of age appear to be specially prone to suffer. Between the age of three and twenty years the mortality of females from enteric fever is greater than that of males. The higher death-rate at these ages is due, not to greater liability on their part to contract the disease, but to a COMMUNICABLE DISEASES 445 higher case mortality, i.e., a larger proportion of attacks proving fatal. During the period 1871-80 the mortality from enteric fever in England and Wales was at the rate of 0-33 per 1,000 living at all ages ; but the death-rate from this disease has undergone for a long period, and is still undergoing, a steady and sensible diminution year by year. In 1869 (the first year in which enteric fever returns, as separate from " fever," are obtainable) the death-rate was 0-39 per 1,000, whilst in 1908 the death-rate was only 0-075 per 1,000, a fivefold reduction. The average death-rate for the four years 1905-8 was o-o8 per 1,000. This result may be attributed to the improvments in water supply, sewerage and domestic sanitary arrangements, throughout the country generally, that have been so marked a feature in the social progress of the last forty years. The proportion of deaths to attacks in enteric fever cannot be accurately stated, owing to the number of mild cases that escape recognition. In typical cases the mortality varies from 15 to 20 per cent, of the attacks. The average mortality of cases notified in London is i6-2 per cent. In early life the type of the disease is less severe than in adolescence and adult age. Enteric fever is most prevalent, and causes the largest number of deaths, in the late autumn. The seasonal mortality curve (see fig. 79) is seen to rise in August, and attain its maximum late in October or early in November, from which point, with the exception of a slight rise in February, it gradually falls. In our large towns a hot and dry summer often tends to aggravate the intensity of the autumnal rise ; and this fact, together with its special seasonal prevalence, appears to point to a high tem- perature being necessary for the proper development of the specific poison in polluted soils, etc., and for the attainment of its greatest degree of virulence. It must be remembered that the earth at a few feet from the surface heats much less rapidly than the air, and that the highest annual temperature in the soil is not attained until late in the summer or early in. autumn. It is now established that the infection of enteric fever may be conveyed in shell-fish, more especially in oysters, mussels, and cockles, which are collected from tidal waters where the water is liable to considerable pollution from sewage ; and it has been shown that the specific bacilli of enteric fever and of 446 HYGIENE AND PUBLIC HEALTH cholera are capable of existing in oysters and cockles for some days, and in sea-water for several weeks. Klein has shown that when infected oysters are kept in clean, frequently changed, sea-water, they rapidly clear themselves of the bacilli. Legisla- tive measures are therefore required in the interest of public health to prohibit the laying down of oysters in dangerous localities ; and to that end all oyster layings, fattening beds, and storage ponds should be made registrable after approval by the sanitary authority, and also subject to frequent inspection. Section 4 of the Infectious Diseases (Prevention) Act, 1890, which enables authorities to prohibit the supply of milk which is causing, or is likely to cause, disease, might also, with modifi- cations, be made to apply to oysters and other shell-fish. The public should, moreover, be guarded against the importation of infected oysters from abroad. The presence of typical B. coli communis in considerable numbers in the body of the shell-fish is usually regarded as sufficient evidence of fsecal contamination, as in shell-fish derived from waters free from pollution these organisms are not found. It is noteworthy that in enteric fever and in cholera, especially when due to polluted water, an outbreak is often preceded for several weeks by cases of " diarrhoea," which may be instances of the mild or " ambulatory " type of the disease. For instance, in the Spanish- American war of 1898 it was found that, in the volunteer camps, 15-3 per cent, of the soldiers who had had no previous diarrhoea developed enteric fever, whereas only 6-8 per cent, of those who had so suffered developed the disease. Where flies abound, it is probable that enteric fever is very frequently transmitted through their agency, the flies directly conveying the contagion on their legs from infected excreta to some article of food. Considerable evidence of fly-borne enteric has accumulated from the experiences of recent military cam- paigns, and infected dust is also believed to be an agent in the transmission of the disease. It is the experience of numerous localities that enteric fever may be endemic notwithstanding a water supply of undoubted purity. In these localities — generally poor and crowded — there are "sani- tary circumstances which generally conduce to soil pollution, such as defective house and yard drainage and sewerage, unpaved or COMMUNICABLE DISEASES 447 badly paved yards around houses, allowing refuse to pollute the soil, and, above all, defective privy middens containing con- siderable accumulations of excreta, much of the liquid part of which finds its way into the soil. Many observers have ascer- tained that the incidence of the disease is always heavier on houses with dry closets than on those with water-closets ; and, among the former, those with middens are more frequently infected than those with pails, the diflerence being more marked the poorer the class of houses (Boobyer). Dr. Newsholme has pointed out that Nottingham and Leicester possessed two features in common, some years ago : a conservancy system of excrement disposal, and a high death-rate from enteric fever. Whereas Nottingham has made but slow progress in the adoption of the water-carriage system, in Leicester the progress has been rapid ; and as regards enteric fever the death-rate in Nottingham is still high, while that in Leicester has undergone a very marked diminution. The explanation of these circumstances is found in the now established fact that the Bacillus typhosus will remain alive in soil containing organic matter for many months ; and when the conditions of soil temperature and surface moisture are favourable, there may be some multiplication of the bacillus, under favourable circumstances the growths surviving even from one summer to another. Flies and dust may also have some share in the propagation of infection from privies and middens to neighbouring dwellings ; whilst uncleanly habits, with their tendency to produce contact-infection, are favoured by the retention of excreta! matters in the vicinity of houses. That the disease is frequently communicated by personal intercourse is repeatedly demonstrated by its spread to those in attendance on a patient in dwelling-houses, and even in hos- pitals. Goodall has shown from the experience of twelve of the large Metropolitan Fever Hospitals during eight years, that for every 1,000 cases of enteric fever admitted as many as sixteen of the stafi contracted the disease. Dr. Childs, from a study of the chief outbreaks in this country, concludes that, where the public water supply is infected, the ex- plosive outburst of the epidemic is not indicated by notifications until two or three weeks after the actual infection comes into operation ; that the abnormal number of cases of antecedent diarrhoea is a suggestive premonitory sign of an outbreak of 448 HYGIENE AND PUBLIC HEALTH enteric fever, and should be bacteriologically examined ; and that a large proportion of those who are infected are never notified. The numerous outbreaks (Caterham, Middlesbro, Tees Valley, Worthing, and Maidstone) in which the disease has been shown to be conveyed through the medium of drinking water, point to the necessity of exercising a constant supervision and sanitary control over all sources of drinking water, both by the establish- ment of protected areas upon the sites from which water is col- lected for drinking purposes, and also by systematically ascertain- ing the degree of purity of the water by means of repeated chemical and biological examinations. Pettenkofer has shown that in Munich there was a remarkable correspondence between the rise of the subsoil water and the decline in the prevalence of enteric fever, and vice versa. He does not profess to explain this relationship, but demonstrates that the movements of the ground water were an invariable index to the extent of enteric fever incidence in Munich. The serum diagnosis of enteric fever (Widal) is an important means of aiding the clinical diagnosis of the disease ; and since it is in the public interest that the diagnosis should be prompt and certain in the case of a disease which so often has a masked and insidious onset, many sanitaiy authorities now provide medical practitioners with a so-called " diagnosis outfit," con- taining a small capillary tube for collecting and sealing up some of the blood of a suspected patient. The blood is returned to the local offices, where arrangements are made for testing it at the public expense. The diagnosis outfit also comprises a sterilized swab in a tube for collecting suspected exudation or membrane from the throats of patients thought to be suffering from diphtheria. Similar provisions have also been made in some districts for enabling medical practitioners to avail them- selves of the bacteriological diagnosis of tuberculous sputum. Such diagnoses add definiteness to administrative procedure, qud isolation, disinfection, and the admission of patients to hospital wards. The evidence so far recorded of Widal's test establishes the fact that the reaction of the blood on the Bacilli typhosus, causing a characteristic clumping of the latter, and a total arrest of motion within a definite time limit, may be delayed, or occasion- ally may not be obtained, in cases of genuine typhoid infection ; COMMUNICABLE DISEASES 449 and also that it may in some instances occur in non-typhoid cases, though not in an intense degree, nor if high dihition of the serum l3e used. The average of successful diagnoses approximates, however, to 90 per cent. In carrying out this method of diagnosis, all that is necessary is to draw a small quantity of blood from the finger or ear of the patient into a capillary tube. The serum reaction is performed by diluting the serum 25, 50, or 100 times with a typhoid broth or emulsion, and then making " hanging-drop " preparations of the different dilutions, which are examined under the microscope for signs of clumping and loss of motility in the bacilli. A time limit of half to two hours, according as the dilution is a low or high one, is given by most bacteriologists. The value of anti-typhoid inoculations is now obtaining general recognition. The latest report of the results of anti-typhoid inoculation in the British army in India {Army Medical Depart- ment Report, 1908) show that the attack-rate in inoculated men is reduced to rather less than one-half, and the case-mortality to about two-thirds of the rates in men who have not been inocu- lated. The protection conferred by two inoculations appears to be somewhat greater than that conferred by one. The material generally used for anti-typhoid inoculation is a suspension of the dead bacilli obtained from a culture killed by heat. DiarrhcBa. Diarrhoea is, of course, merely a symptom of very many dis- eases. But in the sense here understood it means those acute specific attacks of illness of which the diarrhoea is the most prominent symptom, which occur so geneially in persons of all ages, but more especially in infants and young children, towards the middle or close of the summer. The death-rate from diar- rhoeal complaints remains remarkably constant through the winter and spring, but with the onset of hot summer weather in many large towns an extensive outbreak occurs, the chief incidence of which falls upon those at the two extremes of life, or who are enfeebled in health. This epidemic diarrhoea is in many cases of a choleraic nature, accompanied by cramps, spasms, and signs of collapse, and appears to be due to con- sumption of tainted food, or of impure water, or to the breathing of fouled air. The putrefactive changes which occur in food and fouled water or soil are all more rapid and intense under 29 450 HYGIENE AND PUBLIC HEALTH the influence of a high temperature ; and it is quite reasonable to believe that many of these diarrhoeal attacks are due to the action of the bacterial agents of putrefaction, or of their products, when taken into the system. In some of these cases of acute diarrhoea, the B. enteritidis of Gaertner has been found, whilst other cases of epidemic diarrhoea are associated with the B. enteritidis sporogenes — a sporing anaerobic organism first isolated by Klein from milk sold in small retail shops, and since found in sewage, in water polluted by sewage, in the excreta of patients suffering from diarrhoea, in horse dung, and in various articles of food. Morgan, working at the Lister Institute for Preventive Medicine on stools of patients suffering from summer diarrhoea in the London Hos- pitals, found a bacillus of the non-fermenting lactose group to be the predominant organism. This is now known as Morgan's bacillus. But it appears probable that summer diarrhoea is due to several associated organisms of the coli type. Many different terms are employed to designate the disease officially known as " epidemic diarrhoea," and this fact leads to great difficulties in classifying death returns. The terms em- ployed include : — diarrhoea, epidemic diarrhoea, dysentery and dysenteric diarrhoea, intestinal (or enteric) catarrh, gastro- intestinal (or gastro-enteric) catarrh, gastro-enteritis, muco- enteritis, and gastric catarrh. This confusion of terms leads to much discrepancy in the classification of death returns ; and early in 1900 the Royal College of Physicians authorized the use of the term " epidemic enteritis " or, if preferred by the prac- titioner, " zymotic enteritis," as a synonym for epidemic diar- rhoea, and recommended the entire disuse of the other terms mentioned above. Dysentery arises in a very similar way to diarrhoea. The effect of a chill, on which so much stress has been laid, is probably to increase the susceptibility of the system to the poison. It may be that chilling sets up a slight enteritis, whereby the normal resisting power of the lymphoid tissue in the bowel wall is lowered, so that the organisms present in the bowel are enabled to get a foothold and multiply in the intestinal walls. Attacks of dysenteric diarrhoea, with discharges of blood and mucus per rectum, are occasionally associated with outbreaks of diarrhoea in this country, and are not uncommon amongst the inmates of lunatic asylums. It is then known as " colitis," and COMMUNICABLE DISEASES 451 is probably communicable from the sick to the healthy (Mott and Durham). Although it is unquestionable that dysentery and acute diar- rhoea in the vast majority of cases appear to rise de novo (indepen- dently of the contagion of a previous case), yet it is certain that the diarrhoeal evacuations help to spread the disease in certain instances. It has been shown that the infection may be carried in water, and boiling the drinking water has stopped the out- break. Some years ago, Dr. Hope of Liverpool conducted an inquiry in order to determine the relative mortality from diarrhoea among infants of artisan parents, classified as follows : First, the entirely breast-fed ; secondly, those fed partly on breast milk and parth^ on artificial food ; and, thirdly, the entirely artificially fed. He found that for every death from diarrhoea which occurred among breast-fed infants under three months old, fifteen occurred among those of the mixed class, and that for every death from the same cause among the breast-fed and mixed class combined, twenty-two occurred among the entirely artificially fed. From the seasonal curve for diarrhoea it appears that the mortality begins to increase about the middle of June, rises rapidly to its maximum at the end of July or earlj^ in August, and falls somewhat less rapidly throughout August, September, and October. The following is a very brief epitome of Dr. Ballard's observations : — The summer rise of diarrhoeal mortality in the large towns does not commence until the mean temperature recorded by the earth thermometer, placed four feet below the surface, has attained somewhere about 56° F. — no matter what may have been the temperature previously attained by the atmosphere, or recorded by the i-foot earth thermometer. The maximum diarrhoea mortality of the year is usually observed in the week when the 4-foot earth thermometer attains its mean weekly maximum. The diarrhoea mortality declines with the 4-foot earth thermometer, and this decline takes place very much more slowly than that of the atmospheric temperature or of the i-foot earth thermometer, so that the mortality from epidemic diarrhoea may continue long after the air temperature has fallen, even into the fourth quarter of the year. The earth temperature at a depth of 4 feet is valuable as a 452 HYGIENE AND PUBLIC HEALTH measure of the cumulative effect of the sun's heat, the variations in earth thermometers following those of a thermometer above ground at an interval of about three or four daj^s. On an average, twenty-four hours are required for the sun's heat to penetrate to a depth of i foot, the actual time varjdng somewhat with different soils. The soils most favourable to a high diarrhoea mortality are those of sand, gravel, or marl (in which the constituent particles are small but freely permeable by air and water), and which contain organic matters of animal origin from " made ground," from manured surfaces, or from soakage of excretal refuse from privies, cesspools, and sewers. The soil must be moist, but the moisture must not be sufficient to preclude the free admission of air between the interstices ; the moisture of the soil may arise from surface water sinking into the earth around houses, as well as from capillary attraction of a high subsoil water from below. Other factors conducive to a high diarrhoea mortality are domestic overcrowding, darkness and dirtiness of premises, and the keeping of milk and other foods in underground cellars ex- posed to telluric emanations, or in pantries liable to the entr}'- of drain or sewer air. It is also very probable that milk kept in open jugs, and other articles of food, become infected \\dth the Bacillus enteritidis sporogenes and other organisms, through the agencj^ of fhes and of dust containing particles of horse excreta from the streets. Among the more, important preventive measures must there- fore be placed the prompt removal from dwellings of animal and vegetable refuse (the breeding place of flies), the protec- tion of food from flies, and the more frequent cleansing and watering of streets and yards in dry weather, so as to reduce dust. As previously stated, the disease is mainly one of early child- hood (0-5 years), over 80 per cent, of the mortalitj^ occurring under two years of age ; but its incidence is b}' far the greatest on hand-fed infants, hence female factor^^ labour, bj^ depriving infants of their natural food, is a contributing cause. The attacks are usually extremely sudden in their onset ; and that diarrhoea is merely one s^nnptom or feature of the illness is shown by the fact that man}/ of the organs of those who have succumbed are found to be highly degenerated, more especially the kidneys, COMMUNICABLE DISEASES 453 the liver (fatty degeneration), and the spleen. The lungs, too, are often the seat of pneumonic inflammation. Dr. Newsholme's researches point to the following circum- stances as determining the incidence of diarrhoea : (i) Towns with water-carriage sewage have, as a rule, less diarrhoea than those practising other methods of removal. (2) Towns with the most perfect scavenging arrangements have least. (3) Towns having the lowest diarrhoeal mortalities are situated on impervious soils, though the converse scarcely holds good ; and steep gradients favour a low diarrhoeal rate. (4) Given two towns, alike in sanitary and social circumstances, the rate is proportionate to the height of the temperature and the deficiency of rainfall, more particularly during the third quarter. (5) There is a general inverse relationship between rainfall and diarrhoea, and a direct relationship between temperature and diarrhoea. (6) The soil is a great factor in the causation of diarrhoea, but its influence may be largely discounted by impervious paving in streets and yards and impervious flooring to houses. (7) The incidence of diarrhoea follows more closely the want of rainfall than the mean temperature of the air ; and the efficient washing of streets, swilling of yards, and flushing of sewers reduces it. (8) The disease increases largely in prevalence when the 4-foot earth thermometer reaches 56° F., or when the mean weekly tempera- ture of the air rises to about 63° F. Preventive measures are mainly designed to prevent the pollution of the air and soil in and around houses, to encourage the practice of habits of domestic cleanliness, and the protection of food from all sources of pollution. More especially during the summer months should all milk be boiled shortly before use, and the feeding bottles for infants should be kept scrupulously clean. All foods should be stored in a light airy place and care- fully protected from dust and flies ; fruit and vegetables should be thoroughly cleaned before consumption ; and no tainted food or unripe or overripe fruit should be eaten. During the decennium 1891-1900, the death-rate in England and Wales from diarrhoeal disease was 0-73 per 1,000 living at all ages. Under five years of age, the death-rate was 4-3 per 1,000 ; and although this high rate is largely contributed to by the improper feeding of infants, there can be no doubt that insanitary conditions, of the kinds named above, play a large part in its production. For the ten years 1871-80, the death-rate in 454 HYGIENE AND PUBLIC HEALTH England and Wales from diarrhoeal diseases was 0-93 per 1,000 living at all ages, and for the ten years 1881-90, o-68 per 1,000. For the four years 1905-8, the rate averaged 0-58 per 1,000. House-Flies. — The commonest species of house-fly, and the most predominant in the interior of houses, is Musca domestica. Next comes the lesser house-fly, Homalomyia canicularis, and then the blue-bottle flies, CallipJiora voniitoria. Musca lays its eggs by preference in horse manure, but \vill also lay in cow-dung, human and other excrement, and ashbin refuse. The usual period from the laying of the egg to the pro- duction of the fly is from twelve to twenty days. Absence of sufficient moisture and warmth leads to delayed development or to the production of small and imperfect flies. Flies become sexually mature in from two to three weeks after hatching out. A female fly will lay from four to six batches of eggs, each batch containing from 120 to 150 eggs. The larvae pass through three stages of varying durations, under favourable conditions the three stages being completed in less than fourteen days. The development of the imago will take four or live days longer. The larvae require warmth and moisture, whilst the pupae require warmth and dryness. These conditions are best afforded in collections of horse manure. Although all species of house-fly are exceedingly prolific, the numbers in any season are largely affected by such adverse conditions as low air temperatures, heavy rainfall, and absence of suitable material for the develop- ment of the larvae. Flies will, under suitable conditions, breed in winter, and there can be little doubt that the seasons are connected by living flies, and not by pupae. The spring increase usuall}^ commences in April or May in covered collections of fermenting horse manure. The great upward rise in the curve of fly prevalence is usually seen to commence in the first week of July, a maximum being reached some time in August or September, according to the air tempera- tures prevailing in any particular year. With the commence- ment of October, a sharp decline in fly prevalence usually sets in. This annual decline is partly due to the onset of cold weather, which causes the flies to become lethargic and to remain indoors, so that fewer eggs are laid in dung and refuse, and partly to the destruction effected amongst the larvae by a beetle — the Empusa musccB — which increases largely in numbers in August and Sep- tember, and kills innumerable larvae. COMMUNICABLE DISEASES 455 Although in some years in urban populations there is often a considerable amount of correspondence between the curves of fly prevalence and of diarrhoea prevalence or mortality, still this correspondence is by no means invariable ; and it has been noted on more than one occasion that the diarrhoeal curve begins to decline some time before the fly curve begins to drop, whilst the uprises of the two curves in successive years often present dissimilar features or discrepancies, which would hardly be observed if flies stood to diarrhoea in the direct relation of cause and effect. Tuberculosis. Tuberculosis is a disease to which all warm-blooded animals appear to be susceptible. The degree of susceptibility varies amongst different races of men, and amongst individuals of the same race. The offspring of phthisical parents appear to be born with a certain degree of susceptibility of tissue to attack by tubercle. It is for this reason that the disease was believed to be hereditarily transmissible. If, however, the disease is congenital at all — i.e., directly transmissible from parent to child — it can only be so to a very trifling extent. Bang has shown that when the calves of tuberculous cows are separated from their mothers and placed under hygienic conditions, they do not develop tubercle in any greater degree than the calves from healthy parents. He found that tubercular lesions at birth are extremely rare, and when present are due to infection through the placental circulation. Investigations by Delepine, Boltz, etc., show no observed tuberculosis in the first, second, and third weeks of life ; and Koch has found that guinea pigs remain healthy if reared apart from tuberculous parents. The universality of the infection and the extent of human resistance are demonstrated by the circumstance that post- mortem examinations of persons of over forty years of age very generally disclose some old localized tuberculous lesion in the lungs, although such persons have never suffered from the disease in a recognizable form. According to Behring's view, the majority of human tuber- culosis is acquired during infancy, and remains latent in the glands until circumstances render the body a suitable soil for the multiplication of the germ. The Registrar-General includes in the term " tuberculosis," 456 HYGIENE AND PUBLIC HEALTH " phthisis," " tabes mesenterica," " tubercular meningitis," and " other forms of tubercular disease and scrofula." If the vital statistics of tuberculosis in this country during the past half-century are studied, it is found that — 1. There has been a marked and progressive reduction in the death-rate, and that the reduction is most marked during the 10-35 years age-period. 2. There has been a still greater reduction (of nearly 50 per cent.) in the death-rate from pulmonary tuberculosis or phthisis, this reduction having been most marked at the several age-periods ranging from infancy up to thirty-five years, and greatest among females. 3. There has been a large increase in the death-rate from tabes mesenterica under one year of age, and the reduced mortality for the 0-5 years age-period has been insignificant. This fact seems to point to the disease being maintained among infants through the agency of infected milk, but some of the increase may be due to a more extended use of the term " tabes mesen- terica " in the registration of infantile deaths. The principal predisposing causes of the disease are : Foul air {vide pp. 174-175) ; dusty occupations (the male death-rate from tuberculosis of the lungs is nearly half as much again as the female) ; dampness of site and of premises ; dirtiness and dark- ness of dwelling ; poverty with its attendant insufficiency of food and liability to exposure ; and alcoholism. Tissue injuries and malformations of the chest are less prominent predisposing causes. The part which " overcrowding " and foul air play in promoting the prevalence of phthisis is well shown at Salford (Dr. Barry and Mr. Gordon Smith's inquiries— data supplied by Dr. Tatham). Thus, in districts where all the houses were built on the vicious system known a,s " back to back," the phthisis death-rate was 5-2 per 1,000 living ; where 56 per cent, of the houses were so built, the rate was 3-6 ; where 23 per cent, only were so con- structed, it was further reduced to 3-3 ; and, lastly, where there were no " back to back " houses — that is to say, where all the houses were provided with some means of light and air both in front and to the rear — the rate was only 2-8 per 1,000. These results are all the more remarkable because, with the exception of the absence of means for through ventilation, the back to back houses on the whole were, in Dr. Tatham's opinion, in better sanitary condition than the other houses. Similar results have COMMUNICABLE DISEASES 457 been obtained by other observers and bj' Dr. Darra Mair, of the Local Government Board (see Report of Medical Officer of the Local Government Board, 1908-9, p. xix). Buchanan has sho\\Ti that the effect of drying the soil, in the case of to\\Tis where the level of the subsoil water was previously high, was to greatly diminish (by I to \) the death-rate from phthisis. The connection between phthisis and moisture in the soil, which had been previously pointed out by Bowditch of Massachusetts, was thus confirmed by Buchanan. The materies morhi, the bacillus of tubercle, is contained in the expectoration of phthisical persons. WTien this is allowed to dr\' and mingle with the dust of rooms and streets, the bacillus ma}^ be inhaled by others, and so infect them. Dujardin- Beaumetz gives a striking history of eleven out of twenty-three clerks in an office being attacked during the course of twelve years, as the result of the introduction of the disease by the first sufferer. The floor of the office was rough, no spittoons were provided, and the air was dust-laden from recent sweeping when the men arrived in the morning. The floor was planed and beeswaxed, expectoration was prohibited except into the spittoons which were supplied, and the cleansing done overnight, as far as possible, with damp cloths, with the result that no further cases occurred. The infection may also be swallowed, or directly inoculated from discharges. As already stated, milch cows are particularly susceptible to tuberculosis, and in advanced cases of the disease their milk may contain the bacillus (see p. 360). The flesh of bovines, when eaten in a partiallj' cooked condition, may also be capable of conveying the disease. Dr. Koch has maintained that human tuberculosis differs from bovine tuberculosis, and cannot be transmitted to cattle ; and he furthei holds that bovine tuberculosis is scarcely, if at all, transmissible to man. The former conclusion is based on experi- ments, in which he failed to infect nineteen young cattle (and subsequently asses, sheep, and goats) with human tubercle bacilli, but he invariably succeeded when he used tubercle bacilli of bovine source. The second conclusion is based upon the con- tention that if meat and milk introduce the infection into man, there must be in the latter primary tubercular lesions in the intestines, and these are believed to be rare. Dr. Koch's views have not met with much support from other 458 HYGIENE AND PUBLIC HEALTH authorities, but owing to his great position as a bacteriologist, the English Govemment considered it desirable to refer the whole question to a Royal Commission, which has already issued three reports. The conclusions arrived at by the Royal Commission appointed to inquire into the relations of human and bovine tuberculosis are given in the Second Interim Report (1907) as follows : — " There can be no doubt but that in a certain number of cases the tuber- culosis occurring in the human subject, especially in children, is the direct result of the introduction into the human body of the bacillus of bovine tuberculosis ; and there also can be no doubt that in the majority at least of these cases the bacillus is intro- duced through cow's milk. Cow's milk containing bovine tubercle bacilli is clearl}' a cause of tuberculosis and of fatal tuberculosis in man." Out of sixt}' cases of human tuberculosis investigated bj^ the Royal Commission, in 14 01 23 per cent, the tuberculous material obtained from the cases, when injected subcutaneously into calves in the form of emulsions, either prepared directty from the original material, or indirectty, from the tuberculous organs of guinea pigs infected with that material, was found capable of producing a generalized progressive tuberculosis in the experi- mental animals. The Commission found that this generalized progressive tuberculosis was due to the virus containing the bacilli of bovine tuberculosis, and that the vira containing the bacilli of human tuberculosis, in which a bovine source could be excluded, were far less virulent to bovine animals, and could not set up in them a generalized progressive tuberculosis. Out of the sixty cases of human tuberculosis investigated by the Ro3'al Commission, twentj-^-eight possessed clinical histories indicating that in them the bacillus was introduced into the bod}^ through the alimentary canal. Of these t^^'enty-eight cases, 13 or 46 per cent, were sho\\'n to contain the virulent form of organism, which alone produces in bovine animals a generalized progressive tuber culosi>, and which was therefore identical with the bacillus of bovine tuberculosis. The above facts seem to indicate that a very considerable pro- portion of the human tuberculosis contracted b}^ ingestion and primary invasion of the abdominal organs, is due to tubercle bacilli of bovine source. Under the term " pseudo-tuberculosis " a whole series of COMMUNICABLE DISEASES 459 lesions, similar to those induced by the Bacillus tuberculosis, is included. This condition, which is rare in man, is mostl}^ caused by some aspergillus or streptothrix, and more rarely by nematodes ; but in either case gi'ey nodules and caseating tubercles present appearances very liable to be mistaken for tuberculosis, both in quadrupeds and birds. A Bacillus pseudo- tiiherciilosis was isolated by Pfeiffer from some of these cases, and more recently Klein has found the same bacillus in water, milk, sewage and sewage effluents. It is pathogenic for animals, producing lesions like the Bacillus tuhercnlosis, but no giant cells are found in them. Animals are killed by it sooner than by the tubercle bacillus. The disease kno^^^l as actinomycosis is some- times mistaken for tuberculosis, and vice versa. The preventive measures which may be taken to reduce tuberculosis may be summarized as — 1. The compulsory notification of phthisis. It is generally considered ^vise to precede this by a term of voluntary notification of the disease. But in the opinion of many who have had experience of the voluntary system, it proves of little value in practice, owing to the fact that the relatively few cases that are notified are so poor as to be unable to observe any precautions, or so ill as to be in the last stages of the disease. 2. The removal of those conditions of domicile and of occupa- tion which are known to promote the incidence of the disease, including the regulation of certain dusty trades. 3- The diffusion of knowledge (by medical men, leaflets, etc.), regarding the nature and modes of spread of the disease, and the precautions which should be taken in order to prevent its ex- tension. A continuous supply of fresh air, admitted through the window, can be tolerated night and day if either of the following arrange- ments is made : [a) Raise the lower sash of the window for 6 inches, and then closely fit, into the open space below, a wooden board. Air then enters where the upper and lower sashes overlap, without causing a draught. (&) Open the window at the top for 6 inches and fix a muslin curtain, or nail a piece of muslin, so that it covers the open part. By this device draughts are very much reduced. (c) A screen reaching to a little above the head of the sufferer 4*30 HYGIENE AND PUBLIC HEALTH can be placed alongside the upper part of the bed, on the window side. No draught mil then be felt by the sufferer. 4. The testing of sputum and other suspected discharges, and of milk, meat, etc., supposed to be tuberculous, by the sanitary authority free of charge. 5. Local authorities to undertake, without charge, the dis- infection of houses recently occupied b}^ phthisical persons. 6. The establishment of sanatoria and isolation accommoda- tion for the cure of phthisical patients, and the isolation of those who are a distinct source of danger to fellow lodgers or workers. Newsholme has pointed out that the death-rate from phthisis has declined to the greatest extent in those countries in which the ratio of institutional to domestic relief has been highest ; and that the admissions to workhouse infirmaries, hospitals, and lunatic asylums have greatly increased in this country during the past thirty- five years. 7. The enforcement of measures against spitting in public conveyances and in places of public resort. 8. The efficient sanitary supervision of dairy farms, dairies, and milkshops. The periodical veterinary inspection and testing (by tuberculin) of milch cows, and the removal of tuber- culous animals from the herd. The prohibition of the sale of milk of cows affected with tuberculosis. 9. The proper inspection of meat in public abattoirs, and the adoption of due precautions for the control of imported meat and milk. There is at present a considerable divergence of opinion re- specting the desirabilit}^ of making the disease compulsorily notifiable. If " tuberculosis " were made notifiable, the term would cover an enlarged cervical gland, white swelling of joints, and h3'diocepha]us — conditions which are in no sense a source of danger to others — so that notification should be restricted to phthisis or " tuberculosis with discharges." It will be convenient to group the main arguments advanced for and against the compulsory notification of phthisis. Those who favour such notification urge that it would educate the public as to the seriousness of the risks of its spread ; that the measure is essential in order to obtain knowledge of the exact distribution of the disease, and this knowledge is a necessary preliminary to the discovery and removal of all of those conditions which promote the incidence of the disease ; that upon notifica- COMMUNICABLE DISEASES 461 tion the case could be visited, certain precautions directed, and disinfection carried out ; that an attempt could then be made to detect and deal with incipient tuberculosis in other members of the famil}^ ; that the necessary measures of precaution could be left in many cases to the medical attendant and the patient ; that it would not be necessary to deprive the patient of em- ployment, except in advanced cases, and where this is found to be unavoidable it is better that one should suffer than the many ; and, furthermore, success is claimed for the system of compulsory notification as practised in parts of New York, and in Sheffield, where it is stated that there is no opposition either on the part of the public or of the medical practitioner. Those opposed to such notification hold that the long duration of the disease (averaging three years in cases ending fatall}^) would cause much difficulty in bringing it under any valuable measure of municipal control; that the fact of making it notifiable and classing it with the other infectious diseases would cause the public to exaggerate the risks of infection, and lead to social ostracism and to difficulties in the way of the sufferers gaining a livelihood ; that the consequent desire to keep the existence of the disease a secret would seriously affect the thoroughness of notification ; that the health officer can do practically nothing to ensure the adoption of efficient precautions, and that a serious effort to ensure the adoption of the necessary precautions would necessitate frequent inspections, and much undesirable friction as the result ; that the notification records for the entire country would be very inexact, for phthisical patients are pre-eminently migratory, either from choice or from necessity (from loss of work), and many cases would be repeatedly notified in different districts ; that there has been a great reduction in the mortality from the disease Avithout notification. Many, while favourable to the compulsory notification of the disease, are of opinion that as a preliminary measure some hospital isolation provision for the most advanced and dangerous cases should be provided, and that some provision should also be made for sanatorium treatment of the earty stages of the disease in necessitous patients, and for those who would suffer loss of employment or support by reason of their isolation. If such municipal sanatoria are established, a considerable number of beds will be necessary, because of the prolonged residence of each patient in the hospital ; but great good would accrue if only 462 HYGIENE AND PUBLIC HEALTH short residence were afforded, with the object of training the patient to practise the necessary precautions. In Germany sanatoria for the poor have been established by municipalities, by benevolent associations, and by insurance companies ; and France, Norway, and Russia have State sanatoria for the poor. The economic results of the institution of the sanatorium system by insurance companies in German}- have fully justified the expense involved. In the absence of State insurance of the working classes in this country, the duty of founding sanatoria for the poor must fall on the Sanitary and Poor Law authorities. Although there has been a tendencj^ to exaggerate the good results to be derived from the sanatorium treatment of consumption, the value of the treatment is very considerable and has been abundantly testified to, more particularly in Germany, where more than a hundred sanatoria exist. But it is necessary to make a careful selection of the cases to be admitted, if the best results are to be obtained from the expenditure entailed. Cases of recent origin with limited lesions and little or no fever may be expected to derive considerable benefit from the sanatorium treat- ment, but a carefully selected chronic case may be found to benefit also, sometimes more so than some of the early and acute cases. Another necessary condition of success is the retention of the patient for a suffi- ciently long period (six months, on the average) before he is discharged, and even then regard must be had to the fact that he is very liable at any time to a relapse. With the view of reducing this risk it is often necessary that the individual should not return to his old occupation and environ- ment ; and, therefore, it seems desirable in connection ^^dth such institu- tions that there should be an After-Care Committee, whose duty should be to keep in touch with the discharged individual, to advise him, and (where necessary and possible) assist him in obtaining suitable outdoor occupation. Failure to comply -with the above provisions ma}' result in the sanatorium treatment proving a costly failure. The general features of the sanatorium treatment are as follows : As much as possible of the Life of the patient is spent in the open air ; at certain stages absolute rest is required, at others graduated exercise ; careful and generous feeding is an important part of the treatment ; mas- sage, baths, and cold sponging are also necessar^r for certain cases ; and the educational and disciplinarjr effects should be such as to continue of lasting value to the patients. It is necessary that the patients should be under almost constant medical supervision ; they should be carefully classified, and most of them should be visited three times daily, the temperature taken and directions given mth reference to food, exercise, etc., in accor- dance with their condition. Therefore there should be one medical man to not more than forty patients. It is furthermore desirable in connec- tion ^vith such institutions that there should be provision in the grounds for some kind of labour, especially when the sanatorium is a poor-class one. The employment of suitable patients in a little gardening, poultry farming, bee-keeping, or other light labour, not only does something to prevent them from becoming lazy, but serves to train them in outdoor pursuits, and this training they can sometimes turn to account after leaving the sanatorium. At the Frimley Sanatorium of the Brompton Hospital for Consumption, the Resident IMedical Officer, Dr. Patterson, has introduced a system of graduated labour, bj'^ which patients can be COMMUNICABLE DISEASES 463 led on, stage by stage, to undertake the most laborious forms of manual work such as is ordinarily performed by navvies. This graduated system of labour has been found to have an important influence on treatment and cure of the disease, the effect of the graduated exercise being to cause auto- inoculation — that is to say, the tubercular toxins, as the result of exercise, are introduced into the systemic circulation, and tend to raise the resisting power of the individual, in the same way as do inoculations of dead bacilli and their products in " vaccine treatment." The site of a sanatorium is a matter of prime importance. The ideal site is the southern slope of a hill, sheltered from the north and east winds by rising ground or trees. There should be a wide clearing of any trees on the south side, and to a less degree on the other aspects. The aim is to obtain a site with pure air, abundant sunshine, clean and dry soil, a low but equable temperature, and protected from winds. The site should be of easy access, not too far from a railway station, and well away from a high road and the dust which may arise from it. For an institution of 100 beds it is desirable to have 100 acres of land, in order that there may be sufficient ground to provide protected walks for the patients, for keeping cows, for growing vegetables, and for providing work for convalescents. Dotted about the grounds there should be a large number of seats. Prob- ably 100 beds are sufficient for any one institution ; and not more than six beds should be placed in one ward. In the more expensive sanatoria a large proportion of the bedrooms are single bedrooms, which is of course an ideal arrangement. The ideal sanatorium consists of a number of isolated chalets surrounding the central administrative block, each chalet to accommodate one patient. The chalet need be only of the size of a small room, with an added verandah. It should be raised from the ground and provided with windows in all four directions. A very good arrange- ment is to have two-thirds of the accommodation provided in chalets, and the remainder in one main building. The main building should have balconies with verandahs and French windows, so that the beds may be wheeled out on to the balconies, and bedrooms of at least 1,500 cubic feet capacity with floors made of teak or oak on cement concrete. The linoleum frequently used in Germany and elsewhere to cover the floors is not satis- factory. Washable distemper walls with a smooth surface are desirable ; the lighting should be by electricity, and the warming by hot water pipes. Electric fans for ventilation are sometimes desirable in winter. In connection with a sanatorium provision must be made for disin- fecting and incinerating infected material, and a dispensary, pathological laboratory, consulting-room, mortuary and post-mortem room, laundry and drying-room, baths, operating theatre, library, committee room, recreation room, private dairy, ambulance, and electrical engine-house have all to be provided. It will be seen, therefore, that a sanatorium is of necessity an expensive provision ; but all arrangements for the treatment can be made on quite a satisfactory basis at a cost of from £100 to ;^200 a bed, and there is no occasion to spend the very large amounts which have often been spent on costly structures in this country. The Anti-Tuberculosis Dispensary is an important provision in the campaign against tuberculosis. Such a dispensary, should be in effective touch with the homes of the suffeiers, and should be linked up with the Municipal Public Health Department, a sanatorium, a hospital for advanced cases, and an after-care association. It should be central, and constitute itself a bureau of information upon the disease, and a link with all institu- 464 HYGIENE AND PUBLIC HEALTH tions and local provisions for dealing with infected persons. It must provide nurses and health workers to visit the homes and to instruct the occupants, and suppty the means for the bac- teriological examination of sputum ; it should dispense necessary medicines, sputum bottles, disinfectants, and, where the patient's condition seems to warrant it, even foodstuffs and articles of clothing. It should therefore enlist the support of local charitable organizations. Epidemic Influenza. Influenza in its epidemic form is an infectious disease, and should be classed with specific fevers. Nothing very definite is kno\vn of the etiology of influenza, but it does not appear to show a preference for any particular localities, nor to follow alwa^^s the same channels of communication, and it has prevailed in- dependently of season, climate, and weather. The disease does not seem to associate itself especially with insanitary surroundings, and the incidence upon the poor is generall}^ lighter than upon the better class of the population. Although now regarded as infectious, and propagated mainly by human intercourse, it was at first supposed that influenza was spread chiefly by an air-borne miasm, and not by personal infection or fomites in the ordinary way. The facts relied upon were the rapidity of spread of the epidemic, and the supposed simultaneity of outbreak upon large numbers of people. But it is now recognized that the rapiditj^ of spread is not greater than that of human intercourse with modern facilities of travel, and that scattered cases usually precede the general onset of the epidemic upon a community. The epidemic, moreover, has often been observed to travel in directions opposed to the prevailing winds, and to be independent of any particular kind of weather. There can be no doubt that those engaged in out- door occupations are often first attacked, but such people — especially postmen and policemen — may be exposed to con- tagion before the rest of the population. Equine influenza occasionally precedes the human disease in its epidemic form, but it is doubtful if the maladies as seen in animals and men are really identical, i.e., dependent upon a common cause. The chief arguments in favour of personal communicability are : — (i) The very frequent occurrence of cases in succession in the same household. (2) In many instances the first case in a household or neighbourhood can be traced to exposure to COMMUNICABLE DISEASES 465 infection from a previous case, or to a visit to an infected locality. (3) Tlie special incidence of the disease upon persons liable to come into contact with infection — e.g., medical men and nurses. (4) Persons living under circumstances in which the possibility of infection can be excluded (prisoners in gaols, sailors at sea, lighthouse keepers) have escaped influenza altogether. (5) That, as a general rule, in each country it has appeared first in the capital or ports of entry, and the towns have been infected earlier than country places. (6) That neighbouring communities have in certain instances been affected at considerably different dates. The sudden, almost simultaneous, attacks of large numbers of people, following upon the appearance of a few scattered cases, is accounted for by the very general susceptibility to the disease, and its short incubation period. There is considerable evidence in favour of the bacillus of Pfeiffer, Kitasato, and Canon being the specific organism of influenza, it being found in almost pure cultures in the bronchial secretions of influenza cases, but not in other allied diseases. As regards age and sex incidence, those in the middle periods of life (twenty to sixty years) are most attacked ; people over sixty come next, and children least. Males at all ages are more liable to attack and to severe illness than females. All depressing influences, chills, and fatigue are said to favour the development of the disease ; but vigorous health is no pre- ventative, and no guarantee that the malady will assume a mild type. The incubation period is usually between two and four days, but may be only one day, or may extend to five. The average duration of an attack is ten days. The duration of infectiveness is not certainly known, but may continue into the stage of convalescence. One attack is not protective, and relapses are frequent. Three types of the disease are known, in which the respiratoiy organs, the alimentary system, and the nervous system are, respectively, most affected. In different epidemics one or other of these types may prevail more extensively than the others. During an epidemic the direct mortality from influenza as a primary cause of death may not be more than 0-5 per 1,000 ; but if to this death-rate we add the mortality indirectly due to influenza (the excess of deaths from pneumonia, bronchitis, and heart diseases over the average of non-influenza years) , the death- rate from this disease and its after consequences is not far short 30 456 HYGIENE AND PUBLIC HEALTH of 2 per 1,000, or nearly equal to the total zymotic death-rate now recorded in many large to\vns. During the past five years epidemics have prevailed in various parts of the country, but the resulting mortality has been much less than in the first five years of the appearance of the disease, subsequent to i8go. About 50 per cent, of the deaths from influenza are of persons aged sixty years and upwards. As regards prevention, theoretically, notification of cases, isolation of the sick, disinfection of premises, and disinfection of the excretions, especially of the sputum and of soiled linen, should be, as for other infectious diseases, the proper means of checking or stamping out an epidemic. But such measures are really impracticable for general adoption, owing (i) to the difficulty of making an exact diagnosis in the early stages of an epidemic, or of mild cases at any time ; (2) to the "udde and rapid diiSusion of the infection, and to the fact that the wage-earning periods of life are most affected (the movements of adults being far more difficult to control than those of children) ; and (3) to the impossibilit}^ under the circumstances of treating influenza as a dangerous infectious disease, and inflicting a penalty upon those found exposing themselves in public places. An effort, however, should always be made to promptly isolate the first case occurring in a house or institution and to carefully disinfect the sputum ; and while the disease is prevalent it is well to avoid exposure to cold and fatigue, to clothe the bod}" warmlj', to a^'oid indulgence in excess of alcohol, and not to visit places to which large numbers of the public resort. In the earl}^ autumn of 1904 an epidemic, which presented some unusual features and embraced 162 cases, occurred in Hertfordshire, the main features of which were subsequently described by Dr. R. A. Dunn, whose attention was first drawn to several cases of apparent influenza in members of a single family, where one member developed symptoms of scarlet fever and another those of cerebro-spinal irritation. Some of the cases in this Hertford epidemic were bacteriologically investigated by Dr. Gordon, who found that the common causal factor appeared to be the micrococcus catarrhalis. The outbreak differed bacteriologically, and in some respects epidemiologically and clinicall)-, from scarlet fever, cerebro-spinal meningitis, influenza or rotheln, and its hybrid qualities are interesting and significant. COMMUNICABLE DISEASES 467 Contagious Ophthalmia. There are two kinds of contagious eye disease : the grey granulation (trachoma) and purulent conjunctivitis ; the former appearing to predispose the sufferer to take the latter. These diseases are not uncommon in industrial schools and barracks which are badly ventilated, and where the inmates are not supplied with separate basins and towels for ablution. They are chiefly transmitted from the sick by inoculation of the eyes of the healthy with the secretions and discharges left on bed linen and towels ; but it is also probable that the contagion is carried through the air in dried epithelial or pus cells. The ophthalmia caused by gonorrhoeal infection of the eyes, and the ophthalmia neonatorum, inoculated from purulent vaginal discharge, are especiall}^ virulent and destructive forms of eye disease. Ophthalmia neonatorum is productive of about one- tenth of all cases of blindness, and for at least one-third of the blindness in inmates of British blind schools. One of the rules issued by the Central Midwives Board is to the effect that, " As soon as the child's head is born, and, if possible, before the eyes are opened, its eyelids should be carefully cleansed," with clean, lukewarm water. Moreover, whenever there is inflam- mation of the eyes, however slight, medical help must be sought. This disease has been made compulsorily notifiable in a few districts. In all forms of purulent ophthalmia a pyogenic micro-organism — the Staphylococcus pyogenes aureus oi albus — ■ is usually the active cause of the disease. Cerebrospinal Fever, or Epidemic Cerebrospinal Meningitis. The specific character of this disease is now generally recog- nized, but probably some cases so diagnosed are really suffering from tubercular meningitis or meningitis due to pneumococcus infection.-"- Cerebro-spinal meningitis is not an infrequent complication of many febrile diseases, but this form is never epidemic or communicable ; nor is it attended by the purpura or herpetic eruptions characteristic of cerebro-spinal fever. The 1 Sir Thomas Barlo-vv and Dr. Lees have recently drawn attention to a form of meningitis in children, which is now known as posterior (non-tuberculous) basic meningitis — due to a diplococcus closely allied to the diplococcus of Weichselbaum, found in epidemic cerebro-spinal menin- gitis. It is usually held now, that posterior basic meningitis is a sporadic form of cerebro-spinal meningitis. It appears to be endemic in many large cities and towns in this country, on the Continent, and in America. 468 HYGIENE AND PUBLIC HEALTH latter is also distinguished by the absence of any associated disease. Anomalous forms of cerebro-spinal fever have been mistaken for sunstroke and enteric fever. The disease is relatively rare in this countn,^, being more prevalent in the United States and certain localities on the contirient of Europe, and is probably on the increase. An organism having a diplococcus form and often called the meningo- coccus [Diplococcus meningitidis intracellular is of Weichselbaum) is found in the cerebro-spinal fluid, and is believed to be the specific organism ; and the same organism has been found in cases of infantile paralysis. Animals, especially horses and pigs, are probabh' also liable to the disease. The diplococcus is said to be constantly present in the nasal discharge of the sufferers, and not infrequently in the nasal secretions of those in attendance upon the sick. This discharge is sometimes so profuse as to cause the disease to be mistaken for influenza, and it is probabl}^ the main channel of infection, but the infectivity of many cases appears to be exceedingly sHght. Since, however, direct personal infection probabl}' plaj^-s a part in the spread of the disease, it is well to endeavour to isolate the sick, and to apply suitable measures of disinfection. 0\'ercrowding and bad air appear to predispose to attack. The disease affects children and 3"0ung people, sometimes sporadical!}^ and often in epidemic waves ; and the case mortalitj^ is generaUy ^^ery high — often 50 and sometimes reaching 80 per cent. The diagnosis can be confirmed bacteriologicallj' bj' a lumbar puncture (v\-hich is almost painless) below the end of the spinal cord ; and an examination foi the diplococcus can be made in the cerebro- spinal fluid so obtained. Lumbar puncture, with the removal of about 30 c.c. of fluid, is also a palliative and curative measure ; and in the latter respect antimeningococcus serum (obtained from horses immunized for many months with strains of cocci from human sources) is useful. Epidemic Pneumonic Fever. That pneumonia may occur in epidemics, or e\^en pandemics, has been recognized for man)' years. The mortalitj^ of several outbreaks in this countr}' has attained the proportion of 5 per 1,000 living of the community. So far as has been ascertained, neither meteorological nor insanitarv conditions appear to exercise any marked influence on the epidemic prevalence of pneumonia. COMMUNICABLE DISEASES 469 Puerperal Fever. Puerperal fever is generally caused by the introduction of infection into the genital tract from without the body, and usually by the neglect of aseptic precautions as regards the hands and obstetric instruments, during and immediately after child- birth. The term " puerperal fever " has been defined by the Royal College of Physicians of London as including " septicaemia, pyemia, septic peritonitis, septic metritis, and other acute septic inflammations in the pelvis, occurring as the direct result of childbirth." Various micro-organisms have been found associated with the disease, e.g., Streptococcus pyogenes, Staphylococcus aureus, the Gonococcus, and Bacillus coli communis. Insanitary conditions, more especially the fouling of air by overcrowding and drainage defects, probably 'play some part in determining the occurrence of the disease ; and there is some evidence that the infections of erysipelas and of scarlet fever have some relationship to that of puerperal fever. To prevent the spread of " puerperal fever," the midwife or lying-in attendant should cease attendance on other lying-in women until thorough disinfection has been accomplished. This should include a hot bath for the person, with the use of soap and disinfectants, thorough cleansing with soap and disinfectants of the hair, hands and finger-nails ; steam disinfection of all personal clothing ; and sterilizing in boiling water of all mid- wifery instruments, catheters, and douches. The obstetric bag should be sprayed inside and out with a disinfectant spray, and a clean lining and pockets substituted for the old ones. Cancer. The causes determining the prevalence of this disease are still wrapped in obscurity, and the view that cancer is due to a parasite, which possesses some degree of infectiveness, is losing ground. Certain investigations seemed to indicate that cancer, like enteric fever, has an endemic prevalence, and that it affects in a higher degree populations living in low-lying river valleys with clay soils than those on high, dry, and non-retentive soils. Such endemic areas might be close to others on which the disease rarely occurred ; and isolated " cancer bouses," or groups of such houses, in which successive families have suffered from cancer, though in no way related to each other, were held by many to 470 HYGIENE AND PUBLIC HEALTH exist in certain districts ; but the evidence both as to endemic areas and cancer houses is by no means strong. All races of mankind are liable to cancer, and likewise all verte- brate animals— with the possible exception of reptiles — whether they be living in a state of nature or in captivity. The histo- logical lesions characteristic of the disease throughout the verte- brates are identical with those found in man. Cancer in the lower animals has the same higher incidence in old age, and therefore the same relation to the duration of life as in man. Cancer has been successfully inoculated from mouse to mouse, the new tumour being of exactly the same nature as the original one. A mouse cancer will only grow in other mice of the same race ; that is to say, a wild mouse cannot be inoculated with tame mouse cancer, and vice versa. Propagation succeeds as well, and perhaps better, in young mice as in old ones. The cancer cells transmitted experimentally from one mouse to another continue to grow and divide in the inoculated mouse. The tissues of the new host do not acquire any cancerous pro- perties ; they merely react to the presence of the cancer cells, and supply them with nourishment. The process is fundamentally different from all known processes of infection. (Bashford.) The death-rate from cancer varies considerably in different parts of England and Wales, ranging in the year 1905 from 483 and 763 among males and females respectively, in Durham ; 526 and 717 respectively, in Glamorganshire, to 1,400 and 1,504 among males and females respectively, in Huntingdon- shire, and 1,190 and 1,611 respectively in Cardiganshire. During the past fifty years there has been an increased mor- tality registered from the disease in England and Wales, as the following table serves to show : — Deaths per 1,000,000 Living at all Ages. 1851-60. 1861—70. 1871-80. iS8i-go. 1891— 1900. 1901-1905. Males . . Females I9S 434 242 519 312 617 430 739 598 903 723 997 This increase is probably not altogether real, but is to some extent due to better diagnosis and certification of causes of death. " The cancerous affections of males are in much larger proportion internal or inaccessible than are those of females. COMMUNICABLE DISEASES 47I and consequently are more difficult of recognition ; so that any improvement in medical diagnosis would add more to the male than to the female figures " (Ogle). It is a significant fact, therefore, that among males aged thirty-five to forty-five the rate of increase has been 8g per cent., while among females of the same age it has not exceeded 37 per cent. Moreover, in Frankfort-on-Main, the deaths are classified into those from cancer of inaccessible and of accessible regions, and the increase of cancer is confined to the former. The greater number of suivivals of late years to the higher ages will also account for a slight increase in the incidence of a disease of a degenerative type such as cancer. But despite these facts some of the increase appears to be real, and in this increase there is a maiked pre- dominance of cancer of the digestive organs. Statistics fail to show any true hereditary tendency ; and as to the cause of the disease our present knowledge admits of little more than the statement that local irritation and the abuse of alcohol appear to predispose to it. Rheumatic Fever. It is now recognized that this disease is a specific disease, and quite distinct as to its origin from ordinary rheumatism. The facts supporting this view are : — -(i) Excessive, or even epidemic, prevalence tends to manifest itself at irregulars interv^als of from three to six years. Longstaff has shown the very striking analogy that exists between the mortality curves in this country of rheumatic fever, erysipelas, and puerperal fever, both when plotted out as annual death-rates for a period of years, and also when drawn to represent the average weekly deaths of a series of twenty years. The annual curves and the seasonal curves of all three diseases rise and fall together in a very remarkable manner, suggesting if not an actual community of origin, at any rate a co-relation of distinctive character. (2) Dr. Newsholme's researches have shown that there is a very definite relationship between deficient rainfall, low ground water, and high soil temperature on the one hand, and the prevalence of rheumatic fever on the other. In Norway the disease is compulsorily notifiable by medical attendants, and exceptional opportunities are thus afforded in that country of studying the epidemiology of the disease. Elsewhere, the evidence collected is generally derived from hospital returns. (3) The type of the pyrexia, and 472 HYGIENE AND PUBLIC HEALTH the articular and cardiac disturbances, are best explained on the microbic doctrine. (4) The marked effect of the administration of salicylates has long been claimed as proof in support of the specific nature of the disease. Several bacteriologists in this country and abroad have described a diplococcus in acute rheu- matism, which they have isolated from the endocardium, peri- cardium, fibrous nodules, tonsils, and urine in cases of the disease. When inoculated into animals (rabbits), the latter die with arthritic and cardiac lesions from which the diplococcus has again been isolated. Syphilis. There can be little doubt that the causative organism of this disease is the Spirochcsta pallida, an extremely minute and delicate, spirally twisted, thread-like organism, which is actively motile, the character of the movements being a rapid rotation on its long axis as well as a progressive movement (Leishman). The organism is present in the substance of and in the discharges from the primary sore or chancre, and can best be seen under a high power of the miscrocope with dark ground illumination, when the spirochaete will be observed as an actively moving, illuminated object against the dark background. By this means it is possible to make a diagnosis of syphilis on the first appear- ance of a venereal sore, although the failure to find Spirochcsta pallida does not necessarily imply that the venereal sore is not specific. The spirochgetes may also be found in the indurated glands, in the various secondary eruptions of syphilis, and also in the blood of syphilitic patients in certain stages of the disease. They are, however, onh^ very rarely found in the tertiary lesions of syphilis. In congenital syphilis, on the other hand, the spirochaetes may often be found in large numbers and widely distributed in the tissues. There is now strong reason to believe that certain common and fatal diseases, which were not formerly regarded as having any connection with syphilis, are in reality the late after-effects of syphilitic infection. Amongst these may be mentioned general paralysis, tabes dorsalis, aortic sclerosis, and possibly congenital idiocy or imbecility as a result of congenital syphilis. The first three of these diseases are now often designated " paia-syphi- litic " affections. The serum diagnosis of syphilis, which has been rendered pos- sible by the researches especially of Wassermann, Neisser, and COMMUNICABLE DISEASES 473 Bruck, is now capable of referring these so-called " para-syphi- litic " affections to their true origin, and also enables a diagnosis to be made in cases of tertiary syphilis of uncertain nature. For an explanation of the Wassermann reaction reference should be made to standard works on pathology and bacteriology. In this country an attempt was made by the Contagious Diseases Act of 1864 to limit the spread of venereal diseases in certain military and naval garrison towns. Any woman charged with being a prostitute and diseased, and plying her trade within certain limits, could be summoned before a magistrate, who had power to order her to be taken to a certified hospital for medical examination. If found to be suffering from a contagious venereal disease, the magistrate could order her detention for treatment for a period not exceeding three months. A later Act of 1866 enabled a justice to order any woman charged with being a prostitute to submit herself to a periodical medical examination for any period not exceeding one year. These Acts continued in force until May, 1883, when an order was issued abolishing the compulsory examination of women ; and they were finally repealed in 1886. It is very doubtful if these Acts had any real effect in con- trolling the spread of venereal disease in English garrison towns. Only a certain proportion of the diseased prostitutes were evei brought under control in the manner indicated by the Acts ; whilst those who escaped police supervision, and the men who consorted with them, were free to spread infection with im- punity. Notwithstanding the absence of any CD. Acts, the prevalence of venereal diseases in the British army in the United Kingdom has been steadily diminishing of recent years. This fortunate result is attributable to greater temperance amongst the soldiers, a higher standard of education and intelli- gence, more opportunities for healthful recreation both of mind and body, and the greater interest displayed by regimental officers of all grades in the health and well-being of the men, and in keeping them fit for the duties of theii calling. Although in the British army, both at home and abroad, much has been done by education, precept, and rational amusements for the men's leisure time to reduce the incidence of venereal disease in the troops, a very great deal has also been effected by improved medical treatment, and especially by the " continuous " treatment with intramuscular injections of mercury until a cure 474 HYGIENE AND PUBLIC HEALTH has been effected, to reduce the sicknes? and invahding from syphiHs that formerly contributed so largely to the wasting of the ranks. This method of treatment may in its turn be re- placed by the new anti-syphilitic remedy devised by Ehrlich, who, in the substance known as dioxi-diamido-arseno-benzol (" 606 "), appears to have evolved a substance which is, on injection, absolutely destructive to the specific organism ; whilst in the small doses of about 0-5 to 0-7 gramme required for this purpose it is believed to be without actively injurious effect on healthy living tissues. The treatment, however, is still in an early experimental stage, and time must elapse before the permanency of cures can be attested. Tropical Diseases. Asiatic Cholera. Cholera is endemic in the delta of the Ganges, and probably also in other parts of India and the Orient. Epidemic extensions take place from time to time, the disease being imported from these " homes of cholera " into far distant countries, by sea or overland, by means of persons suffering from it, and possibly by means of infected articles. The three main routes which cholera has taken from the endemic area in India to Western Europe are as follows : (i) Through the north-western provinces of India to Afghanistan, and thence by caravan routes to Khiva and Russia ; (2) from Southern India up the Gulf of Persia, and thence to Syria and Egypt, and across Persia to the Caspian Sea ; (3) mainly by pilgrim traffic to the Red Sea ports and Egypt, and thus to the Mediterranean. The usual mode of propagation of cholera is through drinking water. The specific poison is contained in the copious bowel discharges of the sick, and may iind its way through the soil on which the dejecta are thrown, into streams, wells, or tanks. It is also possible that the contagion is at times transmitted through the air by the dried choleraic discharges being borne into the air by currents of wind ; although the fact that the cholera germs are rapidly killed by drying is opposed to this view. If flies feed on infected material, the organisms may be found in them twenty-four hours afterwards. Haffkine also has shown that in an infected district flies can contaminate milk with cholera spirilla, if the milk be kept in open vessels ; so that COMMUNICABLE DISEASES 475 it seems probable that cases of apparent transmission of the disease through the air may in reality be due to the agency of flies. Temperature and moisture are controlling factors of great importance. When the disease is imported into a temperate climate, the intensity of the epidemic is invariably felt in the late summer and autumn, and dies away with the approach of cold weather, possibly to again acquire epidemic intensity in the following summer. It is evident, therefore, that the specific virus can only attain its full virulence where the temperature of the air, and therefore of the soil, is sufficient. The combination of mois- ture and heat of soil, characteristic of the Ganges delta, appears to offer the most suitable envirormient for the cholera virus. In India, Cunningham has shown that the common bacilli, which are found in the evacuations of cholera patients, and which are regarded as the specific cause of the disease, when introduced into polluted water or soil, tend rapidly to disappear, as they are attacked and destroyed by the saprophytic bacteria always present in such circumstances ; but in some cases they have been found alive even after two or three months in cholera dejecta kept at room temperature. The incubation period of cholera is usually very short — one or two days ; but it may occasionally be prolonged for ten days or more. The evacuations are most infective during the height of the disease. In epidemic periods the proportion of deaths to attacks is greatest during the period of maximum intensity of the epidemic. When the epidemic is first commencing, and after it has begun to subside, the recoveries may considerabh^ exceed the numbers of deaths. The preventive measures which have hitherto acted most successfully in keeping the disease out of these islands have reference to our " first line of defence," i.e., the coast. By far the most important are contained in the provisions of the Cholera Order of the Local Government Board, but other valuable measures have been : (i) The Order prohibiting the importation of rags from all infected ports ; (2) the Order prohibiting the landing of " filthy and unwholesome aliens," unless they first satisfy the medical officer of health of their freedom from cholera, and give their names and destinations ; (3) the provision of the means of isolating the infectious sick at our ports ; (4) the placing of these ports in a good sanitary con- dition by dealing with insanitary dwellings and areas, so as to 4/6 HYGIENE AND PUBLIC HEALTH remove, as far as possible, all dangerous breeding grounds for the germs ; and (5) the adoption of every possible precaution to safeguard the purity of public water supplies. The issue of printed notices by the local authority, in which instruction is given as to the means to be adopted by the indi- \ddual to guard against infection, is a useful measure. In such handbills it should be stated that raw vegetables and fruit should be avoided ; that extreme cleanliness- in the household should be adopted, since cholera is essential!