Aw was aa RUNS RN MIRC OT ~ AionuOu Wea ES > Ra mace Wa oon SCC te BINLOOUGR Ny a ONC HAT ‘ Re aOR Ce Rano A) Sere) Se Site o ian as wi A AAW i ia wee Pt hd at Ke HA CAP RSS ey : OKA MEK aK COMA ead of PS AN CA CAC BAA Pen Hi sy ee Ks my OME: CAAA An } Ay ROKK SaCn EO OORT has A - 6 wy Ae v G i ey os ae is Bf f i AAT AACA ER EA or tyty one Ah Ae teAL ay AAAS Cae fs waa CORNELL UNIVERSITY. THE Roswell P. Flower Libravit” | THE GIFT OF ede ee ROSWELL P. FLOWER |S | FOR THE USE OF oa * & THE N. Y. STATE VETERINARY COLLEGE R: 18907 ae 8394-1 Corneil University Library SF 255.J54e Essentials of milk il HTT ESSENTIALS OF MILK HYGIENE A PRACTICAL TREATISE ON DAIRY AND MILK INSPECTION AND ON THE HYGIENIC PRODUC- TION AND HANDLING OF MILK, FOR STUDENTS OF DAIRYING AND SANITARIANS BY C. O. JENSEN Professor in the Royal Veterinary and Agricultural College of Copenhagen, Denmark. TRANSLATED AND AMPLIFIED BY LEONARD PEARSON Dean of the Vetermary Faculty of the University of Pennsylvania, State Veterinarian of Pennsylvanin, Member of the Advisory Board of the State Department of Health, and Member of the Board of Health of Philadelphia. ILLUSTRATED PHILADELPHIA AND LONDON J. By LIPPINCOTT COMPANY COPYRIGHT, 1907 BY J. B. LipprncoTt COMPANY Published June, 1907 Electrotyped and printed by J. B. Lippincott Company The Washington Square Press, Philadelphia, U. S. A. CONTENTS. PAGE AUTHOR’S PREFACE (TO THE ENGLISH EDITION).........-.0.0-. 0 -V TRANSLATOR’S PREFACE ............... ice dpdierareaue’ & ce deh teat, NA INTRODUCTION ......... alee ees aig wlban ee pF bates sae Same 9 MILK AND ITS COMPOSITION ............. Suge eae. ee 12 HARMFUL PROPERTIES .............. fies Boas Gee 8 Re peslersese 60 PASTEURIZATION AND STERILIZATION ......... Straits RN ia eek 12s THE USE OF MILK FOR INFANTS ........00 000 cece ee ec ee ee eeee 147 Pusiic CONTROL OF THE PRODUCTION AND HanpLiING or MILK.... 157 AppeNpDIxX I.) Tires Mitk Supply OF COPENTIAGEN............. 239 APPENDIX II. GeRMAN INSTRUCTIONS FOR PRODUCING NURSERY WETS thc hio.2. so ashes fot aati oduct ans ana neds Geese ee ee 249 APPENDIX III. Tue MILK COMMISSION OF PHILADELPHIA...... 25) Appenpix IV. A Score Carp ror Dairy FARMS.............. DOF APPENDIX V. THE MILK CoMMISSION OF Essex (o., NEW JERSEY se sieve oe Galan Seestingieie & Gites eo teh tion ch etta oth aes ans 259 APPENDIX VI. Report oF THE ROYAL COMMISSION ON TUBER- CULOSIS: . iagaies- ees wn awiewanws DG Ale raranerereue eSeegsdiee aaenersnes ane Cons 269 INDEX: cae. os0a 4: Bib pain Sake ate Sea eae Sacsow goes asa ded QF AUTHOR’S PREFACE. (TO THE ENGLISH EDITION.) Ix the hygienic movement of the times the control of the production and handling of milk has not been given a prominent place. But the significance of this subject is now plain and everywhere efforts are being made to institute such a control or to improve it. The efforts of cities to secure a wholesome supply of milk must of course differ and be adapted to local conditions, but they must all be governed by the same principles and rest on exact knowledge of the composition of milk and of the dangers that are to be avoided. In the preparation of this book it has been my hope that it would not only be of use to my Danish col- leagues, but that my colleagues in other countries would find it to be of service to them. lor this reason I pub- lished a Danish and a German edition simultaneously and for the same reason I have been very glad to grant Prof. Pearson’s request for permission to prepare an English edition. C. O. JENSEN. TRANSLATOR’S PREFACE. Tue production of market milk is a rapidly growing industry. The demand for milk in cities is continually increasing and there is reason to believe that the rate of inerease will advance. The milch cow transmutes the pasturage and forage of the farm into edible protein, lactose and fat—into units of nutriment for man—at less than one-half the cost of similar units in beef produced by the steer. Milk is not only the most economical but, when pure and undefiled, it is among the most wholesome and it is the most easily digestible of all foods of animal origin. These are the strongest possible reasons for its extended use. Qn the other hand, there is no other food that, under ordinary conditions, is so exposed to contamination, that is so easily contaminated or that so fosters contami- nation as milk. Hence the necessity for the study of milk hygiene. The subject is a broad one. Milk hygiene involves some knowledge of the physiology of cows, especially with relation to breeding, lactation and nutrition; of comparative pathology, particularly the various dis- eases of the udder of the cow, the abnormal conditions that affect milk secretion, and the infectious diseases of cattle and of man that may be transmitted by milk; of bacteriology, in regard to the pathogenic organisms and the saprophytes that oeeur in milk, their effects, their behavior under various conditions and especially at different temperatures; of the chemistry of milk and ity adulterations and, besides these, there must be added vii TRANSLATOR’S PREFACE certain, important chapters from animal husbandry, dairy husbandry and dairy industry. Until quite recently, milk inspection in the United States has been carried on by untrained men who have had little, if any, knowledge of the sources or nature of the contaminations of milk or of the means by which they must be avoided; their whole technical equipment has consisted in a few rule-of-thumb tests to detect gross adulterations. A large number of milk inspection services are still organized on this basis. In several cities, however, attention has been paid to microscopic and bacteriologic examinations of milk, and it has been shown that a very large proportion of the supply fails to meet even a moderate standard for cleanliness, thus re- vealing the need for measures at the seat of production and during transit to prevent injurious contaminations. It is becoming increasingly manifest to sanitarians that more must be done to protect consumers from the unwholesome conditions and the diseases propagated and transmitted by milk and the broader men in dairy industry realize that milk must be made safe and be pro- tected if it is to find and retain its proper place in the dietary of the people. This makes a demand for a discussion of milk hygiene from the standpoint of the sanitary supervision of market milk—from the side of the man who is to do the practical work of protecting the milk supply—and it is this demand that Professor Jensen’s book is planned to meet. Lronarp Prarson. viii PART J. INTRODUCTION, Cow's milk has a peculiar place among our food stuffs in that it is not only an important and indispens- able part of the daily dietary of inost people, but it is being used more and more for the feeding of infants and, indeed, is often almost the exclusive food for children during the first years of life. It is, therefore, quite natu- ral that at present when the science of hygiene is receiv- ing so much attention—especially in relation to the large cities—that there should be a demand for a reliable supervision of market milk. It is true that the milk trade in cities has been subject to a certain inspection, but attention has been directed to only one side of the question, to the possibility of adulteration, and to pro- vide that fat is not removed and that there is no alteration in the composition of the milk. From the standpoint of hygiene this is merely of secondary im- portance because it is in other ways that milk aequires dangerous properties and may, indeed, become the means of spreading virulent diseases. A properly organized milk control of the present day ean not, therefore, be restricted to determining that milk offered for sale is unadulterated. On the contrary, it must be its chief purpose to prevent milk possessing injurious properties from coming into the market and to prevent market milk from acquiring such properties during the time that it is being handled and stored. Since it is possible only by means of a thor- ough, tedious examination to determine whether a given 9 10 MILK HYGIENE sample of milk is unwholesome, milk control can not be restricted to a simple inspection of the milk or to taking a sample for further examination. To insure real safety, the inspection must be broadened to cover the health and feeding of the cattle, the cleanliness of the producing plant, the method of handling and caring for the milk and the condition of health of the people who come in contact with it. Milk control is, for the reason stated, more difficult and more expensive than, for example, meat inspection, and this is undoubtedly one of the principal reasons why the control of milk produc- tion and the milk trade is so defective in most countries. During recent years, a somewhat comprehensive con- trol of the milk trade in its various relations has been carried out in a number of large cities, but a thoroughly satisfactory system does not exist and will be difficult to establish on account of its cost. Jn Denmark, a long step has been taken in the matter of milk control through the voluntary initiative of a single large com- pany which, at a time when milk hygiene was receiving little attention, inaugurated a very comprehensive system of control, and thereby set an example that has been followed by other large companies, not only in Copenhagen but also in foreign countries. These com- panies have, in some respects, carried their control to a point far beyond that contemplated at the time by the public authorities. Copenhagen is on the point of supplementing its health laws in relation to the milk trade within its limits, As it is chiefly through the work of Veterinarians that meat inspection has gradually increased and is now conducted in a scientific manner, so, to a large extent, we have to thank the Veterinarians for the fact that- the control of the production and sale of milk is grow- INTRODUCTION Ly ing steadily. Not only is important scientific work being carried on by them in several directions, which supplements the work of chemists and physicians, but the necessity for milk control is constantly being pointed out in meetings of veterinarians, in the International Veterinary Congresses and in the Congresses for Hygiene. A special journal is devoted to «questions pertaining to milk hygiene, in conjunction with meat inspection, and separate courses in milk hygiene are given in many Veterinary Colleges. What follows is essentially the substance of lectures given by the author in the Veterinary and Agricultural College of Copenhagen. On some points in the prepara- tion of the book, the lecture notes have heen expanded ; for example, in citing the instances of disease resulting from milk possessing injurious properties. Since vet- erinarians are frequently consulted, hy sanitary officers and by dairymen, in regard to the adulteration of milk, it is considered to be desirable to discuss rather thor- oughly the composition of milk, the variations that occur under different conditions, and the adulterations. It is also considered to be appropriate to briefly treat upon the use of milk as food for infants. Division oF SuBJECT The subject matter of this book is divided into the following parts: Milk and its composition. Injurious properties that milk may possess. Pasteurization and sterilization of milk. The use of milk for infants. In order to prevent the expansion of the book to unnecessary proportions, the hygiene of other dairy products as cheese and butter, and milk preparations as condensed milk, milk powder, ete., is not discussed, PART II. MILK AND ITS COMPOSITION. I. THE MILK GLANDS AND MILK SECRETION. Tue tissue of the milk glands is shown by macro- scopic examination (Fig. 1) to be composed of small lobules separated by bands of connective tissue in which lie the larger blood vessels, the nerves and the excretory ducts and in which there is sometimes a considerable quantity of fat tissue. The gland tissue itself is com- posed of complexly branching glandular tubes which, during the period of lactation, are provided with numerous globular distensions, so that the type of the milk gland is intermediate between that of the alveolar and tubular types. The glandular pockets are provided with a membrana propria (Fig. 2) and are lined with epithelial cells. In young and farrow animals, the cells are thin and square or high and narrow, and resemble superficial epithelium. During the period of lactation these cells become large and tense. This epithelium is usually composed of but a single layer, although, in old cows, it is sometimes found to be composed of several layers. Toward the end of gestation, the secretory function of the udder begins with the production of colostrum or the so-called ‘‘beast milk.’’ This is a thick, reddish or yellowish fluid with a taste more salty than that of nor- mal milk, and under the microscope (Fig. 3) it is seen that it contains numerous free fat globules and a large number of round or mulberry shaped cells—the so-called colostrum bodies—that are filled with fat globules. 12 section of udder tissue of w cow. Low magnification. One entire lobule is shown and parts of five others, Microphotograph. Section of the udder tissne of a eow High magnification. Shows individual glandular pockets with their endothelial lining and the connective-tissue tramework, \iero- photograph. Colostrum.—The udder secretion of a cow that has recently ealved. tamed lightly with osmicacid, causing the fat globules to become dark. Shows several colostruin bodies and fat globules. Microphotograph, Milk.- The fat globules are shown as light circles on a dark background. Micro- photograph. THE MILK GLANDS 13 Some cells are seen that have a distinct ameboid movement; these are leucocytes that have wandered through the epithelium into the glandular pockets and have taken up some globules of fat. Besides these, there are to be found some epithelial cells that have undergone more or less degeneration. The chemical examination of colostrum shows its principal constituents to be: water, proteids (especially globulin and albumin, and also casein and nuclein com- pounds), sugar, fats and cholesterin, and, besides these, lecithin, various salts and other substances in smaller quantities. Colostrum differs from normal milk in its higher percentage of solids and especially in its higher content of globulin, albumin, nuclein compounds and lecithin. The chemical composition of colostrum differs slightly among animals of different species. In the course of a few days, the secretion of colostrum passes into milk seeretion so that at the expiration of about one week, the secretion possesses the characteristic ap- pearance and composition of milk. The microseopic picture of milk is quite different from that described above. .\ very large number of fat droplets (milk globules, Fig. +) of varying sizes, and a small number of more or less degenerated cells (eolos- trum bodies, gland cells) are distributed uniformly in a transparent fluid, the milk plasma. It was formerly thought that milk secretion differed in important particulars from other secretions in that, it was considered, it occurred through partial destrue- tion of the gland cells. It was supposed that during secretion the cells became longer and swollen, that the nucleus receded to the base of the cell while the part pointing toward the cavity of the alveolus became filled with numerous small fat globules. It was thought that after this ‘‘ fatty degeneration ’’ reached a certain 14 MILK HYGIENE stage, there was a pouring out and solution of this part of the cell, that the fat globules were transformed into milk globules and the albuminous part of the cell protoplasm became part of the milk fluid and that the remaining portion of the cell, with the nucleus, was soon regenerated, whereupon a fatty degeneration again oc- curred in the regenerated portion of the cell. Recently, doubts have arisen as to whether, during the production of milk, there is, after all, a material disintegration of the cell protoplasm. Ottolenghis’s investigations appear to show clearly that milk secretion is an active cell process precisely as other secretions are, and that it does not depend upon the destruction of the cell. The destruction of entire cells and their elimination appears to occur only to a limited degree, but the presence of karyokinetic figures shows that, here and there, in the gland, such a disintegration does occur with consequent reproduction. The milk from animals of different species contains the same ingredients, namely: water, albuminoids (es- pecially casein and albumin), milk sugar (lactose), fats and inorganic salts. In regard to quantitative compo- sition, there are marked differences between the milks of animals of different species. Among the ingredients of milk it is supposed that casein is the direct product of the gland tissue, globulin of the broken down parts of cells, while it is not known whether albumin originates at the same source or comes from the blood. Concerning the origin of lactose, there are different opinions. Some investigators suppose this material is formed in the liver from glycogen or related materials, while others think, and indeed with reason, that it is formed in the udder by synthetic building up of glucose and galactose. The latter cannot, as such, have been taken up with the food, but must have been THE CONSTITUENTS OF MILK 15 formed in the body by a breaking down of the galac- tins of the food. Others regard lactose as a product of certain proteids (glycoproteids). Milk fat is de- rived partly from the fat in the food, partly from the fat tissues of the animal; but these fats undergo a material transformation in the tissues of the udder, so that certain easily recognizable fats, even when taken up in quantity with the food, are either not visible at all in the milk or appear in very small quantity or are merely transitory. Doubtless, milk fat—just as fat tis- sue—may also be derived from the carbohydrates of the food. Among the other ingredients of milk, citric acid does not originate in the food, but results from metabolism. Milk secretion, to a great degree, bears tlie impres- sion of specific action of the cells which, however, may be influenced by external circumstances, but usually only temporarily. This is naturally of great importance for the young animal, which is nourished entirely or chiefly on its mother’s milk, as frequent and sudden changes in the composition of the milk would be harmful, if not dangerous. Milk secretion, it appears, may be checked through the influence of the central nervous system, but is regu- lated through the sympathetic nerve centres. In this connection, observations agree that certain irritant drugs (as pilocarpine) and other influences that decid- edly affect the secretory function of other glands, influ- ence milk secretion very little if at all; furthermore, section of the nerve trunks of the udder does not disturb secretion. II. THE CONSTITUENTS OF MILK As already mentioned, milk of different mammals consists essentially of the same materials, namely: water, protein, sugar, fats and inorganic matter; but 16 MILK HYGIENE great differences are shown by quantitative analyses of the milk of the different species. Water. The quantity of water usually amounts to 80 to 90 per cent. of the weight of the milk; under certain circumstances and with some animals it is even consider- ably less. With the whale, the quantity of water is scarcely 50 per cent. Proteids. Of proteids, the three following are always found: casein, lactalbumin and lactoglobulin. A kind of albumose-like compound is sometimes found in insignifi- eant quantity—the so-called animal gum—which is also found in certain tissue and in the saliva, and probably comes from the breaking down of glycoproteids (mucin, ete.). Moreover, other proteids are often described as normal constituents of milk (albumins, albumoses, meat acids, ete.), but it is safe to conclude that these do not occur in fresh milk, while such compounds are readily formed by bacteria and ferments and can be formed by chemical means. Casein is a nucleo-albumin and, as such, it contains phosphorus. It is insoluble in water, but, by virtue of its property as an acid, it forms soluble salts with alka- hes. There are two series of casein salts, basic and neutral; the solutions of the latter have a milky appear- ance. Casein is found dissolved in milk in the form of a neutral lime salt, which aids in giving to milk its white, opaque appearance. When boiled, a solution of casein is overcast with a thin membrane of coagulated casein; but a real coagulation, as it occurs in albumins and globulins, does not take place. When the fluid has reached a certain degree of acidity casein coagulates at 75° C. and the precipitated casein is not again soluble. After the addition of diluted mineral acids or of acetic acid, casein is precipitated as flakes or lumps, but under- goes no chemical change and is again easily soluble in THE CONSTITUENTS OF MILK Ty lime water and diluted alkalies. The separation depends only and solely upon the breaking down of the casein calcium compound. By rennet (chymosin, etc.) casein is precipitated as flakes (human milk and donkey milk), or as a firm gelatinous mass (e.g. cow’s milk). The dif- ferent modes of precipitation do not appear to come from the differences in the casein, but are due to the dif- ferent salt content of the different kinds of milk. Under the influence of chymosin, casein is transformed into paracasein, Which in its compound with lime is insoluble in water and, therefore, may be precipitated in this way. The action of the rennet ferments is quite different from the precipitation of casein by acids. With the pre- cipitation of paracasein, an albumose-like proteid re- mains in solution (whey proteid), so the action of the rennet ferment is to split the casein. By the growth of bacteria in milk, the casein is often thrown out of solution, either as a result of the formation of acids or by the chymosin-like effect of ferments produced hy bacteria. Sometimes the separation occurs from the joint action of the ferments and the acids that are formed. In pepsin digestion, casein is dissolved with the formation of albumoses (caseoses) and paranuclein, which is rich in phosphorus. In the organism, para- nuclein is dissolved by the pancreatie juice, is absorbed, and is excreted with the urine as phosphorie acid. Tt has often been said that casein, as it is found in the milk of different animals, is not the same and, as evidence of this, reference has, incorrectly, been made to the different ways in which casein separates from milks acted upon by rennet. A more important indica- tion, although the observation requires confirmation, is in the claim that in the pepsin digestion of human milk no paranuclein is formed. According to Hammarsten’s thorough work, casein appears to show no chemical dif- BD) 18 MILK HYGIENE ference in different kinds of milk. The latest investiga- tions concerning the powers of the organism to form specific anti-albumins (precipitins) following the injec- tion of albumin solutions, prove, however, that the casein of different species of animals has certain dif- ferences, even though these are so slight that they can- not be detected chemically. The lactalbumin is very similar to the albumin of the blood, but it appears to differ from this in some particu- lars. It coagulates at about 70° C., and, like all other albumins, it is not precipitated in a neutral solution of sodium chloride and magnesium sulphate, but it is precipitated in a saturated solution of ammonium sulphate. The lactoglobulin occurs in milk in very small quan- tity, merely in traces, while colostrum is comparatively rich in this substance. It coagulates at 75° C.; it is pre- cipitated in the same way as serum globulin and, like serum globulin, is insoluble in water, but is soluble to some extent in weak salt solution. Carbohydrates. Of the carbohydrates, lactose, or milk sugar, occurs as a constant constituent in the milk of the cow and of most other mammals. Some investiga- tors claim that in colostrum there is a monohexose, which is probably glucose, and it is not unlikely that in the milk of certain animals other kinds of sugar appear; for example, it is cited that a peculiar kind of sugar, tewficose, is found in considerable quantity in the milk of the Egyptian buffalo. Lactose (C,,H,.,0,,; + H,O) is a disaecharid which is split by hydrolysis (e.g. by means of heating with dilute acids, action of ferments) into glucose (grape sugar) and galactose as follows: Ci, Ay, OW + Hy O = Cs Hip Og +t Cs Hi, Os Lactose Glucose Galactose TELE CONSTLITVENTS OF JTL 19 Lactose has been found only in milk and must be formed in the organism; but this formation, as has already heen stated, is not yet thoroughly understood. Commercial lactose is derived from whey as hard rhom- Ine crystals which have a slightly sweet taste and are soluble in six parts of cold water. By the action of Inicro-organisins, lactose may ferment in different wavs. Certain yeasts and bacteria cause an alcoholic fermen- tation, while other bacteria split lactose, forming lactic acid (causing ‘* souring ’’ of milk) and several other substances as by-products (C'O., H, formic acid, butyric acid, ete.) ; still other bacteria form as their chief pro- duct, butylalcohol, succinic acid or acetic acid. Certain moulds are able to forin oxalie acid from lactose by oxi- dation. Lactose, like glucose, reduces Fehling’s solution when heated. Fats ave found in the milk as small droplets or elob- ules, which accumulate upon standing into a layer of cream, and which are easily separated from the other constituents of milk by means of centrifugal force. Upon shaking milk or cream, the globules of fat grad- ually coalesce into larger drops and lumps (butter). It was formerly thought that the fat globules were sur- rounded by a membrane, but now it ix generally believed that it is not so. However, under the microscope one can see a border on certain individual fat globules, which is to be regarded as a remainder of broken-down cell protoplasin. Milk fat consists of a mixture of different fats, the principal of which are olein, palmitin and stearin, which are the neutral triglycerides of the correspond- ing fatty acids. Besides these are found the triglycer- ides of myristic acid and of butyrivc and eapronie acids (the last two volatile) and also traces of triglyceride of other fatty acids (vaprylic, caprinic, laurinie and arach- 20 MILK HYGIENE inic). The composition of the fat is subject to numerous variations and these are not alone racial peculiarities, for individual traits, the composition of the food and external conditions of life not infrequently influence it. Other Substances. Milk contains other substances in very slight quantities: urea, kreatin, kreatinin, leci- thin, cholesterin and citric acid. It is not yet known if these appear in the milk of all animals or whether some of the substances are characteristic of certain animals only. Besides these substances, milk contains some inor- ganic salts in solution, which remain after evaporating and burning the milk. The ash consists of lime, potash, sodium, small quantities of magnesia and traces of oxide of iron in combination with phosphoric acid, chlorine and sulphuric acid. The small surplus of basic sub- stances in the ash were in combination with citric acid and, perhaps, with other organic acids. Phosphoric acid and lime exist partly as soluble compounds, partly in combination with casein. 0.60 | 0.63 | 0.52 Wats a geotnh caemeenaaennd 3.40 3.90 | 11.90 110) 1.09 3.48 Lactose ...........--..- 4.60 | 4.40 3.48 6.00 °° 665 | 7.12 Rallis sccuxeerreuyen tse 0.75 | 0.80 | 105 | 040 O31 | 0.25 | i \ \ IV. VARIATIONS IN THE COMPOSITION OF COW’S MILK It has already been stated that the composition of the milk of the cow, as well as that of other animals, may vary more or less. So far as the variations of cow’s milk are concerned, they are not very great, still they are of sufficient importance to make it necessary to take them into consideration in connection with its pro- duction, sale and control. The above figures give ap- proximately the average composition of cow’s milk and, of course, correspond with the composition of market milk, which consists of a mixture of milk of several or many cows.* The separate constituents vary in quantity “These are Danish figures; in America the average for market milk is higher. [L. P.] VARBEATIOSS IX COV "S ATER ai in different degrees, the fat content varying the most, the albumin, Jaetose and ash ingredients less. In ‘rich "milk the fat content often considerably exceeds the average, while the proportions of protein and lac- tose are never much higher than the averages given. On the other hand, with thin, poor milk the fat per cent. may fall far below the average, while the proportions of protei and lactose depart but slightly from the average. These variations are not due merely to the elimination of water from the milk, that is, to a simple concentration, but rather to a qualitative variation in the activities of the eland cells. Just as is the case with other glands, the milk glands may be stimulated to ereater activity, so that the quantity of secretion increases, but its chemical eompo- sition is not disturbed, or only slightly, or temporarily, until the gland tissue has accustomed itself to the new condition. Drinking a large quantity of water causes no increase Inmilk secretion; the eland cells do not secrete more water than the quantity required to maintain the proper proportion to the milk solids. Food containing much water has no permanent effect upon the composition and the quantity of the milk. The influence of such materials as piloearpine and atropine, which increase or reduce other secretions in a great degree, have no direct, or only a very slight influence on the milk secretion, apparently because this is con- trolled by the sympathetie nerve centres. The various conditions that have, or are believed to have, an influence upon the chemical composition, and especially upon the fat content of milk, are considered in the following para- eraphis. 