REPORT ON THE PREVENTION OF MALARIA IN MAURITIUS BY RONALD ROSS D.P.H., F.R.C.S., D.Sc, LL.D., F.R.S., C.B. Nobel Laureate President Honoraire de la SocUti Midicah de tUe Maurice Corr. EtTi, Acadimie de Midecine Corr. Esiero, Accademia di Assoc. Fel., College of Physicians of Pliila Qfficier de I Ordre de Leopold II Major, Indian Medical Service, Retired Professor of Tropical Medicine, University of Liverpool and Liverpool School of Tropical Medicine Medicina di Torino Philadelphia PRINTED BY VVATERLOW AND SONS LIMITED, LONDON WALL, LONDON (Eornell HnittccBitg SItbrarg Jtlfaca, Sfjni fork THE CHARLES EDWARD VAN CLEEF MEMORIAL LIBRARY BOUGHT WITH THE INCOME OF A FUND GIVEN FOR THE USE OF THE ITHACA DIVISION OF THE CORNELL UNIVERSITY MEDICAL COLLEGE MYNDERSE VAN CLEEF CLASS OF 1874 1921 Cornell University Library RA 352.M45R82 Report on the prevention of malaria in IVI 3 1924 000 288 385 REPORT 0\ THE PREVENTION OF MALARIA IN MAURITIUS Mi Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000288385 REPORT ON THE PREVENTION OF MALARIA IN MAURITIUS BY RONALD ROSS D.P.H., F.R.C.S., D.Sr., LL.D., F.R.S., C.B. Nohel LaitreaU Prisiclent Hon or aire de la .Sociiti Mcdicale de Tile Mauri or Corr. Etr., Acadi!//iie de Midecine Corr. Estero^ Aceadeniia di JMedifina di Torino Assoc. Fel.., College of Physicians of rhiladelphia Offuier de I'Ordre de Leopold If Major, Indian Medical Service, Retired Professor of Tropical Medicine, University of Liverpool and Liverpool Scliool of Tropical Medicine PRINTED BY WATERLOW AND SONS LIMITED, LONDON WALL, LONDON To His Excellency Sir cavendish BOYLE, K.C.M.G. Governor of Mauritius Dated, the 15th June, 1908 University of Liverpool Your Excellency, In a letter No. 16148 of the 9th May, 1907, the Right Honourable the Earl of Elgin, His Majesty's Secretary of State for the Colonies, informed me that your Excellency desired me to visit Mauritius in order to report on measures for the prevention of malaria there. With the consent of the University of Liverpool and of the Liverpool School of Tropical Medicine, I was able to accept the duties, and the honour, involved in this mission. In sub- sequent letters the Secretary of State adopted the suggestions that I should visit Mauritius at the commencement of the next malaria season, and that I should remain there at least three months in order to collect the information required for my report. In accordance with this decision, I left' England on the 23rd October, 1907. Arriving in Mauritius on the 20th November, I was able to complete my studies by the 25th February, 1908, on which date I was permitted to return to England, where I arrived on the 28th March. I have now the honour to present for your Excellency's consideration my Report on the Preven- tion of Malaria in Mauritius. VI 2. I trust that I may be permitted, before proceeding to my subject, to refer to several points connected with my visit. On hearing of my mission, Surgeon-General Sir Alfred Keogh, K.C.B., Director-General of the Army Medical Service, was kind enough to appoint Major C. K. P. Fowler, Royal Army Medical Corps, to assist me in the work, especially as it affected His Majesty's troops in Mauritius. Major Fowler arrived in the Colony before me, but left with me ; and I should like to add that I have received from him the greatest possible help in connection with my study of malaria, not only among the military, but also among the civil population. 3. During the visit it was necessary for me to carry out inspections of numerous localities in the Island. I was able to spend ten days at Port Louis, and to examine, sometimes frequently, the principal towns and villages, and many of the sugar estates. I am very greatly indebted to the Hon. Dr. Lorans, Director of the Medical and Health Department, for the excellent arrangements which he made for the performance of these duties, and, not less, for the benefits of his advice and of the information which he collected for me. I owe my sincere thanks, for accompanying and assisting me on many of these inspections, to Dr. Edwards, C.M.G., Chairman of the Town Board of Commissioners of Curepipe ; to the Hon. Dr. Laurent, Mayor of Port Louis ; to the Hon. Sir William Newton, K.C., Chairman of the Board of Ouatre Bornes ; to the Hon. Mr. Trotter, Chairman of the Board of Rose Hill and Beau Bassin ; to the Hon. Mr. Leclezio, Member of the Council of Government for Moka ; to the Hon. Mr. Dumat, Member for Savanne ; to the Hon. Mr. Gebert, Member for Grand Port ; to the Hon. Mr. Duclos, Member for Flacq ; to the Hon. Mr. Souchon, Member for Riviere du Rempart ; to the Hon. VI 1 Mr. Sauzier, K.C., Member for Pamplemousses ; to the Hon. Mr. Antelme, Member for Black River ; and to the Sanitary Wardens of the Districts. 4. It was necessary also to obtain for the purpose of my report much statistical and other information ; and I am much indebted, for the promptness and regularity with which this was collected, to the Hon. Sir Graham Bower, K.C.M.G., Colonial Secretary; to Dr. Lorans ; to the Hon. Mr. Trotter, Protector of Immigrants; to the Hon. Mr. Le Juge de Segrais, Director of Public Works and Surveys ; to Mr. P. Koenig, Director of Forests and Gardens. I am particularly grateful to Dr. Bolton, Medical Officer and Inspector of Immigrants, for the copious information and the most useful advice which he gave me regarding malaria on the Estates ; to Dr. Castel, Dr. Keisler, Dr. Masson, Dr. Milne, of the Health Department, for their laborious computations of the spleen-rates in Schools and Villages ; and to Dr. Bour, Dr. Chauvin, Dr. Clarenc, Dr. Guerin, Dr. Harel, Dr. Leclezio, Dr. Lesur, Dr. Menage, Dr. de la Roche, Dr. Senneville, Dr. Tennant, Dr. Ulcoq, Dr. Vinson, for their similar studies on the Estates. I am much obliged also to Dr. Clarenc and Dr. Lesur for valuable literature reorarding o o the original outbreak of malaria in Mauritius, in 1865-67 ; to Dr. de Chazal for his excellent report on the recent outbreak at Phoenix ; to Dr. Momple for information regard- ing Sanitary Legislation ; to Mr. Naz of the Health Depart- ment ; to Mr. A. Walter of the Observatory, for information on certain meteorological points ; and to Drs. Cretin, Gromett, Lafont, Lesur, Menage, Rouget, and all the members of the medical profession whom I met in Mauritius, for help rendered in various ways. 5. Early in the course of my studies, your Excellency was pleased to place at my disposal the services of vin Mr. d'Emmerez de Charmoy, Curator' of the' Museum, whose early and admirable work on the Culicidee of Mauritius and on malaria there, carried out partly in conjunction with Mr. Daruty de Grandpre, is well known to students of these subjects. The assistance of Mr. d'Emmerez, and, I may add, the voluntary help rendered by Mr. Daruty, proved to be invaluable to us ; without their aid we should not have had time to complete the essential laboratory work which it was our duty to attend to. Major Fowler and I would like it to be considered that, as regards the examination of cases of malaria and of mosquitoes, these gentlemen acted in scientific collaboration with us. 6. The whole subject of the prevention of malaria in Mauritius was frequently discussed with many members of the medical profession in the Island ; and on the 24th January, owing- to the kindness of Drs. Clarenc and Chevreau, President and Secretary of the Societe Medicale, I had an opportunity of considering the matter with that body. I think it may be accepted that there will be a very general consensus among the profession as regards the principal measures to be undertaken. 7. The nature of these measures became evident fairly early in the period of my mission — though indeed they had been recognised long previously. It had therefore appeared to me to be highly desirable that, before the submission of this report, and during my stay in Mauritius, some attempt should be made to commence the necessary organisation on a preliminary scale by training a small staff of men to the work. Your Excellency responded at once to this suggestion by placing the sum of Rs.6,000 at the disposal of the Medical and Health Department for the purpose. Out of this fund ten " moustiquiers '' and ten working gangs of three men each were enlisted, were instructed in the duties described in the Report, and, even before I left, had done a considerable IX amount of work. Moreover, the Chairman of Ouatre Bornes, Curepipe, and Beau Bassin, and the municipality and District of Port Louis commenced similar measures ; the managers of many of the Sugar Estates asked for the services of the moustiquiers ; a small fund, generously subscribed to by the Hon. Mr. Souchon, Messrs. Ireland and Fraser, and the Bank of Mauritius, was started to supply working gangs to certain villages ; and the elected members of Council for the Districts took similar action. On the 29th January 1 had the honour to deliver a public lecture on the subject before your Excellency at Curepipe, and, on the 8th February, a similar one before the Mayor and Councillors of Port Louis. Before I left, your Excellency appointed Mr. d'Emmerez de Charmoy to superintend the malaria work under the Medical and Health Department, as a temporary measure pending the receipt of this report. 8. Among larger measures for the suppression of malaria recently undertaken in Mauritius, I should like to mention the drainage of the marshes at Phoenix by your Government and the handsome assistance given by the Imperial Govern- ment through the military authorities. 9. We are also much indebted to Major General Creagh, C.B„ Commanding the Troops ; to Colonel Peterkin, Major Wilson, Lieut. Buchanan, and Lieut. Wallace of the Royal Army Medical Corps ; to numerous Officers of the Garrison ; and to a large number of private gentlemen in Mauritius ; all of whom have helped us in many ways. 10. Lastly, Sir, our warmest thanks are due to yourself, not only for much personal kindness, but for the great assistance which you have always been pleased to give us. I can only hope that the marked and intelligent interest in the subject of malaria shown by everyone in Mauritius will be ultimately rewarded by a large reduction in the disease, and an increase of health and prosperity throughout the Colony. PREFACE. The prevention of malaria must always make demands on the public purse and, in the case of estates and plantations, on the private purse also. Hence all recommendations for dealing with the disease should be supported by thoroughly reasoned arguments in their favour ; and such reasoning must obviously be based upon our modern knowledge of the subject. I have therefore thought it advisable to commence this Report with a chapter written in non-technical language on malaria in general — a course which is demanded the more because there is no good text-book on the subject. I fear that there is considerable evidence of haste in the work. The necessity for completing it as early as possible, in order to permit of preparations being made for the commencement of the proposed campaign at the beginning of the next malaria season, has been exigent. The labour of tabulating and analysing the returns of the spleen-census (probably the largest one ever made), and of considering the historical statistics of malaria in Mauritius, has occupied much of the available time ; and I have been obliged to defer to another opportunity the examination of many questions of theoretical interest arising from these figures. In making my recommendations I have endeavoured to select only those preventive measures which, I think, are certainly feasible and which, when combined in the way indicated, are likely to give the best and most definite results for the least expenditure ; and I have considered very carefully the special organisation required for the prevention of malaria in the tropics. Summaries of the substance of the Report are contained in sections 2 1 and 40. Ronald Ross. University of Liverpool i$th June, 1908 CONTENTS. PART I.— MALARIA IN GENERAL PAGE Section i. History .... .... i 2. Compendium of Facts regarding Malarial Fever . 7 The parasites and the fever — the mode of infection — facts about mosquitoes — personal prevention — public prevention 3. The Duration of the Infection . People in a Locality . . 13. The Number, Length of Life, and Diffusion of Anophelines in a Locality ..... IS 18 19 21 22 4. The Parasites between the Relapses . 5. Causes of the Relapses .... 6. The Proper Duration of Treatment 7. The Proofs of the Mosquito Theorem . 8. Do other Insects carry Malaria? . 23 9. Is Malaria due to the Soil ? . . 24 10. What do we mean by the Amount of Malaria in A Locality? ... .29 11. Factors which influence the Infection Rate. . 30 12 Conditions which change the number of Infected 33 37 PART II.— MALARIA IN MAURITIUS Section 14. Short Description of Mauritius . . 41 15. The Outbreak of Malaria in Mauritius . . 43 16. Explanation of Outbreaks of Malaria . 49 17. Further History of Malaria in Mauritius . 52 18. Statistics of Malaria in Mauritius since the Outbreak .56 The general death-rates of certain non-malarious islands — the general death-rates of Mauritius — monthly variation in the deaths — the declared fever mortality — cases of malaria admitted into hospitals and asylums — cases of malaria attending the hospitals and dispensaries XIV PART W.—tonliinied. PAGE Section 19. The Measurement of Malaria in Mauritius . 65 Recent statistics — direct methods for measuring the amount of malaria in a locality — the endemic index — does kala-azar exist in Mauritius ? 20. The Spleen-rates of Children in Mauritius, and OTHER details .... .69 Total spleen-rate — total probable endemic index — some small sources of error — average spleen — local distribution — the imported spleen-rate — the effect of altitude — relation lietween the spleen-rates and general death-rates — the parasites and the fevers in Mauritius 21. SUMMARY OF FACTS REGARDING THE AMOUNT OF MALARIA IN MAURITIUS 73 PART III.— PREVENTION OF MALARIA IN MAURITIUS Section 22. Brief History of the Prevention of Malaria . . 76 23. The Prevention of Malaria in Ismailia, the Federated Malay States, Hong Kong, the Panama Canal Zone, etc. . . . . 80 24. Preliminary considerations regarding Prevention 91 Form of government — the first preliminary to success — necessity for repeated measurements of malaria — limits of expenditure on anti-malaria work — all measures against malaria must be continued indefinitely — some legislation and discipline necessary — special organisation advisable — a firm continuous government policy necessary 25. The various Preventive Measures considered . 95 Isolation — punkas and segregation — case reduction — quinine- prophylaxis — Anopheline reduction — public instruction 26. The various Preventive Measures compared . loi 27. The general Preventive Measures selected for Mauritius . . . .104 28. The Periodical Spleen-Census . 104 29. Treatment of Children in Schools and on Estates 106 30. Other Quinine Distribution ... . 108 For towns, villages, and isolated houses — for the estates — preparation ahd despatch of quinine preparations — remarks 31. House Protection . . . . . .112 32. Mosquito Reduction . . . . .112 33. Details of Minor Works . . . . -113 Xature of worlds — organisation of workmen in gangs — total number of gangs required for Mauritius — number of workmen required for towns, villages, and populous areas — minor works on estates — the mousliquiers — the malaria autliority — tools and implements PART III.— continued. PAGE Section 34. Details of Major Works . . . -119 35. Legislation and Administration . . 120 Amendments of laws — existing sanitary staff — plague service — standpipes — drains and gutters — water channels — marshes on private property 36. Notes on Prevention in the Towns . . -123 Port Louis — Curepipe — trees in towns 37. The Annual Malaria Repor'j- . . . 127 38. Miscellaneous Suggestions . . . . .127 Intercepting drains —rubble drains — stoning irrigation pits and water channels — rough canalisation — holes in rocks and trees — mosquito plants — the introduction of M. rossii 39. The General Plan of Campaign . . . -130 40. SUMMARY OF PRINCIPAL RECOM- MENDATIONS, AND APPROXIMATE COST 131 ADDENDA 1. The Mosquitoes of Mauritius . . . -133 2. The Clairfond outbreak with Report by Dr. de CiiAZAr, AND map . . . . . . -134 3. The question of the River Reserves . . 140 4. Statistical error ... 144 REFERENCES . . 146 ANNEXURES 1. Letters from Dr. Bolton and Dr. Malcolm Watson . . . . . . . . -147 2. Correspondence regarding water-channels . . 149 3. Draft Legislation 151 4. Rough estimates of workmen and works, prepared — (A) By the Medical Department, . . -153 (B) By the Immigration Department, . . . ■ iS5 (C) By the Public Works and Surveys Department, . 164 TABLES I. Population, deaths, and dfxlared fever deaths . II. Declared fever deaths in the several districts . III. Cases of malaria attending hospitals and dispensaries . . . . IV. Spleen-rates of children — A. on sugar estates B. in schools ...... C. in various localities D. summary E. according to altitude . F. compared with death-rates in districts PLAN OF CLAIRFOND MARSHES . PHOTOGRAPHS 1-4. Views ...... 5-10. Houses ...... 11-17. Breeding places of Anophelines. 18-20. Breeding places of Culicines 21. Child with greatlv enlarged spleen 22. Net for measuring output of Anophelines 23-25. Rough training of streams . PAGF, 172 174 174* 17s . . . 178 . iSi 183 184 . 185 . 186 189 191 194 198 "; 20b slines . 200 201 REPORT ON THE PREVENTION OF MALARIA IN MAURITIUS. PART I.— MALARIA IN GENERAL. I. HISTORY.— Malarial Fever was well known to the Ancients, who certainly recognised three main facts connected with it. They observed that the disease occurs in several different forms, the qitartan, the tertian, and the co7itiniied form. They knew that it tends to be most prevalent in the vicinity of marshes ; and that it may be reduced by drainage. The Middle Ages added little to our knowledge of the subject. In 1640, however, the specific remedy for the disease, the so-called Cinchona or Peruvian Bark, began to be known in Europe ; and in 1820 Pelletier and Caventou extracted from this substance its essential principle, quinine. The extensive use of the drug made by physicians ultimately showed that it does not cure all fevers, but only those which possess the so-called intermittent tendency — that is, the tendency to a succession of attacks at regular periods. This fact enabled them to separate these fevers clearly from the others, known as the Continued Fevers. It is true that the Intermittent Fevers may become continued at times ; but, as Torti showed in 1712, this is merely due to the overlapping of the successive attacks. In 1691, Morton, and in 1716, Lancisi, strongly emphasised the ancient opinion that the Intermittent Fevers are caused in some way by noxious effluvia from marshes. Accepted widely throughout the world, this hypothesis ultimately gave another name to the Intermittent Fevers, namely, that o{ Malarial Fever — which connotes that the disease is due to bad air. It should, however, be clearly recognised at this point that the last conception was entirely an hypothesis — a conjecture. It was absolute^ true that Intermittent Fever is caused in some way by something which emanates from marshes ; but it was never proved, either by induction or by experiment, that this "something" is the air of the marsh. The conception regarding the " bad air " was therefore nothing but an attempt to explain with plausibihty the great fact that the Intermittent Fevers are, for some reason, certainly connected with marshes. Nevertheless, it shortly began to be accepted everywhere as a dogma. Later still, when these fevers were found to occur in certain places where there were no marshes, the dogma was expanded into the hypothesis of the telhiric miasma. According to this the malarial poison exists, not only in marshes, but anywhere in certain soils, especially where there is much decaying vegetation. It was thought that if such soils be disturbed in any way the poison will rush out into the air and infect the neighbourhood. Here again there was no experimental evidence, and the whole speculation rested merelj' on some loose inductions. About the middle of last century, however, the science of experi- mental pathology came into being. We no longer accepted coincidences and conjectures as proofs, but studied disease by strict experimental methods. Gerhardt produced malarial fever in men by inoculating them with a small quantity of blood taken from patients — thus proving that the disease is caused by an organism existing in the blood ; and in 1880 Laveran discovered this organism itself It proved to be a minute animal parasite of very low order, and visible only by the microscope, which lives in the blood in enormous numbers. Some years later Golgi and others showed that these minute bodies proliferate indefinitely in human blood by the simultaneous production of spores ; that the successive attacks of fever in the patient commence at the moment when the spores are set free from the parent organisms ; and that there are at least three varieties of the parasites, all of which can be distinguished by the microscope — namely, one which produces spores every three days and causes quartan fever, one which produces spores every other day and causes tertian fever, and one (at least) which causes less distinct, but often more dangerous, attacks. About the same time Danielewsky showed that closely allied parasites occur in birds (they have now been found also in monkej's, bats, and squirrels) ; and discovered many more distantly related organisms in numerous animals. Laveran, Marchiafava, Celli, Bignami, Canalis, and many others made a close study of infected persons. Romanowsky and Ziemann developed a method of staining the parasites which serves to demonstrate them with certainty ; and Theobald Smith discovered a nearly related parasite of cattle which is carried from ox to ox by a species of tick — as he proved b}- direct experiment. This brilliant series of researches, which were soon confirmed and amplified by numbers of observers in many parts of the world, gave us most exact and detailed information regarding the processes which cause the disease in man. But a great problem still remained — to ascertain the route by which the parasites enter the human body. As soon as these had been discovered, many workers, remembering the connection between Malarial Fever and marshes, sought for them in such localities, thinking that they probably bred there and infected man by inhalation ; and others, especially Celli, Agenore, and Calandruccio, attempted to cause infection by the air or -water taken from malarious localities — but all without success. In the meantime another, but very old, hypothesis had been revived. Even some centuries ago it was stated in certain religious books of Ceylon that mosquitoes can produce fever ; and the same idea now occurred to several eminent men of science. It must be remarked, however, that the views of these authors were still only speculations, which they themselves did not verify by serious experiments (although such might easily have been attempted), and that their hypotheses were often as much wrong as right. Obviously the whole problem was a very difficult one, which could be solved only by long thought and investigation. This was attempted by my own work, commencing in India about 1891 and not concluded until 1899. It became early apparent that the old hypothesis of an aerial miasm was not tenable, simply because the disease was frequently too local to be assigned to any widely-diffusible poison. Early in 1895, therefore, I commenced an experimental study of the mosquito hypothesis. After long failures with the commoner kinds of mosquito of the genera Culex and Stegotnyia, I succeeded at last (Augu.st, 1897) in growing the malignant parasite of man in mosquitoes of the sub-family Anophelina. Next year the life-history of the whole group of these parasites was worked out in the case of one of the parasites of birds in a mosquito of the genus Culex, and the wonderful and unexpected result was obtained, both on microscopical evidence and by the actual production of the disease among the birds, that the malarial infection takes place through the proboscis of the mosquito. After an interruption, I was finally able to demonstrate the exactly similar life-history of all the human parasites in the Anophelines costalis and funestus in Sierra Leone in 1899. This completed the solution, but at the end of 1898 my «'ork had already been verified by Koch, Daniels, Bignami, Bastianelli and Grassi, the latter of whom, entirely by following my methods, infected healthy men in Italy and showed that the tertian parasites are also carried by Anophelines in that country. These results \\ere rapidly confirmed and amplified by a host of observers — by Daniels, Stephens and Christophers of the Malaria Commission of the Royal Society, by various expeditions, and by many private workers. Koch discovered the important fact that native children are the principal source of infection in the tropics. Ziemann, Fernside, Buchanan and Manson produced infections by mosquitoes in more human beings, the last in the middle of London, by mosquitoes brought from Italy. Low and Sambon remained free from malaria in the Campagna by living in a mosquito-proof house. Austen, Giles, Stephens and Christophers, Howard, Blanchard and Theobald studied the mosquitoes themselves, the last producing his exhaustive monograph on the subject. The similar development of several parasites allied to those of malaria has been worked out in various insects. Local mosquitoes and their habits have been studied in many place.s — notably by Daruty de Grandpr6 and d'Emmerez de Charmoy in Mauritius. It should be added here that even before the discovery of the malaria parasite Manson had worked out part of the life-history of Filaria bancrofti, the worm which causes elephantiasis and allied diseases, in a species of mosquito ; and that a little later Finlay conjectured that yellow fever, the scourge of tropical America, might be carried by the same insects. Now, following the suggestions of my work on malaria, James and Low (1900) completed the life- history of Filai'ia bancrofti, and showed that it also probably gains an entrance into the human body through the mosquito's proboscis ; and Reed, Carrol, Lazear and Agramonte proved (1901) by the most conclusive experiments that yellow fever is transmitted in the same 5 way. Hence we are now certain that at least three diseases of man are carried by mosquitoes ; while dengue and some other fevers may perhaps be added to the list. Bruce had long previously shown that Tsetse Fly disease is carried by the insects of that name. My studies had been undertaken solely with the object of im- proving our methods of preventing malaria ; and the history now turns to this, the most important branch of the subject. When my work commenced little was known about mosquitoes. Only about one hundred species had been distinguished ; the classification was elementary ; and the little knowledge of their habits we possessed was not generalised, was buried in the works of a few entomologists, and was not familiar to sanitary science. Thus King in 1883, and Bignami in 1896 evidently thought that all mosquitoes breed in marshes; and even Manson in 1896 believed that they live only for four or five days. But the long Indian researches, carried out in many parts of that empire, brought to light several generalisations which I have subsequently found to hold good in countries so far apart as Sierra Leone, Gambia, the Gold Coast, Lagos, Panama, Ismailia, Greece, and Mauritius, and which should now be men- tioned briefly, as they form the basis of the prevention of disease by mosquito reduction. Thus mosquitoes do not live only for a few days, but for a month or more, even in captivity — feeding and laying their eggs regularly during their life. The commonest mosquitoes in the tropics nearly always belong to three groups, now known as Culex, Stegomyia, and Anophelina, which carry different parasites, have different habits, and can be generally distinguished by certain salient characteristics which are easily recognisable by any one — even by native villagers. All mosquitoes tend to abound most nearest to their breeding places, and can with certainty be reduced in numbers anywhere by appropriate and continuous measures directed against the latter. Culex and Stegomyia breed principally in artificial collections of water (in the tropics) ; but the Anophelines breed principally in natural collections of water. The last point was made out in India and Sierra Leone from 1897 to 1899, and gives a full explanation of the long-known connection between malaria and marshes — the mosquitoes which carry malaria breed in marshes. For the same reason it is unlikely (as indeed my work had already proved) that Ctilex and Stegomyia carry malaria — because they do not breed so much in marshes as elsewhere, for example, in pots and tubs round houses. Lastly, the fact explained and justified the ancient method of reducing malaria by drainage — that is, by mosquito reduction. At the same time this ancient method was now rendered much more simple, cheap and yet exact by the knowledge that we have to drain only those waters which breed Anophelines. The improved system, and the precise habits of the larvK of the insects upon which it depends, were first described by me in a series of articles (i;* during my first visit to Sierra Leone in 1899. I proposed, in short, to free towns of malaria by the simple and radical process of clearing them of mosquitoes by destroying the breeding places of the insects. Unfortunately, however, the extraordinary objection was urged that this measure would be useless, owing to the immigration of mosquitoes from without (section 13) ; and for three years I failed in obtaining a trial for my method. At last, in 1901-2, it was put into practice at my visits to Sierra Leone and Ismailia, in the latter place with the most brilliant success ; and was also used with as good results in the Federated Malay States by Dr. Malcolm Watson. In the meantime the discovery that yellow fever is carried by Stegoinyia, led the Americans, under Gorgas, to adopt similar measures in Havana and subsequently at Panama. In detail, the system is some- what different for the two diseases, as the habits of the carrying insects are dissimilar ; but the great principle, the idea of making a general clearance of mosquitoes and diseases together is the same. In places where it is intelligently followed it will probably reduce sickness at one sweep by from one-quarter to one-half or more. Like Listerism, however, the idea has spread slowly, and the practice more slowly still. The history of the progress made will be found in a recent paper by me (2), and in section 22. Meanwhile other methods of prophylaxis were urged by various workers. Koch and Celli elaborated prevention by quinine, and put it into practice in Italy and elsewhere ; and Celli, Manson and others advocated the protection of houses by wire-gauze ; while administrators like Sir William MacGregor adopted all methods. Very successful results have been obtained ; but the conditions in the tropics are as a rule more favourable for the radical measure of drainage. * The references will be found on page 146. It is impossible in this brief history to mention the names of all the workers — even of some of the most distinguished — who have built up our modern knowledge of malaria ; and the details mentioned have been given only in order to convince the lay reader that that knowledge was not obtained in a day, and is not a mere speculation on the part of the medical profession. 2.— COMPENDIUM OF FACTS REGARDING MALARIAL FEVER.— (i) The Parasites and the Fever. — Malarial Fever occurs more or less in all warm climates, especially in the summer, after rains, and near marshy ground ; and produces a quarter or more of the total sickness in the tropics. It is caused by enormous numbers of the minute parasites of the blood, called Plasmodia or Haemamoebidse. These parasites are introduced into the blood through the proboscis of certain species of the mosquitoes called Anophelines. On being introduced, each parasite enters one of the red corpuscles of the blood, in which it lives and grows. On reaching maturity each parasite produces a number of spores which escape from the containing corpuscle, and enter fresh corpuscles ; and this method of propagation may be continued indefinitely for years. Thus, though only a few hundreds or thousands of the parasites may have been originally introduced through the mosquito's proboscis, their number rapidly increases, until as many as some millions of millions of them may exist in the blood. At first, while the number of parasites is still small, the infected person may remain apparently well. When however the number is large enough, he begins to suffer from fever. The parasites tend to produce their spores all at the same time ; and it is at the moment when these spores escape that the patient's fever begins. The fever is probably caused by a little poison which escapes from the parasites with the spores. After from six to forty hours or more this poison is eliminated from the patient's system ; and his fever then leaves him temporarily. In the meantime, however, another generation of parasites may be approaching maturity, and may cause another attack of fever like the 8 first ; and so on, indefinitely, for weeks or months. In this manner the attacks of fever follow each other at regular intervals. But it often happens that before one attack has entirely ceased another one commences ; so that the attacks overlap each other, and the fever is continued. After a time, even without treatment, the number of parasites may decrease, until not enough of them are left to produce fever ; when the patient improves temporarily. It generally happens, however, sooner or later, that the number of parasites increases again ; when the patient again suffers from another series of attacks. Such relapses are frequently encouraged by fatigue, heat, chill, wetting, dissipation, and attacks of other illness. They may occur at intervals for many years after the patient was first infected, and after he has m.oved to localities where there is no malaria. It is probable that so long as one parasite remains alive in the patient's blood, he may remain subject to such relapses. Besides fever, the parasites often produce anaemia and enlarge- ment of the spleen, especially in patients who have suffered from many relapses. Death is sometimes caused by sudden and grave symptoms. Chief among these are the symptoms known as Blackwater Fever, or Hemoglobinuria, which generally occurs in old and neglected infections. Death is also often caused during the course of a malarial infec- tion by other diseases, such as pneumonia or dysentery, acting on a constitution enfeebled by the parasites. If the patient survives, the parasites tend to die out of themselves without treatment after a long period of illness, leaving him more or less " immune." The parasites are of at least three kinds, which can easily be dis- tinguished in blood placed under the microscope. These are (i) the parasite which produces its spores every three days and causes quar- tan fever ; (2) the parasite which produces its spores every other day and causes tertian fever ; (3) parasites which cause the so-called malignant fever, in which dangerous complications most frequently occur. Closely similar parasites are found also in monkeys, bats, squirrels and birds. As proved by centuries of experience. Cinchona bark, from which quinine is made, possesses the power of destroying the parasites and curing the infection. But it will not generally destroy all the parasites in the body unless it is given in sufficient doses and continued for several months. (2) The Mode of Infection. — Besides those forms of the malaria parasite which produce spores in the human body, there are other forms, male and female. When certain species of the mosquitoes called Anophelines happen to feed on a patient whose blood contains the parasites of malaria, these are drawn with the blood into the insect's stomach. If the sexual forms of the parasites are present these- undergo certain changes in the mosquito's stomach ; the females pass through its wall ; and finally fix themselves to its outer surface — that is, between the stomach and the skin of the insect. In this position they grow largely in size, and after a week, in favourable circumstances, produce a number of spores. The spores find their way into the insect's salivary glands. This gland secretes the irritating fluid which the insect injects through its proboscis under the human skin when it commences to feed, and the spores can easily be found in the fluid by the microscope. Thus when a proper species of Anopheline, which has more than a week previously fed upon a patient containing the sexual forms of the parasites of malaria, next bites another person, it injects the spores together with its saliva under his skin — that is generally into his blood. These spores now cause, or may cause, infection or re-infection in this second person, as described at the beginning of this compendium. Numerous birds and men have been infected experimentally in this manner. Thus the parasites of malaria pass alternately from men to certain mosquitoes, and back from these mosquitoes to men. A very large number of parasites are known which pass in this manner from one animal to a second animal which preys on the first ; and back again from the second animal to the first. 10 It is not known with certainty when and how this process first commenced ; but probably all such parasites were originally free living animals, which, by the gradual evolution of ages, acquired the power of living in other animals. Thus also, it is evident that malarial fever is an infectious disease which is communicated from the sick to the healthy by the agency of certain mosquitoes. From the time of the ancients it has been known that malarial fever is most prevalent in the vicinity of marshes. The parasites of malaria have never been found in the water or air of marshes ; nor in decaying vegetation ; nor in the soil. But the Anophelines which carry the parasites breed in marshes and marshy pools and streams. Rising from these marshes, they enter the adjacent houses and feed on the inmates, mostly at night ; biting first one person and then others ; and living for weeks or months. If an infected person happens to be present in any of these houses, the infection is likely to be carried by the Anophelines from him to the other inmates, and to neighbouring houses. Thus the whole neighbourhood tends to become infected, and the locality is called " malarious." In such localities, it is easy to find the parasites of malaria in the Anophelines of the proper species ; even in as many as 25 % of them. Such Anophelines \\'hen taken from a malarious locality to a healthy one {e.g. from the Campagna near Rome to London) will still infect healthy persons whom they have been caused to bite. So also, in malarious localities, the Anophelines bite the healthy new-born children and infect many of them. Such children, if not thoroughly treated, may remain infected for years ; may become anaemic and possess enlarged spleens ; and may spread the infection to others. Later however, at the age of twelve years or more, the survivors tend to become " immune." In many malarious localities, almost every child has been found to contain the parasites of malaria, or to possess an enlarged spleen. In such a locality therefore, the infection is constantly passed on from the older children, or from adults, to the new-born infants ; so that the locality may remain malarious for years or for centuries. II Similarly, a new-comer arriving in such a locality is very likely to become infected, especially if he sleeps in an infected house, even for one night. A locality is said to be malarious only when healthy persons become infected in it ; not when persons who have become infected elsewhere happen to reside in it. A locality is malarious only when it contains persons already infected with the parasite, and also sufficient numbers of the proper species or varieties of Anophelines to carry the infection to healthy persons. The chances of infection tend to be great in localities where there are already numerous infected persons, not treated with quinine ; or where there are numerous Anophelines of the proper species, not prevented from biting. Conversely, the chances of infection tend to be less where infected persons are excluded, or properly treated with quinine ; or where the Anophelines are few in number, or are prevented from biting. (3) Facts about Mosquitoes. — Gnats, which in the tropics are commonly called mosquitoes, belong to the zoological family of insects known as the Culicidse (from the Latin culex, a gnat). They are distinguished from other insects by a number of characters ; and always possess only one wing on each side, and a long proboscis. Like that of other insects, their life is divided into four stages, the egg; the larva (or caterpillar) ; th.& pupa (or chrysalis) ; ajid the imago (or adult, winged insect) . The egg is laid on water or near it, and in warm moist weather hatches out in a day or two. The larva is entirely aquatic, and always lives in water. It swims and dives by means of paddles and hairs, and feeds on various aquatic organisms. It cannot however breathe under water, but must always rise to the surface in order to obtain air. After a week or more it becomes a pupa. The pupa still remains in the water, generally floating on the surface. After two days or more its skin cracks and the imago emerges. The imago remains standing for a little while on the empty floating skin of the pupa and then flies away. Both males and females are able to suck fluids through the proboscis. As a rule the 12 male feeds only on the juices of plants ; but the female sucks the blood of men, beasts, birds and reptiles. The female returns to water every few days in order to lay her eggs, of which she may deposit several hundreds at a time ; and then seeks another meal. Female gnats have been kept alive in captivity for months. In unsuitable weather, both males and females may take refuge in damp places such as cellars, wells, outhouses and woods, where they may remain dormant for months until better conditions prevail. As a rule, gnats like other animals tend to remain in the locality where they were born ; but a few may occasionally stray to some distance. When a strong wind prevails they usually take shelter ; but on warm, still nights or days many of them may wander to a distance of half a mile or more from their breeding places. If however plenty of places exist near at hand where they can obtain food, there is no reason why they should travel further for it. They must also remain near water to drink and to lay their eggs in. Gnats are favoured by warm weather ; by plenty of water suitable for their larvae ; by abundance of food ; and by the absence of various kinds of bats, birds, fish, insects and spiders which devour them or their larvae. During its life, a single gnat may succeed in biting many persons or animals, and in propagating diseases amongst them. The family of Culicidae or Gnats is divided into many sub- families and genera, and contains some five or six hundred known species. Although all these species have many habits and structural characters in common, yet they all differ in small details. These have been described at length in a number of special books written on the subject. In the tropics, as a broad general rule, the gnats which most concern human beings belong to the groups called Ctdex, Stegoinyia and Anophelina. Cidex pipiens is a very common gnat in Europe, and allied species are found almost everywhere in the tropics. The larvs: occur principally in tubs, barrels, cisterns and other vessels containing water, in stagnant ditches, garden pits, holes in rocks and trees, and so on. They possess a long breathing tube close to the tail fins, and float at the surface of the water with the end of this tube attached to the " surface film," and the head hanging downwards. 13 When disturbed, they wriggle at once to the bottom. The adult insects generally present a uniform grey appearance, with pale yellowish bars across the back of the abdomen, and plain unspotted wings. They bite almost entirely in the evening and night, and principally indoors (in the tropics). The parasite which causes elephantiasis, namely the Filaria bancrofti, is carried by them in a manner very similar to that in which the Anophelines carry the parasites of malaria. Stegoniyia fasciata and 5". scutellaris are very common in the tropics, but much less so in temperate climates. The larvae breed in much the same places as those of Culex, but more frequently in vessels. Any old biscuit or oil tins, flower pots, broken bottles, and crockery, tubs and barrels, choked drains, roof gutters, &c., in which rain or other water has collected, is almost sure to contain them, and they frequently occur in holes in trees and in certain plants. They possess a short stumpy breathing tube, and float head downwards, like the larvae of Culex. The adult insects are more or less striped or speckled black and white, and have plain unspotted wings. They bite chiefly in the day time, and often abound in woods and in the shade of trees. In America Stegomyia fasciata carries yellow fever. The Anophelines consist of about 120 known species, some of which carry malaria, and are always found in malarious places. The larvae occur chiefly in water on the ground, particularly in water which stands or flows amongst grass or water weeds. Thus they abound in the weedy margins of rivers, streams, lakes, and ponds ; in small sluggish streams and streamlets ; in water-courses, drains and gutters choked with weeds ; in pools of rainwater lying on grass ; in pits from which earth has been removed, such as the " borrow pits " by the side of railway embankments ; in cisterns and pits used for watering gardens ; in ornamental waters ; in hollows in rocks ; and in water at the bottom of boats, &c. Thus while the larvae of Culex and Stegoniyia occur in any small collections of water, such as those which abound in and around houses, on the other hand the Anophelines are essentially marsh mosquitoes — owing to which malaria is always more or less connected with marshy conditions, and is called Marsh Fever, or Paludism. The larvae feed chiefly on the surface of the water — on which they float like sticks, and not with the head hanging downwards. When disturbed they swim away backwards on the surface, and sink to the bottom only when much alarmed. They have no breathing tube like those of Ciilex and Stegomyia. The adults are speckled brown and white, or black and white ; and the wings are not plain but generally possess three or four black marks along or near the front border. When the insect is seated at rest on a wall the tail projects outward at an angle from the wail ; whereas the Culex and Stegomyia sit with the tail hanging downwards, or even nearly touching the wall. All these facts enable an)'one to distinguish at sight both the larv<-E and the adults of Anophelines from those of Cidcx and Stegomyia. Anophelines bite chiefly at night or in the dusk — owing to which the malarial infection is generally acquired at night. They enter houses, but also bite in the open in spots sheltered from wind. (4) Peisonal Preventiott.~l{ they can avoid it, people should not go to live in known malarious places, or in the vicinity of marshes, or close to an infected native population. Even in such however, the chances of infection can be much reduced by the careful use of mosquito nets. The net should not have the smallest hole. It should be hung inside the poles, when these are provided, and not outside them. It should be tucked under the mattress all round, and should never be allowed to hang down anywhere to the floor ; and it should be stretched tight, in order to allow every breeze to enter, and not be hung in loose folds, which check ventilation. Those who can afford it should protect the windows of the house with wire gauze, and provide the doors with automatic closing arrangements. It is especially advisable to protect a room or a part of the veranda, for sitting in during the day or evening. Punkas and electric fans, not only drive away mosquitoes, but also keep the body cool, comfortable and vigorous, even in great tropical heat. Where there is great danger of malaria fi\'e grains (^rd gramme) of quinine should be taken regularly every da}' just before breakfast ■ but it is advisable to take a double dose at least once a week — say on every Sunday. In such localities, the hands and feet may also be protected by gloves and boots ; but these cannot always be endured owing to the IS heat ; and it is preferable instead to carry and use constantlj' a palm-leaf fan, with which mosquitoes can be largely driven off, and the body kept cool. It is extremely dangerous to sleep in a house which is occupied, or has recently been occupied, by infected persons, especially native children ; or in or close to an infected native village. (S) Public Prevention : — As a broad general rule, malaria causes from a quarter to half the total sickness in the tropics. Malaria can always be greatly reduced, or may even be extirpated, in any locality. Large marshes in populous places must be drained, deepened, or filled up. A proper permanent organisation must be established for dealing with the smaller breeding places of Anophelines, and for distributing quinine, especially to infected children. Other measures can be adopted where called for. The cost is likely to be more than recouped by saving in life, labour, invaliding, medical attendance, and hospital accommodation. The campaign will remove other mosquito-borne diseases as well as malaria ; and will tend to improve general sanitation in' the locality where it is undertaken. 3. THE DURATION OF INFECTION.