}^ a filth disease ; that all milk and water should be boiled shortly before use ; and that on the occurrence of diarrhoea in any indi\ddual, medical advice should be at once sought. \\Tien the danger of an outbreak becomes imminent in any district, a staff of nurses should be enlisted, arrangements made for the use of any available buildings as temporary hospitals, a large stock of disinfectants provided for gratuitous distribution, and measures taken for the supph' to medical practitioners of anticholera inoculations. Outbreaks of cholera have often .been preceded by sporadic cases of severe diarrhoea, which are probably unrecognized cases of the disease. The provisions of the Cholera Order have supplanted those of Continental quarantine in these islands, and are doubtless far more successful in practice. The facts which tell against the efficiency of quarantine as practised elsewhere, are certainly sufficienth' strong to warrant the adoption by all countries of the English s\^stem. The detention of persons on board an infected ship for many da^^s is not a measure calculated to protect the health}^ from infection and to limit the spread of the disease, whilst the delays thus caused are ruinous to trade. Such measures ha^'e been sho^^^l to be unnecessary in this countr5\ and, omng to frequent evasions, they often fail in their object of keeping the disease out of foreign ports. In Malta the provisions of Italian quarantine continue to be practised, but the British system is in application at Gibraltar ; the result is that Gibraltar generally escapes from imported infectious disease, whereas Malta almost invariably suffers. A very \dgorous sj^stem of quarantine, moreover, utterly failed to prevent cholera crossing the great natural barrier afforded by that huge inland sea, the Caspian, when the disease appeared on its eastern shores on the occasion of the last great \dsitation of cholera to Europe. COMMUNICABLE DISEASES 477 Land quarantine — by which is implied the drawing of a cordon of soldiers or police round an infected area — generally also fails in its purpose. Dysentery. This is not a disease of common occurrence in this country, except perhaps in lunatic asylums, where it is known as colitis. It is distinguished clinically from acute diarrhoea (summer diarrhoea, English cholera) by the fact that the stools contain slime and blood, and there is much tenesmus. The disease also has a great tendency to become chronic, which is unusual in summer diarrhoea. Dysenteiy is a very common and fatal disease in tropical countries. In temperate climates it is rarely seen except in times of war or famine. It is eminently associated with condi- tions of defective hygiene, e.g., fouling of the water supply or of the soil in the neighbourhood of habitations by excreta, over- crowding in houses or in camps, and insufficient, coarse, or bad food. In tropical and sub-tropical countries, where these in- sanitary conditions, or some of them, continuously prevail, dysentery tends to become endemic, and to assume epidemic proportions, if circumstances are favourable to its spread. There are many varieties of dysenteric disease, and but very little is known as to their causes, or as to whether they are types of the same disease differing merely as to their severity, or whether the different varieties may not be distinct entities each having a different mode of origin and method of propagation. One type of dysentery is known as " amoebic dysentery," from the fact that in this type a protozoon, the Amceba coli, is in- variably present in the stools ; but it is not known with any certainty that the amceba is actually the cause of the dysentery. There are many cases of dysentery, and even some having a great clinical resemblance to amoebic dysentery, in which the amoebce cannot be found ; moreover an amoeba, indistinguishable from the dysentery amoeba, is sometimes found in the healthy stools of people in good health. According to Schaudinn, however, there are two varieties of amoeba to be found in the intestine — one a pathogenic and the other a saprophytic organism, which differ somewhat from each other in morphology and in methods of reproduction. The Amceba coli is very frequently found in the contents of the liver abscesses, which are so often associated with chronic dysentery, and this indicates the presence of 47^^^ HYGIENE AND PUBLIC HEALTH amcebae in the intestinal tissues around dysenteric ulcers. Amoeba coli is seldom found in the stools during epidemic prevalence of dysenter}^ In these epidemic cases Shiga has isolated a bacillus {Bacillus dysentericB) which somewhat resembles the Bacillus typhosus, and whilst it does not agglutinate in serum from typhoid cases, agglutinates with the blood serum of cases of epidemic dysentery in dilutions of one in ten. This bacillus has some claim to be regarded as specific in epidemic types of dysentery. In some cases of colitis, or asylum dysentery, in this country Durham has isolated a micrococcus, so minute that it readily passes through a Berkefeld filter, from the blood, liver, spleen, kidney, and bile of affected patients. Dysentery is undoubtedly to a large extent a water-borne disease, like enteric fever, but like the latter disease its propaga- tion is at times effected by means of dust and flies. Much light was thrown on these methods of dissemination of the disease during the South African Boer war. As in cholera, and other tropical diseases, chill, bad or irritating food, mental depression, etc., play a very important part as predisposing causes, and are by many still regarded as the exciting causes of dysentery. Plague. An epidemic disease having the character of bubonic plague is referred to by many old writers, as far back as 2,000 years ago, as prevalent in Egypt, Libya, and other parts of North Africa. The most appalling European visitation was that in the fourteenth century, known as the " Black Death," which was supposed to have had its origin in China in 1334 ; this out- break lasted many years. The Great Plague of London made its appearance in 1664, lasted about one year, and destroyed at least 63,000 persons. China and the western parts of India appear to have always suffered most ; and it is generally recorded that plague has attacked districts for a number of successive years, with short intervening periods of apparent freedom. China does not seem to have suffered much in recent years. For example, it has not been present in Pekin, Shanghai, and other large towns, but only in Hong Kong. Occasionally from here it has found its wa}^ to Canton and Macao by direct inter- course, but even then it appears not to be able to get a footing. COMMUNICABLE DISEASES 479 Although rare in equatorial regions, it occurs in hot and cold weather, wet and dry seasons, on dry and damp sites, and at all altitudes. In India plague generally decreases during the hottest weather, and recrudesces \vith the onset of the colder seasons. The disease is of microbic origin, and is due to the bacillus isolated at Hong Kong in 1894 by Kitasato and Yersin. This bacillus is found post-mortem in the blood, the spleen, and other internal organs, also in the unopened buboes, the sputum, faeces, and urine. The infection can be contracted by inocula- tion, inhalation, or by swallowing ; and human sufferers are not the sole carriers of contagion. Rats, mice, bandicoots, guinea-pigs, monkeys, pigs, and probably sheep, goats, dogs, and other animals may also suffer from the disease, which in China and the Himalayas has long been called " the rats' disease." Fleas and flies have been shown to die in large numbers in plague laboratories, and to contain the Bacillus pestis. Like mosquitoes they may act as carriers. There is evidence to show that rats may be affected before human beings ; and it is certain that the continuance and spread of the disease is often favoured by the presence of these highly susceptible animals, many out- breaks having been attributed to infected rats, conveyed from an infected to a non-infected port in grain-carrying ships. It is probable that the infection is conveyed from rat to rat, and from rats to human beings by means of fleas, and that on the death of a plague-stricken rat, the fleas — already engorged with baciUi — Cleave the body and find their way into houses where they attack man, inoculating him through the " bites." Klein states that the B. -pestis as found in the rat is of a different type to that isolated from man. The human type is much more virulent than the rat type, and they present also permanent and definite differences in morphological, cultural, and physiological respects. The rat type quickly loses its virulence when sub-cultured artificially, whereas the human type retains its virulence for long periods during sub-culture, and, unlike the rat type, recovers full virulence by a renewed passage through the animal body. The original virulence of the rat type, when once lost, cannot be regained by animal passage. Direct contagion from the sick to the healthy appears to be a minor cause of spread, Europeans having suffered but very little while in attendance on Indian patients. Like typhus fever. 48o HYGIENE AND PUBLIC HEALTH plague appears to be associated with conditions of poverty, filth, and overcrowding, and with soil polluted by organic matter. It has not yet been demonstrated that drinking water has acted as a disseminator of the virus, although experiments show that the plague organism can live for a long time in water. Fomites retain and spread the infection. There are three distinct types of the disease : — the bubonic, the pneumonic, and the septicsemic ; but the first named is so much more common than the others that the disease is very generally known as " bubonic plague." The incubation period of bubonic plague varies from two to seven days ; and generally within twenty-four hours, or less, from the onset of symptoms the buboes appear in the groin, the armpit, the region of the neck, or more rarely elsewhere. Death frequently takes place within forty-eight hours of the onset of symptoms, a fatal result being rare after the eighth day. The disease varies so much in its clinical aspects and severity as to justify a rough classification of cases into severe and mild pestis major and pestis minor) ; but the tendency nowadays is to restrict the term pestis minor to cases of enlargement of glands (not venereal in origin), which are often seen just before and during a true outbreak of plague, and in which the Bacillus pestis cannot be demonstrated. The preventive measures against the disease include : The compulsory notification of the disease, the discovery of cases by house-to-house inspection (where necessary), and the early bacteriological diagnosis of the mild or " ambulant " types of the disease which have been observed to precede an outbreak.^ 1 The following directions for obtaining and forwarding for bacterioscopic examination material from a suspected case of plague, have been issued by the Medical Of&cer of the Local Government Board. (a) From the living person : — 1. Clean with soap and water and then with alcohol the last phalanx of either the second or third finger. When dry, or after mopping "with a clean cloth, put a piece of tape round the proximal end of the last phalanx so as to cause venous congestion. Prick the palmar surface of this phalanx with a sterile needle, and immediately take up the exuding blood in two sterile capillary tubes such as are used for collecting vaccine lymph. These tubes when charged should be sealed at both ends. 2. When there is a discharging bubo, collect fluid therefrom in capillary tubes as in the case of blood. When this discharge is not of a sufficiently fluid character for collection in this way, place some of it in a small glass- stoppered phial, previously well washed out with alcohol, care being taken that no alcohol remain in the phial. 3. If expectoration be obtainable, collect some in a phial in the manner prescribed in Section 2. COMMrNICABLF DISEASES 481 Prompt and efficient isolation and disinfection should follow upon the discovery of the cases ; and those living in the same house with a plague patient (the so-called " contacts ") should be removed from their homes to a quarantine house, to be kept under observation for ten days. Both prophylactic and curative inoculations with Haffkine's vaccine and Yersin's plague serum, respectively, are further measures of undoubted value, which should be practised when possible. The total destruction of the rats in an infected area is eminently desirable to check the spread of the disease, but the due execution of this precaution has hitherto presented insuperable practical difficulties. People should be advised to keep their houses rat-free, and if possible rat-proof : to provide no food for rats, and to keep cats. The numbers of rats may be materially reduced by trapping or poisoning, or by asphyxiating them in their hiding places with a mixture of carbonic acid and carbon-monoxide gases, or with sulphurous acid gas, and their dead bodies should be immediately burned. Efforts have been made with some success to com- municate an epizootic disease to rats and mice by means of the Danysz bacillus, which, while not communicable to man, would spread among the rodents and cause their destruction. The Danysz bacillus is genetically related to the paratyphoid group of organisms, which also includes the Bacillics enteritidis of Gaertner. Some care should be exercised in the destruction of rats by means of food which has been soaked in cultures of the Danysz bacillus, as there is reason to believe that human beings have been rendered ill by contamination of their food with this bacillus. There is some reason to question the accuracy of the statement that the Danysz bacillus is harmless to man. Merchant vessels should take the necessary steps for the destruction of rats on board before loading and upon discharge, and also to prevent intercommunication during loading and discharge between ship and shore rats. Further, owTiers of river- side warehouses and granaries should make systematic efforts [b) From the dead body : — 1 . Cut out any inflamed lymph-gland, together with some of its surround- ing tissue, and place the whole in a wide-mouthed glass-stoppered bottle, previously well washed out with alcohol, care being taken that no alcohol remains in the bottle. The bottle should have the stopper well secured and sealed. 2. Obtain also a piece of the spleen, dealing with it in the same manner. 31 482 HYGIENE AND PUBLIC HEALTH to exterminate rats, and to prevent rats leaving ships ; cables covered \vitli fresh tar at each end and fitted with special conical guarded collars should be used, and footbridges should be raised during the night. Fumigation ^^ith sulphurous acid gas effectually destroys rats in a closed hold, but this can only be used after the hold is cleared out, because of its injurious effect upon many cargoes. The admixture of COg and CO, obtained from burning charcoal, is cheap and without injurious effects upon the most delicate goods ; it is, however, a more dangerous gas to human beings, and extreme precautions must be taken against accidents. Any rats found on a " suspected " vessel must not be handled, but plunged wdth tongs into a bucket of carbolic solution until they can be burnt. No rats must be thro^^^l overboard into the harbour. The evacuation of infected houses, and even of infected dis- tricts, has been attended \\dth good results in India, the people being housed temporarily some distance away, while the sufferers are isolated, and the infected clothes and premises disinfected. To guard a district against the importation of the disease, all persons coming from infected localities should be subjected to at least seven days' surveillance ; and provision should be made for the medical inspection of all incoming persons at the railway centres, and at other means of approach to the district. Any- one found to be suffering from the disease must submit to hospital isolation, and suspects must be detained temporarily in quarantine camps. As the disease is essentially a filth disease, everj^ effort should be made, by improved scavenging and the removal of insanitary conditions, to stamp out the possible foci of infection. Experiments have sho%vn that a soap emulsion of kerosene oil is a valuable agent in the disinfection of plague- infected rooms ; and that fleas exposed to the action of this pulicide are almost always killed in two minutes. Haffkine's prophjdactic against plague consists of a fluid pre- pared bv gro\\dng plague bacilli in goat, beef, or mutton broth on which floats a small quantity of clarified butter. The bacilli attach themselves to the oil globules, and form stalactitic growths projecting into the broth. After about four weeks, when six crops of stalactites have been formed, the culture is heated to 70° C. for an hour, to kill the Bacillus pestis, and a little weak carbolic acid solution is added to prevent the growth of ex- traneous organisms. A copious deposit is produced which COMMUNICABLE DISEASES 483 should be well shaken and diffused throughout the liquid before the vaccine is finally bottled. The usual dose for inoculating an adult is 2 to 3 c.c, and the inoculation should be repeated in from twelve to twenty days. A good deal of reaction results, the temperature rising to 102° F., sometimes to 104'^ F., with a feeling of general malaise and pain at the seat of inoculation. The India Plague Commission has recently reported that inocula- tion of Haffkine's fluid sensibly diminishes the incidence of plague attacks, and also the fatality of attack among the inoculated population. Yersin's serum is prepared in the same way as diphtheria antitoxin, by inoculation of horses with living cultures of plague bacilli. The immunity given by inoculation of Yei sin's serum is of much shorter duration than that due to Haffkine's prophy- lactic. Fifteen days is about the limit of the immune period due to the serum, whereas Haffkine's fluid may be protective for several months ; but it is claimed that Yersin's serum is also curative, when once the disease has declared itself. Malaria. It has now been demonstrated (Manson, Ross, Koch, Grassi, Celli) that man is the temporary host, and the mosquito the definitive host, of all known malarial parasites. In addition to man, however, monkeys, bats, and other vertebrates may har- bour the parasite ; and Manson suggests that in the absence of vertebrates, one mosquito may become directly infected from another, and so keep the parasite alive. These parasites pass their asexual life, and prepare their sexual forms, in the human blood, while they complete the sexual cycle of life in the middle intestine of the mosquito. Those mosquitoes capable of affording lodgment to the specific parasites, and of infecting man by means of their punctures, appertain to the genus Anopheles. Some species, but not aU, of Anopheles can be distinguished from the genus Culex — the common gnat, a harmless insect — by the cir- cumstance that, when the former alights on an object, the long axis of the body is almost vertical to the resting surface, while in Culex it is parallel ; the Anopheles, moreover, does not make so loud a humming sound as the Culex. In Anopheles the palpi are the same length as the proboscis, in Culex they are much shorter. The mode of production of malaria in man is briefly as follows : In an infected Anopheles mosquito the veneno-salivary glands 484 HYGIENE AND PUBLIC HEALTH lying on each side of the fore part of the thorax, and the ducts leading from these glands to the base of the mosquito's pro- boscis, contain the spindle-shaped sporozoites (malarial). When the infected female mosquito bites a man, these sporozoites are injected into his blood. In the blood the sporozoites multiply, find entrance into the red blood corpuscles, and grow at the ex- pense of the haemoglobin, so as to be recognizable as malarial parasites eight to ten days after infection. The parasite is then seen as a pale ill-defined disc of protoplasm occupying a larger or smaller area of the red corpuscle, and containing a number of black pigment particles — melanin. These scattered pigment groups subsequently concentrate into one or two larger central groups, around which the protoplasm arranges itself in minute segments, which finally become spores. The blood corpuscle then breaks down, and the spores and melanin are liberated into the liquor sanguinis. The melanin and some of the spores are then absorbed by the phagocytes, but others of the spores attach themselves to undamaged red blood corpuscles, which they enter. In these newly infected corpuscles the para- sites exhibit active amoeboid movement, shooting out and re- tracting long pseudo-spodia, and grow at the expense of the haemoglobin. As the parasite becomes larger the amoeboid movements lessen, and just before sporulation and the com- pletion of the asexual cycle, the parasite is passive. At a later stage of the malarial illness, certain sexual forms of the parasite may be seen in the blood, these assuming either the form of crescents (malignant ague) or large intra-corpuscular forms (benign ague). In the male type of crescent the protoplasm is hyaline, and the pigment loosely arranged ; in the female the protoplasm is faintly granular, and the pigment arranged as a well-defined ring about the centre of the parasite. If human blood containing these crescents or large intra-corpuscular forms is ingested by the female Anopheles mosquito into its stomach, certain changes take place. In the male crescents or parasites active movements set in in the pigment, and one or more flagella are suddenly shot out from the periphery of the parasite, which have characteristic waving movements. Some of the flagella break away, and approaching the female parasites enter their substance through a minute papilla on the surface. Only one flagellum enters each female ; no second flagellum can effect an entrance. After impregnation the female parasite COMMUNICABLE DISEASES 485 assumes a vermicular form, and becomes motile. It then pene- trates the wall of the mosquito's stomach, and lodges itself amongst the muscular fibres, and may here be seen as an oval or spherical body with sharp outline, thirty-six hours after the mosquito has fed on infected human blood. During the next few days a vast number of minute, slender, spindle-shaped nucleated bodies — the sporozoites — are developed in the parasite, now much enlarged ; a week later the capsule containing the sporozoites bursts, and the latter are discharged into the mid- gut of the mosquito. From here they pass by means of the blood stream into the veneno-salivary glands, and the sexual cycle is completed. Typical ague is either " quartan " — pyrexial attack every seventy-two hours ; " tertian " — every forty-eight hours, or " quotidian " — every twenty-four hours. The rigors intro- ducing the attack coincide in point of time with the liberation of the spores from the red corpuscles ; and it is believed that the fever is determined by the setting free of the toxins generated by the parasites in the blood corpuscles. During the hot and sweating stages of the attack it is probable that the toxins are in process of elimination from the blood. During the intervals between the attacks there occurs the infection of red corpuscles not previously affected, and the growth, maturation, and sporula- tion of the parasites within the corpuscles. In the remittent and continued (malignant) types of malaiia, there has probably been a mixed infection with parasites belonging to the various types of ague above mentioned, together with the malignant crescent-forming parasites, so that sporulating parasites may be met with at all stages of the disease, and the fever is not intermittent, but continued, with remissions. Blackwater or Hcemoglohinuric Fever sometimes occurs in those who have been subject to occasional attacks of malarial fever. This disease is very frequently fatal ; but, if recovered from, the malaria parasites, which were present in the blood prior to attack, generally disappear during the process of hsemoglobinuria, which may thus terminate for good a chronic malarial infection. The haemoglobinuria secures the destruction of all the parasite-infected red corpuscles, and their included parasites, and therefore seems to be a method of spontaneous cure of a malarial infection. Nothing is known as to the cause of the occurrence of blackwatei fever, apart from its association with malarial parasites in the blood. 486 HYGIENE AND PUBLIC HEALTH The soil plays only an indirect part in the propagation of malaria, by its favouring or otherwise the life and development of the malariferous mosquitoes. The most favourable soil for malaria is that which permits of the formation and continu- ance of pools of stagnant water containing algae or water weeds, which are the habitat of the eggs, larvae, and nymphae of the genus Anopheles. Rice fields, whether the water is stagnant, running or inter- mittent, always afford a favourable nidus for the Anopheles larvae. It is generally admitted that chilling of the body predisposes both to the onset of the primary infection and to relapses. The inhabitants of malarious districts in the tropics acquire some degree of immunity, as a rule, after a few years of life in these regions. Among prophylactic methods should be included the ability to make an accurate diagnosis of the complaint, and to recognize the plasmodium in blood submitted for examination. After diagnosis the patient should be isolated, if possible, in some place where malarial mosquitoes do not exist, for he is otherwise liable to be bitten by infected mosquitoes, and thus to become the subject of contemporaneous infection by various different malarial parasites. Moreover, mosquitoes which feed upon him are capable of disseminating the disease ; for, by reason of the sexually developed parasites in his own blood, he is a source of infection to uninfected mosquitoes, and consequently to man. He should also be energetically treated with quinine, which lapidly destroys the parasite in the blood. The pro- phylactic measures are directed towards the protection of the infected person from mosquitoes, the protection also of the non-infected, and the destruction of the larvae in the water. For this latter purpose kerosene appears to be efficient, if rightly used. The kerosene acts mechanically by asphyxiating the lar-vse and nymphae, which float fiat with their breathing tubes on the surface of the water ; it must therefore form a stratum, covering the whole surface of the water. The most suitable time for destroying the larvae is the winter or the beginning of the spring, when they are fewest in number in the water, and new generations have not yet made their appearance. Approximately i oz. of the oil to every fifteen square feet of surface is sufficient. Among the odours which are obnoxious to the mosquito are COMMUNICABLE DISEASES 487 tmpentine, menthol, and garlic ; among the fumes, tobacco and simple wood smoke ; among the gases, the most practical and efficacious destructive agent is sulphurous acid. In malarial districts an effort should always be made to pro- tect the body against the bites of all proboscidian insects, especi- ally at night, by means of veils, gloves, and mosquito curtains, or by inunction of the skin with oil or liniment containing camphor or eucalyptol. It should be a rule not to go out of doors after sunset, and suitable clothing should be worn to protect the body from chills. Since Anopheles larvse are mostly found in stagnant pools containing algae, all such pools should be filled in, drained, or otherwise dealt with, so as to permit of no place remaining where the mosquitoes can deposit their eggs. The same remarks apply to tanks, cisterns, water butts, refuse tins, etc., which are very frequently the breeding places of mosquitoes. All the old observations regarding malaria can now be accounted for, and their real significance understood. Thus it is an old theory that malarial miasm rises from stagnant water, that malarial outbreaks depend on rainfall, that they can be obliter- ated by drainage of the soil, and that they are often due to disturbance of the soil — all of these being factors which determine the existence of puddles affording suitable breeding grounds for Anopheles. Old observers have also noted that malaria is most likely to be conti acted about sunset and at night, that the " miasm " did not extend to any great elevation above sea- level, and was not carried by high winds. These facts are all explained by the mosquito theory of infection, for the insects issue forth at sunset, and pursue their search for food through the night, never mounting high in the an, and avoiding windy or stormy nights. Yellow Fever. This is a specific disease with an incubation period of from two to six days. Like malaria, yeUow fever is propagated by a mosquito, but the species is known as Stegomyia fasciata. The organism transmitted to man by the bite of the mosquito has not yet been identified. It appears to be so minute as to be ultra- microscopic ; but it undoubtedly exists in the blood of those affected, although only in a state capable of being retransferred to the mosquito during the first three or four days of the disease, as it is only mosquitoes that have fed on patients during the first 488 HYGIENE AND PUBLIC HEALTH three days of the fever that are found to be infective. The organism evidently undergoes some developmental process in the mosquito, as it is found that it is not until twelve days have elapsed after feeding on yeUow fever blood that the insect is capable of conveying infection to healthy men. This infective power it retains for at least fifty-seven days. Malta or Mediterranean Fever. This is a disease of often ver}^ prolonged duration, made up of a series of febrile attacks, with intervals of freedom or com- parative freedom from attack. The disease is due to an organism, the Micrococcus melitensis, which is found in the spleen, but not in the general circulation, and is therefore of little direct use in diagnosis. The disease is readily conveyed by inoculation, but does not appear to be directly communicable from the sick to the healthy by infected discharges, fomites, or other channels of infection The Micrococci melitensis are readily agglutinated by the serum of those affected mth the disease, and this fact is a great aid in diagnosis. The Commission appointed to in- vestigate the disease in Malta, reported that Maltese goats may harbour the micrococcus, and that their milk may be infected \\ith the organism. Goat's milk is the common source of supply in ]\Ialta, and it has been established by the work of the Com- mission that in Malta these animals are the chief, if not the only means, by which the disease is spread. The micrococcus is found in the excreta of goats, and the udders maj^ become infected b}^ infected excretions or soil, but the animals them- selves may exhibit no signs of any illness. The discovery as to the part played by goat'? milk in the transmission of the disease was made in 1906, and since that year the use of goat's milk has been prohibited in military and naval barracks in Malta. In the British army in Malta in 1905 there were 643 admissions to hospital for Malta fever, in 1906 (when the prohibition began to take effect) there were 161 admissions, in 1907 11 admissions, and in 1908 7 admissions. Not onl}^ goat's milk, but also cow's milk is now prohibited, as the latter animals have been sho^^^l to be liable to contract the disease, and to be as dangerous as goats. The result of the administrative procedure of 1906 has practically been to ex- terminate Malta fever as a cause of sickness and invaliding in the British army. COMMUNICABLE DISEASES 489 Leprosy. Although leprosy is almost certainly the result of the intro- duction into the body in some way, not clearly understood, of a specihc organism — the Bacillus leprcB — yet some doubt still exists as to whether this disease is ever conveyed by direct or indirect communication between the sick and the healthy. The wives, husbands, or parents of leprous patients, who have elected to be segregated with them on the Island of Molokai — one of the Hawaiian group — do not appear to succumb to the disease in any exceptional proportion as compared with the general popu- lation of the islands. Dr. Ashburton Thompson's recent investi- gation into the subject supports the view that " the vast majority of instances of apparent spread of leprosy by infection are spoilt by having been observed on areas of recognized endemicity, so that the influence of locality cannot be excluded. ..." It seems probable that leprosy enters the system by way of the upper respiratory tract ; but it is possible that fleas, etc., may inoculate the disease. Beri-heri. Beri-beri is a disease of wide distribution. It is occasionally to be seen in our docks amongst the crews of ships arriving from the tropics, but is more especially a tropical disease. It occurs generally in limited epidemics, in particular houses, institutions, plantations, mines, etc. ; but it may spread over large areas, only attacking, however, limited foci in such areas. The case mortality ranges from 5 to 50 per cent. (Manson). There is no evidence that it is communicable from man to man. The disease is characterized by difficulties of movement, often attended with some atrophic paralysis (more particularly of the limbs), by disorders of sensation, oedema of the skin, and dropsy of the serous cavities. There are several types of the disease ; in one the nervous symptoms predominate, in another the respiratory system is most affected, and in a third (oedematous type) the circulating organs. The disease is essentially a chronic one, and it is said that dirt, dampness, and overcrowding predispose to it. Possibly patients with open wounds may infect others, luit the disease does not appear to be communicable in any other sense. Many ascribe a food origin to the disease (viz., a poison which develops in stale, uncured rice), and it has 49^ HYGIENE AND PUBLIC HEALTH been shown that a change of food, the administration of fat and a liberal diet containing nitrogenous food are valuable in arrest- ing symptoms. The etiology of the disease, however, must stiU be regarded as obscure. This disease is liable to be mistaken for alcoholic or arsenical neuritis, malarial cachexia, pellagra, scurvy and pernicious anaemia. Dr. Hamilton Wright, after prolonged study of Beri-beri in the Malay States, holds that the disease is transmissible by a germ in the faeces of those affected, which leads a saprophytic existence in infected earth, floors, etc. The germ being ingested with infected food, after an incubation period of about ten days, sets up a specific duodenitis, which evolves the nerve poison. After about three weeks the duodenitis subsides, but the damaged nerves only slowly recover, the neuritis persisting with fluctua- tions in intensity over a period of many months. Dr. Wright claims that by feeding experiments he has induced in monkeys all the symptoms of Beri-beri. In the Malay States, where Beri-beri is very rife, the Tamils are almost completely immune from the disease. T. T. Clarke ascribes this immunity to the fact that the Tamils boil their rice before husking it, whilst in the affected communities it is the custom to husk the rice raw, thus allowing it to become contaminated by matters in the husk. The Tamils also take a quantity of pungent substances in their food containing essential oils, which may exert some prophylactic action. Fraser and Stanton are of opinion that Beri-beri is associated with the consumption of white rice as the staple food, such rice having lost substances in the process of milling which are essential for the nutrition of nervous tissue. These substances exist in adequate amount in the original grain, and in super- abundant quantity in the polishings from white rice. The prevention of the disease will be achieved by substituting for ordinary white milled rice, an unshelled rice in which the polishing process has been omitted ; or by the addition to a white rice diet of articles rich in those substances in which such rice is deficient. Dengue. This specific febrile disease is peculiar to warm climates, and is characterized by severe muscular and articular pains, and sometimes by a cutaneous eruption. It is especially prevalent in the dry, hot seasons of very warm climates, so that a high COMMUNICABLE DISEASES 49I temperature is doubtless one factor which determines incidence. One attack is generally protective, and the disease spreads by personal communication. Filariasis. The parent filarise [Filaria Bancrofti) are long, hair-like trans- parent nematode worms, three or four inches in length. The two sexes live together, often coiled about each other, and are found in the lymphatics of affected men, in lymphatic varices, and sometimes in the larger lymphatic vessels, and in lymphatic glands. The diseases which the adult filarise give rise to are of wide distribution in the tropical and sub-tropical world, and are endemic chyluria, various forms of lymphatic varix, probably tropical elephantiasis arabum, and other obscure tropical affections. The worms cause obstruction to the flow of lymph in the impli- cated vessels, and the lymphatic areas drained by these vessels are cut off from the general circulation. There then follows a rise of pressure in the occluded lymphatics, with consequent varicosity or lymphatic oedema, or a combination of the two. After fecundation of the female nematodes by the males new generations of embryo filariae are poured into the lymph. These eventually pass into the general blood circulation by way of the thoracic duct and the left subclavian vein. These embryos {Filaria nocturna) are minute, transparent worm-like organisms, about sV inch in length, each enclosed in a delicate sheath. The filariae are only found in the peripheral circulation during the hours of night. During the day they retire to the larger arteries and to the vessels of the lungs (Manson). Should the females of certain species of mosquito {Culex fatigans) feed on the blood of a filariae-infected man — which they do almost exclusively at night time — the filarise enter the stomach of the mosquito. Here the filariae escape from their enclosing sheaths, and swim freely in the blood. They then migrate from the stomach and enter the thoracic muscles of the mosquito, where they develop enor- mously — growing to xV inch in length — and acquire a mouth, an alimentary canal, and a trilobed tail. They next quit the thorax, and enter the head, where they coil themselves up close to the base of the proboscis, and await an opportunity to enter a warm- blood vertebrate host, when the mosquito feeds on such, and so complete the cycle of their existence. In man the periodic nocturnal migrations of the filarise from the large vessels to the peripheral circulation is evidently an adaptation to the nocturnal 49^ HYGIENE AND PUBLIC HEALTH habits of the mosquito, so as to secure the change of host to the mosquito necessary to complete the cycle of existence, and the propagation of the species. Sleeping Sickness. The Report of the Commission on Sleeping Sickness in Uganda shows that this disease is caused by Trypanosoma Gamhiense. This organism (flagellated haematozoon) is a minute, colourless, transparent, active vermicule, provided with a long flagellum at its anterior extremity, which is found free and active in the liquor sanguinis of those affected with the disease. It is never seen in the red corpuscles. The trypanosomes are conveyed from the sick to the healthy by the tsetse fly — glossina palpalis — and not by other biting flies. Reproduction of the trypano- somes is effected in the alimentary canal of the tsetse fly by longitudinal division. In the early stage of the illness there is polyadenitis — multiple invasion of the lymphatic glands by trypanosomes — sleeping sickness being the last stage of the disease and invariably fatal. The disease is confined to the " fly -belts " of equatorial Africa, i.e., those regions where the tsetse fly is found at one or another season of the year. In the sleeping sickness areas in Uganda from 50 to 75 per cent, of the inhabitants are in the stage of polyadenitis, and are carrying on their ordinary work, presenting no symptoms of illness. The disease is slowly spreading in the fly-belt, and will eventually extend to its northern and southern limits. A nkylostomiasis . This is an endemic anaemia, which is very prevalent in the tropics, but is generally known in Europe as " miners' anaemia." It is caused by a parasitic nematode worm, the Ankylostoma duodenale, whose habitat, as its name implies, is the small in- testine of man. The worms attach themselves to the mucous membrauL-, and from the blood obtain their nourishment. The worms measure from 6 to 15 mm. in length, and sexual intercourse between males and females takes place in the intestine. The female produces an enormous number of fertilized eggs, which pass out in the faeces of the host. The embryos pass their lives in mud, earth, or muddy water, and may be transferred to man either by means of the water drunk, or by soiled food or hands, KPTZOOTIC DISEASES 403 when they pass at once into the digestive tract ; or they enter tlie skin, usually of the feet or legs, gaining access to the lym- phatic vessels, and later to the subcutaneous veins ; having entered the circulation, they reach the oesophagus, stomach, and duodenum, where they become sexually mature. The disease occurs in all tropical and sub-tropical countries, and is known in Southern Europe and Belgium. It has recently been introduced into deep Cornish mines in England, where the depth of the mine ensures a relatively high temperature of the underground workings. It is undoubtedly spread in mines by miners defaecating underground on to the earth, no proper system of fgecal collection and removal being adopted, or fully availed of by the men, if provided. A diagnosis is best made by an examination of the faeces for the ova of the worm, which have a regular oval form, with smooth transparent shell, through which two or four light grey yolk segments can be seen. The encapsuled larvae of the worm may live in water for a year or more, and they are very resistant to most disinfectants, but creosote kills the larvae quickly, and a solution of the sulphate of iron is also valuable. Fortunately the large majority of British coal-mines are too cold for this worm, which leads to a condition which very seriously incapacitates the infected miners. Epizootic Diseases. Anthrax. This specific disease affects cattle most frequently, but all animals are capable of being infected. The infection generally enters the body through the alimentary tract, but it may be introduced through the respiratory tract, and also through the skin by inoculation (by the stings of insects, through abrasions, etc.). When the soil becomes infected, as by discharges from animals, the disease may spread rapidly and extensively through herds. Pasteur and others have held, on experimental evidence, that when animals dead of the disease are superficially buried, earth worms may be instrumental in conveying the specific organism to the surface. The grass may become extensivelj/ contaminated by discharges from sick animals, and the specific organism, in the form of spores, can persist for considerable periods in decomposing animal and vegetable matter. Animals 494 HYGIENE AND PUBLIC HEALTH feeding on infected pastures may become inoculated through wounds inflicted on the buccal mucous membrane and the tongue by silicious grasses, probably too, by swallowing the spores with their food. The disease is most prevalent on warm, loose, moist soils, rich in organic matter, especially in swampy, boggy districts, and during the summer months. Animals may also be infected by infectious refuse from factories where hides, etc., are dealt with, and from the use of certain manures and imported food stuffs. Man may be infected from the living animal, but he is generally infected during the process of killing and skinning diseased animals, and possibly by eating the flesh. In this country the sorting and handling of wools, hides or hair (especially horsehair from Russia and China) imported from abroad is most frequently responsible for the disease, hence the popular name of "wool- sorter's disease." It appeals that the blood-stained wool or hair are the actual carriers of the germs of anthrax ; hence the amount of blood staining is a rough measure of the danger to the operatives. Man is infected either by direct inoculation of a wound or abrasion on the face and hands, arms, and legs, which give rise to the malignant pustule, or by inhalation of dust containing spores into the mouth or lungs, when general infection of the system follows, usually proving fatal in the course of a very few days. The symptoms of general infection are usually obscure, and appear to depend upon the organ with which the virus first comes in contact ; if the dust is swallowed, the stomach and bowels are chiefly affected ; if inhaled, the lungs. Bacilli are found in the serum of the pustule, and in the blood after death. Infection through the alimentary tract is rare. In man it is much more common for the disease to start in the respiratory system, the lesions being found in the trachea or bronchi, and spreading to the bronchial and other thoracic glands, and finally to the lungs. In the lung cases many bacilli may be found in the local lesions in the chest, but few are found in the other organs or in the blood, until just before death. BaciUi are rarely found in the secretions. The disease may assume the following types, each of which is also met with in man : t- I. " Apoplectic " : Symptoms of cerebral apoplexy appear ; the animal is taken suddenly ill, staggers, and .falls, and dies in EPIZOOTIC DISEASES 495 convulsions in from a few minutes to one hour at most This is the most usual form in sheep and goats. 2. A condition of excited restlessness is followed by convulsions, stupor, and death, as if from apoplexy. The symptoms last from two to twenty-four hours in this form, which is the most usual in cattle. 3. " Anthrax fever " : This is the most common form, lasting from twenty-four hours to seven days. High fever and frequent colic are followed by symptoms similar to those of the last type, but the grave symptoms are intermittent, and their duration is more prolonged. 4. " Carbuncular disease " : Characterized by circumscribed cutaneous swellings, at first hard, hot and painful, and later becoming cold, painless and with a tendency to slough, but not to suppurate ; oedematous swellings of the skin ; similar swell- ings on the mucous membrane of the mouth, pharynx, larynx, and rectum ; irregular fever ;^ dyspnoea, difficulty in swallowing; muscular spasms. This form generally lasts from three to seven days, and is very fatal, the case-mortality amounting to some 25 per cent. The post-mortem diagnosis depends upon : (i) The discovery of the bacillus, and the results of its inoculation into mice ; (2) haemorrhages of variable size, often evident in all the organs and in the subserous, submucous, and subcutaneous tissues, and serous infiltration and congestion of organs generally ; (3) swell- ing of the spleen to from two to five times its normal size : the liver, kidneys and lymphatic glands are also enlarged, though to a less degree ; (4) a tar-like condition of the blood. The bodies are often well nourished ; there is an absence of rigor mortis ; rapid decomposition sets in, and where there is consider- able oedema there may be wide areas of necrosed skin. In this disease, as in some others, such as chicken cholera, rabies, and swine fever, the virus can be attenuated by the 1 The following are the symptoms of fever in cattle : The temperature {per rectum) is generally about 41° to 42° C. ; the external temperature of the body is unequally distributed ; the hair stands on end and loses gloss ; feeding and rumination are suspended ; great depression ; eyes dull and congested ; tongue protruded ; often diarrhoea ; short panting respira- tions ; frequent small pulse (60 to 120 per minute) ; nostrils dry or covered with foam ; in cows, secretion of milk is diminished and the teats are hot ; rigors. In horses the symptoms are similar ; the temperature is generally about 39't;° to 41 '5° C, and the pulse from 80 to 100 per minute, 496 HYGIENE AND PUBLIC HEALTH various methods mentioned on page 403. When cultivated at 42° C, the bacilli of anthrax produce no spores, and the intensity of their virulence decreases day by day. This attenuated virus (or it may be the waste products of its metabolism) when inocu- lated into susceptible animals, inhibits the growth of the specific microbes when introduced into the body, and is so found to confer immunity for a time from the disease in its virulent form. The same result can be attained when the bacillus from one species of animal is passed through a different species. If the bacilli of sheep or cattle are inoculated into guinea pigs, the organisms taken from the guinea pig are attenuated for sheep or cattle, and confer immunity from subsequent attack. Pasteur used two vaccines : Vaccine I. grown at 42° C. for twenty-four days, and Vaccine II. grown at 42° C. for twelve days, and therefore less attenuated than Vaccine I. The method as used for sheep, cattle, and horses is as follows : — ^The animal is inoculated with Vaccine I. (5 drops for sheep, 10 for cattle and horses), and after twelve days with Vaccine II. Fourteen days later an ordinary virulent culture can be injected without ill effect, and the animal remains immune for a year or more in many cases. Quite recently mice have been rendered immune against anthrax virus by injection of an albumose (a proteid body) isolated from cultures of the anthrax bacilli, of whose metabolism it is no doubt a waste product (Hankin) . The quantity of anthrax albumose necessary to produce immunity is extremely minute. Sclavo's anti-anthrax serum has been used in this country during the past year or two with encouraging results. Sanitary Precautions. — ^The opening of bales and the sorting of hides should be carried out in special well-ventilated rooms only by experienced workmen, and by those whose hands and arms are quite free from any abrasion. Any suspected wool or hides should be well moistened before handling ; but a safer procedure would be to disinfect all bales by steam under pressure prior to handling, although this is liable to damage them. Anthrax is, however, the most protean in its manifestations of all trade diseases and the most difficult to control. Disin- fection of horsehair by steam would not at first sight seem difficult, but experiments have hitherto shown that penetration into hydraulically pressed bales is impossible, and that even when they are not hydraulically pressed the environment of the spores, EPIZOOTIC DISEASES 497 embedded as they are in grease and dirt, offers a great obstacle to successful disinfection. However, adequate steam disinfection, provided the bales are opened and the horsehair spread out (in which operation, of course, danger is incurred), will give a certain guarantee of the destruction of the anthrax contagion. Mechanical downward exhausts, actuated by a fan, should be provided beneath the sorting benches to draw away the dust, which should be collected in a washer or condenser. The water from the washer should be well boiled before it is emptied down a drain. If the dust is collected dry, it must be carefully gathered together and burnt. The dust must not be allowed to reach the external atmosphere, or it may be blown long distances and infect grazing cattle. The premises must be kept clean ; the floor of the sorting room should be impermeable, and washed down with disinfectant solution daily. i There must be adequate provision of air space and ventilation. Dr. Legge, H.M. Medical Inspector of Factories, suggests the following precautions for the prevention of the disease : — 1. That all workers should wear overalls. 2. That no one with any cut, sore, or abrasion of the skin should be allowed to work unless he can be absolutely protected from contamination. 3. That all workers should wash themselves frequently, and especially before taking food. 4. That all cases of illness, especially if connected with any swelling or boil, should be immediately intimated to the manager, in order that the disease may be attacked in its earliest stages, and that other workers similarly exposed may be warned of their danger. 5. That the bales should be immediately immersed in water, and that no handling of the raw material be permitted except in the wet state. This will prevent dust, and the risk of con- tagion then will only be possible through an abrasion of the skin. No reliance can be placed on protection from dust by the use of fans, respirators, or currents of air. The germ must be killed. 6. That the hair should be boiled — say for thirty minutes — in order to cleanse it, and soften the agglutinated discharges which may contain the germs, and that afterwards steam should be applied for the same time at a pressure of 0-15 atmosphere. 32 498 HYGIENE AND PUBLIC HEALTH If, however, it be desired to effectually disinfect by boiling, with- out continuing it so long as to destroy the material, it could be accomplished by using a 2 per cent, solution of potassium per- manganate, and afterwards bleaching with a 3 per cent, solution of sulphurous acid. 7. That all dust and residue be frequently collected and carefully burned. . By the Anthrax Order (1899) of the Board of Agriculture, dung and other litter from the place of outbreak are to be burnt, or disinfected and buried to the satisfaction of the inspector. CarccLses must either be buried in lime, with the skin on, as soon as possible at a suitable place to which animals will not have access, and at a depth of not less than 6 feet below the surface ; or they must be destroyed by exposure to a high temperature, or by chemical agents in a horse-slaughterer's or knacker's yard, or other place approved for the purpose by the Board. A carcase of a diseased or suspected animal shall not be buried or destroyed otherwise than by the local authority, nor be removed from the farm or premises upon which the animal died or was slaughtered, except for the purpose of being buried or destroyed. Before a carcase is removed for burial or destruction, all the natural openings must be plugged with tow or other suitable material saturated with a disinfectant. In no case shall the skin of the carcase be cut, nor shall anything be done to cause the effusion of blood, except by a veterinary inspector and for the purpose of microscopical investigation. Disinfection in cases of anthrax shall be performed by the local authority at their own expense, and shall consist in thorough sprinkling with freshly burnt lime or other suitable disinfectant, and subsequent washing with limewash containing in each gallon 4 ounces of chloride of lime, or J pint of commercial carbolic acid. The measures applicable to infected fields are left to the discretion of the local authority or their inspector. Under the Factory and Workshop Act (1901), all cases of anthrax occurring in factories and workshops must be notified to the chief inspector of factories. Tuberculosis in the Lower Animals. The disease is characterized by nodular deposits (tubercles), frequently translucent and hard, and about the size of a millet grain, which cannot be shelled out from the surrounding tissue. EPIZOOTIC DISEASES 499 The disease is most frequently found in cattle, pigs, and birds, but occasionally in all warm-blooded animals. The symptoms in cattle commence insidiously, and are as follows : A dry, short, jerky, cough ; increased sensibility of the chest walls ; at a later stage, spasmodic paroxysms of cough, especially in the early morning ; percussion sounds dull over cir- cumscribed areas ; dyspnoea (shown by the extended position of the head and neck) ; diminished secretion of milk ; flatulence ; intermittent colic, with alternating diarrhoea and constipation ; hsematuria ; enlargement of glands ; irregular fever ; excessive emaciation ; weakness ; often peritonitis, and swellings of bones and joints. Animals frequently come on heat and remain so for a long time, cows mounting their fellows, but rarely becoming fecundated by bulls ; and pregnant cows frequently abort. Brain excitement, convulsions, paralysis, staggers, and sudden collapse, often supervene during the last stages. Tuberculosis of the udders is characterized by a diffuse, painless, and compara- tively firm swelling, usually of one quarter of the udder (one of the posterior quarters as a rule) ; the milk at first is normal, then becomes thin and watery, with flakes, and generally, though not always, the specific bacilli are present. The pudic glands are also enlarged. The condition differs from ordinary mammitis or garget, by the gradual increase in the size of the swelling and in the comparative absence of pain on pressure. The post-mortem diagnosis is chiefly made from the lungs and serous membranes, which are found to be studded with the tubercle nodules. In the lungs the nodules frequently form grape-like clusters which project from the pleural surfaces. The lymphatic glands of the body generally are often enlarged and affected with tubercles. According to the experience in the public abattoirs of Germany, the different organs are affected in the following order of fre- quency : Lungs 75 per cent, of all the cases, visceral pleura 55 per cent., peritoneum 48 per cent., costal pleura 47 per cent., bronchial and mediastinal glands 29 per cent., liver 28 per cent., spleen 19 per cent. ; no other part of the body is affected in more than lo per cent, of the cases, and the udder is affected in only i per cent. ' In pigs the starting point of the infection is generally in the intestines, as the infection is almost invariably swallowed ; in cats it is chiefly in the lungs. The disease is sometimes found 500 HYGIENE AND PUBLIC HEALTH in goats, and therefore the popular belief that goat's milk is safe is not warranted. In birds the leading symptoms are : Emacia- tion, pallor of the mucous membranes of the eyes and mouth, loss of appetite, vomiting, diarrhoea, swellings of joints, tumours, and sometimes ulcers. In applying the tuberculin test for diagnostic purposes, the animal is first allowed to become cool and quiet ; then the temperature is taken per rectum, the thermometer being allowed to remain in for five minutes. The normal temperature of bovine animals ranges from 38° to 39° C. It is convenient to inject the tuberculin (35 to 45 minims according to the age and size of the animal) into the neck or shoulder, late in the evening, so that the observation of the reaction temperature may be made early next day. The animal must not be regarded as certainly tuber- culous unless the temperature at some time during the following day shows a rise of at least 1-2° C. above that of overnight. The rise may be as much as from 2-3° C. Animals suffermg from advanced tuberculosis often fail to show a marked temperature reaction, or if they are already feverish (i.e., temperature above 39° C), the reaction may not be noticeable. The test must not be repeated until at least a month has expired, as the animal win often not react again in a less period. This fact, it has been suggested, opens the door to fraud, as a dishonest salesman could inject his animals a few days prior to sale, and then sell them as tuberculosis free. Those animals which react should be isolated, and fattened for food, if the disease is in the initial stage and strictly localized to the lungs. Actinomycosis. This disease affects cattle (especially calves), pigs, horses, sheep, and man. The symptoms are of long duration, and include : Aversion to food, because of pain in mastication ; swollen jaw and tongue ; copious s-alivation ; difficulty of swallowing, and dysp- noea, from growths in the pharynx and larynx ; swelling of the parotid region, which is covered with tumours of varying size ; later, the affection of the cervical vertebrae causes paralysis, and symptoms resembling phthisis result from the implication of the lungs. To diagnose this disease from tuberculosis, parotitis, cellulitis, etc., the nodules and abscesses should be incised, and a search made for the ray fungus. EPIZOOTIC DISEASES 5OI The post-mortem diagnosis is established by the discovery of tubercle-like nodules and large lobulated tumours, sometimes very soft, at others hard, usually in the upper or lower maxillary bones. These consist of connective tissue stroma with numerous interspersed nodules, varying in size from a millet seed to a pea. These nodules contain the sulphur-yellow actinomycosis granules, about the size of a grain of sand ; they may develop into cold abscesses, which contain the small yellow tufts of the fungus. MacFadyean describes these nodules in animals as becoming hard and calcifying like tubercles, but rarely forming abscesses. On the sides and under-surface of the mucous membrane of the swollen tongue are to be seen rounded, slightly raised, brown spots, through which shine very minute yellow nodules. In the pharynx there are generally soft, fungoid, pedunculated growths with smooth surfaces, and these may form in the oesophagus, larynx, and trachea. Elastic, firm nodules, generally from a hazel nut to a man's fist, or larger in size, may be seen in the skin and subcutaneous tissue, chiefly of the head and neck. The lymphatic glands in the neighbourhood of the neck are generally also affected. In the lungs, disseminated, firm, whitish-yellow nodules are seen, varying in size from a millet seed to a pea, which become calcareous in the centre ; or there may be large purulent foci. It is not certain if the disease can be communicated to man by contagion or infection, or by eating the infected flesh. In man the symptoms are : Abscesses, chiefly in the bones of the face and in the tongue. The liver, lungs, intestines, and skin may also be the seats of the primary lesion. The lungs, liver, kidneys, peritoneum, intestines, and brain may become infected by metastasis. Probably, as in animals, it is transmitted exclusively by portions of plants, which are studded with the fungi. Rabies. In this disease the virus is contained in the saliva of rabid animals, such as dogs, wolves, horses, bovines, cats, pigs, sheep, goats, and even birds. The disease is spread by inoculation into the skin through the bite of a rabid animal . The incubation period in dogs is from three to six weeks on an average, with a minimum of a few days and a maximum of several months. The symptoms of canine rabies assume two forms — i.e., the " furious madness," which is the more frequent, and the 502 HYGIENE AND PUBLIC HEALTH " dumb madness." The symptoms in the fmious form follow each other in three stages : (i) The melancholy, (2) the irritative, and (3) the paralytic. Stage i generally lasts from twelve to forty-eight hours, and is marked by capricious appetite, the animal being sullen, nervous, excited, irritable, and distrustful ; it bites at everything, and often swallows foreign bodies. There is sometimes abnormal itching at the site of the bite. Stage 2 lasts three or four days, and is characterized by attacks of fury (which may continue for some hours) and convulsions, with remissions. The animal is very irritable, and often tries to run away ; it shows an excessive morbid desire to snap, and later to bite, often with such force as to break its teeth. The animal does not try to bite human beings unless approached. Paralysis of the vocal cords often causes a change in voice. Hallucinations are more prominent than mania. In Stage 3 the animal is much emaciated, the hair stands on end and is rough, the eyes are sunken and glassy, and the power of swallowing is lost owing to paralysis of the muscles of deglutition ; paralysis of the lower jaw then supervenes, and the jaw drops down, the tongue hanging out ; the hind quarters next become paralyzed. The whole stage is attended by paroxysms of excitement, which grow less and less frequent, until the animal dies between the fifth and tenth day. Dumb madness differs mainly in the absence, or very short duration, of stage 2. In man there is premonitory pain in the cicatrized wound from the bite, general malaise, swelling of the neighbouring Ijnnphatic glands, and aversion to fluids. In the second stage reflex spasms, delirium, and mania supervene, the spasm affecting chiefly the throat when attempts are made at swallowing, and being excited even by the sight of water or the thought of drinking ; there is also much anxiety, uneasiness, and thirst, and the patient slavers, because of the inability to swallow the saliva. The third stage is characterized by paralysis and spasms, and death supervenes in from two to four days. Whilst in the man the usual period of incubation after the infliction of a bite by a rabid dog is somewhere about six weeks, it may be as short as six days or as long as two years (Horsley). The rabid virus is chiefly contained in the nervous centres, and it is presumed that the disease only shows itself when these centres are attacked by the virus. This view explains the unequal EPIZOOTIC DISEASES 50:} length of the incubation period in different cases, the incubation period being governed by the time taken by the virus to travel from the point of inoculation up to the central nervous system, and for its development therein. If the virus travels up the nerves the incubation is long, but if conveyed in the blood stream the incubation may be very short. Horsley gives the death-rate among persons bitten by in- dubitably rabid dogs as on the average about 15 per cent. ; that is to say, about 85 per cent, of the persons bitten are insus- ceptible, or, at least, escape the action of the virus, for rabies once developed is almost invariably fatal. Pasteur elaborated a system of treatment by protective inoculations, which has proved of great value. Shortly, it may be described as follows : The virus from the central nervous system of a rabid dog or wolf is inoculated subdurally into a rabbit ; a second rabbit is similarly inoculated from the first, a third from the second, and so on until a virus of maximum intensity is obtained — killing a rabbit in seven days. The spinal cord of a rabbit thus killed by this virus is submitted to a drying process (by calcium chloride), at a temperature of 25° C, for a certain number of days (one to fourteen). By this means the virulence of the virus is diminished and eventually destroyed by drying for fourteen days. The person undergoing the treat- ment is inoculated first with an emulsion of a cord, which has been dried for fourteen days ; on succeeding days he is inoculated with cords which have been dried for thirteen, twelve, eleven, etc., days ; and finally with a cord which has been dried for only one day, and is therefore highly virulent. Persons who have been bitten by indubitably rabid animals, and have submitted them- selves to the Pasteur treatment within a few days of the infliction of the bite, have almost invariably escaped. The death-rate, instead of 15 per cent, in the unprotected, is only 1-36 per cent, in the protected. During the ten years 1886-95, the mortality in protected persons was only 0-48 per cent. (Muir and Ritchie). For the more dangerous wounds the number of inoculations is greater, and the use of the recent cords is more rapidly brought into operation. This is the " intensive " treatment, which is used in severe cases, as bites on naked parts and wolf bites. In this country rabies is spread by infected dogs. Where muzzling regulations and the slaughter of stray dogs have been enforced, the disease is rapidly exterminated. 504 HYGIENE AND PUBLIC HEALTH The diagnosis of the earlier symptoms largely depends upon whether proof is forthcoming of the animal or man having been bitten by a rabid animal. The post-mortem changes in canine rabies are neither constant nor specfic ; but the following diagnostic appearances may be mentioned — emaciation, dark blood, hyperaemia of mucous membranes and of many of the internal organs, the frequent presence of foreign bodies in the pharynx and oesophagus or the stomach, which often contains such articles as straw, hair, feathers, string, wood, or pebbles, but very little or no food. Frequently small haemorrhages are seen on the surface of the gastric and buccal mucous membrane, and the intestines are generally found to be empty. Foot and Mouth Disease. Foot and mouth disease is peculiar to ungulates, and therefore occurs chiefly in cattle, sheep, pigs, and goats ; but all wild ruminants are liable to it. The disease is rarely fatal. The symptoms in cattle are : Vesicles and ulcers on the oral mucous membrane, and on the skin of the coronet and of the interdigital space (sheep, goats, and pigs are usually affected only on the feet). The small yellowish-white vesicles on the gums, tongue, buccal mucous membrane and lips gradually increase in size, until they become as large as a five-shilling piece, when the vesicles burst, leaving ulcers. There is much salivation, and rapid and great emaciation. The milk is colostrum-like in appearance and taste ; and in milch cows the exanthem often spreads, by the act of milking, to the udders and teats. There is often violent inflammation of the udder, with sero- sanguineous discharge ; sometimes ulcers form on the pharyngeal mucous membrane, and there is dyspnoea and nasal and bronchial catarrh. Occasionally the vesicles form on the skin at the base of the horns, also on the vulva and vagina, and on the general surface of the skin. As regards the feet, there is first a painful swelling of the coronet, especially between the toes and towards the plantar cushions ; then lameness results. Erysipelatous inflammation sometimes supervenes, and later on ulcers and abscesses ; as a result, the hoofs may be shed. The general constitutional symptoms are those of pyaemia. In the malignant type, symptoms supervene resembling EPIZOOTIC DISEASES 505 apoplexy, and the animal dies suddenly from paralysis of the heart, due to the development of toxins. The disease may be transmitted to man through milk, butter, and cheese, or is inoculated through wounds in the hands and arms. The symptoms are : Fever ; disturbance of digestion ; vesicles on the face (lips and ears), the fingers, the arms, the female breasts, and the mucous membrane of the mouth, pharynx, and conjunctiva ; abdominal pains ; and vomiting. Occasionally death supervenes in young persons. The disease is not conveyed by eating flesh. A few outbreaks have been reported among infants fed upon infected cow's milk. Glanders. Glanders and farcy are now recognized as different manifesta- tions of the same disease. It is essentially an equine disease, affecting horses, donkeys and mules ; but it may be transmitted from horses to many other animals, including man, by direct inoculation. In some years the disease causes a considerable mortality in this country among horses. It may be transmitted by ingestion, inhalation and inoculation. The symptoms may be those of either acute or chronic glanders. Acute glanders is a very rapidly progressive specific infective disease. The prominent symptoms are : High temperature ; rigors ; muco-purulent nasal discharge, which later becomes sanguineous, the visible mucous membrane being covered with small nodules and ulcers, which are frequently confluent and covered with diphtheritic-like sloughing masses ; dyspnoea ; and roaring inspirations. There are also oedematous swellings, nodules, and ulcers of the skin ; inflammation of the lymphatic vessels (especially in the neighbourhood of the head) ; swelling and suppuration of the lymphatic glands ; difficult deglutition, diarrhoea, and rapid emaciation. This form is invariably fatal in from three to fourteen days. Chronic glanders has an insidious origin. The symptoms are : Chronic nasal catarrh, with discharges, which later become less sticky and yellow, and temporarily sanious, these haemorrhages from the small ulcerous erosions being frequently the first visible sign. Later on nodules, and finally ulcers, appear on the nasal mucous membrane, and swelling of the submaxillary glands follows. Frequently there is cough and dyspnoea, and generally §ome irregular fever ; wasting is marked ; and in the late stages 506 HYGIENE AND PUBLIC HEALTH there may be oedematous swellings of the limbs, abdomen, and chest. Glanders of the skin is less common in chronic glanders than in acute, the favourite sites being the limbs, shoulders, breast, and hypogastrium. The nodules or boils (" farcy buds ") vary from a pea to a walnut in size, and may disappear to some extent, although they generally undergo change into ulcers ; the efferent lymph vessels are swollen into knotted cords, the heads of which often become ulcerated. Affected lymphatic glands are often enlarged, and later become indurated or suppurate. In man the disease is set up by direct inoculation of the in- fected secretions, usually into an abrasion of the skin. The parts usually infected are the hands, the nasal mucous membrane, the lips, and conjunctivce. Infected parts become swollen and painful, and the lymphatics inflamed ; there is fever ; nasal discharge ; ulcers on the nasal mucous membrane ; pustules and abscesses in the skin ; ulcers in the mouth, pharynx, and larynx, and on the conjunctiva ; articular swellings are often present ; and sometimes intense gastro-enteritis. Death may ensue in from a fortnight to a month, or the disease may become chronic. The fatality is great unless the disease is strictly localized, and is treated early by cauterization. A horse showing no outward symptoms of the disease may be glandered, and a source of infection to others. The diagnosis is assisted by the inoculation of other animals (field mice and guinea pigs) for the observance of symptoms, and by the injection of " mallein." Recently too the Widal reaction has been used to diagnose the disease. " Mallein " is a preparation made from the bacilli of glanders in a manner analogous to tuberculin. It is injected subcutane- ously at the base of the neck, after the animal's temperature has been taken. The increase in temperature within twelve hours should exceed 2° C. for a certain diagnosis, and 1-2° C. to warrant suspicion. There is also a large painful swelling at the site of inoculation (in the horse) , and a swelling of the farcy buds. The preventive measures which should be taken against the disease have generally been restricted to those embodied, in 1892, in an Order of the Board of Agriculture. That Order provided for compensation for slaughter of affected and suspected animals, and certain powers were given for securing the ex- amination of horses by veterinary siurgeons, and for controlling EPTZOOTTC DISEASES 507 the disease when discovered. Dead bodies were ordered to be buried 6 feet deep in their skins, and covered with a sufficient quantity of quickhme or other disinfectant ; or the local authority- was empowered, with the consent of the Board, to have the body, which had been disinfected prior to removal, cremated or treated by chemical agents. Complete measures of prevention and stamping out would include : (i) A systematic and repeated inspection of horses m affected localities, and the employment of " mallein " for diag- nostic purposes ; (2) the avoidance of common drinking troughs ; (3) the prompt separation of all suspected horses and the slaughter of all diseased ones ; (4) the prompt cleansing and disinfection of infected premises ; and (5) newly purchased horses to be quarantined before being introduced into a stud. A Departmental Committee, which reported on glanders in 1899, made the following recommendations : 1. That the Board of Agriculture should exercise a more extended supervision of the working of the Glanders or Farcy Order. 