li^iyjylLii'.^ UL^U \i'^ li oU THE PREVENTION OF MALARIA PRESENTED TO HIS MAJESTY THE KING BY HER ROYAL HIGHNESS PRINCESS CHRISTIAN Honorary President Liverpool School of Tropical Medicine THE PREVENTION OF MALARIA BY RONALD ROSS, D.P.H., F.R.C.S., D.Sc, LL.D., F.R.S., C.B. NOBEL LAUREATE WITH CONTRIBUTIONS BY Professor L. O. HOWARD, United States Colonel W. C. GORGAS, Panama Mr J. A. LE PRINCE, Panama Sir R. BOYCE, West Indies Dr W. T. PROUT, Jamaica Dr H. WOLFERSTAN THOMAS, Amazon Region Dr OSWALDO CRUZ, South Brazil Dr IAN MACDONALD, Spain Professor A. CELLI, Italy Professor C. SAVAS, Greece Professor C. SCHILLING, German Possessions Dr ED. SERGENT, French Possessions Mr H. C. ROSS, Egypt Dr a. BALFOUR, Khartum Dr L. BOSTOCK, South Africa Dr P. MURISON, Durban Dr M. WATSON, Malay States Professor T. TAKAKI, Formosa Colonel C. H. MELVILLE, Troops in War Major C. E. P. FOWLER, Troops in Peace WITH MANY ILLUSTRATIONS NEW YORK E. P. BUTTON & COMPANY 1910 ?UBLI : HEALTH . LIBRARY PREFACE Malarial fever is perhaps the most important of human diseases. Though it is not often directly fatal, its wide prevalence in almost all warm climates produces in the aggregate an enormous amount of sickness and mortality. In India alone it has been officially estimated to cause a mean annual death-rate of five per thousand ; that is, to kill every year on the average 1,130,000 persons — a population equal to that of a great city. This is more than the mortality of plague at its height or of cholera and dysentery combined. The total amount of sickness due to it is incalculable, but may be put by a rough estimate at between a quarter and a half the total sickness in many tropical countries. Often all the children and most of the adults are infected by it. Unlike many epidemic diseases it is not transient, but remains for ever in the areas which it has once invaded. It tends to abound most in the most fertile countries, and at the season most suitable for agricul- ture. Very malarious places cannot be prosperous : the wealthy shun them ; those who remain are too sickly for hard work; and such localities often end by being deserted by all save a' few miserable inhabitants. Malaria is the great enemy of the explorer, the missionary, the planter, the merchant, the farmer, the soldier, the vii 215031 viii PREFACE administrator, the villager and the poor ; and has, I believe, profoundly modified the world's history by tending to render the whole of the tropics comparatively unsuitable for the full development of civilisation. It is essentially a political disease — one which affects the wel- fare of whole countries ; and the prevention of it should therefore be an important branch of public adminis- tration. For the State as for the individual, health is the first postulate of prosperity. And prosperity should be the first object of scientific government. Fortunately, as often remarked, malaria is of all diseases the one regarding which we possess perhaps the fullest knowledge. We know the cause of it and the manner in which it is spread. We know a specific cure for it, and several efficient methods of prevention. It is our own fault then if we do not reduce it as much as possible. The literature of the subject dates back for more than two thousand years. To write a complete book on malaria, including references to all that has been worthily said or done in connection with it, would be a gigantic task. The history, the symptoms, the pathology and the treatment would fill several volumes ; a long essay could be written on the parasites ; an entomological work on their carriers ; and a full account of the laws of diffusion, of the local distribution, of the preventive measures, and of the numerous preventive campaigns which have been conducted since the time of the ancients, would of itself occupy many hundreds of pages. But the task would be largely an unnecessary one, because we already possess many good books on PREFACE ix the medical, parasitological and entomological aspects of the subject. Regarding prevention, however, especially in the light of the great developments which followed the discoveries of twelve years ago, there is much need for yet another work. Though certainly based upon biological knowledge, this part of the subject presents also its own problems for solution. The diffusion of disease is a theme which requires exact, and indeed mathematical analysis ; and the art of controlling it belongs, not only to the medical man, the parasitologist and the entomologist, but even more to the experienced hygienist, the engineer, the administrative officer and the statesman. On considering how best to meet the demand, I concluded that the only satisfactory way was to collect in one volume the thoughts and observations of the able men who have themselves worked in this laborious field, or who are in the best position to furnish the required information ; and my warmest thanks are due to those who have given me so much of their valuable time and labour. My own part consisted merely in attempting to compile a preliminary analysis of the general problems and difficulties before us. Some readers will perhaps be surprised when they fail to find in a book on the prevention of malaria any description either of the parasites and their carriers, or of the necessary technique. But in these days almost every medical man in the tropics, at least any one likely to be entrusted with the charge of anti-malaria work, is sure to be already familiar with these details. More- X PREFACE over, the present volume should be written largely for the use of readers who are neither medical men nor zoologists, but who may be called upon to deal with the administrative side of the subject ; and minute technicalities would be as useless to them as they would be superfluous to the trained biologist. I have there- fore determined to limit myself to matters which will, I hope, be useful to the advanced student without being unintelligible to any educated reader — that is, to a logical consideration of the broader (and often more neglected) principles of the subject. An historical introduction is always necessary to give coherence to ideas ; and I have taken the opportunity to write as complete and accurate a one as my space and knowledge permit of. The summary of facts which follows (taken from my report on Mauritius) may be useful in propagandism ; the experimental inoculations of men by means of blood drawn from patients or of infected Anophelines have been collected with care because of their fundamental importance in the modern theory of malaria ; and I trust that these three first chapters will suffice to convince the busy layman that this theory has been based upon something more than mere conjecture. In the chapters on the parasitic invasion of the individual and of the community, I have departed con- siderably from medical custom by laying much stress upon quantitative, or rather enumerative, ideas. We should distinguish between subscience, the mere study of objects, and science, the study of causes. Measure- ment is the very basis of science ; and the neglect of PREFACE xi it and of logical deductions founded upon it are too common in biology. It is scarcely true to say that malarial fever is caused by a parasite and propagated by a mosquito : it can be caused only by many parasites and widely propagated only by many mosquitos. The how much and the how many are at least as important as the bare facts. I am convinced that if more exact results are desired, pathology must in the future tend more toward exact enumerative methods. As for epidemiology, it is principally a mathematical subject — the route of infection being given, the rate of in- fection depends upon laws like those which govern the diffusion of gases or heat ; and ignorance of this has led to many wild statements regarding the spread and prevention of malaria. But the subject has yet to be developed, and Chapter V can approach it only in an elementary manner. Chapter VI is abbreviated owing to the details contained in the following one, to which it is largely introductory. The contributions in Chapter VII are arranged geographically, as far as possible, and have been printed in the authors' words without modification. A useful index has been found impracticable ; but a detailed table of contents is given at the end of the volume. The omission of several important matters must be explained and apologised for. Some good campaigns have been left undescribed because I could not find reporters for them and failed in obtaining otherwise all the necessary particulars regarding them ; not in any way because they should not have been included. A chapter on the local distribution and cost of malaria xii PREFACE would have been useful, and was attempted. The older books contain much on the former point ; but the information given was based upon evidence which would scarcely satisfy us to-day, and accurate details could not be obtained without such long enquiry that I was forced to abandon the project entirely. Lastly, refer- ences to much good literature have been omitted or curtailed — not because such literature is of secondary importance, but because the object of the book is to present a general discussion of particular points rather than a complete record of all the known facts and hypotheses. But there is another reason for these omissions. Owing to grants recently given by the Advisory Committee for the Tropical Diseases' Re- search Fund (collected by the British Colonial Office), we are now preparing in Liverpool, not only for new researches, but for an exhaustive descriptive biblio- graphy of malaria, in which, I trust, all the literature both of general and of local interest will be collated and compared. Indeed before long the whole of this immense subject will perhaps be dealt with in the only adequate manner possible — that is, by a special Bureau appointed for the study of it ; and this book is intended to be a necessary preliminary to that work. I hope that most of the matter contained in it will be of use to any one who proposes to undertake a genuine campaign against malaria. For this purpose we require a knowledge, not only of biological technics and of the various possible preventive measures, but also of the broad principles of sanitary statesmanship. The pre- vention of malaria on a large scale is a great economical PREFACE xiii as well as a great humanitarian undertaking. A genuine campaign does not consist merely in the formation of inexpert committees, the passing of ordinances for the screening of water-butts, and the issue of wise advice to the public. To be permanently and economically successful, it must always be a permanent concern of the State, requiring careful measurements of the amount of sickness present, a nice appreciation of the measures most suitable for the locality, exact estimates of their cost compared with the cost of the disease, a well- considered organisation, and, above all, a fixed deter- mination to succeed. The world requires at least ten years to understand a new idea, however important or simple it may be. The mosquito theorem of malaria was at first ridiculed, and its application to the saving of human life treated with neglect, jealousy and opposition. But now, owing to the labours of many of those who have contributed to this volume, and of all of those who have so long and so patiently studied the subject, we are assured of final success. To them and to the memory of them this book is dedicated ; but we must not rest content until the principles so well established by them are followed in every civilised country of the world. I hope, too, that mosquito reduction will before long be undertaken in most of the towns in the tropics, whether they are malarious or not. RONALD ROSS. University of Liverpool \st June igio. CONTENTS CHAP I. HISTORY Section I. 2. )> 3- )) 4- Ancient Times .... Early Modern Times Discovery of the Parasites Speculations regarding the Mode of Infection 5. Researches regarding the Mode of Infection 6. Confirmations and Extensions . 7. Recent History of Prevention 8. Remarks ..... SUMMARY OF FACTS REGARDING MALARIA {Suitable for Public Instruction) Section 9. The Parasites and the Fever „ 10. The Mode of Infection . „ II. Facts about Mosquitos . „ 12. Personal Prevention ,, 13. Public Prevention III. THE FUNDAMENTAL OBSERVATIONS AND EXPERIMENTS Section 14. The Parasites cause the Disease „ 15. Experimental Blood Inoculations „ 16. The Parasites develop in Certain Mosquitos „ 17. Experimental Mosquito Inoculations IV. THE PARASITIC INVASION IN MAN . Section 18. The Onset of the Invasion „ 19. The Further Progress of the Invasion . „ 20. The Decline of the Invasion „ 21. Average Duration of Untreated Infections „ 22. Enlargement of the Spleen and Liver . „ 23. The Effect of Quinine ,, 24. Summary ..... XV PAGE I I 6 8 10 20 26 29 43 49 49 54 / 58/ 60 62 62 66 76 . 77 86 86 98 104 122 127 134 143 CONTENTS Section 25. )) 26 ?i 27 of CHAP. V. MALARIA IN THE COMMUNITY . . . . Is the Infection caused otherwise than by Anophelines ? . Some Definitions Conditions required for the Production New Infections in a Locality 28. Laws which Regulate the Amount of Malaria in a Locality .... 29. Laws which Regulate the Number of Ano phelines in a Locality 30. Explanation of Various Phenomena 31. The Measurement of Malaria 32. The Mortality and Cost of Malaria PAGE 145 VI. PREVENTION ...... Section 33. List of the Possible Preventive Measures V for 34. Protection against the Bites of Mosquitos 35. Mosquito-reduction 36. Prevention by Treatment 37. Selection of Measures Domestic Prophylaxis 38. General Sanitary Axioms 39. Selection of Measures for Public 40. Conduct of the Campaign VII. SPECIAL CONTRIBUTIONS Personal and Prevention No. of Section. Contributor. Country. 41 Professor Howard United States , 42 Colonel Gorgas Panama V 43 Mr Le Prince Panama 44 Sir Rubert Boyce West Indies . 45 Dr Prout Jamaica 46 Dr Wolferstan Thomas Amazon Region 47 Dr Oswaldo Cruz South Brazil . 48 Dr MacDonald Spain . 49 Professor Celli Italy . 50 Prof. Dr Savas Greece 51 Prof. Dr Schilling German Possessions 52 Dr Sergent French Possessions 53 Mr H. C. Ross Egypt . 54 Dr Balfour Khartoum CONTENTS xvii No. of Section. Contributor Country PAGE 55 Dr Bostock South Africa 543 56 Dr Murison Durban . 549 57 Dr Watson Malay States 554 58 Professor Takaki Japan 563 59 Professor R. Ross Other Countries . 568 60 Colonel Melville Troops in War . 577 61 Major Fowler Troops in Peace 600 ADDENDA .... 621 62 Suggested Terminology for the Phenomena of Cytogenesis 621 63 Notes on the Malaria-bearing Anophelines . 622 64 Examples of Legislation 636 65 Notes .... 638 REFERENCES 645 CONTENTS IN DETAIL . 664 LIST OF ILLUSTRATIONS NET FOR MEASURING THE OUTPUT OF MOSQUITOS FROM A MARSH — CLAIRFOND, MAURITIUS. BANKS OF A STREAM ROUGH-TRAINED FOR RS.O-37 A RUNNING FOOT FOR BOTH BANKS (MAURITIUS). . To face page l66 PLAN OF VACOAS CAMP AND CLAIRFOND MARSHES . To face page l88 FIG. I. SS. VINCENT. PART SECTION OF SHIP SHOWING MOSQUITO PROTECTION TO DOORS AND PORTS. „ 2. SKETCH SHOWING MOSQUITO PROTECTION FOR DOORS, VENTILATORS AND PORTS. SS. VINCENT. DOOR, PORT AND VENTILATOR. „ 3. METHOD OF ATTACHING WIRE-GAUZE SCREEN TO FRAMES. „ 4. DOORS AND PORTS. „ 5. BOAT DECK — POOP AND BRIDGE DECK. „ 6. MAIN DECK To face page 388 TABLE 3. RESULTADOS DA CAMPANHA ANTI-PALUDICA NO XEREM To face page 398 BANKS OF THE ILISSOS, ATHENS, UNTRAINED. BY DR CARDAMATIS. BANKS OF THE ILISSOS, TRAINED. BY DR CARDAMATIS. To face page i^^O FIG. I. F. C. MAILLOT. „ 2. PETROLAGE D'UNE MARE, GITE A ANOPHELINES. „ 3. RECHERCHE ET PETROLAGE DES GITES A ANOPHELINES. „ 4. GITE A ANOPHELINE DANS UNE OASIS SAHARIENNE. „ 5. MAISON PROTEGEE PAR DES GRILLAGES, CONTRE LES MOUSTIQUES. „ 6. DEFENSE M^CANIQUE (PORTES ET FENETRES GRILLAGEES). „ 7. EXAMINATION OF CHILDREN. „ 8. SAMPLE CHART FOR PUBLIC INSTRUCTION . To face page 480 xix XX LIST OF ILLUSTRATIONS FIG. I. AN EXCELLENT TYPE OF MOSQUITO - PROOF HOUSE AS BUILT BY THE TRANSVAAL GOVERNMENT. „ 2. AN EXAMPLE OF ROUGH BUT EFFICIENT MOSQUITO PROOFING IN THE VELDT. „ 3. AN INGENIOUS IDEA. „ 4. A GOOD EXAMPLE OF MOSQUITO-PROOF HOUSE. „ 5. JOINT OFFICES OF THE WITWATERSRAND NATIVE LABOUR ASSOCIATION, AND THE PORTUGUESE DEPARTMENT OF EMIGRATION AT RESSANE GARCIA, PORTUGUESE EAST AFRICA. „ 6. ACTUAL BREEDING - PLACES OF ANOPHELINE MOSQUITOS ON THE CROCODILE RIVER, EASTERN TRANSVAAL. „ 7. COMFORT WITH SAFETY. „ 8. ACTUAL BREEDING - PLACES OF ANOPHELINE MOSQUITOS IN THE EASTERN TRANSVAAL. To face page 544 1. PORT LOUIS, MAURITIUS, BARRACKS AND HUTS. 2. THE CAUSE OF THE MALARIA AMONGST THE TROOPS IN THE HUTS. 3. ANOPHELINE BREEDING-GROUND IN A COLONIAL CANTONMENT (MAURITIUS). 4. PART OF AN OLD FRENCH FORTIFICATION AND . MOAT NEAR PORT LOUIS, MAURITIUS. 5. COOLIES "ROUGH TRAINING" A STREAM. THE SAME FINISHED. 6. INDIAN VILLAGE IN THE MIDDLE OF A MARSH (CLAIRFOND, MAURITIUS). 7. A NATIVE HUT IN THE SAME VILLAGE. 8. CLAIRFOND MARSH IN MAURITIUS, WITH VILLAGE NEAR BY To face page 6zo THE PREVENTION OF MALARIA CHAPTER I HISTORY 1. Ancient Times. — Dr Richard Caton has kindly tried to ascertain for me whether there are any distinct references to malaria in the ancient Egyptian writings ; but informs me that he knows of none in the medical papyri or temple inscriptions, and that Dr J. H. Walker confirms this state- ment. It should be noted that Strabo (first century B.C.) observed that Alexandria, in spite of marshes in the neighbour- hood, was free from malaria in his time ; and even at the present day the disease does not abound in Egypt as much as might be expected. In Greece and Italy, however, malaria has been well known for more than two thousand years ; and Greek and Italian authors have collected many references to it in old writings. Recently Mr W. H. S. Jones has given us a laborious and exhaustive study of the subject made in the light of our present knowledge [1907, 1909]. The first-named authors have always taught that the disease was very prevalent in those countries from the first ; but Mr Jones, following a tentative suggestion of mine, gives many reasons in favour of the view that it may have entered them from without during historical times, and may subsequently have exerted considerable influence upon their civilisation. Thus, there are few references to it in the earliest literature, A 2 HISTORY [Sect. but many in later writings. Homer (say iioo B.C.) mentions what might be malaria, but only once {Iliad, xxi. 31); and Hesiod (say 735 B.C.), though he lived at Orchomenos on the shore of Lake Kopais, now intensely malarious,^ and dealt with rural subjects, makes no clear reference to it. Theognis (say 550 B.C.) probably mentions it, and Heroditus (494 B.C.) possibly so. Jones infers from the medical writings attributed to Hippocrates that paludism was known in the medical schools before his birth (about 460 B.C.) ; and from the Wasps of Aristophanes (425 B.C.) that it " was attracting particular attention at Athens " at that time. About 429-400 B.C. the Athenians erected on the Acropolis a statue to Athena Hygieia, and introduced the worship of Asclepius, tending to show that " ill health was distinctly on the increase " ; and after this "references to fevers became much more numerous," and malaria probably very common in Greece. He describes accurately and fully the effect which this must have had on its civilisation. Apart from the literature, I am strongly of the opinion, based upon many considerations, that malaria could scarcely have been very rife in Greece before the height of its prosperity. The people were too vigorous and warlike. The gymnastic training of youths could scarcely have been possible if enlarge- ment of the spleen had been very prevalent. The figures on the tombstones, though evidently idealised, do not suggest to my own medical apprehension anything resembling a malarious race ; and the open-air life and ceremonies do not suggest a malarious country. The ancient flourishing population round Lake Kopais, for example, would have been simply impossible if the disease had been as rife then as it is now. It is now very rife there and in most of the Grecian villages ; and there must have been a time when the change took place. Quite possibly it was introduced about the fifth century before 1 In 1906 I found that twenty out of forty children at Orchomenos were suffering from enlarged spleen in June, that is before the malaria season. i] ANCIENT TIMES 3 Christ by soldiers or slaves from abroad, as it was certainly introduced into Mauritius in 1866 (section 30(21)). Spreading gradually up the valleys, it would have tended to destroy rural prosperity, to drive the people into the healthier towns (as in Mauritius), and, assisted by other causes, to sap the vigour and physique of the race [Ross, 1906]. It is well known that the ancient Greeks recognised the quartan, tertian, quotidian and semitertian (probably malignant tertian) varieties of paludism, and many of its accidents ; and were acquainted with its seasonal and local variability, and, above all, with its frequent prevalence near marshes. This last point is most germane to our present part of the subject. Thus there is an old story that Empedocles of Agrigentum (say 550 B.C.) "delivered Selinus (in Sicily) from a plague by draining its marshes, or by turning two rivers into them " — that he was able, as Matthew Arnold says, to " Cleanse to sweet airs the breath of poisonous streams." Doubt has of course been thrown on the story ; but whether it is true or not matters little. The mere fact that such a tale was told proves that the Greeks, even at an early date, had become in some way aware that marshes tend to generate sickness, and, still more important, that by drainage or other treatment this may be prevented. There are many passages connecting malaria with marshes. Thus as already stated Strabo (first century B.C.) says that Alexandria, in spite of its site, was free from marsh-fever even in his time. "It is to be inferred from this," Mr Jones says, " that damp places were generally known to be unhealthy, so that exceptions to the rule were noticed by observers as remarkable phenomena." Hippocrates (Airs, Waters, Places) noticed that those who live in low, meadowy and hot districts tend to be neither tall or well-built, but stout, fleshy, dark-haired, dark-coloured, bilious, and wanting in courage and endurance. For ancient Italy we have a similar theory, namely, that 4 HISTORY [Sect. references to paludism are scanty in the earlier writers, but very abundant in the later ones. Mr Jones notices, both for Greece and Italy, that many of the most ancient settlements appear to have been made on sites which are now pestilential — suggesting that they were not so unhealthy when they were first selected. Professor R. C. Bosanquet tells me that some of the oldest settlements in Crete, made during the wonderful ancient civilisation of that country thousands of years before Christ, were situated at spots which are now intensely malarious. Many areas round Rome, now scarcely habitable, were the homes of great and prosperous peoples in the prehistoric period, and were later full of the country villas of rich Romans.^ Those who consider that malaria was always very prevalent in ancient Greece and Rome cite legends such as that of the destruction of the Lernean Hydra by Hercules — the Hydra being supposed to be symbolic of malaria. Lerna is a marshy district in Greece, and the Hydra was fabled to inhabit the marshes and to ravage the country round it. It is possible, however, that the fable refers merely to the drainage of the swamps for agricultural purposes. In Italy there was a vast and very old system of soil-drainage by cuniculi^ probably constructed by the Etruscans ; and some have suggested that this drainage was carried out against malaria, and that it enabled the ancients to build villas at spots now deadly. Here, again, the object of the drainage was more probably agricultural. I should like to believe that it was a sanitary drainage, but find difficulty in doing so. Drainage against malaria must obviously be an urban and not a rural measure. The cost of draining all the country round Rome merely for sanitary purposes would have depleted the sanitary budget even of the logical ancients. Mr Jones's view appears the more probable — namely that the disease was possibly introduced at the time of the first foreign expansions, both in Greece and Italy, and that it gradually became intensified owing to the ^ See also F. Genovese [1909]. i] ANCIENT TIMES 5 causes described in sections 30 (20). North [1896] ascribes the intensification to rural depopulation — due to wars or to economical changes. I think it more probable that the malaria produced, or helped to produce, the rural depopulation ; and we now have the living picture of the process before our eyes in Mauritius. Possibly also the disease has always had a tendency to eliminate or repel the fair strain of blood from the north, leaving the darker southern strains predominant. But the effect in Italy was probably less than in Greece, owing to the much smaller proportion of malarious area in the former. Of course the Roman writers, both medical and non-medical, were acquainted with the leading facts about paludism mentioned above. The erudite Varro (116-28 B.C.) says in his Renan Riisticamm, " Animadvertendum etiam si quo erunt loca palustria, et propter easdem causas, et quod crescunt animalia quaedam minuta, quae non possunt oculi consequi, et per aera intus in corpus, per os ac nares perveniunt atque difficiles efficiunt morbos" — that in marshes there are animals too small to be seen, but which enter the mouth and nostrils and cause troublesome diseases. Other famous passages are from Columella (about the first century B.C.), who says that bogs breed insects armed with stings, and pestilent swimming and creeping things, from which come obscure diseases. Here we have malaria connected not only with the marsh, but with insects or germs bred in the marsh. Cicero and Seneca say that paludism depopulated certain districts. Mr Robert Gladstone and Mr Jones have kindly called my attention to several passages referring to mosquito nets, called conopeuni by the Romans, after the Greeks (our word canopy). Herodotus first noted with surprise the use of them in Egypt ; and they are referred to later in Varro {^De Re Riistica 2, 10, 8), Horace {Epodes, 9, 16), Propertius (3, 11, 45), Juvenal (6, 80), and Paulus Silentiarius {A7tihologia Palatind). Horace says, "And among the military standards, oh, shame ! the sun sees a 6 HISTORY [Sect. mosquito curtain ; " and Propertius calls these nets foeda (foul or disgraceful). Evidently the ancients felt towards them as do many of our own more manly colonists who prefer annoy- ance and even sickness to disgrace ! But Paulus Silentiarius thought that they were useful for a post-prandial siesta in order to save the slaves the trouble of using a fly-flapper. Varro said that women, lately confined, spent a number of days in them ; and Juvenal said that they were used to cover the cradles of the rich and noble. On the 6th February 1905, Sir Henry Blake, Governor of Ceylon, called the attention of the Ceylon Branch of the Royal Asiatic Society to the fact that certain ancient Sinhalese writers, who lived certainly more than 1400 years ago, had connected fever with mosquitos. The original authority appears to be Susruta, in the chapter on Insects which forms the last chapter of his book on Poisons. He says that there are five kinds of mosquitos, one of which " produces the same symptoms as deadly insects." J. Jolly, however, discussed the subject [1905], and thinks that Susruta was merely referring to the irritation caused by the bites. He attributed malaria, J. Jolly says, to derangement of the humours. Personally, so far as I can judge, I doubt whether these writers ever really connected malaria, even in imagination, with the insects.^ 2, Early Modern Times. — Little was added to our know- ledge during the next thousand years ; but about 1640 the inestimable boon of Cinchona bark was introduced into Europe. The Countess d'El Cinchon, wife of the Viceroy of Peru, had been cured of fever by means of it in that country, where it had been discovered by the Indians near Loxa (?) ; and she was wise enough to send it home to Europe. The use of it, after many checks, gradually spread ; and in 1820 Pelletier ^ I can ascertain little about malaria in early days in America ; but according to a suggestive paper by O. Effertz, the disease was probably introduced there from Europe, just as the converse happened with syphilis [1909]. 2] EARLY MODERN TIMES 7 and Caventou extracted the alkaloid quinine from it. But the discovery of this specific has not only proved to be a blessing for the treatment of untold millions of human beings, but also enabled Morton [1697] and Torti [1753] to separate the malarial fevers, which are cured by it, from those upon which it has no influence, and by this means to differentiate and study the symptoms of the former. Morton also recalled the old hypothesis of the marsh ; and this was amplified by Lancisi, who repeated the views of Varro and Columella in greater detail in his book De noxiis paluduni effluviis. He stated that fevers disappear after drainage, and attributed the poison either to inorganic or organic emanations from the marsh. He studied mosquitos, and even suggested inoculation by them as a possible means of infection — though he also thought that their larvae foul drinking water [17 17]. It is now apparent that the world had been gradually becoming aware during centuries of the paludic nature of malarial fever, not by direct experiment or even by investiga- tion, but by a kind of subconscious experience based on public observations. In Italy especially, where of all civilised countries the disease was most prevalent, this process was most apparent — so much so that, as North describes [1896], the peasantry can often tell at sight which localities are likely to be " malarious." More than this, by similar general observation, the good effect of assainment of marshes had become equally notorious there. Thus, as early as 1667, Doni wrote a work called De Restituenda Sahibj'itate Agri Romani ; and references to a succession of works carried out on this principle, which I now call the principle of Mosquito Reduction, are given by Celli [1901]. At the same time efforts were made by many observers, such as Morton, Lancisi, Lind, Pringle, to explain the paludic connection ; and these resulted in the formation of the hypothesis of the pahidic miasma. This was supposed to be some kind of infecting emanation from stagnant water, either chemical, or as Lancisi suggested, organic ; but in no 8 HISTORY [Sect. cases, apparently, were experiments made to test the point. Later, when it was observed that malaria may sometimes occur where there is no marsh, the hypothesis of the paludic miasma was extended to that of the telluric miasma, according to which the poison exists not only in marshes but anywhere in suitable soil, from which it rises at night or when the soil is disturbed. This speculation, for it is nothing more, is not quite dead even yet, though the observation which originated it is easily ex- plained otherwise. The word " malaria " {maV aria or bad air) is derived from it. 3. Discovery of the Parasites. — Last century, however, pathological science was no longer content with mere guesses at the truth, but began to demand strict microscopical and experimental evidence. Applied to paludism, this method gave an early reward. In 1847, H. Meckel discovered innumerable black granules in the blood of an insane patient ; and the discovery was subsequently confirmed and amplified by Dlauhy, Virchow, Heschl, Planer and Arnstein — the granules now being known under the name of the paludic pigmejit, or melanin, or haematozoin (Sambon).^ For a long time they were thought to be due to a chemical action of the paludic miasma on the red cells of the blood. About the same time many laborious attempts were made to discover some animal or vegetable organism which lives in marshes and produces paludism. As long ago as 1846 Rasori (cited by S. Calandruccio) made an extraordinary prediction on this subject. " For many years," he said, " I have held the opinion that the intermittent fevers are produced by parasites that cause the successive paroxysms of fever by their repro- duction, which occurs periodically more or less rapidly according to their species " — and this has proved to be exactly true. Many writers attributed the disease to various marsh-growing vegetables. In 1862 Salisbury in particular, after considerable ^ I suggest the name Plasmodin, which is still more exact. 3] DISCOVERY OF THE PARASITES 9 study, blamed a kind of Pabnella; and after 1878, a number of Italian workers, Lanzi and Terrigi, Edwin Klebs and C. Tommasi-Crudeli, thought that they had actually incriminated certain fungi or bacteria, which they said swarm in malarious places, occur in the blood, produce spores before each paroxysm of fever, and cause similar infection in animals. These findings were even confirmed by Marchiafava and other Italians ; but have now been completely discredited. In 1878, however, A. Laveran commenced his studies of the subject at Bone in Algeria, by following up the granules of pigment, already referred to, in the blood of living patients. He was struck by the fact that they were frequently contained within cells possessing active amoeboid movements ; and, finally, on the 6th November 1880, at Constantine, he detected the microgametes issuing from the male cell. Though at the time he did not know the nature of this phenomenon, it convinced him that he was dealing with a living parasite of the human red corpuscles. In fact the black granules are merely the excrementitious matter produced by the parasites from the substance of the red cells, and contained within their bodies, or released in the tissues of the host.^ About the same time C. Gerhardt proved that healthy persons can be infected by the inoculation of blood of patients suffering from paludism [1884]. His experiments were after- wards verified by many workers, and demonstrate (apart from the microscopical discovery of the parasites) that the disease is not due to any gaseous emanation from marshes, but is a true infection by some living virus. In 1886 and subsequently, C. Golgi, who v/as favourably situated in Pavia for the work, showed clearly that the parasites 1 Recently R. Blanchard (Archi. de Parasitologic, vol. vii. 1903) would have us believe that one P. F. H. Klencke had discovered the parasite of malaria before Laveran ; but it is perfectly obvious from Klencke's drawings, given by Blanchard, that his "parasites" are merely the usual artifacts found in fresh blood. Klencke, moreover, was not studying malaria at all, but "vertigo." Medical literature is full of such simulacra. lo HISTORY [Sect. reproduce by simultaneous sporulation ; that the febrile paroxysm in the patient commences at the moment when these spores are liberated (just as Rasori had divined) ; and that the parasites of quartan and mild tertian fever are morphologically different [1886]. A little later, Canalis, and Marchiafava and Celli dis- covered similar facts regarding the malignant parasites, and showed that they differ from the quartan and mild tertian parasites ; and Marchiafava and Bignami suggested that they are of two varieties, the malignant tertian and the quotidian. In 1885 Danilewsky discovered similar parasites in birds and several other animals ; and subsequently Marchiafava, Celli, Bignami, Mannaberg and others, made many careful studies of the parasites, and of their effects in human beings ; Romanowsky found the proper way to stain them ; and many observers verified these researches in various parts of the world — the literature amounting to some hundreds of publications, 4. Speculations regfardin^ the Mode of Infection.— But the question now arose — an all-important question in connection with the prevention of the disease — How do these parasites manage to effect an entry into the blood of men and animals ? Most observers, remembering that the disease often abounds in the neighbourhood of marshes, assumed at once that Laveran's parasites must be capable of living in a changed form in stagnant water ; and some actually sought them there. Thus Grassi and Calandruccio suggested that a free living amoeba is really the external stage of the organism. On the other hand, experiments to infect healthy persons by water from marshes, made by Marchiafava and Celli [1885], Marino [1890], and especially Agenore Zeri [1890] failed entirely. Zeri gave marsh water to nine persons to drink in doses from r5 to 3 litres a day for a number of days. To another five persons he gave the water by clyster ; and to sixteen by spray inhalation — yet no paludism followed. Like all negative results, his are not absolutely con- clusive — since the failure may have been due to some unforeseen 4] DISCOVERY OF METAXENY ii condition absent from the experiments ; but his paper is too important to have been forgotten as much as it has been. Before describing my own Indian researches which com- menced at this point, it is necessary to survey our general parasitological knowledge, together with the state of thought regarding malaria, at the time. Discoveries concerning Laveran's bodies, which are animal and not vegetable organisms, have a line of descent from previous discoveries concerning animal parasitology, and not directly from bacteriology. Many of the large animal parasites of man and animals have been known to us from antiquity, but until the beginning of the eighteenth century, were supposed, like other low forms of life, to be created in each host by " spontaneous generation." Even long after Redi (1668) proved that this hypothesis did not hold for certain insects, it was still supposed to apply to the parasites. Gradually, however, large numbers of the latter were discovered, and Pallas put forward the view that they originate, like other animals, from eggs, which escape from an infected person or animals, and are by chance swallowed by another host. Such a history is, in fact, quite correct for many parasites ; but in 1790 Abildgaard made the remarkable discovery, by experiment, that the parasites, called Bothriocephalus solidus and Ligula, inhabit for a part of their lives certain fish, and reach maturity only in certain water-fowl which happen to swallow the infected fish. This appears to have been the first found instance of the wonderful process of metaxeny,^ or change of host. The idea was lost sight of for years until Eschricht in 1 84 1, and Steenstrup in his famous work on the alternation of generations of Trematodes (1842), recalled it. It was finally established for Cestodes by F. Kiichenmeister, physician to the Duke of Saxe Meiningen, in 1851-1853, by means of direct experimental feeding methods first used by him. Metaxenous ^ I use this word on the authority of De Bary, who employs the incorrect form metoxenous in the above sense — see his book on Fungi, Mycetozoa, and Bacteria. Trans. Clarendon Press, Oxford, 1887, p. 387. 12 HISTORY [Sect. parasites are those which spend part of their life in one kind of animal, and the rest of it in another — generally the early part of their existence in one host, and the mature sexual part of it in another host which preys upon the first one, as in the rabbit and the dog, the mouse and the cat, swine and men, and so on. Moreover, he proved that the eggs or young of the mature parasites are able to pass back again into individuals of the first species of host, from which they are again trans- ferred to the second species of host — and so on, ad infinitum. This great discovery, which may almost be called the basis of modern parasitology, was rapidly verified by Kiichenmeister and Leukart for many parasites. At first it was applied to those of the higher animals; but before 1858 Leukart dis- covered that the Nematode worm, Cucullanus elegans of the perch develops in the little aquatic Arthropod called Cyclops, or the Water Flea. Next, perceiving the resemblance of this worm to the famous Filaria medinensis, or Guinea Worm of man, he suggested in the same year (1858) to the young Russian naturalist and traveller, Fedschenko, that the latter parasite may also pass a stage of its life in a Cyclops. The Guinea Worm lives under the human skin, and emits its young through an ulcer which it produces in the integument — the young next finding their way into water. A few months later Fedschenko proved by experiments in Turkestan that Leukart was right. He watched the development of the embryos in the Cyclops ; but did not complete the cycle by infecting men from the latter. He supposed, however, that men become infected by accidentally swallowing infected Cyclops in drinking water.^ ^ For an account of this discovery see R. Leukart, Die Menschlichen Parasiten, 1876, vol. ii. p. 704. As it is an extremely important discovery, I have been at considerable pains to ascertain the exact dates. It will scarcely be believed, but Leukart's complete works are difficult to obtain in this country. I am indebted to Dr R. T. Leiper for having studied the question. The facts appear to be as follows : In 1858 Leukart (when at Naples) suggested the idea to Fedschenko, who was then about to proceed to the East ; but did so as a secret (?). In 1865 and 1866 Leukart first published his account of the development of Cttcullanus in Cyclops, but merely hints at the idea that F. medtnensis has a similar development, without mentioning Cyclops as the possible second host. In 1869 Fedschenko seems to have returned from 4] TRANSMISSION OF FILARIAE 13 In 1868 another important case was discovered by Leukart and Melnikoff in Leukart's laboratory. They found that the yowngoi Dipylidimn caniniuvi {Taenia cucumerina), sl parasite of dogs and cats, develops in the dog-louse ^ — this being, I believe, the first case in which a parasite of a mammal was found to be transferable by any kind of vermin which feeds on that mammal. The great credit due to Leukart in connection with these discoveries has been much overlooked of late. Filaria bancrofti^ a human parasite, was discovered in the adult form by Bancroft in 1876, though its embryos had been found by Demarquay in 1863 in chylous fluid, and by Lewis in blood in 1872. In the Lancet, 12th January 1878, Cobbold mentions a suggestion of Bancroft, dated the 20th April 1877, that the worm (which is closely allied to F. medinenszs, and indeed to Cucullanus) might be carried by mosquitos. In 1877, P. Manson, in Amoy, China, came to the same conclusion, and on examining a number of mosquitos fed on a Chinaman whose blood contained the embryos, discovered that these develop in the tissues of the insects just as the embryos of F. medinensis develop in Cyclops? This was the first time that metaxeny was found to occur with any parasite between man and mosquitos ; but Manson did not observe the development of the embryos to a stage much more advanced than that observed by Fedschenko in the Cyclops. He thought also that mosquitos die on the surface of water a few days after feeding on blood ; and that the partially developed embryos then liberate themselves from the dead insects, and, after swimming free in the water, are swallowed by human beings. But he did not prove this; and indeed, in 1900, G. C. Low and S. P. James, acting on the evident suggestions of my work on Turkestan and to have published his paper in Russian, describing the development of F. medinensis in Cyclops. The last, then, must be taken as the date of publication of the discovery. Dr A. Jacobi, Leukart's biographer, can give me no further information. ^ R. Leukart, Die Menschlichen Parasilen, 1876, vol, ii. p. 704. " P. Manson, Filaria sanguinis hominis a7id Certain New Forms of Parasitic Diseases. London, 1883. 14 HISTORY [Sect. malaria, made observations which lead us to think that the embryos return to human beings through the insect's proboscis. By his detailed studies, however, Manson has built up most of our present knowledge on the subject of filarial disease in man. It should be noted here that all these examples of metaxeny apply only to the higher parasites, the Helminths or Worms, and that in some of the cases, including those of Fedschenko and Manson, the life-cycle had been by no means completely ascertained — so much so that many doubted whether the observed development of the embryos in Cyclops and Culex could be looked upon as a genuine stage of metaxeny. But the bodies discovered by Laveran belong to a much lower, in fact to the lowest, class of animals — the Unicellular ones. Though many organisms of this class — amoebas, gregarines, coccids, trypanosomes — have been discovered in various animals, yet up to 1889 not one of them had been proved to be metaxenous. During this year, however, a remarkable dis- covery was made by Theobald Smith and F. L. Kilborne in America in connection with the disease called Texas cattle- fever. For a long time the farmers had thought that it is caused by certain cattle-ticks. Smith and Kilborne now showed that the disease is due to minute parasites of the red corpuscles, akin to the parasites of malaria but not belonging to the same group, called Piroplasma bigeminuni ; and that they are inoculated in some way into healthy cattle by the bites of young ticks born from a parent tick which has fed upon a diseased ox. This fact was conclusively proved by direct experiment, and suggested that these Piroplasmae, which are unicellular animals, might also be metaxenous like so many of the higher parasites. But the observers failed in following out microscopically the life-history of the Piroplasma in the ticks, and therefore did not actually prove any alternate generation in them.i ^ T. Smith and F. L. Kilborne, Investigations into the Nature, Causation and Prevention of Texas or Southern Cattle Fever. Government Printing Office. Washington, 1893. 4] VARIOUS HYPOTHESES 15 Meantime, however, there had been many vague conjectures to the effect that several diseases may be produced by biting vermin. Thus, as just mentioned, American farmers had long thought that Texas cattle-fever is carried by cattle-ticks. Many travellers also related that African natives ascribed a peculiar sickness to the bites of another kind of tick ; and others said that the deadly nagana of cattle in parts of Africa is probably due to the bites of the tsetse fly. And similar speculations connecting both yellow fever and malaria with mosquitos had long been rife. Generally derided at the time, these views were speedily forgotten ; and it is only of late that many of them have been resuscitated and discussed as instructive relics of the past. It will, I think, interest the reader to follow the gradual development of our knowledge of this important subject. I have already mentioned the curious utterances of Varro, Columella, the ancient Sinhalese books, and of Lancisi, regard- ing insects and fever. Nuttall [1899, p. 75] gives statements by Lustig, Rubner, Koch and myself, to the effect that the peasantry in Italy, Tyrol, East Africa, and Assam seemed to have vague ideas of the same kind. Dr R. H. Kennan informs me that he has found an old ordinance of Freetown, Sierra Leone, dated 1812, in which the inhabitants (mostly freed slaves) are enjoined to keep the road in front of their plots in good condition in order to prevent the formation of " stagnant pools which generate disease and mosquitos over the town." In 18^, Dr Josiah Nott, of Mobile, Alabama, appears to have stated that both yellow fever and malaria may be transmitted by mosquitos, and refers to the speculation as having been already advanced as regards malaria. In 1854, however, Louis- Daniel Beauperthuy^ a French medical man, born in Guadeloupe in 1808, gave the hypothesis in greater detail [1854]. As a " travelling naturalist " for the Paris Museum in Venezuela, he studied both these diseases microscopically, and concluded that they are produced by a venomous fluid injected under the skin by mosquitos, like the poison injected by snakes. Marshes, he i6 HISTORY [Sect. says, are dangerous because of the mosquitos bred in them, not because of their effluvia. He stated that several species of mosquito carry yellow fever, but mentioned especially "the sancudo bobo with legs striped with white " — probably the Stegomyta calopus} which we now know is really the agent. But he mentions no experiments in support of his opinions, which seem to be only ingenious speculations based upon general thought and observation. In 1 88 1, and subsequently, Charles Finlay of Havana repeated a similar hypothesis, apparently independently of Nott and Beauperthuy [1881]. His views, however, differ in an important particular. While Beauperthuy seemed to think that mosquitos originally obtain the disease-giving poison from the marsh in which they breed (and Varro, Columella, and Lancisi believed the same), Finlay held (regarding yellow fever) that they obtain it from sick people. In other words, he thought that the insects simply convey it from patients to healthy persons. The proboscis of a mosquito which bites a patient becomes contaminated by germs in his blood ; the germs multiply in the proboscis ; and then enter the blood of any person whom the mosquito bites next — ^just as bacteria may be carried on a soiled surgical instrument from one person to another. He thought that an insect which had only just bitten a patient could convey the virus ; but that the longer it lived after biting the patient the more the germs would multiply in its proboscis, and the larger the dose given to the healthy person would be. He also considered that the mosquito with striped legs {Stegomyta calopus) is the agent of yellow fever. He records some experiments ; but they must have been very doubtful, since we now know that mosquitos which have bitten a patient must live for no less than twelve days before they can infect a healthy person. Like Beauperthuy, he rightly conjectured the species of mosquito which carries yellow fever, and actually placed them in the hands of the men who ultimately solved the problem. ^ J. Guiteras says not (Lancet l8th June 1910). 4] VARIOUS HYPOTHESES 17 He was acquainted with Manson's researches on the develop- ment of Filaria bancrofti in mosquitos.^ In 1883 Dr A. F. A. King wrote an able paper on the subject [1883] in which he gives no less than nineteen reasons why mosquitos are likely to carry paludism. These are: — (i) that both paludism and mosquitos are connected with marshes; (2) that they both require a temperature of over 60 degrees F. ; (3) are checked at freezing point ; (4) abound most near the equator and sea-coasts ; (5) have an affinity for dense foliage ; (6) can be screened off by trees ; (7) can be transported by winds ; (8) are encouraged by turning the soil ; (9) are affected by "bodies of water"; (10) are diminished by cultivation and settlement; (11) keep near the surface of the ground; (12) abound most after sundown; (13) and in the open; (14) are destroyed by fires ; (15) are not so common in cities ; (16) are most prevalent in autumn ; (17) are arrested by mosquito nets ; (18) affect infants (which are generally protected by nets) less than adults ; and (19) attack whites more than other races. This was by far the best exposition yet given. Though arguments (4), (13), (14), (18), and (19) are not sound, while arguments (5), (6), (7) are very doubtful, and though the most cogent argument of all was not known to him, the cumulate effect of his careful and well-arranged reasoning was very strong. Like Beauperthuy, he held that the insects bring the poison from the marsh and inoculate it by their bites. He was acquainted with Manson's work, but not with Laveran's. His paper was speedily lost sight of, and was not resuscitated until my researches had cleared up the question. About the same time Laveran suggested the same idea [1884, p. 457] in a short sentence: "Do mosquitos play the same role in paludism as infilariasis ? " he said. "The thing is not impossible, and we must note that mosquitos abound in all marshy places." ^ For further details see the interesting book, Mosquito or Man, by my colleague, Sir Rubert Boyce. John Murray, London, 1909. B i8 HISTORY [Sect. Also about the same time, during his famous studies on cholera in India, R. Koch had the same notion ; but he mentioned it only in his lectures to students [Nuttall, 1899, p. jy, and Ross 1905, p. 73]. Ten years later, and some years after I had commenced my studies of the subject, P. Manson supported the mosquito hypothesis in a rather short paper [1894]. But he added a new and a stronger argument to those already given. In the blood of man the parasites of malaria consist chiefly of forms which reproduce themselves indefinitely by spore formation ; but in addition to these there are other forms which appear to possess no function in the human body, but which, shortly after the blood containing them is drawn from the patient's finger, often emit long and actively motile filaments which may break away from the parent cell, and wriggle about rapidly in the fluid under the microscope. For a long time these bodies had been the subjects of discussion. Some observers, chiefly of the Italian school, held that they represent only the dying struggles of the parasite ; others, including Laveran and Danilewsky, thought that they are really living bodies ; and Mannaberg even suggested that they may be connected with the life -history of the parasites outside the human body — though he did not explain how this could be. Manson now offered an explanation. He thought that when a mosquito sucks the blood, these parasites enter its stomach with the blood, and there, in a few minutes, emit their motile filaments just as they do under the microscope. The motile filaments, he thought, were flagellated spores, which next pass through the walls of the mosquito's stomach and take up their abode in its tissues, where they must deyelop further. Two years later he repeated this hypothesis [1896] with the assistance of my preliminary researches, but added some conjectures as to the future fate of the " flagellated spores." He still thought that mosquitos die on the surface of water a few days after laying their eggs in it. The malaria germs 4] VARIOUS HYPOTHESES 19 might now escape from the dead insect into the water, with which they might be swallowed by men ; or they might be blown about with the dust and be inhaled ; and they might also be swallowed by mosquito larvae and so propagate them- selves indefinitely in the insects, apart from man. Roughly, the life-history of Laveran's bodies was, he thought, similar to that which he considered Filaria bancrofti to possess. \^ A few months later A. Bignami attacked Hanson's views for several reasons [1896]. He refused to admit that mosquitos can take the parasite from human beings, but supposed, con- versely, that human beings take it from mosquitos. In support of this he merely adduced some of the reasons previously given by King. Several other writers supported or opposed the hypothesis about the same time. This is a short, but, I think, a fairly exact account of these hypotheses. The importance of speculations of this kind is apt to be either underrated or overrated. Modern science does not look upon them with much favour unless those who publish them strive also to verify them. It is easy to sit at home and weave many hypotheses ; but attempts to verify them generally demand endless labour, expense, self-sacrifice or even danger, and often fail, or, even if successful, win little reward. There were many before Columbus who imagined America ; but between the dream and the reality an ocean had to be traversed. All the conjectures mentioned above have proved wrong in many particulars. Mosquitos do not bring the virus from the marsh to the man, nor from the man to the marsh. The truth has proved to be far more wonderful than any hypothesis. It is curious that no one recognised the suggestion which should have been obtained from the phenomenon of metaxeny amono- some other parasites, namely, that the mosquitos might carry the virus from man to man. I was driven to this in 1896- 1897 just before the fact was revealed. On the other hand, such speculations often serve a useful purpose by giving some direction to practical work. Thus 20 HISTORY [Sect. those connected with Texas cattle-fever, nagana, and tick- fever greatly limited the , labour of research by suggesting the actual species of the alternative hosts, namely certain ticks and tsetse flies ; and those of Beauperthuy and Finlay suggested the Stegomyia calopus as the agent of yellow fever. With regard to paludism the earlier hypotheses, critically looked at, suggested nothing more than that there might possibly, or probably, be some connection between mosquitos and the disease. Hanson's idea regarding these forms of the parasites (gametocytes) which produce the motile filaments (microgametes) was, however, more than a mere speculation — it was an induction based upon our general knowledge of parasites. As he said, these bodies must have some meaning and object. It was difficult to imagine that they could have any other object except to infect some suctorial animal — probably mosquitos. But this idea led us no further ; it gave no clue as to how and where the parasites live in mosquitos, how they return to man and infect him, and in which of the hundreds of species of mosquitos they exist. It was only a glimmer in the darkness — but it was something. Obviously the truth could be obtained only by a long and determined investigation of the whole subject. "^ 5. Researches regrarding" the Mode of Infection.