— The foregoing sections show that we have acquired much knowledge about malaria ; but several points remain to be discussed. The discussion is the more necessary because these points, although of cardinal importance in connection with the art of prevention, receive no acleauate attention in text books. The first question is this : Hoa\' long after a non-immune person becomes infected do the parasites remain in his blood, provided he receives no medical treatment and no fresh infection ? We must first ask : How long may they possibly remain ? In every case they certainly remain while the fever lasts ; that is, in untreated cases, for some weeks or months, at least. Sailors infected during a few days' stay in a West African river come to Liverpool after a month's journey at sea, and are frequently found to be infected for weeks and even for months after their return to Liverpool. In such cases re-infection on board vessels is not likely, owing to the rapidit)- 1 6 with which mosquitoes are blown out of a steamship : and malarial infection in England at the present day is almost unknown. I have found the parasites in several persons after residence in England for six months : and in one case they were certainly found in Liverpool after four years' absence from any malarious locality. Another case well known to me was that of my father. He had suffered much from malaria in India. In 1880 he left India permanently and resided in the South of England. In 1889 he informed me that he still con- tinued to have one or two attacks every year ; and a little later I witnessed one of these ^a typical attack with severe rigor followed by high fever, and without symptoms of influenza or other disease. His blood was not examined. I have also been told by three different persons that they continued to suffer from occasional attacks twenty years and more after leaving the tropics. In such cases microscopical verification is difficult to obtain owing to the fact that a large dose of quinine is generally taken at the onset of the paroxysm. We have therefore the right to say that the infection occasionally remains for some years. The next question is : How long does it remain on the average ? That is to say, out of a thousand untreated persons removed from possibility of re-infection, how many will continue to have attacks after one, two, three years, and so on ? I can suggest only one way to obtain a reply. Taking Northern India, for example, we observe that the Anophelines do not begin to abound until July and disappear in November or December. The admissions for malaria continue all the year, but show a great increase in September or October, that is, as we may expect, two months or so after the reappearance of the Anophelines. Hence we may infer that the admission rate for malaria before the annual appearance of Anophelines is due chiefly to relapses occurring among persons infected in previous years ; while the admission rate after the appear- ance of the Anophelines is due to relapses plus fresh infections or re-infections. In other words, the minimum admission rate for the year represents roughly the relapses only ; while the difference between the maximum and the minimum rates is caused by the new infections. The Annual Reports of the Sanitary Commissioner with the Government of India give abundant material for this enquiry. It will be seen that in station after station and year after year, the 17 admission rate for Intermittent Fever tends to be lowest in February and March and to be highest in September, October and November, That is, the admissions begin to increase about two months after the commencement of the rains, and continue to increase with the accumulation of cases until November, after which a decline, due to recoveries, occurs. The October maximum may be from two to five or more times greater than the February minimum. For illustration, I select at random the Native Troops on the North- West Frontier, Indus Valley and North-West Rajputana; Returns (tables) for 1900-5, Table XXXV., Group VII. ADMISSIONS. Avprao-p Average ^"^'^ strength J- ^- ^' ^- M. J. J. A. S. O. N. D. Total to 1,000 strength 1900 ... 15,861 328 168 109 121 246 357 301 246 499 1,611 1,189 920 6,095 384-3 1901 ... 16,951 400 198 265 437 483 583 509 461 628 1,712 1,101 522 7,299 430-6 1902 ... 16,472 309 248 199 297 475 338 449 482 568 867 1,166 764 6,162 374-1 Average... 16,428 379 205 191 285 401 326 420 396 565 1,397 1,152 735 6,519 396-8 Here the average maximum in October is more than six times greater than the average minimum in March, and the increase must be due to the new infections caused by the summer hatch of Anophelines. Of course the difference is not always so marked. In the south of India, owing to the warmer winter, the insects breed and infect more continuously; and in other places, where there are streams, lakes or irrigation waters, they are not so dependent on rainfall. As a very rough estimate then, I am inclined to infer that after the six winter months, during which we may suppose few fresh infections to occur, the cases would tend to fall to about one- quarter the original maximum number. Suppose now that we could suppress entirely the next summer rise, and that the admissions for relapses continue falling at the same rate, namely to one-quarter, every six months ; at the end of twelve months, the cases would be one-sixteenth the original maximum ; and at the end of eighteen months would be one-sixty-fourth of it, and so on. In other words half the cases tend to recover every three months, if no re-infection occurs. Thus out of i,ooo original cases, 500 would remain infected at the end of the first quarter ; 250 at the end of the second ; 125 at the end of the third ; and three or four after two years. The truth Hes somewhere near these figures, but so many factors are concerned in the result that it is difficult to make a more exact estimate. For example, the Indian statistics refer to soldiers who were certainly given medical treatment ; and this treatment must have resulted in reducing the number of relapses, although it was evidently insufficient to cure the cases altogether. Again, if many of the patients have suffered from malaria in childhood (as most Indians have) many would be partially immunised, and the number remaining infected after a given lapse of time would be less than with people exposed to the disease for the first time. But the estimate of a 50 per cent, reduction every three months may be adopted for the present as a working hypothesis, which will at least serve to give precision to our ideas. 4. THE PARASITES BETWEEN THE RELAPSES.— If the infec- tion is not cured at once, the patient suffers from a succession of relapses with intervals of several weeks between each, the parasites being found readily in the blood during the relapse, but not so easily during the interval. Marchiafava and Bignami were, I believe, the first to suggest that they enter upon a latent (^.^., an encysted) phase in the interval, but admitted that they could find no microscopical verification of this conjecture. Several writers thought that certain known forms of the parasites (the sexual forms) serve to continue their existence at these times ; and quite recently F. Schaudinn repeated the same speculation. There is, however, no need for it. My own position has always been that the parasites simply vary in numbers within the body, as the tubercle bacillus does. When they are numerous the patient suffers ; when they are few he does not feel them. It is easy to estimate the number of malaria parasites in a patient by comparing them under the microscope with the number of red blood corpuscles. In severe cases the number of parasites may exceed 10 % of the number of red corpuscles. For example, we made a careful estimate in the blood of a soldier from Vacoas early this year, and found that his parasites numbered 12 % of his red corpuscles. Now a medium person of 1 50 lbs. (68 kilograms) body- weight, contains about 25,000,000,000,000 red corpuscles ; so that this man must have contained about 3,000,000,000,000 parasites 19 when his blood was taken. When there is less fever the parasites (excluding the sexual forms, which do not produce fever) are much fewer. If there is only one parasite to 100,000 corpuscles, that is, only 250,000,000 in the whole body, there will be little fever, and it will be difficult to find the parasites at all in the small droplet of blood examined. Hence, when the parasites fall below this standard (which may be fixed at this figure for a rough estimate), the patient will scarcely feel them, and the physician may scarcely be able to find them. If they number only a few thousands, they will not be discoverable ; and yet they will be amply numerous enough to keep the infection alive — ^just as a few rats in a ship will suffice to keep the ship infested, i.ater on the parasites may increase again, and reach sufficient numbers to produce another attack of fever and to be again discoverable by the microscope. As I have said, no one has yet succeeded in proving the existence of a resting stage of the parasites, -though many attempts have been made. The task should be easy with the parasites of birds ; but in 1899 I searched many infected birds in vain — only the ordinary forms could be found.- Moreover, with a resting stage we should expect to find relapses occurring after definite intervals — that is, in regular biological cycles ; but in my experience they occur quite irregularly. The explanation given above is sufficient and probable ; and no other one is required until it has been proved to be wrong. S. CAUSES OF THE RELAPSES.— But it will now be asked, what causes the parasites to increase and decrease in the manner suggested above ? Probably the same thing that causes the increase or decrease of other invading organisms — the varying resistance of the host. When the resistance is great, the parasites diminish ; when it weakens, they multiply. Probably anything which weakens the resistance — fatigue, heat, chill, dissipation, other illness — tends to encourage the parasites and to precipitate a relapse. This is shown by a large number of observations. Probably every military surgeon who has dealt with malaria infected troops has noted that a heavy march or parade has been followed by numerous admissions into hospital for relapses. A costly item in military expeditions is the invaliding of infected soldiers who, though 20 able to do the light work of peace time, break down with relapse after relapse of malaria when subjected to the fatigues of war. In 1889 I was in charge of a regiment of picked Madras troops sent by sea to Rangoon for active service in Burma. The voyage was oppressive and rainy, and most of the men were frequently wet through ; and dozens of them began to be attacked with typical malaria while still at sea. African travellers frequently remark that their native carriers are attacked even during the first days of a journey. Every planter knows that when his coolies are first put upon the heavy work of the season, scores of them suffer from fever. Engineers often observe the same thing. The frequency with which relapses of malaria follow upon other diseases, such as pneumonia, influenza, typhoid, and venereal diseases, or upon child-birth, accidents, and surgical operations, is well known to the physician, and has resulted in the ancient aphorism that the intermittent tendency is apt to be impressed on all diseases occurring in old cases of malaria. Most educated febricitants will aver that exposure to great fatigue, heat, or wetting will encourage relapses ; and probably a large number of cases of so-called sunstroke or heat- stroke are due merely to this cause, often perhaps aggravated by intemperance. For definite statistical evidence, however, I wish to call attention to a phenomenon which I have named the " hot weather rise" in the malaria admission rate. This is well seen in the Indian statistics referred to in section 3, even in the small table there given. Alrpost throughout India the admissions tend to increase slightly in the months of March or April, and this increase is so constant that it cannot be due to accident. To what then is it due ? The season is too early for the rise to be attributed to fresh infections by A nophelines ; and I can therefore place it only to the score of relapses caused by the rapidly increasing heat of the tropical spring. Quite on other grounds I have long been forced to infer that great external heat is favourable to the parasites of malaria, both human and avian. Thus the obstinacy of cases in the hot weather and the great improvement caused by removal to a hill-station or to Europe are well recognised by practitioners. In 1898 I frequently took infected birds from Calcutta to the Himalayas and back again, and was always struck by the fact (which was very inconvenient for my researches) that the parasites diminished greatly when the birds were 21 in the mountains and increased again when they were brought back to the plains. Moreover, while i [ per cent, of the Calcutta sparrows were found infected in August, Dr. Daniels and myself had great difficulty in obtaining infected birds in December and January. I assume then that the " hot weather " rise is merely due to relapses encouraged by the temperature. It is easy to conjecture why the temperature should have this effect, on the ground that the parasites breed more rapidly in the hot weather in the expectation, so to speak, of finding the mosquito-host which bites only at that season. In fact, warm weather is their natural climate, and doubtless they can feel its influence even in the artificially heated medium in which they live. The malarial infection, then, is one which may last for a long time and cause many relapses, and I have dwelt at some length on this point because, as will be seen later, confusion in regard to it is apt to generate confusion in regard to the mode of propagation of the disease. 6. THE PROPER DURATION OF TREATMENT. — By treatment is here meant treatment with the specific, quinine, given in any of the methods usually adopted by practitioners. The question is, how long must it be continued in order to extirpate the infection entirely. It is a very important question as regards both cure and prevention, but is not sufficiently regarded either in text-books or in practice. In many of the former the drug is recommended to be given while the fever lasts and for a few weeks later. In military practice the soldier is often, or indeed generally, discharged to duty a few days after the temperature has returned to normal. The result is that the patient frequently falls sick again with a relapse, is treated again in a similar manner, and so has relapse after relapse, until he becomes a chronic febricitant, or a cachectic, or dies of blackwater fever. It is impossible to deny the frequency of such inadequate treatment in malaria because one is called upon over and over again to see patients who give this history. Obviously the final aim of treatment is not merely to reduce the present attack of fever, but to remove the parasites altogether ; and for this the patient must be kept under observation and treated for a considerable length of time. The period which I have always suggested is three months in temperate climates and four in the tropics (in view of the observation that the parasites flourish more 22 readily in the latter). If a relapse occurs within these periods, the treatment must be recommenced from the beginning. I have known numerous cases cured by such a course, but still am not willing to declare that it is sufficient for all patients. Needless to say, warnings against reinfection should always be given. Many practitioners think that intramuscular injection is so much more potent than medication by the mouth that with it a shorter course will suffice. The question arises here chiefly in connection with prevention (section 24) ; but also in connection with the treatment of coolies. With them, as with soldiers, it is bad economy as well as bad medical practice to return men to duty, or at least to release them from observation and outdoor treatment, before a complete extirpation of the infection has probably been effected. Not only do they tend to be useless as workers, but they spread infection among the healthy ; and strict rules should be made on the subject in every plantation and factory. 7. THE PROOFS OF THE MOSQUITO THEOREM.— The word theorem is used here in its correct sense as expressing not a mere speculation, but a body of established fact. I wish now merely to summarise the proofs by which the mosquito theorem has been established. They are briefly as follows : — 1. Every stage of the life history of the parasites, not only in infected men, but in Anophelines of the proper kind who have been fed upon them, has been closel)^ followed, described, and figured by many competent observers. 2. No such parasites have ever been found in Anophelines of the same kind which have been fed only on healthy persons. 3. Healthy persons bitten by infected Anophelines at the proper time have subsequently developed the symptoms of malarial fever, and have been found to contain the parasites. 4. The same phenomena have been observed in the closely allied malaria of birds ; and similar phenomena in the case of many other parasites. 5. Where the Anophelines have been banished, as at Ismailia, the disease and the parasites have also disappeared. I might add that the great weight of all this evidence can perhaps scarcely be fully appreciated except by those who have made a study 23 of pathology and parasitology, and have read the voluminous Mtera- ture of the subject. But the theorem has now been before men of science for nearly ten years, and has been so completely accepted by them that the public may safely follow them without misgiving. 8. DO OTHER INSECTS CARRY MALARIA.— But though the general theorem has been so definitely determined, we are not quite so certain regarding several details. If Anophelines can carry malaria, why not other insects ? First, we should note that not all, but only certain species of Anophelines carry it, and that according to some, only certain varieties of some of these species are effective. As a fairly general rule, animal parasites are very particular in their choice of hosts. Thus, no one has succeeded in infecting animals with human malaria, and the probability is that it will not exist in many kinds of mosquitoes. Between 1895 and 1899 I failed entirely in infecting several species of Culex and Stegomyia, though I made experiments on hundreds of the insects ; and these results were confirmed by the Italian observers, by Stephens and Christophers, and by many others. But nevertheless such negative results are never absolutely conclusive unless enormous numbers of experiments are made, because it is always possible that some condition such as of temperature or humidity, may have been overlooked, or that the proper species or variety may not have been used. But there is a strong argument against mosquitoes in general being concerned, namely that from the oldest times malaria has been known to be connected with marshes, while many mosquitoes, such as most Culex and Stegomyia, do not breed in marshes as a rule, but in petty collections of water round houses. If these carry malaria, then malaria should abound everywhere, especially in towns, and not so exclusively near marshes. A good contrast is found in the case of yellow fever, which does abound in towns and not particularly near marshes — for the simple reason that it is carried by Stegomyia. On the whole then, though we cannot say definitely that malaria is not carried by other hosts than Anophelines, yet there are strong reasons for this opinion. At all events we are fairly certain that all insects which carry it must be marsh-born, like the Anophelines ; so that the principal preventive measure of drainage is not seriously affected by the question. 24 9. IS MALARIA DUE TO THE SOIL ? — Even after the mosquito theorem was established, many capable medical men remained of the opinion that there might be another method of infection as well. They still thought (and indeed some still think) that the soil gives off an infective effluvium, or miasma, which produces malaria in those who inhale it. Let us e.xamine this hypothesis with care. As stated in section i, the ancients knew that malaria abounds mostly near marshes. It was only reasonable to suppose, then, that the disease is produced by something which comes from the marsh. When Laveran discovered the parasites in 1880, everyone thought that they originate in marshes, but (as already noted) efforts to prove this by experiment were failures. When the Anophelines were incriminated, and were at the same time shown to breed in marshes, the connection between the marsh and malaria was so well explained that there seemed to be no longer any need for the old miasmic hypothesis. Nevertheless it still received the confidence of many, for reasons which I will now classify and criticise. (i) Mosquitoes may abound where there is no malaria. — This is quite true, but has no bearing on the case. When people talk of there being many mosquitoes in a locality they generally refer to Culex and Stegomyia, which so frequently swarm in houses in the tropics. But these do not carry malaria, and their prevalence does not, therefore, affect the question. (2) Malarial infections may occur where there are no Anophelines. So far as we know, this is not true. In not a single case as yet has it been proved by competent observers that Anophelines are absent when fresh malarial infections are occurring. I say competent observers, because untrained persons are not at all to be relied upon to find them. For example, the Hon. Dr. Strachan and I once spent two nights at Ibadan, near Lagos, in a new house in which I did not see a single mosquito the whole time. In the mosquito trap however (a net with a small hole or two and a man inside for bait), five or six, mostly Anophelines, were captured each night ; so that the insects were really very numerous. Again, in Mauritius, we failed for some weeks, even with the aid of a number of trained " moustiquiers, " to find the real culprits at Clairfond marsh (addendum 2): It is obvious that an " ordinary visitor " might easily be misled in circumstances like these. 25 We must not expect that in every malarious locality, the malaria- bearing gnats are the commonest. Their presence is often lost among swarms of other mosquitoes ; but nevertheless it is the few and not the many which work the mischief. In other places, as at Ibadan, the unwary observer, failing to see any mosquitoes at all, might go away declaring that there were none ; whereas, as a matter of fact, there may be many. The Anophelines are often very surreptitious in their visits to houses — thej- may pour in late at night and leave before day- break (as Stephens and Christophers first showed) ; and they are not such domestic insects as the Culicines. Our moustiquiers stated that the Anophelines at Clairfond scarcely commenced feeding before 9 p.m. or later, either in verandas or in the open (addendum 2). Again, it is quite possible that at the moment when we visit even an intensely malarious place, few Anophelines at all may be there It does not follow that they abound equally all the year round. Even in the rainy season, they often appear, not continuously, but in swarms ; and between the swarms few may be visible. Thus, in one such place many years ago I obtained only a single individual, though the rains had commenced. Want of recognition of this fact has led even capable students of the subject to declare,, without sufficient reason, that there is no constant ratio between the amount of malaria in a locality and the number of Anophelines. (3) Attacks of malarial fever may occur where there are no Anophelines. This also is quite true; and the fact has been cited over and over again in opposition to the mosquito theorem. For instance, persons may suffer from attacks of malaria anywhere — in Britain, on high mountains, and in the arctic regions. As we have seen, there is a rise in the malaria rate in India in April, before the Anopheline season has commenced. Attacks are very common in the winter, in the desert, and far out at sea. In Mauritius and elsewhere it has often been noticed that the disease is very prevalent in planta- tions and factories at times when the workmen undergo their most strenuous labour, as when furrows are being dug, crops transplanted, etc. Soldiers and coolies frequently fall sick when commencing active service and works of construction ; and all this without any particular or excessive prevalence of the Anophelines. Most of such cases are of course merely instances of relapse of malarial fever. The mosquito is responsible only for the initial 26 inoculation, not for the subsequent relapses, which, as stated in section 3, may continue for years anywhere, from the north pole to the south pole. The occurrence of an attack quite apart from the Anophelines has therefore no bearing on the question unless it can be proved to be the first attack. But even this will not always suffice to prove that the infection can be caused in other ways than by mosquitoes. One often meets patients who give the following history : that they had lived long in a malarious place without having suffered from fever, but on returning to the coast and embarking for Europe, they were attacked while out at sea. On examining such patients, I have always found, either that the fever was not certainly malaria, or that the patient had been in the habit of taking quinine regularly when he lived in the malarious place. On embarkation he thinks himself safe and leaves off the quinine ; but without his knowledge he was probably infected all the time ; and the quinine taken by him had sufficed to keep down the numbers of parasites without extirpating them entirely. Hence, when he discontinued the drug on board ship, the parasites began to multiply rapidly and shortly gave him fever. As it was his first attack, he comes away with the belief that he was infected on board the ship, and is cited as a case in which the malarial infection was produced where there were no Anophelines. It is proper however to admit that while most such cases can be explained in a similarly easy manner, we meet one occasionally which is more difficult. But I have never yet met one in which explanation on the mosquito theorem was quite impossible. Every recorded case, even one recently recorded in the south of England, may have been bitten by an infected Anopheline. (4) Malaria is produced by digging. — In section i we saw that the theory of the marsh miasma gradually grew into the telluric hypothesis, according to which malaria is caused by a poison which exists in suitable soil and which escapes from it when it is disturbed ; and instances which apparently support this idea are still cited. From what has just been said, the reader will gather that many of them are probably only relapses occurring among previously infected workmen ; while others may quite possibly be caused in the usual way by Anophelines bred in marshes close to the spot where the soil has been disturbed. Both of these explanations are extremely probable in 27 the case of large operations such as railway and canal works, where hundreds of native workmen are crowded together, housed in rough tents or huts, and perhaps exposed to much fatigue and to the attacks of many mosquitoes. But nevertheless malaria may be caused actually by the digging, though not in the way suggested by the telluric hypo- thesis. I believe that this point was first cleared up by my own obser- vations made in connection with the Sierra Leone railway in 1899. Severe malaria had occurred along the course of the railway while it was being made. On visiting the scene we found innumerable puddles full of the larvae of the Anophelines by the side of the railway embankments, in the "borrow pits" from which earth had been taken for building the embankments, and even under the railway " sleepers." I saw the same thing in connection with the Lagos railway in 1901, and near the Greek village of Moulki in 1896. In fact the matter has now become a common-place with the students of malaria. Hence we must end by admitting that disturbance of the soil is really apt to cause malaria ; but that it may do so, not by liberating any telluric miasm, but by encouraging the breeding of Anophelines, and the occurrence of relapses among the workmen. We see, therefore, that there is little or no evidence in favour of the idea that malaria may be caused by other agencies than by the Anophelines. Let us now examine the strong arguments which may be cited against the hypothesis. I have already argued the case against other insect carriers (section 8). The case against the telluric miasm is very much stronger. In the first place, all experiments to infect men with air or water brought from malarious localities have failed (section i). Secondly, if malaria were due to any particular kind of soil under certain conditions (as has been supposed) it should always be present where that soil and those conditions exist. But we know that actually it comes and goes. For example, it came to Mauritius in 1866, and to Reunion in 1867 ; it is still absent from Seychelles and Rodrigues, though favourable conditions for it exist in those islands (annexure i) ; and it has disappeared from Great Britain. But the soil and the climate of these areas have not changed. Thirdly, if the poison is diffused in the air it ought to affect everyone within a considerable area round the generating centre ; 28 but as a rule the disease is limited to the immediate vicinity ot the marsh (addendum 2). Fourthly, the telluric miasm ought to attack especially those who are engaged in digging, but I have never observed that cultivators and gardeners suffer much more than their neighbours ; while, as a matter of fact, it is generally the children and even the infants who suffer the most. Lastly, the idea that the parasites can live in soil, water and air, as well as in men and mosquitoes is extremely improbable in the light of our general knowledge of parasites. The last is probably the clinching argument. Living organisms do not possess independent properties ; but accord more or less in their structure, capacities, habits and life-history with other organisms. We are cognisant of thousands of parasites of men, animals and plants ; and what we know of the parasites of malaria shows that they are not markedly exceptional. In fact they belong to a class of parasites which infect two hosts, one of which feeds on the other — as, for instance, parasites of the deer and the tiger, the mouse and the cat, the ox and man, the ox and the cattle tick, and now man and mosquitoes. The general law is, therefore satisfied by the known life-history of malaria. We have no reason to expect another life-history for the malaria parasites in soil, water or air, any more than for the other parasites. Then again, every animal possesses only the limited powers which have been given to it by the evolution of ages, and for which it has acquired definite organs and habits of life. The mole burrows, the fish swims, the bird flies, the parasite occupies the higher animal or plant. But if this telluric hypothesis is sound, what remarkable animals must these parasites of malaria be ! They already possess a structure wonderfully adapted for their life in men and also in mosquitoes ; but we must now expect that they are also able to burrow like the mole, swim like the fish, and fly like the bird ! To do all these things they must have the suitable organs ; and not only this, but they or their spores must be protected against heat and cold and hosts of enemies in soil, water and air. If all this were true we should have to put the parasites of malaria in a special class by themselves, apart from the rest of creation. These reasons have now led pathologists and parasitologists (who can perhaps appreciate their weight better than othefs) ' to abandon 29 the telluric hypothesis as a likely one. There is no evidence in favour of it, and there are very strong arguments against it. The true theorem is obvious. The connection between malaria and the marsh, so long known to suffering humanity, is now fully explained by the fact that the Anophelines breed in the marsh. There is no necessity to believe that the germs also breed in the marsh. Malaria comes from the marsh, not because the germs of the disease come from it, but because the carriers of the germs do so. It is the same thing in the end. The ancient theory was quite right. Malaria is caused by a marsh miasm. The Anophelines themselves, the mosquitoes, are the march miasm. 10. WHAT DO WE MEAN BY THE AMOUNT OF MALARIA IN A LOCALITY?— It is very necessary to obtain perfectly clear ideas on this point. If we could examine all the people in a locality and could ascertain exactly where and when each patient was infected, we could then divide all the cases into two classes, namely, those who were infected outside the locality and those who were infected within it. We might call these classes respectively the imported cases and the indigenous cases ; and the ratio of the numbers of each class to the total population of the locality might be called respectively the imported malaria rate and the indigenous malaria rate. The imported cases may be very numerous in some places, such as military stations, into which badly infected regiments are introduced ; or sanatoria or hill stations, such as Curepipe in Mauritius, where patients congregate for change of air or security. Or they may be very few, as in rural villages, the inhabitants of which do not migrate much. If, then, we talk of the amount of malarial /ever in a locality, we include both classes, since the imported as well as the indigenous cases may suffer from relapses in it. But if we talk of the amount of malaria in it, we generally mean the amount of malaria which is or has been contracted within it — that is we refer to the indigenous cases only. It is often difficult or impossible to distinguish whether a case was or was not infected within the locality. Careful enquiry may fail to determine the point ; and there are many cases which were originally infected without, but which have been cured and then 30 re-infected within — so that if we omit these from our Hst of indigenous cases we shall obtain wrong results. Again, many of our indigenous cases may have emigrated elsewhere since becoming infected. In many localities, however, unless people are especially attracted or repelled to or from them, the number of emigrants and immigrants will tend to be equal. That is to say, on a rough average, as many patients will be leaving the locality as entering it ; so that the total malaria rate of the locality will represent fairly accurately the indigenous malaria rate. The indigenous cases may be further classified according to the dates when they were infected ; some may have been infected a month ago, others two months ago and so on. If we ascertain the number of persons infected in a year or in a month, we can obtain what may be called the annual or monthly infection rates of the locality. When we say that a place is very malarious, we mean that its infection rate is very high. When we say that it is very malarious at a given season, we mean that its infection rate is very high at that season — not necessarily at other seasons. These rates are difficult to obtain, and, in fact, can be obtained only after mathematical investigation. Similar rates may be ascer- tained for all diseases ; and I have suggested the name pathometry for this branch of study. As a rule in medical statistics, most of the considerations given above are ignored ; with the result that the statistics are often quite useless. We shall consider later (section 19) the best methods for measuring the amount of malaria in a locality. II. FACTORS WHICH INFLUENCE THE INFECTION RATE.— The infection rate varies, not only in neighbouring places, but even in the same place from year to year. It rose suddenly from zero to a high figure in Mauritius in 1866 : and has long fallen to zero in Britain. What is the cause of these variations ? This question is so important as regards both the general theory of malaria and the subject of prevention that we must endeavour to obtain clear ideas about it by careful reasoning. The number of infections occurring in a locality during any interval of time (say one month) depends on the number of infected Anophelines ; which in its turn depends on the number of 31 Anophelines which have bitten previously infected persons. We can therefore calculate the former if we can calculate the latter. Let / denote the average population of the locality ; mp, the average number of infected persons in the locality during the first month of the enquiry ; and imp, the average number of these whose blood contains enough of the sexual forms of the parasites to infect Anophelines. Here m and i are fractions, since mp must be less than p, and imp less than mp. Next, let a denote the average number of Anophelines in the locality capable of carrying malaria, and ba the average number of these which succeed in feeding on a single person during the month. Here b must be a very small fraction, since probably many mosquitoes never succeed in biting men at all, and of those that do succeed only a few will have bitten a particular individual. Hence the average number of Anophelines which have bitten the suitably infected persons during the months will be baimp. Now if any of these insects are, in their turn, to infect human beings, they nmst survive for at least a week or more, in order to give time for the parasites to mature within them ; and by no means all of them will survive so long. Let s be the average proportion of Anophelines which can survive for that period ; then sbaimp will be the number of the infected mosquitoes which have survived long enough to infect men in their turn, where s is also a fraction. But not all of these will find opportunities to bite human beings again, though they have survived long enough to do so. Let f be the proportion which succeed in biting. Then fsbaimp will be the average number of infected Anophelines which succeed in infecting men ; and if each of these infects a separate person and only one person, the same expression will denote the average number of persons infected during the month. Thus fsbaimp not only gives the monthly number of infections occurring among the population p, but also shows that this number depends upon the factors f, s, b, a, i, m. The greater these factors are, the greater will be the infection rate. If m, the proportion of infected persons at the beginning of the enquiry, is high, the infection rate also will be high, but if in = o to begin with, that is, if there are no infected persons in the locality to begin with, then there will be no new infections, because the Anophelines cannot 32 become infected — as at present in Britain. Again, if a, the total number of Anophelines in the locality, is high, the infection rate will also be high (if the other factors remain the same) ; but ii a — o, new infections will cease. The factors i, s,f, b, are likely to be fairly constant and may be roughly calculated. Thus i denotes the proportion of infected persons capable of infecting Anophelines of the proper kind ; and we shall not be far wrong if we take it that, on the average, only one quarter of the malaria patients contain enough parasites ripe for this function ; so that we may put 2'=j. Again, s denotes the proportion of Anophelines which can survive for a week or more, and will vary with the number of enemies of mosquitoes present, the warmth of the weather, the abundance of the food, and so on ; but at a rough estimate it might be put at ^ ; so that we may write s^\. The factor / denotes the proportion of Anophelines which succeed in biting human beings during one month — that is, I suppose, during their average life. It must be less than J because only about half the Anophelines, the females, attempt to bite human beings, and certainly all of these do not succeed in their quest. Let us therefore put_/'=J. Lastly b denotes the proportion of Anophelines which succeed in biting one individual. Now if/ is the human population of the locality, and / is the proportion of f Anophelines which can bite any of these, then obviously-^ is the f ^ proportion which can bite only one person ; that is, i5=— • and as we 1 ^ ' have taken /= J, then b= -j—- Let us now consider an example. Let the population, />= 1,000 ; let m=\, so that mp, the number of infected persons = 500. Then of these only one quarter will be able to infect Anophelines ; or imj> = 125. Next suppose that there are 12,000 Anophelines (a) in the locality, or 12 to each person. Then since only J of these, or 3, are likely to succeed in biting, baimp, the number of them which have bitten the 125 suitably infected persons,=:3x 125 = 375. But of these only about \ are likely to survive long enough to infect people in their turn ; that is, sbaimp = 125. Lastly only about J of the survivors are likely to succeed in biting again ; so that the final residue of infecting Anophelines, given by/s-(^fl/;«/, amounts only to 31-25. If each of these bites a single and a different person,- 31 people will now become 33 infected. Thus the infection rate of the locahty during the month will be 3T25 % of the population. If we adopt the values suggested above for the constants z, s,f, b, namely, ^, -g-, \, -jj respectively, we have, No. of infections ^ fsbainip — ^r^^ To obtain the infection rate per 100 of the population, we have to multiply the number of infections by — ■, so that : — P Infection rate % = =[92 • ^ ~^ ' T' "^^^^^^Y '> that is to say, the monthly infection rate per 100 of the population equals roughly half the malaria rate multiplied by the number of Anophelines in the locality to each person. Thus in a village in which there are 1,250 people, 750 infected persons, and 3,000 Anophelines, the malaria rate is 0'6, the number of Anophelines to each person is 2'4, and the monthly infection rate % is 0"72. That is, if a person lives in the village for a month, his chances of becoming infected will be as 72 to 10,000. Such calculations as these, which may appear far-fetched to many, are useful, not so much for the numerical estimates yielded by them, but because they give more precision to our ideas and a guide for future investigations. Thus, whatever numerical value the symbols f s, ii, i, in, p may have, we see that the infection rate is dependent not only on two of them, a and ;«, as is often stated, but on all, and is therefore not so easy to calculate as may be thought. 12. CONDITIONS WHICH CHANGE THE NUMBER OF INFECTED PEOPLE IN A LOCALITY.— The number of infecting mosquitoes which succeed in biting again is fsbaimp. If we adopt the values for /, s, b, i, suggested in the last section, this becomes . inp. Now, if all these bite different people, some 192^ will bite healthy people and give them fresh infections ; and others will bite persons already infected. If, as before, nip is the number of persons already infected, then / — nip, that is, (1 — ;«)/, will be the number of healthy people. Hence, by proportion, the number of the infecting mosquitoes which bite the healthy people will be (1 — m) j^,< j^- '>^P \ ^"d if each bites a different person. 34 and each person becomes infected, the same expression will denote the addition made to the number of infected persons in the locality at the end of the month. But during the same time some of the persons originally infected may have recovered. Let us denote the number of these by rinp, where ;- must be a fraction. Hence, if the number of newly infected persons, (1 — ^Oy^r . mp is greater than rmp, the number of recoveries, the total number of infected persons will be increased ; but it will be decreased if the former is less than the latter. Thus the change depends upon whether (1 — w/)^— „-, is greater or less than r. In section 3, I estimated roughly that half the infected people remain ill after three months. Thus VJ remain ill after only one month, and 1 — Vi. or 0-2063, recover ; so that we may write for a rough estimate, r — 0-2063. Thus the malaria remains unchanged if ,-^-=, — = :; ; that IS, if 192/' 1 — 7«' ' _^ _ 39-60 / 1 — m ' that is, if the number of Anophelines to each person is about 40 r . If m, the original malaria rate, is very small, the rate will remain constant if there are not more than 40 Anophelines to each person. If it is high, say \, it will remain constant even when the number of Anophelines is doubled. If the 40 number of Anophelines is higher or lower than ^j , the malaria will increase or diminish, as the case may be. Of course the actual number 40 is only a rough approximation, because we have adopted more or less arbitrary values for the constants /, s, /, r, and because we have made certain assumptions which may not be quite exact. But, as I have said, the calculation is useful, not for its numerical results, but because it helps to give precision to our ideas. It is often thought and said that, if the mosquito theorem is true, malaria should exist wherever there are any Anophelines of the proper kind, and when this is found not to be the case, the theorem is doubted. Similarly, it has often been stated that anti-mosquito measures will be useless because, as long as any Anophelines remain, the disease \\\\\ remain also. But 3? these fears will now be seen to be groundless. The Anophelines must not only exist but must be numerous, if the disease is to remain constant or to increase. The above calculation suggests that they must average at least 40 to each person during a month if this is to happen ; and if they fall below this standard, the malaria will begin to diminish. Whether the figure 40 is quite exact or not does not matter — the important thing is that there is and must be some standard, whatever it is. And a little thought will convince us further of this valuable law. Obviously, unless the number of Anophelines is large, the dangers and difficulties which confront them will end by making them too few to infect numerous enough healthy persons to compensate for the recoveries among patients which are happily always occurring, and the disease will diminish and die out — as has frequently happened. It is possible to obtain the general malaria function or expression which gives the number of infected persons after the lapse of .r months, but the full calculation is scarcely necessary for this report.* If, how- ever, m is Small, and if m^p denotes the number of infected persons at the end of .r months, then approximately inj)=(\ — r + sif'-yvip. This increases or diminishes wnen x increases, if 1 — f + sip — is a f greater or less than unity, that is, if sif- — is greater or less than r. P If J, t,f, r have the values already suggested, so that the malaria rate increases or decreases indefinitely if a is greater or less than about 40/. The function is what is called an exponential function, and changes slowly at first, and rapidly later. Thus, suppose that mp = 2 (so that the epidemic starts with only two cases) ; that/' = 1,000 and a =. 136,000. Then m^ = (#)* . 2. From this we find that the number of infected persons will be about 2, 3, 4, 7, 10, 15 in successive months, rising to 115 after ten months, and 665 after twenty months. This explains the outbreak of epidemics * I hope to publish the full analysis later. Obviously, deaths and other factors have been omitted from consideration in the above rough eslimates. 3A 36 consequent on the introduction of cases from without, in places where there are enough Anophelines. The same equation holds approximately, even when in is high if a is comparatively small — that is, if the mosquitoes are reduced ; but in this case the malarial rate will fall. Suppose that ;« = J and p = 1,000, so that there are 500 infected persons to start with ; and let a — 8,000. Then ,£, — - — '-. Hence the number of infected 192/ 6 persons in successive months will be 500, 417, 347, 289, 241 ; falling to 64 in ten months, and 8 in twenty. In this case the malaria decreased even when there were as many as eight Anophelines to each person. If all the Anophelines are destroyed, vixp = (j — rYnip = {^TdZl^mp that is, the cases diminish according to the adopted rate of recovery (section 3) without an}- new infections occurring. If/ = 1,000 and mp = 500 as before, the number of infected persons in successive months will be 400, 396, 314, 250, 198, 157, 125 ; falling to 50 in ten months ; 5 in twenty ; and 4 in two years. This fall is not much greater than that shown in the preceding paragraph ; so that the reduction of Anophelines from 6,000 to zero does not make very much difference. In other words, in order to produce a marked diminution in the malaria rate, it is not necessary to get rid of every Anopheline — a reduction will suffice.* The important question now arises, What reduction must be made in the number of Anophelines in order that the malaria rate shall fall to an assigned fraction in a given time .' Suppose that in the village of 1,000 inhabitants the malaria rate has been stand- ing at about \, so that on the average 500 people in it have been infected. Then -= - — ^ — 80; so that there must have been about / J- 2 80 Anophelines to each person in the village. Now, suppose that we do not possess sufficient funds to make a complete clearance of the mosquitoes, but would like to reduce the malaria rate to one-tenth of the population in one year, what reduction must we make in the number of Anophelines to effect this object ? From the approximate general equation, when a is small, we have ^ = 192*v-^_152. p m * Compare page 148. 