1. Breed peculiarities. (‘ows of different breeds give milk of somewhat different composition. In gen- eral, it is believed that breeds from the highlands and 28 MILK HYGIENE mountainous regions give a richer milk, while breeds from the lowlands yield milk poorer in fat. There are, it is true, exceptions to this rule, e.g., the Allgauer and the brown Swiss cattle give rather a poor milk, while the Devons and the Normandy cattle give milk rich in fat. As an example of breeds that give milk especially rich in fat we may mention the Jerseys and the Guern- seys, whose milk contains an average of 4.5 per cent. to 5.5 per cent. fat, also the Harz cattle, whose milk is reported to contain an average of 5.8 per cent. fat. On the other hand, milk of the Swiss cows has only 3.0 per cent. fat, that of the Angler and Breitenburger and other breeds only about 3.13 per cent. to 3.15 per cent. fat. The average of the Danish breeds can hardly be placed higher, being about 3.2 per cent. to 3.4 per cent. fat. 2. Individual peculiarities. The figures given above are averages only. The milk of different individuals varies more or less so that in the same breed there are individuals that give milk rich in fat, and also those whose milk has a percentage of fat below the average of the breed in question. The production of rich milk is, therefore, a distinctly individual property that is due to the physiological peculiarities of the gland cells of the animal, and which appears, to a great degree, to be hereditary. Among cows of the same breed may be found some whose milk contains 4.0 per cent. or more of fat and, on the other hand, there are many that give milk containing only about 2.5 per cent. fat; indeed, not infre- quently the percentage of fat is still lower, and from Germany there are records of cows that give milk con- taining not more than 1.5 per cent. of fat. Such cows are frequently and in large numbers excluded from the best herds, so when herds are made up of purchased cows, the mixed milk from such cattle often contains but VARIATIONS IN COW’S MILK 29 little fat and may not exceed 2.25 per cent. to 2.75 per cent.* Wlule it is searcely possible, as will be discussed later, to influence the composition of milk materially or permanently by alterations in the quantity and com- position of the food, still it may not be entirely impossi- ble to influence the young animal by skilful or by appropriate feeding in such a way as to encourage it later to produce milk rich in fat. But thoroughly reliable data on this point are not available. 3. The age of the cow. Although the quantity of milk varies according to the age of the cow, so that it is usually greatest during the third to the fifth lactation periods, the chemical composition appears to remain almost unchanged from year to year (Hittcher) ; yet it is apparent that fats as well as other ingredients decrease with great age. +. The stage of the lactation period. The colostrum secretion is not especially important. The true milk secretion very quickly attains a considerable volume, but falls off gradually after a longer or shorter time. until the secretion ceases altogether or is insignificant. to- wards the end of the period of gestation. Some cows, however, continue to milk very well up to calving and to the new period of lactation. It was emphasized above that colostrum differs essentially, both morpho- logically and chemically, from normal milk. Further- more, the composition of milk during the first part of tlie lactation period differs from that secreted toward the close. a. Colostrum. The first colostrum is whitish, vellow- ish, or even reddish to brownish; it is slimy and has a *It should be borne in mind that the cattle here referred to are of heavy milking lowland breeds not represented in America. [ly P.] 30 MILK HYGIENE specific gravity of 1.040 to 1.080. Its microscopic ap- pearance has been described before and, in part, its chemical composition. Gradually, the appearance and the composition of the secretion changes until, in the course of about a week, it becomes pure milk. This gradual development is illustrated by the following analysis given by Eugling: Number of hours after calving. Normal ilk. are 10 | 24 | 48 | 72 E Water sac cos wainaarenaen (one 78.77 80.63 85.81 86.64 87.75 CASEIN idcaisan. oeandoanes 2.65 4.28 4.50 3.25 3.33 3.00 Albumin , a 9 sox » 2 5 Giobulin fete 16.56 9.32 6.25 2.31 1.03 0.50 Extractives ........... 3.54 4.66 4.75 4.21 4.08 3.40 SUGAT fits, Scien ane cnn as 3.00 142 2.85 3.46 4.10 4.60 NGM ac pace tsenea hvedeuastieanens 1.18 1.55 1.02 0.96 O82 0.75 These figures show that the chief difference in the composition of milk and colostrum consists in the greater albumin and globulin content of the latter, which arises partly from the presence of numerous colos- trum bodies, in consequence of the presence of which colostrum coagulates when heated. Another important difference is the low sugar content o/ colostrum; accord- ing to Tereg the sugar of colostrum is not lactose, but is grape sugar, or perhaps a mixture of this and galactose. Of the substances that are extracted with the fat, about 13.8 per cent. consists of cholesterin and 8.0 per cent. of lecithin. Among other peculiarities shown by colostrum of the cow may be mentioned its acid reaction and the fact that after the addition of rennet it does not coagulate at all, or only very slowly. b. Wilk. Shortly after calving, while the secretion VARTATIONS IN COW'S ATILE ol is abundant, the milk is generally a little less rich in solids and especially in fat than it is later when the secretion begins to fall off; with some cows the differ- ence is not very great, but with others it is considerable. In the last month the secretion falls off rapidly and often ceases entirely; at the same time the proportion of solids usually increases and this is especially the case in relation to fat. The milk gradually acquires a decided alkaline reaction to litmus paper and not infrequently develops a salty taste. The changes in composition are shown in the following table, which gives the results of analyses, made by Fleischmann, of the inilk of one cow which calved January 28th. With this cow, the percentage of fat during the period of lactation rose from 3.055 to 8.500; but this significant increase occurred almost entirely in the last month when the cow had become an old milker. At the sane tine the quantity of albumin, lactose and salt (i.e., solids not fat) increased only from 8.14 per cent. to 9.00 per cent. The chemical composition of milk of some cows does not change noticeably during the whole period of Tac- tation, and the percentage of fat as well as the other solids may even fall off a little at the end of the lactation period. Fleischmann gives a table showing analyses of the milk of such a cow for the whole lactation period: the daily quantity of milk in April was 19.8+ kg., on the 31st of January following it was 3.6 kg. The fat per- centage, which had varied between 2.56 and 2.97, fell in January to 242. 2.60, 2.32, and 2.48 upon different analyses. The percentage of solids not fat also fella little. 5. The time and method of milking. It is commonly believed that there is always a slight difference between the chemical composition of the morning and the even- 32 MILK HYGIENE ing milk in that the latter is richer in fat than the for- mer. Numerous investigations have given very varia- ble results that may be explained by the short duration of the test, by the daily variations of the composition of the milk, ete. Some larger experiments relating to LACTATION PERIOD Daily - Solids Fat content quantity Specific Fat. not fat. of the total of a gravity. Per cent. Per cent. oo April sey seus eaes sewer 11.55 1.0291 3.033 8.140 27.15 May sendin oon accu deans 11.95 1.0290 3.264 8.166 28.56 JUTO? ais 5 tS doe as Bloor 10.45 1.0287 3.405 8.113 29.56 DUS die daducn aaaeD aes 8.82 1.0283 3.458 8.027 30.11 AU BUS te esicesttcess sees x cana 9.66 1.0287 3.586 8.149 30.57 September. .......... 9.07 1.0289 3.650 8.230 30.72 October see wesvae dates 7.67 1.0292 3.434 8.247 29.39 November ............ 6.63 1.0299 3.823 8.501 31.01 December............. 5.11 1.0300 4.267 8.616 33.11 JaANMaRy sss cides alee 3.0 1.0302 5.050 8.823 36.40 VANUALY Bie2sa2ce danas 2.7 1.0300 5.400 8.843 37.91 January 4............ 2.8 1.0299 4.720 8.680 35.22 January 6............ ' 2.3 1.0307 5.470 * 9.032 37.71 January “Tessayeea sand 2.4 1.0299 5.440 8.824 38.14 PaNUary Byzcercesesvs 2.3 1.0304 5.250 8.911 37.07 Jantiary Se ves evaceys 2.3 1.0310 5.200 9.054 36.48 VRNUELY TWO. yacwenews 21 1.0308 5.090 8.980 36.17 January 11............ 22 1.0308 5.100 8.982 36.22 January 1l4............ | 1.9 1.0277 6.900 8.565 44.60 January [sca cwswrge 1.3 1.0301 8.300 9.446 46.77 January 18............ 14 1.0288 7.480 8.958 45.50 many animals and extending over a long period, have proven that the morning milk does not differ from the evening milk in fat content when the period between the milkings is equally great and the feed, the amount of drinking water taken, etc., are the same. But in prac- tice this is not the case, because usually a small dif- ference exists, so that where there is a larger quantity VARIATIONS IN COW’S MILK 33 of milk there is a smaller percentage of fat. Fleisch- inann found hy continuous investigations of one herd of 120 to 130 cows during one year, that on the average for the whole year the morning milk contained a little more fat than the evening milk (3.260 per cent. against 3.183 per cent.), while the quantity of morning milk was a little less than that of the evening milk (4.143 kg. against 4.616 kg.). There is a slight difference dependent upon the sea- sons; it has been shown that in the summer the morning nulk contains a slight excess of fat while in the winter the evening milk is the richer. It follows that since the quality of milk is influenced hy external influences, there can be no general rule to define the difference between morning and evening milk but, usually, if no other con- ditions arise, this difference is comparatively small. It is commonly believed that three milkings a day cause not only the production of a greater quantity of inilk, but also a somewhat greater percentage of fat, but it can scarcely be said that there is definite proof of an increase in the percentage of fat. If the milking is done by a strange or inexperienced person, the flow is diminished. This also influences the quality of the milk. The first and the last milk drawn differ greatly in fat content. It is supposed that the fat globules adhere firmly to the walls of the duets, as a layer of cream, and are freed from these only with dif- fieulty. The following figures show the results of analyses by de Vriezes, who found in the first streams 12 per cent. fat; after drawing about one-quarter the quantity of milk, 2.1 per vent. fat; after drawing about one-half the quantity of milk, 3.6 per cent. fat; after drawing about three-quarters the quantity of milk, 5.2 per cent. fat; in the last milk. 7.1 per cent. fat; in the very last drops of milk drawn, 10.0 per cent. fat. 3 34 MILK HYGIENE Therefore, by milking a single cow, one can obtain milk of the greatest variety of fat content, which must be considered when samples are taken from individual animals for the purpose of examination. According to Hittcher’s investigations, the situation seems, singularly enough, to be wholly changed if the calf is permitted to suck the cow; the milk that remains is not rich, but is much poorer in fat. Fats. Percent. Solids not fat. Per cent. Number of the cow. Minimum. Maximum. Minimum. Maximum. 1 2.621 4.698 7.859 8.771 2 2.160 3.404 7.293 8.707 4 2.163 3.965 7.702 8.743 5 2.543 3.900 7.636 8.577 6 2.096 3.446 7.753 8.893 7 2.257 3.837 7.974 8.914 8 2.690 4.117 7.943 8.897 9 2.566 4.709 8.197 10.050 10 2.464 6.000 7.728 8.939 i 2.741 4.649 8.305 9.371 12 2.509 5.505 8.582 9.550 13 2.645 4.724 8.389 9.623 14 2.097 4.173 8.394 9.131 15 2.437 4.234 8.031 9.046 16 2.326 4.637 8.040 9.363 18 2.537 4.390 8.098 9.170 The opinion expressed in recent years, that by a special method of milking the average fat percent- age of milk of mdividual cows may be raised, is in- correct. 6. Daily variations. Daily examinations of milk of individual cows show that not only the quantity of milk undergoes change from day to day, but, at the same VARIATIONS IN COMMS ALLE 30 tine, strange to say, the chemical composition of the milk is subjected to daily variations that may reach considerable extent. Knowledge of this is naturally of the greatest importance in the detection of milk adul- teration. The table on page 34 is given by Fleischmann to show the minimum and maximum fat percentages in the milk of a series of cows examined daily during an entire period of lactation. As is shown, the percentages of fat differ consider- ably even in milk from the same cow; one cow, number 12 in the table, produced milk differing in fat content as much as 100 per cent., that is, from 2.509 to 5.505 per cent. Cow No. I. | Cow No. V. , Cow No. VIL. Cow No. VITE. 3.214 3.040 2.566 | 3.591 2.869 2.825 is dated 3.592 28nd 3 3ve 3.080 | 3.244 2.862 ors 3.314 2.932 nate 3.043 2 gee 2790 3.24 3.790 2.329 3.047 3.070 2.996 2.308 Aen 2.847 3.369 2.616 2.816 3.685 3.272 3.334 3.199 3.749 3.189 3.381 3.732 4.031 3.267 3.402 3.620 3.927 3.068 3.316 3.522 3.792 5.795 3.344 | 3.492 3.844 3.470 2.970 | 3.633 The variations are not always gradual, but occur spasmodieally, as is evident from the figures above, taken from Fleischmann’s work on milk. The numbers in the perpendicular columns give the percentage of fat for successive days; the figures above the dividing line date from the beginning of the lactation period of the cows, while below the line the figures given refer to 36 MILK HYGIENE the end of the milking period. The examples are chosen in order to make plain the daily variations with the individual animals. One inay find even greater variations by examining the morning and evening milk. As examples, some re- sults are given from the daily examinations of milk from the above mentioned cows number I and number V, the figures referring alternately to the morning and _ the evening milk on successive days: Cow No. 1. Cow No, V. MOMiitiids 26sec atanmee diane neas Yeon. 3.180 Byening sc os cinkox take vemragine xara eO40 2.940 MoTning naccess je aians oma Sema. a enaied 3.240 2.710 MGNIN Gis, tia Galcnae siege auane ola eee tale 3.995 2.900 Mornings ecavey scan cx gris eels ieee ba 8ee 2750 VGHING: 25 eae cede ane ae dees Sede ae 3.700 MOnmings: fcc staunaeeaies sens eeeeco B00 — VCNING, «acc -oecapentaes Vacs ails 3.250 MOP.» 2cacus ied Seon aod 4.100 2.360 INVORIN GS 5 nay vein soagine chan anaes 3.815 3.560 Morning: .jechsnag eaas seeewers eee o4 oe 4.145 4.530 EVCNING 55.9: 444-8 25954 ¢4vudusee ges 6 3.485 3.180 MGTMIN OS 5 coe cent x Se Yad guisgatpeles Vi due 4g 4.085 3.220 VINOMINGY 22s: cede Reale Me Ae aa eAR nents 2.785 2.800 MORNIN Givns weagae eoteee heme aee eRe 3.690 JENETIN Gs cs daaces a Poe cutee gaccentass 3.590 3.100 The changes in the quantity of solids not fat (protein, lactose and salts), as is apparent from the above tables, are much less than those of the fat, and especially do lactose and salts vary but little. The reasons for these dail) variations in the quan- titative composition of milk are not yet wholly under- stood, but are to be sought in everything that in any way has an unfavorable influence on the animal; changes of food (see below) or of the times of feeding and drink- ing, changing to a strange place, restlessness in the sta- ble, storms, cestrum, changes at milking, ete. Very often no definite reason can be discovered and it appears that VARIATIONS IN-COW'S AIDE 37 such variations may take place without external causes. With cows that have suckled their calves, after separa- tion from the calf, there is usually a very noticeable de- crease of fat in the milk, which is sometimes made good by a subsequent considerable temporary increase. 7. The influence of food. It is an old and, in some places, still commonly accepted opinion that the compo- sition and the quantity of the food have an important influence on the composition of the milk and more espe- cially on its fat content. Paln and cocoanut meal and several other food stuffs, are said to cneourage the pro- duction of rich milk, while, on the other hand, distillery slops, for example, are said to cause the production of poor milk. During recent years, numerous investiga- tions undertaken abroad as well as in the experimental laboratory in Copenhagen, seem to have proven that it is not possible by changes of food to bring about a noticeable permanent effect upon the composition of the milk. The activity of the udder cells, as is shown from the daily variation in the composition of milk, is easily thrown out of equilibrium, but such a condition is only temporary. With changes of feeding, this condition appears quite plainly, nearly every change very quickly causing a variation in the composition of the milk, especially the fat percentage, so that sometimes this rises, sometimes, ¢.g., When distillery slops and simi- lar moist foods are fed, it falls off more or less. But this variation always seems to be merely temporary : in the course of a day or so, sometimes, however, not until the end of a couple of weeks, the average percentage returns. This is the case even when food of only one kind, as distillery slop and, indeed, when food especially rich in fat, is fed; in these eases, also, the change in percentage will be only temporary (Henriques and C. TIansen). 38 MILK HYGIENE To be sure, there are many reports in print of other results, but upon examination these are found to extend over so short a period that the temporary changes had not yet disappeared, or they refer to inves- tigations with different cows whose milk was not suf- ficiently examined, or to cows that did not receive the same food in the beginning of the experiment, or, finally, sufficient allowance was not made for the daily varia- tions and for those that occur at different stages of the lactation period. The temporary changes in the composition of milk which occur after a change in the food, may be consid- erable, but here, too, the question of individual peculiari- ties enters, so that the changes shown by two cows under the same conditions may differ materially. It is of an old belief, that the change from dry food to green causes an increase in the fat content of the milk. The investigations in the Danish experimental labora- tory have proven this; they show that the fat percent- age under these conditions may increase 0.5 per cent., with some cows it increased even 1.0 per cent., but this increase lasted only a few weeks. Also, when changing the ration to include some of the oil cakes, a similar increase in the percentage of fat has been observed, but seldom more than about 0.5 per cent. On the other hand, as stated before, there are observations of tem- porary falling of the fat from 0.25 per cent. to 0.5 per cent. when a change of food is made to distillery slops or similar rations. It is, then, possible to show that the udder reacts rather characteristically to certain changes in the ration and especially to some food stuffs; but this reaction is lost when the cow has become accustomed to the new food. Under such conditions, simultaneously with the increase of the fat percentage there frequently occurs a VARIATIONS EN COW'S MILK 39 decrease in the quantity of milk, while, on the other hand, a lessening of the percentage of fat is often accom- panied hy an increase in the volume of the milk. Although recent experiments have thrown much light upon the influence of food on the milk secretion, yet there is need for further information on many points. For instance, it is not known with certainty if it is pos- sible hy long continued, particularly unfavorable, one- sided composition of food, to produce lasting changes in the fat content of milk and in the solids not fat. Lactose occurs in milk in but one form and the char- acter of proteids is not affected by the nature of the foods. On the other hand, the milk fats vary, sometimes there is more and sometimes less olein, which affects the consistency of the butterfat, and the percentages of vola- tile fatty acids may vary considerably. It has often been said that the fats taken with the food do not pass un- changed into the milk. Only when a great quantity of food, rich in a kind of fat that can be distinguished chemically, is fed, is if possible to find small quantities of that fat in the butterfat of the milk. But little is known positively concerning the causes of the variations in the cemposition of the butter- fat and especially eoneerning the influence of the food upon it. The milk fat may originate in the fatty tissue of the animal, from the fat stuffs taken with the food and, apparently, also, direetly from the carbohydrates consumed. There are a number of other conditions, as the composition of the ration, excessive feeding with fatty foods, starvation, ete., that have some in- fluence in this direction but, as they are of no sanitary importance, it is unnecessary to discuss them here in detail. It is generally believed that odors and tastes pass from the food that is consumed into the milk. The 40 MILK HYGIENE milk of the Alpine cows is noted for its aromatic taste. Feeding with beet leaves, turnips, malt sprouts, ete., is supposed to be the cause of the taste and odor of beets or a burnt taste and odor in the milk. We do not yet know how much influence is to be attributed to the food. In some cases, the offensive odor and taste is undoubtedly due to the activity of bacteria in the milk— indeed, it is doubtful if the ‘‘ beet taste ’’ and the ‘‘ burnt taste ’’ ever come from the food (see below). Peculiari- ties of breed may possibly be the cause of the aro- matic milk of the Alpine cows. On the whole, it is highly probable that the food has some influence on the taste and odor of the milk [this is unquestionable in the ease of garlic,] bat by no means all of the substances in milk that have special odors and tastes are secreted with the milk, The ash ingredients of milk are not generally influ- enced to a great extent by the amount of salts taken with the food; even a considerable iron or phosphorie acid content of the food causes no direct increase of these materials in the milk; still, certain sulphates, as Glauber’s salt, given in large quantities are excreted in small quantity with the milk, and consequently cause an increase in sulphuric acid in the ash. While it is true that feeding influences the compo- sition of milk only to a slight degree, it is nevertheless true that the quantity of milk is dependent to a very great degree on the amount and composition of the food. 8. The significance of sexual conditions. The occur- rence of cestrum and pathological conditions of the generative organs cause a decrease in the milk secre- tion; therefore it has been assumed that these conditions may also cause changes in the chemical composition of the secretion, yet this does not always appear to be the case. VARIATIONS IN COW'S ALEK 41 a. Hstrian has a very different effect on the milk secretion of individual cows. Kiihn found no effect, but von Kleuze found such a great albumin content that the milk could not he boiled, and Schaffer established a remarkably high fat content. On the other hand, Fleisch- mann found only 0.714 per cent. fat in the evening milk of a cow that had come in heat in the course of the day, though the morning milk contained 3.56 per cent. fat. On the whole, it may be said that normal cestrum often induces a passing disturbance of the normal secretory activity of the udder, b. Nymphomania, which has no slight influence on the nature of the meat, and reduces the milk secretion considerably, probably influences the nature of the milk also. Only a single analysis of such milk is given by Schaffer; the quantity of fat and lactose had not changed, but the quantity of protein was remarkably high, namely, 5.72 per cent. ce. Ovariotomy. Asis known, it is frequently claimed that spaying performed on healthy cows during the first months of the lactation period eauses a considerable lengthening of this period, an inercased daily sceretion, and greater fat content of the milk. Tlowever, it ean hardly be said that this is sufficiently established; and especially, it is not to be considered as proven that ovariotomy is able to raise the fat content; in faet it is most Hmprobable. Ovariotomy performed on uympho- maniac cows causes, among other things, the possibly abnormal milk secretion to return again to normal. d. wfbortion, The experiments that were conducted by Schaffer and Hess have shown that abortion, which has such great influence on the quantity of milk, has no influence on its composition. The same statement ap- plies to the retention of the afterbirth, in so far as this causes no general illness. 42 MILK HYGIENE 9. Exercise and work. According to a number of different experiments at hand (Dolgich, Torssell, and several others) daily exercise increases milk secretion so that not only the amount of milk increases, but also the total quantity of fats. Sometimes, indeed, the per- centage of fat increases, and, as a rule, the percentage of casein diminishes, while the other constituents are affected irregularly. Work does not necessarily influence the milk secre- tion to a great degree (Morgen), but generally causes a slight diminution in quantity and there is an increase in the percentage of fat and a proportionate but smaller increase in the percentage of protein and ash. HExhaust- ing work causes not only a material decrease in the quantity of milk, but also a disturbance in the whole secretion, so that even vegetable fats are excreted in the milk in unchanged condition (Dolgich). 10. Disease of the cow often brings about a decrease and sometimes even an entire cessation of the milk secretion. In diseases of the udder, the milk under- goes, as will be seen later, very important chemical changes. There is very little positive knowledge of the changes in the composition of milk during diseases that are not localized in the udder. Apparently, it is usually the rule that the daily variations in the composi- tion increase, or, in other words, that the secretion is thrown out of equilibrium. Frequently, in the beginning of disease, there is found an abnormally large pecentage of fat that results from the often sudden decrease of the quantity of the secretion. A salty taste which occurs not infrequently, might possibly mean an inerease in the quantity of protein and ash (secretion of blood serum). According to long-standing opinion, milk has an abnor- mal taste in cases of indigestion of all sorts and under these conditions it also curdles easily. VARIATIONS IN COWS ATILK 43 11. Medicines. It is an old opinion that a number of different medicines help to increase the milk secre- tion and the fat content of milk, and for this reason, so- called ‘‘ milk powders ’’ are still used. The different materials (fennel, anise, caraway, calamus, bitters, sul- phur, antimony compounds, ete.) cannot change the secretion of normal animals, and it ix doubtful if they are able to recall the milk secretion after it has been checked through disease. Other medicines as quinine, belladonna and alu, are supposed to he able to check the secretion as, also, rub- bing the udder with opodeldoc, oil of rosemary and the hike; but their action is questionable. Drugs like iodine and phosphorus, that act especially on gland tissue, are able to check the secretion or cause it to stop alto- gether. The excretion of medicines in the milk will be considered later. Summary. Irom the above, it is evident that the gland cells of the udder of cach cow are adjusted to secrete milk of a rather definite chemical composition which, however, changes during the lactation period, but that these cells react to a number of different influences as a result of which they may temporarily secrete milk of a somewhat changed composition. As would be expected, the limits for the variations in the composition of cow's milk are reported differ- ently, but milk of a composition that is not included in the limits below is indeed very rare. Water Casein Albumin Fat Lactose Ash SS—she PHS ONO PA—ATHs 4-586 0.35—1.21% It appears that the fat content is subject to great variations; but, if we leave out of consideration old milking vows, these variations are much less. The quantity in milk of solids not fat (casein, albumin, lac- 44 MILK HYGIENE tose and salts) is far less variable. This applies espe- cially to lactose, which seldom shows the given mini- mum and maximum percentage. In the detection of adulterations, the percentage of lactose furnishes, there- fore, a better guide than the percentage of fat. By mixing the milk of the members of a herd, the individual variations in composition are more or less equalized, so the composition of the whole quantity approaches the average for cow’s milk. There are, however, some herds in the milk of which the percent- age of fat is much higher than in others; this is a inatter of selection or of breed, so, of course, the composition of milk of separate herds will not be the same. As cows usually calve at certain seasons the number of fresh cows and old milkers is not the same at all seasons and, for this reason, the composition of the milk changes. We have the following figures showing the average per- centage of fat as found upon daily analyses of milk from three large herds. February May August November a. 3.18 ace 3.61 BAT b. 3.69 3.56 3.64 BT G 3.03 3.38 8.51 3.32 In herds a and c¢, particularly, calving is distributed unevenly, which causes the percentage of fat to be 0.5 per cent. lower in winter than in summer. Many of the external influences that have been men- tioned as applying to the individual animal and that result in a temporary change in the composition of the milk, may apply, at the same time, to all of the animals in a herd and thereby influence the fat content of the herd milk. This is seen when there is a change of food, disturbance in the stable, storms, extreme heat and so on. However, variations in the composition of the entire quantity of milk caused in such ways are, in most cases, CHANGES IN THE SECRETION 45 less than those of single animals, for all members of the herd are not affected in the same degree and quite often the animals react in opposite ways under the same circumstances so that these variations are, in part, equal- ized after the milk has been mixed together. The larger the herd, the smaller the probability of all its members hemg influenced in the same way at the same time— and, therefore, the variations from the normal will be so much less. For the same reason, the variations are considerably less when the milk of several, but always the same, herds, is mixed. So far as we know, there are no data in Denmark concerning the limits of the composition of normal mar- ket milk, and these are not sufficiently established in other places—yet it may be assumed that the specific gravity does not vary beyoud 1.029 to 1.034, the content of solids not fat does not exceed 8.6 to 8.8 per cent., and the fat varies from 2.75 to 3.5 per cent? ” V. CHANGES IN THE SECRETION DURING DISEASES OF THE UDDER Diseases of the udder that cause material changes in the character and the composition of the udder secretion are: udder contusion, udder cedema, embolism and thrombosis, mastitis, udder tuberculosis, udder actino- mycosis and tumors. 