— These really began with the old attempts mentioned in section 3 to find the infective organism in marsh water, and with those mentioned in section 4, and culminating in the negative efforts of Zeri [1890] to infect healthy persons with such water. Parallel researches on various worms and on Piroplas7na bigeminuni were referred to in the last section. I have now to describe my own work. Entering the Indian Medical Service in 1881 I was much struck by the misery caused among the people by this and other diseases; and in 1889, during leave in England, studied bacteriology and public health, with a view to undertaking pathological investigations. On return- ing to India I was especially drawn to the difficult problem of 5] RESEARCHES ON INFECTION 21 paludism, regarding which the facts observed by me did not accord well with the old hypothesis of a marsh miasma. I was at first led to the ideas of Broussais that the disease might be due to intoxication from intestinal organisms. In those days it was almost impossible to obtain much literature in India ; and Laveran's discovery was obscured by writers who, in attempting to find his parasites in the blood, found only natural objects which resembled them. I detected the error and, with many others, doubted his discovery in consequence, and failed to find his organism — though I obtained much valuable practice in microscopical work. In 1894 I returned to England, where P. Manson showed me the true Laveran's bodies. He also told me his new mosquito hypothesis ; and I reminded him that the same idea had been mooted by Laveran. Next year I returned again to India, determined to work out the whole subject thoroughly. The details have been previously recorded in my Nobel Lecture [1905], but the reader should know the following points. Little was then recorded regarding the structure, habits, or classification of mosquitos ; and I could obtain no literature on the subject, and was obliged to find out everything, including the technics, for myself. I was not then aware of the specula- tions of Beauperthuy, Finlay and King, or the discovery of Smith and Kilborne. There was nothing to guide me as to the species of mosquito concerned, as we had no right to assume that the malaria- bearing species is necessarily the commonest in any malarious locality ; and as metaxeny was not known at that time among unicellular parasites of animals, there was nothing to indicate the form or position that Laveran's bodies would, by supposition take in the insects. The study of these minute organisms was moreover much more difficult than that of the large worms already investigated ; and the proper method of staining was not then known. In May 1895 I fed Ciilex and Stego7iiyia,hxQ^ from the larva 22 HISTORY [Sect. on patients with the gametids (crescents) in their blood, and showed that the motile filaments were, as usual, extruded in the insects' stomachs. But I speedily found that, owing to their minute and delicate structure, it was impossible to follow them further, as Manson had suggested should be done. I was therefore obliged to adopt a new procedure of my own. The insects were kept alive after being fed for several days, and were then exhaustively searched for any parasites they might contain. If such parasites were found it was possible that they might be the developed motile filaments ; and the point could be cleared up by subsequent experiments. This method was extremely laborious, but was the only one possible. For more than two years the results were completely negative. Meantime, following the later conjectures of Manson, I tried to infect healthy persons by giving them to drink water in which fed mosquitos had died. By some accident the first case appeared successful ; but twenty-one succeeding experi- ments practically failed [1896]. For this and other reasons I abandoned this part of Manson's hypothesis, and began to think that the insects probably carry the parasites from man to man, either depositing them by defaecation on the skin of healthy persons, or inoculating them under the skin after puncture. In August 1896, Mr Appia, Assistant Surgeon of the Civil Hospital at Bangalore, kindly submitted to the suggested experiments. Many Stegomyia and Ctilex, previously fed on patients, were fed on him a few days later. There was no result — the mosquitos being of the wrong species, and the period between the feedings being too short [1896]. Bignami now criticised Manson's hypothesis [1896]; but I made a number of experiments in support of it, and showed that the extrusion of the motile filaments is really a living process and not a "death agony" as many had thought [1897]. My repeq,ted failures, however, now persuaded me that I had probably been working with the wrong kinds of mosquitos — 5] RESEARCHES ON INFECTION 23 Culex and Stegomyia ; and in April 1897 ^ went to an intensely malarious spot near Ootacamund in the Nilgiri mountains, in order to see if I could find another likely kind. There, for the first time, I saw an Anopheline — the really culpable kind ; and also made several observations which made me finally abandon the second part of Manson's hypothesis and adopt the view that the insects carry the parasites in some way from man to man [1898]. A few months later I returned to Secunderabad, where I had commenced my mosquito work in 1895, and was at last rewarded with success. On the 20th and 21st August I found the zygotes of the parasites in two large dapple - winged mosquitos which had been bred from the larva, and fed on a case containing crescents. This fortunate observation gave the clue to all that followed, because it indicated the form and position of the parasite in the insect, and also the variety of insect capable of carrying it. The problem was practically solved, and only details and formal proofs required to be ascertained. Figure i. .*. • ' '% •■ '• .* .' i4 HISTORY [Sect. The matter was reported at once to Government, and the medical press [1897]. Unfortunately no more of the large dapple-winged mosquitos could be obtained, but I found the pigmented cells in a Culex which had been caught feeding on a case of tertian malaria, and also in one of a smaller kind of dapple - winged mosquito. On this I wrote to Manson telling him to expect the full solution of the problem in a few weeks. Next day, however, I was ordered to proceed to Kherwara, a place a thousand miles distant, where there was little malaria at the time. Owing to this interruption I have never been able to identify exactly the two species of dapple- winged mosquitos ; but from their general characters, the markings on their wings and the shape of their ^%^'s>, they were obviously Anophelines. I remained at Kherwara from September 1897 to February 1898, when the Government was good enough to put me on special duty to continue my researches in Calcutta. On arrival there I found it impossible to work with human malaria, chiefly on account of the riots caused by Mr Haffkine's anti - plague inoculation, and therefore attacked the malaria of birds. According to Hanson's hypothesis, the motile filaments were flagellated spores capable of living in mosquitos' tissues ; but my pigmented cells contained plasmodin, which cannot exist in spores. The discrepancy was explained by a series of researches made in 1896, Metchnikoff and Simond had found similar motile filaments in Coccidiuni oviforvie of rabbits, and suggested that they are really sperms and not spores [1897] J and a little later MacCallum' and Opie in America actually observed, in the case of one of the malaria parasites of birds {Halteridmm) and one of those of men, these sperms in the act of fertilising the female cell [1897]. My pigmented cells were therefore the fertilised cells, or zygotes, still carrying the plasmodin which they originally possessed. In March 1^8, I found these bodies again in Culex fatigans 5] RESEARCHES ON INFECTION 25 fed on birds containing Plasmodium {Proteosomd) danilevskyi. In a few months, by means of rigid experiments, the develop- ment of the parasites in the insects was fully ascertained. On the 4th July I observed the extraordinary fact that the proto- spores (sporozoites) of the parasites enter the insects' salivary or poison glands, thus suggesting that infection is produced by the bites of the insects. I had thought that this might be the case, but none of us had ever really imagined such a wonderful process — nature surpassed the divination of all of us! In July and August I infected twenty-two out of twenty-eight healthy sparrows and some other birds, by means of the bites of Culex fatigans which had been previously fed on infected birds. These experiments gave the fundamental solution of the problem, and the first proof of metaxeny among unicellular parasites of animals — just as Kiichenmeister's had proved the process to hold for higher organisma. They exhibited, with the assistance of MacCallum and Opie's observation, the whole development, step by step — the position and form of the parasites in mosquitos, and the wonderful method of infection. Owing to the great similarity of the avian and human parasites, there was no doubt that the latter had the same history — and indeed the stages of these up to the fifth day had already been found by me a year previously in Anophelines. I was now anxious to complete the work on human malaria, but was ordered to leave the subject and attack the difficult one of kala-azar. This, with the writing of the necessary report, occupied me for nearly six months, until I left India in February 1899. I then joined the newly-formed Liverpool School of Tropical Medicine ; and at the end of July set out with E. E. Austen, Entomologist at the British Museum, and Dr H. E. Annett, of our School, to complete my study of the human parasites. In a few weeks I was able to show that the parasites of quartan, tertian, and malignant fever all develop in Pyretophorus cos talis or Myzomyia funesta, precisely as the Proteosoma of birds develops in Culex fatigans. This 26 HISTORY [Sect. completed the task ; and I now turned to the subject of practical prevention. 6. Confirmations and Extensions. — My observations of the parasites in mosquitos were published by myself in a series of papers on i8th December 1897, 26th February 1898, 21st May 1898, nth October 1898, and 24th January 1899 ; and also, owing to official delay in regard to some of my reports, by Manson on 1 8th June 1898, July, and 24th September 1898. My paper [May 1898] contained a full account with plates of the necessary technique invented by myself, and of the stages of Proteosonia in the mosquito up to the sporulation of the zygotes — the mode of infection being published in the later papers by Manson (to whom I had telegraphed the news in time for the Annual Meet- ing of the British Medical Association at the end of July), and also by myself [October 1898]. Moreover, I had sent numbers of my specimens to him and to Laveran ; and, in fact, by August 1898 my researches were well known to most workers at the subject in Europe and America. The first to confirm them was R. Koch, with Kossel, who in September followed completely the development of Pro- teosoma in Culex ne^iiorosus, and demonstrated a point which I had not had time to deal with, namely, how the zygotes traverse the wall of the insect's stomach [1899]. In December, C. Daniels, sent by the Royal Society to examine my results, arrived in Calcutta and confirmed them [1899]. He and Dr Rivenberg also assisted me greatly at that time. Until my researches were published, the Italian writers had generally disbelieved in the mosquito hypothesis, though A. Bignami had accepted it on the lines of Lancisi and King. Now, however, they made strenuous efforts to follow ; but they reached no tangible result until November, when Bignami, in the light of my experiments on birds, infected a man in Rome with mosquitos brought from Maccarese [November 1898]. A 6] CONFIRMATIONS AND EXTENSIONS 27 few weeks later A, Bignami, G. Bastianelli and B. Grassi found the zygotes of malignant malaria in Anopheles maculipennis, fifteen months after my original success with the same parasite in Secunderabad, and four months after the whole life-cycle of the parasites, as exemplified in Proteosoma, had been fully published by Manson and myself They were thus able to forestall the completion of my work on the human parasites, but did so entirely by following my previous researches, while my time was being wasted over a lengthy report on kala-azar — a duty which I was not permitted to postpone. Being very favourably placed for the work, and not being subject as I was to interruptions, they succeeded in infecting three more persons, and were able to publish numerous papers with coloured pictures, which greatly popularised the subject. They proved one important new fact, however — that the tertian parasites also are carried by the Anophelines ; and I verified this later in Sierra Leone.^ ^ The relations between the work of these authors and of myself are exactly dis- cussed in my lecture [1905]. For a long time some writers attributed to them the discovery of the mosquito-cycle of the important human parasites, and to me only the study of the humble Proieosoma of birds. But according to zoological rules, priority in the discovery of the life-history of any group of organisms belongs to that investigation which first discloses the new life-history in any member of the group — which is only just, since there is usually little difficulty in repeating the same observations for other members of the group. The life-history of Proteosoma there- fore holds the priority in the case of all similar life-histories ; and is in fact identical with those of the human parasites, and indeed almost the same as those, since found, of other unicellular organisms. Efforts were also made, with the same object, to dis- credit my original successes of 1S97 with the human malignant parasites by the statement, contrary to the printed evidence of my words [December 1897], that the mosquitos used by me had not been bred from the larvae — although the men who made these efforts were apparently actually committing at the time the very fault of which they wrongly accused me. In a later work B. Grassi occupied many pages in trying to persuade the world that he had discovered the " Anopheles malariferi indipendentemente da Ross" [1900, p. 31]. Unfortunately for him he had referred to my work in a paper [October 1898] which he had published two months before he "discovered" anything at all. There is no doubt that he and his colleagues recognised the genus of my "dapple-winged" mosquitos from several statements of mine, and were thus able easily to find the parasites in members of the same group in Italy. The Italian work was due mainly to Bignami and Bastianelli, and not to this author as erroneously stated in many monographs and articles. Laveran has made similar remarks about his own work [1907, p. 13J ; and the matter is mentioned here because such misstatements are apt to discourage genuine work [Ross, 1905]. 28 HISTORY ., ^[Sect. In November 1899, I^- Koch, who has given suclT great discoveries to pathology, added another in connection with malaria. He found in the valley of Ambawara in Java that while large numbers of the native children showed the parasites in their blood, the adults seemed to be comparatively free from them, and had obviously become partially immune. Thus in most very malarious places it is chiefly the children who suffer from the acute disease. The blood of those who survive gradually produces something which after a number of years has the power of reducing and perhaps extinguishing the parasite invasion. From this it follows that in such localities the Anophelines must become infected principally from the native children {see section 31 (9)). In the summer of 1900, P. Manson carried out an important crucial experiment. A number of Anopheles maculipennis, fed on cases of mild tertian, were brought from Italy to London, and were allowed to bite P. T. Manson there on several occasions. He developed the disease on the 13th September, the tertian parasites being found in his blood a little later. The insects were also allowed to bite G. Warren, who was similarly attacked fourteen days afterwards. At the same time L. Sambon, G. C. Low and two others lived for three of the most malarious months in one of the deadliest places in the Roman Campagna, Ostia, without contracting the disease, because they spent the nights in a hut protected by wire gauze against the entry of mosquitos. On many other occasions healthy persons have been similarly infected on the lines of my experiments with birds in July to August 1898. As already mentioned Bignami and Bastianelli infected four persons in Rome (which is itself free from malaria) in 1898- 1899. Subsequently C. F. Fearnside at Rajamundri in India infected seven out of eight persons, including himself, in 1900-1901 [1901]. W. Schiiffner infected himself and two others at Delhi, Sumatra, in August and September 1901, two with tertian and one with malignant 7] PREVENTION 29 malaria, by means of certain Anophelines [1902]. N. Jancso infected ten out of fifteen persons at Kolozsvar in Hungary in 1904 by means of A. maculipennis (section 17). My work on the Proteosoma of birds has been confirmed by Koch [1899], C. Daniels [1899], B. Grassi [1900], R. Ruge [1901], Ed. and Et. Sergent [1907], R. O. Neumann [1908]. The mosquito cycle of the human parasites has been further worked upon by Fernside [1901], Stephens and Christophers [1899-1903], Schiiffner [1902], Jancso [1904], Schaudinn and others. Reviewing this history we shall see that the great stream of research on malaria, descending to us through more than two thousand years, is composed of three main tributaries finally mingled together. One tributary rises in the work of the ancients on the different clinical forms, and consists of the discovery of the cinchona bark ; the work of Torti (1753) ; the discovery of the plasmodin by Meckel (1847); of the parasites by Laveran (1880); and of the confirmations and extensions of Golgi, Danilewsky and many others. Another tributary consists of the ancient observations con- necting the disease with marshes ; the speculations of Varro, Columella, Lancisi, Beauperthuy, King, Laveran, Koch and Manson ; and the valuable researches of those who tried to find the organism in marshes. The third tributary consists of the early work on para- sites ; the discovery of metaxeny by Abildgaard (1790), Steenstrup (1842), and Kiichenmeister (1851); the discoveries of Leukart, Fedschenko (1858), Melnikoff (1868), Manson (1877), regarding certain worms; that of Smith and Kilborne (1889) regarding Piroplasma ; of Bruce on trypanosomes my work on human and avian malaria (1895 -1899); and the confirmations and extensions which followed. 7. Recent History of Prevention. — It is open to question whether the extensive drainage works of the ancients had 30 HISTORY [Sfxt. been carried out for sanitary or for agricultural purposes ; but there is no doubt that for several centuries the Italians, and other nations, have known how to control malaria by drainage and allied measures. In fact, for a long time the state- ment that drainage reduces malaria has been generally accepted as a medical dogma. As soon as the mosquito theorem began to become consolidated, the question arose whether the new knowledge would not provide us with some easier and cheaper method of prevention. My own studies had been undertaken principally for this object ; and the following observations of mine were connected with it. As early as 1884-1885 in Bangalore, and many times since then, I had noticed that Stegomyia and Culex could be largely reduced in numbers in my own house by emptying out the stale rain-water collected in tubs and pots in the garden. On one occasion I offered to reduce these mosquitos in the regimental mess - house, but the adjutant objected because, he said, I should be disturbing the order of nature ! But I satisfied myself as to the possibility of making such a reduction by my own personal experiences in many parts of India. After incriminating my dapple - winged mosquitos (Ano- phelines) in Secunderabad in 1897 I studied .their habits there and in Kherwara, Calcutta, the Darjeeling Himalaya region, and Assam,^ and noted the following points. » The eggs of the Anophelines were more or less boat-shaped, and possessed a peculiar membrane which gave them the appearance of having a row of oars on either side — thus differing from the eggs of the Culex and Stegomyia. They were also apt to arrange themselves in triangular patterns on the surface of the water. The larvae floated flat on the surface and had no long breathing tube — being thus unlike those of the other common groups. The adults were generally differentiated by having spotted (dappled) wings ; a shape more suited for 1 I could obtain no information on mosquitos in India at that time, not even at the Indian Museum in Calcutta. 7] PREVENTION 31 long flight ; and a peculiar attitude, when resting, at an angle to the surface to which they clung. These points would enable any one, even uneducated labourers, to distinguish them. But above all, my native assistants and myself noticed everywhere that the larvae do not generally breed in the pots and tubs occupied by those of the other groups, but mostly in pools of water on the ground. This led me at once (1897) to the explanation of the central fact that malaria is connected with marshes. If Culex and Stegomyia had been responsible for the disease it would not have possessed this relation — it would have been connected with pots and tubs, etc., just as yellow fever, which is carried by Stegomyia, is connected with them. 1 did not then know that the quartan and tertian parasites are also carried by Anophelines, but guessed, from the well - known relation referred to, that they were carried by some kind of marsh-breed- ing gnats, and not by the pot-breeding ones. The explanation was now clear ; the ancients were quite right — the disease is caused by an emanation from the marsh. That emanation, how- ever, is not a gas, nor even a contagimn vivum, but an insect. It was observed also that the Anophelines do not breed so much in large open bodies of water, such as lakes, rivers and reservoirs, but more in small, shallow, and often grassy pools and puddles where they can obtain shelter from wind and fish ; and that like other mosquitos, they abound most in proximity to their breeding - places. Putting all these facts together, I reasoned that we now possessed a much cheaper and easier method of prevention. Previously, we had been obliged to drain a whole area at great cost ■ now we should be able actually to seek out and determine the exact malaria- producing pools, namely, those which contain the larvae, and then to fill up or drain these alone ; and I naturally inferred that if the old method had been feasible (as it had been in many places), the new method would be still more easily feasible, and at less expense. Before leaving India I described my proposals in a short report 32 HISTORY [Sect. to Government, dated the i6th February 1899, and published five months later without date, and with a title given apparently by the editor [1899]. The matter is so important, and my views have been so much misreported, that I must reiterate exactly what I said. I pointed out that mosquitos in general " are seldom to be found in the larger bodies of water " ; that to get rid of them locally " it will suffice to empty out or drain away or treat with certain chemicals the small collections of water " in which they breed ; that the Anophelines " seem to choose only rain-water puddles and ponds too large to dry up under a week or more, and too small or too foul and stagnant for minnows." I said that such pools "are not common in most parts of India except during the rains," and "seem to be so isolated and small that I think it may be possible to exterminate this species under certain circumstances." I added, however, that " I wish to be understood as writing with all due caution on these points." " I limit this statement to certain localities only, because it is obvious that where the breeding- pools are very numerous, as in water-logged country, or where the inhabitants are not sufficiently advanced to take the neces- sary precautions, we can scarcely expect the recent observations to be of much use — at least for some years to come. And this limitation must, I fear, exclude most of the rural areas in India. Where, however, the breeding - pools are not very numerous, and where there is anything approaching a competent sanitary establishment, we may, I think, hope to reap the benefit. . . . And this should apply to the most crowded areas, such as those of cities, towns and cantonments, and also to tea, coffee and indigo estates, and perhaps to military camps." " In making these suggestions I do not wish to excite hopes which may ultimately prove to have been unfounded." I concluded by urging further investigations on the malaria-bearing mosquitos of India and their habits. Though the report, being hurriedly written, might have been more exactly expressed in places, it is correct enough. 7] MOSQUITO REDUCTION 33 As it was the original statement of the radical anti-malaria measure — which has since been used with success in many parts of the world, and will certainly be adopted in the future as a fundamental principle of tropical urban sanitation — the reader should now clearly grasp what exactly was proposed. Animals tend to abound most where the local conditions are most favourable to them. Conversely, if we can make the local conditions unfavourable, they should become less numerous. Also, malaria being carried by certain Anophelines, should, as a broad general principle, be most common where they are most common, and should be reduced where they are reduced. I proposed, therefore, to reduce their numbers by measures I directed against their breeding-places. But this proposal was obviously not meant to apply to the whole world, but only to places where the measures were most likely to be feasible — that is, generally to " crowded areas," and not to " rural areas." A square mile of town, containing thousands of ratepayers, may be assumed to have money available for such work ; while open country, containing perhaps only a few scattered houses, has no such funds. Moreover, mosquito-reduction in a town will benefit thousands of people, while in the country it will benefit only a few — and that for the same cost. An identical principle applies to pipe water-supply and to pipe-sewerage systems — these are frequently given to towns, but not so often, even in Europe, to widely-scattered farmhouses. If then, I argued in effect, a town can afford to provide its inhabitants with a piped water-supply, or a sewerage system, it ought also to be able to keep them free, partially at least, from such dangerous insects as mosquitos. At that time I had had a rather exceptional experience of practical sanitation, having been specially appointed by the Government of India to improve the sanitation of a large Indian town (Bangalore), and I knew what I was writing about. As a general rule it would be much cheaper, I thought — and probably every practical engineer or health officer will agree with me — to make a great reduction 34 HISTORY [Sect. of mosquitos in most towns, than to instal and maintain a piped water-supply or sewerage system. I held also — and still hold — that the same measures might be feasible in some cases, even in plantations, military camps and villages.^ Unfortunately there are many people who seem to regard any new idea as a personal affront — who never try to under- stand the author, who disregard his reservations, and who attribute to him any absurd opinion ! I was immediately accused of proposing to destroy every mosquito throughout India and Africa, and of trying to upset the order of nature, and so on. Still worse, many others accepted this idea without understanding the practical details, and did much harm by attempting the work in quite unsuitable places. Lastly, some rejected the idea, but pretended to test it experimentally — and of course failed. In 1899, owing to the efforts of a number of medical men and men of affairs, and largely to the recent work on malaria, schools of tropical medicine were opened in Liverpool and London. At my inaugural lecture at the former (published at the same time as the previous paper) I repeated the same suggestions [1899]. Judging from my Indian experi- ences, I overrated somewhat the difficulty of reducing Culicines ; but concluded by invoking experiments on such points. West Africa, a great country hitherto paralysed by malaria, had long attracted me as an objective for practical preventive work, and I dreamed that it might be revolutionised by it. Hence, no sooner was the Liverpool School of Tropical Medicine opened, than I proposed to the Committee that I should be sent there to study the subject in detail. Conse- quently I left England in July (1899) with Dr H, E. Annett of the School, and Mr E. E. Austen of the entomological department of the British Museum, to see what could be done in Freetown, the capital of Sierra Leone — long known as the 1 Malcolm Watson (section 57) is now extending Anopheline reduction to rural areas as well as towns. See also sections 42 and 43. 7] MOSQUITO REDUCTION 35 "white man's grave." As already stated (section 5) we quickly incriminated two local Anophelines, P. costalis and Myzomyia funesta, as carriers of malaria ; and then set out to study their habits with a view to elaborating the principle of mosquito- reduction for practical sanitation. Before we left it was arranged that our work should be published anonymously in the medical press as promptly as possible for the guidance of others ; and I consequently wrote a series of four articles which were published in the British Medical Journal in September and October [1899.] The first two of them described the finding of the carriers ; but the two latter (30th September, p. 869, and 14th October, p. 1033) gave the leading points in the habits of the Anophelines, the broad distinctions between them and the Culicines, the nature and distribution of their breeding pools, and other matters connected with the general theory of malaria, together with a plate showing the characteristic attitude, and one showing a characteristic breeding - pool. In all these points these Anophelines of Sierra Leone proved to be generally similar to those which I had studied in India. The articles drew wide attention to the subject ; and in fact formed the basis of work on the reduction of mosquitos for malaria done since then ; though, being anonymous, they are not often referred to in the literature of the subject.^ Being obliged to hurry back, we could spend only seven weeks in the Colony ; and, as we were only private individuals, we could not carry out our recommendations. In February 1900 we published our report ; in the main body of which I summed up my results and recommendations with plates and figures. Operations for reducing the Anophelines were divided into those meant to prevent their breeding, such as draining ^ In 1899, G. H. F. Nuttall resuscitated some older works about mosquito-reduction. C. Finlay and A. F. A. King had recommended it hypothetically, and C. B. Aaron, L. O. Howard and others did practical experiments with oil, and other agencies ; but these attempts (of which I was ignorant) do not constitute anything like the practical sanitary policy drawn up by me. 36 HISTORY [Sect- or filling the pools or treating them with Culicicides (oil, tar, lime, etc.) ; and the destruction of the adults or larvae. I devoted a whole section to discussing the local conditions under which such operations were likely to be successful, and concluded as follows : — "(i) Operations against Anopheles are least likely to be effectual in level, water-logged localities, and in places where the insects breed in pools which cannot easily be found, or cannot easily be treated. (2) Operations will probably be easier in country which is not quite level, or where the rain- fall is not great. (3) They promise to be very easy in extremely dry places. Lastly, it goes without saying that we can scarcely ever attempt to deal with Anopheles in large rural areas. On the other hand, we may reasonably hope to reduce them, if not to exterminate them, in the principal centres of population and civilisation — that is, just in the places where the prevention of malaria would be most useful — provided always that we make intelligent and persistent efforts to do so." Also, both in this report and in a previous small book of instructions for laymen [1899], I dxscwssed personal prophylaxis by the use of mosquito nets, etc., and the reduction of Culicines round houses ; and I also pointed out how much Europeans in Africa suffered from not being segregated from the natives as they are in India [February 1900, p. 45].^ I have described these thoughts and studies at some length, because they constitute the conclusion of my work commenced five years previously, long before others had considered the matter worth touching, and therefore have, I think, the right of priority. But, as I have already stated, immediately after the publications of my work in the middle of 1898, numbers of medical men and naturalists began to take up the matter in many parts of the world. The classification and habits of the 1 I said also on the same page that a single intelligent native agent might "do a great deal of good " as regards the reduction of Culicines in many towns. On the strength of this I have recently been accused of proposing to rid the whole of Freetown of malaria by the services of one man only ! 7] QUININE 37 Anophelines and other mosquitos specially interested them, and innumerable papers and works on the subject began to be poured out. The entomological results were invaluable. Whereas in 1898 only about a hundred species of Culicidae were known, we have now recognised about six hundred, which have been carefully described in valuable works by E. E. Austen, G. M. Giles, L. O. Howard, R. Blanchard, and especially in an exhaustive monograph, by F. V. Theobald, and by many others. Regarding the habits of the insects my findings have been generally confirmed, without very much really new matter being added. Some of the observers, being new to the subject, have laboriously recorded facts (such as the abundance of gnats near their breeding-places, or in ground-floors of houses, or in dark corners, or on dark surfaces, or their transportation by carriages, and so on) which, I think, were perfectly familiar to all who have lived much amongst them.^ Returning to the subject of prevention, we must now note that an important new method was suggested by R. Koch during his visit to Italy in 1898 — namely, prevention by treat- ment of cases. This was tried at once by B. Gosio in Grosseto in Italy [1900]. Towards the autumn of 1899 Koch went with R. Pfeififer and H. Kossel to Batavia, where he discovered his law regarding the frequency of infection in native children ; and in December proceeded to German New Guinea, where he success- fully used his method of prevention at Stephansort [1900]. This method is entirely different to the ancient one of drainage, or to my modification of it. It aims, not at the reduction of the carriers of the parasites in a locality, but at the reduction of the parasites themselves by the general and complete treatment by ^ Also many habits have been ascribed to mosquitos, which exist only in the imagination of the writers. Thus Nuttall says [1899] that Aaron suggested destroying mosquitos by placing small lamps in trays of petroleum over ponds or marshes round dwellings. The gnats, attracted by the light, would fall into the oil. In 1900 two Italian writers, one of whom is supposed to have led the way regarding the mosquito malaria theory, not only approved this absurdity, but added the suggestion that the lamps " be furnished with powerful (j-?V) reflectors turned away from the house." I have never in my life seen mosquitos attracted by lamps. 38 HISTORY [Sect. quinine of all infected persons in the locality. If this is done, he argued, the Anophelines, however numerous they may be, will be innocuous, as they will find no parasites to carry. He describes the method ably, and says : " After all these experiences I consider myself warranted in stating that we are in a position, by means of the procedure which I have described, to make every malarious region, according to circumstances, wholly or nearly free from malaria." The method is invaluable, and there is no real rivalry between it and my method. Most admirable, too, has been the work in Italy, led by A. Celli, himself one of the most distinguished students of malaria. In 1899 he published an excellent text-book, in which he presented the whole subject of prevention according to the " new researches," with a history and accounts of various preventive measures. This was followed by innumerable researches and practical campaigns throughout the country — which have made a great reduction in the disease. All methods have been adopted, but principally perhaps the various quinine methods. Italy, however, is a temperate European country, with conditions very different to those which prevail in the tropics — and the malaria there is mostly rural. Still another method consists in the screening of houses by wire-gauze, a defence long employed in America against mosquitos. It was now used in Italy against Anophelines ; was much encouraged by the experiment of L. Sambon and G. C. Low in the Campagna in 1900 ; and has been widely employed at Panama. In 1898, the Colonial Office and the Royal Society appointed a commission, consisting of C. W. Daniels, J. W. W. Stephens and S. R. Christophers, to follow up my work. Daniels left the commission in 1899 after some good work in British Central Africa ; but the other observers were sent at my recommendation to West Africa during the same year. There they continued our researches of 1899, but laid special 7] YELLOW FEVER 39 stress on segregation for Europeans. They found many interesting facts about mosquitos, and also developed very fully the subject of infection of native children, and the causes of local malaria in West Africa. In 1901 they were sent to India at my suggestion, and continued similar work there. Their valuable observations are contained in a series of reports [1899-1903]. Also following our first expedition to Sierra Leone, the Liverpool School of Tropical Medicine sent out a stream of expeditions, all of which gave useful information about local malaria, or started practical measures. At the end of 1900 a very important event occurred — W. Read, J. Carrol, J. W. Lazear and A. Agramonte proved in Havana that yellow fever is carried by Stegotnyia calopus {fasciata) just as malaria is carried by Anophelines. They proved this by direct experiment on men ; but did not succeed in finding the yellow fever organism either in man or in the mosquito. Early in 1901 General Leonard Wood instructed the Chief Sanitary Officer of Havana, then Major M. C. Gorgas, to commence operations against these insects. In a few months the disease was banished from Havana. It was very disappointing at this time that so little had yet been done in British possessions to combat malaria by any of the measures rendered possible by the previous dis- coveries. There was a brilliant exception. On my visit to Sierra Leone I had met Dr H. Strachan, the Principal Medical Officer of Lagos, and he took up the matter with great interest. Fortunately the Governor of Lagos, Sir William MacGregor, himself a medical man (like General Leonard Wood), immediately saw the value of the new ideas, and began to push malaria prevention in Southern Nigeria in a most admirable way by all methods — drainage, quinine, wire-gauze and public instruction. But elsewhere local bodies had ignored the subject almost entirely. Even in Sierra Leone, where the way had been pointed out exactly, and where the disease was 40 HISTORY [Sect. the principal enemy of the colony, little had been done. The Acting Governor, now Sir Matthew Nathan, who had been very sympathetic during our visit in 1899, had left for the Gold Coast ; and, beyond appointing a single person for a few months to check the mosquitos, the municipality of Freetown had dropped the matter. Calcutta, where also I had suggested an anti-mosquito campaign in 1899, had done the same. Every- where, my proposal to reduce mosquitos in towns was treated only with ridicule. Early in 1901, therefore, I determined to try and give an object lesson in the work recommended by me. A rich gentleman of Glasgow kindly offered me ;^2,0C)0 to defray expenses ; and others helped me in various ways. On the 2nd July I arrived with Dr M. Logan Taylor, at Freetown, and, with the support and approval of the Governor, Sir Charles King Harman, commenced the work at once. Since 1899 I had gradually become convinced that anti- mosquito campaigns had better be conducted, not only against Anophelines, but against all kinds of mosquitos at once ; and this opinion was strongly reinforced by the yellow fever dis- covery just made, and also by the fact that certain Culicines carry filaria. In fact, since then I have always maintained the opinion which may be put as follows : // is one of the first sanitary duties of all municipalities and town councils in warm climates to keep down as much as possible the numbers of mosquitos within the area placed under them. We therefore engaged the services of twenty men, to whom the Governor added twelve ; and with these we removed piles of mosquito- breeding rubbish from the back yards of houses, and drained, emptied, filled up or oiled numbers of Anopheline pools. I returned to my duties in Liverpool on the i6th August; but M. Logan Taylor continued the work. In September C. W. Daniels of the London School of Tropical Medicine arrived in Sierra Leone, and reported favourably on the work ; and in January 1902 I visited it again for a week to watch progress. 7] VARIOUS CAMPAIGNS 41 There is no doubt that a great reduction in the number of mosquitos was effected by our measures ; but, of course, our work was meant only for a temporary object lesson, and we stated clearly that the improvement would last only if our measures were continued by the local authorities. Later in 1902, however, Logan Taylor reported that these authorities did not appear very anxious to continue them ; and we consequently closed the work when our money was expended — having done, we thought, as much as private persons could do.^ After my third visit to Freetown, Prince August d'Arenberg, President of the Suez Canal Company, asked me to advise regarding the prevention of malaria at Ismailia on the Canal. I arrived there in September 1902 with Sir VV. Macgregor, who did me the honour to accompany me. The town was swarming with both Culicines and Anophelines ; and efforts to control the malaria by liberal quinine distribution had not succeeded. I advised a continuance of this measure with general mosquito-reduction. In this case "intelligent and persistent efforts " were made ; and within a year the insects of both groups were almost entirely banished, and the ad- missions for malaria reduced from about 2,000 a year to 214. Since then, endemic malaria has entirely disappeared. Dr A. Pressat says that he originally reduced the disease by means of a mosquito brigade of only four men qui a tout fait [1904]. Scarcely less brilliant was the campaign at Klang and Fort Swettenham in the Federated Malay States, commenced in 1 90 1, and carried out chiefly by Dr Malcolm Watson. At Hong Kong also, a campaign was commenced at the same time, and carried out chiefly by Dr J. C. Thomson with very good results. Several anti-mosquito campaigns have been con- ducted in the United States; and in 1906- 1907 my brother, E. H. Ross, acting under the orders of Sir Horace Pinching, 1 A year later it was pretended that our efforts had failed, and the only thanks which we ever received for our pains was a subterranean effort to injure us. 42 HISTORY [Sect. completely cleared Port Said of Culicines. Other campaigns have been those of Dr A. Balfour at Khartoum, of many officers in Candia, some West Indian Islands, the East Indies, and Durban. In 1906 I went to Greece to advise regarding malaria at Lake Kopais ; and in 1907 to Mauritius (with Major C. E. P. Fowler) to advise the Government on malaria prevention there. As regards magnitude, however, the great American campaign, under Colonel Gorgas, against both malaria and yellow fever, at Panama ; that of Oswaldo Cruz at Rio Janeiro ; and that, so well guided by Drs Ed. and Et. Sergent in Algeria, have long held public attention. Descriptions will be found under the appropriate sections in this book. In spite of these brilliant examples, however, little was attempted against malaria for many years in the vast bulk of tropical countries. It is true that questions in Parliament and elsewhere often led to assertions that much was being done ; but those who really know what might have been done, and who were in a position to obtain the information from men on the spot, remained far from satisfied. On 23rd April 1906 the Earl of Elgin, Secretary of State for the British Colonies, issued a circular at the instance of Colonel Seely, M.P., to all Governors of Crown Colonies asking for specific details on this point. In September of the same year I read a paper at the 14th International Congress of Hygiene at Berlin [1907] in which I described what had been done in some tropical localities, and also criticised the lack of efforts in others. Still, however, little effect was produced, and I came to the conclusion that in many malarious places the authorities had no real desire to carry out anti-malaria measures, or else were entirely ignorant of how to do so. For example, though they always urged lack of funds as an excuse, they often omitted to do things which would cost almost nothing, such as to undertake the measure- ment of malaria, to issue careful reports, or to form the nucleus of an organisation. At the end of February I visited the Medical Congress at 8] REMARKS 43 Bombay in order to ascertain what work was being done in India, but met only with disappointment. A few months later, therefore, I gave a lecture at the Royal Institution of Great Britain, in which I ventured to complain very strongly regarding this state of affairs [1909]. Fortunately this has been followed by a considerable improvement. An anti-malaria league was started in South Africa, and the Indian Govern- ment held a conference on malaria at Simla, which practically endorsed all our teaching. Moreover, other movements for the generalisation of anti-malaria measures are now on foot, and will, I hope, produce better results. 8. Remarks. — Such in brief is the august history of malaria — and some day it will be considered as being no unimportant part of the world's history. To the thoughtful student of human affairs it contains many points of interest. We should note in the first place that several methods of prevention were well known long before the mosquito-theorem was established. Probably the ancients, and certainly the Italians, since the time of Lancisi (171 7), were so well acquainted with the good effect of drainage that this principle was accepted as a dogma in all the medical schools. The excellent results of quinine, both for cure and prevention, have also been well known, at least since the time of Maillot in Algeria (1834) — so well known in fact that the Government of India has sold the drug for many years at the public post-offices for a small price. Even the benefit of using a mosquito-net during sleep was, I remember, looked upon as an elementary doctrine when I first went to India in 1881. The mosquito-theorem has merely verified and precised these old ideas. It was therefore I think possible, long before 1899, to reduce the disease anywhere on a large scale. Efforts in this direction would have been invaluable in numbers of settlements in Africa and in the East and West Indies ; but were, I believe, seldom if ever made. Certainly many intelligent medical men 44 HISTORY [Sect. advocated them ; but there is a wide interval between the suggestion of public health measures and their execution. Where they were commenced they were soon abandoned ; no continuous public policy against the disease seems ever to have been adopted ; settlements were left for years at the mercy of marshes known to be poisonous ; and the methodical distribu- tion of quinine remained undreamed of. I have little doubt that if more intelligence had been shown in these respects many of these settlements would have already grown into prosperous states. Laveran's discovery of 1880 was one not only of theoretical, but of practical, importance. It enabled medical men to dis- tinguish with certainty cases of malarial fever from other diseases, and, after making the diagnosis, to treat the patient methodically. But many years elapsed before it began to be used for these purposes. The parasites were not seen in India, for example, until 1887 (by Vandyke Carter). I did not hear of the dis- covery until 1888, and did not see the parasites until 1894. Scarcely half a dozen men were studying them in India at that time. The use of the microscope scarcely became general anywhere in the tropics until after 1900; and quite recently medical men have told me of hospitals which were not even provided with these indispensable instruments. Numbers of others had never read the fundamental literature ; and up to the present day many colonies possess no sufficient organisa- tion for circulating recent medical papers. Yet in most tropical countries there were large public medical services which ought to have been properly provided for in these respects. It is surprising, when we remember that malaria often causes a third of the sickness in a place, to note that Laveran's discovery was not immediately followed by public investigations on the subject, especially as to the route of infection.^ The work was done almost entirely by private persons. Even when ^ In 1898 the Government of India appointed me to undertake researches on malaria— this being, I believe, the first case of the kind. 8] INACTION 45 information was thus obtained, it was left for years untaught in the medical schools, or neglected in practice. But worse than this, little has been done even to encourage the private workers. Indeed I know of several cases where such workers have received for their pains nothing but the ridicule of less laborious colleagues, and the persecution of jealous superiors.^ There was no reason why the prevention of malaria accord- ing to the new methods should not have been commenced after 1899 in every civilised malarious country. Such countries possess responsible governments and expensive sanitary and medical services — in fact all the machinery required for the work. But the efforts actually made have been due almost entirely to isolated enthusiasts, while in many places nothing approaching a genuine campaign has even yet been attempted. In others, again, some efforts have been reported, but their perfunctory nature is only too apparent to those who are acquainted with the subject. Yet the work has been done, and well done, in many places. Why then has it not been done in all? The facts are undeniable. In numerous localities the disease causes not only an immense amount of sickness, but a great loss of efficiency amongst officials, soldiers, workmen and the general public, and a corresponding waste of public money and reduction of prosperity. It can be combatted only by well- organised government action ; and governments admit their responsibility in such matters. Yet governments have taken little part in the investigation of malaria, and have even neglected to utilise for practical purposes the investigations of others. Nor is the case of malaria the only one of the kind. Filiriasis is very prevalent in many localities, where it produces numerous unpleasant diseases ; yet P. Manson's discovery of 1877, that the parasite is carried by mosquitos, has scarcely ever been utilised up to the present (except perhaps in the case ^ The treatment of my brothers in Egypt is well known. In British administration we do not expect gratitude for scientific work ; but is there anything more childish than to punish such labours by gratuitous persecution ? 