2. That notification should be made either to a constable or to a veterinary inspector. 3. That where practicable the local veterinary inspector should not engage in private practice. 4. That it should be made obligatory for veterinary surgeons to notify cases of glanders of which they become aware. 5. That occupiers or owners of knackers' yards should notify any case of glanders found in animals taken to their yards for slaughter. 6. That horses that react to the " mallein " test should be considered as possible sources of infection. 7. That horses that the veterinary inspector may consider to have been exposed to contagion should be dealt with in the same manner as suspected horses, but with certain reservations. 8. That the slaughter of all animals showing clinical symptoms of glanders should be made compulsory. 9. That compensation for horses slaughtered solely on account of reaction to the " mallein " test should be on a higher scale than that for a " clinically " diseased horse. Many of the foregoing recommendations have been adopted in the Glanders or Farcy Order of 1907. 508 HYGIENE AND PUBLIC HEALTH Variola. Variola occurs in most of the domestic animals. Cow-pox (variola in the cow) was first experimentally transmitted to man, in 1796, by Jenner, who proved, in 1798, that it conferred im- munity from small-pox. The close relationship existing between the various kinds of variola found in man and other animals is proved by their reciprocal power of conferring immunity. Cow- pox in man is protective against small-pox, and the latter is also protective against the former. The symptoms of variola in animals (which appear after an incubation period of about a week) are divided into several stages : (i) The prodromal stage, which lasts a day or two, is characterized by fever, catarrhal affection of the mucous mem- branes, and erythema of the skin ; (2) in the eruptive stage, lasting from six to eight days, red spots suddenly appear, which become nodules of the size of a pin's head, surrounded by a red ring, and which after a few days form bluish-white vesicles, often with a depression in the centre ; (3) in the stage of suppuration, which lasts two or three days, the vesicles become pustules, and the temperature, which had fallen during the eruptive stage, again rises ; (4) in the stage of exsiccation, which lasts from three to five days, the pustules dry up into yellowish, and later on into dark brown crusts or scales, which fall off, leaving shining red cicatrices. Sometimes the eruption is confluent, and the type of th6 disease may also be haemorrhagic. Cow-pox chiefly attacks young cows, the eruption being generally confined to the teats and udder ; fever is absent or slight ; and the prognosis is very good. The disease spreads slowly in a shed from animal to animal, and the eruption lasts altogether about twenty-one days. The lymph of cow-pox, or " vaccine," was introduced for vaccination in man by Jenner in 1798. As cow-pox is com- paratively rare, " humanized " vaccine, or vaccination from man to man, was subsequently employed ; but owing to the drawbacks attending this practice, animal vaccination has been recently reintroduced. For the cultivation of the vaccine, calves three to six months old are taken, the skin over the lower part of the abdomen is shaved and disinfected, and the lymph from a previously vaccinated calf is inoculated. Vesicles mature in EPIZOOTIC DISEASES 509 from four to five days, and tlie lymph collected from these is used for human vaccination or for the further inoculation of calves. One calf yields from i,ooo to 3,000 doses of lymph. The vaccine may be preserved in (i) capillary tubes, in which it loses strength and becomes inert ; or (2) it may be kept in the dry condition by scraping off the lymph and crusts, drying them, and then placing them between two glass slides and sealing with paraffin — the vaccine then keeps for months ; or (3) it may be rubbed down with glj^cerine and preserved in capillary tubes. Scarlet fever is said to affect the lower animals, but this is probably due to a confusion of the disease with petechial fever — ■a disease characterized by haemorrhages in the skin and internal •organs, such hsemorrhages in the skin varying in size from a pea to a half-crown piece. Scarlet fever in man has probably no sort of relation with any disease of cows. Klein's statements as to the relationship between human scarlet fever and a bovine eruptive fever have never been confirmed, and cows have been proved to be immune to human scarlet fever (Crookshank, MacFadyean, Edington, McCall, Axe, and others). Bubonic plague may affect rats, pigeons, mice, cats, monkeys, and pigs ; and flies, fleas, and mosquitoes may communicate the disease. The cholera of birds (fowl typhoid) ; swine erysipelas, swine fever or hog cholera ; epidemic pleuro-pneumonia in horses, bovines, and goats ; cattle plague, splenic apoplexy, and quarter ill, have not been shown to be communicable to man. Whether the dysentery of cattle and domestic animals, the influenza of horses, asses and mules, and the diphtheria of birds, calves and pigs, are etiologically identical with the similarly termed diseases in man is at present unknown, but the balance of evidence is opposed to such a view. The disease called " thrush " in human beings is found in calves, foals, and birds, and is due to the same fungus. The Piroplasmoses. This term embraces a number of distinct infective diseases, the causative agent — a piroplasma — being transmitted from one animal to another through the agency of ticks. The piroplasmata are protozoa. They are pea-shaped micro-organisms, and are 510 HYGIENE AND PUBLIC HEALTH found singly, or in pairs, or in multiples of pairs within the red blood corpuscles of an infected animal. Larger sausage-shaped extracorpuscular parasites are also described by Nuttall, which he thinks may be gametes, as they resemble the malarial crescents of human blood. The diseases caused by piroplasmata are Texas fever (Redwater of cattle), Rhodesian fever (cattle), and Carceag (European sheep). There is also piroplasmosis of the dog (South Africa), horse, donkey, and mule (South Africa), monkey (Uganda), and Rocky Mountain fever in man, which is also probably due to piroplasma infection. In Brazil fowls are apt to suffer from spirochaete disease, which is a tick-transmitted infection, the splrochgete greatly resembling the spirillum of relapsing fever in man. All these diseases commence with fever, followed by a great destruction of blood corpuscles by the piroplasmata, and the serum becomes tinged with haemoglobin, which finds its way into the urine. Haemoglobinuria and icterus are the usual, but not invaiiable, symptoms. Manson has pointed out the similarity between the piroplasmoses and blackwater fever of man, as regards the characteristic symptoms — haemoglobinuria and icterus, the latter disease being usually regarded as a manifesta- tion of malaria. Immunity from a fresh attack follows upon recovery in piroplasmosis, but the immunity appears to be due to the fact that the parasites persist for long periods in the blood of recovered animals, although not demonstrable microscopically. Consequently such animals may be the means of propagating infection indefinitely in tick-infested countries. The ticks, which are the carriers of the piroplasmata from infected to healthy animals, belong to the class Arachnoidea (spiders, mites, etc.). They derive their nourishment entirely, by sucking the blood of their hosts (terrestrial vertebrates). Ticks are very widely distributed, but they are most numerous in warm countries. The eggs are laid by the female tick in recesses in the ground, and after some time six-legged, larvae are hatched out and crawl upon the surrounding vegetation. Here they wait their opportunity, until they can attach themselves to a warm-blooded host, whose blood they suck. In some species of ticks, the larvae having gorged on blood, drop off the host on to the ground, there to undergo their metamorphosis into eight- legged nymphae, which in turn attach themselves to a fresh host, and again drop off when gorged, to develop on the ground THE INVESTIGATION OF DISEASE OUTBREAKS 5II into adult ticks. In other species the metamorphosis from larva to nymph may take place upon the host ; and in other species again the whole cycle of changes from larva to adult tick may take place on the host. It follows, then, that in some species only the adult ticks act as carriers of the piroplasma parasite, whilst in others larvae and nymphae as well as adult forms may play their part in propagating piroplasmosis. The Investigation of Disease Outbreaks. In endeavouring to arrive at the cause of an outbreak of disease in a community, it is very seldom possible to obtain absolute and positive proof that a certain circumstance and certain phenomena stand in the relation of cause and effect. It is generally only feasible to show that there is a greater probability in favour of one set of circumstances being the cause of the outbreak, than of any other set, because of their more direct relationship to the phenomena observed. In tracing the origin of any outbreak, all the antecedent facts should be ascertained with regard to every individual instance of illness, with a view to subsequent comparison of the factors respectively of agreement and disagreement in relation thereto. In addition similar inquiries should sometimes be made in respect of persons living under apparently identical conditions with those who have been attacked with illness, but who have not them- selves fallen victims, with the object of ascertaining if there is a strongly dividing line separating the antecedents of the sick from those of the healthy. The method of reasoning employed is that which is known in logic as the joint {inductive) method of agreement and difference. If on inquiry it has been ascertained that a particular antecedent is traceable in the history of all cases that have developed illness, whilst this particular antecedent has been as invariably absent in the previous history of the persons otherwise similarly circum- stanced, but who have remained unaffected, such antecedent is the probable cause of the illness — the probability increasing as the number of incidents which conform with the facts increase. Thus for example, if in an outbreak of acute gastritis from supposed ptomaine poisoning, affecting a number of people who partook of a common meal, it is ascertained that those affected all partook of a particular dish, whilst those unaffected as in- 512 HYGIENE AND PUBLIC HEALTH variably abstained, the presumption would be very strong that the implicated dish contained the poison, which was the cause of the illness ; and the greater the number of those from whom this evidence is obtained, the more likely is this presumption to be true. - In outbreaks of infectious illness, however, the essential facts are always more difficult to obtain, and when obtainable are not always recognized as having any direct relation to the observed phenomena, partly because the incubation period of such diseases is much longer than in cases of acute irritant poisoning, and the incubation period itself is subject to greater variation, and partly because there is more than one possible cause — often a multiplicity — which have to be borne in mind by the investigator. This is especially true of epidemics of enteric fever, where the incubation period may vary from seven to twenty-one or more days, and the infective agent may be intro- duced into the body by a variety of channels. To separate out in a possible period of over a fortnight, those antecedents in the previous history of an enteric fever patient, which are of direct con- cern, from irrelevant details which can have no bearing upon the point at issue, is a work which can only be adequately performed by a mind trained to elucidate such phenomena, and well stored wdth the knowledge which alone can serve to separate efficiently the wheat from the chaff. In such investigations conclusions are often arrived at which carry little conviction to the minds of critical observers ; and this frequently happens from the adoption alone of the inductive method of agreement, the method of difference being too often discarded. It cannot be too much insisted upon that the collec- tion of certain data showing that aU the cases of illness have had a common antecedent — such for instance as the consumption of a certain water or food ^\^thin the supposed period of incubation — is no proof that such antecedent is the cause, in the absence of fruther proof that, in respect of others living under similar conditions, but who are unaffected, their previous history is unassociated with the particular antecedent circiunstance, which is so invariably present in the historj^ of those affected. In manj^ instances it must happen that the antecedent suspected of being the cause is only found in a majority of the instances where illness has ensued — not in all ; and is even present in some few instances, where illness has not ensued. These exceptions are often capable of explanation, and do not neces- THE INVESTIGATION OF DISEASE OUTBREAKS 513 sarily invalidate the whole argument, where the origin of infec- tious disease is concerned. A good rule for the investigator to bear in mind is to be very- careful to exclude all the more commonly recognized causes, before he ventures to assign as a cause some circumstance of an unusual character in that connection, which appears to him to fit in with the facts. Sometimes the facts appear capable of explanation on two hypotheses, one more or less familiar, and easily intelligible, the other more novel and puzzling. The first should be excluded as far as exclusion is possible, before the second is adopted. Sometimes the experimental method is available as an aid to the arrival at a sound conclusion of the cause of an outbreak or epidemic ; and it occasionally happens that what are to all intents and purposes unconscious " experiments," occur to verify hypo- theses previously unsubstantiated. For instance, an outbreak of diphtheria in a school is attributed to the presence of a boy with a chronic nasal ulceration and discharge. The boy is sent to his home, and the outbreak terminates. On his return to school some weeks later, other boys who have relation of some sort with him, develop diphtheria, and bacterioscopic examina- tion shows that the Klebs-Loeffler bacillus is present in the nasal secretion of this boy, who has been the unwitting carrier of infection. Again, experiment on a large scale has demonstrated that rats carry the infection of plague, and are a means of con- veying it to man ; and the part played by mosquitoes (Anopheles) in the propagation of malaria has been strikingly confirmed by experiment on the human subject ; and the same is true of yellow fever. In conclusion it may be said that in any investigation of a disease outbreak, the really important matter is the due appre- ciation and collection of all the facts which have a bearing on the subject, and their marshalling in a systematic and intelligent manner. It may be possible on these foundations to hypothesize a cause for the outbreak ; but should this be unascertainable on the facts reported, there is no reason to deplore a failure, which in the light of future knowledge may be capable of explanation. It is far better to record the facts irrespective of any theory as to their origin, than to endeavour to make the facts fit the theory. 33 514 hygiene and public health The Isolation of the Infectious Sick. This can only be attained by a system of compulsory notification of all infectious diseases to the sanitary authority of the district. It will then generally be possible to isolate the first case or cases of the disease as they occur, to destroy the infection alreadj/ generated, and to control the movements of the individuals with whom the sick person may have come into contact. Without compulsory notification it must almost necessarily happen that the disease obtains headway before it is recognized, and then the most persevering efforts too often fail to obtain such a control as will prevent its widespread dissemination. There are many who are in favour of a greater extension of the range of notifiable diseases, and would advocate the notifica- tion of influenza, cerebro-spinal fever, dysentery, ague, remittent fever, glanders, syphilis, septicaemia, purpura, tuberculosis, pneu- monia and acute rheumatism. As preventive measures are not limited to the control of infective diseases, good results might follow, and much valuable knowledge would accrue by the adoption of some system of compulsory notification of certain non-infectious illnesses. The isolation of all cases of contagious disease must be regarded as a most desirable measure, but is absolutely indispensable in the case of the epidemic diseases with air-borne contagia, if it is hoped to limit their spread. Tubercular diseases are rarely isolated, but it is probable that such a measure applied to tuberculosis with discharges would have a considerable effect in limiting their spread. The more usually inoculable diseases — with the exceptions of leprosy, where segregation of the sick should be rigidly enforced, and of contagious ophthalmia — do not seem to demand measures of isolation. A difficulty arises in the case of measles that the pre-eruptive stage is infectious, and that before the isolation can be effected other susceptible persons have probably caught the infection. In measles and whooping cough also, the contagion is so diffusible and universal that few can hope to escape ; and the tender age of the sufferers in these and other infantile complaints renders them less suitable for hospital treatment than is the case with older children and adults. Wheie removal to hospital is not feasible, isolation must be attempted by placing the patient in a room by himself at the HOSPITALS 515 top of the house, all communication with the othei inmates being forbidden ; and the aerial connection between the sick-room and the rest of the house must be broken as much as possible by hanging up outside the door a sheet kept constantly soaked with some disinfectant liquid. Nothing must be allowed to pass out of the sick-room unless previously disinfected, and all dressings, poultices, and rags should be immediately burnt after use. Hospitals. The aggi-egation of a large number of sick persons suffering from a variety of diseases or recoveiing from surgical operations, in one common building is a necessity of modern life, but is now recognized as being often attended with risks and dangers from which the patient treated in his own home is to a large extent exempt. In former times this cro\^'ding together of the sick in hospitals led to outbreaks of erysipelas, p^-jemia, and hospital gangrene in the srugical wards, the contagion appearing to be conveyed from one patient to another through the air, or by means of the hands or instruments of the surgeon or nurse. The antiseptic treatment of wounds and injuries, and the greater care bestowed on the construction and management of hospitals, have nearly eradicated these terrible diseases from modern hospital practice : but when from any cause the surgical wards of hospitals are overcrowded, and the cleanliness and frequent dressings 01 wounds cannot be attended to, these septic diseases are almost sure to make their appearance. It has often been noticed that cases of open wounds from injury or operation recover far more rapidly when treated in the open air, or in huts and tents practically open to the air, than when confined in close buildings ; and the same is true of most acute infectious diseases. For such the breathing of pure air is a prophylactic worth more than all the drugs in the Pharmacopoeia. The first principle, then, in hospital construction and manage- ment is bound up in an abundant supply of pure air to the patients. The putrescent organic effluvia from the skins and lungs of sick persons, which, if not more copious, are certainly more deleterious than those from healthy people, must be diluted with fresh aii and rapidly carried away. For each patient in a medical ward the superficial floor space should not be less than 100 square feet, and the cubic space 1,000 cubic feet. The air should be changed at least three times in an hovti, 5l6 HYGIENE AND PUBLIC HEALTH which would give 3,000 cubic feet of fresh air per head per hour. In wards containing patients suffering from phthisis, a higher set of figures should be taken. For infectious disease hospitals the minimum floor space should be 144 square feet, and the minimum cubic space 2,000 cubic feet per head, changed three or four times an hour. Each bed should have at least 12 linear feet of wall space. The window surface should be in the proportion of i square foot to about every 70 feet of cubic space, in order that the wards shall be well lighted. At night time the wards are best lighted by electric light, and failing that by incandescent gas burners. For general hospitals it is found that the most convenient number of patients that may be treated in one ward is on an average thirty, this being the number which one nurse can readily supervise. In an oblong ward with thirty patients, each patient to have 100 square feet of floor space and 1,000 cubic feet'of air space, 3,000 square feet of floor space will be required and 30,000 cubic feet of air space. The 3,000 square feet of floor space will be available if the ward is 120 feet long and 25 feet wide. As there are fifteen beds on each side of the ward, the longitudinal wall space for each bed will be 8 feet, and the distance between any two beds (themselves 3 feet wide and 6 1 feet long) will be 5 feet. The width of 25 feet is a convenient one, as it allows a passage 11 feet wide between the two rows oi beds for the whole length of the ward, and permits of thorough cross ventilation between the opposite windows, and the flooding of every part of the ward with daylight. To provide the 30,000 cubic feet of air space the ward must be 10 feet high. It would be better to have the height of the ward 12 feet, which would allow 1,200 cubic feet of air space per patient. Any height above 13 or 14 feet is useless for purposes of ventilation, and should be discounted in calculating the cubic space per head. The circular ward system has been advocated. It has several advantages, such as the absence of corners for the accumula- tion of dust, the aspect facing all corners of the compass, by which the ward obtains sunlight at all seasons of the year and at every hour of the day, and the facility offered to nurses and attendants in passing from one bed to another. On the other hand, if a circular ward is to accommodate the same number^of patients as an oblong ward, having an equal floor measurement HOSPITALS 517 and cubic contents, the beds of the patients, which are placed around the wall, must be very closely packed together, and the 8 feet of wall space per head cannot by an^' possibility be attained. Thus, for a circular ward to have 3,000 square feet of floor space, the diameter of the circle must be 61-8 feet. The circum- ference of the circle will be 194 feet. From this must be de- ducted the width of the entrances of two lobbies or passages, say 13 feet, which leaves 181 feet of wall space for thirty beds, or about 6 feet per bed at the head of the bed. The circumference of the smaller circle formed by the feet of the beds is 153 feet, which gives 5 feet per bed at their feet, or an average of 5-5 feet for each bed. This means far too close approximation of the beds, and the creation of an evil not encountered in the oblong wards. There is a large open space in the centre of the ward unoccupied, which is of little use to the patients crowded together at the circumference. It has been proposed to utilize this space for the nurses' room or for a central staircase ; but both these plans would create obstruction to cross ventilation and access of light, whilst the central staircase would act as a shaft for the passage of foul air from one ward to another. There is a growing disposition to provide small wards in fever hospitals, as such wards appear to be more favourable to the patient's recovery and to reduce the risk of secondary infections. They facilitate, moreover, some classification of the patients according to the severity of the attack and the stage in the disease at which they have arrived. It is deskable to provide a little extra space in the female wards, as children of both sexes may be nursed in them. Provision should be made for the entrance of warmed fresh air to the wards in winter ; this may be effected by Galton's ventilating open fire-place, or by a ventilating stove or stoves placed in the centre of the ward. Shorland's Manchester grates are much used. For warming purposes, hot water pipes should also be placed in the ward, as they may be required during very cold weather. They should be placed in a position convenient of access for cleansing any space behind or below them, and should not be fixed in channels or chased recesses in walls or floors. Radiators heated by hot water are now more commonly used than " hot-water pipes." To secure the best kinds of natural ventilation, the ward should 5l8 HYGIENE AND PUBLIC HEALTH have opposite windows reaching nearh^ to the ceiling, and the upper portion of each Mindo\\' should be provided ^\-ith side flaps and made to revolve on its lower border into the ward, so as to admit fresh air during ^^■arm weather in an upward, slanting direction. Hinckes-Bird's arrangement ma\^ also be applied to the \\indows. It is sometimes desirable to have an inlet for fresh air, which can be warmed in ^^inter, close to the floor at the head of each bed, in order to ventilate the space under the bed, and at once carr}' away the respired air and effluvia from each patient. The inlet is now generally arranged in connection A\-ith the hot-water radiator. For the escape of the heated and xitiated air, extraction shafts may be provided, opening near the ceiling, which should be joined together, the smgle shaft so formed being then carried up in close contact with the stove or chimney flue, in order that the colmnn of air in it may not be allowed to cool and hinder the up draught. In summer, when the stoves are not in action, the same result mav be produced b}'' burning gas in Bunsen burners at the bottom of the extraction shafts, or by means of a revolving fan at the top of the shaft. Recent experience, however, shows that extraction shafts unless easilj" accessible throughout their entire length for cleans- ing, are undesirable, and it is preferable to reh^ upon \nndow openings and chimney flues for the escape of vitiated air. In the ventilation of hospital wards, the " propulsion " or " plenum " method is regarded vith fa\-our, because when air is propelled into a building the source of supply can be chosen, and the air can be cleansed, warmed, and brought to a suitable hygrometric condition. The chance of infection being carried aerially from ward to ward is lessened, from the circumstance that the air supply to each ward can be kept quite distinct and separate. There is, however, one condition essential to the success of the " plenmn " system of ventilation, which is generalh' regarded \\-ith disfavour, viz., that the movement of air must be kept absolutely under control, and consequently that the opening of windows cannot be permitted ; moreover, the maintenance of the air at the same uniform temperature, humidity-, and rate of movement, tends to hsLve rather an enervating and depressing effect upon patients and nurses. The General Hospital at Birmingham is \-entilated by this system. In this building the main air ducts are carried under the corridors, from which separate flues are carried up to the several wards. HOSPITALS 519 the air outlets being at the floor level. The vitiated air is carried away through ventilating turrets at the ends of the wards. Where an extraction system alone is relied upon, the entering air is incapable of regulation, both as to its source and its amount. Fig. 81.— Hospital Slop-Siak with Flushing Rim and Bed-Pan and Slipper Douches. The water-closets, bath-rooms, and slop-sinks should be placed in a block outside the ward, but connected with it by a cross ventilated lobby. By this means, if disconnection of waste 520 HYGIENE AND PUBLIC HEALTH pipes and ventilation of soil pipes are properly attended to, there is no risk of foul drain air gaining access to the ward. Proper hospital slop-sinks are necessary for washing and emptjdng bed-pans, spittoons, and urine slippers. They should be made of porcelain, enamelled fireclay, or aluminium, should be of large size, at least 15 inches square at the top, \vith upward sluice or jet for cleansing the bed-pans, and should be flushed from a waste-water preventer. Almost as important as good ventilation is the provision of internal surfaces (walls, floors, and ceilings) to the waids, which will not hold or absorb organic effluvia. The occurrence of erysipelas and surgical fever in the past has been favoured by wooden floors \^dth chinks and crevices between the boards. The organic matters from poultices and dressings find their way into these crevices, and accumulate under the flooring. The floors of the wards should be covered mth oak parqueterie, or with solid wood block flooring \vithout chinks or cracks, laid on a bed of concrete. Narrow, well-seasoned deal boards, tongued and grooved, are less satisfactory, but far cheaper. The surface should be painted, or stained and varnished, and kept clean without washing. The parqueted floors should be oiled and beeswaxed ; or melted parafhn may be ironed into the woodwork, which it penetrates for about J inch, forming an unbroken surface which remains good for years. Other materials for hospital floors are teak and maple boards (tongued and grooved), linoleum laid direct on the coke breeze cement of the fire-proof floor, terrazo (marble chips set in cement), and various patented materials like " doloment," " stonwod," and " eubasolith," which are formed of compressed sawdust, shavings, and cement. Terrazo is rather cold and slippery, and the patented floors are liable to crack. Linoleum is found to answer well, as it is warm, elastic, and non-slippery. It should not be laid over a boarded floor. It is most essential to avoid washing floors with water. The air of the wards is bj^ this means chilled from evaporation when the floor is drying. All cornices, corners, and ledges should be avoided in the wards, and angles rounded off, so as to offer every facility for cleansing. The waU surfaces should be impermeable. Glazed brickwork or glazed tiles set in Portland cement afford, perhaps, the best and most easih^ cleaned surface, but they are apt to condense HOSPITALS 521 moisture on their surfaces. The walls may also be coated with Keen's cement or Robinson's fire-proof cement, painted, or even distempered, if tiles are too costly. Ceilings may be cemented and painted, or limewashed. The bedsteads should be of iron, with spring wire mattresses, and, in the surgical wards, provided with movable fracture boards. It is very important to reduce the furniture of the ward to a minimum, and to allow no curtains, hangings, or drapery of any sort. Excreta, sputa, dirty dressings, and poultices must be removed from the wards at very frequent intervals. In the case of in- fectious disease hospitals, it is very desirable that the solid refuse matters should be burned. This can be done by means of a small destructor furnace in connection Avith the boiler-house or heating furnace of a large hospital. No harm has been shown to result from allowing the drains from a fever hospital to empty into the public sewer, or from the slop waters being disposed of by sub-irrigation. For the exercise of the patients, covered balconies on the southern or western aspect of the building should be provided ; and in large towns, where space for a garden is wanting, a flat roof affords a valuable exercise and recreation ground. In some of the more recently constructed hospitals, it has been found convenient to place the kitchens and sculleries at the top of the building, and to use gas and steam for all culinary purposes. Every town should have hospital accommodation for the isola- tion of cases of infectious disease. The amount of accommo- dation required will depend upon the character of the population and the rate of its increase, the housing and the habits of the people, and the amount of intercourse with other places from which infectious disease may be introduced ; but it may be stated generally that there should be at least one bed to every 1,000 of the population, when this is largely composed of the industrial classes. A site should be chosen outside the town, in a thinly populated neighbourhood, with a southern exposure, a dry subsoil, a good fall for drainage, and easy of access from the town. Separate pavilions should be set aside for the separate accommodation of each different disease to be treated. The best arrangement is to place the pavilions on a north and south line, with easterly and westerly aspects, so that every side can receive sunshine. 522 HYGIENE AND PUBLIC HEALTH HOSPITALS 523 Where space will admit, the system of one-storied pavilions is far the best for all hospitals, and is especial!}'- suited for those intended for infectious diseases. The pavilions are connected with one another and with the administrative blocks by corridors which are, or may be, open to the air ; and all risk of transference of foul air and effluvia from one ward to another is thus avoided. In laige to\\Tis a certain amount of crowding on a limited area is indispensable, and wards of two or more stories in height must be built. Even in these the S3^stem of disconnected pavilions should be aimed at, and the staircases require careful planning to prevent them acting as shafts for the passage of air from one ward to another. The external air space around the wards should be ample, and overshadowing by high buildings in the neighbourhood must be carefully avoided. Hospitals constructed of semi-permanent material have been found successful in the British Army, and the same principle is now being applied in civil hospitals. The weight of the structure is taken by steel uprights and girders resting on concrete founda- tions, whilst the wall spaces between the steel supports are filled with hollow bricks of earthenware or terra-cotta. The air cavity acts as a non-conductor, and prevents loss of heat. Such build- ings are much cheaper to erect than permanent brick structures, and are likely to prove much more lasting than gah^anized iron and wooden buildings. The wards should be warmed b}' hot- water radiators, as well as by open fireplaces, especially where the building is in an exposed position. Similar buildings have been constructed of steel framework with double uralite slabs, so as to form a hollow wall. If such buildings are erected of more than one story, the floor should be of fire-proof construction (coke-breeze cement resting on steel girders). In epidemic periods it ma}' be necessary to supplement existing hospital accommodation, and for this puipose tents (in summer) or huts of galvanized iron, wood, Willesden waterproof material, 01 Doecker's material (a waterproof composition resembling leather), can be erected. Huts of the last three materials are preferable to iron, as they are easier to warm. The floors should be raised a foot from the ground, and the ridge of the roof should be used for ventilation as well as the windows. If these huts are constructed with hollow walls, the temperature in cold weather can be properly maintained with eflicient \'entilation — a difficult task without hollow walls, owing to the thinness of the materials. 524 HYGIENE And PUBLIC HEALTH As the wood and waterproof compositions used in the construc- tion of these hut hospitals are hable to rot and decay, they can only be regarded as temporary structures, and as soon as the emergency which necessitated their erection is ovei, they are best pulled down and destroyed. As the late Sir Richard Thorne pointed out, the provision for isolating infectious cases is best carried out with deliberation in non-epidemic periods. Extemporized hospitals, erected to meet the demands of a sudden outbreak, are often not ready for occupa- tion until the immediate cause for their erection has passed by, and they provide accommodation of a very indifferent sort. A memorandum of the Local Government Board states that in a village a small cottage, capable of isolating four cases in two separate rooms, should at least be provided ; but a minimum in other cases should be four small permanent wards of brick, stone, or concrete, this accommodation being capable of being extended, if need be, by tents, or huts. As some future extension is almost inevitable, the administrative block should be built in excess of the requirements at the time of construction. It is never desirable to accommodate more than twenty persons per acre, and the hospital buildings should always be 40 feet from the boundary fence, which should be at least 6 feet 6 inches in height. Temporary (wood and iron) hospitals are not approved of by the Local Government Board ; for if these are constructed so as to ensure a fairly equable ward temperature, the cost is about the same as that incurred in the erection of ordinary brick buildings, while they are less durable and more expensive to keep in repair. Moreover, wooden lined wards are not adapted to the varying needs of a permanent building, and the risks from fire are very great in such wooden structures. Certain general regulations must be observed in all fever hos- pitals. No member of the staff must leave the premises without first changing the outer garments ; tradesmen must never be permitted to pass beyond the boundary wall or fence ; the visits to the patients should be limited to the nearest relatives and the most intimate friends of those patients who are dangerously ill, and then one visit only of fifteen minutes' duration should be sanctioned each day ; all visitors should be made to wear overalls on entering the ward, and to wash their hands and faces on leaving it ; they should also be warned against entering any public conveyance immediately after quitting the ward. HOSPITALS 525 Hospital buildings will include ward blocks, an administrative block for the housing of the staff and stores, and out-offices, such as laundr}^ mortuary, and disinfecting station. The administra- tive block should be placed so as to control the entrance to the hospital grounds in the absence of a porter's lodge, and it should be built on a scale somewhat in excess of what may be first re- quired, so that it will be sufficient for future extensions of the hospital. The drains from each ward block should be trapped from the common drain, and separately ventilated. CHAPTER X SCHOOL HYGIENE I. Notes upon the School Premises. In selecting the site for a school, regard should be paid to a central po?ition and the facilities of access b}'" the scholars. A noisy site is very undesirable, and. if a quiet site cannot be ob- tained, the building should be set back at least 60 feet from the street. In planning a school building the schoolrooms must be the prime consideration ; the building should be a number of school- rooms properh' disposed, and not a whole cut up into school- rooms, whose size and arrangement are dependent upon the size and shape of the building (E. R. Shaw). If possible, the rule should be observed that lines dra\Mi from the bottom of the walls of the building to the tops of the nearest adjacent buildings should not make a greater angle than 30° with the horizon. It is desirable that the building should never exceed two stories in height, and the main corridors or haUs should be at least 10 feet in width and well lighted. A corridor or pavilion plan of buildings is preferable to the type in which the class- rooms are grouped around a central hall. The satisfactor}' lighting of school classrooms demands suffi- cient light in ever}^ part of such room, even on dull daj'S. ^\^lereas the predominant light should fall on the scholar's left, it is not desirable that aU the light should do so, or the scholars may cast shadows on the desks of those working immediately on their right. It is important that there should be no glare from the light ; with the object of avoiding this, the wdndows should be fitted with outside linen shades to cut off sunshine, and in the case of artificial light the globes should be glazed and capable of absorbing excess of ultra-violet rays. Occasionally ordinary window illumination has to be supplemented by prism panes and reflectors, the latter being placed at an angle of 526 SCHOOL HYGIENE 527 35°. For artificial illumination either electric inverted lamps or incandescent inverted gas - burners should be employed. These lights should be placed at a height of about 6 feet from the floor and at intervals of about 6 feet apart, measuring from the first light, which should be placed a little to the left of the first seat in the first row facing the teacher. A sufficiently good test of illumination would be the power of an individual with average vision to read small pica, with ease and comfort, at a distance of 12 inches from the eyes. The generally accepted standard for artificial illumination is at least 10 to 15 candle metres on desks, and this would not represent more than one-third of the usual daylight standard. (A candle metre represents the light from a standard speim candle at a distance of I metre.) The area of the windows, clear of sash frames, should be from one-fourth to one-sixth of the floor space of the room. The windows should reach as high as the ceiling of the room, and open directh^ into the external air, and the intervals between them should be as small as possible. The height of the sills from the floor should never be less than 4 feet. The defective lighting in schoolrooms is one of the chief causes of short-sight ; the child, not being able to read its book when placed at the proper distance (at least 12 inches) from its face, stoops over the desk to lessen the distance ; the eyes converge when brought too near the object, and the muscular strain thus induced leads to a yielding of the plastic eyeball, with an elonga- tion of its antero-posterior axis, and myopia results ; i.e., the image of the object seen forms in front of the retina (unless the object itself is very close to the eyes), and is blurred and indis- tinct. Imperfect lighting leads to the use of artificial light, which often causes vitiation of the atmosphere. Seats and Desks should be arranged parallel with one another, but at right angles with the windows. To avoid shadows when writing, the scholars should sit with the left hand nearest the main windows, so that the chief illumination may be from the left front. There is then plenty of light on the objects on the desk, but the rays are not reflected directly into the eyes of the scholars, as they are in front illumination with desks facing the windows. If the predominant light comes from the scholar's right, then the shadow of his hand, while writing, falls upon the paper. Desks should be from 15 to 18 inches broad, and should slope 528 HYGIENE AND PUBLIC HEALTH at an angle of about 15° for writing and 45° for reading. The height of the seat from the ground should equal the length of the scholar's legs from sole of foot to knee. The distance of the front of the seat from a perpendicular line let fall from the edge of the desk should never exceed i inch. The perpendicular distance of the seat from the edge of the desk should be one- sixth of the scholar's height. The front to back measurement of the seat should be two-thirds of the upper leg, and the front edge of the seat should be rounded. Seats and desks should be adjusted to the scholars twice yearly. The heights of scholars of the same age often vary as much as 10 inches. Girls grow most between 12 and 14 ; boys, between 14 and 16. There should be a straight back to the seat, with a curved pad or cushion to fit into and support the small of the back and loins to the level of the shoulder blades. The space, on a common seat, for each pupil, should equal 20 to 24 inches ; there should be 10 inches between the rows of seats, and the rows should not extend to mthin 24 inches of the wall. From each seat one should be able to see the sky. There should be a small raised platform for the teacher. Single desks and seats are good, but extravagant of floor-space. Dual seats and desks may be recommended. The Sheffield type, consisting of a continuous desk with six separate seats, is far preferable to a long common seat and desk. For young children prolonged posture at desks is bad, and the lesson hours should be broken by frequent short intervals for play. Blackboards should possess dull or matt surfaces ; they must always be placed in a good light, and any matter shown upon them must be large and well spaced. Suitable arrangements for the warming of school classrooms, must be provided to maintain a temperature of 65° F. in the infant department, and one from 56° to 60° F. in classrooms for the older children ; this must be done while considerable quantities of fresh air are being admitted, and never at the expense of fresh air. It may be taken for granted that if rooms are not properly warmed they will not in practice be properly ventilated. For warming purposes, the best method is the low- pressure hot-water system, with sufficient radiators and pipes. Roughly, from 12 to 16 feet of low pressure piping is necessary for every 1,000 cubic feet, in classrooms ; and 18 feet should be SCHOOL HYGIENE 5^9 provided in infant departments and in rooms at the end of a circuit. The ventilating fire-grates constitute the next best method of warming in small classrooms ; two smaller grates should be provided rather than one, wherever this is practicable. A good expedient is to provide a fireplace that has a boiler immediately behind it, which supplies hot water to a system of pipes leading from it around the classroom, through radiators, and back again to the boiler. The walls and furniture of class- rooms should always be warmed to about 60° F. before the children enter. Every classroom should have a thermometer, placed away from the fire, and at breathing level. Except in very small class- rooms, fires must be supplemented by some other heating agency. Hot-water pipes should always be made to assist ventilation. Stoves are not desirable, but, when introduced, they should be ventilating stoves and provided with chimneys. The warming of corridors and lobbies is of great importance. Some system of artificial ventilation, with a supply of warmed fresh air, is necessary for schoolrooms where the amount of cubic space per head is very limited. The English Education Depart- ment requirements are only 100 cubic feet of space per scholar and 10 square feet of floor space. These are the minimum requirements ; but even with double these amounts, adequate ventilation by natural means in cold weather would be produc- tive of draught and a great lowering of temperature in the room. Dr. Newsholme is of opinion that good average requirements for schools are, for each scholar, 150 cubic feet of space, 15 square feet of floor space, and 1,500 to 1,800 cubic feet of fresh air per hour. The problem of the ventilation of many school classrooms is rendered a very difficult one from the circumstance that a series of rooms, considerably overcrowded, may be occupied almost continuously for as long as three hours. With the cubic space available, theoretically the air should be changed twelve times an hour, winter and summer alike, if it is to remain clean and fresh ; meanwhile the temperature of the classroom has to be maintained at about 60° F. No natural agencies are sufficient under these circumstances. Even mechanical ventilation, pro- viding previously warmed air, would be severely taxed. Short of mechanical ventilation, the situation demands (a) suitable provision for warming incoming air ; [h] cross ventilation of the 34 530 HYGIENE AND PUBLIC HEALTH classrooms, and frequent occasions for flushing the rooms with fresh air, by opening all windows. The Plenum method of ven- tilating school premises does not often prove a success, and the object-lesson of permanently closed windows is a bad one for the children. Educational results are in no small measure dependent upon the air results, and insufficient air renewal in school classrooms is an important item in determining school fatigue. The mental and physical depression caused by the insufficient air renewal cannot be explained by the increase in carbonic acid. It is doubtless due to the increased temperature and humidity of a stagnant atmosphere, being responsible for an interference with the heat-regulating mechanism of the human body. It is important, therefore, that the wet and dry bulb temperatures of school classrooms should be continuously recorded, and that an effort should be maintained to keep the dry bulb temperature between 56° and 60° F., and the wet bulb temperature between 53° and 56° F. The walls of a schoolroom should preferably be painted or distempered, so that they can be washed, and any colouring should be pale and subdued (a soft greenish-grey is recommended) ; unnecessary projections (cornices, etc.) which can harbour dust should be avoided. The best y?oors are made of hard wood in narrow planks, with dovetailed or matched joints ; these may be beeswaxed and polished at intervals, and should always be swept daily. All staircases should be at least 5 feet wide and fire-proof, and faced at the ground floor by a wide door, opening outwards towards the street. The cloakrooms must be capacious, specially heated and ventilated. Cloakrooms should be cross- ventilated, and, to favour air renewal, it is a good plan to put wire-netting in the upper panels of the doors. The provision should be in the proportion of about a cloakroom to every 120 scholars. The hanging hooks for hats, etc., should be from 15 to 18 inches apart in the girl's cloakroom, and at least 9 inches apart in the boys' cloakroom ; and never more than two rows of hanging pegs should be placed upon one stand. If pegs are arranged on both sides of a stand, a partition of fine wire-netting should be pro- vided, so as to keep the articles on the two sides from touching. It is desirable to have a separate cloakroom for each classroom, SCHOOL HYGIENE 53I and for the pegs to be numbered and scholars made to keep their pegs. Covered sheds should be provided for recreation when it rains ; and if space is unprocurable on the adjoining ground, a basement or a flat roof may be designed to meet the purposes of a covered playground. It is essential that the scholars should receive plenty of physical drill and exercise in the open air. Under a proper system of medical inspection, commencing physical defects can be promptly detected and remedied by appropriate exercises. Suitable closet and lavatory provision for schools should pro- vide a prompt and rapid removal of excreta, which should be inaccessible to the scholars after deposition, the whole installa- tion being an object-lesson of cleanliness and sanitary practice. The seats of water-closets should not exceed 14 inches in height for the older children, and from 11 to 12 inches for the youngest. Water-closet seats, urinal places, and lavatory basins should be provided in the proportion of at least five of each of these provisions to every 100 boy scholars ; and with girls and infants the water-closet seats should amount to at least 7 per cent, of scholars. Generally speaking, there are too few lavatory basins and clean towels provided in our schools. In places where there is insufficient water for flushing urinalsy a good cheap and lasting material for coating the surface which receives the urine is cement coated with a mixture of pitch and tar. In country schools, where water-closets are not practicable, privy pits should always be replaced by pails (as where privies exist the water-supply is very frequently from adjacent wells), and earth-closets provided. After use, the earth is best put in a shallow trench, and covered over ^vith 3 or 4 inches of soil, and the soil collected from this site should be stored in a drying-shed in small quantities prior to use. One of the modern types of trough water-closet or latrine {vide p. 95) is sometimes used for schools, but the flushing provision must be adequate and systematically regulated. Separate closets with separate flushing cisterns are to be preferred. All dormitories must be well lighted and ventilated, and at least 400 to 500 cubic feet of space should be aUov.^ed for each scholar under 12 years of age. The drinking cups used in common by most scholars may be a means of communicating disease, such as diphtheria. Many 532 HYGIENE AND PUBLIC HEALTH cups should, therefore, be supplied in place of the one or two only which are generally provided. Arrangements should also be made so that the cups, after use, are continually exposed to flowing water during play houis ; and the cups should be well cleansed \\dth wet sand at least twee a week. In the " Crystal Stream " drinking fountain no cups are necessary, the scholars directly taking the water as it issues in weak upward jets from the fountain. The school premises should provide the best possible hygienic environment for the scholars, and should present an object- lesson of cleanliness, brightness, good taste, and of scrupulous regard for all sanitary demands. The teacher is not concerned with such matters as the selec- tion of site and the planning and construction of premises, but can alwa3^s secure the best sanitary circumstances under the existing conditions, and often an improvement in respect of these conditions. The effects and ^'alue of environment, in so far as the school- child is concerned, are of a twofold nature — viz., the physical and educational. The educational effect and value is capable of further subdivision into the educational effect upon the scholar of sanitary;' precept and practice, and the effect of the sanitary environment in favouring or other^^dse the mental re- sponse, and thereby promoting the general educational results. Nothing is more disabling from the standpoint both of the teacher and the taught than foul air ; and the effect of im- proving the atmospheric conditions is, in the classroom as in the workshop, to improve the quality and amount of the work performed. Dirt should be reduced to a minimum, as by clean boots, clean scholars, clean clothes, and chalk-troughs to blackboards. All dirt-harbouring arrangements in classrooms should be reduced to a minimum — viz., cupboards, shelves, projections (cornices, etc.), platforms, hangings. All decorations on walls should be easily cleanable, and the floors and walls washable. At the end of the school-day doors and windows should be opened, and the floors swept with a damp broom, or after appli- cation of wet sawdust ; the cloakrooms, corridors, etc., to be included. Frequent cleansing and disinfecting precautions are more par- ticularly caUed for in the infant departments ; and in such SCHOOL HYGIENE 533 departments, upon every Saturday, the floors, seats, desks, tables, and window-sills of classrooms, the surfaces of cloakrooms (in- cluding hat-pegs), and the floors of halls and passages, should receive a liberal application of hot water containing washing soda, and good yellow soap ; finally, the washed surfaces ma}^ be sprayed with a little disinfectant solution. In making the choice of a disinfectant, one of the coal-tar series (izal, cj/llin, etc.) ma}^ be selected, which is capable of forming a fine and homogeneous emulsion mth water, and possesses a carbolic acid coefficient of at least 12 ; and if all vertical surfaces are sprayed with a sufficiently fine spray from below upwards, there is no risk of any unsightly stains remaining upon walls, etc. It is hardly necessary to add that all drinking- vessels should also be specially cleansed once a week. Upon alternate Saturdays the whole school premises should be similarly treated ; and upon every fourth Saturday some addi- tional items should be included in the scheme. Then all wood- work to a height of 6 or 7 feet should be scrubbed ; all cupboards, ventilating openings, bookcases, and storerooms should be cleansed and sprayed ; and maps, books, etc., should be taken outside the buildings and well dusted. Dustless oils, if used fresh and applied to floor surfaces for several days before these surfaces are used, tend to prevent dust from rising, and may be recommended. The material costs about five shillings a gallon, and requires to be applied just before the commencement of each school term. All waste-matters upon school premises should be burnt, when possible ; and failing this, promptly deposited in covered, movable, metal dustbins, placed out of reach of the scholars. The Disinfection of School Premises should generally be per- formed by the Sanitary Authority, or under their directions. 2. Notes upon the School Child. The Nervous System contains the machine of the Mind ; it receives and interprets vaiious sense-impressions, regulates all the vital functions of the body, and controls or commands the muscular system. It should be the cardinal stud}' and concern of the teacher. Wrong or slovenly acts, at first under conscious control, may in time develop into subconscious or unconscious habits. Hence the necessity for a careful attention to the formation of good 534 HYGIENE AND PUBLIC HEALTH habits of thought and of action, and for the early correction of bad habits or tendencies. 'Even in health, children differ greatly ; and in mental educa- tion the special needs of the individual must be studied. Per- manent injury results from premature or excessive stimulation of the brain faculties, by impairing the whole nervous system, and the general health and development of the brain and body suffer as a consequence ; it is therefore opposed to all the objects of education. Mental Fatigue is less due to overwork than to wrong work at the wrong time and in the wrong way. It is accompanied by a slight increase in the cardiac pulsations and blood-pressure ; by depressed muscular force and lessened cutaneous sensibility. It may be measured by the ergograph, the sesthesiometer, and the quality of any set work (such as sums, writing to dictation, etc.). The Symptoms of Brain Fatigue and " Over-pressure " are : (a) Normal and Transient. — Yawning, lassitude, wandering eyes and inattention, drowsiness, fidgetiness, slow or faulty response to words of command and questions, head balance impaired, little or purposeless movement. (&) Continued and Abnormal {Over-pressure). — Nerve-signs: Irregular muscular movements — chiefly of fingers, eyes and mouth ; knitting of eyebrows and overaction of frontal muscles ; defective muscular balance of the body (especially of the head) ; excessive reflex actions ; the abnormal position of the hand when held out in front at word of command (slight drooping of thumb and fingers) ; stuttering ; restlessness and frequent twisting of body and neck. Impairment of the delicacy of touch perception. Irritabilit}^, grumbling, and excessive sensitiveness to reproof. Facial expression of exhaustion or anxiety ; open mouth ; lower eyelid baggy and relaxed. Languor, listlessness, headache, speedy fatigue, dulness or apparent stupidity ; slow or inaccurate response to questions or commands ; excessive drowsiness or wakefulness ; night terrors ; walking in sleep ; poor bodily de- velopment and impaired health (pallor, failure of appetite, poor digestion, feeble circulation, etc.). It is a predisposing factor to chorea, hysteria and epilepsy. Scholars EspeciaUj^ Liable to Suffer from Over-pres- sure : Delicate nervous children (apt to be irritable, pas- sionate and emotional) ; constitutionally weak children ; anaemic, badly fed, rapidlv growing, excitable and mentally precocious SCHOOL HYGIENE 535 children. Those exposed to bad air or bad conditions of study ; bad teaching and unhealthy home conditions ; too Httle sleep and recreation ; defects of sight, hearing, etc. ; excessive strain of vision, etc. ; the period of puberty. The Prevention of Brain Fatigue : A Hygienic Time-Table is of prime importance — one which economizes the brain energy and directs it aright : — Short lessons, but length varying with the subject (no lesson should take more than three-quarters of an hour) ; a proper sequence and variation of subjects ; proper regard to stage of development of the scholars and the im- maturity and instability of the nervous system in the early years of school life ; sufficient intervals for rest, recreation, physical exercise and food. Fresh air ; quiet classrooms ; strict limitation of the subjects selected for, and the duration of, home lessons. Home work not to take more than one hour ; revision work only ; and never before lo years of age. An observant teacher will see the first signs before exhaustion results, and will discover when imperfections of vision and hearing are causing strain and brain fatigue. Apparent Dulness may be due to defects of hearing or vision ; poor nutrition or injudicious teaching ; illness ; bad air ; insuffi- cient recreation and sleep (child-labour). Mentally Defective children make poor progress in studies and show unusual peculiarities of temperament and of moral perception. In the term " mentally defectives " those who are merely dull and backward are not included. The former are incapable of benefiting much from ordinary school education ; and, in their own interests and in the interests of other scholars, they should be early removed to special institutions, where they may be trained in manual work and kept under permanent observation and control. Children suffering from word-blindness, word-deafness, and moral imbecility also demand special provision for education. Chorea (St. Vitus's Dance). — Occurs chiefly in girls between 7 and 14. Onset gradual. Constant twitchings of body, face, limbs or hands. Things are dropped because of impaired control and power of muscles. The child is generally below normal weight. Hysteria. — Especially in emotional girls at age of puberty. Emotional outbursts ; morbid sensations (ball in throat, etc.) ; 536 HYGIENE AND PUBLIC HEALTH paralytic symptoms, etc. Fits are of gradual onset, with sobs, laughter or other emotional display, then with a scream the girl falls violently convulsed and apparently insensible ; she rarely injures herself, and never bites the tongue. Epilepsy. — Momentary palsy of face, then sudden uncon- sciousness, stiffening of body, biting of tongue, hands clenched, and con\Tilsive movements of limbs and muscles of face (face distorted and blue from congestion). The fit is followed by drowsiness. The physiological necessity for adequate rest and recreation and good physical training must not be ignored. These reduce the number of cases with signs of brain disorderliness and the number of dull children. The importance of quality and quantity of sleep as affecting the working capacity of the brain cannot be exaggerated. Sleep is necessary for the growth and repair of both ph^^sical and mental tissues, and deficient sleep is a great factor in mental dulness and malnutrition. The quantity of sleep which is desirable during school ages is as follows : — Years of Age. Hours of Sleep. 4-8 . . . . . . 12 9-12 . . . . . . II 12-14 . . . . . . 9-10 14-20 . . . . . . 9 A well-ventilated bedroom (open windows), absolute quiet, darkness, and a warm bed, favour sound and refreshing sleep. The development of the nervous system of a child is one of great importance from the educational standpoint. In child- hood, especially from 3 to 10 years of age, the nervous system is unstable, rapidly developing and easily tired. Since mind and body act and react upon each other, the body suffers if excessive demands are made upon the brain, and the brain suffers if excessive demands are made upon the body. The coarse large movements of earlj^ childhood slowly become finer with the gradual development of the complex co-ordinations necessary for fine movements. Thus, up to 5 years of age a child should be educated through the senses and its activities ; then the memoiy should be developed, and good habits and training cultivated. SCHOOL HYGIENE 537 And after lo years of age the child's reasoning powers and imagination develop. Probably. the chief period of character formation is from 5 to 8. Psychologically, it is to be remembered that the young child is very imitative, craves for approval, and seeks to emulate ; it is naturally curious, and its activities are incessant ; these latter must be controlled and directed to useful educational ends — - physical, moral, and mental. Any tendency to such defects as selfishness and falsehood must be early checked, always remem- bering that the will to do comes first, and inhibitory powers (the will not to do) later ; hence the truth in the old pedagogical maxim, " Don't say don't." Vision. — In children the eye is relatively short from before backwards, and the child has to compensate for this by muscular effort, which involves eye fatigue and nervous strain ; moreover, the still developing nerves of the retina are easily tired. In early life the eyes are soft and plastic, and readily yield to con- ditions favouring defective vision. The eyesight of at least 20 per cent, of scholars is defective, and in 10 per cent, it is seriously defective. Affections of vision are, therefore, among the most common hindrances to school work. The strain of correction where vision is faulty leads to eye fatigue, which causes brain fatigue and diminished perception ; furthermore, brain fatigue leads to general constitutional results. The causes of eyestrain are : Too continuous eye-work, and a bad time-table ; fine and indistinct work, and work brought too near the eyes ; bad or faulty lighting of room ; bad posture in reading and writing. Predisposing causes are foul air and over- heated room, debility and poor nutrition of scholar. The printing, etc., of school books is of great importance. *"' Double piC2." shouW be selected for infants, and " pica leaded "' for older school children. The Symptoms of Defective Vision are : Headache, generally frontal, worse at night and relieved by sleep ; a sense of fulness in head ; redness of eyeballs and eyelids ; watering of eyes ; blinking ; partial closing of eyes when looking at distant objects ; frequent rubbing of eyes ; heat and pain in eyes ; dizziness, and sometimes nausea or even vomiting ; squint ; irritability, neuralgia, and impaired general health ; books held within 538 HYGIENE AND PUBLIC HEALTH 12 inches of the ej/'es ; confusion of letters — especially h and h, e and c ; inattention and apparent stupidity. Short-Sight (myopia) is rare before 8 years of age, and increases greatly as we pass from lower to higher grades at school ; hence an illustration of the injurious effect of school life upon the scholars' eyesight. This condition is due to the " long e^^e " with the too distant retina ; and hence concave lenses are needed. It is most liable to develop in delicate children with poor muscular and nervous tone, and especially when parents are myopic. Convalescence from acute fevers, bad air, bad habits, night work, overheated rooms, favour the condition. Prominent eyes with large pupils suggest myopia. Bad posture during reading and writing may cause myopia, and myopia may cause bad posture. Long-Sight (hypermetropia). — This condition is due to the " short eye " with the too near retina ; and hence convex lenses are needed. This is the most common eye defect in young children. Eyestrain is continuous in school, and there is no relief by bring- ing objects nearer, as in short-sight. Small deep-set eyes, with contracted pupils, and red, watery eyes, suggest long sight. Astigmatism. — Blurred images and indistinct vision at any distance, due to eyeball (especially the cornea) being asym- metrical, and thus part of object is seen out of focus. The con- dition is generally congenital, and often exists with long- or short-sight. The child who peers or who looks obliquely probably has astigmatism. Squint is generally due to the focussing power of the two eyes being unequal and overstrain of certain eye muscles. Squint usually comes on at about 3 years of age ; and the con- vergent squint of children is generally associated with long-sight. A squinting eye is a non-seeing eye, and early treatment is necessary to prevent serious complications. Glasses do not weaken the eyes, but strengthen them ; they conserve the sight, prevent headache, etc. ; and prevent squints, or may even cure them. Colour-Blindness. — Most colour-blind people cannot tell red from green, and call them shades of the same colour. Ophthalmia and Conjunctivitis. — Redness of eyes, crusts on margins of lids, with loss of eyelashes ; extreme sensitiveness to light ; excessive watering of eyes ; formation and discharge of yellow matter. SCHOOL HYGIENE 539 Habit- Spasm. — This is due to the spasmodic contraction of the ciliary muscle in the direction of the muscular movement which has predominated for some time. It is a visual " cramp," most frequently observed in nervous girls of over ii years of age ; and rest, fresh air, and good feeding are demanded. Congenital Word-Blindness. — In this condition the visual recog- nition by the eye-brain is abnormally slow or congenitally defec- tive. The scholar has no visual memory for words or letters, or the brain acts slowly in interpreting such objects as letters. The condition causes dulness in learning to read and WTite. The vision is tested by Snellen's cards, which contain letters of diminishing size from above downwards. By these cards normal vision can read wdthout effort the letters on the line marked 6, when the child stands at the standard distance of 6 metres, or 20 feet. Normal vision is expressed bj^ putting 6 as a numerator, and the number opposite the smallest tvTpe which the child can read, at the standard distance of 6 metres, as the denominator ; hence good vision is expressed as !!.. If, however, the child could only read the type of the line marked 12, its vision w^ould be expressed as xV; or one-half of normal, ^k i? often advocated as the standard for the elementary school child ; and it is only when the vision is worse than this — say one-third normal, or less — that the child is measured for spectacles. Vision should be tested on admission to school, and once during each year of school attendance, assuming the child to be over 6 years of age, and capable of interpreting what it sees. Any facial distortion or oblique or advanced position of the eye must be noted ; one eye should be tested at a time, and if the child already wears glasses, the test should be applied wdth the glasses on. Colour-blindness may be sufficiently tested for school purposes by means of a few skeins of bright green wool, mixed with a mass of confusion colours, among which reds figure prominently. If the child can pick out all the skeins which match a pale green skein, vision may be pronounced normal in this respect. To conserve vision, school books should meet the following requirements : Sufficient thickness of paper ; type large, thick- faced, and well-defined ; letters and lines well spaced, and good margins to the pages ; ink black ; paper white or tinted yellow ; no type allowed which necessitates the holding of the book at a less distance than 12 inches. Best types are " double pica " for very young children, " pica leaded " for children 6 to 11 years. 