1. Contusions of the udder and the teats which fre- quently are caused by cuffing and blows and hy kicking and tramping by other cows, éte., produce hemorrhage of the udder tissues, bloody serous infiltration, or, possibly, death of the udder tissue. The changes in ‘Jersey herds, ete., not included. “The figures given above relate to Danish cattle, practically all of which are of two breeds which furnish milk containing a much Jower percentage of fat than is furnished by most of the herds producing market milk in Ameriea. [L. P.] 46 MILK HYGIENE the secretion consist, in part, of an admixture of blood plasma that is usually invisible and, in part, of blood. The latter may appear in freshly drawn milk as drops of blood or as little clots. When more bleeding occurs, the milk is liable to be diffusely colored reddish and it will color the milk from the other quarters, and even colors the milk of other cows reddish when mixed with it. This admixture of blood cannot be proven by the common guaiae method, for fresh milk will give the same reaction. The proof is most easily gained by means of microscopic examination of the sediment obtained by centrifuging the milk, whereupon the red blood corpuscles are easily recognized among the milk globules. 2. Udder edema. It may be supposed that in udder cedema, which frequently is very severe soon after calv- ing, there is an admixture of transudate with the secre-- tion, but, so far as known, no investigations have been made in regard to this matter. 3. Embolism and thrombosis occur occasionally in the udder and cause gangrene of a gland or of a part of one; frequently there is gangrene of the skin and of the teat of the quarter affected. Milk secretion ceases and in its place there is a bloody serous exudate. 4. Mastitis. Inflammations of the udder cause quite characteristic changes in the secretion, which often stops entirely to give place to a purulent exudate. a. Mucous catarrh. When drawn, the milk contains small yellowish flakes and lumps which, upon standing, unite into a slimy, dirty, grayish sediment or, together with the cream, form a lumpy, dirty colored layer on the top of the milk. In severe attacks the secretion may be viscid, slimy and sticky. b. Purulent catarrh. In the beginning, the secretion is unchanged but for the presence of small flakes of pus CHANGES IN THE SECRETION 47 and fibrin. The milk secretion decreases more or less quickly while the pus cells and fibrin increase in number and, finally, the secretion is replaced by a viscid, whitish or yellowish purulent exudate or by a quantity of yel- lowish serous exudate which contains clumps of pus and fibrin. In many cases, the udder shrinks and the exuda- tion ceases without the return of the milk secretion; in other cases, milk secretion returns either during the same period of lactation or after the birth of the next ealf. In catarrh of the udder, lactese decreases in quan- tity while the other ingredients—except asl—undergo no quantitative change in the mildest cases. Among the ash ingredients, phosphoric acid, lime, magnesia and potash decrease materially in quantity, while sodium chloride occurs in more than normal quantity. In cases when the secretion is mixed largely with exudate, the quantity of lactose still further decreases and the casein content drops, while albumin and globulin (also fibrin) increase. e. Parenchymatous mastitis. The changes in the secretion correspond essentially with the changes in purulent catarrh, but they occur very suddenly and may disappear as rapidly. The chemical analysis shows changes similar to those in eatarrh; the lactose often dis- appears entirely, while the albumin and globulin in- crease greatly in quantity. The fats may increase or decrease, the salts change as in eatarrh. d. Gangrenous mastitis. The real milk secretion ceases while a bloody-serous liquid is secreted which, on account of the existence of bacteria of putrefaction, is frequently mixed with gas and has the odor of putre- faction. The chemical changes that take place in mastitis are mainly traced to partial or entire cessation of the real milk secretion and to a simultaneous elimination of 48 MILK HYGIENE an exudate having a greater or less admixture of pus cells. e. Udder tuberculosis. In many cases, the secretion remains almost imperceptibly changed for a long period, as only very small flakes are intermixed with it. Later on, it decreases in quantity, grows thinner and contains more flakes, and, finally, it is yellowish or reddish, se- rous, contains clumps and flakes and becomes more like pus. Chemically, the milk gradually undergoes the same change as in cases of other forms of mastitis (Storch). f. Actinomycosis and tumors of the udder no doubt cause changes in the appearance and the composition of the secretion, but no investigations have been made on these subjects. In mastitis, tuberculosis and actinomycosis of the udder pathogenic bacteria are found in the milk; these will be discussed later. VI EXCRETION OF FOREIGN MATTER WITH THE MILK The milk glands may serve to excrete foreign mat- ter which, in some way, has found entrance into the organ, just as the kidneys and other glands do. Such an excretion does not take place to as great an extent as was formerly believed, which, considered from a biologi- cal standpoint, seems most natural, for the excretion of foreign matter would prove a great danger to the young animal dependent on its mother’s milk for food. Yet there are not a few, and sometimes very harmful, sub- stances that are excreted from the organism through the udder and, therefore, it is one of the problems of milk hygiene to prevent the milk of such cows as are affected in this way, from being used, just as the physician must always consider, in the treatment of mothers and wet nurses, what influence medicines to be given may have on the nursing child. EXCRETION OF FOREIGN MATTER = 49 Reports differ as to what foreign substances are excreted with the milk. These differences of opinion may be accounted for in part by the fact that many sub- stances are not excreted in noticeable quantity until the animal has taken relatively large amounts of them. Sometimes individual peculiarities operate, for it may be that some inflammation not entirely healed, local induration or similar changes in the tissues of the udder, in short, the injuries that remain after mammitis, favor such an excretion. It has been mentioned before that the milk contains only traces of iron, and this fact alone is a proof that iron compounds are not usually excreted with the milk; even after the consumption of a great quantity of iron during a long time, the iron content does not rise. ('on- cerning other metals, compounds of copper, lead and antimony? are exereted only in very small «uantity, so that even a prolonged adininstration of these substances to mileh cows usually brings about no harmful effects. According to investigations by Baum and Neeliger, the lead content of milk does not increase beyond 0.0009 to 0.002 per cent., even after treating cows with large doses, and this quantity is without importance, even to quite small children. On the other hand, mereury is easily excreted through the udder, when this substance is taken through the digestive organs or when absorbed after applications to the skin. JTodine and arsenie also easily enter the milk in considerable quantity. Opinions differ concerning alkaloids. It is a facet, however, that morphine, strychnine, atropine and vera- trin are, under certain circumstances, excreted with the 77n the older literature, there are recorded a number of observa- tions which indicate that tartar emetie may be exereted with the milk in large quantity 4 50 MILK HYGIENE milk in such large quantities as to be dangerous to chil- dren. Other substances which can easily be excreted with milk are salicylic acid, earbolic acid, aloes, croton oil and senna, also the active principles of colchicum, hyoseyamus and euphorbium. This is also supposed to be the case with mustard; still there is good reason to believe that it is true only if mustard is taken with the food in large quantities. It has often been observed that diarrhea occurs in people who have used the milk of cows fed upon food that is moulded, or that has undergone putrefactive fermentation. It is presumed, therefore, that some of the substances which are formed under these conditions in the food materials of the cow may be excreted with the milk. But it is possible that in such cases there is contamination of the milk from the food during milking and so, in this way, bacterial changes may occur; these have not been entirely excluded. It was stated above that aromatic substances in for- age plants are apparently excreted in slight quantity and may give a ‘‘taste’’ to the milk. [The garlicky taste that is so common in milk in the Spring in the Hastern United States is due to garlic in the pastures.] We find, too, that strongly smelling medicines (asafctida, ether, certain volatile oils, but not all) that are given to the cows may impart a taste to the milk. It is highly probable that toxic substances which are formed in the organism during disease, and also such substances that, for example, are reabsorbed from the uterus, may sometimes be excreted in the milk, but there is no definite information on this subject. On the other hand, we know that antitoxins are in part eliminated from the blood of the mother animal through the udder and, through this channel, they may be used by the young to its benefit. CHANGES IN MILK ol VII. CHANGES IN MILK CAUSED BY MICRO-ORGANISMS Milk found in the glandular passages and cisterns of the healthy udder is usually sterile. On the other hand, the ducts of the teats and, still more, the ends of the teats usually contain bacteria and, therefore, the milk when drawn is infected with them. This is more apt to he the case when the milk comes in contact with the hands of the milkers, or when it is poured into the not always sterile bucket, or when particles of dirt and dust from the udder or the skin of the cow, from the clothing of the milkers or from the air, drop into the milk. Before the milking is finished, a considerable number of different bacteria have been added to the milk and though, for a time, it has bactericidal properties, that is, It is able to kill bacteria or, at least, to prevent their growth, vet the number of bacteria does not diminish noticeably but, in the course of time, imereases enor- mously. Shortly after milking, thousands, even hun- dreds of thousands, of bacteria may be found in each cubic centimetre. In inflammatory processes, eatarrh, tuberculosis and ectinomycosis of the udder, infected wounds at the open- ing of the teat, ete., bacteria are more or less numerous in the milk before it is drawn. In benign udder inflam- mations bacteria disappear almost entirely with the cessation of the disease, but oceasionally it happens that the bacterial growth continues for a time in the milk contained in the glandular passages, after the seeretion has become apparently quite normal and after all signs of inflammation have disappeared. In general infections, not localized in the udder, as a rule no microbes are exereted with the milk. An excep- tion to this is foot-and-mouth disease (aphthous fever), in which the milk of the affected cows often contains vir- 02 MILK HYGIENE ulent material, the nature of which is not definitely established. During this disease, several noticeable changes occur in the milk and it is, therefore, very prob- able that pathological processes take place in the cells, of the gland and so an excretion of virus is only to be expected. In other acute diseases, as anthrax, hemor- rhages may occur in the tissues of the udder and the admixture of bacteria from the blood follows naturally. The changes in the milk caused by microbes, and par- ticularly by bacteria, which comprise by far the greatest number of micro-organisms of milk, are very numerous. These are most readily studied by working with sterile milk (the best way is to use milk which was taken from the udder in sterile condition, for milk undergoes quite essential changes when heated) and with pure cultures of bacteria. The most important changes are the following: a. The milk is unchanged in appearance, reaction, odor and taste in spite of bacterial growth. b. The bacteria form alkali (probably ammonia) ; the reaction grows more and more alkaline and when, after some time, a certain alkalinity is reached, the fat is saponified, the neutral casein-lime compound becomes a base and, as a result of this, the milk is changed to a yellowish translucent, whey-like liquid. c. The bacteria split up the lactose, forming acid. The main product of this division is lactic acid, some- times d-lactic acid, sometimes l-lactic acid, sometimes a mixture of both, i-lactic acid. The reaction may be ex- pressed by this formula: C,,.H,,0,,+H,0O—4(C,H,O,). In fact, however, this process is far more complicated for beside the lactic acids, a number of other com- pounds are formed in small quantity as by-products: alcohol, valerie acid, acetic acid, succinic acid, carbonic acid, ete. After a certain amount of free lactic acid has CHANGES IN MILK 53 been formed, coagulation of the casein occurs—at room temperature—which either is precipitated as flakes or thickens to a firm, jelly-like substance (curdling of milk) and frequently contains small gas bubbles. At a higher temperature, coagulation occurs in the presence of a smaller percentage of acid. If coagulation is caused by acid, alone, the process unquestionably is a simple separation of the casein-lime compound by which the casein, insoluble in water, is precipitated unchanged. When the casein is filtered out and treated with lime water, it dissolves readily. In heating sour milk to 70° C. and above, a real coagulation will occur, however, and the precipitated casein cannot be dissolved in lime water. After the formation of lactic acid has reached a cer- tain degree (about 0.8 per cent., which corresponds to an amount of acid in 100 c.c. of milk that requires for its neutralization about 100 ¢.c. of a one-tenth normal solu- tion of Na.Q), the activity of the bacteria ceases, for they cannot thrive in the strongly acid liquid, and the greater number of bacteria rather quickly perish. The different bacteria and yeast fungi which may be the cause of lactic acid fermentation, are not sensitive to the same degree of acidity, and under the influence of these various forms, the milk becomes sour irregularly. These various organisms are influenced very largely by exter- nal conditions, in respect to their ability to produce lactic acid, so that sometimes a longer and sometimes a shorter time is required to sour milk, while, in other cases, their ability to produce this change is almost lost. Of the micro-organisms which ean produce a lactic acid fermentation, are to be considered the lactic acid bacte- ria used in creameries (a group, the various species of which have not been definitely differentiated), certain yeast-like fungi (Saccharomyces lactis and Saccharo- myces acidi lactici) the Bacillus coli communis, strep- o¢ MILK HYGIENE tococci and the pyogenic staphylococci. Some of these, in addition to producing an acid, develop a ferment which has an action somewhat similar to that of rennet (see below). d. Bacteria may form a rennet-like ferment which causes the milk to form a coagulum of the consistency of jelly, without souring. The ferment, which can be iso- lated comparatively easily from many bacteria, has effect in the same manner and under similar conditions as chymosin. The precipitated casein cannot be dis- solved again by treatment with diluted lime water, and it may be assumed that the ferment has produced a change of the casein into paracasein, whose compound with lime is not soluble, as is well known. has collected some reports on this subject: of 210 typhoid patients not less than 45 (more than 20%) excreted bacilli with the urine, and Petruschky *° found that the number of bacilli in the urine exceeded 170,000,000 per ¢.c. It will be evident to every one who is familiar with existing conditions and customs, especially in the country, that under these circumstances no extreme or unusual carelessness or 25 Deutches med. Wochenscehr., 1890, p. 824. 26 Zentralbl. f. Bakteriologie, XXIII, 1898, No. 14. TYPHOID FEVER a accident is necessary to afford an indirect or direct means of carrying typhoid bacilli into the water or milk. The typhoid bacillus can multiply rapidly in milk and greatly increase in number in the course of a short time, it resists the commencement of acid formation but is partly checked and killed by great acidity; yet it is not certainly killed by the degree of scouring to which cream is subjected before churning. Bolley and Field have found that typhoid bacilli will live at least ten days in butter [and Bruck has shown that they were virulent after 27 days]. Hence, not only milk and cream but also buttermilk (epidemic in Hamburg; Frinkel and Ixoster), newly made butter and fresh cheese may be bearers of virulent typhoid bacilli. The typhoid bacillus is destroyed by pasteurization at 80° C. (176° F.) and heating for a few minutes at 70° to 75) C. (158) to 1677 F.) will kill it. Care must be taken to heat the whole volume of milk to this temperature. (See ‘* Pasteuri- zation.’’) In pure culture, the typhoid bacillus does not change the appearance of milk and alters its reaction but little. It is very difficult to detect it in milk, as it is in drinking water, for its colonies in gelatin are very similar to those of the colon bacilli. To detect it, the milk must be sown in the usual method in gelatin plates and then as great a number as possible of suspicious colonies iso- lated. These are then implanted in fermentation bulbs in bouillon, some of which contain grape sugar and some sugar of milk. Those forms which cause an acid reac- tion in the milk sugar bouillon or those which ferment the grape sugar with the formation of gas or which do not change the reaction of the grape sugar bouillon are to be rejected. Only those cultures which give a strong acid reaction without producing gas in the grape sugar bouillon, are really suspicious and these must be sub- 112 MILK HYGIENE jected to a far more searching examination before they can be identified as typhoid bacilli.27 It is unnecessary to pursue this subject further, since the demonstration of the typhoid bacillus in market milk is not, as yet, a prac- ticable procedure in milk inspection. Jensen’s investigations have shown that there are several kinds of typhoid bacilli, distinguished from each other by a somewhat different fermentative power. It appears to be possible that by means of cultures from different patients one may determine what cases of typhoid belong to one and the same epidemic. b. Diphtheria. Diphtheria not infrequently appears to be spread by milk from milk shops or by that deliv- ered from codperative dairies, but less frequently than typhoid fever. N. Flindt ** has given a detailed account of such an epidemic in the neighborhood of Holbeak in which the disease was being spread for a long time by milk from a cooperative dairy. He states: The epidemic occurred in June, 1889, and soon became violent. Fifty-one per- sons were sick at the end of the month, 16 cases occurred the following month and in August and September 6 more; 3 patients died. Everything tended to prove that milk delivered from the codperative dairy had contained the contagion and this belief was strengthened by the fact that two persons from the dairy were affected. The exact mode of entrance of the infectious material into the milk was not traced. The case is remarkable in that the milk appears to have been contaminated for quite a long period. **C. O. Jensen: On Vanskelighederne ved Typhusbacillens Diag- nose og om Racer af Typhusbacillen. (On the Difficulties of Diag- nosing Typhoid bacilli and on the Races of Typhoid bacilli) Hospitalstidende, 1901, p. 1193. *8 Ugeskrift for Laeger, 1890, p. 405. DIPHTHERIA 113 A large epidemic of diphtheria 2? which broke out among the inhabitants of the villages along the coast north of Copenhagen, in 1881, offered conditions of prop- agation which strongly signified that milk was the means of spreading the contagion. In 1893 a small epidemic was noted in Lund, Sweden, when eight persons in different families were sick with diphtheria. These cases were traced to the use of milk from a farm near Lund which was infected with diph- theria.*° Quite an extended epidemic occurred in 1886 in Frim- ley, Mngland; in the course of a few days 70 cases of diphtheria occurred, distributed in more than 30 fam- ilies, 15 eases being fatal. All the sick had received milk from the same dairy. Not one case of diphtheria oc- eurred during this time among those using milk from other dairies."! [The medical literature of recent years contains many reports of milk-borne outbreaks of diphtheria, a number of which are gathered and summarized by Swithinbank and Newman."* The following case, cited in their summary, is instructive. At Ashtabula, Olno., 100 persons became affeeted with diphtheria in Decem- ber, 1894. The houses in which the disease occurred were widely separated but milk was taken at all of them from the same dairyman. On the farm of this dairyman, a workman had a very sore throat, probably diphthe- ritie. This person had assisted in the work of the dairy while suffering acutely from sore throat. Of 44 house- holds investigated, it was found that 32 had received 2" Veeskrift: for Lacger, SSL. 29 Thospitalstidende, 1805. "Ret. in Milehzeitung, 1886, p. S35, = Bacteriology of Milk. s 114 MILK HYGIENE milk directly from this sick person; the other 12 had received milk from the same dairy but it had been deliv- ered by another man. In this outbreak there were 24 deaths. L.P.] . Toa certain dlegrec, pasteurization may conceal a tainted condition which exists before heating. Quite an abundance of bacteria of putrefaction and other bacteria may be present, or the lactie acid fermentation may have hegun to take place; these bacteria are killed by pas- teurization, consequently the fermentations and changes that were under way are interrupted. Under such cir- cumstances, one cannot tell by the appearance or taste of milk that it is damaged and that it contains the products of decomposition of the albumen, or, possibly, even toxic substances. On the whole, there is no way, at the present time, of determining whether or not pas- teurized milk was damaged hefore it was heated, while, with respect to raw milk, the keeping quality and bac- 140 MILK HYGIENE terial content furnish sufficient evidence regarding its true condition. +. The bacteria surviving pasteurization are, for the most part, the quick growing bacteria of putrefaction which are inhibited in raw milk by the lactic acid bac- teria, but in pasteurized milk they multiply very fast and undoubtedly they are capable of generating poisonous substances. It has been suggested, therefore, that a pure culture of lactic acid bacteria be added to milk after pasteurization in order to check the bacteria of putrefaction. 5. In purchasing pasteurized milk, one cannot tell if | NUMBER OF SAMPLES NUMBER OF BACTERIA IN 1 C.C. Ordinary whole milk Pasteuriz’d whole milk 0-10 = 2 10-50 = 100-500 - 2 500-1,000 = + 1,000-5, 000 - 1 5,000-10,000 = 10 10,000-20,000 = 6 20,000-50,000 12 50,000-100, 000 - 7 100,000-1,000,000 7 66 1,000, 000-5, 000,000 ] 20 5,000,000-10,000,000 7 9 Above 10,000,000 1 3 Total number of samples... 9 142 it be fresh or old and cannot determine, from its appear- ance, if putrefaction has begun or if only a few bacteria are present. That this objection to the sale of pasteur- ized milk is valid, is shown by the Copenhagen health PASTEURIZATION 141 Commission, in its report, especially that for 1899, on the nuinber of bacteria in pasteurized milk, as compared with the number in unpasteurized milk. It is evident that these figures do not seem to favor pasteurized milk, and the situation is still less favorable if one considers that the bacteria in raw whole milk are chiefly lactic acid bacteria, while in pasteurized milk the greater part consist of bacteria of putrefaction. The figures above cited for the year 1899 are especially high, but the summary given below is made from examina- tions of pasteurized milk extending through a period of several vears 247 NUMBER OF COLONIES IN J GER: 1896 T8U7 1Sys Tsita 1900 one = Below 100,000 22 26 12 44 } 40 100,000-1 000,000 J 5) 19 (8 | By Above 1,000,000 l 17 ie | Lb Total number of sumples 23 ae 48 142 ! 105 This increase in the number of strongly infected sam- ples occurs coincidently with the equipment of many milk establishments for the production of ‘* pasteur- ized *? milk and apparently without such careful direc- tion as to make it certain that the whole quantity of milk was really heated to the required temperature ; that this was the case is indicated by the result of investiga- tions of the health commission in the year 1899, which show that of 36 samples of pasteurized cream 2, and of 99 389 samples of pasteurized milk 23 could not stand the “7 Stadslaceens Aarsberetninger (Annual Report of the City Phy- sician). Copenhagen. 