46 HISTORY [Sect. of G. C. Low's work at Barbados). Another example (and I could quote many) is that of the entry of plague into India in 1896 — an event which has destroyed millions of lives and wasted millions of money. Precisely similar complaints are frequently heard regarding diseases of animals and of crops, and regarding mining, manufactures and commerce. The student will do well to ask himself the cause of this phenomenon — which is of fundamental importance in connection with our subject. We recognise, of course, that the world is by no means perfect ; but for this very reason we should endeavour to extricate the causes of its imperfections. The following points may be suggested for consideration, or correction, by the reader. The principal cause of the faults referred to seems to me to lie in a curious tone of thought which is now very prevalent, especially in this country ; according to which all matters of practical utility to mankind are looked upon as being rather base preoccupations for the more perfect type of human being. The study of nature, the extirpation of disease, the management of cities, invention, the development of agriculture, manufactures and commerce, and the organisation of prosperity are inferior things. We are to seek a higher level in personal manners, literary criticism, eloquence, sport, party politics, sectarian dogma, and so on. It is the modern equivalent of Indian fakirism, by which, lost in various lofty speculations, we are tauerht to remain content in the midst of starvation and disease. This spirit, fostered in us from childhood, leads to false ideas of government. The scientific side of administration is apt to be forgotten in the noise of endless and despicable party strife ; progress ceases while we discuss abstract notions about law, liberty, representation, nationalism and so forth ; the machine refuses to work while the mechanics are quarrelling over the lubrication. The result is precisely what may be imagined — cities built without sense or forethought, filthy slums, hovels filled with disease, gulfs of destitution ; and the voices of 8] IRRATIONALISM 47 those who would better this state of affairs by scientific methods are lost among the yells of the opposing factions. Though in the tropics we are still spared many of the evils of party government, the same spirit of inutilitarianism often remains. Money which would suffice for the assainment of whole towns is wasted rather on the construction of extrava- gant town halls and post-offices. The cost of a new hospital would often suffice to prevent more cases of sickness than are treated in it ; and that of invaliding to prevent the disease which causes it. The British Government spends ;^ 15,000,000 a year on the education of children ; but gives, I believe, literally nothing for the scientific investigation of scarlet fever, measles, whooping - cough, chicken - pox and mumps, which work such mischief among these same children — a fact which by itself proves the illogical nature of the educa- tion given. Similarly in the tropics I have seen a large class of coloured children, almost all of whom were suffer- ing at the time from fever or enlargement of the spleen, being taught the dates of accession of the Plantagent kings ! We all know how often sanitation receives only the crumbs which remain at the bottom of the public pocket after all the other departments have been well fed — the final triumph of fakirism. But we must not blame the general public alone. We are familiar with the manner in which individual medical men give their services, not only to medical science, but for the gratuitous treatment of the poor ; yet nevertheless the medical profession as a body possesses little influence or power in public affairs. It is a body without a head. It does not take a high enough stand with the public regarding scientific and sanitary matters. The duty of the profession does not lie merely in teaching and in the cure of the sick, but in everything that appertains to the health of the people. Yet it is apt to be dominated, not by this lofty ambition, but by other ideals ; and it therefore seldom bestirs itself regarding 48 HISTORY [Sect. 8 its higher duties. Can we wonder then that governments also are apt to neglect the same duties ? Several high officials have told me that medical men do not often become good administrators. This is probably due to the fact that governments seldom take enough care in the selection of their administrative medical officers. I have seen many able men in such posts, but others who were not fitted for them. The head of a large sanitary or medical depart- ment should possess a full knowledge of the recent scientific and practical advances in his subject. Too often we find officials who have been promoted merely on account of seniority, or in consequence of self-service ; men who express contempt of these recent advances because they know nothing about them ; who have no ideas, and who make no efforts. Such men, when taxed with defects in their department, always complain that the Government does not grant enough funds. But they are the responsible heads of those departments ; and if their advice is neglected they should resign their post. In 1730 Dr Thomas Fuller {Exanthematologia, Charles Rivington, London — quoted by W. S. Thayer) wrote: "Can any man, can all the Men in the World, tho' assisted by Anatomy, Chymistry, and the best Glasses, pretend positively and certainly to tell us, what particles, how sized, figured, situated, mixed, moved, and how many of them, are requisite to produce a quartan ague, and how they specifically differ from those of a tertian . . . ? " We are now able to tell all these things. They have been written in hundreds of books^ and are familiar to thousands of students. Those who belittle the powers of science are not always, perhaps, the wisest of men. The history of malaria contains a great lesson for humanity that we should be more scientific in our habits of thought, and more practical in our habits of government. The neglect of this lesson has already cost many countries an immense loss in life and in prosperity. CHAPTER II SUMMARY OF FACTS REGARDING MALARIA {Suitable for Public Instruction) 9. The Parasites and the Fever. — Malaria, or Malarial Fever, is also known by the names Paludism, Marsh Fever, Jungle Fever, Ague and Periodic Fever. It is often called by local names such as Country Fever, West African Fever, Burma Fever ; and varieties of it are called Intermittent Fever Remittent Fever, Pernicious Fever and Blackwater Fever, Malarial fever occurs more or less in all warm climates, especially in the summer, after rains, and near marshy ground ; and causes 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. These parasites are introduced into the blood through the proboscis of certain species of the mosquitos 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 49 D ^' 50 SUMMARY OF FACTS REGARDING MALARIA [Sect. 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 each parasite with the spores. After from six to forty hours or more this poison is eliminated from the patient's system ; and his fever then tends to leave him. In the meantime, however, another generation of parasites may be approaching maturity, and may cause another attack of fever like the 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 a long time after the patient was first infected, and after he has moved to localities where there is no malaria. It is probable that as 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 enlargement of the spleen, especially in patients who have suffered from many relapses. Death is sometimes caused by sudden and grave symptoms. lo] THE PARASITES AND THE FEVER 51 Chief among these are the symptoms known as Blackwater Fever, or Haemoglobinuria, which generally occurs in old and neglected infections. Death is also often caused during the course of a malarial infection by other diseases, such as pneumonia or dysentery, acting upon a constitution already 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 at leasFof three kinds, which can easily be distinguished in blood placed under the microscope. These are (i) the parasite which produces its spores every three days and causes quartan 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. -' If a little blood containing any one of these species of parasites is taken from a patient, and is then injected into a vein of a healthy person, the latter will almost certainly soon become infected with the same species of parasite. Closely similar parasites are found 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 ; and as long as a single parasite remains alive in the blood, infection is continued and the patient may be subject to relapses. At least five grains (1/3 gramme) of sulphate of quinine should be taken by an adult patient every day without fail for four months ; but he should consult a medical man regarding de- tails of the treatment. 10. The Mode of Infection Besides those forms of the 52 SUMMARY OF FACTS REGARDING MALARIA [Sect. malaria parasite which produce spores in the human body, there are other forms, male and female. When certain species of the mosquitos 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 summary. Numerous birds and men have been infected experimentally in this manner. Thus the parasites of malaria pass alternately from men to certain mosquitos, and back from these mosquitos 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. lo] THE MODE OF INFECTION 53 It is not known with certainty when and how this process first commenced ; but probably all such parasites were origin- ally 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 mosquitos. From the time of the ancients it has been known that malarial fever tends to be 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. Attempts to produce infection by these have always failed. But the Anophelines which carry the parasites breed in marshes and in 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 neighbour- ing 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% or more of them. Such Anophelines when 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 54 SUMMARY OF FACTS REGARDING MALARIA [Sect. 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. 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 parasites, 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. 11. Facts about Mosquitos.— Gnats, which in the tropics are commonly called mosquitos, belong to the zoological family of Insects known as the Culicidae (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. ii] MOSQUITOS 55 Like that of other insects, their life is divided into four stages, the egg ; the larva (or caterpillar) ; \hepupa (or chrysalis); and 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 lai^a 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 male feeds only on the juices of plants ; but the female sucks the blood of men, beasts, birds and reptiles. The female often 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, out-houses and woods, where they may remain for months until better con- ditions 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 the distance of half a mile or more from their breed- ing places. If, however, plenty of places where they can obtain food exist near at hand, 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 generally favoured by warm weather, by plenty of water suitable for their larvae, and by abundance of food. 56 SUMMARY OF FACTS REGARDING MALARIA [Sect. They tend to be diminished by 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 Culex, Stegomyia and Anophelina. Culex pipiens is a very common gnat in Europe, and allied species are found almost everywhere in the tropics. The larvae 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. When, disturbed, they wriggle at once to the bottom. The adult insects gener- ally 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 or allied species in a manner very similar to that in which the Anophelines carry the parasites of malaria. Stegomyia calopus and allied species 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 tin or oil tin, flower-pot, broken bottle and crockery, tub or barrel, choked drain, roof ii] MOSQUITOS 57 gutter, etc., 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 daytime, and often abound in woods and in the shade of trees. In America Stegomyia calopus carries yellow fever. The Anophelines consist of about one hundred and twenty 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 rain water 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, etc. Thus while the larvae of Culex and Stegomyia occur in the small collec- tions of water which abound in and around houses, on the other hand the Anophelines are principally -marsh tnosquitos — owing to which malaria is generally 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 Culex and Stegomyia. The adults are speckled brown and white, or black and white ; and gener- ally the wings are not plain, but 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 58 SUMMARY OF FACTS REGARDING MALARIA [Sect. wall ; whereas the Culex and Stegoniyia sit with the tail hang- ing downwards, or even nearly touching the wall. All these facts enable any one to distinguish at sight both the larvae and the adults of Anophelines from those of Culex and Stegoniyia. 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. 12. Personal Prevention. — If they can avoid it, people should not go to live in known malarious places, nor in the vicinity of marshes, nor 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 allov/ed to hang down anywhere to the floor ; and it should be stretched tight, in order to allow every breeze to enter, and should 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 mosquitos, but also keep the body cool, comfortable and vigorous, even in great tropical heat. Where there is great danger of malaria, five grains (1/3 gramme) of quinine should be taken regularly every day 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 heat ; and it is preferable instead to carry and use 12] PREVENTION 59 constantly a palm-leaf fan, with which mosquitos can be driven off and the body kept cool. A small butterfly-net of white (not green) muslin may be kept in the house for the purpose of catching troublesome mosquitos during the day ; and the servants may be taught to use it It may sometimes be easier to kill all the mosquitos in a room in this manner than by fumigation. Mosquito traps consist of boxes lined with black cloth. Attracted by this colour mosquitos enter the box for refuge during the day. The lid or shutter is then suddenly closed and the insects within are killed by a little ammonia or chloroform poured into the box through a protected opening. Or, the lid can be made to slide down to the bottom of the box in such a manner as to crush the inmates. To fumigate a room thoroughly for mosquitos all the chinks in the doors and windows should be closed by pasting paper over them. Then burn the culicide as follows (Sir Rubert Boyce) : — 1. Sulphur. — Allow 2 lbs. of sulphur to 1,000 cubic feet. Use two pots, place them in a pan containing I inch of water to prevent damage, and set fire to the sulphur by means of spirit. Duration. — Three hours. 2. Pyrethrum. — Allow 3 lbs. to 1,000 cubic feet, and divide amongst two or three pots, using the same precautions as with sulphur. Duration. — Three hours. 3. Camphor and Carbolic Acid. — Equal parts camphor and crystallised carbolic acid are fused together into a liquid by gentle heat. Vaporise 4 ozs. of mixture to each 1,000 cubic feet ; this can be done by placing the liquid in a wide shallow pan over a spirit or petroleum lamp ; white fumes are given off. To avoid the mixture burning, the fumes should not come in close contact with the flame of the lamp. Duration. — Two hours. 6o SUMMARY OF FACTS REGARDING MALARIA [Sect. Remember that sulphur tarnishes metal work and injures pianos, sewing machines, chronometers, telephones, etc. The camphor-carbolic mixture is one of the most agreeable and effective of the various agents. Many mosquitos may be killed, without troubling to cover the chinks with paper, simply by picking up and destroying the stupefied insects near the windows after the fumigation. The householder should always take care that no stagnant water is allowed to remain anywhere in his premises in cisterns, drains, gutters, tubs, jugs, flower-pots, gourds, broken bottles and crockery, old tins and other rubbish, or in holes in trees, or in certain plants such as wild pineapple — in all of which mosquitos are apt to breed. If the water cannot be emptied out, the larvae of the mosquitos in it may be destroyed by pouring a little kerosine oil, or in the case of drinking water, a little eucalyptus oil, upon the surface. This should be done once a week ; and the householder should make it a habit to inspect his premises for this purpose every Sunday. Cisterns and tubs containing drinking water should be kept screened in such a manner as to prevent mosquitos laying their eggs on the surface of the water. If he follows this advice the house- holder will generally obtain a great reduction in- the number of the insects in his house. If, however, the plague continues, he should appeal to the local sanitary authorities. 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. 13. Public Prevention.— As a broad general rule, malaria causes a quarter or more of 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. 13] PREVENTION 6i 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 may 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. CHAPTER III THE FUNDAMENTAL OBSERVATIONS AND EXPERIMENTS 14. The Parasites cause the Disease. — Having studied the history and a general outline of our subject, we must now examine the fundamental observations and experiments in greater detail. It is advisable to begin with the evidence which proves that the parasites are really the cause of the disease, (i) The parasites are not found in those who have not suffered from malarial disease. Laveran discovered the para- sites of malaria at Constantine, Algeria, in 1880. Since then the blood of hundreds of thousands, possibly of millions, of patients suffering from various diseases must have been examined, during the ordinary course of clinical work, in the civilised countries of the globe. Yet I have never heard of a single case in which Laveran's parasites are reported to have been found by a competent observer in persons who have never had malarial fever. For example, in Britain, which is now practically non-malarious, they are never seen in the vast numbers of hospital patients. In only two cases that I know of have they been observed in men who have never been out of this country, and both these patients suffered from the characteristic symptoms of malarial fever.^ In the tropics they are often found in persons, especially children, who have no fever at the moment of examination ; but that is another matter. Such persons generally show other symptoms of the disease ; and I know of no case which has been proved to 1 See the articles by Copeland and Smith [1906] and Easton [1909], and page 214. 62 Sect. 14] FUNDAMENTAL OBSERVATIONS 63 have the parasites without having had any symptoms of the corresponding malady. (2) The parasites can ahvays be found in a large proportion of malaria cases. The amount of blood examined under the microscope is extremely small compared with the total amount of blood in a patient's body ; so that if the parasites are not very numerous they may easily be overlooked, even by a skilled observer. Moreover, many cases come under observa- tion only after the parasites have largely diminished in numbers ; or do not remain under observation long enough for a thorough search for the parasites to be made. Hence we can scarcely expect to find the organisms without fail in every patient. But the experience of thirty years proves that the percentage of successes depends almost entirely on the care with which the search is made. Since Laveran's discovery the parasites have been found by innumerable observers in large proportions of their cases. To mention a few — Laveran himself observed them in 432 out of 480 cases in Algeria [1891, p. 30]; W. S. Thayer and J. Hewetson in nearly all of 333 hospital in-patients in Baltimore [1895] ; A. Billet in all of 395 cases in Algeria [1901] ; W. Duggan in all of 400 cases in Sierra Leone [1897]. In Secunderabad, India, without attempting exhaustive search, I found the parasites in 69 out of 112 cases [1896]. Similar figures are given in most papers on the subject, and the matter has now become a commonplace of clinical medicine. (3) The patient' s fever begins at the moment when the spores of the parasites are liberated. This important fact was discovered by C. Golgi at Pavia, towards the end of 1885, and proves that the fever depends upon the parasites. In a masterly paper [1886] the author describes his study of forty cases of malaria, mostly quartan. In twenty-two of these he followed the de- velopment of the parasites in the peripheral blood pari passu with the progress of the malady ; and he gives five of the cases in detail as examples of his finding. 64 OBSERVATIONS AND EXPERIMENTS [Sect. The first classical case was that of a woman suffering from untreated simple quartan fever (attacks occurring every three days). Her blood was examined at 11.30 A.M. on the 2nd November, at the moment when her fever was expected to commence, and was found to contain a few full - grown parasites, and many other ripe ones full of spores. The attack commenced at noon while the blood was being examined. Next day there was no fever, and the blood contained only young parasites. The next day (4th November), there was still no fever, but the young parasites had now grown larger and occupied 3/4ths to 4/5ths of the containing haematids. On 5th November, three hours before the expected attack, the blood again contained nearly mature parasites, some with commencing spore formation. An hour before the attack these were increased in number. The attack then commenced at noon. Three hours later only a very few sporulating forms occurred ; and five hours after the attack all of them had disappeared, being again replaced by numerous young parasites. On 6th and 7th November the same development of the parasites occurred as on the 3rd and 4th ; and on 8th November there was a third attack of fever with parasites as on the 2nd and 5th. Quinine (i '5 grammes) was given on the loth ; and a fourth attack of fever occurred at 5.30 P.M. on nth November. The next case described by Golgi was one of "double quartan," that is, two sets of parasites reaching maturity on different days — one set giving severe attacks on 24th, 27th and 30th November, and the other mild attacks on the 23rd, 26th, 29th and so on. The parasites of each set developed just as in the first case, independently of those of the other group. The third case was at first triple quartan ; then, owing to the dying out of the different sets of parasites, double, and lastly single, quartan — the parasites always undergoing the same cycle of development. The fourth and fifth cases need not be described here. These beautiful studies were quickly confirmed by W. Osier 14] FUNDAMENTAL OBSERVATIONS 65 [1886, 1887], by many Italian workers, and by Mannaberg. Such facts have also now become a commonplace of clinical medicine. (4) The different types of malarial fever are caused by different species of parasites. Since the time of the ancients clinicians have been acquainted with three different types of fever, the quartan, the tertian, and the irregular or malignant type. This variation of type was equally surprising and inexplicable until Golgi, after elucidating quartan fever, commenced a study of tertian, and showed that it is produced by a parasite which is morphologically different from the quartan parasite, and reaches maturity every two, instead of every three, days. As in quartan, however, the patient's fever begins at the moment when the spores are liberated [1886, 1889]. Golgi also suggested that the third variety of fever is associated with a third variety of parasite — that which produces the well-known " crescents " ; and this was proved to be the case by P. Canalis [1890] and Marchiafava and Celli [1890], who made a detailed study of the organism. Numerous confirmations followed, and the observa- tions are now in general use for clinical diagnosis. (5) Both parasites and the fever may be reproduced in healthy persons by the inocidation of infected blood. This has been done successfully in fifty-one cases, which will be described in the following section, (6) Both the parasites and the fever may be reproduced in healthy persons by the bite of infected mosquitos. This has been done successfully in thirty-six cases, which will be described in section 17. These facts are more than suflficient to prove that the parasites cause the disease. Additional but less precise arguments are : — (7) The severity of the illness depends roughly on the number of parasites present. First suggested by Laveran and Golgi [1886], this theorem is now generally accepted, but rather on the grounds of common experience than on precise estimations. E 66 OBSERVATIONS AND EXPERIMENTS [Sect. (8) Quinine reduces both the parasites and the fever. This theorem, first suggested by Laveran, is now accepted every- where, but still requires more precise study. (9) Certain secondary symptoms are caused by the accumulation of the parasites in certain organs. As frequently proved in the case of the malignant parasites. (10) Both the parasites and the fever tend to disapt>ear in a locality if the carryitig A nophelines are greatly reduced in number. As shown in many places, notably Ismailia. 15. Experimental Blood Inoculations. — These classical experiments, commenced independently of Laveran's discovery, and giving independent proof of a contagium vivum in malaria, are of fundamental importance. The first experiments were those of A. Dochmann [1880]. One drop of the contents of vesicles of Herpes labialis of a boy suffering from quartan was inoculated subcutaneously into a healthy man on 8th February (?) 1880. The man had rigors and fever the same evening and on nth February, and malaise on 14th February, no symptoms occurring in the intervals. Subsequently three men were similarly inoculated with herpetic serum from a girl with quotidian. This was followed by five days' quotidian in one of the men, and none in the others. Lastly, a girl was similarly inoculated on 12th April, and had fever on 14th and i6th April. There appears to have been no incubation period, and I agree with Laveran that the cases must be rejected. The admissible cases are now given and numbered for reference. Case I. Gerhardt [1884]. — Source, quotidian fever; i c.cm. of blood taken at end of rigor and injected subcutaneously into B. S. on nth August 1882. Subject had slight fluctuations of temperature 22nd to 26th August, and severe rigor and fever on 27th, 28th, 29th August. Quinine 2 grams on 29th ; recovery after two days. Case 2. Ibid. — Source, quotidian fever ; blood (? quantity) 15] BLOOD INOCULATIONS 67 taken during attack, and inoculated into K. G. at 2.15 P.M. on 4th July 1883. Subject attacked at 6 P.M. on loth July, and again at about 3 P.M. on nth, 13th, 17th, 23rd, 25th, 28th, 29th, 30th (severe), 31st July. Quinine 2 grams daily, ist to 6th August. Recovery followed. Note. — The author appears not to have heard of Laveran's discovery ; but his work was careful and good. Case 3. Marchiafava and Celli [1885]. — Healthy subject was inoculated subcutaneously with 0*5 c.cm. of blood taken from quotidian cases during attack on i8th July and 15th August (?) 1884. Again, intravenously with 0*5 c.cm. taken from a quotidian case during rigor on 21st August. Again, intravenously, with i c.cm. taken from a case of double tertian (? malignant) six hours before attack, on 26th August. Subject had strong rigor one hour after this last injection, and further attacks on 27th, 30th August, and ist, 3rd September, when quinine was given. Isolated attacks occurred up to October. Case 4. Ibid. — Subject, who had previously had malaria and was said to have been cured, was inoculated intravenously with 06 to 3'0 c.cm. of blood from various cases on 31st August, 4th and 6th September. Left hospital. Returned to hospital with fever on loth September. Daily attacks like those of the source of blood inoculated on 6th September, the period of incubation being said to be seven days. Case 5. Ibid. — Healthy subject inoculated with I'O c.cm. of blood from three cases, subcutaneously or intravenously on 6th, 9th and 13th September. Strong rigor on 20th September, and fever till 25th. Note. — Confused experiments. Type of parasites not clearly seen (before Giolgi's work). Mariotti and Ciarrochi, in whose clinics the work was done, also reported it. 68 OBSERVATIONS AND EXPERIMENTS [Sect. Case 6. Gualdi and AntoHsei [1889, No. 225]. Source reputed to be quartan ; 3 c.cm. injected intravenously. Subject attacked ten days later with malignant parasites. Case 7. /did. — Same source, dose and injection. Another subject. Attacked twelve days later, also with the malignant parasites. JVote. — In these two cases the quartan of the source seemed to have produced malignant in the subjects ; but the authors stated later [1889, No. 264] that the source was subsequently found to contain malignant as well as quartan parasites, the former also being observed microscopically — so that the result of the experiments was not surprising. Case 8. Antolisei and Angelini [1889, Nos. 226, 227]. — Source, mild tertian ; blood (? quantity) taken at beginning of fever ; injection intravenous. Subject attacked with fever after eleven days ; mild tertian parasites. Case 9. ll>td. — Same source as previous case ; i 5 c.cm. of blood taken at the same time ; injection intravenous. Subject attacked almost at same hour as previous case. The same parasites. Case 10. Gualdi and Antolisei [1889, No. 264]. — Source, quartan ; 3 c.cm. of blood injected intravenously. Subject attacked after twelve days; quartan parasites. Case II. /did [1889, No. 274]. — Source, malignant parasites with apyrexia and (?) crescents only ; 2 c.cm. of blood, intra- venous. Subject attacked with irregular fever on ninth day, and asexual malignant parasites on tenth day. Crescents on eighteenth day. Case 12. Di Mattel [1891, No. 121]. Source, malignant; (?) quantity of blood injected intravenously. Subject, a case of quartan which had (?) recovered spontaneously. A few days 15] BLOOD INOCULATIONS 69 later small unpigmented asexual forms, and crescents twenty- five days after inoculation. Case 13. Ibid. — Source, quartan ; (?) quantity of blood, intravenous. Subject, a case containing crescents only. Subject attacked after fifteen days with quartan parasites, the crescents diminishing in number. Note. — These two cases show that a second species of parasite can be added to a previous invasion. The disappearance of the crescents in Case 13 need not have been due to the new invasion. Case 14. Calandruccio [? 1891]. — Source, quartan ; i c.cm. of blood, subcutaneously injected on ist December 1890. Subject, the author himself, attacked with quartan on iSth December ; relapses after two and three months. Case 1 5. Ibid. — Source, a case showing (?) only crescents ; r5 c.cm. subcutaneous. Subject, the author after recovery from previous infection. After fifteen days was attacked by severe rigor and fever, and then crescents after three days. No young asexual forms found. Several relapses. Case 16. Ibid. — Source, quartan ; i c.cm. of blood (?) sub- cutaneous. Subject attacked after twelve days with quartan. Case 17. Ibid. — Source containing only crescents ; i"5 c.cm. (?) subcutaneous. Subject the same as in previous case, four months later. Crescents found in spleen on eighteenth day, and in peripheral blood on twentieth day. No asexual forms. Note. — Author seems to have believed with Grassi and Feletti that the crescents were a species by them- selves {Laverania). Case 18. Bein [1891]. — Source, mild tertian. Blood drawn by leeches, taken out by a syringe, and injected to the amount of 2 c.cm. in this and the three following cases. Subject attacked on twelfth day with mild tertian parasites. 70 OBSERVATIONS AND EXPERIMENTS [Sect. Case 19. Ibid — Source, mild tertian. Same procedure. Subject attacked on twelfth day with mild tertian parasites. Case 20. Ibid. — Source, mild tertian. Same procedure. Subject attacked on tenth day with mild tertian parasites. Case 21. Ibid. — Source same as in last case. Same pro- cedure. Subject attacked on tenth day with mild tertian parasites. Note. — Four attempts failed. The injection was intra- venous in one case, subcutaneous in the others. The type of fevej- was not always the same as that of the source, being sometimes simple and sometimes double tertian ; but this is easily explicable. The same parasite was always found in the subject. Case 22. Baccelli [1892]. — Source, tertian ; 3 c.cm. of blood injected intravenously. Subject attacked with double tertian parasites after six days. Case 23. Ibid. — Source, quartan ; 4 c.cm. of blood contain- ing few parasites, intravenous. Subject attacked with single quartan after eleven days. Case 24. Sacharofif [1894]. — Source, malignant. Blood drawn by leeches, which were kept on ice for four days ; 1/4 c.cm. of this blood injected subcutaneously on 4th October (?) 1893. Subject, the author himself, had rigor and fever on i6th and 17th. Malignant parasites found on latter date. Note. — This experiment was made during the course of study of the vitality of the parasites in leeches kept at freezing point. A second experiment, with blood kept thus for seven days, failed. Case 25. Bignami and Bastianelli [1894.] — Source, malig- nant ; 2 c.cm. taken at close of paroxysm ; numerous parasites. Subject attacked after (?) three days with the same parasites. 15] BLOOD INOCULATIONS 71 Case 26. Ibid. — Source, malignant; 5 c.cm. of blood with moderate number of parasites, at close of paroxysm. Subject attacked after (?) four days with the same parasites. Case 27. Ibid. — Source, malignant ; 3/4ths c.cm. of blood with moderate number of parasites ( ? scanty). Subject attacked after five days with the same parasites. Case 28. Ibid. — Source, malignant; i/Sth c.cm. with (?) numerous parasites. Subject attacked after four days with same parasites. Case 2<^. Di Mattei [1895]. — Source, quartan; 2 c.cm. sub- cutaneous, on 14th August (?) 1894. Subject attacked with simple quartan on ist September (sixteen days). Case 30. Ibid. — Same source and same injection on same date. Subject attacked with simple quartan on 25th August (eleven days). Note. — Two other cases, injected subcutaneously with 0*5 and I'O c.cm. failed. Case T^i. Ibid. — Source, malignant; 2 c.cm. of blood from epistaxis injected subcutaneously in two places on i8th September. Subject attacked with malignant parasites on 3rd October. Fever on 3rd, 4th, 5th, 9th, loth October. Crescents on nth; quinine on i6th. Fever again on 17th; quinine ; recovery. Note. — In this paper author re-describes his earlier experi- ments [1891], and also describes eight negative attempts to transfer the malaria of birds from bird to bird or bird to man, and four negative attempts to infect birds from men. Case "^^2. Bignami [1898]. — Source, malignant; less than one drop of blood, subcutaneous. Subject attacked after six days with the same parasites. Case 33. Ibid. — Similar to the above. Subject attacked after ten days with the same parasites. 72 OBSERVATIONS AND EXPERIMENTS [SECT. Case 7,4. Mannaberg [1905]. — Source, benign tertian; 0'2 c.cm. of centrifugated blood taken during paroxysm ; sediment injected subcutaneously. Subject attacked after twenty-one days with the same parasites. Case T,^. — Celli and Santori [1897]. Source, quartan; 4 c.cm., subcutaneous. The same parasites in subject after twenty-five days. Case 36. Idz'd. — Source, quartan ; 4 c.cm., subcutaneous. The same parasities after twenty-five days. Case 37. /(^/^. — Source, quartan ; 4 c.cm., subcutaneous. The same parasites after twenty-five days. Case 38. Id/d. — Source, malignant ; i'5 c.cm., subcutaneous. The same parasites after thirty days. Case ^g. Ibid. — Source, malignant ; r5 c.cm., subcutaneous. The same parasites after six days. Case \o. Ibid. — Source, malignant ; r5 c.cm., subcutaneous. The same parasites after seventeen days. Note. — In all these six last cases the blood was mixed with sera of horse, buffalo or cattle before being injected, in the hope of immunising the subject. Case Of! . — Elting [1899]. Source, benign tertian; 3 c.cm, of blood containing half-grown parasites injected intravenously on 7th August (?) 1898 at (?) Baltimore. Subject had a slight rise of temperature next day and sharp rise to 39*9° C. on loth. Benign tertian parasites next day. Case 42. Ibid. — Same source ; 2 c.cm. taken and injected 'he same day. Fever on fifth day ; benign tertian parasites on the previous day.' Case 43. Ibid. — Source, malignant, with numerous asexual forms and a few sexual ones. Blood injected (?) 1-5. to 4-0 c.cm. 15] BLOOD INOCULATIONS 73 (?) intravenously on 28th August (?) 1898. Fever night of 30th to 31st ; malignant parasites on 31st; crescents on 6th September. Case 44. Ibid. — Same source, method and date. Asexual malignant parasites found in subject ist September with commencing fever. High fever on 3rd, and crescents on 8th. Case 45. Ibid. — Same source and method. Inoculation of subject 29th August, followed by a short rise of temperature in ten hours, after which there was no fever till 5th September. Asexual malignant parasites on previous day (4th), and crescents on nth. Case 46. Ibid. — Source, malignant — Case 43 above. Blood (?) quantity taken a few days after appearance of asexual forms, and (? how) injected on 1st September. Asexual malignant parasites found on third day after injection, and thirty-two hours before first rise of temperature. Crescents on ninth day. Case 47. Ibid. — Same source, method and date. Fever on 4th September, and asexual malignant parasites on same day. Crescents on 1 1 th. Case 48. Ibid. — Source, malignant — Case 46. Blood contained numerous asexual forms, and 1*5 c.cm. injected intravenously on 9th September. Asexual malignant parasites on 13th, fever on 14th, crescents on 20th. Case 49. Ibid. — Two sources — malignant and benign tertian. Two or three drops of blood containing only malignant parasites injected subcutaneously (?) date. Next day 4 c.cm. from benign tertian case injected intravenously. Short rise of temperature two hours after second injection ; then normal for five days. Fever seventh day after first injection, and malignant parasites next day. Benign tertian parasites ten days after second injection ; both flourished together. Crescents seventeen days after first injection. Case 50. Ibid. — Two sources — benign tertian and malignant 74 OBSERVATIONS AND EXPERIMENTS [Sect. later. Blood from former, 4 c.cm. containing numerous parasites, injected subcutaneously. Slight rise of temperature six hours later. Marked fever on seventh day, and benign tertian parasites on tenth day. On the third day after first rise of temperature ( ? ten days after first inoculation) the subject was inoculated with ( ? quantity of) blood containing numerous asexual malignant parasites — intravenously. These were recovered in blood of subject four days later, together with numerous tertian parasites. Fever suddenly ceased eighteen days after first injection ; then seven days apyrexia with only one or two tertian parasites each day. But twenty-six days after first injection, quotidian fever with both parasites began. Quinine and cure. Case 51, Rosenau, Parker, Francis and Beyer [1904]. — At Vera Cruz. Source, double benign tertian (" heavy " infection) ; 2 c.cm of blood during rigor, mixed with equal part of salt solution, injected intravenously into subject at 2 p.m. on 6th November 1903. Slight reaction within an hour. Typical fever and parasites at 7 a.m. on loth November, double infection (section 19 (4)). This closes the list of positive experiments, but four important negative ones with blood containing (?") only sexual parasites remain to be recorded. Negative Case i. Thayer [1898, p. 75]. — Source, a patient, convalescent from first attack, had had quinine for four days, during which none but crescentic and ovoid forms were found in the peripheral circulation. A hypodermic syringe full of his blood was injected into median basilic vein of subject in August (? year). The latter was carefully observed for five weeks, but never showed fever or parasites. Negative Case 2. Elting [1899]. — Source, malignant, with crescents and asexual forms, treated for eight days with four hourly doses of 5 grains (o'325 grams) of quinine, until only the crescents were left. Subject, injected intravenously with 15] BLOOD INOCULATIONS 75 3 to 3*5 c.cm. of blood on (?) date, never showed fever or parasites. Negative Case 3. Ibid. — Same source, injection and date. Subject showed neither fever nor parasites. Negative Case 4. Ibid. — Same source, injection and date. Subject had slight transient rises of temperature two and six days after inoculation. No characteristic fever or parasites. Note. — These four cases give strong reason for supposing that the sexual forms (crescents) are not in any way concerned in the reproduction of the parasites in the blood of the patient who contains them (section 20 (4) ). I am much indebted to Professor A. Celli for obtaining for me from Professor Giulio Galli an account of two interesting experi- ments performed by the latter, showing that malarial blood may be inoculated without result into subjects who are taking quinine. Negative Case 5. G. Galli [ ? ]. — Source, benign tertian, many parasites ; 0'5 c.cm. of blood was injected subcutaneously into subject, a healthy woman who had been given 0'4 grams of "state" quinine daily for five days. The same dose was continued on ist, 2nd, 5th, 6th, /th, 12th, 13th, 14th day after inoculation, and then stopped. Subject remained in hospital for forty-two days after inoculations, but showed no sign of malarial infection. Negative Case 6. Ibid. — Same source, amount of blood and method of inoculation. Subject, a healthy woman, was given o"4 grams of quinine daily two days before inoculation, and six days after. She remained in hospital thirty-two days after inoculation, but showed no sign of malarial infection.^ Remarks. — I have verified most of these cases from the original literature ; but for a few of them the literature has not been obtainable. I have also omitted a few cases regard- ing which I can obtain no references. ^ See also section 65 (5). 76 OBSERVATIONS AND EXPERIMENTS [Sect. 16. The Parasites develop in Certain Mosquitos. — I commenced the study of the mosquito-theory of malaria in Secunderabad, India, in April 1895. Numbers of mosquitos of the genera Odex and Stegomyia were allowed to feed on patients whose blood contained the sexual forms of the parasites, and were afterwards dissected in the hope of finding in them some developmental stage of the organisms. This investigation was continued without success until August 1897. Many hundreds of insects of various species (undetermined) of these genera were thoroughly searched, and many hundreds more were examined less completely — strong evidence in favour of the view that the parasites do not develop in these kinds of gnats. On the 20th and 21st August 1897, I found the zygotes of the malignant parasite in two Anophelines (species undeter- mined) bred from the larvae and fed on a case of crescents. In September, I found them again under the same conditions in a mosquito of another species of Anopheline [December 1897 and February 1898.] About the same time MacCallum and Opie demonstrated the sexual nature of the crescents [1897]. On the 20th March 1898 I found the zygotes' of one of the malaria parasites of birds, P. danilevskyz Grassi and Feletti 1 890 {Proteosovia Labbe), in Culex fatigans, and worked out the life-cycle of these parasites in the insects [1898]. It was however of fundamental importance to prove that the bodies found in the mosquitos were really descended from the parasites found in the birds ; and the following proofs were obtained : — (i) The bodies in the mosquitos contained the characteristic plasmodin (pigment) of the parasites in the birds. (2) Their growth and development were observed in detail in the insects. (3) Out of 249 mosquitos fed on birds with no parasites or other parasites, not one was found to contain the 17] THE MOSQUITO CYCLE 77 bodies referred to ; but, out of 245 mosquitos fed on birds showing P. danilevskyi, 178 or 72% contained them. (4) Out of 10 mosquitos fed on a sparrow without parasites, none contained the zygotes. In 10 mosquitos, fed at the same time on a sparrow with moderate parasites (i/iooo^ haematids), 292 zygotes were counted. In 10 mosquitos fed at the same time in a sparrow with many parasites (1/50 haematids) 1,009 zygotes were counted. (5) In July to August I succeeded in infecting 22 out of 28 healthy sparrows, and some other birds, by the bites of infected mosquitos [1898, 1905]. This work was speedily confirmed by R. Koch [1899], by C. W. Daniels [1899], and, subsequently, by many others. I completed my work on human malaria in 1899 in Sierra Leone [1899, 1900] ; but in the meantime Bignami, Bastianelli and Grassi had already observed that the human parasites have the same life-history [1898- 1899.] Since then the life-cycle of the parasites in mosquitos has been studied by many workers (section 6). 17. Experimental Mosquito Inoculations. — We should begin by referring briefly to the early studies which showed that malaria cannot be communicated by marsh water. After the efforts of Salisbury in 1866, Balestra in 1869, Safford and Bartlett, Archer, Bargellini, Klebs and Tommasi - Crudeli — well summarised in the paper of the last named [1879] — to incriminate various organisms as the cause of the disease, several Italians carried out good researches on the effect of drinking water. Celli failed in infecting six people by water brought from the Pontine Marshes [1886] ; and Brancaleone and Marino performed similar experiments. The work of Agenore Zeri [1890] was very complete. He gave water from ^ Very roughly computed. 78 OBSERVATIONS AND EXPERIMENTS [Sect. the Pontine marshes and elsewhere to nine persons to drink in doses between 3 and i"5 litres a day for five to twenty days each. To sixteen others he administered the water in the form of inhaled spray ; and to five others by rectal injection. All the experiments were negative. Yet they should have succeeded if we suppose that the plasmodia live in such water and infect either by the respiratory or digestive passages — unless we assume that they died in the water during transit to Rome, where the experiments were conducted. In 1895-1896 I made twenty-two experiments with a view to infecting healthy persons with drinking water in which mosquitos had been allowed to lay their eggs and die [1896]. The first case was, by a coincidence, attacked with fever ; but as all the rest proved practically negative, I decided that no reliable evidence had been obtained one way or the other. A. Bignami, in a paper discussing Manson's hypothesis [1896], stated that he had failed some time previously in causing infection by the bites of mosquitos brought from malarious places. He believed with King that the insects bring the poison from the marsh, and I presume that his mosquitos were therefore collected at random. This hypothesis was not in accordance with parasitological teaching. The first correct experiments on mosquito-inoculation were performed by myself in August 1896. At that time I began to abandon part of Manson's hypothesis according to which the insects take the parasites from man and deposit them in water — I began to think that the insects take the parasites from man and also inoculate them into man. A number of several kinds of Culex and Stegomyia were therefore allowed to feed on various cases of malaria — one of which contained all the three species of parasites — and were then fed, after being kept for several days and on several occasions, upon Mr Appia, Assistant - Surgeon to my hospital in Bangalore, India. The result was entirely negative, the mosquitos being of the 17] MOSQUITO INOCULATIONS 79 wrong kinds, and the interval between the feedings too short [30th October 1896]. The first successful mosquito inoculations were those of birds, Calcutta, June to August 1898. Four sparrows and a weaver-bird, which had frequently been found to contain no parasites, and had been often used for controls in my laboratory for that reason, were bitten towards the end of June, on several nights in succession, by numbers of Ctilex fatigans heavily infected with P. danilevskyi. On 9th July they were all found to contain "swarms of the parasites." The experiment was next repeated on many more birds under proper conditions, with the following results : — (i). Out of twenty-eight healthy sparrows twenty-two or 79% were infected in this manner. (2). One of the six sparrows that escaped the first experi- ments was infected on a second trial (the remainder died). (3). Out of two crows and four weaver - birds, free from P. danilevskyi, one of the crows and all the others became infected. (4). Out of five sparrows, originally containing a very few P. danilevskyi, four showed a much more copious infection after the experiments. The experiments were quite decisive. At that time in Calcutta I found these parasites only in fifteen out of one hundred and eleven wild sparrows, and then only in small numbers in the blood. But, as I used large numbers of heavily - infected mosquitos, the produced infections were extremely copious, as many as ten to sixty parasites being counted in each field of the microscope (oil-immersion lens). The incubation period was always four to seven days. This success was reported in England by telegram, and was published by Manson at the end of July 1898. The following experiments have subsequently been per- formed on men. 8o OBSERVATIONS AND EXPERIMENTS [Sect. Case I. Bignami [November 1898]. — Some months later Bignami succeeded in infecting a man by following my methods. A number of mosquitos caught in infected houses at Maccarese were fed on a malaria-free inmate of the Santo Spirito Hospital, situated in a part of Rome where there is no malaria. They were fed on him nightly from 26th September to the end of October 1898, and belonged to Anopheles inaculipenms, and two species of Culicines. The subject was attacked with slight fever on 31st October, and severe fever the next two days ; quinine being given on 3rd November, In spite of careful search, the parasites (malignant) were not found until 3rd November, about forty hours after the first marked rise of temperature. Several relapses occurred later. Case 2. Bastianelli, Bignami and Grassi [1898- 1899]. — Anopheles niaculipennis caught at Maccarese were fed from 13th November to 2nd December 1908, on a healthy subject in the same hospital. Fever commenced on 3rd December and continued daily until 9th ; quinine on the 7th. Mild tertian parasites found on first day of fever. Parasites found also in the mosquitos. Note, — This fortunate experiment revealed that the tertian parasites also are carried by A. niaculipennis. Gametids appeared on 6th December. Case 3. Ibid. — Seven A. niaculipennis caught in an infected house at Tre Fontane were fed, each one once, on loth, nth, 13th December 1898 on a subject in the same hospital. The protospores were found in the salivary glands of two out of three of these insects examined. Subject attacked with fever on 29th December, the mild tertian parasites being found next day — two sets. Gametids on the 31st. Case 4. Ibid. — Three A. inaculipennis were fed on a case of crescents between loth to i8th December 1898, were incubated at 30"" C, for two days, and were then re-fed on a 17] MOSQUITO INOCULATIONS 8i healthy subject on 2nd and 5th January 1899. All three mosquitos were found to be infected, and two of them had protospores in their salivary glands. Subject was attacked with fever from 14th to i8th January. Quinine on i6th. Malignant parasites found on 15th and disappeared under quinine on 17th, No crescents found. Case 5. P. Manson [1900]. — Ten A, viaculipennis were fed on a case of double benign tertian in Rome on 17th, 20th, 23rd August 1900, and bit P. Thorburn Manson in London on 29th and 31st August, and 2nd and 4th September. Also thirty-five of same species were fed on a simple benign tertian case in Rome on 6th and 7th September, and on the same healthy subject in London on loth and 12th September. Fever began on 13th September, and continued on 14th, 15th, i6th and 17th. Benign tertian parasites found on i6th for the first time. Quinine on 17th. Relapse nine months later. Case 6. Rees [October 1900]. — A second subject, Mr Warren, was bitten by the second batch of mosquitos fed on previous subject at about the same time (not given). Fever commenced on 28th September after about fourteen days' incuba- tion, and seemed to have continued for some time. Parasites in phagocytes on 30th. Benign tertian parasites on 2nd October and subsequently. Quinine on 3rd. Author says that this case showed more parasites than the previous one, as he was bitten by more mosquitos. Case 7. Fearnside [1901]. — The following series of seven cases were obtained at Rajamundri, India, in i9(X)-i90i. Un- fortunately, the Anophelines were not identified, but the author states that only one species was used. Source, benign tertian, copious, sporulating on 17th December, when the Anophelines were fed. Insects were re-fed on the author himself on 20th December and ist and 8th January 1901. Tertian fever began on the 14th. Benign tertian parasites found on 18th. No quinine. F 82 OBSERVATIONS AND EXPERIMENTS [Sect. Note. — Author had suffered from mahgnant malaria with haemoglobinuria in 1891 ; but that, apparently, did not affect the present experiment. Case 8. Fearnside [1901]. — Source the same, and Anophelines fed on same date. Subject (an Indian) bitten on 28th December. Tertian fever on iSth January. Benign tertian parasites on 2ist. Case 9. Ibid. — Sources, two cases of benign tertian. Anophelines fed 12th and 13th December. Bit subject (Indian) on 27th. Benign tertian on nth January. Benign tertian parasites on 13th. In notes, author says that only one Anopheline inoculated the subject. Case 10. Ibid. — The same source. Anophelines infected 1 2th December and bit subject (Indian) on 26th. Tertian fever on 20th January, and tertian parasites on 25th. Apparently the same (one) mosquito used as in previous case. Case II. Ibid. — Source, double infection of malignant and of benign tertian. Anophelines infected i6th December, and bit subject (Indian) on 28th. Fever on 9th January, and malignant parasites on nth; doubtful tertian parasites on 12th. Case 12. Ibid. — Same source. Anophelines fed on same date and bit subject (Indian) on 28th December. Fever, 13th January. Malignant and benign tertian parasites on 14th. Note. — Of two other cases experimented with by Fearnside one appears to have failed, and one to have contracted fever after fifteen days, the finding of the parasites not being noted. Author states that protospores were found in all the Anophe- lines used. Case 13. Buchanan [1903]. — Experiments done at Nagpur, India. Source, malignant. Anophelines (species not given) fed 25th December 1901 to 8th January 1902, and bit subject 17] MOSQUITO INOCULATIONS 83 loth to 17th January. Fever 27th January, and malignant parasites. Case 14. Buchanan [1903]. — Source, malignant. Anophe- lines fed 13th to 23rd January 1902, and bit subject 24th to 27th January. Fever 12th February, and malignant parasites. Case 15. Ibid. — Source, malignant. Anophelines fed 24th January to 4th February 1902, and bit subject 7th to 19th February. Fever 19th February, and malignant parasites. Case 16. Ibid. — Source, malignant. Anophelines fed 27th January to 4th February 1902, and bit subject 4th to 20th February. Fever 23rd February, and malignant parasites. Case 17. Ibid. — Source, malignant. Anophelines fed 29th January to nth February 1902, and bit subject 12th to 23rd February. Fever 3rd March, and malignant parasites. Note. — Three attempts to infect from malignant sources failed. In two other cases, however, there was no fever after the mosquito inoculations, but crescents were found after twelve and eight days. These are not accepted here. Case 18. Ibid. — Source, quartan. Anophelines (? species) fed 30th January to nth February 1902 ; and bit subject from 14th to 27th February. Fever 25th, and malignant parasites {not \.\\os,& foimd in source). Note. — Four other cases from quartan sources failed. Anophelines not identified. Case 19. Ibid. — Source, benign tertian. Anophelines fed 8th to 20th January 1902, and bit subject 21st to 25th January. Fever 4th February, and benign tertian parasites. Case 20. Ibid. — Source, benign tertian. Anophelines fed 15th to 25th January 1902, and bit subject 28th January to I oth February. Fever 15th February, and malignant parasites {not XhosQ found in source). 84 OBSERVATIONS AND EXPERIMENTS [Sect. Case 2 1 . Buchanan [1903]. — Source, benign tertian. Anophe- lines fed ist to 13th February 1902, and bit subject 15th to 25th February. Fever 23rd February, and benign tertian parasites. Case 22. Ibid. — Source, benign tertian. Anophelines fed 2nd to 14th February 1902, and bit subject 17th to 22nd February. Fever ist March, and benign tertian parasites. Note. — Five other attempts to infect from tertian sources failed. Case 23. Schiiffner [1902]. — Experiments in Sumatra with two species of Anophelines, apparently Cellia kochii Donitz, and a Myzomyia. Source, benign tertian. Anophelines fed (?) 