37 Here a- = 12 ; '^ = i ; 1921271 = about 168 ; and therefore | = 16. Hence we must reduce the Anophelines to one-fifth if we wish to reduce the malaria rate in the same proportion, that is, from a half to one tenth, in a year. If we are given two years for the reduction, the Anopheline ratio need not be less than 27, or one-third of the 80, which might be cheaper to effect. The following table gives the fall in the number of infected persons, which, according to the formula, should occur if a is reduced to 2/, to /, to \p, and to zero : — Li Months 1 2 3 4 10 20 = 2/ Cases 500 407-2 331-7 270-1 220-0 64-2 8-2 = P » 500 402-0 323-2 259-9 209-0 56-5 6-3 = y „ 500 399-4 319-1 254-9 203-9 52-9 5-6 = » 500 396-8 314-9 250-0 198-4 49-6 4-9 Of course, the greatest fall in the cases occurs when there are no Anophelines ; but even when there are two Anophelines to each person, the fall is not very much less. 13. THE NUMBER, LENGTH OF LIFE, AND DIFFUSION OF ANOPHELINES IN A LOCALITY,— The important ratio - denotes the average number of Anophelines to each person in a locality ; and we have seen that, if it falls below the critical figure of 40 about ^j , the malaria rate will diminish. The number may seem somewhat high ; but we must remember the values we gave to the constants / and s. We judged that only one-quarter of the Anophelines are likely to succeed in biting human beings ; that only one-third of these are likely to survive for a week or more ; and that only one-quarter of the remainder are likely to succeed in biting a second person. Hence only one in forty-eight is ever likely to give infection. What really is the average number of adult Anophelines in a locality ? It is impossible to say. Sometimes in a single room twenty or more of certain species may be captured ; at other times they are difficult to find. At Clairfond, in Mauritius, our moustiquiers were searching for some weeks before they caught a single P. costalis, which is the carrier there. As a rule, in the houses of Indians about one Anopheline for each occupant may be a rough 38 average for the insects actually caught. But the insects caught are probably mostly the gorged and gravid ones, which have recently had a good meal, the majority escaping out of doors in the morning. On the whole, it is quite possible that close to marshes there may be a hundred or more Anophelines to each person. My experiment to estimate the output oi Myzorhynchus viauritianus from the Clairfond marsh (addendum 2) showed that 1,000 square yards of marsh might yield 423 every night, or 12,690 a month during the season. As to the length of life of mosquitoes. It used to be thought that they live only for a few days, until I kept them alive by repeated feed- ings for a month or more in 1899. Since then Stegoinyice have been kept in captivity for several months. Anophelines are more difficult to manage, but will live for some weeks. Such experiments, however, give little evidence as to the question. What is the average length of life of the insects in nature ? In captivity they are preserved from enemies, wind and weather ; but, on the other hand, probably suffer from their imprisonment. The only criterion which I can suggest is a somewhat curious one, based on the length of life of their parasites. Thus the parasites of malaria and yellow fever and the worms called ■Filaria bancrofli take from one to three weeks to develop in the insects. Hence I infer that the average life of the hosts probably exceeds that period, as otherwise the parasites would have little chance of completing their life cycle. Of course, large numbers of gnats hibernate and aestivate for months, but this suggests only their maximum life. What we want to know is their average life. I fancy that a month may be a good rough estimate during the most favourable season. The diffusion of mosquitoes is a question of the first importance in the prevention of mosquito-borne diseases. When I first proposed in 1899 to rid towns of malaria by clearing them of the breeding places of mosquitoes, many people objected at once that the clearance would be futile, as the insects would certainly rush in on all sides from the surrounding uncleared country ; and for three years no one could be persuaded to try the measure. In fact, an experiment was attempted later in India which showed that, if anything, the clearance increased their numbers ! In 1903, however, the brilliant examples of Ismailia and the Federated Malay States served to discredit such 39 fancies. In 1904 I read a paper (3) in which the whole subject was examined from a mathematical or rather logical basis, and the following points were made clear. The diffusion of mosquitoes depends on laws which regulate the diffusion of all animals. The animals within a given area consist partly of natives and partly of immigrants ; and the larger the area the smaller will be the proportion of immigrants to natives. If the population (that is, the number of animals) is in a static condition in a country, the number of immigrants and emigrants which cross a given length of border will tend to be equal and opposite — that is, the number of immigrants into an area will be compensated for by the number of emigrants out of it. If we suppress the birth-rate within the area, the population must henceforth, after the death of all the natives, consist merely of immigrants. If the area is large, and if such suppression does not specially attract the immigrants, the result must be that the population will be greatly reduced. Obviously, if we were to suppress the human birth-rate in Mauritius without increasing the rate of immigration into it, or checking the emigration out of it, the human population would be vastly reduced in time. A precisely similar thing must happen with the mosquito population. The immigrants constitute only a small fraction of the natives, and when the latter cease to exist, the population must fall (see also 4). The rate of the fall according to radius of area was a difficult mathematical question, for which I attempted only a partial answer ; but I asked Professor Karl Pearson, F.R.S., to solve it. This he has done in a thorough and admirable way (5). For example, he shows that, if we suppress mosquito propagation within a circular area one mile in diameter, the mosquito density will be reduced at the centre to only 3 % of the normal mosquito density outside the area. A quarter of a mile from the centre it will be 18 %, and at the boundary of the area it will be 75 % of the normal density. If we clear a rectangular patch of country, two miles long and one mile broad, the mosquito density at the centre will fall to I °/o. If we clear a square of one mile wide, the density at the centre will be 2 /^ ; at a quarter of a mile from the boundary it 40 will be 1 1 % ; and at the boundary it will be 50 %, or one-half. Of course these mosquitoes found in the area after propagation has been checked within it consist entirely of immigrants. Take, for example, the case of a village of 1,000 people collected within a circle of a ^-mile radius in which the number of infected persons has been standing at 500. In this case, by last section, there must have been about 80 Anophelines to each person. Now, let us drain within a circle of ha)f-a-mile radius round the centre of the village. Then the mosquito density at the centre will be 3 %, and at the outskirts of the village 18 %, or 14-4 to each person at most. Hence, by last section, the number of infected persons will fall as follows : — Months 01 2 3 4 10 20 500 472 445 420 396 279 156 But, of course, the average number of mosquitoes in the village would be less than 18 to each person, and the fall in the malaria would be greater. Professor Pearson's estimates, like mine, are based on values of constants conjectured by myself on a basis of general probability, not determined by investigation. I have had no opportunity to make such investigation ; and no one else has attempted it — the enquiry would be difficult, and would demand mathematical as well as experimental skill. In the meantime, however, there is this excuse for adopting tentative values — that the process enables us to form a clear mental picture of the factors concerned in malaria rate, and, perhaps, to investigate them in the future. Lastly, we should note that what are called constants above may be constant only for definite or even short periods. Thus the number of Anophelines varies from season to season, and may increase or diminish in the same locality owing to the formation or disappearance of breeding pools. If it were not so, the malaria rate would tend either to vanish or to reach the maximum ; but generally it increases and decreases at different times, according to fluctuations in the value of this constant. 41 PART II.— MALARIA IN MAURITIUS. 14. SHORT DESCRIPTION OF MAURITIUS.— The island of Mauritius is situated in the Indian Ocean, about 550 miles east of Madagascar, and lies between the parallels 19° 50' and 20" 31' south latitude and 57" if and 57° 46' east longitude, thus being just within the Tropics. It is 36 miles long and 28 miles broad, has an area of 705 square miles, and a coast line of about 154 miles. It consists of a table-land, of which the highest ridge, 2,300 feet above the sea, runs across the island in a N.E. direction. On either side of this ridge there are extensive plains, sloping down gently, or more abruptly in places, to the sea. Several small mountain ranges, of which the highest peak is 2,711 feet high, border the table-land. Near the sea, especially to the north and west, the plains have little elevation. Numerous small rivers cross the plateau from the medial watershed to the sea, cutting out deeper and deeper channels as they go. The mountains and parts of the plains are well wooded, but most of the surface of the island is under sugar cane cultivation. The geological formation is volcanic. The climate is that of tropical islands, warm, equable, and humid. The cooler season lasts from May to October, the warmer from November to April. The mean annual temperature at the Observa- tory (near sea-level) is put at 74-75° F., the mean lowest being about 58-59° F., and the mean highest about 87-88° F. The prevailing wind is the S.E. trade wind ; and severe cyclones occur in the warm season. Rain falls at all seasons, but there are two rainfall maxima, one in February and one in August, and two minima, one in June and one in September. The mean annual amount and number of days of rain vary with elevation and other factors from about 33 inches and 86 days to about 1 50 inches and nearly 300 days — the rainiest spots being at elevated points exposed to the S.E. wind. Heavy falls occur with the cyclones. Mauritius was discovered by the Portuguese in 1507, and occupied in 1589 by the Dutch, who, however, abandoned it in 17 12. Three j^ears later the French took possession of it, and in 18 10 it was occupied by the British. In 1834 the slaves were set free ; in 1835 the importation of Indian immigrant labour commenced, and in 1865-66 malaria first appeared in the island. At the census of 1901 the population was found to be S73,33t), and was divided officially into General Population (i 1 1,440), Indian Population (259,086), and Military and Shipping (2,810). The " general population " included whites, Africans, and half-castes. At present the population is estimated at 375,400 (1906). The capital, Port Louis, is also the principal seaport, and with the small surrounding district had a population of 50,342 in 1906. Recently the population has been drifting more and more to the cooler and healthier district of Plaines Wilhems, on the table-land, which, in 1906, showed a population of 66,157, gathered mostly in a chain of towns and villages along the railway. Chief of these towns are Beau Bassin (750 feet), Quatre Bornes (1,050 feet). Phoenix and Vacoas (1,400 feet), and Curepipe (1,800 feet). Other villages are Pamplemousses, Poudre d'Or, Flacq, Mahebourg, SouiUac, Rose Belle, and Moka, most of which also are tending to lose many of their inhabitants for the same cause. The island has a network of railways, by which it can be traversed in about two hours. Scattered over the country there are about a hundred sugar plantations and factories, each with a considerable population of Indian coolies ; and villages and huts of Indians abound almost everywhere, mostly hidden among trees. As might be expected in so old and civilised a colony, it possesses many good buildings, not only in the towns, but on the sugar estates and in the villages. Many of the private houses, especially in Port Louis, are two-storeyed ; but the majority are built on the model of the Indian bungalow, with a single floor and verandas, and servants' quarters behind, lying within a garden or " compound." The lower class of house is not so good, and is largely made of wood (though not raised on piles) ; and the lowest class is the mud hut of the Indian, or even a structure composed of old pieces of kerosene oil tins, the danger from cyclones being the reason given for such poor buildings. Churches, schools, and other public institutions are numerous.* Plaines Wilhems district has an extremely good water supply from the Mare-aux-Vacoas, and other pipe supplies are given to Port Louis and several villages ; but wells and streams are largely resorted to. Food is good and cheap. Horse and mule transit * Views of the plateau, of the houses, &c., will be found in the Photographs at the end of this Report, 43 is expensive owing to loss of animals on account of trypanosomiasis (surra). Night soil and rubbish conservancy is placed by the Health Department in the hands of contractors, and, in my opinion, is fairly well carried out. Labour is fairly cheap, though not so cheap as in India, as unskilled labour costs about Rs.15 a month. In 1906 the birth rate was 33-5 per mille, and the death rate 40 per mille. The Revenue and Receipts for 1905-6 amounted to Rs. 1 1,169,783, and the expenditure to Rs. 9, 91 5,863, of which Rs. 749, 827 was spent on the Medical and Health Department and on quarantine. At the census of 1901 there were 93,031 "houses" in the Colony, each containing 4'2 5 persons on the average. In the same year the average density of population was 534 persons to a square mile, almost equal to that of England. 15. THE OUTBREAK OF MALARIA IN MAURITIUS,— When Bernardin Saint-Pierre wrote his classical tale, Paul and Virginia (published in 1789), the scene of which is laid in Mauritius, there could have been no endemic malaria in the island. The author, who had lived there, pictured it as a country of pastoral romance, benign and healthy as it was beautiful. The hero and heroine, born in the island of white parents, and supposed to live in the Vallee des Pretres, very little above sea-level, were represented as vigorous ideal types of the European race. Yet the author evidently knew of the existence of malaria elsewhere, for he describes the death of the heroine's father from fever contracted in Madagascar, and says "he landed (in Madagascar) at that unhealthy season which commences about the middle of October, .... which prevails in that country for six months in the year, and which will for ever baffle the attempts of the European nations to colonise that fatal soil " — quite evidently malaria. No mention is made of a similar disease, or of similar results, in Mauritius, although an excellent description is given of the hot weather in December, including a reference to the " noise of insects which seek to allay their thirst in the blood of men and of animals." Yet we read that, when the Dutch first attempted to settle in Mauritius, they brought over numerous slaves from Madagascar, who afterwards peopled the island. Unless Madagascar was newly 44 infected between that time and the date of Saint-Pierre's novel, many of these slaves must probably have had fever ; and this fever should have spread in Mauritius if the conditions had been favourable. The introduction of slaves from Africa continued during the French occupation, and early last century many Indians began, to find their way to the island. In 1835 the wholesale importation of indentured Indian coolies (with women and children) commenced. Infected regiments from India and elsewhere have frequently been introduced. Hence cases of malarial infection must have been brought in, not only by scores, but probably by hundreds and thousands, from the beginning of the history of Mauritius. Yet there is abundant evidence, apart from that in Paul and Virginia, to prove that no endemic malaria existed there before 1865 — that is to say that, though cases were introduced from without, the disease did not spread in the island before that date. Then, however, the great tragedy occurred, and in two years the island of pastoral romance fell to the condition of West Africa or the Himalayan Terai. It is not necessary for the purposes of this I'eport to compile a laboured account of the outbreak, and I will therefore give only the outlines. The literature of the subject is large. Shortly after the commencement of the epidemic the government very wisely appointed a commission of enquiry, which published a bulky report in 1868 (6). Since then numerous publications on the subject have appeared. An admirable summary has been published by so great an authority as Dr. Andrew Davidson, who was in Mauritius at the time (7) ; and I have read a valuable critique in manuscript on the subject by Dr. A. Lesur. After studying probably most of this material, I conclude that endemic malaria on a large scale certainly appeared in Mauritius for the first time in 1866. The evidence in favour of this opinion may be summarised as follows. (i) Almost all medical writers on Mauritius prior to 1866 state definitely that there was no endemic malaria there. Some note ex- pressl}' that, when cases occurred, they were imported cases. Others remark with surprise on the absence of the disease, in view of the fact that all the conditions which favour its prevalence in other countries were present. Such testimony is really conclusive in itself. We may object that, after all, the writers may have made mistakes of diagnosis. 45 and that malarial fever might really have existed, but was returned under other names. But the total amount of fever of any kind was small, and medical men of wide experience in the tropics must be credited with sufficient acumen to detect malarial fever, even before the discovery of the parasites. If the disease had existed even to a fraction of its present prevalence, the fact would certainly have been noted, not only by physicians, but by the general public as well. As a matter of fact, it was " conspicuous by its absence " — so much so that Mauritius was considered a sanatorium for sick officers from India and elsewhere. (2) The medical statistics of the troops in Mauritius demonstrate the same fact quite clearly. I give the figures for malarial fevers (collected by Major Fowler). Years . 1838-54 185s 1855 1857 1858 1859 i860 1861 Admissions per 1,000 .. 0-6 0-56 5-02 4-08 22-39 31-89 21-13 3-04 Deaths per 1,000 . 0-0 00 0-0 0-0 0-0 0-0 1-7 0-0 Years 1862 1863 r864 1865 1866 1867 1868 Admissions per 1,000 21-6 2-52 1-65 2-06 21-32 1487-06 1243-26 Deaths per 1,000 1-45 0-50 0-55 0-0 0-56 16-61 10-0 Years 1B77-86 1887-96 1897 1898 1S99 1900 I90I Admissions per 1,000 1171-0 608-2 406-1 380-0 245-0 207 389 Deaths per 1,000 54 3-12 1-32 0-0 0-0 2-0 4-6 Strength 463 429 Years igo2 1903 1904 1905 1906 1907 Admissions per 1,000 369 150 201 524 137-4 231-6 Deaths per 1,000 ... 0-0 0-0 0-7 3-7 0-84 1-96 Strength ... 425 746 1,358 1,357 1,193 1,019 The small rises in 1858 and 1862 were due to relapses among troops newly arrived from India and China. The enormous rise in 1867 was due to the appearance of endemic malaria. The compara- tively high figure for 1905 was probably due to mobilisation of the troops during the malaria season. The death rate tends to fall more and more owing to improved treatment and to early invaliding. Dr. Davidson remarks: — " From 1823 to 1858, out of a strength varying, as a rule, from 1145 to 2321, there were 51 admissions into the military 46 hospital for intermittent fever, which gives an average of less than two cases per annum. During these thirty-five years only one death occurred from intermittent fever. During the same period there were only ten cases of remittent fever, with no deaths. It is doubtful whether during this period a single soldier was admitted for paroxysmal fever contracted on the island." The admissions into the Civil Hospital at Port Louis told the same story, there having been only twelve for malaria during forty-five years. (3) Perhaps the most conclusive statistical evidence was that adduced by Dr. C. Meldrum, F.R.S., C.M.G., in 1880-90 in quarterly reports on the relations of climate to disease in Mauritius (8). His argument is this. Previous to 1867 the deaths in the colony were fairly evenly distributed from month to month, without any special rise at any particular season, except, of course, when various epidemics occurred. Since then, however, the whole character of the mortality returns has changed owing to a marked rise in the number of deaths during the summer — that is, the malaria season. This rise is precisely what occurs in all very malarious regions ; so that the absence of it before 1867 shows that there could have been little malaria then in the island (see also section 18, 4). Although that disease did not exist, there were other fevers which prevailed, and which have somewhat confused the issue. Chief of these was a fever locally known as Bombay fever. It was much studied by the commission of enquiry, and by many medical men later, especially Drs. Barraut and Lesur. It attacked chiefly the Indian population ; was most prevalent during the cool months ; was epidemic, " contagious," fatal, and prone to relapses ; did not become chronic, and was not influenced by quinine ; was accompanied by enlargement of the liver and jaundice ; and was not particularly prevalent in marshy areas, Dr. Lesur thinks it was merely relapsino- or spirochaete fever ; and Davidson suggests this, and also considers that many of the cases were due to typhoid. In these views I entirely concur. Curiously enough, directly the epidemic of malaria commenced, the Bombay fever disappeared ; and Dr. Lorans has asked me to suggest an explanation. It may be that the disease really did disappear at that moment owing to accidental coincidence (and relapsing fever always comes and goes) ; but there is another 47 explanation, namely, that, when the great epidemic commenced, the two fevers were confused, and the minor one was lost among the numbers of cases of malaria, under cover of which, so to speak, it gradually died out. In those days, of course, microscopical diagnosis between the two diseases was not known. But it should be remarked that from 1862 to 1865 another fever seems to have appeared, which the Commission called the " spurious Bombay fever." This occurred entirely among Indians, but was not contagious. At the same time Dr. Beaugeard, Medical Officer of the Civil Hospital at Port Louis, stated that " Cases of ague have been admitted occurring in persons who had long been resident in the Colony, and in others who had never left the island at all — those latter, however few, still existed prior to 1865." Some of the medical witnesses before the commission also stated that they had seen a few indigenous cases as far back as (?) 1857. We must therefore admit the possibility, if not the probability, that scattered indigenous cases had been occurring in Mauritius prior to 1865. Dr. Davidson thus describes the onset of the great epidemic : — " Sporadic cases of malarial fever contracted in the island were observed from the beginning of 1865 and throughout the year. They were few in number, and seem to have been chiefly confined to the marshy localities near the mouth of Grand River, or to the unhealthy spots near the shore in Port Louis. A slight local epidemic occurred towards the end of the year 1865 among the Indian labourers on Wolmar Estate, a specially marshy locality on the sea- coast in Black River district. A considerable number of cases were also observed in November on Albion Estate, and near the church at Petite Riviere, at the latter place from the 15th to the 25th November." These cases attracted little attention at the time, but next year the epidemic broke out with severity. On Albion Estate there were 207 cases and 31 deaths, and on Gros Cailloux Estate 517 cases and 41 deaths, during 1866. From these it spread north and south. It crept up to Port Louis, Arsenal, Pamplemousses, and elsewhere during the first half of 1866. Southward it spread to Bambou and further. At the first invasion it occupied, according to Davidson, 13^ miles of sea coast, and spread from two to four miles inland. After June it began to abate during the cool season ; but at the 48 commencement of the next warm season (1866 to 1867) it broke out with increased violence. Not only were the same districts affected worse than before, but the disease " invaded the whole of the west coast from south to north, passed round the northern extremity of the island, and extended down the east coast as far as Grand River S.E." At these extremities it was arrested by mountain ranges. During 1867 the epidemic raged in the occupied territory, extending along sixty miles of coastline. Accounts of eye-witnesses of the fever at Port Louis recall descriptions of plague and cholera. One quarter of the inhabi- tants died during 1867 from all causes, and more than one-fifth from fever alone. The survivors " were so prostrated by disease that the living were scarcely able to bury the dead." The highest mortality in Port Louis in one day was 234, on the 27th April 1867, and 6,224 during the whole month, out of a population of 87,000. In the whole island, out of a population of 360,378, there were 31,920 deaths in 1867 ascribed to fever alone ; and the total death rate rose from 32 per mille in 1866 to I20'S in 1867. The actual malaria death rate was probably about 90 per mille. Those who have witnessed malaria in its worst will not doubt these figures.* The third wave, starting in November 1897, completed the conquest of the island by occupying the south and south-east coast. Of course, it reappeared after the winter lull in the areas previously attacked; but in 1868 the death rate was only 10,923 for the whole island, about a third of that of the previous year. Though it spread inland, especially in the Flacq district, it failed then, as now, to reach some of the highest areas of the table-land. At its worst, the fever was, as usual, of the remittent type. Many of the cases were certainly blackwater fever, a point which (as I have not seen noted before) strongly supports the theory that that disease is purelj' malarial, since it does not seem to have existed previously in the island. The usual pernicious paroxysms were common. I cannot find any statistics regarding the percentage of the deaths which occurred among children. For further details, Davidson's book is the most accessible (7). It is most necessary to note that a similar first appearance of malaria occurred in the sister island of Reunion, 125 miles distant, shortly after the outbreak in Mauritius. Davidson gives the date as * Fever Enquiry Commission's Report, page 23. 49 1869, but others adopt an earlier one. MacAuliffe, in his book "Cilaos" (1902), says that it commenced in 1865, owing to the arrival of the ship Eastern Empire with immigrants from Calcutta in December 1864. He saw the immigrants two months later, and thought they had recurrent typhus (? relapsing fever) ; but later the epidemic took the malarial type, and prevailed chiefly round marshes. He warned the inhabitants of Cilaos (12 14 metres high) against the marshes near the town ; but nothing was done, and malaria entered the locality in 1901-2, in spite of its altitude. Possibly the sickness of 1865 was nothing but relapsing fever, and true malaria did not enter until later. At all events, malaria appeared in both these islands almost simultaneously, while it still remains absent from Rodrigues and the neighbouring islands, and from Seychelles, in none of which Anophelines have been found. The Anophelines of Reunion hitherto recorded are Py7'etophoriis costalis (the deadly African and Mauritian one) and Myzorhynchus coustani ; and malaria is extremely prevalent in the island at the present. 16. EXPLANATION OF OUTBREAKS OF MALARIA. — This astonishing occurrence caused much perplexity at the time among the more thoughtful students of malaria. It showed that the disease is at all events not due to any inherent poisonous property of soil, but rather that it might be caused by some living organism capable of invading a country from without. Numerous hypotheses were proposed. Indian immigration was accused of introducing the poison, though a similar introduction by natives of Madagascar, as well as by Indians, had been possible for centuries. Certain ships which arrived in 1865 were suspected — but ships had been arriving for centuries. Floods and droughts were blamed — but floods and droughts had occurred for centuries. Disturbance of the soil in connection with the railway and other works in the Black River district afforded a popular refuge from the difficulty — but it was pointed out that the soil had often been disturbed ; that the largest railway work, done in 1864, was not followed by malaria, and that laying the gas supply in Port Louis in 1864-5 remained equally harmless. The mosquito theorem gives a ready solution of the problem. The appearance of malaria in a locality depends upon the introduction [a) of Anophelines capable of carrying the disease, and {b) of infected 50 persons (section 12). Hence the Mauritian outbreak can be readily explained in either or both of two ways. The carrier of malaria in Mauritius is at present Pyretophorus costalis, the dangerous African Anopheline, and it might have been introduced a little time before the outbreak. Mosquitoes do not easily travel far on board ships. They find difficulty, I imagine, in obtaining water to drink and lay their eggs in, and are apt to be swept away by the wind when seeking it ; while the movement and vibration prevent them from resting or feeding in comfort (as I have actually observed on several occasions). Sometimes, however, they endure these difficulties with success. On several ships, especially river steamers, I have found Culicines breeding in water cans in the cabins, and once in flower vases on an ocean steamer. Possibly Anophelines may be equally successful, but only, I think, on rare occasions, when there are open tubs on deck, or heaps of rain- collecting fruits or vegetables, and so on. For short voyages Anophelines might certainly live in the hold. But for proof that P costalis is not easily transported in this way I may note only that it is not found in the Seychelles, Rodrigues, or the neighbouring smaller islands, and that (fortunately) it has not yet reached India. In other words, if it can be transported at all on board ship, it can be transported only in a very small percentage of ships. Hence it is quite reasonable to suppose that the ships which visited Mauritius from the date of its discovery until about 1865 did not carry P. costalis, but that, at last, about that time, a single ship was unfortunate enough to bring them. Quite possibly the insects were breeding on that ship, and equally possibly the same vessel conveyed them to Reunion about the same time. We must remember also that it is necessary for the insects, not only to survive the voyage, but to obtain a foothold in their new possession — a serious difficulty, which must tend to limit their diffusion still further. But, supposing that, on a single occasion, all these difficulties were overcome, the further course of events would be obvious ; the new country would be overrun by the invaders in the course of a year or two. Next, if there are infected persons present, and the mosquitoes become numerous enough (section 11), healthy persons would be attacked, and an epidemic would begin. All this is very obvious ; but there is another possible explanation 51 of the appearance of endemic malaria in a country — which has not yet been suggested. Suppose that the AnopheHnes have been present from the first, but that the number of infected immigrants has been few. Then, possibly, some of these people have happened to take up their abode in places where the mosquitoes are rare ; others may have recovered quickly ; others may not have chanced to possess parasites in suitable stages ^vhen they have been bitten. Thus the probability of their spreading the infection would be very small. Or, supposing even that some few new infections have been caused, yet, by our rough calculations in section 12, unless the mosquitoes are sufficiently numerous in the locality, the little epidemic may die out after a while — for instance, during the cool season. And, if the number of infected persons introduced from out- side remains small, this state of things may continue for years or centuries — the disease will fail to make headway and will die out. Now, suppose that the number of infected immigrants is suddenly greatly increased. Then much larger numbers of mosquitoes will become infected, and may in their turn infect more healthy people than the recovery rate will compensate for. Endemic cases will begin, will increase ; at first slowly, then rapidly, until suddenly there will be a wide-spread epidemic. It is like the case of a careless person who throws lighted matches into a dry jungle ; the first matches may fall on rock, bare ground, or damp vegetation, but at last one will set the forest on fire. On the whole I incline to the opinion that the first explanation is the more plausible one in the particular case of the great outbreak in Mauritius and Reunion — I think that P costalis was probably introduced a little previously. It is difficult to believe that, if this gnat had been present from the first, and had been as widely diffused as now, the disease would never have spread from the hundreds of infected Africans and Indians who must have entered the Colony during nearly three centuries. No very specially large immigration occurred before the outbreak. True, there were 20,283 immigrants in 1865 ; but as many or more had been introduced in 1843, 1854, 1858, and 1859— in the last year 48,377 — without causing any epidemic. The occurrence of a few sporadic endemic cases (the " false Bombay fever " cases) would fit either theory ; and so would the fact that the epidemic spread from 4A 52 a centre at Petite Riviere. Either, by the first theory, the P- costalis landed there, and spread rapidly round the coast ; or else, by the second theory, the first effective concentration of imported malaria cases occurred there. On the other hand, the facts that the disease occuned almost simultaneously in Mauritius and Reunion, and that P. costalis has not yet reached the smaller neighbouring islands, are strongly in favour of the first theory. Other local outbreaks, however, such as the recent one at Phoenix, I am more inclined to attribute to the second cause, or to both together. The whole subject of the invasion of countries by malaria is of great historical interest. There are many reasons for thinking that Greece and Rome were attacked in ancient times as Mauritius was in modern days. The matter has been ably discussed by Mr. W. H. S. Jones, M.A. (ii). 17. FURTHER HISTORY OF MALARIA IN MAURITIUS. — From the date of its introduction, the disease has become permanently endemic in the lower parts of the island. Before attempting to examine details, it will be advisable to mention the various enquiries on the subject which were made from that time up to the present date. In May, 1867, the Government appointed, as already stated, a Fever Enquiry Cominission to report upon the causes of the outbreak ; and their report was published next year (6). It is a bulky volume, containing a vast mass of evidence, mostly in the form of a questionaire in which numerous medical men and others record their observations and opinions on the epidemic. A full description is given by Dr. Barraut, the General Sanitary Inspector ; and the Commission adds its own conclusions and recommendations. Among the latter, I note, especially, re-afforestation, cleansing of rivers, " so that their waters may run clear, and no longer stagnate in pools," and drainage or filling of marshes. The whole book is a very interesting one. In 1 88 1 Dr. C. Meldrum, Director of the Observatory at Pamplemousses, issued a large report (8) on The Relations of Weather to Mortality and on the Climatic Effects of Forests — which is only the abstract of the full title of the work ! It is an able production, packed with suggestive remarks and figures well analysed. The author shows that before 1867 the mortality in the island did S3 not possess the summer increase which it has exhibited ever since ; concludes that this increase is due to malaria, which in its turn is encouraged by certain conditions of rainfall and temperature, and goes on to suggest a theory regarding cyclical variations of death rates all over the world. He recommends drainage of marshes, re-wooding of mountains and slopes, draining of streams in the interior so as to create reservoirs, and strict sanitary rules. The report was apparently written by request of a sanitary commission which was appointed in 1879 "to enquire whether the General Board of Health had been successful in its attempts to check and abate the prevalent fever,'' and also whether the sanitary works performed by this body had given results commensurate with the outlay. This commission seems to have concluded that, though the expenditure of the Board of Health had amounted to Rs. 1,596,488 during nine years (about iJ^i 5,000 a year at that time), yet that the mortality of Port Louis and the rural districts had been on the increase since 1870. In 1888 Dr. Meldrum wrote another report dealing with the subject (9). In this he states (page 20) that "the total death rate of the Colony has increased from an average of 28'03 for the five years 1871-75 to an average of 3 2 '88 for the five years 1881-85, and the fever death rate from an average of I2'55 to an average of i8'50." He considers that the increase is due to malaria, and is not due to poverty, increase of population, or decrease of sanitary works ; that the increased expenditure of the Board of Health (now amounting to nearly five million rupees during sixteen years) has not been accompanied by any improvement in public health ; and that a similar increase in the expenditure of the Poor Law Commission from Rs. 279,000 in 1879 to Rs. 367, 546 in 1886 is partly due to malaria. Later he wrote a third report of a similar nature (10), bringing the figures up to date. In 1891-92 Mr. O. Chadwick, C.E., C.M.G., wrote a series of reports on engineering matters, including sanitary works, which have been collected in one volume (12). He emphasises many of Dr. Meldrum's remarks and recommendations ; but he objects to too many trees in towns, such as Port Louis, because, as he remarks, " though afforestation is in every respect desirable, a town is not the place for it." He recommends underground sewers for Port 54 Louis. He does not easily credit the hypothesis that malaria is due to turning the soil, and insists on surface and subsoil drainage against that disease. Like Dr. Meldrum, he suggests that reservoirs for irrigation could be easily constructed in the course of the streams. He gives other advice, with most of ^\•hich I entirely concur, and urges reorganisation of the public health administration. Dr. Davidson's book Geographical Patlwlogy (7), published in 1892, gives an excellent account of the malaria in Mauritius up to that date. He admits the connection between the annual increa.se of malaria and of rainfall, but shows that the former does not really depend on the actual amount of the latter — that heavy rain is not always followed by heavy malaria. In Ordinance No. 32 of 1894-95 the Government amended the constitution of the General Board of Health, created a Medical and Health Department, and amended and consolidated the laws relating to the public health. The Director of the Department was made president of the board, which now became purely consultative. Two sanitary wardens, possessing public health diplomas, were to be appointed, and numerous other changes were ordered. This organisation was certainly a great improvement, and much in advance of the same department under many other governments. It is remarkable, as evidence of the slowness with which new discoveries affect mankind, that Laveran's discovery of the parasites of malaria, made so long previously as 1880, had scarcely yet been put to scientific or practical use in the tropics, including Mauritius, and is hardly mentioned in most medical works, including Davidson's book and Meldrum's reports. When, however, in 1897-99 the mode of infection by means of Anophelines was established, Mauritius almost led the way in recognising the fact. As early as May 1900 M. Daruty de Grandpre, Superintendent of the Museum, and M. d'Emmerez de Charmoy, Assistant Superintendent, report (13) that they have been following the work since 1899; that they have found in Mauritius five species of Culicines and three of Anophelines ; and that one of these, P. costalis, " has the same area of dispersion as the malaria in Mauritius." The second )'ear they published a most excellent paper on mosquitoes and their role in the propagation of malaria and filariasis (14). The anatomy and life history of the insects were investigated in detail, and recommendations for prevention 55 made. I believe that Drs. Alfred and Aime Lesur had been among the first in Mauritius to study the parasites themselves. With great promptitude, Government appointed a second Malaria Enquiry Committee (1901). All this time the disease had been ravaging the coast and lower parts of the island, apparently unchecked by the expensive measures which had been taken — now waning, now waxing, now almost disappearing, now flaring up in epidemics. The wealthier residents had been practically driven out of these regions ; the beautiful houses of the planters could be occupied only during two or three months of the cool season ; their families could no longer enjoy rural life at the seaside, as they were able formerly to do. Every- where the villages became more and more deserted. Even the patient Indians sought the upper regions. From 5 per cent, to 30 per cent, of the labour in the malarious plantations was often incapacitated by fever, thus hampering further the resources of the planters, already greatly reduced by the fall in the price of sugar. Houses fell into ruins, or were removed part by part to healthier areas. The population of the capital. Port Louis, which had always suffered most of all, began to fall. The richer citizens now used it only as a place of business by day, returning to the plateau every evening, as the citizens of London retire to the suburbs. Even the houses were removed ; and everywhere one sees the ruined basements, overgrown gardens, deserted fountains, and mouldy gateways of the more prosperous past, now surrounded only by the poorest huts of Indians. It is the classical picture of a great endemic epidemic. Plague and cholera visit a country and vanish ; but malaria and dysentery remain. Still, however, there was a secure refuge — the central table-land. But suddenly a part of this was invaded by a sharp epidemic — much to the consternation of everyone. The disease broke out in the summer of 1900-01 in a district of Moka, 1,400 feet above sea- level. Dr. Clarenc, the medical officer, reported promptly and ably on the occurrence, and the second Enquiry Committee was appointed. It consisted of Dr. Lorans (chairman), Dr. Edwards, C.M.G., Dr. Rohan, Dr. Clarenc, Dr. Bolton, Dr. A. Lesur, and M. Daruty de Grandpre. The suggestions of the committee were not only quite up to date, but were as good as could be made. Streams near Moka S6 clogged with vegetation were cleaned out, and quinine was distributed ; with the result that the epidemic ceased. Curepipe, Grandport, Savanne, and other localities were visited, and similar work was started in them. Later on M. d'Emmerez de Charmoy was appointed Technical Assistant to the Committee for the purpose of continuing the study of mosquitoes and their haunts, and for disseminating knowledge on the subject among the public. With the latter object in view, the committee concluded its report with a set of instructions. The only defect which can be found in the work of this committee was that it was not generalised, nor continued long enough. Early in 1906 the public alarm was intensified by another outbreak on high ground, namely, at Phoenix (1,400 feet), close to Curepipe. This epidemic, which is fully described by Dr. de Chazal in this report (addendum 2), occurred in connection with the large Clairfond marsh, for the drainage of which Government allotted funds, which, with the assistance of the Imperial Government, sufficed for the purpose, the work being nearly completed when I left. In addition to the literature referred to above, many other reports and papers on the subject have been published — notably articles in the Bjdletin de la Society MMicale de I' lie Maurice ; a report on fever at the Beau Bassin Central Prisons, 1901 (15), and a correspondence on the high death rates on sugar estates, 1906 (16). There is also, of course, a large official correspondence connected with malaria, showing the concern with which the disease has been viewed ; and, lastly, we have the excellent Annual Reports of the Medical and Health Department and the Annual Reports on the Estate Hospitals — all giving evidence of work done by the Health and Immigration Departments. 18. STATISTICS OF MALARIA IN MAURITIUS SINCE THE OUTBREAK. — The writings referred to above, together with the Annual Reports of the Registrar-General of Mauritius on Births, Deaths, and Marriages, give us an enormous mass of figures on the subject of malaria in the colony. After a careful consideration of them, I conclude that it will not be advisable to attempt an exhaustive analysis of them in this report. The figures have already been given in the publications mentioned, and have already been ably analysed 57 by Dr. Meldrum and others. To repeat them at length would double the size of this report, without yielding information of corresponding value. I shall therefore discuss them now as briefly as possible, and will then proceed to examine by other methods the present state of malaria in the Colony — which, after all, is the important point. (i). The General Death Rates of certain Non-malarious Islands. — It is advisable to commence by noting the death rates in the Seychelles and other islands, where neither Anophelines nor malaria exist. For the Seychelles, we have — Years ... ... ... ... 1904. 1905. 1906, Population 20,418 20,767 20,976 Death rates per 1,000 16-12 14-98 16-48 The average death rate for the seven years preceding 1904 was I7'07. Out of 359 deaths in 1906, 21 % occurred in infants under one year of age, 18 % in children under five years, 46 % in people under seventy years, and 15 % in people over seventy. In 1904 no fewer than five centenarians died, one having reached the age of 1 14 years. On two visits to the Seychelles, I was assured by his Excellency Governor Davidson, C.M.G., and by the chief Medical Officers that the deaths are rigorously registered and the vital statistics well kept. The following table gives the deaths in a number of non-malarious Population Deaths. Average at Census 190T. •. Death Rate Islands. igo2. 1903. 1904. 1905. iqo6. per 1,000. Rodrigues 3,437 72 69 64 29 98 19-3 Diego Garcia ... 526 14 18 12 18 9 27-0 Agalega 372 18 8 8 7 17 31-2 Peros Banhos ... 184 7 2 2 6 5 24-0 Coetivy 143 11 3 4 5 3 36-4 Salomon 119 3 4 6 3 3 32-0 Six Islands 117 4 3 2 2 6 29-0 St. Brandon 87 2 7 1 8 6 55-3 St. Jean de Nove 75 1 2 1 2 16-0 Eagle Island 74 1 1 5 3 6 43-0 5,134 133 117 104 82 155 31-3 The death rates are slightly too high, as they are computed on the population for 1902 only ; but still they show much higher figures than Seychelles. To what is this due ? On studying recent reports by Drs. Bolton and Keisler, I find that there is a considerable degree 58 of sickness on many of the islands, incixiding beri-beri, infantile tetanus, dysentery and diarrhcea, ovarian and uterine diseases, &c., while there seem to be no fully qualified medical men on most of them. At Seychelles and at Rodrigues, however, where the death rates are low, medical advice is accessible. Of course, there is considerable statis- tical error for the lesser islands, owing to the smallness of their population, but I think that we may attribute their mortality largely to insufficient medical attendance. (2). The General Death Rate of Mauritius. — Dr. Meldrum has carefully compared these statistics with those of Mauritius. The annual death rates of Rodrigues and Seychelles from 1872 to 1880 averaged I5"8 and 20"5 respectively. In Mauritius, from 1804 to 1824 inclusive, the average white population was 7,106, with a mean death rate of iS'Sq, and the average " free population " (exclusive of slaves) was 9,419, with a mean death rate of I2"53. Thus the total mean death rate was i5"26. For the five years from 1825 to 1830 the average population, exclusive of slaves, was 24,502, and the mean death rate was iva^a,. All this time deaths among the slaves were not recorded. In 1829, however, there were 18,019 slaves, and these had an estimated death rate of 34" 53 — much higher than that of the whites and free coloured people. After 1831, according to Meldrum, the deaths among the slaves were registered, and they were emancipated in 1834. From this point, then, the registered death rates were higher. The following table gives them from 1831 to 1906 per 1,000 of population : — ... 1831 1832 1833 1834 183s 1836 1837 1838 1839 J840 Mean. ... 26-8 31-3 27-4 39-8 360 31-0 37-2 30-7 39-0 30-0 32-9 , . 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 Mean. ... 41-5 42-4 34-6 584 39-5 32-7 29-3 26-4 308 31-5 367 ., 1S51 i3s2 1853 1854 185s 1856 1857 1858 1859 i860 Mean. ... 26-5 28-1 29-6 84-6 33-0 50-6 26-1 28-1 30-9 31-6 36-9 Years Death rates Years Death rates Years Death rates , Years Death rates Years Death rates Years Death rates I8bl ItiC2 1863 1864 1865 1-866 1867 186S 1869 1870 Mean. ... 31-1 41-5 34-8 34-1 33-4 32-1 120-5 56-7 35-0 22-6 44-2 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 Mean. .. 25-6 26-8 33-7 29-5 24-9 27-5 29-6 27-2 32-1 28-1 28-5 ... 1881 1S82 1883 1884 1885 1886 1887 1888 1889 1890 Mean. ... 29-9 350 35-5 31-2 33-5 28'9 34-4 304 33-7 34-3 32-7 59 Years Death rates . Years Death rates . 