142 MILK HYGIENE Storch test, which showed that they had not been heated to 80° C. (176° F.). When we compare the advantages and disadvantages it will be found that there is serious doubt as to whether it 1s advisable to endeavor to obtain general pasteuriza- tion of market milk, as has been suggested by many. A well organized and well conducted large milk business may be in position to carry out pasteurization with safety and to obtain all the various advantages that result from this process but, undoubtedly, it would be necessary for the great majority of establishments to be kept under comprehensive, strict and expensive con- trol by the health authorities which, even then, could searcely be effective. II. STERILIZATION By sterilization of milk is understood a long contin- ued boiling, or heating to a temperature above the boil- ing point as 105° to 110° C. (220° to 230° F.). The superiority that is claimed for sterilization over pasteur- ization is that all of the bacteria are killed and the milk, consequently, will keep for an unlimited time. But nearly al] the examinations of ‘‘sterilized milk’’ bought in the market, that have been made, up to the present time, have shown that the milk is not sterile but con- tains the spores of bacteria. On the whole, sterilization offers no special advantage over pasteurization, on ac- count of the unpleasant taste of sterilized milk, due to changes in the albumen and lactose, and on account of the greater expense connected with it. Sterilization has the advantage only when it is a question of keeping the milk a long time or transporting it a long distance, and in this case the principle followed is essentially the same as that followed in the preparation of preserves in STERILIZATION 143 hermetically sealed cans. Considerable advance has been made in recent vears in regard to the preparation of such preserved, canned, milk, in that the boiled and Fic. 10. Kleemann’s high-pressure pasteurizer and regenerative heater. a, water of condensation b, to the cooler. burnt taste las been prevented by pumping the air out of the milk before heating it and by the exclusion of oxygen during heating, so that a high temperature is possible and a safer sterilization is accomplished without seriously affecting the taste. Another difficulty which it has been necessary to contend with, the separation of cream, and of butter formation during storage, seems hy degrees to have been overcome. For the purpose of sterlizing milk, instead of the usual apparatus built according to the Fjord system, tightly closed machines are used, so that the tempera- ture of the milk van be raised above the boiling point, and through these the milk is foreed by means of a small 144 MILK HYGIENE pump. There is a large number of such machines. In Germany they are commonly used for simple pasteuriza- tion. Of the machines most used in recent years, the Fig. 11. OQ Section, to show construction of apparatus shown in Fig. 10. u, entrance for milk; } exit for milk ; ¢, steam-chamber; d,steam-opening ; e, safety-valve. so-called ‘‘ regenerative heater ’’ is to be commended be- cause it saves much steam. It is built according to the principle that the hot milk flows past the entering cold STERILIZATION 145 milk (only a thin metal plate separating them) so that both streams of milk have opposite directions; by this means, there is the advantage that the hot milk, even be- fore it leaves the sterilizer, is somewhat cooled without expense, While the cold milk gains quite a little heat be- fore it is heated by the action of the steam. In this way, Fig, 12. Mor’s regenerative milk-heater. steain, as well as ice, is saved. Machines built in accord- ance with this principle differ much in appearance. Some, for example the apparatus shown in Fig. 10, which is one of the newest, consists really of two parts, the ster- ilizer proper (the ‘+ high pressure pasteurizer *') and an apparatus quite similar (‘* the regenerative heater ’’) 10 146 MILK HYGIENE in which the stream of warm milk works upon the incom- ing cold milk. Both parts have the same construction, which is easily seen from Figs. 10 and 11. Other ma- chines of this kind (for example, Mor’s regenerative milk heater, Fig. 12), are simpler in that both processes take place in the same machine. For sterilizing milk meas- ured into bottles, machines which are described and figured on pages 136 and 137 (Fig. 9) are used. PART V. THE USE OF MILK FOR INFANTS THe advantages of inilk as a general food for man are so well known that no further discussion is neces- sary; but the special use of milk for infants, as a sub- stitute for mother’s milk, offers certain points of inter- est which merit further consideration. It is logical first to review the behavior of milk and the changes that occur in it during digestion. Under the influence of the gastric juice, the proteids undergo a process of splitting up in the stomach. The albumin and = globulin are’ first) changed into syn- tonin and then separated into albumoses and, probably, peptone. Casein behaves somewhat differently. Tt is transformed by the hydroehloric acid of the gastric juice into an acid calcium salt and then, under the influence of rennin, it undergoes a change, during which whey albu- min ix formed, into ealeie paracasein, whieh separates as acurd. The ealcie paraeasein is then split by pepsin into albumin and paranuclein (pseudoneuclein) which is pre- cipitated but which is afterwards dissolved hy the pro- longed action of the gastric juice, being broken up into an albwmin-like material and phosphorie acid. The albu- mins that are formed by splitting of the casein are later changed into albumoses (caseoses) and peptone. Ac- cording to recent imvestigations it appears that these substances may undergo still other changes before they are absorbed. Through the action of rennin, an albu- min-like substanee (plastein) is formed and through the 147 148 MILK HYGIENE action of an intestinal ferment (erepsin) the splitting of peptone is continued into di- and mon-amido acids. Little is known as to the resorption and use of these substances. There is a difference of opinion regarding the fate of the milk sugar; some think it is absorbed from the intestines unchanged, but others are convinced that it is first inverted into dextrose and galactose. The absorp- tion takes place more slowly than is the case with glu- cose, maltose and cane sugar. The absorption of milk-fat takes place as that of other fats, with a preceding saponification. It is well known that cow’s milk is being used more and more as food for infants and for small children. As a substitute for mother’s milk, there are some objections to it, however, and if used for nursing babes, it must receive especial treatment. This is on account of the fact that it differs materially in chemical composition from human milk and that it constantly contains micro- organisms, and, sometimes, even pathogenic forms. The differences in composition of human milk and cow’s milk are shown hy the averages given below: Water. Casein. Albumin. Fats. Lactose. Salts. Woman’s milk... 87.92 0.58 0.52 3.43 (12 0.2 Cow’s milk...... 87.75 3.00 0.50 3.40 4.60 HOTS [Human milk appears to vary more in composition than cow’s milk. This may be due in part to the greater difficulty in obtaining a fair sample than is the case with cow’s milk. It is known, for example, that the compo- sition of the fore milk and the strippings differ consid- erably, and if small samples of milk are drawn from a cow’s udder at irregular times during the day, before and after regular milkings, the samples will be of very different composition. Besides this, the less regular life MILK FOR INFANTS 149 of the woman and the nervous influences to which she is subject may tend to make her milk more variable than that of the even-going cow. The figures, however, that are given in the above table show less proteids than were found hy most of the leading authorities. The average composition of woman’s milk, as determined by a large number of andlvses, is given by Richmond as follows: Water. Proteids. Fat. Lactose. Ash. Woman’s milk............0.... BS.2 1a 3.3 8.8 02. Johanssen, however, found but 1.1 per cent. of pro- teids, as an average for 25 samples, thus agreeing, in this respect, with the figures given on page 148 which are from Gottlieb. L. P.] The first thing to he considered is that the quantity of total proteids in cow’s milk is more than three times [or more than twice] the quantity in human milk, so that a child nourished with cow’s milk has apparently a considerably greater nitrogen assimilation than a child nourished in the natural way. It is not known with cer- tainty what significance this has for the health of the child, but it is not safe, off hand, to eonelude that the highly nitrogenous diet is advantageous. Moreover, the ehief part of the protein of ecow’s milk consists of a casein, which, in contrast with the casein of human milk (the proteids of human milk do not give a curd with ren- net), is precipitated in the stomach as large curds and in a form that apparently makes it less digestible. Great importance has been attributed by some to the fact that human milk often contains more fat than cow’s milk and, it is affirmed, on this aecount the nutritive value of human milk is greater than cow's milk. But sinee we know that the fat content of human milk is sub- ject to great variation (for individual peculiarities see page 24) no particular importance can be attributed, in 150 MILK HYGIENE general, to this difference. On the other hand, the fact must be considered that the fats in the two kinds of milk differ somewhat chemically, and that cow’s milk contains much more volatile fat (butyric acid) than human milk. These other important conditions should be mentioned: the decided different proportions of lactose which, doubtless, is of value in the nourishment of the child, and the small quantity of lecithin in cow’s milk, to which great importance is now ascribed in metabolism. It is doubtful if the greater quantity of citric acid and of inorganic salts in cow’s milk has an unfavorable influ- ence on the nourishment of the ehild. Many attempts have been made to correct the defects of cow’s milk and to make it a more appropriate food for infants. By diluting cow’s milk with water, the percentage of salt is proportionately decreased so that the casein coagulates in the stomach in flakes, just as the casein of human milk, and at the same time there is a proportion- ate diminution in the percentage of the total proteids. But there is also a decrease in the quantity of albumin as well as of the other ingredients of great nutri- tive importance—lecithin, lactose and fat—which is decidedly disadvantageous. In order to remedy this, the milk is often diluted with barley- or oat-water or the proper quantity of milk- or grape-sugar is added. Others have used cream diluted with water; by this means an appropriate quantity of protein and fat can be had, and since fat may be substituted for lactose, the deficiency of the latter makes little difference. To make cow’s milk approach human milk more closely, and to make it more easy of digestion many methods of preparation, some of them rather complex, have been proposed, and some have been used commer- cially. The following are examples of such preparations : MILK FOR INFANTS 151 “Gartner’s fut milk ’’ is prepared in the following way: cow’s milk is diluted with water to such an extent that the casein content corresponds to human milk, then it is so centrifuged that the milk flowing from the cream tube has a fat content which agrees with that of human milk. The milk is put into bottles and sterilized. The composition of the ‘‘ fat milk ’’ may, of course, be changed at will; the average composition of such a prep- aration made in Germany is: fat, 3.7 per cent.; proteids, 1.5 per cent.; lactose, 2.2 per cent. “ Voltmer’s mother’s milk ’’ is the name given to a milk preparation that is sometimes marketed in the form of ‘‘ milk,’’ and sometimes is condensed and sold in cans. The preparation is somewhat complicated; fresh centrifuged cow’s milk is heated to 100° C. (212° F.) and distilled water, cream and sugar are added to it in such quantity that the content of proteids, fat and sugar correspond to human milk; the mixture is now exposed to the action of pancreas ferment which proccss changes the casein into albumoses. The preparation is sterilized at LOS” to 10a! (. (215.6° to. 221° B.) or evaporated and poured into vans which are sterilized after solder- ing. .\ccording to several analyses, the composition of the commercial product is, approximately: fat, 2.8 per ecnt.; proteids, LS per cent. (about three-fourths of this is albumose); sugar, 6.2 per cent.; and salt, 0.4 per cent. “Backhaus’s infants’ milk’’ is similarly prepared. The cream is separated by the centrifuge; the skimmed milk is heated to 40° C. (104° F.) and rennet and trypsin are added. In the course of half an hour the precipi- tated cheesy mass is filtered out; by this means a part of the casein can be taken out, while the rest is trans- formed into easily digestible albumoses. The action of the ferments is stopped by heating, and cream and sugar 152 MILK HYGIENE of milk are now added. The preparation, which is mar- keted in a sterilized condition, has been widely recog- nized. Its composition may easily be varied. For small children a preparation of about the following composi- tion is made: fat, 3.1 per cent.; casein, 0.6 per cent.; albumin, 1.0 per cent.; lactose, 6 per cent.; ash, 0.4 per cent. Gottlieb has proposed that sweet whey, cream, sugar of milk and lime’ water may be mixed together in such proportions that the composition of the mixture will closely resemble human milk. [‘‘ Modified milk’? as developed and prepared by the Walker-Gordon Laboratory Company, with the scientific aid of Dr. T. M. Roach, has been in use in the larger cities of America and in London for a number of years; it was first prepared and sold in Boston in 1891. Such milk is dispensed upon physicians’ prescrip- tions, and is prepared by mixing whole milk, cream, whey, skim milk, lactose and water or other substances, if ordered, as lime water, starch, barley-water. etc., in the proportions required to give accurately the desired per- centages of protein, fat, sugar, ete. It is dispensed in round bottles (‘‘ tubes ’’) each of which contains suffi- cient milk for a single feeding. The bottles are plugged with cotton-wool. The milk is produced on farms be- longing to or under the control of the company and most exacting precautions are taken to protect it from con- tamination. The milk is served raw, pasteurized or sterilized, as ordered. Usually it is pasteurized and if the proteids consist chiefly of those present in whey, the tempera- ture reached during pasteurization is not permitted to exceed 155° F’. By means of modified milk the nutritive requirements of the individual child can be supplied. In Po MILK FOR INFANTS 153 Many special preparations similar to the above have been used abroad and have received the approval of pediatrists. In Denmark, however, they are used but little and they will never have a very broad field on ac- count of their high price. In France, asses’ milk is quite commonly used as a substitute for human milk and in Dresden an establish- ment has been started for the production of asses’ milk, which is desired partly because of its great similarity to human milk and partly because of its favorable effect in indigestion of children. On account of the small milk yield of the donkey, this milk is much too expensive to be used generally. For the same reason, mare’s milk has been used in some places, but only to a limited extent. Goat’s milk has been suggested as food for infants, and large herds of goats have been maintained in some places for this purpose—principally on account of fear of tuberculous infection from cow’s milk. The prevalent opinion of the infrequency of tuberculosis in goats is untenable, since they are very easily infected and may suffer, just as cows do, with udder tuberculosis. There- fore, there is no reason to prefer goat’s milk to cow’s milk. In by far the majority of cases in which the mother has not enough milk, or her child will not nurse, cow’s milk is used as a substitute. The question has often been discussed as to whether and, if so, what special require- ments should be made for milk intended for infants, and different answers are given. It was formerly thought that the composition of the cow’s food had a marked influence on the chemical composition of her milk, and upon its character, and on account of this opinion it was formerly required in Germany that cows kept for this purpose must be fed nothing but dry food the entire year. The price of such milk has been considerably in- 154 MILK HYGIENE creased on this account. In Denmark also, similar, though less strict, requirements were made for the pro- duction of milk for infants. During recent years, how- ever, views concerning the effect of the forage on the quality of the milk have changed materially, and it has been observed by many that babies have been fed with- out discoverable detriment on milk from cows fed with green fodder, turnips, oil cakes, etc., and, indeed, in some instances, with brewery grains. There does not appear to be adequate ground for the requirement that cows kept to produce nursery milk should be restricted to this one sided diet. On the other hand, there is need for an active control of the sanitary conditions of the produc- ing herd, for the public must be assured that milk sold at a high price especially for the use of infants may be fed to them without danger of a grave infection of some kind. The nature of the requirements which, in our judgment, should be made concerning the production, handling and sale of ‘‘ nursery milk ’’ are considered later. The mortality among children during the first year of life is very significant. In Norway and Sweden, from 1891 to 1895, on the average, 10 per cent. died each year; in Denmark, 14 per cent.; in Finland and Switzerland, 15 per cent.; in Prussia, 20.5 per cent.; in Baden, 22 per cent.; in Wurtemberg, 25 per cent.; in Bavaria, 27 per cent.; and in Saxony, 28 per cent., while the mortality in Austria and Hungary is 25 to 28 per cent. The mor- tality is greatest in large cites, somewhat less in small cities and least in the country. Different cities show different death rates; for ex- ample, from 1886 to 1895, on an average, each year 13 per cent. of the children less than one year old died in Lyons, 15 per cent. in Christiania, 16 per cent. in Paris and London, and the death rate in Berlin reached 25.3 MULK FOR INFANTS 155 per cent., in Budapest 28 per cent., in Munich 31.4 per cent. and in Ingolstadt even 40.9 per cent.** In Copenhagen, the mortality, during the first year of life, has decreased significantly; 1877 to 1886, 20.85 per vent. died each year; in the next decade 19.04 per cent., during 1897 to 1899, 17.87 per cent., while only 15.55 per cent. died in 1900. Infant mortality is also on the deerease in the provincial cities, and this is certainly true of many large cities abroad. A comparison of normally fed children with chil- dren fed on raw or prepared cow’s milk, shows a far greater death rate among the latter. If the cases of dis- eases and death are arranged according to the separate months, it is noticed that in most cities there is a marked increase of deaths in July and August and a propor- tionate decrease in September, and this increased mor- tality pertains almost exclusively to children fed arti- ficially. By far the greater part of the fatal diseases are af- fections of the stomach and the intestines as eatarrh, colics and cholera infantum. Although the causal con- ditions are not fully explained, it may be stated that cow’s milk appears to induce a predisposition to intes- tinal infections, on account of its varying and hetero- gencous composition. The diseases are to be attributed to the action of microbes; possibly in some cases to bae- teria that have formed toxie substances during their development in the milk, but in the greater number of cases it is, doubtless, a question of the presence of patho- venice microbes in milk (streptococci, proteus- and colon forms). Therefore, milk intended for infants should be sterilized. Opinions differ as to whether heating with steam for an hour (Noxhlet’s method) is to be preferred “S These Heures are taken from Ohlens’ Die Mileh und ihre Beden- tuug, 1905. 156 MILK HYGIENE to brief boiling or to pasteurization, since it is thought that long cooking affects the digestibility of the casein. Through the zealous efforts of physicians, it has been possible, during recent years, to cause the general ac- ceptance of the practice of sterilizing milk for infants and the reports show that this has had a favorable influ- ence in preventing disease and death. There are, however, some children with whom cooked cow’s milk does not agree, as it causes continual indiges- tion and loss of weight so that, indeed, when six months old they may weigh less than at birth (infantile atro- phy). This condition is often improved at once if a wet nurse is procured for the child or if asses’ milk is used; or a change to raw cow’s milk may lead to quick recovery. An explanation of these different effects of cooked or raw cow’s milk cannot be given here, since there is no convincing reason for the opinion that cooked milk is harder to digest than raw. Possibly the favorable effect of raw milk can be attributed to the presence of sub- stances antitoxic to some of the poisons absorbed from the intestinal canal, which antitoxins are destroyed by heating the milk. [In America, the balance of opinion among pediatrists appears to be in favor of clean, raw milk, specially produced, of low bacterial content and from a reliable source (‘‘ certified milk ’’) ; or milk that has been pasteurized at a moderate temperature (155° to 185° F.) and that has not been boiled. L. P.] PART VI. PUBLIC CONTROL OF THE PRODUCTION AND HANDLING OF MILK NATURALLY there are great differences in different countries in the way cities are supplied with milk and in the manner in which it is handled after it reaches the cities. Tn general, it may be said that there is no diffi- culty in supplying small towns, as herds are sometimes to he found within their limits and usually enough milk is brought in from the immediately outlying districts. It is different with the larger cities and, with respect to them, the milk business has been greatly changed dur- ing the last 20 to 30 years. The conditions in Copenha- gen may serve as an example, as they do not differ mate. rially from those found in other large Huropean cities. Copenhagen was once supplied with milk chictly from the brewery herds and other herds within the city, and by farmers from the adjoming country, who delivered milk to their own regular customers in the city; now the conditions are wholly changed. The continual growth of the city and the constantly increasing lygienie demands have caused the almost complete discontinuance of cattle keeping within the city, and proximity to the large city has greatly affected the character of the farming nearby, so that the breed- ing of cattle and dairying have fallen off. On the other hand, on aecount of easy transportation bv railroad, farmers living at quite a distance van deliver their milk to advantage in Copenhagen, and at this time the city is 137 158 MILK HYGIENE supplied with milk not only from the island upon which it is situated but also from the surrounding islands. This facility of transportation by railroad and boat has led to the establishment of milk depots that receive the milk from the farms, handle it appropriately and deliver it to their customers, selling it either from established sales places, or from wagons. This evolution in the handling of milk, which has occurred in most of the large cities of other countries as well, marks an important advance in hygienic methods. The mileh herds in the cities and the retail shops con- nected with them were very often the source of grave epidemics; the uncontrolled sale of milk by small farm- ers has had the same unfortunate result, and there is danger, too, inthe small shops, as the limited space makes it difficult to prevent the various members of the family from coming into too close contact with the milk contain- ers and with the milk itself. Large companies are better able to bear the expense resulting from the observance of hygienic requirements, and the sanitary control of these may be much more easily effected than in the case of numerous small con- cerns. It is to be observed also that many of the large milk establishments have voluntarily adopted standards for the production and handling of milk that are in ad- vance of requirements of the health authorities. There are no proven cases of milk epidemics traced to infec- tion through milk from well conducted large concerns; no doubt the mixing of a large quantity of milk lessens the danger of infection, since usually a certain amount of infectious material is necessary to produce infec- tion. On the other hand, however, the mixing together of a great quantity of milk, weder unfavorable condi- tions, may be particularly dangerous because if a milk epidemic were caused it would be very widely spread. HANDLING OF MILK 159 A strictly enforced control is, therefore, no less neces- sary for large establishments than for small. The first large milk company established in Co- penhagen was the Copenhagen Milk Supply Company which, more than 25 years ago, at a time when milk hygiene was still on a low plane in Denmark, as it was abroad, established, voluntarily, a comprehensive stand- ard covering the condition of health, the cleanliness and the feeding of the herd, the health of the milkers and other employees and the proper handling of the milk. This company rapidly developed a very important busi- ness and has been imitated in Denmark and in other countries. Several new companies have made even greater advances in the adoption and enforcement of liygienie requirements. Moreover, the large, well organ- ized milk companies have had a very great influence in foreing the small coneerns to handle their milk with much greater cleanliness and eare. The most familiar ways of retailing milk in cities, are: the milk is drawn and sold in established shops or it is drawn or dipped from tanks carried on wagons, or, thirdly, the milk is first bottled, or is placed in cans that are closed and sealed. The last method is decidedly the best and it is now rapidly displacing the other methods. When milk is measured out on the street, it may easily be contaminated by dust and dirt blown about by the wind, and as the delivery buckets are carried from one kitchen to another, there is a possibility that ther may carry contagion. This method of delivery is also at- tended by the possibility of defective measuring, ete., by the deliveryman. The hygienic requirements that should be established with relation to the milk supplies of cities, will doubtless lead to a further change in the milk business as this is apparently going more and more into the hands of a 160 MILK HYGIENE few large companies while the number of small con- cerns is steadily decreasing. [In America this tendency toward centralization of the business is very marked in most large cities, and especially in New York and Boston. The reason, how- ever, is economic and is similar to the causes for con- solidation in other lines of trade. L. P.] Since milk, as has been said, ean acquire harmful properties in different ways, since its composition may vary considerably, and since it may be adulterated in many ways, the milk business must be supervised by public authority, under appropriate laws or ordinances. Formerly, in most large cities, the occasional examina- tions had reference only to the fat content of the milk (transparency test, determination of the specific gravity, ete.), and in many places, even at the present time, no further progress nas been made. But our present knowledge makes it obvious that such an examination, in comparison with the standard that should be estab- lished to guard against dangerous milk, has relatively little importance. The public control, therefore, is not to be limited to an examination for adulteration and souring or ‘‘ spoiling ’’ of milk on the market, but must extend to the production and the care and treatment of the milk (including the condition of health of those per- sons who come into direct or indirect contact with it). The enforcement of complete regulations for this pur- pose, of course, is accompanied with great difficulties, and there is no city in the world whose measures in this respect can be said to be ideal. A point to be avoided in such a control is a great increase in expense which would raise the price of milk. This would be a hardship for the public, the importance of which from the eeconomie and hygienic view points, must not be underrated. In the inauguration of a thorough-going supervision it may HANDLING OF MILK 161 be necessary to interfere considerably with the methods of producing and handling milk as these have gradually developed. Local conditions will have an important in- fluence on the establishment of a system of control and will determine the rapidity with which the various re- quirements can be fulfilled. General laws governing the production and handling of milk, are lacking in most countries. Only a few coun- tries (1.¢., Portugal in 1900) have enacted such laws and there is not much evidence as to the practical success of these requirements for a whole country. Ina large num- ber of the cities of Europe somewhat detailed regula- tions have been adopted in regard to the milk trade; but these regulations, even in the same country, differ very much. Dresden may be mentioned as an example of a large city with excellent modern regulations for the handling of milk. (Published July 31st, 1900, with amendments of February 26th, 1901.) In order to estab- lish a uniform system in Prussia, the Prussian govern- ment in 1899 published a circular of information to mu- nicipalities with detailed instructions for a judicious regulation and supervision of the milk trade. In many of the small cities there is either no control at all or a very defective one. [The following table from a report by H. E. Alvord and R. A. Pearson on the milk supply of 200 cities and towns in the United States shows the subjects of most frequent legislation in connection with market milk in 126 cities, the milk ordinances and regulations of whieh were examined with especial care. The most popular subjects for legislation are readily seen. ll 162 MILK HYGIENE SUBJECTS. \Nowmen SUBJECTS SME OF CITIES OF CITIES Dairies: '\Care of milk: License or permitrequired| 12 Milk vessels to be nonab- Special authority for in- sorbent ...........-++- 55 spections.............. 58 Milk vessels to be thor- Pure water supply....... 8 oughly cleaned ........ 32 Drainage of barnyards...; 12 Milk to be promptly re- Stables : moved from the stable..| 11 Proximity to other build- Straining ......-.----..-- 9 L1G sis aw te aoanarees 6 Cooling and aérating..... 15 DiGht fouindarcca saan anes « 15 Conditions of storage..... 23 Vertilatotics.siarccneees 32 |/Sale of milk: Floor space.........-.--- 15 Licenses, or permits...... 92 Air space ............4-, 10 Licenses to be publicly Cleanliness............-. 47 displayed ........... 24 Removal of manure...... 25 Source of supply to be Drainage.............05- Bye Posted i c.c02346 seers 14 Other than dairy animals General inspectionin cities} 75 to be excluded......... 4 Signs on wagons ......... 79 Sanitary milk room...... 14 Unsanitary milk prohib- Employees : ited.. pea piven ats eeigihats 109 Personal cleanliness ..... 20 Coniseationt of impure Contagious disease (to be milk Jade esas seg he s 30 reported) ............. 15 Desuiie standard for com- If exposed to contagious position bette ees seen 67 diseases. +s sis¢4 enacees 25 Skimmed mill prohibited) 12 Skimmed milk permitted eons. conditionally .......... 61 Provisions for examina- Bottling at farm.......... 8 te) ee 58 Storage of milk forsale...| 23 Diseased cows ........... 24 Milk tickets to be used but Unwholesome food for- ONCE ec opadaaces sarens 16 bidden:: i: sisssseesg ees 77 Milk wagons to becovered| 12 Pure water supply....... 40 Milk wagons not to carry Cleaning cows........... 27 garbage ............... 