15th July (?) 1902, and bit subject, the author himself, on two days (?) 25th July. Fever, double tertian, nth August and benign tertian parasites. Case 24. Ibid. — Same source, and Anophelines fed same date, and bit another subject on same date. Fever on same date, single tertian ; and tertian parasites. Case 25. Ibid. — Source, malignant. Infected Anophelines bit subject (Chinaman) on 20th, 21st August (?) 1902. Fever 5th September, and malignant parasites 7th. Case 26. Jancso [1905]. — A long series of admirable experiments on the effect of temperature on the development of the parasites in Anopheles inaculipen?iis \ carried out at Kolozsvar, Hungary, Source, benign tertian. Six Anopheles fed 23rd September (?) 1904, and kept at 21° C. for twenty- three days. Subject bitten i6th October, had fever on 15th day. Benign tertian parasites on i6th day. Case 27. Ibid. — Source, malignant. Fifty-two Anopheles fed 26th October (?) 1904, kept at 30° C, and bit subject 3rd to 13th November. Fever 15th ; malignant parasites i6th. Case 28. Ibid. — Same source. Anopheles fed on 29th 17] MOSQUITO INOCULATIONS 85 October and kept at 30'' C. Subject bitten 6th to 8th November by more than twelve. Fever i6th, and malignant parasites on 1 8th. Case 29. Jancso [1905]. — Same source, and mosquitos. Subject bitten by six on i6th November. Fever 22nd, and malignant parasites 26th. Case 30. Ibid. — Source, malignant. Anopheles fed 15th November and kept at 22-24'' C. Subject bitten by seven on 30th. After ten days, fever and malignant parasites. Case 31. Ibid. — Same source and mosquitos. Subject bitten by one Anopheles on 3rd December. After fourteen days, crescents in blood. Case 32. Ibid. — Same source and mosquitos. Subject bitten on 6th December by two Anopheles. Quinine 1-2 grams on 12th and 13th. Fever and malignant parasites on 18th. Case 33. Ibid. — Source, malignant. Anopheles fed 24th September at 30^ C, and afterwards kept at 20° C. Subject bitten on 21st October by one Anopheles, strongly infected. Quinine i gram on 28th and 29th. Fever on 4th November and crescents on 6th. Case 34. Ibid. — Source malignant. Anopheles fed 24th September and ist October at 30" C, and then kept at 15-17° C. Subject bitten 7th November by two of these with glands infected. Fever and crescents on iSth. Case T^^. Ibid. — Same source. .^4«<7//z^/^j fed 25th September and ist October and kept at varying temperatures from 8-30' C. Subject bitten by two of these (both infected) on 13th and iSth October. Fever 24th and crescents 25th. All these cases have been verified by me in the original literature ; but there are probably some other experiments which have been overlooked.^ ' See section 65 (5). CHAPTER IV THE PARASITIC INVASION IN MAN 18. The Onset of the Invasion. — It does not lie within the province of this book to give a full description of the pathology and symptoms of malarial fever — a subject which is dealt with in many works. But before proceeding to our proper theme, we shall do well to examine a certain number of questions, especially some upon which little stress has been laid in the publications referred to. We should begin by attempting to obtain a clear picture of the onset and progress of the parasitic invasion in man. Our first care should be to consider the number of organisms engaged in the invasion — a subject which has been much neglected. For example, in the eighty-six cases of successful experimental inoculations of men, I cannot find a single one in which correct estimates of the number of parasites, in the source, the carrier, or the subject, have been even attempted. Certainly, these experiments prove the main theorem, that the parasites cause the disease ; but they might easily have been used to obtain many valuable pathological data in addition. We are thus forced (at present) to rely largely upon calculation for our figures. (i). The imviber of parasites in the mosquito. — The number of parasites which enter a mosquito when it feeds on a patient depends {a) on the amount of blood sucked up by it, and {b) on the number of parasites in that blood. The insects feed during variable periods — for a few seconds if disturbed, or perhaps 86 Sect. i8] ONSET OF INVASION 87 during the whole night upon a sleeping person. While feeding they void, every ten seconds or so, some of the fluid part of their meal ; so that during a whole night they may possibly consume much more blood than one stomach-full. A mosquito fully gorged in this manner may (perhaps) consume several cubic millimetres of blood. It would be easy to settle this point by allowing a number of mosquitos to feed during I, 2, 3, 4 . . . minutes, and then killing and weighing them and their dejecta. For example, as R. Newstead has shown ("Reports Li v. Sch. Trop. Medicine, Liverpool," 1905, vol. xvii. p. 25), the tick Ornithodorus tnoubata weighs 0*027 grams before feeding and o'26o grams after feeding. D. Thomson and myself find, in researches now being conducted in my clinic in Liverpool, that 6-7000 crescents per c.mm. of blood is not an exceptionally high number. Supposing that only half of these are females, it is still very unlikely that so many could ever develop, after being fertilised, in one insect — a large or very large proportion probably perish from phagocytosis and other causes in the stomach contents. The largest number of developing zygotes found by me in one insect {C. fatigans gorged on blood with P. danilevskyi) was 445. Ten of these mosquitos fed all night on a bird with moderate parasites (i/iooo haematids) were found to contain an average of 29 zygotes each ; and ten of them fed on a bird with many parasites (1/50 haematids) contained an average of 100 zygotes each [May 1898]. But I do not know what proportion of the parasites in these birds were sexual forms.^ The number of zygotes found in Anophelines naturally fed on human blood does not very often, I think, exceed fifty — but this is probably due to the manner of feeding. The number of ingested sexual parasites which reach maturity and develop protospores depends {a) on the susceptibility of the insect, {b) on the temperature, and {c) possibly many other conditions. Jancso [1905] finds that the zygotes develop best at 24-30° C, ^ See reference to paper by S. T. Darling in section 65. 88 THE PARASITIC INVASION IN MAN [Sect. temperatures above and below these limits retarding the process (A. macidipennis) \ and that they die if the mosquito is kept constantly below i6' C. after feeding. On the other hand, they often continue to grow if the carrier is subjected merely to an intermittent low temperature. Regarding the susceptibility of various species of mosquitos much work remains to be done. (2). The number of protospores in the salivary glands. — I may have overlooked references, but do not know that the average number of protospores in matured zygotes has ever been exactly estimated. I should give the number (merely as an impression) at about a thousand. Not all of these effect an entry into the salivary glands. Here, again, there seem to be no exact counts. I fancy that more than 10,000 of them will seldom be found in the glands of a single Anopheline, while often there may perhaps be only a few hundreds at a time (subject to correction). (3). How many protospores enter the human blood? — This must depend (a) upon the number of spores in the biting insect's salivary gland, and {b) upon the number of times it is allowed to bite its victim. I think that mosquitos inject their poison before commencing to suck. If this is the case, an insect which bites a person several times (as, for instance, when he is asleep) is likely to inoculate many more protospores than one which succeeds in biting only once. In the former case several thousand spores may perhaps be introduced ; in the latter case perhaps only a few. But not all of the spores which have entered are likely to live. Probably many perish by falling outside the blood stream or by becoming a prey to phagocytes. (4). Further development of the protospores. — F. Schaudinn observed that if protospores are taken from a mosquito's salivary gland and are mixed with blood under the microscope, many of them may actually be watched entering the haematids, where they become the young intracorpuscular parasites familiar to students. These now begin to grow and to develop a second i8] ONSET OF INVASION 89 generation of spores, which should be called deutevospores. The latter attack fresh haematids, within which they grow, and develop a third generation of spores, which we may call tritospores ; and so on indefinitely. (5 ). The number of spores produced by each species of parasite. — The parasites of malaria are described in detail in the text- books. Since the time of Golgi, all observers admit that they belong to three types at least, each of which differs morphologically, and markedly so, from the others. I assume, for the sufficient reasons frequently given, that these three types are three different species. The number of spores pro- duced by each species is variable, and different authors give different figures (probably the number has never been accurately estimated). I adopt the following names and figures for the present : — Plasmodium malariae Laveran, 1881. The Quartan Parasite ; produces say 6-12 spores every three days. Plasmodium vivax Grassi and Feletti, 1890. The Benign Tertian Parasite ; produces say 15-20 spores every two days. Plasmodium falciparum Welch, 1897. The Malignant Parasite ; produces say 6-20 or more spores every two days. Some authors consider that there are two if not three varieties (or ? species) of malignant parasites. I am inclined to agree with them, but have not yet satisfied myself sufficiently on the point to admit it in my classification. (6). The onset of the invasion. — Let us suppose that a mosquito has inoculated several thousand protospores, but that only one thousand of these have succeeded in entering the haematids. After two or three days, according to the species of parasite, each will produce a variable number of deutero- spores. But, probably, not all of these will succeed in infecting fresh haematids ; many may be devoured by phagocytes, or be destroyed by other agencies, while passing from one haematid to another. And the same thing is likely to happen with every successive generation of spores. Hence only a proportion of 90 THE PARASITIC INVASION IN MAN [Sect. the spores actually produced are likely to enter fresh corpuscles. Suppose that i,ooo protospores of P. vivax have entered haematids, and that, on the average, only lo out of the 15-20 spores actually produced in the successive generations succeed in entering fresh haematids. The parasites should then multiply as follows : — No. of days 024 6 No. of parasites 1,000 10,000 100,000 1,000,000 No. of days 8 10 12 No. of parasites 10,000,000 100,000,000 1,000,000,000 and so on. In the case of P. malariae the multiplication should be slower, if the number of spores given above is correct. But in that of P. falciparum the data are too uncertain for calculation. (7). The number of haematids in an average man. — According to accepted standards we have — {a) I c.mm. of blood contains 5,000,000 haematids. {b) The specific gravity of blood (male) is about I057"5. (<:) The total amount of blood weighs about 4-9/100 of the total weight of the body.^ From these data we calculate that 3,000,000 c.mm. of blood weigh 3" 1 7 kilograms, and will be contained in a man weighing 6474 kilograms (142 lbs. English, or about 10 stone), and that these 3,000,000 c.mm will contain 15,000,000,000,000 haematids. This may then be taken as the normal number of haematids in an average healthy man of about 64 kilograms, or 10 stone, in weight. The reader should endeavour to form some tangible idea of this enormous number. If he were to try to count it at the rate of 100 a minute day and night without cessation, he would have to spend 285,000 years over the task ! ^ The ratio of blood to body weight was formerly estimated at about 1/13, but the estimate has recently been reduced in consequence of better methods of measurement. i8] FEVER-PRODUCING NUMBER 91 (8). The lowest number of parasites required to produce the first illness. — We can scarcely imagine that one protospore, or even many thousands of these minute bodies, can produce any marked symptoms in the patient ; and, in fact, we learn from the fundamental experiments that as a rule no symptoms appear for some days after the moment of inoculation — this period being commonly called the incubation period. But as the parasites increase at every generation, a time must come when the number of them will suffice to cause illness. Can we determine this number? No serious attempt has yet been made to do so, or, indeed, to find any exact correlation between the number of parasites and the amount of sickness. There are many difficulties in the way. It is not always easy to estimate the number of parasites, and still less to know when precisely the illness commences. In most of the experimental inoculations, some illness, or even sharp fever, has occurred before any parasites have been found by the microscope. On the other hand, Elting has been able to find the parasites in some of his cases before the onset of the fever. The question is probably determined partly by the skill and patience of the observer, partly by the susceptibility of the patient, and partly by the " virulence " of the parasites. A laborious search may reveal the parasites when they are comparatively few in number ; and on the other hand, a patient who has never been previously infected will probably begin to suffer earlier during the course of the invasion than one who is partially " immune." But for a broad general rule we may, I think, accept the principle (pending more exact researches) that if we cannot find the parasites after careful search, their number is not usually sufficient to produce fever. Hence I calculate that they will not generally be numerous enough to cause illness unless there is at least one parasite to 100,000 haematids ; that is, 50 parasites in i c.mm. of blood; or 150,000,000 in a man of 10 stone (64 kilograms^ in weight. (9). The time required to examine blood microscopically. — It 92 THE PARASITIC INVASION IN MAN [Sect. is very necessary to have clear ideas upon this point. Suppose that the diameter of a " field " seen by an oil-immersion Objective and a No. 2 Ocular measures 0*165 mm., or nearly i/6th of a millimetre. Then by moving the specimen across this field of vision, searching it as we move it, we shall cover, after traversing sixty times the diameter, a strip nearly ro centimetre long, and 0"Oi65 cm. broad. Examining strip after strip in the same way, when we have examined sixty strips we shall have covered nearly one square centimetre of area. The time required for this will depend upon the care with which we must examine the successive fields as they pass under the eye. If we can search at the rate of twenty fields a minute, we can search a whole strip in three minutes and a whole square centimetre in three hours. If the object is large and easily visible we shall be able to move the specimen faster than this ; if it is small and delicate, the observer must be fairly expert to search so quickly. Now suppose that we must examine a thin film of liquid blood spread under a coverglass. If the average depth of the film is only 0*00025 mm. (2*5^ or about 1/3 the diameter of haematid), then i c.mm. of the blood will be spread out under 4 sq. cm. of area — that is, over the whole area occupied by a square coverglass of 2 cm. side. To do this will require twelve hours' continuous work. If the average depth of the film is 3*3 3/u the c.mm. of blood will cover a space of 3 sq. cm., requiring nine hours' search ; but in this case we shall be more liable to overlook small objects, though we shall more easily find large ones. With an average depth of 2*5/x, i sq. cm. of film will normally contain 1,250,000 haematids. One-sixtieth of this, that is, one strip as defined above, will contain 20,833 haematids ; so that, if we are fairly expert, we should be able to search 6,944, ^^ ^^Y 7)000 haematids a minute. With an average depth of 3'S3/m, i sq. cm. of film will contain 1,666,666 i8] TIME REQUIRED FOR SEARCH 93 haematids, which can be searched at the rate of 9,259 haematids a minute. In the former case a single circular field of the microscope, 165^ in diameter (area 0*0209 sq. mm.), will contain an average of about 261 haematids. In the latter case it will contain about 345 haematids on the average. There are, of course, more than 3,600 squares of 165^ side in a square centimetre; and therefore four and three times this number of squares must be examined to search i c.mm. of blood in films of 2'5/ji and 3'33^t in depth respectively. If we could examine the squares at a rate so fast as one a second, three to four hours would still be required to search i c.mm. completely. To search the whole of the 3,000,000 c.mm. of blood contained in a man of about 10 stone in weight would therefore take, at the quickest rate, more than 1,027 years. I have just estimated roughly that the parasites will probably be numerous enough to cause fever if they number 1/100,000 haematids. If it requires twelve hours to search I c.mm. of blood containing 5,000,000 haematids, 100,000 haematids can be searched in a little less than fifteen minutes ; so that if the parasites are so few as this we can expect to find them at the rate of about one every quarter of an hour. But chance intervenes here : if we are lucky we may find the first parasite almost at once ; if we are unlucky we may have to search several hundreds of thousands of haematids before finding an infected one. There is always the danger of overlooking a plasmodium even when it should have been seen. In a dry stained film the blood is spread out over a wider area, so that there are only about 150-200 haematids in a circular field of 165/ji. I think therefore that the larger pigmented parasites are less quickly found in such than in liquid films ; but on the other hand, the smaller plasmodia, being characteristically coloured, are detected with much greater certainty — as Marchoux showed [1897]. On the whole, I think that the two methods are about equal in diagnostic value. In my "thick-film" process [1903], i c.mm. of blood 94 THE PARASITIC INVASION IN MAN [Sect. occupies only about i/Sth of a sq. cm. of area, or less, so that there should be twenty to thirty times more haematids and parasites per field. But the latter require more skill for detection (section 65). Such calculations demonstrate the absurdity of supposing that there are no plasmodia present in a person because we fail in finding one after a few minutes' search. As a matter of fact, even if as many as 150,000,000 plasmodia are present in an average man, the chances are that ten to fifteen minutes' search will be required for each plasmodium found ; while if we are careless or unfortunate we may have to look much longer. (10). TJie period of incubation. — To resume our study of the invasion — we saw in subsection 6 that, in the case of P. vivax, 1,000 protospores should produce 100,000,000 parasites in ten days and 1,000,000,000 in twelve days. The former number would probably be insufficient to produce fever in the patient, and the latter would be more than sufficient. Hence the illness would probably begin on the twelfth day after inoculation. It is usually thought that the incubation period must depend exactly upon the number of organisms injected either by the mosquito or by the experimenter ; but this is not always correct. The proliferation of P. vivax at the rate of ten spores at each generation every second day, starting with various initial numbers, should be as follows : — No. of days 028 10 {1,000 i 0,000 10,000,000 100,000,000 2,000 20,000 20,000,000 200,000,000 3,000 30,000 30,000,000 300,000,000 10,000 100,000 100,000,000 1,000,000,000 15,000 150,000 150,000,000 1,500,000,000 Thus, starting with 1,000 protospores, the number of parasites required to produce fever, namely 150,000,000, will not be attained until the twelfth day. Starting with 2,000 protospores, this number will, it is true, be attained on the i8] INCUBATION PERIOD 95 tenth day, two days earlier; but after this point we shall have to increase the number of protospores originally injected up to 15,000 before we can reduce the incubation period by another two days. In other words, if we estimate correctly, 2,000 protospores should give as long an incubation period as 14,000 protospores, or seven times as many, would give. That is, it makes little difference to the patient whether he is bitten by one or by seven mosquitos, each of which injects 2,000 protospores. I suppose that even two or three protospores, if they survive, would set up infection. I have assumed that P. vivax increases tenfold at every generation, but this is a mere guess. The following table gives the first seven powers of some natural numbers and also the proliferation of a single plasmodium according to various rates, from fivefold to twentyfold. The party-line shows where the numbers, if multiplied by 1,000, would reach the fever-point. Powers of Natural Numbers. 5 6 7 25 36 49 64 81 100 121 144 169 196 225 400 125 216 343 512 729 1,000 1,331 1,728 2,197 2,744 3,375 8,000 I 625 1,296 2,401 4,096 6,561 10,000 14,641 20,736 28,561 38,416 50,625 160,000 3,125 8,776 16,807 32,768 59,049 100,000 15,625 46,656 117,649 8 9 10 262,144 531,441 1,000,000 II 12 13 14 15 20 161,051 248,832 371,293 537,824 659,375 3,200,000 1,771,561 2,985,984 4,826,809 7,529,536 11,390,625 64,000,000 ] 78,125 I 279,936 823,543 2,697,152 4,782,969 10,000,000 19,487,171 33,831,808 52,748,517 105,413,504 170,859,375 1,280,000,000 This table may prove useful for estimating the average rate of increase of the various parasites, exact experiments upon which are much needed. I think it possible that more spores may be produced early in the infection than later; and also that there is likely to be a much smaller mortality among the spores at first than there is later, when the germicidal powers of the host become (hypothetically) stronger 96 THE PARASITIC INVASION IN MAN [Sect. The following table gives the incubation periods actually found in the fundamental inoculation experiments described in sections 14 and 16, omitting the doubtful results. The cases are numbered as in those sections. I. P. MALARIAE: Blood Inoculations. Case 10 13 14 16 23 Quantity of blood c.cm. 3 ? I I 4 How injected ven. ven. cut. cut. ven Incubation (days) 12 IS 17 12 II Case 29 30 35 36 37 Quantity of blood 2 2 4 4 4 How injected cut. cut. cut. cut. cut Incubation .... 16 II 25 25 25 {No JHOsquito inoculations.) 2. P. VIVAX: Blood Inoculations Case 8 9 18 19 20 21 Quantity of blood c.cm. ? 15 2 2 2 2 How injected ven. ven. ? ? ? ? Incubation . ■ II II 12 12 10 10 Case . . 22 34 41 42- Quantity of blood 3 0-2 3 2 How injected ven. cut. ven. ven. Incubation . 6 21 3 5 3. p. VIVAX: Mosquito Inoculations. Case No. of mosquitos Incubation . 9 ID II 24 25 27 ? I ? ? ? 6 21 15 25 17 17 15 4. /*. FALCIPARUM : Blood Inoculations. Case Quantity of blood How injected Incubation . 15 I '5 cut. 15 17 cut. 18 24 0*25 cut. 12 25 2 ? 26 5 ? 27 07s i8] INCUBATION PERIOD 97 4. P. FALCIPARUM : Blood Inoculations. Case . 28 31 32 33 38 39 Quantity of blood 02 2 ? ? 15 1-5 How injected ? cut. cut. cut. cut. cut Incubation . 4 15 6 10 30 6 Case 40 43 44 45 46 47 48 Quantity of blood 1-5 I •5-4-0 I •5-4-0 I •5-4-0 r5-4-o I •5-4-0 1-5 How injected cut. ven. ? ? ? ? ven Incubation . 17 2-5 4 7 4 3 5 5. p. FALCIPARUM: Mosquito Inoculations. Case No. of mosquitos Incubation . 26 30 31 33 34 35 ? 6 7 2 I 2 15 6 10 12 14 II From these figures we collect the following extremes and averages for the incubation period in days per case. Lowest Average Highest Quartan, blood inoculation . II 17 25 Tertian, blood inoculation . 3 ID 21 „ mosquito inoculation 15 18 25 Malignant, blood inoculation 2-5 8 30 „ mosquito inoculation 6 II 15 As we might expect, P. malai'iae gives the highest average incubation period, P. falciparum gives the lowest, and the mosquito inoculations have distinctly longer periods than the blood inoculations. The short periods given by some of the blood inoculations may be easily explained. When discoverable in ordinary thin- film preparations, the parasites may number anything from 50 per c.mm., or less, to 200,000 per c.mm., or more. In the latter case there will be 200,000,000 parasites per c.cm., so that if I c.cm. or more of such blood is injected, the subject should receive enough parasites to produce fever at once (by 98 THE PARASITIC INVASION IN MAN [Sect. hypothesis) in a non-immune person ; and this has almost occurred in some of the cases. But, besides the number of parasites contained in the inoculated blood, there is another question requiring consideration ; that is, whether many of them are not killed in the syringe. In spite of the experi- ments of Bein and Sacharoff (18-21 and 24), I think that this is possible, or even likely. The experiments of Celli and Santori (35-40), in which various sera were mixed with the inoculated blood, generally show long incubation periods, probably due to such destruction of the parasites. It is un- fortunate that the inoculated parasites have not been counted in a single one of these experiments. We need not refer here to incubation periods determined by observation of natural infections. 19. The Further Progrress of the Invasion. — We now endeavour to trace the progress of the invasion after the commencement of the fever. (i). Increase of the parasites. — In assuming that about fifty Plasmodia per c.mm. are required to produce the first illness, we must remember that this applies only to a single set of parasites. If the patient contains several sets, each sporulating on different days, the total number of plasmodia should by hypothesis be several times larger. Moreover, it does not follow, if fifty Plasmodia per c.mm. are sufficient to produce the first attack, that they will suffice to cause subsequent ones after the patient has become (hypothetically) habituated to their poison. Lastly, the various species may vary in " virulence." As I have said, this number, which may be called the pyrogenous limit, is merely a rough estimate of mine. Long researches are required to obtain a more exact figure from observation, but it may be useful to give a few of the first counts made by D. Thomson and myself in cases in Liverpool, that is, not in fresh infections : — 19] PROGRESS OF THE INVASION 99 Case. Date. I. Quartan 24.1. 1910 M 25.I.1910 5) 26.1. 1910 27.1. 1910 3, Malignant 10.I.1910 3- Malignant 1 1.1.1910 4- Malignant II.I.1910 5- Malignant 13.I.1910 Temperature. 397 C. = 27 P.i slight rigor (? temp.) 37-40. slight rigor = 4 P. normal = P. 396 C. = 26 P, 4ro C. = 4o P. 38oC. = io P. 3870. = 17 P. Parasites per c.mm. 1,500, mature 83, mature 150, mature 36, mature 58,000, young forms 300,000, young forms 15,000, young forms 55,000, young forms In the malignant cases, the young forms, being merely the offspring of the mature parasites which caused the corresponding forms and which were at the time in the inner organs, do not give the number of the parent forms ; but we may form a rough estimate of the latter by dividing the number of young forms by ten. The quartan case (triple) gives some justifica- tion for the figure which I have tentatively selected as the pyrogenous limit (addendum i). From this point, to judge from the experimental inoculations and also from general clinical experience, the progress of an untreated case is generally that the parasites continue to increase in numbers till they may reach the figure of several hundred thousands per c.mm. No accurate computations of the increase of the parasites seem to have been attempted even where their numbers are large enough for easy enumeration. If they increase by 10 at each generation, they should multiply from 50 to 5,000 in four days for tertian parasites, but there is reason to suppose that the increase now begins to be considerably checked. (2). The viaxinmin number of parasites. — I do not consider that 200,000 young malignant parasites per c.mm. is exception- ally high. In Mauritius we found in a fatal case 12/100 of the haematids infected. Several authors record 30/100, and Rogers ^ Here P. stands for the Pyretic Scale which I propose for pathological work. It is merely the Centigrade Scale between 37° and 47° divided into 100 parts. Thus : — 0° P. =37° C. =98 '6° F. =29 '6° R. = normal human blood temperature 30° P. =40° C. = 104° F. =32° R. =high fever. loo THE PARASITIC INVASION IN MAN [Sect. [1908, p. 222] mentions a fatal case " with more parasites than corpuscles." Three or four parasites are frequently found in one haematid. Similar copious infections are the rule in genus Haemoproteiis {Halteridium) of birds. There are innumerable references to this part of the subject in the literature, but none of them are exact. Many authors give the proportion of their cases in which they have detected the Plasmodia in a single thin-film specimen — that is, I suppose, in numbers over about 50 per c.mm. Rogers states that out of his successful cases they were detected in a minute or two in 78% and in over five minutes in 10% [1908, p. 220] ; but he failed to find any parasites in 10-20% of undoubted malaria cases. Other observers have had still more failures. In Liver- pool we nearly always succeed if fever is present, but the blood is generally distributed to a class. It is obviously a question not only of the number of parasites, but of skill ; and I should add that not all of those who write on the subject are as expert as may be imagined. According to the classical theorem of Marchiafava, Celli and Bio-nami, the sporids of P. falciparum tend to retire to the inner organs after reaching a certain size. I remember a case where I undertook to demonstrate the plasmodia to a sceptic, and found for the purpose a case swarming with young malignant parasites. A few hours later, however, when the sceptic saw the case, they had all vanished ! Nevertheless, I think that this theorem requires to be better verified by strict numerical work, as it is possible that much of this supposed disappearance from the peripheral circulation is due to the death of the organisms (addendum i). (3). Limiiatien -of the invasion. — Clearly, if the parasites can continue to multiply for ever "aT the original rate, every untreated case would infallibly die. We are therefore obliged to admit that something happens to check the invasion. The subject belongs to the pathology of malaria, but we should note the following points. 19] PROGRESS OF THE INVASION loi The arrest of the invasion may be due to one or both of two causes. Either the parasites themselves begin to lose their power of reproduction, or else they or the body produce some- thing which opposes them. I doubt the former hypothesis, because the same number of spores appear still to be formed ; because the parasites do continue to reproduce in smaller numbers for months, or even years ; and because in some cases they actually do continue multiplying until they kill the patient. Whether they are destroyed by their own toxins, or by some germicidal substance produced by the host, is a question which deserves much more attention than it has received. The idea that they are destroyed solely by the phagocytes is no longer generally accepted. Whatever it is, the germicidal substance appears usually to increase in power with the number of the parasites, and there- fore to check the invasion at its height. On the other hand, the failure of many inoculation experiments suggests that some persons possess such a substance from the first — unless the failures have been due to some unseen error. Out of six birds which escaped infection in my mosquito inoculations, one (the only survivor) was infected on a second trial ; and the same thing happened in some of the human experiments. The literature contains many references to the sudden disappearance of a whole generation of plasmodia — not in consequence of quinine, but frequently following rest in bed, good food or shelter from heat. In the quartan case mentioned in subsection (i), a large brood followed the sporulation of 24th January, but of these, without quinine, only about 36 per c.mm. reached maturity three days later. Many observers describe the appearance of death — loss or change of staining capacity, and so on — among the parasites on such occasions. (4). TJie illness is due to a toxin. — This point also belongs to the pathological side of the subject. Omitting reference to the older hypotheses, it is now almost certain that the patient's fever is connected with the discharge of some toxic substance I02 THE PARASITIC INVASION IN MAN [Sect. from each mature sporid at the moment when its spores are scattered in the serum. Some of the older inoculation experi- ments made with blood taken from a source in the state of rigor — that is, at the moment when the sporids are breaking up — were followed by an immediate slight reaction, suggesting that that blood contained a toxin as well as parasites. These results are, however, scarcely definite enough to prove the point, especially as the inoculation of healthy blood is sometimes followed by such a reaction. But the following excellent experiments of Rosenau, Parker, Francis and Beyer [1905] were much more decisive. Case I. At Vera Cruz, Mexico, at noon on 27th October 1903, 100 c.cm. of blood were drawn from F. Martinez, suffer- ing from a declining paroxysm of P. falciparum ; temperature 38"2° C. (=12 P.); parasites, young sporids and also gametids. The serum of this blood was separated, diluted with an equal part of salt solution, passed through a Chamberland B. filter (tested), and injected (20 c.cm.) into J. Ojeira, and (equivalent) into L. Peredo. Neither subject showed any symptom. Case 2. At the same place, at 12.30 on 6th November 1903, A. Mendez was suffering from a severe benign-tertian rigor (double infection) ; temperature 39*1° C. (21 P.), rising to 40*2° C. (32 P.). At that moment 125 c.cm. of his blood were drawn and defibrinated. To 25 c.cm. the same quantity of salt solution was added, and the mixture was passed through the same filter. The filtrate had no figured elements, but showed a red tinge, and 9 c.cm. of it were injected at 1.40 r.M. into the right basilic vein of L. Peredo. Thirty-five minutes later the subject " began having chilly sensations and headaches, and presently went to bed covering himself with his blanket (2.25 P.M.), Five minutes later (2.30) he was having a violent chill, his teeth chattering so that we could not trust the thermometer in his mouth." Patient was pale and vomited. Chill lasted to 3.15 p.m.; vomited again at 3.30; fever rose 19] PROGRESS OF THE INVASION 103 rapidly to 387° C. (17 P.) at 4 p.m., nearly normal at 10.30 P.M. Authors put the duration of the paroxysm at about eight hours. Case 3. At same place and date, at 2 P.M., 2 c.cm. of the same blood of A. Mendez, mixed with an equal volume of salt solution, but unfiltered, were injected intravenously into J. Ojeira. Subject " reacted within an hour, with a slight rise of temperature and nausea, and four days afterwards developed a typical malarial paroxysm, with many tertian parasites in his peripheral blood." Typical fever (double infection) with a few parasites at 7 A.M. on loth November. (Case 51 of section 14.) In this case the preliminary rise of temperature, which began within an hour after injection, reached 37'9° C. (9 P.) and lasted five hours. Thus, both the subjects inoculated with the blood of Mendez taken during rigor had attacks of fever similar to that of the source ; but the first subject inoculated with filtered blood did not become infected, while the second subject inoculated with unfiltered blood became infected with the same parasites as in the source. Unfortunately, no estimate is given of the number of parasites in the inoculated blood. The infection of Mendez was, however, said to be "heavy" — let us suppose 10,000 parasites per c.mm. We may thus calculate : — The toxin of 45,000,000 benign tertian parasites in 4*5 c.cm. of blood caused eight hours' fever, reaching to 387'' C. (17 P.) in Peredo. The toxin of 20,000,000 of the same parasites in 2 c.cm. of blood caused five hours' fever, reaching to 37*9° C. (9 P.) in Ojeira. The corresponding ratios, namely, 4'5/2"o, 8/5, 17/9 (taking o P. as the normal temperature), are not dissimilar. The pyro- genous limit here suggested is lower than my arbitrary figure of 150,000,000; but I may have underestimated the infection of Mendez, and the weights of the subjects are not recorded. I04 THE PARASITIC INVASION IN MAN [Sect. The corresponding paroxyzm of Mendez himself rose to 40'i' C. and lasted five hours ; but his was an old case, and cannot be compared with the others. We do not know the nature of the toxin, but I have always thought it likely to be some soluble constituent of the plasmodin. It is generally supposed that the various species of plasmodia produce toxins of different strength (or virulence) ; but we should await better proof of this. (5). Antitoxins. — Just as the body certainly produces some germicidal property capable of limiting the number of the parasites, so it must certainly produce some antitoxic property capable of destroying, or at least eliminating, their poison. We do not know its nature, but infer for the follow- ing reasons that its power increases with time : — (i) From the time of the ancients it has been observed that malarial fever begins with remittent fever, due to the overlapping of the paroxysms, and ends with intermittent fever, due to the shortening and separa- tion of the paroxysms. This shortening of each attack of fever is not always accompanied by a decrease in the number of parasites, and must therefore be due to something which reduces their effect on the body. (2) Old cases, especially children, often scarcely feel the paroxysm, although considerable fever may be present. I have observed in many untreated cases that the number of parasites continues to increase, although each attack of fever tends to become more and more mild. This suggests that the antitoxic power of the blood tends to be developed sooner than the germicidal power. 20. The Decline of the Invasion.— (i). The period of regular paroxysms. — It is not easy to find untreated cases for study, but from such as I have been able to examine or to read about. 2o] DECLINE OF THE INVASION 105 I infer (subject to correction by more exact numerical methods) that the following course of events occurs : — After reaching a figure of say 50 or 500 per c.mm. the parasites tend to increase more slowly owing to the increasing germicidal power of the blood. That is, while each sporid still produces (?) the same number of spores, a greater and greater number of the young parasites are killed ; so that the invasion tends to reach a limit of something like 1,000 to 10,000 mature sporids at every generation. But this limit may not be reached perhaps for some weeks. In the meantime the increasing antitoxic power of the blood tends to shorten each paroxysm more and more ; the fever, at first remittent, breaks up into a series of intermittent attacks. Thus, though at each paroxysm the total number of parasites may be slightly increased as that number approaches the highest limit, yet the parallel increase of the antitoxic power annuls the effect of the parasitic increase, so that the patient now often suffers from a long series of paroxysms of almost equal intensity, which give the typical classical picture of a malarial fever. This period may last, I think, for some weeks, but of course the process may be subject to modification. Thus, food and rest may help the patient, while in some cases death may occur in spite of quinine from an unlimited propagation of the parasites. Fortunately, however, the period ends abruptly in most cases even without quinine. The paroxysms become very mild, and then, suddenly, the sporids undergo an immense fall in numbers ; and this stage of the disease ends. The collateral incidents and symptoms are minutely described in pathological books, and it is necessary here to refer only to some important points. According to the elementary law of Golgi, a patient may contain, not only one set of parasites sporulating every second, or every third day (as the case may be), but two or three sets sporulating on different days. He may also contain sets of io6 THE PARASITIC INVASION IN MAN [Sect. parasites of different species. The rule generally accepted is that each set of parasites continues its own evolution independently of other sets which may be present. But much more precise work requires to be done on this point, and on the following : — {a) The exact increase of severity, if any, of a paroxysm due to the simultaneous sporulation of two sets of parasites of different species on the same day. {b) Does one set of parasites affect the body-reactions against another set of the same or of a different species ? if) Do different sets of the same species tend to coalesce ? {d) Explanation of the (apparent) extinction of one set long before that of another. The presence of different sets may obviously be ascribed to inoculation of the patient on different dates. This matter has already been touched upon, but not exhaustively, in some of the inoculation experiments, especially in those of Di Mattei, Elting and Jancso. Besides fever, the parasites produce anaemia. This has often been measured absolutely, but never exactly in correlation with the number of parasites. It is supposed that the toxin of the Plasmodia destroys many of the haematids which are not mechanically broken up by the parasites themselves. More exact researches are also required regarding the absolute and relative leiicocytic variations in correlation with the number of Plasmodia. The different species produce paroxysms of somewhat different type and intensity. Many authors quote figures, but without correlation with the number of parasites. Thayer and Hewetson [1895] give i r8 hours as the average duration of the single benign tertian paroxysm, about ten hours as that of quartan paroxysms, and twenty to twenty-one hours as that of the malignant paroxysms. The massing of the malignant parasites in the inner organs, and many other details, are 2o] ONSET OF SEXUAL FORMS 107 pathological matters. The enlargement of the spleen and liver will be dealt with in section 22. (2). The appearance of sexual forms. — With the quartan and benign tertian parasites, these forms begin to be seen very early after the plasmodia become numerous enough to be found at all. It is very doubtful whether they are or are not produced in broods at any given moment during the course of the invasion or during the development of a single genera- tion ; and still more doubtful how long a single gametid can live in the blood of the patient. The opinions of many writers may be quoted, but, unfortunately, they are only opinions. Schaudinn's case will be referred to presently. The malignant gametids are much more easy to study. They begin to appear about a week after the onset of the fever and may remain circulating in the blood for several weeks. We do not know what determines their appearance, but the asexual forms and the fever frequently vanish when they appear (which may often be due to the fact that quinine influences the sporids more than it affects the crescents). In untreated cases, how- ever, we may often find both forms together for many days, though the sporids are apt to be scanty. In such cases there may be slight oscillations of temperature, which some writers have attributed to the crescents. Often, also, the sporids may be still present in large numbers though they are too few to be detected. In infected sailors in Liverpool we often find crescents with great certainty, unless the earlier infection is cut short with quinine. But many writers complain that in certain localities they cannot find them as frequently as might be expected, and I have had the same experience in India and West Africa. To explain such cases I have surmised that the production of sexual forms may be largely influenced by season — that they may be produced abundantly for a few weeks, but only at that time of year when the local carrying Anophe- lines are most abundant. Caccini [1902] says that several observers have noted the absence of crescents when the new io8 THE PARASITIC INVASION IN MAN [Sect. malaria season is imminent, and that he himself has never found crescents in Italy from April to June. For another example, I found very few crescents at the foot of the Darjeeling mountains in 1898 at a place where they had been frequently seen by another observer a few months earlier. But this is a mere conjecture, and one which requires long study for verification ; and it scarcely explains why sailors in Liverpool have crescents so regularly. The early use of quinine — to which sailors are not addicted — may also explain the paucity of crescents in many cases. Lastly, it is possible that the sexual forms are produced only during the earlier stages of an infection — that in an old infection, when, so to speak, parasites become worn out, they no longer produce sexual forms, just as the oldest broods of human cells fail to produce them. In my experience crescents are common during the first few months of an infection, but comparatively rare at later stages. Failure to find " flagellated forms " (spermatophoria) must be generally due to faulty technics. (3). The period of rallies and relapses. — We have seen then that the period of regularly repeated paroxysms generally ends after a few weeks, even without treatment, in a great decline in the number of sporids. The gametids, especially the crescents, may still remain numerous, but the asexual forms which cause the illness diminish so much that they fall below the pyrogenous limit and cannot easily be found. The patient now improves in health. His paroxysms cease, his haematids increase, his spleen diminishes, and he begins to gain flesh again. I call this the rally. From this point two things may happen. The patient may recover completely, or — without reinfection — he may suddenly suffer from a relapse. In the relapse all the old symptoms of the period of regular paroxysms, sometimes less in intensity and sometimes worse, recur. The fever may recommence with the remittent form, and may then, as before, become intermittent. The 2o] RALLIES AND RELAPSES 109 anaemia and the splenomegaly — not yet completely recovered from since the first attack — will again increase, and to a greater degree than at first. Large numbers of sporids will again be found in the blood, and may be followed as before by crops of gametids. Finally, in most cases, even when untreated, recovery, accompanied by a great decrease of sporids, will occur again. This is followed by another rally, which in its turn 7nay be followed by another relapse — and so on, indefinitely, for months or perhaps years. Such, in my opinion, is the normal course of malaria, whether untreated or badly treated. But as the former kind of case can scarcely ever be observed, my opinion is based, not upon continuous observation of many cases, but upon correlation of different periods in different cases. I think, however, that most students of tropical malaria share that opinion. During the whole of this period the emaciation, anaemia, splenomegaly and secondary symptoms tend to increase with each relapse and to diminish with each rally. But the increase seems at first to be generally greater than the decrease, though by a diminishing increment. Thus, after some months the patient tends to reach a condition in which these symptoms arrive at something like a fixed limit — considerable emaciation, anaemia, splenomegaly, oedema, dyspepsia, etc. This condi- tion is well known as that of chronic malaria, and is only too frequently seen in malarious places, especially among children. In most cases, especially in children, after the fixed limit has been reached a general improvement sets in. After all, the disease is essentially a benign one. Each relapse now affects the patient less and less, and the secondary symptoms begin to decrease more with each rally than they increase with each relapse. After an unknown average duration, complete recovery certainly occurs in the large majority of cases, without any serious treatment. Such cases are said to have become partially immune. no THE PARASITIC INVASION IN MAN [Sect. On the other hand, deatJi occurs in many as the result of " pernicious paroxysms," intercurrent affections such as dysentery and pneumonia, or general weakness assisted by poverty caused by inability to work. Of course this picture — or rather sketch — is modified by many conditions. Patients who have already become partially immune during childhood or after many attacks, suffer much less on reinfection ; and good food and change of climate benefit the case, while complications such as dysentery, sprue and ankylostomiasis, have the opposite effect. The most usual modification is that caused by inadequate treatment, and I continue to see many such cases in Liverpool. The history is always the same. The patient has been instructed to take quinine during his attack, and for a week or two afterwards. This is insufficient, and the inevitable relapse occurs. But the patient seldom falls into the extreme condition of wholly untreated cases. The drug has not extirpated the infection, but it has checked each relapse as it occurs, and has controlled the anaemia and splenomegaly. Such especially is the condition of the infected sailors of whom we see so many in Liverpool. They still have relapses, but the spleen is not markedly enlarged and the anaemia not very pronounced. Works written on malaria in temperate and often more civilised countries do not always give a complete picture of the disease as it occurs among poor natives in the tropics. This is due to the fact that the more general use of quinine in the former tends to abbreviate the course of the infection. On the other hand, the great majority of cases in the countless malarious villages of the tropics are cases of chronic malaria — untreated, subject to frequent reinfections, and with anaemia, enlargement of the spleen and numerous relapses. In temperate climates, our cases are mostly in the early period of regular paroxysms ; in the tropics they are mostly in the long-continued period of rallies and relapses. (4). The parasites during the rallies. — The general observa- 2o] THE PARASITES DURING THE RALLIES iii tion that the degree of fever depends ceteris paribus upon the number of parasites suggests that when there is no fever the parasites are likely to be at least scanty. Hence, as is to be expected, in the rallies between relapses few sporids, and indeed very often none at all, can be discovered in the small quantities of blood examined under the microscope — though, of course, the gametids (which do not seem to produce fever) may still abound. Nevertheless, when the relapse occurs, the sporids again appear in detectable or large numbers. What happens to them when they disappear and reappear in this manner ? We can easily observe that the number of parasites, when they are numerous enough to be found, often varies largely. It is therefore equally easy to infer that when we can no longer find them, this is due simply to the fact that they have become too scarce to be found. But many writers seem to think that when they cannot find sporids none exist, and have therefore sought other explanations of the disappearance and reappear- ance referred to. Years ago Marchiafava and Bignami suggested that when they disappear for long periods the parasites may become encysted somewhere in the inner organs ; or that they may die out altogether, and that the relapse may be caused by spores which escape from phagocytes in which they have been living in a dormant condition. No evidence has been given for these views ; yet it should be easy to obtain in the malaria of birds, which remain infected for months. In 1898 I examined many birds in vain for the supposed encysted forms. Golgi, Mannaberg and others thought that crescents keep the infection alive during the rallies. Thus Mannaberg said [1894, p. 302]: "These relapses in localities free from malaria are to be explained only by the persistence of parasites possessing certain powers of resistance (probably the crescentic bodies) within certain tissues." But why are any special powers of resistance required ; and how explain relapses with the parasites which do not produce crescents ? Many authors. 112 THE PARASITIC INVASION IN MAN [Sect. working, I believe, with unstained films, have described and figured sporulation of crescents ; but others attributed this merely to post-mortem vacuolisation. We have never found sporulating crescents in stained films in Liverpool, though numbers of these bodies are examined in class. B, Grassi [1901] suggested that the relapses are caused by parthenogenetic reproduction in the gametids. This idea was followed up by F. Schaudinn [1903]. A patient who had suffered long from P. vivax was attacked on 29th April and ist May, and was found to contain both sporids and gametids. A rally now occurred, during which daily examination disclosed varying numbers of gametids only. On 25th May these parasites were more plentiful. Next day curious changes were noted in the female gametids, suggesting that they were producing spores similar to those ordinarily produced by the asexual sporids. The author considered this to have occurred independently of fertilisation by the male gametids, and to be due to parthenogenesis. The same day (26th May) the patient had a slight rise of temperature to 38*4° C, and in the evening ordinary young sporids were found. Next day only these forms occurred. On 28th May there was a typical attack with temperature reaching 4075° C, and with the usual sporids. Next day only gametids were again found. The author care- fully described the parthenogenetic forms and traced the corresponding changes in the nucleus. These observations were hailed as an important discovery by many writers, especially zoologists. They have been partially repeated by Maurer [1902], Bluml and Merz [1908], Harrison [1909] and others ; and many of the younger and more confident workers have spent much time in attempts to verify them, or have seen objects like those described by Schaudinn. But the objects twice seen by Maurer are not in any way proved to be parthenogenetic forms ; while those observed in six preparations by Bluml and Merz are supposed by the authors to be more probably cases of production of gametids by gametids — another 2o] THE PARASITES DURING THE RALLIES 113 hypothesis ; and these authors do not agree with Maurer. Harrison admits that the supposod " gametoschizonts " seen by him may be merely double infections of haematids by a gametid and a sporid. Craig [igo6] thinks that " intracorpuscular conjugation " may maintain the infection. It is easy to see under the microscope objects which suggest this or that hypothesis, but only the most patient and long- continued labours suffice to prove the truth. Schaudinn's case seems to me of doubtful value. I note especially that between 1st and 25th May the number of gametids varied, and was increased on the latter date. But this variation suggests that they were being produced all the time. The gametids are supposed to be produced from ordinary spores ; so that we are forced to infer that a number of sporids, some of them generating gametids, were present in the patient's body, although they were too few to be detected in the small quantities of blood examined by the author. On 25th May they probably increased in number sufficiently to induce a slight attack of fever, and were then mistaken for parthenogenetic gametids. On 28th May they produced a typical attack ; and that is all. The supposed nuclear changes were reported on evidence of no great value. The cells were not actually observed undergoing the development which the author describes. He merely inferred the existence of the development from a study of different cells in what he thought were different stages of that development. Worst of all, no numerical estimates are given. The same author enunciated many other hypotheses on similar evidence. I doubt whether parthenogenesis occurs with the parasites of malaria, for the following reasons : — {a) If it occurs in one species it ought to occur in all. It ought therefore to be easily observed in birds' malaria, and in crescents. I have been examining the latter for fifteen years and have never seen in them anything suggesting parthenogenesis. Yet they possess a definite and uniform outline which should H ii4 THE PARASITIC INVASION IN MAN [Sect. be much modified by such cellular changes as Schaudinn described. A. Carducci [1905], though favourably inclined towards the parthenogenetic speculation, failed after careful search in finding any evidence of it in crescents.