1891 1S92 1893 1894 1895 1896 1897 1898 1899 1900 Mean. 27-2 384 40-9 29-0 37-1 41-9 29-5 31-9 34-8 34-8 34-6 igoi 1902 1903 Tgo4 1905 1906 40-3 340 39-9 322 406 40 35-4. Mean. 37-8 Mean of 76 years The mean annual death rate for the 36 years from 1831 to 1866, before the epidemic of malaria developed, was 35'3, and for the 40 years from 1867 to 1506, since malaria has been present in the island, was ^S'?' — almost the same. It might therefore be inferred that malaria has had no effect on the death rate ; but this inference can only be accepted if it can be shown that no influence has been at work to counterbalance the influence of malaria — that is, to decrease the death rate, while the malaria has increased it. Comparing the Mauritius death rates before the development of malaria in 1867 with those of the lesser islands, we observe that they are not very dissimilar. Mauritius was then probably in much the same condition regarding medical assistance as the islands are now in. I suspect that fully qualified medical assistance was not always avail- able, and know that what was available was not nearly so expert as at the present day. Probably much loss of life occurred at childbirth, or owing to smallpox and undeveloped surgery, and the sanitary organisation was certainly immature. Many serious epidemics swept the colony. In i837-40there were epidemics of measles and smallpox ; in 1841, 1842, 1844, 1845 epidemics of smallpox and relapsing fever ; in 1854, 1856, 1861-63, epidemics of cholera — all of which must have greatly swelled the death rates in the days before malaria. Since then, so far as I can ascertain, there have been only minor epidemics of measles and influenza, while the plague has caused only about 5,000 deaths since 1899. I cannot find (in time for this report) when compulsory vaccination was introduced, but it must have made a large reduction in the mortality. On examining the figures, we find that, after the great rise in mortality during 1867 and 1868, due to the epidemic of malaria, there was a most marked decrease, the death rates for the whole decade 1871-80 averaging only 28'5. This is a phenomenon frequently seen after severe epidemics. As Meldrum remarks, " Many persons died who, if there had been no epidemic in 1867-69, would probably have died in 1870-72," or later. But there 6o are other explanations. The great mortahty during the epidemic was largely due to the fact that the supply of quinine ran short. Later the drug was poured in, and taken widely. It was evidently not given in quantities sufficient to exterminate the malaria in all the patients, but it must have saved, from then up to the present, many thousands of lives. Lastly, there was probably a great development of natural immunity among the survivors of the great epidemic. The assumption that malaria has had no effect on the mortality since 1 868 implies, therefore, the assumption that the whole of medical science and practice, vaccination, quarantine, quinine, and sanitary organisation have done nothing since that date to reduce the mortality. More correctly, the matter should be put in this way : that, since the death rates now are much the same as they were before malaria entered the island, the effect of the disease has been to counterbalance all the results of medical and sanitary science during the last forty years, put together. After all, the remarkable fact remains that, of the four neigh- bouring islands, Seychelles, Rodrigues, Mauritius, and Reunion, the first two, which have no Anophelines and no malaria, possess a death rate of less than 20 per jiiille, while the other two, which possess both, have a death rate of 35 and more, or about double. (3). Monthly Variation in the Deaths. — ■ As a general rule, in malarious countries the admissions for malaria and the total number of deaths tend to increase largely in the rainy season ; but in non-malarious countries this variation does not occur with regularity. In the following table I give the average monthly deaths from all causes {a) in the Seychelles during three years, 1901, 1902, and 1904; {b) in Mauritius during 1861-66 (excluding 1862 before the entry of malaria; (c) in Mauritius during 1870-89, that is, for 19 years after the entry of malaria; and id) in Mauritius during three recent years. Average Population. Seychelles 1901-04 19,442 Mauritius 1861-66 345,275 1,003 Mauritius 1870-S9 353,958 Mauritius 1904-06 376,974 1,012 981 1,307 1,314 1,357 1,262 1,597 1,284 1,125 1,089 1,285 909 J. F. j\l. A. M. J. J. A. S. 0. N. D. 31 28 27 30 26 33 30 23 26 27 26 25 ,003 936 987 920 972 898 970 971 947 970 910 967 790 809 1,005 1,043 1,118 1,059 1,004 893 783 759 718 740 6i If we divide the highest figure in each of these lines by the lowest figure in the same line, we obtain the fractions 1-35, no, 1-55, and 176 — the first two for Seychelles and Mauritius before malaria, the latter two for Mauritius after the entry of malaria. That is to say, the ratio between the highest and lowest monthly deaths tend to be greater in malarious places. Dr. Meldrum gave statistics to show that the greatest mortality tends to occur about two months after the heaviest rainfall. This is now easily explained by the impetus given to the breeding of mosquitoes by the rains. A few weeks later many new infections would be produced by them, causing or accelerating deaths a few weeks later still. (4) The Declared Fever Mortality. — In every civilised com- munity at the present day deaths are registered with sufficient care to make the total mortality returns fairly reliable ; but it is quite another matter regarding returns which attempt to give accurately the various causes of death. Even where only qualified medical men are permitted to furnish death reports, the sources of error are numerous. Many patients die from a complex of causes ; and others are not seen by a medical man until they are in extremis, or even until after death — such being particularly the case with children, whose deaths constitute such a large proportion of the total. In malarious countries deaths due to many diseases are apt to be returned under the heading of fever, especially by unqualified registrars, thus swelling the declared fever mortality ; while, on the other hand, many deaths from malaria are returned under the headings of secondary complaints which have really only precipitated the fatal ending — thus reducing the declared fever mortality. On the whole, then, the fever death rates are very apt to be unreliable. In Mauritius, however, with its dense population and large qualified medical staff, the error is, I think, likely to be less than in any other tropical country I have seen, including India ; and we must remember that the factors just mentioned, which tend to increase or decrease the error, must also tend to neutralise each other. The following figures give the average monthly fever deaths in Mauritius during two sets of years : — J. F. M. A. M. J. J. A. S. O. N. D. Totals. ''^'''" ^ per 1,000. 1870-89 ... 393 437 578 629 673 601 518 430 369 358 335 351 5,674 15-9 1904-06 ... 377 428 662 673 666 565 328 305 363 350 321 338 5,382 14-3 62 They agree very closely, and show a distinct seasonal variation. The fe\er mortality is least in November and greatest in the autumn months, as usual. This fact itself gives strong evidence in favour of the view that the fever returns in Mauritius are not as unreliable as might be supposed. Had there been very great error, the probability is that that error would have been equally distributed over all the months, so that the known malarial seasonal variation would not have been so apparent. But we find that the maximum monthly deaths are twice the minimum, as might be expected. Of course, in a disease which relapses so frequently, deaths may occur long after the infective season ; while chilly weather kills many cachectics — facts which account for the continuance of some deaths during the cool season. The sets of years just given correspond with the two latter sets given in the previous table. By subtracting the fever deaths from the total deaths, we obtain a remainder of deaths declared not to be due to malaria. J. F. M. A. M. J. J. A. S. O. N. D. Totals. ^^'^" J -^ -* per i.ooo. 1870-89... 397 372 427 414 445 458 486 463 414 401 383 389 5,049 14-3 1904-06... 640 553 645 641 691 697 1,269 979 756 739 964 571 9,145 24-3 The sudden rise in July in the last line was apparently due to an outbreak of influenza in 1906, which carried off a number of old and debilitated persons. Excepting when such epidemics occur, the non-malarial deaths show no such marked seasonal variation as the malaria deaths do. As Dr. Meldrum demonstrated, this absence of seasonal variation was the characteristic of the total deaths in the Colony before malaria broke out in it. There is, however, always a slight summer increase owing chiefly to dysentery and diarrhcea, and a winter increase owing to influenza, chest affections, and so on. Tables I and II give the population, deaths, declared fever deaths, and other necessary details, for many years. During the seven years 1900-06 the declared fever deaths averaged 5,384 per annum, or 3i'0 % of the total deaths, and I4'0 per mille of the total population. (5). Cases of Malaria admitted into Hospitals and Asylums. — There is an immense amount of statistical material on this subject. I propose to epitomise it as briefly as possible. The following table is taken from the Reports of the Director, Medical 63 and Health Department. It gives the total admissions into the various government hospitals and asylums (numbering fourteen in 1906), and also the number of admissions due to malaria and the number of deaths during the seven years 1900-06. Years ... ... igoo. igoi. 1902. 1903. 1904. 1905. T906. Total. Total admissions 15,449 18,542 17,874 20,867 17,492 20,735 20,371 131,330 Total deatlis 1,152 1,313 1,01? 1,277 973 1,267 1,221 8,221 Malaria admissions ... 2,848 4,182 3,360 4,788 3,039 5,123 3,674 27,014 Malaria deaths 84 70 35 94 37 91 38 449 Enlargement of spleen 163 546 467 507 395 669 672 3,419 Deaths from enlarge- 2 8 24 15 21 30 40 140 ment of spleen. The average total annual admissions were 18,761 ; the average admissions for malaria (as given above) were 3,859, and the average deaths for malaria in these institutions were 64" i a year. The percentage of admissions due to malaria was 2o'6 %, and the percentage of deaths from malaria to admissions for malaria was I '66, or only 16 in a thousand. This case mortality occurred in hospital in spite of the best treatment. We must not infer that it would be equally low outside hospital, especially among the poorest classes and the children, who, as I witnessed myself, often take no treatment at all. Nevertheless, it suggests that the declared mortality from fever in the colony must be too high. The Hon. Dr. Lorans makes some pertinent reinarks on this subject in the report for 1906. The case mortality was ro2 % in that year ; and applying it to the number of deaths attributed to malaria in the returns, we should have to admit that, according to the same ratio, there were 582,700 cases of the disease in the island during the year — about three attacks to every two persons. Certainly the Indian admissions for malaria do often exceed half the strength, or sometimes the whole strength, even among troops ; but this is only at isolated stations. It seems that since 1899 the M^a'zVa/ certification of deaths was more generally and systematically enforced in two of the districts, Port Louis and Plaines Wilhems ; with the result that the declared malaria death rate fell at once in these areas to a fraction of the former figures. In Table II, I give Dr. Lorans' useful table showing the annual total and malaria deaths in the various districts for eleven years. For example, in Port Louis and Plaines 64 Wilhems in 1896 the malaria deaths were about half the total deaths ; but in 1904 they fell to about one-sixth and one-ninth of the latter, respectively. More exactly, the malaria deaths during 1896, 1897, and 1898 were 45'3 % of the total deaths; but during 1899- 1906 they were only 2 5 '2 % of them — by which we may infer with some degree of probability that before 1899 20 % of the total deaths had been wrongly returned under the heading of malaria. This therefore would bring down the average declared fever mortality from 3 ro % of the total mortality to only ii'o % for the whole island during the seven years 1900-1906. But we must now turn to an item in the last table not yet considered, namely the hospital cases and deaths due to enlargement of spleen (with which I have included the small proportion of cases of splenitis). These have not been previously added to the malaria cases ; but, for reasons which will be given in the next section, I infer that they should be. They make the serious addition during 1900- 1906 of 3,419 hospital cases and 140 hospital deaths. The total malaria cases now stand at 30,433, or 23-2 % of all the cases ; and the total malaria deaths at 589, or i'935 % of the malaria cases. This puts the hospital case mortality of malaria in Mauritius at nearly 2 %. As will be seen in the next section, the cases of enlargement of spleen treated in those hospitals are only a minute fraction of the cases existing throughout the island ; and the same thing evidently holds regarding the cases of fever. The total number of deaths in hospital given in the above table was 8,221, and the deaths from malaria, 589, or 7'i %. Supposing the same ratio were to hold for the whole island, then the malaria deaths would have been only 9,324 for the seven years, or an average of 1,332 deaths a year, instead of the average of 5,384 malaria deaths in the general mortality returns — a great difference. But we must again remember that the deaths in hospital are not likely to be so great as those outside. (6). Cases of Malaria attending the Hospitals and Dispensaries. — In addition to the patients treated inside the various hospitals, a great number attended them and the dispensaries (numbering twenty-eight in 1907) as out patients. The Director of the Medical and Health Department (Dr. Lorans) was kind enough to collect for me the 6s number of such attendances for malarial disease during past years ; and I give the figures in Table III. Only a few of the institutions have records extending further back than 1878; and I have consequently taken the statistics only for the thirty years from then to 1907 inclusive. Altogether 403,918 cases of malaria visited the institutions during that period, averaging 13,464 a year— though of course not all these cases were different persons, many attending for medicine over and over again. During the last seven years the attendances averaged 23,637 a year. The figures do not always indicate the local prevalence of malaria, because many of the patients come from a distance. For example, at Moka, which is generally healthy. Dr. Clarenc states that many patients visit the hospital from Failles, which is unhealthy. So also the Curepipe dispensary is attended by many from Phcenix and Black River. During 1907 the total attendances at these institutions for all causes numbered, according to information given me by Dr. Lorans, 79)053! while the attendances for malarial diseases alone was 28,294, or 35'8 % of the total attendances; a very high ratio. Dr. Lorans' figures separate malarial diseases into fever, cachexia, and enlargement of the spleen. On examination, I infer that the distinctions have been made somewhat arbitrarily, and, indeed, it is often difficult to make any, so that I have thought it best to lump them together in Table III. The total numbers, however, were as follows : — Malarial Fever ... Malarial cachexia Enlargement of spleen Total malaria* ... Dysentery... Totak Percentages to '-°^^'^- total Malaria. 358,079 87-6 26,394 6-4 24,021 5-8 408,494 — 38,713 9-4 Dysentery was included in the return at Dr. Lorans' suggestion for the purpose of comparison — a very useful one being obtained. 19. THE MEASUREMENT OF MALARIA IN MAURITIUS.— Having considered past statistics, we must now endeavour to obtain some idea of the present prevalence of the disease. (i). Recent Statistics. — The figures for 1907 have not reached • This total is in excess of that given by Table III., because the latter deals with attendances during only thirty years, while the former goes back some years earlier. S 66 Dut those for i 906 will suffice for the Total. Malarial. Percentage. 377,532 — — 15,118 5,827 38-5 40-0 15-4 38-5 20,371 4,346 21-3 1,221 78 6-4 23,759 4,306 181 79,053 28,294 35-8 fear, few results. The following table : — Population (1906) Declared deaths (1906) Death rates per mille . . Admissons (1906) Hospital deaths (1906) Hospital cases (1907) ... Dispensary cases (1907) We thus have many figures but, I general fever mortality returns probably have a large margin of error, and it is difficult to say how far the hospital statistics apply to the entire population. We cannot say how many patients attend hospital more than once, or how many never attend at all. (2). Direct Methods for Measuring the Amount of Malaria in a Locality. — The principal point to be ascertained is, by section 10, the proportion of infected persons in the locality, but this is not given, either by death rates or by attendance at hospital. The ideal way to ascertain this ratio would be to search for the parasites in the blood of every person in the locality. But the parasites often cannot be found, even when they must be present in considerable numbers. Even when they are fairly numerous the search for them in a single person may occupy a skilled worker for half an hour or more, and may have to be repeated on several occasions. I doubt whether such a worker could examine properly the blood of a thousand people under two months' hard work. If he were to content himself with examining smaller numbers by what is called " random sampling," the statistical error might be considerable. Hence to estimate correctly the proportion of infected people throughout a large population like that of Mauritius would be a great task. There is, however, a much easier though less rigid method, which consists in examining the people for the enlargement of spleen which occurs so frequently in cases of malaria. This can be done literally in a few seconds for each person. The people to be examined are lined up, and then made to pass the examiner one by one, while an assistant writes down the result ; or else the facts may be ascertained by a rapid house to house visitation. Thus a large 67 population can be dealt with in a much briefer time than would suffice for a thorough blood-examination. The method is a very old one, which was often practised in India, The best method, however, when practicable, is to combine the two. (3). The Endemic- Index. — This useful term was proposed by Stephens and Christophers to denote the proportion of persons with parasites in the blood. I suggest, however, that the term parasite- rate would be more suitable for this purpose ; that the term spleen- rate should be given to the proportion of people with enlarged spleen due to malaria ; and that the term endemic-index should be reserved for both of the others together — or rather for the proportion of infected persons ascertained by all methods. The combined methods were used by me in Greece in 1906. Out of 60 infected children whose blood and spleen were examined very carefully, 27, or 45 % had enlarged spleen, but parasites too few to be found; 21, or 35 % had both enlarged spleen and parasites numerous enough to be found ; and 12, or 20 % had parasites but no enlargement of the spleen. Now, if we had taken only the parasite- rate or the spleen-rate we should have obtained too low an estimate. The combined method is especially useful, because early cases of malaria generally show numerous parasites but have little enlargement of the spleen ; while older cases, in my experience, show the converse. For practical purposes, the parasite-rate can be determined only (with much trouble) for small populations ; and for large ones, such as that of Mauritius, we must resort to the spleen-rate. But when we confine ourselves to the latter, we ought to add a certain percentage for cases in which, had we examined them, we would probably have found parasites, though they had no enlarged spleen. In the Greek cases, there were 12 such for 48 with enlarged spleens ; and though these cases were too few to give a very reliable estimate, we may for the present accept the proportion for rough calculation. In practice also, we usually confine our examinations to children — say of under 16 years of age. This is done for several reasons. Children are easily accessible in schools, or, for a small reward, in villages. Men are generally out at work, and women often object to the examination. But the most important reason is that adults have in many cases become partially immune (section 2). Thus if we 5 A 68 were to take people of each year of age from one to a hundred, say a thousand of each age, we should find that the endemic-index rises from one to about ten years, and then falls ; until at puberty the bulk of people in a malarious locality show few signs of the disease, though they may occasionally suffer from short attacks and are probably really infected all the time. If, however, we had examined only the adults, we should have discovered few objective symptoms of malaria in them, and might have come to the conclusion that there was no malaria in the locality. It, therefore, becomes apparent that we do not really possess any very practical method for determining the exact ratio of infected persons in a locality. We can find children with enlarged spleens or with numerous parasites ; but when partial immunity has banished these symptoms we are left in doubt. A person is " infected " as long as any parasites are left in him, but, unfortunately, we can never find definitely whether or no they have died out completely. All we can do is to take the children up to some arbitrary age, say i6, and then compare results. If none of them show signs of infection, the place is healthy. If some are infected, all we can state is that the endemic-index among so many children examined is such-and-such ; and we must examine enough children to avoid statistical error. (4). Does Kala-Asar exist in Mauritius ? — A most important point remains to be studied. There are several diseases, besides malaria, which cause enlargement of the spleen ; but only one of these causes wide-spread enlargement, such as malaria does. This is the famous Indian disease kala-azar, which is produced by the minute parasites called Leishmania donovani. Where it exists the spleen-test for malaria becomes obviously unreliable. Hitherto it has never been found in Mauritius. Unfortunately during my stay there, no opportunity for searching for the parasites in the liver and spleen presented itself; but we examined several suspicious looking ulcers in vain. Owing to the large Indian immigration one would expect to find the disease in plenty ; but, on the whole, I infer that it is absent, or rare. I was sent by the Government of India to investigate kala-azar in Assam in i8g8 : but neither in Mauritius nor in Greece did I observe cases altogether similar. The kala-azar patient has a depressed, anxious expression which is not often seen in malaria ; the liver is generally enlarged, as 69 well as the spleen ; there is generally a continued fever not cured by quinine ; and the patient almost invariably dies. Now if all, or even a fraction, of the children in Mauritius with enlarged spleen have kala-azar the death-rate would be appalling. As a matter of fact, the children recover. The malady which causes enlargement of spleen among them, as in Greece, is a benign affection. It is also too frequently accompanied by the parasites of malaria, and too easily cured by quinine, to leave much doubt as to its nature. I gather then that the carrying agent of kala-asar is probably absent from Mauritius ; and that the spleen-rate will, therefore, give a reliable estimate of the endemic-index there. 20. THE SPLEEN-RATES OF CHILDREN IN MAURITIUS, AND OTHER DETAILS.— With these considerations in view, I advised Government, when I reached the Colony, to carry out a systematic spleen-census of the child population. This was done ici) by the Sanitary Wardens, Drs. Castel, Keisler, Masson, and Milne, for the children in schools ; ib) by the Medical Officers of the Sugar Estates and Factories for the children belonging to them ; and by Dr. Milne, Major Fowler and myself for a certain number of children scattered in villages and hamlets. Owing to the large number of children examined, the work was arduous ; and my warm thanks are due to these gentlemen for their assistance, and also to Dr. Lorans and Dr. Bolton for their supervision of the statistics. So far, as I know, it is the largest spleen-census which has ever been taken. The details are given in Table IV. (i) Total Spleen-Rate. — At the census of 1901, out of 370,831 persons whose ages are recorded, there where 178,139 children of 1 5 years and under, or 48^04 % of the total. In 1906 the total population is estimated by the Registrar General at 377,532; so that according to the same proportion there ought to have been 181,366 children in that year, or say 182,000 children of 15 years and under in 1907. The following table gives the results of the spleen-test (carried out for the most part early in 1908). Children Children with Percentages examined. enlarged spleen. ^ Children on Estates 18,909 6,307 33-3 School Children 6,188 1,455 235 Miscellaneous 5,925 2,833 47-8 Totals ... 31,022 10,595 34.1 70 Thus, out of about 182,000 children in Mauritius, 31,022 were examined and 10,595 were found to have enlargement of the spleen ; or 34-1 %. The statistical percentage of error according to the Poisson-Pearson formula (addendum 4) is only 0-693, and may be neglected. Hence we may calculate that out of all the 182,000 children under 15 years of age in Mauritius, one-third probably suffer from enlarged spleen. (2). Total Probable Endemic-Index.— V>ut if we had examined the blood of all these children for the parasites of malaria (which was of course quite impossible in the time at our disposal) we should certainly have found a proportion of them containing the parasites, but not having enlargement of the spleen. According to the rough Greek estimate (section 19), these would number as many as a quarter of the spleen cases. Adding this proportion, we estimate that 13,244 children, or 427 % of the total, would probably have shown objective symptoms of malaria had we examined them all. Thus the endemic- index for children of 15 years or under in Mauritius early in 1908 may be put at about 42'7 %, or over two-fifths. The children were examined largely before the great annual rise of malaria begins. Had we examined them later, the endemic index would certainly have been much larger. (3). Some Small Sources of Error. — It is likely that some of the children examined in the schools, on the estates, and elsewhere were the same children. I have not been able to ascertain the likely proportion in time for this report. But, as we are here dealing with ratios, the matter will not seriously affect the general result. I have just been informed by Dr. Bolton that few of the children of the indentured coolies on the estates attend the schools, and that in his opinion the overlapping cannot exceed 0'25 %, and will not therefore seriously alter the returns (annexure i). Another point. I asked for children of 16 years and under to be examined. This was unfortunate, as the census deals only with five- yearly groups. But for the same reason, just given, the error caused may be practically neglected. Moreover, the exact ages of the poorer classes are always very doubtful quantities. (4). Average Spleen. — I asked for records, not only for enlarge- ment of the spleen, but for degree of enlargement — whether the enlargement was small, medium, or great. I have collected the 71 figures for 30,137 children examined. The enlargement is given as none in 19,711, or 6^4%; as small in 4,381, or I4'5%; medium in 3,479, or 11-5% ; and great in 2,566, or 8'5%. As a rough estimate I take the " small," the " medium," and the " great " enlargements as being, respectively, three, six, and nine times the size of the normal spleen, which is taken at unity. Hence, adding together the children with no enlargement, three times the children with small enlargement, six times and nine times those with medium and great enlargements, and dividing by the total numbers examined, we obtain what I call the Average Spleen. This works out at 2^54 for Mauritian children early in 1908, with small statistical error. See also Table IV, D. I do not think that this estimate has been attempted before. It is likely to give a more delicate index of the amount of malaria in a locality than the mere spleen rate ; but, unfortunately, medical men may differ as to the standards of small, medium, and large ; and the estimate is, therefore, not rigid. (5). Age and Sex Distribution. — I asked also for the ages and sexes of the children to be recorded. As a matter of fact, the ages generally have to be guessed by the examiner ; so that here again the estimate is far from rigid. In fact, on scrutinising the figures, I find so many elements of doubt that I have finally decided to omit the full age analysis from the table ot details — more especially as it would add immensely to the bulk of figures. But I have computed the totals for 4,025 children with enlarged spleen on the estates, and find that they were distributed according to age as below : — Age I 2 3 4 5 6 7 8 Children 208 254 293 285 311 346 340 355 Age ... 9 10 II 12 13 14 IS 16 Children 247 328 192 255 172 185 153 97 Thus there were 1,351 children with enlarged spleen of five years and under; 1,648 of five to ten years ; and only 1,056 of ten to sixteen years. Out of the same number of children with enlarged spleen, 2,095 were males, and 1,930 were females — showing no marked difference. (6). Local Distribution. — The declared deaths from fever in the various districts during the last eleven years, 1896-1906, will be found in Table II, and the spleen rates and average spleen in Table IV. Flacq and Black River districts have the highest spleen rates and 72 average spleens ; and Plaines Wilhems and Moka the least. The local prevalence of malaria varies so greatly, even within a few hundred yards, that it is quite impossible to examine all the details here. (7). The Imported Spleen Rate. — In every locality anywhere near to a malarious area there must be a certain number of imported cases which will give a small spleen rate by themselves. This I call the imported spleen rate. As a rough rule it must tend to vary inversely as the square of the distance from the infectious area. On reference to Table IV it will be seen that there are small spleen rates in Moka and Plaines Wilhems ; and the remarks of the reporting Medical Officers show that these are mostly imported — although in both these districts there are a few infecting centres. Of course the imported spleen rate tends to be increased in places which are frequented from outside, as Curepipe ; but on the whole I think that, if the spleen rate of a locality is not higher than 5 %, there is likely to be little endemic malaria there. If only a few children are examined, so that the statistical error is large, the apparent rate may be much higher than this without giving proof of endemic malaria. For instance, in the schools of Moka the rate is 20'5 % according to Dr. Castel. This is large enough to suggest a malarial focus somewhere there ; but on the other hand the statistical error is nearly 8 °/o, so that the true spleen rate may be anything between 12 % and 28 %. Quite possibly the lower figure may be due only to importation, especially in schools. (8). The Effect of Altitude. — That malaria decreases with increased altitude is known everywhere, and has been frequently noted in Mauritius, where the conditions are very suitable for such a variation. Dr. Meldrum (10) and the writers of the Annual Medical Reports and Reports of the Estates Hospitals have frequently shown that the death rate tends to diminish with altitude. Table IV, E gives the variation of the spleen rates according to altitude in a large number of children in Mauritius. Altitude must affect malaria chiefly by reduction of temperature — one degree Fahrenheit (0'S6° C.) for every 300 feet. Temperature affects it in many ways. Cold is inimical to mosquitoes ; it retards the development of the parasites within them, and also, I think, in man ; and causes men to wear more clothing and to shut up their 73 houses at night. On the other hand, large breeding places close at hand may neutralise all these factors — as, for instance, near the Clairfond marsh at Phoenix (1,400 feet). Hence, while the average infection rate diminishes with altitude, local rates must vary largely owing to other factors. (9). Relation between the Spleen Rates and General Death Rates. — In Table IV, A, giving the spleen rates on estates, the death rates averaged for the two years ending June, 1907, are also given. But there is a large statistical error in these death rates, owing to the small numbers of deaths on many of the estates ; so that the relation between them and the spleen rates cannot be dealt with satisfactoril}'. In Table IV, F the same figures are given for whole districts, and are therefore more useful ; but I have been obliged to give the death rates for 1906, as those for 1907 (which should have been shown in order to correspond with the spleen rates) have not yet reached me. There is evidently a marked, though not exact, relation — ^which I will not analyse without the figures for 1907. The separate death rates of estates are not an exact measure of the malaria in them, owing partly to statistical error. (10). The Parasites and the Fevers in Mauritius. — There is nothing of importance to our present purpose under this heading. The parasites can be found easily in man and in P. costalis, and do not differ in any respect from those observed all over the tropics. All species were seen by us. To determine which was most abundant was not necessary, and would have required many months' special work. Quartan abounds at Phcenix, and the malignant parasites are common. The clinical features of the disease have been excellently studied in many scientific papers, especially in those of the Societe Medicale ; and call for no remark here. Blackwater fever is common (addendum 2). 21. SUMMARY OF FACTS REGARDING THE AMOUNT OF MALARIA IN MAURITIUS.— A. The following figures give important averages during the seven years 1900-06 : — (i) The average population of Mauritius was 384,676. (2) The average total deaths per annum were 14,139. 74 The average annual total death rate per mille of population was 37-4. The average annual deaths reported as due to fever were 5,384 (doubtful). The average annual death rate per mille of population reported as due to fever was I4'0 (doubtful). The average reported fever deaths were 3 1 'O % of the average total deaths (doubtful). (3) The total admissions into the hospital for all causes averaged 18,761 a year. The admissions into the hospitals for malarial diseases alone averaged 4,348 a year, or nearly one quarter (23"2 %) of the total admissions. The total deaths in hospital from all causes averaged I,I74 a year. The deaths in hospital from malarial diseases alone averaged 84 a year, or 7' i % of the total deaths. The ratio of deaths in hospital from malaria to admissions into hospital for that disease (case mortality) was r93S %■ (4) The attendances of out-patients at all the hospitals and dispensaries for malaria alone averaged 13,464 a year since 1878. In 1907, alone, the total attendances for all causes were 79,053, and for malaria alone were 28,294, or 35'8 % of the total. B. (i) There are about 182,000 children of fifteen years and under in Mauritius. (2) Out of 30,137 of these examined in all parts of Mauritius at the end of 1907 and the beginning of 1908, that is, before the middle of the malaria season, 19,711, or 65 "4 %, had no enlargement of the spleen ; 4,381, or I4'5 %, had small enlargement of the spleen ; 3,479, or ii'5 %, had medium enlargement ; 2,566, or 8' 5 %, had great enlargement. From these data it may be computed roughly that the average spleen of Mauritian children is 2" 54 times the normal size. (3j Out of 885 more children examined, 169 were found to have enlargement of the spleen. Thus, out of a total of 31,022 children examined, 10,595, or more than one-third (34-1 %), had enlargement of the spleen. 75 Hence probably, out of the 182,000 children in Mauritius, about 62,062 suffered from enlargement of the spleen. (4) If we suppose that children without enlargement of the spleen, but with the parasites in the blood, numbered as many as a quarter of the spleen cases, then we must infer that at the beginning of last malaria season 427 % of all the children in Mauritius— that is, about 77,714 children in all — were infected with malaria. Dr. Bolton, Medical Officer of the Immigration Department, estimates that malaria costs the Estates in Mauritius Rs.650,000 a year in loss of labour, and the labourers themselves Rs. 150,000 in loss of wages, besides similar losses to the general community (annexure i). 76 PART III.— PREVENTION OF MALARIA IN MAURITIUS. 22. BRIEF HISTORY OF THE PREVENTION OF MALARIA.— In sections 2 and 1 1 it was made clear that malaria will not remain in a locality (i) unless the carrying agents (Anophelines) are numerous enough ; (2) unless there are enough infected persons to infect the carriers ; and (3) if the insects are prevented from biting human beings. There are thus three groups of preventive measures which may be employed by public authorities to reduce the disease, namely : — (i) Anopheline Reduction, (2) Case Reduction, (3) Isolation. The ancients knew that drainage reduces malaria ; and the statement has become a sanitary aphorism for centuries. Numbers of instances occurring in Italy and France are cited in text-books. The total disappearance of the disease from Britain and its decrease in Holland and other countries has been certainly due in part to drainage of marshes, and in part to other causes — chiefly, I think, the frequent treatment of cases with quinine, and (?) the general use of glass windows which appears to have followed the repeal of the window tax early last century. Thus all the preventive measures mentioned above were used — unconsciously. The Anophelines were reduced by drainage, the cases by quinine, and the remaining insects were largely prevented from feeding by the glass windows. But though drainage against malaria has been frequently used, it has been more frequently neglected. The Roman Campagna, for example, and many marshy settlements in the tropics have been allowed to remain malarious, in spite of the remedy being known. This has been due to many causes — to the expense of drainage ; to the small political influence of the medical profession ; to faulty public education ; and, not least, to scepticism regarding the truth of the dogma, owing to absence of full explanation of it. When, however, the Anophelines were shown in 1897-99 to be the carriers of malaria, the reason why drainage reduces the disease was clearly 77 revealed — it removes the stagnant weedy surface waters which breed the insects. In other words, drainage of the soil, as applied to malaria, merely means Anopheline reduction and nothing else. At the same time, as already stated in section i, the new knowledge greatly improved our methods. Instead of being forced to drain a whole area, we could now define exactly which waters were or were not dangerous, and could deal with the latter by several other means than by drainage — thus cheapening the whole process, and rendering it more exact and feasible. The precise details of the method were first laid down in 1899 (i); and were first put into practice in a complete manner at Ismailia and in Klang and Port Swettenham in the Federated Malay States, in all of which localities the disease was banished in a couple of years. Later the same method has been made the basis of the great sanitary work of the Americans in the Panama Canal Zone, and has been attempted with more or less energy elsewhere. Latterly Anopheline reduction has been merged in the wider and still more useful measure of general mosquito rediLction, especially at Ismailia, Panama, and Port Said. Meanwhile the second great anti-malaria measure, that of case reduction, hadheen originated by Koch and Celli as early as 1900. These observers felt doubt as to the possibility of mosquito reduction (since established), and urged that the best way of dealing with malaria would be to leave the mosquitoes alone, but to cure the human patients, from whom the insects become infected. Thus, though mosquitoes would continue to abound, they would find no parasites to carry. The classical example of the use of this method was Stephansort, in New Guinea, which was cleared of malaria by Koch in a few months. Much similar work has been done in German possessions and in Italy, and also among the troops in India. The third measure, that of isolation or protection from bites oj mosquitoes, has been unconsciously in use for a long time. The ancient Egyptians and Romans used to employ mosquito nets during sleep ; and I well remember being told, when I first went to India in 1881, that they would ward off malaria. Since 1898 I have always strongly advocated the use of them for that purpose. In America wire gauze screens for the windows and verandas of houses have long been employed ; and these were now strongly recommended, especially in Italy, as a protection against malaria. The experiment 78 of Low, Sambon, and Rees, who lived for two months of the malaria season in the Campagna in a mosquito-proof house without becoming infected, strengthened this recommendation. Though the experiment added nothing to our knowledge, and was not a strict test (since infection in two months is by no means a certainty anywhere), it was so widely advertised that wire-proofing was adopted in several places, notably in Lagos and Panama. Other precautions, such as boots, gloves, and veils, culicifuges (applications to the skin to keep off mosquitoes), and so on, were urged by some writers. Lastly, Stephens and Christophers emphasised the necessity for the segregation of Europeans in the tropics, on the ground that, if they live far from native villages, they are less likely to be bitten by infected mosquitoes — an excellent suggestion. Last year I attempted to collect available information on the subject of anti-malaria campaigns in many countries. The task was difficult, owing to the inadequacy of most of the official and other reports on the subject ; but I published what facts I could ascertain (2). Work on a large scale in British possessions was first commenced in an admirable way at Lagos by Sir William MacGregor, who, however, was forced later by ill-health to leave the tropics — much to the loss of tropical sanitation. Other campaigns have been commenced in Sierra Leone, the Gold Coast, British Gambia, Hong Kong, many stations in India, Durban, Khartum, Candia, St. Lucia, Havana, Mauritius (section 17), besides Italy, Greece, and French and German possessions. The campaign in Sierra Leone was commenced in 1901 by Dr. Logan Taylor and myself, and was favourably reported on at the time by Dr. C. W. Daniels ; but it is impossible to obtain adequate details of what has happened there since we left, and the statistics show little improvement. A campaign at Mian Mir,'in India, was a failure, owing to insufficient expenditure and other reasons which I analysed in a paper published in 1904 (4). The campaigns in the other localities mentioned have been more or less successful, so far as I can ascertain. Last year I urged that the authorities would do well to collect information on the subject in the form of special malaria reports ; and, owing to the request of Colonel Seely, C.B., M.P., the Right Honourable the Secretary of State for the Colonies was good enough 79 to order such reports for his department. These have recently been published by the Advisory Committee of the Colonial Office for the Tropical Diseases Research Fund (17). On studying them I find that they give little evidence of a thorough and practical policy against malaria in most of the colonies. Strangely enough, all accounts of two of the best campaigns, namely, those at Klang and Port Swettenham, in the Federated Malay States, are omitted ; while the campaign at Hong Kong is repre- sented only by a single inadequate extract from a medical report. Similar extracts, often consisting of only a few lines, constitute all that is given for many colonies. One medical officer (Perak) remarks that '' with our heavy rainfall the banishment of puddles and other suitable places for the breeding of mosquitoes is practically impossible " — ignoring the fact that this is just what has been done in the neighbouring State of Selangor. Free quinine, lectures on elementary hygiene, and covering of water barrels seem to constitute all that has been attempted in many localities. In several of the West Indian Islands, it is admitted that nothing at all has even been attempted. Statistics, where they are vouchsafed at all, are generally quite inadequate ; and I have searched the reports in vain for any account of so simple and easy a measure as a spleen census. Suitable anti-malarial organisations have not really been constituted. The reports generally suggest the idea that the colonies have still much to learn regarding the prevention of malaria. There is much talk at present of research and instruction on tropical diseases ; but it would seem that, though the cause and the mode of prevention of the most widespread and important of tropical diseases — one that often causes as much sickness as all the other diseases in the tropics put together — have already been discovered and taught, yet that little or no action is to follow the acquisition of that knowledge. Nevertheless good work has been done in some of the colonies. I note especially Southern Nigeria (Lagos), where Dr. Strachan, the first Principal Medical Officer in West Africa to attempt malaria reduction by modern methods, and the Director of Public Works have continued the efforts of Sir William MacGregor by drainage, quinine, wire gauze, public instruction, and other methods. The former admits a great improvement in the health of the European officials. In Ceylon quinine has been largely issued at the cost of 8o Rs.73,299 during 1906, not including wages of distributors. At Bathurst (Gambia), where the work was started in 1901 by my junior, Dr. Button, according to my instructions, a malaria gang of ten men has been appointed for the purpose of " minor works," and the health of the European officials has improved ; but it appears that the larger swamps cannot be touched (?). In the island of Samarai (Papua) Anophelines are stated to have been entirely exterminated by the drainage of a swamp. The good work in Mauritius has already been touched upon (section 17). I will now proceed to a description of the leading examples of malaria reduction by modern methods, taken from my publication already referred to (2). 23. THE PREVENTION OF MALARIA IN ISMAILIA, THE FEDERATED MALAY STATES, HONG KONG, AND THE PANAMA CANAL ZONE, ETC.— (i). Ismailia. — The town of Ismailia was founded by the great Ferdinand de Lesseps in 1862 at a little distance from the middle point of the Suez Canal and close to the salt lake, Timsa. Though built in the midst of the desert, which surrounds it everywhere with its ridges of white sand like the undulations of a vast snowfield, it has nevertheless now grown to contain about 8,000 inhabitants, most of whom are employees of the Suez Canal Company. Supplied with fresh water by means of a canal from the Nile, it possesses many good houses, gardens, and well- appointed streets, kept in admirable order by the officials of the company under the able and energetic President, Prince Auguste d'Arenberg, who himself resides here for many months every year. Immediately after the construction of the fresh water canal in 1877 malaria appeared for the first time in the town, which had been previously noted for its salubrity. The cases gradually increased in number until in 1886 almost all the inhabitants suffered from fever. In 1901 the President, having recognised the new discoveries, deter- mined to employ them against this troublesome epidemic, and commenced by sending a member of his highly competent medical staff. Dr. A. Pressat, to Italy to study the subject. Early next year, however, shortly after the commencement of the operations at Freetown, he invited me to go Ismailia to advise upon the best means of attacking the disease. I arrived there in September, 1902, with 8i Sir William MacGregor, who did me the honour to accompany me, and with Dr. Pressat on his return from Italy.* On our arrival we found all the officials of the company keenly alive to the importance of the work. They had already detected the Anophelines in the town, had urged the general employment of mosquito nets, and had commenced an active quinine prophylaxis. On the other hand, the town was still swarming with mosquitoes. Even in the house of the President, where we were lodged, there were multitudes of Culex, which we showed were being bred in the well- constructed cesspit under the house ; while abundance of Anophelines were found in the houses of the employees, and were evidently carrying the disease everywhere in spite of the mosquito nets and the segregation of the Europeans. I felt, therefore, that here, as in other places where I had studied the subject, we should have to introduce the radical method of mosquito reduction if we wished for complete results, and I reported strongly in favour of this course. As Dr. Pressat has said, we formed " the conviction that we should establish for Ismailia a plan of campaign sensibly differentfromthat which we had seen followed in Italy, where the campaign against mosquitoes occupied only a secondary rank — so that this destruction appeared to us to be the capital article of our programme " (p. i3o).t We found the larvae of the Anophelines at once in various collections of water, principally in some small brackish marshes in the sand and some waters of irrigation, but happily not in the main fresh water canal, where small fish destroyed them. The campaign, conducted with intelligence and energy, presented no great difficulty. The marshes were filled up with sand, the irrigation channels were deepened or treated with oil, while the cesspits were soon rendered uninhabitable for the larvae of Culex. As Dr. Pressat has said.J he was able to effect the preliminary work with a " mosquito brigade" of only four men, " qui a tout fait." Although hundreds of men were employed later for large permanent works, this was only after the mosquitoes had already disappeared " grace a notre brigade de quatre hommes." I may perhaps be pardoned for dwelling on this fact because it fully * Ross : Report on Malaria at Ismailia and Suez. Liverpool School of Tropical Medicine, Memoir IX., 1903. t Pressat : Le Paludisme et les Moustiques. Masson et Cie., Paris, 1905. X Pressat : Prophylaxie du Paludisme dans I'Isthme de Suez. La Presse Midicale, 3oJuillet, 1904. 6 Cases of Malaria. Years, 1,800 1897 1,400 1898 1,450 1899 1,900 1900 2,500 1901 2,050 1902 1,750 1903 1,100 1904 1,350 1905 1,150 Caees of Malaria. 2,089 1,545 1,784 2,284 1,990 1,551 214 90 37 82 justifies the advice which I had given more than three years previously, but which had been met everywhere with scepticism. The results were most striking. It should be remembered that, as nearly all the inhabitants of Ismailia were employees of the Suez Canal Company, and as no other fever was prevalent in the town, exact statistics for many years had been possible. I give the following approximate figures from Dr. Pressat's works from the time when malaria first appeared in 1877 to 1905 : — ■ ,T Cases of v Y="'- Malaria. ^^^"• 1877 300 1887 ... 1878 400 1888 ... 1879 500 1889 ... 1880 400 1890 ... 1881 450 1891 ... 1882 480 1892 ... 1883 550 1893 ... 1884 900 1894 ... 1885 2,000 1895 .. 1886 2,300 1896 ... For more exact figures I must refer to Dr. Pressat's works. Since 1904 nearly all the cases have been relapses among persons previously infected, and last year the company officially reported that " toute trace de paludisme a disparu d'Ismailia." Of course, the treatment of old cases has constantly proceeded parallel to the anti-mosquito campaign. But the fortunate inhabitants have been relieved not only of malaria, but of the constant annoyance caused by the insects. In 1902 we were constantly being bitten in the houses. Now, as man}- visitors to Ismailia have testified,* one can sleep there without nets. This does not imply that the insects are absolutely unknown in the town, but only that their numbers have been very greatly reduced. Absolute extirpation is scarcely possible without bonification over a very wide area, but, as mathematically shown, reduction to a small percentage is much more feasible, and there are evident logical reasons for supposing that the amount of an insect-borne disease must ultimately vary, cateris paribus, as the square of the number of the insects. The cost of the work has been officially reportedf as being * Boyce : The Anti-malaria Measures at Ismailia. Liverpool School of Tropical Medicine, 1904. t Official Report of the Compagnie Universelle du Canal Maritime de Suez. Suppression du Paludisme a Ismailia, 1906. 