540 HYGIENE AND PUBLIC HEALTH and " small pica leaded " for the older children ; small type annotations disallowed ; the lines of the school book not to exceed 4 inches in length. Hearing. — Generally from 12 to 20 per cent, of scholars are defective in their hearing. The Signs of Defective Hearing and Ear Disease are : The child misses spoken words or directions ; strained attention in class ; inattention and apparent stupidity ; early exhaustion from lessons ; mouth-breathing ; earache ; head- ache ; discharges from ears ; giddiness ; impaired general health. The Causes of Defective Hearing are : Adenoids and enlarged tonsils ; inflammation or abscess in the middle ear from inflam- mation or disease of nose or throat (catarrh, measles, scarlet fever, diphtheria, etc.) ; wax in ears. On admission to school the hearing should be tested, and subsequently once a year. The testing is always difficult, and many tests have been suggested, such as the whisper test, the stop-watch test, the tuning-fork test, the audiometer, and acu- meter. Probably the best test is the forced expiratory whisper (stage whisper) at the standard distance of 20 feet. The child must not see the lips, and so should be placed with the back to the teacher ; both ears should be separately tested, the child being made to repeat numbers. In some noisy classrooms it is necessary to examine several apparently normal children, and get these to establish the standard distance for the test in that particular room. Through the auditory word-centre the child grows to associate words with ideas ; then the motor word-centre (for speech) develops ; and the two becoming linked up, the child imitates the sounds that it hears. The visual word-centre develops later, and becomes linked up wth the auditory and motor woid- centres for speaking and writing ; and then by memory (the storage of impressions) the child can name and write printed or heard words, and recall the object to which the word relates. A child suffering from word-blindness has not this visual word- centre properly developed, and one suffering from word-deafness has a defect in the auditory word-centre ; but vision and hearing in all other respects may be normal. Early attention to defects of sight and hearing will either lead to a cure or will prevent matters going from bad to worse, and thus save the scholars from grave educational losses and dis- abilities in after-life. SCHOOL HYGIENE 54I Exercise. — The muscles contain in their substance about one- quarter of the blood of the whole body ; their action promotes the circulation of the blood, and hence plays an important part in promoting the general nutrition. During muscular exercise the force and frequency of the heart's action are increased ; the respirations are more frequent and deep ; and the functional activity of the organs of digestion and excretion (skin, kidneys, and bowels) is increased. The development of the nervous and muscular systems are interdependent, and both are promoted by muscular activity. Hence muscular exercise promotes an active circulation of the blood generally throughout the body ; develops the muscles and improves the carriage and symmetry of the body ; trains, through the nervous system, the action of the muscles and the " muscular sense " ; promotes the sym- metrical development of the brain, and healthy and vigorous brain power ; and generally improves body nutrition and maintains the body functions in health. Furthermore, physical exercises at school counteract the harmful tendencies of bad posture, and reduce the number of cases of nervous disturbance among scholars. They can be made to correct faulty and defective conditions in the scholar's develop- ment, and also any acquired bad habits of posture or deport- ment ; to provide a profitable diversion from brain work ; to aid in school discipline and develop qualities of alertness, decision and activity. All exercise should be taken in the open air when possible, and, where under cover, the conditions should be made to ap- proximate to open-air conditions as much as possible ; all clothing should be light and loose ; boots must not be stiff and tight round the ankles ; flannel or woollen garments should be worn next to the skin : excessive fatigue from too violent and pro- longed exertion should always be avoided, as otherwise too great a strain is thrown upon the heart ; only gentle exercise should be taken directly after a meal. Phj'sical exercises should be gradu- ated to suit the ages of the scholars ; sickly and deformed children, convalescents from diphtheria, etc., and those who have walked long distances to school, require special considera- tion and specially selected exercises ; the exercises must not be too exacting between the ages of 13 and 16, and in the case of rapidly growing and overgrown children ; such faults as holding the breath, stooping or contracting the chestji and the uneven 542 HYGIENE AND PUBLIC HEALTH performance of the exercises, must be corrected ; suitable pre- cautions must be taken to avoid chills after exercise. For scholars over 8 years of age the school curriculum should include a scheme of organized games, those being selected which are best calculated to develop the physical, mental, and moral qualities of the scholar. In addition, certain drill exercises are needed ; and after fourteen years of age gymnastics are desirable — especially when any particular group of muscles needs training or strengthening. Better results are obtained from short daily exercises than from longer exercises at greater intervals. Ling's Swedish system of exercises has for its object the harmonious development of the skeleton, the muscular system, and the internal organs. Each movement is required to be a brisk, deliberate, and forcible response to the word of command ; and special apparatus is used, including wall-bars, vertical ladders, horizontal ladders, climbing ropes, rope ladders, horse, vaulting-box, etc. Folk-dances are to be encouraged, inasmuch as they inspire a love of physical exercises, and develop neuro-muscular co- ordination, and are graceful accomplishments. On the subject of physical exercises the revised syllabus of physical exercises for public elementary schools, issued by the Board of Education, may be very profitably consulted. There is much to be said in favour of occasional five-minute " fresh-air drills " in school classrooms. To this end certain " health monitors," appointed each week, should be told to open all windows and doors, when a deep-breathing exercise is main- tained for about two minutes. For the deep-breathing exercise the following orders are given : " Stand erect !" " Attention !" " Hands on hips !" " Shut mouths \" " Breathe in !" (slowly given), " Breathe out !" (slowly given). The " Breathe in !" and " Breathe out !" are repeated six times. After a few moments' pause, the exercise is repeated another six times. This is then followed by a smart physical drill of sjonmetrical arm movements for three minutes. During these exercises the scholar must stand erect, and the head must not be thrown back. Posture and Deformity. — In early life the bones consist partly of cartilage or gristle, and therefore readily yield, but ossification is practically complete at 12 years of age ; hence a child, under favouring conditions, may become deformed. SCHOOL HYGIENE 543 A bad position, for instance, remaining uncorrected for some time, may in certain children lead to permanent deformity, which displaces and compresses important organs. The children who are most liable to such deformities are rickety, strumous, debili- tated and overgrown children, with poor muscular tone, and especially such children between the ages of g and 14. Rickety Children may generally be distinguished by their large heads and prominent foreheads, small stature, " pigeon-breasts," bow-legs, enlarged abdomens, and they may be knock-kneed or flat-footed, and give evidence of poor nutrition. Rickety children are generally to be found in the infants' department. It is important that they should not be allowed to stand too much and that bad posture should be corrected. Such children specially require regular physical exercises and fresh air. Strumous Children are often beautiful children with fair delicate skins ; they are especially prone to glandular trouble and are often narrow-chested. The causes of Bad Posture at school are : Too protracted work at desks — especially writing (faulty school programme) ; bad seats and desks ; bad school books ; bad lighting of classroom ; bad habits ; too fine and too near work ; short-sight ; ill-health and bodily weakness. The evil results follow if seats are too high, too low, too narrow or too fiat, and have no spinal support ; if desks are too high, too low, too narrow, and have faulty slopes ; if too great distance between seats and desks, or seats and desks too near. The seat and desk should be adjusted to each scholar at least twice a year. The results of bad posture are : Compression of chest, and interference with free movements of the chest in respiration and with the circulation of the blood ; interference with the func- tions of abdominal organs ; round or uneven shoulders and lateral curvature of spine ; bad habits of body carriage ; early fatigue ; short-sight and headache. Spinal Curvature — Lateral. — Is especially prevalent in girls of about the age of puberty. First a drooping of one shoulder may be noted, and then the shoulders or hips (generally the right only) " grow out " ; backache, lolling, and stooping occur ; later the crooked spine is very evident. Posterior. — Common in weakly and rickety children ; round shoulders result. Angular. — Due to disease (caries) of spine ; cannot straighten back ; pain on 544 HYGIENE AND PUBLIC HEALTH percussion. Spinal curvature leads to displacement and com- pression of important organs, and, at school ages, though generally easily prevented, is extremely difficult of cure. With Good Posture the head is erect and poised directly above the spine, and the two shoulders, hips and elbows, are level ; if sitting, the thighs are at right angles with the trunk and the forelegs are at right angles with the thighs. If seat and desk fit the scholar he sits squarely in this attitude, with his work in front of him ; his posture is sjnnmetrical, and therefore his muscles are acting equally and are well-balanced, and this ensures a minimum of muscular effort and discomfort. Muscular effort is involved in standing, and to a less extent in sitting still. The Respiration in children must be free from any obstruc- tion — whether in the nose or throat, or from interference with free chest movements, as by tight clothing or bad posture. The signs of obstruction to respiration in the nose and throat are : Open mouth ; muffled nasal voice ; often a vacant and un- intelligent expression ; snoring ; frequent colds and nasal dis- charge ; breathing not free and often noisy ; mental dulness ; deafness ; cough ; nostrils compressed and poorly developed (if long-standing) ; and if child rickety, often " pigeon-chested." The value of deep -breathing exercises is very great, especially in the growing child. They assist the circulation of blood, and develop the chest capacity ; they are also of value in children with early adenoids and spinal curvature, or who stammer. The advantages of cultivating a habit of nasal breathing are :— The individual is less liable to sore throats and consequent ear trouble ; dust or dirt in the inspired air gets filtered off to a great extent in the nose, from which it can be dislodged without being either inhaled or swallowed ; and the nasal secretion pos- sesses some power of inhibiting the growths of micro-organisms which may be retained on the mucous membrane. Nasal discharges may signify : Catarrh, influenza, measles, adenoids, diphtheria, scarlet fever, or ulceration or foreign body in the nose. Breathing foul air for a short time may cause : Languor, mental dulness, drowsiness, yawning, headache, faintness, nausea, and even vomiting ; but breathing foul air day after day gives rise to serious and lasting consequences, including : Debilitation ; loss of tone and vitality, and therefore poorness of appetite and impaired digestion ; increased liability to infectious disease ; SCHOOL HYGIENE 545 throat and lung complaints and consumption ; anaemia or poor- ness of blood ; indications of impure blood, in bad complexion, skin eruptions, etc. It is also favourable to rickets. By the Circulation of the Blood the following objects are achieved : Food and oxygen are conveyed to the tissues for their nourish- ment, growth and repair ; the heat (which is generated in the muscles and the glands) is distributed over the body ; and waste matters are carried from the tissues to the excretory organs. The following symptoms in scholars probably indicate some departure from the normal in either the composition of the blood or the heart's action Extreme pallor — especially of lips, gums or the inside of eyelids ( = anaemia) ; languor ; irritability ; faintness ; disinclination to play and breathlessness on exertion ; emaciation ; coldness of extremities ; palpitation or pain over region of heart ; blueness of. nose, ears or finger-tips. Children with poor blood and defective circulatory system? are impaired mentally and physically. Their special needs call for some reduction in the mental and physical work de- manded of normal scholars ; suitable exercises (including deep- breathing exercises) will aid the circulation ; but to maintain the blood good in quality and quantity proper food and abundance of fresh air are necessary. Bad feeding and bad living predispose to scurvy and purpura — conditions which are characterized by haemorrhages about the body. The causes of Enlargement of the Lymphatic Glands are : Pediculi, wounds, sores and eruptions on skin or scalp ; throat or ear trouble ; carious teeth ; scrofula or struma. Enlarged lymphatic glands may be observed or felt up the sides of the neck (cervical), at the upper and back part of the neck (occipital), in the groins (inguinal), and immediately above the internal condyles of the humerus. It is important to keep The Skin clean. Dirt impedes the important work of the skin and throws extra work upon other organs ; it favours skin blemishes (blackheads, pimples, etc.), boils, abscesses, and the harbouring of parasites and germs of disease. It is most important to develop cleanly habits in school children. The hair, face and hands should always be clean, and the nails kept short. A weekly wash in hot water and a weekly change of underclothing are necessary to these ends. Warm haths cleanse the skin and thus promote its healthy 35 546 HYGIENE AND PUBLIC HEALTH functions. Cold baths have a stimulating and tonic effect and reduce liabilit}^ to catch colds. S\\dniming baths provide physical exercise, promote health, and afford opportunities of acquiring a useful accomplishment. A bathman or instructor should always be present. Warm baths should be from 95° to 100° F. Hot, 105° to 110° F. Cold, 55° to 60° F. Smmming baths about 70° F. 1' For schools the advantages of shower baths over slipper baths are : Fresh clean water constantly appUed ; more econom- ical of time ; clieaper ; danger of infection reduced ; more stimulating. A weekh^ shower bath (5 to 10 minutes) with soap and warm water, at about 90° F., is desirable. The benefits of school baths as testified by school teachers and doctors are : Greater cleanliness of scholars' underclothing ; reduction in skin diseases and vermin ; increased self-respect of scholars ; good moral influence on homes ; better school work claimed by some. It is of great importance to keep the Hair and Nails clean. When there are lice (pediculi) and their eggs (nits) in the hair, the child is generaUy pale and poorly nourished, dirty and miserable ; a peculiar drj' look about the hair, and scratch marks on forehead or behind ears. Lice or nits will be seen (especiall}- when the hair behind the ears is raised and examined) ; scalp dirty, and often sore places on scalp. (Nits are smoky-brown, oval, glistening bodies, and should be looked for about half an inch from the roots of hairs.) Where there are sore places or scabs the hair should be cut short, and in the case of scabs a linseed or bread poultice should he applied. The head ma}* be cleansed from lice by the applica- tion of carbolic oil overnight, and a thorough washing of the head ^^ith soft soap and water the next morning, after which the hair should be combed thoroughl}^ with a fine-tooth comb repeatedly dipped in vinegar. This treatment should be repeated daily, when the worst head should be completely freed of lice in the course of a week. ^Vhere there is difficulty in keeping a child's head clean, the hair should be worn short. Ringworm. — Is most common between 5 and 10 years of age. It gives rise to one or more circular patches on the top of the child's head ; the patches are covered with fine white powder}^ scales, and the hairs on the part are dull and mostty broken off. The treatment is difficult and should be under medical direction. SCHOOL HYGIENE 547 Ringworm of the scalp is often spread by the caps of scholars ; and this is one of the reasons why each child should have a numbered peg in the cloakroom and children should never exchange caps. It is difficult to tell when a child has completely recovered from this disease, and children frequently return to school too soon. All cases should be regarded as infectious where broken-off stumps of hair are to be observed with a lens, and when such stumps, after removal and washing with ether, and mounting for a few minutes in lo per cent, potash solution, show spores of ringworm. Owing to the prolonged loss of educa- tion frequently entailed by this complaint, the educational authorities of some large cities have instituted special ringworm classes. Ringworm of body is most common on the face, side of neck, wrists and hands. Like ringworm of the scalp, it has a tendency to relapse, and to recover spontaneously at the end of the school period. Impetigo Conlagiosum. — ^This condition is distinguished by the presence of small, isolated, flat vesicles, generally first to be observed upon the face. The contents of the vesicles become milky, and then purulent, and after a few days crusts or scabs form, in size from a split pea to a shilling. The face, scalp, hands and arms may show these vesicles or scabs, and the condition is very prone to spread. Favus. — In this condition, which is of rarer occurrence, orange-coloured crusts are to be observed on the scalp. The hair is brittle and dull, but not generally broken off short ; and there is sometimes a mousy odour to be observed. It is generally seen in children of poor physique and low nutrition, and has not much tendency to spread. The treatment is very similar to that of ringworm. Scabies or Itch — In this complaint papules, pustules, excoria- tions, and fissures may be seen, more especially between the fingers. It is highly contagious, and demands prompt medical treatment. The Clothing of school children must be light and loose, so that it does not interfere with any natural function or movement, and it should be suitably distributed, so as to help to regulate the body temperature and to guard the system from chills. Some common and easily corrected errors in the clothing of scholars relate to articles which by their pressure and constriction 548 HYGIENE AND PUBLIC HEALTH interfere with the circulation of the blood, the function of im- portant organs, or free muscular movements (such as tight collars or neck-bands, garters, stays, bodices, belts, braces, etc.) ; or which by their weight and ill-fit lead to deformity and awkward gait, such as heavy, ill-fitting boots. Food is not only necessary to repair the wear of the tissues and to furnish heat and energy, but for growth also, in children. School children require relatively more food than adults, because the food has to provide for the growth and the greater energy generally manifested. More especially is an abundance of good food necessary between 10 and 14 in girls, and 14 and 20 in boys. Children of the ages indicated require each day about the following amounts of water-free food constituents : Seven Years. Ten Years. Fourteen ^ rears. oz. oz. oz. Proteids 2'0 2-5 3.0 Fats . 2-3 3.0 3-S Carbo-hydrates 8-0 iO'7 12-7 Mineral matter 07 0-8 0-8 I3'0 17-0 20'0 The symptoms of insufficient or wrong feeding are : Emacia- tion ; deficient and flabby muscles ; arrested growth ; anaemia and sallow skin ; looseness of bowels ; lassitude, inattention and mental dulness. The conditions known as Rickets or Scurvy are favoured by wrong feeding. The Education (Provision of Meals) Act of igo6 enables Education Authorities to provide meals for school children, and to recover the cost from the parent, where possible. Where this provision is made at the schools, the teachers often assist in the cooking, and the elder girls are also encouraged to do so. The elder girls thus receive some of the instruction in simple cooking which is so necessary. This knowledge should be supplemented at continuation classes. The rules for the diet of school children embrace a plain, wholesome, generous, nutritious, digestible, and varied fare, in which the amount of fresh meat allowed is limited, and fresh fruit, and baked and stewed fruit, should figure prominently. Raw apples and nuts, in addition to their nutritive value, are specially good for the teeth, more particularly at the end of a meal. The craving for sweet things should be met by supplying SCHOOL HYGIENE 549 these in reasonable quantity at the end of a meal, after the appe- tite has been first satisfied. Indigestion may arise from : — ^Bad teeth ; improper mastica- tion ; irregular meals ; tough and improper food ; too frequent meals ; food too hot ; stewed tea ; tight belts, stays, etc. The good habits to be cultivated are : — Slow eating and good chewing ; sufficient but not excessive food ; regular meals ; regular evacuations ; the cleaning of the teeth. Bad teeth may cause : — -Pain and loss of rest ; abscess and the swallowing of pus ; enlarged glands and disfiguring scars ; indiges- tion ; foetid breath ; the habits of eating soft food and imperfectly masticating the food ; grave constitutional conditions due to malnutrition. An abscess in connection with the temporary teeth may affect the development of the permanent teeth, and this may lead to imperfect mastication and defective articulation. Quite 85 per cent, of scholars give evidence of some degree of dental caries. WHien this condition is extensive the physical measurements are generally below the average. A tooth attacked with caries tends to promote the spread of the con- dition to other teeth. The preservation of the teeth is most important, and the conservative treatment should commence before 8. A yearly inspection of the teeth is therefore desirable, and the general use of tooth-brushes should be considered an essential act of cleanliness. The value of Anthropometrical Data is considerable. They enable us to learn whether growth is occurring at an exceptional rate at any age, and thus to make provision for the fact that the powers of mental and physical application are thereby reduced. In this connection it is important to note that excep- tional growth is most liable to occur at or about puberty, and that growth in height without a corresponding increase in weight demands attention. If growth is found to be deficient, it may indicate insufficient food or clothing, an excessive expenditure of energy in mental work, or the onset of some disease. Good nurture promotes growth, and hence the height and weight are indications of nutrition. It is for this reason that children of the better classes are heavier and taller in both sexes than those of the poorer classes. Dr. Kerr has pointed out that dullards are generally below the mean height. The effects of heredity and home environment, underfeeding, neglect, and 550 HYGIENE AND PUBLIC HEALTH bad conditions of the. mother's life (before and after birth) are very evident in the anthropometrical data of schools in the very- poor districts of large cities. The only anthropometrical data which it is found possible to obtain at present under the scheme of medical inspection of elementary school children, relate to the weight and height ; but in many private schools chest measurements are also taken at the level of the nipple, both after emptying and expand- ing the lungs. The chief aims of anthropometrical observations are as follows : 1. To determine averages and standard deviations at different ages and for both sexes, having due regard to racial and environ- mental differences. 2. To correlate mental and physical growth, with a view to testing the efficiency of different systems of education and of indicating the amount of work that may advantageously be attempted at different ages, thereby minimizing the dangers of overpressure and adapting education to local needs. 3. To mark out the phj^sically or mentally unfit for special educational treatment. 4. Where the deviation is abnormal in a number of indi- viduals, a whole school, or a whole area, it would point to the necessit}^ for special investigations of social conditions and environment. The subjoined table shows that : 1. Boys are heavier than girls up to 12, but soon after 12 they lose their superiority for three years, regaining it by 16. 2. In boys the greatest increase occurs from about 14 to 16, in girls from about 12 to 15. 3. The rate of gro^vth is irregular or interrupted. Bo5^s are taller than girls up to 12, when girls pass them, and retain an advantage to nearly 15. 4. In boys the greatest annual increases are from 5 to 6 (almost 3 inches) and from 14 to 15 (about 3 inches) — viz., at the beginning and the end of elementary school education. 5. In girls the greatest annual increase is about 12. ' 6. In girls the annual increase is more uniform than in boj^s up to 14. 7. In girls growth begins to slow down between 12 and 13, and at 14I girls have nearly completed their growth, while boys grow rapidly up to 19. SCHOOL HYGIENE 551 8. Girls of 13 and 14 are generally taller and heavier than boys of the same age. Anthropometrical Measurements (Anthropometrical Committee of THE British Association), 1 Age. s Average Weight (in pounds). Average Height (in inch es). Boys. Increase. Girls. Increase. Boys. Increase. Girls. Increase. 39-9 39-2 . 41-03 40-55 6 44-4 4-5 41-7, 2-S 44-00 2-97 42-88 2-33 7 49-7 5-3 47-S S-8 45-97 1-97 44-45 1-57 8 .H-9 5-2 S2-I 4-6 47-05 1-08 46-60 2-15 9 60-4 5-S S5-S 3-4 49-70 2-65 48-73 2-13 10 67-S 7-1 62-0 6-5 51-84 2-14 5 1 '05 2-32 II 72'0 4-5 68-1 6-1 53-50 1-66 53-IO 2-05 ' 12 76-7 4-7 76-4 8-3 54-99 1-49 55-66 2-56 13 82-6 5-9 87-2 IO-8 56-91 1-92 57-77 2-11 14 92-0 9-4 96-7 9-5 59-33 2-42 59-80 2-03 IS i02'7 10-7 106-3 9-6 62-24 2-91 60-93 1-13 16 iig-o i6-3 II3-I 6-8 j i 64-31 2-07 61-75 1 0-82 3. The Spread of Infection in Schools. Among the means of spreading infection by personal communi- cation, compulsory school attendance at the most susceptible period of life must occupy a prominent place. At the present time we are dependent in our efforts to prevent the spread of infection in schools on (a) the compulsory information supplied under the Infectious Disease Notification Act, and (&) on the information supplied by teachers and others, as to measles, whooping-cough, etc., in the districts where these diseases are not compulsorily notifiable. It is now usual for the medical officer of health, on the receipt of the notification of a case of infectious disease in the person of a child attending school, to inform the school authorities of the case, so that all children in the same house attending school may be excluded until the premises are declared free from infection. If the child attacked is promptly removed to an isolation hospital, the room, clothes, and bedding can be at once disinfected, and the other children may be allowed to return to school on the expiration of the number of days corresponding to the maximum incubation period of the disease in question. If the child attacked is kept at home during its illness, the other children in the house must be excluded from school until the recovery of the patient, and 552 HYGIENE AND PUBLIC HEALTH the disinfection of the premises. The diseases for which these precautions are especially necessary are small-pox, typhus, diphtheria, and scarlet fever ; and measles and whooping-cough, when such children are attending the infant departments of schools. It is safe to conclude that, excluding the infant department, the large majority of children attending school have already suffered from measles ; but in this, as in other infectious diseases, the proportions of those who have previously suffered will vary in different schools, and in different classes ; and it is a great advantage in our efforts to control the spread of infectious disease to be able to refer to an infectious fever history of the scholars in each class. In the case of measles and whooping- cough, school closure rarely proves of value ; good results have more often been obtained by closing a classroom on the ninth day after the occurrence of the first case, for five days ; and then readmitting to the class only those who are quite free from any suspicious S57mptoms. A similar procedure may be adopted in reference to mumps, chicken-pox, and whooping-cough. During the prevalence of measles all children with " colds " should be excluded for three days, and the same rigid exclusion of all those who might conceivably be sickening has to be prac- tised during the prevalence of other infectious diseases. In those cases where it seems desirable to go beyond the closure of a classroom or of a department and to close the school, neigh- bouring schools should be included in special circumstances, and the Sunday-schools should then also be closed. But only when there is imminent risk of an epidemic, or when the evidence points to a school or class as a source of infection, should class or school closure be resorted to. Certainly school closure in urban dis- tricts never offers the same advantages as school closure in rural districts, because in the former case the children mix so much out of school. The best preventive results are to be expected from a prompt exclusion of all suspects and carrier cases of infection ; and as school teachers become better informed and more skilled in detecting suspicious cases of early infection, and as a frequent medical inspection of scholars during the epidemic prevalence of disease is more generally provided, the occasions on which school closure is demanded will become few and far between. In this connection it is only necessary to allude to the significance of brief absences of SCHOOL HYGIENE 553 scholars, when infectious disease is prevalent in the district. and the dangers of then attempting to maintain high average attendances. Whenever a sufferer, a contact, or a suspect, is excluded from school, it is important that a knowledge of this fact should be shared by the school medical officer, the medical officer of health, and the head-teacher of the school ; and that preventive measures should include such inter-notification as will secure this end. Moreover, the school-attendance officer should notify any such cases not already known to the school medical officer, the medical officer of health, and the head-teacher. It may also be neces- sary to obtain the closure of elementary schools for defective sanitary arrangements, which appear to have some connection with illness (such as enteric fever, diarrhoea, or diphtheria) occurring amongst the scholars. To enable a decision to be arrived at as to what extra measures are called for, in order to reduce the spread of infection at schools, it is necessary to appreciate the fact that a larger part of the spread results from undiagnosed mild cases of infection than from children resuming school attendance too soon after the disease has been diagnosed and treated. The measure which has met \\dth most favour is to submit the scholars to repeated medical inspections during the exceptional prevalence of infec- tious disease, and to exclude all suspects from school attendance. A good knowledge of the early sjonptoms of infectious diseases enables teachers to take similar action day by day. It is most im- portant that greater efforts should be made to promote this know- ledge among school teachers. A medical man or woman should in non-epidemic times examine the scholars occasionally, wdth the view of detecting those numerous conditions which unfit a scholar temporarily for school attendance, or which require early correction, such as developmental defects, faulty vision, over- pressure, and diseased conditions not necessarily infectious. He should also be able to make a prompt examination of every pupil referred to him at any time by a teacher, and should lecture to and instruct the teachers upon the sjmiptoms of disease in school life. All suspicious cases should be excluded from school, and after diagnosis should be handed over to the care of their regular medical attendant, when such exists. The common symptoms of fever are : — Irritability, peevish- ness and drowsiness ; nausea and vomiting ; shivering fits ; head- 554 HYGIENE AND PUBLIC HEALTH ache ; loss of appetite, coated tongue and thirst ; frequent pulse and respirations ; hot, dry skin or sweating ; temperature above 100° F. The chief special symptoms of infectious fevers are : — Diphtheria.' — Extreme prostration ; sore throat, with dirt}^ white patches on tonsils ; often noisy breathing and hoarseness, swelling of glands at angles of lower jaw and nasal discharge (" Nasal Diphtheria "). No rash. Scarlet Fever or Scarlatina. — Sore throat ; vomiting ; " straw- berry tongue " ; bright red rash, first on neck and upper chest, and then spreading over bod}/ ; later a branny peeling of skin. May be discharge from ear. Measles. — Symptoms of a bad " cold in the head "; then after three days a blotchy dusky-red rash appears on face and hands, soon spreading over body ; often a hard cough ; sometimes sore throat. German Measles. — A rash, somewhat similar to Measles, but preceded by sore throat instead of cold in head. Whooping- Cough. — A week or two of ordinary cough and then a series of short violent expiratory coughs, followed by a long crowing inspiration (" whoop "), which may be followed by vomiting or nose-bleeding. Mumps. — Painful swellings at sides of the neck, in front and below ear ; sometimes only on one side. Enteric or Typhoid Fever. — Frontal headache ; pains in limbs ; nausea and vomiting ; prostration ; generally diarrhoea. A few small pink spots, chiefly on abdomen, after the tenth day of illness. Small-Pox. — Sickness, backache and considerable illness for a day or two ; then pimples appear, first on face ; these become watery blebs in 3 days and crusts in another few days. Chicken-Pox. — Mild fever. Scattered pimples, first on bod}/ and fewest on face ; rapidly becoming water}/ blisters. Crusts in 4 or 5 days. N.B. — If child has been vaccinated Small-pox is generally very mild and resembles Chicken-pox. Typhus. — Marked fever ; great nervous disturbance (prostra- tion, depression, etc.). Mulberry-hued spots and mottling of skin in parts — chiefly over stomach and on chest. Influenza. — Shivering attacks ; sneezing ; running of eyes and nose ; pains in limbs ; great prostration ; often cough. SCHOOL HYGIENE 555 Epidemic Cerebrospinal Fever. — Intense headache ; persistent vomiting ; stiffness and retraction of neck ; pain down spine ; drowsiness ; varied rashes. Tuberculosis of Ltmgs (Consumption). — Lassitude ; loss of strength ; wasting ; cough and shortness of breath. The danger of infection is not necessarily proportional to the severity of the attack. " A sudden cold in the nose or throat, a hot face, unnaturally bright eyes, a rash, a swollen neck, a cough ending in the charac- teristic whoop, a fit of sickness or shivering, a day or two of un- usual irritability, are all signs which no one can afford to neglect." — Board of Education. The circumstances favouring the spread of infectious diseases at school are : Mild and unrecognized cases ; " carrier " cases ; and those incubating and in early stages of infectious diseases (especially Measles and Whooping-Cough). The close personal contact of scholars in classrooms and at play. The favourable ages of the scholars. The too hasty return to school of sick children and " contacts." The favouring circumstances of cloakrooms, and of school books, etc., used in common. The special precautions when an epidemic threatens or is established, are : — Inspection of Scholars. Cleansing and Disinfection. The exclusion of children with possible Fever symptoms, such as — If Diphtheria. — ^Those mth sore throat, enlarged glands in neck or nasal discharge. If Scarlet Fever or German Measles. — ^Those with sore throat. If Measles or Influenza. — Those with severe " cold," with sneezing, redness of eyes and running of nose. If Whooping-Cough. — Those with a violent cough. // Small-Pox. — -Those with headache, vomiting and pain in back. If Enteric Fever. — Those with diarrhoea and abdominal dis- comfort or pain. // Mumps. — Those with a swelling in front of or below ears. The Education (Administrative Provisions) Act of 1907 re- quires the Medical Inspection of all elementary school children at the period of commencing school attendance, and on such other occasions as the Board of Education may direct, and gives the local Education Authority power to make such arrange- 556 HYGIENE AND PUBLIC HEALTH ments in the health interests of the child as the Board of Educa- tion may sanction. Since the passing of this' Act the Board of Education has issued several circulars upon the subject of the medical inspec- tion of children in public elementary schools. In the circular issued November, 1907, stress is laid upon the fact that school hygiene cannot be divorced from home hygiene, and that, gener- ally speaking, the work of the inspection should be supervised by the medical officer of health of the authority which appoints the Education Committee. In appointing assistants for this work, it is suggested that preference should be given to medical men and women who have been trained in State medicine or hold the Diploma in Public Health, who have had some definite experience of school hygiene, and special opportunities for the study of dis- eases in children; the teach er,the school nurse (where such exists), and the parents or guardians of the child must heartily co-operate with the school medical officer ; the character and degree of medical inspection is to embrace medical examination and super- vision, not only of children known to be weakly or ailing, but of all children of the elementary schools, with a view to adapting and modifying the system of education to the needs and capacities of the child, procuring the early detection of unsuspected defects, checking incipient maladies at their onset, and furnishing the facts which will guide educational authorities in relation to the physical and mental development of the school child. The Board maintains that not less than three inspections during the school life of the child will be necessary to secure the results desiied — namely, the first at the time of admission to school ; the second at or about the third year of school attendance ; and the third at or about the sixth year. A further inspection im- mediately before the departure of the child into working life is also advocated. It is required that the inspections should be made in school hours and on school premises ; and that the facts revealed by inspection must be entered in a register kept at the school, a copy of the entries being transmitted to any other school to which the child may go. Every school medical officer must report annually to the Local Education Authority, and send two copies of the report to the Board of Education ; the report to deal with the calendar year. Local Education Author- ities are to make arrangements without delay for obtaining amelioration of the evils revealed by medical inspection. SCHOOL HYGIENE 557 In a circular issued in August, 1908, the Board of Education draws attention to the fact that the school medical officer of the Local Education Authority is for the first time recognized, in the Education Code of 1908, as an officer having specific functions, as follows : 1. Those of reporting on the working and effect of any arrange- ments made under Article 44 for educating children at open-air schools or other places selected with the view to the improve- ment of the health and physical condition of the children. 2. The power of advising or approving the closure of the school on account of infectious disease. 3. The power of authorizing the exclusion of certain children from school on the grounds that such exclusion may prevent the spread of infectious disease. The New Code also makes it a condition of grant that satisfac- tory provision for the medical inspection of children shall be made. In this circular it is further pointed out that where medical inspection reveals defects, the first step should be to notify parents, and to urge the desirability of obtaining treat- ment by medical practitioners ; that a school nurse is useful in assisting in the work of medical inspection, and in applying, or showing the parents how to apply, remedies for minor ailments ; that after efforts to obtain the provision of spectacles by the child's parents or by any voluntary associations have failed, the Board will consider proposals for a Local Education Authority to provide these free of charge ; that before direct treatment of ailments is undertaken by the Local Education Authority, whether by means of a school clinic or by themselves supplying and paying for medical treatment, full advantage should be taken of the benefits of such institutions as hospitals, dispensaries, etc., to the funds of which they are empowered to make a contribution. To whatever extent medical inspection may lead to the detec- tion and alleviation of physical defects in school children, to a corresponding extent will children gain in general health and development ; better results will be obtained from the teaching at school ; the more healthy and physically fit child wiU be less a drag upon the resources of the family ; and the State and pos- terity will benefit from a healthier stock. Dr. Thresh has compiled the following statistical table (1909J, compiled from the results of the medical inspection of over 55^ HYGIENE AND PUBLIC HEALTH 40,000 children in certain counties and towns in England during igo8 and 1909 : orted to be suffering Uncleanly head and b Enlarged tonsils from- ody ^ Apparent Average Percentage. i8-o 13-0 Defective vision 13-0 Defective nutrition 8-0 Adenoids . 8-0 Badly decayed teeth Eye disease Bodily deformity Skin disease 8-0 3.0 2-4 1-9 External ear disease 1-8 Heart disease i-S Lung affections . Mentally defective Tuberculous disease 1-4 1-3 0-8 Summary of Regulations (London County Council) with Regard TO THE Exclusion of Children from School on Account of Infectious Diseases. Disease. E.xclusion of Children suffering from the Disease. Small-pox. Cholera. Diphtheria. Merabraneous Croup. Scarlet Fever or Scarla- tina. Erysipelas. Typhoid Fever or Enteric Fever. 'Measles. Exclusion of Children living in Houses where the Disease exists. (i) Until the medical at- tendant certifies, if the case is treated at home. (2) Until after discharge from hospital. ( 1 ) If the case is treated at home, until a medical certificate, based upon bacteriological exami- nation, is furnished. (2) Until a fortnight after date of discharge from hospital. (i) Until the medical at- tendant certifies, if the case is treated at home. (2) Until a fortnight after date of discharge from hospital. (i) Until thfe medical at- tendant certifies, if the case is treated at honae. (2) Until after discharge from hospital. At least one month. Until 7 days shall have elapsed after the date of the certificate from the Medical Officer of Health that the house is free from infection. In the event of the head-tea- cher not receiving the certificate that the pre- mises are free from in- fection, it becomes his duty to send to the of&ces of the local Sani- tary Authority, in order that he may procure it. Not to be excluded. No proceedings to be talien to enforce attendance if xAIedical Officer of Health specifically orders ex- clusion. Infants. — All infants to be excluded, until Monday following 14 days from occurrence of last case. SCHOOL HYGIENE 550 Summary of Regulations (London County Council) with Regard TO THE Exclusion of Children from School on Account of Infectious Diseases. — Continued. Disease. Measles. Mumps. Wliooping- cough. Chicken-pox. Ringworm, Favus. Ophthalmia, (BUght). rrachoma. Scabies (Itch). Consumption. Exclusion of Children suffering from the Disease. At least one month. One month. As long as the cough con- tinues, but not to be readmitted until at least 5 weeks from the commencement of whooping. Two weeks, or until every scab is off scalp or body. Until medical certihcate is obtained that the child is cured. Where- ever certificates are not readily procurable, teachers to exercise their discretion as to readmission, and, if in doubt, to ask school nurse. Exclude if the disease is accompanied by cough- ing or spitting. Exclusion of Children living_ in Houses where the Disease exists. Seniors. — If child has had the disease, not to be excluded. If child has not had the disease, ex- clude until Monday fol- lowing 14 days from occurrence oi first case. Infants. — All infants to be excluded for such time as medical attendant considers necessary. If no medical attendant, for three weeks. Seniors. — If child has had the disease, not to be excluded. If child has not had the disease, ex- clude for the same period as infants. Infants. — -All infants to be excluded two weeks. Seniors. — If child has had the disease, not to be excluded. If child has not had the disease, ex- clude for two weeks. Infants. — All infants to be excluded two weeks. Seniors. — If child has had the disease, not to be excluded. If child has not had the disease, ex- clude for two weeks. Not to be excluded. Ditto. Note. — If a medical attendant or the Medical Of&cer of Health should certify, in any special case, that the above periods of exclusion should be extended, teachers are to observe their instructions, and to at once com- municate with the Medical Of&cer (Education). ibo HYGIENE AND PUBLIC HEALTH SCHEDULE OF MEDICAL INSPECTION ISSUED BY THE BOARD OF EDUCATION. Schedule of Medical Inspection. Date of birth 1. Address School I. — Name II. — Personal History : (a) Previous illnesses of child (before admission). ]\Ieasles. Whooping- Chicken- cough, pox. Scarlet Fever. Diph- theria. Other Illnesses.2 (b) Family medical history (if exceptional).'^ 1. Date of inspection . . . . 2. Standard and regularity of atten- dance^ . . . . . 3. Age of child ^ . . . . . 4. Clothing and footgear^ III. — General Conditions. !;. Height" ...... 6. Weight^ 7. Nutrition^ . . . . . 8. Cleanliness and condition of skin^*^ Head Body IV. — Special Conditions. 9. Teeth" 10. Nose and throat 12 . Tonsils .... Adenoids .... I Submaxillary and cervical glands 11. External ej-e disease ^^ 12. Vision^* ..... R L 13. Ear disease ^^ .... 14. Hearing 1^ .... 15. Speech I'' .... 16. Mental condition ^^ . V — Disease or Deformity.^^ 17. Heart and circulation-^ . 18. Lungs 21 19. Nervous system 22 20. Tuberculosis 2 3 . 21. Rickets^* 22. Deformities, spinal disease, etc.^'' 23. Infectious or contagious disease ^^ 24. Other disease or defect.^" . Medical ofiScer's initials II. III. IV. General Observations. Directions to Parent or Teacher. SCHOOL HYGIENE 561 Reference Number N'OTES FOR INSPECTING OFFICER. of Note. ^ Date of birth to be stated exactly, date of month and year. - " Other illnesses " should include any other serious disorder which must be taken into account as affecting, directly or indirectly, the health of the child in after-life — e.g., rheumatism, tuberculosis, congenital syphiUs, small-pox, enteric fever, meningitis, fits, mumps, etc. The effects of these, if still traceable, should be recorded. •^ State if any cases of, or deaths from, phthisis, etc., in family. * Note backwardness. 5 Age to be stated in years and months, thus, 5t"V. ^ Insufficiency, need of repair, and uncleanliness should be recorded (good, average, iDad). ''' Without boots, standing erect with feet together, and the weight thrown on heels, and not on toes, or outside of feet. ^ Without boots, otherwise ordinary indoor clothes. Height and weight may be recorded in English measures, if preferred. In annual report, however, the final averages should be recorded in both English and metric measures. ^ General nutrition as distinct from muscular development or physique as such. State whether good, normal, below normal, or bad. Under- nourishment is the point to determine. Appearance of skin and hair, expression, and redness or pallor of mucous membrane, are among the indications. ^'^ Cleanliness may be stated generally as clean, somewhat dirty, dirty. It must be judged for head and body separately. The skin of the body should be examined for cleanliness, vermin, etc. ; and the hair for scurf, nits, vermin, or sores. At the same time ringworm and other skin diseases should be looked for. ^^ General condition and cleanliness of temporary and permanent teeth and amount of decay. Exceptional features, such as Hutchinsonian teeth, should be noted. Oral sepsis. ^^ The presence or absence of obstruction in the naso-pharynx is the chief point to note. Observation should include mouth-breathing ; inflamma- tion, enlargement, or suppuration of tonsils ; probable or obvious presence of adenoids, polypi ; specific or other nasal discharge, catarrh, malformation (palate), etc. ^3 Including blepharitis, conjunctivitis, diseases of cornea and lens, muscular defects (squints, nystagmus, twitchings), etc. 1* To be tested by Snellen's test types at 20 feet distance (=6 metres). Result to be recorded in the usual way — e.g., normal V. =^. Examination of each eye (R. and L.) should as a rule be undertaken separatel}^. If 6 the ^ . be worse than -, or if there be signs of eyestrain or headache, fuller examination should be made subsequently. Omit vision testing of childten under six years of age. ^^ Including suppuration, obstruction, etc. ^^ If hearing be abnormal, or such as interferes with class-work, subse- quent examination of each ear should be undertaken separately. Apply tests only in a general way in case of children under six years of age'. 1^ Including defects of articulation, lisping, stammering, etc. ^^ Including attention, response, signs of overstrain, etc. The general intelligence may be recorded under the following heads : [a) Bright, fair, dull, backward ; (&) mentally defective ; (c) imbecile. Omit testing mental capacity of children under six years of age. ^^ Under the following headings should be inserted particulars of diseased conditions actually present or signs of incipient disease. The extent of this part of the inspection will largely depend upon the findings under previous headings. ^° Include heart-sounds, position of apex-beat, anaemia, etc., in case of anything abnormal or requiring modification of school conditions or exercises. 36 562 HYGIENE AND PUBLIC HEALTH 2^ Including physical and clinical signs and symptoms. 22 Including chorea, epilepsy, paralysis, and nervous strains and disorders. ^^ Glandular, osseous, pulmonary, or other forms. 2* State particular form, especially in younger children. 22 Including defects and deformities of head, trunk, limbs. Spinal curvature, bone disease, deformed chest, shortened limbs, etc. 2^ Including any present infectious, parasitical, or contagious disease, or any sequelae existing. At each inspection the occurrence of any such diseases since last inspection should be noted. ^'' Any weakness, defect, or disease not included above — e.g., ruptures — specially unfitting child for ordinary school life or physical drill, or requir- ing either exemption from special branches of instruction, or particular supervision. CHAPTER XI DISINFECTION As already mentioned, the virus of a contagious disease undergoes enormous multiplication in the body of the sick person, and is cast off during the period of illness in the mucous discharges and secretions, in the breath, and from the skin. The contagion infects the air around the patient, and infects the bedding, clothes, and furniture of the sick-room. Disinfection aims at the destruc- tion of the virus in these various situations. In the first place, it would be natural to suppose that the infective particles might be destroyed before leaving the body, or as soon as they are carried into the air ; but chemical reagents strong enough to destroy specific micro-organisms would cause injury when taken into the system or when diffused into the air around the patient. Where the virus is only contained in the evacuations, as in enteric fever, these can be at once disinfected b}^ chemical solutions ; but in the case of the other common infectious maladies complete disinfection of a room and its contents is only possible when the patient is convalescent and no longer a source of infection himself. No agent can be regarded as a disinfectant unless it is capable of destroying the organisms with which it is brought into contact ; agents which merely inhibit bacterial growth and prevent de- composition are known as antiseptics ; while others, such as charcoal, which oxidize or absorb odorous products, are termed deodorants. Liquid disinfectant preparations are preferable to solid, for they can be much more efficientl}^ distributed ; and until a solid disinfectant is in solution, it is powerless to act directly upon organisms. The final results attained in disinfec- tion are greatly influenced by the nature of the material to be disinfected. Infectious organisms are always in association with a greater or less amount of other organic matter under natural conditions ; and the practical question which has to be answered 563 564 HYGIENE AND PUBLIC HEALTH is : — \Miat is the required strength of any disinfecting agent to ensure destruction of a given infection in its natural en\dronment ? Since disinfectants are intended for the destruction of the germs of specific diseases, it has long been recognized that the only satisfactory,' method of judging their relative values is by ascertaining the actual strengths at which the\- must be employed in order to kill these germs under certain fixed conditions. It is true that bacteriologists have already determined the action of many disinfectants on a variet}' of micro-organisms, but owing to the emploMuent by different obser^-ers of different methods, different organisms, and different standards of comparison, the discrepancy as to the relative value of disinfectants, that ma}- be found in the literature on the subject, is most perplexing, ^^1lat is wanted is a standard method of comparison that shall be both scientific and easily practicable, in which the various agents are tested side by side under precisely similar conditions. With this object Rideal and Walker have proposed that phenol should be taken as the standard disinfectant, and Bacillus typhosus as the standard germ in such tests. The suggested method of working is as follows : — ^To 5 c.c. of a particular dilution of the disinfectant in sterilized water are added 5 drops of a 24 horn- blood-heat culture of Bacillus typhosus in broth ; the mixture is shaken, sub-cultures are taken every 2^ minutes up to 15 minutes, and these are incubated for at least 48 hours at 38° C. The temperature during medication should be from 15 to 18^ C, and the standard broth employed should have a reaction of + 15. The strength or efhcienc}- of the disinfectant can then be expressed in multiples of carbolic acid, as follows : — a dilution of the disinfectant being obtained which does the same work as the standard carbolic acid dilution, the former is divided by the latter, and thus a ratio is obtained which is called the " carbolic acid coefficient." The method is useful as one upon which it majT- be found possible to base a practical test ; but it does not tell us of the strength at which the various disinfec- tants must be emploj-ed in actual practice, because it does not take into account the influence of the associated organic matter upon the potentialities of the disinfectant. In other words, we have not in practice to disinfect the typhoid organism in a broth culture, but the organism implanted in faeces and urine,' and often more or less protected from chemical disinfectants by siurrounding organic matter. DISINFECTION 565 In the Martin-Chick (Lister Institute) test for the standardiza- tion of disinfectants for practical purposes, the temperature for medication is fixed at 20° C, an interval of 15 minutes is allowed for the disinfectant to act on the test organism {Bacillus typhosus), and the germicidal value is not determined upon the naked organism in broth culture, but an emulsion is made containing 3 per cent, of human fseces, dried at 102° C, and subsequently sterilized by steam at 120° C, to which the test organism is added. The results obtained by the Martin- Chick test indicate " phenol coefficients," which are very much less than those obtained by the " drop " method of Rideal and Walker. From this it would appear that the germicidal proper- ties of many disinfectants of the coal tar series are very much reduced when the test organism is surrounded or protected by organic matter of the nature of human fasces. A modification of the Rideal- Walker " drop " method has been suggested {The Lancet, November 20, 1909), in which Bacillus coli communis is advocated as the test organism, instead of Bacillus typhosus. Disinfection may be carried out in several ways : — • 1. By burning or exposure to high temperatures (hot air, steam, boiling). 2. By the action of oxidizing agents (atmospheric air, ozone, nitric peroxide, peroxide of hydrogen, chlorine, chlorates, bleach- ing powder, etc.). Oxygen burns up all organic matter into carbonic acid, ammonia, and water ; but it exercises no selective influence on bacteria. Certain organisms die at once in atmo- spheres containing oxygen ; some cannot exist in the absence of oxygen ; while others are indifferent either to its presence or absence. Fresh air is universally regarded as a powerful, if slow, disin- fectant. Its powers in this respect are mainly due to the molecular oxygen contained in it ; if, however, oxygen can be liberated in a nascent atomic condition, its activity considerably exceeds that of atmospheric oxygen. The disinfectant properties of fresh air are enhanced by the actinic rays of sunlight. Rays of sunlight, in the presence of air and moisture, will destroy even resistant organisms after varying periods of exposure ; but there is no evidence of the destruction of the spores of anthrax bacilli by this means. The actinic rays probably exert their effects by promoting oxidation, or possibly by leading to the production of small quantities of ozone and peroxide of hydrogen — two powerful 566 HYGIENE AND PUBLIC HEALTH oxidizers. The ultra-violet rays are much more powerful in this respect than the infra-red. 3. B}^ the action of reducing agents (sulphurous acid, ferrous sulphate, etc.). 4. By agents which enter into combination with albumin (perchloride of mercury, sulphate of copper, etc.). These kill b}^ their action on the albumin of the organism ; or, by pre- cipitating the albuminous matter around the germ, they may rob it of its nourishment. 5. By agents which exercise a direct poisonous effect on micro-organisms (perchloride of mercur}^, iodide of mercury, phenols, etc.). Deodorants act by absorbing (slaked lime), condensing (char- coal), or oxidizing (permanganate of potash) odorous gases or vapours, such as sulphuretted hydrogen, ammonia, the com- pound ammonias, and some organic vapours. Many deodorants (charcoal, permanganate of potash, etc.) possess but little dis- infecting power. Having regard to the circumstances of actual practice, it must be borne in mind that no disinfectant can be expected to act instantaneously, for it cannot be brought to bear in sufficient volume upon all the organisms present ; hence the agent should possess some degree of permanence in its action. Those disin- fectants, for instance, which, by giving up oxygen, soon expend themselves in contact with organic matter, are inferior to sub- stances like carbolic acid, which have greater permanence of action, and exert a direct toxic effect upon organisms. In practice, no agent of the kind which does not perform its functions within a limit of about thirty minutes can be regarded as satis- factor3^ Preference should be given to one which is non- poisonous to the higher forms of animal life, cheap, readily soluble in water, and otherwise convenient in use. It should not injure utensils in which it is placed, or articles exposed to its action, nor should it possess an offensive odour. Burning. — This, the most efficient means of disinfection, can be applied often in the sick-room itself to all articles of little or no value. Rags used for receiving the discharges from the mouth and nose, or from the open wounds of patients in an in- fectious state, should be promptly placed upon the fire, before thej^ have time to become dry. Old mattresses, pillows, and other large articles which are not required for further use should DISINFECTION 5O7 be saturated ^vith paraffim and burned. This is generallj^ done in the small destructor which forms part of a disinfecting station. The stools of cholera and enteric fever patients may be cremated ; if no destructor be available for the purpose, they must be mixed with plenty of sawdust, and the mixture then saturated with paraffin and ignited. Boiling. — Infectious material which can be boiled for twenty minutes is thereby as a rule efficiently disinfected ; but there is evidence that some of the more resistant organisms {B. anthracis) maj^ resist boiling for longer periods. This method is most fre- quenth- employed for the purpose of disinfecting bed and body linen. It is important to bear in mind that if the articles are stained with albuminous matter, such as blood or faeces, the boiling tends to fix the stains ; on this account the stains should first be removed by soaking in cold water, and, if necessary, by rubbing with a little soap. Faeces have been disinfected in cauldrons by means of steam, or by boiling with strong solutions of Izal, etc. Hot Air. — This method of disinfecting textile articles is rapidly falling into disuse ; for the high temperature required to destroy resistant organisms injures the articles exposed, and an incon- veniently long period of exposure is necessary to secure sufficient penetration of the heat into the interior of bulky objects. Dry air being a bad conductor, the heat penetrates slowly and imper- fectly. Resistant bacteria placed in the interior of mattresses may survive an exposure of some three hours, even when the temperature to which the surfaces of the mattresses are exposed reaches 140° C. ; but a temperature exceeding 120° C. would certainly damage many articles, such as wool, leather, and silk. By this method, therefore, fabrics are often damaged by scorch- ing ; but, short of this, they are liable to suffer a change in colour, to shrink, and to lose elasticity and gloss. Stains, especially those of an albuminous nature (blood, faeces), are liable to become fixed ; but these can always be removed prior to disinfection by soaking and subsequent rubbing in cold water. Fusible sub- stances, such as glue and wax, are melted, and the overdrying renders many articles brittle. Dry heat is serviceable for articles of leather, -morocco, and india-rubber, and for furs, books, and some other objects which are injured by the employment of the more efficient method next to be described. 568 HYGIENE AND PUBLIC HEALTH Steam.— Stesim under pressure penetrates into bulky and badly conducting articles, such as mattresses, pillows, and clothing, far more rapidly than dry heat. As such steam penetrates into the interstices of a cold body, it undergoes con- densation, and imparts its latent heat instantaneously to the cold objects in contact with it. When thus condensed into water, it occupies only a very small fraction (about toVt) of its former volume. To fill the vacuum thus formed, more steam presses forward, in its turn yielding up its latent heat and becoming condensed, and so on until the whole mass has been penetrated. On the other hand, hot air in yielding up its heat undergoes contraction in volume, only to a very small extent as compared with that undergone by steam in con- densing to water. Body lice and their eggs are destroyed by exposure to steam at 100° C. for ten minutes, or to boiling water for five minutes. The various stoves now employed for disinfecting by steam may be classified as follows : 1. Stoves in which steam without pressure is employed. These are of course cheaper, but, as the temperature of the steam does not exceed ioo° C, less efficient than — 2. Those in which steam at low pressure (2, 3, or 5 pounds per square inch) is used. Although the temperature of 110° C, which can be reached by these stoves, is sufficient for most purposes, a higher temperature can never be employed in them. These stoves, though cheaper, are therefore less efficient than — 3. Those in which steam at high pressure (10 pounds and over) can be employed. A temperature of 115° C. to 120° C. — which should not be exceeded — can be obtained in these stoves ; and an exposure of articles for from a quarter to half an hour will suffice for their disinfection. The higher the pressure of the steam, the more rapid the penetration, and the less time required for disinfection. The steam, which must be free from air, may be current or con- fined. Current steam serves to drive the air out of the interstices of fabrics, and thus to aid penetration ; but since more steam is used, more fuel is consumed. In the stoves using steam confined under pressure, the steam should be allowed to escape from time to time, as this serves to displace the air (otherwise often compressed) in the centre of bulky articles. The greatest effect DISINFECTION 569 is of course produced when the steam has been under very high pressure. The steam employed may be saturated or superheated, the former being far preferable to the latter, omng to its more rapid and thorough penetration. The use of superheated steam, there- fore, involves a longer exposure in the chamber, and a greater expenditure of fuel, in addition to an increased liability to injure articles. The distinction between saturated and superheated steam is an important one. By increasing the pressure, steam may be generated at temperatures exceeding ioo° C, but it always remains saturated steam ; if, however, the steam is further raised in temperature without increasing the pressui-e, as may be done by bringing it into contact with a surface raised above its own temperature, it becomes superheated. Now, super- heated steam has properties similar to those of a gas, and will not condense until it has parted with all its " superheat " by the slow process of conduction ; whereas saturated steam, being a vapour, condenses at once on objects which are but slightly cooler than itself. Since penetration depends upon condensa- tion, the disinfectant value of superheated steam does not much exceed that of dry air. The amount of " superheat " which is generally given to the steam in practice is not, however, sufficient to cause it to act very differently from saturated steam. Steam, therefore, should not be superheated, or only to so slight an extent that it can at once condense upon any object slightly cooler than itself. The time required for disinfection by steam obviously depends on the organism to be destroyed, the bulk of the infected articles, and the pressure of the steam employed. The best researches indicate a temperature of 115° to 120° C. for twenty minutes, as alone trustworthy in all cases. Satisfactory provision must be made to ensure that the infected articles are not allowed to become too wet, as otherwise colours are liable to run ; and the disinfected articles should be fairly dry on removal. By bearing the foregoing facts in mind, an opinion upon the suitability and efficiency of any steam disinfector can be readily formed. The rapidity of the penetration of heat into articles is ascertained by placing them within a thermometer, which when the required temperature is reached causes a bell to ring hy reason 570 HYGIENE AND PUBLIC HEALTH of the mercury completing the circuit of an electric current from a batter}'. The efficiency of the provision for drying the articles is gauged by the amount of moisture remaining in them after removal from the stove, as calculated by the increase in weight of the article. The maximum temperature reached in the stove and the uniform distribution of the heat may be tested by means of recently standardized maximum thermometers \\T:apped up in blankets and exposed in the stove ; and the pressure within the stove can be ascertained at an}^ time by the external pressure gauge. The construction of the apparatus must be such as to combine simplicity of design \\ith facilitj' of management — so that highly skilled labour is not an absolute essential. The machines made under Washington Lyon's patents are most used in this countr}-. The " Nottingham " stove, made by Goddard, Massej^ and Warner, consists of a rectangular chamber with a double wall or jacket, the lower part of the jacket con- taining water and serving as the boiler. Steam is made to occupy the space between the double wall, at a pressure of some 20 pounds ; this serves to heat the walls of the chamber, and to a less extent the articles inside it, so that when the steam, also at a pressure of about 20 pounds, is allowed to fill the chamber, the condensation which would otherwise take place upon the walls of the chamber is prevented, and only a slight initial condensation on the surface of the now heated infected articles results. Articles are thus kept comparatively dry ; but before they are removed they are further dried, either by allowing the steam to remain in the jacket, after that in the interior of the chamber has been removed, or preferably by drawing off the steam from the chamber and then drying by means of a current of hot air. The hot air (heated bj^ steam, so as to limit the temperature and guard against scorching) can be drawn into the chamber by means of a vacuum apparatus. Steam exhausts are emplo^^ed in some apparatus to produce a partial vacuum in the chamber prior to the admission of the steam, and these greatly promote, by the withdraw^al of air, the rapidity of penetration. One of these stoves, of medium size, costs about £250. The stove {Washington-Lyon) made by ^lanlove, Alliott and Co., is oval in section, and the steam is led into the jacket and the chamber of the stove from a special detached boiler. The DISINFECTION 571 disinfector is fitted v^dth a vacuum apparatus and hot-air chamber. In working, steam is first admitted into the jacket ; then a vacuum is created in the oven, so as to withdraw air. Steam is then admitted into the oven, and a pressure equivalent to a temperature of 140° F. or 150° F. maintained for twenty- minutes. A vacuum is again produced, and finally air heated by passing over the steam coils in the hot-air chamber is ad- mitted, so as to dry the steam-heated articles. The whole process occupies rather over thirty minutes from the time the infected articles are introduced into the oven. There is an advantage in having a separate detached boiler, which can be readily inspected and tested for boiler insurance purposes. The Equifex Disinfector is a non-jacketed cylinder, into which steam at a pressure of 10 pounds, and a temperature of about 115° C, is admitted. The steam which first enters is allowed to blow off, so as to displace the air in the chamber ; and the pressure of the steam can be intermitted so as to facilitate penetration. Condensation upon the walls of the cylinder is prevented by an arrangement of coils inside the chamber which are first filled with steam at high pressure ; and articles are subsequently dried by hot air. A low-pressure apparatus is also made of the Equifex tj^pe. A medium size Equifex stove costs about ;£25o. Reek's Stove is a non-jacketed cylinder, in which current steam is employed at about i| pounds pressure (about 105° C), The apparatus is very simple and handy. Its special feature is an arrangement for the introduction at the top of the chamber of a shower of cold water, which falls upon an umbrella-shaped plate, and is thus diverted from the articles which have been disinfected. The sudden introduction of the cold shower after the goods have been disinfected causes a rapid condensation of all live steam, which is carried away ^vith the water through an outlet in the bottom of the stove, air entering automatically through a valve in the front of the apparatus to restore the partial vacuum produced by the condensation of the steam. In this way the chamber is freed of the steam, and the articles are dried ; but the drying is not quite so complete as in most other forms of apparatus. The original stove has been improved by sur- rounding the disinfecting chamber with a water-jacket, by which sufficient heat is retained to dry the clothes when air is admitted. 572 HYGIENE AND PUBLIC HEALTH Thresh's Stove. — Here current steam is emploj^ed, \'\ithout pressure, at a temperature of about 105° C, the " superheat " being obtained b}^ using in the boiler a calcium chloride solution, the boiling point of which is considerably' above that of water. The lower part of the jacket of the cylinder, which contains the saline solution, acts as the boiler, and is heated by a small furnace. The steam, which enters the chamber, escapes continuous^ through a chimney. For the subsequent displacement of the steam and for the dr\dng of the articles, hot air is dra^^^l into the chamber through a coil of tubes, -which is surrounded and heated bv the boiling solution. The medium size stove costs about ;^I25. A current saturated pressure steam disinfector (Delepine- Jones) has been lately introduced b}:^ the Thresh Disinfector Companj'. Steam disinfectors are made portable, so that they may be taken to infected premises, or be moved from tillage to village. Their cost varies from about 60 to 150 guineas, according to the size. In all those apparatus in \^-hich steam is employed at a low pressure or in a superheated form (i.e., at temperatures not exceeding 104" to no" C), objects should be exposed for at least one hour. A disinfecting station should comprise : 1. Two rooms completely separated from each other by a wall, into which the stove is built, so that it communicates with both rooms. The infected articles are brought into one room and placed in the stove, and after disinfection the}' are removed from the other end of the stove, which opens into the non-infected room. No infectious material must be allowed to enter the non- infected room, and there should be no direct means of com- munication between it and the infected room. The workers in the infected side should always wear " overalls." The floors and walls of both rooms should be made of some smooth and non-porous material, which can be readily and efficienth' cleansed by water ; and exceptionall\- good provision should be made for ventilation and light. 2. An incinerator or destructor, pro\'ided ^^•ith a small second hre to cremate the products of imperfect combustion before thev pass up the flue. 3. Separate sheds must be provided for [a) vans emplo3-ed to DISINFECTION 573 bring in infected articles, and (b) those employed to return the disinfected articles. 4. A laundry and bath-room sometimes form part of a dis- infecting station, a charge being made for any laundry work undertaken. 