^ {b) I have frequently seen relapses occur in cases of P. falciparum in which no crescents at all could be found, Carducci notes the same (see section 65). {c) In four experiments (see end of section 14) blood containing numerous crescents only was injected into healthy persons by capable observers without producing any infection whatever. Yet I showed in 1 895- 1 896 that crescents live on ice and for hours under vaseline. Why then, if Schaudinn's hypothesis is true, did they not infect any of these four persons ? {d) If relapses are caused merely by some natural develop- ment in the parasites we should expect them to occur more or less independently of the state of health of the host — which does not seem to be the case (see subsection 6). {e) If it occurs at all, parthenogenesis ought to be common enough to be demonstrable with ease and certainty. This subject is of great importance in connection with the prevention of malaria. Crescents withstand much medication with quinine, and if they keep the infection alive in patients, it follows that quinine loses much of its value as a public pro- phylactic against malaria. But, while I am quite ready to accept any evidence for it which may be offered, at present I do not think that the Grassi - Schaudinn speculation is even nearly proved. The fact that the parasites disappear at each rally and re- appear at each relapse is explained quite easily and sufficiently. In the rallies they become too few to cause fever or to be ^ H. M. Neeb [1909] in a paper just to hand shows careful, but I think still quite inconclusive, work in favour of parthenogenesis in crescents. 2o] THE PARASITES DURING THE RALLIES 115 detectable in the small quantities of blood examined ; in the relapses they become numerous again, I cannot see that a simpler or more satisfactory explanation is required. We observe the same process in relapsing fever, tuberculosis, trypanosomiasis and other diseases. A good writer once said : " It is hardly conceivable that it (the parasite) should remain in the general circulation, passing through its ordinary cycle of existence, without causing any symptoms whatever. Further, the failure of repeated examina- tions of the blood of patients who have previously suffered from malaria to reveal the presence of the parasite renders this most unlikely." It is impossible to accept such a train of thought. If 150,000,000 sporids cause but little fever in a man of medium weight, 1,000 or 100 should cause none at all, and yet will be quite sufficient to keep the infection alive in him. But if the parasites are so few, what chance has the medical man of finding a single one? If even 1,000 parasites are present in a man of 10 stone weight, the chances are that we must search 15,000,000,000 haematids before we find one parasite. At the rate of 10,000 haematids a minute we shall have to search for 1,500,000 minutes, or for twelve hours a day for more than five years, before we succeed. Or we may put it in this way — that 150,000 examinations, each of ten minutes' duration, must be made. In seven autopsies on cases of " latent malaria," C. F. Craig [1909] found only the ordinary parasites in the spleen. Four of these contained malignant parasites, yet no crescents at all were found in the spleen. (5). Probable cause of the rallies and relapses. — According to this simple hypothesis (which I will continue to adopt until a better one is established) the rallies are probably due to a great destruction of the parasites by some germicidal power of the blood, or of their toxin by some antitoxic power, or more generally to both. And the relapses are probably due to decrease in both of these factors of resistance. ii6 THE PARASITIC INVASION IN MAN [Sect. It is not within our province to discuss these factors now. The general experience that many cases improve without treatment, and merely after good food and rest in bed, proves that such factors exist ; and, as already stated, if they did not exist every case would certainly perish. Many diseases — tuberculosis, trypanosomiasis, relapsing fever, leprosy, etc. — exhibit such variations in intensity. We picture to ourselves a long struggle between the invaders and the opposing force — first one side triumphs and then the other, and death or recovery finally ends the contest. Just as rest and good food encourage the resistance, so, probably, anything which weakens the patient — fatigue, chill, heat, dissipation, other sickness — tends to encourage the parasites. Educated patients often declare that their fever is brought on by such causes. Military surgeons recognise that when infected troops are despatched upon arduous military duties numbers of them begin to fall sick at once, even though it may not be the season of fresh infections. Travellers and planters complain of the same thing as regards their porters or coolies ; and medical men notice the frequency of malarial relapses after typhoid fever, venereal diseases, child - birth, accidents, etc. ■ I think that external heat probably tends to encourage relapses. Although the temperature of the body remains much the same, the parasites may possibly be stimulated by the heat in some way, owing to the fact that warm climates are specially suitable to them and to their dissemination by mosquitos. Thus in my experiments on birds in 1898, I noticed that when the birds were taken to the cool climate of the Himalayas their parasites greatly diminished, and when they were brought back again to Calcutta their parasites increased again. In the hot weather in Calcutta 11^ of the sparrows examined contained P. danilevskyi\ but early in the cool weather few were found to be infected. This point requires exact experimental study. A. Caccini [1902] thinks 2o] CAUSES OF RALLIES AND RELAPSES 117 that excessive heat does not have much effect, but notes the frequency of relapses in benign tertian in spring ; and it seems to me that the onset of warm weather rather than the heat itself is most likely to be the encouraging factor, since the germicidal power is probably heightened after the first relapses in spring. It is interesting to note that in India there is generally a small but well-marked rise in the admission rates of troops at the commencement of the warm weather in March to April. For example, I take at random the Native Troops on the North- West Frontier, Indus Valley, and North- West Rajputana (" Reports of the Sanitary Commissioner with the Government of India "), and give the averages for the three years 1900- 1902. AVERAGE ADMISSIONS. Strength Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 16,428 379 205 191 285 401 326 420 396 565 1,397 1,152 735 Here there is a marked increase between March and April, that is, at the commencement of the hot dry weather, long before the advent of the breeding season of Anophelines. It may, however, be due to the awakening of infected hibernating mosquitos (section 21). Why, if the germicidal power is strong enough to destroy large numbers of the parasites, does it not destroy all of them ? I presume that, as in other forms of life, the hardiest individuals often succeed in withstanding the opposing forces unless they are too strong ; that a few of the plasmodia survive until the germicidal power is fully developed — when the entire brood is exterminated. What is it that determines the length of the rally, or apyrexial period ? Probably {a) the number of plasmodia left alive at the end of the previous attack, and {b) the strength of the germicidal power of the patient. If the parasites are reduced to about the number of protospores originally inoculated, and the germicidal power weakens rapidly, the former will now multiply again at a rate somewhat similar ii8 THE PARASITIC INVASION IN MAN [Sect. to their first rate of proliferation — so that the length of the apyrexial period should be roughly equivalent to the original incubation period. If the germicidal power is strong, or is fortified by quinine, the plasmodia left alive after the previous attack should multiply so slowly that the apyrexial period may be indefinitely prolonged. Under such circumstances a few parasites may perhaps continue to breed for months in a patient, without causing the smallest symptoms, and yet, if the germicidal power is reduced for a moment, may be able at any time to multiply again sufificiently to produce another attack. The same thing probably happens with irregular or insufficient quinine medication. The long intervals which fre- quently occur can be explained equally well on this hypothesis. We do not know why the resistance of the host should be affected by his general state of health or by external conditions. That such is the case affords another argument against the idea that the relapses are due merely to some normal development of the parasites. The study of immunity in malaria should yield important facts for the study of immunity in general. I merely touch upon the subject here. Cases are often reported in which the patient during the relapses suffers from malaise, dyspepsia, and so on, rather than from fever, although the parasites are numerous enough to be found. In such, I presume, the antitoxic power of the blood has become better developed than the germicidal power. Cases in which a relapse immediately follows a chill or accident are explained perhaps by the hypothesis that the chill or accident has immediately reduced the antitoxic (not necessarily the germicidal) power of the blood. (6). Frequency of the relapses. — All clinicians recognise that in untreated or badly-treated cases a considerable number of relapses may occur before complete recovery is established. Cases giving a history of say three to ten relapses are very common. But we are indebted to A. Caccini [1902] for giving us a very able and full analysis of this question. In 2o] FREQUENCY OF RELAPSES 119 1899- 1901 he was entrusted by Professor Ballori, Director- General of the Hospitals in Rome, with the care of a special department for the study of malaria, and set himself to the task of examining these questions methodically. The cases studied by him were as follows : — Type First Attacks Relapses Total Quartan 525 330 855 Benign Tertian . . . 1,086 934 2,020 Malignant .... 2,275 i»429 3,704 Totals . . . 3,886 2,693 6,579 Many of the cases were given quinine, so that this proportion will not accurately represent the proportion of relapses in untreated cases — which should be much larger. The author excluded all cases in which the parasites were not found. He endeavoured to ascertain as exactly as possible the history of each case, not only by enquiry of each patient, but by reference to hospitals and localities where they had been treated ; he kept many cases in hospital for long periods, and he gives a careful record of his results, I will mention here only his untreated cases. Two cases of benign tertian, untreated, were kept under observation in bed in hospital for nine months. The following table gives the duration in days of their successive relapses and rallies : — Rel. Ral. Rel. Ral. Rel. Ral. Rel. Ral. Rel. Ral. Rel. Case I . . . 17 13 16 16 14 19 15 17 12 10 19 Case 2 . . . 15 17 16 15 18 20 17 6 10 9 Both patients were robust, had the same diet, and were not allowed to suffer from cold or damp or intercurrent affections. Nineteen similar cases studied for shorter periods showed the same phenomena. The author notes that out of 120 untreated cases of benign tertian, the relapses occurred more frequently in the spring (March to May). He thinks that the rallies con- tinue from 5 to 18 days, which he calls apyrexial periods of short interval. But he also notes and distinguishes rallies of I20 THE PARASITIC INVASION IN MAN [Sect. long interval, lasting 3 to 4 months, which he says occurred in 152 persons who had not revisited malarious places in the mean- while. The rally lasted under 2 months in 60 cases ; under 70 days in 29 cases ; 90 days in 20 cases ; and from 90 to 120 days in the remaining cases. He also quotes the case of a band of 75 Calabrian workmen who had become infected at Foggio in July 1900, and had sub- sequently taken quinine until December. On 8th September 1901, 14 months after the first infection, 62 of these men were exposed to a severe wetting with rain, while the remaining 13 found shelter. On loth September and the six following days, every one of these 62 men was attacked with relapses. The intervening rallies since their last attacks had lasted for 7 months in 2 of the men ; for 7-5 months in 3 ; for 8 months in 12; for 9 months in 10; for 10 months in 15; and for 13 months in 20. Those who had not been wetted by rain escaped. It is supposed that none of the cases had been subject to re- infection. In quartan the author found that out of 118 cases kept without treatment relapses occurred only in 8 which had been exposed to chills and other predisposing causes. He thinks that quartan relapses chiefly as a consequence of such causes — unlike tertian, which relapses under any conditions. The length of the rally depends upon the care which has been taken of the patient ; but the author quotes six cases of relapse occurring after long intervals (6 to 10 months). He says also that in some cases of experimental inoculation of quartan by him (no reference) the incubation period could be prolonged at pleasure by keeping the subject at rest in bed, etc. Regarding malignant fever, Caccini gives the following lengths of the rallies in 44 untreated persons : — Days . 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 Cases . 9 I 5 I 7 I I I I I I I 2 6 1 3 2 The author suggests that there is some radical difference between relapses at short and at long intervals, but I cannot 2o] FREQUENCY OF RELAPSES 121 find that he proves his case. He agrees with all observers in attaching great importance to the determining factors of relapse, which he says are, (i) absence of good food and health, (2) gastro-intestinal troubles, (3) fatigue, (4) traumatism, (5) sudden chills, damp, and wetting, (6) change of climate, (7) certain foods and medicines (?) due to intestinal disturbance, (8) intercurrent sickness. To these I would add : — (9) anxiety, sorrow, shock or fright, (10) alcoholic and other excess, (11) sudden exposure to a tropical sun, (12) premature cessation of quinine. It is, of course, understood that these determinants act by reducing temporarily the host's resistance, but we do not know exactly how they do so. Caccini endorses the common opinion that quartan and tertian, especially the former, are most prone to relapses. In malignant, the original illness is more severe and (probably for this reason) relapses are not so common. I will refer to his important results with quinine in section 23. Celli [1901] gives a useful table showing primary cases, relapses and pernicious cases in the Roman Hospitals for 1 892- 1 898. The following are the totals for the seven years : — Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Total Primary 864 676 724 793 809 696 2,912 5,157 4,440 3,875 3,074 1,967 25,987 Relapses 581 358 319 341 353 205 522 949 1,031 1,156 989 716 7,520 Pernicious 21 — — — i 45 62 67 64 56 32 330 Thus, excluding the pernicious attacks, out of a total of 33,507 cases, 75% were reported to be primary and 25% relapses — that is, three to one. f22 THE PARASITIC INVASION IN MAN [Sfxt. Relapses are referred to in many other works, but the informa- tion given is scanty. The illness being generally slighter, patients do not often come to hospital in consequence of it ; and in most cases quinine distorts the clinical picture (section 22). Relapses after long intervals are frequently mentioned. The case of P. T. Manson (section 16, case 5), who had a relapse nine months after the original infection, followed by three months' quinine treatment, is well known. In one case at the Royal Southern Hospital I found the parasites in a patient who said that he had left the tropics four years previously (records unfortunately lost). In Britain we have many returned officials who say that they continue to have occasional attacks after return from malarious colonies — more than twenty years have been mentioned to me by three persons ; but as each attack lasts only for a day or two it is generally impossible to verify the point microscopically. My father left India in 1880, but in 1889 still complained of occasional attacks. A little later I witnessed one of these — a sudden severe rigor followed by high fever and a typical sweating stage. The blood was not examined, but the paroxysm was almost certainly a quartan or tertian one. So far as I remember there was no determining factor in this case. 21. Average Duration of Untreated Infections.— Persons may therefore remain infected for several, and possibly for many years ; just as some may recover spontaneously after the first series of attacks. But from the public health point of view an important question remains to be answered, namely, how long does the infection continue in untreated cases on the average} That is, if 1,000 persons, simultaneously infected, were to be removed simultaneously to a perfectly healthy area, where they are kept untreated, how long would their infections continue.? It is impossible to say at which particular moment the last parasite dies out in a patient's blood, and no adequate researches have been made on the point. We are therefore forced to rely upon certain calculations. 2i] DURATION OF INFECTION 123 The cases of malaria at Ismailia from 1900-1905 are given officially as follows : — Years . 1900 1901 1902 1903 1904 1905 Cases . . 2,284 1,990 1,551 214 90 37 In 1901-1902 quinine was largely distributed in the town, but after my visit at the end of 1902 the Anophelines were banished, the quinine also being continued to those who took it. Since 1905, and probably since 1902, there has been no endemic malaria, such cases as occur being found only in persons infected outside, or being merely relapses. Hence we infer, as a very rough calculation, that of the 1,551 persons who were ill in 1902, less than 1/7 (214) remained ill in 1903, and less than 1/17 (90) remained ill after two years. But here quinine expedited the recovery on one side of the account ; while on the other side of it many of the cases that remained were probably due to external infection. Another way to estimate the reduction is, I suggest, to consider the statistics of some country where fresh infections suddenly cease owing to the abrupt onset of a sharp winter and the consequent cessation of mosquito breeding and mosquito biting. I select as an example the Punjab, a large malarious area in the extreme north-west corner of India, and give the figures of admissions furnished by the annual " Reports of the Sanitary Commissioner with the Government of India." The years 1899 to 1903 have been selected because after the latter date quinine began to be administered much more regularly. Nevertheless, subsequent figures show very similar monthly variations — as in fact are shown by the same statistics for other parts of India. The ratios under each monthly average are obtained by dividing by it the following monthly average — so that these ratios give the monthly factor of increase or decrease in the number of admissions. The striking regularity with which the maximum is reached in October and the minimum in February will be observed. < l^OO "100 t^ On 1^00 fv. i-H CO On O vO t^vO "- kj Tj- OnnO -^ On O ^ L«-> "1 ClO »— < < CO CO VO ON M ON H b ■>^ iri u-i Tj- u-> l-Tt o 1-1 •* On n ►-• CO h H " O ON CO Tf Tj- o OO o" O OOO I- vO r^ ON cj ON I^ 1-1 ON t^ ON 11 u-i -^ ro u-i ^ 00 Tj- 0} vonO VO on >-i b Q " 00 ro N 00 '^ b Q " -^ « '-'" to 1^00 M OO vO VO CO nO CO O OO M „ >" « OO O "^ On ^ NO ^ CO ~ M CO -^ CO NO o M vO \0 " rv b o CO ^ r^ - q^ b Z 2; « M M C« 1-1 N *^ t^ "^OO \0 N lO ON M t-voo CO ON VO VO ^ - NO CO '^ -1 CO 00 ^ >- COCO VO t^ VO NO CJ u-i CO t-^O On 00 b o --^ CO 0;00^ "^ On b o -~ o c? 'f CO i-T pT rT (S t^ ON t^ O ON VO a en vO O " O r) o NO •J CO CO O O NO 00 t-^ M O 00 O -i- t^ ^ Q, VO rv. cooo^ O^ nO_ u^vO m\0 ^-o lO l-T ►T CP k^ >^ KH rt On t^ OnnO VO NO bb ro i-ovO ro OO ON > bi) O I^nO •* ri NO 3 t^ ? t-;; o^ o^ -^ q_ -^ < t:}- CO ltinO ■^ "^ '" < "^ "-T rT "^ i-T ^ CO ^00 coco 1-4 NO _>^ O On M ^ — Ml o i33 CO On O O " CO CO "5 CO -t -^ O CO CO ■p On t>vCO 1-1 r^ o^ Ln CO Tf rj- -T^ 1- ^ 1 — > mT hT < 1) P< -1 00 t-x O n r^ cu Tf -I- UTO NO t^ o (S « o « o VO N 3 »- uo On r^ Tj- Lr\ (N 1 5 r^NO VO t^ i^ 00 * -1- fi -i- ri CO CO C/5 «" c g >-. ii-» u-t ui O O On t^ >, NO r) -^nO On VO CO c^ S 00 -^ -* n U-. NO On rt :^ OnnO VO On t^ r» u-i M CO CO CO CO b H .^ nO ■^ OnOO CO NO '-, W ^ > „ '^ f~^oo rv. ri Tt ^ On 's_ On VO tv.0O r^ CO Tf a "-> Tj- ON -> O NO P < a. O 00 •* N On . ON »-< < CO «-i CO n c-i C4 < Tt M On VO n VO ^ nO O nO CO - N CO « On VO t~^ f< P> VO 1^ O ►- nO CO -i- t^ VO 2 ON ■^ C< 00 CS HH NH f) w r) « i-i ^ CO C4 NO ■* CO VO " _Q CO nO O 00 -* ON CO J2 rr M >-i O nO „ M 4J r^ t^ ON — CO rs CO ►I 00 t^ •* On NO t-^ fct, *"* »-• ^ fc VO r) Tj-vO CO ■^ ^ •^ r) u^ TfNO N CO CO 1-1 r^ p^ "* VO t^ rt -* CO — On n -^ vr\ 1 — . nO •^- ■* On t^ 00 NO 1 — . CO — rj- -1 « c-< b vO vnco t^ VO NO b ^ O r) 1-1 \0 r^ £ T^f ~ O NO N o bo OO vO CO CO On -* bb rt « vooo OO CO 4> q^>^ -^no^ q^ ON c N CO O "^ VO CO 0^ v^ OO^ncTnO^ VO r^ NO Ul rf r4 nO CO O CO ^ 1 1 55 Tt ■«*■ ■* -"l- -^ "* V i CO O^ O^ On On u V 00 ON ON ON On b. V K- u > nl > a < Pi 1 < Pi >< < CO W o 5 U < H O [-1 .00 ■<* "^ N fO M •*oo o "^ r^ o O o \0 »J^0O vO vO 00 Q o M \0 r» -1 O -i- 00 \0 00^ ooo o^ O^ o mo r^ rh u-> r-^ Ln 00 r^ N CO \0 O <^ vr^ Cl^OO \0 fO l^ ■„ M ^ t^ CO O O OO vO •* 1 — . two vO 00 t^ u-i M O "- CO O O fO 'i- 5 vO ■-• \0 M O^ "^ '^ ro O vO \0 ►- "- 00 M vO fO M '-' " OO CO -* O ^ ^ i-n Q < 00 Tf- CI t^ O M r' CO -^ "^ ^ ^^ ■^ M 1 r^ N O «J^ - " Tl- ca CO •* CI fO „ J3 vO O O -' 'J^ vO C^ CT^« C» t^ M vO p CI C< CI CO CI N „ 5 u en ir^vO •* ■* <^ O N O C» ro O t~^ (^ ^ CI O <> ("i <^ "-^ « LovO 00 vO O u-i u-> •^ t^ >-< •^ CO i/i ro cP cr CO Ov O " «!' CO 00 rt <: P^ 126 THE PARASITIC INVASION IN MAN [Sect. For the European troops the maximum (835) is 6-47 times the maximum (129), which occurs four months later. For the native troops, the maximum (2,955) is 6-41 times the minimum (461) — almost the same. For the prisoners the maximum (1,045) is 3*93 times the minimum (266) — a smaller ratio. Thus, for 1,000 admissions in each class during October the following numbers were admitted in February: — October February European troops . . . 1,000 154 Native troops .... 1,000 156 Prisoners 1,000 254 A certain amount of quinine was doubtless given to all these classes, and many of the Europeans were probably moved to hill stations after April to May. It is easy to under- stand the small rate of recuperation of the prisoners — a constantly changing class drawn from the lowest ranks of the population and depressed by their imprisonment. Hence I infer that the rate of recovery of the European and native troops during the four months is probably too favourable for an estimate of the same rate among a large untreated native population. On the other hand, the quinine' treatment of the prisoners may be cancelled by their circumstances, so that their rate of recovery should be something similar to that of the general population. We may therefore, perhaps, assume as a rough but convenient estimate for the latter that what may be called the reduction factor is about 0*25 in four months — that is, that 1,000 cases should be reduced to 250 in that time by spontaneous improvement. We observe in the statistics given above that there is an almost constant but slow increase in the admissions from February onward. Whether this is at first due to heat relapses or to infections by hibernating Anophelines (section 20) is not known ; but if no such increase were to take place, we might suppose that the same rate of recovery would hold for 22] ENLARGEMENT OF THE SPLEEN 127 the rest of that year. In other words, we might suppose that any number of patients brought to England would be reduced by recovery to one quarter (0*25) every four months — that 1,000 cases would become 250, 62, 15, in four, eight, twelve months respectively, and so on. This is, I fear, a very rough estimate, but I know of no other method of making any estimate at all. Hence we may perhaps infer that 3/4 of our untreated cases will recover in four months; i5/i6of them in eight months; 31/32 of them in a year, and so on. But these figures are based upon the gaol statistics of the Punjab — that is, upon those of natives, most of whom have probably had malaria in childhood. What may happen in the case of a completely non-immune and untreated population I cannot say. For such we might adopt a still lower rate of recovery, say 1/2 or 50% every three months ; that is, 1/2 would recover in three months, 3/4 in six months, 7/8 in nine months, and 15/16 in a year. On the whole, this is probably the nearest estimate. Celli [1901] gives the admissions into the Roman Hospitals during thirteen of the years between 1864 and 1898 — numbering nearly 93,000 altogether. I subjoin the monthly totals for the reader to study in connection with the above remarks. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Total 4.673 3.732 3)9o6 3,921 3,575 2,553 8,844 17,678 15,203 12,755 9,531 6,621 92,992 22. Enlargement of the Spleen and Liver.— This is a con- dition of importance in the prevention of malaria, as it often enables us to estimate the amount of the disease in a locality. We must now note the following points regarding it. The average weight of the spleen of a healthy man of 60 kilograms in weight is estimated to be 171 grams (Vierordt), or 2'85/iooo of body-weight. In healthy adults the edge of it cannot be felt under the ribs, but the reader should note that this can often be done in small infants. The organ commences to enlarge during even the first 128 THE PARASITIC INVASION IN MAN [Sect. paroxysm of malarial fever, the increase in the area of splenic, dullness being quite appreciable. In the first apyrexial period the enlargement decreases, but as attack follows attack the sum of the successive increments is greater than that of the successive decrements, so that a more and more marked tumour results. Innumerable measurements have been recorded. Kelsch and Kiener [1889] state that in eighty autopsies they found the weight to vary from 400 to 1,500 grams, and to average 914 grams (chronic malaria). I think that even small and irregularly administered doses of quinine tend to check the increase very much. Thus in untreated native children one often finds the organ an inch or more below the ribs after a few attacks, while there is frequently no enlargement in Europeans even after many attacks. In sailors who have reached Liverpool after weeks' or months' fever on the homeward voyage from West Africa, we find as a rule scarcely any enlargement. In 1895 my regiment in Secunderabad, India, was full of malaria as proved by the microscope and the clinical symptoms, but on making a spleen census by order of the authorities I found only four men with enlarged spleen out of about eight hundred. In both these instances a certain amount of quinine' is or was given — not enough to cure the patient, but enough to check the splenomegaly. The pathological changes are discussed in detail in the text-books and need not be described here. Laveran [1907, p. 391] considers the pathology and seems to think that the enlargement is due to local irritation caused by the accumula- tion of the parasites in the organs, which is their " siege d'election." Others connect the enlargement with the defensive process. The arguments are far from conclusive on either side. On the whole, from general observation, I consider that the following propositions are probably true : — (i). That in a given number of infections of the same 22] ENLARGEMENT OF THE SPLEEN 129 duration (a) in children and (d) in adults, the children will show a greater degree of splenomegaly. (2). That in a given number of infections of the same dura- tion (a) in Indo-Europeans and (3) in Negroes, the former will show a greater degree of splenomegaly. I cannot speak regarding Mongolians. (3). That in a given number of infections of the same duration (a) in untreated persons and (d) in persons of the same age and race treated even slightly with quinine, the former will show a greater degree of splenomegaly. (4). That in a given number of infections of the same duration (a) in persons infected only once, and (d) in persons who have been subject to repeated infections, the latter will show the greater degree of splenomegaly. (5). That the number of parasites tends to vary inversely as the degree of splenomegaly ; that is, that the parasites tend to die out in persons with very large spleen. (6), That a hot and damp climate, or insufficient food, or certain diets, or bad drinking water may possibly favour the development of splenomegaly ; in other words, that the degree of splenomegaly may not always be an exact measure of the amount of malaria in a locality. I cannot give anything approaching proof of these proposi- tions, but merely suggest them for future consideration and investigation. On the other hand, some general facts have been more strictly ascertained. Before considering them we should remember that many of the older observations have been invalidated by the discovery in 1903 that kala-azar a disease which causes great enlargement of the spleen and liver and abounds in parts of India, Algeria and other countries, is not I I30 THE PARASITIC INVASION IN MAN [Sect. malaria, but is due to a different organism, Leishmania donovani, Laveran. Before this date the two diseases were frequently confounded, as, for instance, by myself in my report on kala-azar [1899]. If therefore we wish for accurate figures we must first ascertain whether kala-azar is present or not, or at least whether it is very prevalent. This is generally not difficult, for the following reasons : — (i). Kala-azar is extremely fatal, whereas malaria is benign ; so that the presence of the former is soon felt in a locality, (2). The parasites of both diseases can be detected during life and post-mortem. (3). The symptoms of kala-azar, though somewhat similar to those of malaria, are much more intense. The patients often have a look of suffering and melan- choly not so frequently observed in malaria. I was much struck with this difference when comparing splenomegalous children in Greece and Mauritius with those suffering from kala-azar in Assam. In the absence of this disease, then, we may generally ascribe most of the cases of enlargement of the spleen to malaria, especially if they are numerous. They are generally extremely numerous in most malarious localities where quinine is not much taken. In 1907- 1 908 Major Fowler and I, assisted by the Sanitary Department and the medical men of Mauritius, made a large " spleen census " in that colony. We examined children of fifteen years of age and under, in all parts of the island. Out of an estimated total of 182,000 such children we tested 31,022, and found enlargement of the spleen in 10,595, or more than one-third (34'i/ioo). Moreover, in 30,137 we recorded the degree of enlargement, and found that it was small in 4,381, or 14-5/100 ; medium in 3,479 or 11-5/100; and great in 2,566 or 8-5/100— a total of 10,426 with enlargement. This differentiation of degree suggests the possibility of 22] ENLARGEMENT OF THE SPLEEN 131 obtaining a figure which I call the average spleen index. Taking a normal spleen at 171 grams, a very large spleen of 1,500 grams would be about nine times that size. We may therefore define a small enlargement as being about three times the normal size ; a mediuui enlargement about six times the normal ; and a great enlargement about nine times the normal — the same ratios holding for children also. Thus in order to find the average spleen, we multiply the numbers under each heading by the size-ratio, add the results to the number of children with no enlargement, and divide by the total number of children examined. We thus have (19,71 i-j- 4,381 X 3 + 3,479x6 + 2,566x9) -^30,1 37 = 2*54 the average spleen for Mauritius (section 31). From these and other data I compiled the following tables [1908] showing the relation between the spleen rates and altitude, and the spleen rates and the general death rates in Mauritius. SPLEEN RATES ACCORDING TO ALTITUDE ( 'Mauritius). Altitude in Feet. Children examined. Spl sens. Total with spleen. Spleen rate. Average spleen. I 3 6 9 100 5,210 2,623 1,030 732 734 2,587 49-6 3-20 200 4,843 2,593 813 765 633 1,250 46-4 3-i6 300 3,559 2,208 616 457 258 1,351 37-6 2-59 400 2,817 1,432 651 473 262 1,386 49-2 3-01 500 1,246 786 193 177 90 460 36-9 3-48 600 830 518 106 128 78 312 37-5 274 700 1,963 1,373 227 235 122 590 30-0 2-27 800 1,398 1,241 80 41 36 157 in 1-65 900 624 478 52 48 46 146 23-4 2-14 1,000 972 901 47 II 13 71 73 1-26 1,100 782 736 18 9 7 46 5-8 I-I4 1,200 858 751 49 28 '9 107 12-4 1-28 1,300 130 124 6 4-6 1,400 1,991 1,556 185 160 90 435 21-8 194 1,500 612 586 10 12 4 26 4-2 119 1,600 112 105 3 4 7 6-2 1-31 1,700 ... ... 1,800 765 740 13 "6 5 25 3-2 113 132 THE PARASITIC INVASION IN MAN [Sect. SPLEEN RATES COMPARED WITH DEATH RATES BY DISTRICTS— (Mauritius) Class. Districts. Death rates Average 1905-1906. Spleen rates. Average spleen. Pamplemousses zrz 39'6 2-62 Riviere du Rampart 307 24-6 1-97 Flacq 30 "9 59-6 3-45 Estates only Grand Port 24-5 48-0 3-25 Savanne 287 21-5 1-85 Black River 39-5 567 3-56 Moka 187 4 '4 1-23 ■ Plaines Wilhems 27'0 8-6 1-43 Average of the above 297 32-9 2-42 /Port Louis 36-6 35-6 2-66 Pamplemousses 46-1 457 3 '04 Riviere du Rampart 397 27-6 2*12 Flacq 42-4 627 3-89 All Classes - Grand Port 38-6 42-4 2-97 Savanne 32-5 23-0 1-96 Black River 44-2 58-2 3-63 Moka 31-1 II-2 1-52 ^Plaines Wilhems 31-9 14-3 I -61 Average of the above 40-3 35-6 2 "60 The exceptionally high figures at an altitude of 1,400 feet (426 meters) were due to a serious local outbreak at the large village of Phoenix in Plaines Wilhelms district, most of which is high and healthy. It should be understood that the higher altitudes in Mauritius are plateaus rather than sloped hillsides, so that the variation is probably due merely to difference of climate. The accepted rule is that the temperature falls i" F. for every 300 feet (or 1° C. for i6^'6 metres) of altitude. A still larger spleen census was carried out in Ceylon towards the end of 1908 by the orders of the Principal Civil Medical Officer (Sir Allan Perry). He estimated that the total number of children under fifteen years in that island were 1,622,766, and the following table gives the result of the census (" Report of the Advisory Committee for the Tropical Diseases 22] ENLARGEMENT OF THE SPLEEN 133 Research Fund for the year 1909" — Blue Book of Colonial Office). Province. Children examined . Enlargement of spleen. Spleen Rate. Average Spleen. Total. Small. Medium. Great. Northern . Southern . Eastern . N. Western 1 N. Central i Uva . Sabaragamuwa Central . Western . 1 11,371 15,022 6,476 17,024 5,087 5,177 7,154 14,362 10,585 5,438 2,847 2,266 9,064 3,215 2,291 2,046 2,804 2,350 31,421 2,567 1,794 1,449 4,675 1,491 1,088 1,049 1,631 1,867 1,194 600 572 2,975 1,100 686 527 817 417 8,888 777 453 245 1,414 624 517 470 356 66 4,922 39-91 18-95 34-99 53-25 63-20 44-20 28-60 19-52 22-20 34-05 2-52 1-67 2-19 3-08 3-64 2-88 2-i8 1-70 1-59 Total 92,258 17,611 2*29 These large figures correspond closely with those obtained in Mauritius. They give not only valuable information regarding the local prevalence of malaria, but show how enormously wide- spread the disease must be — for neither Ceylon nor Mauritius can be called very extremely malarious. The figures in Ceylon were collected after the malaria season, and those of Mauritius during the early part of the season. The correspondence between the spleen rate and the number of persons found to contain the parasites will be discussed in section 31 (2). According to theory the spleen rate should fall with the distance from marshes. This point was carefully worked out by Major Fowler and myself in the outbreak at Phoenix, Mauritius. We found, not only that such a fall occurred, but that it was so extremely rapid and marked as to be beyond all possibility of chance distribution (section 30 (i) and map). The older writers lay down that the liver is generally enlarged in malaria. Kelsch and Kiener [1S89] say that its average weight is 2-3 kilograms, but that it may weigh up to 134 THE PARASITIC INVASION IN MAN [Sect. 4 kilograms; but they worked in Algeria, and it is quite possible that there, as elsewhere, cases of kala-azar were included. I was struck both in Greece and in Mauritius, where kala-azar is not supposed to exist, with the absence of any marked enlargement of the liver in the great majority of the children who had splenomegaly. More definite data are required on this subject. 23. The Effect of Quinine. — After the earlier physicians had established the utility of cinchona for malaria it began to be much discredited owing to its employment in doses too small to be effective. This error was rectified by Maillot [1834], who after a long struggle persuaded the medical profession to adopt larger doses in consequence of his experience in Algeria. But up to the end of last century, another error, equally great, was very generally made — the drug was not continued long enough to prevent relapses. When I went to India in 1881 it was the rule in military practice to return soldiers to duty three days after the cessation of fever. I believe that I was one of the first to call attention to this absurdity [1S96, p. 43]. When I myself was infected next year I prescribed for myself a rigorous quinine treatment for four months, and had no relapses in consequence ; and I have always taught this rule since then. The practice is now much better, but I still see numerous patients, especially from West Africa, who have been enjoined to take quinine for a fortnight after recovery ! Need- less to say, haemoglobinuria is often the result. A third error, still often made, is to withhold the drug until the fever has fallen. Much work has been done on the absorption and elimination of quinine by the body — more recently by Kleine [1901], Jacoangeli [1903], Mariani [1903 -1904], Modigliana [1905], Giemsa and Schaumann [1907], and others. The absorption is measured by the elimination, which takes place principally through the urine, in which the presence of the drug is easily 23] QUININE 135 revealed by chemical analysis ; and the results may be sum- marised sufficiently for public health work as follows : — After intr-avenous injectiort, cinchonism follows in a few minutes. Baccelli, who first suggested such injections, employed solutions of I gram of quinine in 10 parts of physiological salt solution — to be used only in severe cases. After being taken by the mouth, the first traces of the drug may begin to appear in the urine in about fifteen minutes ; but this period varies largely for different salts. The maximum elimination occurs between four to twelve hours after ingestion. Most of the drug is eliminated before thirty-six hours, but traces of it may be found even after nine days. Only about 1/3 of the dose escapes destruction by the body. The more soluble salts appear much more quickly in the urine than the less soluble ones, but the latter are finally absorbed as well as the former. So also, the salts are more quickly absorbed from an empty stomach ; but the total amount absorbed from a full stomach is finally quite as large. Given in repeated small doses, the drug appears to be better absorbed than when it is given in a single dose of the same total weight. After intramuscular injection, the salts are not absorbed so quickly, especially if given in strong solution. This is due to local precipitation (Giemsa and Schaumann). Thus while nearly 40/100 of quinine taken by the stomach may be eliminated in three days, only about 12/100 given intramuscularly in a i/i solution is eliminated in the same time. But with a i/io solution about 23/100 of the salt (bihydrochloride) is eliminated after intramuscular injection. On the other hand, D. Sandro [1909] favours intramuscular injection because absorption through the liver is thus avoided. He also finds that the drug remains longest in the spleen (twenty hours). After rectal injection, quinine appears in the urine in twenty- five minutes. As the drug is not completely eliminated for several days it 136 THE PARASITIC INVASION IN MAN [Sect. is cumulative in its action ; so that a daily dose will keep the blood impregnated with about twice as much as is given at each dose [from Mariani, 1904]. Fever does not affect the absorption, but gastro-intestinal troubles do so if severe enough. The following table shows when some of the various salts appear in the urine : — Salt. Equivalent Solubility. 1 Appears in of quinine. 1 urine. Bihydrochlorate 72-0% I/I 15 minutes Hydrochlorate 8r8% 1/40 15 Acetate 84-0% 30 Citrate 67-0% 1/820 30 Bisulphate 59-1% I/II 30 Sulphate 73-5% 1/800 45- „ Tannate 20*0% slight 180 „ Euquinine 8i-o% 1/12,500 For further details the laborious papers referred to above, especially those of Mariani and Giemsa and Schaumann, should be consulted. In large enough doses quinine produces ringing in the ears, deafness, giddiness, headache, dilatation of the pupils, urticaria and erythema, and, in poisonous doses, convulsions, muscular weakness and amblyopia.- A very small percentage of people are unable to take even small doses ; Dr Macalister had a case in the tropical clinic of the Royal Southern Hospital at Liverpool who could not endure even 0'03 grams.^ I have observed in experiments on myself that quinine taken just before a meal causes tinnitus auriiim in about half an hour, thus proving its rapid absorption ; but taken after a meal it does not produce this effect so quickly, while it tends to cause much dyspepsia, especially if given in pill form, and leaves a 1 Very variable figures are given. I adopt some of those furnished to me by Howards & Sons. 2 G. Baermann has recently reported [1909] a death due to two doses of 1/2 gram of quinine hydrochlorate — collapse, blood in dejecta, extravasation in organs. ^ I have just seen a patient who confessed to the rather exceptional drug-habit of quinine. He acquired a craving for it, and found great difficulty in breaking himself of the habit. 23] QUININE 137 taste in the mouth which remains until the next meal. For myself, therefore, I always prefer to take it just before meals, especially before breakfast. This is also often the best time, according to Torti's law, for destroying the plasmodia. The action of quinine upon the parasites has been studied by many observers. Binz [1867] was the first to study the effect of weak solutions of quinine on Protozoa. Laveran states that a 1/10,000 solution kills the plasmodia in vitro. Romanowsky and Mannaberg [1894] found that in patients who had been taking quinine the parasites possessed badly staining nuclei, that many of the spores within the sporocysts were dead, and that the understained parasites had a peculiar appearance. Numerous studies have been made subsequently on the subject, as by Ziemann [1906] and Craig [1906], which give a somewhat different picture of the death-process. Nearly all observers have agreed that quinine exerts much less influence on the gametids, especially the crescents, than upon the sporids, though Ziemann thinks that the male gametids are more easily affected. Many of the younger writers ascribe relapses to parthenogenesis in gametids which survive all quinine treat- ment in this manner. Gualdi and Martirano [1901] state that as much as 2-5 grams of quinine in single dose, or i"0-i'5 grams daily, are not sufficient to banish crescents. I note that it is not always easy to state that the observed forms are really due to quinine and not to the germicidal action of the blood ; and indeed that they are really abnormal forms at all ; and also that strict enumerative methods have not been used. An important point in connection with the prevention of malaria is that Bignami and Bastianelli, Gualdo and Martirano, and Schaudinn [1903] have succeeded in infecting Anophelines from patients who had been taking quinine. Schaudinn's case had been taking i gram thrice a week. Ziemann remarks that this suggests that the male gametids are not destroyed as he thought. It also suggests that cases of crescents are likely to prove sources of infection in spite of energetic treatment. 138 THE PARASITIC INVASION IN MAN [Sect. The article of Caccini [1902], which I quoted in part in section 20, gives valuable information on the effect of quinine treatment on the prevention of relapses, and therefore on the extermination of the invasion. After all, this is the most important part of the subject from the point of view of pre- ventive medicine. He summarises his cases of benign tertian as follows : — (i). Of 145 cases treated early and systematically a relapse occurred in 37%. (2). Of 301 cases treated systematically, but started some- what late, a relapse occurred in 30%. (3). Of 1,002 cases with daily quinine, a relapse occurred in '5%. (4). Of 50 cases treated with quinine at height of fever, a relapse occurred in 80%. (5). Of 55 cases treated with quinine during the sweating stage, a relapse occurred in 80%. (6). Of 291 cases to which quinine was given irregularly, a relapse occurred in 85%. (7). Of 120 cases to which quinine was not given at all, there was only one in which no relapse occurred. The author explains that by " early and systematic treat- ment " he means quinine given on alternate days in doses of i'5-2'0 grams per day in three or four doses, with about half an hour's interval between them, starting the administration three hours before the (expected) commencement of the fever. But the treatment was suspended after seven days. By " systematic but late treatment " he means the same scale of treatment commenced later in the case. By " daily quinine " he means daily administration of 1-2 grams without reference to the hour of onset of fever, the treatment being suspended after seven to te?i days. Apparently in all cases " the cure was recommenced every time that a relapse set in." The figures prove fairly clearly the following : — (i). The best results (only 15% relapses) were obtained with daily doses of quinine. 23] QUININE IN RELAPSES 139 (2). Good results (only 30-37^ relapses) were obtained with the so-called systematic treatment. (3). Bad results (80-85// relapses) were obtained by the use of quinine late in the paroxysm. (4). The unfortunate (? unavoidable) suspension of the treatment after seven to ten days has invalidated most of the author's results regarding the length of the apyrexial period, since, obviously, the parasites would begin to multiply again from the moment that the quinine was stopped and would produce another attack when, a week or so later, they had multiplied sufficiently to do so. It is true that he says in his summary that " though the treat- ment is prolonged beyond the seven days the relapse occurs all the same ; but this was done apparently only in twenty cases altogether (so far as I can follow the intricacies of the paper), and, as every one in practice knows, to order a medicine is one thing, to get it taken is another. With regard to quartan fever there is nothing to add. With regard to malignant fever the author is very emphatic on the point that relapses occur between the fifth and twenty- first days of apyrexia, in spite of energetic quinine treatment ; for example, in the case of 90 work-people discharged from hospital after temporary cure, and 792 patients kept in hospital for thirty days, all the former and all except 24 of the latter relapsed. All that the author is able to admit is that the relapses occurred sooner in those discharged from hospital than in those retained there. Unfortunately, he is quite vague as to the continuity of the treatment. In one place he says that " this of course, occurred in patients who had continued the quinine treatment in doses of 1-2 grams per day," and in another place that this had been done "even after the cessation of the febrile attacks," but I do not clearly gather that the treatment had been sufficie^it and continuous through- I40 THE PARASITIC INVASION IN MAN [Sect. out. Obviously the whole investigation, meritorious as it was, has lost much of its value owing to the uncertainty intro- duced by the discontinuous methods of quinine administra- tion employed. Regarding relapses after " long intervals " the same element of doubt exists. I suppose that as long as a single sporid remains alive in the blood, the parasites may again reach the pyrogenous limit after a sufficient interval, if the drug is discontinued or continued in insufficient doses. A very careful enquiry is demanded before we can admit with the author that quinine has no effect on the occurrence of such relapses. Subsequently A. Carducci [1905] made a similar analysis of 50-60 cases at Rome. He infers that relapses at short intervals occur from the 6th-9th days of apyrexia, mostly on the 7th day, but that in quartan and tertian a relapse is often passed over. He recommends i gram of quinine on the ist, 2nd, 5th, 6th, 8th, 13th, 15th days of apyrexia, and 1$ gram on the 7th and 14th days in order to check this weekly return, and so on for months and months. With this medication he was able to prevent relapses in most of his cases, but remarks that they recurred if the quinine was discontinued. On the whole, after studying this and much other literature, I think that there is probably no special periodicity in relapses — that the periodicity noted by some observers was probably due rather to their own periodical methods of medication than to any other cause. If marked periodicity in relapses exists, it should have been widely observed long before now amongst the immense number of cases occurring in military practice — it would certainly have been observed by the military as well as by the medical officers. But I can find few notes to this effect, and certainly remember nothing of the kind in my own practice. As stated in section 20 (6) I am at present inclined to think that relapses occur after quite irregular intervals, determined by secondary causes or insufficient treatment, rather 23] QUININE IN RELAPSES 141 than by any inherent property of the parasites ; but that there may be some tendency to periodical failure of the germicidal powers (section 65). Regarding the reputed failure of quinine to prevent relapses, I again remain dissatisfied with the evidence. It appears to me to be merely a question of sufficiency and continuity of treatment. On the other hand, there appears to be a large mass of evidence in favour of Torti's law that quinine should be administered two or three hours before the commencement of the paroxysm, if this can be determined. Many authors — Laveran, Koch, Manson, Ziemann, Carducci and others — have suggested various systems of discontinuous dosage, such as the administration of large doses once a week, or twice a week, or every four days, or for two consecutive days every week, or every seven days after the first day of apyrexia, and so on. Owing to the temporary retention of the drug in the blood there is difficulty in understanding the rationale of such proposals. Moreover, a large dose every few days is much more distressing to the patient than a smaller dose every day, and, for this very reason, is apt to be neglected or postponed by him. There appear to be no evidence that the Plasmodia become habituated to quinine as trypanosomes do to atoxyl. Personally, therefore, I prefer the continuous method ; that is, a dose at least once a day. It seems to have given the best results in Caccini's cases, and is recommended by Celli. We should here distinguish carefully between what may be called medical and hygienic therapeutics. The former is the therapeutics of the physician at the bedside ; the latter, that which is to be recommended to the general public — who are, in fact, called upon to treat themselves. Refinements in medication which are possible in the former case are not possible in the latter one, and therefore the simplest possible rule is the one which is to be preferred for hygienic therapeutics (section 36). 142 THE PARASITIC INVASION IN MAN [Sect. Regarding the duration of treatment required to exterminate the parasites, we have no complete data. The case of T. Manson, who was infected in London in 1900 and was treated for three months, relapsed after nine months. In India the after-treat- ment of the European troops is continued for six weeks after discharge from hospital, resulting in a considerable reduction in the number of admissions. Thus out of ninety primary cases in two stations there were only seven relapses (" Annual Report of Sanitary Commissioner, 1907," p. 11). Teaching on this point differs largely, but I have always given four months as the Dmthnum period, and doubt whether even this is quite sufficient. No harm is done if the patient continues some quinine for six months. With regard to the different preparations of quinine, much more strict work by enumerative methods on the effect of the various salts on the parasites is required. Estimations of the amounts excreted in the urine and so on give but partial information on the germicidal action — which is the point of importance. The more soluble salts — bisulphate, bihydrochloride, hydro- bromide — are most easily absorbed, and appear most quickly in the urine. The less soluble salts — sulphate, citrate, tannate, euquinine — are absorbed much more slowly, but, finally, in just as much quantity. Exact enumerative experiments are therefore required to decide which of these groups of salts have the most germicidal action. Much has been said recently in favour of the tannate, e.g. by Nardelli [1909] and Deaderick [1909].^ It seems to be slowly but largely absorbed ; it remains in the blood ; it is inexpensive, nearly tasteless and very suitable for prophylactic use by children (section 36). Methylene Blue ■ was suggested for malaria by Guttmann 1 AndCeIli[i9io]. 24] SUMMARY 143 and Ehrlich [1891], and has been studied by Thayer [1892], De Blasi [1902], Wood [1905], Ruge [1906] and others. Atoxyl has been recently tried by Koch, Grosch [1907] and various Greek observers. The general conclusion is that it does reduce the sporids to some extent, but not so well as quinine. The investigations must be revised and extended. The methylene blue must be pure, and should be given in coated pills or capsules up to i gram or more a day ; the atoxyl may be given by injection up to o'2 grams twice a week. These and other drugs are not yet of importance for preventive purposes. 