83 about 50,000 frs. for the original drainage and filling up of the pools, with an annual expenditure of 18,300 frs. for the mosquito brigade, oil, maintenance, &c. This amounts to an initial expenditure of about 6'25 frs. and an annual expenditure of about 2'3 frs. per head of population — a small price to pay for the benefits given. It has been said by the opponents of mosquito reduction that the success at Ismailia was not real, but merely consisted in the statistical transfer of cases from the heading of malaria to that of other fevers consequent on better diagnosis. This is untrue, as there is no other fever there. It has also been said that the success was due to the exceptionally easy conditions at Ismailia. True, the conditions are not so difficult as in places like Panama and Sierra Leone, but I have seen many areas where they were quite as easy as in Ismailia, but where nothing whatever has been done. The success at Ismailia is absolutely unquestionable. It is due chiefly to mosquito reduction and also largely to cinchonisation. We owe it entirely to the intelligence and capacity of Prince d'Arenberg and his excellent staff. (2). Federated Malay States. — Commenced even before the cam- paign at Ismailia, as ably conducted and almost as decisive, the work at Klang and Port Swettenham, in the Federated Malay States, is an equally distinguished example of the radical method of malaria reduction. Klang is a town of 3,576 inhabitants (in 1901), situated on the banks of the river of the same name, in the State of Selangor, on a flat, swampy area lying between the river and a semicircle of low hills. In September, 1901, as the navigation of the river of Klang presented difficulties, a new port called Port Swettenham was opened five miles down the river from Klang on an area reclaimed from mangrove swamp. The population of the two settlements together was about 4,000 in 1903, while that scattered through the surrounding district was about 14,000. The rainfall averages about 100 inches (3 metres) a year. The full history of the campaigns in these two towns is given in the excellent papers by Dr. M. Watson, the district surgeon, and Mr. E. A. O. Travers,* the state surgeon. In the latter part of * Travers : An Account of Anti-malaria Work . in Selangor. Journal of Tropical Medicine, Sept. 15th, 1903. Watson : The Effect of Drainage and other Measures on the Malaria of Klang, Federated Malay States. Journal of Tropical Medicine, Nov. i6th and Dec. 1st, 1903. Ibid.: Second Report. Journal of Tropical Medicine, K^tAi'A, 1905. Travers and Watson : A Further Report. Journal of Tropical Medicine, July 2nd, 1906. 6a 84 IQOI malaria became very serious in both towns, and, according to Dr. Watson, perhaps not more than three houses in the whole of Klang escaped infection, while the workmen at Port Swettenham began to leave the place. Dr. Watson immediately set himself to collect statistics, to observe the local Anophelines, and to take the pre- liminary steps for the campaign. Supported by Mr. Travers and the Sanitary Board and by the intelligence and liberality of the Government, he soon obtained realisation of the recommendations of himself and his colleagues made on the lines laid down by me (i). At Klang work was commenced in 1901 by extensive clearing of undergrowth, followed by drainage in the next year. The swamps in the town were rapidly filled in, and a contour drain to intercept the inflow from the surrounding hills was cut. At Port Swettenham forest and mangrove swamp were felled, and a complete drainage scheme, prepared by the state engineer, was carried out. In both towns, pending completion of the drainage, mosquito brigades were appointed ; and their employment was extended subsequently under the name of " town gardeners." When the epidemic had already begun to subside, wire gauze was supplied to many of the houses, and an active quinine distribution was commenced. All the measures have been well maintained since then. As regards cost, Mr. Travers and Dr. Watson state that at Klang it amounted at the end of 1905 to a total of ;£'3,ioo, with an annual expenditure of ;^2io for town gardeners and of £60 for clearing drains. For this money 332 acres (134 hectares) have been dealt with, including virgin jungle, dense secondary growth, and swamp. At Port Swettenham the total cost has been ;£'7,ooo to the end of 1905, with an annual upkeep of £140. For this no acres (45 hectares) of mangrove swamp were drained, and a considerable area has been levelled, partly to provide building sites. The cost per head of population has therefore amounted to about ;^i. 4s. up to the end of 1905 — a very small charge considering the heavy rainfall and the dense vegetation of the country. These towns did not possess the exact statistics of Ismailia for a long period previous to the campaign. Great credit is therefore due to Dr. Watson for the care and skill with which he has determined the results of his 85 measures. The following table is compiled from the figures given by him : — Resul'i's of the Anti-malaria Campaign in Klang and Port Swettenham. (From the Journal of Tropical Medecine, July 2nd, 1906, by Mr. Travers and Dr. Watson.) Population of Klang and Port Swettenham about 4,000 in igoi and now largely increased. District population 14,000 in 1901. Anti-malaria campaign commenced (only in Klang and Port Swettenham) in 1902. I. — Cases of Malaria admitted to Klang Hospital from the Two Towns compared with those admitted from District. Years ... ... 1901 1902 1903 1904 1905 Towns 610 199 69 32 23 District 197 204 150 266 353 2. — Deaths in Klang and Port Swettenham. Years ... ... 1900 1901 igoz 190,3 1904 1905 Fever 259 368 59 46 48 45 Other diseases 215 214 85 69 74 68 3. — Deaths registered in District, excluding Towns. Years ... ... igoo 1901 1902 1903 1904 1905 Fever 173 266 227 230 286 351 Other diseases ... 133 150 176 198 204 271 4. — Infected Children in Towns and District. November and December, 1904. Klang. Port Swettenham, District, Ctiildren examined 173 87 298 Children infected 1 1 101 November and December, 1905, Children examined 119 76 247 Children infected 1 59 5. — Sick Certificates and Sick Leave granted to Government Kmployees. (Numbering 176 in 1901 and 281 in 1904.) Years ... ... ... 1901 1902 1903 1904 1905 Certificates 236 40 23 14 4 Days of leave 1,026 198 73 71 30 To these figures Dr. Watson adds that so great has been the reduction of the malaria that he has lost a large part of his private practice as District Medical Officer. Regarding the reduction of mosquitoes, he remarks : — " A definite improvement in the health of Klang was evident when only the swamps nearest to the main groups of houses had been dealt with, and while other swamps within the town were still untouched. The mosquitoes from these did not appear to travel any distance, and there has been no evidence of 86 dangerous immigration of Anophelines from the extensive breeding places which, until the middle of 1904, existed just outside the town boundary, and some of which still remain. Yet the species breeding in these swamps were identical with those breeding within the town." The objection raised against the campaign at Ismailia — namely, that it possesses a dry soil and climate — cannot be raised against the well-conducted campaign of the Federated Malay States, and the world owes a debt of gratitude to the Government of these States, to Mr. Travers, and especially to Dr. Watson, for the fine example which they have set. (3). Hong Kong. — One of the earliest and best of the campaigns in British territory. The city of Victoria, usually called Hong Kong, runs for nearly five miles along the north of the island of that name at the mouth of the Canton river in South-east China. The island, 1 1 miles long and from two to five miles broad, consists of a broken ridge of hills, rising to nearly 2,000 feet, and the city is built on a hill sloping down to the water, some of the terraces and houses being 500 feet above sea-level. There is also a large residential district on the mountains reached by a cable tramway. The soil is granitic. All along the face of the hill on which Victoria is built there are beds of streams, known as " nullas," which used to swarm with anopheline larvse. The population of the colony was 377,850 in 1905, of which 10,835 were whites (nearly half belonging to the British Army and Navy). The rainfall is from 70 to 80 inches a year. Malaria has been always very prevalent here, and I remember that in 1881 the colony was cited as an example of the telluric miasma due to decaying granite. The first researches on the new lines were commenced as early as May, 1901, by Dr. J. C. Thomson,* who undertook an exhaustive study of the mosquitoes and their breeding-places. He examined over 32,000 specimens, of which he found about 4 per cent, to be Anophelines, and in November advised an active anti-malaria campaign by drainage, clearing of jungle, " training " of the nullas, the use of wire gauze, oiling pools, and quinine prophylaxis. As seen by his excellent papers,t his recommendations were not of a general * Thomson: The Distribution of Anopheles and Cule.x at Hong Kong. BrU. Med. Jour. 1901, vol. i. , pp. 749 and 1379. t Ibid. : Malaria Prevention in Hong Kong. Official Report, containing many letters, 1900-1903. 87 nature, but were particular, practical, and exact. These recommenda- tions were rapidly acted upon by the Government. Since 1901 all the nullas or water-courses within and near the city were " trained " — that is, rendered so smooth and even that the Anophelines could no longer breed in them ; and much similar work was done wherever most needed elsewhere by training water-courses, buying up rice fields, and so on. The details of the campaign are so numerous that it is impossible to give them here. They will be found in the publications given in the bibliography and in a good paper by Mr. J. M. Young,* who took part in the early stages of the work. The results are given in the annual sanitary reports of the colony and in a recent address by the medical officer of health, Dr. W. Francis Clark. t Dr. Thomson informs me that before estimating them it is necessary to remember that malaria can never become extinct in Hong Kong owing to the fact that some 3,000 to 4,000 natives come and go from and to the country districts every day, and that a number of these will remain infected in spite of all local measures. Neverthe- less the figures show a rapid diminution both in the admission and in the death-rates. Malaria Statistics of Two Large Hospitals. Years 1S97 1898 1899 1900 1901 T902 1903 1904 1905 Admissions 1,021 865 780 1,220 1,294 752 568 433 419 Deaths 197 126 63 163 132 128 63 58 54 Admission Rate of Police for Malaria. Years i8g6 1S97 1898 ,899 I goo 1901 1902 1903 1904 1905 Admission, % ... 32 25 19 31 42 44 19 18 11 12 Dea THs FROM Malaria. Years 189S 1897 189S 1899 19CX) 1901 1Q02 1803 1904 1905 Population ... 239,419 — — — — — — — — 377,850 Total deaths ... 533 554 530 546 555 574 425 300 301 285 Deaths in city (Chinese > ggo 302 280 218 242 281 189 152 90 87 The official sanitary reports give similar figures. The improve- ments have, of course, varied much in different localities. Thus in 1900 the western end of Bonham-road used to be one of the worst * Young : The Prevention of Malaria at Hong Kong. Brit. Med. Joitr., 1901, vol. ii., p. 683. t Clark: An Address on the Prevention of Malaria in Hong Kong. Noronha & Co., Hong iCong, 1906. districts. Now in 1905 it is reported not to have sent a single case to the Government Civil Hospital.* With regard to cost, Dr. Clark reports that up to the end of 1905 the Government had expended about ;^5,ooo on anti-malaria measures, and estimates that .£'6,500 would be spent by the end of 1906 — a small amount to pay for the good that has been done. The campaign in such a thickly populated district must be difficult. A larger expenditure would probably have produced still more marked results, and it would have been useful to estimate the endemic-index in various parts of the area. I am much indebted to Dr. Thomson and also to Mr. J. Bell for the detailed information which they have been so kind as to send me, but which I have no space to give more fully. (4). Panama Canal Zone. — As is well known, the attempt of the French to cut the canal through the isthmus was foiled principally by yellow fever and malaria, and I was told that their effort had cost quite 50,000 lives. The Americans took possession of the works early in 1904, at a time when the mode of propagation and of prevention of both diseases was well known, and they wisely determined to commence their labours with sanitation. Colonel Gorgas, assisted by a capable and enthusiastic staff, was put in charge, and attacked the work with knowledge and energy. I visited the place at his invitation in the autumn of 1904, and was a witness of the skill shown in his dispositions. The country is one of the worst to deal with which I have ever seen. Hilly, with a great rainfall, a loose, crumbling soil, a luxuriant vegetation, and innumer- able small marshes and pools, it was evidently the very stronghold of malaria. Step by step, with the aid of numerous experts and hundreds of workmen, the Americans cleared the forests, drained the pools, and banished the Stegomyia. The details and the results will be found in the monthly and annual reports of the workf and in a recent address by Colonel Gorgas. + Put briefly, the results * Reports on the Health and Sanitary Condition of the Colony of Hong Kong, 1900-1905, p. 54. t Reports of the Department of Health of the Isthmian Canal Commission, Monthly and Annual. Government Printing Office, Washington. % Gorgas : Sanitation in the Canal Zone, /onrnal of the American Medical Asso- cialion, July 6th, 1907. 89 are that in 1906, amongst 5,000 white American employees, the total death rate was only 7 per mille, and of this only 3"8 per mille were due to disease. Last April the daily sick rate of the total force of about 40,000 people was only 17 per mille. Colonel Gorgas says : — " Among 6,000 Americans in the employ of the Commission, including some 1,200 American women and children, the families of these employees, we have but little sickness of any kind, and their general appearance is fully as vigorous and robust as that of the same number of people in the United States." These published statements are fully borne out by private communications from individuals living there. Colonel Gorgas adds : — " I think the sanitarian can now show that any population coming into the tropics can protect itself against these two diseases (yellow fever and malaria) by measures that are both simple and inexpensive . . . . ; and that again the centres of wealth, civilisation, and population will be in the tropics as they were in the dawn of man's history." Sir Frederick Treves, who visited Panama last February, read an interesting paper on preventive medicine there, before the Royal Society of Medicine, Epidemiological Section, on the 22nd May, 1908 (18). Regarding malaria, he said: — "The crusade against malaria has been even more elaborate. Every new arrival on the isthmus is handed a printed circular explaining the cause of malaria and the means of its prevention, and advising the constant use of quinine in doses of at least 3 gr. a day. Quinine is placed on the table in the dining rooms and boarding camps, and large quantities of the drug are distributed broadcast. In the month of September, 1905, for example, 675,000 gr. were dispensed, mostly for prophylactic purposes. A large number of men are kept constantly employed in cutting down the dense tropical undergrowth, in mowing or burning the grass, in making and lining ditches, in filling in swamps, and in oiling the surface of any pool or puddle in which mosquitoes might breed. Others are employed to inspect water tanks and barrels, to destroy such as can be dispensed with, and to screen such as are retained. As an example of the work of the anopheles brigade it may be noted that in 1906, in Colon alone, the surface oiled amounted to 330,000 square feet. New ditches were cut to the extent of 200,000 lineal feet. Of these ditches, 20,000 feet were stoned or cemented. Two million lineal feet of old ditches were cleared, go graded, stoned, or filled in. The area of brush and grass cleared amounted to 21,000,000 square yards. Never has a crusade been carried out with such completeness, for never has a chief sanitary officer had so free a hand. It is needless to point out that the mere oiling of pools does not constitute the sole prophylactic measure against malaria. In a well-to-do town in the tropics it may be supposed that the land has been thoroughly drained and every suspected area oiled, but there are still many varieties of vegetation which afford a breeding place for mosquitoes ; as instances may be cited pines and such a palm as the traveller's palm. It may be sure that the pine grower will not sacrifice his harvest in the public interest, nor will the wealthy resident allow the palms, which are the glory of his garden, to be cut down. It is much to be hoped that a list will be forthcoming of garden and other plants in which mosquitoes breed. On the Canal Zone no such list was needed. The place denounced was swept bare." Colonel Macpherson, C.M.G., R.A.M.C., who also has recently visited Panama, informs me that the total cost of the sanitary measure there is 2,000,000 dollars per annum, or about one-tenth of the total annual expenditure on the canal work. This includes the whole medical expenditure. (5). Anti-Stegomyia Campaign at Port Said. — Although Stegomyia does not carry malaria, it is such a pest in the tropics that it ought to be attacked if possible. It has been almost completely banished from Port Said by a campaign carried out under the orders of the Governor, Mouheb Pasha, and the recent Director of the Egyptian Sanitary Department, Sir Horace Pinching, by my brother, E. H. Ross. Port Said has a crowded population of 56,000 people of many nationalities ; and the insects used to breed chiefly in cellars and cesspits under the houses, the rainfall being small. The cost of removing them amounts to sixpence per annum per head of popu- lation. Dengue and other fevers have simultaneously disappeared from the town, and also from Ismailia, where similar work has been done (19, 20). (6). Italian and other Campaigns. — I do not propose to describe these, as the conditions under which they were effected are not very similar to those in the tropics. In Italy there is a white population, close to large cities and with plenty of medical attendance at hand, 91 so that the measures said to be most suitable have been chiefly quinine prophylaxis and isolation. In Greece the campaign has only just begun, and in many other places few statistics are available. 24. PRELIMINARY CONSIDERATIONS REGARDING PRE- VENTION. — At the beginning of section 22, the various measures for public malaria reduction were given as (a) mosquito reduction, (d) case reduction, and {c) isolation. It is obvious that any one of these, if completely carried out, must result in the complete suppression of endemic malaria in any locality. Unfortunately, however, public funds are limited, and the question arises, which of these measures will give the best results for the least expenditure ? The subject is a favourite one for discussion at medical con- ferences, but the conclusions are not always useful, owing to frequent inexperience in some of the speakers. Yet during the last ten years we have acquired considerable experience regarding the utility and feasibility of the various measures ; and, I think, the men who have actually done the work — Gorgas, Pressat, Watson, and others — are agreed as to which are best. The answer to the question is, of course, much modified by local conditions. Of what race and degree of intelligence are the inhabi- tants ? Are we dealing with cultivated or uncultivated rural areas ; with villages, towns, or cities ? What is the rainfall ? Does it fall mostly in summer or winter? Is there a sharp winter, or an arid summer? Is the ground flat, or gently or abruptly sloped ? Is it pervious or impervious, high or low, forested or bare? What are the crops, and how are they watered ? Are the people wealthy or poor ? How are they housed ? What are the methods of communication ? Is there sufficient medical attendance ? Is registration of death good ? Is the form of government arbitrary, political, or practical ? Has the medical profession any influence in it ? And, above all, what is the state of the public purse? It is advisable to begin with some general remarks. (i). Fonn of govermiunt. — It should be understood at once that with certain forms of government real malaria reduction is simpl)- out of the question. I refer not only to the uncivilised despotism, but also to what is frequentl]/ worse, the small uncontrolled municipalit}', and minor " free " elected government. Every sanitarian recognises 92 at a glance the unfortunate territories ruled by such. The ill-made roads and gutters ; the crumbling walls ; the dirty unpainted houses, built anywhere and anyhow ; the foul yards, with noisome latrines, and littered with rubbish ; the leaking water-pipes ; the choked street drains, converted into cesspits ; the idle police ; the scanty workers, and the numerous officers. We can see at once that the funds which should be devoted to making the place tidy, clean, and healthy for the good of the public are being diverted to other uses. The public councils and offices are the prey of persons who gain their position by advertisement, and who know and care nothing about management ; and order, discipline, and science are unknown, while the councillors pretend to quarrel over childish political issues which have long ceased to interest educated persons. To appeal to such to carry out a sustained anti-malaria policy is quite futile. No such body, so far as I know, has ever yet attempted this task. As Sir Frederick Treves points out, the great work at Panama is due simply to the strong scientific form of government in force there. If, then, any real sanitary work is to be expected, the form of government must be such that defaulting local authorities can be forced to attend to the duties for which they were appointed — foremost among which is sanitation. (2). The first preliminary to success. — Granted then that we have to deal with a rational and practical form of government, the first step for that government to take is to decide definitely whether or no it really intends to attack the disease. Sanitation is a form of war. It requires money, discipline, organisation, and thought. A scientific government recognises that widespread disease is a great bar to prosperity, and can be fought only by concerted measures, which are mostly beyond the powers of the individual citizen, and must be, at least, directed by authority. On the other hand, it is the guardian of the public purse, and must refuse to sanction expenditure which may lead to no result. It must therefore begin by obtaining an estimate of the amount of mischief produced by the disease, and of the cost of reducing it thoroughly. Obvious as this principle is, it is frequently, if not generally, neglected ; no real efforts are made to measure the disease (as described in section 19) ; and the efforts made to reduce it are often merely nominal, and consist only of popular lectures on mosquitoes and rules about placing wire gauze on water-butts. (3). Necessity for repeated measurements oj malaria. — Not only 93 should the disease be measured to begin with, but the process should be repeated regularly in order to ascertain whether the preventive measures, whatever they are, are producing the desired effect. With organisation, the spleen test can be applied once, if nottwice, a year without serious difficulty. The authorities can thus obtain data to justify their expenditure, and can also ascertain which localities most require it. Without such methodical estimates, the anti-malaria campaign may show no tangible results, even if they exist, and will probably be abandoned before long. (4). Limits of expenditure on anti-malaria work. — Theoretically it would be justifiable to spend as much money for the prevention of malaria as the disease costs the community. It is a great source of waste of money («) by deaths and reduction of population ; {b')\>y loss of manual labour in plantations, factories, farms, &c. ; ic) by sickness among government labourers and officers ; {a) by invaliding and deaths among higher officials and soldiers (annexure i). Practically, however, governments must be limited, not only by their own revenues, but by that part allotted to the medical and sanitary budget. Perhaps the best estimate under this head may be formed by comparing the total amount of sickness due to malaria with that due to all causes — generally a large percentage. It may be argued, for instance, that, if malaria causes one-third the total sickness, then one-third the medical budget should be expended on its prevention. This would be scarcely fair, as other diseases often produce a greater mortality though less sickness ; but the argument helps to put the matter in a clearer light. In many countries, while the total expenditure on medical staff, hospitals, dispensaries, conservancy, sewerage, water- supply, quarantine, registration, &c., is great, that on the prevention of malaria, which may cause nearly half the total sickness, may be almost nothing. Yet it might be urged that if malaria could be banished, the people would really receive more benefit than by most of the other sources of expenditure put together. Both Dr. Meldrum and Mr. Chadwick have touched upon this point. (5). All measures against malaria must be continued indefinitely. — It is well that this should be understood clearly to begin with. The work, if it is to be anything but a futility, will be a permanent burden upon the estimates. It might be possible, I think, to extirpate the disease entirely from an island like Mauritius — but this 94 could be done only at greater cost than is likely to be faced at present ; and even after that, \ery stringent quarantine measures would have to be taken to exclude infected immigrants. But with good organisation the disease can, I consider, be so largely reduced that many items of the cost of the campaign will also ultimately diminish — perhaps very largely. That is all that can be promised. At the same time the cost to Government ought to be recouped by saving to the public, and consequent addition to revenue. (6). Some legislation and discipline necessary. — Although much anti-malaria work can be done without troubling the public, yet, if it is to be done with economy, the public must be called upon to take their share of the burden as well as of the advantages. Certain petty laws and regulations are necessary, and the public must comply with them. One of the most serious difficulties in the way of all sanitary improvement everywhere lies in the inadequacy of punishment often given by magistrates for sanitary contraventions. Fines are too small to be deterrent ; endless petitions are allowed ; and the time of the sanitary departments, which should be spent on useful work, is used up in attending courts and writing up cases — a simple waste of public funds. This is not freedom but licence. It is a very low form of civilisation in which individuals are allowed to abuse the freedom which civilisation has given them by poisoning or infecting their neighbours. If those who make and administer the laws were called upon to sit by the side of dying patients, as medical men too often are, and to watch the effects of the bereavements that follow, they would not so often treat these serious offences as jests or as petty failings. The success of the work at Panama has been largely due to the great powers given to the health department, and to the stringent discipline exerted ; and the public themselves have become thankful for this wise severity. Sanitary discipline is like the discipline of the sick room, against which only the most foolish patient rebels — to his own sorrow. (7). Special organisation advisable. — As already frequently stated, in some countries malaria causes nearly as much sickness as all the other diseases put together. The prevention of it therefore deserves very serious and special attention from the Government. There must be a special working organisation ; and as a rule it should be placed under an officer of the Health Department, purposely selected for his 95 knowledge of the subject and his capacity for scientific administration. He should be ordered to prepare every year a special malaria report, detailing the annual measurements of malaria, and the practical work done by his department. So far as I can see, without some such organisation, the work is not likely to be either general or thorough. (8). A firm contitiiwiis Govenunent policy absolutely necessary. — Although many of the successful campaigns mentioned above have been due to the enthusiasm and intelligence of individuals, success is not likely to be continued without a determined policy on the part of the Governments concerned. Permanent success is beyond the power of individuals. If Governments wish for lasting results on a large scale, they must make up their minds to push the preventive measures at all costs. Laws must be enforced, inefficient officials removed, and the proper expenditure incurred, regardless of popular talk. After all, unlike the prevention of plague and cholera, that of malaria gives little trouble to the public ; but that is all the more reason why it should be prosecuted with resolution. 25. THE VARIOUS PREVENTIVE MEASURES CONSIDERED.— We must now examine the actual preventive measures mentioned at the beginning of last section. (i). Isolation. — Suppose that the number of mosquitoes, and also the number of infected persons in a locality are allowed to remain as before, but that the former are prevented from biting the latter ; then further infection both of insects and of human beings would cease. This means that all the infected persons in a locality are to be isolated from mosquito bites until they recover. Not only this, but infected persons outside the locality, and within the range of immigration of mosquitoes, must be treated in the same manner ; and persons entering the locality even for a single night must be examined. This measure may be called isolation of the sick. Again, suppose that the mosquitoes and infected persons are left alone, but that the healthy persons are isolated from mosquito bites. This also would put a stop to further infection ; but healthy persons outside the infected locality, and within range of infected mosquitoes coming from it, must also be protected ; and so must persons who visit the place even for a night. This measure may be called isolation of the healthy. 96 Either of these methods by itself would imply the careful and repeated medical examination of all the persons in a locality, and also of visitors. But it is not always possible to say, even after prolonged microscopical search of the blood, whether a person is infected or not ; and many people show the parasites only occasionally when they suffer from relapses. Others remain infected for years, and would, theoreti- cally, have to be isolated all that time. To carry out all the necessary examinations, a large and expensive medical staff would be required. Hence neither measure by itself is, usually, practicable, but both must be combined in a uniform system oi general isolation from mosquito bites. There is an exception — the case of a locality in which only a few cases are beginning to occur. Here such cases may be notified and carefully isolated for the sake of the public. The attempt has been made at Durban, but abandoned ; and it has often been proposed in America. The cases must be controlled with the rigour adopted against plague, yellow fever, or cholera, but owing to the long continuance of the malaria infection, for a much longer period. General isolation from mosquito bites is attempted by the use [a) of culicifuges ; {b) of clothing ; {c) of mosquito nets; and {d) of screens to the windows. Culicifuges are medicaments, such as kerosine oil, lavender oil, and many patent fluids, for keeping away the insects. They may act for an hour or two ; but the effect soon wears off. It is absurd to suppose that a large general population will ever consent to use such substances every day and night, indefinitely for years. They are useful (?) only for personal prophylaxis. The same must be said of special articles of clothing — gloves veils, boots. Useful at specially dangerous moments, the)^ are never likely to be used generally. Mosquito nets round the bed at night are the first essential of personal prophylaxis. For years I have depended entirely upon them ; and almost everyone of experience in the tropics does the same. I consider that, of all the Anopheline bites which an unprotected person would suffer in twenty-four hours, at least 90 % would probably be inflicted during his sleep at night. Hence, in my opinion, the jealous use of a mosquito net reduces the chances of infection anywhere by 90 % ; and though I have been in many malarious places and do not trouble to take quinine, I have only once been infected — and that was 97 before I had ascertained the route of infection. But a small net costs five rupees — the wage of a labourer for ten days in Mauritius. Nets wear out quickly ; it is difficult for the occupants of poor huts to use them for themselves, and still more for their children ; and they could scarcely be forced by law to do so. Mosquito proofing, or the protection of whole houses or parts of houses with wire gauze, has long been used in the more southern states of America. It is employed (on a great scale) against yellow fever and malaria in Panama ; by Sir William MacGregor and Dr. Strachan in Lagos ; and at the Observatory and Central Prisons in Mauritius. " Tinned wire gauze " costs at least twopence a square foot, and brass and copper gauze costs half as much again — besides the cost of construction. The screens are most useful and pleasant. They exclude not only mosquitoes, but other insects and also the glare of the sun and the damp after rain ; and they should certainly be used if possible in all public buildings and in good private houses. The cost is, however, prohibitive for the poor classes of house. Some of these, which are nothing but bamboo and leaf shelters, would practically have to be covered all over, at an expense greater than the value of the structure. Thus proofing is generally a measure only for the well to do. There can be little doubt by sections 1 1 and 12, that even if a part of the population could be induced to adopt isolation against mosqui- toes the result would be great — the new infections might fail to keep pace with the recoveries, and complete extinction of the disease might follow, especially if case-reduction is adopted in addition. Even for the poorest populations then, isolation must not be neglected : and I shall make definite recommendations under this head in section 31. Isolation can never be complete. People must labour out of doors, where Anophelines frequently bite ; nets and screens get out of order ; and it is especially difficult to isolate children, the principle homes of the parasites. But for the same reasons as apply to mosquito and case-reduction (section 12), the theoretically complete measure is not necessary. Even partial adoption of it may suffice to break the vicious cycle. (2) Punkas and segregation. — These are measures for the well-to- do. In 1899 I pointed out that Europeans in India are so much more healthy than those in West Africa, probably because they adopt these 98 measures (i). Even in India their health is better in the large can- tonments, where nets, punkas and segregation are generally used, than in the planting districts where they are frequently neglected. This has probably been one of the chief causes of the magnificent success of the Indian empire as compared with the comparative failure of the African colonies. Punkas not only keep the body cool, but also drive away a large proportion of flies, and segregation protects from other diseases besides malaria. Both are forms of isolation. The latter has been strongly urged against malaria by Stephens and Christophers and by Button ; and should be used when possible. Without the other measures, it must be very complete to be effective. It failed at Ismailia ; and also at Vacoas, where last January, seventy British soldiers were infected in the barracks, although the infecting native village is more than half a mile distant (addendum 2). Theoretically it is a class measure, and must be accompanied by restrictions which are difficult to enforce even with regard to troops. (3) Case-reduction. — Suppose that the number of mosquitoes is allowed to remain as before, and that they are not prevented from biting, but that the number of infected persons is reduced by treatment to zero , then further infection must cease. This means, if cessation of fresh infections is to be immediate, that all infected persons, not only in the locality to be protected, but within mosquito-range outside it, are to be sought out by skilled medical men and treated to the point of complete cure. If gradual reduction is permitted, a more partial measure is still likely to be successful. The detection of cases can be effected only with the difficulty and expense referred to under " isolation of the sick." To this must be added the difficulty and expense of thorough treatment. I infer in section 6 that each case must be treated for several months on the average in order to extirpate the parasites. Moreover, the bulk of the cases are generally the children of the poor ; and the parents of these must be induced to give them the thorough treatment recommended. Repeated examinations will also be necessary ; and infected immigrants must be dealt with — a great difficulty in some cases, for instance that of market towns. For all these purposes a considerable medical staff is necessary, requiring a constant expenditure. 99 (4) Quinine prophylaxis. — This is really a form of case-reduction. To the person who takes it, quinine is not exactly a prophylactic It does not exclude the parasites ; it merely destroys them in some cases after they have entered the body. For personal prophylaxis it is valuable at times of danger ; but as a measure of public prophylaxis •it is difficult. We urge, in fact, that every healthy person in a locality shall take the drug continuously in the expectation that he might at any moment be bitten by an infected Anopheline. We thus attempt to provide for case-reduction among the newly infected, as distinct from the old declared infections. But the perpetual use of quinine is always trying to the system, while the contingency of being bitten by an infected mosquito is not always certain ; and many people will prefer the risk of malaria to the certainty of dyspepsia and other symptoms produced by quinine. Moreover I infer, though I am not sure, that as large doses must be taken to quell a new infection as to check an old one — that is, that the prophylactic dose must be as large as the therapeutic one. It is therefore difficult to persuade a large population, consisting let us say of poor labourers, to adopt such a measure continuously. For officials and soldiers it is generally possible ; but even then is objected to. On the other hand, the general quinine treatment of a whole population, both sick and healthy, saves the trouble and expense of constant medical examination, though it adds to the amount of the drug used. But this difficulty may also be removed by a form of case-reduction, which I shall presently propose for Mauritius — namely the treatment of children with enlarged spleens. (5) Anopheline reduction. — Suppose that the number of cases is allowed to remain as before, but that the Anophelines are banished, then further infection must cease. This implies, if cessation of infection is to be immediate, that every breeding place of the insects within the area to be protected and also within mosquito range outside it is to be abolished. But a less thorough measure is still likely to produce more gradual reduction (section 12). Mosquito-reduction is based on the certainty that if the birth- rate of the insects within a given area is abolished, their numbers will be reduced, not only in that area but for some distance round 7A lOO it ; and will consist hereafter only of chance immigrants from without. The amount of the reduction will vary as the size of the area treated. The birth-rate is abolished or reduced by complete or partial treatment of the waters in which they breed ; by drainage, deepening or filling of marshes and pools by dragging out the water weeds ; by " training " the banks of streams, by introducing fish, using oil and other measures. All this requires (a) a capital expenditure and {d) an annual expenditure ; and can be effected only by a special organisa- tion indefinitely continued. The expense will vary largely according to local conditions. By section 12, malaria will not continue in a locality unless the carrying Anophelines are above a certain standard in number. Hence absolute suppression of the insects is not necessary ; and a mere reduction below the standard should suffice to produce gradual decrease.* Practically, Anopheline-reduction may be merged in general mosquito-reductio7t, which costs little more to effect ; and adds greatly to the advantages of the measure. (6) Public instruction. — Lectures and pamphlets, though frequently repeated, are never attended to by more than a minute proportion of the public ; and even school lessons are soon forgotten. Again, of those who have actually listened to instruction, very few trouble to act upon it. Numerous lectures and pamphlets on malaria will scarcely succeed, perhaps, in inducing one per cent, of the public to be more particular in the use of nets, to take a little quinine for a few weeks, or to collect broken bottles and tins in their back yards ; and in this I speak from frequent experiences. More than these things, the private individual can scarcely do. He cannot undertake either case-reduction or mosquito-reduction in his neighbours' houses ; nor force them to adopt isolation. It is well therefore to give public instruction on these matters ; but the authorities must not hope to banish, or even seriously to reduce, malaria by this means alone. To do so is to abdicate public prophylaxis altogether — to attempt to throw on the individual the duties which can only be done by the State. Of course the individual must take his share of the work, but it must be in the form of part payment of the expenses of the concerted measures adopted. Public instruction by itself is as useless against malaria as against plague and cholera. * See page 148, lOI 26. THE VARIOUS PREVENTIVE MEASURES COMPARED.— On comparing the above measures, the first consideration which must strike the practical sanitarian is the following. Isolation and case- reduction require compliance on the part of the public ; mosquito- reduction does not. To use culicifuges and mosquito-nets ; to put screens to the windows and verandahs ; to take quinine day after day ; to force one's children to take it ; to attend dispensaries for the drug ; and to submit to constant inspections ; require an endless amount of trouble on the part of thousands of people. Will the people take the trouble ? What can be done by poor labourers who must be at work at daybreak ; or by their wives who labour equally at household affairs ? Have they the time to wait for hours at the dispensary, or to rub unguents all night on their children ; or the money to buy mosquito-nets ? And to enforce attention to such details requires equal trouble on the part of the authorities— an army of inspectors and medical attendants, and an armoury of laws and regulations. What practical sanitarian is there who does not recognise what all this would mean — endless trouble, expense and perhaps friction with the people ? On the other hand no one objects to the drainage of swamps and clearing of watercourses, which can be done at once by the authorities without (as a rule} troubling anyone. Here then an immense advantage — which will be most apparent to those most experienced in sanitation — lies with mosquito-reduction. Next, case-reduction guards against malaria only ; but isolation and mosquito-reduction against all mosquito-borne diseases — filariasis, yellow-fever, and probably dengue and other fevers. Here then, case-reduction is at a disadvantage. Again, isolation gives only partial and temporary respite from mosquitoes ; mosquito-reduction, where thoroughly carried out, a much greater security. The presence of many mosquitoes, especially Stegomyia, is a perfect curse in the tropics. One is bitten all day and everywhere. To get rid of them — even to reduce them — is a great boon. I remember Port Said before and after this was done ; and many people have told me of the blessing conferred by the campaign at Ismailia — quite apart from the reduction of malaria. Here then^ mosquito-reduction again has the advantage. Lastly, mosquito-reduction has a great general sanitary advantage which is not conferred by the other measures. It forces the sanitary I02 department to maintain always a minute inspection of the area in its charge— to keep the yards free from rubbish, the waterways open, the drains free, the cisterns clean, the gardens and open spaces dry. It tends therefore to become a kind of general insurance policy for good sanitation. Hence, theoretically, mosquito-reduction has the advantage in every way. It does not demand trouble and direct expense on the part of individuals. It does not require the continued use of a nauseous and dyspepsia-ginng drug. It can be enforced by the authorities without troubling the public. It protects from other diseases besides malaria, and also from a general source of annoyance ; and it helps the whole cause of sanitation. Practically however, questions of cost and feasibility have to be considered. It is almost impossible to give an estimate of the cost of mosquito-reduction, which must depend everywhere on the nature of the soil, the slope of the ground, the rainfall, the vegetation, the existence of large marshes, the character of the drainage and of the sanitary establishments already in use, and so on. The figures for Ismailia and the Federated Malay States include large items in excess of the actual anti-mosquito campaign, and those for Panama cannot be obtained. At Port Said the Stegoniyia reduction (complete) costs about sixpence per head of population per annum (section 22). But those who imagine that the other measures will cost much less are mistaken. Consider for example the case of a small town in the tropics containing, let us say, 2,000 tenements and 10,000 inhabitants of all classes — that is, mostly poor and coloured people. To supply them all with ordinary muslin mosquito-nets would cost several thousand pounds, and several hundred pounds a year for depreciation, besides a constant outlay for inspections. Wire gauze to the houses, even to the better-class houses alone, would add vastly to this expenditure. Free quinine distribution, at the rate of eighteenpence per ounce of the drug would cost perhaps .^'soo a year, if done generally, without including the large expense of the medical establishment necessary, and the endless trouble caused to the inhabitants. It is quite possible that mosquito-reduction for the whole place might be effected in many cases for a fraction of this expenditure. Thus for Ismailia, Pressat reports emphatically that he was able to do the I03 essential work with only four men ! For iTsoo a year — which would probably be much less than the cost of medical attendance, quinine, mosquito nets, and wire gauze — we could employ in Mauritius a staff of thirty or forty workmen to keep the waterways clear during the whole year, without troubling the inhabitants at all. I have no doubt which alternative would be chosen by a health officer of experience. Of course, the case may be different where there are large marshes with difficult outlets ; but even here drainage may often be recouped by enhanced value of land for buildings, sites, &c., as in the Federated Malay States. For larger towns and cities the case is even more clear. As a rule the cost of Anopheline reduction must vary directly as the size of area dealt with ; though in crowded towns it may often be less, owing to so much of the space being occupied by houses and streets. Hence, by draining a square mile of city we shall benefit thousands of people ; whereas by draining the same extent of open country we might benefit only a few houses. That is to say, the cost of Anopheline reduction varies as area, not as population. But the expenses for isolation and case-reduction vary as population and not as area. Hence, I enunciate the following general law ; the greater the density of population, the greater the advantages of mosquito- reduction per unit of cost. In rural areas mosquito-reduction may ndt be nearly so advantageous. Many absurd statements are made on this point bj- people who have never considered the subject properly, and who seem to imagine that the measure is proposed for the world in general. No one has ever made such a suggestion. Mosquito- reduction is for the city, the town, and perhaps the village ; not for the wilderness. We do not propose to drain forests and fields for the good of the birds and beasts. For isolated houses, quinine, isolation, and treatment of small neighbouring waters, if possible, are called for ; but larger works can be indulged in only by rich house-owners, not by the authorities. Also in small towns and villages situated in the midst of large marshes, or marshy forests, or flat waterlogged country, the cost of mosquito-reduction may be too great. This must not be assumed hastily, without preliminary trials on a small scale ; but, assuming this to be so, resort can then be had to the other measures. I04 On examining such considerations we shall see that for a large-scale public malaria campaign amongst a general population we are practically reduced to two or three measures. Such measures as the use of culicifuges, mosquito-nets, house-proofing, punkas, segregation, quinine prophylaxis for the healthy, cannot really be forced on the whole population. The campaign must depend upon mosquito-reduction, treatment of the sick, especially the children with enlargement of the spleen, isolation in certain localities only, and regular measurements of the amount of the disease. Hitherto, for convenience of comparison, I have considered each measure separately, but obviously two or more may be combined. Instead of carrying out each measure by itself com- pletely, it might be cheaper to carry out two measures partially. This will be more clearly understood by a study of section u. For instance, a partial mosquito-reduction combined with a partial case-reduction would be likely to have excellent effects. But it is fruitless to consider further such details as these in connection with the general subject, as they obviously depend on local conditions. 27. THE GENERAL PREVENTIVE MEASURES SELECTED FOR MAURITIUS. — I will, therefore, now proceed to choose the measures which, in my opinion, are likely to do most good in Mauritius for the expenditure of money and labour involved. They are the following : — (i) A periodical spleen census of children in schools and on estates. (2) Treatment of children with enlarged spleen in schools and on estates, and a certain amount of quinine distribution. (3) Occasional house protection. (4) Mosquito-reduction where advisable, (a) by minor works, and {Ir) by major works. (5) A suitable organisation and an annual malaria report. Before proceeding to state the details, I should like to premise that I do not wish to make rigid recommendations regarding them. Experience will doubtless suggest many useful modifications which may safely be left to the future. 