574 HYGIENE AND PUBLIC HEALTH Liquid Disinfectants. Solutions of the follo^^^ng substances are employed : Perchloride of Mercury (HgCl^, corrosive sublimate). — ^This is one of the most powerful and one of the most convenient dis- infectant agents known. It forms a colourless, non-odorous DISINFECTION D/D solution, which is, however, poisonous to human beings. Unless the solution is acidulated, it has a marked precipitating effect upon albumin, and its power of penetration into the interior of particles of organic matter is thereby limited. It acts as a direct poison to bacteria, and also exerts its disin- fectant action by coagulating their protoplasm. One part of the salt to i,ooo parts of water constitutes a stronger disinfectant than even 5 per cent, carbolic solution, and it is trustworthy for the disinfection of non-spore-bearing bacteria ; but i in 500 is necessary for spore-bearing bacteria. The solution should not be stored in metal receptacles, as it corrodes them, and is then liable to decomposition. It should always be made distinctly acid, and a little colouring matter should be added to guard against its being swallowed in mistake for water. For the same reason it should be placed in dark blue bottles bearing a large poison label. Half an ounce of per chloride of mercury, i ounce of hydro- chloric acid, and i grain of aniline blue, to 3 gallons of water, is a mixture which costs about fourpence, and furnishes a non- staining disinfectant solution, containing about i in 1,000 of the per chloride. The salt has been made up into tablets of about i ounce each in weight, so that one tablet to a quart of water furnishes a solution of i in 1,000 of the perchloride. This constitutes a portable form, convenient to travellers and troops on the march ; but there is risk in introducing the tablets, which look verj^ like sweets, into ordinary households. Mercuric Iodide (Hgig) is less poisonous than the perchloride, and does not precipitate albumin to the same extent. Its dis- infectant power is at least equal to, and there is evidence that it even excels, that of the perchloride. It constitutes an excellent disinfectant solution for the hands. Although insoluble in pure water, it is readily soluble in the presence of excess of iodide of potassium. Like the perchloride, it attacks metals. Phenols are obtained from tar distillates as dark oih^ liquids, which contain in the crude State, besides the many members of the phenol group, the neutral tar oils. Phenols are poisonous, possess a caustic action, and coagulate albumin. Carbolic Acid (CgHgO) is the member of the group most em- ployed for disinfectant purposes, although its powers are slightly inferior to those of cresylic acid (C7H8O). It is not a true 576 HYGIENE AND PUBLIC HEALTH deodorant, but it masks offensive gases and vapours by its own strong and unpleasant odour. A 5 per cent, solution at least must be employed against resistant organisms. Many trade pro- ducts, consisting of oils procured from the destructive distillation of coal, are on the market, and they for the most part possess disinfectant value similar to that of carbolic acid. They are mostly dark brown liquids which, when added to water, form milky emulsions, one advantage in their use being that they are practically non-poisonous, and somewhat cheaper than pure carbolic acid. Izal, containing a body allied to the phenols of the carbolic acid series, is a powerful and valuable disinfectant ; it is practically non-poisonous. It mixes well with water and has an agreeable odour. According to Klein, an emulsion of i in 200 disinfects non-spore-bearing organisms in 5 minutes, and a 10 per cent, solution kills even the virulent spores of Bacillus anthracis in about 15 minutes. Cyllin is very 'similar to Izal in its disinfec- tant property. Saprol is a dark brown oily fluid, much used in Germany ; it appears to be of similar strength to carbolic acid, and possesses the advantage that, while its contained phenols mix with a liquid, an oily film floats over its surface. The disinfectants, like izal, cyllin, lysol, sanitas-okol, sanitas- bactox, kerol, MacDougal's M.O.H. fluid, Lawes' fluid, Cooke's cofectant fluid, Jeyes' fluid, etc., which are coal tar derivatives, contain varying proportions of phenols, neutral oils, resins and fatty acids, and water. Most of them are able to form emulsions with water by reason of the presence of the resins and fatty acids ; but in some a non-resinous emulsifier, such as gelatine, is used. It seems probable that the activity of these disinfectants is in part dependent on the fineness of the emulsification formed when the crude article is mixed with water. The fine particles of an emulsion are in a constant state of Brownian movement, and thus a kind of bombardment of the micro-organisms is kept up by these incessant movements of the disinfectant molecules. In the presence of organic matter, however, whether in solution or in suspension, the Brownian movements of the particles of the emulsion appear to be impeded, with the result that the germi- cidal action of the emulsified disinfectant is not nearly so great as when it has to act only on the naked organism. Where the organisms to be destroyed are in the presence of an excess of organic matter, it is possible that emulsions may have but little advantage over clear solutions. DISINFECTION 577 Chloride of Lime (CaClgO, bleaching powder) is a mixture of chloride and hypochlorite of calcium, and should contain about 35 per cent, of available chlorine. It gives off a most unpleasant odour. Chloride of lime solution is made by first stirring up the bleaching powder with a little water so as to make a thick cream, and then diluting to the required extent. The solution exerts a corrosive action on metals ; it tends to dissolve the albimiin of faecal and other matter, and its powers may be entirely exhausted upon such organic matter, bacteria conse- quently escaping. The disinfectant and deodorizing action of the solution is due to the fact that, in presence of moisture and carbonic or other acids, hypochlorous acid (HCIO) is liberated, and this acts as an oxidizing agent by splitting up into HCl, and O. A 1-5 per cent, solution of the powder (about 2J ounces to the gallon), containing 0-5 per cent, of available chlorine, should generally be employed, except when dealing with organisms whose resistance is known to be slight ; in such cases experiments show that a solution containing i part of chlorine in 1,000 ^^dll suffice. Sodium Hypochlorite, like bleaching powder, possesses consider- able disinfecting power on account of its available chlorine. The strength at which it should be employed must be governed by the fact that the solution should contain in practice at least 0-5 per cent, of available chlorine, except where organisms of little resistance are to be dealt with. A liquid on the market, sold as Chloros, contains 10 per cent, of available chlorine. Solutions of hypochlorites are apt to lose their strength somewhat on keeping ; they should therefore be kept tightly stoppered in a dark place. The absence of lime renders a solution of sodium hypochlorite preferable to one of bleaching powder, when the disinfectant is to be emptied down the drains. Hypochlorous Acid is formed by the electrolysis of sea- water (Hermite process), which is thereby constituted a powerful deodorizing, but weak and unstable, disinfectant solution. The electrolysis of a solution of magnesium and sodium chlorides produces a mixture containing available chlorine in a more stable condition than is the case with electrolysed sea-water. Hydrochloric and other mineral acids are markedly disinfectant when employed in such strengths as will give the solution a marked acid reaction. Sulphate of Copper (CuSO^). — In 5 per cent, solution this salt is a powerful disinfectant. It acts by coagulating albumin and 37 57^ HYGIENE AND PUBLIC HEALTH b}' exerting a poisonous action on bacteria. It will absorb ammonia, the compound ammonias, sulphuretted hydrogen, etc., and is therefore a useful deodorant. Chloride of Zinc (ZnCl2) is a poisonous salt with very similar properties to those of sulphate of copper. A lo per cent, solution, to which a little hydrochloric acid has been added, should be employed where spores are concerned, but 5 per cent, will suffice for non-spore-bearing bacteria ; it has, however, a corrosive action if used in solutions containing much more than 5 per cent, of the salt. Its disinfectant powers are somewhat inferior to those of sulphate of copper, but they are far superior to those of ferrous sulphate. " Burnett's Fluid " contains about 50 per cent, of ZnClg. Ferrous Sulphate (FeS047H20, Green Copperas) acts mainly by its reducing action while taking up oxygen to become a ferric salt. It is a feeble disinfectant unless used in great strength (20 to 30 per cent.), but it is a good deodorant, absorbing ammonia and sulphuretted hydrogen. In practice it is suitable only for excreta, as it stains badly, and tends to form iron moulds. The same general remarks appl}' to FegClg, which is, however, a feeble oxidizer. " Chinosol " is a readily soluble crystalline yellow powder, \v\t\i a slight aromatic odour, belonging to the quinoline group. Its solution is non-poisonous and non-corrosive, does not coagulate albumin, and possesses marked deodorant properties. There is satisfactory' experimental evidence to show that a i in 1,000 solution \\dll rank ^^'ith perchloride of mercury solution of similar strength. Potassium Permanganate (K2Mn20g) is an oxidizing agent which can only be used in practice in weak solutions as a deodorant, since a 5 per cent, solution, at least, is required for the dis- infection of resistant organisms. A solution of this strength would be expensive, and would stain everything ^vith which it came in contact. Gases, like sulphuretted hydrogen, reducing salts in solution, and the more unstable organic matter, first rob the permanganate of its oxygen ; and the whole of the permanganic radical may be reduced to black manganic oxide, or even to a lower oxide, before the bacteria are destroyed. " Condy's Red Fluid " is a mixture of the permanganate and sulphate of soda. DISINFECTION 579 Formic Aldehyde (CHOH), in solution of i to 2 per cent., is a liquid giving off an irritating odour, and ranking high as a rapid disinfectant and deodorant ; it costs far less than carbolic acid of equal disinfectant strength. An aldehyde is an alcohol dehydrogenated ; thus, wood spirit (methyl alcohol, CH3OH), when deprived of Hg, becomes CHOH, called formic aldehyde because it very readily changes to formic acid (CHOOH). In aqueous solution the gas can be concentrated to about 40 per cent., in which state it is sold as " Formalin." Sanitas Fluid has the odour of pine wood and is a practically non-poisonous liquid. Used in the strength of 10 per cent, in water it is said to be capable of destroying non-spore-bearing organisms in 10 minutes. It is one of the less powerful disin- fectants. Gaseous Disinfectants. Formic Aldehyde is also used as a gaseous disinfectant. The aldehyde vapours, which are non-poisonous, but very irritating to the eyes and throat, are powerfully disinfectant and deodorant. So far as their application for the purpose of the surface disin- fection of rooms is concerned, they may be regarded as likely to fulfil aU the requirements of general practice, if they are employed in sufficient quantities. Formic aldehyde is more rapidly disinfectant than equal quantities of sulphurous acid, and it does not affect colours or (with the exception of iron or steel) metallic surfaces, although it fixes stains of blood or faeces. It is somewhat difficult to confine to the room, but there is no danger and little difficulty attending its practical application if the rooms are well sealed up. Formalin vapour is most efficacious at a temperature of 70° F. and a humidity of 70 per cent. ; if temperature and humidity are much below these optimum conditions, the disinfection can hardly be regarded as reliable. The production of the gas by means of specially devised methyl- alcohol lamps is often imperfect and unsatisfactory in practice. In these the aldehyde is generated by allowing the vapour of wood alcohol, well mixed with air, to pass over the surface of red-hot platinum, when the alcohol is converted into aldehyde and water. The gas can best be liberated from formalin by means of Trillat's apparatus, in which the formalin is heated under pressure in an autoclave. A little calcium chloride is 58o HYGIENE AND PUBLIC HEALTH placed in the solution, which is then known as " formo-chlorol/' and as the boiHng point of the calcium chloride solution is above 100° C, and the aldehyde is given off below 'that temperature, it may in this manner be obtained in a practically dry state- When the attached pressure gauge registers a pressure of 40 pounds in the autoclave, the vapours are allowed to escape through a long thin copper tube, which is passed through the keyhole into the infected compartment. The apparatus costs about £18. Half an hour is required to get up the necessary pressure, and in an ordinary sized room the vapours would be allowed to escape for about half an hour. From ^ to i litre of formo-chlorol should be employed for every 1,000 cubic feet, an extra quantity of the liquid being used in the autoclave to guard against danger from drying up. About twenty minutes is required to rid each litre of formo-chlorol of its aldehyde. This constitutes the best known means of liberating large quantities of the aldehyde. Owing to the large quantities which can be generated and the high diffusibility of the gas, the method is specially suitable where passages, corridors, or stair- cases, with communicating rooms, require disinfection at the same time. The drawbacks against the adoption of the method by sanitary authorities are the weight of the apparatus and the time consumed in getting up steam and charging the room. . If an attempt is made to concentrate aqueous solutions of the aldehyde beyond 40 per cent, polymerization ensues, and a white precipitate of paraformaldehyde forms. This material is made into small tablets and sold as " Paraform Tablets," each weighing about one gramme. A considerable amount of the aldehyde may be obtained, in a very convenient manner, by means of a spirit lamp so constructed that the hot and moist products of combustion from the lamp act upon these paraform. tablets. Twenty-five tablets should be employed to every. 1,000 cubic feet of space. Ligner's glyco-formal vaporizing apparatus has furnished better results in the hands of experimenters than those obtained from the use of paraform tablets. The apparatus consists of a ring boiler in which steam is generated and driven into a reser- voir containing a mixture of formic aldehyde, glycerine, and water, which are thus vaporized and injected in fine sprays into the room. The apparatus costs £/^. The gas is neutralized by ammonia ; and, if necessary, the last DISINFFXTION 581 traces can be removed from a room by exposing vessels containing a little dilute solution of ammonia. Goggles, specialh'' made so as to protect the eyes, maj' l)e worn when the room is unsealed. The Autan method of producing formaldehj^de is as follows : For every 1,000 cubic feet of room space to be disinfected take 5 ounces of potassium permanganate crystals, and place in a metallic pail. Take ^ pint of formalin (40 per cent, formic aldehyde) and pour over the permanganate crystals. After a few seconds chemical action takes place between the perman- ganate and about one-lifth of the formaldehyde, which produces heat sufficient to evaporate nearty all the remainder. The room must be closed and sealed in the ordinary way, and kept closed for six hours. Where formalin is not available, 100 para- form tablets (i gramme each) may be taken, crushed into a powder, placed in a pint of hot water, which is rapidly brought to boiling point, and used as if it were liquid formation. Double the amount of potassium permanganate should be used — namely, 10 ounces, instead of 5 ounces, per 1,000 cubic feet. In all cases the amount of the permanganate needed is exactly half the weight of the liquid to be added. Sulphurous Acid (SOg) is a gas with a density about double that of the atmosphere, and which therefore diffuses badly. It has a slight bleaching action, which is not sufficient, however, to militate against its use. In association with moisture it has marked disinfectant powers, a 5 per cent, solution killing the spores of Bacillus anthracis, and a i per cent, solution killing non- spore-bearing bacteria, within twenty-four hours, according to Koch ; but used in the gaseous foim it is little more than anti- septic. Like other acids, sulphurous acid absorbs ammonia, compound ammonias, and organic bases (ptomaines, etc.) ; it decomposes sulphides and sulphuretted hydrogen, and reduces or enters into combination with organic matter ; it also probably exerts a direct toxic effect on bacteria. The old process of disinfecting a room by sulphurous acid is rapidly going out of use, now that equally convenient and more efficient methods are available. The former very general practice admitted of division into two stages : 1. The charging of the atmosphere for from six to twenty-four hours \\dth from i to 2 per cent, of the gas. 2. A subsequent thorough aeration of the room for several hours — an essential feature of this method. 5S2 HYGIENE .\XD PUBLIC HEALTH The gas was generated and employed as follows : 1. Rolled sulphur was broken up into pieces of about the size 0I a marble, placed in an iron vessel, and then moistened with a little spirit and ignited. At least 2 pounds of sulphur was advo- cated for ever\' 1,000 cubic feet of space, about 2 per cent, of sulphurous acid being thereby furnished to the atmosphere. The fact that the sulphur did not always bum out was a drawback to this method, and it was therefore found preferable to employ — 2. Sulphur candles, in which the powdered sulphur, mixed ^^ith inflammable material, was placed in a small metal saucer and lighted by a ^^ick. These in\'ariably bum out, and were verj^ convenient and expeditious in use. 3. An ordinan,' benzoline lamp filled ^^ith carbon bisulphide ; as this bums, sulphurous acid is given off (CS.2 + 262= CO2 + SO.^ + S). 4. The gas can be liquefied by a pressure of three atmospheres (about 45 pounds to the square inch), the liquefied gas being passed into metal C5-Iinders holding about 20 ounces. In use, a short piece of lead pipe with soldered end, which conmiunicates \\ith the interior, is cut off, and the c^iinder placed in a basin with the cut surface downwards, when the liquid, being relieved of its pressure, passes into the gaseous state. At least two cylinders were recommended to ever)? 1,000 cubic feet of space, for the contents of one cylinder would furnish sUghtly under i per cent. The cost of the cylinders is one shilling each. There is experi- mental e\-idence that the gas hberated from the liquid state is not so efi&cient as that obtained directly from the burning of sulphur. Accidents bj^ fire, when burning sulphm- was used, have been ver\^ rare, but to guard against them it is well to support the burning sulphur over a pail or basin of water. This water, especiall}' if hot, aids in saturating the atmosphere, and thereby increasing the disinfecting power of the gas, although probably the moisture alreadj^ in the atmosphere is sufficient to full}:' h3'drate the sulphurous acid produced. On account of the weight of the gas, it should be liberated as high in the room as possible — i.e., from the seat of a chair placed on a table. Sulphurous acid gas is verj^ useful for the purpose of destroying vermin, and in this respect it is far more powerful than formic aldehyde. The gas is so irrespirable that it is often impossible to enter and unseal the room containing it. A wet towel, moistened \\dth DISINFECTION 583 washing soda, and placed over the mouth, will always enable the operator to enter. As bronze, gilt, and copper surfaces are tarnished by the sulphur fumes, these should, where detachable, be wiped with i per cent, carbolic and placed just outside the room prior to the liberation of the sulphurous acid. Chlorine (CI). — This gas has most of the defects of sulphurous acid ; it is a very irritant and heavy gas, which diffuses badly, and moisture is essential to its disinfectant action. Compared with sulphurous acid, it is a heavier gas, possessing greater bleach- ing properties, and somewhat more irritant ; it is less convenient in use and more expensive. On the other hand, when present to the extent of i per cent, in the atmosphere, its disinfectant power considerably exceeds that of a similar strength of sul- phurous acid. The disinfectant and deodorant properties of the gas depend upon its affinity for hydrogen. Thus, in the presence of moisture, and especially in daylight, it releases nascent oxygen (Cl2 + H20=HCl + 0), which burns up organic matter, including bacteria. It decomposes sulphuretted hydrogen (Cl2 + SH2=2HC1 + S), and also ammonia (3CI2 + 8NH3-6NH4CI + N2). It is usually produced by the action of sulphuric or hydro- chloric acid on bleaching powder — (CaClgO + 2HC1= CaCl2 + H2O + CI2). It is advisable to use 2 pounds of bleaching powder and about I pound of the commercial acid for every 1,000 cubic feet of space. The mixture should be divided into several parts, because of its bulk and to ensure distribution of the gas, and placed as high in the room as practicable. Some experiments indicate the necessity of using much larger quantities of the bleaching powder for the more resistant infections. The powder contains about 35 per cent, of available chlorine, and it must be kept dry. All metal fittings and articles of silk, etc., should be removed beforehand ; and if great difficulty is experienced in entering the room for the purpose of unsealing, the operator should first saturate a towel with weak ammonia solution and place it over his mouth. 584 HYGIENE AND PUBLIC HEALTH Bromine (Br) is a heavy gas, more irritating than chlorine, more destructive to articles exposed to it, and also more expensive. It is readily given off from the volatile fluid known as " liquid bromine." As mth chlorine, the presence of moisture is essential to the disinfecting action of the gas. Iodine (I) is a heavy gas some eight times heavier than air, and more than three times as heavy as chlorine. This circum- stance, added to the fact that it stains exposed articles and is not a powerful germicide, excludes iodine from the list of serviceable gaseous disinfectants. Hydrochloric Acid (HCl) fumigation has been advocated. Like other acids, it has marked disinfectant properties, which are doubtless mainly due to the circumstance that any marked acidity is inimical to germ life. Nitrons Acid (HNOg). — Nitrous acid acts as an oxidizer owing to the circumstance that it readily parts with oxygen to oxi- dizable matter and becomes nitric oxide (NO). This gaS com- bines with the oxygen in the atmosphere (2NO + 02= 2NO2), and thus serves as a carrier of oxygen to oxidizable matter. Nitrous acid, therefore, remains constantly active and is not used up like chlorine, over which it also possesses the additional advantage that it does not destroy organic colouring matters. But the reddish fumes of nitric peroxide (NOg) are very irritating, and their disinfecting powers are inferior to those of chlorine. For every 1,000 cubic feet of space at least 3 ounces of nitric acid should be mixed with an equal volume of water, and the mixture poured upon i ounce of copper shavings placed in an old jar or basin — 3Cu + 8HNO3 = 3Cu(N03)2 + 2NO + 4H2O. Vaporized Phenol (C^HgO). — Although it is claimed by some that the use of this agent succeeds well in practice, such large quantities have to be employed that the odour which remains after use is extremely persistent. The phenol, placed in a bottle- shaped metal receiver, may be vaporized by means of an iron rod made red hot, which is placed inside the receiver and allowed to remain there. A pint of phenol can be vaporized in this way. Solid Disinfectants. These can only be conveniently and effectually employed as deodorants in the form of powders DISINFECTION 585 Powders are made containing phenols, sulphurous acid, etc., but they all lose strength on keeping. Carbolic Powders. — The " vehicle " for the carbolic acid is frequently lime, which is often in very great excess. There is a resulting formation of carbolate of lime, and the powder soon becomes practically inert, for the reason that it contains little or no available carbolic acid. The best class of carbolic powders are warranted to contain at least 15 per cent, of phenols, silicious matter, not lime, being used as their basis (" carbolized silicate powders "), or absorbent wood fibre, or peat (" carbolized peat- powders "). All such powders are liable to lose from i to 2 per cent, of carbolic acid by volatilization. Slaked Lime is a good deodorant, as it absorbs sulphuretted hydrogen and most organic vapours. Like bleaching powder, it exerts a caustic action, and attacks metals. Bleaching powder (chloride of lime) deposits about 40 per cent, of lime, and should not, therefore, be put down drains. A mixture of equal parts of " Sanitas Powder " and lime is a good deodorant, which of itself gives off no unpleasant odour. Carbon condenses gases in its pores, and oxidizes them by means of the condensed oxygen therein contained. Vegetable charcoal is a better deodotant than animal, but both forms should be only employed when freshly prepared and dry. Ordinary Soap possesses marked disinfecting properties. There is little or no advantage in using soaps impregnated with small quantities of disinfectants. Room Disinfection. Wearing apparel and bedding should be steam disinfected ; and if carpets, curtains, rugs, and upholstered articles were not removed when the sick-room was prepared for the patient, these should also be set aside for steam disinfection. Thus the disin- fection in the room is practically one of surface disinfection only, for no gas or vapour, employed at the current temperature and pressure, possesses powers of penetration to any valuable degree. To be satisfactory in practice, methods of room disinfection must be efficient but must not injure the articles exposed. The facility of application and the cost are also important considera- tions. There are three well-known methods of disinfecting the exposed surfaces, in rooms, involving ; — . r 586 HYGIENE AND PUBLIC HEALTH 1. The use of sprays or atomizers, by which the disinfectant (in solution) can be applied directly in the form of a very fine spray to the surfaces of the room. 2. The washing of all surfaces with a solution of the disinfectant, or the rubbing down of such surfaces with breadcrumbs. 3. Fumigation, in which the air is charged ^\ith the dis- infectant in the form of a gas or vapour, for a period of from six to twenty-foui hours. In this method the room should be, as far as possible, hermetically sealed — the windows closed and chinks pasted over with paper, the chimney outlet closed up, and the door crevices and keyhole carefully pasted over. Before the room is again occupied all the flat surfaces of the room upon which dust can settle should be washed do^^^l with some disinfectant solution. In the case of schools and hospitals, the skirting and floor boards should be removed and washed, and all ventilators should be swept out and disinfected. 4. It is advisable in most cases to strip the waU papers and limewhite the ceiling as a further precaution. After the room has been dealt with, the bedding, clothes, etc. should be placed within canvas bags, which should be damped outside with water, and then taken to the van for removal to the disinfecting station for steam disinfection. The moistening of the bag is a precaution against the dislodgment and escape of bacteria from it during the removal of the articles from the room, through the house, and to the station. As mistakes sometimes happen, it is necessary to make out a list of the articles removed from each house, and to obtain the signature of some responsible person to this list. The use of canvas bags, which can be placed vnth their contents direct into the stove, reduces the possibility of the mixing of articles from different houses, and obviates the necessity of the man at the station handling the infected articles. Any articles, however, which are stained, and require to have the stains removed before being placed in the stove, would be overlooked unless a special bundle is made of them ; and books, leather articles, feathers and furs, which are injured by steam disinfection, must be separately collected together. The individual engaged in preparing a room for disinfection should always wear overalls, which should be afterwards left behind in the room, and removed with the other articles for steam DISINFECTION 587 disinfection. This precaution diminishes the risk of the infection lieing conveyed from the sick-room, and when the disinfection is performed by the sanitary authority the precaution serves as a useful object-lesson to the people. A great deal has been claimed for the spray method of disin- fection in France, where it is the official one. The efficiency of a good sprayer must depend on its ability to deliver the liquid in the most finely divided state possible, for the more this requirement is met, the more uniform will be the distribution of the disinfectant. The Equifex sprayer consists of a metal reservoir, which holds the disinfectant, and is lined with ebonite, so that the metal is not attacked. The fluid is driven through a spray nozzle by means of a hand pump, which forces air into the reservoir. An extremely fine spray, at a velocity sufficient to ensure a slight degree of penetration, is made to issue from the end of a metal tube of such a length that it can be held close to all the surfaces to be treated. The cost is from £8 to ;^I6. The spraying process must be carried out in the most complete manner, inch by inch, over all the surfaces it is intended to disinfect. It is calculated that to efficiently disinfect 800 square feet of wall space two hours' spraying is required. Lumley's " Invicta " spray requires no pumping when at work, the disinfecting solution in the tank of the apparatus being brought under an air pressure of 45 pounds to the square inch, which causes the spraying. This is a much cheaper form of spray producer than the Equifex. The disinfectant solutions to be preferred in spraying are : Perchloride of mercury, formic aldehyde, " Chinosol," or sodium hypochlorite. The operation of disinfecting a small room occupies one hour. Washing and rubbing methods appear to be efficient. All the horizontal surfaces of a room may be washed down, or coated with disinfectant by means of a large paint brush, and the vertical surfaces may be wiped and stroked with a rag moistened with the disinfectant. When a brush is employed, two coats of the disinfectant should be put on, one with vertical strokes and the other with horizontal, to ensure that the disinfectant reaches all the crevices. The German official method is to rub down the walls with bread — ordinary German loaves, forty-eight hours old, being employed, cut into pieces 6 inches square, with the 588 HYGIENE AND PUBLIC HEALTH crust at the back to afford a firm hold. The crumbs having been swept up and burned, the walls and ceiling are thoroughly sprinkled with carbolic solution, and the floors a.nd furniture are washed with this solution. An advantage which is claimed for gaseous disinfectants is that their use necessitates, before the room can be reoccupied, a thorough exposure to fresh air for several hours— itself a useful adjunct to disinfection. While the room is occupied by an infectious patient, it is a very general custom to hang a sheet outside the door, and to keep this sheet constantly moistened with disinfectant. There is a tendency to regard the practice as useless, but its retention is certainly to be advocated. Although such a sheet cannot present an impassable barrier to the passage of infection, it must tend to limit the infection ; and its presence serves as a warning to all, and an object-lesson of the constant necessity for precaution. The infectious sick-room should be kept clean by means of damp sweeping and dusting. It has been demonstrated that minute drops of infected moisture may be spra,yed into the room by a patient coughing, sneezing, or even speaking ; and that such drops may be scattered to a distance of 4 feet from the patient. Books. — Books, leathern articles, furs, and feathers liable to injury by being placed in a hot air stove may be disinfected in a small compartment in which formic aldehyde vapours, in sufficient quantity to furnish 3 per cent, to the atmosphere, are generated. The compartment is then sealed for three or four hours. In the ceiling of the compartment several lines of wire are loosely fixed, so that the books can be suspended by their covers, the pages being open, fan-shape, to admit the disinfectant ; or the articles may be placed upon perforated shelves arranged above the apparatus from which the formic aldehyde is being liberated. Dead Bodies should be wrapped in a sheet soaked in " Izal " (2 per cent.), carbolic acid (5 per cent.), perchloride of mercury (i in. 500), formic aldehyde (i per cent.), or other disinfectants of equal strength. Cremation is specially desirable in the case of infectious bodies. GuLLEYS may be sprinkled over with a good carbolic powder, or with a mixture of equal parts of " Sanitas Powder " and lime. Bleaching powder has too unpleasant an odour, and it badly corrodes the metal grids. DISINFECTION 589 Stools, etc. — ^To disinfect enteric fever stools, cholera evacu- ations, tubercular sputa, and other discharges from the infectious sick, either liquid disinfectants, boiling, or cremation must be resorted to. The following liquid disinfectants may be employed : Acid solution of corrosive sublimate (i in 500) coloured blue with aniline. Preparations containing carbolic or cresylic acid (10 per cent.), or four tablespoonfuls of the acids to i pint of water. Solution of sulphate of copper or ferrous sulphate (10 per cent.). Solution of formic aldehyde (4 per cent.). Bleaching powder solution acidified (4 per cent.). All solid stools should be broken up with a piece of stick and thoroughly mixed with the disinfect- ant. The agent must be allowed to remain in contact with the infected material for at least half an hour ; and all disinfectant solutions must be added to the matter to be disinfected in such quantities that they are present in the whole mixture to the re- quired extent, as indicated above. Even then, some of the excreta may escape disinfection. Sputum is disinfected with great difficulty by means of liquid disinfectants ; and either burning or steam for 20 minutes should be employed in preference to other methods. Enteric and cholera stools are preferably disinfected by the following means : — Boiling for half an hour under steam pressure ; boiling for half an hour with i in 20 carbolic acid solution ; mixing with a relatively large amount of straw or sawdust, then saturating with parafhn or petroleum and burning ; mixing with coal dust and ashes, and burning in an incinerator with a high flue. The impossibility of disinfecting or sterilizing large volumes of sewage or night soil by the use of chemical reagents, unless applied in enormous and ruinous quantities, need hardly be insisted on. Small quantities of chemical reagents may be very efficient deodorizers, for offensive smells are thus concealed or destroyed ; but the removal of offensiveness must never be regarded as equivalent to destruction of infection. Hands.^ — The disinfection of the hands is a matter of great difficulty, and it is, therefore, wise to protect the hands, where possible, by wearing thin india-rubber gloves. The best practical means of dealing with infected hands is to scrub them thorough!}' with soap and hot water, using a nail brush assiduously, and then to steep them for a quarter of an hour in a solution containing I in 500 of the iodide of mercury dissolved in the iodide of 590 HYGIENE AND PUBLIC HEALTH potassium. It is useful to have a little alcohol added to the disinfectant solution. Ships. — Clayton gas is a useful means of disinfecting ships. The Clayton apparatus consists of an iron furnace specially constructed to burn sulphur in a current of air, a flexible rubber hose conveying the gas from the apparatus to any part of the ship. The gas contains about 15 per cent, of sulphurous acid together with some sulphuric acid. It is usually recommended that one pound of sulphur is required for the disinfection of 250 cubic feet of space, so that there may be from three to five per cent, of the gas in the atmosphere of the compartment to be disinfected. There is testimony to the fact that all rats and insects in a ship are destroyed in two hours in these circum- stances ; but, although the method is valuable for cabins and empty holds, owing to the rapid absorption of sulphur di-oxide by most articles of cargo its use on this account for laden vessels is restricted. Pathogenic bacteria require a somewhat larger percentage of the gas and an exposure of several hours ; and sporing specific organisms (such as Anthrax) cannot be thus disinfected. Although the application of the process is subject to considerable limitations, it is better on the whole than either of the processes which have been suggested involving the use of carbonic acid or carbon monoxide ; for, with these disinfectants, rats, etc., die in their hiding-places, whereas they more often come out into the open to die, when exposed to sulphurous acid. The Disposal of the Dead. Cremation is the most sanitary method of disposal of the dead. The method is of great antiquity, and was commonly employed by the ancient Greeks and Romans. The body can by this method be reduced, within the space of two hours, to a small quantity of odourless ash, which can, if the relatives of the deceased so desire, be preserved in sealed urns in a columbarium adjacent to the crematorium. Cremation, too, prevents the pollution of the ground — a pollution which is of a dangerous character when the bodies of those who have died of infectious diseases are interred. This method of disposal of the dead is making, progress in this and other countries, and several crematoria have been provided in Great Britain during recent years. Temperatures of 1,800 °- DISINFECTION 591 2,000° F. are now attained in the furnaces ; and the heated gases from the furnace perform their work in under two hours. The main objections which are raised against cremation at the present day are based on sentimental and rehgious grounds, which time and education wiR remove, for the ultimate effects of cremation and earth burial are precisely the same. In earth burial the ultimate resolution of the body into its component elements may take a year or many years to accomplish, whereas by incineration the same products are formed in as many hours. These products are largely gaseous, and whereas in cremation special provision is made to completely burn them up wdthout offence, in earth burial they necessarilj' pollute the soil, and escape into the general atmosphere. There are only two real objections which can be raised against cremation : — -namely, the cost of the process, and the fact that the complete destruction of the body involves also the destruction of e\'idence of certain crimes. As regards the first objection, the original cost of erection of a crematorium is considerable, and the working expenses are high ; but, where there is a crematorium within easy access b}^ road or rail, cremation can now be carried out at about the same cost as earth burial. To meet the second objection, State ofl&cials could be appointed, as in France and German}', to inquire into and verify the death certificates ; and, as a means to the same end, the English Cremation Society has drawTi up a code of very stringent rules (including two independent certifi- cates of death) which must be complied with before a body can be cremated. Earth Burial. — ^This method causes pollution of both soil and air, and should be discontinued ^^ithin the borders or in the near neighbourhood of towns and thickly populated districts. As the old burial grounds in to\\-ns become filled up they have to be closed, and these can then be converted into open spaces and garden recreation grounds. Burial sites at a distance from the town must then be provided, at great cost and much incon- venience to the ratepayers. It is necessarj-, in order to carr}^ out earth burial under the most favourable conditions, to provide from a quarter to half an acre of land to every i,ooo of the population for some fourteen years, according to the suitabihty of the soil for the purposes of interment. A sandy and calcareous loam is the best soil for a graveyard ; 592 HYGIENE AND PUBLIC HEALTH a stiff clay, which retards dissolution, is the worst. In clay sites, moreover, the ground is liable to crack in very dry weather, and the gases of putrefaction may then find a direct outlet to the surface of the burial ground. Coarse gravel, comparatively free from any binding material, and broken rock are too loose and open to constitute good soils for burial sites ; and chalk' is contra-indicated on account of the risk of fissures transmitting impurities to the air above or to a water supply below. An isolated tract of ground, ^vith good surface falls for natural drainage, and having a considerable thickness of fine sand and sandy loam, or sandy and loamy gravel, resting upon a deep bed of clay, would constitute an ideal site. The earth should have a depth of not less than lo feet, and graves should never be dug deeper than 8 feet from the surface. In every case a space of at least 2 feet should intervene between the bottom of the grave and the surface of the subsoil water. As at present practised, with the use of lead shells and strong wood coffins-, the method of earth burial preserves the bodies for a very long period. Nothing whatever is gained by this lengthy preservation ; and the aim of rational earth burial should be to facilitate the ultimate reduction of the body into its component elements. To this end, the body should be placed in an easily perishable coffin of wdckerwork or of unprepared wood, and the grave should not be deeper than 3 to 5 feet from the surface — the earth being very much more active as a destructive and purifying agent in the upper layers not exceeding 5 feet in depth from the surface, than it is at greater depths. By the use of quicklime in earth burial the soft tissues of the body are rapidly destroyed, and the process of decomposition is completed at a comparatively early period. Other methods of disposing of the dead are : — (i) By simple exposure to the air, as practised by the Australian aborigines ; (2) committal to the sea ; (3) the exposure of the body in the open air, so that the fleshy parts may be eaten by vultures, a method followed by the Parsees of India in their Towers of Silence ; (4) desiccation or mummification. Embalming was commonly practised in ancient Egypt. The abdominal viscera were extracted by incision on the left side, and the cavity was then cleansed with palm oil and filled with, myrrh, cassia, and other odoriferous substances. The body was ultimately wrapped in very numerous layers of cloth and DISINFECTION 593 sealed up hermetically. In the modern method of temporarily preserving bodies, the cavities of the chest and the abdomen are emptied and washed with camphorated spirit ; the organs are then similarly washed and injected with some preservative fluid before thej^ are replaced. The vascular system is also in- jected with a preservative fluid, it being a common practice to inject into the carotid artery some 6 to 8 pints of a mixture consisting of carbolic acid i part, glycerine lo parts, alcohol 50 parts, and water 40 parts. The surface of the body should be lubricated with vaseline containing 5 per cent, of carbolic acid, and it is advisable to fill the cavities of the body with cotton wool soaked in glycerine containing 5 per cent, of carbolic acid. Recently a method has been demonstrated of preserving bodies by exposure for 3 or 4 weeks to the vapour of formic aldehyde (Rechter's method). Underneath the open wire shelf, on which the body rests in the sterilizing chamber, an ice closet is placed, in order to inhibit by cold the action of the intestinal bacteria, until the formic aldehyde vapour begins to produce a distinct antiseptic effect. 38 CHAPTER XII STATISTICS Statistical Inquiries. The science of statistics consists in the collection of individual facts, with the view of grouping them into different classes accord- ing to certain definite characters they possess. The rule to which attention must be specially directed in differentiating a series of facts, is that the points of difference or characteristics on which a group is to be formed should be common to each member of that group, but absent from the members of aU other groups. The dividing character must be constant, and must be definite. It does not foUow that, because in any series of cases the groups bear a certain numerical proportion to the total number of cases, these proportions will be the same in any subsequent series of like cases, unless the numbers dealt with in",the first case are infinitely large. ^ . . The relative values of two or more series are as the square roots of the number of units of observation ; and thus by in- creasing the number of observations in any inquiry, the value (or accuracy) increases as the square root of the number. The smaller the number of individual facts on which the groups are founded, the greater is the possible deviation from the proportions which may be observed in any subsequent series of like facts. By Poisson's Rule the limits of error, or the degree of approximation to the truth of the numerical relations existing between the units or groups of a series, may be ascertained. Let M = total number of cases in the series recorded. ,, m = number of cases in one group. ,, n = number of cases in the other group. m n Then m + n=M., and ,^ and ,, are the proportions of each MM ^ ^ 594 STATISTICS 595 group to the whole. But on subsequent occasions, with another series of like cases, the proportions may be ^ ^ / 2.m.n m . / 2,.m.n — ••I-2V : or 2 V • M M3 ' M W And the same holds good with n group of cases. The larger the value of M, the less will be the value of the fraction of which M^ is the denominator, and consequently the smaller the limit of error. Example. — M = 100 cases of fever. m= 25 cases which die. n= 75 cases which recover. Then the proportion ^ or ;J- may be in other instances + + 2\/—^^4^=°'25 + °'^225 =0-3725 ; ■* V ioo3 or A_2x/^^-^---^-—=0'2S -0-1225 =0-1275. That is to say, the number of deaths out of 100 other cases of the same fever, instead of being 25, may be as many as 37, or as few as 13. The arithmetical mean of a series of figures is obtained by adding together the numerical values of the figures, and dividing the total by the number in the series. This mean number will have a higher numerical value than belongs to some of the figures composing the series, and a lower numerical value than belongs to others. The less the difference between the mean and the figures of the series, the greater is its value, and the more closely does it conform to a true average. The relative values of two or more similar series are as the reciprocals of the I squares of the probable errors ; that is as . 2 , where pe is the probable error. The probable error is approximately two- thirds of the mean error, and implies that, if the series were prolonged indefinitely, the error would probably as often exceed as fall short of this mean. It is obtained as follows : I. Find the mean of the series of observations ; find the mean of all the observations above the mean, and subtract the mean from it ; this gives the mean error in excess. 2. Find the mean of all the observations below the mean, and subtract the latter from the mean ; this gives the mean error in deficiency. 596 HYGIENE AND PUBLIC HEALTH Add the two quantities (mean error in excess and mean error in deiicienc}^) , and take the half ; this is the mean error. The various means are : a+h+c+d+e The arithmetical mea-n= The geometrical mean = Jah c d e The harmonic mean =11111 + ,+--+ -5 + - a b c a e The quadratic mean= V 5 If the terms of the series are equal, the above means are all identical. If the terms are unequal, the quadratic mean is the highest, the arithmetical comes next, and then follow the geometrical and harmonic means. The value or reliability of an average or arithmetical mean, when applied to any one factor, is evidently dependent upon the degree of approximation between the average and the various factors numerically expressed. Thus, in two streets A and B, each containing 20 houses, the average number of persons per house may be the same, but the value of the average in its applicability to any particular house in either street may be very different. Thus, if in street A 10 houses have 8 inhabitants, 6 have 4, and 4 have 2, the average is 5-6 persons per house ; whilst in street B i house has 7 inhabitants, 10 houses have 6, and 9 houses have 5, the average again is 5-6 per house. But the value of the average is, according to biometricians, in inverse ratio to the standard deviation, usually denoted a-, which is obtained by the following mathematical formula : N in which n^ n^, etc., are the number of factors having the same values or measurements, and a^ a^, etc., are the number of units separating each group value from the mean value of the whole N. The standard deviation in the case of street A will be found to be 25, whilst in the case of street B it is only 018.^ _ /iox2'42 + 6x i*62+4x 3'62 :2-S. (B) „„ i„ culated on .In iLnT''''" Married Female tion, aged 15-45. Population, aged, 15-45. Illegitimate Birth Rate cal- culated on Unmarried and Widowed Female Population, aged 15-45. 1870-2 . 1880-2 . 1890-2 . 1900-2 . 1908 35-3 34-0 30-7 28-6 26-5 153-7 147-7 129-7 1 14-8 1 06- 1 292-^ 286-0 263-3 235-5 217-6 17-0 I4-I lo-s 8-5 8-0 Approximately 70 per cent, of the decrease in the birth rate during the past 35 years (based on the proportion of births to the female population aged 15-45) results from decreased fertility of married women, some part of this decrease being attributable to changes in their age constitution ; about 10 per cent, may be ascribed to the decrease of illegitimacy, while the remaining 20 per cent, is due to the decrease in the proportion of married women of conceptive ages in the female population. The tendency in modern times to postpone marriage to a later age than formerly is shown by the fact that in 1871 15-2 per cent, of the married women aged 15-45 were comprised in the group 15-25 years of age, whereas in igoi only 12-4 per cent, of the married women were in this group. The later age of marriage for women curtails the period within which'^children can be born. 1 Sixty-seventh Annual Report of the Registrar-General, 6l2 HYGIENE AND PUBLIC HEALTH Mean Annual Birth Rates per 1,000 in Urban and Rural Areas. Urban. j Rural. Calculated on Total Population at all ages. 36-7 35-7 32-0 29-8 Calculated on Female Popula- tion, aged 15-45. I43-I 140-6 124-6 1 1 1-4 Calculated on Total Population at all ages. 31-6 30-3 27-8 26-0 Calculated on Female Popula- tion, aged 15-45. 1870-2 . 1880-2 . 1890-2 . 1900-2 . 1 158-9 IS3-5 135-6 120-7 The lowering of the birth rate is seen from this table to be as much a feature of rural as of urban communities. The best statistical evidence of the health of a community is, of course, furnished by the corrected death rate, although a sick rate ("morbidity rate ") would furnish still better evidence. The registration of sickness, however, would be open to many fallacies and abuses. The scant returns which are available in this country (i.e., from sick clubs, friendly societies, industrial organizations, hospitals, army, na^'y, police, etc.) are onh' concerned with disabling sickness, among what are often selected lives, and are of little value for the purpose under consideration. On an average, there are two years of sickness suffered to each death registered. The death rates from the principal zjrmotic diseases, from tuberculosis, phthisis, and acute diseases of the lungs, afford most valuable evidence of sanitarj^ condition. The zymotic death rate is the number of deaths from the seven principal zymotic diseases multiplied by 1,000 and divided by the popu- lation. The seven principal zymotic diseases of the Registrar- General are : small-pox, measles, scarlet fever, diphtheria, whooping-cough, " fever " (i.e., typhus, enteric fever, and simple continued fever), and diarrhoea. The Z3anotic death rate for England and Wales in 1909 was i-i2. Of these, enteric fever mortality is the best test of sanitary condition, caused as it is by specific faecal contamination of soil and water ; whilst diarrhoea, with its special incidence on young children, is notably associated with insanitary surroundings. The other zymotic diseases, although probably favoured in their onset and fatality by un- hygienic conditions, also indicate, when the mortalit}^ from them is high, a failure on the part of the sanitary authoritj- to control STATISTICS 613 their spread by disinfection and isolation. Tuberculosis, phthisis, and acute diseases of the lungs, are most prevalent and most fatal among communities where overcrowding in dwellings or workshops is allowed to exist, or where sites are damp and the subsoil saturated \\-ith water. Thej^ may thus be taken as evidence of a certain class of insanitary conditions, usuallj' associated with poor town populations. The rate of infantile mortality, though influenced solely bj' conditions affecting those under one year of age, also ranks high as evidence of the health of a community. Annual Death Rate per i ,000 IN 1871-80, ] 881-90, AND 189I-I9OO. England and Wales (Persons). 1871-80. 1881-90. 1891-1900. All causes ..... 21*27 19-08 l8-2I ' Small-pox . 0-23 0-045 0-013 Measles 0-38 0-44' 0-414 Scarlet fever 0*72 0-33 0-158 Diphtheria . 0-I2 0-16 0-263 Whooping cough 0-51 0-45 0-378 Typhus 0'06 o-oi; 0-003 Enteric fever 0-32 • 0-20 0-174 Simple continued fever j o-io 0-025 0-006 Diarrhoea and dj-sentery I 0-93 0-67 0-734 Zymotic diseases . 1 3-47 2-36 ^•143 Phthisis 1 2-12 1-72 1-392 Other tubeicular diseases 0-75 0-70 0-622 Cancer 0-46 1 0-58 0-75S The mean age at death of a population is obtained by adding together the ages at which people die, and dividing the number of years lived by the number of deaths. It is merely an expres- sion of the average age at death of a population, and gives no e\-i- dence of the health or sanitary condition of the communit}-. ^^^len a population is rapidly increasing by excess of births over deaths, the mean age at death is low, because the population is largely composed of J'oung persons. When a population is nearly stationary, the proportion of old people to the total popu- lation is large, and the mean age at death is high. The mean age at death, therefore, gives information as to the ages of the dying and, per contra, of the living in different communities, but nothing more. A life table represents a generation of individuals passing 6l4 HYGIENE AND PUBLIC HEALTH through life to extinction. The calculations of a life table relate to an arbitrary number of individuals supposed to be born simultaneously, and to exist under the same conditions as those which apply to a given community. Usually the population is assumed to start with a million births, and these are divided into males and females in proportion to the actual number of births of either sex that have occurred in the given community during an intercensal period of ten years. The mathematical probability of survival of every individual for each year of life is then cal- culated from data obtained from the actual community, and thus the hypothetical life table population becomes the medium for the record of facts concerning the vitality of a given population. The probability of survival from the beginning to the end of each age period = The number of survivals at the end of the period The number living at the beginning of period and for the purposes of a life table the numbers of either sex living at the end of each age-period may be obtained by multiplying the number commencing the period by the above fraction. By this means the numbers in each successive age-period are gradu- ally diminished to extinction, since the factor is always less than unity. The column of the life table showing the number of survivors at each age-period for both sexes is thus obtained. It need hardly be said that the larger the number of the population involved, and the longer the period of time from which the data of the population are obtained, the more reliable will be the various estimations of the life table. Hence it is a common practice to take the mean figures, both as to population and deaths at different ages, from the accumulated data of two censuses and the intervening years. But the above facts are first obtained in five and ten yearly age-and-sex groups of the population, so that the lives and deaths of each age-group have to be distributed artificially to each year of age included in the groups. The fact that several methods may be adopted for this distribution accounts for the main differences in construction of various life tables. In many tables the " graphic " method has been adopted. The method is briefly as follows : — On paper ruled into equal squares is laid down a base line or Abscissa, and along this are marked off the proper number of squares representing the different age- STATISTICS 615 periods. On the base line is constructed a series of parallelograms of such a height that, in accordance with a scale of population given at the left-hand margin, the area of the parallelograms shall represent the total number of lives at risk for each age-period. Thus, if for males the total number of lives at risk for ages 0-5 has been found to be 20,000, the parallelogram for this 20,000 age-period should read to the height of = 4,000, against the scale of population. A curved line is now drawn tlirough the upper borders of these parallelograms, as free from bends and irregularities as possible, and in such a fashion that the area cut off from each parallelogram shall be equal to the area added to the same. The base line is already divided into equal spaces representing single years of life, and vertical lines are drawn through the centre of each of these spaces upwards to join the curved line. The height to the point of junction of each of these vertical lines with the curved line above referred to is read off against the scale of population, and will give the lives or deaths for each year of age {see fig. 95). The most important columns of a life table for any popu- lation show the numbers surviving at each year of age, the years of life lived subsequent to each year of age, the sum of the years lived in and after each year of age, and " the mean after- lifetime " or " expectation of life at any age." The life table is very valuable for comparing the vitality of a community at one period with that of another period, or with that of another community. By furnishing, by the law of probability, the expectation of life of the different members of the community, it supplies a valuable comparative figure for vital statistical purposes, and one which, by enabling us to measure the probability of life and death, affords a scientific basis on which the calculations for life assurance are made. A life table recently constructed by the late Dr. T. E. Hayward is made to show what the effect on the longevity of the present population of this country would be (i) if phthisis could be eliminated as a cause of death, and (2) if the high phthisis mor- tality formerly prevailing was now being maintained. The mean duration of life or expectation of life at birth differs widely from the mean age at death, when the population is con- tinuously disturbed by a fluctuating birth rate, immigration, and emigration, although when the population is stationary they 6i6 HYGIENE AND PUBLIC HEALTH coincide. Thus, the mean duration of life in England (i88i-go) for males, as calculated from a life table, was 43-66 years ; whereas the mean age at death was only twentj^-nine years. It must be borne in mind that this difference is due to the fact that the mean duration of life is calculated from life tables in which all the members of a hj^pothetical population are traced through life, while the mean age at death is a calculation based upon the 6-10 1015 I5J0 2025 25-35 Fig. 85. — Graphic Method. Male population — numbers living or lives at risk. actual registered deaths in a population disturbed by fluctuations of both immigration and emigration. Life tables show how many of a given number born live through each year of age, and what is the sum of the number of years they live ; the sum of these years divided b}^ the lives is the mean duration of life (mean after-lifetime at birth or expectation of life at birth). It is not the same thing as the probable duration of life, which is the age at which a given number of children born at the same time are reduced one-half ; the chances, therefore, of their dying before or after that age being equal. The mean duration of life for males (English life table, 1891-igoo) was 44-13 years, whilst the probable duration of life was about 53 }'ears. STATISTICS 617 Mean after-lifetime is a more accurate expression than expec- tation of life, as, strictly speaking, the time which it is expected a person will live is the time which it is an even chance he will live ; it is then strictly the probable duration of his life. But it has been thought advisable to retain here the term " expectation of life," as being the term usually employed in life tables. ■'• It must be understood, however, to mean, whenever expressed, the mean after-lifetime, and not the probable duration of life. It has been shown by the late Professor de Chaumont that the mean duration of life may be approximately calculated from the birth rate and death rate by the following formula : where h = birth rate per unit of the population, and d^ death rate per unit of the population. f 2 I I \ Then mean duration of life = \ — ^ ^ f + I I X 11^) " (i Jf This formula, however, is really only applicable when the birth rates do not depart much from the average of the whole country. Dr. Tatham has shown how a figure, representing what he terms " life capital," can be obtained with the assistance of a life table. If the most recent mortality returns for a single year are compared with the mean of those obtained for a succession of the 3'ears immediately preceding, the comparison will generally be a favourable one to the most recent year. The difference in the number of deaths wiU be the lives saved to the community. If each life gained be multiplied by the mean expectation of life for the corresponding age-period, we obtain the gain of life capital of the community for each age-period, and from this the gain for the whole community can be ascertained. Life tables not only furnish the mean duration of life or the expectation of life at birth, but also the mean after-lifetime or the expectation of life at any age — that is, the length of time a person of any age may be expected to live. The expectation of life at any age is calculated from the numbers living at the age in question and from the years of life they subsequently live, just as is the mean duration of life (expectation of life at birth). ^ The English Life Table for 1891-1900 and many earher life tables will be found in the Supplement to the 65th Annual Report of the Registrar- General (Part I.). 6l8 HYGIENE AND PUBLIC HEALTH For ages between twentj^-five and sevent\-five, Willich's formula also gives approximate results. If x= expectation of life, and a = present age, then .r= f (80 —rt). Life tables afford an excellent test of the health of a community. By the English table for 1891-1900, the expectation of life at birth for males is 44"i3 j^ears ; whereas it was 43 '66 bj^ the table of 1881-90, and 39-91 b}^ the 1834-54 table. Among females, the expectation of life was 41-85 and 47"i8, respectively, in the two earlier tables, and 47-77 by the new table. The expectation of life increases every year in both sexes up to the third j'ear, when it is 54-26 for males and 56-49 for females, the dangers to life of the period of infancy being then passed. Subsequent to the third 5-ear, the expectation of life graduall\' decreases for each year of -age. As compared with the old life table of 1838-54 the expectation of life for males by the most recent table is onh" higher up to the age of 33 j'ears, and beyond that age is lower. For females the most recent table shows an expectation of life higher up to the age of forty-seven, as compared with the 1838-54 table. The causes of this alteration in figures between the newest and oldest life tables appear to be that by improved sanitary surround- ings the lives of infants and children have been saved in the recent period which were sacrificed in the former, thus increasing the expectation of life during childhood, youth, and early man- hood. After reaching adult age, males are now subjected to conditions which are not more favourable to life — probabh^ less so, from increased competition and difficult}- in gaining a liveli- hood — than existed between 1838-54 ; and this, together with the fact that some of the lives saved in childhood are probabh' unhealthy ones, which would have perished under the old in- sanitary conditions, accounts for the expectation of life being now actually less for adults over 33 years of age than formerty. Females, being less subject to the adverse conditions of males, and living more at home, are likel}^ to derive benefit from improved sanitation after reaching adult age, as is indeed plainly sho\ATi by the life tables. After the age of forty-seven, however, the unhealthj' female lives saved in infancy begin to influence the expectation of life. Although b}^ the male life table the expectation of life after 33 5^ears is less no\\- than fifty years ago, the numbers living at each year of age up to 81 years are greater by the STATISTICS 619 1891-1900 table than by the 1838-54 table ; after 81 the numbers living are less. By the female life table the numbers living up to the age of 91 are greater by the new than the old table. It is thus seen that there has been a great saving in life, in recent years, of males and females up to ages which embrace practically the entire lifetime. Although out of a given number of children born more survive and reach the later age periods than formerly, it must not be thought that individual life is lengthened ; for, as the life tables show, individual life is shortened after reaching a certain age in both sexes, the reduction in the expectation of life being due to an increased mortality during the later age-periods. The death rates of infants under one year, and of children under five years, are most important, as they afford very positive evidence of the sanitary condition of a community. The death rates of infants under one year should be stated as so many deaths in a year to 1,000 registered births, this rate being known as the " rate of infantile mortality." This rate has the advantage that it can be computed with certainty from an accurate register of births and deaths ; whereas the other death rates, except in census years, have to be calculated from an estimated population, and are not, therefore, so accurate. The rate of infantile mortality is liable to considerable fluctua- tions year by year, the fluctuations being largely determined by the increased or diminished incidence of summer diarrhoea. The rate in this country furnished no evidence of any continuous reduction until quite recently, and the deaths under one year of age still continue to form some 25 per cent, of the total deaths. The chief registered causes of infantile mortality are as follows : — Debility, inanition and prematurity of birth, diarrhoea and dysentery, measles and whooping cough, convulsions, accidents (including " overlying "), bronchitis and pneumonia. Seventy per cent, of the total infantile mortality is generally ascribed to the above-mentioned causes. The rate of infantile mortality among illegitimate children is about double that of children born in wedlock. Infantile mortality is usually highest in the districts having a very high birth rate ; this is probably due to the fact that high birth rates occur in relatively poor-class communities. For England and Wales, in the ten years 1891-1900, the mean number of deaths of male infants under one year to 1,000 births 620 HYGIENE AND PUBLIC HEALTH was i68, of female infants 138, and of both sexes 153. For the year 1909 the rate for both sexes was only 109, which is the lowest on record. The decline in the infantile mortality rate in England and Wales commenced about the yesir 1900, and with the exception of the year 1904, has continued almost uninterruptedly to the present time. Year. 1899 1900 I9OI 1902 1903 1904 1905 1906 1907 1908 1909 Infantile Mortality Rate. 163 154 151 133 132 145 128 132 118 120 109 The deaths of children under five should be stated as death rates per 1,000 living under that age. The average rate for male children for England and Wales 1906-8 was 46-2 per 1,000, for female children 38*3 per 1,000, and of both sexes 42-3. No doubt some part of this infant and child mortality, which is preventable, is due to other causes than insanitary conditions controllable by local authorities, such other causes being m.aternal neglect, insufficient and improper nourishment, etc. Still, just as a sustained rate of general mortality above 17 for 1,000 always implies unfavourable sanitary conditions (Dr. Farr), so it may be said that rates of mortality amongst infants and young children, which exceed the rates prevalent in the country gener- ally, are mainly indications of bad sanitary conditions in the communities in which they occur. About one-third of the deaths of children under one year of age occur during the first month of life, and about one-fifth during the first week ; about half occur during the first three months. This circumstance is largely accounted for by unfavourable ante-natal conditions. There is a large and increasing infantile mortality from diarrhoeal diseases and premature birth disclosed by the Registrar-General's returns for England and Wales. The importance of a right use of vital statistics, and of avoiding unfounded and erroneous deductions, is so great that it will be weU to further indicate some of the errors and fallacies, which are either inseparable from, or are introduced into the subject. STATISTICS 621 In the first place, the data derived from the census returns are incomplete and sometimes fallacious : e.g., old people are often ignorant of their precise age, and frequently overstate it when very old ; females often wilfullj^ misstate their ages ; and young children are often returned as one or two years old when they are only in their first and second years. Again, the population is only an estimate in the intercensal periods, and considerable errors in the estimation often arise ; it is for this reason that a five-yearly census is so much to be desired. The registration of births and deaths, and the certification of the causes of deaths, are subject to many fallacies, arising from fault}' diagnosis, indefinite certification, and the lack of uniformity in the nomen- clature of disease ; whilst many births escape certification from ignorance, shame of illegitimacy, or from the parents' desire to avoid vaccination. The use of such terms as " convulsions," " jaundice," and " dropsy," for instance, should be avoided, whenever the true cause of these sjnriptoms can with reasonable certainty be substituted. It is impossible, also, to correctly classify deaths which are returned as due to two or three distinct maladies, without any indication as to which was the primary cause of death. Various classifications of deaths have been sug- gested and employed ; they may be based on symptoms, causes, the tissues and organs affected, or the parts of the body affected considered anatomically. The latter is the classification suggested by Farr and Bertillon ; and it would probably insure a greater precision in classification, and favour a more just comparison of the deaths from various causes than any other. The Society of Medical Officers of Health has issued certain rules as to the classification of causes of death. It is advised, as a general rule to select, when several diseases are mentioned in a certificate, the disease of the longest duration, but any one of the chief infective diseases should be selected in preference to any other cause of death ; and definite diseases, ordinarily known as " constitutional diseases," should have preference over those known as local diseases. When apoplexy occurs in conjunction with definite disease of the heart or kidneys, the heart or kidney disease, as the case may be, should be preferred ; and when hemiplegia is certified in conjunction with embolism, the embolism should be selected. Diarrhoea should be ascribed as the cause of death only when mentioned alone or in connection with some other indefinite cause such as convulsions, teething, marasmus. 622 HYGIENE AND PUBLIC HEALTH etc. In addition to deaths ascribed to diarrhoea alone or as above indicated in the certificate, deaths from intestinal catarrh, epidemic enteritis, or zymotic enteritis, should be included under diarrhoea. But deaths from gastric catarrh, as weU as from gastro- enteritis and enteritis (\vithout the prefix epidemic or zymotic), should be excluded. The death rate of seaside places is seldom correct. A certain number of visitors are always included in the estimation of the population, and it is not easy to exclude their deaths. The domestic servants in a community introduce a further fallacy in vital statistics, since they rarely die in service. Although counted in the population of the district where they reside, they frequently return to their homes in rural districts, when seriously ill. and unfit for further service. The death rates of general hospitals can never be justly com- pared, because of the ^^arying nature and gravity of the cases admitted from time to time, the varying proportion of medical to surgical beds, etc. The death rate is often stated as the number of deaths to every lOO occupied beds, but it is better to express the deaths as a ratio of the number of cases treated to a ter- mination. Occupation plays an important part in determining mortality, some occupations being far more healthy than others. Occupa- tional mortality is calculated from the deaths occurring in any particular occupation. For purposes of comparison the death rates among those employed at corresponding age-periods must be taken, allowance being thus made for the varying age constitu- tion of those engaged in the different occupations. A comparative mortality figure for different occupations may be obtained by taking the deaths occurring in a standard popidation, such standard population to consist of the exact number of males in the whole population between twenty-five and sixty-five years of age who would supply 1,000 deaths annually. Dealing with the deaths of 1890-2 and the population of 1891, Dr. Tatham shows that 1,000 deaths occurred among 61,215 males between twenty-five and sixty-five years of age ; whereas the number of deaths among a similar number of medical practitioners only amounted to 966 ; or, in other words, the same number of men aged twenty-five to sixty-five (having equal numbers at the various inclusive ages) that would furnish 1,000 deaths among all males, would only give 966 among medical practitioners. STATISTICS 623 An obvious fallacy in SLXiy attempt to gauge the relative healthi- ness of different occupations results from the fact that certain trades attract the more robust and muscular, whilst others demanding less strength attract the weaklings. The mean age at death cannot be taken as an index of the healthiness of an occupation, because some employments are filled b}^ older men, who have proved their worth or have filled minor posts during many years, while other classes of laboiir requiring less skill and experience are much more largely filled b}' those 3'ounger in life. Instances of the more usually employed graphic methods of representing statistical results can be seen in the annual reports of medical officers of health. Erroneous conclusions are apt to be formed bj^ comparing the mortalitj^ curves on scales which are not identical. " Spot maps " — maps of the district, on which the deaths or cases of various infectious diseases are indicated on the locality where they occur — furnish valuable graphic expressions of any grouping of such deaths or sickness, and are much employed by medical officers of health. They should, however, usually be employed to express these occurrences for short periods only. Spot maps, covering a period of several months or a year, are not often of much value for the purpose which they are designed to subserve. CHAPTER XITI SANITARY LAW AND ADMINISTRATION Sanitary Areas and Authorities. By the Local Government Act, 1894, England and Wales are divided into — (i) administrative counties, (2) county boroughs. The administrative counties are diAdded into urban and rural districts with the exception of the County of London, whichis divided into twenty-eight ]Metropolitan Boroughs. The follo\\T.ng table shows the areas, the authorities, and the chief Acts having relation to public health which the sanitary authorities administer : Authoritv. Administrative Count V County Borough Municipal Borough Urban District (of County) County Council Town Council INIunicipal Council Urban District Council Rural District (of Countv) Rural District Council Sanitarj- Acts Administered. Appeal Authority under Local Go- vernment Act, 1894, a^JKl under sec. 299. Public Health Act, 1875. Rivers Pollution Prevention Act, 1876. Isolation Hospitals Act, 1893. Mid%\dves Act, 1902. Local Sanitary Acts. Public Health Act, 1875. Pubhc Health Acts Amendment Act, 1890 (adop- tive). Sale of Food and Drugs Acts, 1875, 1879, and 1S99. ^lar- garine x4.ct, 1887. The Sale of Horseflesh Act, 1889. Canal Boats Acts, 1877, 1884. Public Health Interments Act, 1879. Factories and Workshops Act, 1 90 1, so far as relates to sanita- tion. Housing of the \^'orking Classes Act, 1S90, 1899. Infec- tious Diseases Notification Act, 1889. Infectious Diseases Pre- vention Act, 1890 (adoptive). Dairies, Cowsheds, and Milk- shops Orders, 1885, 1886, 1899. Rivers Pollution Prevention Act, 1876. The Cleansing of Persons Act, 1897. The Notification of Births Act, 1907 (adoptive). The Housing and Town Planning Act, 1909. All the Acts above cited as ad- ministered by Urban Sanitary Authorities, A\dth the exception of certain sections of the Pubhc Health Act, 1875, and of Part I. of the Housing of the Working Classes Act. Public Health (Water) Act, 1878. 