24. Summary. — The doctrine of the parasite invasion given above may be summarised as follows : — The infecting Anopheline probably injects at a single feeding from a few to several thousand protospores of one or more species of Plasmodium. Many of the injected protospores probably perish ; but the survivors enter haematids and begin to multiply at an average rate depending upon their species and, possibly, certain other factors. When the number of parasites reaches something like 50 per c.mm. of blood the patient begins for the first time to have definite symptoms of illness. About the same time some kind of germicidal power which opposes the invasion begins to come into play, and tends, in the great majority of cases, to limit the number of parasites below a fatal number. At the same time some increasing antitoxic power tends to reduce their effect upon the host. The further history of the invasion is probably that of a constant struggle between the parasites and the germicidal power, tending, in the great majority of the cases, to the final victory of the latter. In untreated or non-immune cases, this struggle generally 144 THE PARASITIC INVASION IN MAN [Sect. 24 produces a long series of relapses, which tend to be precipitated by many secondary influences acting on the host. Finally, after this series of rallies and relapses the patient appears often to reach a stage of partial (or ? complete) immunity. Possibly, if reinfection does not take place, something like half the cases tend to recover spontaneously every three months. The effect of reinfections upon the severity or duration of the case has not been estimated. The case may be cut short at any time by death, spontaneous recovery, or quinine. There is no reason why we should suppose that the infec- tion is maintained by encystment or parthenogenesis or other special arrangements of the parasites, and the existence of such phenomena has not been proved. This doctrine can scarcely be verified by the continuous study of entire cases, and is therefore based rather on the comparison of different periods in the history of many different cases, and on reasoning from numerous data.^ The careful student of the literature of the pathology of malaria will be struck by the immense amount of admirable work done on the subject. Ideas of number and quantity, however, are often completely disregarded — a common fault of biological work — with the result that many of the secondary theories and explanations will require to be examined over again by more laborious, enumerative and quantitative methods.- ^ I have held it, in the absence of a better doctrine, since 1895, and have always taught it in my lectures and publications. " See section 65. CHAPTER V MALARIA IN THE COMMUNITY 25. Is the Infection caused otherwise than by Anophelines.— Having considered the parasitic invasion of the individual, we must next examine that of the community. It was shown in sections i6 and 17 that infection is produced by the bite of certain mosquitos ; but after proof of this was obtained, several capable students of malaria expressed a doubt as to whether this is the only route of infection. We can scarcely wonder, then, if the general public sometimes have similar doubts, and the Health Officer must be always prepared to discuss the matter fully in public. The following questions are easily answered : — ( I ). Do mosquitos exist where there is no malaria ? — They do ; but this has no application to the subject, as only certain species carry malaria. (2). Does malarial fever occur where there are no mosquitos? — Very frequently, as on board ship in mid-ocean, on high mountains, or in Britain in the middle of winter; but such cases are always relapses. (3). Do Anophelines exist where there is no endemic malaria ? — In many places, as in Britain ; but the presence of infected persons, as well as of carriers, is required, and, moreover, both must be in sufficient numbers (section 28). (4). Does endemic malaria occur where there are no Ano- phelines? — No case of this has yet been established. So far as we know, Anophelines exist in all warm countries, and in most temperate climates during the summer. 145 K 146 MALARIA IN THE COMMUNITY [Sect. But the Anophelines are often difficult to find. Thus, I had been working on the mosquito theory of malaria for two years before I noticed this group of gnats. Duggan [1897] said that there were few mosquitos in Freetown, Sierra Leone, but we found numbers there two years later. In 1901 I observed none flying about in a new house at Ibadan, Lagos, West Africa ; but five or six, mostly Anophelines, were captured two nights in succession within an old mosquito - net with holes in it, in which a servant slept. If so many had been able to enter through the holes during the night, how many (though none were observed) must have been flying about free ? They abound in Britain, though the general public scarcely ever notices them. Before the presence of Anophelines in any locality can be denied, a trained observer must be employed to search for them. Many workers have made similar notes on this point. It does not follow, because the insects are scarce in a locality at the moment when we visit it, that they do not abound in it at some other season. (5). Is it possible to become infected in uninhabited localities ? — Some people, such as several sportsmen and travellers I have met, have stated that they acquired malaria in such places. One told me that he had frequently been attacked a few hours after entering a certain big-game district. We ask in reply {a) what about the incubation period ; {b) whether the traveller was unaccompanied by servants ; and (c) whether he had travelled in a balloon ? We must obviously pass through many inhabited places, where the risks of infection may be great, before reaching the wilderness ; we must have servants and carriers with us ; and we may indeed have had the parasites in our own blood, without knowing it. (6). If mosquitos become infected froin men and m.en from, mosquitos, how and when did the process first commence ? — This question is always asked by the most intelligent person present ; and I only wish that we knew the answer. It is concerned 25] INFECTION FROM THE SOIL 147 with the whole subject of the evokition of metaxenous parasites. Leukart supposes, of course, that they were once free Hving organisms, which acquired the habit of Hving first in one host and then, for greater security during the necessary period of migration, in another; and Grassi, and A. J. Chalmers [1902] have tried to fit this hypothesis to the case of malaria. But there are certain grave difficulties, and for the present it is sufficient to note that, we must be satisfied with the facts as we find them. (7). Has it been absolutely proved that malaria does not come from the soil? — It is always very difficult to prove a negative hypothesis of this kind. We never know what surprise Nature does not keep in store for us ; we are not omniscient, and wonderful things happen. But the fact that we cannot prove that malaria does not come from the soil is no proof of the hypothesis that it does do so. We are not sure that elephants do not exist in the moon ; but our ignorance here does not prove that they do exist there. Malaria may just possibly rise from the soil ; but there is no evidence at all that it does so. In my experience, those who argue in favour of this speculation nearly always confound relapses with original infections. True, we occasionally meet with cases which are not easy to explain on the mosquito theory, but I have never met one which could not possibly be explained by it. On the other hand, there are many strong, very strong, arguments against the idea that malaria is bred directly in the soil or in the marsh. In the first place, all experiments to infect men with air or water brought from malarious localities have failed (section 17). 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 148 MALARIA IN THE COMMUNITY [Sect. islands, 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 every one within a considerable area round the generating centre, but as a rule the disease is limited to the immediate vicinity of the marsh. Fourthly, the telluric miasm ought to attack especially those who are engaged in digging, but I have never obsened 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 mosquitos, 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, {>arasites 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 mosquitos. The general law is, therefore, satisfied by the known life-histor)- 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 p>owers 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 h\pothesis 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 mosquitos ; but we must now 25l OTHER CARRIERS 149 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 others) to abandon 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 mosquitos, are the marsh miasm. (8). Do other insects besides Anophelines carry malaria ? — 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 mosquitos. 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, ISO MALARIA IN THE COMMUNITY [Sect. 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 mosquitos in general being concerned, namely, that from the oldest times malaria has been known to be connected with marshes, while many mosquitos, such as most Culex and Stegojnyia, 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 most 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. (9). Do the human parasites live also in animals? — In 1898 in Calcutta, my servant, Mahomed Bux, became, suddenly infected with malaria, which he thought he had acquired while collecting mosquitos fed on infected birds. At present, how- ever, no one thinks that the parasites of men and of animals are the same. The attempts of Di Mattel and others to infect birds from men were all negative. ( I o). Do the parasites enter the eggs and larvae of mosquitos ? — In 1898 also, I thought that the protospores of P. danilevskyi might enter the eggs of the carrying mosquitos, but all my attempts to find them there were failures. More recently Schaudinn [1904] has sought to revive this hypothesis ; but he gave no proof of it. Such a thing happens, however, with Piroplasma in ticks, and has been suggested as possible in the case of yellow-fever. If it happens in malaria, the parasites would be passed on, not only from mosquito to man, but also 26] DEFINITIONS 151 from mosquito to mosquito. I have had no opportunities for examining the subject further, but may add that my studies on the point in 1898 were very careful. We should not accept the suggestion, even tentatively, without much better evidence. 26. Some Definitions. — We are therefore almost sure that infection with the parasites of malaria occurs in nature only through the bites of mosquitos — probably only of certain species of Anophelines. But this statement is not nearly sufficient for all the purposes of prevention, and we must discuss the subject in much greater detail. Why does the disease vary in amount from place to place, or even in the same place from season to season, or year to year ? Why does it disappear from some countries and appear in others? The whole subject of the prevention of malaria is based upon a rational study of these questions, and the reader who is called upon to undertake such work must exert himself to consider them thoroughly. We must first have clear ideas upon the following points : — (i). The cases of malarial fever which occur within a given locality belong, of course, to two classes, the indigenous cases and the imported cases. The first are those who were infected within the locality ; the latter, those who were infected outside it, but who, after immigration, remain infected within it. The latter class may be very numerous in military stations, hill stations, and sanatoria. But they also abound in many villages of which the inhabitants are given to working elsewhere during the malarious months ; and among bands of immigrant workmen. On the other hand, in small towns and villages with fixed populations most of the cases are apt to be indigenous ones. It is often difficult to determine the proportion of each class because many of the imported cases may be reinfected within the area 152 MALARIA IN THE COMMUNITY [Sect. of observation, while many of the indigenous cases may have emigrated since infection. (2). By the malaria rate of a locaHty I mean the percentage of persons who contain plasmodia at some given moment. We may divide this into the indigenous malaria rate and the imported malaria rate. The former may also be called the malarial endemicity of the place. (3). By the malaria index, or endemic index, of a locaHty I mean the percentage of persons in whom any evidence of malarial infection was found at some given moment. It will be clear from Chapter IV that such evidence cannot generally be found in all the cases of malaria in a locality — many may contain plasmodia without showing them or any objective symptoms of them. Conversely, many people may show evidence of past infection, such as enlarged spleen, without containing plasmodia at the moment. We may divide the endemic (or malaria) index into the adult, the juvenile and the infantile endemic index} (4). By the daily, monthly or annual inoculation rate of a locality I mean the percentage of persons who were inoculated or reinoculated by mosquitos during the day, month or year referred to. (5). When we talk of the amount of malarial fever in a locality we generally refer to the total malaria rate in it. When we talk of the amount of malaria in it we generally mean its indigenous malaria rate. When we say that a place or a season is very malarious, we mean that the inoculation rate is very high for that place or season. 1 The term " endemic index " was first used by Stephens and Christophers to denote the percentage of children showing the parasites in the blood, but the above definition is more correct. 27] CONDITIONS OF INFECTION 153 (6). By the malarial case mortality we mean, of course, the proportion of infected persons who die of the disease. (7). By the malarial mortality we mean the proportion of the total population who die of the disease. (8). I use the word ratio to denote a proportion, and the word rate to denote a percentage. The latter is obtained by multiplying the former by one hundred. 27. Conditions required for the Production of New Infections in a Locality. — From what has been written already it will appear that new infections can occur in a locality only if all the following conditions exist : — (i). That a person whose blood contains a sufiflcient number of gametids (sexual forms) is living in or near the locality. (2). That an Anopheline capable of carrying the parasites sucks enough of that person's blood. (3). That this Anopheline lives for a week or more after- wards under suitable conditions — long enough to allow the parasites to mature in it. (4). That it next succeeds in biting another person who is not immune against the disease or is not protected by quinine. To these we must now add the following principle : — (5). That few or no new infections will occur in a com- munity unless the persons with gametids in their blood and the carrying Anophelines are sufficiently numerous. This last proposition is the basis of the public prevention of malaria. Although tacitly admitted, it is never properly discussed in the monographs, and the reader must therefore examine it here in detail and as precisely as possible. Let us suppose that we have to do with a population of 1,000 people living over an area in which indigenous malaria does not exist ; and suppose that one of these people is an 154 MALARIA IN THE COMMUNITY [Sect. imported case with suitable gametids in his blood. Next, suppose that a single suitable Anopheline is liberated within the area. What are the chances that this insect will ever cause a new infection ? First, we observe that not every mosquito can succeed in biting human beings at all : suppose that the chances are 4 to I against this happening. Next, we observe that as there is only one infected person among the i,ooo people in the place, and as the particular Anopheline liberated in the area may bite any one of these people, the chances are i,ooo to i against its happening to bite the patient, even if it succeeds in biting at all. That is, altogether, the chances against its biting the patient are 4,000 to i. But suppose that this has happened. It must now live for a week or more afterwards, and not all mosquitos live so long. Suppose that the chances are 3 to i against this particular Anopheline living long enough to mature the parasites in it — so that the chances are 12,000 to i against the Anopheline reaching the infective stage. But it must now bite a second person. Suppose that the chances against this are, again, 4 to i. Thus the total chances against this Anopheline inoculating another person will be something like 48,000 to I. In other words, if instead of liberating a single Anopheline within the area of observation we had liberated 48,000, the chances are that only one of these would succeed in biting the patient, and would also live long enough to become infective and to bite a second person. Of course, by bad luck, so to speak, a larger proportion of the insects might succeed in this ; but, on the other hand, by good luck, none at all might succeed. Such calculations, though obviously based on con- jectural data, yet suffice to show the absurdity of supposing that the presence of a few Anophelines must cause an epidemic of malaria. Or we may consider the subject as follows : — Suppose that 48 Anophelines on the average live near the infected person. Then, if the conjectural data are sound, 1/4 of these, or 12, 27] CONDITIONS OF INFECTION 155 will succeed in biting him ; 1/3 of these, or 4, will live for a week or more ; and only 1/4 of these, or i, will succeed in biting another person. If 48 Anophelines live near each one of the 999 healthy people, there will be 47,952 Anophelines" which can bite only healthy people, and which cannot therefore cause new infections. Thus, on the average, only i out of 48,000 Anophelines will succeed in infecting another individual. If instead of only one person with gametids in the blood there are 2, 3, 4 ... or more in the locality, then if there are 48 Anophelines on the average to each person, 2, 3, 4 ... or more new infections may be caused. Thus, obviously, the number of new infections in a locality, that is, the inoculation rate, depends on two factors (other things being equal), namely, the number of Anophelines and the number of previously infected persons in the locality. It is useful to put these thoughts into simple symbolic language. Let/ denote the human population of the locality ; nip the number of malaria - infected persons ; and imp the number of these with gametids in the blood. Here vi and / are fractions, since 7np is less than /, and imp less than mp. Also m may vary from o to i, since the number of infected persons may be anything from zero to the whole population. The fraction i, being the proportion of infected persons with gametids in their blood at the moment of enquiry, may be put at 1/4, or may be much less. Again, let a denote the number of Anophelines (of some malaria - bearing species) to each human being — so that ap denotes the total number of Anophelines in the locality, and aimp the number of Anophelines compared with the number of persons with gametids. Let b be the proportion of these (say 1/4) which succeed in biting ; s the proportion (say 1/3) which succeed in maturing the parasites ; and b the proportion which succeed in biting another person. Then bsbaimp gives the number of Anophelines which succeed in infecting persons. 156 MALARIA IN THE COMMUNITY [Sect. We have assumed that b^ij^, •$'=i/3. 2= 1/4; so that if each of these bites a different person, we shall have — No. of \noc\x\2A.\ons = b'^saiinp = amp I ig2 Inoculation rate % = — ^- • — = about h am. '° 192 p That is to say, the inoculation rate per icx) of population equals about half the malaria ratio (w) multiplied by the mosquito ratio {a). For example, in a village containing 1,250 people, 750 infected people, and 3,000 Anophelines,/'= 1,250, m = o-b, rt = 2"4; and we calculate roughly that the number of infecting Anophe- lines, and also of inoculations, will be about 9*4. The inoculation rate per cent, will be about 1/2 (2*4XO"6) = o72 ; that is, the chances of being inoculated in the village will be as 72 is to 10,000. Or suppose that in another village half the people are in- fected, and there are about twenty Anophelines to each person. Then the chances of becoming infected there will be about 5/100. Such calculations may appear far - fetched to many ; but they 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. 28. Laws which Regfulate the Amount of Malaria in a Locality. — The number of infecting mosquitos which succeed in biting again is b^saiinp. If all of these bite different people, and all these people are healthy, and all become infected, this expression will also denote the number oinew infections occurring in the locality. But, of course, the infecting mosquitos may often happen to bite on the second occasion, not healthy persons, but persons already infected, especially if the pro- portion of the latter is large. If, as before, mp denotes the number of persons already infected at the beginning of the enquiry, then/ — ?;// or (i —m)p denotes the number of healthy people. Hence by proportion 28] LAWS OF DIFFUSION 157 the number of infecting mosquitos which bite healthy persons (on the second biting) will be x, where X : U^saimp :: {i—m)p : p or X = b'^sai {i — m) mp . . . . (i) and if each bites a different person and each person becomes infected, the same expression will denote the number of new infections which occur in the locality — that is, will denote the addition to the number of malaria cases there. But this is not the whole change which may occur. While, during the period of observation, new infections are being pro- duced, it may happen that some of the old cases may have recovered. The number of those old cases was originally mp : let rmp denote the number of those who have recovered during the period of observation — so that r is a fraction. Hence the whole number of cases in the locality will have increased or decreased at the end of the period of observation, according to whether b'^sai (i — ;;/) mp, the number of new cases, is greater or less than rmp, the number of recoveries. Thus (neglecting common factors) the change depends upon whether b-sai {\ —in) is greater or less than r. Suppose that no change occurs — that the recoveries exactly equal the new infections. Then b'^saz {i—in) = r .... (2) From this equation we can calculate the values of a and m when the amount of malaria in the locality remains constant — that is, if we know the values of b, s, z, and r. Suppose that the period of observation is one month. Now, in section 21, I estimated roughly that only about half the cases of malaria remain infected after three months. If this rate holds for smaller periods, we may suppose that the ratio of people who remain infected after only one month will be given by the cube root of 1/2 — that is, by 07937 ; so that the pro- portion of those who recover in one month will be 1—07937. That is, we may write r = 0*2062. Let us take the values of b, s, t as suggested in the previous section — so that b-si= 1/192. 158 MALARIA IN THE COMMUNITY [Sect. Hence the new infections will equal the recoveries if a{i- m) = 192 X 0-2062 = 39-59 = 40 {say) ... (3) and the malaria will increase or diminish in the locality accord- ing to whether a{\ —in) is greater or less than 40. Thus, if in, the original malaria rate, is very small, the malaria will not increase unless a, the monthly number of Anophelines per head of human population, is greater than 40. On the other hand, if ;;; is a larger fraction, say 1/2, the malaria will not increase unless a is greater than 80. If in is still larger, say 3/4, the malaria will not increase unless a is greater than 160. This suggests that the malaria rate is not likely to increase indefinitely unless the number of mosquitos is enormous. On the other hand, if the number of Anophelines is below the figure given by the equation, the malaria rate ought to begin to fall, because the new infections can no longer keep pace with the recoveries. It should be noted that by the number of Anophelines we here mean the number of different Anophelines which may bite each person during a whole month, and not the insects which may be, so to speak, allotted to each person at any one moment. We say one month because this is the period we have selected for observation — the period during which we suppose that 0*2 or I /5th of the cases recover. If we had selected one week for the period of observation, the proportion of recoveries would, of course, be lower (about 0*056 142), and the number of different Anophelines to each person, required to compensate for the recoveries during the week, would be correspondingly less (as shown by the equation). Now, what will happen if the malaria rate, instead of remaining constant, increases or decreases ? On the one hand, will it increase until every one becomes infected ; or, on the other hand, will it decrease until it vanishes? We have supposed that inp denotes the number of cases at the beginning of the enquiry, which lasts, let us say, for a month. Let ni^, tn^ip, w^p , . . denote the number of cases 28] LAWS OF DIFFUSION 159 at the end of i, 2, 3 . . . months respectively. Then if the other figures remain constant, we have, m^p = original cases -\- new infections — recoveries = vip + b'^sai ( I — w) mp — rmp . . . . . (4) and as the same process repeats itself month after month we continue to have, m^p = Wj/ + d'^sai ( i — m■^) m^p — rni^p m^p = m^J) + b'^sai ( i — vi^ w^p — rm^J) and so on. We can calculate m^ from the first equation. Substituting its value in the second equation we calculate m^ ; and substituting this in the third equation we calculate m.^ ; and so on indefinitely. If r=o'2 and b^si='00% the value of the 7ith term of the series m^p, m^ . . . m„..,p, m„p may be written in „p = {160 -\- a — am „..,) m„..,px o-oo^ • • • (S) Let us now consider for examples the case of a village containing 1,000 people of whom half are infected at the beginning of the enquiry. By equation (3) of this section, and also by this equation, if the number of different Anophelines per person during one month {a) is 80, the malaria will neither increase nor decrease, so that w„ will always be the same as w, namely, 0*5. But if a is greater or less than this, the malaria will increase or decrease accordingly. (i). First, suppose that there are 100 different Anophelines per person during a month — so that the malaria should increase. Thus we calculate, m^p = {i6o+ 100— iooxo"5)x 5x0*5 = 525 W2^ = (i6o+ 100— iooxo'525)x5xo-525 = 544'5. Proceeding in this way we find that the number of cases should increase every month as follows : — Increase of Cases with 100 Anophelines Months I 2 3 4 . finally Cases 500 525 544 560 571 600 i6o MALARIA IN THE COMMUNITY [Sect. But how do we reach the last figure ? As we calculate the number of cases month after month we observe that they always increase, but by a constantly decreasing increment. Finally, this increment becomes very small, so that the number of cases approaches a fixed limit. It is easy to calculate this limit mathematically (as will be done presently), but we can also calculate it very simply as follows. If the number of cases does ever arrive at a fixed limit, so that it no longer increases, then equation (3) of this section must hold ; that is, the number of cases and the number of mosquitos will be exactly balanced according to the formula a (i— ;//) = 40. From this we have, when this exact balance is reached, m=\— Afi\a (6) Here = oi'iginal cases + new infections — recoveries {or deaths), and from this we shall still be able to argue that a limit must be reached when the new infections exactly balance the recoveries. We may therefore conclude, (i) That the amount of malaria in a locality tends towards a fixed limit determined by the number of malaria- bearing mosquitos and by other factors. (2) That if the number of malaria-bearing Anophelines is below a certain figure, that limit will be zero. It is often thought and said that malaria should exist wherever susceptible Anophelines exist, and that anti-mosquito measures will therefore be useless so long as any of these insects remain. But more careful reasoning will convince us that malaria cannot persist in a community unless the Anophelines are so numerous that the number of new infections compensates for the number of recoveries.^ 29. Laws which Regfulate the Number of Anophelines in a Locality. — We have seen, then, that the amount of malaria in a locality depends (among other factors) upon the number of suitable Anophelines, and upon the proportion of them which succeed in biting human beings, in living long enough to mature the parasites, and in biting human beings again. ^ See section 65 (10). 29] OUTPUT OF MOSQUITOS 165 We must now study these points in greater detail. Unfor- tunately, although much entomological work has recently been done on mosquitos, such important subjects as these have received little attention. (i). The otitpiit of mosquitos from marshes. — I know of no adequate studies on this point. In 1908, in Mauritius, I stretched a mosquito-net over 9 square yards (7"5249 square metres), and counted every day the mosquitos hatched within it. The selected spot (Clairfond Marsh) was covered with rank grass, the roots of which were submerged by an inch or two (2"5-5 cm.) of water. It was sheltered by trees, and was an ideal spot for the breeding of Myzorhynchus mauritianus Daruty and D'Emmerez, 1900 (an Anopheline which does not carry malaria). The observations were continued for sixteen days in January (the warm rainy season), and only this kind of mosquito was found. Altogether thirty males and thirty-one females were obtained,^ giving an average of 0*423 per square yard per diem, or 5,062 per 10,000 square metres. Numbers continued to hatch out on the sixteenth day. During the daytime the adults took refuge in the grass, from which it was necessary to expel them. Clairfond Marsh is about 1,400 feet (427 metres) above sea - level (section 30 (21) ). This output (about 5,000 mosquitos per diem for 100 yards square of marsh) seems to have been rather large, as when the net was placed in another position the yield was much smaller. Taking twenty days as the average life of an Anopheline (conjecture), 100,000 of them should thus be in existence on any one day in the neighbourhood of such a marsh of about 100 yards or metres square. Of course the output is sure to vary from point to point of a marsh, according to the breeding capacity of different depths of water, etc. ; and it will also vary from ^ Nuttall and Shipley found equal numbers of males and females with A. maculipennis also [January 1902]. i66 MALARIA IN THE COMMUNITY [Sect. day to day according to the amount of rain, wind and sunshine. Correct and sufficient observations on these points are much needed. They could be made by the use of small square tents of muslin netting, supported by a central pole, and pegged out with weighted margins over a unit of area (say 1 square yard). We might thus ascertain not only the mosquito output but the length of the aquatic life of mosquitos under natural conditions, and other facts. Of course a number of such tents must be used to avoid much error of random sampling. (2). The average life of the winged insects. — It used to be thought that mosquitos feed on one occasion, lay their eggs a few days later, and then die. But in 1898, observing that this short period did not suffice to allow the malaria parasites to develop fully in Culex fatigans, I ascertained that these insects could be kept alive in captivity for a month, and possibly much more, by repeated feedings [21st May 1898] ; and I obtained the same results with certain Stegomyiae and AnopJielines. Since then, similar observations have been made on many mosquitos. Thus Goeldi [1905] kept . a female Stegomyia calopus alive for 102 days, and a male one for 72 days. The average life in captivity of 15 females was 53 days, and of 1 1 males was 50 days. My general experi- ence has been that it is easy to keep various species of Anophelines alive in captivity for two or three weeks, but not so easy to keep them longer. Nuttall and Shipley [1902] kept A. niaculipennis for 56 days, and found that the females tend to live longer as winter approaches, possibly in connec- tion with hibernation (Woldert). It has long been known that many mosquitos hibernate and aestivate. Females appear to live in captivity longer than males. Better experiments with large mosquito-houses, fixed in the open air under natural conditions, should be made. But such observations do not settle the important question. NET FOR MEASURING THE OUTPUT OF MOSQUITOS FROM A MARSH— CLAIRFOND, MAURITIUS. BANKS OF A STREAM ROUGH-TRAINED FOR RS.O-37 A RUNNING FOOT FOR BOTH BANKS (MAURITIUS). {^To face page i66. 29] AVERAGE LIFE OF MOSQUITOS 167 what is the average \\{g of mosquitos in nature? In captivity they doubtless suffer from confinement, but, on the other hand, are preserved from their natural enemies and from heat, wind and weather, which probably destroy immense numbers of them. We should like to know what percentages survive for one, two, three . . . weeks. Numerous experiments on the point could be performed, but have been neglected. In the meantime, I have always taught the following hypothesis. The average natural life of an animal is likely to exceed that of any parasitic organisms which it may contain. The latter have been instructed, so to speak, by the evolution of centuries, as to the length of time they should spend over their development, so as to have the best chance of being propagated to other hosts. Thus Filaria bancrofti requires about three weeks to develop in Culex. Now, if the average life of Culex were less than three weeks, the filariae would have a much smaller chance of pro- pagation. Doubtless, therefore, the average life of Culex exceeds three weeks or a month. Similarly, plasmodia require about ten days to develop in Anophelines, and I therefore suppose that the average life of these insects reaches about three weeks or more. But this reasoning suggests only the lower limit of average life. Evidently a longer average life would improve the chances of propagation of the parasites. The mosquito death-rate must, of course, vary largely in consequence of many factors, such as season, enemies, local conditions of shelter, etc. On the whole, I think that we shall not be far wrong if we accept our previous estimate that only about one-third of the carrying Anophelines live for ten days — long enough to allow the Plasmodia to mature in them. (3). The proportion of mosquitos which succeed in biting human beings. — With most species only the females, that is, let us say, half the number, suck blood at all. When a number of females are liberated all night within a mosquito-net occupied by a man or by birds, only a variable proportion are found next morning to be fed. Numerous observations have been made, i68 MALARIA IN THE COMMUNITY [SECT. by myself, among others, which show that the insects are not very hungry for about twenty-four hours after hatching out from the pupa, or immediately after laying their eggs. With species which attack animals (birds, cattle, dogs, etc.), the chances are that the proportion of insects which succeed in biting men varies with the proportion which exists between the number of men and of these animals in the locality. Men must be more difficult to reach than defenceless animals (or children). The richer classes often use mosquito - nets ; and poor natives, especially Indians, generally cover themselves from head to foot with a sheet during sleep, besides filling their huts with smoke at night time, and keeping their doors and windows shut (the common habit, even in hot climates). Access to people in upper storeys, with small open windows, must often be difficult to these feeble insects, especially while any breeze is blowing. I have suggested that possibly a quarter of the Anophelines may succeed in biting human beings once, a third may live for ten days more, and a quarter may succeed in biting again — that is, that only about 1/24 of the females can ever have any chance of carrying malaria. But this applies only to. the pro- portion of mosquitos to each person in the place, and supposes, moreover, that the human beings are evenly distributed in the locality, and are fairly accessible. In thinly-inhabited places the ratio will probably be much smaller, and in crowded ones, larger. I think that many insects which have failed in pro- curing a meal during the night may die of starvation (in my experiments on birds a number of dead mosquitos were generally found in the nets every morning). Numbers of gorged mosquitos are probably devoured by bats, birds and spiders, or are killed by sufferers. On the whole, then, an average ratio of 1/24 is perhaps too high. Many observers have studied the proportion of naturally-fed Anophelines which contain plasmodia. In 1899 I found the parasites in 27 out of 109 P. costalis caught in a military 29] MOSQUITO DENSITY 169 hospital in Freetown, Sierra Leone, in which one quarter of the men examined contained them [1900]. Stephens and Christophers found them in 6/70 of Anophelines in the same town [5th April (?) 1900]; in 5-10% in Africa "as a rule"; and in some villages up to 50% [1903]. Ziemann, A. Plehn, the Sergents, and many others have found similar rates. Unfortunately, such observations do not help us much, because the mosquitos caught in houses may possibly be only or mostly those which have already obtained human food, and are waiting for more. In the huts of poor natives, and in badly-managed barracks and hospitals where many unprotected people sleep in the same room, a single mosquito may often be able to bite several persons during the one night. In such houses the chances of infection must be enormously increased, and the practice of congregate sleeping must be one of the principal causes of the diffusion of malaria. (4). The number of Anophelines in unit of area. — Nothing approaching accurate scientific work has been done on this subject. There are many references in literature to " few mosquitos," to " many mosquitos," to " swarms of mosquitos," to "des centaines de milliers de millions," and so on. Theobald [1901, I. 72] describes having twice seen clouds of male and female C. cantans in the English Fens, darkening the air, and producing a sound which could at times be heard a quarter of a mile distant. He says that W. W. Smith records that a train in New Zealand " passed through a wall of mosquitos three-quarters of a mile in length, twenty feet high, and eighteen inches thick " ; and he mentions dense masses of gnats " like columns of smoke." If there were ten mosquitos to the cubic foot in this "wall," there would have been only 1,188,000 insects in the whole collection — not a large number considering the possible output (i). Such phenomena merely suggest that occasional " swarming " occurs with mosquitos as with other animals (including man). I70 MALARIA IN THE COMMUNITY [SECT. Anophelines hi houses have been frequently caught and counted, especially by Stephens and Christophers and recent observers in India. The numbers may vary from zero to many hundreds in a single room, especially in thatched huts. They may also vary from house to house, and according to distance from breeding waters. It is impossible to quote any correct averages. I have thought, as a general conjecture, that one Anopheline for each human occupant might be adopted as a kind of standard for comparison ; but, of course, near marshes the numbers often rise to 50,100, or more in each room, or even to each person. We cannot estimate the number of any species in unit of area by the number caught in houses in that area, unless we know the proportions of that species found inside and outside houses respectively, at the hour of the day when the search is made. As we can never know this proportion exactly, the number of insects caught inside houses is no exact guide to the total number existing within the area of observation. Different species appear to differ largely as to the amount of time they spend in human habitations. I define do^nestic mosquitos as those which pass a large part of their lives in houses, such as C. fatigans, S. calopus, M. rossii ; though even with these species we do not know exactly how many hours they spend indoors and out-of-doors respectively. I define sub-domestic mosquitos as those which enter houses only for the purpose of feeding, and wild mosquitos as those which never enter houses at all.^ Some species, such as M. mauritianus, are found in verandas of houses, but not commonly in rooms. The average output, average length of life, and average number per unit of area of any species of mosquitos are correlated quantities which can be ascertained only by the most careful measurements, such as have never yet been attempted (so far as I can ascertain). 1 Arribalzaga and Ficalbi give similar classifications. The latter's is based on the habits of the larvae. 29] MOSQUITO DENSITY 171 In the previous section I computed roughly that malaria is not likely to persist in a locality where the pathophoric Anophelines number less than about forty different individuals to each person during a month. It would be very difficult to ascertain anywhere how many different mosquitos there are to each person, but the attempt should be made. Mere personal impressions on the point are apt to be very wrong. The victim, surrounded by many assailants, tends to magnify their number from one to ten, and from ten to a hundred. The use of a white muslin hand net, with which his enemies can easily be caught, will disclose the truth. I am inclined to adopt the following standard. The mosquitos in a room or veranda are nu^nerous if a single person is attacked by more than five at a time, and very numerous if he is attacked by more than ten. There are few houses in the tropics where one is not solicited day and night by two or three mosquitos. If we count the number of Anophelines found in a set of houses every day for a number of days, we could obtain the average number to be found indoors for each person living in the locality. But we cannot say that all these are different mosquitos. We may, however, attempt a very rough com- putation as follows : — Suppose that on the average there are 10 Anophelines to each person every day. Then, if all the insects are changed every day — that is, if each insect lives only 24 hours on the average — there should be about 10x30 = 300 different insects to each person during a month of 30 days. If, however, the insects live for 15 days on the average — that is, are changed twice a month — there should be about 10x30/15 = 20 different insects to each person during the month. If the insects live 30 days, there should be only 10 different ones to each person. Thus if n is the average number of mosquitos found per diem per person, a is the number of different mosquitos per person during a month of 30 days, and / is the average life of the mosquitos in days, 172 MALARIA IN THE COMMUNITY [Sect. we should then have roughly a = jiXTplL If ^ = 27 and /= 20, then a = ^o, the number roughly computed as the malaria- maintaining limit. To sum up — if we think over these points carefully (and this has not always been done), we shall be convinced of the great difficulty of forming any accurate notion of the mosquito- density of any species anywhere. The enquiry would demand a laborious study of the output, which must vary from week to week ; of the average life, which must also vary ; and of the average numbers found in houses and in mosquito traps (section 12). It would require the services of a number of trained " moustiquiers," and the error would amount to say 10% or more, even with the most careful observations. (5). Variation of mosquito-density from place to place. — It would be very interesting to determine the rate at which the mosquito - density falls at different distances from a single breeding-place. Stephens and Christophers [5th April (.?) 1900] showed that in Freetown, Sierra Leone, the insects were abundant in houses near certain breeding-waters, but diminished markedly at greater distances. An exact enquiry would be very difficult. We could estimate the numbers caught in houses and traps at various distances from a single pool in an otherwise sterile area. Here one source of error, the relative domesticity of the species investigated, would cancel out from the ratios ; and ceteris paribus the propor- tions caught should indicate the proportions present. But other sources of error, facilities for obtaining food and shelter in different houses, might disturb the results. An empty farm close to a marsh might, for instance, attract many fewer insects than a small, crowded village half a mile away. Never- theless, we know that as a broad general rule, mosquitos tend to diminish with distance from their breeding-place ; but the exact curve of diminution has not been ascertained. (6). Variation of mosquito-density from time to time. — Here, too, we could count the number of mosquitos in houses and 29] OUTPUT PER BREEDING-SURFACE 173 traps for a series of days, and the factor of relative domesticity would be eliminated from the ratios. The total variation obviously depends upon two factors, that of output and that of longevity. If both the birth-rate and the death-rate are increased or diminished, the total density might remain the same, a fact which seems sometimes to have been forgotten. (7). Variation of mosquito-density due to food, etc. — Abundance of food certainly has a great effect on domestic Culicines, which tend to swarm in crowded and poor habitations. Pro- bably it has a similar effect on sub-domestic Anophelines, though these may not be so much in evidence. I mean that abundance of food probably tends to increase the output, although the total breeding surface remains the same. This would be due to the fact that the females find food more easily and consequently lay more eggs. Thus malaria may perhaps increase in a locality, not because of the increase of breeding-places or rainfall, or because of the introduction of more imported cases, but simply because an increase of the human population has provided more food for the Anophelines (section 30 (9), (12), and (21) ). (8). Relation of mosquito-output to extent of breeding-surface. — This is a point of great importance as regards prevention. If we reduce the extent of breeding-surface to a given pro- portion, what will be the exact effect on the number of mosquitos ? {a) The number of larvae in a collection of water will depend (i) on the number of eggs laid in it, and (2) on the suitability of the water — temperature, shelter, absence of enemies, food. {b') Probably that number cannot exceed a certain limit ; that is to say, there must be a maximum possible output per unit of breeding-surface at any season. if) Probably also the actual output is often less than the maximum possible output, the deficiency being due to absence of enough food for the females, 174 MALARIA IN THE COMMUNITY [Sect. destruction of the adults, inaccessibility of the water, etc. {d) The maximum possible output per unit of breeding- surface is likely to vary with season, and to be much greater during the warm season when the food of the larvae is probably more abundant, and their development quicker. From these data we infer as follows : — {e) Suppose that the breeding-surface of a locality is yielding the maximum output, and is then suddenly reduced in extent, say to half or a quarter the previous area. Then a proportional fall must occur in the total output of mosquitos in the locality. (/") Next, suppose that the breeding-surface was yielding only a fraction of the maximum possible output when the extent of it was reduced. Then the fall in the total output of mosquitos may not be so great. The females, which formerly laid their eggs in the part of the area which has been drained, may now resort to the pools which are still allowed to remain, and may increase the output of these by stocking them with an additional number of eggs. Thus, though the total breeding-area is reduced, the part of it which remains may have a larger output ; so that the total output in the locality may remain the same as before. {g) But this compensation has its limits. If the reduc- tion of breeding-area has been great, the pools that remain may often be inaccessible to the females, or may become overstocked with eggs and larvae, for which they cannot provide enough food. At best, the total output cannot exceed the maximum possible output of the waters which remain. {h) If the drainage operations have been commenced early in the season, before the breeding - season is fully 29] OUTPUT PER BREEDING-SURFACE 175 developed, and if they have not been complete, then, as the breeding-season advances, the waters which remain will still continue to have an increasing output ; so that the total output of mosquitos in the locality may continue to increase in spite of the partial drainage operations, I say that, if any breeding - waters at all are left, the output will increase from month to month as the breeding-season advances to its maximum ; but this does not mean that the total output after the drainage operations is not less than the total output in the previous season before the operations. The thoughtless observer, seeing an increase of mosquitos due to the seasonal increase of output in the waters left undrained, may jump to the conclusion that the drainage has had no effect. But a comparison of the total output before and after the drainage would probably correct this error. The two issues have frequently been confounded — as, I think, at Mian Mir. Of course, if any breeding - waters at all remain, a certain number of mosquitos will continue to be poured out, especially at the height of the breeding - season ; but it is scarcely likely, ceteris paribus, that a small breeding-surface can have as great an output as a large one, and it certainly cannot have more. We conclude then as follows : — (i). That cete7'is paribus the output must tend to vary with extent of breeding-surface. (2). But that the two curves will not always exactly coincide. For example, if the breeding-surface is reduced to a half, then the output of mosquitos will also be probably reduced very considerably ; but it may not be reduced exactly in the same proportion. If the breeding- waters are entirely removed, then, of course, the output in the locality must entirely cease. 