28. THE PERIODICAL SPLEEN-CENSUS. — The objeas of this will be to determine, (l) The localities most affected by malaria ; los (2) The effect of the preventive measures ; (3) The children who require treatment. The proposals are as follows : — (i) That a register of all children of fifteen years or under with enlarged spleen be kept at each school by the schoolmaster, and at each estate hospital by the dispenser. (2) That this register should contain the age, sex, and name of the parents of each child with enlarged spleen (but not necessarily of the other children) ; with columns for noting whether the enlargement is small, medium, or great, and a column for remarks. (3) That an examination of all the children attending each school, or living on each estate, should be made every quarter of the year (for the present) by the appropriate medical or sanitary officer. (4) That at this examination the medical officer should select all the children with enlarged spleen, and should direct the proper entries to be made in the register. (5) That twice a year (for the present) the figures in the register of each school or estate hospital should be collected by the school- master or dispenser, and that the result should be forwarded, countersigned by the medical officer, through the proper channels to the Medical and Health Department. (6) That this half-yearly report should give the total number of children attending the school, or on the estate, and the number of children with small, medium, or great enlargement of the spleen. (7) That the half-yearly reports of all the schools and estates should be collected by the Malaria Authority of the Medical and Health Department, and submitted in the form of Table IV of this report to Government (twice a year). (8) The half-yearly reports should be submitted for June and December of each year ; that is, after and before the annual malaria season. (9) For the estates, the half-yearly reports should also give the total number of infants of two years of age or under on the estate, and the number of these suffering from enlarged spleen. (10) The half-yearly reports may also contain remarks by the medical or sanitary officer on the number of the children with enlarged spleen, who, in his opinion, were probably infected at a io6 distance from the school or estate ; and on any local sources of infection which he thinks may exist. Remarks. — The census here recommended will evidently be made on the lines of that already taken for me by the Health and Immigration Departments (section 20) ; but will be still more exact. The quarterly examinations are required for the purposes of treatment advised in the next section ; and the half-yearly reports for the purpose of giving Government repeated and correct measurements of the amount of malaria present throughout the Colony. The quarterly examinations should, I suppose, be made, on the estates, by the medical officers of the estates ; and, in the schools, by the sanitary wardens, according to the discretion of Government. I do not propose that they shall all be made on the same day or even in the same month. So long as they are made once a quarter, the exact date may be left to the convenience of the examiner. I fear that a certain amount of trouble may be caused ; but, owing to the rapidity with which children can be examined for enlargement of the spleen, it will not be much ; and as soon as the registers are in order it will become less. The information given will be invaluable for the campaign ; and I do not think that any other country will have made such an attempt to obtain it. The infant spleen-rate, mentioned in (9) above, will be particularly useful, as it will afford a very correct estimate of the infection-rate on each estate. The percentage of infants, who become infected within two years, will be a good measure of the chances of infection in the locality in that period. I regret much, that I omitted to ask for this information in connection with the spleen-census just taken. The first census under this scheme may I think be carried out in September of this year ; so as to prepare for the next malaria season. 29. TREATMENT OF CHILDREN IN SCHOOLS AND ON ESTATES. — This measure is the most feasible kind of case-reduction for Mauritius. Its objects are, (i) To improve the health of the individual children ; (2) To prevent them from becoming a source of infection to others. I07 Children are the principal homes of the parasites, and can be treated more methodically in schools and on estates than elsewhere. The proposals are as follows : — (i) That the examining medical or sanitary officer shall, at each quarterly inspection, indicate the children with enlarged spleen who should be given quinine, and the dose for each. (2) That the quinine should be regularly given to the children for whom it is ordered, by the schoolmaster in the case of schools ; and by the dispenser in the case of estates. (3) That at the next quarterly examination, the examiner shall indicate the children who, he thinks, are now cured ; and also any children who, he thinks, have become infected since the last examination. (4) That he may also order quinine for children who show no enlargement of the spleen, but who, he thinks, are infected, or likely to become infected, (5) That the quinine be given gratuitously (at least in Government schools); and may be discontinued by order of the medical officer for a child with whom it is found to disagree. With regard to dosage and mode of administration of the quinine, I would advise that the matter should be left largely in the hands of the medical officers, whose skill will be well proved by the results of the quarterly inspections. They should however report generally in their half-yearly returns on the special system of treatment adopted by them. Personally I have always preferred small and frequently repeated doses to occasional large ones — which is also Professor Celli's view. The former method does not disturb the health of the patient so much, and appears to be equally effective against the parasites (which do not seem to become resistant as trypanosomes do against atoxyl). School children may be given a small dose by the schoolmaster every morning on coming to school ; and it is perhaps particularly necessary to guard against upsetting them by over-doses. But for children on estates, who must visit the hospital specially for the purpose (it is not safe to trust parents to give it J a larger dose two or three times a week would certainly be more convenient. A very useful scale of daily dosage is at the rate of one grain of sulphate of quinine (or its equivalent in other salts) for every three years of age, or io8 rather, of bulk appropriate to age. For dosage twice or thrice a week, one grain for every two years of age is a good scale. I am not much in favour of quinine chocolates, and the like. The form which appears to me the most convenient in every way is that of the freshly made pill, or other form of bolus, which can be swallowed with water without leaving much taste. Each school may be supplied with large bottles or canisters, one containing pills of one grain, the next pills of two grains, and so on. Perhaps it would be safer not to allow pills of more than three grains of quinine for schools. The younger children may be bribed by the present of a sweet to be given after the pill. With the proposed system (unless a better one can be devised) the examining medical officer visits the school only once a quarter, and must consequently instruct the schoolmaster as to what he should do during three whole months. It may not be considered advisable to dose the children every day during these three months — though this might, I think, be done without danger. In such case it may perhaps be advisable to order that the drug be given only during the first fortnight of each month. For the estates, which are visited frequently by the medical officers, the matter may safely be left to them. The drug may perhaps be given for more days during the malaria season ; but should not be stopped during the non-malarious, cool season, which, I think, is a very good time to extirpate the infection, especially in the older cases with enlarged spleen. Further details, and modifications of the system here proposed, must be left to the Medical Director. 30. OTHER QUININE DISTRIBUTION.— The object is to make as great a re,duction as possible in the number of cases of malaria in the colony, with a small expenditure of money. The proposals are as follows : — A. For towns, villages and isolated houses. (i) That five " Quinine Dispensers" be appointed to distribute the drug among the sick by means of house to house visitation ; namely one for Port Louis, one for Pamplemousses and R. du Rampart Districts, one for Moka and Flacq Districts, one for Grand Port and Savanne Districts, and one for Plaines Wilhelms and Black river Districts. 109 (2) That these men be duly qualified dispensers, acting under the Malaria Authority in the Medical and Health Department. (3) That each dispenser shall be stationed at a convenient centre in the area allotted to him, and shall spend the whole of his time in house to house distribution of quinine to those who, he thinks, require it. (4) He shall be provided with a small portable case, which he himself can carry, containing a day's supply of the medicine. (5) The case shall contain six phials or canisters filled with quinine pills of half a grain, one grain, and two, three, four and five grains each ; pills of different sizes being placed in different phials. (6) He shall also be provided with a uniform, or an official badge. (7) On coming to a house he shall offer the quinine gratis to all persons who suffer from fever or enlargement of the spleen. (8) He shall not demand or take any payment whatever, either for medicine, or for his advice. (9) He shall advise each person who accepts the quinine to take one pill every day, just before the morning meal, and shall give at one time to each person enough quinine for not less than seven days and for not more than fourteen days. (10) The doses given should be as follows : — Age in years 1 1-3 3-6 6-9 9-12 over 12 Age in grains ...... f 1 2 3 4 5 (11) He shall visit most frequently the most malarious localities, according to the direction of the Malaria Authority. (12) He shall not be debarred from giving the quinine, in the doses and to the amount laid down, to any person who demands it, provided that he thinks the person is suffering from fever or enlarged spleen, or is in imminent danger of becoming infected. (13) The Quinine Dispensers shall be well instructed in their duties ; in a knowledge of malaria in general ; and in examining persons for enlargement of the spleen. (14) They shall report briefly on their work once a month. B. For the Estates. (i) Every adult on any estate who is known to be suffering from malarial fever or enlargement of the spleen shall be treated in no hospital, or given enough quinine to be taken in his own home during not less than seven days and not more than fourteen days. (2) The treatment of every such case, either in hospital or out of it, shall not be discontinued until the medical officer thinks that the person has been completely cured of the infection ; unless good reason is shown for discontinuing it (see section 6). (3) If possible, a report should be made every half-year of the total number of different persons on each estate who have been treated for malaria during the half-year — this report to be included in the one advised for children in section 28 (6). C. Preparation and despatch of quinine pills. This will have to be done, I presume, by special workers at the Medical Stores ; but I would prefer to leave details to the Medical Department. The pills should be as fresh as possible, and should be despatched in bulk to the various destinations. I venture to deprecate any demand for detailed returns regarding their issue by schoolmasters and dispensers, as such returns cause much trouble, which will result only in decrease of the issue. Leakage will be better ascertained by comparing the amounts issued by a school- master or dispenser with the number of persons to whom he has given it, as returned in the half-yearly reports. The pills had better be supplied in large numbers in order to save the trouble, expense, and delay of asking for and sending small parcels. Efforts should be made to distinguish Government quinine by a certain colour, as done in India ; or by stamping the pills or other preparations. The authorities must guard against the possibility of their quinine being subsequently retailed to purchasers, or even exported. Too many precautions, however, will have the effect only of ruining the whole scheme, the object of which is wide distribution, for the sake of saving a few pounds of the drug. For the same reasons, efforts to sell it to the well-to-do, while giving it away to the poor, are likely to be futile. The cost of collecting the money will probably exceed the profits, and the trouble of doing so will limit the distribution. Government must, I fear, face a certain loss from leakage, which should be looked upon as an unavoidable part of the general cost of the campaign. Remarks. — A system has already been in force in Mauritius since 1904 by which the drug has been sold or given away by the Ill masters of thirty-five government schools. They have been remunerated at the rate of Rs.30 per annum, for which they kept an accurate register of expenditure of quinine and receipts by sale. During the first eight months of 1907 only 3,803 applications for the drug were made ; and since the commencement of the scheme only about 35 lbs. of it altogether were issued (from 1904 to the end of 1907), although it was given to the general public as well as to sick children attending the school. This amount is insufficient to affect the disease seriously. On the other hand, a dispenser who was appointed to distribute quinine from house to house at Phcenix gave away 20 lbs. of it from January to September 1907. This year, while we were investigating the outbreak at Phoenix, the same dispenser continued this work ; and every week visited about 200 houses, and gave away about 19,000 grains (3"3 lbs.) of quinine to about 650 sick, or nearly 30 grains to each. The result, partly of this and partly of drainage, has been, I hear, the rapid cessation of the outbreak. There is therefore no doubt as to which of the two methods, dep6t distri- bution or house to-house distribution, is likely to be more effective. My recommendation to appoint house to house Quinine Dispensers is therefore based on the latter method (devised by Dr. Lorans). In fact, experience proves that the sick poor cannot or will not frequently attend schools and dispensaries for quinine ; they must have it put into their hands, or they will not take it at all. I must therefore advise that the old method of general distribution by schoolmasters be superseded by the new methods given above. The schoolmasters will now distribute only to the sick children attending their own institutions (for which I do not think they can ask to be paid). The exact number of five Quinine Dispensers has been specified somewhat arbitrarily, and only tentatively. Doubtless experience in working may lead to modifications in this and other details. The Quinine Dispensers may also be used to distribute vermifuges, such as santonine and beta-naphthol, and sulphur ointment for scabies; and generally to "keep an eye" on sanitary matters. They should be appointed in the Health rather than in the Medical Department. I have said nothing about distribution of quinine at the ordinary dispensaries, as this may be left to the medical officers. I would only suggest that doses for a fortnight or a week at least should 112 be given to out-patients, in order to save tliem frequent attendances for the medicine. We must always remember that, if quinine is to be used at all as a general public measure against malaria, it must be poured out wholesale. Otherwise it can have little effect. 31. HOUSE PROTECTION. — The object of this measure is to exclude Anophelines in localities where, owing to large marshes or much forest, they cannot easily be reduced. I suggest it chiefly as a prospective vicarious measure. The proposals are as follows : — (i) That a small committee, consisting, say, of the Director of the Medical and Health Department, the Director of Public Works, the Medical Officer of the Immigration Department, and the Malaria Authority (proposed hereafter), should be appointed to consider if any type of house can be designed which will exclude mosquitoes, and which can be reasonably insisted upon by building laws for future adoption, especially on the estates and for the Indian population. (2) That the Malaria Authority might make experiments with a few Indians' houses, as they are built at present, to see if they can be cheaply protected by wire or muslin netting. Remarks. — I have some doubts whether either can be done ; but the attempt would be worth making for places like Post of Flacq or Petite Riviere, where mosquito reduction would be almost hopeless without large expenditure. In such cases this measure, combined with quinine distribution, seems to be the only refuge. For general sanitary reasons I think it would be highly advantageous to the Colony if better houses could be demanded by the building laws. 1 always like to state as a sanitary aphorism that people live at the level of their houses. Poor and dirty houses mean poor and dirty people all over the world. To a large extent, the house makes the man. The opportunity may therefore be taken for a new departure in this respect. I can see no reason why coloured populations should not live in better houses in civilised countries. 32. MOSQUITO REDUCTION. — The object of this measure is to keep down the number of Anophelines in certain localities, so that new infections caused by them will no longer keep pace with the recoveries, and the disease will consequently tend to die out. 113 This object is attained by removing as far as possible the conditions favourable to the insects. The works required may be divided into two classes, minor and major works. By vtinor works I mean those which can be continuously carried out without the special services of an engineer, such as the clearing of water channels and drains, release of surface pools, filling of holes, removal of house breeding-waters, cutting of underwood, &c. By major works I mean those which require to be designed by an engineer, such as the drainage of some swamps, the canalisation of some streams, &c. By bonification of an area, I mean all the works necessary for reducing mosquitoes in it. The measure is advised, as a rule, only for densely populated areas. The proposals are as follows : — A . For minor works. (i) That sufficient Workmen be continuously employed in the towns and villages, and on the estates, to do and to maintain the minor works. (2) That a number of men, who may be conveniently called Monstiquiers* be engaged to detect the breeding places of mosquitoes, and to assist otherwise in the works. (3) That an officer, to be called the Malaria Authority, be appointed under the Medical and Health Department to superintend the works ; to advise regarding them and other details of the anti- malaria campaign ; and to draw up an annual report. (4) That some legislation for facilitating the works be considered. (5) That some useful administrative adjustments be considered. B. For major works. That major works for draining, deepening, or filling marshes, or for canalising streams, &c., be undertaken when funds allow — {a) If such waters cannot be dealt with efficiently or economically by minor works ; and (b) If the neighbouring population is large enough to justify the expenditure. 33. DETAILS OF MINQR WORKS. — (0 Nature of zvorks. — The habits of Pyretophorus cost(ilis, which is responsible for the malaria in * This useful term was invented by Colonel Peterkin, R.A.M.C, P.M.O., of the troops in Mauritius. 8 114 Mauritius, have been well known since 1899, when I described them in Sierra Leone (i). Daruty de Grandpre and d'Emmerez de Charmoy have added details for Mauritius (13, 14), and have stated that the insect " has the same area of dispersion as the malaria." A full account of the habits is therefore unnecessary here. The insects breed chiefly in stagnant or gently running water amongst grass and weeds, and also in holes and pits in the ground, hollows in rocks, cisterns, ponds, " regards " (or pits made in connection with water mains), and so on. The methods of dealing with them are equally well known ; and the Malaria Committee of 1901 has conducted the work absolutely correctly since that date. In a letter dated the ist January, 1908, I advised Government to start minor works at once, so that I might be able to assist in training a number of men during my stay in the Colony. His Excellency the Governor promptly allotted Rs.6,000 for the purpose ; and with this sum the Medical Department hired ten moustiquiers and ten gangs of three workmen each for the work. These were fairly thoroughly trained by Major Fowler, Dr. Castel, Dr. Keisler, Dr. Menage, M. d'Emmerez, myself, and others, and did much useful work before my departure. It is therefore unnecessary to burden this report with laboured descriptions of details. The actual work required may be classified as follows : — («) Keeping clear of weeds and other obstructions built street gutters and surface drains. (i>) Clearing of weeds, levelling, and discharging roadside ditches and channels. (c) Keeping made water channels clear of weeds and pools. {d) Removing grass, weeds, and pools from the margin of ponds and streams, and rough canalisation of the latter. {e) Discharging, filling, or deepening surface pools where practicable. (/) Discharging leakage from standpipes. (£■) Filling or oiling certain pits. (k) Concreting hollo .vs in rocks and holes in trees. (z) Cutting undergrowth. (7 ; Dealing with house waters and other useful work in spare time, especially in the cooler and drier non-malarious season. "5 (2) Organisation of workmen in gangs. — This is better than to allow each man to work by himself. I generally suggest small gangs of three men each ; a headman at eighteen or twenty rupees a month, and two labourers at sixteen or fifteen rupees — the whole gang to cost fifty rupees a month. The headman must do manual work, but must also be responsible for the others on account of his larger salary. In some places larger gangs may be advisable, and it may prove advantageous to appoint headmen of tried capacity on larger salaries for whole localities. Indians of the inali cX^si, are especially good at this kind of work, and are generally already experienced in it. Two of our gangs drained considerable areas of the Clairfond marsh by themselves. It is astonishing what a large amount of work a gang like one of these will do when constantly employed at it. They will clear in one day several hundred yards of obstructed water- course, or roughly canalise a long stretch of stream. They become more expert with practice — ^a further argument for employing them continuously. (3) Total number of gangs required for Mauritius. — It is extremely difficult to form any exact estimate on this important point. The details of other countries are useless, as conditions vary so much. Nothing but experience extending over a year or two can decide the question. Moreover, reduction of the gangs may be possible after the execution of permanent or of certain preliminary works. In a letter dated the i6th January, 1908, I asked Governm.ent for information regarding the total length of water channels, open drains, and roadside gutters, and the annual sum spent for the repair, cleansing, and supervision of them. It was not found possible to give exact details ; but I was informed (Colonial Secretary, No 496/08 of 17/2/08) that there were about 800 miles of roadside gutters in rural areas and 296 miles of drains and gutters in towns and villages, or about 1,100 miles in all. It was still more difficult to ascertain the lengths of streams, number of pits and pools, &c., requiring bonification. I was therefore driven to fall back on the personal opinion of men of large experience in the Colony — perhaps the best course from the beginning ; and in letters to the Colonial Secretary dated the 5th January, 1908, 1 begged Dr. Lorans, Director of the Medical Department, and Dr. Bolton, 8 a ii6 Medical Officer of the Immigration Department, to advise me upon the point out of their large knowledge of the local conditions. Their replies are given in effect in annexure 4, and should be generally looked upon as the basis upon which the work can be started, subject to modifications suggested by further experience. It will be seen that Dr. Lorans estimates (very roughly, of course) that 104 gangs may be required for the rural districts and extra- urban Port Louis district, at a cost of Rs.62,400 per annum. Dr. Bolton suggests a somewhat different scheme in detail for the estates, for which he required 48 labourers at Rs.i6 a month each and 16 sanitary guards (moustiquiers). Added together, these schemes would require 360 labourers (exclusive of moustiquiers) for the villages, rural districts, and estates of the whole island. In addition to these, gangs would be required for the towns, namely, Port Louis, Curepipe, Quatre Bornes, and Rose Hill and Beau Bassin. It is very difficult to make a -specific recommendation as to the total number of men required. If I place the estimate too high, funds will be wasted ; if too low. Government will be misled as to the cost of the work. But it is necessary that I should state some figures to start with ; and I therefore adopt the conclusion that it is better to ask for a little too many men to commence the work than to ruin it by asking for too few. My suggestions are as follows : — (4) Number of workmen required for towns, villages, and pop7ilous areas {excluding estates). Locality. Number Annual Cost. ■' of Gangs. Port Loiiis town 5 3,000 Curepipe town ... ... ... ... 3 1,800 Quatre Bornes town 2 1,200 Rose Hill and Beau Bassin town... ... 3 1,800 Port Louis extra-urban ... ... ... 4 2,400 Pamplemoiisses ... ... ... ... 10 6,000 R. de Rempart 9 5,400 Flacq 15 9,000 Grand Port 14 8,400 Savanne 9 5,400 Plaines Wilhems 13 7,800 Black River 10 6,000 Moka 12 7,200 109 65,400 117 Each gang is estimated to consist of three labourers and to cost roughly Rs.50^ a month. Thus the whole force will amount to 327 men. Dr. Lorans' estimate (annexure 4) is adopted for areas out- side the towns. The authorities of the latter should, I think, maintain the thirteen gangs allotted to them. The estimate is a liberal one, and every effort should be made to economise. Thus 1 think that the twenty-five gangs for Plaines Wilhems and Moka may soon be reduced, the men being used else- where. As a general principle, where the spleen rates are low, less work is called for ; but there may be other factors, such as the importance of a locality, which demand more work as a precaution. (5) Minor works on estates. — Owing to the large number ol labourers at their disposal, the managers of the sugar estates and factories should, I think, be able easily and always to effect their own minor works. Many of them told me that they were only too willing to do so, but they did not understand what exactly to do. At Union Vale, Grand Port, we found one morning an obstructed streamlet which was causing the malaria on the estate. Before evening it was cleaned out from beginning to end. Before I left, applications for the services of the moustiquiers were coming in rapidly from the managers, led by the Hon. M. Souchon, the Hon. M. Sauzier, the Hon. M. Dumat, and others. What is fundamentally necessary for the estates is guidance. The managers may be trusted to have enough intelligence to remove conditions which cause them such loss of money (see Dr. Bolton's letter in annexure 7). What I propose then for the estates at present is that they should be visited frequently by the Malaria Authority and by the Government moustiquiers, who should tell the managers what exactly to do. If the work is not done, the Immigration Department can be made aware of the fact. A manager said to me, " We want no law to force us to eat — nor to force us to get rid of malaria." Of course, if this policy fails, legislation may, if necessary, be adopted. (6) The Moustiquiers. — Ten of these men were appointed, and their functions were well understood before I left. These are — ia) To seek out all breeding places in the area entrusted to them ; (U) To keep a surveillance over the working gangs. They must all be well trained, reliable men, and should report Il8 direct to the Malaria Authority or other superintendent. I recom- mend that moustiquiers be appointed as follows : — For Plaines Wilhems ... ... ... 3 Port Louis town and district ... ... 2 The other seven districts ... . . ... i each For the estates ... ... ... ... ... 3 There will thus be fifteen of them. The three men for the estates had better live near the Malaria Authority in order to assist him in his inspections or to be despatched wherever he shall direct. The remainder should live at convenient centres. The men had better mostly be Indians or Mauritius-born Indians of the servant class, who are especially apt at the work. The pay of the junior five may be put at Rs.20 a month ; that of the next five at Rs.25 ; of the four senior men at Rs.30 ; and of the head moustiquier at Rs.35. This would stimulate proficiency. Their salaries would therefore amount to Rs. 4,560 altogether. There is considerable risk in the occupation — three of our ten men became badly infected before I left the Colony ; they should, therefore, be provided with mosquito nets. Pans for collecting larvae and travelling expenses are necessary. (7) The Malaria Authority should be an officer who is thoroughly acquainted with the subject of malaria and also of mosquitoes and their habits. He should serve under the Director of the Medical and Health Department. He will require a clerk and office allowance, but should be troubled as little as possible with the correspondence which paralyses so much work ; and an office in his private house would save much time in travelling. He will require full facilities for travelling. All his time should be spent on superintending and organising the general campaign against malaria, but examination of mosquitoes and other necessary microscope work will constitute a part of his duty, so that he will require the necessary microscopes and appliances (this does not mean a large laboratory). Seeing the great importance of the post, I do not think that the salary could well be put at under five hundred rupees a month. Further details of organisation had better be left to the Malaria and Health Department, but I would earnestly beg that the holder of the post, while he should be held 119 entirely responsible for success, should be disturbed as little as possible in his important task. Many of the local gangs could with advantage be put under the immediate superintendence of Sanitary Wardens, or Medical Officers, who may be willing to undertake such a duty — which will not be heavy. It is advisable to bring into play as much local interest as possible. (8) Tools and impleme^its . — These must be supplied through the Medical Department, and kept where convenient. I forbear to give further specification of details, which \\'ould only hamper the organisation. 34. DETAILS OF MAJOR WORKS. — In reply to my request for information, Government forwarded to me (Colonial Secretary, No. 24/08 of 17/2/08) the excellent minute and annexures of the Hon. M. P. le Juge de Segrais, Director of Public Works and Surveys, which are printed in annexure 4, C of this report. In this the Director gives a rough estimate of the total cost of the major works which may be required throughout the island, amounting to Rs.630,000, with an annual expenditure of Rs.44,300 for maintenance by means of 205 workmen with the necessary number of sirdars. This scheme will serve as a base for future work ; but it should be looked upon for the present as an ideal, not to be forgotten, but not to be attempted too soon. The general principle to be remembered in considering the matter is contained in the words, minor works before major works. It would be folly to commit the Colony to a large capital expenditure until the absolute necessity for this becomes quite apparent ; and it cannot become apparent unless the minor works and other methods of prevention have been tried for some time. The whole area of the island will then have been studied accurately with regard to breeding places ; the working capacities of the gangs will have been gauged ; the marshes and streams which cannot be improved by minor works will have become known ; the disease will have been attacked everywhere by case reduction as well as by mosquito reduction ; and the results will have become apparent. Then, if and where the major works are found to be necessary or economically advisable, they should be carried out. But to rush upon the major 120 works without such preliminary experience would be unwise, except in cases where the necessity for them is already quite obvious. The same idea evidently underlies paragraph 7 of M. le Juge de Segrais' minute. For example, there was no doubt about the propriety of draining the Clairfond marsh. To deal with it effectively by minor works would have cost more than the interest of the capital expended on the major work ; it was situated in an important locality, was causing an immense amount of sickness among both the civil and military population, and was threatening Curepipe with a similar epidemic. On the other hand, the drainage of the marshes of Post of Flacq cannot be recommended with similar cogency. Lastly, we must remember that capital spent means interest lost. The sum of Rs. 100,000 would not go far for major works, but the interest of it would support about twenty-four workmen indefinitely. And, moreover, the major work, when completed, would require a certain annual expenditure for maintenance. I therefore recommend after careful consideration that for the present attention be concentrated on the minor works. There are, however, some major works which, I think, certainly do unquestion- ably require early execution, namely, the drainage of the marshes of Curepipe, La Louise, Pamplemousses and Centre of Flacq, and the canalisation of the minor streams of Port Louis (section 36). 3S. LEGISLATION AND ADMINISTRATION.— (l) Obviously the economical working of the scheme suggested above will depend largely on excellence of administration ; and to assist in this, certain small amendments of the laws will be useful. I made a careful study of Ordinance No. 32 of 1894-95, which is practically the Health Act in force for Mauritius, and concluded that some additions would facilitate the anti-malaria campaign. These were drafted out and submitted to the Medical and Health Department, and were carefully matured by the Director, the Acting Assistant Director (Dr. Momple), and the Procureur-General. The resulting draft legislation is printed in annexure 3 of this report, and will, I hope, be further considered by Government. Every effort should be made to prevent the abuse of the right of appealing against sanitary orders and convictions connected with them (section 24). 121 (2) There is already a considerable sanitary staff, consisting of a Chief Sanitary Officer, three Sanitary Wardens, sixteen Sanitary Inspectors at salaries from Rs.960 to Rs. 1,500 a year each, and twenty-two Sanitary Guards at salaries of Rs.360 each, costing Rs. 52,740 per annum altogether (Blue Book, 1906). Its duties are multifarious — inspections, conservancy, contraventions, &c. ; but it may be able to give assistance to the anti-malaria work, if the Director thinks this possible. (3) Since the entry of plague in Mauritius in 1899 there has also been a considerable special plague service, which has been so successful that only about 5,000 cases have occurred since then, the number being now greatly reduced. The cost of this service is estimated at Rs. 168,640 for the year 1907-08 (Estimates). Here again help may be given to the malaria service ; while, on the other hand, the latter may also be able to help the former. These matters are not in my province to discuss, and must be left by me to the excellent organising capacities of the Medical and Health Department. (4) On the i6th January, 1908, I wrote to Government in order to call attention to leakage from standpipes which occasionally causes conditions favourable to Anophelines. In replies under letter of the Colonial Secretary No. 493/08 of 22/2/08 and of 17/2/08, it was stated that the defect was due to wear and tear, to thefts and mischievous breakage of taps which the present law does not adequately prevent, and to insufficient funds for repair. At Port Louis the Mayor proposed to increase these funds. At Beau Bassin and Rose Hill the Chairman of the Board made the excellent suggestion that a "fountain keeper" at Rs.i8 a month should be appointed to look after the matter, and also drafted legislation on the subject (his letter No. 1,790 of 17/2/08), which I hope Government will consider. (5) In section 33 (3) I alluded to correspondence on roadside ditches, drains, and gutters. It seems possible that the duty of clearing, cleansing, and repairing these could be largely handed over to the malaria gangs, with whose work it is closely connected. The duty now lies in the hands of the Public Works Department, which spends about Rs.6,000 on it ; of the Health Department, which allots a small sum ; and of the Towns, in which the cost cannot 122 easily be extricated from that of conservancy. Port Louis puts the figure at about Rs. 21,000 a year; Curepipe at Rs.5— 600 for cleansing ; Quatre Bornes at Rs.442 ; and Beau Bassin and Rose Hill at Rs.710 for cleansing and repairs. Perhaps the two departments first mentioned might be willing to transfer the money to the malaria service ; while the towns could utilise their expenditure under this heading for forming the nucleus of the malaria gangs which I advised in section 33 (4) they should possess. (6) On the 14th January, 1908, I called the attention of Government to the facts that there are in the Colony many water- channels used for conveying water from rivers and springs to plantations and factories, and that they often breed Anophelines ; and asked who exactly were the owners, and whether they could not be compelled by law to keep them in order, or to fill up those which have fallen into disuse ? Replies were sent to me under letter of the Colonial Secretary, No. 422/08 of 20-2-08. My letter and the reply of the Procureur-General are printed in annexure 2. From the latter it would seem that the channels are owned by private persons who could be compelled, at least after legislation, to do as I suggest. (7) On the i6th January, 1908, I wrote a similar letter regarding the important subject of marshes on private property. In this I asked whether the owners could be forced by law to drain such marshes, or to pay for the drainage of them by Government ; especially in view of the fact that such drainage might greatly enhance the value of the property ? In reply I was informed (Colonial Secretary, No. 497/08 of 30-1 -08) that the question, which presents many difficulties, had already been under consideration ; that in the opinion of the Law Officer, marshes could not be held to be nuisances in the statutory sense of the work ; that legislation had been proposed, but was not easy to effect ; and that H. E. The Governor hopes that my report would assist in finding some practical solution of the difficulty. The answer seems to me to depend upon the questions (a) whether the existence of the marsh is or is not the fault of the owner ; and {b) whether the removal of it would or would not benefit the general public as well as himself For instance, if there is in existence a sufficient and practical outfall for the marsh, or other means of dealing with it, in the owner's property, but one which the owner 123 neglects to use, or refuses for his own profit to use ; and if he neglects to render the marsh innocuous by such reasonable minor works as may be recommended by the Medical Department ; and if it is proved by the examination of the spleen-rates of the people living near the marsh, or by other methods, that the marsh is actually causing sickness, or, in the opinion of the Medical Department, is likely to cause sickness ; then, I think, he (the owner) may be forced to do the work. As a matter of fact a marsh in a malarious country is a nuisance, because it is certainly and absolutely a danger to the public health, as known since the time of the ancients, and as recently proved by the case of the Clairfond marsh in Mauritius (addendum 2) ; and the fact that this is not recognised by law proves only the inefficiency of the . latter. If a person can be forced to remove or cleanse a latrine, he ought most certainly be forced to remove or discharge a marsh — and for the same reason. On the other hand, if the owner of a marsh has done all reasonable minor works to render it innocuous ; if the major work is beyond his means or cannot be carried out on his property ; and if the marsh is not causing, or is not immediately likely to cause, public sickness ; then I doubt whether he can fairly be forced to undertake the expense. Each case must be judged on its merits ; and in many cases Government would feel it to be more fair to pay at least a part of the expense. But I think that legislation to compel the defaulting owner should certainly be passed. In the meantime, however, I recommend (as in the previous section) that attention be concentrated on the minor works. It is only after they have failed, that the major works can be definitely demanded. 36. NOTES ON PREVENTION IN THE TOWNS.— The scheme advised above is a general one ; but I may add a few notes for the Towns. (i) Port Louis. — Major Fowler and I spent ten days in a close inspection of the capital, which constitutes the most thickly peopled part of the small district of the same name (15 square miles). The population of the whole district has recently been steadily diminishing, as shown at each successive census. Year 1846 1851 1861 1871 j88i 1891 igoi Population 45,212 49,909 74,128 63,015 66,466 62,046 52,740 124 The decrease commenced after the great epidemic of malaria in 1867, during which year alone one-quarter of the inhabitants died from all causes. It has probably been accelerated by the facilities given by the railway to the wealthier inhabitants to sleep in the cooler areas of Plaines Wilhems, and to visit the town only for business during the daytime. The death rate of Port Louis has always been in excess of that of the whole island, as shown by the chart in the annual reports of the Registrar-General ; has been steadily rising (apparently) ; and averaged 56'97 or nearly 57"0 per mille during the seven years 1900-06. It rose to 67'9 in 1901 and to 6o"4in 1903. In 1906 it was I05'6 in the Eastern Area of the town. Out of 2,003 children examined by Dr. Keisler in the schools of Port Louis, 706, or 35^4 per cent, had enlarged spleen early this year. The average spleen of all the children was 2'64 times the normal. These are slightly above the means for the whole island, but school children generally give lower rates than estate children, of whom there are none at Port Louis. Major Fowler and I, greatly assisted by Dr. Keisler, and three moustiquiers, made a careful search for Anopheline larvae. The principal breeding places are the uncanilised lengths of the three little streams, the Pouce, La Paix, and Trichinopoli streams which traverse the town proper. The two first of these rise in the hills which surround the small plain in which the town lies. High up, their beds are stony and usually nearly dry except for an occasional pool ; but further down there is running water. The Trichinopoli stream apparently commences from the discharge of a water supply pipe. All three when they enter the town are well canalised till they reach the sea. Above the canalisation the water runs through grassy borders and breeds numerous Anophelines (photograph 17). A larger stream, the Latanier river discharges to the east of the town and breeds ^4. costalis plentifully. There are marshes at Fanfaron Bastion (away from many habitations). The insects are also found in the "regards," in ooze from leaking water-pipes, and similar waters ; but our men generally searched for them in vain in the numerous and well-made stone gutters v/hich border the streets. There was not much breeding in the Cassis stream ; but the larvs were found here and there in pits, hollows, and channels. On the whole I consider that the uncanalised parts of the I2S four streams first mentioned are responsible for the disease in Port Louis. The spleen rates were high anywhere near them. At Tranquebar, close to pools in the upper part of the Pouce, all out of 32 children suffered — some very severely. Generally, near the canalised part of the streams the town appeared to be more healthy, but of course the insects could wander in from outside— though we never found a single Anopheline while we where at Government House. The measures which I recommend are : — {a) The spleen census and treatment of children in schools described in sections 28 and 29. (i^) House-to-house quinine distribution (section 30). ic) I would strongly urge that an extensive house-to-house spleen census of children in Port Louis should be undertaken in September, October and November next. The object of this will be to ascertain exactly which are the most malarious spots, and whether they are contiguous to the uncanalised streams, as I suspect, or to other breeding places, with a view to justifying the major works presently suggested. In 1901 there were 12,876 houses in Port Louis district ; too many to examine thoroughly, But certain blocks of houses 'might be taken in the healthiest part, as round Government House, and the results compared with those obtained at — -let us say, [a) close to the Pouce at Tranquebar and south-west of the Champ de Mars ; {b) east and west of Plaine Vert, south of the Market ; (^r) south of the Latanier ; and {d) near the Cassis streams, &c. I fear that the labour will be considerable ; but, if enough children are examined, say over 2,000, the results ought to be striking and useful. I suggest that it be done by two or three medical officers, each working a strip between the streams from the sea upwards towards the source of the former, so that each can make his own comparisons. (d) For minor works, rough canalisation of the lesser streams, as frequently shown by me to the Mayor (Dr. Laurent, who has long taken great interest in the work) and as largely tried by Dr. Keisler, should on no account be neglected after and before the rains. I think that the pools then formed fill the town with Anophelines. During the rains the large floods render such work much more difficult. The frequent leakage from water-pipes, and 126 mosquito-breeding in the " regards " and elsewhere must be dealt with rigorously by sufficient gangs. The Mayor has wisely discouraged too many trees. As he says, " a town is not the place to grow a forest in." At the same time this is a secondary measure, as Anophelines very rarely breed in holes in trees. (e) For major works ; the Pouce must ultimately be canalised right up to Junction Road Crossing ; the La Paix and Trichinopoli streams up to Boulevard Victoria. Before, however, recommending anything like the canalisation of the Latanier, an expensive work, I should like to see more evidence that it really causes much sickness, and that cheaper methods will not succeed in reducing the amount it does cause. The same thing must be said of the intercepting drains round upper contours rightly commenced some time ago. If other measures fail, they must be proceeded with (on advice by the best engineers). (2) For Curepipe I ha\'e nothing to add to the advice given when I was in the Colony — namely to drain the marshes as soon as possible. This can be effected by deepening the bed of the Mesnil ; the cost will not be large ; and the matter has already been urged by many, including the Town Engineer, M. Hugues. Although there is little endemic malaria in the town, yet Dr. de Chazal's opinion that there is some must be accepted ; and though we could find only a few /-'- costalis in the Curepipe marshes, yet they may become much more numerous in the future. The recent outbreak at Clairfond, at the doors of Curepipe, and the case of Cilaos in Reunion, give a warning which it is not wise to ignore. An outbreak at Curepipe will be a most serious affair for the town. Hundreds of the wealthier people and their children would probably become infected ; the value of property would fall ; and the last stronghold against the disease would be conquered. Cases already occur among the poorer classes to the north, or are immigrating from outside ; and a sudden swarming of P. costalis might easily occur as the result of a hot summer. The outbreak might be as sudden as disastrous. This is one of the instances in which I think a clear case exists for the major works. (3) The marsh at La Louise, Quatre Bornes, causes considerable 127 sickness and ought to be removed as soon as funds allow. The cost is estimated at Rs. 30,000 (annexure 4, 3). I have no further detail to add regarding the towns, except perhaps a protest against the excessive number of trees at Quatre Bornes and Beau Bassin and Rose Hill. They exhale an enormous amount of damp (as I was informed by M. Koenig and Mr. Walter) ; they shut out the breeze ; and they breed and shelter mosquitoes. It may be a matter of taste ; but to me a house in the tropics closed in by too many trees is very unpleasant. Perhaps the best way to encourage a reduction of trees on private properties is to allow the malaria gangs to do the felling in the dry weather when other work is slack, on charge of a small percentage of the wood — or without charge. 37. THE ANNUAL MALARIA REPORT — This should commence with a tabular statement, giving all the details entered in section 2 1 of this report, not only for the current year, but for past years for comparison. The general remarks by the Malaria Authority should follow, stating totals of malaria statistics, work done, expenditure, and results. The following tables should be added. Table I. ; School Children. — Average total children, children with enlarged spleen, spleen-rate, average spleen, and children treated in each school ; the averages being made up from the four quarterly inspections. Similar figures for the previous year should be given for comparison. Table II. ; Estates. — The same items ; and also infant spleen-rate and average number of adults under continuous treatment, and remarks regarding works done or required. Table III. ; Towns, Villages and Populous Localities. — Follow- ing Dr. Lorans' table (annexure 4 of this report), and giving the number of gangs employed in each place, spleen-rates of local schools and estates, and results. Table IV. ; Major works and their cost. Table V. ; Establishment, salaries, quinine, implements, office and other expenditure. Such a report will enable Government to judge whether or no value is being received for the money spent. 