624 SANITARY J.AW AND AlJMINlSTRAtlON 625 Authority. Parish, forming part of a Rural District Poll- Parish Council Port Sanitary Authority- County of London I London County Metropolitan ' Council Boroughs ' Borough Councils Sanitary Acts Administered. Certain sanitary po-wers under the Local Government Act, 1894, section 8, but not in substitution of those exercised by the Rural District Council. Assigned by the Local Government Board, and practically those of an Urban Sanitary Authority. Regulations of the Local Gov- ernment Board. The Public Health (Ships) Act, 1885. The Metropolis Local Management Acts, Public Health (London) Act, 1 89 1, etc. Port Sanitary Authorities. Under the Public Health Act, 1875, section 287, the Local Government Board may by Order constitute any sanitary authority, or a combination of sanitary authorities, whose district or districts abut upon any port in England or Wales, the port sanitary authority — either temporarily or permanently. The Order may assign to the port sanitary authority any of the po-wers, duties, etc., of an urban sanitary authority, so far as applic- able to a port, and to vessels, -waters, or persons -within its jurisdiction. These duties include the appointment of a medical officer of health and of an inspector of nuisances, the duties of the former being prescribed by a special Order of the Local Government Board. In addition, this officer has to carry out the Board's Cholera Regulations of 1890 and 1892, and any Regulations made by the Board prohibiting the importation of rags from infected foreign ports, or requiring that they shall be disinfected or destroyed to the port medical officer's satisfaction (1893 Order). The disinfection must be by steam. Dirty and disused bedding or clothing arriving from certain ports, -whether belonging to emigrants or other-wise, can only be landed for destruction or disinfection. A port sanitary authority discharges duties, under public health legislation, -which are very similar to those performed by urban sanitary authorities. The port sanitary authority has not full control in matters affecting the sanitation of vessels, as the sanitary provisions of the Merchant Shipping Act, 1894, a^re not administered by them, and ships belonging to British and Foreign Governments are exempt from their inspection. The port sanitary authority exercises its po-wers under the folio-wing Acts, Orders, etc. : (i) The Public Health Act, 1875, and the Public Health (London) Act, 1891, under which any ship or vessel lying in any river, harbour, or other water within the district of the local authority, is subject to the same treatment with regard to nuisances, as premises on land ; (2) the Public Health (Ships) Act, 1885, which extends to ships the provisions of the Public Health Act, 1875, which apply to hospitals and infectious disease ; (3) the provisions of the Infectious Diseases Notifica- tion Act, 1889, which are applicable to ships ; (4) the Public Health Act, 1896, which repeals the Acts relating to quarantine, and defines the powers of the Local Government Board to make Regulations (under the Public Health Act, 1875) as to cholera, yellow fever, and plague as follows : — (a) Signals to be hoisted by vessels having such diseases on board ; (b) ques- 40 626 HYGIENE AND PUBLIC HEALTH tioiib to be answered by masters, pilots, aud passengers as to cases of disease on board during the voyage ; (c) the detention of vessels and persons aboard ; {d) certain duties to be perfornaed by the master, pilot, etc. These Regulations (1S96) also reqixire that infected ships must hoist a yellow and black flag, which must be displayed between sunrise and sunset when within three miles of the coast. Lender the existing Regulations " Ever}- ship is deemed to be infected in which there is or has been during the voyage, or during the stay of such a ship in the port of departure, or in a port in the course of such voj'^age, any case of cholera, yellow fever or plague," and the term " cholera " includes " choleraic diarrhoea." Under the Paris Convention, 1903, injected ships are those where there has been any case of cholera or plague on board ^vithin seven days of arrival in port. Suspected ships are those where there have been any cases of cholera or plague on board at the time of departure, or during the voyage, but no fresh cases within seven days. A place must be appointed for the mooring of all infected ships, and when the Customs Officer finds or suspects that a ship is infected he must order the ship to be anchored in this place and acquaint the sanitary authority of the fact, when none of the passengers or crew may leave the ship ; the medical officer of health must visit and inspect within twelve hours, or the ship may proceed ; and, if he is of opinion that any ship is infected, he raust certify to the master of the ship and the sanitary authority' and inform the Local Government Board ; the master must moor to an appointed " mooring place." where the medical officer of health shall examine every person on Iward ; and no one may leave the ship. Infected persons must be removed to a hospital, or the ship may be constituted the hospital ; suspected persons ma^- be detained on board or in hospital for forty-eight hours ; other persons shall satisfy the medical officer as to their names, places of destination and addresses at such places, and the clerk to the sanitary authority must transmit this informa- tion to the sanitary authorities of the districts to which such persons are going ; every person who, within forty-eight hours after landing, shall arrive at any other address than that furnished, must notify in writing his fresh address to the medical officer of health of the district in which such place is situate. The master, under the direction of the sanitar}- authority, must bury infected dead bodies (properly loaded) at sea, or deliver to sanitary authority for burial ; all necessarj^ disinfection is to be carried out at the cost of the owner and to the satisfaction of the medical officer of health ; where a ship comes from a place infected with cholera, yellow fever and plague (though not itself infected), or has filthy and unwholesome persons on board, the medical officer of health may issue certificates (one to the sanitary authority' and one to the master) to prevent the landing of such persons until they satisfy the medical officer as to their names and addresses at places of destination ; bilge water, and water that may be ordered to be pumped out before the ship (whether infected or from an infected port) enters a dock or basin, and all casks or tanks containing drinking water, are to be emptied and cleansed if required. If any person wilfully neglects or refuses to obey or carry out or obstructs the execution of any of these regulations, he is liable to a penalty not exceeding ;^ioo and ;^50 for each day of continuing offence. An International Conference was held at Paris, 1903, and a Convention was agreed to dealing with the precautions to be adopted to prevent the introduction of cholera, yellow fever, and plague. On ships infected with plague, the rats >nitst be destroyed either before or after the discharge of cargo, within a maximum period of forty -eight hours. Precautionary measures shall be adopted at infected ports on the SANITARY LAW AND ADMINISTRATION 627 tieparture of vessels ; and an Act was passed in 1905 enabling the Loca Government Board to make regulations as to this. For the i)iirpose of administering these powers the port sanitary autho- rity shall appoint a medical officer of health and sanitary inspectors. In a large port the services of one or more assistant medical officers are generally required, especially when cholera or plague threatens ; the medical officers then take duties in rotation. In the sanitary inspection of ships the following matters claim atten- tion : — The condition of the crew's quarters with regard to ventilation, lighting, cleanliness, and protection from weather ; cubical capacity and floor areas (there should be a minimum of 72 cub. ft. and 12 sq. ft. of floor space for each man) 1 ; general cleanliness ; the efficiency of sanitary fittings and the condition of the bilges and bilge-water ; the source of supply and storage of drinking-water, the accessibility for cleansing purposes and the protection of tanks, etc., from contamination. The inspection of food- stuffs brought to the port, and their seizure when unwholesome or unfit for the food of man, is an important branch of port sanitary work. The work of checking the spread of infectious disease aboard and pre- venting its importation is another important branch of work. It is performed in precisely the same manner as on shore, as is also the subse- (juent disinfection. Copies of the regulations relating to various infectious diseases are printed in several languages and distributed among ship- owners, consuls, captains and all interested. By-laws relating to infectious diseases have been made by nearly all port sanitary authorities. These require inter alia that : A vessel arriving with any person on board suffering from a dangerous infectious disorder is required to stop at a certain specified place, and acquaint the medical officer of health. The vessel shall remain there until boarded by the medical officer of health, who may order the master to land the case at the hospital of the port sanitary autho- rity, if proper accommodation can be provided therein. By-laws may also be made for keeping in hospital, for so long as may be necessary, any persons, brought within their district by any vessel, who are infected with a dangerous infectious disease. As the Customs Officers are the first to receive intimation of sickness on board any vessel approaching the port, it is desirable that the Customs Depot and the Port Sanitary Offices should be adjacent to each other, so that all information of infectious illness can be easily and promptly re- ported to the sanitar3/ authority. The Port Sanitary Hospital should be well isolated and at a convenient distance from the mooring station. Commonly the City Fever Hospital is used for the reception of all sea- borne cases of infectious disease excepting cholera, plague, yellow fever or small-pox. In connection with plague-infected ships, every effort must be made to prevent rats from landing and to destroy them so far as possible. The employment of an experienced rat-catcher appears to be the best solution of this difficulty. The rats caught alive on board should be killed and, with the bodies of those found dead, destroyed in the ship's furnaces. \\Tien any vessel has had dangerous infectious disease aboard, the medical officer of health inust give notice thereof to the medical officer of health of any port in the United Kingdom whither such vessel is about to sail. The Canal Boats Acts, 1877 and 1884, and the Regulations made under these, are also administered by certain port sanitary authorities. 1 These measurements have been increased by the Merchant Shipping Act, 1906, to 120 cubic feet and 15 superficial feet respectively. 628 HYGIENE AND PUBLIC HEALTH Ship-Borne Rats mid Plague. In view of the susceptibility of the rat to plague, and of risk therefore of importation into this country by shipping of plague-infected rats, sanitary authorities of seaports should be on the alert to prevent intro- duction of the disease into their districts in this waj'. T . On the arrival in port of a vessel whereon, during the voyage, plague or sickness suspected to be plague has occurred, measures should be taken to secure the destruction of the rats on board the vessel. Until this has been done, endeavour should be made to prevent rats leaving the ship, by mooring the vessel a sufficient distance from other ships and from the shore, and by placing guards on cables and hawsers in use for mooring purposes. 2. In the case of vessels that have come from places infected with plague, but on board of which no plague or suspected plague has occurred, strict inquiry should be made on their arrival in port as to mortality or sickness among rats during the voyage. Should this have occurred, the authority would do well to obtain the body of a sick rat for the purpose of ascertaining the nature of the malad}^ affecting those animals on board the vessel. In the event of the malady being found to be plague, the ship should be dealt with as under Paragraph i. 3. Exceptional sickness or mortality among rats on board any vessel within the district, whatever may have been her port of departure, should be viewed with suspicion and as giving occasion for action similar to that indicated under Paragraph 2. 4. Rats when destroyed on shipboard should not be handled ; they should be at once cremated. 5 . In the event of rats on board any ship being found to be infected with plague, all parts of the vessel frequented by those animals should, as far as possible, be disinfected. 6. The authorities of seaport towns invaded by plague should endeavour to secure the destruction of the rats of the town, not least those inhabiting the docks and quayside warehouses. ^Measures should be taken to guard against shore-rats making their way on board vessels lying in the port, and an attempt made to destroy all rats on board ships about to proceed on their voyage. Captains of such vessels should be urged to take steps during the ensuing voyage for the destruction of rats that may have remained alive on board their vessels notwithstanding the action of the local authority. The Local Government Board has also published (August 26, 1892) a set of Precautions against the Infection of Cholera, a General Memorandum on the Proceedings which are advisable in Places attacked or threatened by Epidemic Disease, and a Memorandum on Plague. The Aliens Act, 1905. Immigrants may not be landed in the United Kingdom from an immi- grant ship except at a port at which there is an immigration officer ap- pointed under the Act, and may not land at any such port unless first inspected by such ofhcer in company with a medical inspector, such inspection to be made as soon as practicable. Leave to land may be withheld in the case of undesirable immigrants, but the master, owner, or agent of the ship or the immigrant may appeal to the immigration board of the port, and the board, if satisfied that leave to land should not be withheld, may grant leave. An undesirable immigrant is one who cannot show that he has in his possession or is in a position to obtain the means of decently supporting himself and his dependants (if any) ; or if he is a lunatic or an idiot, or owing to any disease or infirmity appears likely to become a charge upon SANITARY LAW AND ADMINISTRATION 629 the rates or otherwise a detriment to the public ; or has been sentenced in a foreign country with which there is an extradition treaty, for a crime, not being an offence of a pohtical character ; or if an expulsion order under tliis Act has been made in his case. In the case of immigrants who prove that they are seeking admission to this country solely to avoid persecution or punishment on religious or poli- tical grounds, or for political offences, leave to land must not be refused on the ground of want of means, or the probability of their becoming a charge on the rates. The same applies to immigi-ants who having resided six months in this country have been refused admission to a foreign country, and return direct therefrom, and to those who were born in the United Kingdom, and are British subjects. The Secretary of State may, if he thinks fit, in respect of any alien certified to be convicted by any court of any felony, misdemeanour, or other offence punishable by imprisonment without the option of a fine, make an expulsion order requiring the alien to leave the United Kingdom within a fixed time, and thereafter to remain out of the United Kingdom. Medical Officers of Health and Sanitary Inspectors. By the Public Health Act, 1875, section 189, every urban and rural sanitary authority is required to appoint a medical officer of health and an inspector of nuisances ; but two or more districts may be combined by the Local Government Board to form a combined sanitary district, with one set of officers for the whole combination. County Councils under the Local Government Act, 1S88, section 17, may appoint a county medical officer of health. If any part of the salary of a medical officer of health is repaid to a local authority out of Imperial funds, the Local Government Board has the same power of approval of his qualifications, appointment, duties, salary, and tenure of office, as it has in the case of a poor law medical officer (Public Health Act, 1875, section 191). By section 18 of the Local Government Act, 1888, every medical officer of health appointed after the passing of the Act must be legally qualified in medicine, surgery, and midwifery ; if appointed after January i, 1892, to a district having at the last census 50,000 inhabitants or more, he must be the registered holder of a diploma in public health under sec- tion 21 of the Medical Act, 1886, or have been during three consecutive years prior to 1892 a medical officer of health of a district with a popu- lation at the last census of not less than 20,000, or have been for not less than three years a medical officer or inspector of the Local Government Board. If no part of the salary of the medical officer of health is repaid to the sanitary authority, the Local Government Board need not be consulted, nor is their approval necessary as regards qualifications, appointment, salary, or tenure of office. If a portion of the salary is repaid, the medical officer cannot be removed except with the sanction of the Board, and if suspended the Board may remove the suspension. The duties of both classes of officers are the same under the Local Government Board's regulations of March 23, 1891. In London ever};- medical officer of health must reside within his district or within one mile of its boundary. He must not be appointed for a limited period only, as may be done outside London. He is removable by the Local Government Board, as well as by his sanitary authority, with the consent of the Local Government Board. In other respects the post is similar to that of an extra [Metropolitan officer as regards appoint- ment, qualifications, tenure of office, and duties. 630 HYGIENE AND PUBLIC HEALTH In London every sanitary inspector appointed after January i, 1895, must be a holder of a certificate of an examining board approved by the Local Government Board, or must have been during three consecutive years preceding 1895 a-ii inspector of a district containing a population of not less than 20,000. Outside London there is no qualification required by statute for inspectors of nuisances. In London every sanitary authority is required to appoint an adequate number of fit and proper persons as sanitary inspectors ; and the London County Council has power to insist upon a sufficiency of inspectors for each Metropolitan Borough. By-Laws and Regulations. . Under the various statutes relating to public health, sanitary authorities have power to make by-laws. These by-laivs should supplement, not vary or supersede, the express provisions of the statutes. If repugnant to the laws of England or to the provisions of the Acts, they are uliva vires and of no effect. Reasonable penalties may be provided for in the by-laws for neglect or infringement of their requirements. All by-laws must be con- firmed by the Local Government Board, and when so confirmed have the force of law. Regulations do not, as a rule, provide for the infliction of penalties, nor require confirmation by the Local Government Board. Both by-laws and regulations are usually drafted upon models issued by the Local Government Board. Every urban sanitary authority must make by-laws in respect of common lodging houses and slaughter houses, and every rural sanitary authority must make by-laws in respect of the former. With respect to all other matters on which by-laws may be made, it is optional to do so, unless required by the Local Government Board. Both urban and rural authorities may make by-laws in respect of cleansing and scavenging ; tenement houses occupied by members of more than one family ; hop and fruit pickers ; tents and vans ; and mortuaries. Urban authorities may in addition make by-laws for new streets and buildings, markets and fairs, offensive trades, open spaces, and cemeteries. Urban powers may be granted by the Local Government Board to rural authorities, including the making of by-laws ; and the adoption of the Public Health Acts Amendment Act, 1890, enables a rural authority to make certain bj-'-laws in respect of new and old buildings. Regulations may be made by any sanitary authority under the Dairies, Cowsheds, and Milkshops Order with respect to dairies and cowsheds ; also under the Public Health Act, 1875, for the management of post- mortem places provided by the authority ; and under the same Act for the removal to, and detention in, hospital of infectious patients taken ofif ships and vessels. In London the County Council has power to make by-laws for a great variety of purposes relating to new streets and roads, plans and sites of buildings, drains and sewers, etc., under the Metropolis Local Management Acts and London Building Act, 1894. LTnder the Public Health (London) Act both the County Council and the local sanitary authorities are required to make by-laws on a variety of subjects which will be alluded to in their proper place. Sewers. Public Health Act, 1875. Definition. — Sewer includes sewers and drains of every description, except drains of, and used for the drainage of one building only, or premises within the same curtilage. It follows from this definition that sewers may be on private land, as well as in or beneath streets or highways SANITARY LAW AND ADMINISTRATION 63I which are dedicated to the public. The meaning of the word " curtilage " is obscure, although it is generally held to signify the boundary wall of the premises ; blocks of artisan dwellings, separated from each other by an open causeway, were held to be within the same curtilage (Pilbrow v. Vestry of Shoreditch) . All sewers, with the exception of certain private sewers, are vested in the local authority. The local authority must keep all sewers under their control in repair, and must make such sewers as may be necessary for effectually draining their district. They must cause the sewers under their control to be so constructed, ventilated, and cleansed, as not to be a nuisance or injurious to health (sections 13, 15, 19). Where complaint is made to the Local Government Board that a local authority has made defaidt in providing their district with sufficient sewers, or in the maintenance of existing sewers, that Board can compel the local authority to perform its duty in the matter of such complaint (section 299). The owner or occupier of any premises within the district of a local autho- rity is entitled to drain his house into a sewer after due notice, and on condition of complying with the local authority's regulations for the making of communication between sewers and drains (section 21). Section 26 prohibits the erection of any building over a sewer of an urban authority without the written consent of such authority. This section applies to combined drains which are sewers on private land, as well as to sewers in public roads and highways. Public Health Acts Amendment Act, 1890 [adoptive). In places where this Act has been adopted, where two or more houses belonging to different owners are connected with a public sewer by a single private drain (that is to say, a drain on private land with which adjacent house owners are not at liberty to make drain connections), and the local authority has reason to believe that such drain is defective or a nuisance, the local authority can, under the powers conferred by section 41 of the Public Health Act, 1875, after twenty-four hours' notice to the occupiers, proceed to open the ground and expose the drain, and, if found defective, execute such works as may be necessary to make the drain secure and sound, and recover the expenses so incurred from the owners of the houses. For the purposes of this section, therefore, under the Amendment Act of 1890, the drain of more than one building, where the buildings belong to different owners, is a drain for which such owners are responsible ; but if the different buildings belong to one owner, such drain is a sewer, for which the local authority is responsible. Sections 16 and 17 of the same Act prohibit the introduction into any sewer of any matter which would interfere with the flow of the sewage, or by which the sewer may be injured, and prohibits the introduction of any chemical refuse or liquids of any kind having a temperature exceeding 110° F., which either alone or in combination with the sewage cause a nuisance, or are dangerous or injurious to health. Metropolis Local Management Acts, 1855 and 1862. In London the definition of sewer is the same as in the provinces under the Public Health Act, 1875, with the exception that the combined drain of a group or block of houses, drained by a combined operation under the order or with the sanction or authorization of the local sanitary authority (or, prior to 1855, of the Metropolitan Commissioners of Sewers), is a drain for which the owner or owners of the houses are responsible, and not a sewer (1855 Act, section 250; 1862 Act, section 112). Recent decisions 632 HYGIENE AND PUBLIC HEALTH of the High Court of Justice and of the Appeal Courts have shown that if the scheme of drainage sanctioned by the authority has been departed from in material particulars, or if the drains of other houses have been connected surreptitiously, or without authorization, subsequent to the passing of the plans, the combined drain is a sewer, and repairable by the local authority. In fact, no combined drains, except those which have been sanctioned by authority, and which at date practically conform with the plans passed by the authority, are drains ; otherwise they are sewers, repairable by the ratepayers at large. The control of the main sewers in London and of the disposal of the Metropolitan sewage is vested in the London County Council, whilst the street and other branch sewers are vested in the Borough Councils, with whom lies the regulation of the method of making communications between all lio;ise drains and sewers. As in the provinces, there is a penalty imposed for building over any sewer or interfering with any sewer without the consent of the local authority ; and there is a prohibition from dis- charging into any sewer any matters which would interfere with the flow of the sewage, or any liquids which would damage the sewer or create a nuisance. Disposal of Sewage. Section 17 of the Public Health Act, 1875, expressly states that nothing in the Act shall authorize the discharge of sewage into any natural stream or water course until the sewage has been freed from all excrementitious or other foul or noxious matter. Sections 27 to 34 of the same Act give powers to local authorities to construct works for the disposal of sewage, either within or without their districts. For this and other purposes local authorities can borrow money on the credit of the rates, subject to the sanction of the Local Government Board (section 233). The regulations applicable to the exercise of borrowing powers, which must be complied with, are set out in section 234 of the Act. Rivers Pollution Prevention Act, 1876. By section 7 of this Act sanitary authorities must give facilities to manu- facturers to carry their waste waters into the district sewers, provided such waste waters do not affect prejudicially the sewers, or the disposal of the sewage on land or otherwise at the outfall, or are not themselves injurious from a sanitary point of view or by reason of high temperature. There is no obligation on sanitary authorities to construct new sewers to receive manufacturing waste, if their existing sewers are only just sufficient for the ordinary requirements of the district, and are unable to receive larger volumes of manufactory refuse. House Drains. Public Health Act, 1875. By section 23, a local authority can require the owner or occupier of any house which is within their district, and which is " without a drain sufficient for effectual drainage," to make a drain to empty into any sewer which the local authority is entitled to use (for this purpose), which is not more than 100 feet from the site of such house — i.e., from the boundary of the land on which such house is situate. If no such sewer is situate within TOO feet of the boundary, then the drain may be made to empty into a covered cesspool or other receptacle, not being under any house, as the local authority may direct. Such drain or drains must be of such material and size, and laid at such levels and with such fall, as the surveyor to the local authority may direct, SANITARY LAW AND ADMINISTRATION 633 By section 25, urban authorities can insist on newly erected houses, or houses which have been rebuilt after being pulled down to the ground floor, being drained in a similar manner to the above. No newly erected or rebuilt house may be occupied until a proper drain has been provided. The examination or testing of drains (not involving the opening of the ground) is provided for by section 102 of the Act, which directs that any officer of a local authority shall be admitted into any premises between the hours of 9 a.m. and 6 p.m. for the purpose of examining as to the exist- ence of any nuisance thereon. If it is necessary to open the ground to examine the state of a drain, a written application must be made by some person to the local authority, stating that the drain of the premises in question is a nuisance or injurious to health. The local authority must then in waiting empower their officer, after twenty-four hours' -written notice to the occupier of the premises, or in case of emergency without notice, to enter such premises and open the ground. In the event of the drain being defective, notice is to be served upon the owner or occupier to carry out the necessary works ; or the local authority may itself execute the works, and recover the costs so incurred from the party or parties who are liable (section 41). Section 40 of the same Act requires every local authority to provide that all drains within their district are constructed and kept so as not to be a nuisance or injurious to health. By section 157 of the Act, urban authorities may make by-laws with respect to the drainage of buildings, but such by-laws cannot be made to apply to any building erected in any place which, on August 11, 1875, was included in an urban sanitary district before the Local Government Acts came into force in such place, or any building erected in any place which, on that date, was not included in any urban district before such place became included in an urban district, by virtue of any order of the Local Government Board. In places where the Public Health (Amend- ment) Act, 1890, Part III., has been adopted, section 23 extends the opera- tion of drainage by-laws to buildings erected before the time above mentioned, and also enables rural authorities to make such by-laws. It must be clearly understood that drainage by-laws — that is to say, by-laws specifying the materials from which drains are to be constructed, their jointing, gradients, ventilation, disconnection, methods of connecting branches, etc. — cannot be made to apply to existing drains or to drains of existing buildings. They are applicable to drains about to be laid for new or old buildings — i.e., to new drains of new buildings or to new drains of old buildings, which for one reason or another are about to be redrained. Existing drains cannot be condemned and new drains required because they — the existing drains — do not comply in whole or in part with the regulations contained in drainage by-laws. Where existing drains are found to be so defective that they cannot be repaired so as to render them sound, and obviate present and future nuisance, notice can be served for them to be relaid. In such a case it is probable that a local authority can insist on the new drain complying with their drainage bj^-laws. Metropolis Local Management Acts and Public Health {London) Act, 1S91. Practically the same provisions exist in London for dealing with house drainage as in the provinces. The Metropolis ^Management Act, 1855 (section 202), gave powers to the Metropolitan Board of Works to make drainage by-laws, and such by-laws have been prepared by the London Count}' Council. Section 15 of the Public Health (London) Act imposes a £5 penalty on any person who wilfully destroys, or damages, or stops up, or interferes 634 HYGIENE AND PUBLIC HEALTH with, any drain, so as to cause it to be a nuisance or injurious or dangerous to health — a section very useful in restraining the acts of mischievous or evil-disposed persons. Section 42 of the same Act imposes a ^20 penalty on any person who so repairs or constructs a drain as to cause it to be a nuisance, or injurious or dangerous to health — again a most useful section in preventing scamped or defective work. Water-closets, Sanitary Conveniences, and Sanitary Fittings. Public Health Act, 1875. Every house within the district of a local authority must have a sufficient water-closet, earth-closet, or pri-\'y, and an ashpit, furnished with proper doors and coverings ; and no house may be erected or rebuilt without similar sanitarj^ accommodation (sections 35 and 36). It is for the local authority, acting on the advice of its officers, to deter- mine in each case what constitutes the sufficiency of a water-closet, earth- closet, or privy. Under these sections a proper supplj^ of water to flush a water-closet can be enforced. As regards the conversion of privies into water-closets — a policy now largely taken up in the " privy " towns of the Midland and Northern counties — the local authority has no power to make a general order enforcing the replacement of privies by water-closets, but has power in any particular case to require the conversion, if satisfied that the privj^ is not sufficient for the health requirements of the people who use it (Tinkler v. Wandsworth Board of Works). Under section 157, urban authorities are empowered to make by-laws as to water-closets, earth-closets, privies, ashpits, and cesspools, in the same way as to drains (see ante, p. 633) ; and these by-laws are extended in the same way by the Public Health Acts Amendment Act, 1890. Every local authority must provide that all water-closets, earth-closets, privies, ashpits, and cesspools are constructed and kept so as not to be a nuisance or injurious to health ; whilst the provisions of section 41 apply equally as for drains where it is desirable to open the ground — e.g., for the examination of a privi,^ or cesspool (see ante, p. 633). Public Health Acts Amendment Act, 1890. Section 21 imposes a ids. penalty on any person who injures or improperly fouls a sanitarj'^ convenience which is used in common by the occupiers of two or more separate dwelling houses, or by other persons ; and a similar penalty', with a daily 55. penalty, is imposed upon all persons using a common closet which is in such a filthy condition as to be a nuisance or annoyance, from want of proper cleansing, in the absence of proof as to who is the person actually in default. Public Health {London) Act, 1891. Very much the same provisions apply in London as in the provinces. The County Council has made by-laws under section 39 of the Act which apphj- to all new fittings in new or in existing buildings (water-closets, soil pipes, earth -closets, ashpits, cesspools, dung receptacles, and their acces- sories). As before said (see p. 633), existing sanitary fittings must not be condemned because they do not conform to the bj^-laws, but all new fittings to replace existing ones must complj^ with the by-laws. In addition, every person who intends to fix a new water-closet, earth-closet, etc., is required to give notice of such intention to the local authority (municipal borough). Every local authority (municipal borough) has made by-laws under the same section (39, 2) vnt\\ respect to the keeping of water-closet?. 5-\NITARY LAW AND ADMIN ISTR.\TIOX 635 supplied with sufficient water for their effective action. Sections 15 and 42 of the Act (see p. 633) apply equally as in the case of drains, whilst section 46 incorporates section 21 of the Public Health Acts Amendment Act, 1890, above mentioned. Anj^ person who thinks himself aggrieved by any notice or act of a sanitary authority under these sections may appeal to the London County Council, whose decision shall be final. XUISANCES. Public Health Act, 1875. The nuisances with which Public Health Acts are concerned are con- ditions which are either actually injurious to health or are liable to be injurious (i.e., dangerous) to health. These conditions are more or less defined in the Acts relating to public health ; hence these nuisances are also called " statutory- nuisances." These Acts provide the methods and machinery for summarily (i.e., expeditiously) dealing wth this class of nuisances, but this does not exclude the invoking b}'- any person aggrieved of the Common Law statutes should he not be satisfied \\ith the remedies pro%-ided by the special Acts. Nuisances which interfere with comfort or with the enjovment of life, and are not ejiisdern generis with those specifically mentioned in the Public Health Acts, having no obvious relation \\"ith dangers to health, are onlv remediable by the ordinary operations of the Common Law, and not bv the piiblic health statutes. Nuisances are defined in section 91 of the Public Health Act, 1875 : 1. "Any premises in such a state as to be a nuisance or injurious to health." The word "premises" includes "messuages, buildings, lands, easements, and hereditaments of any tenure." It has been ver\' generally held that it is not necessary to prove actual injury to health, but simply to prove that the nuisance is of such a nature as to be capable of acting prejudicially upon health. For instance, damp, dirty, and dilapidated premises, or houses invaded by bugs or other vermin, are nuisances under this subsection, because the}' are all capable of affecting injuriously the health of the occupants. 2. " Any pool, ditch, gutter, water course, privy, urinal, cesspool, drain, or ashpit so foul or in such a state as to be a nuisance or injurious to health." Under this subsection, a ver\' great deal of the sanitary work of local authorities is carried on. The enforcement of the paving of yards and areas about houses is usually required under this subsection, to obviate nuisance from standing pools of dirty water. 3. " Am- animal so kept as to be a nuisance or injurious to health." 4. " Any accumulation or deposit which is a nuisance or injurious to health." Trade or manufactorv deposits are exempt, if not kept longer than necessary for the purposes of the business, and if the best available means have been taken to obviate injury to health. 5. " Any house or part of a house so overcrowded as to be dangerous or injurious to the health of the inmates, whether or not members of the same family." From 300 to 400 cubic feet per head is usually taken as the minimum permissible, with half these amounts for children under ten years ; but in every case attention should be paid to special cir- cumstances — e.g., the amount of ventilation obtainable, the condition of the room, the class of people, the relationship of the persons over- crowded, etc. There are other nuisances relating to the cleanliness, ventilation, and overcrowding of factories and workshops, and to smoke, which will be dealt with later on. Section 92 requires the local authority- to cause an inspection of its district to be made from time to time, to ascertain what nuisances exist 636 HYGIENE AND PUBLIC HEALTH calling for abatement, and to enforce the provisions of the Act, in order to abate the same ; and section 102 (see ante, p. 633) gives powers of entry to the officers of the local authority to earn,;- out the provisions of the Act, between the hours of 9 a.m. and 6 p.m., and in cases of nuisances arising in respect of am?- business, at any hour when such business is in progress. Public Health [London) Act, 1891. The provisions relating to nuisances in London are the same as in the provinces. In order to prevent the possibility of nuisances being held to be only conditions which have actually caused injury to health, the words " or dangerous " have been introduced into this Act, so that the various sections read, " a nuisance, or injurious or dangerous to health." In London also (inhabited) premises without water fittings are a nuisance, and an occupied house without a proper and sufficient supply of water is a nuisance, which in the case of a dwelling house renders it unfit for human habitation (section 48). By section 100 it is provided that the County Council, when satisfied that a local sanitarj'- authority has made default in doing its duty under the Act, with respect to the removal of any nuisance, the institution of any proceedings, or the enforcement of any by-law, may themselves do what is necessar}^ to carry out the provisions of the Act, and recover the costs from the defaulting authorit^^ On complaint by the County Council to the Local Government Board that a sanitary authority is in default in executing or enforcing the provisions of the Act, the Board may, after inquiry, make an order limiting a time for the performance of the duty by the sanitary authority, enforceable by mandamus ; or the Board may appoint the Count}^ Council to perform the duty, and in that event the Council is invested with all the powers of the sanitary authority, and can recover from the latter all expenses incurred, or can recoup themselves by levying the amount by a rate. ~By section 299 of the Public Health Act, 1875, the Local Government Board has similar powers in respect of urban or rural authorities who have raade default in enforcing any of the provisions of the Act which it is their dut}' to enforce. The Count}?^ Council may make the complaint to the Board, and may be appointed by the Board to execute the provisions of the Act neglected by the local sanitary authority (Local Government Act, 1894). Procedure to abate Nuisances, and to carry out the Provisions OF THE Acts. Public Health Act, 1875. Sections 94 to 100 deal with the procedure necessary. Information of a nuisance may be given by any aggrieved person, any two inhabitant householders, any of&cer of the local authority, the relieving officer, or police officer. A complaint having been made to a local authority of the existence of a nuisance, it is the dut}^ of the sanitary inspector (inspector of nuisances) to visit the premises or place, and to report to the next meet- ing of his board (local authority). The latter, if satisfied of the existence of a nuisance, directs that a notice shall be served (Form A, Schedule IV) on the person by whose act, default, or sufferance the nuisance arises or continues — or, if such person cannot be found, on the OAvner or occupier of the premises on which the nuisance arises — requiring him to abate the same within a specified time, and to execute the works necessary for that purpose. Where the nuisance arises from the want or defective construe- SANITARY LAW AND ADMINISTRATION 637 tion of any structural convenience, or where there is no occupier of the premises, the notice inust be served on the owner, but where the nuisance arises from the neglect or default of the occupier, the notice must be served on the occupier. Where the person causing the nuisance cannot be found, and it is clear that the nuisance does not arise or continue by the act, default, or sufferance of the owner or occupier of the premises, the local authority may themselves abate the same. " Owner " under this Act means the person for the time being receiving the rack-rent of the lands or premises in question, whether on his own account or as agent or trustee for any other person, or who would so receive the same if such lands or premises were let at a rack-rent ; the latter term meaning rent which is not less than two-thirds of the full net annual value of the property out of which the rent arises. Notices may be in print or writing, or partly in either, and are authenti- cated by the signature of the clerk, surveyor, or inspector of nuisances of the local authority. The notice may be served by delivering it or posting it by registered letter to the residence of the person to whom it is addressed. The notice need not be addressed to any particular individual, but can be addressed to the owner or occupier of the premises, as the case may be, and either left upon the premises, or, in the case of the premises being empty or there being no person on the premises to receive the notice, it may be hxed to some conspicuous part of the premises (sections 266, 267). Should the notice or any of its requisitions not be complied with within the time specified, it is the duty of the inspector to report the matter to his board at its next meeting, who should instruct him to make a complaint before a justice (sworn information of the facts), who thereupon is to issue a summons (Form B, Schedule IV), requiring the person on whom the notice was served to appear before a court of summary jurisdiction. The summons must be applied for within six months of the date of the original offence ; otherwise all further proceedings are invalidated. On the hearing of the summons, it will be necessary for the inspector to give evidence as to the existence of the nuisance, the dates of his visits to the premises, and the service of the notices in proper form. He must also be prepared to prove the ownership in case a particular person is sum- moned as owner, which is usually done by the production of the rent book or the evidence of a tenant of the house. If the court is satisfied as to the existence of a nuisance, it may make (i) an abatement order (Form C) — an order to abate the nuisance within a specified time, and to do any works necessary for that purpose — or (2) a prohibition order (Form C), prohibiting the recurrence of the nuisance, with necessary works. The court may at the same time inflict a penalty not exceeding ;^5. Where the nuisance proved to exist is such as to render a house unfit for human habitation, the court may make (3) a closing order, prohibiting the use of the house for human habitation until rendered fit for that purpose. If the person on whom the magistrates' order is made fails to comply with its requirements within the time specified in the order, he can be again summoned ; and if he fails to satisfy the court that he has used all due diligence to carry out such order, he may be fined 105. per day during his default (abatement order), or 20s. per day (prohibition order). If the local authority prefers, it may direct its officers to enter the premises and execute the works specified in the order of the court, and recover in a summary manner the expenses so incurred from the person on whom the order is made (County Court proceedings). A person convicted under these sections can appeal to the next Court of Quarter Sessions, within fourteen days after the hearing, provided he gives notice of such intention to the local authority and enters into the necessary recognizance. GjS HYGIENE AND PUBLIC HEALTH Public Health (London) Act, 1891. The procedure in London is practically the same as that above detailed, with the exception that hy section 3 of the London Act a sanitary inspector is required to send a " written intimation " of the existence of a nuisance as soon as he becomes aware of it, to the person who may be required to abate it. The written intimation should be merely an intimation of the existence of a nuisance, and should not contain any threat of subsequent proceedings. In very many cases these written intimations lead to the abatement of the nuisance, without recourse having to be made to the service of statutory notices authorized hy resolution of the local authority. Furthermore, in the London Act " any person " may give information of a nuisance. Both urban local authorities in the provinces and the Metropolitan local authorities are empowered to delegate to a committee their powers as to the reception and service of notices, the taking of legal proceedings, and generall\ the execution of the sanitar}'- provisions of the Acts. Smoke Nuisances. Public Health Act, 1875. Section yi dehnes as a nuisance any fireplace or furnace used in any trade or manufacturing process which does not as far as practicable con- sume the smoke arising from the combustible used therein. There is. however, a proviso that, in the event of a person being summoned for this particular form of nuisance, the court must hold that no nuisance had been created, and must dismiss the complaint, if it is satisfied that the furnace is constructed in such a manner as to consume as far as practicable, having regard to the nature of the manufacture or trade, all smoke arising there- from, and that such furnace has been carefully attended to by the person in charge. The same section also defines as a nuisance any chimney (not being the chimney of a private dwelling house) sending forth black smoke in such quantity as to be a nuisance. In dealing with these smoke nuisances, notices are required to be served under the Act in the same manner as for the other statutorj- nuisances. If evidence is forthcoming that the smoke issuing was black and in such volume as to be a nuisance to the neighbourhood, in the absence of rebutting evidence, the magistrates are bound to convict. Should, hoAvever, the smoke not be black, but any lesser shade of colour (broAAoi, yellow, etc.), evidence must be adduced by the prosecution either that the stoking is at fault, that coal of unsuitable quality is being used, or that the furnace is not constructed so as to consume as far as practicable the smoke arising from the combustible used therein. All these, naturally, are matters much more difficult of proof than where the only evidence necessarj^ is the proof of black smoke and nuisance, and are also much more liable to be upset by rebutting evidence called on behalf of the defendant, who is entitled to show that the furnace is constructed in such manner as to con- sume as far as practicable, having regard to the nature of the manufacture or trade, all smoke arising therefrom, and that such furnace has been carefully attended to by the person having the charge thereof. The court must hold that no nuisance is created within the meaning of the Act, and dismiss the complaint, if satisfied that such is the case. The inspector should alwajrs make time observations, showing for each hour the number.^ of minutes of black smoke, of coloured smoke, and of absence of visible smoke respectively, and should produce this evidence in court. SANITARY LAW AND ADMIN ISTKATK^N 639 Public. Health [London) Act, 1891. In Loudon the smoke sections (23 and 24) of the Public Health (London) Act, 1 89 1, contain practically identical provisions, the authorities being the various borough councils. Scavenging and Cleansing. Public Health Act, 1875. Section 42 provides tliat every local authority may, and when required l)y the Local Government Board shall, themselves undertake or contract for (i) the removal of house refuse from premises, (2) the cleansing of earth- closets, privies, ashpits, and cesspools, (3) the cleansing and watering of the streets. If the local authority fails, without reasonable excuse, after written notice from the occupier of any house, to remove refuse or cleanse a privy, cesspool, etc., within seven days, the defaulting authority is liable to pay to the occupier 55. per day during such default. When the local authority do not themselves undertake or contract for the removal of house refuse and cleansing of privies, etc., they may make by-laws imposing those duties on the occupiers of premises, together with the cleansing of footways adjoining their premises. Urban authorities may also make by-laws for the prevention of nuisances arising from snow, filth, dust, ashes, and rubbish, and for the prevention of the keeping of animals on premises so as to be injurious to health. In urban districts no swine may be kept in any dwelling house so as to be a nuisance, rhe model by-laws of the Local Government Board require that swine must not be kept within . . . feet of any dwelling ; the distance should be JOG feet, under no circumstances should it be less than 60 feet. An urban authority may also give notice by public announcement requiring the periodical removal of all manure or other refuse from mews and stables. Penalties are incurred for infringing these notices made by public announce- ment, without any further notice being required to be sent to the person in default. Public Health Acts Amendment Act, 1890. I'nder this Act sanitary authorities have power to cleanse alleys and courts, which are not highways, and to charge the occupiers of the houses abutting on the courts with the cost of doing so. Public Health {London) Act, 1891. In London, footways as well as streets must be cleansed by the local authorities. If they fail to do so, they are liable to a fine of ;^20. The London authorities are also required to remove all house refuse from prem- ises. They are liable to a ;£20 fine if they neglect to do so for longer than forty-eight hours after the receipt of a complaint. Dustmen are prohibited from asking for gratuities. Local authorities may be required to remove trade refuse from any premises, but the occupier of the premises must pay a " reasonable " sum for the removal. Any question as to what constitutes trade refuse is to be settled by a Petty Sessional Court (magis- trate). Periodical removal of manure is required as under the 1875 Act. The collection of house and street refuse is deemed an offensive trade in London, and the County Council has control over the local authorities in this matter as if the business was an offensive trade. In London no swine may be kept on any premises within 40 yards of any street or public place. Every sanitary authority is required to make by-laws (i) for the pre- 040 HYGIENE AND PUBLIC HEALTH vention of nuisances from snow, ashes, filth, etc., in any street ; (2) for prevention of nuisance from offensive matter running out of trade premises ; (3) for tlie keeping of animals on any premises ; (4) for the paving of yards and open spaces in connection with dwelling houses. Straw and tan may be laid in the streets to prevent noise in case of illness. The County Council is required to make by-laws for prescribing the times — (i) for removing by road or water faecal, offensive, or noxious inatters or liquids, and the construction and covering of the vessels used for the purpose ; (2) as to the removal and disposal of refuse, and the closing up of privies and cesspools. These by-laws must be enforced by the local sanitary authorities. Water Supply. Public Health Act, iSjS- Power is given to all authorities, both urban and rural, to provide their districts with a supply of water proper and sufficient for public and private purposes (section 51). By section 62 a local authority may, on the report of their surveyor that any house within their district is without a proper supply of water, give written notice to the owner of the house requiring him within a specified time to obtain such supply, provided that it can be furnished at a cost not exceeding the water rate authorized by any local Act in force within the district, or in the absence of any local Act at a cost not exceeding 2d. per week. By section 70, on a representation being made to a local authority that within their district the water in any well, tank, or cistern, public or private, which is used, or likely to be used, by man for drinking or domestic purposes, or for manufacturing drinks for the use of man, is so polluted as to be injurious to health, the local authority may apply to a court of summary jurisdiction for a summons against the owner or occupier of the premises to which the well, tank, or cistern belongs. The court may at the hearing of the summons make an order for such well, tank, or cistern to be tem- porarily or permanently closed, or for the water to be used for certain pur- poses only. If the court sees fit, it may cause the water complained of to be analyzed at the cost of the local authority. Public Health {Water) Act, 1878. Section 3 makes it the duty of every rural sanitary authority to see that every occupied dwelling house within their district has within a reason- able distance an available supply of wholesome water sufficient for the use of the inmates of the house. When, on the report of an officer of the rural authority, it appears that an occupied dwelling house has not such a supply, and that it can be provided at a cost the interest of which at the rate of 5 per cent, would not exceed 2d. or T,d. per week, as the Local Government Board may determine, the authority may serve a notice on the owner to provide such a supply, within a specified time. If such notice is not complied with, a second notice may be served, to the effect that after one month from the date of its service the authority will themselves pro- vide such supply. At the expiration of the month, if the supply has not been provided, the authority may themselves execute the necessary works, and recover from the owner the expenses so incurred. By section 6 it is enacted that no newly erected or rebuilt house in a rural district may be occupied unless the owner has obtained a certificate from the sanitary authority that there is provided within a reasonable distance of the house an available supply of wholesome water sufficient for the use of the house. Section 7 requires every rural sanitary authoiuty to take such steps from SANITAR^il" law AMU ADMINISTRATION O4I time to time as may be necessary to ascertain the condition of the water supply within their district ; and section 11 authorizes the Local Govern- ment Board to invest by order any urban sanitary authority with all or any of the powers of this Act conferred upon rural authorities. London. In London the water is supplied by the Metropolitan Water Board taking water from the Thames, New River, Lea, and deep wells in the chalk. Their powers and duties are regulated by private Acts of the eight Water Companies, the predecessors in title of the Metropolitan Water Board, and by the Meti-opolis Water Acts of 1852 and 1871. The Local Government Board has certain powers of control ; for instance, it may make periodical examinations of the water, approve new sources of supply, approve the regulations made by the companier as regards pipes, taps and other house fittings for the prevention of waste or contamination, and also hold inquiries into complaints made by consumers as to the quality or quantity of the water supplied for domestic use. The London County Council has power to require a constant supply of water in any district in place of an intermittent supply. The Board serves notices on the houses in the district to alter their pipes and fittings to meet the require- ments prescribed for a constant service, and unless the Board can show that more than 20 per cent, of the houses have not adopted the prescribed littings, the supply must be made and continued constant. The County Council has power to supply the prescribed fittings on default of the owner or occupier of premises scheduled for a constant supply, and recover the costs so incurred. By section 48 of the Public Health (London) Act, 1891, a newly erected or rebuilt house must not be occupied until the sanitary authority has certified that it has a proper and sufficient supply of water ; and an occupied house without a proper and sufficient supply of water is a nuisance liable to be dealt with summarily under the Act, and if it is a dwelling-house, shall be deemed unfit for human habitation. This term " a proper and sufficient supply of water " is not sufficiently definite to include the provision of a water supply to every floor of a house let out in separate tenements 1 (Marylebone Police Court, 1905). By section 49 the Water Board, on cutting off the water of an inhabited dwelling house, is required to give within twenty -four hours written notice of the fact to the sanitary authority of the district under a £10 penalty. By section 50 every sanitary authority is required to malce by-laws for securing the cleanliness and freedom from pollution of tanks, cisterns, and other receptacles used for storing water for drinking or domestic purposes, or for manu- facturing drinks for the use of man. The other powers are similar to those in the Public Health Act, 1875, with the exception that in the case of wells, tanks, or cisterns, of which it is desired to obtain the closure it is only necessary to prove that the water is " so polluted, or likely to be so polluted, as to be injurious or dangerous to health." By the Water Companies (Regulation of Powers) Act, 1887, the Water Board is prohibited, under a ^^5 daily penalty, from^ cutting oflE the water supply for non-payment of water rates in the case of houses for which the rates are compounded, and the water rate is payable by the landlord. In London the rateable value of such houses must be ;£20 or under, and in the provinces ;£io or under. Rivers Pollution. By the Rivers Pollution Prevention Act, 1876, the following acts which might pollute a stream or interfere with its due flow are prohibited : (i) The 1 But this has since been provided for under the London County Council's General Powers Act, 1907. 41 642 HYGIENE AXD PUBLIC HEALTH discharge into any stream of solid refuse of am- manufactory or quarry, or an}- rubbish, cinders, waste or putrid solid body ; (2) the discharge of solid or liquid sewage matter, unless the best practicable and available means have been adopted to render harmless such matters ; (3) the dis- charge of an}- poisonous, noxious, or polluting liquid from any manu- factorj-, ^vith the same proviso ; (4) the discharge of any solid or liquid matter from anj- mine, with the same pro%-iso. A sanitarj^ authority can enforce the Act bj- taking legal proceedings, but only with the consent of the Local Government Board in the case of (3) and (4). That Board, in gi\-ing or withholding consent, must have regard to the industrial interests involved, and to the circumstances and requirements of the locality. If a sanitarjr authority declines to initiate proceedings, any aggrieved person maj- apply to the Local Government Board, who maj- direct the authority- to proceed. In this Act " stream " includes the sea to such extent, and tidal waters to such point, as ma}-, after local inquiry, and on sanitar}- grounds, be determined by the Local Government Board, by order published in the London Gazette ; save, as aforesaid, it includes rivers, streams, canals, lakes, and water courses, other than water courses mainl}^ used as sewers and empt\-ing directly into the sea. " Solid matter " does not include particles of matter in^suspension in water. " Polluting " does not include innocuous discolouration. Owing to the great manufacturing interests involved, and the safe- guards against procedure so abundantly introduced into the Act, it has been but little put into operation to prevent pollution of streams in the manufacturing counties. By the Rivers Pollution Prevention Act, 1S93, where anj- sewage matter falls or flo%vs or is carried into any stream after passing through or along a channel which is vested in a sanitary authorit}^ such sanitan,- authority shall, for the purposes of section 3 of the Rivers Pollution Prevention Act, 1876, be deemed to kno^^-ingl}'- permit the sewage matter so to fall, flow, or be carried. Cellar Dwellings. Public Health Act, 1875. There is no definition of cellar or underground room in this Act, but in the Public Health (London) Act, 1891, an underground room includes any room of a house the surface of the floor of which room is more than 3 feet below the surface of the footway of the adjoining street, or of the ground adjoining or nearest to the room. L'nder the 1875 Act anj^ cellar in which anvone passes the night is deemed to be occupied as a dwelling (section 74) . The Act prohibits the occupation of cellar dwellings not lawfull}?- occu- pied prior to the passing of the Act ; and existing cellar dwellings may only be occupied on certain conditions. No cellar maj^ be occupied separately as a dwelling (i.e., it may be occupied by a familj- in conjunction with other rooms on any other floor of the house, but not when used solely by one tenant or family) uifless the following requisitions are complied with : (i) Unless the cellar is 7 feet in height from floor to ceiling through- out, 3 feet of this height being above the level of the street or ground adj Dining ; (2) unless there is an open area outside extending along the entire frontage of the cellar at least 2^ feet wide and sunk 6 inches below the level of the floor of the cellar ; (3) unless efiectually drained by a drain which is nowhere less than i foot below the level of the floor of the cellar ; (4) unless there is appurtenant to the cellar the use of a proper water- closet, earth-closet, or privj-, and ashpit ; (5) unless the cellar has a fireplace with chimnev and flue, and an external window of at least 9 superficial feet in area clear of the sash frame and made to open. In the case of SANITARY LAW AND ADMINISTRATION 643 a back cellar occupied along with a front cellar as part of the same letting, the window need not have a larger area than 4 superficial feet. Steps in the area giving access to the cellar are permitted, if not across or oppo- site to the window, and at least 6 inches away from the external wall. Similarly, steps are permitted to give access to the building above if not across or opposite to the window (section 72). There is a penalty of 205. for every day a cellar is permitted to be occupied which does not comply with the above provisions, after notice from the sanitary authority ; and in the case of two convictions within three months, an order may be made for the closing of the cellar. Public Health {London) Act, 1891. Under the London Act the ceiling of the cellar need be only i foot in height above the level of the ground or street adjoining when the open area is 6 feet or more in width. The open area must be properly paved and drained, and must be not less than 4 feet wide. The walls of the room must be constructed with a proper damp course and secured against dampness of soil, the soil immediately below the room being effectually drained. Any drain passing under the room is to be constructed of gas- tight pipe, and the room is to be secured against the rising of any effluvia or exhalation, and to be effectually ventilated. The window of the room is to have a total area clear of sash frames equal to at least one-tenth of the floor area of the room, and is to be so constructed that one-half at least can be opened, the opening extending to the top of the window. In other respects the provisions are similar to the Act of 1875. Unless the sanitary authorities in London have specially dispensed with or modified any of the above requisites which involved, at the time of the Act coming into force, structural alterations of buildings (which they had power to do within six months of the commencement of the Act), the above provisions 'now apply to all underground rooms in London separately occupied as dwellings. The modifications or dispensations might not in any case alter the requirements of the Metropolis Management Acts which were in force prior to 1891. Two or more underground rooms occupied together, and not in con- junction with other rooms above the basement, are deemed to be separately occupied as dwellings, and it is for the defendant to show that the under- ground room or rooms are not separately occupied. Evidence (such as the presence of a bed) giving rise to a probable presumption that some person passes the night there, is evidence until the contrary is proved. Common Lodging Houses. Public Health Act, 1875. There is no definition of common lodging house in this Act, but it is usually held to mean a lodging house in which persons of the poorer class are received for short periods (usually a night), and, although strangers to one another, are allowed to inhabit a common sleeping room. As to the liability of charitable shelters to be registered and treated as common lodging houses, the latest legal decision is to the effect that, unless main- tained for profit, such shelters are exempt. Every common lodging house is required to be registered with the local authority, who must keep a register for the purpose, but may not register any such house until it has been inspected and approved for the purpose by one of its officers. A notice, with the words " Registered Common Lodging House," is to be affixed to the outside of the house. Every local authority must make by-laws (i) as to the number of lodgers that may be received, and as to the separation of the sexes ; (2) for promoting cleanli- ness and ventilation in such houses ; (3) for the giving of notices and the 644 HYGIENE AND PUBLIC HEALTH taking precautions in the case of any infectious disease ; and (4) generally for the well ordering of such houses. The model by-laws of the Local Government Board provide inter alia that the cubic space per head in the sleeping rooms is not to be less than 300 feet, two children counting as one adult ; that no person above ten years of age must sleep in a room occupied by persons of the opposite sex, but rooms may be set apart for the sole use of married couples if every bed is screened off. No bed must be occupied by more than one male over ten years of age. The floors are to be swept daily, and washed once a week. Windows are to be opened fully for an hour in the morning, and the same in the afternoon. Beds must be stripped of clothes and exposed to the air for an hour each day, and must not be reoccupied within eight hours of being vacated. All refuse and slops must be removed from the rooms before ] i> a.m., and all utensils cleansed daily. The windows, yards, closets, and ashpits must be kept clean and in good order ; and a sufficient supply of basins, towels, and water must be provided for the use of the lodgers. In the case of infectious disease occurring, the keeper of a common lodging house must carry out all the measures and adopt all the precautions directed by the medical officer of health. The Act requires all walls and ceilings to be limewashed twice a year (April and October), and the keeper may be required to make a daily report to the local authority as to the persons resorting to his house. He must give immediate notice of any illness or fever amongst his lodgers to Ihe medical officer of health and to the poor-law relieving officer of the union or parish. In London the common lodging houses are regulated by the Common Lodging Houses Acts of 185 1 and 1S53, the provisions being practically identical with those above given. Until recently these houses were under the supervision of the Metropolitan Police ; they are now, however, con- trolled by the London County Council. Houses let in Lodgings. Public Health Act, 1875 {Section 90). Local authorities are empowered to make by-laws for houses let in lodg- ings or occupied by members of more than one family. The by-laws thus made provide (i) for fixing the number of persons who may be taken in as lodgers, and for the separation of the sexes ; (2) for the registration of the houses ; (3) for their inspection ; (4) for enforcing drainage and privy accommodation, and for promoting cleanliness and ventilation ; (5) for the cleansing and limewashing of the premises, and for the paving of the courts and yards ; (6) for the giving of notices and the taking of precautions in case of any infectious disease. Houses in which the rooms are let at or above a certain weekly rental, to be determined by the local authority, are usually exempted from the operations of these by-laws. The minimum cubic space permitted is usually 400 or 450 cubic feet per head in the case of a room used both as a dwelling and sleeping room, and 300 or 350 cubic feet in the case of a room used for sleeping purposes only. The other regulations that can be made arc very similar to those enumerated as applicable in the case of common lodging houses, with the exception that it is seldom that any such by-laws attempt to enforce the separation of the sexes, and the limewashing need only be carried out once a year (April). Public Health {London) Act, 1891 {Section 94). In London every sanitary authority (borough council) is required to make and enforce similar by-laws for houses in its district which are let in lodgings or occupied by members of mure than one family. SANITARY LAW AND ADMINISTRATION 645 Offensive Trades. The offensive trades enumerated in the PubUc Health Act, 1875 (section 112), are those of a blood boiler, bone boiler, fellmonger, soap boiler, tallow melter, and tripe boiler. The model by-laws of the Local Government Board, in addition to the above, also relate to the trades of a leather dresser, tanner, fat melter or extractor, glue maker, size maker, blood drier, and gut scraper. Section 1 1 2 prohibits any person from establishing anew within the district of an urban sanitary authority, without their consent in writing, any offensive trade. There is a ;£50 penalty, and a continuing penalty of 40s. a day. Urban authorities may make by-laws with regard to these trades. In regard to trades, other than those above specified, which are alleged to be offensive, they must be shown to be ejusdem generis with those mentioned as offensive in the statute. 1 On the certificate of their medical officer of health, or of two medical practitioners, or of any ten inhabitants of the district, that a trade process is causing effluvia which are a nuisance or injurious to health, magisterial proceedings must be taken by the urban sanitary authority against the defaulters for the recovery of penalties. Similar proceedings may be taken in respect of a nuisance arising from an offensive trade, carried on outside the district, in a court having jurisdiction in the place where the offensive trade is situate. The by-laws of the Local Government Board which form the model for the by-laws that may be made by urban authorities, contain provisions for securing — (i) The storage of offensive materials in air-tight receptacles, so as to prevent escape of effluvia ; (2) the passage of offensive vapours arising during processes of melting, boiling, etc., from the pans, either through the furnace or through con- densers and thence through the furnace, so as to deprive them of all noxious properties ; (3) the maintenance of efficient drainage on the premises, and the cooling of hot liquids before discharge into the drains ; (4) the maintenance of the floors in good condition, and their daily cleansing, also the daily removal of all sweepings and refuse in covered receptacles ; (5) the maintenance of walls in good order, their periodical scraping to remove any adherent filth, and their limewashing twice a year ; (6) the cleansing of all utensils and vessels when not in i;se ; (7) facilities for inspection by the sanitary authority's officers. Under the Public Health (London) Act, 1891, the County Council is the authority for regulating offensive trades, making by-laws, and taking proceedings. The business of a soap boiler may be carried on provided that no animal oils or fats, other than olein, are used in the manufacture. The fine for establishing anew in London the trade of blood boiler, bone boiler, manure manufacturer, soap boiler, tallow melter, or knacker, iS;^50, with a daily continuing penaltj^ of ^50. These businesses are absolutely prohibited from being started. With the consent of the London County Council, a fellmonger's, tripe boiler's, or horse slaughterer's business may be newly established. Unsound Food. Public Health Act, 1875 (Sections 116-119). Any medical officer of health or inspector of nuisances may at all reason- able times inspect any animal, carcass, meat, poultry, game, flesh, fish, fruit, vegetables, corn, bread, flour, or milk exposed for sale, or deposited 1 By the Public Health Acts Amendment Act, 1907, any trade or manu- facture may be notified as an offensive trade by the sanitary authority, if confirmed by the Local Government Board. 