176 MALARIA IN THE COMMUNITY [Sect. (9). Flock-migrations of viosquitos. — We have hitherto con- sidered the mosquito population of locaHties as if it consisted solely of insects born in the locality. But, obviously, many of the insects found in any area must have entered from without ; and we must now examine the subject of mosquito-migration. By flock-migration I mean the simultaneous movement of large numbers of animals of the same species in the same direction — such as we are familiar with in the case of wild cattle, swallows, locusts, etc. Does anything of the kind occur with mosquitos? Howard [1901] quotes a letter in which flock- migrations of immense numbers of mosquitos are reported to have been twice witnessed by the same observer in America, It was supposed that the insects had originated in a large marsh 35 miles distant ; and they were numerous enough to cloud the sky, and bend down the grass with their weight, Nuttall and Shipley conjecture [January 1902] that the phenomenon may be due to " overstocking of a given locality by a species." If it has occurred once, it ought to occur frequently enough to be recorded more often. There is always the danger that a large local hatch-out may be responsible for the occurrence. (10). Visitation of ships. — Mosquitos frequently visit ships half a mile or more from the shore. We must not infer that they have purposely travelled so far in search of food. Winged animals which have once started on a flight across water seldom have the sense to return. At Highcliffe, England, I once watched numbers of butterflies {P. brassiccB) flying out to sea from the shore on a still morning — none were coming back. Birds and insects, lost in this manner and wearied with flight, naturally board passing ships for rest. Sometimes, however, a ship anchored close to shore may be attacked by mosquitos which have perhaps scented their prey from a distance. On the other hand, I have often been on board such ships without noticing many mosquitos. Once I spent a night in a small open boat, rowed down a river in Burma, but observed at the 29] TRANSPORTATION OF MOSQUITOS 177 time that not a single mosquito attacked us, though the night was still and warm. (li). Transportation by ships and vehicles. — I have known Ctilex and Stegoniyia to breed in water-jugs and flower vases on board ship, and they frequently breed in bilge-water and wooden water barrels. But as soon as the ship starts on her voyage most of the insects seem to be blown out of the cabins. Nuttall [1899] says that Roe once observed a dozen foreign species of mosquitos on board a ship lying at quarantine in New York. This was probably a sailing ship, as the vibration of steamers seems to prevent the insects coming to rest. Balfour notices that Anophelines are brought into Khartoum in boats. Every one who has lived in the tropics has observed that mosquitos occur in carriages and railway trains. During the heat of the day the insects seem unwilling to leave the vehicle, though it is in motion, and may thus be transported consider- able distances. But vehicles which introduce mosquitos may also remove them, and it is absurd to suppose that the small numbers carried in this way can often influence the malaria rate. (12). Transportation by rivers and winds. — Nuttall, Cobbett and Strangeways-Pigg [1901] suggested that rivers may trans- port eggs, larvae and pupae, but I think that most of the latter would be devoured before they have travelled very far. Many people imagine that mosquitos are carried by winds. Householders who breed them in their own premises like to ascribe their presence to marshes some miles away. The authors just quoted state [1901, p. 8] that Fernald described how mosquitos at Cold Spring Harbour, Long Island, New York, were blown there from a distance of 15 miles by the south wind ; but Nuttall and Shipley [1902, p. 61] quote Weeks as correcting this by showing the existence of many breeding- places at Cold Spring Harbour itself. When I arrived at Freetown, Sierra Leone, in 1899, every one thought that the local mosquitos came from marshes a mile or more distant : they were really being bred in every house in the town. I M 178 MALARIA IN THE COMMUNITY [Sect. could mention many more experiences of the same kind. Statements regarding wind - transportation must be received with great reserve, because here, also, a local hatch-out may be responsible for the facts stated. In Mauritius in 1908 I placed pickets of trained " mousti- quiers " at different distances from Clairfond Marsh with instructions to catch all the Anophelines which attacked them. The men sat out late at night and brought us their captures in the morning. Their conclusions were that the insects scarcely move about at all when there is much wind. On still, warm nights, however, especially after rain, the pickets caught both P. costalis and M. mauritianus half a mile from the marsh. These facts are opposed to those who believe in frequent wind- transportation, but accord with the views of Howard and others, and myself, Occasionally, of course, a few insects may be swept away by wind, but in most cases wind merely drives them into shelter. In fact, whenever there was any wind our "moustiquiers" caught adults only in sheltered spots behind houses, hedges or woods. I fancy that gnats, like other animals, dislike being swept away from their own haunts into unknown regions., I have always used the following good argument against the notion that wind transports mosquitos to any great extent. If this were so, sea-shores constantly swept by sea-breezes ought to be nearly free of them ; but I can certainly bear witness to the fact that this was not the case in Madras and Port Said, when I was in those towns in 1881-1884 and 1902. A strong sea-breeze blowing through a house with all the windows and doors open will not, in my experience, drive out the Culicines, nor even reduce their numbers. (13). Velocity and length of flights. — I am not aware of any experiments on these points, but I have frequently observed Stegomyiae flying against breezes which I judged to be blowing at over five miles an hour. They can easily follow a man walking, and perhaps a trotting horse, I suppose that they 29] FLIGHT OF MOSQUITOS 179 fly at the rate of about eight miles an hour, roughly computed. At this rate an insect might easily cover ten or twenty miles a day, and if it were akvays to fly in the same direction from its breeding-place^ might traverse a hundred miles or more during its life. Many absurd statements, such that mosquitos can fly only half a mile or so from their breeding-place, continue to be made. It is not a question of what is their power of flight, or how far they can fly, but of how far they actually do fly on the average. My proposals to reduce malaria by dealing with the breed- ing waters were long ridiculed because it was thought that as soon as the local output was checked mosquitos would rush in from outside to fill up the deficiency. Several eminent biologists held this opinion, and a ridiculous experiment was undertaken, apparently in the hope of proving it. In 1903-1904, however, I attempted a carefully reasoned consideration of the whole subject — so vital to the interests of malaria prevention ; and showed in a lecture [May 1905] that the average wanderings of the insects, and indeed of all animals, must be limited by laws of chance. I will now explain that reasoning as simply as possible. (14). Tlie random scatter of animals from a given point. — Suppose that an animal is liberated at a given point — for instance, a mosquito from a box — and suppose that it can find its food equally well anywhere in the surrounding country, and is not drawn towards any particular spot, or driven anywhere by wind or other things ; what are its movements likely to be.? We can imagine that it may just possibly continue always to move in the same direction, so that when it dies it will be found at the greatest possible distance from the point where it was liberated. Or it may move for half its life in one direction, and for the other half of its life back again — so that it will die actually at the point where it started. But both these courses i8o MALARIA IN THE COMMUNITY [Sect. will scarcely ever be adopted. In the vast majority of cases, the animal will move for a short distance, first in one direction, then at an angle in another direction, then again at another angle, and so on until it dies. Its movements will resemble those of a grain of dust placed on a level plate in a jolting railway carriage ; or the random walk of an intoxicated person in a mist ; or that of a cow grazing on a uniformly succulent meadow. What are the chances that when the animal dies or ceases to move it will be found at a given distance from the starting-point ? Obviously, it will most probably be found somewhere near the starting-point. There is no reason why it should move more in one direction than in another. The chances are equal that, at any change which it makes in the direction of move- ment, it will next move north, south, east or west. Hence its various movements will always tend in the long run to annul each other — so that it will tend to finish near where it began. But there is no certainty that its various movements will annul each other exactly ; hence, most probably, it will not be found exactly at the starting-point, but only somewhere near it. Or we may put the problem thus. Suppose that a million Anophelines are liberated from a single breeding-pool in the midst of a country where they can obtain food equally well at any point, and suppose that we know their average rate of movement and length of life : how many of them will be found at a given moment at a given distance from the pool ? Most of them will be found, not exactly at the breeding-pool, but close to it. A few will be found further away, and a very few at the extreme limit of possible flight. What precisely will be the ratio of insects at a given distance from the pool ? In my lecture just mentioned I attempted a partial mathematical treatment of the problem, but the matter was beyond my mathematical powers, and I therefore referred it to Professor Karl Pearson, who, with J. Blakeman, obtained 29] RANDOM SCATTER i8l a correct and complete solution, based on the laws of chance [1906].^ It is not possible to give their complicated mathematical analysis here, but I will presently mention some of their results. Besides its application to the prevention of mosquito-borne disease, the mathematical theory of migration has manifest and important applications in general biology, as, for instance, to the theory of evolution and the study of local variation of race. The general results obtained from the calculations may be put as follows : — {a). Unless mosquitos are drawn or driven in any particular direction or directions, their number will tend to be greatest somewhere near the breeding-pool, and to diminish progressively at greater distances from it. {b). Per co7zlra, if the mosquitos are very numerous, then, ceteris paribus, the breeding-pool is likely to be near at hand. These laws are confirmed by the general observation of many workers and of the public. For example, Stephens and Christophers [25th April 1902] conclude that the "flight" of M. culiczfacies, N. fuliginoszis and N. stephensi in Nagpur, India, is " frequently a quarter of a mile, but does not extend to half a mile." (15). Exceptions. — These will be due {a) to flock-migration, if it occurs ; {b) to carriage by vehicles, boats and wind ; and (f), more generally, to food-pursuit. The law of random scatter applies only if the country affords equal facilities for feeding in all directions, but if this is not the case, the insects must, of course, go where they can find their food. Thus if there is only one breeding-place and one feeding-place somewhat far apart, the females must always traverse that distance between feeding and laying their eggs ; and if the distance is great, probably few of the females will succeed. If there is only one feeding-place in the midst of many breeding-places, such as a village surrounded by marshes, ^ This paper is not mentioned in the medical text-books. i82 MALARIA IN THE COMMUNITY [Sect. then quite possibly all the females which can reach the feeding- place will focus themselves upon it. Here a law which has not been investigated, though it is most important as regards prevention, comes into play. What is the maximum distance at which a female mosquito can scent her human prey? If this is one mile, then, in the case of the single village, drainage for the purpose of freeing it from mosquitos would have to be carried out for a radius of one mile round ; if only half a mile, then for a radius of half a mile ; and so on. (i6). Diviinutioji of mosquitos round a cejitral sterile patch. — Suppose the case of a plain with numerous breeding-places scattered uniformly over it, and suppose that there is a central sterile patch in it — that is, a patch where, owing to natural or artificial causes, the insects cannot breed : how will this patch affect the mosquito density round it ? The answer is obviously that the mosquitos round the patch will be diminished by exactly the same numbers as the patch would have produced if it had been allowed to continue yielding an output of mosquitos. That is, by the law of random scatter, the diminution will be greatest over the patch, progressively less as we recede from it, and none at all at a sufficiently long distance from it. If the patch is very small, the diminution will be very small, even at its centre, and will be hardly appreciable at a short distance from it. Here, of course, numbers of mosquitos will be able to fly across the patch. If, however, the patch is a large one, few of the mosquitos migrating inwards from its margin will be found, according to the law of random scatter, at its centre. Suppose, for instance, that by this law only i/ioo mosquitos are found i,ooo metres from the centre of a breeding-pool ; then conversely, in a sterile patch of 1,000 metres' radius, only about i/ioo of the mosquitos breeding at the patch's margin will be found at its centre. The diminution in mosquito-density due to a sterile patch 29] EFFECT OF STERILE PATCH 183 will be felt not only over the patch itself, but to a considerable distance beyond it. That is, the mosquitos will be diminished just so far and by just so many as the patch would have put out by random scatter if it had been an isolated breeding patch, and the surrounding country had been sterile. That is, the diminution of density due to an isolated sterile patch and the increase of density due to an isolated breeding patch must always be, ceteris paribus, equal. From this it follows, in the case of a very large isolated sterile patch, that the mosquito-density exactly at the margin of the patch should be exactly one-half the normal mosquito- density. This law was stated in my paper, and has been confirmed by Pearson and Blakeman. I gave also a diagram showing the fall of the mosquito- density on either side of the straight boundary of a large sterile patch, and now reproduce the more exact curve shown by Pearson and Blakeman for certain constants roughly estimated by me. Fig. 2. -\^ \ hrt^ of fmijrAfioa htt. of Immigration. •i \ 1 \ 0? .1 \ *» V iQ V Rfduied DensiTy. i84 MALARIA IN THE COMMUNITY [Sect. To understand this, we suppose that the mosquitos (or other animals) are breeding as usual on the left — that is, in the Area of Emigration, and that many of them are wandering across the boundary into the sterile area (Area of Immigra- tion). The curve beginning on the left shows the fall of the mosquito-density. Slow at first, it increases rapidly as we approach the boundary from outside. Exactly at the boundary it is exactly one-half. Inside the boundary it continues to fall, rapidly at first, and then more slowly as we approach the centre of the sterile area. At the centre, if the patch is sufficiently large, it should be nearly or practically zero. The following diagram from my paper shows the same thing in plan. Fig. 3. a Effecr o? dTa.ind.gc oP a. thCuld-T iTea. , i. IwundiTv 0? drained fl.Tea.. MoMuil'o-deniit'y keftina to diotimsK aX The tiTcU, &• iecome% orte-haJp aTthe bounda.W, b, 3.nd •& $mail, in^vppreciable, OT 2eio af and within fhe circle, c 29] IMMIGRATION AND SIZE OF AREA 185 We should also understand the following simple proposi- tions. If a straight line is drawn across a country in which mosquitos (or other animals) are wandering equally and at random, then as many will wander from left to right of the line as from right to left. Moreover, the longer the line the more animals will wander across it, ceteris paribus, in unit of time. This should hold also for circles. Thus, if we draw two circles, one 100 metres in radius and the other of 1,000 metres, ten times more animals should wander across the circum- ference of the latter than across that of the former. Thus the number of immigrants into the large circle should be ten times the number into the small one. But the mosquito or animal density is obtained by dividing the total number of animals by the size of the area ; and the area of the large circle is 10 x 10= 100 times that of the small one. Thus, though ten times more mosquitos actually wander into the large circle, yet the average mosquito density due to immigra- tion alone in the large circle will be only one-tenth that in the small circle. Now if both these circles contain sterile areas, the mosquitos within them can consist only of immigrants. Hence the total mosquito density in the large sterile patch will be only one-tenth that in the small one. In other words, the larger the sterile patch the smaller will be the mosquito density due to immigration into it from outside. That is, the larger the area of drainage the more effective it will be. It has often been thought, absurdly enough, that the mosquitos in an area may not always be reduced by render- ing it sterile. This can never happen ceteris paribus, because the number of immigrants can never equal the number of immigrants plus the number of natives. But if the area is very small it may breed so few natives that the reduction after it is sterilised will not be noticeable. But by suitably increasing the radius of the sterile patch we can reduce its average immigration density to any small figure we please. Of course, the immigration density is not uniform, but. i86 MALARIA IN THE COMMUNITY [Sect. as already stated, begins at the boundary, at a fraction of the normal density, and from that fraction diminishes rapidly towards the centre, where, if the sterile patch is large enough, it may become practically zero. Pearson and Blakeman have made some exact estimates based on rough constants supplied by me. For example, in a circular sterile patch one mile (r6 kilometres) in diameter the mosquito density should be reduced at the boundary to about 75% of the normal density; to i8% a quarter of a mile from the boundary ; and to 30% at the centre. If the sterile patch is two miles long and one mile broad, the central density should be 1%. In a sterile square mile, the density should be 50% at the boundary, 11% half-way to the centre, and 2% at the centre. In section 28 I attempted to calculate the probable fall in the malaria rate which may result from a decrease in the number of mosquitos. 30. Explanation of Various Phenomena. — In the previous sections I have endeavoured to give the general theorem of the spread and prevalence of malaria. We have now to apply this theorem to the explanation of numerous phenomena which have been observed in connection with the epidemiology of the disease. From section 28 (equations 4 and 7) we have the two following formulae : — Variation Fonuula, m^ = nt + U^si'a ( i — in) m — rnt — m + 0'005 a (i —vi) ;;/ — 0"2 m (say) Static Formula M = i — rjb'sia = I — 200r/a (say). The Jlrst formula suggests the manner in which malaria varies in a locality. Here in is the proportion of infected persons at the beginning of the enquiry ; a the proportion of different carrying Anophelines to each person (healthy or infected) during the enquiry ; r the rate of recovery ; d the 3o] CONNECTION WITH MARSHES 187 proportion of Anophelines which succeed in biting men ; j' the proportion of AnopheHnes which succeed in maturing the parasites ; i the proportion of patients with gametids in their blood ; and, finally, m^ the proportion of infected persons at the end of the period of enquiry. Here 7//, r, b^ s, i, in are all fractions. I suppose conjecturally that if the enquiry lasts one month b'^si =0'00$ (about), and r = 0'2. The second formula suggests the final or static level M^ to which the proportion of infected persons falls so long as the proportion of Anophelines, «, and the other factors remain about constant. The exact numerical values of b, s, z, do not materially affect the general argument. The equations omit several minor factors, but are still useful for giving precision to our ideas. (i). Connection with marshes. — The fact that malaria tends to be very prevalent near marshes was observed by the ancients, has given the name paludisni to the disease, and is perhaps the most fundamentally important fact of our subject. It is easily explained because most Anophelines breed principally in marshy waters, and because, by the law of random scatter in (14) of last section, they will generally tend to be most numerous near their breeding-pools. By the static formula, the larger a becomes, the more M approximates to unity — that is, almost the whole population becomes infected. Per contra, the further we recede from an isolated marsh or other isolated breeding area, the smaller the mosquito density becomes, and M falls in value. When we reach such a distance from the marsh that a becomes 40 (conjecturally) or less, the static malaria tends to disappear altogether. Of course there are many factors which may possibly modify the exact paludo-peripheral distribution of malaria ; such as the existence of abruptly-rising ground, or of open water, or of thick forest close to the marsh ; or (?) a strong wind con- tinuously prevalent in one direction. Species of Anopheline may affect the radius of distribution. Where there are many i88 MALARIA IN THE COMMUNITY [Sect. scattered breeding-places within range of influence of each other, the malaria will tend to be more equally distributed. The fundamental fact has been noticed, if not studied, everywhere, especially in Italy. Stephens and Christophers [April 1902], in a paper on the factors which determine endemicity, conclude from a number of scattered observations in India that "other things being equal, there is a direct relation between the extent and proximity of breeding-grounds, the number of Anopheles in the houses, and the endemic index." Unfortunately they give only ratios, and these only for entire villages at various distances from the breeding- grounds. In 1908, C. E. P. Fowler and I made an exhaustive study of spleen rates of children in houses scattered close round the Clairfond Marsh in Mauritius (section 30 (21), and map opposite). We found an extremely rapid fall in the spleen rates even at a distance of 200-300 metres from the principal pools of the marsh. In the three rows of barracks of the British soldiers, the nearest of which was 850 yards {jjy metres) from the nearest pool of the marsh, and the furthest about 200 metres further, Colonel Peterkin, the Principal Medical Officer, found that the ratios of malaria cases to men were 31/206=150/1,000, 22/252 = 88/1,000, and 2/62 = 32/1,000, in the successive rows. Many other instances might be cited from the literature. The definition of the word " marsh " as here employed is a very important point. Webster, for instance, defines a marsh as *' a tract of soft wet land commonly covered partially or wholly with water." This definition includes the marshy borders of rivers and lakes, etc. ; but we must extend it, for the purpose of our present technical meaning, to exclude the idea of permanence. In our sense, marshes may be quite temporary — may exist only for a few weeks during the rainy season, or season of floods, or wet cultivation. The reader must not imagine that Anophelines breed only in permanent marshes. I have often thought that water - logged country VET ROAD fractions give the spleen ratios : \To face page iSS. PLAN OF VACOAS CAMP and CLAIRFOND MARSHES. Settle lOOO feiit to tfui incA. RAVET ROAD Enlargement of spleen in children living round Clairfond Marsh. The principal pools are shown in black. The fra thus 9/24 denotes that 9 out of 24 children had splenic enlargement. tions give the spleen ratios : 3o] CONNECTION WITH SOIL AND SLOPE 189 may often be really less favourable to them than a usually dry country which may be covered during the rainy season by extensive temporary marsh. In permanent pools, the larvae probably have many enemies — fish, beetles, tadpoles, other larvae — which cannot live so easily in the shallow, evanescent pools caused by rain at certain seasons. It is quite possible that for this reason a unit of temporary marsh has an actually larger annual Anopheline output than a unit of permanent marsh, and this consideration may help to explain the great prevalence of malaria in certain dry countries, as in the north of India. (2). Connection with soil. — Obviously, an impermeable soil is likely to possess more collections of surface-water than a loose, porous one, and thus to increase a, the number of Anophelines. A sub-soil stratum of rock or clay has often been mentioned as increasing malaria. It is possible, also, that certain soils are favourable to the breeding of the local malaria-bearing mosquitos, while others have the opposite tendency. There is much old literature on this point — written when malaria was attributed to the soil. After considering it, I think it is scarcely worth reference, although much of the work was carefully done. There is never any proof that the variations of malaria attributed to differences of soil were not really due to other causes. I am far from saying that soil exerts no influence on the endemicity ; but J can find no decisive evidence that it does so, apart from the merely mechanical effect of permeability. The matter deserves more exact study by modern methods. (3). Connection with slope. — i\brupt hillsides have little malaria as a rule, but Anophelines often breed in dry beds of torrents, as (for instance) described by F. Smith and A. Pearse in Sierra Leone [1904]. I was infected in 1897 in such a place, Kalhutti, near Ootacamund, India [February 1898], and the native servants of the house were attacked there also. Small flat valleys among 3o] CONNECTION WITH SOIL AND SLOPE 189 may often be really less favourable to them than a usually dry country which may be covered during the rainy season by extensive temporary marsh. In permanent pools, the larvae probably have many enemies — fish, beetles, tadpoles, other larvae — which cannot live so easily in the shallow, evanescent pools caused by rain at certain seasons. It is quite possible that for this reason a unit of temporary marsh has an actually larger annual Anopheline output than a unit of permanent marsh, and this consideration may help to explain the great prevalence of malaria in certain dry countries, as in the north of India. (2). Connection with soil. — Obviously, an impermeable soil is likely to possess more collections of surface-water than a loose, porous one, and thus to increase a, the number of Anophelines. A sub-soil stratum of rock or clay has often been mentioned as increasing malaria. It is possible, also, that certain soils are favourable to the breeding of the local malaria-bearing mosquitos, while others have the opposite tendency. There is much old literature on this point — written when malaria was attributed to the soil. After considering it, I think it is scarcely worth reference, although much of the work was carefully done. There is never any proof that the variations of malaria attributed to differences of soil were not really due to other causes. I am far from saying that soil exerts no influence on the endemicity ; but J can find no decisive evidence that it does so, apart from the merely mechanical effect of permeability. The matter deserves more exact study by modern methods. (3). Connection with slope. — Abrupt hillsides have little malaria as a rule, but Anophelines often breed in dry beds of torrents, as (for instance) described by F. Smith and A. Pearse in Sierra Leone [1904]. I was infected in 1897 in such a place, Kalhutti, near Ootacamund, India [February 1898], and the native servants of the house were attacked there also. Small flat valleys among I90 MALARIA IN THE COMMUNITY [Sect. mountains are apt to be very malarious. Slope acts mechanically on the drainage, but the labour and heat of climbing predispose to chills and relapses. Flat plains at the foot of mountains — called /erai in India — are notoriously unhealthy. This is due to the fact that they receive all the surface-drainage of the rain on the mountains, the water flowing from which immediately stagnates on the flat levels. After heavy rain a whole mountain seems to ooze with moisture at its base, springs often appearing considerable distances away on the plain. Whether mosquitos often find their way far up slopes is doubtful. In 1899 we observed scarcely a single Anopheline in the barracks at Tower Hill, a small open hill in the centre of Freetown, Sierra Leone, with numerous breeding-pools only about 500 metres distant. Infections among people living at a small height on slopes is probably more often due to the visits they pay to the plain, rather than the visits paid by the Anophelines of the plain to them. (4). Connection ivith vegetation. — Several Anophelines are known to breed in plants and trees. Certainly, many Culicines do so, and also seem to like the shelter from sun and wind given by dense vegetation. Our "moustiquiers" in Mauritius had no difficulty in securing Anophelines in the densely - wooded " river reserves." But I do not know any numerical researches which have been made to prove that any malaria-bearing species abounds more in woods than on open ground (see, however, sections 57 and 63). It has been proved statistically by Mr Walter of the Mauritius Observatory that the damp exhaled by trees increases the number of rainy days, and especially the afternoon rainfall so frequently seen in the tropics. For this reason alone, there- fore, trees should favour the breeding of mosquitos. It is generally held that a screen of trees shuts out malaria and mosquitos — this being one of King's original arguments in favour of the mosquito theory. Stephens and Christophers 3o] CONNECTION WITH RAINFALL 191 also accept the hypothesis. It is a likely one, but better proof is required. The fact that the true Plasmodiidae have hitherto been found only in men, monkeys, bats, squirrels and perching birds is a curious one, which suggests an arboreal connection. (5). Connection with rainfall is manifestly due, in the case of summer rain, to the increased mosquito output. Rain also tends to bring on relapses, and therefore to increase the factor — since patients with frequent relapses tend to show more gametids than those without them (section 20 (6)). Thirdly, I think that it increases the biting factor, b, and quite possibly reduces the recovery factor, r. Hence, on all counts it must tend to increase the malaria. Winter rain may possibly reduce r, but, if the winter is cold enough, can have little other effect. Thus in Greece most of the rain falls in the winter, when there is little new infection. Much spring rain, however, has a very disastrous and well- known effect, as it fills the pools just when the weather is becoming warm enough for breeding. This has been especially noted in Greece. Statistics support the common statement that malaria inoculation occurs most frequently at the beginning and the end of great summer rains. At the height of these rains, when they are copious, the ground is often covered with more or less running water, frequently containing myriads of small fish, and too disturbed for much breeding. On the other hand, in countries with small total summer rainfall, the maximum breeding is more likely to occur at the height of it. There was a bad outbreak in the north of India in 1908, when most of the rainfall was concentrated in the month of August. Innumerable statistics showing the connection between rain- fall and malaria might be reproduced here. Unfortunately, while they prove the existence of the connection, they do not enable us to discriminate between inoculations and relapses. 192 MALARIA IN THE COMMUNITY [Sect. Most probably the variation formula is affected by changes in all the factors mentioned above. (6). Connection with temperature, like that with rainfall, is probably due to increase of all the factors and decrease of the recovery factor r consequent on exposure to heat or sun. Warmth is, of course, an essential to copious breeding, but great dry heat must tend to desiccate the pools. An important question remains to be considered. In low latitudes the temperature is generally uniformly hot all the year round, so that the Anophelines should be able to breed at all seasons, especially where the rainfall is also fairly evenly distributed. But in higher latitudes the breeding can occur only during the short hot weather. Hence we should infer that the Anopheline factor must always be higher in the former, and the malaria more abundant. But statistics often show that just the opposite happens. For example, in the north of India, where the winters are sharp, the total fever rate is generally considerably higher than in the south, where there is no winter. Malaria is, or was, intense at Peshawar in the extreme north, and scarce in Calcutta, Madras, Rangoon and Colombo. But this law does not always hold, for malaria is common in Panama, Colon, Lagos, Freetown and Port Louis (Mauritius), all of which have a climate very similar to that of the four Indian coast towns. (I write from personal acquaintance). The probable explanation is as follows. So far as we can judge, not all the Anophelines can carry malaria, and various carrying species differ in carrying power, thus modifying the carrying factor, s. It does not follow that of all the Anophelines of a country those with high carrying power breed best in a uniformly warm climate. Stephens and Christophers showed this well in their paper just referred to. Thus M, rossii, with a low carrying power, prevails most in Calcutta and Madras. See ( 1 1 ) below. (7). Connection with altitude. — It is well known that malaria 3o] CONNECTION WITH ALTITUDE 193 tends to diminish and cease at an altitude of about 500-1500 metres above sea-level. The exact limit probably depends upon the latitude. I was infected in 1897 at 1,800 metres in the Nilgiri mountains in India. The disease abounds at Cilaos, Reunion, at 1,214 metres. The text-books quote many similar cases, but these often require verification. It is more interesting to ascertain the gradual fall in the malaria curve with altitude. Stephens and Christophers, misled, I think, by insufficient random sampling, thought that altitude under 4,000 feet (1,219 metres) "does not seem to play an important part," but our copious figures of spleen rates in Mauritius (section 22) prove that it does. That island, consisting almost everywhere of plateaus sloping gradually downward and therefore being capable of breeding at all the altitudes (from o to 549 metres), gives an excellent opportunity for the enquiry, as will be seen by study of the table referred to. The carrying Anopheline was probably entirely M. costalis. As is well known, the temperature of the air tends to fall about 1° F. for every 300 feet of altitude (about 0"56' C. for 100 metres). The general decrease of malaria with altitude is probably due mostly to this fall in temperature, but in Mauritius, and perhaps in many other places, other factors besides temperature may retard the breeding of the local carriers at the higher levels. The following table, calculated from that in section 22, gives the spleen rates and average spleen for groups of altitudes : — altitudes {feet) 0-300 3-600 6-900 9-1200 12-1500 15-1800 fall of temperature 0° F. i 2 3 4 5 spleen rates 44*5 41-2 31-5 8-5 10-2 47 average spleeft 2-98 3"o8 2-03 r23 r56 r22 The exceptional figures at 1,200- 1,500 feet were due to the epidemic round Clairfond Marsh. Apart from these, the fall, both in spleen rates and average spleen, is not noticeable under 600 feet, and then becomes very rapid up to 1,200 feet — after which, under normal circumstances in Mauritius, the malaria N 194 MALARIA IN THE COMMUNITY [Sect. is slight, or possibly only imported. Other facts will be elicited when governments get into the way of collecting spleen rates annually, as they should do. (8). Comparative freedom of centre of towns, — It is generally stated as a commonplace that malaria abounds less in the centre of towns and more in the suburbs ; and, from my own general observation^ this appears to be the case in all the larger towns known to me. But the matter requires strict enquiry by measurements of malaria made on proper principles from the centre outward. The probable explanation is that the Anophelines, though they may breed in small numbers in wells, cisterns, gutters, waste from water-taps, etc., in towns, yet cannot generally propagate so copiously and freely there as in the more open regions in the outskirts. Probably, also, as the wealthier people generally live in the better built and paved centre of a city, the recovery factor is increased and the gametid factor decreased there by the good medical treatment usually accessible to these classes. But there is also the following factor. (9). Effect of density of hwinan population. — Suppose that in a locality the mosquito population remains the same, but that the human population varies : what will be the effect of this variation on the malaria ratio? By the static formula M=i—4.oja; but a is the number of Anophelines, not in unit of space, but per unit of human population. If, therefore, the latter is doubled while the total mosquito population remains constant, a will be halved ; and so on. Thus the static malaria ratio tends to decrease with increase of the density of the human population. That is, other things being equal and the Anophelines being supposed to breed equally everywhere, the malaria ratio should be higher amongst a scattered rural population than in a dense urban one, because, evidently, the number of Anophelines per person will be less in the latter. But I am not sure that if the human population varies, the mosquito population will generally remain the same. Unless 3o] CONNECTION WITH POPULATION 195 the latter find abundance of food independently of the former, their numbers are likely to diminish if the former diminishes (section 29 (7) ). This will depend largely upon whether the local carrier is a domestic, sub-domestic or wild species, and on other circumstances. If the total mosquito population varies directly with the human population, the factor a, and therefore the static malaria, should remain constant — that is, change of density of the human population will not affect the result. If the mosquito population diminishes as the human popula- tion increases, the malaria ratio should fall greatly — as in well- drained towns. If the former increases with the latter but more rapidly, the malaria should increase. It may happen that when the human population begins to increase the local breeding surface is already yielding its maximum output of mosquitos. In this case the increase of the human population should cause a decrease in the static malaria ratio (section 29 (8) ). In all these cases the malaria ratio is not, of course, the same thing as the total number of patients. If the local carrier belongs to a species or variety which feeds almost entirely upon man, and if the human population is greatly reduced, it may perhaps follow that this species can no longer continue to thrive in the locality — so that the malaria should die out. Dr Castel showed me a large marshy area in Mauritius which, he said, was formerly thickly inhabited ; but the disease became so prevalent there that the people deserted it in large numbers. Now it contains only a few scattered huts, the occupants of which show a low spleen rate (with P. costalis). (10). The "■ regional factor" — It often happens that two neighbouring tracts of country, apparently similar in all respects such as climate, breeding surface, habits of people, differ largely in the malaria ratio. Stephens and Christophers [25th April 1902] attributed such variation to "undefined causes which we have termed the regional factor. The regional factor 196 MALARIA IN THE COMMUNITY [Sect. may be largely due to species, but more accurate and detailed observations on the distribution of Anopheles and malaria are necessary before this can be decided." It may be due to many small things which, though not very apparent to the observer, may largely affect the mosquito factors b, .y, a. Thus the local carrier in the larval stage may require a certain kind of food which abounds in water lying on certain soils present in one locality and not in others. Again, certain soils may favour special enemies of the larvae of the carrier — small fish, beetles, cannibal mosquito larvae, parasites ; while certain classes of vegetation may favour enemies of the adults. All these are likely to be very potent causes of variation in the mosquito factors, though they may not be easy to detect without long enquiry. If we attribute the regional factor merely to "species" of carrier, we have still to " explain our explanation," since we must show why a given species abounds more in one area than in another. Hence I define as follows. By regional factors I mean all those local conditions, apart from mere extent of breeding surface, which influence any of the mosquito factors b, s, a\ that is, local conditions which influence the output per unit of surface, the biting power, and the maturing power of the local Anophelines. (ii). The species factor. — This influences b and s, the biting and maturing powers of the carriers, which probably differ largely with the species or even variety of the carrier. Where these factors are high, a lower number of Anophelines will produce a given amount of malaria. Thus tropical Africa appears on the whole to be more malarious than India — that is, the chances of becoming infected in unit of time and season in Africa are said to be greater in Africa than in India. This may be because good carriers such as P. cos talis and M. funesta abound more in the former. In India the bad carrier, M. rossii, seems often to crowd out the more pathophoric species. 3o] THE SOCIAL FACTOR 197 The local prevalence of good carriers or bad ones must depend not only on regional factors but on the general zoological laws which determine diffusion of species.^ (12). The social factor. — The factor b depends not only on the appetite, energy and enterprise of the mosquitos, but also on the intelligence, social status and habits of their victims. Stupid, poor, lazy people, living in badly-made huts, without much clothing and without mosquito-nets, are sure to be bitten much more easily than more civilised races. People who burn wood or cow-dung in their houses in the evening, or who rub their skins with oil, earth or sandal-wood, or who close their rooms at night, may perhaps be bitten less than others. The subject is too complex for detailed examination here. The habits of man and mosquito are probably often correlated. Thus where the principal carrier is an out-of-doors biter, people who sleep or work at night in the open are likely to suffer. Alcoholism, opium, etc., lead to neglect of precautions. Children are sure to be easy victims. Farm stock and dogs may satisfy many insects, and punkas and fans drive away others. Neglect of precautions against being bitten is likely, not only to increase the biting factor, but also, by section 29 (7), the total number of mosquitos. Famine, poverty and other diseases will reduce the recovery factor. (13). Possible el^ect of malaria on the Anophelines. — As earl)' as 1898 I thought it possible that the parasites might injure their insect hosts, as well as their human ones. If this happens we can readily understand that an epidemic of malaria might tend to limit itself by killing large numbers of the carriers as well as men. Thus, during an epidemic year, so many of the insects might die that the breeding might subsequently be reduced for some time. But there are reasons against this view. I could never satisfy myself that C. fatigans, even when 1 Possibly also on the insects' food (section 48). 198 MALARIA IN THE COMMUNITY [Sect. extremely heavily infected with Proteosovia, died sooner than when not infected at all. Probably they do so, but only to a slight extent. Then again, only a small percentage of infected mosquitos are heavily infected, so that the malaria infection is not likely to make a material difference in their death-rate. Lastly, even a severe epidemic among them will quickly be compensated for by their rapid proliferation. (14). Seasonal variation. — This is a matter of universal observation. As a general rule in the northern hemisphere the disease reaches its maximum prevalence in the autumn, say October or November. At that point, a rapid decline, the winter fall, generally begins, and this continues for several months until early spring, say February or March, when the winter minimum occurs. The spring rise now takes place, and the disease tends to increase with more or less regularity until the next autumn maximum. Of course, the seasons are reversed in the southern hemisphere. Innumerable illustrative statistics might be given ; but every one is acquainted with the phenomenon, and the examples in section 20 will suffice for our present purpose (note that in the Italian figures the minimum is reached in June). The causes of seasonal variation will be apparent from a study of the variation formula given at the beginning of this section. Thus the winter fall is probably due to diminution of the factors h, .v, a, in consequence of the cooler temperature or drying-up of the rains, or of both ; and also possibly to increase of the recovery factor owing to the more bracing climate. On the other hand, the spring rise is probably due to just the opposite changes in these factors, and possibly also to the emergence of Anophelines which have been hibernating through the winter. In the tables in section 20 I have given the ratios between the average admissions for successive months. These can be compared with the variation formula, by supposing that m is the malaria ratio for any given month, and m^ the malaria ratio 3o] SEASONAL VARIATION 199 for the next month. Then, dividing the variation formula throughout by ;//, we have, injjn = I + b-sra{ \—in) — r. Thus, take the monthly averages and ratios of the native troops, and suppose that only the number of men actually infected were admitted (section 31 (5)) into hospital every month. Then, out of 43,330 men there were on the average 922 infected men in February and 1,030 in March. Thus m = 922/43,330 ; m^ = 1 ,030/43,330 ; m^jm =1-12; i-m = 0-98 ; and therefore, I • 1 2 = I + 0*98 b"sza — r. Supposing that b, s, z, r have the values assigned at the beginning of this section, we calculate from this that a = (o*i2 + o'2)/o*oo49 = 65. That is, as a rough estimate, there may have been about 65 carrying Anophelines per person during the month February to March in order to increase the infected persons from 922 to 1,030, and the admissions from 461 to 515. Similarly, in order to cause the great rise in admissions among the native troops from averages of 1,689 in September ^° 2,955 i" October, we may estimate roughly that 175 Anophelines may have been present. In order to cause the commencement of the winter fall from 2,955 admissions in October to 1,932 in November, we shall have from the formula a negative number for a — that is, according to our data, there should be no Anophelines biting at the time. But of course our data are only speculative ones, and, as already stated, the factors b and s, as well as the Anopheline factor, are likely to vary with season. Moreover, my estimate that the recovery factor r equals about 0*2 is probably too high for the earlier months of infection. (15). Anmial variation. — This also is a matter of general observation. In every country there are " good years," " bad years " and " years of epidemic." This variation, when it occurs over large areas, is probably due principally to the influence of 200 MALARIA IN THE COMMUNITY [Sect. climate, i.e., rainfall, number of rainy days and temperature, on the Anopheline factor. In the statistics of section 20, the numbers of admissions differ not only for the whole years, but also for the same month in different years, and for the European troops, native troops and prisoners, respectively, during the same year. It is interesting to note that a considerable rise in the total annual admissions may, by our formulae, be produced by a comparatively small rise in the Anopheline factor. Thus among the native troops there were 11,293 admissions in 1903 against 19,567 in 1901. But by the static formulae the former number would be given by « = 55 and the latter by a='jo. It would be almost impossible, for the reasons given in section 29 (4), to detect this increase in the number of Anophelines (28%) by ordinary observation. Hence the unwary observer might assume that the rise in the number of cases was independent of the rise in the number of Anophelines. In fact this is one of the principal stumbling-blocks of students. They observe a considerable annual variation in the number of cases with- out, apparently , any great Anopheline variation. But I doubt whether an Anopheline variation of as much as 50% or even 100% would be easily detectable by the very unsatisfactory methods of counting mosquitos at present known to us. If there are over 40 different Anophelines to each person per month, we should probably be able to find only two or three daily in his house — and possibly less if the insects are " wild " ones. This number might be doubled or trebled without producing a change which would be readily noticed even after careful observation, and long-continued random sampling would be required to establish the variation over a tract of country. Yet, as we have just calculated, a 28% increase in the Anophelines might cause a 42% increase in static malaria — that is, an increase of admissions from 11,293 to 19,567. While, I think, the annual variation is generally due to climatic causes, it is very possible that other factors often 3o] EFFECT OF IMPORTED CASES 201 influence it — such as poverty caused by increase in the cost of food (which would diminish the recovery factor), or move- ments of the population which might act in various ways. (16). Effect of imported cases. — In section 28 I argued that, whatever the original number of cases may be, the malaria in a locality tends finally to settle down to a fixed static ratio determined by the various constants. Thus if we take the case of a village of 1,000 people, half of whom are infected to begin with, with 60 Anophelines per person, the rate would fall until, finally, about 333 persons are always infected. If we had started in the same village with the same number of Anophelines, but only one infected person, then the rate would rise until the same number of infected persons are found. But the reader must not infer that the original malaria ratio is of no consequence — that it does not matter whether many cases are imported or not. True, the ultimate static ratio should be the same, but many months may elapse before this limit is reached. If there have been about 333 cases in the village for months or years past, and we now add 167 imported cases, then (neglecting the small change in the total population) we should have 500, 475, 455, 438 and 424 cases in the four following months; that is, 167, 142, 122, 105 and 91 more cases than there would have been in the village if no imported cases had been introduced. This would probably be looked upon by the villagers as a serious epidemic due to some climatic cause. On the other hand, suppose that there have been 40 Anophelines per person in the village. Then the static malaria there would be zero. But if 500 of the villagers are now replaced by 500 infected persons, the 40 Anophelines, though insufficient to maintain static malaria, would be suffi- cient to spread the disease to some extent among the villagers ; as will be seen by comparing examples 3 and 6 of section 28 — that is, the examples with 40 and with o Anophelines. In four months the former will have 500, 450, 409, 376, 348 202 MALARIA IN THE COMMUNITY [SECT. cases, some of them among the healthy villagers ; and the latter will have only 500, 400, 320, 256, 205 cases, all among the imported persons. Thus in the former there will be 50, 89, 120, 143 cases among the villagers, who will, of course, suffer from an epidemic. But in the end the epidemic will die out. In this village then, 40 Anophelines per person will suffice to spread the disease to some extent from the imported cases to the healthy villagers, though the various small epidemics which may be caused in this way will tend ultimately to die out. But suppose that owing to the blocking of some stream the Anopheline factor is increased to 60. The imported cases will now not only spread the disease to the healthy villagers, but the epidemic, instead of dying out, will continue to increase until the static limit of one-third of the population is reached. The village, which previously suffered only from sporadic out- breaks due to imported cases, will now become permanently infected. Yet this great change will be due merely to the small increase of Anophelines from 40 to 60 pei' person — an increase which few observers would be able to detect. It is unnecessary to labour this matter further — I have already laboured it perhaps too much. The point to be understood is that a small Anopheline variation — too small to be easily observed — may yet make a great difference in the local endemicity. Below a certain figure the Anophelines will be, according to the laws of chance, too few to produce enough new infections to keep pace with the natural recoveries. Above that figure they will be sufficient for the purpose, and the malaria ratio will rise to a definite static limit. So far, this theorem has been already given in section 28 ; but we now perceive another point of importance. Though the Anophelines are too few to maintain a static endemicity, yet if any at all are present they may suffice (provided that the other factors b, s, i, r do not possess prohibitive values) to cause small temporary spreadings of the disease from imported 3o] ISOLATED ABNORMAL AREAS 203 cases among the local population. Only in the case where there are practically no Anophelines will the imported cases have no effect at all. The reader will easily grasp this law by comparing the examples in section 28. The reader should also remember another point. Our formulae are based upon the calculation of average chances. Thus, if the average Anopheline factor is over forty, and a single case of malaria is imported, we argue that the chances are that the disease will spread in the locality. We do not say that the disease must or will spread to a certainty. The laws of luck come in here. The distribution of Anophelines cannot be absolutely uniform in any locality. The imported case may come to reside at a spot where there are few Anophelines, so that the chances are that the disease will not spread at all. Or he may reside where the Anophelines are a little more numerous, so that only a small temporary epidemic may be caused. Or, if he happens to live where there are many Anophelines, a permanent rise in the malaria rate may be produced. Yet in all these cases the average Anopheline factor for the whole area under consideration may be anything. Thus, again, the imported case may have no gametids in his blood ; or he may arrive in winter and recover before the mosquito season ; or he may use mosquito - nets. This will be a case of good luck ; but by bad luck none of these events may occur, and an epidemic may be started or increased. We must now consider some special cases of importation. (17). Isolated supervialanous or infravialariotis areas. — Suppose the case of a country in which the static malaria is generally low, but in which an isolated area becomes, from any cause, more highly malarious : what will be the effect of that patch of high endemicity upon the health of the surround- ing country of low endemicity ? Evidently, unless the inhabi- tants of the supermalarious patch are strictly confined to it, some of them will tend to wander away from it, especially if, as often happens, they are actually driven out of it by its 204 MALARIA IN THE COMMUNITY [Sect. unhealthiness. If there are any Anophelines at all in the surrounding country, these emigrants, when infected, may cause local spreading, slight, severe, transient or permanent, according to the local factor. In any case they will tend to increase the surrounding endemicity. To calculate the increase from the variation formula, we must add, month by month, the imported cases to the number of cases remaining over from the previous month. Thus, though the static malaria ratio of the surrounding country might be naturally low, the continued importation of cases from the focus of high endemicity might raise it very considerably. It may be said that this process cannot continue for ever, because the focus would soon become depopulated. This certainly happens in some very unhealthy spots ; but in others the population of the focus is maintained by constant immigra- tion, so that it continues to be a perennial source of danger to the neighbours. And its influence may be felt for consider- able distances. Now, consider the converse case — that in which an isolated patch of low endemicity exists in the midst of a larger area of high endemicity. The effect should be just the opposite. There should be obviously less malaria in the whole country than if the inframalarious patch had not existed at all ; and the larger the healthy patch, the larger its influence will be. In other words, we assume that inequalities of malaria distribution have results similar to those of inequalities of heat distribution or mosquito distribution. The superheated objects or supermalarious areas tend to add heat or malaria to the surrounding objects or areas. But I am not clear that this resemblance always holds. Thus the people, and perhaps the Anophelines, in the supermalarious patch may, after a time, become so immune that they will no longer add very much to the surrounding ratios. Conversely, the non-immunes in an inframalarious patch may raise the ratio there owing to " extraneous infection " (19). (18). Effect of mass - migratio7is. — Suppose that a large 30] EXTRANEOUS INFECTION 205 number of persons, with a given malaria ratio, are suddenly and simultaneously moved into a country possessing a different malaria ratio : what will be the effect ? Such events frequently happen, as when a regiment of soldiers coming from England or from a very malarious country is moved into a moderately malarious country ; or when numbers of coolies are collected in a locality which has a different malaria ratio from that in which they were collected. The effect will probably be that there will be an epidemic in both cases. An inframalarious regiment of non-immunes from England is sure to suffer to a degree determined by the local factors. Its own men will be the principal ones to suffer, but the numerous fresh cases among them will tend to react on the local population. In the case of the introduction of a supermalarious regiment, the surrounding local population will suffer most, and will in turn react on the men of the regiment. In both cases the malaria ratio will ultimately tend to settle down to the static ratio of the locality. Examples of both of these cases are of frequent occurrence. Large bodies of labourers collected for various kinds of engineering works are liable to cause outbreaks, either among themselves or among the surrounding population, according to the respective endemic ratios and the local factors. This will be especially the case if the aggregation of human beings causes an actual increase in the local Anopheline factor (9). In such a case the aggrega- tion may have all the bad effects of a patch of high endemicity described in the last subsection. (19). Extraneous infection. — By this I mean the infection of people during occasional visits outside their usual habitation — a very important case. There are many villages the malaria ratio of which under natural conditions would be low, but in which it is maintained at an unnaturally high level by the fact that the inhabitants work in more malarious areas at certain times of the year. Thus in the village of Mazi (575 inhabitants), situated several hundred feet above the Plain of 2o6 MALARIA IN THE COMMUNITY [Sect. Kopais in Greece, I found malaria infection in twenty out of forty children examined [1906]; but there were scarcely any possible breeding - pools among the broken hills round the village. The apparent anomaly was easily explained by the fact that every year nearly the whole population descends to the plain for the harvesting in August (the most malarious month), and camps there for days or weeks at a time. As the most malarious months are also generally those of the greatest agricultural activity, extraneous infection is probably one of the principal equalisers of malarial distribution. In fact, the result is the same if the factors of endemicity are temporarily raised in a given locality, or if the people temporarily migrate to another locality where the factors of endemicity are higher. The local endemicity depends upon the local factors, only if the local population remains stationary. Of course if there are any local Anophelines at all, persons infected extraneously will tend to spread the disease to some extent among those who do not leave the locality. Thus adults infected while harvesting at a distance may infect their children when they return home. (20). Slow changes zk endemicity. — Seasonal, annual and other variations such as we have considered are constantly occurring in every malarious country ; but, besides these, certain slow but persistent changes, sometimes affecting very large areas, are often observed, or at least reported. It is stated that a whole country is gradually becoming more and more, or less and less, malarious. As undeniable examples I may quote the entry and increase of malaria in Mauritius, and its disappearance from Britain. How explain the phenomena ? They may be due, not to one, but possibly to any or all the factors concerned in the malaria equation. Let us first consider each of the possible factors in turn. {a) The Anopheline factor, that is, the number of carrying insects per person, may slowly and persistently vary. As shown in (15) a scarcely-appreciable variation in this factor 3o] SLOW CHANGES 207 may produce a striking change in the endemicity. Thus with 60 Anophelines per person the static malaria ratio should stand at about one-third ; but it should stand at double that with the Anophelines at 120. Yet few persons would be able to observe this difference in the number of the insects ; and as no census has been taken in the past, the scientific student would possess no standard for comparing the present with it. Yet many things may occur or concur to influence this factor to a considerable degree. Thus it is well known that long but inexplicable undu- lations occur in the weather-cnrv&s. These often affect only certain tracts of country, and have marked results upon the local crops and prosperity. They may thus quite possibly make a considerable percentage of difference in the Anopheline output, besides tending to influence the recovery factor. It would be difficult to state precisely what the exact effect of the weather might be. Excessive rainfall might either increase or decrease the Anopheline output, especially of certain species, according to local breeding conditions. Thus we should observe the change in the malaria without being able to draw a very clear correlation curve between it and the weather. Again, according to Walter [1908], afforestation has a marked effect on the number of rainy days. The great exhalation of moisture from vegetation tends to increase the afternoon thunder showers which occur so frequently over tropical lands (but not seas) at certain seasons. It has con- siderable influence on crops, and doubtless helps to keep breeding-pools filled. Irrigated cultivation is evidently likely to have a large similar effect, especially with extensive irrigation works and with certain corps. High -class roads and railways tend to obstruct natural surface drainage and also to provide numerous breeding-pools in the " borrow-pits " along their route (section 57) ; and I have seen the undoubted effect of them in Sierra Leone, Lagos, Panama and Mauritius. 