5 Milk rejected at calving Sellers to register custom- THING) s ev cae aa arceeew es 33 Ci hie sa Liiitigds thitencis 7 HANDLING OF MILK 163 While the establishment of milk control on the part of the public leaves much to be desired, private initia- tive, as mentioned before, has led to significant sanitary improvement, in that large stock companies have been formed in many cities to provide sanitary milk and have voluntarily subjected themselves to extra expense for guaranteeing and controlling it. In some respects, this voluntary control far surpasses what the publie could impose at this time. Appendix I gives the require- ments of the youngest company in Copenhagen (‘* Tri- folium ’’), which shows how far a private company may varry this sanitary control, and these regulations may well serve as a model for other places. While the companies referred to established their own requirements and determined the extent of the con- trol to which they submitted, another very successful plan has been inaugurated in Stockholm, which consisted in the establishment, in 1885, by private initiative, of a milk commission of 9 members, including + physicians, 1 veterinarian and 1 chemist. The members of this com- mission are chosen in part by the Board of Health and in part by the Medical Society. This commission has outlined a comprehensive control, which ineludes all who desire it and who are ready to bear the expense con- nected with it. The business advantages of this control are such that a higher price than usual is obtained for the milk produced under it. Since the legal requirements in the different cities vary and are adapted to the local conditions, it is not possible to give a concise, epitomized view of existing regulations; *® the following, however, is an *” For a review of the loeal milk inspection laws of the United States and recommendations, see * The Milk Supply of Two Hundred Cities and Towns,” by H. E. Alvord and R. .\. Pearson. U.S. Dept. of Avr, B.A. I. Bulletin No. 46, Washington, 1903. 164 MILK HYGIENE attempt to define the requirements which, from a sani- tary standpoint, are to be considered necessary or desirable. In order to be effective, the legal or police require- ments covering the milk trade, must contain detailed regulations concerning : The production of milk. The care and handling of milk. The prevention of adulteration. The prevention of the sale of tainted or damaged milk. In respect to the enforcement of these regulations in cities, the supervision will rest—at least in Denmark— with the local health authorities, and preferably with a veterinarian appointed by this authority, who will con- duct the inspection of the milk establishments with the codperation of the police, and take the necessary sam- ples for further examination. In small cities, the inspec- tion of the production of the milk may also be under- taken by the same veterinarian; but in the larger cities, as a rule, this is left to the local veterinarians in the coun- try, and the various dealers or herd owners are required to furnish certificates, that should be drawn up on a prepared blank and be submitted to the health office con- cerned. I. REGULATIONS REGARDING THE PRODUCTION OF MILK Public supervision of the production of iuilk presents great difficulties and has been carried out in but a few places. In the ordinances of most cities, there are cer- tain requirements pertaining to the production of milk, but their enforcement is not always provided for. In several cities every owner of cattle who delivers milk in the city, either directly or indirectly, is obliged to appear before a public authority and pledge himself to observe REGULATION OF PRODUCTION 165 the existing legal requirements or those that may be made later, and especially to report every change in the make up of hisherd. This isa good arrangement. The actual observance of these requirements should he con- trolled hy frequent visits of a veterinarian appointed hy a central authority or by occasional visits of the local veterinarian, but the latter plan is not so satisfac- tory. Such a regulation would, of course, be particularly diffieult in large cities as, for example, Copenhagen, which receives milk not only from a very large number of large and small herds, the cows in which are often changed, but is supplied with milk from a large part of the country. On the other hand, the regulations men- tioned can be adopted without great difficulty in small cities, although they might cause dissatisfaction at first among the dairy farmers. In aqmost of the larger cities, up to the present time, little has heen done except to publish notices in regard to the regulations respecting the production of milk, but no reports have been de- manded of producers and no special control has been provided to enforce these regulations. The local boards of health have the right to investigate cases which are reported and if necessary to forbid the sale of milk from the premises involved. [In the United States, there is a certain amount of dairy farm inspection under the authority of the states. In Massachusetts, herds are inspected by the Cattle Bu- reau of the Board of Agriculture, in Pennsylvania by the State Livestock Sanitary Board, on request from loeal boards of health that their milk supplies be exam- ined into; in several states, herds and premises are in- spected under authority of the State Dairy and Food Commissioner, the Commissioner of Agriculture or the State Board of Health. In no state, however, is there a 166 MILK HYGIENE systematic inspection of all dairy herds, excepting in Massachusetts, where the inspection is made for the pur- pose of controlling bovine tuberculosis. A number of cities, on the other hand, require periodical inspection of the herds from which they obtain their milk supply. LP The control to which a number of large milk com- panies have submitted voluntarily, either from philan- thropic motives or because driven to it by competition, consists chiefly in frequent, regular visits from vet- erinarians to the milk producing herds, during which not only the conditions of health of the cows but also their food, the cleanliness of the stables, the handling of the milk, and the health of the milkers are the objects of a more or less effective supervision. Some establish- ments have provided a separate organization for super- vising the health of the employees. It is self-evident that the methods of such companies, however good their private supervision may be, must be subject to the supe- rior control of health officers. [It will be observed that the author dwells not so much on the importance of the recognition of infective organisms in milk as on their exclusion. Unquestion- ably it is infinitely better, from the standpoint of the public health, to prevent the contamination of milk than, by means of laboratory examination, to discover evi- dences of contamination in a sample representing a quantity of milk that has already been consumed. Milk is not a food that is kept long; it cannot be put away in storage until a sanitary examination has been made, and then released for consumption, or destroyed, according to the result of the examination. Only the briefest inspections can be made while the milk is en route from the producer to the consumer. The supply continues as a flowing stream, and is REGULATION OF PRODUCTION 167 never just alike at different times or places. The lab- oratory examination of a milk sample gives some infor- mation as to the condition of that sample and, by infer- ence, as to the conditions under which a certain quantity of milk was produced and handled on a given day. But some of the contaminations of milk that are most dan- gerous cannot be detected by routine examinations in the laboratory, if at all, excepting by their effects on the consumer; among such contaminations are those caused by the specific organisms of tuberculosis, typhoid fever, diphtheria, scarlet fever and the materies morbi of many diseases of cows. Therefore, so far as the pre- vention of the infection or pollution of milk is concerned, it is more important that the milk be produced under such conditions that contamination is well guarded against than to know the condition of a vertain quantity that has already heen used. The laboratory examination of milk is, however, of much value in checking and controlling the accuracy of farm and herd inspections, which inspections are de- signed to prevent infection and pollution, while the lab- oratory discovers contaminations that have already occurred. The author’s position on this general subject is quite analogous to the opinion that is now held by sanitarians in regard to the way in which the purity of the water supply should be obtained and insured; that is, by clean- ing and guarding the source. It ix well to lock the stable door before the horse is stolen. But it has, thus far, been impossible in America, excepting in a few isolated instances, to impress the public sufficiently to lead to the establishment of a sys- tematic inspection of the sources and methods of hand- ling and transporting milk. Reasons for this condition are, the paucity of specially trained men for this ser- 168 MILK HYGIENE vice and, on this account, the difficulty health officers have experienced in securing inspectors to do such work in a satisfactory way and, secondly, the expense. A properly equipped dairy farm inspector must have had special training, and must be familiar with, and be able to apply, facts from pathology, bacteriology, zodtechnics and dairy husbandry. Dr. William T. Sedgwick has emphasized the impor- tance of control of the source of the milk supply, to pre- vent pollution, as follows: *° ‘“ Tt should never be forgotten that if water were to be drawn, as milk is, from the body of a cow standing in a stable, by the hands of workmen of questionable clean- liness, and then stored and transported over long dis- tances in imperfectly cleaned, closed cans, being further manipulated more or less, and finally left at the doors at an uncertain hour of the day, few would care to drink it, because its pollution and staleness would be obvious. It is clear, moreover, that it requires and deserves more eareful treatment than water, for it is more valuble, more trusted and more readily falsified or decomposed.”’ Dr. Rowland G. Freeman has stated his opinion as to the importance of controlling the source of the milk sup- ply, rather than to attempt to determine its character by bacteria counts, in these words: ‘‘ It seems to me that while the counts of bacteria are exceedingly valuable as an exponent of cleanliness and proper handling of milk, they should be used only to prevent carelessness at the dairy and to stimulate better methods and discipline. ‘¢ The opinion of a milk commission of representa- tive men (experts) based on an actual knowledge of the management of the dairy is of vastly more value to the 40 Sedewiek, Principles of Sanitary Science and the Publie Health. New York and London, 1902, page 279. REGULATION OF PRODUCTION 169 medical profession and to the public than any statement regarding the precise number of bacteria in the milk upon any given day or days. The most important things, after all, are such a régime as shall make con- tamination by pathogenic organisms improbable, and at the same time insure that the milk is produced under such conditions of cleanliness that other bacterial con- taminations will be reduced to the minimum.’’ L. P.] a. The condition of health of the herd. The ideal requirement that only milk from a perfectly healthy herd may be marketed, cannot be maintained. The pub- lic, therefore, must be satisfied to demand that the health condition of the herd is such that its milk docs not pos- sess Injurious qualities. If infectious diseases which are transnussible, through milk, to man, break out in the herd, the sale of the milk should be forbidden as long as danger of infection be present. If individual cases of infectious or other diseases oceur which may lvad to the contamination of the milk of the affected cows by patho- genic bacteria or toxins, it must be the duty of the owner to prevent this milk being mixed with the other milk, and, indeed, wholly to prevent its use as food for man. Such regulations as the following may be regarded as necessary : The use of the milk from the whole herd is to be dis- continued if foot-and-mouth disease, lung plague or anthrax occur, also in the case of extended outbreaks of transinissible infections of the udder, septic enteritis, cowpox, or of any toxic disease of a large part of the herd. The milk of individual cows should not be used, and affected animals are immediately to be removed from the stable, in cases of tuberculosis affecting the udder, the uterus or the intestines and when the lungs are so affected as to occasion physieal symptoms: also, milk 170 MILK HYGIENE from cows suffering from anthrax or rabies (bitten by affected animals), and that from cows with mastitis, with inflammation of the uterus and retention of the afterbirth, inflammation of the intestines or severe diarrhea, and with severe cellulitis or abscesses and suppurating wounds. Milk should not be used from cows suffering from any sort of febrile disease or intoxication, with pox or suppurating sores on the teats, with inflammation or other disease of the udder, constipation or diarrhea, Moreover, it should not be used from cows that are being treated with medicines that have a strong odor (volatile oils, ether, asafcetida and the like), with alkaloids or potent glycosides, with preparations of iodine, arsenic, mereury, antimony or lead. A very proper requirement is that milk from cows that have recently calved is not to be mixed with the rest of the milk, for the beast milk (colostrum) differs greatly in composition from normal milk and may have a harmful effect on small children. For 6 to 8 days after calving, the milk should not be mixed with the other milk. Also, milk from cows approaching the end of the period of gestation and which are only giving a little milk, should not be mixed with that intended for sale, because it is often quite alkaline and may differ a good deal in its composition from normal milk. The complete observance of these requirements is, evidently, very difficult to control. In part, one must rely on the honesty of the owner, who should be held responsible for failure to comply with the legal require- ments. When a dairyman is under contract to furnish milk to a company having its own conditions and regula- tions, he may be held accountable for failure to fulfil the obligations he has undertaken. In general, it can be REGULATION OF PRODUCTION Let said that the observance of the conditions that are out- lined above, as well as those that will be mentioned later, can he expected only when the dairy farm is under the ispection of a veterinarian who is entirely independent of the owner. Therefore, when it is possible, one should endeavor strongly to arrange for such veterinary supervision. Naturally, it is of some advantage to make inspections now and then, at irregular times, but if the control is to be really effective, the visits must take place frequently, and with some degree of regularity. Preferably, the visits should not be more than fourteen days apart be- cause, in that time, tuberculosis may attain such develop- ment that bacilli may be excreted with the milk, and dis- eases of the udder often develop acutely and follow a short and rapid course, thus making frequent examina- tions necessary. Only in cases in which the milk is sub- jected to a really safe process of pasteurization before it is sold, should a less frequent inspection be considered sufficient. [This amount of supervision, a visit to each produc- ing farm every two weeks, is not attainable with relation to the milk supply of the large cities of the United States, nor is it to be regarded, in the present provi- sional state of the sanitary development of the country, as necessary. That producing farms should be under some supervision, all agree. The amount of supervision that is necessary varies with the conditions. Ifa given herd is known to be infected with tuberculosis and infested with other diseases, if the premises are bad and the owner careless, then frequent inspections should be made until there is decided improvement; on the other hand, if a certain herd is known to be clear of tuber- culosis, calf cholera, infectious gargets, ete., if the prem- ixes ave good and well kept and the owner intelligent and 172 MILK HYGIENE careful, longer intervals may safely be permitted to elapse between visits. After an inspector has gone over his ground and has become acquainted with local condi- tions, and the individuals, the question of frequency of visits should be left to a larger extent to him. The number of inspectors required is of course in direct proportion to the frequency of inspections. If a single inspector could visit all of the dairy farms sup- plying a given city in one year, about twelve inspectors would be required to visit these farms each month. It is estimated that the number of inspectors that would be required to carry out an adequate system of dairy farm inspection for the city of Philadelphia is about 20. About 60 to 80 country inspectors would be required for the city of New York. L. P.] For herds supplying “‘ nursery milk ’’ or ‘ infants’ milk,’’ decidedly rigid requirements must be made be- cause, so far as possible, this milk must be so produced that it can be used in its raw state by children and invalids without any danger whatever. Therefore, dealers should not be permitted to sell milk under these names if the herds are not under the inspection of a public veterinary officer; and the inspec- tions should take place at least every fourteen days, preferably every week. It must be required that ‘‘ nurs- ery milk ’’ shall come only from herds absolutely free from tuberculosis (7.e., herds that are tested with tuber- culin at least once every year, and to which only abso- lutely healthy animals are allowed to be added), be- cause the diagnosis of some dangerous forms of tuber- culosis is often very difficult and, in the earlier stages, even impossible, and because it has been proven impossi- ble to prevent the occurrence of the dangerous forms merely by the removal of animals in which tuberculosis is clinically apparent. Besides, the definite requirement oe REGULATION OF PRODUCTION 173 must be made that the delivery of milk must cease in- stantly if numerous cases of septic enteritis or strepto- coccus mastitis appear and also if ‘* calf cholera ’’ occurs malignantly or endemically. Moreover, the prompt removal from the herd is de- sired of every animal that has fever, or any kind of infectious disease. It is the duty of the owner himself to discontinue the delivery of the milk and to undertake the necessary isolation, when occasion may arise be- tween the visits of the veterinarian, and he should eall the veterinarian as soon as any suspicious disease may appear. These requirements are already enforced hy private companies and so there ean be no question as to whether it is possible to carry them into effect but, up to the pres- ent time, they are enforced by the public in only a few cities. b. Feeding the herd. As has already been stated, it is now the belief that the composition of the milk does not depend in any material degree on the composition of the food, and that injurious substances are not ex- creted through the udder to the extent that was formerly supposed. Therefore, one is not justified in forbidding the use of such a number of foods as has been done and is still done by some large cities. Only such foods should be prohibited as are decomposed (inouldy, putrid or fermenting), or materials containing great numbers of resistant bacteria of fermentation (creamery refuse, frozen forage, the offal of root crops, ete.), or excessive quantities of unnatural food materials (the refuse of some manufactories, distillers’ slops, malt, molasses ete.), and strongly smelling vegetable matter (turnip tops, cabbage, green forage containing poisonous plants, ete.). The use of other food stuffs should be forbidden in such quantities as are injurious to the cow (turnips 174 MILK HYGIENE causing diarrhea, concentrated feed causing indigestion, poisoning by cotton-seed and nut-cake, etc.). It has been required in some cases that cows supply- ing ‘‘ nursery milk ’’ shall be fed only upon dried fod- der, and the use of oil meals has been restricted. By this means, milk has been obtained which is good and uniform, but it is so very expensive that its use is re- stricted. Our present knowledge of the effect of food upon milk does not sustain this requirement. But, it should be observed, the stable and cows can be kept clean much more easily if the cows are fed exclusively upon dry foods than when they are fed in part upon turnips or other green food. Therefore, if this one-sided method of feeding is not demanded, great emphasis must be placed on cleanliness with respect to herds supplying nursery milk. It is not inappropriate, however, to make some extra requirements in regard to feeding cows pro- ducing nursery milk. For example, food stuffs, such as distillers’ slops, malt and molasses, as well as all fodder which, fed in large quantities, may be injurious to cows, should not be used (buckwheat, lupine, mustard, rape, cakes mixed with mustard, cotton-seed meal, nut-cakes, potatoes, ete.). Of course it is difficult to prove that a ration containing a small quantity of these materials would impart injurious properties to the milk; but it is safest, when it concerns milk for small children, to avoid any possible danger connected with the use of such foods; the more so, as this prohibition would have no influence at all upon the cost of production of the milk. Nor should one be allowed to give so great a quantity of turnips or green fodder to cows that are stabled that they suffer from diarrhea, even to a slight degree. [There has been much discussion and, in the past, much difference of opinion, as to the propriety of using REGULATION OF PRODUCTION 175 silage as a food for milch cows, and especially as food for cows producing nursery or certified milk. The building of silos and the ensiloing of crops are new procedures in America, as elsewhere, and methods both of construction and filling have undergone rapid development. Only a few years ago, when square, poorly built silos were used, some of them built as pits, below ground, and before silage cutters and elevators had been developed, and when it was the practice in some cases to ensilo green maize stalks without cutting, and in bundles, there was much decomposed, putrid and mouldy silage, which had a very offensive odor and which was decidedly objectionable as food for dairy cows or, indeed, for any animals. In these days, however, silos are better made and better filled; they are usually round or octagonal, thus facilitating even filling and settling, machinery for cut- ting has heen perfected, so that the silage is divided into short lengths of from one-half to one inch, and Indian corn, the chief silage crop, is no longer used in the soft, immature state, but is permitted to come al- most to maturity. Putrefaction does not occur in prop- erly handled silage. The fermentation that takes place is caused partly by bacteria and partly by enzymes in the maize plant. Good silage is a wholesome, nutritious food that is appetizing and comparatively easy of di- gestion. Silage is fed to cows on nearly, if not quite, all of the large farms in America devoted to the production of certified and nursery milk. It is not known to be subject to any objection other than if fed in too large quantity it produces an undesirable degree of laxativeness, and if fed just before or during milking, if it is not first class, the odor of the silage may be eliminated with or ab- sorbed by the milk. This is avoided by feeding it after 176 MILK HYGIENE milking and by not allowing the residues to accumulate in or about the stable. Frasier +! has shown by some tests made with milk from cows fed silage of good quality that no objection- able flavor or odor was imparted to the milk either when the silage was fed before, during, or after milking. In- deed, in 372 tests made, silage milk was preferred in 233, or 60 per cent. L. P.] A further demand in reference to herds supplying nursery milk should be established—that frequent and sudden changes in food should be forbidden, as the com- position of the milk immediately after such a change is often materially altered, and it is more probable that when the udder is ‘‘ surprised’’ by such a sudden change the secretory function is thrown out of equilib- rium and abnormal, and possibly injurious, substances are secreted with the milk. ¢. Cleanliness in the stable and during milking. In order to guard, so far as possible, during milking, against pollution with dirt and, at the same time, with bacteria, the most thorough cleanliness of the cows and the stable, and care on the part of the milkers, is to be desired. However, it is very difficult to establish detailed regulations in this respect, and no less difficult to en- force them. We usually find that the regulations under this heading are confined to the concisely stated orders that cows and stables must be kept clean; that, at milk- ing, the greatest possible cleanliness must be observed and that, just before milking, the udder and teats are to be washed. However, where the conditions permit the establish- ment of more detailed regulations, as in the larger milk 41 Wilber J. Frasier, Bulletin No. 101, Agricultural Experiment Station, University of Hlinois, Urbana, 1905. REGULATION OF PRODUCTION Lat companies, which are under private control, this should be done. In this connection, the following regulations which, first, the Copenhagen Milk Supply Company and, afterward, other companies in Copenhagen, have fur- nished to their producers stand as an example to be unitated : 1. The stable must be so built that the urine has an unobstructed exit and the floor must be of such nature that it may easily be kept cleau. The cows must be well bedded and, for this purpose, no spoiled or rotten straw or hay can be used, nor straw or hay that has previously been used for packing. The stable must be kept as clean as possible. In the morning, the manure must not be removed until after milking; in the afternoon, at least one hour should pass after mucking out before milking. After cleaning the stable, it should be thoroughly aired, unless the ventilating system is particularly good, so as to render this unnecessary. 2. In order to prevent the hind quarters of the cow from becoming too dirty, the hair of the tail, on the udder, the flanks and on the outer side and the rear of the thighs should he clipped before the cow is stabled in the fall. Besides this, the cow should be cleaned with a eurry comb and brushed every day. Definite and more stringent regulations concerning the cleanliness of the stable and the cows should be made in summer, if they are fed in the stable, and in winter if green (laxative) fodder is used. 5. When the cows are kept in the stable, their teats are to he washed with clean water and dried with a clean cloth. If the udder is dirty, this, also, must be washed and dried. If the cows are milked in pasture, this cleansing cannot be done so satisfactorily [and there is less occasion for it], so it is usually best to confine the washing of the teats and udder to such of the cows te 178 MILK HYGIENE as are apparently soiled with manure or earth. If there are sores upon the teats these must be carefully washed off. Instead of washing, one may rub the udder with a dry cloth or brush it and then rub in a little neutral fat [as vaseline ].** 4. The milkers must have a special dress to be used only during milking, and this must be washed as often as necessary. The milkers must wash their hands be- fore milking, and during milking they must have plenty of clean water and clean cloths at hand with which to wash not only the teats but also their own hands, as often as is necessary. 5. Milk pails, milk strainers and milk cans must be carefully cleaned in the dairy house. If it be necessary to rinse out the pails or strainers when milking in the pasture, only clean water which has been carried to the place must be used and not that from a reservoir in the pasture. d. The health of the attendants. A very important point in milk hygiene is the condition of health among the workers in the dairy and of the milkers and, indeed, among’ all persons who are connected with milk produc- tion. As has already been emphasized, there are a num- ber of infections diseases of man which can easily be transmitted through milk and which have appeared in many instances as extended ‘‘ milk epidemiecs.’’ Fre- quent inspection hy a physician of all persons connected 42 (This reference to milking cows at pasture, which has now become unusual in most parts of America, is explained by the Danish custom of keeping cows tethered out of doors the entire summer. During this season, the cows are allowed to graze on grass and especially planted forage crops, which are harvested by the cows without waste, as the tether pin to which the tie rope is attached is moved but a few feet at a time and is not moved again until the forage within reach has been consumed. Water is earried to the cows in tanks on wagons. L. P.] REGULATION OF PRODUCTION 179 with the business is searcely feasible, both because it would be an expensive procedure and because, in most cases, it would meet with great opposition and tend to increase labor difficulties. But the following regulations are regarded as neces- sary and they should be incorporated in public ordi- nances : The sale of milk shall cease immediately if typhoid fever, searlet fever, diphtheria, or other malignant in- fectious disease breaks out among people living in the farmstead ; 4" the sale shall not be resumed until a physi- cian’s certificate has been received showing that all dan- ger of infection is over."