646 HYGIENE AND PUBLIC HEALTH in any place for the purpose of sale, or of preparation for sale, and intended for the food of man, the proof that the same was not exposed or deposited for any such purpose, or was not intended for the food of man, resting with the party charged. If such animal, etc., appears to be diseased, or unsound, or unwholesome, or unfit for the food of man, the officer may seize it, and convej'' it to a magistrate, who, if satisfied, condemns the same, and orders it to be destroyed. The person from whom the seizure is made may then be proceeded against by summons to a court of summary juris- diction, and is liable to a fine of £20 for every piece of food seized, or to imprisonment for three months. There is a ;^5 penalty for obstructing or impeding the sanitary authority's officer in the execution of his duty. In the event of permission being refused to enter any premises for the purpose of discovering if anj^ unsound food is concealed therein, a com- plaint on oath must be made to a justice, who can grant a search warrant. There is a penalty of ^£20 for obstructing an officer who is armed \vith a search warrant. The Public Health Acts Amendment Act, 1890, extends the power to inspect and seize to all articles intended for the food of man sold or exposed for sale ; it also provides for the condemnation of any article by a justice without previous seizure. Similar provisions exist in London. In addition, proceedings may be taken against the vendor of unsound food to a private individual, if it can be shown that at the time of purchase the food was in such a condition as to be liable to be seized and condemned. Public Health [Regulations as to Food) Act, 1907. By the Public Health (Regulations as to Food) Act, 1907, the Local Government Board is empowered to make Regulations authorizing measures to be taken for the prevention of danger arising to public health from the importation, preparation, storage, and distribution of articles of food or drink (other than drugs or water), intended for sale for human consumption. In the year 1908 the Local Government Board issued regulations to be enforced by port sanitary authorities and any municipal council or district council whose borough or district includes or abuts on any part of a customs port, which part is not within the jurisdiction of a port sanitary authority. The Regulations as to unsound food require that the medical officer of health may examine any food either before or after it has been landed from a ship -within the district. If any unwholesome food is discovered, it may be seized and carried away, or its removal maybe forbidden until the material has been examined by a justice, except when the food is surrendered for immediate destruction. If a justice is satisfied that food is unwholesome, and that there is no proof that it is not intended for human consumption, he may condemn the food to be destroyed ; but where he is satisfied that the food is not intended for human consumption he shall dismiss a complaint, after preparing a statement containing a detailed description of the food, which will enable it to be subsequently- identified, and a copy of this statement must be furnished to the sanitary authority. A justice may grant a search warrant to a medical officer of health in cases where food has been landed and access to premises for the purpose of inspection has been refused. A detailed record of all the unsound food destroyed must be kept by the sanitary authority. The medical officer of health is empowered to take samples, and, where neces- sary, he is allowed fortj'^-eight hours for the necessary examination. It is an offence to fail to answer truly all questions put with reference to food. Authorities may be combined for the purposes of these Regulations ; and disputes may, on the application of all the parties, be referred to the Local Government Board for determination. SANITARY LAW AND ADMINISTRATION 647 Very similar Regulations were also issued in the year 1908 relating to foreign meat. In these regulations the foreign meat is classified in three classes and " Foreign meat unclassed." Foreign meat of Class i includes scrap meat, or other pieces of such shape or in such condition as to afford insufficient means of identification with definite parts of a carcass, but which is not in the form of sausage or other prepared article of food ; it also includes tripe, tongues, and kidneys to which a chemical antiseptic has been applied, and any unsalted, unsmoked, or uncured part of a carcass of a pig. Foreign meat of Class 2 includes the entire carcass of a pig which has not been prepared as bacon or ham, and is without the head in its natural state of attachment to the carcass, and -without the lymphatic glands in their natural position. Foreign meat of Class 3 includes the severed parts of the carcass of a pig, which have not been prepared as bacon or ham, and which is in a package carrying an official certificate. An " official certificate " means a mark, stamp, or label, which is recognized by the Board as admissible as evidence that the meat has been certified by a competent authority in the place of origin to be free from disease at the time of slaughter, and that the meat has been prepared and packed Avith proper safeguards. The Regulations require that when the officer of Customs finds or suspects that foreign meat of either Class i or Class 2 is aboard a ship, he shall require that it shall not be removed from the ship until examined by the medical officer of health ; or if it has been delivered overside, it shall not be removed in the meantime. The officer of Customs, however, may exercise his discretion with reference to meat of Class 2 or foreign meat unclassed, and he may or may not call upon the medical officer of health to examine it. On receiving notice from the officer of Customs, the medical officer of health must forthwith proceed to examine the meat ; he may either certify that it may be forwarded to its place of destination, or he may forbid the removal of the meat for any purpose other than exportation. Every written notice and certifi- cate must sufficiently describe the meat to suffice for its identification, and the medical officer of health must furnish a copy of any certificate to both the officer of Customs and to the importer. The medical officer of health may examine meat which has been removed from shipboard while it is within his district, even after the removal has been sanctioned by the officer of Customs ; and if the meat is found unsound, he may forbid its further removal for any other purpose other than exportation. Within twelve hours after the receipt of a copy of a notice by the medical officer of health the sanitary authority shall give notice to the importer that, unless within twelve hours he gives a Avritten undertaking that he will export the meat at his own expense, or will prove that the meat is not intended for sale for human consumption, the meat will be destroyed under the supervision of the medical officer of health. Detailed records of the destruction of foreign meat must be kept by the sanitary authority ; the medical officer of health is empowered to take samples of foreign meat ; it is an offence not to answer truly all questions put ; authorities may com- bine for the purpose of carrying out these regulations ; and differences may, on the application of all the parties affected, be referred to the Local Government Board for determination. Horseflesh. By the Sale of Horseflesh Regulation Act, 1889, which applies to the whole United Kingdom, the flesh of horses, asses, or mules must not be sold or kept for sale for human food except in a shop or stall, over which is an announcement, in legible characters 4 inches long, that horseflesh is sold there ; nor may horseflesh be sold to any purchaser asking for other meat. 648 HYGIENE AND PUBLIC HEALTH Slaughter Houses. By section 4 of tlie Public Health Act, 1875, a slaughter house includes knackers' yards and an^^ building or place used for slaughtering cattle, horses, or other animals for sale. By section 169 of the same Act, an urban authority may provide (public) slaughter houses, sometimes called municipal abattoirs, and must make by-laws for the management and charges for the use of them. They may also license existing slaughter houses, and v%dthout their licence no place may be used for the purpose which was not so used prior to 1875. This licence does not require periodical renewal when once given. With regard to slaughter houses in use prior to the Act, they need not be licensed, but they must be registered with the local authority. The owner or occupier of a licensed or registered slaughter house is required to af6x a notice to that effect on some conspicuous part of the premises. In places where Part III. of the Public Health Acts Amendment Act, 1890, has been adopted, licences for slaughter houses may be limited to twelve months, and may be revoked if the occupier has been convicted of selling unsound meat or exposing it for sale. This Act does not apply, so far as regards licences for limited periods, to slaughter houses already licensed or registered before the adoption of the Act. The Local Government Board has suggested the follo^ving rules as to site and structure, which should be complied with by slaughter houses seeking a licence : (i) The premises should not be within 100 feet of any dwelling house, and should be freel}^ exposed to the air on two sides at least. (2) Lairs for cattle should not be within 100 feet of a dwelling house. (3) The slaughter house should not be below the ground level. (4) The approach should not be on an incline of more than one in four, nor pass through any dwelling house or shop. (5) There should be no room or loft over the slaughter house. (6) The water tank must be of adequate size with its bottom not less than 6 feet above the floor of the slaughter house. (7) There should be thorough ventilation of the slaughter house. (8) The floor should be well paved with asphalt or concrete, laid -wdth proper slope and channel to a gully, Avith trap and grating, the bars of which should not be more than | inch apart. There must be efiectual drainage. (9) The surface of the walls in the interior should be covered with hard, smooth, impervious material to a sufficient height. (10) There must be no water- closet, privy, or cesspool within the slaughter house. (11) There must be no direct communication between the slaughter house and any stable, water-closet, privy, or cesspool. (12) Every lair for beasts must be properly paved, drained and ventilated. No habitable room is to be constructed over any lair. The Local Government Board has also issued model by-laws as to — (i) Applications for licences for existing premises or for erection of new premises. (2) Registration of premises. (3) Access for inspection by sanitary officers. (4) Water to be supplied to every animal in a lair. (5) Mode of slaughter : cattle to be secured by the head before felling. (6) Drainage, water supply, and ventilation. (7) Cleanliness of premises : walls and floor to be kept in repair, and cleansed within three hours after slaughtering ; walls and ceiling to be limewashed four times yearly. (8) No dogs to be kept in a slaughter house ; and no other animal unless intended for slaughtering, and then only in a lair, and not longer than necessary to prepare it for killing by fasting. (9) All refuse, blood, manure, and garbage to be placed in suitable vessels of non-absorbent material with close fitting covers, immediately after slaughtering, which are to be re- moved within twenty -four hours, the vessels being then cleansed. All skins, fat, and offal to be removed within twenty-four hours. SANITARY LAW AND ADMINISTRATION 649 Any person guilty of an infringement of the by-laws, when in force jj^ a district, is liable to have his licence suspended for two months, on cOj^_ viction before justices, or revoked in the case of a second offence. In London all slaughter houses are annually licensed by the Londgj^ County Council. Dairies, Cowsheds, and Milkshops. Under the Contagious Diseases (Animals) Acts, 1878-1886, the Local Government Board has issued the Dairies, Cowsheds, and Milkshops Orders of 1885, 1886, and 1899. The main provisions of these orders are as follows : (i) Every cowkeeper, dairyman, and purveyor of inilk must be registered in a register to be kept by the sanitary authority of the district. Cowkeepers and dairymen who only make or sell butter and cheese, and persons who sell milk from their own cows in small quantities to workmen or neighbours, need not be registered. (2) No new dairy or cowshed may Fig. 86. — A Sanitary Cowshed. Double Byre with Central Feeding Passage. be occupied until provision is made to the reasonable satisfaction of the sanitary authority for the lighting, ventilation, air space, cleansing, drain- age, and water supply of the premises. (3) As regards existing dairies and cowsheds, these matters must be attended to as far as is necessary or proper for the health and good condition of the cattle, the cleanliness of the milk vessels, and for the protection of milk against infection. (4) No cowkeeper or dairyman suffering from a dangerous infectious disorder, or having been recently in contact with a person so suffering, may milk cows, handle milk vessels, or assist in the trade so far as regards the production, distribution, or storage of milk, nor may he allow any person so suffering to do so. (5) After a month's notice from the local authority, no water-closet, privy, cesspool, or urinal is allowed to be within, or communicate directly with, or ventilate into any dairy, milk store or milkshop. (6) No milk store or milkshop is to be used as a sleeping apartment, or for any other purpose likely to cause contamination of the milk. No swine may be kept in 650 HYGIENE AND PUBLIC HEALTH cowsheds or milk stores. (7) The milk of a cow suffering from cattle plague, pleuro-pneumonia, foot and mouth disease, or tubercular deposits in the udder (when so certified by a veterinary'- surgeon), shall not be mixed with other milk, shall not be sold or used as human food, and shall not be sold or used for food of animals, unless it has been boiled (see also London County Council General Powers Act, 1904). The above order of the Local Government Board also confers power upon any urban or rural sanitary authority to make and enforce regulations for the inspection of cattle in dairies and coAvsheds ; for prescribing and regulating their lighting, ventilation, cleansing, drainage and water supply ; for securing the cleanliness of milkshops, milk stores, and milk vessels ; and for prescribing precautions to be taken by all purveyors of milk against infection or contamination. Each cow is usually required to have a space of 8 feet by 4 feet in a separate stall, and two cows 8 feet by 7 feet in a common stall. The minimum air space is usually fixed at 600 cubic feet, but when the ventila- tion is imperfect, 800 cubic feet are required per head. The .floors must be imperviously paved and drained to gullies situated outside of the shed ; the lower parts of walls to be of non-absorbent material ; there must be no communication of the cowshed with a water-closet or privy ; and 12 gallons of water must be provided for the use of each cow. All milk vessels to be steamed or scalded immediately after use. The Model Regulations of the Local Government Board issued in 1899 distinguish, as regards overcrowding in cowsheds, between those from which the cows are habitually turned out during a portion of each day to graze on grass land, and those in which the cows are not turned out. As regards the latter, the Regulations provide for 800 feet of air space for each cow, no space to be reckoned which is more than 16 feet above the floor. For the former class of cowshed no such provision is made. As regards the milking of the cows, it is provided that at the time of milking the udder and teats of the cow must be thoroughl^^ clean, and the hands of the milker must be clean and free from all infection and contamination. In those districts which have adopted the Infectious Disease Prevention Act, 1890, the medical officer of health, if of opinion that the consumption of milk from any dairy situate within or without his district is likely to cause infectious disease in his district, may, by order of a justice of the peace of the district in which the dairy is situate, inspect such dairy, and, if accom- panied by a veterinary inspector, inspect the animals therein. If satisfied that the milk sent out from the dairy is likely to cause infection, the medical officer reports to his authority, who may give notice to the dairj^man to appear before them, after twenty-four hours' notice, and make an order on him not to supply any more milk within the district for a prescribed period. In London the Public Health (London) Act, 1891, confers similar powers upon the medical officer of health. In London cowhouses have to obtain an annual licence from the County Council, and all purveyors of milk have to be registered with the Council. All cowsheds and dairies are subject to the Council's by-laws, and notice of the occurrence of any case of infectious disease on the premises has to be sent to the Council. For the above purposes the term " dairy " " includes any farmhouse, cowshed, milk-store, milk-shop, or other place from which milk is supplied, or in which milk is kept for purposes of sale." Infectious Diseases. Infectious Disease {Notification) Act, 1889. This Act, which was formerly permissive, is now made compulsory throughout the country. The compulsory notifiable infectious diseases are : Small-pox ; cholera ; SANITARY LAW AND ADMINISTRATION 65I diphtheria ; membranous croup ; erysipelas ; scarlet fever or scarlatina ; t3rphus ; typhoid or enteric, relapsing, continued, and puerperal fevers. A local authority may by resolution make an order extending compulsory notilication, either temporarily or permanently, to any other infectious disease not included in the above list, but the resolution must be confirmed by the Local Government Board. The diseases to which compulsory notification has been more commonly extended are measles, whooping- cough, chicken-pox, and diarrhoea when cholera is threatened. There lias been some agitation in favour of including pulmonary tuberculosis amongst the notifiable diseases, but the Local Government Board has not "so far sanctioned this step, except in the case of Sheffield (see below). The persons required to notify to the medical officer of health of the district are : («) The head of the family to which the patient belongs ; and in his default the nearest relative of the patient present in the building or in attendance on the patient ; and in default of such relatives every per- son in charge of or in attendance on the patient ; and in default of any such person the occupier of the building, shall, as soon as he becomes aware that the patient is suffering from an infectious disease to which this Act applies, send notice thereof to the medical officer of health of the district. (b) Every medical practitioner attending on or called in to visit the patient shall forthwith, on becoming aware that the patient is suffering froin an infectious disease to which this Act applies, send to the medical officer of health for the district a certificate stating the name of the patient, the situation of the building, and the infectious disease from which in his opinion the patient is suffering. There is a 40s. penalty for failing to send the notice or certificate as required. No proceedings can be taken after a lapse of six months from the date of commission of the offence. Although dual notification (by the householder and by the medical practitioner) is here provided for, notification by the householder is rarely, if ever, insisted on by sanitary authorities. The notification by the house- holder, or relatives, or person in charge, or occupier, is a safeguard for those cases in which medical assistance is not sought, but the practical difficulty of proving that any lay person was aware of the nature of an infectious disease occurring in his family or house is so great as to render the application of this section to concealed cases of infectious disease exceedingly difficult. Every medical man called in to see a case of infectious disease is bound to notify, even although this has already been done by another practitioner. In practice, however, this is but very seldom insisted on. Crown buildings are exempted from the operation of the Act. Compulsory Notification of Phthisis. The compulsory notification by medical practitioners of cases of tuber- culosis of the lung came into force in Sheffield on the ist November, 1903, under powers conferred by Section 45 of the Sheffield Corporation Act, 1903, and remain in force for 7 years from the date of the passing of the Act, unless continued by Act of Parliament or by Provisional Order of the Local Government Board. The forin of certificate required to be given by the medical practitioner is the same as under the Infectious Disease Notification Act, except that in addition to the name, sex, age, and place of residence, there must also be a statement as to the employment or occupation of the person so suffering (so far as can be reasonably ascertained). The fees payable for_ notification, and the penalty for failure to notify are the same asunder the Notification Act. 652 HYGIENE AND PUBLIC HEALTH No provisions contained in any general or local Act of Parliament relating to infectious disease apply to tuberculosis of the lung, or to proceedings relating thereto under Section 45 of the Shef&eld Corporation Act, 1903. \Miere the medical officer of health certifies that the cleansing and disinfection of any building would tend to prevent or check tuberculosis of the lung, the Town Clerk gives notice in writing to the owner or occupier of such building that the same or any part thereof will be cleansed and disinfected bj- the Corporation, unless the owner or occupier informs the Corporation within 24 hours from the receipt of the notice that he will cleanse and disinfect to the satisfaction of the medical officer of health within the time fixed in the notice. If the owner or occupier fails to inform the Corporation or fails to cleanse and disinfect after having so informed, the building can be cleansed and disinfected by the Corporation. With the consent of the owner or occupier the building may be cleansed and disinfected without going through the above described formality of giving notice in writing. The medical officer of health is also empowered to give notice in writing requiring books, clothing, bedding, or other articles which have been exposed to the infection of tuberculosis of the lung to be delivered over to the Corporation for removal for the purpose of disinfection. There is a £^ penalty for failing to comply with this requirement. Public Health {Tuberculosis) Regulations, 1908. In 1908 the Local Government Board issued an order in pursuance of Section 130 of the Public Health Act, 1875, as amended and extended by the Public Health (London) Act, 1891, and the Public Health Act, 1896, to provide for the notification to medical officers of health of cases of pul- monary tuberculosis occurring amongst the inmates of poor-law institu- tions or amongst persons under the care of district medical officers. Article IV. of the order directs that the medical officer of a poor-law institution shall, within 48 hours after his first recognition of the symp- toms of pulmonary tuberculosis, in the case of a poor person who is an inmate of the institution, post to the medical officer of health for the sanitary district in which the person resided immediately before he became an inmate of the institution a notification of the case. The notification must be made on a printed form, as set out in the schedule to the order (Form A). Article V. directs that a similar notification (Form B) shall be posted to the medical officer of health by the district medical officer in the case of any poor person suffering from pulmonary tuberculosis on whom he is in medical attendance according to his agreement with a Board of Guar- dians. The notification must be posted within 48 hours of the first recog- nition of the symptoms of the disease, and be addressed to the medical officer of health of the sanitary district in which the poor person resides. Under Article VI. it is the duty of the superintendent of a poor-law institution to post to the medical officer of health on a printed form (Form C) a notification of the actual or intended place of destination and address at that place of any person leaving the institution in respect of whom a notili cation has been made by the medical officer of the institution under Article IV. The notification must be posted within 48 hours after the departure of the person to whom it relates, and must be sent to the medical officer of health of the sanitary district in which the intended destination of the person is situate. Article VI f. provides that a relieving officer shall notify any change of address (other than by admission to a poor-law institution) of a person SANITARY LAW AND ADMINISTRATION 653 in respect of whom a notilication has been made under Article V. by a district medical officer. The hotiiication must be made on a printed form (Form D), be posted within 48 hours after the relieving officer has obtained accurate information respecting the change of residence, and be sent to the medical officer of health of the sanitary district in which the address to which the person moves is situate. The remuneration allowed is one shilling for every notification made by a medical officer of a poor-law institution or a district medical officer, but for re-notiiications (where in relation to any one case two or more notifica- tions have been already posted by the medical officer to the same medical officer of health) the remuneration is sixpence for each notification after the first. In the case of a superintendent of a poor-law institution or a relieving officer the remunei-ation is threepence. In all cases the remunera- tion is payable by the Council of the sanitary distirctfor which the medical officer of health acts. Article IX. provides that nothing in the Regulations shall have effect so as to apply or to authorize anyone to put in force with respect to a person in relation to whom a notification has been made any enactment which renders him or any other person liable to a penalty, or subjects him to any restriction, prohibition, or disability affecting him or his employment, occupation, means of livelihood, or residence, on the ground of his suffering from pulmonary tuberculosis. Subject, as aforesaid, a Council, on the advice of their medical officer of health, may, in respect of the poor persons so notified, for the purpose of preventing the spread of infection from pulmonary tuberculosis — (i) take all such measures, or do all such things as are authorized, in any case of infectious disease, or of dangerous infec- tious disease, by any enactment relating to public health, and as have reference to the destruction and disinfection of infected articles or the cleansing or disinfecting of premises ; (2) take all such measures or do all such things as are appropriate and necessary for the safe disposal or de- struction of infectious material, produced and discharged, as a result of pulmonary tuberculosis ; and otherwise for the prevention of the spread of infection from any such material ; (3) afford or supply' all such assist- ance, facilities, or articles as, within such reasonable limits as the cir- cumstances of the case require and allow, will obviate, or remove, or diminish the risk of infection arising from the conditions affecting the use or occupation of any room, when used or occupied b}'- the poor person as a sleeping apartment ; and (4) furnish for the use of the poor person, on loan or otherwise, any appliance, apparatus, or utensil which will be of assist- ance for the purpose of any precautions against the spread of infection. A Council, on the advice of their medical officer of health, may provide and publish or distribute, in the form of placards, handbills, or leaflets, suitable summaries of information and instruction respecting pulmonary tuberculosis and the precautions to be taken against the spread of infection from that disease. Public Health Act, 1875. Provisions against Infection. — Where any suitable hospital is provided within or near the district of a local authority, any person who is suffering from any dangerous infectious disorder, and is without proper lodging or accommodation, or lodged in a room occupied by more than one family, or is an inmate of any common lodging house, or is on board any ship or vessel, may, on a certificate signed by any legally qualified medical prac- titioner, by order of any justice, be removed to such hospital at the cost of the local authority. This order may be addressed to a constable or to an officer of the local authority, and any person who wilfully disobeys or obstructs its execution is liable to a ;^io penalty. 654 HYGIENE AND PUBLIC HEALTH A suitable hospital would be an isolation or infectious disease hospital provided by the local authoritj-, or established out of charitable funds, or the isolation wards of some general hospital or infirmary- adapted for the treatment of infectious cases. The magistrate must be informed of the consent of the hospital authorities to receive the case. There is no definition of " dangerous infectious disorder " in this Act, but it is usually held to denote anj^ of the diseases which are compulsorily notifiable in the district. With regard to other diseases, it lies in the discretion of the magistrate before whom a case is brought, to determine whether anj^ particular infectious complaint is of a " dangerous " character, to prevent the spread of which precautions must be taken. The words " without proper lodging or accommodation " are vague, but the most recent legal decision is that they have reference to the unfitness of the lodging or accommodation for the reception and treatment of a case of infectious illness, and to the possible danger to others from in- adequate isolation of the case. The earlier decisions in efEect ruled that the words had no such reference, and were only intended to apply to tramps and casuals sleeping out of doors or in places not intended for human habitation. " Legally qualified medical practitioner " means a person registered under the ^Medical Act, 185S. When it is intended to apply to a magistrate for an order for compulsory- removal, notice of the time and place of making the application should be given to the patient or his friends. The officers entrusted with the duty of carrvdng out the removal of the patient are not justified in employing force, either to enter the premises or apartment occupied by the patient, or to remove him if a strenuous resistance is offered. In such cases the only remedj^ is to summon the obstructing party with a view to the recovery of the ;^io penalty. The magistrates' order for removal does not carry wdth it the power to detain the patient in hospital until he is recovered or no longer infectious. Local authorities may provide ambulance carriages for conveying in- fectious cases to hospital, and disinfecting stations, and need not make any charge for the use of the ambulances or for disinfecting infected goods. They may also destroy infected articles and compensate the owners. They are also empowered to undertake the disinfection and cleansing of infected rooms or houses, free of charge to the occupiers. Any person who, while suffering from any dangerous infectious disorder, wilfully exposes himself without proper precautions against spreading the said disorder in any street, public place, shop, inn, or public con- veyance, or enters any public conveyance ^^dthout previoush- notifying to the driver that he is so suffering ; and any person being in charge of any person so suffering who wilfuUj'- exposes such sufferer ; and any person who gives, lends, sells, transmits, or exposes, \^-ithout previous disinfection, any bedding, clothing, rags, or other things Avhich have been exposed to infection, is liable to a penalt)'' not exceeding /5. The word " Avilfully " is equivalent to knowing!}-. There can be no offence if there is no knowledge of the infectiousness of person or thing. The words ' ' in charge ' ' are indefinite, but they clearly appl}- to children, scholars in boarding schools, and patients in public institutions, but they do not necessarily extend to domestic servants. Every owner or driver of a public conveyance must immediately provide for the disinfection of such conveyance after it has to his knowledge con- veyed any person suffering from a dangerous infectious disorder. Penalties are also provided against any person (including innkeepers) who knowingly lets for hire any house or part of a house in which any SANITARY LAW AND ADMINISTRATION 655 person has been suffering from any dangerous infectious disorder, without having the same disinfected to the satisfaction of a medical practitioner. Any person, also, who lets a house or part of a house, and on being ques- tioned by an intending tenant makes false statements as to the non- existence of infectious disease within six weeks previously, is liable to a penalty of £2.0 or a month's imprisonment. Any local authority may establish a hospital for infectious diseases in its own district, and there is no restriction on the establishment of such a hospital in a neighbouring district ; nor is it necessary to obtain the consent of the sanitary authority of the district in which it is proposed to establish a hospital. Section 133 enables any local authority, with the sanction of the Local Government Board, to provide a temporary supply of medicine and medical assistance for the poorer inhabitants of their district. This section is intended to apply to times of epidemics, such as small-pox, cholera, plague, etc. Infectious Disease [Prevention) Act, 1890. This is a permissive Act. Any urban or rural sanitary authority may adopt the whole Act or one or more of its sections. The provisions of the Act, if adopted, shall apply to the infectious diseases specifically mentioned in the Infectious Diseases Notification Act, and may be applied to any other infectious disease in the same manner as that Act may be applied to such disease. That is to say, at the discretion of the sanitary authority it may be made obligatory on the public to take the same precautions to prevent the spread of measles, whooping-cough, or chicken-pox, as are necessary in the case of small-pox or typhus. By section 1 5 of the Act, local authorities are required to provide, free of charge, temporary shelter or house accommodation with any necessary attendants, for the members of any family in which infectious disease has appeared, who have been compelled to leave their homes to enable them to be disinfected. Section 5 provides that on a certificate of the medical officer of health, or other registered practitioner, the sanitary authority can give a written notice to the owner or occupier of infected premises that the premises will be cleansed and disinfected by the authority at the cost of the owner or occupier, unless such owner or occupier within twenty-four hours replies stating that he will do the work himself to the satisfaction of the medical officer of health. Where the owner or occupier is unable to effectually cleanse or disinfect the premises, this may be done without notice by the officers of the local authority, at the cost of the latter. Section 6 enables local authorities to compel the delivery by house- holders to them of infected goods for the purposes of disinfection, and provides for compensation to be paid by local authorities in the event of any damage to the goods. Section 1 3 prohibits any person from knowingly casting into any dustbin or ashpit any infectious rubbish. Section 7 prohibits under a £10 penalty the concealment of the existence of infectious disease by any lodger or tenant of a room, rooms, or house, who is giving up his tenancy, in cases where infectious disease has existed within a period of six weeks from the time of ceasing occupation. The concealment is of two kinds : [a) In not giving notice to the owner, and leaving the house or rooms without having them disinfected to the satis- faction of a medical practitioner ; {b) in knowingly making false answers when questioned by the owner of the house, or by a person negotiating for the hire of the house or rooms. This section supplements sections 128 and 129 of the Public Health Act, 1S75, which (see p. 654) heavily penalize 656 HYGIENE AND PUBLIC HEALTH owners or landlords for letting infected lodgings or making false statements when questioned as to the existence of infectious disease. Section 12 provides for the detention in hospital, on the order of a magistrate, for a specified time, of any person who is a patient in an in- fectious disease hospital, and who would not on leaving such hospital be provided with accommodation, where proper precautions could be taken to prevent the spread of infection. Under the Public Health Act, 1875, only persons removed to hospital from ships can be detained in hospital, under regulations made by the sanitary authority. Public Health {London) Act, 1891. The infectious diseases sections of this Act incorporate the various sections of the Acts already mentioned as dealing with this subject. The London notification certificate differs from that required by the Infectious Disease (Notiiication) Act, 1889, in that the age and sex of the patient must be inserted, and also whether the case notified by the practitioner occurs in his private practice or in his practice as medical officer of any public body or institution. The fees are the same under this Act as under the Notification Act — namely, 25. 6d. for a private case notified, and 15. for a public case. Every municipal borough has power to extend compulsory notification to diseases other than those in the scheduled list (see p. 655) in its own district, whilst the London County Council has similar powers for the whole county of London. There is no power conferred on provincial County Councils to extend the Act to other diseases, as has been done for the London County Council. In London the " dangerous infectious diseases " to which the provisions penalizing concealment and negligence refer, are those scheduled in the compulsorily notifiable list. In consequence of this in London it is not compulsory to take any precautions with regard to the sufferers from mumps, whooping-cough, or other non-notifiable disease, with the excep- tion of measles, which is now specially scheduled as a " dangerous infectious disease." As in the Infectious Diseases (Prevention) Act, each sanitary authority has a discretionary power as to applying the penalizing sections to diseases ordinarily non-notifiable, but which have been rendered com- pulsorily notifiable by resolution. The provision of disinfecting stations and goods removal vans by sanitary authorities is compulsory, and the disinfection is gratuitous, no costs or expenses incurred being recoverable by the sanitary authority. By section 70 no case of dangerous infectious disease may be conveyed in a cab, tram, omnibus, or other public con- veyance. The use of all public conveyances for such purposes is absolutely prohibited in London. An ambulance carriage must be obtained from the Metropolitan Asylums Board whenever it is desired to convey a person suffering from a notifiable infectious disease from one place to another, for which a charge of 55. is made. The fever hospitals of the Metropolis are under the control of the Metro- politan Asylums Board, and so is the removal of patients in ambulance carriages to or from the hospitals. The cases admitted to the Board's hospitals are small-pox, diphtheria, scarlet fever, enteric fever, and typhus. The Board is unable to acquire sites for the erection of hospitals unless with the consent of the Local Government Board. Isolation Hospitals Act, 1893. The Act does not apply to London, Scotland, or Ireland, nor to any English county borough. It applies, with the consent of the Town Council, to boroughs having a population of 10,000 or over, and without such SANITARY LAW AND ADMINISTRATION 657 consent to boroughs of less than 10,000 population, if the Local Government Board by order direct that the Act shall apply to such borough. Applications may be made to a County Council for the establishment of an isolation hospital for infectious diseases by a local authority within the county, or by twenty-five or more ratepayers in any contributory place — a contributory place having the same meaning as in section 229 of the Public Health Act, 1875. If the County Council is satisfied that a prima facie case is made out for a local inquiry as to the necessity for the establish- ment of an isolation hospital, they may direct such inquiry to be made. The County Council may also direct the medical officer of health of the county to make an inquiry as to the necessity of an isolation hospital being established in any particular district in the county ; and in the event of the medical officer reporting that such a hospital ought to be established in any district, they may take the same proceedings for the establishment of such hospital as if a petition had been presented for the establishment of such a hospital by the local authority of the district in question. After the local inquiry the County Council may make an order dismissing the petition, or constituting " a hospital district " out of one or more local areas, and directing an isolation hospital to be established for such district. A local area under the Act means an urban or rural sanitary district, or a contributory place. The County Council then forms a hospital committee, which is given powers to acquire a site, and to erect, manage and maintain an isolation hospital. Power is given to make a scale of charges for the patients in the hospital, and no patient is to suffer any disqualification or loss of franchise by reason of his treatment. Mortuaries, and Disposal of the Dead. Public Health Act, 1875. Any local authority may, and if required by the Local Government Board shall, provide a mortuary. The body of any dead person may, by order of a justice, on the pro- duction of a medical certificate, be removed to a mortuary, if it is in such a state as to endanger the health of the inmates of the house in which it is kept. The same power of removal applies to the body of a person dead of an infectious disease, if kept in a room where persons live or sleep. Infectious Disease {Preventioii) Act, 1890. No infectious corpse is to be retained for more than forty-eight hours in a dwelling place, sleeping place, or workroom without the sanction of a medical practitioner. Section 9 gives power to prevent the removal of an infectious corpse from a hospital to the home of relations, or to any place except a mortuary. Section 10 enables a justice to order the removal of a dead body to a mortuary, and its immediate burial, if considered advis- able, on the application of the medical officer of health ; and section 1 1 provides for the case of removal of an infectious corpse in a public con- veyance, which is unprovided for in the Act of 1875. London. The London Act contains almost identical provisions to the above, but the provisions for the most part relate to the bodies of persons who have died not of " any infectious disease," but of a " dangerous infectious disease." 42 658 HYGIENE AND PUBLIC HEALTH Cemeteyies and Burial Grounds. Information of a death must be given to the Registrar of Births and Deaths within five days ; or, when a notice is sent along with a medical certificate, within fourteen days. By the Public Health (Interments) Acts, 1879, both urban and rural authorities may provide cemeteries for their districts, and must do so if required by the Local Government Board on the ground of inadequacy of existing burial places, or of these being a danger to the public health. The Act forbids the construction and laying out of a cemetery within 200 yards of any dwelling house, unless with the consent of the owner and the occupier of such house. An existing burial ground may be closed by the Home Secretary by Order in Council under the provisions of the Burial Act, 1853. Interments within the walls of churches built after 1848 are forbidden by the Public Health Act, 1875. The Regulations for Burial Grounds issued by the Home Secretary in 1863 provide inter alia — (i) For the fencing and under-draining of the site, to prevent water rising into any grave ; (2) grave spaces to be laid out, and a corresponding plan kept, such spaces to be 9 feet by 4 feet for adults, and 4J feet by 4 feet for children under twelve years ; (3) a register of graves is to be kept ; (4) a body buried in a walled vault is to be cemented in, and never afterwards disturbed ; (5) only one body to be buried in a grave at one time, unless members of the same family ; (6) no grave to be reopened until fourteen years have elapsed for an adult, or eight years for a child, unless to bury another member of the same family, in which case at least I foot of earth is to be left undisturbed over the previously buried coffin ; (7) no adult body to be buried within less than 4 feet of the level of the ground ; a child under twelve may be buried within 3 feet. By section 141 of the Public Health Act, 1875, local authorities may make by-laws for the management of cemeteries. The Cremation Act, 1902, gives powers to burial authorities to provide and maintain crematoria. The site and plans of the crematorium must be approved by the Local Government Board, and the crematorium must be certified by the burial authority to the Secretary of State to be complete and properly equipped, and built in accordance with the plans. No crema- torium may be constructed nearer than 200 yards to any dwelling house, except with the consent of the owner and occupier of such house ; nor may it be within 50 yards of any public highway, nor within the consecrated part of the burial ground of any burial authority. The Secretary of State makes regulations as to the maintenance and inspection of crematoria, and as to the practical working of the cremations. The Cleansing of Persons Act, 1897. By this Act any local authority has the power of cleansing persons and their clothing from vermin, when an application is made to them ; and local authorities may expend any reasonable sum on buildings, appliances, and attendants that may be required for the carrying out of the Act. The London County Council (General Powers) Act, 1904. By Part IV. (Sanitary) of this Act, on the certificate of the medical officer of health that any articles in any house or part thereof are in such a filthy, dangerous, or unwholesome condition that health is affected or endangered thereby, or that the cleansing or purifying, or destroying of any such article is requisite to prevent risk of, or to check infectious disease, the sanitary SANITARY LAW AND ADMINISTRATION 059 authority may cause any such articles to be at their own expense cleansed or purified or destroj'ed, compensation being given to the owner for un- necessary damage or for articles destroyed. On the certificate of the medical officer of health that any house or part thereof is infested with vermin, the sanitary authority must give notice to the owner or occupier requiring him within a speciiied time to cleanse such house or portion thereof, and if so required in the notice to remove the "wall papers, and to take such other steps for the purpose of destroying and removing vermin as the case may require. A fine not exceeding ids. a day may be inflicted for every day during which default is made in com- plying •with the requirements of the notice ; and after the expiration of the period specified in the notice the sanitary authority may themselves do the work and recover summarily as a civil debt all reasonable costs and expenses. Section 22 enables any sanitary authority to require the removal of any sanitary convenience erected in or accessible from any street which is a nuisance or offensive to public decency, and to require the reconstruction of the same so as to abate the nuisance and remove the offence against public decency. Section 23 enables sanitary authorities to cause fixed ashpits to be removed and their site cleared, wherever movable ashpits have been provided. Section 24 gives powers for the entry and inspection of premises for the purposes of the Act. By Part V. (Tuberculosis of the Udder in Cows), if a veterinary surgeon appointed by the London County Council for the purposes of the Dairies, Cowsheds, and Milkshops Order, 1899, suspects that any cow in any dairy, farm or cowshed situate in the county (exclusive of the City) is suffering from tuberculosis of the udder, he may cause such cow to be removed from the farm or cowshed. The value of the cow must then be agreed between the Council and the owner, and the Council shall cause the cow to be slaughtered and its carcass to be examined by a qualified veterinary sur- geon. If the cow is found to have suffered from tuberculosis of the udder, three-fourths the value as agreed must be paid by the Council to the owner, the sum, however, not to exceed ;^22 105., and one half the costs of any independent veterinary surgeon who may have been employed as valuer. If the coAv was found to be free from tuberculosis of the udder, the whole value of the cow must be paid, the sum not to exceed £T)0, and a further sum of ;^i, and the costs of any independent valuer. The Prevention of Epidemic Diseases. Public Health Act, 1875. Section 130 enables the Local Government Board to make regulations for the treatment of persons infected with cholera or other epidemic disease, and for preventing the spread of these diseases on land, and on sea up to the three mile coast limit. By section 1 34, whenever any part of England appears to be threatened with or is affected by any formidable epidemic, endemic, or infectious disease, the Local Government Board may make regulations for (i) the speedy interment of the dead ; (2) house to house visitation ; (3) medical aid and accommodation ; (4) for the promotion of cleansing, ventilation, and disinfection, and for preventing the spread of disease. The local authority of any district within which such regulations are declared to be in force is charged with the execution and enforcement of the regulations. By the Public Health Act of 1889, regulations made by the Local Government Board in relation to cholera or choleraic diarrhoea may be put in force by officers of Customs, and may provide for the deten- tion of vessels and of persons on board vessels. The same provisions are in force in London. 660 HYGIENE AND PUBLIC HEALTH The Notification of Births Act, 1907. The Act requires that, if adopted, the local authority shall bring the provisions of the Act to the attention of all medical practitioners and midwives practising in their area. These provisions may be briefly summarized as follows : Primarily, the "duty" of notifying a birth to the medical officer of health devolves upon the father of the child, if he be resident in the house at the time of its occurrence ; secondarily, upon " any person in attendance upon the mother at the time of, or within six hours after the birth." The notice must be " given by posting a prepaid letter or postcard . . . within thirty -six hours after the birth," or by delivery of a "written notice of the birth (in either case) at the office of the medical officer within the same time." The local authority are required to " supply without charge addressed and stamped postcards, containing the form of notice, to any medical practitioner or midwife, residing or practising in their area, who applies for the same." The notification is " in addition to, and not in substitution for, the requirements " of the Act " relating to the registra- tion of births," and it applies to any child born " after the expiration of the twenty-eighth week of pregnancy, whether alive or dead." Liability to a penalty not exceeding 20s. is incurred by any person who fails to give notice of a birth. The Children Act, 1908. Many of the provisions of this Act are designed either to promote the moral and physical health of children or to reduce infantile mortality. The Act came into operation on April i, 1909. It consolidates and amends the law relating to the protection of children and young persons, reformatory and industrial schools, and juvenile offenders ; and otherwise amends the law with respect to children and young persons. Part I. deals with infant life protection, and requires that anyone under- taking, for reward, the nursing and maintenance, for more than forty- eight hours, of one or more infants under the age of seven years apart from their parents shall notify the local authority of the fact within forty-eight hours, and shall repeat the notification on change of residence ; notification must also be given within forty-eight hours of the death of any such infant, and within twenty-four hours a notification must be sent to the coroner. Such person must have no interest in any life assurance policy with refer- ence to a' child in their charge. Every local authority must prosecute inquiries to ascertain whether any persons liable to notification are residing in the district, and if so, shall provide infant protection visitors. Local authorities may combine for the purpose of executing the above provisions of the Act, and they may exempt any particular premises from visitations ; they may fix the number of infants which may be kept in a dwelling, and may obtain the removal of any infant from overcrowded, dangerous, or insanitary premises, or from the custody of any negligent, ignorant, drunken, immoral, or criminal individual. Offenders under this part of the Act are liable to six months' imprisonment or a fine, and the above provisions do not extend to any relative or legal guardian of an infant. The local authority in London is the County Council and elsewhere the guardians of the poor. Part II. deals with the prevention of cruelty to children and young persons. When the death of an infant under three years of age is caused by suffocation in a bed occupied by another person of over sixteen years of age, and the other person at the time of going to bed was under the influence of drink, such other person is liable, on conviction of neglect, to imprison- SANITARY LAW AND ADMINISTRATION 66l inent or line. It is an offence to cause any child or young person to beg, or to fail to protect a child under seven years of age against the risks from burning in a room where there is an open fireplace grate ; to allow children or young persons to be in brothels ; or to cause or favour the seduction or prostitution of a girl under the age of sixteen. Where there is an offence under this Act, a child or young person may be removed to a place of safety and taken out of the custody of a convicted person, and the parent or person liable to maintain the child may be made to contribute to the cost of maintenance. Part III. deals with juvenile smoking, and imposes a penalty for selling cigarettes to children and young persons. A constable or park-keeper may seize cigarettes in the possession of children and young persons, and steps may be taken to prevent cigarettes being obtained from automatic machines, where any such machine is being extensively used by children or young persons. Part IV. deals with reformatory and industrial schools ; the certification, inspection, and management of such schools ; the children liable to be sent to them ; the power to subsequently apprentice or dispose of such children ; the expenses of the school ; the establishment of day industrial schools, etc. Part V. deals with juvenile offenders, and requires, inter alia, that a child or young person shall be kept apart from adults during detention in a police station ; certain restrictions are imposed as to the punishment of children and young persons, including the abolition of the death sentence. The provision of places of detention is also dealt with. Part VI. contains miscellaneous and general clauses. A person giving intoxicating liquor to any child under five, except in sickness ; or a publican allowing a child to be in the bar of licensed premises, except during the hours of closing, render themselves liable to a fine. A very important section (122) is the following : i. A local education authority may direct their medical officer, or any person provided with, and, if required, exhibiting the authority in writing of their medical officer, to examine in any public elementary school, provided or maintained by the authority, the person and clothing of any child attending the school, and if, on examination, the medical officer, or any such authorized person as aforesaid, is of the opinion that the person or clothing of any such child is infected with vermin, or is in a foul or filthy condition, the local education authority may give notice in writing to the parent or guardian of or other person liable to maintain, the child, requiring him to cleanse properly the person'and clothing of the child within twenty-four hours after the receipt of the notice. 2. If the person to whom any such notice as aforesaid is given fails to comply therewith within such twenty-four hours, the medical officer, or some person provided with and, if required, exhibiting the authority in writing of the medical officer, may remove the child referred to in the notice from any such school, and may cause the person and clothing of the child to be properly cleansed in suitable premises and with suitable appliances, and may, if necessary for that purpose, without any warrant other than this section, convey to such premises, and there detain the child until the cleansing is effected. 3. Where any sanitary authority within the district of a local education authority have provided, or are entitled to the use of, any premises or appliances for cleansing the person or clothing of persons infested with vermin, the sanitary authority shall, if so required by the local education authority, allow the local education authority to use such premises and appliances for the purpose of this section upon such payment (if any) as may be agreed upon between them, or, in default of agreement, settled by the Local Government Board, 662 HYGIENE AND PUBLIC HEALTH 4. Where, after the person or clothing of a child has been cleansed by a local education authority under this section, the parent or guardian of, or other person liable to maintain, the child allows him to get into such a condition that it is again necessary to proceed under this section, the parent, guardian, or other person shall, on summary conviction, be liable to a fine not exceeding 105. 5. Where a local education authority give notice under this section to the parent or guardian of, or other person liable to maintain, a child, re- quiring him to cleanse the person and clothing of the child, the authority shall also furnish him with written instructions describing the manner in which the cleansing may best be effected. 6. The examination and cleansing of girls under this section shall only be effected by a duly qualified medical practitioner, or by a woman duly authorized, as hereinbefore provided. 7. For the purpose of this section, " medical officer " means any officer appointed for the purpose of Section 1 3 of the Education (Administrative Provisions) Act, 1907. For the purposes of this Act, the expression " child " means a person under the age of fourteen years, and " young person " one who is between fourteen and sixteen years of age. The Vaccination Acts. The Principal Acts are those of 1867, 1871, and 1898. The Act of 1867 required that the parents or custodians of every child born in England should, within three months after its birth, take it or cause it to be taken to the public vaccinator of the vaccination district, in which the child resides, to be vaccinated ; or should within the same period cause it to be vaccinated b}^ some medical practitioner. Defaulting parents or custodians are liable to prosecution by the vaccination officer, who is required to be appointed by the guardians of every union or parish (Act of 1871). On summons, magistrates can make an order directing the child to be vaccinated ; and in the event of this order being disregarded the vaccination officer can proceed for penalties against the defaulter. The Act of 1871 also rendered it an offence for any person to refuse to allow a public vaccinator to take lymph from any child that he has vaccinated ; and also re-enacted the prohibition of inoculating any person with small-pox. The Act of 1898 extends the period within which an infant may remain unvaccinated from three months to six ; nor need the child be taken to the public vaccinator. The public vaccinator of the district must visit the home of the child for the purpose of vaccinating it, if the parent or custodian so requires. If a child is not vaccinated within four months of its birth, the public vaccinator must, after at least twenty-four hours' notice to the parent, visit the home of the child, and offer to vaccinate the child with glycerinated calf lymph, or such other lymph as may be issued by the Local Government Board. No child is to be vaccinated if, in the opinion of the public vaccinator, the operation cannot be safely done, owing to the insanitary condition of the house, or the recent prevalence of infectious disease in the district. In such cases a certificate of postponement is to be given, and notice is to be sent to the medical officer of health. No parent or custodian shall be liable to any penalty under the Act of 1867, if within four months from the birth of the child he satisfies two justices or a stipendiary magistrate in petty sessions that he conscientiously believes that vaccination would be prejudicial to the health of the child, and within seven days thereafter delivers to the vaccination officer a certificate by such justices or magistrate of such conscientious objection. The Act prohibits SANITARY LAW AND ADMINISTRATION 663 the making of a second order, directing that a child shall be vaccinated, in the case of any person who has been previously convicted of non-com- pliance \vith a similar order relating to the same child, unless the child has reached the age of four years. The Act also empowers the Local Govern- ment Board by Order, in the event of serious risk of outbreak of small-pox, to require the guardians of any poor-law union to provide vaccination stations ; and to modify the provisions of the Act as to the visitation of the child in its own home by the public vaccinator. The Vaccination Act, 1907. The Vaccination Act of 1907 has so amended the Act of 1898 as to sub- stitute a statutory " declaration of conscientious belief " for the provision as to satisfying two justices, or a stipendiary magistrate, of such belief which formerly obtained, and the modification in question came into operation at the beginning of 1908. The chief anomalies of the present vaccination law are that the Acts are administered by the poor-law guardians, and not by the sanitary authorities, who are otherwise charged with all public health matters ; and that the vaccination officer is appointed by the guardians, but is required by the Local Government Board to administer the Acts inde- pendently of the persons or board appointing him. Mid WIVES Act, 1902. This is an Act to secure the better training of midwives and to regulate their practice. It prohibits women, who are not certified under the Act, from taking or using the name or title of midwife, or any name, title, or description implying that they are certified under the Act, or specially qualified to practise midwifery, or recognized by law as midwives. Any person so offending is liable on summary conviction to a fine of £$. After April I, 1 910, no woman may habitually and for gain attend women in childbirth otherwise than under the direction of a qualified medical prac- titioner, unless she is certified under the Act. The penalty is ;^io. For two years subsequent to April i, 1905, a woman may claim to be certified under the Act if she holds a certificate in midwifery approved by the Central Midwives Board, or produces satisfactory proof that at the passing of the Act in 1902, she had been at least one year in bona fide practice as a midwife, and bears a good character. The Central Midwives Board consists of four medical practitioners and five other persons, whose duties and powers provide for the framing of rules regulating the issue of certifi- cates, the courses of training, the conduct of examinations for certificates, and the practice of midwives, including their suspension and the removal of their names from the roll for disobedience of rules. The councils of counties and county boroughs in England and Wales are appointed as local supervising authorities over midwives within their areas of jurisdiction. These powers may be delegated to any district council within the area of the county. Besides a general supervision, the supervising authority may investigate charges of malpractice, or mis- conduct, and report to the Central Midwives Board ; they may suspend a midwife from practice, to prevent the spread of infection ; and keep a current copy of the roll of midwives accessible to public inspection. Prosecutions for offences under the Act may be undertaken by the local supervising authority. 664 HYGIENE AND PUBLIC HEALTH Housing of the Working Classes. The principal Act dealing with the displacement of working class popu- lations from unhealthy areas and houses, and the rehousing of the displaced people, is the Housing of the Working Classes Act, 1890. Unhealthy Areas. Part I. of the Act is concerned ^vith unhealth}^ areas. The authorities for this part of the Act are the urban sanitary authorities, and in London the London County Council and the Corporation for the City. A medical officer of health is empowered to make an ofl&cial represen- , tation to his authority — [a) that am- houses, courts, or allej'^, are unfit for human habitation ; {b) that the narrowness, closeness, and bad arrange- ment, or the bad condition, of the streets and houses or groups of houses within such area, or the want of light, air, ventilation, and proper con- veniences, or any other sanitan,- defects, or one or more of such causes, are dangerous or injurious to the health of the inhabitants, either of the buildings in the said area or of the neighbouring buildings ; and that the evils connected with such houses, courts or allevs, and the sanitary defects in such area cannot be effectually remedied otherwise than by an "im- provement " scheme for the rearrangement and reconstruction of the streets and houses %\'ithin such area. The medical officer of health may make a representation on his own initiative, or he maj^ be required to make it on the complaint of two or more justices of the peace of the district, or of twelve or more ratepayers. The local authority, on recei\dng the ofiicial representation, may pass a resolution to the effect that such area is an unhealthy area, and that an improvement scheme ought to be made in respect of it. After passing such resolution, they shall forthwith proceed to make a scheme. The scheme may pro\ade for the reconstruction and rearrangement of the streets and houses in the area, and generalh^ for the opening out of the area, and the mdening of approaches in order to improve the ventilation. The scheme must provide for proper sanitarj^ arrangements, and for such dwelling accommodation for the working classes displaced as the Act directs. Due publicity must be given to the scheme, and notices must be served on all persons interested. Application is then made by the sanitan.' authorit}- to the Local Government Board for a provisional order con- firming the scheme. A local inquiry' is then held by the Board, as to the correctness of the official representation and as to the sufficiency of the scheme. A provisional order may then be made by the Board authorizing the scheme, and this is subject to confirmation by Act of Parliament. In London, representation may be made to the London County Council by any medical officer of health of a district, as well as by the county medical officer. The confirming body is the Local Government Board, and accommodation must be pro\'ided in or near the scheduled area for the whole number of the working classes displaced. The Local Government Board, however, if satisfied that there is no necessity to rehouse all the working classes on the cleared area, ma}' accept in substitution equally convenient accommodation not in or near the area, and may dispense with the obligation to rehouse to the extent of one-half the number displaced. Both in the country and in London this part of the Act is practically unworkable. The cost is prohibitive, and the delays ensuing from the complexity of procedure often allow of a lapse of many years between the condemnation of the area and rebuilding on the pjeared sites. SANITARY LAW AND ADMINISTRATION 665 Unhealthy Dwelling Houses. Part II. relates to individual unhealthy dwellings or to small groups of dwellings. The medical officer of health, on his own initiative, or on the requisition of four inhabitant householders, makes an official representation to his authority that a dwelling house or houses are in a state so dangerous or injurious to health as to be unfit for human habitation. The authority may then direct proceedings to be taken against the owner before a court of summary jurisdiction for the closure of the houses so represented. The court, on the hearing of the summons, may make a closing order for the houses, and may inflict a penalty upon the owner of ;^20. Under the Housing of the Working Classes Act, 1903, if in the opinion of the local authority any dwelling house is not reasonably capable of being made lit for human habitation, or is in such a state that the occupation thereof should be immediately discontinued, it is not necessary to serve notices on the owner or occupier of the premises to abate the nuisance before applying for a summons for a closing order (Sec. 8). The owner, under this Act, of leasehold premises, of which less than twenty-one years is unexpired, is not the lessee, but the ground landlord. Consequently the ground landlord by this Act is made responsible for the condition of premises over which he may have no control whatever. Notice of the closing order is then served upon the occupying tenants of the houses, with notice to quit. Defaulting tenants who do not vacate the premises are liable to a penalty of 205. a day during disobedience ; but as such tenants have seldom any goods to distrain upon, and magis- trates are reluctant to send them to prison, it is usually exceedingly difficult to get rid of the tenants, who continue to inhabit the premises until the houses are pulled down around them. If nothing has been or is being done to render the closed dwelling houses fit for human habitation, and it is represented to the authority that the continuance of the buildings is dangerous or injurious to the health of the public or of the inhabitants of neighbouring dwelling houses, the authority must pass a resolution that it is expedient to order the demolition of the buildings. Notice of this must be served upon the owner, who is entitled to attend a meeting of the authority, to be held not less than one month after the service of the notice, for the further consideration of the resolution, when he may state his objections to the demolition. At this meeting an order must be made for the demolition of the buildings, unless the owner undertakes to execute forthwith the works necessary to render the houses fit for human habitation. If the houses have not been demolished within three months of the making of the order, the local authority may proceed to demolish them themselves. Any person aggrieved by an order of the local authority under this part (II.) of this Act may appeal against the same to a Court of Quarter Sessions. Until this appeal has been heard or ceases to be prosecuted, the whole procedure under the Act has to stand still. This power of appeal by any aggrieved person practically makes the Act unworkable if opposition is encountered. The cost and the delays ensuing are prohibitive. Under Part II. representation may be made as to " obstructive " build- ings — that is to say, buildings which stop or interfere with the light and air about neighbouring buildings, or which prevent measures being carried into effect for remedying sanitary evils attaching to such buildings. The owner of the obstructive buildings is entitled to be heard by the local authority before an order is made for the demolition of the buildings. The site of the buildings may either be purchased under compulsory powers or by agreement, and compensation is settled by arbitration. Improvement or reconstruction schemes may be made under this part 666 HYGIENE AND PUBLIC HEALTH (II.) of the Act — (a) in respect of unhealthy dwelling houses for which demolition orders have been made ; (b) in the case of unhealthy areas which are too small to be dealt with under Part I. The improvement scheme may provide for the opening up of the area, the widening of streets and approaches, and the reconstruction and rearrangement of the buildings with the erection of dwellings for the working classes. The procedure is then very much the same as under Part I. — the appli- cation to the Local Government Board for a provisional order, the holding a local inquiry, and the making of a provisional order. This order requires no confirmation if the area is purchased by agreement. If the land is to be acquired by compulsory purchase, the order must be published and notice served upon the owners. If within two months after publication there is no petition by the owners, the order may be confirmed by the Board ; but if there is a petition, the order is not valid until confirmed by Act of Parliament. In London it has been customary for lengthy disputes to take place between the local district authorities and the London County Council, as to whether schemes of improvement of unhealthy areas should be under Part I. or Part II. of the Act. In the former case the cost is borne by all ratepayers of London as a Metropolitan improvement, whilst in the latter the greater portion of the cost becomes a local debt. In the event of the representation relating to only ten houses, it must be made under Part II. In case of dispute the Local Government Board has power to appoint an arbitrator to decide as to whether the scheme is to be under Part I. or under Part II. In the latter event the County Council may be required to contribute to the expenses of the scheme. In consequence of the disputes, the great cost, and the complexity of procedure and resulting delays, the Act has been practically a failure. ' Working Class Lodging Houses. Part III. of the Act relates to the provision of working class dwellings. This part of the Act is now entrusted to the municipal boroughs in London. Prior to November, 1900, the London County Council was the authority. In other urban sanitary districts Part III. may be adopted with the sanction of the Local Government Board ; in rural sanitary districts, it may be adopted after inquiry by the County Council as to the necessity of providing working class accommodation by parochial means. Land may be acquired by a local authority either by agreement or by compulsory purchase, as provided by sections 175 to 178 of the Public Health Act, 1875. On the land, buildings suitable for lodging houses for the working classes may be erected, fitted, and furnished. The local authority may purchase or lease lodging houses already erected or to be built. The general management, regulation, and control of the lodging houses vests in the local authority, who may make by-laws for this purpose. Any tenant in receipt of poor-law relief is disqualified from remaining a tenant, except in case of accident or temporary illness. The Housing Act also contains the following important provision : " In any contract for letting for habitation by persons of the working classes a house or part of a house, there shall be implied a condition that the house is at the commencement of the holding in all respects reasonably fit for human habitation." This section applies to houses let at a rental at which the rates may be compounded for — namely, ;^20 per annum in London, and ;^io in. the provinces.. SANITARY LAW AND ADMINISTRATION 667 By the Housing of the Working Classes Act, 1900, local authorities are now empowered to acquire land outside their own districts for the purpose of erecting lodging houses for the working classes. The Housing, Town Planning, etc., Act, 1909. Under this Act, Part III. of the Housing of the Working Classes Act, 1890, is extended to and takes effect in every urban and rural district in which it has not so far been adopted. Section 10 provides that where a complaint is made to the Local Government Board («) as respects any rural district by the Council of the county, by the Parish Council, or by any four inhabitant householders ; or (5) as respects any county district, not being a rural district, by the Council of the county, or by four in- habitant householders ; or (c) as respects the area of any other local authority by four inhabitant householders of the area, that the local authority have failed to exercise their powers under Part II. or Part III. of the Housing of the Working Classes Act, 1890, in cases where those powers ought to have been exercised, the Local Government Board may cause a public local inquiry to be held, and, if satisfied that there has been such a failure on the part of the local authority, may make an order directing that authority, within a limited time, to carry out such works and do such other things as may be mentioned in the order for the pur- pose of remedying the default. The Local Government Board must take into consideration the necessity for further accommodation for the housing of the working classes in the district, the probability that the required accommodation will not be otherwise provided, and the other circum- stances of the case, and whether, having regard to the liability which will be incurred by the rates, it is prudent for the local authority to undertake the provision of such accommodation. Where the order of the Local Government Board is not complied with by a District Council, the Local Government Board, with the consent of the County Council, instead of enforcing the order against the District Council, may make an order directing the County Council to carry out the required works. An order made by the Local Government Board must be laid before both Houses of Parliament, and may be enforced b}^ mandamus. By Section 11, where it appears to the Local Government Board that a local authority has failed to perform its duty under the Housing Acts of carrying out an improvement scheme under Part I. of the Act of 1890 or has failed to give effect to any order as respects an obstructive building, or to a reconstruction scheme under Part II., or has failed to cause to be made the inspection of its district required by the 1909 Act, the Local Government Board may make an order requiring the local authority to remedy the default and I0 carry out any requij-ed works within a fixed time. This order also is enforceable by