38. MISCELLANEOUS SUGGESTIONS.— (i) Intercepting drains. — Since returning to England I have had the advantage of meeting 128 Dr. Malcolm Watson whose good anti-malaria work is described in section 22. A letter from him, describing several important experiences of his, is given in annexure i ; but he also strongly impressed upon me the advantage of draining small marshes by intercepting, or so called circumvallatory, drains in preference to cutting channels through or across the marsh. The former are both cheaper and more effective. (2) Rubble-drains. — These consist of a channel of the requisite depth cut through or round a marsh and filled up with stones — large stones at the bottom and small ones at top. The water percolates through the stones, and is said to carry away the silt automatically, and the stones prevent the growth of grass and weeds in contact with the water, so that mosquitoes cannot breed in it. They might be tried in convenient localities. (3) Stoning irrigation pits and water-channels. — Such pits are frequently made for storing water for irrigating gardens. There are a number (about 10 pits per acre) close to the prison at Beau Bassin. They cannot be filled up without causing hardship ; but they can be cemented, or (a cheaper method) lined from edge to bottom with large stones embedded roughly in the earth. One of Dr. Castel's gangs dealt with a number of pits close to Pleasance Estate in this manner in a few days. The owner can be warned to keep them in order. The same thing can be done for any water-channels which are not apt to be swept by floods. The stones prevent very rapid growth of vegetation on the banks. When the channel is filled with the stones, instead of being only lined by them, we have the rubble drains just referred to. (4) Rough canalisation. — This consists in collecting the stones on each side of a stream, or deepening the bed where necessary, in order to remove marginal pools and vegetation and to give a straight constant flow to the water. Photographs 23-25 well illustrate the kind of work. That on the Mesnil was done before my arrival by the Forest Department, at the instance of the Medical Department. It cost only R.o-37 a running foot for both banks, but remained perfectly good during my stay. Of course lower down the streams floods may carry away such slight work ; but it is demanded at the end of the rainy season in order to remove the stagnant festering pools which might otherwise breed mosquitoes during the whole of the dry 129 weather. Experience will show when and how it is best to carry out this measure [see also addendum 3). (5) Ho/es ill rocks and trees. — The fact that Culicines breed in these is frequently cited as a great difficulty in the way of mosquito- reduction. As a matter of fact, nothing is more easy than to deal with such breeding-places. Where the work is called for, the gangs are sent round, to fill up the holes with gravel and concrete. For trees it is better to employ boys, who do the work with rapidity. (6) Mosquito plants. — The Culicines breed largely in holes in trees in Mauritius, but they also breed in certain plants. On page 1 1 of (17) a list of mosquito-breeding plants in Ceylon is given. In Mauritius Bilbergia splendida, an introduced kind of flowering pine- apple, breeds large numbers of Stegomyia, and is planted in many gardens. Photograph 19 shows a cartload removed from a single house, the inmates of which said they could not sit in the verandah on account of these insects. This plant ought to be rooted out everywhere at sight. The Traveller's Palm contains water, but on cutting down to it we generally failed in finding larvae — though these sometimes occur in it. A few larvje exist in other shrubs, and bamboos — even in sugar canes ; but the important breeding-places are the usual tubs, pots, tins and broken bottles round the houses. The houses at Vacoa were much infested by Culicines, and we carried on a constant war against them. All we could say was that they were certainly reduced in our house — but by no means banished. The explanation probably is that the adult insects are very long lived (as also observed elsewhere), so that it is long before the old ones die off. Nevertheless I would urge a continuous campaign against them in the towns. The cost is trifling, and the gain to health and comfort likely to be considerable. The work can easily be done by the malaria gangs, or ordinary sanitary service, at convenient times. (7) The introduction of Myzoniyia rossii. — ^When in Mauritius, I suggested the idea that it might be useful to introduce this Indian Anopheline, which does not carry malaria, in the hope that it might crowd out the fatal P. costalis in marshes which cannot easily be drained. If this would really happen the boon to the Colony would be great, and would be achieved at small cost. But experiments on the matter are first required, and may perhaps be carried out by the Malaria Authority. I30 39- THE GENERAL PLAN OF CAMPAIGN. — I would urge most strongly that the campaign be not confined to certain localities, but be extended at once to all the more populous parts of the Colony, especially as the estimated cost cannot be considered as being ver)' large. Minor local campaigns will only fritter away considerable sums without producing any marked effect on the immense total of sickness caused by the disease. The campaign should be commenced generally, simultaneously and vigorously over the whole Island, before the commencement of the malaria season ; if possible in September or October next. The first step, which can be taken without special apparatus in, let us say, September, should consist in the medical examination of as many as possible of the children in the schools and on the estates ; the provision of registers ; and the continuous and energetic treatment of children suffering from enlargement of the spleen, according to sections 28 and 29. The object of this will be to destroy the parasites in as many as possible of the patients before the advent of the breeding season of the Anophelines. It is important that the treat- ment should be commenced earliest in the lowest parts of Mauritius, where the malaria season first begins. At the same time the five Quinine Dispensers should be selected and set at work, according to the suggestions of section 30, in the most malarious places. While this work is proceeding, the gangs required by section 33 should be organised according to Dr. Lorans' rough estimate (annexure 4, A), and should be pushing the minor works vigorously by not later than November, so as to check the early breeding of Anophelines. Simultaneously the Immigration Department and the managers of malarious estates should strain every nerve to do the same work. They should be supplied by the Medical Department with a printed plan of campaign and instructions. The Municipality of Port Louis, the Town Boards, the District Councils, and other bodies, particularly the Societe Medical, should be invited to assist. All medical officers who are willing to help should be asked to do so by watching the distribution of quinine and the work of the gangs. 131 Meantime, I trust, the necessary funds, with a sufficient margin for extra calls (next section), can be allotted. The Malaria Authority should be appointed under the Medical Director as soon as possible, for the early organisation of the gangs. Quinine, and the organisation for making and distributing preparations of it, must be provided perhaps first of all ; and implements for all the gangs should be ready by November. Further details must be left to the Medical Director and the Malaria Authority. The great strategical object is to deliver as heavy a blow as pos.sible upon the disease at the commencement of the malaria season, in the assurance that every case then cured and every infection then prevented will save many infections later on. It will be most wise, and moit economical, to spare no expense in the attainment of this object. The greater the success, the greater will be the reduction of the malaria expenditure in following years. 40. SUMMARY OF PRINCIPAL RECOMMENDATIONS, AND APPROXIMATE COST. — The principal recommendations are : — (i) Periodical medical examinations of children in schools and on estates, and the continuous treatment of all of them who are found to be suffering from enlargement of spleen (sections 28, 29). (2) Continuous house-to-house distribution of quinine, where necessary, by five Quinine Dispensers (section 30) ; and continuous treatment of fever patients on estates (section 30). (3) Continuous performance of " minor works," where required, in towns, villages and populous areas, by about 109 malaria gangs, consisting of about three workmen each ; and of similar works on estates (section 33). (4) Employment of fifteen moustiquiers (section 33). (5) Appointment of a Malaria Authority (section 33). (6) Execution of " major works " when called for (section 34). (7) Appointment of a Committee to consider house-protection (section 31). (8) A special spleen-census for Port Louis (section 36). (9) An annual malaria report (section '^J^. (10) Some legislation (section 35 and addendum 3). The measures to be adopted over the whole island, and to be 9 A. 132 started simultaneously, if possible before the commencement of next malaria season (section 39). The approximate cost may be roughly estimated as follows : — Items. 1. Salary of the Malaria Authority ... 2. Salaries of 5 Quinine Dispensers (say) 3. Salaries of 1 5 Moustiquiers 4. Salaries of 109 gangs (327 men) ... 5. Cost of quinine (say) 6. Preparation and dispatch of quinine (say) 7. Office of Malaria Authority (say) ... 8. Implements, &c., for gangs (say, Rs. 50 a 9. Travelling expenses for staiff (say) . . . 10. Margin for possible calls Total gang) Rs. per annum. . . 6,000 . . 6,000 •■ 4,560 .. 65,400 .. 30,000 ■■ 3,600 .. 1,500 .. 5,450 . . 2,000 . . 10,490 135,000 This amounts to ;^9,000 per annum, or about Rs. 0'36 per head of population per annum, and V2 % of Revenue. Notes. — Item 4 is a rough estimate (section 33). The salaries and implements of 13 of the gangs, amounting to Rs. 8,450, ought, I think, to be met by the Towns. Items 5 and 6 may be considerably underestimated. Item 10 should be large, in order to defray many expenses which may be required at first, especially if a very active campaign is under- taken, as advised. The cost of the quinine and possibly of the gangs may diminish considerably if the campaign is markedly successful (section 24, 5). Major Works. — These, requiring capital expenditure roughly estimated by the Public Works Department at Rs. 630,000 for the whole Colony, are advised to be undertaken, in part, only when and where the other measures have failed ; but early attention is recom- mended to be given to the marshes of Curepipe, La Louise, Pample- mousses, and Centre of Flacq, and the streams of Port Louis (annexure 4, C). 133 ADDENDA. ADDENDUM i. — THE MOSQUITOES OF MAURITIUS. — M. d'Emmerez de Charmoy has given me a list of Mauritius mosquitoes. They have already been studied in Mauritius by him and M. Daruty de Grandprt- (14 and 22). Three new species of Culex were obtained during our stay in the Colony, and have been described for us by M. d'Emmerez but the details are unnecessary for this report, and I have published them separately (21.) Anophelines. — r. Pyretophorus costalis Loew 1866. Proved to be a carrier of malaria in West Africa by myself and colleagues in 1899 (i). The principal carrier in Mauriiius. Abounds round the coast, but also inland and was found by our moustiquiers at Clairfond Marsh (1,350 feet above sea level), where it has been causing the recent outbreak. A few larvfe collected at Curepipe. Apparently much more scanty on the plateau than M. Mauritianus. Proved to carry malaria in Mauritius by Daruty and d' Emmerez (21). Out of 73 caught at Clairfond and carefully examined during our visit (Daruty, d'Emmerez, Fowler, Ross), 10 or 12,"] per cent, were infected. Habits already well known. Breeds chiefly in water standing or flowing gently amongst grass and other vegetation and also in bare pools. Caught in houses, verandas, and in the open. 2. Myzorhynchus mauritianus d'Emmerez and Daruty 1900. Very common everywhere in Mauritius, especially on the plateau. Abounds at Curepipe. Apparently does not carry malaria. Out of 54 fed on malaria patients only one contained the zygotes, and these we considered by their size to have died after penetrating as far as the stomach wall. Until more experiments have been made however, I am not willing to state definitely that this species cannot carry malaria under any conditions. All out of 56 caught wild were negative. 3. Nyssorhynchus maculipalpis Giles 1902. Not common. A few specimens only caught by Major Fowler at Fanfaron Bastion, Port Louis, and recently at Clairfond. CuLiciNAE. — 4. Scuiomyia notoscripta Skuse 1899. The commonest " Stegomyia " in Mauritius. Abounds in the shade of woods. Biles in the day time. Breeds in tubs, tins, gutters, cisterns, holes in trees and rocks, in Bilbergia splendida, etc. 5. Stegomyia fasciata Fabricius 1805. Common near the sea shore, but more scarce in the highest parts of the island. 6. Culex fatigans Wiedmann 1828. Very common all over the island. 7. Culex tigripes d'Emmerez and Daruty, 1900. One of the largest species known. Common in Mauritius. Does not frequently bite man. Larvs are cannibals. 8. Culex annulioris Theobald 1901. Only one specimen, taken by Colonel Peterkin, R.A.M.C. 9. Culex arboricolis n. sp. d'Emmerez de Charmoy (21, 1908). Found in holes in trees at Vacoas, Mauritius. Scarce. 10. Culex ronaldi n. sp. d'Emmerez de Charmoy (21, 1908). Larv£E found at Fanfaron Bastion by Major Fowler, but scarce. 11. Culex fowleri n. sp. d'Emmerez de Charmoy (21, 1908). From larvfe caught by Major Fowler. Scarce. 134 I have little to add regarding the insects. The leading facts about the commonest species are already quite familiar, and the habits in general are the same in Mauritius as I have observed them since 1895 to be in many parts of the world (section 2, 3). One fact is worth mentioning. In several parts of India I had observed Stegomyia abounding in woods, but had noted that these insects did not seem always to enter houses close to the woods — suggesting that the former may be of a different variety, though possibly of the same species, as those which so frequently persecute the inmates of houses. I observed the same thing in Mauritius. Only a few insects might be in the house at a time when they swarmed in the shade of trees in the garden. It is worth studying whether the house variety does not breed in pots and tubs, etc., while the woodland variety breeds in holes in trees, bamboo stumps, etc. Some further facts are given in the following addenda. ADDENDUM 2.— THE OUTBREAK AT CLAIRFOND, PHCENIX. — This epidemic was raging close to the military barracks and to our own house, when we were in Mauritius. It afforded a very good object lesson regarding both the prevalence and the prevention of malaria. Phcenix is a considerable village situated on the plateau (1,300-1,400 feet above sea level) on the main road from Port Louis to Curepipe, which there runs in a north-westerly and south-easterly direction. To the west of the road and the village there was, until recently, a large marshy area called the Clairfond Marsh, made by a number of springs which spread themselves over a flat area (vide map).* The better class houses lie along the road ; but numerous huts of Indians (mostly) exist further west, actually among the pools and streamlets of the marsh. Still further west there is a dry open area traversed by the Rivifere Sfeche, beyond which on a considerable open plain, the well-built barracks of the troops are situated. Further west again there are the villages of Vacoas and La Caverne. To the east of Phoenix there is open ground rising to the estate called Highlands ; and to the south the road rises towards Curepipe (1,800 feet). Until recently, the whole of this area was healthy, in spite of the large marsh ; but endemic malaria began to appear in 1903. Dr. de Chazal who has long practised in the neighbourhood has very kindly given me a full history of the epidemic, which I reproduce below. THE OUTBREAK OF MALARIAL FEVER AT PHCENIX. Bv Dr. de Chazal. This village was considered healthy until the year 1903, when a small epidemic of malarial fever broke out. I have practised in this District since 1890. Cases of fever among natives had come under my notice from that time ; but it was not till the former year that I saw well-to-do people become affected. In my own house, where my people had been settled since 1866, a case of malarial fever, of local origin, had never occurred among any member of my family until 1903, when I first noticed tertian ague and demonstrated the parasites in the blood. (i) The presumed cause of the epidemic. — A part of the "Highlands" Estate, made up of the land now occupied by the Mihtary Government, "Clairfond," and "Mesnil," with their marshy ground, was sold in 1897. The River known under the name of " Riviere Sfeche " divides this land into two parts. The Military Government settled to the west of the river and natives to the east. * Page i86. ' 135 In July 1898, a regiment of natives from Central Africa was brought to Mauritius. The men were taken to Phoenix as soon as they landed. They were not stationed at Port Louis, so as to avoid contracting fever. The men suffered very little from malarial fever, only three cases of ague and one of remittent fever being recorded among them during that year. This regiment left Mauritius in 1900, and during their stay here they had remained at Phcenix exclusively. In 1899 a Bengal Infantry regiment was introduced in Mauritius and quartered at Port Louis, where the Sepoys suffered so much from malarial fever, that they were brought to Phoenix for a change and placed under canvas on the ground now used for polo practice. The services of Army Medical Officers not being available in 1898-1899, these two regiments were handed over to me ; I had lo attend to the sick and to supply medicines. The African regiment suffered from influenza in July and August. 1898, and the Indian Sepoys from malarial fever. The Indians were quartered in Port Louis and the sick brought up to Phoenix for short periods. In r902 a second Indian regiment (Rajputs) were brought to Mauritius. The Africans left the island, as already stated, in 1900, the Indians in November, 1906. The sepoys caused a great increase of the Indian civil population at Phcenix, Clairfond and Mesnil villages. Small shops were built to meet the trade opened by the native soldiers. Many new huts were erected for the accommodation of a fairly large population of native dealers who travelled all over the island, to and from Phoenix. Of the two Indian regiments, one was kept in Port Louis and the other at Phoenix, alternately, for six months at a time. In order to ascertain if it was the presence of these natives, who settled at Phoenix from the year 1897, that caused an increase of fever in the district, it would be necessary to consult the records of the public dispensaries or the sick rate of the troops quartered at Phcenix camp, but, unfortunately, these records had been kept in such a way that they are not trustworthy until 1906 for the Military Department, and until 1904 for the pubhc dispensaries. All that I can positively state is that I did not notice a marked increase of fever in the district until the year 1903, five years after the arrival of Indian sepoys suffering from malarial infection. (2.) The prevalence of fever in this district prior to the epidemic is/igoy — That fever was prevalent in the district as early as 1892 can be certified by medical practitioners and by consulting the records of the public dispensaries. These records, prior to 1904, indicate the total number of attendances, each attendance being reckoned as a separate case ; i.e., if a patient came to the dispensary three times during the year, three cases of fever were entered in the books, whilst since 1904 if th(f patient came for the same disease more than once only one case of fever was entered. Only the numbers from 1904 will therefore be given. The following table shows the gradual increase of the disease in some of the districts from which the patients who attended at one of the dispensaries, that of Vacoas, were drawn. Years. Phcenix. Mesnil. Eau Couliie. Caverne. V. Cantons. Solferino. Croisie. Rainfall. 1904 41 51 67 81 32 12 52 76-46 1905 .. 68 88 71 202 67 55 113 126-86 1906 .. . 107 99 73 506 114 90 170 91-53 1907 .. . 398 152 113 411 109 154 179 9200 136 The information gathered by consulting the Dispensary records are of some value, for they contribute a fair index of the sanitary condition of the district. The numbers given indicate the proportion in which the fever has increased from year to year. The population of these districts can be safely taken as remaining stationary, except that of Phcenix village, which has decreased since the departure of the native regiments in 1906. (3.) The course of the epidemic. — The disease began to make itself very apparent in 1906, although it had already begun to increase in the previous year. The following table shows the total number of cases of malarial fever at Vacoas Dispensary. Year. 1904 1905 1906 1907 No. of Cases of Malaria. 346 843 1,147 1,487 It was in November, 1906, that the numbers began really to increase at the Dispensary. In March, 1907, the Government started quinine treatment and prophylaxis at the patients' homes. The dispensary records would have been higher in the latter year if this had not been done. The rainfall, taken within 50 yards of the Mesnil marshes, is given in inches. The returns from the camp apply to European troops. 1Q06. 66 206 91-53 Military. Phoenix and Mesnil. Rainfall inches. Military. Phcenix and Mesnil. Rainfal inches /• •■ 4 10 8-25 4 38 4-13 F. 1 17 10-79 2 27 10-30 M. .. 8 31 13-99 11 57 . 8-00 A. .. 16 23 0-88 13 62 14-34 yl/ .. 9 19 8-26 24 66 7-13 /■ •• 7 18 3-70 24 60 10-83 /• ■■ 5 13 9-47 28 54 2-61 A. .. 2 10 4-12 13 26 0-16 S. .. 3 9 4 61 22 25 4-61 0. .. 3 12 4-88 8 23 4-88 N. .. 6 20 1-10 3 40 1-10 D. .. 2 24 11-50 9 72 11-50 161 550 9200 (4) Influence of vicinity of mwsh on the causation of fever in neighijouring houses. — In order to record cases of local infection only those houses are mentioned whose occupants were old settlers in the district and who had not previously suffered from malarial fever. It must be noticed, on referring to the chart which is annexed, that the road leading to Phcenix railway station marks the hm.it of the Clairfond marshes towards the north. To the south of this road, there are many springs, streams, and marshes scattered over the area called " Clairfond" and "Mesnil." The first case of fever occurred in January, 1906, in the house marked I on the chart. The occupants of No. 2 house were attacked in August, ij )) 3 !) ,) November. ), I! 4 jj ,, December. No. 137 In 1907 the incidence of the disease was as follows : — The occupants of No. 5 house were affected in February. „ „ 6 ,, „ March. i> „ 7 >. 1. April. 8 „ „ June. ,, ,, 9 „ ,, September. ,, ,, 10 „ ,, December In 1908 fresh cases occurred. The occupants of No. 11 house were attacked in January, and those of No. 12 in February. Up to February 20th, 1908, the following houses had not been affected viz. : those marked Nos. 13 to 26 in the chart. The European soldiers in the Phcenix camp began to be affected in January, 1906. Some cases even occurred in 1905 ; but it was not till the month of March, 1906, that the cases became numerous. These examples demonstrate the following facts : — (i) That the houses situated nearest the marsh were affected first. Nos. I, 2, 3, 4, in 1906. (2) That to the north of the road which marks the hmit of the marsh, viz. : that leading to Phcenix Station, some houses were affected much later. No. 7 in April, 1907; No. 8 in September, 1907; No. 9 in December. The other houses situated still further to the north of this road were spared and are still spared up to this day, February 20th, 1908, viz. : houses Nos. 14-19. (3) That the fever has no tendency up to the present to spread towards the West, along the railway line, beyond the camp, nor towards the North, both these regions being free from marshes or springs. Natives living in these districts are, however, becoming gradually affected. The occupants of the houses mentioned will probably become affected later. The influence of the vicinity of the marsh in causing fever is thus very apparent— the nearer the house is situated to it, the earlier its occupants contract fever, These examples also show that the fever spreads slowly but surely to greater distances from the place where it first broke out. (5) Blackwater Fever. — During the epidemic eight cases of Hsemo- globinuria fever were noticed at places marked H. on the chart. These, it should be noticed, all occurred in the immediate vicinity of the Clairfond Marsh, except one case which occurred in a patient who first lived in a house marked No. 3. He suffered so much from fever in this house that he moved to house No. 27 where he was attacked with Hfemoglobinuria fever four weeks later. These cases show that the type of fever was most severe in the area which is the most marshy ; for Hsemoglobinuria is considered, and I think rightly so, as an index of the gravity of the malarial infection. As a digression, I may mention the following facts concerning these cases of Hfemoglobinuria fever. One case occurred in June, 1907 ; two cases occurred in July ; two cases occurred in September ; one case occurred in November; one case occurred in December, 1907; one case occurred in February, 1908. All these cases got well without taking quinine. This drug was administered in some of the cases only after the blood had disappeared from the urine, after and during treatment by bichloride of calcium. 138 None of these cases left Phoenix. They got well in the same houses where the disease began. These facts are mentioned because it is beheved by some medical men that : — (i) The disease occurs in the cold weather. (2) That quinine hypodermically is the best treatment. (3) That removal to some other place is highly desirable. (6) Remarks about Curepipe .—Th&t malarial fever is prevalent at Curepipe is seen from the records of the Dispensary of that town. The disease shows a marked increase in 1907. No. of cases of Y^^"^' malarial fever. 1904 473 1905 620 1906 644 1907 1,032* The patients who attend at this dispensary come from the town_ itself and from the numerous " free " villages scattered around, for a radius of from half to three miles. Curepipe attracts a great many people in search of employment, who come there already infected by the malarial parasite ; but on making a careful enquiry I had no hesitation in stating that there are a good many cases of local infection. The following table shows the gradual increase in the number of attendances from malarial fever at the Curepipe dispensary and the localities from which these patients come. Lower Midland Other Year. Camp Fouque- reaux. Riviere Seche. Trou aux Botanical Cerfs. Gardens. Forest Side. Old Loretto Convent. part of Curepipe Road. and XVIth mile. parts of Curepipe. 1904 20 20 19 12 58 4 45 18 177 1905 16 25 12 16 78 19 55 24 192 1906 21 35 17 17 87 18 111 13 199 ]907 101 49 20 50 133 34 114 54 203 Dr. DE Chazal's Report ends here. On our arrival Major Fowler and I, greatly assisted by M. Daruty and M. d'Emmerez, and a number of moustiquiers, made a careful study of the epidemic. Our results were as follows : — (i) Sfken-rates. — These gave most interesting data. We began by examining 163 children collected at Phoenix village, not only from the village, but from some distance outside it, and found that they had an average spleen-rate of 55'3 % and an average spleen of 3-i6. Next we made repeated house to house examinations of 339 children living close to the marsh or a little distance from it, and found an average spleen-rate of yi'i % and an average spleen of 4'i2 (Table IV, C). But the important fact was ascertained that the children living very close to the pools of the marsh had a far higher spleen-rate than those living only a few hundreds of yards away. This confirms Dr. de Chazal's statement based on clinical observations. The spleen-rates, however, give a much more decisive proof of the relation than the clinical observations do, because there is much less statistical error with them, owing to the large number of children examined. * Much of this was probably due to cases from Phoenix, where there is no dispensary, so that patients often go to Curepipe. — R. Ross. 139 Our results are entered in the map in the form effractions. For example, 3/7 denotes that three out of seven children were found to have enlargement of the spleen. But, owing to the smallness of the map, the fractions are not entered for each house (of which we examined iig), but for clusters of houses. The results however are apparent enough. Near the pools (marked black) the spleen rate is nearly 100%. As we advanced southwards up the slope towards Curepipe the spleen rate fell at once almost to zero, and remained at this all the way there, and in Curepipe itself. At the village of Vacoas and La Caverne {i}^ to 2 miles from Phoenix) not a single child out of 104 examined had enlarged spleen ; and on Highlands Estate (i mile), the ratio was only 3 to 50. The rate is high at Phoenix, to the east of the road ; but this is due to a small marsh in the river Mesnil. Hence this interesting house-to-house spleen census gives a most convincing proof of the law that malaria and Anophelines abound most only very near to breeding places. I do not remember to have read before of the use of the spleen test for obtaining such exact and valuable information. It is evidently capable of similar use elsewhere — wherever we wish to mark down the precise source of the disease ; and I have therefore recommended its employment in Port Louis for determining the exact effect of the streams (section 36). (2) The troops attacked. But this law is only one of averages, and exceptions occur. Just before our arrival the 2nd Battalion of the Loyal North Lancashire Regiment had come to the barracks at Vacoas. They remained well for a few months ; but suddenly at the end of December, 1907, an epidemic of malaria occurred among them. There were 7 1 cases in January. Some women and children were attacked, and there were five deaths and many invalidings. Yet the barracks are half a mile from the marsh. In addition, several residents in neighbouring houses became infected during our stay. (3) The diffusion of the Clairfond Anophelines. In order to study this point, I directed a number of the moustiquiers to search for the Anophehnes in the houses at Clairfond marsh and at various distances from it. They used to sit up at night with lanterns, and captured the insects that came to bite them. Many were caught at Clairfond, but very few at any distance ; showing that, as calculated by Professor Karl Pearson and myself, migration to a distance is not great. It was reported that the migration is greatest on warm still nights, and least on windy nights — ^just the opposite to what is generally believed. In fact, cold, rain, and wind seem to make the insects disappear. Very few, and then only M. mauritiafius, were caught in the barracks before I left; but it does not follow, because few are caught in a place during the two or three hours when they are being looked for, that many may not visit that place during a longer period. One mosquito a night on the average means 184 during six months; and the bite of a single infected mosquito means infection. Many of the troops were possibly not infected in the barracks at all, but while walking about in the evening. The men used frequently to enter or pass Phoenix village. On the other hand, the cases were decidedly more numerous in the barracks nearest to the marsh. Major Fowler has studied this part of the subject more thoroughly. F. costalis was caught both inside and outside houses, but M. mauritianus chiefly outside, in verandas, in woods, under bamboo hedges, and in other sheltered places. Three of our moustiquiers were infected while catching the 140 former. In our own house (number XXIV on the map) we caught only one or two Anophelines {M. maurifianus) altogether, showing that very few reach a mile from the marsh. (4) Infected mosquitoes at Clairfond. All efforts to find the parasites in the M. maurifianus, either caught wild or fed on malaria patients, failed — with the exception of one insect in which dead zj'gotes occurred. We were therefore for some time at a loss how to explain the malaria, when suddenly one of our men brought in a single P. costalis, which had never hitherto been found so high on the plateau. Both this and the next P. costalis czxi^'i. were found to be infected — thus clearing up the mystery. Subsequently many others, both larvjE and adults, were procured in the marsh. Nevertheless they were always much fewer than M. mauritianiis — scarcely one to fifty. This shows the absurdity of supposing that the infecting mosquitoes in a locality must be the most numerous ones there. (5) Tlie output of mosquitoes from a marsh. I do not remember any previous efforts to ascertain this point. Accordingly, I stretched an ordinary mosquito net over nine square yards of the Clairfond marsh in the manner shown in photograph 22, and counted the mosquitoes caught within it every day. They were all M. mauritianus, no Culicinse being found ; and numbered 30 males and 31 females during 16 days, giving an average of ©•423 mosquitoes per square yard per diem, or 423 for a thousand square yards. Numbers were still hatching out at the end of 16 days. During the day the adult insects took refuge in the grass, from which they had to be beaten out. Many equally simple experiments could be undertaken with much advantage to practical sanitation. (6) We readily found all species of tiie parasites in the people at Phcenix and neighbouring areas. (7) Before I arrived. Government had already commenced to drain the marsh, and a further sum of Rs. 11,000 was allotted later on. In addition to this, owing to the representations of H.E. the Governor, of General Creagh, C.R., and of Colonel Peterkin, R.A.M.C., the War Office gave a considerable sum for the same purpose, in view of the outbreak among the troops. The marsh was therefore nearly drained by the time I left. In the meantime the Medical Department had employed a Quinine Dispenser for house-to- house distribution (section 30) ; and the result was that at my departure infected children were becoming markedly more difficult to find. I hear that the improvement has been maintained. In conclusion, I strongly recommend that a second house-to-house spleen census be taken at Phcenix village in next January, in order to compare the results with those given in the accompanying map. ADDENDUM 3.— THE QUESTION OF THE RIVER RESERVES.— The chief product of Mauritius is sugar. It has been shown by years of observa- tion that the amount produced by her magnificent fields varies as the rainfall multipUed by the number of rainy days. Now it has long been a dogma of forestry that forests tend to increase the rainfall. For this and other reasons, Mauritius possesses a Forest and Gardens Department, costing Rs. 142, 377 in 1906 (Blue Book). Although the whole island is well wooded, the true forests exist mostly on the mountains or higher parts of the plateau, where they are carefully guarded by the law. In addition, however, there is an old law which prevents the cutting of trees, without permission of the Forest Department, HI within a distance of from lo to 50 feet from the edge of certain parts of rivers and streams. The result is that in most parts of Mauritius, wherever there is a small river or stream, or even a stony channel, there is generally found a strip of thick, and sometimes impenetrable, vegetation, consisting both of large trees and underwood, and extending from the stream to the top of the ravine made by it, in the deep shadow of which the water runs along almost hidden from sight. These strips of jungle are called the "River Reserves.'' Recently the question has arisen whether, whatever may be their good effects, their existence is beneficial to the health of the people who hve near them. It has been pointed out that nuisances which tend to pollute the streams (which are largely used for drinking) are often committed in the shelter of the wood, and may cause ankylostomiasis ; and that the water is further polluted by dead leaves of bamboos and other plants, which lie soaking in the pools. More recently, Dr. Bolton, Medical Officer of the Immigration Department, being directed to report on the cause of the high death rate on certain sugar estates, came to the conclusion that on many it was due chiefly to malaria caused by Anophelines breeding largely in these River Reserves (July, 1906). His reports were forwarded for an sxpression of opinion to the .Societe Medicale, which endorsed his views, and advised " la suppression et le maintien de la suppression des reserves forestiferes le long des riviferes dans tout centre de population de la zone malarienne et a 3 et 400 mfetres en aval et en amont de ces centres " (August, 1906). The matter was now put before the Woods and Forests Board, which considered it at various meetings for more than a year. During the same time the Director of Forests (Mr. Koenig) wrote reports in which he maintained the utility of the River Reserves, and criticised some of Dr. Bolton's conclusions. Finally H.E. the Governor asked me (Colonial Secretary, No. 9,826/06 of 15/2/08, with correspondence enclosed) for my views on the question. I have carefully considered this literature, as well as reports by Mr. Thompson (1880) and Mr. Gleadow (1904) on the Forests of Mauritius. I also had opportunities to discuss the whole matter with Dr. Lorans, Mr. Koenig, Dr. Bolton, and many others, and will do my best to throw some light on the controversy. The first questions which arise relate to matters of fact, (i) Is it really true that forests ijicrease the rainfall? In this connection I had the advantage of being able to read in manuscript an able report on the subject by Mr. Walter, of the Observatory. By analysis of a mass of meteorological statistics he concluded that certain large denudations of forest which occurred in the island some decades ago had certainly had a small but definite effect on the rainfall. The total rainfall had not been markedly changed, but there had been an appreciable decrease of the number of rainy days — one of the most important factors in sugar cane cultivation. From another paper of his (and also from other articles I have read) it would seem that trees suck up moisture by their roots and exhale it into the atmosphere by their leaves in large quantities. On calm days this exhaled moisture increases the humidity of the air until saturation and a fall of rain occur — thus explaining the afternoon showers so frequently seen over the land (but not at sea). Hence trees would be, as it were, syphons which tend to draw up water buried in the soil and to distribute some of it over the fields — in other words, valuable irrigators. 142 But the effect of the whole extensive denudations referred to had not been large. I have unfortunately mislaid my notes on Mr. Walter's report ; but if I remember aright there was evidence of only a small percentage of decrease in the number of rainy days. Now the entire extent of River Reserves put together amounts, I believe, only to 2 or 3 % of the total forest in Mauritius. Hence, I presume, the removal of the ei^tire River Reserves would scarcely diminish the number of rainy days by more than a small fraction. Still further, the proportion of River Reserves and other wooded water channels within 400 metres of populous centres must be only a small fraction of the entire River Reserves and other wooded water channels ; so that the removal of these parts only, as advised by the Socie'te Medicale, would have (I should think) an absolutely inappreciable effect either on the total rainfall or on the number of rainy days. If the denudation of large areas has had little effect, surely that of a few hundred yards of narrow strips of ground near a few populous centres could have scarcely any at all. But other benefits are attributed to the Reserves. It is said that they break the force of the wind on the cane fields ; and I think that they do — but only to a very small percentage on the average. They prevent the water running away too quickly to sea ; they check erosion of the banks by floods and the washing away of the soil by heavy rains. But while admitting these points, we must again remark that it is not proposed to denude all the streams but only small parts of them near " populous centres." Now let us turn to the other side. (2) Is it really true that the River Reserves cause malaria .? Dr. Bolton drew his conclusions from a comparison of a number of estates which he divided into two classes, namely. Class A, in which a stream, river, or marsh exists in the vicinity of the Camp, and Class B, in which they do not exist. The death rates for the first half of each of the years 1903, 1904, 1905 tended to be higher in Class A than in Class B ; while, taking the average estate death rate for the district as a mean, the death rates of Class A were above it and those of Class B were below it. Unfortunately, owing to large statistical error, death rates are not very reliable quantities for such a comparison. Spleen rates would obviously give much sounder information ; and the details for 1907-08 will be found in Table IV, A. These will not necessarily accord with Dr. Bolton's figures, since they were collected two years later, and also because, owing to the confusion of names adopted for some of the estates, I cannot always identify his localities ; but they generally support his argument. On averaging the spleen rates for the districts I find as follows :- — Class A. Class B. Av. Spl. R. Av. Spl. R. Pamplemousses ... ... ... 55' 7 21'8 Flacq 67-1 53-8 Grand Port 68-8 44-0 Savanne 20-9 27-7 Savanne is the only exception ; but the sources of error are so numerous that the figures are worth but little. There may, for instance, be breeding places in Cla.ss B not included in those mentioned ; while in Class A some of the waters may be too distant to have any great effect. I trust that the spleen census and the results of the minor works proposed in sections 28 and 33 will definitely clear up the question in a year or two ; but at present I cannot say that the River Reserves (or more generally the wooded water channels) have been fully convicted of causing all, or even much of the malaria, near them — at least, by statistical evidence. 143 Speaking generally, however, they are certainly dangerous. There is no doubt whatever that the Anophelines do breed in the streams ; but they breed in water along lengths of grassy margin, and in pools in rocks, &c., not in the trees. I am not certain that the trees affect the question much one way or the other. In fact, as pointed out to me by Mr. Koenig, the shade of large trees is inimical to the growth of grass, which is generally scanty under them — and it is grass in ivater which is the danger. Moreover, I can quite imagine that a thick growth round a stream must make ingress or egress much more difficult for mosquitoes. On the other hand, trees do breed Culicinse, and shelter all mosquitoes ; and our mousdquiers easily captured Anophelines in the Reserves — suggesting that women and children who go to draw water may often become infected there. And the objections to the Reserves on account of nuisances still stand. Before proceeding to consider recommendations, two more points have to be discussed, (r) It is, I think, perfectly agreed to by both sides in the controversy that the undergrowth in the Reserves is quite unnecessary. Mr. Koenig informed me that his department requires the large trees, not the dense growth of useless bushes under them ; and it is precisely this under- growth which the Health Department objects to. There is therefore no reason whatever why it should be retained. The removal, at least near villages and coolie camps, will give free access to the streams not only to the people but to the malaria gangs. Nothing more is required than what was so excellently done by the Forest Department itself to the Mesnil at Phoeni.x, as well shown in photograph 25. The second point is one which I have heard raised, but which, I think, few will assent to. It is that, if they are of use to the planters, the Reserves should be maintained even if they do cause malaria. From a humanitarian point of view, this proposition is open to strong criticism. It suggests in brief that human life may be exploited in the interests of individuals. But no civilised state can allow such a thing ; and the Immigration Department in Mauritius has been expressly constituted to protect the indentured coolies. From a rational economical point of view, however, the proposition is still more unsound. If it could be proved that the small parts of the Reserves near populous centres really add materially to the output of the estates, then something might be said for maintaining them. Even then, however, the question would arise whether the loss to the estates from the malaria would not more than counterbalance the gain from the Reserves. People who urge this proposition seem to have completely forgotten this last item. As Dr. Bolton says (annexure i), the day's work of a cooUe is worth from R.I "2 5 to R.i'5o to an estate during the season. When 10 % or more of the men are " down with fever," the loss must mount up to hundreds and thousands of rupees to a single malarious estate during the year. Dr. Bolton adds (18/7/06) : — " On many estates new immi- grants have to be imported to make up for the loss of labour through sickness. They cost Rs.200 each on landing, but in reahty a great deal more if the cost of those who desert or die is added to that of those who remain. On some estates more than 25 % of the new immigrants imported within the last three years have deserted. Add to this 5 % of deaths. The remaining 70 out of 100 men therefore cost Rs. 20,000, equalling Rs.285'7 per head for five years, or Rs.5yi4 per year, or Rs.4'76 per month." He remarks also that numbers of convalescents have to be put to light work, which means that ten men have to do the work of six, and says, " The low price 144 of sugar, the high price of transport, labour, and provisions, leave a very small margin, if any, of profit, so that any economy in the cost of production becomes a matter of serious import." Does anyone suppose that a few hundred yards of jungle planted along a stream is ever likely to compensate a planter for such heavy and constant losses caused by malaria ? It therefore seems to me that, if Government is finally driven to decide between River Reserves and malaria sanitation, it would do wisely to clear away the former without much hesitation. For the practical needs of the moment, however, my single recommendation is as follows : — The promotion of a bill to allow riverain proprietors to cut down, destroy, or remove any uprooted or dead tree, and also any bush, weed, or noxious growth, found or growing on their property, with proper clauses to notify the Forest Department before this is done, with a view to saving such trees as this department may wish preserved. The bill might be on the lines of the proposed Ordinance of 1905, framed by the Directors of the Forest and Medical Departments, but with the compulsory clauses changed into permissive ones. (I understand that the bill was lost owing to these compulsory clauses.) In sections of the bill the Medical and Health Department might be allowed to do the work after notice. The wood removed might be given to the remover, i.e., the proprietor, the Medical or the Forest Department (if this is possible), whichever does the work. A system must be considered by which the Forest Department will not impede the work either of the owner of the property or of the Medical Department, by delay in specifying or notifying which trees are to be left alone (for example, the trees to be preserved may possibly be marked). So far as I can see, this bill would meet all the requirements of the case, and would satisfy all parties. The' Forest Department admits that it does not wish to retain the worthless growth, and I believe everyone else wishes to get rid of it. Many planters told me that they were only too willing to remove it, but that they were prevented, or hampered, by the laws. If the owner does not wish to do the work, the Medical Department can do it for him. If he refuses permission, I fancy that he could be compelled to give it under the draft legislation in annexure 3— though perhaps a special clause will be required to cover this point. The actual work can be done, where required, by the malaria gangs, especially during the winter months. I would not advise limitation of the bill to any particular localities, e.g. those near populous places, unless the Forest Department wishes to preserve undergrowth as well as trees in spots far removed from habitations. In conclusion I must add that the exact effect of the streams in causing malaria can be ascertained only by watching the results of the minor works and by taking the spleen census frequently, as already recommended. The facts will declare themselves automatically in the course of the work. Here, as elsewhere, labour lights itself. ADDENDUM 4.-STATISTICAL ERROR. The Poisson formula for statistical error is well known ; but it may be advisable to give here an addition made by Professor Karl Pearson, which will be particularly useful for taking spleen rates in villages and towns. Let 7\''be the total number of children in a locality ; n be the number examined, and x be the number with enlarged spleen. Then - x 100 will n be the spleen ^-^te among the n children examined. But we shall have no 145 right to infer that the same rate will hold for all the N children in the locality. Let e % denote the percentage of error. Then Thus, when ?i = N, or all the children in the locality are examined, the statistical error vanishes. fi 1 For example, let i\^= 800, n = 200, and x = 100. Then 1 - ^^3-1 - about f ; and ^ =100. Hence ^-^ = 573 = 8-65. So that we can infer that the spleen rate of the total 800 children is between (50 + 865;^ and (50-8-65;/^; that is, between 58-652 and41-35X. The following square roots are useful : — ^/2=1-41 73=1-73 75 = 2-24 76 = 2-45 77 = 2-64 78 = 2-83 710 = 3-16. 