! (‘are must be taken that the milk does not come in contact in any way with persons in whose household one of the above-mentioned diseases exists, nor those who have discharging sores or skin diseases of the arms, hands or face. In addition, the local authorities should have the right to forbid the sale of milk if this is known, or be- lieved, to be the eause of an epidemic, even though no source of infection be proven on the farms in question. Several of the large milk companies of Copenhagen have established even more rigid regulations in regard to the health of the personnel and they insure the en- forcement of these rules by allowing the producer full value for his milk, when he holds it back on account of the occurrence of disease. The value of such a provision is obvious. ec, The water supply. Sinee typhoid bacteria (and 4° The farmer’s residence and the cow stable adjoin, so that they are, practically, parts of the same building, on most of the small farms of Denmark.] 44°The danger of infection from persons recovering from typhoid fever and diphtheria continues for a long time.] 180 MILK HYGIENE other pathogenic bacteria) may gain access to milk through water used to wash the milk vessels, care must be taken that pure water be provided on the farms from which market milk is sold, and that polluted or infected water is not used for cleansing the dairy utensils, nor the udder, nor shall it be used for the cows. [Contam- inated water has also done harm when used for cooling milk and it is believed to have led to the infection of milk, indirectly, through the soiling of the skin of the. cow, as when wading through a foul stream. L. P.] f. The care of the milk. Immediately after milking each cow, the milk must be run through a fine metal strainer into a container. The strainer holds back only the larger pieces of dirt and some of these are dissolved by the continuous pouring of the milk, and bacteria are washed through, so it is advisable, so far as possible, to prevent the dirt that has been removed from coming into contact with the milk that is to follow. But it cannot be said that a strainer has yet been made that solves this problem in a satisfactory way; therefore one must get along by frequently cleansing the strainer from the par- ticles of dirt. Of course, it is very difficult to insure the observance of such a stipulation. Sufficiently rigid re- quirements in regard to the cleanliness of the milk sold and the seizure of impure milk, followed, perhaps, by the imposition of a fine would aid in enforcing the regula- tion. After the milk is drawn, it must be carried to a place prepared for this use and which must be used for no other purpose. This room must be well ventilated, clean and have an impervious floor. The milk must be cooled as soon as possible by pass- ing it over a cooler or by putting the cans into tanks containing ice water. If it is nursery milk, the cooling must be very carefully done, so that the temperature REGULATION OF PRODUCTION 181 may not execved 10° C. (50° F.). Milk should be kept chilled until it is ready to be shipped and then it must be guarded carefully against high temperature by protect- ing it from the sun, transportation by night, ete. If the transportation of milk requires a long time, it must be cooled to a low point, and, while it is not well to allow the whole quantity to freeze, in recent years a partly frozen milk (the outside layer frozen in the cans) - or the addition of frozen milk to the other milk have been successfully used. [Milk shipped long distances in America is sent in refrigerator cars. Some milk is on the railroad 10 hours before it reaches market. Milk shipped short distances is usually not sent in refrigerator ears because, on the short runs, the cars have to be opened so often at local stations that there would be a great consumption of ice. Tf such milk is thoroughly chilled by the use of ice before it is shipped, it usually arrives in good condition; but if it ix cooled only by the use of well or spring water it is an uncertain commodity in the hottest weather. Bot- tled milk is shipped in wooden boxes with broken ice packed around the bottles, Helm‘ has proposed that milk shall be shipped in square, instead of round, eans, so that they may be packed more closely and thus make a solid block, of low temperature, which may be covered over if neves- sary, and which will remain cold much longer than a loose collection of round cans, between which the warm air may freely cireulate. This style of can is shown in figure 14. L. P.] Only well-tinned metal cans which are easily cleaned should be used for keeping milk (Fig. 18); these should be closed and sealed when transported by rail or boat. 4° Wilhelm Helm, Die Milehbehandlung, Liepziz, 1903. 182 MILK HYGIENE Il. REGULATIONS CONCERNING THE SALE AND DELIVERY OF MILK Just as supervision is necessary of the herds which produce the milk, and in regard to the care of milk at its source, so also is supervision necessary after it comes into the hands of the wholesale and retail dealers. This supervision is much easier to carry out than that with relation to production. The regulations governing sale and delivery must embrace not only the methods of handling the milk and Fie. 14. Fig. 13, f _\_ [° sy Danish milk-cans. Helm’s milk-eans. the health of the attendants, but there should also be rules concerning the place in which the milk is sold, the manner of selling it and the labelling of the goods. a. Preparing the milk for delivery. Although small concerns subject the milk to no especial treatment from the time it is received until it is sold, this is not the case with the large companies. These have considerable work to perform in the handling of milk and its delivery to customers. The milk [under the Danish system] is received from the stations in a more or less cool condi- REGULATION OF SALE 183 tion and the cans are put into ice water in order to chill the milk sufficiently. It is then poured into a tank and mixed, thus making its composition uniform. Then fol- lows a process of cleansing, wherein the milk is either passed through a centrifuge, so constructed that the cream and the milk are not separated, but only particles of dirt are thrown out, or it is passed through a filtering apparatus which holds back some of these particles. A gravel filter is frequently used for filtering. This is a tank which is filled with layers of gravel of different degrees of fineness, through which the milk is slowly forced. The gravel is cleansed daily by washing and roasting. Only the particles of dirt are removed by this process; the number of bacteria is not appre- clably reduced. A filter made of numerous layers of fine linen, tightly stretched, has been used successfully in- stead of the gravel filter. The cloth part is renewed after cach use. This method has, among others, the ad- vantage that the filtering may take place directly into the can from which the milk is drawn off for sale, or the apparatus may be so arranged that while the milk is being filtered and run off, it is at the same time cooled. The ‘‘ clarified ’’ milk is put into metal cans or glass bottles in which it is to be sold. This filling is sometimes done automatically, so that incorrect measuring is not possible, and sometimes by means of a machine similar in construetion to those used in filling beer bottles. If the milk is to be pasteurized, it is first filtered, then run through the pasteurizer and over the cooler, into the delivery can; or it is placed in the clean bottles or cans that go into the pasteurizer or sterilizer (see page 139). The public will searcely require ordinances contain- ing exactly detailed regulations in regard to these differ- ent processes. Generally it is required only that the 184 MILK HYGIENE vessels and apparatus used shall be entirely clean, that the milk be handled with the greatest cleanliness and be kept in well-tinned metal cans or in glass or earthenware vessels with perfect glazing, containing no lead, and that all vessels shall be so constructed that they will not be difficult to clean. Special regulations should be established for the pas- teurization of milk. If the heating is of short duration, it is desirable that the milk be heated to 80° C. (176° F.) and cooled immediately afterward. The following re- quirements should be established for heating at a lower temperature: Milk should be raised to a temperature of 65° to 70° C. (149° to 158° F.) and held there for one- fourth hour or it should be kept for one-half hour at a temperature of 60° to 65° C. (140° to 149° F.). The pasteurizer should be known to act accurately enough to attain the required temperature with certainty. b. The places for keeping and selling milk. The places in which milk is handled must be light, airy and easy to keep clean; therefore, they must be provided with an impervious floor and a good drain, and good, pure water must be easily accessible. The salesplaces must likewise be bright, airy and clean and, in addition, there are a number of special requirements. Milk should not be allowed to be sold in the same shop with other goods, with the exception of certain foods (as bread, honey, flour, butter, margarin and eggs), which cannot, either by their odor or in any other way, have a deleterious influence on the flavor and the keeping quality of the milk. Conducting a laundry, or a similar business, in the same place in which milk is kept or handled, should not be permitted. Of course, the apartment must not be used as a dwelling or a sleep- ing room, and it should not be in direct communication with sleeping rooms. If the place used for keeping and REGULATION OF SALE 185 selling milk is in communication with living rooms, as happens in small premises, then it is positively neces- sary to have the apartments separated by a thick door, which shall be kept closed. c. The condition of health of the attendants. The same rules that apply to attendants in the places of production should he binding upon those at the salesplaces. How- ever, as the enforcement of these rules naturally meets very great difficulties, in most cities action has been limited to making the regulation and then punishing those guilty of offences that are, by chance, discovered. Several large concerns (¢.g., some in Copenhagen) have voluntarily enforced strict regulations in regard to the health of attendants. In order to be sure that no suspicious disease among them or in their houscholds shall escape being reported, they provide free medical services and also pay full wages to every employee who is temporarily absent from his work on account of iUlness in his family. (Compare regulations governing the producers for this society, page 178, and Appendix I, page 241.) Moreover, the public health department of the gov- ernment must be authorized—possibly upon the pay- ment of indemnity—to close milk businesses for a longer or shorter time, which are known to spread contagion, even though it cannot be shown just where the infection comes from. This authority must also apply to milk shops, when eases of typhoid fever, scarlet fever or diphtheria exist among people who work with the milk. If it is proven that the infection did not occur in the shop, the milk and the cream may be sold after steriliza- tion, if care is taken to see that this is thoroughly done. A milk shop is to be kept closed as long as there is dan- ger that it may distribute infection. d. Marking and packing the milk. The requirements 186 MILK HYGIENE in respect to marking milk for sale form quite an impor- tant part of the regulations on the handling of milk, be- cause these have a very important bearing on the pre- vention of adulteration. The kinds of milk and milk products which are of importance are whole milk, ‘‘ half milk,’’ skim milk, cream and buttermilk. Whole milk is the usual name for normal cow’s milk which has not been deprived of any of its fat or other ingredients. As the fat content of milk is far from being uniform, and as partial skimming, or the addition of skimmed milk, is, therefore, not easily detected, many attempts are made to deceive by these falsifications. In order to prevent the sale of milk that may be unadulter- ated but which is too poor in fats, and in order to lessen the number of adulterations, a minimum content of fat and solids has been established in many cities, as well as the limits of the specific gravity. Milk which does not contain the required amount of fat cannot be sold as whole milk; if it is so sold it is considered adulterated. Reinsch ** has made a comparison of these require- ments in the German cities. Among 63 ordinances, 60 contain such a minimum limit for fat; 37 of these place the limit at 2.7 per cent., 5 at 2.4 per cent. to 2.5 per cent., 7 at 2.8 per cent., 9 at 3 per cent. and only 2 have established a higher minimum at 3.2 per cent. to 3.3 per cent. In 19 ordinances, the minimum content of solids varies between 10.5 per cent. and 12 per cent.; most require 11 per cent. to 11.5 per cent. Twenty- five place the limits of specific gravity; 10 of these as 1.028 to 1.034, 8 as 1.029 to 1.033 and 5 as 1.029 to 1.034, while a single one provides 1.027 to 1.034. [The German standards are low because the fat con- tent of the milk of some of the breeds of dairy cows *6 Die gesetzliche Regelung des Milehverkehrs in Deutschland, Hamburg, 1903. REGULATION OF SALE 187 in Germany is very low. It would be quite impracti- cable tou enforce higher standards under such cireum- stances. In 26 states of the United States there are laws estab- lishing inilk standards.** The limits for fat are from 3 per cent. (in one state only is the limit below 3 per cent. ; in Rhode Island it is 2.5 per cent.) to 3.5 per cent. (in one state, Massachusetts, for half the year, the limit is 3.7 per cent.). For total solids, the limits are from 12 per cent. (in one state only is the standard lower: Ohio, during May and June, it is 11.5 per cent.) to 13 per cent. The standards for cities and towns vary within the same limits; some are established by the state standard and some by the cities themselves. L. P.] It is evident from the above requirements that it is difficult to agree on percentages and standards which may be considered perfectly Just and reasonable. If the requirements are placed too high, the owners of a num- ber of herds (especially those made up of purchased cows) soon find it impossible to deliver milk in the cities ; if the requirements are placed too low, the object of reg- ulation is attained only to a very limited extent. There- fore, it has been suggested that different grades of whole milk be established. Leipzig and Dresden have such w provision, under which only milk with a minimum fat content of 2.8 per cent. to 3 per cent. is permitted to be sold as ‘‘whole milk I quality,’’ while unadulterated cow's milk of less fat content ean be sold under the name ‘‘whole milk Il quality’’; in Leipzig, however, this ean be marketed only with the designation of the fat content. Several other Saxon cities have similar “ H. E. Alvord and R. A. Pearson, The Milk Supply of 200 Cities and Towns, US. Dept. of Agr., B. A. I. Bulletin No. 46, Washington, 1903. 188 MILK HYGIENE provisions, under which milk containing less than 2.8 per cent. fat can be sold only with a definite statement of the fat content. It must depend upon local conditions whether such a provision is desirable or not, and also whether it is re- garded as wise to establish a minimum fat (and solid) content, and at what point these should be placed. [Legal standards for milk are, by some, objected to on two grounds; first, that it is unfair to establish a mini- mum standard so high that it will exclude the milk from some cows, and, second, that if the standard is low it will encourage dealers to dilute rich milk to a point just above the standard. As to the first objection, it does not appear to be un- reasonable that an article of food sold as milk shall be required to contain a certain minimum amount of nutri- ment. Entirely aside from the adulteration of milk, which such standards are established to check, it is pos- sible to select and develop herds of cows of certain breeds that will furnish milk of very low fat and solids— not fat content. What has occurred in this direction is shown by reports on the weekly analyses of the milk of a herd of cows at Jaschkowitz,** where the milk ran down to 2.47 per cent. fats and 7.88 per cent. solids not fat. The lowest average for the herd for a month was: fat, 2.60 per cent.; solids not fat, 8.06 per cent.; total solids, 10.66 per cent. The official records of Holstein cows *® show that many individuals yield milk contain- ing less than 3.0 per cent. of fat, and some as little, for a time at least, as 2.6 per cent. This tendency could, undoubtedly, be intensified if the absence of milk stand- 48 Bericht iiber die Tatigkeit des Milchwirtschaftlichen Instituts zu Proskau fiir das Jahr 1905-1906. 49°C. B. Lane, Record of Dairy Cows in the United States, U. S. Dept. of Agr., B. A. I., Bulletin No. 75, Washington, 1905. REGULATION OF SALE 189 ards favored it. In other words, the milk could be wa- tered through the cow. The tendency among breeders of Netherland cattle in America (and largely on account of milk standards) is to inerease the fat content of their milk, and many such cows yield milk containing 4 per cent. to 4.5 per cent., and, exceptionally, even 5 per cent. of fat. In regard to the second objection, the dilution of rich milk is scarcely more likely to be practiced if there is a minimum standard than if there is none, and it ean be prevented quite as effectively by law, inspection and penalty with a minimum standard, as without one. All of the existing standards in the United States are much below the average quality of the milk sold in the cities to which the standards apply. It is proposed by Wing *® that no special standard he established, but that each dealer be required to guarantee his own stand- ard, and that he be held responsible if his milk be found below this guarantee. Some dealers now sell bottled milk of different grades, containing cither 4+ per cent. or 5 per cent. of fat, but all of it is above the minimum standard, L. P.] Special rules must he made for milk sold under the name ** infants’ milk” or nursery milk,” and it must be required that this shall come absolutely from herds that are under constant veterinary inspection and whose condition of health and cleanliness and feed are gov- erned by special requirements (see page 17+). In a number of German ordinances, in addition to these re- quirements, the minimum fat content is placed at 5.0 per eent., Which is considered fair. [In the United States “Certified milk’? is usually required to contain 4 per cent. fat.] | Another regulation which is justly put upon 50H, H. Wine, Milk and its Products, New York and London, 1899, 190 MILK HYGIENE the dealer in nursery milk is that the milk shall be sold only in clear glass bottles and that the bottles shall be cleansed or sterilized before they are filled. It should be required that milk sold as ‘‘ controlled ”’ (‘‘certified’’ or ‘‘guaranteed’’) shall come from herds that are under constant and competent veterinary in- spection. Half skimmed or ‘‘ half milk ’’ is milk from which a part of the fat has been removed. It is well to estab- lish a minimum fat content of 1 to 1.5 per cent., as already has been done in some German cities. [In most cities in America, milk that is below the minimum standard, as half skimmed milk is, can be sold legally only as skimmed milk. There is no grade for milk between whole milk and skimmed milk. The desira- bility of establishing such a grade may well receive care- ful consideration. The same end could be gained by the adoption of Wing’s suggestion, but its enforcement would entail administrative difficulties. L. P.] [Skimmed milk is milk from which the cream has been removed by hand skimming or from which the but- ter-fat has been extracted by means of a centrifugal sep- arator. The former kind may contain from 0.5 per cent. to 1.5 per cent. fat, while the latter rarely con- tains more than 0.3 per cent. fat and sometimes as little as 0.01 per cent. The sale of skimmed milk is wholly prohibited in some American cities, as in New York. This prohibition is placed on account of the great in- clination on the part of some dealers to sell skimmed milk as whole milk and the difficulty of detecting and preventing this practice. It is possible, however, to secure a proper observance of the law on this subject, as is proven by the experience of cities in all countries, and it would be far better for the rich City of New York to employ more inspectors, if necessary, to prevent fraud REGULATION OF SALE 191 in the sale of skim milk than to deprive the poor of this wholesome, nutritious and cheap food. It should be required in every case that vessels con- taining skim milk shall be permanently and conspicu- ously marked. To deliver or to store skimmed milk in an unmarked container on the premises or wagon of a dealer should he regarded as evidence of intent to de- fraud and should subject the violator to penalty. Skimmed milk should contain not less than 9.25 per cent. of milk solids. L. P.] Cream, for the production of which the same sani- tary requirements are necessary as for milk, should be sold with the fat content designated, if there is no local regulation to grade it or establish fat percentages. [The percentage of fat in cream varies from 8 per cent. to 50 per cent. or more. The usual quality, as sold in the market, contains about 15 per cent. to 20 per cent. fat. The standard for cream, as established by the U. S. Department of Agriculture, ix IS per cent. Heavy, rich eream contains from 30 per eent. to 40 per cent. fat. L. P.] [Buttermilk requires no special standard except that it be made from clean milk, and in a cleanly way. It is largely used as a summer beverage and, as typhoid bacilli and other pathogenic forms will live in it for some time, it is important that it be protected from con- tamination. An imitation of buttermilk is sometimes made in eity milk shops by churning sour skimmed milk. LP] Pasteurized milk, The following regulations are proposed for milk that has been heated and that is to be sold ax ** pasteurized ’?: Under this name, and without a more detailed statement, should be understood milk that has been heated to at least 80° (. (176° F.); if the milk is pasteurized at a lower temperature, this must be 192 MILK HYGIENE distinctly marked upon the bottle or can, and the milk must not be permitted to go upon the market until the method has received official sanction. Sterilized milk should be sold only with a statement of the way in which sterilization has been done, and not until after the method has been inspected and approved. But it is not enough merely to establish such requirements; the sani- tary officers must see to their enforcement, partly by vis- iting the pasteurizing and sterilizing establishments, partly by taking samples and examining the milk sold. Fortunately, it is possible to determine by chemical means whether milk has been heated to 80° C. (176° F.) or not. These tests are based on an observation by Arnold and have been developed by Babcock, Storch and others.5!| The principles are the following: Storch’s method: 5 ¢.. of milk are poured into a test tube; a drop of weak solution of hydrogen dioxide (about 0.2 per cent.), which contains about 0.1 per cent. sulphurie acid, is added, and 2 drops of a 2 per eent. solution of paraphenylendiamin, then the fluid is shaken. If the milk or the cream becomes, at once, indigo blue, or the whey violet or reddish brown, then this has not been heated or, at all events, it has not been heated higher than 78° C. (172.5° F.); if the milk becomes a light bluish gray immediately or in the course of half a minute, then it has been heated to 79° to 80° C. (174.2° to 176° F.). If the color remains white, the milk has been heated at least to 80° C. (176° F.). In the examination of sour milk or sour buttermilk, lime water must be added, as the color reaction is not shown in acid solution. alrnold’s guaiac method: a little milk is poured into a test tube aud a little tincture of guaiae is added, drop by drop. If the milk has not been heated to 80° C. (176° F.), a blue zone is formed between the two fluids; heated milk gives no reaction, but remains 51 VWeating milk to a high temperature coagulates the albumin and globulin and the milk loses its property of curdling by the action of rennet. By this change one may discover that it has been heated, but not determine whether the milk has been heated to 80° C. (176°F.), that is, if it has been pasteurized. REGULATION OF SALE 193 white. The guaiae tincture should not be used perfectly fresh but should have stood a few days and its potency have been determined. According to the observations by Glage, the guaiac-wood tincture appears to be more reliable than the harz tincture. Zink recommends the addition of a few drops of weak solution of hydrogen dioxide, as this causes the reaction to be much surer and sharper. Of the two methods, the guaiac method is preferable in that the tincture is very lasting and may be kept a year without becoming ineffective, while the paraphenylendiamin solution must be renewed quite often; on the other hand, the guaiae method is, perhaps, hardly so accurate as the Storch method. Other substances are useful as reagents in combination with hydrogen dioxide, as solution of potassium iodide with starch (Storch, du Roi, Kohler and others) and ursol (Utz); besides these, a methylene-blue-formalin solution (Sehardinger) has been suggested for this purpose. [Storch’s test may also be used for the purpose of detecting the adulteration of fresh milk with diluted condensed milk. In this case it is well to make the test comparative by running a parallel sample of milk known not to have been heated. L. P.|} The sale of milk preparations which are made either by using foreign additions or by some special manipula- tion of the milk should be permitted only when the milk has been produced under the requirements above stated and only on declaration of the composition of the prep- aration. Milk containers. In ease the milk is retailed in containers, there should be some. stipulation in regard to these. Metal cans should be of tinned iron; for tinning, no tin should be used that has more lead than is absolutely necessary; the form must be such that they can be easily cleaned. Bottles are to be made of clear glass so that every impurity is noticeable; their form must, likewise, make satisfactory cleansing possible. In recent years, the large milk companies have en- 13 194 MILK HYGIENE deavored in their own interest, as well as in that of the public, to provide sealed stoppers or covers for delivery bottles and cans, which more surely prevents their being opened before delivery and which makes it impossible for an unscrupulous person to fill anew, with milk or cream, the vessel which, from accident or improper rea- sons, was partly or wholly emptied. With metal cans, this security is most easily effected by the use of a simple lead and wire seal, applied after filling. A per- fectly reliable closure for the bottles, on the other hand, offers some difficulty, because it is so expensive. The accompanying illustrations show some of the methods used. Fig. 15 shows a method of closing which corre- sponds to that used on mineral-water bottles. After closing, a label is pasted over the top; this method is somewhat expensive and does not furnish a satisfactory guarantee as the label is easily loosened. Fig. 17 shows Fie. 15. Copenhagen. The upper part of the neck is perforated, and after the bottle has been closed by the insertion of the stopper, a wire is drawn through the holes and se- cured with a lead seal; this method gives efficient pro- tection but is somewhat expensive. Fig. 16 shows a method used during recent years in Germany, which is cheap and quite satisfactory. In the inside of the neck REGULATION OF SALE 195 there is a small groove; after the bottle is filled, it is closed with a paraffined pulpboard cap which is pressed down into the neck of the bottle by means of a stamp, with its edges in the groove; at the same time, the cap is marked, and it cannot be taken out without being torn. A similar cover, a pasteboard cap which is pressed a little way into the bottle (without the groove), is used by many milk concerns, but this gives little security, as the cap can easily be taken out and a new one substituted. [Paper or wood-pulp discs (sterilized) used as stop- pers may be sealed by pouring on top of them a little melted paraffine. This method is used by some dairies that produce certified milk. The customary method, however, among the best dairymen, is to cover the top of the bottle, after it is closed with the usual disc, with a cap of parchment paper, held around the neck of the bottle with a wire, cord or rubber band; or a cap of heavy tin foil is used, which is pressed down around the shoulder at the mouth of the bottle, and this holds its position quite well. Both of these methods have the ad- vantage of thoroughly guarding the mouth of the bottle and the dise that confines the milk. The lip of the bottle, over which the milk must be poured, is prevented from becoming soiled. These methods, however, do not afford such complete protection against tampering with the contents of the package as is furnished by a lead seal. However, if the box in which the bottles of milk are shipped from the farm to the distributing point, or to the customer, is sealed with a lead seal, as is done by some producers, the protection is sufficient. The usual practice among average dairymen is to depend on unparaffined and unsterilized wood-pulp dises, upon which is often printed the name of the dealer. Small dealers (and some large ones as well) some- times indulge in the most vicious and unsanitary prac- 196 MILK HYGIENE tices in regard to bottling milk. They pour milk into bottles from cans in their wagons or hand carts on the street, exposing it to dirt, and, worst of all, they some- times fill bottles that have not been cleaned, or that have not been properly cleansed. Milkmen have been known to take a soiled bottle from the house of a customer, fill it with milk on a dirty wagon, while the wind is blowing dust about, close it with a dise taken from a coat pocket, perhaps from alongside a handkerchief, and then deliver it in the next house. It is not surprising that it has been seriously proposed to prohibit the use of milk bottles. But the bottling of milk marks-a distinct sanitary ad- vance, where it is carried out in a proper manner. It should be provided by public regulation that milk shall be delivered in bottles only under the following conditions : 1. Before they are filled, bottles shall be washed and sterilized, or they shall be cleansed by the use of some method that has the approval of the sanitary authorities. 