mandamus. Section 1 2 enacts that on complaint by a Parish Council or four inhabitant householders, a County Council ma}' hold an inquiry into the alleged negligence of a Rural District Council to exercise its powers under Part III. of the 1890 Act. If satisfied of the default, the County Council may resolve that the District Council's powers under Part III. be transferred to itself, and such powers are accordingly transferred. Under section 13, a County Council may, after notice to a Rural District Council, apply to the Local Government Board for an order conferring upon it the powers conferred upon district councils by Part III. of the 1890 Act, and the Board may make such an order. Section 14 provides that in any contract made after the passing of the Act for letting for habitation a house or part of a house at a rent not 668 HYGIENE AND PUBLIC HEALTH exceeding (a) in London ^Afi, (b) in a borougii or urban district mtli a population of 50,000 or upwards ;£26, (c) elsewhere £16, there shall be implied a condition that the house is in all respects reasonably fit for human habitation, unless the premises are let for a term of not less than three years, not determinable by either party before the expiration of the term, and the lessee undertakes to put the premises into a condition reasonably fit for occupation. Section 15 provides that section 14 shall, as respects contracts to which section 14 applies, take effect as if the condition implied bj;- that section included an undertaking that the house shall, during the holding, be kept bv the landlord in all respects reasonably fit for human occupation. If it appears to the local authority- within the meaning of Part II. of the Act of 1890 that the undertaking implied by virtue of this section is not com- plied ■with, the authority shall, if a closing order is not made with respect to the house, by written notice require the landlord within twenty-one days to execute such works as may be necessary' to make the house in all respects reasonably fit for human habitation. Within twenty-one days after the receipt of such notice the landlord maj^ by ■\\Titten notice to the local authority- declare his intention of closing the house, and thereupon a closing order shall be deemed to have become operative in respect of such house. If the notice given by the local authority is not complied with, the authority may do the work and recover the expenses as a civil debt, or the authority may by order declare the expenses payable by annual instalments in five 3'ears, with 5 per cent, interest. The landlord is given power of appeal to the Local Government Board against any notice requir- ing the execution of works, and also against any demand or order for the recover}' of expenses. Sections 17 and 18 amend the procedure of the 1890 Act with regard to closing and demolition orders. It now becomes the duty of a sanitary authority, on the representation of its medical officer of health, that a dwelling house is in a state so dangerous or injurious to health as to be unfit for human habitation, to make an order prohibiting the use of the dwelling house for human habitation until in the judgment of the local authority the dwelling house is rendered fit for that purpose. Notice of a closing order must be served forthwith on everj^ owner of the dwelling house, and any owTier aggrieved by the order may appeal to the Local Government Board within fourteen days after the order is served. B}- section 49 the expression " owner " includes all lessees or mortgagees of an}' premises except persons who are lessees, the original term of whose leases is less than twenty-one years. The local authority must serve notice of the closing order on every occupying tenant of the dwelling house, and the tenant is required to quit within fourteen days after the service of the notice. In default of leaving the house, the tenant is liable on summary conviction to be ordered to quit the house %vithin a specified time. The local authority may make to everj- tenant who quits a reasonable allow- ance for removal expenses, such sum to be recoverable from the owner. If the owner does not consent to the amount determined by the local authority, a court of summary jurisdiction maj^ fix the amount. The local authority shall determine a closing order made by them, if satisfied that the dwelling house has been rendered fit for human habitation. If, on the application of any owner of a dwelling house the local authority refuse to determine a closing order, the O'wner may appeal to the Local Government Board within fourteen days of the refusal. A room habitu- ally' used as a sleeping place, the surface of the floor of which is more than 3 feet below the street adjoining, shall be deemed to be a dwelling house so dangerous or injurious to health as to be unfit for human habitation if it is not on an average at least 7 feet in height, or does not comply with SANITARY LAW AND ADMINISTRATION 669 regulations made by the local authority or by the Local Government Board for securing the proper ventilation and lighting of such rooms, and their protection from dampness, effluvia, or exhalation. The closing order made in respect of such a room shall not prevent the room being used for purposes other than those of a sleeping place. Where a closing order in respect of any dwelling house has remained operative for three months, the local authority shall consider the question of the demolition of the house. Every owner of the house must be given a month's notice, and is entitled to be heard when the question is con- sidered. The local authority may make a demolition order if of opinion that the house has not been rendered fit for human habitation, or that the necessary steps are not being taken to render it fit, or that the con- tinuance of the building is a nuisance or dangerous or injurious to the health of the public or of neighbouring inhabitants. The operation of the demolition order may be postponed for six months if the owner under- takes the execution of the necessary works to render the house fit for habitation. Notice of a demolition order must be forthwith served on every owner of the house, and any owner aggrieved may appeal to the Local Government Board within twenty-one days. Sections 32 and 23 of the Act of 1890 are repealed, but sections 34 and 35 are not repealed. Section 34 requires the owner to demolish a building within three months after the demolition order becomes operative ; whilst section 35 allows any person aggrieved by an order of the local authority, if he is not entitled to appeal to the Local Government Board, to appeal to a court of quarter sessions, when all further work and proceedings are stopped until the appeal is determined. In the case of owners of con- demned property whose original leases are for a less term than twenty-one years, there is still the same ability to resort to appeals, which not only may unduly prolong the proceedings, but may also involve heavy law costs. Section 43 provides that, notwithstanding any local Act or by-law in force in any borough or district, it shall not be lawful to erect any back-to- back houses intended to be used as dwellings for the working classes, and any such house commenced to be erected after the passing of the Act shall be deemed to be unfit for human habitation. Provided that nothing in the section shall prevent the erection or use of a house containing several tenements placed back to back, if the medical officer of health for the district certifies that the several tenements are so constructed and arranged as to secure effective ventilation of all habitable rooms in every tenement ; nor does the section apply to houses abutting on any streets the plans whereof were approved before May i, 1909, in any district in which any local Act or by-law permitting the erection of back-to-back houses was in force. Part II. of the Act deals with town planning. Section 54 provides that a town-planning scheme may be made in accordance with the provisions of the Act as respects any land which is in course of development, or appears likely to be used for building purposes, with the general object of securing proper sanitary conditions, amenitj^ and convenience in con- nection with the laying out and use of the land, and of any neighbouring lands. The Local Government Board may authorize a local authority to prepare a town-planning scheme in respect of any land within or in the neighbourhood of their area, or to adopt, with or without modifications, any such scheme proposed by all or any of the owners of any land in- volved. A piece of land already built upon, or a piece of land not likely to be used for building purposes, may be included in the scheme. A town- planning scheme prepared or adopted by a local authority must be ap- proved by an order of the Local Government Board, and when approved, byo HYGIENE AND PUBLIC HEALTH it has effect as if it were enacted in the Act. In London local authorities can only prepare town-planning schemes with the consent of the London County Council. The Local Government Board may make regulations for regulating generallj' the procedure to be adopted with reference to town-planning schemes. The Act includes provisions for compensation in respect of property injuriously affected by a scheme, and where any property is increased in value for the recovery by the local authority of one-half of the increase (betterment). Local authorities are authorized to purchase compulsorily or by agreement any land comprised in a town- planning scheme. If the Local Government Board are satisfied on any representation, after holding a public inquiry, that a local authority has failed to take the requisite steps for having a satisfactory town-planning scheme prepared and approved in a case where a town-planning scheme ought to be made ; or has failed to adopt any scheme proposed by owners of land in a case where the scheme ought to be adopted ; or has unreason- ably refused to consent to any modifications or conditions imposed by the Local Government Board, the Board may order the local authority to prepare and submit for its approval such a scheme, or to adopt the scheme, or to consent to the modifications or conditions. Or the Local Government Board may itself approve the proposed scheme, and there- upon the scheme shall have effect as if it had been adopted by the local authorit}^ and approved by the Local Government Board. If a local authorit}'' fails to enforce effectively the observance of a scheme which has been confirmed, the Local Government Board may order the local authority to enforce the scheme or any of its provisions, and execute any works required under the scheme. Any order under this section may be enforced by mandamus. Part III. of the Act requires that every County Council shall appoint a medical officer of health under section 17 of the Local Government Act, the duties to be such as maj'- be prescribed by general order of the Local Government Board, or may be assigned by the County Council. Such officer shall only be removable with the consent of the Local Government Board. He shall have the same powers of entry on premises as are con- , ferred on a medical officer of health of a district. He shall not be appointed for a limited period only, shall not engage in private practice, nor hold any other appointment without the express written consent of the Local Government Board. Every County Council in England, except that of London, must establish a public health and housing committee, and all matters relating to public health and the housing of the working classes must be referred to that committee. The County Council may delegate any of its powers in respect of public health and housing to the com- mittee, except the power of raising a rate or borrowing raoney, or resolving that the powers of a District Council in default be transferred to the County Council. Customs and Inland Revenue Act, i8go. Section 26 (2) provides that the assessment under the inhabited house duty of any house originally built or adapted by additions or alterations and used for the sole purpose of providing separate dwellings at rents not exceeding 75. 6d. per week, shall be discharged by the Commissioners, provided that a certificate of the medical officer of health of the district in which the house is situate shall be produced to them to the effect that the house is so constructed as to afford suitable accommodation for each of the families or persons inhabiting it, and that due provision is made for their sanitary requirements. The medical officer of health is required SANITARY LAW AND ADMINISTRATION 67I to examine any such house in his district on the request of the person liable to pay the house duty, and if the certificate can be properly given he shall certify the same accordingly. Revenue Act, 1903. The Revenue Act, 1903, exempts from inhabited house duty dwelling houses used for the sole purpose of providing separate dwellings of an annual value below ;^20. In the case of dwelling houses of an annual value between ;^2o and ^^40 the inhabited house duty is reduced to 3d. ; and in the case of dwelling houses of ;{40 to /60 annual value, the rate is reduced to 6d. For dwelling houses of an annual value below ;^4o the certificate of the medical officer of health of the district must be produced, as pro- vided by section 26 (2) of the Customs and Inland Revenue Act, 1890. Movable Dwellings. Under the Public Health Act, 1875 (section 314) local authorities are given power to make by-laws for securing the decent lodging and accom- modation of hop pickers within their district. By the Public Health (Fruit Pickers' Lodgings) Act, 1882, such by-laws may be made applicable to persons engaged in fruit and vegetable picking. The Local Government Board has framed model by-laws suitable for tents, sheds, barns, vans, and other places occupied as temporary dwellings. Under these by-laws the habitations must be clean, dry, weather proof, lighted, and ventilated. Sixteen square feet of floor space must be allowed for each adult, and for every two children under ten years. There must be arrangements of screens for privacy where different sexes are accommodated. Cooking places, adequate water supply, and privy accommodation must be pro- vided. There must be a sufficient supply of dry, clean straw, or other bedding. The premises must be kept in a cleanly condition at all times, and limewashed once a year. Sections 9 and 10 of the Housing of the Working Classes Act, 1885, are not repealed, and give local authorities power to deal with movable or temporary dwellings in their districts as regards nuisances, overcrowding, etc., with right of entry of officers, as if they were houses within the district. Canal Boats. Under the Canal Boats Acts of 1877 and 1884, every canal boat used as a dwelling must be registered with the local authority as a dwelling for a certain number of persons of specified age and sex, by whom alone it is to be occupied. The registration authorities are one or more of the sanitary authorities abutting on the canal on which the canal boat plies, as may be prescribed by the Local Government Board. Every canal boat when registered must be lettered, marked as "registered," and numbered in a conspicuous manner, and must show the name of the place to which as registered she belongs. On the appearance of infectious disease on board a canal boat, the boat may be detained to be cleansed and disinfected after removal of the case to hospital. The Local Government Board is empowered to make regulations for canal boats, which the local authorities are required to enforce. These regulations provide that — There must be at least one dry and clean cabin. An after cabin must contain not less than 180 cubic feet of free air space, and a fore cabin 80 cubic feet. There must be ventilation and sleeping 672 HYGIENE AND PtJBLlC HEALTH accommodation. One cabin must contain a stove and chimney. Tliere must be storage for 3 gallons of water. If the boat carries foul cargoes, the hold must be separated from an inhabited cabin by a double bulkhead, with an interspace of 4 inches, the bulkhead next the cargo being water- tight ; the space must be open throughout to the external air and provided with a pump for the removal of any liquid from such space. There must be 60 cubic feet of air space per head for persons over twelve years, and 40 cubic feet for children under twelve. No boy above fourteen or girl above twelve may sleep in a cabin occupied by a^married couple ; and males over fourteen and females over twelve must not sleep in the same cabin unless married. The interior of the cabin must, be repainted every three years and kept clean. Bilge water must be pumped out daily. The master of the boat must notify the occurrence of infectious disease to the sanitary authority of the district he may be in, and to the sanitary authority of the district of his destination ; and if his boat is detained for disinfection, he may not proceed until he has obtained a medical certificate of cleansing and disinfection. Factories and Workshops. Generally speaking, factories are places where mechanical power is used — that is to say, where engines are employed worked by steam, gas, water, or electricity. These are under the control of the Secretary of State for the Home Department, and are inspected by factory inspectors appointed by him. Workshops are places where mechanical power is not used, and, so far as regards sanitation, are supervised by officers of the local sanitary authorities. There are, however, a large number of non-textile factories which are controlled by the Home Secretary whether mechanical power is employed in them or not. These are blast furnaces, copper mills, iron mills, foundries, manufactories of earthenware, lucifer matches, percussion caps, cartridges, tobacco, paper, glass, print works, fustian cutting, printing, bookbinding, and flax scutch mills. Public Health Act, 1875. Section 91 defines as a nuisance any factory, workshop, or work-place — not already under the operation of any general Act (Factory and Work- shops Acts, 1878, 1883, 1891, and 1895I) for the regulation of factories or bakehouses — not kept in a cleanly state, or not ventilated in such a manner as to render harmless, as far as practicable, any gases, vapours, dust, or other impurities generated in the course of the work carried on therein that are a nuisance or injurious to health, or so overcrowded while work is carried on as to be dangerous or injurious to the health of those employed therein. By section 38 local authorities may require in factories or workshops a sufficient number of water-closets, earth-closets, or privies and ashpits, for the separate use of each sex. Private houses which are work -places, and in which no mechanical power is used, and in which the workers are members of the same family inhabiting the house, are exempt. Similar provisions are in force in the Metropolis. ^ Now repealed by the Act of 1901. SANITARY LAW AND ADMINISTRATION 673 Factory and Workshop Act, lyoi. This Act repeals the Factory and Workshop Acts of 1878 and 1883. It also repeals the Act of 1891 except sections 8, 9, 10, and 12, and the first schedule, and the Act of 1895 except section 12, sub-section 3 of section 24, and section 28. The Act is divided into Parts. Part I. deals with health, safety, and accidents. Part II. deals with employment (hours, holidays, overtime, night work, fitness for employment, etc.) ; Part III. with the education of children ; Part IV. with dangerous and unhealthy trades ; Part V. with tenement factories, cotton cloth and other humid factories, bake- houses and laundries ; Part VI. with home work ; Part VII. with work and wages ; Part VIII. with administration ; Part IX. with legal pro- ceedings ; and Part X. is supplementary. Every factory as defined by the Act, except a domestic factory, {a) must be kept in a cleanly state ; {b) must be kept free from efiiuvia arising from any drain, water-closet, earth-closet, privy, or urinal, or other nuisance ; (c) must not be so overcrowded while work is carried on therein as to be dangerous or injurious to the health of the persons employed therein ; [d) must be ventilated in such a manner as to render harmless, so far as is practicable, all the gases, vapours, dust, or other impurities generated in the course of the manufacturing process or handicraft carried on therein, that may be injurious to health. All the walls and ceilings of rooms, passages, and staircases in a fatcory must be limewashed every fourteen months, but painted or varnished surfaces may at similar intervJs be washed instead with hot water and soap, if the paint or varnish is renewed every seven years. Workshops and work-places must be kept in a cleanly state and ventilated, and must not be overcrowded, and they must be kept free from drain, etc., effluvia. A medical officer of health or inspector of nuisances may certify that the cleansing of a workshop is necessary for the health of the workers, and the sanitary authority must then give notice to the owner or occupier to carry out the necessary works. A factory or workshop is overcrowded if there is less than 250 cubic feet of space per head, and less than 400 cubic feet if overtime is being worked. A notice must be fixed in every factory and workshop specifying the number of persons who may be employed in each room. The Secretary of State may supersede the local sanitary authority, if default has been made by the latter in carrying out any of the provisions of the Act, which it is its duty to enforce, and may recover from the authority all expenses so incurred. If a factory inspector deems that there is any act or default or neglect in relation to the sanitary arrangements of a factor}^ or workshop remediable under the Public Health Act, he must give notice of the same to the sanitary authority of the district. It then becomes the duty of the sanitary authority to make such inquiry, and to take such action, within one month of the receipt of the notice, as may be necessary to enforce the law, and also to inform the factory inspector of the proceedings taken. In case of default by the sanitary authority, the factory inspector may himself take the necessary proceedings, and recover the expenses incurred from the sanitary authority. In every factory and workshop adequate measures must be taken for securing and maintaining a reasonable temperature in each room in which any person is employed, but the measures so taken must not interfere with the purity of the air of the room. By special order of the Secretary of State, thermometers may be required to be provided, and maintained in working order, in such places as may be specified in the order. In every room in any factory or workshop sufficient means of ventilation must be 43 674 HYGIENE AND PUBLIC HEALTH provided, and sufficient ventilation must be maintained. A standard of sufficient ventilation may be prescribed for any class of factories or work- shops by the Secretary of State. A workshop which is not ventilated in accordance with this section is deemed a nuisance under the Public Health Act. Factories or workshops in which the floors are wet must be provided with means of drainage. Workshops with undrained wet floors are a nuisance under the Public Health Act. Every factory and workshop must be provided with sufficient and suitable sanitary conveniences for the workers, and with separate accommodation, where both sexes are employed. The Secretary of State by special order may determine what is sufficient and suitable accommodation. By the Sanitary Accommodation Order of 4th February, 1903, it is provided (i) That in factories or workshops where females are employed there shall be one sanitary convenience for every 25 females. Where males are employed there shall be one sanitary convenience for every 25 males, but where the number of males exceeds 100, and sufficient urinal accom- modation is also provided, there may be one sanitary convenience for every 25 males up to the first 100, and one for every 40 after. Where the number of males employed exceeds 500, and the District Inspector of Factories certifies that there is proper supervision and control in regard to the use of the conveniences exercised by officers specially appointed for that purpose, one sanitary convenience for every 60 males is sufficient in addition to sufficient urinal accommodation. Any number of persons less than 25, 40, or 60, as the case may be, must be reckoned as 25, 40, or 60. (2) Every sanitary convenience must be kept in a cleanly state, suffi- ciently lighted and ventilated, and must not communicate with any workroom except through the open air or through an intervening ventilated space. This latter provision need not apply to workrooms in use prior to January i, 1903, which are mechanically ventilated in such manner that air cannot be drawn into the workroom through the sanitary convenience. (3) Every sanitary convenience must be under cover, and so partitioned off as to secure privacy, and if for the use of females must have a proper door and fastenings. (4) The sanitary conveniences must be conveniently accessible to all the persons employed in the factory or workshop. (5) Where persons of both sexes are employed, the conveniences for each sex must be so placed or so secured that the interior shall not be visible when the door is open, from any place where persons of the other sex have to Avork or pass. If the conveniences for one sex adjoin those of the other sex, the approaches must be separate. Factories and workshops in which there is an infringement of the above mentioned provisions of the Act are deemed not to be kept in conformity with the Act, and the occupier is liable to a ;^io fine. The Secretary of State has power by special order to modify many of the above mentioned provisions, where he deems it necessary. Every local authority is required to keep a register of the workshops within its district, and the factory inspector is required to forward to a local authority any notice received by him of the commencement of any workshop within the district of such authority. The medical officer of health of every district council and metropolitan borough must, in his annual report, report specifically on the adminis- tration of the Act in workshops and workplaces, and send a copy of such report to the Secretary of State. A medical officer of health who becomes aware that any child under 14, young person between 14 and 18, or woman over 18, is employed in a SANITARY LAW AND ADMINISTRATION 675 workshop or bakehouse, must give written notice of the fact to the factory inspector. The Act applies to the Metropolis as well as to England generally, and came into operation on January i, 1902. Dangerous and Unhealthy Industries. By the Act of 1901 every medical practitioner attending on, or called in to visit a patient whom he believes to be suffering from lead, phosphorus, arsenical or mercurial poisoning or anthrax, contracted in any factory or workshop, must send to the Chief Inspector of P'actories in London, a notice stating the name and address of the patient, and the disease frona which he is suffering. In any factory or workshop where grinding, glazing or polishing on a wheel, or any process is carried on, by which dust or impurities are gener- ated and inhaled by the workers to an injurious extent, the factory in- spector may require the use of fans or other mechanical means to prevent such inhalation. In every factory or workshop where lead, arsenic, or other poisonous substance is used, suitable washing conveniences must be provided for the use of the workers, and the latter must not be allowed to take their meals, or to remain during meal times, in any room where such substances are used. The following industries have been scheduled by the Secretary of State as dangerous to life and health. The manufacture of white lead, paints, and colours ; the extraction of arsenic ; the enamelling of iron plates ; the manufacture of lucifer matches except such as are made with red or amorphous phosphorus ; the manufacture of earthenware ; the manu- facture of explosives in which di-nitro-benzole is used ; chemical works ; quarries ; the making of red, orange, or yellow lead ; lead smelting ; tinning or enamelling of iron hollow ware ; electric accumulator works ; flax mills and linen factories. Power is given to the Secretary of State to make regulations in respect of any dangerous or unhealthy trade, such regulations requiring the adoption of special precautionary measures as regards cleanliness, ventilation, extraction of dust, etc. The White Phosphorus Matches Prohibition Act, 1908. By this useful piece of public health legislation no person may use white phosphorus in the manufacture of matches, nor sell, offer for sale, or import such matches. Cotton Cloth and Other Humid Factories. The amount of moisture that is permissible in these factories is regulated by the 4th schedule of the Act of 1901, which states the maximum humidity permissible at temperatures (dry bulb) ranging from 35° F. to 100° F. The Act also requires dry and wet bulb thermometers to be provided and maintained in all factories where artificial humidity is produced, and the readings of such thermometers to be recorded three times a day. In such factories the arrangements for ventilation shall be such that during working hours the COg in the air of any part of the factory must not exceed 9 parts per 10,000 of air ; nor must the temperature of any room in the factory be raised by artificial means above 70° F., except in so far as may be necessary in the process of giving artificial humidity to the atmosphere. 676 HYGIENE AND PUBLIC HEALTH Outworkers. In certain special industries specified by order of the Secretary of State, the occupiers of factories and workshops and contractors employed by them, are required to keep lists of outworkers, i.e., persons who do work for their employers outside the factory or workshop, and generally in their own homes. Copies of these lists must be sent twice a year to the sanitary authority of the district in which the factory or workshop is situate. These lists must be examined by the sanitary authority, and the names and addresses of outworkers not residing in the district of the sanitar}' authority must be sent to the sanitary authority of the district in which they do reside. These lists of outworkers kept by the occupier or con- tractor must be open to inspection by any factory inspector or officer of the sanitar}' authority. A sanitary authority may give notice to the occupier or contractor that the place where work is carried on by an outworker is injurious to the health of the persons employed therein. The occupier or contractor must then cease, within one month of the notice, to give out work to be done in that place. No wearing apparel maj' knowingly be given out by any occupier or contractor to be made, cleaned, or repaired, by an outworker who lives in a house where there is a case of small-pox or scarlet fever. The sanitary authority may make an order forbidding any work to be given to an outworker residing in a house of which any inmate is suffering from a notifiable infectious disease. This applies chiefly to the making, mending, cleaning, etc., of wearing apparel. Domestic workshops are private houses or rooms, which are used also as dwellings, and in which the only persons employed are members of the same family dwelling there. They are exempt from the great majority' of the provisions of the Factory and Workshop Act, 1901. Bakehouses. The law (Factory and Workshops Act, 1901) as regards retail bake- houses is administered by the sanitary authorities. A retail bakehouse is a place in which bread is baked, and is sold by retail in a shop occupied with the bakehouse. The officers of a sanitary authority have right of access to a retail bakehouse at any hour of the day or night. All the walls and ceilings of a bakehouse, and all passages and staircases, must be lime- washed twice a year, or if painted must be repainted every seven years, and washed with hot soap and water every six months. No room on the same floor may be occupied as a sleeping room, unless completely separated by a partition from the bakehouse, and provided with a window at least 9 square feet in area, half of which is made to open. No water-closet or privy is to be within the bakehouse, or to communicate directly with it. The cistern supplying water to a bakehouse must not supply a water-closet. No soil drain or drain inlet to a soil drain may be within the bakehouse. An underground bakehouse shall not be used unless it was in use at the passing of the Act of 1901. An underground bakehouse is one of which the floor surface is more than 3 feet below the footway of the adjoining street or ground. Since January i, 1904, an underground bakehouse shall not be used unless certified by the sanitary authority to be suitable for the purpose. No certificate may be given unless the sanitary authority is satisfied that the bakehouse is suitable as regards construction, light, ventilation, etc. In London no underground bakehouses can be used unless so used prior to January i, 1896. By an order of the Secretary of State of December 30, 1903, in under- ground bakehouses 500 cubic feet of space are required for every person, SANITARY LAW AND ADMINISTRATION 677 whilst in above-ground bakehouses, where work is carried on at night by artificial light other than electric light, between 9 p.m. and 6 a.m., 400 cubic feet of space are required for every person. Laundries. The provisions of the Factory and Workshop Act of lyoi apply to laundries carried on by way of trade, or for purposes of gain. The ex- emptions are laundries worked by the inmates of prisons, reformatories, industrial schools, or institutions conducted in good faith for religious or charitable pui'poses, or worked by members of the same family dwelling in the laundry, in which not more than two persons dwelling elsewhere are employed. Laundries in which steam, water, or other mechanical power is used in aid of the laundry process are factories. All other laundries are workshops. In steam laundries (factories), fans or other means must be provided and used for regulating the temperature in every ironing room, and for carrying away the steam in every washhouse. All stoves for heating irons must be sufficiently separated from any ironing room, and gas irons emitting noxious fumes must not be used. The floors must be kept in good con- dition and drained so as to allow water to flow off freely. The Factory and Workshops Act, 1907. This Act amends the Factory and Workshops Act of lyoi with respect to laundries, and it extends that Act to certain institutions. Some further conditions as to the hours of employment of women and young persons in laundries are included. The provisions of the principal Act are made to apply to institutions carried on for charitable or reformatory purposes, and not being premises subjected to inspection by Government officials. If, however, any institution can satisfy the Secretary of State that the only persons working therein are inmates of and supported by the institution or persons engaged in the supervision of the work or manage- ment of machinery, and that such laundry work is carried on in good faith with the purpose of the support, education, training or reformation of persons engaged in it, the Secretary of State may, by Order, direct that the principal Act shall apply to the institution subject to certain modifi- cations. The Secretary of State may arrange that premises which are subject to inspection under any Government department, and which are not factories or workshops (because the work carried on therein is not with the object of trade or gain), shall, as respects matters dealt with by the principal Act, be inspected by a factory inspector, and that the latter shall have the usual rights of entry. Alkali, Chemical, and Other Works. The works which are subject to the Alkali, etc., Works Regulation Acts, 1881 and 1892, include alkali works in which muriatic gas (HCl) is evolved, sulphuric acid, chemical manure, gas liquor, nitric acid, ammonia, chlorine, arsenic, muriatic acid, nitrate and chloride of iron, tar, and zinc works ; also the following, unless no H.2S is evolved, namely, alkali waste, barium, strontium, antimony sulphide, and bisulphide of carbon works. All these works must be registered by the Local Government Board. In alkali works 95 per cent, of the HCl gas evolved must be condensed, and not more than 1 grain of HCl gas per cubic foot of air, smoke, or chimney gases must escape from the works. Sulphurous acid and nitrous gases must not be present in escaping air or smoke to a greater amount than the 678 HYGIENE AND PUBLIC HEALTH equivalent of 4 grains of SOo per cubic foot, at a temperature of 60° F., and at 30 inches barometric pressure. Acid drainage must not be allowed to mix with alkali waste so as to cause a nuisance, and means must be taken to prevent nuisance from alkali waste. Similar regulations apply to the sulphuric acid and other works enumerated above ; and in all cases the best available means must be adopted to prevent the escape of noxious gases and to render them harmless and inoffensive. Adulteration of Food and Drugs. There are three Acts now in force relating to this subject, namely, the Sale of Food and Drugs Act, 1875 ; the Sale of Food and Drugs Act Amendment Act, 1879 ; and the Sale of Food and Drugs Act, 1899. For the purposes of these Acts, the term " food " includes every article used for food or drink by man, other than drugs or water, and any article which ordinarily enters into or is used in the composition or preparation of human food, and also includes flavouring matters and condiments. The term " drugs " includes medicines for internal or external use. These Acts prohibit : (i) The mixing, colouring, staining, or powdering any article of food with any ingredient or material so as to render the article injurious to health, with the intent that the same may be sold in that state ; and no article so mixed may be sold ; penalty for contraven- tion, £so (section 3, 1875 Act). (2) The mixing, colouring, staining, or powdering any drug with any ingredient or material so as to affect in- juriously the quality or potency of such drug ; and no drug so mixed may be sold ; penalty, ;^50 : provided that no person shall be liable to be con- victed if he proves that he was unaware at the time of sale of the food or drug that these were so mixed or coloured (section 4, 1875 Act). (3) The sale, to the prejudice of the purchaser, of any article of food or any drug which is not of the nature, substance, and quality of the article demanded by such purchaser ; penalty, ;^20. Where any niatter has been added to the food or drug, there is no offence if the same has not been fraudu- lently used, but is required for preparing the food or drug as an article of commerce ; neither does this section apply to proprietary or patented medicines or foods (section 6, 1875 Act). Under this section a great majority of the prosecutions for adulteration are instituted. By the 1879 Act it is provided that it shall be no defence to a prosecution that the purchaser, having bought only for analysis, was not prejudiced by the sale ; neither is it a valid defence to prove that the food or drug pur- chased, though defective in nature, or in substance, or in quality, was not defective in all three respects. Section 7 of the 1875 Act prohibits the sale of any compound, article of food, or compounded drug which is not composed of ingredients in accordance with the demand of the purchaser ; penalty, /20. By this section, the making up of medicines in accordance with prescription can be insisted upon, and the section is chiefly of value for that purpose. With regard to the sale of drugs and medicines, these articles must be in accordance with the requirements of the last published edition of the British Pharmacopoeia, both as regards the presence of particular in- gredients, their relative proportions, and their strengths. By section 8 of the 1875 Act, in the sale of articles of food or drugs which are mixed with other ingredients which are not injurious to health and not fraudulently added, there is no offence if the article sold has a label on it distinctly and legibly written or printed to the effect that the same is " mixed." This label must not be obscured by other matter on it (section 12, 1899 Act). By section 9 of the 1875 Act, no person shall, with the intent that the SANITARY LAW AND ADMINISTRATION 679 same may be sold in its altered state, without notice, abstract from an article of food any part of it so as to affect injuriously its quality, substance, or nature ; and no person shall sell any article so altered without making disclosure of the alteration ; penalty, /20. This section is invoked in cases of prosecution for selling skimmed or separated milk. The 1875 Act provides for the appointment of public analysts by local authorities, and for the analysis of articles of food and drugs submitted to them by private purchasers (on payment of a fee of 105. 6d.)', as well as' by inspectors appointed under the Act to purchase samples for analysis^ The form of certificate to be given by the public analyst is set out in the schedule to the Act. In this certificate, in the case of adulterated articles containing foreign ingredients, the public analyst is required to state the parts or percentages of foreign ingredients in relation to the bulk or total weight of the article ; and in the case of foods liable to decompose, he must certify that no change had taken place in the constitution of the article that would interfere with the analysis. By section 14 of the 1875 Act and section 13 of the 1899 Act, the person purchasing for analysis must, after the purchase has been completed, forth- with notify to the seller his intention to have the same analysed by the public analyst, and must divide the article into three parts, to be then and there separated, and each part to be marked, sealed, or fastened up as its nature will permit, and shall, if required to do so, deliver one of the parts to the seller. One of the parts is to be retained for future com- parison, and produced in court in the event of a prosecution. The third part is to be taken to the public analyst, or sent to him by registered parcel post. If the offer to divide is refused, the analyst must divide the sample into two parts, and remit one part to the purchaser for production in case proceedings shall afterwards be taken. Any person refusing to sell to an inspector or officer is liable to a £10 penalty. All proceedings under these Acts must be instituted within twenty-eight days of the date of purchase. The summons must state the particulars of the offence alleged, must not be made returnable in less time than fourteen days from the day on which it is served upon the defendant, and must be served with a copy of the certificate of the public analyst obtained on behalf of the prosecutor (section 19, 1899 Act). At the hearing of the summons, the certificate of the public analyst is sufficient evidence for the prosecution, unless the defendant requires him to be called (section 21, 1875 Act) ; and on behalf of the defendant a public analyst's certificate is sufficient evidence, if a copy has been sent to the prosecutor three clear days before the summons is heard. The justices may order the sample produced in court by the prosecutor to be sent to the Commissioners of Inland Revenue to be analyzed by the chemical officers at Somerset House, and may adjourn the hearing to obtain the Somerset House certificate (section 22, 1875 Act). They must do so at the request of either party (section 21 of the 1899 Act). By section 25 of the 1875 Act, if the defendant prove that he had pur- chased the article as the same in nature, substance, and quality as that demanded by the prosecutor, and with a written warranty to that effect, that he had no reason to disbelieve the warranty, and that he sold the article in the same state as when he purchased it, he is not guilty. By section 20 of the 1899 Act the warranty defence is not available, unless a copy of it has been sent to the prosecutor within seven days after the service of the summons, with the statement that the warranty will be relied on, and specifying the name and address of the person from whom the warranty or invoice was received. This person must also be informed of hho ilYGlE'Nfi KNl) I'UBLIC HEALITK the defendant's intention to rely on the warranty, and h;e is entitled to give evidence at the hearing. Any person giving a false warranty is liable to heavy penalties, unless he prove that when he gave the warranty he had reason to believe that it was true. The system of warranties in the milk trade of towns has had the practical effect of rendering the Acts valueless. The retailer obtains his milk froni the wholesale dealer under a six months' or one year's agreement, which is a continuing warranty for the period covered ; the wholesale dealer is protected by a warranty from the farmer. The Acts did not contemplate the case of successive warranties, with the result that the farmer's warranty is held to exonerate the wholesale dealer in the case of the latter being prosecuted for giving a false warranty to the retail dealer. Milk. — By section 3 of the 1879 Act, an inspector may take a sample of milk for analysis which is consigned from one person to another in pur- suance of any contract. The sample must be taken at the place of delivery, which in towns is usually a railway station, where the milk passes into the hands of the consignee or his servants. By section 14 of the Sale of Food and Drugs Act, 1899, any other article of food may be sampled in course of delivery at the request or with the consent of the consignee. By section 4 of the 1899 Act the Board of Agriculture can frame standards, for the composition of genuine milk, including condensed milk, cream, butter, and cheese, departures from which standard raise a presumption until the contrary is proved, that the article is adulterated. 1 Analysts must have regard to these standards. Any person selling milk or cream in any street or public place raust have conspicuously inscribed on his vehicle or can or churn his name and address (section 9). Every tin of condensed " separated " or " skimmed " milk must bear a label clearly visible to the purchaser — " Machine-skimmed Milk " or " Skimmed Milk " — in large and legible type. No tin unless so labelled may be sold or exposed or offered for sale. Butter and Margarine. — By the Margarine Act, 1887, butter is defined as made exclusively from milk or cream, or both, with or without salt or other preservative, and with or without added colouring matter. Margarine includes all substances, whether compounds or otherwise, prepared in imitation of butter, and whether mixed with butter or not. Every package of margarine must be so marked in printed capital letters not less than f inch square ; if exposed for sale by retail, the label must be printed " Margarine " in letters i^ inches square. When margarine is sold retail, it must be delivered to the purchaser in a paper wrapper on which " Margarine " is printed in capital block letters not less than ^ inch 1 Under the Sale of Milk Regulations, 1901, of the Board -bf Agriculture, it is provided that where a sample of milk (not being skimmed, separated, or condensed milk) contains less than 3 per cent, of milk-fat, or less than 8-5 per cent, of milk solids other than milk-fat, it shall be presumed for the purposes of the Sale of Food and Drugs Acts, 1875 to 1899, until the contrary is proved, that the milk is not genuine, by reason of the abstrac- tion of milk-fat or milk-solids other than milk-fat, or the addition thereto of water, as the case may be. Where a sample of skimmed or separated milk contains less than 9 per cent, of milk-solids, it shall also be presumed that the sample is not genuine. Under the Sale of Butter Regulations, 1902, the Board of Agriculture has stated that where the proportion of water in a sample of butter exceeds 16 per cent, it shall be presumed for the purposes of the Acts, until the contrary is proved, that the butter is not genuine by reason of excess of water. SANITARY LAW AND ADMINISTRATION 68l long and distinctly legible, and no other printed matter must appear on the wrapper (Sale of Food and Drugs Act, 1899, section 6). An officer taking samples under this Act is not required to go through the form of purchase, but otherwise the procedure is the same as under the Sale of Food and Drugs Acts. Any substance not marked as margarine is pre- sumed to be exposed for sale as butter. By the Sale of Food and Drugs Act, 1899, " Margarine " and " Margarine-cheese " must be branded on the package itself, and not solely on an attached label or ticket, in capital block letters ^ inch long. By this Act also margarine-cheese is included in all provisions relating to margarine, and the same measures must be taken to differentiate margarine-cheese and cheese as are necessary to differentiate margarine and butter. Manufactories of margarine and of margarine-cheese must be registered with the local authorities of the district in which they are situate, and notice of registration must be sent to the Board of Agriculture. No margarine imported, manufactured, or sold may contain more than 10 per cent, of butter fat (Sale of Food and Drugs Act, 1899, section 8). The Butter and Margarine Act, 1907. — -By this Act, which came into force on January i, a statutory maximum limit of 16 per cent, of water is imposed in the case of all butters, with the exception of " milk-blended butter," which is to be allowed to have as much as 24 per cent., so long as it is sold by a name which is approved by the Board of Agriculture and one which is not " suggestive of butter or anything connected with the dairy interest." The names under which margarine is sold are to be sub- ject to the same restrictions. The principal advantage of the Act is the substitution of a system of control at the port of importation (through the Customs authorities and the Government laboratory), and in this country at the place of manufacture, for the present methods, which are based almost wholly on analysis of purchased samples. Places where butter is blended " by way of trade " will now have to be registered, and no foreign fats are to be kept on such premises. Wholesale " blending " of butter and margarine making are not to be carried out on the same premises, although exceptions may be made for existing factories. Another considerable advantage of the Act is that it empowers the Local Govern- ment Board to schedule and to regulate the use of preservatives in butter, milk-blended butter and margarine, and it may be hoped that this will speedily be done. A circular has been issued by the Board of Agriculture as to the action which local authorities are recommended to take under the new Act. Apparently the principal duty required of them is to see that butter-blending, milk-blending, and margarine-making premises are all duly registered, and to report to the Board of Agriculture cases where in course of ordinary sampling it is found that the permitted limits of moisture have been exceeded. It may be gathered from the circular that routine inspection of the registered factories will be made by officers of the Board of Agriculture. The circular points out, however, that under section 2 of the new Act local authorities have power to authorize any officer who is authorized to procure samples under the Sale of Food and Drugs Acts to enter any registered butter factory for the purpose of inspection of processes and of taking samples. Spirits. — By section 6 of the Sale of Food and Drugs Act Amendment Act, 1879, brandy, whisky, and rum may be sold 25 degrees under proof and gin 35 degrees under proof. Spirits may be sold diluted to a greater extent, if a customer's attention is called to the fact of greater dilution being practised in the establishment in which he is being served, but not otherwise. The chief provisions of the Sale of Food and Drugs Act, 1899, have been alluded to above. In addition, it may be noted that importers of 682 HYGIENE AND PUBLIC HEALTH margarine, margarine-cheese, skimmed or separated condensed milk, and of other adulterated or impoverished articles of food, unless such articles are conspicuousl}' labelled or described, are liable to a penalty. The Local Government Board and the Board of Agriculture may direct their officers to procure for analysis any article of food in any district. Such officer divides his sample into four parts, sending one part to his board and one to the public anah'st of the district, whose fee is payable by the local authority of the district. If the sample is adulterated, the analyst's certificate is to be sent to the local authority, who are required to prosecute. By this Act also every- local authority is now required to appoint a public analyst _ and to administer the Acts. In case of failure to do so, either the Local Government Board or the Board of Agriculture may. empower an officer to execute and enforce the provisions of the Acts, and the expenses so incurred must be paid by the local authority to the Board on demand. Public analysts to be appointed must furnish such proof of competency as the regulations of the Local Government Board may require. INDEX Abattoirs, public, 346 "ABC" process, 141 Acetylene, 255 Actinomycosis, 332, 500 Adulteration of food and drugs, 390. 678 Aerial spread of small-pox, 410 " After-flush " for valve vr.c, 90 Age and sex distribution, 603 Agglutination tests, 443, 448 Ague {see Malaria) Air, 166 Albo-carbon light, 254 Albuminoids, 309 Alcohol, effects of, 381 Aliens Act, 628 Alkali works, 193, 677 Alkaloids, poisonous, in sewer air, 180 ; in the body, 311 ; in meat, 339 ; produced by specific mi- crobes, 402 Alum, for purif\-ing water, 55 ; in bread, 369 Alumina, sulphate of, as a sewage precipitant, 13S Amalgaline joints, 99 Amines process, 140 Ammonia in water, 64 Amoeba coli, 475 Anderson's process of water filtra- tion, 53 Anemometers, 236 — Robinson's wind, 287 Aneroid barometer, 2S6 Angus Smith's solution, 41 Aniline dyes, 305, 38 5 Animal charcoal for filters, 56 Ankylostomiasis, 117, 492 Anopheles, 483 Anthrax, 398, 493 Anti-cyclonic system, 280 Anti-D trap, 91 Antiseptics, 563 ; in milk, 354 Antitoxins, 404, 440 Aqueducts, i, 40 Areas, "open" and " drs- " for houses, 266 Argand burner, 253 Amott's valve, 223 Arrowroot, 373 Arsenic in wall papers, 205 ; in beer, 380 Arsenical poisoning, 201, 205, 380 Artesian wells, 30 Artificial illumination, 252 — manure factories, 197 Ash-closets, jj Aspiration, ventilation by, 218 Atmometers, 291 Atmospheric pressure, increase of, 275 ; diminution of, 274 Atmospheric electricity^, 297 Attenuation of vira, 403 Autoclave, 579 Averages, 596 Back-to-back houses, 207, 456 Bacteria in rain, 4 ; in drinking water, 65 ; in the soil, 159; in sewer air, 180 ; of intestinal t^'pe, 12, 15, 65 Bacterial sewage filters, 147 Bakehouses, 675 Baking powders, 369 Balance system of ventilation, 233 Barley, 2,7- Barograph, 295 Barometer, 283 Bath heaters, 244 Beans, 2^7 ?> Beer, 380 Bell traps, 121 Beri-Beri, 489 Berkefeld filter, 58 Bilharzia hcFinatobia. 335 Biological examination of water, 65 ; purification of sewage, 143 Birth rate, 601 Blackwater fever, 485 Blood-boiling, 194 Boilers, 5, 251 Bond's stove, 245 Bone-boiling, 194 Bones, nourishment in, 326 Books, disinfection of, 588 683 684 HYGIENE AND PUBLIC HEALTH Boots, 308 Bothriocephalus Jatus , 379 Boyle's valve, 223 Brain fatigue, 534 Branch drains, 104 ] Brandy, 378 Brass founder's ague, 192 Bread, 368 Brewery waste in sewage, 153 Brick burning, 1 92 Bricks, capacity for holding mois- ture, 265 Budde process, 356 Burial, 591 —grounds, 591, 658 Burners, gas, 253 Butter, 366, 680 By-laws, 630 Caisson disease, 276 Calf-lymph, 420 Calories, 319 Canal boats, 671 Cancer, 469 Candles, 257 Candy's sprinkler, 154 Canned foods, 385 Carbo-hydrates, 312 Carbolic acid, 575 Carbon block filters, 56 — -in diets, 317 Carbonic acid, in outer air, 166 ; in expired air, 168 ; in crowded rooms, 169 ; from combustion of gas, 177 ; in wells, 202 Carbonic oxide, 178, 243, 246 Carriers, 406, 438, 441, 443 Catchment basin, 7 Cattle, fever in, 495 — tuberculosis in, 499 Cellar dwellings, 642 Cemeteries, 591, 658 Cerebro-spinal fever, 467 Cesspools, 24, 75 ; emptied by pneumatic pressure, 76 ; fatal results from opening, 182 Chalk fissures, 162 —soils, 30, 264 ; borings, 30 Channel pipes, 104 Charcoal, wood, in sewer venti- lators, 131 Cheese, 367, 681 Chicken-pox, 432 Chicory, 375 Childhood, clothing in, 305 Children Act, the, 659 Chimneys, use of, in ventilation, 218 Chinosol, 578 Chittenden's experiments, 319 Chloride of lime, 577 Chloride of zinc, 578 Chlorine as a disinfectant, 577 Cholera, 474 ; from polluted water, 17, 61 ; in relation to under- ground water, 263 Cholera orders, 659 Chromium poisoning, 201 Cisterns, 45 Clark's process, 50 Classification of causes of deaths, 621 Clay, London, 29 Cleansing of Persons Act, 658 Climate, 272 Clothing, 302 Clouds, 293 Coal, 176 ; combustion of, 177 — dust, 189 Coal gas, 177 ; combustion of, 177 ; escapes of, 179 ; illumination, 253; manufacture of, 1 76 ; puri- fication of, 177 — miners, 188 Cocoa, 376 Coffee, 374 Coke for filters, 151 Cold, effects of, on body, 272 Colza oil, 257 Common lodging-houses, 643 Communicable diseases, 394 ; mi- crobial origin of, 395 Confectionery, colouring matters of, 384 Conservancy systems, 74 Contacts, 406, 422 Contagia, the, 394 Contagious Diseases Acts, 473 Convection, heating by, 244 Cooking, 337 Cooper's ventilator, 221 Copper poisoning, 192 Correlation, 597 Cotton, 302 — factories, 675 Cowls for chimney tops, 218 Cow-pox, 421, 508 Cow's milk, 351 Creches, 325 Cremation, 590, 658 — of house refuse, 70 — of organic vapours, 196 Crops of sewage farms, 163 Cubic space in inhabited rooms, 215; in hospitals, 516; estima- tion of, 235 Curd of human and cow's milk, 349 Custom and Inland Revenue Act, 670 Cyclonic systems, 281 Cysticerci, 327 INDEX 685 Dairies, cowsheds, and milkshops, 649 Damp-proof course, 266 Danysz bacillus, 481 Daylight illumination, 527 Deacon's waste-water meter, 41 Dead, disposal of, 590, 658 Death certificates, 621 Death rates, 602 ; calculation of, 601 ; significance of, 602 ; rural and urban, 604, 609 ; in relation to density of population, 607 ; correction of, for age distribu- tion, 604 ; standard, 604 ; in- fluence of birth rate upon, 610 ; of combined districts, 602 ; at special age periods, 603 ; of special diseases, 612 ; fallacies in connection with, 621 Deaths, in public institutions, 602 Defects, sanitary, in houses, 119 Dengue, 490 Deodorants, 563 Destructor furnace, 70 Dew point, 290 Diarrhoea, 60, 449 ; from meat poisoning, 339 Dibdin's experiments, 147 Diets, 315 ; training, 301 Diffusion of gases, 206 Digestibility of food, 315 Diphtheria, 61, 400, 434; from milk, 359 Dipstone trap, 121 Disconnection of house drain, 105 Disinfectants, liquid, 574 ; gaseous, 579 ; solid, 584 ; standardizing of, 564 Disinfecting station, 572 Disinfection, 563 ; by boiling water, 567 ; by burning, 566 ; by dry heat, 567 ; by steam, 5 68 ; of sick- room by sprays and gaseous air purifiers, 585 ; of stools and sputa by liquid reagents, 589 ; of ships, 590 Disinfectors, steam, 568 Distillation of water, 53 Distributors, sewage, 155 Distoma hepaticuni, 332 Domestic dry refuse, removal of, 68 ; disposal of, 69 Dortmund tank, 140 Drain sewers, 83, 123 Drains, house, 10 1 ; testing of, 113 ; brick, 119 ; law as to, 632 Drying power of air, 290 D trap, 88 Ducat's system, 150 Dust, in air, 186 ; from trade pro- cesses, 189 ; household, 69, 202 Dustbins, 69 Dwellings, movable, 670 Dynamite, 227 Dysentery, 60, 477 Earth system, Moule's dry, 79 —temperatures in relation to diar- rhoea, 451 Education Code, 557 Elastic force of vapour, 291 Electric light, 257 Electricity, atmospheric, 297 Ellison's conical brick ventilators, 222 Embalming, 592 Endemic diseases, 398 Energy obtainable from food, 317 Enteric fever, 441 ; from polluted water, 13, 48,61 ; from milk, 358 ; relation of, to height of ground water, 262 Entozoa, eggs of, in water, 62 Entozoic diseases on sewage farms, 165 Epidemic diseases, 397, 659 Epizootic diseases, 493 Equifex disinfector, 571 —sprayer, 587 Ergot, 371 Erysipelas, 399 Evaporation of rainfall, 3, 7, 20 ; of water on sewage farms, 1 64 Excremental emanations, 1 79 Excreta, human, 72 Exercise, 299 Exit shafts for foul air, 224 Expectation of life [see Mean dura- tion of life) Explosions of boilers, 251 ; of lamps, 256 Extraction, ventilation by, 226 Extractives, 311 Extracts of meat, 347 Fabrics, injury to, by disinfection, 567 Factories, ventilation of, 229 ; and workshops, 672 Faeces, composition of, 72 Fans, extraction by, 230 ; propul- sion by, 231 Fat melting, 195 Fats, 312 Fatty acids of butter, Tj6j Feeding bottles, 324 Fellmonger, 195 Fermentation of organic matters, 1 1 , 179 ; vinous, 378 ; acetous, 379 Fermented liquors, 378 Fevers, symptoms of, 554 Fiddian Rotary Distributor, 154 686 HYGIENE AND PUBLIC HEALTH Filariasis, 491 Filter presses for sewage sludge, 142 Filters, domestic, 56 Filtration of water, 14, 52 ; of sewage, 147, 159 Fireplaces, improvements in, 241 Fish, 346 Fish frying, 197 Flame illumination, 252 Flashing point of oils, 255 Fleas, 479 Flies, 454 Floor space, 215 ; in hospital, 5 1 6 Floors, 270 ; hospital, 520 Flour {see Wheat) Flush tanks, 81 Flushing gates for sewers, 128 Fogs, 178, 293 Food, 309 ; proximate constituents of, 309 ; excess and deficiency of, 322 ; unsound, 645 — standards, 390 Foot and mouth disease, 364, 504 Foot-tons of potential energy, 317 ; of work, 301 Formic aldehyde, 579 Foundations of houses, 265 Friction, loss of velocity in air shafts by, 225 Frosts, as obstacles to sewage irrigation, 164 Fume cremator, 71 Fungi in water, 8 ; in milk, 358 ; in flour and bread, 370 .Fur in boilers, 5, 251 Furnace chimneys, connection of sewers with, 132 Furnace smoke, 210 Furniture, house, 203, 271 Ganister industry, 191 Gas [see Coal gas) — cooking stoves, 337 — iires, 242 — governors, 255 — pipes, pressure in, 254 ; testing of, 179 — works, nuisance from, 193 Gelatine, 311 Germ theory of disease, 395 Germicides, 563 Gin, 378 Glanders, 505 Glossina palpalis, 492 Glucose, 380 Glue-making, 196 Gluten of flour, 369 Goat's milk, 349, 488 Goitre, 61 h*"'* Goux system at Halifax, jy Grates, open, 241 ; smokeless, 241 ; ventilating, 244 Gravel soils, 264 Graveyards, pollution of water by, 27 ; pollution of air by, 186 ; pollution of soil by, 261, 592 Grease gulley, 1 1 1 Greensands, 38 Ground air, 259 — water {see Underground water) Gulley, yard, 109 Gunpowder blasting, 1S8 ; substi- tutes for, 227 Gut scraping, 195 Haemoglobinuria, 485, 510 Haffkine's prophylactic, 482 Haffkine's anti-cholera vaccine, 403 Hardness of water, 5 Hawksley's formula, 7 Heat, effects of, on body, 272 Heating by hot water, 247 — by steam, 250 Hendon cow disease, 359 Hermite system, 140 Hinckes-Bird's window ventilator 220 Hopper closets, 84 ; supply from water main, 49, 122 Horrocks on sewer air, 181 Horseflesh, 335, 647 Hospital fevers, 175, 515 Hospitals, 515 ; isolation, 524, 656 ; temporary hut, 523 ; pavilion, 523 Hot-water pipes, 247 House, construction of, 269 — drains, 10 1 Houses of Parliament, ventilation of, 232 Housing of the working classes, 664 Housing and Town Planning Act, 667 Humidity, relative, 250, 290 Hydraulic mean depth, 125 Hydrocarbons {see Fats) Hydrophobia, 501 Hygrometers, 289 Hypochlorites, 141, 577 Immunity, 403 Incubation period, 395 Industrial poisonings, 198 Infantile mortality, 325, 619 Infants, feeding of, 323 — consultations, 326 Infection, 397, 405 Infectious Diseases (Notification) Act, 650 ; law as to, 653 Influenza, 464 INDEX 687 Inlet openings into rooms, 220 Inoculations, preventive, 403, 406 Insects, infection from, 408 Intemperance, effects of, 381 Intercepting sewers, 123 Intoxication, 382 Investigation of disease, 511 Iron, magnetic carbide of, 52 ; spongy, 52 ; protosulphate of, as a sewage precipitant, 138 Irrigation, sewage, 160 Island climates, 277 Isolation of infectious diseases, 521 Italian rye grass, 163 Joints of drains, 102 Joints, soldered, 98 Kenwood and Butler on sewage treatment, 147, 148 Kerosene oil, 255 Kitson light, 256 Knackeries, 197 Koch on water filtration, 18 Koch's postulates, 396 Koumiss, 35 1 Lactic acid bacilli, 352 Lake waters, 7 Lamps, 255 Latrines, 94 Laundries, 677 Lead, solvent action of water on, 43 —pipes, 42 — poisoning, 43, 198 Leather dressing, 195 Lemon and lime juice, 384 Leprosy, 489 Liernur's system, 135 Life tables, 613 ; old and new, 618 ; construction of, by graphic method, 616 Lime as a sewage precipitant, 138 ; chloride of, 577 — salts in water, 5 Linen, 303 Liquefaction of solids in sewage, 144 Liver fluke, 332 Local Government Board, model by-laws for privies, 74 ; for cess- pools, 75 ; for new streets and buildings, 208 ; for offensive trades, 194 ; provision of isola- tion hospitals, 412 Lodgings, houses let in, 644 London, water-supply of, i, 14 ; basin, geological formation of, 29 ; Building Act, 209 Louvre ventilators, 22 1 Lung diseases, from overcrowding 174 ;Tfrom inhalation of dust, 188 ; from dampness of soil, 262 Mackinnell's ventilator, 224 " Made " soils, 264 Magnesium salts in water, 5, 37 Malaria, 263, 483 Mallein, 506 Malta fever, 488 Manhole chambers on house drains, 107 Manholes, sewer, 125 Manure, manufacture of, 78 ; earth- closet, 79 ; sewage, 142 Margarine, 2,6"], 680 Marriage rate, 611 Marsh air, 186 ; soils, 263 Martin-Chick test, 565 Massachusetts experiments, 17, 145 Mean age at death, 613 Mean duration of life, 615 Means of series, 596 Measles, 427 Meat, 326 ; preservation of, 337 — condemned, 345 — effects of diseased, 338 — extracts, 347 Mechanical stokers, 211 Medical officers of health, 629 Mercurial poisoning, 200 Mercury, bichloride of, as a disin- fectant, 574 Metallic poisoning by water, 62 Metchnikoff's theory, 404 Metropolitan water supply, Royal Commission on, 1 3 Metropolitan sewage discharge. Royal Commission on, 133 Micro-organisms {see Organisms) Middens, 74 Midwives Act, 663 Milk, 348, 680 — condensed, 324, 354 — depots, 365 — dried, 366 — epidemics, 358 — sterilization of, 350, 365 Mineral salts in food, 315 — waters, 377 Miners, lung diseases of, 188 —nystagmus, 191 Mines, ventilation of, 226 — disposal of excreta in, 117 Montgolfier's formula, 219 Mortality, occupational, 187, 622 Mortuaries, 657 Mosquitoes, 263, 483, 487, 491 Mountain climates, 274 688 HYGIENE AND PUBLIC HEALTH Mumps, 432 Miisca domestica, Mustardj 384 454 Nitrates and nitrites, in well waters, 64 ; from oxidation of sewage, 158 Nitrifying organisms, 146, 159 Nitrogen, in faeces and urine, 72 ; in crops of sewage farms, 163 ; in diets, 317, 320 Nitrous acid as an air purifier, 584 Notification of infectious diseases, 650 ; of births, 659 ; of measles, 428 ; of tuberculosis, 459, 651 Nuisances, 639 ; from offensive trades, 194, 645 ; from smoke, 210, 634 ; law as to, 636, 639 Oatmeal, 373 Ocean climates, 277 Offensive trades, 1 94, 645 Ogle's, Dr., comparative mortality- statistics, 187 Oidium albicans, 35S Old age, clothing in, 305 Ophthalmia, contagious, 467 Opsonins, 405 Ordnance map, 9 — datum, 9 Organic matters in water, 64 ; in air, 170 Organisms, aerobic, 144; anaerobic, 1 44 ; in air, 1 72 Osier beds on sewage farms, 164 Outlets for vitiated air, 223 Outworkers, 676 Overflow pipes, from cisterns, 45 ; from cesspools, 83 Oxidation of sewage in rivers, 1 1 ; of sewage in the soil, 159 Oxychloride process, 141 Oxygen in air, 166, 170 Oysters, 157, 445 Ozone, 170 Ozonization of air, 234 Pail system, 76 Pan closet, 88 ; supply from drink- ing-water cistern, 45 Paper making, 198 Paratyphoid fever, 442 Parry Laws and Andrewes, 181 Pasteur-Chamberland filter, ^j Pasteur treatment, 503 Paving, 267 Peas, ^7z Peat acids, 44 Pellagra, 373 Pepper, 384 Percolation of rain, 2, 20 Perflation by \^dnd, 206 Petroleum oils, 255 Petrolite lamp, 256 Phagoc5rtosis, 404 Phenoloids, 576 Phenols, 575 Phosphorus poisoning, 199 Phthisis, produced by foul air, 1 74 ; by dust, 187 ; by damp soils, j 262 ; climatic treatment of, 274 [see also Tuberculosis) Pickles, 384 Pig keeping, 197- Pipe sewers, 126 Piroplasmosis, 509 Plague, 478, 628 Plenum ventilation, 232 Plug closet, 92 Pneumonia, 468 Poisson's rule, 594 Pole's formula, 7 Pollution of rivers, 11; of wells, 23 ; of the soil, 261 Population, estimation of, 600 ; law of, 599 ; census of, 599 Port Regulations, 626 Port Sanitary Authorities, 625 Porter-Clark's process, 50 Portland cement, 102 Potassium permanagnate, 578 Potatoes, 374 Poudrette, 78 Precipitants, sewage, 138 Preventive inoculations, 403 Probability, theory of, 597 Probable duration of life, 616 Propulsion, ventilation by, 231 Proteids, 309 Pseudo-tuberculosis, 459 Ptomaines, 311, 339 Puerperal fever, 469 Pulsometers, 35 Pumps, 33 Purification of sewage, 1 36 — of water, 50 Putrefaction, in river waters, 12 ; of sediment in sewers, 83 ; of meat, 339 Quarantine, 476, 626 Rabies, 501 Radiation, warming by, 240 Radiators, 249 Rain, evaporation of, 2 ; percola- tion of, 2, 20 Rain gauge, 292 — water pipes, no Rainfall, 2 c Rainwater, 3 Ram, hydraulic, 35 INDEX 689 Rats, 479, 628 Reek's disinfector, i;/! Refuse, 68 Regulator valves, 90 Relapsing fever, spirillum of, 401 Relative values of series, 594 —humidity, 250, 290 Reservoirs, water, 7 Respiratory impurity, permissible limits of, 214 Rest, after exercise, 300 Revenue Act, the, 1903, 671 Rheumatic fever, 471 Rice, 373 Rideal-Walker test, 564 Ridge and furrow system, 162 Rivers, 10; pollution of, 11, 632, 641 ; self-purification of, 11 Road paving, 267 Roberts' rain-water separator, 5 Roofing, 270 Rotheln, 431 Rye, 372 Sago, 373 Sanatoria for phthisis, 462 Sand filtration, 15, 16, 17, 18 Sanitary authorities, 625 ; itfspec- tors, 629 — law, 624 Scarlet fever, 423 ; from milk, 358 Scavenging, 68, 635 Schizomycetes, 394 Scholars, hygiene of, 533 School children, 533 ; nervous sys- tem of, 533 ; vision of, 537 ; hear- ing of, 540 ; exercise of, 541 ; postures of, 542 ; respiration of, 544 ; circulation of, 545 ; skins of, 545 ; clothing of, 547 ; food of, 548 ; measurements of, 549 ; infectious fevers of, 554 ; ex- clusion of, 558 School cleaning, 532 School cloakrooms, 530 School desks and books, 527 School drinking cups, 531 School hygiene, 526 School medical inspections, 555 ; schedule of, 560 School w.c.s and lavatories, 531 Schools, ventilation of, 529 ; light- ing of, 527 ; warming of, 528 ; closure of , 5 5 1 ; infection in, 5 5 1 ; inspection of, 556 Scott-Moncrieff's system, 146 Scurvy, 314; infantile, 365 Sea, disch ',rge of sewage into, 133 — salts ill tidal waters, 134 Seasonal prevalence of disease, 413 Sedimentation, 13 Septic tank system, 144 Serum diagnosis, 408, 472 Sewage of midden and water-closet towns, 73 ; average composition of, 1 36; sludge, 141 ; effluents, 157; farms, 161 ; purification of, 136 Sewage disposal, 133; law as to, 632 ; Royal Commission on, 157 Sewerage, combined system of, 123 ; separate system of, 126 Sewer air, 180 ; poisoning from, 183 ; cremation of, 131 — deposits, 83 — gases, 179 — men, health of, 184 — ventilators, 127 Sewers, 123; gradients of, 124; velocity of flow in, 124 ; capacity of, 124 ; shape of, 125 ; construc- tion of, 125 ; flushing of, 127 ; ventilation of, 128 ; movements of air in, 129 ; oiitfall, 132 ; law as to, 630 Shell-fish in tidal waters, 157, 445 Sheringham's valve, 222 Shone' s pneumatic sewage ejectors, 13s Short-sight in children, 537 Silica in water, 43 Silk, 30s Simple continued fever, 433 Siphonage, 81, 94, 10 1 Siphon flush tank (Field's), 81 — gulley, 109 — traps, 92, 105 ; disconnecting, 105 Siphonic closets, 86 Sites of houses, 259 Skin, care of the, 304 Slaughter houses, 346, 648 Sleeping sickness, 492 Slop closets, 94 Slop sinks, 97 — waters, 73 ; disposal of. So Small-pox, 409, 508 ; hospitals, 409 Smoke nuisances, 634 Smoke, prevention of, 210 Soap, 304 Soap-boiling, 195 Sodium hypochlorite, 577 Softening of water, 50 Softness of water, 5 Soil pipes, 97 Soil pipe ventilator, 100 Soils, 259 ; for filter beds, 159 ; for sewage farms, 161 ; favourable to diarrhoea, 452 ; favourable to enteric fever, 445 Specific diseases, 397 Spirits, 378, 681 Spirochsete disease, 472, 510 44 690 HYGIENE AND PUBLIC HEALTH Spongy iron, for purifying water, 52, 57 Spot maps, 623 Sprays, disinfection by, 587 Springs, 20 Stable manure, 69 Stables, 116 Standard deviation, 596 Standards, food, 390 Starches, 313 Statistical fallacies, 602, 603, 608, 620 Statistics, 594 Steam blast for ventilation, 229 — disinfection by, 568 — pipes, 250 Steamships, ventilation of, 239 Steining of wells, 26 Sterilization of water, 54 ; of milk, 353, 365 Stoddart's distributor, 155 Stokers, mechanical, 211 Storage reservoirs, 7 Storm overflows to sewers, 1 24 Storm waters, 1 5 1 Stoves, close, 245 ; ventilating, 245 Stream, definition of, under R.P.P. Act, 642 Streets, paving of, 268 Sub-irrigation, 80 Subsoil, drying of the, 264 ; pollu- tion of, 261 ; drainage of, 123, 264 Sugars, 312, 384 Sulphurous acid in air, 178 ; as an air purifier, 581 Sunlight, absence of, 167 Sunshine recorder, 296 Surface waters, 36, 109 Susceptibility to disease, 403 Sylvester's system of ventilation, 218 Syphilis, 472 Tabes mesenterica, 362 TcBnia echinococcus, 329, 334 — mediocanellata, 329 — solium, 328, 333 Tank sewer, 1 34 Tanks, sewage, 134; precipitation, 139 Tanneries, 195 Tannin, of tea, 375 ; of wines, 379 Tapioca, 27?) Tea, 375 Testing of drains and soil - pipes, 113 Tetanus, 400 Thermometers, wet and dry bulb, 289 ; maximum and minimum, 294 ; solar, 296 ; terrestrial radia- tion, 296 Thresh' s disinfector, 572 Thrush, 358 Ticks, 509 Tidal rivers, sewage in, 133 Tide valve for sewers, 134 Tin miners, 189 Tinned foods, 385 Tobacco, 389 Tobin's tube, 222 Tonsillitis, acute, from foul air, 183 Town planning, 669 Toxins, 339, 402, 405 Trade nuisances, 194 Traps, efficiency of, 1 1 1 — water seal of, 92 Trichina spiralis, 329, 335 Tripe boiling, 195 Tropical climates, 272 Trough closet, 93 Trj^panosomes, 492 Tsetse fly, 492 Tube wells, 27 Tubercle, bacillus of, 399 ; in cow's milk, 360 Tubercular peritonitis from milk, 362 Tuberculin, 500 Tuberculosis, 187, 399, 455, 498, 652 ; from cow's milk, 360 ; from meat, 341 — Royal Commission on, 341, 458 — Dispensary, 463 — Sanatoria, 462 Tumbling bay and flap valve, 132 Typhoid fever [see Enteric fever) Typhus, 433 Tyrotoxicon, 368 Underdrains for filter beds, 159 Underground water, 20, 24 ; curve of , 2 1 , 24 ; varying level of , 2 1 , 260 Unhealthy areas, 664 — dwelling houses, 665 — trades, 675 Unsound food, 645 Upland surface waters, 6, 36 Urea, fermentation of, 73 Urinals, 97 Urinary calculi, 61 Urine, composition of, 72 Vaccination, 414, 431 — Acts, 662 Vaccine lymph, 421 Valve closet, 90 Vapour in air, 291 Varicella, 432 Variola {see Small-pox) Vegetable acids, 314 INDEX 691 Vegetarianism, 311 Vegetation, effect of, on climate, 278 Ventilation, 205 ; of inhabited rooms, 213 Vinegar, 384 Vital statistics, 598 Wall papers, 204 Walls of houses, 265 Warming, 240 Washington Lyon's steam disin- fector, 570 Wash-down closet, 85 Wash-out closet, 86 Waste-pipes, 109 — water meter (Deacon's), 41 — waters, j'i, Waste-water closets, 94 Water, i ; sources, collection, and storage of, 2 ; quantity required , 39; waste of, 41, 47; constant service of, 47 ; intermittent ser- vice of, 45 ; sterilization of, 53; opinion upon purity of, 63 ; com- position of, 36 ; purification of, 50 ; temperature of, in mains, 42 ; subsoil, 259 ; as food, 315 ; law as to, 640 Water-bearing strata, 29 Water-carriage system, 83 Water-closets, 84 ; flushing of, 86 ; law as to, 639 Water gas, 243 Water mains, 40 Water pipes, 48 Waterproof materials, 305 Water samples, opinion upon, 63 Water softening processes, 50 Water vapour in air, 291 Water- waste preventers, 86 Water-wheels, 35 Weather observations, 279 Weight of the air, 287 Well borings, 30 Wells, 23 ; shallow, 23 ; deep, 28 ; artesian, 31 ; tube, 27 ; examina- tion of, 27 Well waters, 37 Welsbach incandescent gas burner, 254 Wheat flour, 368 Whey cream mixture, 351 Whisky, 378 Whooping cough, 431 Widal's test, 448 Wind pressure, 288 Windows as ventilators, 220 — in schoolrooms, 527 Winds, as ventilating agents, 206, 217 ; effects of, on body, 273 Wines, 379 Wool, 303 Wool sorting, 230 Woolsorter's disease {see Anthrax) Work, average day's, 301 Working classes, housing of the, 664 — lodging houses, 666 Worms, round, 334 — thread, 334 Yard paving, 267 Yeast, in bread making, fermenting liquors, 378 Yellow fever, 487 Yersin's plague serum, 481 369; Zinc cisterns, 46 Zymotic diseases, from, 612 394 ; death rates H. K. LEWIS, 136, GOWER STREET, LONDON, W.C. '^^Z. ^^^ ^^ ^ <• 151 1?-:, ili'i •h 'ill hr ;•';;! Ill 'I ■! '!!fj.'')t(rt! m ? iri) l.liii'i.:-^ '!;; 't .ill:'!'' 'II* - ;■ 'm ,;'''l'ii|"' ■ '.. "i::Mrf