146 REPORT ON THE PREVENTION OF MALARIA IN MAURITIUS. REFERENCES. Correspondent (Ross). British Medical Journal, 9, 16, 20 Sept. and 14 Oct., 1899; and Memoir II., Liverpool Sch. of Trop. Med., 1900. Ross. The Prevention of Malaria in British Possessions, Egypt and parts of America. Lancet, 28th Sept., 1907. Ross. The Logical Basis of the Sanitar}' Policy of Mosquito Reduction. Br. Med. Journ., 13 May, 1905. Ross. The Anti-malaria Experiment at Mian Mir, Br. Med. Journ., 17 Sept., 1904. Pearson and Blakeman. A Mathematical Theory of Random Migration. Drapers' Company Research Memoirs, University of London. Dulau & Co., London, 1906. 6. Report of the Fever Enquiry Commission, 1866 and 1867. Mauritius, 1868. 7. Davidson. Geographical Pathology. Y. J. Pentland, Edinburgh, 1892. 8. Meldrum. Relations of Weather to Mortality. Mauritius, 188 1. 9. Meldrum. Mem. on the Death Rates of Mauritius, &:c. Mauritius, 1888. 10. Meldrum. Relations of the Mortality of Mauritius to the Rainfall, &c. Mauritius, undated (about 1890). 11. Jones. Malaria, a neglected Factor in the History of Greece and Rome. Macmillan & Bowes, Cambridge. Also Annals of Trop. Medicine & Parasitology, Vol. II., No. i. 12. Chadwick. Reports on Sanitation, Water Supply, &c. Mauritius, 1891-92. 13. Annual Report of the Museum, 1898-99. Mauritius. 14. Daruty de Grandpre and d'Emmerez de Charmoy. Les Moustiques. Port Louis, Mauritius, 1900. 15. Report of the Committee of Enquiry into the Cause of Unhealthiness of the Beau Bassin Central Prisons. Mauritius, 1901. 16. Correspondence on the high Death-rate on Sugar Estates. Mauritius, 1906. 17. Report of the Advisory Committee for the Tropical Diseases Research Fund. London, 1907. 18. Treves. Preventive Medicine at Panama. R. Soc. Medicine, Proceedings, Vol. I., No. 8, June, 1908. 19. Mouheb Pasha. Lancet, 23 May, 1908, page 1505. 20. Ross. Ann. Trop, Med. & Parasitology, Vol. II., No. 3, 1908. 21. D'Emmerez de Charmoy. On three new species of Culex collected during the anti-malaria campaign in Mauritius in 1908. Ann. Trop. Med. and Parasitology, Vol. II., No. 3, 1908. 22. Report of the Malaria Enquiry Committee, 1901-1902. Mauritius, 1903. 147 ANNEXURES. ANNEXURE i.— Extracts from letters by Dr. Bolton to Professor Ross (written by request). Letter A. Phcenix, January yd, 1908. In 1902 I was sent on a special mission to Diego Garcia, one of the numerous atolls forming the Chagos Archipelago. On my arrival I was told malaria did not exist in the Island — the few cases met with occasionally were among the labourers recruited in Mauritius, where they had contracted the disease. After careful investigation I failed to discover the least indication of malaria infection among the resident population, i.e., those who had never left the Islands. My next step was to search for Anopheles. In spite of the numerous tanks of stagnant water full of Culex larvae, I failed to find a single Anopheles. I was bound, therefore, to come to the conclusion that this fact explained the immunity from malaria enjoyed by a certain proportion of the inhabitants. I stayed a month there, so had ample time to search for the fever host. From Diego I went to Peros Banhos, another atoll 120 miles more to the east. Here again I recorded exactly the same facts. Having always heard that Rodrigues also was free from malaria I requested my son to investigate the matter. 'I'he absence of malaria among the resident population is here again due to the fact that I had occasion to verify last month when I visited the Island, that there are no Anopheles — although other kinds of mosquitoes are plentiful enough and breeding places exist all over the village of Port Mathurin, the capital of the Island. These facts tend once more to prove the correctness of the Anopheline theory, if any further such proof were necessary. I need not say that you may make what use of this letter you may wish. Letter B. Phcenix, 13//? March, 1908. (i) The loss to agriculture resulting from the yearly outbreak of malaria. The total Indian population for the whole Island was 263,971 in 1902 ; in 1907, 100,514 lived on Sugar Estates, viz., 45,526 men, 24,509 women, and 30,479 children. Malaria is rife from February to the end of April — in the most infected locahty the sick rate per diem from malaria alone is some- times as high as 20 % of the total male adult estate population ; on some estates it is lower— and on those situated in the district of Moka and the upper parts of Plaines Wilhems still less. An average of 15 % would be very fair for the low-lying districts. If I leave Moka out altogether then the figures stand thus : Male adult population on estates for the remaining districts, 48,942 — say 39,000 daily, average of 15 % = 5,850— say 5,800, multiplied by 90 days = 522,000 — say 500,000. The value of a day's work is between Rs. 1-25 and Rs. 1-50, so that the loss to the planters is about Rs. 650,000, and to the Indians at an average of R. 0-25 per diem Rs. 125,000 ; a grand total there fore of close upon Rs. 800,000. The figures refer only to the adult male 148 population residing on Sugar Estates. There must now be added to this the women and chokras who are regular workers on estates ; they also suffer from malaria during the season, and are incapacitated from work for days and even weeks. The number of women on estates is 24,000 odd. If we accept 50 % as a fair figure to represent those working in the fields we obtain a total of about 8,000, and 15 % on 8,000 is 1,200— multiplied by 90 days= 108,000 at Rs. o-20=Rs. 21,000. I do not count the chokras nor the loss to the Estate. I find therefore that the loss to the labourers and their wives and children is Rs. 150,000 nearly. Loss to the E.states Rs. 650,000. Total Rs. 800,000. The Indian population residing outside estates is over 160,000. ^ A large proportion work as day labourers on estates and also on fibre factories, and about 600 adult males in the different docks in town. Thirty thousand adult males, approximately, work as day labourers, earning on an average R. 0-55 per diem— a total of about Rs. 15,000 per day— 90 days will represent Rs. 135,000. A loss of 15^ is therefore Rs 20,000. No mention is made of the loss sustained by the blacks who work as day labourers. I have no figures for these. It is no exaggeration therefore to say that the total loss to the labouring classes amounts to quite Rs. 200,000 and to the planters Rs. 650,000, without taking into account extra hospital expenditure, drugs, comforts, &c. All told it would be found that the grand total would come to quite Rs. 900,000. Add to this the expense to Government for the sick treated in the different hospitals and at the dispensaries for malaria and sequelfe during three months, and the respectable sum of Rs. 1,000,000 is attained. (2.) The next question to deal with is the spleen-rates. There are no schools on the Sugar Estates ; but as very few of the children of the indentured coolies attend school there is no danger of any serious over- lapping. The Indian boys attending the Government schools belong to the free class of Indians, i.e. those who do not live on estates. I am certain the overlapping cannot exceed 0-25 %. This is not, I presume, of sufificient import to affect your statistics. Letter from Dr. Malcolm Watson to Professor Ross (written by request).* Eastfield, Bridge of All.\n, 26M May, 1908. On the points on which you ask my opinion, my experience is as follows: — (i.) The health of the community shows very great improvement within three months of the abolition of the main breeding places, and malaria was found to have practically disappeared within a year at Klang, although all the breeding places had not been satisfactorily drained. Ex- perience has shown that it is sufificient to reduce the number of mosquitoes in order to abolish malaria, although one naturally aims at making the reduction of the mosquitoes as great as possible.! (2) Drainage undoubtedly reduces the number of Anophelines in an area. (3) In both Klang and Port Swettenham there was the most convincing proof that there is no dangerous immigration of Anophelines into a drained area from the outside ; for both towns, although surrounded by an enormous acreage of breeding places, were when drained themselves freed from malaria. At Port Swettenham the safety zone was certainly less than a quarter of a mile in some places. * See page 83. t Compare pages 34-36. 149 (4) Anti-malaria drainage can be effectively carried out with a high rain- fall. In Klang the rainfall may reach to over 100" per annum, and thunder- storms, when two inches fall within an hour, are not uncommon. On such occasions the whole town in submerged. Further, where this heavy fall occurs on a mangrove swamp, so low lying that it is covered by all spring tides, anti-malaria drainage was found completely successful. Although when a heavy fall occurs at a time when the tidal valves are closed by a full tide the whole land is submerged, the fall of the tide permits the valves to open, and the land is soon dry. No more discouraging outlook for anti-malaria drainage can be imagined than the above, yet the experience of Port Swettenham shows that there is no difficulty whatever in practice. ANNEXURE 2.— CORRESPONDENCE REGARDING WATER CHANNELS. From Professor R. Ross, Brodick, Vacoas. To The Honourable THE Colonial Secretary, Mauritius. \A,th January, 1908. Sir, I have observed that there are in the Island many water-channels, apparently made for the purpose of conveying water from rivers or springs to plantations or factories, and also much used by people living near them for obtaining water or washing clothes. These channels are often obstructed by vegetation or silt to such an extent that they cause, or tend to cause, malaria along their course. I should be much obliged if I could receive, for the purposes of my Report on Malaria, the following details of information regarding these channels : — 1. To whom do they belong — to Government or to the owners of the Estates and Factories which they serve ? 2. In the latter case is there any law by which the said owners can be forced to keep them in a sanitary condition, not only within the actual pre- mises of the owners, but also in their entire course, as would seem justifiable owing to the fact that they were originally made for the private purposes of such owners ? 3. In the event of there being no law or regulation forcing the owners to keep the channels free from obstruction, thus compelling the Government to do the work for sanitary reasons, is there any means by which the owners can be taxed for the work done on their property ? Is there moreover any means by which other persons who use the water can be made to pay for maintaining the channels in good condition ? The same question will also apply to drains made especially for conveying waste and storm water out of Estates, Factories, and private premises. 4. Lastly, in the case of channels or drains which have fallen into disuse or which are persistently neglected by the owners, is there any means by which the latter can be forced to close them or, better, to fill them in ? (Sd.) Ronald Ross. No. 422/08. Colonial Secretary's Office, Mauritius, 20th February, 1908. Sir, I am directed by the Governor to acknowledge the receipt of your letter of the 14th ultimo on the subject of the cleansing of water channels, and to ISO transmit herewith copies of the correspondence noted in the margin giving the information asked for therein. Professor R. Ross, C.B., F.R.S., J. MIDDLETON, Brodick Vacoas. Assistant Colonial Secretary. No. O.L. 165/08. From The Honourable The Procureur-General to The Honourable The Colonial Secretary. Referring to your letter No. 422/08 of the 27th January last on the subject of the cleansing of water channels, I beg to attach a report from the substitute which affords, I submit, an answer to the questions in the letter from Professor Ross. (Sd.) A HERCHENRODER, Procureur- Getter al. Chambers, \oth February, 1908. 1. This matter, I understand, requires speedy attention, as the stay of Professor Ross in this Island is drawing to a close. I shall therefore deal only with salient features, and omit details. 2. "Canals" are the property of (a) private owners, e.g. most if not all, of the artificial water-courses feeding sugar or aloe fibre factories, or established for the purposes of irrigation ; [b) corporations, e.g. the canals supplying water to the Town of Port Louis ; (c) communities of riverains e.g. the Plaines Wilhems Canal, the Terre Rouge Canal, &c. — I am not quite clear whether there are not also some canals which are the exclusive property of Government ; the Director of Public Works and Surveys may give information on this point, which may however, I submit be overlooked, as it does not bear on the more immediate question of legislating, if need be, in order to compel private parties, communities of riverains &c., to take such measures as may prevent the obstructions of canals, and consequently lessen the sources of dissemination of malaria. 3. Private parties are responsible in general for the keeping of their canals in a proper state of maintenance, repair, tSiC, whether the canals run wholly on lands belonging to such private owners, or partly on such lands, and partly on intermediate lands. (See specially Art. 15 of Ord. No. 33 of 1863.) 4. The same obligation rests on corporations (Ord, No. 35 of 1863, Art. 46 ; Art. 84, S. iii.). 5. It further extends to communities of riverains whose rights and duties areregulatedbyChap.il of Order No. 35 of 1863. Those communities have Syndics (Presidents), and Joint-Syndics (Art. 52 of Ord. No. 35 of 1863) and keepers (Art. 57). An important provision of Chapter II. of the Ordinance is Art. 64, which enacts that every owner of ground through which a canal belonging to a corporation or community of riverains shall pass (Art. 84, S. iii.), shall be bound to keep the canal in its whole course through his property free from obstructions of any kind, including obstruction by plants, branches, roots, &c. (6) I have, I think, given a complete reply to question No. i, save on the point of canals which may be the exclusive property of the Crown. Questions No. 2 and No. 3, paragraph i, are partially answered ; the cycle will, I think, be complete if an enactment is passed on the lines suggested by Professor Ross in another paper, and which we have discussed with the Medical Director. It includes an addition to the definition of a " nuisance," and powers to suppress, within the shortest delay, breeding places for mosquitoes, to incur the necessary expenses, and to charge them against, and recover them from, the parties concerned. The proposed amendments bear specially on Ord. No. 32 of 1894-1895, Art. 29 sqq. and Art. 52 sqq. Canals coming under categories (a), {l>), and {c) in paragraph 2 of this report are provided for, and the draft enactment further contemplates measures to be adopted in the case of canals and other "premises" which may happen to be the exclusive property of the Crown. The projected law on the prevention of malaria will, I believe, meet the second part of Question No. 3, as well as Question No. 4. Drains and channels will, under certain conditions, be treated as "nuisances" under the general law of 1894-95, or they may be dealt with summarily under the proposed enactment. (Sd.) J. EUG. SERRETT, 8/2/08. Ag. S.P.G. The above shows, I submit, the necessity of considering the present question simultaneously with the one on which Dr. Momple has conferred with us. 8/2. (ltd.) J.E.S. ANNEXURE 3.— DRAFT LEGISLATION. Re°oo >i .. 1,500 5 Sebastopol „ ,, i,6oo ,, 800 6 Belle Vue estate Clearing marshes on the estate camp .. 1,000 7 Montagne Bamboiis ... ,, and draining .. 2,000 8 Terrain Dubois Clearing marsh ... ... 500 9 Trois Hots Clearing and improving stream 2,000 10 Bois d'Oiseaux „ .. 1,000 11 Olivia estate Camp ... Clearing of marshes ... .. 1,000 12 La Nourrice and La Commune Clearing and improving of streams on i| miles . .. 3,800 17,400 DISTRICT OF PLAINES WILHEMS (Beau Bassin and Rose Hill Section). No. Place. Description of works required. Probable ^ '1.1 ^ cost. Rs. 1 Plaines Wilhems River Improving and clearing river on a length of 2 miles 5,000 2 Aliphon's premises. Rose Hill ... ... Getting rid of marshes formed by masonry channel 2,500 3 Collector from Edward VII. Street to Plaines Wilhems River ... Large repairs to masonry conduits ... ... ... 2,500 4 Corps de Garde Moun- Draining marsh on the north and eastern side of the 5,000 tain. mountain. 5 Simmierfield drain, Beau Repairs to channel and disposal of the vfater in 3,500 Bassin. absorption well. 6 Beau Bassin, between Construction of a large open drain in fairly rocky 15,000 Allee Mangues and ground on about 5,000 feet. Maingard Street. 33,500 DISTRICT OF PLAINES WILHEMS (Quatre Bornes Sections). No. Place. Description of works required. Probable ^ cost. Rs. 1 La Louise Draining of marshes to discharge at La Fenetre ... 30,000 2 Plaines Wilhems River Clearing and improving river on 2 miles 5,000 3 Riviere Seche, behind Trianon Estate ... Draining marshes (small) ... 1,000 4 Beau Sejour ,. ,, 1,000 5 Mesnil River Clearing'and improving river from Phcenix Old Mill to junction with Plaines Wilhems River. Length 2 miles 5,000 6 Solferino ... ... Clearing of stream terminating in neighbourhood of Solferino on a length of 3 miles ... .. ... 7,500 7 Paj)ayes River ... Clearing and improving river on 2 miles 5,000 54,500 1 69 No. 1 2 3 4 5 DISTRICT OF PLAINES WILHEMS (Vacoas.) Place. Description of works required. Clairfond River Plaines Wilhems River Camp Fouque- raux River Terra Rouge ... Allee Brillant and Camp Fouqueraux Phoenix 7 Perichon stream 8 Papayes River 9 Riviere du Rempart ... 10 Rivers Tatamaka and St. Martin 11 La Croisse 12 Mesnil River 13 Riviere Seche Draining of marshes, already provided for. Clearing and improving on 2 miles ... Probable cost. Rs. 5,000 5,000 3,800 5,000 ,, ,, ij miles ... Marshy streams in the neighbourhood of these roads to be drained on a length of about 5,000 feet Marshes caused by War Department Sewerage works. Should be removed by War Department Clearing and improving stream on I mile ... ... 2,500 Clearing and improving stream on I mile in the neighbourhood of Camp Mapou and Camp Roshe 2,500 Clearing and improving on about 25,000 feet ... 12,500 Clearing and improving on about 30,000 feet ... 15,000 Clearing and improving 2 feeders of Riviere du Rempart on 3,000 feet 1,500 Clearing and improving from Allee Brillant to Phcenix Iron Bridge on a length of about 3 miles 7,500 ,, ,, ,, about 2 miles 5,000 65,300 No. 1 2 3 4 5 6 7 8 9 10 DISTRICT OF PLAINES WILHEMS (Curepipe Section). Description of works required. Place. River Mesnil ... Do. Do. Do. Do. Eau Bleue River Poule d'Eau River Do. Riviere Seche... Do. 11 Curepipe generally 1 L'Esperance ... 2 Providence Lesur 3 Montagne Blanche 4 Pailles 5 La Dagotiere 6 Alma Estate ... Draining marshes near Town Hall ... Deepening stream on about 2,500 feet Draining marshes on Forest side portion Deepening drain along Lees Street Improving course of stream from D'Arifat Street to Allee Brillant, about 10,400 feet Improving course of stream on about 9,700 feet and draining marshes connected therewith Cutting bed of stream on 3,000 feet Improving course of stream on 12,600 feet Improving course of stream on 34,300 feet as far as Allee Brillant Improving course of stream on western side of Curepipe on 5,600 feet ... Draining other small marshes and incidentals, say DISTRICT OF MOKA. Description of works required. Marsh requiring draining about 2 miles of drain . . . A series of marshes requiring draining on about 2 miles ... ... . . Marshy streains in the hamlet to be cleared of vegeta- tion ... Two marshy streams requiring clearing and trimming on a length of about 2 miles Three marshy streams requiring clearing and trim- ming on a length of about 2 miles... Large marsh to be drained ... Probable cost. Rs. 4,000 2,500 4,000 3,000 5,200 4,850 3,000 6,300 17,150 2,800 7,200 60,000 Probable cost. Rs. 5,000 5,000 1,000 5,000 5,000 5,000 26,000 I/O No. 1 2 3 4 5 DISTRICT OF GRAND PORT (Rose Belle Section). Place, Description of worlcs required. Mare Chicose. .. Rose Belle Nouvelle France stream Balisson stream Ruisseau Sec and Tril:)utary 6 Eau Bleue stream 7 New Grove 8 River Tabac ... 9 Bonne Som'ce 10 L'Escalier 11 Carreau Esnouf 12 Ruisseau Copeau Draining of marsh into Ruisseau Tranquille Marsh on Rose Belle estate to be cleared , . , Clearing and improving on about 2 miles ... 2 „ ... 500 feet .. DISTRICT OF GRAND PORT (Mahebourg Section). No. 1 2 3 4 5 Mahebourg Riviere des Creoles Riviere La Chaux. Riviere des Delices Generally Description of works required. Marsh io befilled up ... Clearing and improving on i mile ... Probable cost. Rs. 1,000 1,000 5,000 5,000 6,300 5,000 2,500 6,300 1,300 2,500 5,000 500 41,400 Probable cost. Rs. 1,000 2,500 2,500 2,500 Clearing and improving sources ot streams in the neighbourhood of the following localities : — St. Hubert. Le Vallon. Cent Gaulettes. Beau Vallon Bel Air. Mon Desert. Ansa Jonchee. Virginia. 8,000 16,500 DISTRICT OF SAVANNE. No. Place. 1 Camp Rabaud Hamlet 2 St. Avolt estate Camp Description of works required. Probable cost. laish Rs. 500 3 Britannia 4 Riviere des Anguilles village 5 6 Surinam Hamlet 7 Souillac Village 8 Riambel Hamlet 9 Ste. Marie Hamlet 10 Beau Champ estate Camp 11 Bel Ombre Estate Camp 12 St. Martin Hamlet 13 Petit Cap Hamlet 14 Do. 15 St. Aubin Estate Camp 16 District generally Clearing of marsh Clearing and improving stream (Riv. Dragon) on 1,000 feet 500 Clearing and improving stream (Riv. Dragon) on 1,000 feet ... 500 Clearing and improving Ri\'er on 2,500 feet ... 1,500 Clearing small marsh ... ... ... ... 500 Clearing and improving Riviere la Savanne on 10,000 feet 500 Clearing and improving streams Ruisseau Mitchell and others on 2,000 feet ... ... ... ... 1,500 Drying small marshes ... ... ... ... 1,000 Clearing and improving river on 2,000 feet ... 1,000 Clearing and improving river on 1,000 feet ... 500 Draining small marshes ... ... 1,500 Marsh to be cleared near Cemetery ... ... 4,000 Clearing and improving Choisy river on 1,000 feet 500 Clearing marshes ... ... ... ... ... 2,000 Clearing and improving of streams on 2,000 feet ... 1,000 Add for other parts ... 8,000 25,000 i7r DISTRICT OF BLACK RIVER. No. 1 2 3 4 5 6 7 Place. Albion Gros Cailloiix Mouna La Ferme Flic en Flacq Clarens Tamarin Wolmar 9 Yemen ... 10 Black River ... 11 District generally Description of works required. Draining of Marsh Ditto Ditto Ditto Clearing and improving marsh Draining of marshes ... Improving of marsh, as it iiiay not be drained on account of water rights .V large marshy' district covering hundreds of acres. It seems hardly worth while to spend a lot of money for a very thinly populated place. Might cost Draining small marshes Draining a small marsh Draining other small marshy lands distributed over the district ... Probable cost. 4,000 1,500 3,000 5,000 2,000 1,000 5,000 30,000 1,000 1,000 10,000 63,500 172 TABLE I. GIVING POPULATION, DEATHS, AND DECLARED DEATHS FROM FEVER IN MAURITIUS FROM 1831 TO 1906. Years. Population. Deaths. Death Rate per 1,000. Fever Deaths. Fever Death Rate per 1,000. 1831 92,951 2,495 26-8 1832 93,038 2,917 31-3 — — 1833 93,643 2,561 27-4 — 1834 93,209 3,417 39-8 — 1835 93,631 3,367 36-0 — . 1836 97,534 3,020 31-0 — 1837 103,935 3,862 37-2 — — 1838 115,110 3,533 30-7 — 1839 114,989 4,483 39-0 — 1840 115,476 3,464 30-0 — _ Mean 101,361 3,311 32-9 — — 1841 114,380 4,750 41-5 1842 112,242 4,760 42-4 — . . 1843 144,137 4,993 34-6 — 1844 149,564 8,737 58-4 — 1845 156,967 6,198 39-5 — 1846 162,170 5,305 32-7 — 1847 162,535 4,764 29-3 1848 166,529 4,403 26-4 — 1849 169,770 5,235 30-8 — 1850 176,307 5,547 31-5 — — Mean 151,460 5,469 36-7 — — 1851 184,496 4,890 26-5 1852 199,158 5,591 28-1 — 1853 208,800 6,192 29-6 1854 212,482 17,978 84-6 1855 220,238 7,269 330 1856 223,736 11,312 50-6 — 1857 234,153 6,107 26-1 1858 257,736 7,242 28-1 1859 297,267 9,179 30-9 — 1860 309,901 9,805 31-6 — — Mean 234,797 8,556 36-9 — — 1861 324,287 6,854 31-1 1862 330,575 13,719 41-5 1863 335,310 11,566 34-8 1864 341,392 11,649 34-1 5,789 17-4 1865 360,337 12,042 33-4 5,181 14-8 1866 365,051 11,702 321 4,913 14-0 1867 332,968 40,114 120-5 31,920 99-5 1868 324,370 18,403 56-7 10,923 34-9 1869 322,892 11,295 35-0 6,330 20-6 1870 328,604 7,423 22-6 3,329 10-6 Mean 336,579 14,476 44-1 9,769 30-3 173 TABLE I. — continued. Years. Population. Deaths. Death Rate per i,ooo. Fever Deaths. Fever Death Rate per looo. 1871 319,470 8,171 25-6 3,578 Ill 1872 325,960 8,745 26-8 4,235 12-8 1873 332,476 11,210 33-7 5,031 15-1 1874 339,806 10,019 29-5 4,024 11-8 1875 345,037 8,584 24-9 4,061 11-7 1876 346,390 9,525 27-5 4,845 14-0 1877 349,060 10,335 29-6 5,787 16-6 1878 355,058 9,649 27-2 5,144 14-5 1879 357,774 11,485 32-1 5,303 14-8 1880 360,328 10,143 28-1 5,173 14-3 Mean 243,135 9,787 28-5 4,718 13-7 1881 359,419 10,746 29-9 5,826 16-2 1882 359,322 12,563 35-0 7,483 20-8 1883 360,221 12,770 35-4 6,741 18-7 1884 368,813 11,247 30-5 6,103 16-5 1885 367,288 12,352 33-6 7,423 20-2 1886 368,145 10,624 28-9 5,839 15-8 1887 368,163 12,690 34-5 7,690 20-8 1888 369,302 11,193 30-3 6,110 16-5 1889 372,664 12,567 33-7 7,338 19-6 1890 370,624 12,781 34-5 7,004 18-8 Mean 366,396 11,953 32-6 6,758 18-4 1891 373,985 10,080 27-2 5,003 13-3 1892 374,079 13,055 38-4 5,598 14-9 1893 371,798 15,307 40-9 6,032 ie-2 1894 376,219 10,792 29-0 5,655 14-9 1895 378,041 13,958 37-1 7,509 19-8 1896 374,942 15,843 41-9 8,181 21-8 1897 377,856 11,066 29-5 5,890 15-5 1898 378,872 12,064 31-9 6,507 17-1 1899 379,659 13,222 34-8 4,576 12-0 1900 389,897 13,691 34-8 4,844 12-4 Mean 377,535 12,908 34-5 5,980 15-8 1901 380,212 14,971 40-3 5,612 14-7 1902 383,410 12,716 34-0 4,456 16-6 1903 382,483 15,034 39-9 5,840 15-2 1904 387,395 12,064 32-2 4,333 111 1905 386,128 15,379 40-6 6,764 17-5 1906 383,206 15,118 40-0 5,827 15-2 Mean 383,606 14,214 360 5,472 14-2 174 TABLE II. STATEMENT SHOWING THE DEATHS FROM MALARIA AND FROM ALL CAUSES FOR THE YEARS 1896-1906. Districts. 1896. 1S97. 1898. 1899. 1900. 601 1,982 190 1. Port Louis Malaria All causes .. 1,565 3,184 1,111 2,262 1,394 2,699 789 2,836 802 3,002 Pamplemousses . . . ]\Ialaria All causes .. 1,302 1,966 688 1,110 871 1,282 616 1,319 691 1,346 916 1,626 Riv. clii Rampart ... Malaria All causes .. 598 1,042 308 580 378 674 241 629 219 722 299 839 riacq Malaria All causes .. 1,309 2,065 982 1,572 1,153 1,855 1,002 1,670 1,112 1,961 1,000 1,759 Grand Port Malaria All causes .. 1,007 2,234 915 1,702 691 1,508 625 1,492 690 1,633 823 1,Y51 Savanne Malaria .. All causes ,. 592 1,299 491 974 324 479 374 969 437 992 524 1,231 Plaines Wilhems ... Malaria All causes . 1,012 2,292 783 1,644 944 1,894 346 1,810 384 2,201 351 2,124 Moka Malaria All causes .. 393 1,197 349 787 428 943 231 915 296 1,054 453 1,142 Black River Malaria All causes .. 403 564 263 435 324 460 352 508 416 607 442 685 Port Louis... Pamplemousses Riv. du Rampart Flacq Grand Port Savanne Plaines Wilhems Moka Black River Malaria All causes Malaria All causes Malaria All causes Malaria All causes Malaria AH causes Malaria All causes Malaria All causes Malaria All causes Malaria All causes 1902, 1903. 451 2,428 1904. 378 2,148 1905. igo6. 604 2,543 939 2,926 549 2,416 812 1,509 1,020 1,636 820 1,381 1,084 1,795 985 1,734 243 731 419 940 326 748 498 1,039 531 1,253 811 1,465 1,328 2,121 1,047 1,721 1,557 2,412 1,511 2,401 643 1,538 1,065 2,188 537 1,595 1,090 2,204 643 1,700 368 988 524 1,124 413 976 545 1,212 465 1,156 217 1,957 273 1,950 189 1,684 27; 1,896 292 2,240 352 986 369 976 304 899 427 1,097 479 1,236 406 609 391 631 319 556 350 546 372 638 174' TABLE III. SHOWING THE NUMBER OF PATIENTS WHO HAVE APPLIED FOR TREATMENT AT THE CIVIL HOSPITALS, ASYLUMS, District. Institution. .\ ^ ■' CASES OF MALARIAL FEVER. 1878 1879 1880 i88t 1882 1883 1884 1885 1886 1887 1888 1889 1890 ! 1891 1892 1893 1894 1895 Port Louis ... Civil Hospital Prison Hospital ... Central Dispensary Eastern Suburb Dispensary Western ,, ,, 256 1,467 1,767 1,462 ? 748 1,613 ? - 868 1,934 ? 1,725 1,531 1,874 1,616 ? 3,i41 3,784 ? 3,258 1,652 3,948 1,686 ? 1,214 1,305 ? 1,649 1,641 ? 3,il8 2,439 4,416 1,772 1 ? 1,711 ? ? 2,326 1 3,408 963 '\ 701 1,706 ? 2,934 979 1,649 192 4,459 556 1,66 ? 4,53 44 26 Pamplemousses Long Mountain Hospital ,, „ Dispensary Pamplemousses ,, Terre Rouge ,, 701 874 1,548 ? Riviere du Rempart j7 " Riviere du Rempart Hospital ... ,, „ Dispensary ... Grand Bay Dispensary ... Grand Gaube Dispensary 196 202 188 208 234 200 232 188 140 213 187 204 648 215 362 603 235 270 549 603 24( 47! 37' 59; Flacq Flacq Hospital ... ,, Dispensary , ... ,, . Prison Hospital and 1 Dispensary. | Riviere Seche Dispensary Trou d'Eau Douce Dispensary ... 345 383 252 269 130 348 357 ? 272 50 196 354 39 37 Grand Port Grand Port Public Hospital Mahebourg Dispensary Escalier Dispensary Plaine Magnien Dispensary New Grove Dispensary ... Bois des Amourettes Dispensary 283 285 284 367 412 599 402 553 330 252 359 246 363 382 331 264 459 766 4£ 9£ 64 Savanne Savanne Public Hospital Souillac Dispensary Souillac Prison Hospital and ) Dispensary. f Riviere des Anguilles Dispensary Chemin Grenier and Baie di Cap Dispensary. 169 329 514 1 70 130 397 165 294 77 230 ! 199 693 125 542 148 617 185 380 293 499 278 734 164 459 274 314 321 1 394 1,090 ? 166 230 1,281 ? li 3' 1,1; Black River ...' Petite Riviere Dispensary ,, ... Bambous Dispensary „ ... Case Noyale Dispensary 1,693 1,5S Molia ,, ... Moka Hospital Saint Pierre Dispensary ... Pailles Dispensary 109 76 84 172 243 135 168 27 449 227 99 290 31 182 61 1 50 141 \ 195 24 115 44 207 40 59 186 130 ( li Plaines ^¥ilhenls ... ) J > » Barkly Asylum Hospital... ,, ,, Dispensary Lunatic Asylum Hospital Government Reformatio Hospital Beau Bassin New Central Prison Hospital. Vacoas Dispensary Curepipe Dispensary ■ ■ '\ 456 220 149 2,957 90 179' 135 101 83 109 183 108 72 1 69 55 198 520 235 59 236 245 613 253 80 247 239 748 545 230 102 188 340 170 827 47 32 IC 22 2C 31 91 2,457 2,392 2,813 5,087 4,621 5,805 9,041 7,276 5,036 4,454 7,294 10,944 5,434 10,469 13,282 18,061 17,44 174* TABLE III. SHOWING THE NUMBER OF PATIENTS WHO HAVE APPLIED FOR TREATMENT AT THE CIVIL HOSPITALS, ASYLUMS, AND DISPENSARIES dp MAURITIUS SINCE 1878^ FOR MALARIAL DISEASE. CASES OF MALARIA! FEVER. Total Percentage District. Institution. Means. Cases in to Totals 1878 1879 1880 i88t 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894" 1895 1896 i 1897 1898 1899 I goo igoi 1902 1903 1904 1905 1906 1907 1907. in 1907. Louis ... Civil Hospital 1,462 1,613 1,934 1,531 1,616 3,784 1,652 1,686 1,305 1,641 2,439 ? 1,711 1,706 1,649 1,667 1,266 1,194 1,616 , 1,592 ■ 1,099 1,124 1,301 1,068 909 1,664 1,134 ; 1,019 1,569 6,355 16 Prison Hospital ... 256 ? ? 7 ? ? ? ? ? ? ? ? ? ? ? ? ; 192 ? ? ? 550 1 :;45 272 ? 522 756 520 1,167 2,233 3,254 915 1,009 ? Central Dispensary 1,467 1,767 748 868 1,725 1,874 3,141 3,258 3,948 1,214 1,649 3,il8 4,416 1 2,326 3,408 2,934 4,459 4,537 3,778 2,461 2,133 1 :>39 582 1,174 i 1,412 1,017 846 1,638 1,242 1,168 2,156 3,326 \ 35 Eastern Suburb Dispensary 1 443 1,578 2,282 2,817 2,:>85 349 2,064 3,155 1,415 ? 1,423 2,010 3,454 1,948 9,707 34-6 Western ,, ,, 1,772 963 701 979 556 265 989 2,016 2,308 , "49 1,053 1,806 1,649 1,007 785 1,541 1,141 1,434 1,206 2,874 49-9 lemousses Long Mountain Hospital ,, „ Dispensary 168 433 338 638 213 568 182 910 167 512 222 494 215 ; 592 850 1,284 26 38-5 " Pamplemousses ,, i 178 i 760 1,349 979 668 534 1,089 603 656 791 1,949 33-6 )? Terre Rouge ,, ! 701 874 1,548 ? ? ? ? i 996 766 996 1,183 824 964 692 629 925 1,678 37-5 re du Rempart Riviere du Rempart Hospital ... 196 202 188 208 234 200 232 188 140 213 204 215 235 246 184 197 253 322 182 344 240 249 227 266 178 201 215 1,445 13-9 „ ,, Dispensary 187 648 362 270 472 433 297 332 L48 487 525 257 540 379 477 328 333 381 707 47 Grand Bay Dispensary 549 377 399 258 482 414 518 621 313 607 572 936 740 547 525 1,045 52 " Grand Gaube Dispensary 603 603 593 400 424 828 443 488 1,019 773 626 547 899 732 476 630 1,145 41-5 riacq Hospital ... { 345 252 130 357 272 196 399 201 258 370 274 243 404 338 567 408 446 443 680 341 2,252 30 „ Dispensary 383 269 348 ? 50 354 370 359 326 560 548 459 400 314 219 208 285 193 264 328 470 54 ,, Prison Hospital and ] Dispensary. j I 1 23 17 20 152 !" 86 189 138 Riviere Seche Dispensary 456 308 369 480 518 717 612 659 515 896 73-7 Trou d'Eau Douce Dispensary . . . 353 624 644 B87 739 734 618 613 510 836 678 ? 630 1,412 ? IPort Grand Port Public Hospital 283 285 284 367 412 599 402 553 330 252 359 363 264 459 404 605 468 ! ^416 405 525 55 741 203 588 342 506 403 3,069 16-4 Mahebourg Dispensary ... 382 459 965 715 895 1,003 : 738 709 969 504 1,174 635 1,235 1,042 725 810 1,762 41 Escalier Dispensary 610 1,377 59 882 892 1,006 640 644 516 752 495 386 688 1,206 32 Plaine Magnien Dispensary 647 771 536 608 607 1,064 614 476 665 1,831 26 New Grove Dispensary ... 333 505 321 231 377 316 730 397 363 397 1,459 24-8 Bois des Amourettes Dispensary 246 331 766 647 842 1,006 935 866 829 856 719 900 563 S02 551 548 719 1,868 29 me Savanna Public Hospital 1 130 165 77 199 125 148 185 293 1 278 164 274 321 166 182 129 180 137 122 105 305 92 365 223 299 300 376 : 205 1,310 28 Souillac Dispensary 169 329 514 , 70 397 294 230 693 542 617 380 499 1 734 459 314 394 230 344 194 304 144 200 1 115 790 298 715 637 525 344 518 399 1,327 39 Souillac Prison Hospital and ) i 1 78 160 105 68 102 260 I26 Dispensary. / 41 104 128 131 101 i Riviere des Anguilles Dispensary 1,090 1,281 1,112 1 934 806 579 799 741 882 669 755 689 816 542 624 821 1,249 49-9 ♦ Chemin Grenier and Bale du Cap Dispensary. ? ? ? 1 ' 1 573 535 679 846 950 635 1,326 1,033 1,082 674 592 811 1,651 35-8 River ... ... Petite Riviere Dispensary Bambous Dispensary Case Noyale Dispensary. . . 1,693 1,595 979 643 773 499 513 645 442 331 359 644 307 444 665 137 418 706 274 400 666 314 438 545 228 494 446 356 1 707 573 281 1,162 1,042 1,121 42-5 42-8 31-7 Moka Hospital ... 27 99 31 61 50 24 44 40 59 69 39 88 185 129 124 185 173 213 90 190 133 244 108 1,118 21-9 Saint Pierre Dispensary ... 109 76 84 172 243 135 168 449 227 290 182 141 195 115 207 186 130 156 139 146 260 ' 147 i 134 i 695 344 189 142 339 234 199 208 1,714 10-6 Failles Dispensary ... ...! i i 1 1 865 ? 949 1,141 2,042 827 1,112 1,156 1,889 58-8 :s Wilhems ... Barkly Asylum Hospital... 520 613 545 474 518 584 895 :555 803 897 467 627 499 851 746 822 651 3,940 20-8 ,, ,, ,, Dispensary 235 253 230 327 298 398 512 !304 502 488 399 626 497 697 415 443 414 1,587 28 ,, Lunatic Asylum Hospital 456 220 149 90 179 135 101 83 109 183 108 72 69 55 59 80 102 101 102 184 248 |141 234 312 129 149 106 164 177 154 146 490 31-4 ,, Government Reformatic Hospita 247 188 222 177 186 179 95 136 93 59 124 56 98 91 148 140 116 ? Beau Bassin New Central Prison 340 200 390 596 627 339 425 217 319 295 181 299 229 338 342 1,393 24 Hospital. i ,, Vacoas Dispensary 198 236 239 170 310 250 272 361 |220 180 166 226 493 350 845 1,150 > 1,497 421 3,611 40-9 ,, Curepipe Dispensary 245 748 827 913 969 1,049 503 352 306 473 480 724 473 621 644 25,088 1,032 28,294 647 4,322 23-8 2,457 2,392 2,957 2,813 5,087 4,621 5,805 9,041 7,276 5,036 4,454 7,294 10,944 5,434 10,469 13,282 18,061 17,445 17,629 20,229 21,296 16340 17,834 24,822 22,222 25,231 19,042 31,223 13,464 79,053 35-8 175 TABLE IV.— A. SHOWING THE SPLEEN RATES OF CHILDREN ON SUGAR ESTATES AND FACTORIES, 1907-08 (section 20). District. 1'ample- MOUSSES Riviere DU Rempart. Estate. Flacq. Beau Plan Belle Viie(H) ... Belle VueS.E. Co. L'Esperance Mont Piton Mon Rocher Rosalie ... Rosalie C. Solitude... The Mount 640 1,550 1,510 750 1,200 1,200 992 3,112 1,262 210 ; 949 325 1,180 776 242 501 429 863 631 976 781 238 625] 90' 400; 56-0 30-4 40-7 47-5 25-5 41-8 31-7 45-8 41-8 29-9 37-3 Tennant 515 446 348 73 300 125 379 158 281 Spleens, OW 268 376 348 70 100 95 379 100 261 I 3 1 6 9 115 69 50 34 312 55' 9 315 20! 7 6 22 27 12 9 61 20 11 8 50 21^ 15 9 215 61! 78 25 81 14] 5 Total I with Spleen! "5-43 153 57-1 64 |17-0 33 9-5 48 ,68-6 39 39-0 36 78113 I 45 164 19 34 225 Antoinette Belle Vue(M) ... Beau Sejour and M. Choix. Bon Espoir He d'Ambre A. E. Co. Esperance Labourdonnais ... L'Union (D) L'Union (M) ... Mapoii ... Mon Loisir S. E. Co. Mon Loisir I Mare Seche St. Antoine Schoenfeld (R) 1,900 3,652 2,530 700 2,517 1,824 2,924 1,250 710 1,200 500 1,596 1,085 3,200 1,400 630 350 350 300 50 2,096 1,618 1,572 513 172 1,279 296 1,997 25' 157 200 140 354 328 25-7 23-4 29-9 38-5 35-8 25-8 29-3 27-8 il,997 ,1,207 365 300125 Menage Tennant Menage Tennant 150 , 1,074 28-4 150 219 44-5 ' 50 '1,507 '33-3 , Menage 200 590 I 51-9 I 936 497 458 228 202 139 21 331 719 17 80 79 348 42 20 251 29 . 690 315 408 407 199 199 168 140 498 365 1,010 870 50 32 145 96 117 105 384 384 16 14| 48 17 139 54 1 52 8 45 37 26 3 97 37i 6 3 94 1 69 63! 49 525 i 340 78 77 30-7 9 10 9 14 11 46 13 5, 6 15 121 790 47-4 43-3 19-0 86-2 39-6 39 87 205 60 119 7-8 24-4 50-3 30T 85-0 3-5 1-4 1-3 3-7 2-6 3-0 3-9 1-5 4-8 2-62 1-4 2T 2-6 1-7 5-1 34 9-3 1-3 151 17-4 1-6 15 46-9 3-3 16 16-7 I 1-6 26 24-8 2-2 36 I 94 I 1-5 6 7 7| 11 27, 16 22 13 — 13,945 2,964 541261179 Argy Australia Beau Bois Beau Champ Beau Vallon Belle Rive Belle Vue (A) and Petite Retraile. Bel Etang Constance (A) ... Constance (M) ... Carried forward 6,700 479 750 2,857 1,471 3,500 1,521 922 240 600 450 40 425 400 200 800 300 378 614 198 1,040 2,133 135 562 1,659 1,321 937 31-0? 18-5 38-3 ' 12-5? 43-9 de la Roche ), Lesur de la Roche Lesur 32-4 ?1 de la Roche 36-0 42-2 Lesur de la Roche 55 219 823 40 296 207 228 269 419 248 2,804 27 39T 29 59-2 89 26 2 48 62-3 981 55 102 268 25 99 207 147 86 398 52 9 41 97 126 41 10 11 4 23, 17 31' 25 24-6 2-6 3-9 2-0 4-1 1-97 46 83-7 61 59-8 171 '63-8 15 60-0 1,439 17 30 30 22 82 82-8 78 77, 40| 12 129 61-3 48 58i 35 6 99 67-3 23 24 19 20 63 73-3 74 1II2120' 92 324 81-4 32 12 61 3 21 40-4 429 j504 337 170 1,011 — 4-3 3-2 2-8 26 4-9 3-1 3-3 4-5 4-9 2-5 176 TABLE IV . — A. (continued.) t 4J .2 g Spleens. - ^ District. Estate. ca ■ - ji 1 ri Examiner. IS •S's , Total % '^ 2 Si ii& o".c J3 -A I 3 6 9 with 0.5 tr^ < < — d. HU uw jSpIeer c/Drt <,m Brought forward 2,804 1,439 429 504 337 170 1,011 Flacq Deep R., La 1,947? 300 1,011 : 31-5 Lesur 253 126 77 35| 1£ 127 50-2 3-2 [contd.) Louise and Sebastopol. La Gaiete 1,611 280 1,511 17-5 de la Roche 582 222 82 41 56 43 140 63-1 4-1 > L'Etoile 2,670 418 2,245 24-5 Lesur 668 201 79 56' 56 10 122 60-7 3-3 L'Unite... 1,271 880 806 18-2 de la Roche 216 164 113 25' 16 10 ■ 51 311 2-3 L'Union 945 600 1,059 47-5 „ 311 247 200 241 14 9 47 190 1-8 Olivia 1,201 376 614 40-8 Lesur 222 94 12 25 35 22 82 87-2 5'2 Queen Victoria . . . 3,100 400 1,949 21-6 de la Roche 626 112 57 37 8 10 55 49-1 2-8 La Retraite 1,475 310 — 33-3 ? jj 203 107 54 25 17 11 53 50-4 30 Rich Fund 1,324 700 1,304 32-6 )) 435 37 6 11 8 12 31 83-8 5-2 — — — 30-9 6,067 2,876 1,158 825 582 312 1,719 59-6 3-45 Grand Anse Jonchee 1,609 00 285 43-1 Port Astroea 1,025 600 512 28-4 Chauvin . . 108 59 20 7 20 12 39 66-0 4-6 Beau Vallon 2,769 00- 266 400 1,174 30-9 Guerin 454 19 7 5 3 4 12 '63-2 4-0 Cent Gaulettes ... 1,482 834 23-5 Senneville . . . 302 157 53 31 46 27 104 66-2 4-2 Cluny 2,003 1,000 114 Deux Bras 1,000 700 1,073 16-4 Chauvin 410 210 130 24 39 17 80 380 2-8 Eau Bleu 914 500 to 1,000 330 Ferney ... 3,229 10 1,020 23-3 Guerin 286 24 2 8 8 6 22 91-7 5-3 Gros Bois 2,436 560 787 19-9 Chauvin . . . 195 85 49 9 16 11 36 42-3 3-2 Joli Bois ... 527 750 225 47-4 94 38 34 4 4 10-6 1-2 La Baraque 1,600 600 1,120 23-2 Senneville 233 233 118 28 55 32 115 49-3 3-5 Savinia ... 250 ^^ 488 447 229 74 95 49 218 48-8 5-2 Le Vallon 4,110 20 1,714 18-1 Guerin 442 20 4 5 8 3 16 80-0 '4-7 Men Desert 2,748 200 1,492 31-3 Senneville 446 410 210 91 66 43 200 48-8 3-1 New Grove — 900 952 20-5 Chauvin ... 111 69 55 2 9 3 14 20-3 2-0 Plaisance 2,000 150 1,231 12-4 Senneville 566 566 359 80 97 30 207 36-6 2-6 Riche-en-Eau 2,000 400 1,740 24-4 474 234 72 49 63 50 162 69-2 4-0 Rose Belle 2,858? 900 876 30-0 Sauveterre 653 300 458 17-5 ,^ 124 118 72 20 22 4 46 38-1 2-5 St. Hubert 1,975 650 1,017 29-7 , J 258 242 65 57 70 50 177 73-1 4-6 Union Park 875 1,150 856 13-5 Chauvin . . . 310 128 113 2 9 4 15 11-7 1-6 Union Vale 1,588 200 807 38-5 Guerin 233 21 5 6 5 5 16 76-2 4-7 Virginia 1,200 203 353 24-4 >i 102 20 8 2 5 636 5 355 12 60-0 48-0 4-4 — — — 24-5 — 3,110 1,615 504 1,495 3-25 Savanne Beau Champ 777 125 505 41-9 Ulcoq 187 169 124 20 15 10 45 26-6 2-2 Bel Air 625 225 541 38-8 ), 175 170 87 41 29 13 83 48-8 2-9 Bel Ombre 2,500 100 1,224 34-8 295 269 177 55 29 8 92 34-2 2-2 Benares 1,812 300 977 36-8 , J 308 180 110 42 10 18 70 38-8 2-5 Britannia — 700 1,962 13-7 Chauvin . . . 366 312 287 20 5 25 80 1-2 Chamouny 2,700 450 560 26-3 Ulcoq 217 217 208 2 7 9 4-1 1-3 Combo 996 800 577 28-3 " 165 96 92 3 88 1 57 4 4-2 11 Carried forward — — — — — 1,413 1,085 183 328 — — 177 TABLE IV.— A. (continued.) Dislrict. Savanne (contd. Black River. MOKA Plaines WiLHEMS ^■ Estate. ff < Brought forward Fontenelle Riche Bois 2,000 Riv. des Aiiguilles 571 ! Savannah 2,530 St. Aubin and 2,500 Beau Bois. St. Avoid St. Felix 730 Terracine 1,100 750 125 150 300 800 426 344 1,516 940 1,756 2,774 573 937 1,011 Exi ! 16-9 I Ulcoq 16"5 I Chauvin . 26'6 i Senneville 32"8 I 25-6 1 Ulcoq 27-2 46-4 40-2 28-7 ? Chauvin Ulcoq Spleens. 86 429 326 455 130 188 200 1,413 80 236 268 455 127 188 186 1,085 20 213 147 183' 88 ll! 24 11' 69, 33 432 15 5 111 158 151 11 5 10 20 24: 6 Total I with .Spleen 328 60 23 121 2,953 2,317 334 189 113 23 16 30 35 75-0 9-7 45-1 5-1 12-6 15-9 18-8 636 '21-5 i 1-85 5-3 1-4 2-7 1-2 1-4 1-6 1-6 Albion Medine Tamarin 2,000 , 00 444 1 29-8 2,980 150 885 26-7 5,894 155 1,530 1 42-9 39-5 I Harel 151 324 400 Alma Bel Etang Bonne Veine Cote d'Or iVIelrose ... Minissy . . . Men Desert Pieter Both Valetta ... 8 other Estates 3,221 480 1,215 889 722 2,800 2,542 1,500 1,460 900 1,350 1,200 975 1,140 1,320 1,320 1,420 2,218 1,304 502 974 540 1,102 2,244 1,540 1,367 19-1 30-9 13-7 19-5 3-8 21-5 13-9 24-0 23-4 Leclezio Leclezio Clarenc Leclezio Clarenc 604 219 212 174 296 91 230 317 293 483 86 181 38 173 260 186 95 18-7 800 723 82 168 38 159 247 176 88 704 !l,961 1,874 151 37 51 58 5 114 75-5 324 201 51 42 30 123 36-9 400 140 90 93 77 260 65-0 875 378 192 1 193112 497 56-7 3-9 2-7 4-1 3-56 4 II 2 1 4 6| 0, 7| 4' 2 11 3 1 4 6 23 34 30 7 3-2 4 4-6 13 18-0 14 8-1 13 5-0 10 5-4 7 7-4 19 2-6 87 4-4 1-2 1-4 1-4 1-3 1-2 1-3 1-1 1-23 Bagatelle Bassin Henriette Highlands Reunion ... Stanley and Ebene Trianon . . . 645 1,330 3,000 500 to 1,200 3,200 1,486 2,939 1,362 848 1,400 to 1,700 1,007 925 2,600 1,050 — 382 I23-9 1 Harel 631 39-0 I ,, 353 33-1 726 25-4 512 I 20-8 655 31-4 , Bour 1,463 I 21-3 , Vinson 27 150 173 I I 125 105 222 100 1 93 173 119 125 120 105 105 50 46 105 533 I 533 82 524 1 6i 15 16 23 7 54 3 5 4 - 1,191 1,089 33 35 4 9 23 2 9 34 102 70 31-2 40 80 21-9 1-6 8-6 1-4 2-6 1-2 10 1-2 21 1-1 1-43 Ihe death rates given in this table are averages for the two years ending June, 1907, and are taken from the Reports on Estate Hospitals. The acreage, altitude and population were sent to me separately. In both cases, however, I have not always been able to identify the estates given in various papers, owing to confusion in their names. Many of the examiners gave interesting details about imported cases (see section 20, 6), but these could not be inserted in the tables. 13 178 TABLE IV.— B. SHOWING THE SPLEEN RATES OF CHILDREN IN SCHOOLS, 1907-8 (section 20). ren. Spleens. C V Distiict. School. J Examiner. , ^ '6 12! if) ^ "rt 2i I 3 6 9 ria, 1> a J3 « 39 34 15 5 6 8 19 55-8 4-1 200 165 97 22 16 30 68 41-2 3-2 mousses Road Eastern SuburbGovernment 90 51 28 5 6 12 23 45-1 3-7 „ Girls' 85 49 35 8 3 3 14 28-5 2-1 „ Boys' 84 22 11 3 1 7 11 500 4-0 Nicolay Road Aided 17h> 104 66 14 9 15 38 36-5 2-9 (4) Church of Scotland Aided Total Filles de Marie Convent ... VV 35 22 3 3 7 13 37-1 3-2 ! 87 73 39 16 10 8 34 46-5 3-0 Arsenal St. Aided 134 108 62 23 10 13 46 42-5 2-8 (5) St. Joseph Aided Total Training Government n „ 225 160 137 15 5 3 23 14-3 1-5 171 155 105 22 14 14 50 32-2 2-5 (6) St. Jean Baptiste Total Champ de Lort Girls' n ), 393 286 195 43 24 24 91 31-8 2-3 125 60 44 11 5 16 26-6 1-8 Boys' ... " ...100 31 20 3 5 3 11 35-4 2-8 Bon Secours Convent ...1137 123 98 10 8 7 25 18-?, va (8) Immaculee Conception .. Total Cassis Road Government )I :; ...120 80 66 8 2 4 14 17-5 1-7 203 170 116 30 9 15 i 54 31-7 2-3 Cassis St. Joseph „ „ ...100 62 25 13 9 15 37 '59-6 4-1 Signal Mountain ... ...i ? ^, ...130 59 33 12 6 , 8 26 ;44-0 3-0 Grand River, N.W. ! Total 1 „ 1 80 23 7 6 10 16 69-5 5-0 1 i 1 1 (?) Western Suburb Boys' Total n RosSj Fowler 206 78 40 18 19 1 38 48-7 2-8 — 2,003 ,1,297 305 1 1 179 222 706 35-4 1 2-64 T79 TABLE IV.— B {continued). District. Grand Port School. Rose Belle Government Boys'. Rose Belle Government Girls'. Anse Jonchee Riviere des Creoles Old Grand Port ... L'Escalier Boys' ... ,, Girls' ... MalakoffR.C. Plaine Magnien R.C. Mare d'AIbert Noiwelle France ... PlaineMagnienGovernment Mahebourg Boys' Govern ment. Mahebourg Girls' Govern ment. Mahebourg Girls' R.C. .. „ Boys' Aided .. New Grove R.C ? Total 800 ? ? ? 250 500 1,500 250 900 Masson Savanne . Souillac Convent, Aided ... , , Government Surinam Aided Chemin Grenier, Govern- ment. Grand Bois Bale du Cap Riviere des Anguilles Total 400 Masson Ross, Fowler 144 123 49 51 48 140 68 49 104 125 40 121 101 29 37 22 100 55 27 62 95 37 61 119 73 80 47 68 18 Spleens. Ill , 3 89 6 15 16 11 57 32 19 44 75 35 33 78 51 66 25 54 2 1,152 66 86 58 79 41 59 60 813 :144 116 10 12 14 21 11 43 23 8 18 20 2 28 41 34-5 79 8-2 11-8 48-2 56-7 50-0 43-0 41-8 29-6 29-0 21-1 5-4 45-9 30-1 17-5 46-8 20-6 88-9 339 29-4 1-4 1-5 3-0 3-3 27 2-8 2-2 2-4 2-0 2-0 1-2 3-8 2-S 2-6 1-9 3-3 2-3 5-3 2-30 37 11 10 58 8 12 29 4 12 62 5 8 40 1 21 9 8 53 5 1 449 300 I 43 28 32-7 29 50-0 17 21-5 1 i 2-4 38 67-4 7 11-7 3-1 2-6 3-9 2-0 1-0 4-8 1-4 51 55 149 33-2 2-74 Black I Tamarin Bay River Petite Riviere Cazela Government Case Noyale Total 250 350 Masson 25 55 32 31 17 I 1 29 11 19 5 11 3 7 10 9 16 94-1 5-3 18 62-1 i 3-2 14 '73-7 3-6 8 72-7 3-4 76 20 30 17 I 9 56 73-7 i 3-85 Moka Coted'Or Aided ... St. Pierre Convent Camp Saury R.C. „ Ch. Eng. Moka Government Total 1,200 Castel .1 35 . 31 .' 41 .1 61 .1 95 263 35 31 41 61 95 263 33 29 34 45 68 209 41 2 5-7 2 6-4 7 17-1 16 26-2 27 28-4 54 20-5 1-2 1-1 1-4 1-7 1-9 1-61 i8o TABLE IV.— B ( continued) c Spleens < P] .AINES Wn.HEMS Brown Sequard St. Cure- pipe. 1,800 Castel 181 181 174 1 2 1 ' 7 3-8 1-2 (I) Girls' R.C., Curepipe 151 ' 151 146 4 1 5 3-3 1-1 Boys' ,, „ 130 1 130 123 3 3 i 7 5-4 1-2 Girls' Government, Cure- )) „ 125 ! 125 , 123 2 2 1-6 1-0 (2) pipe. Curepipe Road Aided Total Camp Fouqueraux S.P.Ci. 1,450 71 71 68 3 3 4-2 1-1 658 23 658 1 634 13 6 5 24 3-6 1-15 23 22 1 1 4-3 1-1 (3) , , , , Government Total Camp Mapou, Vacoas 1,400 25 25 22 3 3 12-0 i-y 48 48 44 1 2 4 8-3 1-54 31 31 29 1 1 2 1 6-4 1-3 Glen Park Aided ... ,, 80 80 73 5 2 7 8-7 1-2 La Caverne Aided 87 87 84 2 1 3 3-4 1-1 (4) Vacoas Road Total Phcenix Aided ,, 141 339 141 134 3 3 1 7 1 4-9 ) 1-2 339 320 11 6 2 19 5-6 1-20 39 39 34 3 2 5 12-8 1-4 St. Paul's Convent Ross, Fowler 109 44 30 7 4 3 14 31-9 2-8 (5) Phcenix (Police Station) ... Total Quatre Bornes Government 1,050 Castel 33 33 17 6 2 ' 16 48-4 3-6 — 116 81 16 8 11 35 301 2-38 91 91 72 8 6 5 19 !20-8 1-9 Belle Rose Avenue jj ,, 55 55 50 5 5 9T 1-2 (6) „ Convent Total Rose Hill, Labs. St. 950 ,, 40 40 1 39 1 1 2-5 1-1 186 186 161 13 7 5 25 13-4 1-54 65 65 62 3 3 ' 4-6 1-1 Edward VII. St. jj ,, 55 ; 55 54 1 1 ' 1-8 10 ,, Cli. Eng. Aided )) 70 70 66 3 1 4 5-7 1-2 ,, Mahomed an 98 98 97 1 1 1-0 1-0 Aided. Rose Hill Government jj ,, 75 75 72 2 1 3 40 1-2 „ St. Enfant Jesus n 166 166 156 7 3 10 60 1-2 (7) R.C. Aided ... Total Beau Bassin Ch. Eng. 5) 750 ICO 100 96 3 1 4 4-0 1-1 629 629 603 20 5 1 26 ' 4-1 112 34 34 33 1 1 2-9 VI ,, Convent Ch. 58 58 54 3 1 4 6-9 V2 ,, Guslav Colin St. 72 72 64 5 1 2 8 11-1 1-4 ,, Girls' and Boys' Total Total ») ), ■**• 105 105 100 5 5 4-7 1-1 269 269 251 14 1 3 18 6-7 1-22 — 2,245 2,094 1 8B 33 J30 151 6-7 1-26 Ibl TABLE IV.— C. SHOWING THE SPLEEN RATES OF CHILDREN EXAMINED IN VARIOUS LOCALITIES, 1907-8 (section 20). V ■5 . ' ^'i \ Spleens. L. a, 2«j District. Locality. •3^^ h-xaminer r:^ £ , Total — n >"5. < "1 ' 3 6 9 with crt-^ <:« spleen. Pample- Terre Rouge School and 100 Milne. 206 61 59 48 38 145 66-5 4-2;' MOUSsEi. Village. Pamplemousses School and 200 1 186 58 18 49 61 128 68-8 5-1 Village. 1 Calebasses Village 200 ' 116 22 26 291 39 94 810 5-4 Belle Vue Harel Estate 350 100 88 10 2I 12 12-0 1-3 Long Motintain School and 500 194 82 45 34 33 112 57-7 3-7 Village. ' Riviere du Poudre d'Or School and 50 150 39 34 32 45 111 1 74 4-9 Rempart. Village. Riv. du Rempart School and 150 ' 208 115 32 37 24 93 44-7 3-1 Village. L'Esperance Estate ... 200 174 125 28 12 9 49 28-1 21 Beau Sejour Estate ... 400 100 77 8 8 7 23 23-0 21 Mont Piton Camp 650 100 65 18 14 3 35 35-0 2-3 Klacq. Trou d'Eau Douce School and Village. 50 185 67 49 42 27 118 63-8 3-8 Post of Flacq School and 50 1 162 20 31 39 72 142 87-6 61 Village. i Constance d'A. Estate 100 166 7 41 18 100 159 95-7 7-5 Beau Champ Estate 100 ■ 202 33 49 50 70 169 83-7 5-5 Centre of Flacq School and 150 " 237 25 33 86 93 212 89-4 6-2 Village. Riviere Seche School and 200 „ 202 21 67 46 68 ISl 89-6 5-8 Village. Olivia Estate 350 113 17 25 36 35 96 84-9 4-7 St. Julien Village 1 450 1£0 126 10 5 9 24 16-0 1-8 Rich Fund Estate 1 600 ^ „ 151; 122 15 6 8 29 192 1-8 Sebastopol Village 650 150 117 20 7 6 33 220 1-8 MOKA. Failles Village 200 162 1 29 34 46 53 133 821 6-0 Montagne Blanche School and 900 ■ „ 150 1 137 8 4 1 13 86 1-3 Village. Sans Sonci Estate 950 „ ! 200 1 178 17 2 3 22 11-0 1-2 Quartier Militaire Village ... 1,350 ; 143 129 3,907 1,768 8 677 5 657 1 805 14 2,139 9-7 54-7 1-3 3-83 Grand Port. Nouvelle France Village ... 1,500 Masson 61 60 1 1 1-6 11 Pl. Wilhems. Tintamaree (?) ? n 47 45 1 1 2 4-3 1-2 Black River. Flic-en-Flac Village 40 9 6 15 10 31 77-5 5-2 Bambous School 400 J, 73 32 15 14 12 41 56-1 3-8 Anna Estate ... Carried forward ? 5» -.J9 22 7 29 6 4 17 43-6 2-9 260 168 36 27 92 I82 TABLE IV.— C {continued). V Examiner. Si Spleens. g J Si . District. Locality. < T 3 6 9 Total with II W spleen. Brought forward 260 168 29 36 27 92 Pl. Wilhems. Phosnix, collected children ... 1,350 Ross, Fowler 27-12-07. 163 74 37 46 6 89 55-3 3-16 Do. House to House in 1,350 Ross, Fowler 339 98 104 82 55 241 71-1 4-12 1 19 Houses. Feb. 1908. Highlands Estate 1,400 Ross, Fowler 7-12-07. 50 47 1 2 3 6-0 1-36 Phcenix along Curepipe Road 1,450 38 36 2 2 52 1-10 Le Reduit — Ross 58 55 1 1 1 3 5-1 1-26 Port Louis. Men's Training Government School. Ross, Fowler 169 102 43 17 7 67 39-6 2-34 Savanne. St. Felix Estate 400 }j 30 24 3 1 2 6 200 1-9 Pample- Beau Plan Estate 200 5) 26 4 16 5 1 22 84-6 3-5 MOUSSES. 1,133 608 236 188 101 525 46-3 2-96 Miscellaneous Curepipe 1,800 )) 107 106 _ _ _ 1 0-9 _ Curepipe to Phcenix Road ... 1,700- 1,400 1,350 )' 130 124 — — — 6 4-6 — La Caverne )J 104 104 Henrietta 1,600 62 59 — — — 3 4-8 — Solferino 1,200 ») 51 43 — — — 8 15-7 — La Louise 1,100 )) 63 51 — — — 12 190 — West of Rose Hill . 700 )) 36 30 — — — 6 16-6 — Moka 1,200 )1 62 59 — — — 3 4-8 — Camp Fouquereaux . 1,450 )) 26 26 — — — — — Petite Riviere 200 )) 62 23 — — — . 39 62-4 — Tranquebar 50 » 32 — — — 32 1000 — Port Louis 41 19 — — — 22 53-6 — , Road to Arsenal 100 5> 109 72 716 — — — 37 169 33-9 190 — 885 — i83 TABLE IV.— D. SUMMARY OF SPLEEN RATES (section 20). ■0 E Spleens a 5Pc Total ^Ji 2 S I 3 6 9 "^^ "a uw spleen.