2. Stoppers for the bottles shall be clean (preferably sterilized) and shall be kept only in sterile packages or in a clean metal or glass receptacle provided exclusively for this use. 3. Bottles shall be filled with milk only in a clean room provided for this purpose, and they shall not be removed from this room until they are stoppered. L. P.] Ill. PUBLIC SUPERVISION TO PREVENT ADULTERATION Just as many foods can be adulterated, so also can milk and cream. As the fat is the most valuable ingredi- ent of milk, a common adulteration consists in partial skimming, or in the addition of skimmed milk or water ; less frequently, foreign material is added to the milk in order to give it a better appearance. It can be only excessively rarely that gross adulterations occur, such as the one reported by Sullivan, wherein a sample of PUBLIC SUPERVISION oF ‘“milk *? was found to consist of a mixture of water, white pigment, common salt and a little skimmed milk. There is no general rule as to the frequency of adul- teration. In some cities, it does not appear to be partic- ularly frequent, while in others it is very common. Besides the adulterations found upon official exam- inations of the market milk in cities, the question of fraud sometimes arises in connection with the milk deliv- ered to creameries. In the creameries, it is customary to use some quick method for determining the approx- imate fat content of the milk that is delivered by the various patrons. In the official control of milk in cities two provisional or preliminary tests have long been uxed and these are still depended on to some extent; they consist in the de- termination of the specific gravity and in a test of the transparency. Even when used in conjunction, these tests are not to be relied upon very far, but they can be used, if with sufficient caution, to determine whether a more thorough examination be necessary. If it is de- eided that a laboratory examination is required, a sam- ple should he taken with great care, and sealed and delivered to the appropriate expert for analysis. The specific gravity of cow's milk varies between about 1.027 and 1.040 at 15° C. (60° F.) ; but such differ- ences are to be found only in the milk of certain indi- vidual cows. The specifie gravity of mixed-herd milk usually falls between 1.028 and 1.054. If the specifie gravity is either above or below these limits it is always suspicious. [The average specifie gravity is 1.082. ] Many different forms of apparatus have been pro- posed for measuring the transparency of milk, to deter- mine if it is or is not diluted. However, these instru- ments are all defective and the results obtained by their use are not to be regarded as of any value except to indi- 198 MILK HYGIENE cate whether a sample of the milk should be taken for analysis. The transparency of milk is dependent partly on the size and number of the fat globules, and partly on the casein in solution. As milk with fewer, but large, fat globules has not the same transparency as milk with more, but smaller, ones, even if the fat per cent. be the same, it is evident that these methods of examination may give misleading results. Feser’s lactoscope is the simplest and best instru- ment made for this purpose. As Fig. 18 shows, it con- sists of a glass tube which narrows toward the bottom and is closed with a metal cap which supports a short vertical glass column on which are six black lines; the upper part of the glass has divisions marked with a double row of figures. Four e.c. of milk to be examined are poured into the tube, then enough water is added so that it will reach figure 40 (that is, 36 ¢.c. of water) ; the fluid is now mixed by shaking. If it is not possible to see the lines on the glass column inside the tube, a little water is added and the tube is again shaken; this is continued until the lines become visible. When they can be seen through the diluted milk, the fat per cent. can be read from the seale. For example, if so much water has been added that the fluid reaches figure 60 (60 c.c. water and milk), then the milk has 3 per cent. fat. As already stated, this result cannot be relied upon; in the examination of skimmed milk, quite too high a per- centage of fat is always indicated and, in regard to whole milk, the test may show from 0.5 per cent. to 1 per cent. too much or too little. On account of the unreliability of this method in many places this preliminary test is no longer used and the inspectors take samples, without preliminary inspec- tion, for examination in the laboratory. [In the use of the lactosecope, the individual coeffi- LRASSPARENGY “LEST BS 2 cient is of great moment. Different inspectors will in- terpret the same result quite differently. When one is experienced in examining with the lactoscope the milk of a given breed of cows, he may become so proficient that he can make a fair estimate of the fat content, but Fig; 19; Feser’s Lactoscope. Quevenne’s Lactodensimeter. when another kind of milk is examined the result may not be so accurate. If milk tests normally, both in re- spect to specifie gravity and lactoscopically, it is not apt to be much skimmed or watered. The following is from Leach : ** 52.4. BE. Leaeh, Pood Inspection and Analysis. New York, 1905. 200 MILK HYGIENE “As in the case of the laetometer, the purity of a milk sample eannot be positively established by the lactoscope alone. For instance, a watered milk abnormally high in fat would often be found to read within the limits of pure milk, when as a matter of fact its solids would be below standard. By a careful comparison of the readings of both the lactoseope and the lactometer, however, it is rare that a skimmed or watered sample could escape detection. “Thus, if the specifie gravity by the lactometer is well within the limits of pure milk, and the fat, as shown by the lactoscope, is above 3] per cent., the sample may be safely passed as pure, or as conforming to the standard. ‘“A normal lactometer reading in connection with an abnormally low lactoseope reading shows both watering and skimming, and with an abnormally high lactoscope reading shows a milk high in fat, or a cream. With the lactoseope reading below three, and a low lactometer reading, watering is indicated. A lactometer reading above thirty-three, and a low lactoscope reading, indicate skim- ming.” L. P.J IV. METHODS OF EXAMINATION In order to determine whether adulteration has taken place or not, the examination should cover the follow- ing: The specific gravity of the milk and of the whey, the fat content of the milk, the amount of milk solids, the amount of solids not fat, the specific gravity of the solids, the quantity of fat [and the percentage of ash]. Sometimes, the examination is extended to include the taking of a herd sample under special conditions in order to make a comparison between the sample officially collected and the milk offered for sale. Finally, foreign ingredients are tested for, as ni- trates, starch, [preservatives, artificial color, ‘‘ visco- gen,’’ gelatin, ete.]. a. Taking samples for laboratory examination must be conducted with great care. Upon standing, the cream quickly rises to the top, so that the upper part of the milk contains more fat, even though no definite layer of cream has yet been formed. Therefore, before the test METHODS OF EXAMINATION 201 is made, the milk should be well mixed. In milk that has been thoroughly chilled, it is diffieult to again mix the cream equally, so one must be very exact in taking the sample. It often happens, in the milk shops, that the milk is not well mixed when sold and an examination of what is left may show so low a percentage of fat that one immediately becomes suspicious that adulteration has taken place, although it may not he so. b. Preserving the sample for analysis. If the milk sam- ple is to be kept or shipped, it is necessary to add a pre- servative. For this, potassium dichromate (} grm. to 1 liter) is used, which keeps the milk fluid for a long time; this addition causes an increase in the specifie gravity and the result of the chemical examination is also af- fected. This must he taken into consideration at the final test. It is generally better to add 20 drops of fomua- lin to every liter, yet in this case it is possible that the specific gravity of the whey may be affected, on account of a partial splitting of the casein. It is still better to boil the filled bottle and then close it with a sterilized cork. In taking the sample, it is also necessary to avoid adding water even in the slightest quantity (rinse the bottles with milk), in order that no nitrate shall be added. c. The herd sample. In cases in which adulteration is suspected, comparison may be made of the milk under suspicion with that of the herd milked under super- vision. The importance of the stable, or herd test has been much overestimated. The great variations in the composition of the milk of individual animals, leads one to be careful in putting confidence in a comparison of the fat content of milk on different days; but comparisons may fairly be made between the quantities of solids not fat and the specifie gravity of the whey, which are fairly regular. The stable or herd test is very uncertain, therefore, for individual cows, or small herds, but it may 202 MILK HYGIENE sometimes be used with advantage for large herds, al- though there is seldom cause, even in this case, to apply it. In taking a herd sample, the feeding and the care of the animals should not be varied in any respect, the milking should be conducted by the usual persons at the usual times and in the usual way; less thorough milking gives lower fat content, while particularly thorough milking raises the percentage of fat. The quantity of milk for the day must be mixed together and the sample taken from the whole. As transitory changes occur in the composition of the milk, surer results will be gained from daily examinations for several days than from but one examination. d. Determining the specific gravity of milk and whey. Various instruments are used for this purpose: different areometers, the pycnometer or the hydrostatic scale. The areometer method is the simplest and, at the same time, it is sufficiently accurate, so there is no occasion to describe more in detail the other methods, which require weighings. Quevenne’s lactodensimeter, in some one of its sev- eral modifications, is the areometer in common use. This is made like an ordinary areometer and divided into degrees which correspond to a specific gravity from 1.014 to 1.040, or only from 1.022 to 1.038, since, by the latter division, a greater space is gained between the different degrees, without unduly lengthening the in- strument. From such a lactodensimeter one can easily read off four decimal places. The milk whose specific gravity is to be determined is well shaken and poured into a high glass cylinder of suitable diameter; the areometer is dropped in slowly, in order to prevent its bobbing up and down. [The bulb should be free from adhering air bubbles.] The figures LACTOMETER TESTS 203 on the stem are the second and third decimals of the numbers of the specific gravity, so that 34 is to be read 1.034. For this examination, the temperature of the milk must be 15° C. (60° F.); if it is not, the specific gravity of the milk at 15° C. must be calculated from the specific gravity found and from the temperature, for in milk inspection and analysis this is the standard. With the aid of the tables on pages 204 and 205, one of which is valid for whole milk and the other for skimmed milk, one can casily compute specific gravity for 15° C. from that found at another temperature. If the temperature of the whole milk is 18 C., and the lactodensimeter reads 29, one finds in the table, at the intersection of the perpendicular column 18° C and the horizontal line 1.029, the number 29.6; the specific gravity is therefore equal to 10296 at 15) CL (See tables, pages 204 and 205.) In several of the lactodensimeters (¢.g., Soxhlet’s) there is a thermometer in the instrument, whose scale does not show the degree of heat but gives directly the decimal to be added to or subtracted from the reading on the stem of the laetodensimeter, as the specific grav- itv. If the latter number is, for example, 29, and if the thermometer registers 3.5 above zero, the specific grav- iis at Lor 1s Lee. [The so-called New York Board of [Health lactometer has an arbitrary scale divided into 120 equal parts. One hundred on this seale corresponds with a specific gravity of 1.029, which was supposed to represent the lowest specific gravity of pure milk, and 0 represents 1.000, the specific gravity of water. If the specific gravity of a sample of milk fell to 90 it was supposed to be 90 per cent. pure, that is, to contain 10 per cent. of added water. But the specifie gravity of milk varies so that this cannot be relied on and there is no single advantage MILK HYGIENE 204 ‘yoyuaIyRY sainjeroduay, 00°89 | 06°99 | of F9 | 09°S9 | 08'0G | 00°6E | oB'LG | oF'GG 908 Ts 00°0G | 08'8F | oF OF | 9° FF | 08° SF S98 | OOS | “ag | Fes | wes | OE | LTS | FFE | ate OFS | Wes | Pee T&& Se0'T ees | OSS | LE | FFE | oS | OFS | BES | Ges | ESE | Tes | Bce | LEE Ses OGE PEO T STE | OFS | AES | FES | wcs | OSE | Vs | HSE | Fas | SSS | OBE | STs | ole SIs €€0'T ECS | OSE | LBS | FoS | Gc& | OTE | STS | PTS | FIE | SIS. | OTE | SOE | FE FOS o€0'T S68 | OCE | LTS | FIE | cE | OTE | SOE | HOF | FOE | SOE | OOS | 86e | 16s | $66 TEO'T GTe | BOS | NOE. FOS | ZOE | OOS | 8'6Z | 96% | Fea | 762 | 06% | F8e | LE | ose 0€0'T GOS | 66S | 96% | F6E | G'6S | O'6S | 8'8S.| 98S | Fe | 78s | Tse | OLE | SLs YL 620°T Ge | 68S | WSs. FSS | GS | OSS | MLS | He | Fle | SS | VLse | O2% | 69d L9G 820'T 8s | ete | wie | FLe | Ste Lo | 89a | VOT | Sve | S9s | ode | T9S™ | 09% | 8°oS L420°T TL6 | 696 | 9G | FH | CMG | VG | Vee | Hes | EGa | Fes | Ses | VGa | O's 8To | 920'T 09S | Yes | 9o FC |! ede | OGG | VFe | FE | SFG GFE | Sta | VRS | OTe seo | GZ0'T OGS | Ste | Va | FRG | GFE | OFa | 8&G | Oe | Gea | FSS GSS | LSS BCG | ¥C0'T OFS 'M6a | FEC | GEG | OG | Gs | VGS | Goa | Fea | Sse | Gas | Toa O16 €20'T OES | Seo | Es | Foo | Goa | O@ | SIS | MTS | SI’ | PIS | Els | Sle | TTS | 80E 660°T OCS | SIS | Fle | FIZ | TIS | OTS | SOs | 90s | GOs | FOS | Sos | FOS | Toe 6'6L TZ0'T 6G | 206 | G0e | F0e | Toe | OOS | SST | MST | SKIT | FEL | SGI | GSI | Tél O61 020°T 66L | L6L | S6L | S6T V6r | OBL | SST | LZ8L | M8~l | St | FST | Est stl Ust 610'T 00% | o6T | o8T | ohLT | o9T | oGf | oFL | o€T | oBT | oTT |} OT 06 | o8 ob | 09 i : ) SPLAw ID oytoedg -apBiStued soimyeiod way, ‘AMNLIVANMNAL OL YNIGHOOOY MITTIN DIOHM HO ALIAYYS O1dIDGdS GHL DNILOHAYOD YOd ATAVL 5 () » SPECIFIC GRAVITY DETERMINATION 20°89 | 26°99 | ar | 6 0r cOF | 66S TCE | CRE TRE | OLE Vlg | 698 OO Nee o¢cs OFS | OES | XGE OES BOE L0s 66a Lbs Wxa | Ls Giz | i 69 LNG 8'ge | WG Rte | WS See WES “AMA LV UA CL OL on Vou 1s COE 6G ago OSG ele 9G PYG | FHC | F'8% oF 9 | 09 69 FOF PE Fes Pig roe YE rre FEE Foe TTS f0E RG L8G ele L9G G&G GFE oF OO 08°09 o OF e6E ORE ols | Yyoutaygeg saujrodu1w yz 00°6S° (YOr (VCS OTE og O66 OSG Ol6 9G OSG FG OSS o6 LG oF GG xO0E MOE Sb 66 Wee ORG wlio le Naa OG Nee WS wto Fe Oa | Ls ees wer 6 6e ree Pe es Pe ree rte CEE ese Clg eg vba eRe eB £98 OGe co o Fes Fee PTS FOe Pe FSG LB 9% ro PF wes Woo eSe &6E To CTe f06 be E86 GLE £96 remera ts a GG 06 8F HONG (SE ee 1 Toe (ie Ut Oke aE neTE COE | wba 1 ENG | @1% | a9 eos ets ce aa OF | OFF 8'CP WRE | LNE GLE! (2S O98 yee | FE "OO Oe 1 aes | Ve age | Wee GE ge Te Tok O08 | Org l6a 06a | 066 Txa | 183 | [xe [26 | T T96 P96 P96 Pee Ute Oka | VG 460, Lo GO| 6G oGT apRasHuyy saangwuodaoy 1 o6L t 1 oll DNIGMUOOY MITA GHWWIMS 10 ALIAVYD 06 MMOAdS CL ONILIGUNO.) “SM yeauar). 0F0'T 6£0'T 8e0'T LEO'T 9€0°T GEO'T PEO'T ee0'T o£0'T Te0'T 0€0'T 620'T 820°T L60'T 920'°T GZ0'T ¥20'T €60'T YO OTH VL 206 MILK HYGIENE in this arbitrary scale, which is very confusing. Un- fortunately, however, it has come into rather general use among milk inspectors, especially in the Hastern States. To convert readings of this lactometer into corre- sponding readings of the Quevenne scale, they must be multiplied by 0.29, or, the following table may be used: QUEVENNE LACTOMETER DEGREES CORRESPONDING TO NEW YORK BOARD OF HEALTH LACTOMETER DEGREES. Board of Board of ; Board of Ra cece | ES aces | seer 61 17-7 81 23-5 101 29-3 62 18-0 82 23-8 102 29-6 63 18-3 83 24-1 103 29-9 64 18-6 84 24-4 104 30-2 65 18-8 85 24-6 105 30-5 66 19-1 86 24-9 106 30-7 67 19-4 87 25-2 107 31-0 68 19-7 88 25-5 108 31-3 69 20-0 89 25-8 109 31-6 70 20-3 90 26-1 110 31-9 71 20-6 91 26-4 111 32-2 72 20-9 92 26-7 112 82-5 73 21-2 93 27-0 113 32-8 74 21-5 94 27-3 114 33-1 75 21-7 95 27-6 : 115 33-4 76 22-0 96 27-8 116 33-6 77 22-3 97 28-1 117 33-9 78 22-6 98 28-4 118 34-2 79 22-9 99 28-7 119 34-5 80 23-2 100 29-0) 120 34-8 L.P.] Specific gravity of the whey. In many cases it is of value to determine the specific gravity of the whey be- cause this is much more constant than that of milk, for the reason that the lactose and salt vary less than the fat. SPECIFIC GRAVITY OF WHEY 207 Lescoeur warms the milk to 45° C. (113° F.) and adds rennet; after about one-half hour the whey is pressed out and filtered, then it is cooled to exactly 15° C.; the specific gravity may then vary between 1.029 and 1.031, but if water has been added it decreases significantly, as shown below: Whey of pure milk = 1.0300 Whey of milk+ 10 per cent. water = 1.0275 Whey of milk + 20 per cent. water = 1.0251 Whey of milk +30 per cent. water = 1.0230 Reich recommends that 20 ¢.c. glacial acetic acid be added to 500 ee. milk, that the mixture be well shaken and heated for 5 to 6 minutes to 60° to 65° C. (140° to 150° F.) ina elosed flask, then cooled and filtered; the filtrate is to be heated in a flask until the albu- min coagulates, then filtered again and the spevifie eravity determined after cooling to 15° C. Aceording to his results, this varies between 1.027 and 1.029; a specific gravity of 1.026 is always a sign of the addition of water. If one wishes to apply the determination of specific gravity of whey to milk inspection, it is necessary to develop a definite method, which must be followed out exactly, for, otherwise, the result is uncertain; and he- fore basing a prosecution on the results of this method, one must have made eareful comparisons, with the same method, of normal and watered milks. From investigations that were undertaken in Copen- hagen under Jensen’s direction, it appears that these two methods do not give uniform results. From 35 milk samples the following results were obtained: Rennet method Acid method Specifie gravity Specifie gravity 7 samples 1.0270 to 1.0274 2 samples 1.0257 to 1.0259 7 ff 1.0275 to 1.0279 10 " 1.0260 to 1.0264 15 ae 1.0280 to 1.0284 15 f 1.0265 to 1.0269 1.0270 to 1.0276 St 6 : 1.0285 to 1.0290 208 MILK HYGIENE The addition of water causes a lower specific gravity of the whey. In the examination of adulterated skimmed milk, he found the figures to be 1.0256, 1.0246, 1.0254 and 1.0257 (rennet method) and 1.0242, 1.0234, 1.0238 and 1.0241 (acid method). e. The determination of the fat content of milk. There are many methods for determining the fat content of milk; some of these are too inexact to be considered (e.g., the above mentioned transparency test by means of the lactoscope, and the like), others give very good results but require rather expensive apparatus, still others require exact weighings and work that can be done only in chemical laboratories. Some simple tests are, however, so accurate and so practical that they are available for the work of milk inspection. Among the methods used, besides the transparency test already mentioned, the creamometer should be named, that is, the measurement of the layer of cream which rises when the milk is allowed to stand. Since, however, the thickness of the layer of cream furnishes no reliable gauge as to the fat content, this method can- not be used if there is to be a prosecution. The separa- tion of the cream by a centrifuge of high velocity (Fjord’s test), and subsequently measuring the layer of cream, gives better results and is often used in cream- eries for comparing milks. For general use, however, it is impractical, and not sufficiently accurate. The available methods are, principally, Soxhlet’s method, which was formerly used to a greater extent than it is now; Gerber’s method, [the Leffmann-Beam and the Babcock methods] and methods of chemical analysis. Soxhlet’s method is founded upon the following prin- ciple: the solution of the fat in ether and the determina- tion of the specific gravity of this solution. GERBER’S FAT DETERMINATION 209 The following appliances are necessary for this examination (see Fig. 20): (1) three pipettes of 200, 60 and 10 e.c.; (2) several half liter bottles; (3) two delicate areometers with thermometer, one for whole milk and the other for skimmed milk; (4) one large glas. tube (A) adjusted for flowing water; (5) a smaller glass tube (B) enclosed in A; (6) a rubber bulb with a tube; (7) a larger container filled with water heated to 17° to 18° (. Besides these, the following chemicals are necessary: (S) potassium hydroxide solution of specitie gravity 1.27 (400 er. potassium hydroxide is dissolved in water and after the solution has cooled it is made up to 1 liter); (9) ether, shaken with one-fifth its volume of water and decanted oft; (10) ordinary ether. The milk to be examined is warmed in a water bath to 18° C. and is well shaken. By means of a pipette, 200 ¢.. of this are drawn off and inixed in a bottle with 10 ee. of the potassium hydroxide solution. Then, 60 ¢.¢. of ether are added. The bottle is immediately elosed by a perfectly tight stopper, is violently shaken and allowed to stand one-fourth hour in water at 18° C., during which time it must be shaken frequently. Gradually, the ether dissolves the fat and a transparent layer is formed on the surface. Now the stopper of the bottle is replaced by another (D) and, by means of a bulb, the transparent fat-containing ether is driven up into the tube B which is surrounded in tube A by water warmed to 18° C. The areometer (() is in the inner tube, and after the fluid rises so high that it ean float, the flow is cheeked hy means of a valve q, then the specifie gravity is read. The quantity of fat dissolved is shown, and from this the fat content of the milk can he ealeulated. Soxhlet’s apparatus is xecompanied by tables from which the fat content of the milk ean casily be read, if one has determined the specitie gravity of the fat-ether, and has read its temperature. Gerber’s acidobutyrometer affords a very convenient and aceurate way of determining fat, that is widely used. The method consists in measuring the quantity of fat in an aceurately measured quantity of milk, after the fat has been separated and dissolved in amyl-aleo- hol. Gerber’s instrument (see figs. 21 and 22), consists of a centrifuge, bottles (G) of special shape, and 3 pipettes, ie.: 1 acid pipette to hold 10 e.c.(H) and 2 small pipettes (1, K) of 1 and 11 ¢.e. eapacity. These chem- 14 210 MILK HYGIENE icals are required: crude sulphuric acid of a specific gravity at 15° C. (60° F.) of 1.825, and amyl-alcohol. The examination is made in the following way: 10 ce. Fic. 20. | it I Tl rn i il Y | Soxhlet’s apparatus for fat-determination. of sulphuric acid are measured out by the acid pipette, this is permitted to flow slowly into the bottle G; 1 ce. of amyl-alcohol is measured and poured carefully into GERBER’S FAT DETERMINATION ul. the glass so that it forms a layer upon the surface of the sulphuric acid. Now, exactly 11 ¢.c. of well mixed milk that has been heated to 15° C. (60° F.) are measured and poured into the bottle, which is closed by a rubber stopper and then it is well shaken. The milk dissolves with the generation of considerable heat. The stopper is driven in so far that in the inverted bottle, the fluid Fie, 21 Grerber’s apparatus for fat-determination. reaches the mark 0 on the seale; the bottle is put into the centrifuge and this is set in motion, after it has been well balanced. If the sample is not to be centrifuged at onee, the bottle should be placed in a water bath at 60° to 65 C. (140° to 150° F.). The process of centrifuging lasts 10 minutes with such a machine as shown in figure 21; and in order to keep up speed it is necessary to ac- 212 MILK HYGIENE celerate the motion three times, by drawing the strap. [With some patterns of centrifuge, these that have a velocity of 800 to 1000 per minute, the whirling is com- pleted in 3 to t minutes.] After centrifuging, the bottle is taken out and placed in a water bath at 60° C. (140° F.). The fat forms a clear layer in the top of the tube. Through shifting the stopper, the lower border of the Test bottles and pipettes used in connection with Gerber s method for fat-determination. fat layer can be brought into the same plane with one of the division lines and the thickness of the layer of fat can be read off. One should read from the lower part of the curved upper line. The upper, narrow part of the tube is divided in 90 parts, each line corresponds to 0.1 per cent. fat; for example, if the fat laver reaches line 35, then the fat content of the milk is 3.5 per cent. LEFFMANWS FAT DETERMINATION 213 [The Leffmann-Beam method (sometimes, improp- erly, called the Beimling test) was worked out in ad- vance of the Gerber test, which resembles it. The fol- lowing description is from Leffmann:** ‘‘ The dis- tinctive feature is the use of fusel oil, the effect of which is to produce a greater difference in surface tension between the fat and the liquid in which it is suspended, and thus promote its readier separation. This effect has been found to be heightened by the presence of a small amount of hydrochloric acid. “The test bottles have a capacity of about 30 cc. and are provided with a graduated neck, cach division of which represents 0.1 per cent., by weight, of butter fat. ‘“ Fifteen ¢.c. of the milk are incasured into the bot- tle, 3 cc. of a mixture of equal parts of amyl-aleohol and strong hydrochloric acid added, mixed, the bottle filled nearly to the neck with concentrated sulphuric acid, and the liquids mixed by holding the bottle by the neck and giving it a gyratory motion. The neck is now filled to about the zero point with a mixture of sulphuric acid and water prepared at the time. It is then placed in the centrifugal machine, which is so arranged that when at rest the bottles are in a vertical position. If only one test is to he made, the equilibrium of the machine is maintained hy means of a test bottle, or bottles, filled with a mixture of equal parts of sulphuric acid and water. .\fter rotation for from one to two minutes, the fat will collect in the neck of the bottle and the percent- age may be read off. It is convenient to use a pair of dividers in making the reading. The legs of these are placed at the upper and lower limits respectively of the fat, allowance being made for the meniscus; one leg is 63 VIenry Leffmann, Analysis of Milk and Milk Products. Phila- delphia, 1900. 214 MILK HYGIENE then placed at the zero point and the reading made with the other. Experience by analysts in various parts of the world has shown that with properly graduated bottles the results are reliable. As a rule, they do not differ more than 0.1 per cent. from those obtained by the Adam’s process, and are generally even closer. ‘¢The mixture of fusel oil and hydrochloric acid seems to become less satisfactory when lorg kept. It should be clear and not very dark in color. It is best kept in a bottle provided with a pipette, which can be filled to the mark by dipping. Rigid accuracy in the measurement is not needed.’’ The Babcock method or ‘‘ test’’’ is, in America, by far the best known and most used centrifugal test for fat in milk. The Leffmann-Beam and the Gerber tests are, however, being used more and more, on account of the shorter time required. In careful hands, the Babcock test is very accurate. Small or large outfits, the centrifuges to be driven by hand or power, may be purchased from any dairy sup- ply establishment. The test is made by placing in the special test bottle 18 grams (17.6 cc.) of milk. To this is added, from a pipette, burette or measuring bottle, 17.5 ¢.e. commercial sulphuric acid of a specific gravity of 1.82 to 1.83. The contents of the bottle are carefully and thoroughly mixed by a rotary motion. The mixture becomes brown and heat is generated. The test bottle is now placed in a properly balanced centrifuge and whirled for five minutes at a speed of from 800 to 1200 revolutions per minute. Hot water is then added to fill the bottle to the lower part of the neck, after which it is again whirled for two minutes. Now, enough hot water is added to float the column of fat into the grad- uated portion of the neck of the bottle, and the whirling is repeated for a minute. BABCOCK’S FAT DETERMINATION = 215 The amount of fat is read while the neck of the bottle is still hot. The reading is from the upper limits of the mensicus instead of the lower, as with the Gerber and the Leffmann-Beam tests. A pair of calipers is of as- sistance in measuring the column of fat. L. P.] The chemical methods consist in accurately weighing the fat separated from a definite quantity of milk. The Fig, 23. wu t One form of Babcock’s apparatus for fat-determination.* most exact result is gained by the evaporation of a defi- nite amount of milk (see below) and by the extraction of the fat from the evaporated mass by ether or benzine, which is then evaporated. Quite accurate results are also gained without evaporating the milk, by separating © From * Principles and Practice of Butter-Making,” by McKay and Larsen, by permission of Messrs. John Wiley & Sons, the publishers. 216 MILK HYGIENE the fats from the other ingredients and ascertaining their weight. Gottleib’s method gives results sufficiently accurate for our use. For this method one requires, as apparatus, only a cylinder of 40 c.c. capacity, divided to measure quantities of 0.5 ¢.c., some glass flasks and a long, thin glass syphon. 10 grm. of milk are accurately weighed into one of the small flasks and poured into the glass cylinder; the amount of milk left adhering to the walls of the flask is determined by a second weighing, so that one may know exactly how much has been poured into the cylinder. 1 ec. of 10 per cent. ammonia water (specific gravity 0.96) is mixed with the milk and shaken, then 10 ¢.e. aleohol (95 per cent.) are added and it is shaken again, after which 25 e.c. ether are added. The cylinder is well closed with a cork that has been moistened in water, and shaken hard. 25 ee. petroleum benzine are added and, after repeated shaking, the bottle should be allowed to stand undisturbed at least 6 hours. By that time, the fluid is separated into two sharply marked layers; the upper one is the ether-benzine-fat mixture, the under one contains the water, the lactose and proteids; a whitish sediment consists of phosphates. The volume of the upper layer of the fluid is read off and a determined quantity of it is syphoned off into a small weighed flask. The ether and benzine are now evaporated by mild heat. Thereupon, the flask is allowed to stand a couple of hours in a drying chamber at 100° C., is cooled in an exsiceator and, finally, weighed. From the total volume of the mixture of ether, benzine and fat, and from the quantity of fat in the portion evaporated, the weight of the total fat content of the milk sample can be calculated, and thus the percentage is determined. f. Determination of the total solids in milk. The total solids in milk are determined chemically in the following way: Exactly 10 ¢.c. of milk are measured into a plat- inum or porcelain vessel, the weight of which is already known; the vessel is heated in a water bath to 100° C. until all the water is evaporated. After cooling in an exsiccator, the vessel and its contents are weighed. The difference between the weight found and the original weight of the dish gives the total amount of solids in the milk. If the amount of fat, found in another way, is DETERMINATION OF SOLIDS BLL subtracted, one gets the quantity of solids not fat. By incinerating the contents of the vessel, in a muffle oven, and again weighing, the amount of salts, or ash, is deter- mined. If it is desired to extract the fat from the other solids, to determine the fat percentage, it is necessary before drying the milk to mix with it a weighed quantity of roasted pumice stone; then, after evaporation, the fat is removed hy ineans of ether (or benzine) in an ordi- nary fat extraction apparatus, and is determined by weighing, after evaporating the ether. This work is quite particular and requires a well appointed labora- tory. Moreover, in practical milk control, gravimetric analyses are not indispensable, for one can easily cal- culate the quantity of solids from the specific gravity and the fat, according to the formula derived hy Fleisch- mann. If total solids are represented hy t, the fat per cent. by f and the specifie gravity by s, one has: 100s — 1000 s t= "2% £ + 2.605 207 That is, if wesay f- 3.55 and s —= 1.0327, we get 12.697 2 pee LOOX 1.0327 —- 100 a3 Ron Bye7 t= 12 3.454 (2.005 SS ase: ) = 4200 fetes Another formula proposed by Bertschinger gives quite accurate results: 5f + 100s seas aaa + 0.07 Moreover, tables have been worked out from which the total solids can be read off, if both the other factors are known. Ackermann has constructed an ‘‘ automatic reckoner *’ from which one ean read off one of the fac- tors when both of the others are known, by simply turn- ing circular dises. [Richmond has devised a sliding rule for the same purpose. ] The computation of the solids not fat is very easy. 218 MILK HYGIENE One has only to subtract the fat percentage found from the computed percentage of total solids. The percent- age of fat (p) in the total solids is easily computed according to the formula: p= +x 100 To use the above illustration: p= Bias X 100 == 27.95 Likewise, it is quite easy to determine the specific gravity (m) of the dry milk solids by a simple computa- tion, according to this formula: st ™ =~ st — (100s — 100) Using the same illustration again: 1.03827 >< 12.697 13.112 = 10887 < 12.697 — (103.27 100) ~~ T3a12—s.a7 — 1384 m The specific gravity of the dry solids of whole milk varies, according to the fat content, between about 1.31 and 1.36. V. ADULTERATION AND ITS DETECTION. The most frequent adulterations of whole milk con- sist in partial skimming, dilution with skimmed milk, dilution with water or a combination of these. Skimmed milk is adulterated by the addition of water, and cream by starch, flour, ete. a. Partial skimming of whole milk or dilution with skimmed milk produce the same result; in both cases the fat content is lessened, while the percentage of solids not fat is increased very slightly, and the specific gravity is increased. If the skimming is not so great as to cause the fat percentage to fall below the minimum limit for DETECTION OF ADUELTERATION 219 mixed milk and the specific gravity to rise above its maximum (1.034), this adulteration is difficult to dis- cover, as the considerable variations in normal milk would lead one to expect. It is in these cases that com- parison was formerly made with the stable or herd sam- ples, but, as stated before, these are worth but little in relation to small herds, and even in the case of large ones they are not entirely trustworthy. When it is pos- sible to compare the figures of inspected milk with the results of the herd test, an opinion can be formed as to how great a percentage of the fat content is lacking, from this formula: F—f x- 100 - x I in which F shows the fat percentage in the herd sample and f the fat percentage of the sample under suspicion. Where there is reason for suspicion, the best method for proving the existence of such adulteration ts, in many eases, furnished by the judicial hearing of the persons charged, and the witnesses. In many places, as has already been stated, to prevent such adulterations a minimum standard has been established for the fat con- tent of whole milk. [In America, where there are legal standards calling for 3 to 3.5 per cent. of fat in whole milk, prosecutions for partial skimming or dilution with skimmed milk are not often brought if the sample comes up to this estab- lished standard, although such adulteration may be suspected from a marked disproportion between the fat and the solids not fat. But this proportion is, at best, so variable that it furnishes no definite guide. Tx, P.] Ul. The dilution of whole milk with water causes an increase of volume and, therefore, a decrease in the per- centage of fat, of solids and of the specific gravity of the 220 MILK HYGIENE milk, as well as of the whey. Feser gives the following example: Start with 9 liters of milk of the composition: 3.95 per cent., fat; 8.9 per cent., solids not fat; 1.031, specific gravity. To this add 1 liter of water of this composition : 0 per cent., fat; 0 per cent., solids not fat; 1.000, specific gravity. This gives 10 liters of adulterated milk of the com- position: 3.55 per cent., fat; about 8.0 per cent., solids not fat; 1.028, specific gravity. Further evidence of this adulteration is found in the lower specific gravity of the whey and in the fact that the specific gravity of the dry solids (m) and the fat content (p) of the solids are, practically, normal; in the above example, then: *4 ass sT ee 1.031 X 12.85 1324 _ 4 a5 ~ $T — (00S — 100) 1.031 x 12.85 — (100 X 1.0831 — 100) 10.14 —C a st ot 1.028 “ 11.55 _ 1873 _ 4 597 BS (100s — 100) 1.028 7 11.55 — (100 % 1.028 — 100) ~ 9.073 ~~” Ew 3.95 ana P= + X 100 fogs ~ 100 = 30.738 = x 100 = 3 x 100 = 30.736 p= t * ie5 = 130, If milk samples are available which may be justly com- pared with the milk under suspicion (herd samples taken under fixed conditions; milk from the same large herd; other milk sent by the same shipper or from the same can in the dealer’s possession), then the percent- age of water added can be computed according to Vo- gel’s formula: x= Xx 100 + 100 54M and P represent the specific gravity of the total solids and the percentage of fat in the total solids of whole milk, and m and p the same factors in adulterated milk.] DETECTION OF ADULTERATION 221. In the example just given we have F —=3.95 and f = 5.55, then B95 ‘ p55 100 + 1000 11.11% x that is, exactly 1 part to 9 parts. On account of the great variations in the percentage of fat, one must be very careful with this computation. In detecting this adulteration, the herd sample is of some value, since the solids not fat are subject only to shght variations. In drawing conclusions, therefore, these other factors must have full consideration (esti- mated solids not fat, specifie gravity of the whey), and are of more value as a guide than the percentage of fat. [The percentage of solids not fat should not he less than 8.5 or 9. The percentage of ash is of considerable value in detecting adulteration by adding water. This factor is rather constant, and in pure milk is usually between 0.70 and 0.75 per cent. L.P.] It has been suggested that use be made of the deter- mining of the freezing point of milk and of its conducti- bility for clectricity, since these qualities are consid- erably changed by the addition of water. But these methods are not vet sufficiently developed to he avail- able. On the other hand, there may be some advantage in determining the acidity of the milk, since this is less- ened by dilution (see page 227), yet the lessened acidity may come from other causes. The addition of lactose or cane sugar to milk diluted with water, renders judgment more difficult, since, by this means, the specific gravity of the milk as well as that of the whey, and also the amount of solids not fat, is Increased, While milk is always free of nitrates and nitrites, even if the animals have taken such substances with 222 MILK HYGIENE their food, these are frequently present in water in small quantity. The presence of nitrates or nitrites in the milk, therefore, shows, with certainty, that water has been added. However, the lack of nitrates does not ex- elude this, as all water does not contain nitrates. Even a very small quantity of nitrates and nitrites can be detected as follows: 1.5 ee. of a 20 per cent. calcium chloride solution is added to 100 ec. of milk; the mixture is boiled and filtered. A little of the filtrate is mixed with enough of a 2 per cent. solution of diphenylamin in sulphuric acid to make it milky; a little concentrated sulphurie acid is poured into a test tube and the mixture is added slowly, so that the fluids do not mix; if nitrie acid or nitrous acid is present, a blue zone is formed at the plane of contact. (Soxhlet.) [A simpler test for nitrates is that devised by Richmond. The following description of this test is from Farrington and Woll.®® “Place a small quantity of diphenylamin at the bottom of a porcelain dish, and add to it about 1 ¢e. of pure, concentrated sulphurie acid; allow a few drops of the milk serum (obtained by adding a little acetic acid to the milk and warming) to flow down the sides of the dish and over the surface of the acid. If a blue color develops in the course of ten minutes, though it may be faint, it shows the presence of nitrates, after ten minutes a reddish-brown color is always developed from the action of the acid on the serum. There should be no difficulty in detecting an addition of 10 per cent. of water to the milk by this test, if the water added contained 5 parts of nitric acid, or more, per 100,000.” L. P.] c. The skimming of whole milk in conjunction with the addition of water, or the addition of skimmed milk as well as water, are common methods of adulteration. Tt is easily understood that the fat content is consid- erably lessened in this way, and that also the solids not fat decrease; it is evident, besides, that the percentage of solids not fat (p) 1s lessened and, consequently, the 55 Warrington and Woll. Testing Milk and its Products, 13th edition. Madison, 1904. DETECTION OF ADULTERATION Bea specific gravity of the solids (m) must be increased. The specific gravity of adulterated milk can vary consider- ably, often it ix nearly normal, but frequently it is slightly diminished. Feser has given the following ex- ample of such adulteration: The unadulterated milk had 3.95 per cent., fat; 8.9 per cent., solids not fat; 1.031 specific gravity; by par- tial skimming, it was changed to 2.19 per cent., fat; about 8.9 per cent., solids not fat; 1.034, specific gravity ; hy the addition of water it was further changed to 1.21 per cent., fat; about & per cent., fat free solids; 1.0305, specific gravity. Decisive points for determining if such adulterations exist are the low solid contents, the low fat per cent., the almost normal specifie gravity of the milk, the in- creased specific gravity of the solids (m) which, in the above example, was changed from 1.305 to 1.473, and in the low specific gravity of the whey. If nitrates are proven in the milk there is further support for the con- clusion that it is watered. When a sample of adulterated milk can fairly be compared with another whieh is known to be unadulter- ated (samples taken from the same dealer the same day, milk of a large herd, cte.) [or with an accepted stand- ard] one can form an opinion of the extent of the adulteration by means of a formula derived from Bohm- lander: R M - . xw—W ih 100 ( a He Ir M shows the quantity of water added to 160 grm. of milk; W is the per cent. of water in the unadulterated and w in the adulterated, or suspected, sample; R and r are the percentages in these two samples of solids not 224 MILK HYGIENE fat; EX represents the percentages of fat removed by skimming, while F and f show the beneentage of fat in the two satnoles, In the above case one could find by computation: M= “3 < 90.79 + 87.15 = 1.112 & 90.79 — 87.15 == 13.81 1.21 “4 8.9 10.77 E = 100 (1 — 3.95 02 a) =10 (1 — = 66 Or, in other words, about 14 grm. of water are added to each 100 grm. of milk and about 66 grm. of fat have been taken from each 100 grm. of fat. The effects of the various adulterations may be shown in tabular form as follows :* = b be 3 be gs eee ee lee eee | ge Ba | Be | & &2 |S | Sa fo So. od ° a sg £ an ote $ aa £ gga es ea B ag |eso] sic ie e923 a+ =o O.: o-n ps ered snes a S28 gee gx | £3 | Exe | ESE] Sz | g85 aA? Zc oe oR BOE | GAR 55 ae wm wo [oi Ay | uw Ra Aa Ay 1.029 to - Vk 1.034 |1.029to|] . x | 85to | 1.30to |] 20to 0.7 to Normal milk........ aver Lost | 3 tod 10.5 134 34 0.75 0 Skimmed or diluted Mb aa no very). with skimmed milk 5 | higher change lower |slightly higher} lower | higher 0 8 higher | Water added ........ S| 3 " a | no no ne ae 1| lower | lower | lower | lower change |change lower | + or0 slmmed an : water added....... { ‘change lower | lower | lower | higher]| lower | lower | + or0 Although each form of adulteration has its own char- acteristics yet, in practice, it is often very hard to deter- mine whether a slight adulteration has occurred, be- cause the composition of milk, as explained above, dif- fers so much physiologically—and with the same animal from day to day. Unless there is a distinct departure from the normal, one should be careful in expressing his opinion, especially if he does not know the herd con- * This table is changed somewhat from the one prepared by Jensen [L. P.] DETECTION OF ADULTERATION 22) cerned. Usually, the presence of nitrates is positive, still it must not be forgotten that when the milk can is rinsed a little water may be left, which, if it is rich in nitrates, may cause the milk to show a slight reaction, so that it might appear that water has been intentionally added. Usually water does not contain such a quantity of nitrates as to cause a suspicious reaction when the milk has not really been adulterated. d. Adulteration of partly skimmed and skimmed ‘milk. In most cities no minimum limit is fixed for the fat content of the half skimmed and the skimmed milk, and the only form of adulteration to he considered in this connection is the addition of water. This causes a lowering of the specifie gravity of the milk (from 1.030 to 1.036 to from 1.032 to 1.040) and whey, as well as a diminution in the amount of solids. .\ possible trace of nitrates proves that the milk has been watered. In cities, in which the minimum limit of fat content for partially skimmed milk or skimmed milk has been cs- tablished, the milk is, of course, considered adulterated when it falls below this standard. [In some places there is a standard of 9.25 per cent. total solids for skimmed milk as provided by the U. S. Department of Agricul- ture. ] ec. Adulteration of cream. Cream is sold in different forms, with fat content varying between about 10 per cent. and 30 per cent. (40 per cent.). In some cities, the minimum content of different grades is defined, so in such eases public control must be extended to determin- ing the amount of fat in cream. Of the different adul- terations, the addition of starch and flour are to be mentioned particularly. This is done to make the cream thicker and to give it the appearance of being better than it really is. In raw eream, the proof by micro- scopic examination is simple, as the starch grains are 15 226 MILK HYGIENE shown as irregular, round concentrically formed bodies. Amyloid bodies have been found in milk by Herz; these are like similar bodies previously found in the pros- tates, and somewhat resemble starch grains, but are hardly to be found in such great quantity that, in prac- tice, they have any influence on this examination. After the cream is boiled, the starch grains burst, and cannot be recognized under the microscope. In this case, the chemical test must be applied, which may be used with raw cream also. The simple addition of a diluted solu- tion of iodine, in many cases, gives the milk the well- known blue color; it is better, however, to add a little acetic acid, boil and filter and apply the iodine test to the filtrate. [The presence of ‘‘viscogen”’ is indicated by the greater percentage of ash. ] The detection of other foreign substances, as white earth, emulsion of brain substance, etc., is best made by means of microscopic examination. VI. PUBLIC SUPERVISION TO PREVENT THE SALE OF DETERIORATED MILK The public should not only make and enforce regula- tions regarding the production and handling of milk to prevent adulteration, but it should make regulations to prevent milk being sold in a damaged or spoiled con- dition and, by frequent inspection, these regulations should be enforced. The milk samples that are taken must not only be used for the purpose of determining possible falsification but, at the same time, they should be subjected to a number of other examinations. a. Determination of the appearance, odor and taste. All milk differing from normal in color or appearance (mix- ture of blood or exudate, abnormal secretion, secretion of coloring matter, bacterial alterations), or by odor or taste (abnormal composition, the excretion of odorifer- DETECTION OF DETERIORATION oet ous substances, absorption of strongly odorous matter, addition of foreign matter, bitter, stale, sour, microbic changes) must not be sold and should be condemned. b. Determination of the reaction. This may be done by using red and blue litmus paper. Normal, quite fresh milk has an amphoteric reaction. If the test shows ex- cessive alkaline or acid reaction, it should be examined more closely. An alkaline reaction is frequently shown in the milk of old milking cows; mixed milk, on the contrary, is never alkaline. Sometimes an alkali is added; if so, it can be proven by the test previously mentioned, or, quite easily, by titrating with tenth- normal sodium hydrate solution, with which phenol- phthalin is used as indicator. Normal milk shows an acid reaction to phenolphthalin, so that from 18 to 19 c.c. of tenth-normal sodium hydrate solution must be added to 100 ee. of milk to make the red color appear; if the milk becomes red at onee when phenolphthalin is added, then it is abnormally alkaline and, as a rule, alkali has been added; if a smaller quantity of sodium hydrate solution is necessary, the milk may either have been treated with alkali or diluted with water. If the litmus paper indicates an acid reaction, the degree of acidity of the milk may be determined by means of titrating with tenthnormal solution of so- dium hydrate, using phenolphthalin as indicator. If, to neutralize 100 ¢.e., requires more than 1S to 19 c.c. of tenth-normal sodium hydrate solution, then the for- mation of lactic acid has commenced, and its extent can be measured exactly by determining the amount of standard alkali required to neutralize it. For titrating, an ordinary burette is used with a scale divided into spaces showing 0.1 ¢.c. After the addition of about 0.25 ¢.c. phenolphthalin solution to the milk, the standard sodium solution is dropped in, little by little, 228 MILK HYGIENE until, after thorough shaking, the milk becomes faintly reddish. Then the exact amount of solution that has been used for neutralization is read off, and the degree of acidity determined. If one has to make many titra- tions it is most convenient to use a burette with a supply from a larger tank; such a titrating apparatus can be procured from any dealer in chemical apparatus. [A rapid method for determining the acidity of milk has been devised, which depends on the use of an accu- rately measured amount of alkali dispensed in the form of a tablet. This makes it possible to quickly prepare a standard solution, and the method is very useful for in- spections in the field. If the indicator, phenolphthalin, is included in the tablet, the test is still more convenient. It is made as follows: Tablets are dissolved in a measured quantity of dis- tilled water, sufficient to give a solution of standard strength (usually five tablets make 100 cc. of solution, but this varies with the brand of tablet and the manu- facturer’s instructions must be observed) 18 grm. (17.6 c.c., being measured in the pipette used for the Babcock test) of milk are measured into a white porcelain cup and the alkali solution is added from a measure (burette or graduated cylinder) until the pink color becomes permanent. The amount of solution used shows the percentage of acid in the sample. If a standard of 0.2 per cent. lactic acid has been adopted, then the amount of alkali solution required to show any excess above this limit may be placed directly in the cup and the measured sample of milk added to it. If the pink color remains, there is less than 0.2 per cent. of acid in the sample; if it disappears, there is more than 0.2 per cent. of acid. L. P.] Only a few German regulations give a standard for the acid permitted in market milk. Sometimes, the THE FERMENTATION TEST 229 requirement is made that the milk shall withstand the test of boiling it in a test tube without the separation of flakes or curds, and be able to withstand the, so-called, alcohol test, which is made as follows :*" Exactly equal parts of milk and alcohol (68 per cent.) are carefully mixed in a tube and observed closely. Fresh milk shows no precipitation; in that which is be- ginning to sour, fine flocules are deposited on the walls of the glass and, with greater acidity, flakes and lumps are separated. c. The fermentation test is used to show whether there isan excess of bacteria of putrefaction in the milk. It consists simply in incubating a sample of milk at body temperature for 8 to 16 hours, followed by an examina- tion as to its appearance, odor and flavor. The examina- tion is easily made as follows: Into large test tubes holding at least 25 v.c., that have been carefully cleaned and sterilized, the milk samples, warmed to about 36° C. (97° T*.), are poured. The tubes are closed hy cotton and placed in an incubator or closet, where they are kept at 30° to 55° CL (86° to 95° F.). In the course of eight ov ten hours, and again later, the contents of the tubes are examined. (ood, undeteriorated milk is then sour and curdled and forms a homogeneous coagulun, without much separation of whey or formation of gas. Fre- quently, gas bubbles have split the coagulum and con- siderable fluid has separated. This change, however, does not necessarily signify that the milk was particu- larly rich in bacteria of putrefaction. On the other hand, if the milk curdles and has an offensive odor, or ’ As a result of boiling, separation occurs not only where the milk has reached a certain degree of acidity but also in eases where, as a result of disease of the cow, abnormally large quantities of albumin and of globulin are present, or when there is admixture of colostrum. 230 MILK HYGIENE if the coagulum is beginning to dissolve, or if the milk remains in a fluid state but has a bad odor and taste, these are signs that the milk is contaminated with bac- teria of putrefaction. In the application of this test, it is important not to allow the milk sample to stand too long before the examination is begun, and precautions must be taken to prevent contamination while gathering the sample and during the test. In pasteurized milk, the fermentation test may give general information concerning the bacterial content, through noting the time that passes until appreciable changes take place. Usually such milk does not ‘“ sour.’’ But no precipitate conclusion should be drawn from the results of this test. By boiling the milk for a short time and then incu- bating the samples, a serviceable guide can be obtained concerning the quantity of the spore bearing bacteria in the milk. These will survive the heating, and, as they are not checked in their growth by the lactic acid form- ing bacteria, they increase rapidly and cause the milk to eurdle, by the action of ferments. [Russell °* describes a curd fermentation test used by cheese makers, as follows: ‘‘ When the milk is 95° F., about 10 drops of rennet extract are added to each sam- ple and mixed thoroughly with the milk. The jar should then remain undisturbed until the milk is completely curdled; then the curd is cut inte small pieces with a case knife and stirred, to expel the whey. The whey should be poured off at frequent intervals until the curd mats. If the sample be kept at blood heat (98° F.), for six to eight hours, it will be ready to examine. ‘«The curd from a good milk has a firm, solid tex- 57 A. L. Russell, Dairy Bacteriology, Sixth Edition. Madison. 1905. BACTERIOLOGICAL EXAMINATIONS 231 ture, and should contain at most only a few small ‘ pin’ holes. It may have some large, irregular ‘ mechan- ical’ holes where the curd particles have failed to ce- ment. If gas-producing bacteria are very prevalent in the milk, the conditions under which the test is made cause such a rapid growth of the same that the evidence of the abnormal fermentation may be readily seen in the spongy texture of the curd. If the undesirable organ- isms are not very abundant and the conditions are not especially suited to their growth, the ‘ pin’ holes will be less frequent. — ** Sometimes the curds show no evidence of gas, but their abnormal condition may be recognized by the “imushy ’ texture and the presence of ‘ off’ flavors, that are rendered more apparent by keeping them in closed bottles. This condition is abnormal anid is apt to produce quite as serious results as if gas was formed.”’ Curd fermentation tests have been suggested for use in connection with the supervision of market milk, and C. I. Marshall has made some observations that tend to show their usefulness for this purpose. L. P.] To make regulations in relation to the behavior of milk to these tests would be premature. The general requirement that market milk, and especially infants’ milk, shall not be rich in bacteria of putrefaection is suf- ficient for the present. d. Bacteriological examinations are made when more information is desired regarding the number and kind of bacteria in milk. .\s has been said, this differs greatly, even in freshly drawn milk, and it is searcely possible to state a passing average for the bacterial content of market milk. Nor does it seem to be possible to estab- lish a maximum by ordinance, the violation of which would Jead to the condemnation of the milk. Yet, it is of importance to health officers to have an examination made of the number of bacteria in milk sold, since, by 232 MILK HYGIENE so doing, an opinion can be formed as to the genuine- ness of the claims of the milk companies, as well as the cleanliness and care with which the milk has been han- dled from the time it was drawn until it was sold. There are special reasons for making regular bacteriological examinations of nursery milk; it must be required not only that this shall come from healthy animals and not be exposed to infection with pathogenic bacteria, but, at the same time, it is well to require that it shall not contain an excess of bacteria at the time it is delivered to customers. In this connection, it would be very ad- vantageous to make a stipulation to the effect that ves- sels [bottles] in which infants’ milk is sold shall be pro- vided with a label giving the day on which the milk was produced.