2o8 MALARIA IN THE COMMUNITY [Sect. But whether the increase of total breeding surface produced by them is sufficiently large to modify the average Anopheline factor over a great area is another question. Probably irrigated cultivation has a larger effect. General increase of population may, by section 29 (7), increase the mosquito out- put out of proportion to the increase of the human population, by supplying more food to the female Anophelines ; and diminution of prosperity may have the same result, by (12). Thus many things may modify the Anopheline factor ; and as we possess no exact method of measuring mosquitos it will always be difficult to decide how or why the factor has been changed, or if it has been changed at all. {b) Changes in the carrying and biting factors may occur as the result of a gradual predominance of certain species of Anophelines. As we now know, the fauna and flora of a country frequently change to a considerable extent. Those originally found in ocean islands, like Mauritius and the Seychelles, are apt to be almost swamped by imported species. Quite possibly, therefore, more " virulent " species of Anophelines may gradually increase very greatly in certain areas, at least for a time under certain cycles of weather or with certain kinds of cultivation. {c) Human iuimigratioti into certain areas, especially in connection with large planting, railway, mining or irrigation works, may tend to create /^a of malaria (17); to enhance the local rate by the importation of cases or even of non- immunes; to increase the convection factors s and b, by destitu- tion or bad housing ; or to raise the Anopheline output by additional food. id) The habits of the people may change in consequence of prosperity, famines, pestilences or increase of civilisation. Thus they may use better houses, or houses of two storeys, or mosquito - nets, or glass windows. Or a larger proportion of medical men may practise among them ; or quinine may 3o] EXAMPLES 209 be more accessible ; or they may abandon cultivation for trade or take to cities — and so on. It will always be a very difficult matter to select the most probable factor. The final result will generally be due to the balance of all the forces, some pulling this way and some that. S. R. Christophers and C. A. Bentley have recently [1909] considered that a slow increase in certain Indian areas is due not so much to the Anopheline factor as to (c) — that is, immigration in connection with large economic develop- ments. Their paper is thoughtful, but, unfortunately, they do not deal with their subject quantitatively. They give us no estimate of the degree of the reputed epidemics, of the pro- portion of immigrants and of area occupied by them to total population and area, of their methods of enumerating the Anophelines, and, indeed, of comparing the effects of any of the possible factors. It is evident that immigration and allied factors may have some results, but it is necessary to calculate /iozv much compared with those of other influences. Without some attempt at exact quantitative estimates, the scientific study of the diffusion of malaria is as impossible as that of the diffusion of heat. Many similar medical papers on the subject have the same deficiency. (21). Examples: Mauritius, Isniailia, Clairfond, Britain. — In section i reasons were given for the opinion that malaria might have been comparatively scarce, or entirely absent, in Greece and Italy before the historic period, and that after about 550 B.C. it probably increased greatly in amount. This theorem can scarcely be proved ; but I will now describe briefly the similar events which have occurred within the memory of living persons in Mauritius and Reunion. The island of Mauritius, situated about 550 miles (885 kilometres) east of Madagascar, and lying just within the southern tropic, covers an area of 705 square miles (1,825 square kilometres), rises to a height of about 600 metres in the centre, from which it slopes down more or less gradually o 2IO MALARIA IN THE COMMUNITY [Sect. to the sea. The climate is the usual tropical marine climate, warm, equable and humid, and the vegetation is rich. Dis- covered in 1 507, it was peopled by Dutch and then by French settlers, who were always introducing slaves from Africa and Madagascar. In 18 10 it was taken by the British. The slaves were set free in 1834, and from next year onward an immense importation of coolie labour from India com- menced and continued. Thus more than 20,000 coolies were introduced in each of the years 1843, 1854, 1858 and 1865, and in 1859 no less than 48,377 were imported. Quite certainly large numbers of these immigrants must have been infected with malaria, yet, equally certainly, no endemic malaria occurred in the island all this time. I examined the point with the utmost care for the purposes of my Report to the Government [1908], looked through endless returns and studied the voluminous evidence placed before a Com- mission of Enquiry. A. Davidson [1892] and many other writers have reached the same conclusion. In Saint-Pierre's classical novel Paul and Virginia (1789) no mention is made of malaria in the island. Dr Lorans, the late lamented Medical Director, who always lived there, informed me that there was none when he was a boy. At that time the planters and whites lived in houses scattered all over the country, and they and the British troops and officials lived entirely free from local infection. Relapses of malaria and other fevers such as relapsing fever, were, of course, noted among the immigrants, but the malaria did not spread, though a few medical men suspected the existence of occasional sporadic endemic cases since (?) 1857. In 1865, however, a small outbreak commenced in a marshy district near the capital, Port Louis. Next year the epidemic reached the capital, and in 1 866- 1 867 attained alarming proportions. It was like an epidemic of plague or cholera. One quarter of the inhabitants of Port Louis died from all causes in 1867, and 6,224 out of a population of 87,000 in one month (April). The whole 3o] EPIDEMICS IN MAURITIUS 211 death-rate of the island rose from 32/1000 in 1866 to 120/1000 in 1867, the total population being 360,000. The disease spread in two years all over the lower parts of the island, and has remained, and probably increased, ever since (section 32). In the sister island of Reunion, 125 miles distant, precisely similar events occurred at the same time. There also there had been no previous endemic malaria in spite of the intro- duction of slaves from Madagascar and of Indians from India. How explain this extraordinary and terrible event, which shattered existing notions about malaria? The present carrier is P. costalis, an African, not an Indian mosquito. If it had existed in the islands in large numbers the epidemic would have commenced long previously — certainly with the beginning of the copious Indian immigration, thirty years before its actual commencement. If it had existed in small numbers, below the endemic limit, it ought still to have spread the disease to some extent, according to the reasoning in (16); but most authorities denied that this occurred at all before 1865. More- over, on both these suppositions, the chances are that the epidemic would not have commenced simultaneously in both islands, especially because the Indian immigration into Mauritius was much greater than that into Reunion. I can only conclude, therefore, that P. costalis was introduced from Africa or Madagascar simultaneously into both islands, probably by the same vessel, a year or two before the epidemic ; that it spread rapidly and soon multiplied over the endemic limit ; and that from this point the success and ultimate permanence of the malarial invasion was assured. Of course the inhabitants would not be able to distinguish the new-comer among the swarms of innocuous mosquitos already present, and there appears to be no reason why, after being once introduced, it should not have reached the endemic limit of numbers in a year or two. This therefore appears to be wholly a case of the Anopheline factor. The 212 MALARIA IN THE COMMUNITY [Sect. human factors had been present for at least thirty years without causing the disease. A similar case is that oi Isviailia (section 53). Situated on the Suez Canal in the desert, it remained free from malaria until the fresh-water canal was completed in 1877, when malaria appeared almost immediately. Since then the disease con- tinued to increase with fluctuations, until it was banished in 1902 by proper mosquito reduction. Here again the outbreak was probably due almost entirely to the Anopheline factor. A more difficult case is that of an outbreak in the neighbourhood of Clairfojid Marsh in Mauritius (section 30 (i) map), already frequently mentioned. This marsh existed on a plain 1,400 feet (427 metres) above sea-level, and the epidemic is described in my Report [1908] by Dr de Chazal who had been practising in the neighbourhood since 1890, and by myself, and also by Major Fowler [1908]. The history is as follows : — Before 1903 Dr de Chazal, who lived not far from the marsh, had observed a few cases of malaria, but only among Indians. In that year, however, cases began to occur among well-to-do people living in the neighbourhood, and the epidemic now developed rapidly. The cases at the neighbouring dispensary were as follows : — 1904 1905 1906 1907 346 843 1,147 1,487 and similar rises in the cases of malaria at seven other dispensaries, situated not far away, also occurred. In 1906 the British soldiers in barracks (see subsection i) began to be affected. In 1908 Major Fowler and I witnessed an epidemic of seventy-one cases in January among these troops, and on making a house-to-house visitation, found a spleen rate of 241/339=71%, and an average spleen of 4-12 among the Indian children living round the marsh. The disease was being carried by P. costalis, which our " moustiquiers " found 3o] MALARIA IN BRITAIN 213 with considerable difficulty, and not by M. mauritianus which abounded round the marsh. The marsh was now drained by the Government ; quinine was simultaneously distributed in the houses by ourselves and a dispenser; and the epidemic ceased. How explain it? The marsh had been there as long as any one could remember, and P. costalis, though it prefers sea- level, had probably been breeding in it in small numbers all the time. Indians as well as the richer classes had been living near at hand, and imported cases had certainly been common. Why, then, did not the epidemic commence before? Up to ig02 the population round the marsh had been comparatively scarce, but in that year a great increase of Indians took place owing to the advent of a regiment of Sepoys, and many of these Indians built huts close to the marsh waters. Here, then, might be a case of creation of a focus of high endemicity ; but still I find it difficult to explain the focus without supposing an increase in P. costalis, pari passu with that of the human popula- tion. The case is most probably explained by an increase due to more abundant food in the new huts built close to the marsh, according to sections 29 (7) and 30 (9 and 12) ; and possibly by an increase in the biting factor, due to the growth of the village nearer to the marsh. The disappearance of malaria from Britain has been ably described by G. H. F. Nuttall, L. Cobbett and T. Strangeways- Pigg [1901]. The observers made a careful study of the former distribution of the disease in Britain, and of the present dis- tribution of the Anophelines. The two coincided to some extent — that is, the malaria was within the Anopheline area, but not so extensive. The disease, formerly severe, began to decline early last century, but still lingered on until about 1850. I was "clinical clerk" in St Bartholomew's Hospital in 1879 to a woman with greatly enlarged spleen and characteristic fever, who lived in the Fen Country and had never been out of England. Since that time endemic malaria has entirely 214 MALARIA IN THE COMMUNITY [Sect. vanished from Britain, with the exception of two cases among soldiers (footnote, section 14).^ The three British AnopheHnes are A. maculipennis, A. bifurcatus and A. nigripes. They are all capable of carrying malaria, but Theobald thinks that the first will not bite man in Britain. The authors conclude that the disappearance of malaria has been due {a) to reduction of AnopheHnes by drainage ; {b) to reduction of population by emigration ; and ic) to the use of quinine. I think that {h) is not sound. The disappearance is almost certainly due to the reduction of the Anopheline factor by drainage below the endemic limit, even in the Fen Country, and also to enhancement of the recovery factor by the more general use of quinine. I wonder, however, whether there has been any change in climate, and also whether glass windows have been used more since the beginning of last century. Many other examples might be cited, but the reader will doubtless prefer to consider them for himself. (22). Possible errors in the study of endejnicity. — One is very apt to find the local endemicity too high in comparison with the local number of AnopheHnes to be found in houses. In 1897, in an intensely infected plantation near Ootacamund, India, I found during several visits only one Anopheline (the first I ever saw), although I searched the houses myself and offered the people rewards — and this was at the height of the malaria season. In fact there were so few mosquitos of any kind that I began to doubt the whole mosquito theory (just before the discovery of the zygotes). The local carriers were probably " wild " mosquitos which I did not know how to look for; or else I may have missed the principal hatching-out season. At Clairfond ten trained " moustiquiers " could procure only a few P. costalis every night. We must never assume, ^ Sir Cliftord AUbutt tells me that he saw numerous cases in Cambridge in i860. Nuttall, Cobbett and Strangeways-Pigg verified a case at Norwich in 1898 [1901, P- 31]- 3o] SOURCES OF ERROR 215 without clear proof, that the number of insects seen or caught during a few hours' or days' search affords any exact measure of the number actually present during that period — still less of the number which may be present at other periods. It is often observed that the malaria ratio is high where there appears to be little breeding-surface — that " dry " places seem often to be more malarious than " wet " ones. But we have no right to assume that the carriers always breed more in the deep or permanent pools which constitute " water- logging " than in the shallow, evanescent rain-pools which are often the only waters found in the dryer areas. The latter may perhaps give a much larger output at the proper season than the former can yield all the year round (sections 29 (8) and 30(1)). In some cases the Anopheline factor is probably truly below what we might expect from the malaria ratio ; but such cases may be due to extraneous infection (19), or to immigra- tion from neighbouring areas of high endemicity (16, 17). Statements are frequently made to the effect that though the number of Anophelines in a locality is large the malaria ratio is small — as, for instance, the case reported by Celli [1902]. Here again we must not assume that the number of Anophelines actually found during a few days is an exact measure of those existing all the year round. We have, perhaps, done the counting just at the moment when the insects happened to abound. Or, on comparing two localities, we may have been concerned with a domestic species or variety in the locality where the insects appeared to be more numerous, and a wild species or variety in the other locality. Even where it is proved by continued observation that the Anophelines do really average a high figure where there is little malaria, this will merely suggest that some of the other factors are unsuitable ; for example, the local insects may belong to an immune strain. Thus we have never succeeded in infecting the A. niaculipcnnis round Liverpool from infected sailors. 2i6 MALARIA IN THE COMMUNITY [Sect. In fact those who pretend to study the correlation between the AnopheHne factor and the malaria rate are very prone to make two mistakes : (a) they often fail to consider deeply enough the principles involved, and (b) they are apt to base startling " discoveries " on quite insufificient random-sampling — an error into which, according to Professor Karl Pearson, medical men frequently fall. So far as the human reason enables us to judge, there must be some correlation between the two quantities. When, therefore, we are told — as we frequently are, especially in India — that so-and-so has not observed any such correlation, we naturally look for the detailed figures of his investigations ; and when we find, in place of these, mere statements of opinions and impressions, we naturally infer that it is not the principles which are worthless, but the observations. A person who thinks to settle such difficult questions merely by running from village to village, catching a few Anophelines and examining a few people, can have little knowledge of the nature of scientific evidence. To yield any worthy results at all, the enquiry would demand the most careful and continuous study of all the factors concerned (sections 29 (4), and 31). A mistake frequently made is to suppose that there must be some correlation between the number of Anophelines exist- ing on a given day and the total percentage of infected persons. But the former will tend to influence only the inoculation rate of the future. The total percentage of infected persons will depend upon past factors which may no longer exist. They are often, or generally, connected, but not necessarily always so. Equal errors may be made regarding the measurement of human malaria. For example, the disease is often supposed to be specially prevalent among soldiers, coolies or prisoners ; but this may be merely a statistical error, due to the fact that these classes are under more careful supervision than the general public is. {2^. I have attempted to examine as carefully as possible 3i] OTHER POSSIBLE FACTORS 217 the principal factors concerned in the spread of malaria, but may have overlooked several of importance. The effect of immunity, both among men and Anophelines, deserves much closer study. So also do many questions connected with difference of species of the parasites. It is by no means certain that immunity against one species confers much or any against another. If this is the case, many epidemics may be caused merely by the entry of a species not hitherto pre- valent in a locality ; and the simultaneous prevalance of all three species may lead to a much more serious fever rate. Koch observed [1900] that comparative immunity against quartan seems to have little effect against the other parasites ; but I am not sure that reaction against an existent invasion in a person will have very much effect against a new infection even by the same species. The effect on the local malaria rate of desertion of marshy areas (9) should be similar to that of drainage, and must not be forgotten though it is not often witnessed. Conversely, the effect of approximation to a marsh, as when people come and settle near one (for example, the Clairfond outbreak just described), should be similar to the effect of increase of marsh. Obviously it will come to the same thing if we bring a marsh close to human habitations, or bring human habitations close to a marsh. 31. The Measurement of Malaria;— In section 26 I gave definitions of the terms malaria rate, endemicity, and inoculation rate. We have now to consider how these and other estimates can best be obtained for a given population inhabiting a given area. Note to begin with that we can never obtain any such rates exactly ; and also that the degree of approximation to the truth must always depend on the amount of time and labour we have to spare for the task. Our estimates may be of two kinds, actual or comparative. Comparative estimates are those which seek to compare the 2i8 MALARIA IN THE COMMUNITY [Sect. proportion of infected persons in the same locality at different times, or in different localities at the same time. It may often be much easier to obtain comparative than actual estimates. Let us consider first the different possible methods, and then the respective values of them. (i). The parasite rate and index. — By malaria rate or ratio I mean the percentage or proportion of people who really contain living plasmodia at some given moment — not those who show symptoms. By parasite rate I mean the same thing. Now in section i8 (8) and (9) it was shown that an average man contained about 3,000,000 c.mm. of blood, and that a quarter of an hour is required to examine 1/50 of a c.mm. under the microscope. Thus in that time we can search only 1/ 150,000,000th of a man's blood. In other words, if there are less than 150,000,000 parasites in the patient's blood the chances are that we may not find one, even after a quarter of an hour's search. Hence we can never hope to ascertain with certainty whether a single patient does or does not contain plasmodia, and can therefore certainly never discover the actual parasite rate of any number of people. By parasite index I mean the percentage of persons in whose blood plasmodia are found after fifteen minutes' ^ search — that is, of persons who contain more than about 50 plasmodia to I c.mm. To ascertain even this is a laborious task, requiring for 100 people twenty-five hours' continuous work. Obviously the parasite index must always be less than the parasite rate. What ratio will the latter bear to the former? We do not know. Out of 100 infected persons perhaps only 60 or 70 may contain more than 50 plasmodia per I c.mm. of blood at a given moment. But this is a mere guess, and no accurate studies have been made on the point. The ratio certainly varies largely, but as we do not know it with certainty, the parasite index gives no exact inform^ation ^ Some authors are satisfied with five or ten minutes' search. 3i] THE PARASITE INDEX 219 regarding the actual parasite rate. It gives valuable informa- tion, however, on one point. Every person in whom parasites are found is certainly infected. Hence the parasite index gives at least the viinimuni possible percentage of infected persons — that is, we know that the actual parasite rate cannot be lower tha^i the parasite index. For comparative estimates the parasite index is still more useful, because in them we deal only with ratios from time to time or from place to place. Thus if it has varied from say 20^ to 55^ in two large aggregates of persons examined, we may infer that the actual parasite rate has varied to a similar amount. We do not know what that actual parasite rate was, with the parasite index either of 20% or of 55%, but we conclude that its variation has been, ceteris paribus, similar — that is, from 20% to 55//. As originally observed by Koch and Stephens and Christophers, confirmed by Ziemann, Plehn, Annett, and Button and many workers, the parasite index varies greatly according to age, being generally highest in children (9). Hence comparative estimates must be based on a study of persons of the same age. Race, quinine treatment, and social status seem also to have considerable effect. The method is open to several sources of fallacy. The skill of the observer may make a difference of say 20% or more in the results obtained ; and the time employed in the search for plasmodia is very important. In 1906 I obtained a number of slides of blood from Greek children, and since then these slides have frequently been given for study to the classes of the Liverpool School of Tropical Medicine. On every occasion that this has been done, one or more of the students have discovered parasites in specimens in which they had not been previously found ! In making exact comparative estimates it is therefore necessary to employ observers of the same skill, and to fix the time during which the search must be made. 220 MALARIA IN THE COMMUNITY [Sect But the principal weakness of the method is due to the fact that, owing to the labour involved, only a comparatively small number of people can be examined — so that the error of random sampling is likely to be very large. Thus, suppose that we have examined 50 specimens for 15 minutes each, costing 12-5 hours' work (exclusive of collecting and staining), and have found plasmodia in 25 specimens, we have no right to infer that the parasite index of all the people in the locality will be 50%. The chances are, by Poisson's formula (8), that if we examine another 50 persons we may find parasites in any proportion of them from 30% to 70% — the error being 20%. Thus, if the same observer, using precisely the same methods, examines 50 different persons on two occasions, and finds 25 infected on the first occasion and 35 infected on the second occasion, he still has no right to assume that the actual parasite rate {i.e., the malaria rate) of the locality has risen between the two examinations. The method is probably capable of much improvement by quicker means of microscopic diagnosis (sections 65 (i) ). (2). The spleen rate and index. — This method has been in use for a long time. We know that the spleen enlarges sufficiently to be detected by palpation in a considerable proportion of infected persons. Such enlargement is dis- coverable with certainty and in a few seconds by the fingers pressed under the ribs of the left side, and any one — hospital assistants, nurses and laity — can detect it. The persons to be examined are passed in a line before the examiner, while another person records the results ; and with good manage- ment 100 people can be thus inspected in an hour. Or else we can do the work by house-to-house inspection. In section 22 I gave the results of a "spleen census" of 31,022 children in Mauritius, and of 92,258 children in Ceylon — so that very large numbers of people can be studied by this method. It is open to the following defects : — {a) The enlargement may be so slight in a small proportion 3i] THE SPLEEN INDEX 221 of cases, especially early infections, that it may be overlooked in them if we use palpation only. Generally, however, there is fever, or a history of recent fever, in such cases. {b) The spleen of healthy infants is sometimes so easily palpable that the unskilled observer may think that it is enlarged, {c) Not all infected persons show palpable splenomegaly. {d) Not all splenomegalous persons are necessarily infected. {e) Other diseases, such as kala-azar and various anaemias, cause splenomegaly (section 22) ; but the former is limited to certain tracts of country, and the latter are too scarce to affect large statistics. Generally speaking, widespread splenomegaly is due to malaria. The advantages of the method are : — {a) That the enlargement can be detected, practically with certainty and in a few seconds, by almost any one. {b) That the method can be applied with little trouble to enormous numbers of people, thus practically avoid- ing the error of random sampling. I have never known rupture of spleen to follow palpation ; but the possibility of this must be remembered. We must note that a smaller degree of splenic enlargement can be detected by pe^xussion (as practised by medical men) than merely by palpation. By the former method we can nearly always detect some enlargement in malaria. Thayer [1898] claims that it always occurs. Mannaberg says [1905] that out of 132 cases of different types, "cachexias omitted," he found it in all but one case — in 15 cases (11*4^ of total) by per- cussion alone, and in 116 (88%) by palpation also. Thus the finer art of percussion added nearly one-eighth more to the number of cases disclosed by palpation. Laveran agrees as to the frequency of this symptom, but other authors give lower 222 MALARIA IN THE COMMUNITY [Sect. percentages. It is probably often a question of care in examination. Among sailors treated at the Royal Southern Hospital of Liverpool, palpable enlargement is not very frequent. Many writers give percentages without actuals — that is, nearly worthless figures. L. M. Hope [1904], in a study of 1784 cases, microscopically verified at Pabna, Northern Bengal, states that in 374, or 20%, the spleen was not palpable ; but .she does not state whether the remaining cases were studied by percussion. In 102 Greek children examined by me (4), the spleen was palpable in 48, and parasites were found in 12 which showed no enlargement (by palpation only). Probably, careful percussion would have disclosed some enlargement in all of these cases. On the whole, then, I think we should conclude that some degree of splenic enlargement probably exists in 95-100% of all persons infected with malaria ; but that the enlargement \s, great enough to be palpable only in about 75-90/^. The reader should note this difference between enlargements detectable by palpation or by percussion only. In public health work, which demands the examination of large numbers of people in order to avoid error of random sampling, careful percussion is not generally practicable, or, at least, practised. Thus by the term splenic index, I generally mean the per- centage of persons in whom enlargement is detectable by palpation only. In order to determine the spleen rate accurately, it is necessary to use careful percussion on all persons in whom no enlargement has been found by palpation. If such persons are numerous this may add considerably to the time required for the investigation — say two or three minutes for each person. Another important point has to be considered. We have no right to assume that the parasites are still present in all the cases of enlarged spleen, especially in the older cases with large chronic splenomegaly. Such cases may have become parasite- free by establishment of natural immunity ; but we can never know in how many the parasites have absolutely vanished, or 3i] COMBINED PARASITE AND SPLEEN INDEX 223 have only declined in numbers below the limit at which we can readily find them. In what proportion of persons with enlarged spleen are there no Plasmodia at all ? It is impossible to say ; but we may give 20^ as a rough conjectural estimate. Suppose, then, that 20% of persons with parasites have no palpable enlargement of the spleen, and that 20% of those with palpable enlargement of the spleen have no parasites — or, at any rate, that the two percentages, whatever they may be, are about equal. It then follows that the palpable spleen rate, or splenic index, will give a nearly exact measure of the per- centage of infected persons — that is, of the actual malaria rate of the locality. But at present this theorem, which would be one of great practical importance, is based only on conjectural estimates. Lastly, we must note that the spleen index is probably modified considerably by local conditions, quinine, and the age of the people examined (sections 22 and 31 (9)). (3). Combined parasite index and spleen index. — If we have time we can use the parasite index and spleen index combined. The people should be divided into four classes : ia) those without enlarged spleen or detectable parasites ; {b) those with both ; and {c) and id) those with one but not the other. Thus out of 102 children examined in Greece, we found : — Moulki Parasites only. 5 Spleen only. 23 Parasites and spleen. 12 Nil. 22 Total 62 Mazi . 7 4 9 20 40 Total .12 27 21 42 102 Now if we use the term endemic index (section 26) to denote the percentage of persons in whom malaria is diagnosed by a7ty method, then the endemic index of Moulki at that time was 40/62=64-5%, and of Mazi was 20/40=50%. Provided that we know that the splenomegaly is due only to malaria, and also have time to work out the parasite index, this combined method 224 MALARIA IN THE COMMUNITY [Sect. is obviously more exact than either method by itself. Thus in both these villages together, the parasite index by itself was only 33/102 = 32^, and the spleen index by itself only 48/102 = 47%; while the combined methods give a general endemic index of 60/102=59%. It is important to note that in this example, while the cases with enlarged spleen numbered 48, those with parasites, but without enlarged spleen, numbered 12, or 1/4 of the spleen cases. If this proportion applies generally, the endemic index will be found by adding 25% to the spleen cases. (This figure is, however, too high by the results of Mannaberg and Hope just quoted.) Again, the cases with parasites numbered 33, while those with spleen but without parasites numbered 27, or 9/ 11 of the parasite cases. If this proportion holds generally, the endemic index will be found by adding 82% to the parasite cases. It would thus seem that the spleen index is much nearer the truth than the parasite index — provided that the spleno- megaly is really due only to the malaria. Lastly, we observe that the figures both at Moulki and at Mazi are too small to enable us to make exact comparative estimates of the malaria rate of each village ; and we should probably have done better if we had abandoned the parasite index and had spent the time at our disposal in examining the spleen of every person in the villages. Moulki, on the plain of Kopais, contained 350 people, and Mazi, several hundred feet above the plain, contained 575 people. The figures were obtained in May to June [1906], at the beginning of the malaria season. The number of persons with parasites hit without spleno- megaly seems to me an important figure, because such cases are probably due to recent infections, before the spleen has had time to become enlarged — especially in children. There were no less than 12/102=11-8% of such in these two villages, 3i] AVERAGE ENLARGED SPLEEN 225 suggesting that the spring infections had already commenced. The weather was hot, and A. maculipennis plentiful. (4). Average spleen and average enlatged spleen. — By the parasite index and spleen index, or by both combined, we attempt to estimate the percentage of infected persons in a locality ; but further information can be obtained by recording the degree of enlargement found. For this purpose I suggested in Mauritius [1908] a figure which I call the average spleen (section 22). The observer notes whether the size of the spleen, as roughly estimated by palpation, is unity, or about three times, six times or nine times the normal size — these sizes being called normal, or small, medium or great enlargements. He then multiplies the number of persons found to possess each class of enlargement by i, 3, 6, or 9 as the case may be, adds the products together, and divides by the total number of persons examined. Thus in Mauritius we found, out of 30,137 children of fifteen years and under. Normal spleens Small enlargements Medium enlargements Great enlargements Total 19,711 4,381 3,479 2,566 30.137 Thus the average spleen for children in the island works out at 2'54 times the normal size. Another figure, which I call the average enlarged spleen, is found in the same manner, but without considering the normal spleens ; that is, multiply the small enlargements by 3, the medium enlargements by 6, the great enlargements by 9, add the results, and divide by the total number with enlarged spleen. In the above example, the average enlarged spleen was 5'48. Obviously, according to the rough standards pro- posed, this figure must always lie between 3 and 9. These estimates require a little more time to obtain than the simple spleen index, and should generally be attempted only by medical men. I think that one minute a person will 226 MALARIA IN THE COMMUNITY [Sect. suffice. The information given is more detailed, but also more open to error, since different observers may have different ideas as to what constitute small, medium or great enlarge- ment respectively. The degree of enlargement probably depends considerably upon the factors given in section 22 — racial, social and climatic factors, and age and treatment of the sick. That is, two popula- tions with the same actual proportion of infected persons may have different average enlarged spleens, the difference depending on these factors. The average spleen depends, not only on the degree of enlargement, but also on the proportion of infected persons (general malaria rate), and may be looked upon as an index of the average amount of illness caused by malaria in the community. The average enlarged spleen indicates only the degree of enlargement where it exists. Several useful deduc- tions may be drawn from the figures. Thus numerous small enlargements would tend to indicate many recent infections ; and numerous large ones with few small ones, a past epidemic. The comparative figures for Mauritius may be taken for a standard, as malaria has prevailed constantly there since 1866. The species of parasite may have considerable influence on the degrees of enlargement. C. F. Craig [1909] thinks that the malignant parasites produce most enlargement ; but L. M. Hope [1904] found that in 43 great enlargements malignant parasites occurred in 10, benign tertian in 9, and quartan in 32 (some of the infections being mixed). The study of the splenic enlargement, so important for public health work, has been curiously neglected in medical literature. (5). The fever rate and index. — By fever rate (daily, monthly, annual) I mean the percentage of persons who really have malarial fever during a given period ; by fever index, I mean the percentage of those who have been ascertained to have it. The index must be always lower than the rate. Even 3i] THE FEVER INDEX 227 with soldiers, gaol prisoners and indentured coolies the most careful supervision would be required to detect all the slighter cases. Among troops the bad custom still remains of enter- ing in the books only the more severe cases — which are said to be admitted to hospital, while the slighter cases are only detained. This quite falsifies the malaria statistics, and is due only to bad administration. Besides this, many soldiers disdain to come to hospital for slight attacks. If this is the case among these classes, then we can imagine how difficult it would be to estimate the fever rate among a large civil population. If we could do so, however, we should have a fairly exact measure of the malaria rate — since every infected person probably suffers more or less from illness during at least some part of his infection. But we have no measure of the ratio between the rate and the index. Probably the former is often two or three times the latter, even in the case of troops. But, while it gives little exact information regarding the actual malaria rate, the fever index is still useful. The admissions into military hospitals, civil hospitals and hospitals of gaols and plantations, are generally fairly correctly diagnosed by medical men, and give some idea of the great amount of sickness caused by the disease. The same is true of the large number of attendances for malaria at out-patient departments and dispensaries. The figures are valuable for comparative estimates of variation from time to time or place to place. Both for admissions and attendances, the actual numbers of patients admitted or attending any hospital are not very useful, as they may be influenced by the popularity or accessi- bility of the institution ; but the ratio of admissions or attendances for malaria, compared with those for all causes, is always important, not only for comparative estimates, but because it shows the relative importance of malaria compared with all other diseases. It gives us some basis for fixing the proportion of the public funds which should be expended on 228 MALARIA IN THE COMMUNITY [Sect. the prevention of the former, according to the general sanitary principle enunciated in section 38 (4), namely, that that propor- tion should depend on the relative importance of the various diseases. For example, in Mauritius during the seven years 1900- 1906 we had the following figures : — Average population 384,676 a year. Average admissions for all causes . . 18,761 „ Average admissions for malaria alone . 4,348 „ Thus malaria caused nearly one-quarter (2 3"2%) of the total admissions. Moreover, in the year 1907 alone there were 79.053 attendances for all causes at all the hospitals and dispensaries in the island, and of these 28,294, or 3 5 "8%, were reported as due to malaria. This is an example of the general law that the attendances for malaria are greater than the admissions (in comparison to total attendances and admissions). Obviously only the more severe cases of fever seek admission into hospital, and a much larger proportion of all malaria cases content themselves with mere attendance for advice and medicine. In India in 1901 (before quinine was much given), out of 300,847 troops and prisoners 108,860, or 36-2%, were admitted for malarial fevers ; and these admissions constituted, according to the official figures, 37% of the admissions for all causes. I take this year at random ; and it will be seen on inspection of similar statistics in most tropical countries that similar figures hold roughly from place to place and time to time in most of them. As a very broad general rule we may state that in most, or at least many, malarious countries about one-third of the total population considered require medical treatment for malaria every year ; and also that malaria is responsible for about one- third of the total attendances at hospitals and dispensaries. Or, to be still more general, we may put both these ratios at some- thing between one-quarter and one-half 31] THE CONSTANTLY-SICK INDEX 229 Of course, error in diagnosis vitiates the figures to some extent. Thus many cases of fever are not malarious at all, but may simply be classed under that heading by careless or overworked observers. The symptoms of the disease are, however, so well marked that I doubt whether the total error produced in this manner is really very large — say over 5%. On the other hand, the error of random sampling for the purpose of obtaining a parasite index is often very much larger. M. Watson (section 57) has used hospital statistics well for showing the comparative fall of the malaria rate in drained areas. While the admissions from the drained areas fell rapidly, those from the surrounding undrained territories con- tinued as before. The clinical thermometer may be used more than it is for estimating the endemic index. It could easily be employed together with examination of the blood and the spleen. (6). The constantly -sick rate and index. — By these terms we mean the average proportion of people who are actually ill with malarial fever at a given moment — or who are found to be ill (index). Thus in India in 1901, out of 60,838 European troops, on the average 666, or i'09%, were always ill with malaria — that is, almost the effective strength of a whole regiment. In Mauritius, Dr Bolton, Medical Officer of the Immigration Department, estimated for me that during the malaria season in the most malarious sugar plantations as many as 20% of the total male adult population may be sick from malaria alone on one day. As the malaria season is often also the busiest agricultural season, such a figure means an enormous loss of labour. These estimates are important because they afford some measure of the economic loss due to the disease. Thus in India in 1901 the European troops lost 666x365 = 243,090 working days during the year, besides loss due to death and invaliding, and loss of capacity for war. But as a rule the estimates can 230 MALARIA IN THE COMMUNITY [Sect. be obtained only for troops, coolies of factories and plantations, and prisoners. For the general population we can have no definite figures, and can only calculate them on the basis of the former classes. The average duration of a case can be obtained from the constantly - sick index (or vice versa) from the following formula : — Admissions x average duration = constantly sick x days in year. In India the average duration of a case of intermittent fever among European troops is about two weeks, and of remittent fever about four weeks ; but this, of course, means only the residence of the men in hospital, and takes no note of relapses. The figures will be found in Table IV of the Indian statistics. (7). Malarial death-rates. — In most malarious countries medical certificates giving the cause of death are not demanded. Hence in such countries the public statistics are not reliable as regards the cause of the mortality — that is, we can have no confidence in the number of deaths attributed to malaria in the tables. We can often, however, obtain valuable informa- tion by calculation from the figures of general mortality ; but this subject requires to be dealt with separately (section 32). (8). Random sampling. — Nothing has caused more mistakes in the literature of malaria, and indeed of most medical and sanitary subjects, than ignorance of the great error in reasoning which may be caused by insufficient random sampling. Suppose that we desire to ascertain some general law regarding a large number of objects. Then the only exact way to ascertain the law would be to examine all the objects. Suppose, however, that we have no time to do this ; then we must content ourselves with the attempt to ascertain the law approximately by examining samples. We must take the samples quite at random, and must examine enough of them. Obviously, if the total number of objects is large, we shall obtain no correct deduction by examining only one, two, 3i] RANDOM SAMPLING 231 three ... of them. The more of them we examine the nearer we shall come to the exact truth. Suppose, for example, that we wish to ascertain the pro- portion of leucocytes in a patient which belong to the mono- nuclear variety. We may be very far from the truth if we examine only two or three leucocytes ; nearer if we examine twenty or thirty, or two or three hundred, and still nearer if we examine two or three thousand ; but we can obtain the exact truth with certainty only if we examine all the leucocytes in his body. So also if we wish to know the parasite index in a locality — that is, the percentage of people in whom plasmodia can be found after, say, quarter of an hour's search. If we examine only two or three persons we may be very far from the truth ; we shall come nearer and nearer to the truth by examining more and more of the people ; but we can obtain the exact truth with certainty only by examining every person in the locality. If we have time to examine only some of the people we can obtain only an approximation to the truth. It is a gross error in science, and yet one which is very frequently made, to suppose that this approximation is the truth itself. Take for example the case mentioned in (i) above. Suppose that there are 10,000 people in a place, and that out of 50 people examined we have found the parasites in 25. Then we are quite truthful when we say that the parasite index of the 50 people examined is 50% ; but if we presume to argue, on the strength of this small random sampling, that the parasite index of the whole locality, containing 10,000 people, is 50%, we make a gross scientific error, and say what may be absolutely untrue — what, in fact, may be not even near the truth. Similarly, if we try to estimate the number of Anophelines in this locality by counting them in only a few houses we may make another error equally gross. Lastly, if, after making two such errors, we next proceed to argue that 232 MALARIA IN THE COMMUNITY [Sect. there was no relation between the parasite index and the number of AnopheHnes in the locality, we may perhaps come to a wrong conclusion ; but, whether our conclusion is right or wrong, we shall certainly convict ourselves — well, not exactly of scientific competence ! This error is frequently made tacitly in medical literature by recording only percentages, without giving the actual number of objects examined. For example, an observer says that 40% of a patient's leucocytes were mononuclears, or that 20% of the people in a place showed plasmodia, without stating how many total leucocytes or people were examined. Such statements have no meaning whatever — except that the man who makes them is ignorant of this simple law of reason- ing. A reader cannot judge the value of a writer's deductions unless he knows the actual facts from which those deductions were drawn. Where a writer merely gives a percentage in this manner, we cannot be sure whether he has not deduced it from a study of only a few objects. But we are sure of something else, namely, that he is not acquainted with the methods of accurate reasoning, and are therefore forced to doubt the value of all his deductions. It is necessary to make these somewhat severe remarks, if only in the hope of saving the waste, occasioned by this common mistake, of otherwise excellent work. The reader will now remark that it is impossible to examine all the leucocytes in a patient's body, or all the people in a large district. How many must we examine in order to approach sufficiently near to the truth ? This question belongs to the domain of statistical science and cannot be discussed at length here ; but it is advisable to give the well-known Poisson formula for statistical error, with an addition made by Professor Karl Pearson, the amended formula being particularly useful for the measurement of malaria. Let N be the total number of objects, such as all the leucocytes in a patient's body or all the people in the locality 3i] ERROR OF RANDOM SAMPLING 233 under consideration. Let n be the number of these actually examined (say 200 leucocytes or persons) ; and let / be the number of these found during the examination to belong to a special class — suppose that/ =100 mononuclear leucocytes or persons found to contain plasmodia. Then p\n will be the corresponding ratio among the objects examined — that is, it will be 1/2, or 50^, in the examples referred to. But we have no right to infer that the same ratio will hold for all the N objects under consideration. Let e denote what is called the error, and ^^ the percentage of error. Then by the Poisson- Pearson formula, o/_200 l 2p{n-p) I n-\ Examining this formula, we shall see that when n = N, that is, when we examine all the objects under consideration, the factor i—{n— i)j(N'— i) = o, and the whole error vanishes ; that is, we obtain the exact truth. But if n is small compared with N, this factor, and therefore the error, becomes larger. If A^ is very great, as when we are considering all the leucocytes in a patient or all the people in a large district, the same factor approximates to unity, making the error large — unless n can be correspondingly increased. Thus if, out of 200 leucocytes examined, 100 are found to be mononuclears, then, since N is very large, (;?— i)/(iV— i) = o ; so that ^%=^ioo=io. That is, the error is 10%. We might have inferred, after finding 100 mononuclears out of 200 leuco- cytes examined, that the same proportion (50% mononuclears) would have held for all the leucocytes in the patient's body. But we have no justification for this assumption. The probability is that if we examine another 200 leucocytes, the proportion in this second batch may be anything between SO%+io% and 50%— 10%, that is, may vary from 60% to 40%. All that we can infer, then, from the small sample of leucocytes examined by us, as to the exact truth regarding all the leucocytes in 234 MALARIA IN THE COMMUNITY [Sect. the patient, is that the percentage of mononuclears probably lies between 60% and 40% — a very different thing from the 5°% which we might, ignorantly, have assumed to be the proportion. Now suppose that we have to deal with a village of 800 people, and that we have examined 200 for plasmodia and have found these in 100 of them. Here the factor I -(;«— i)/(iV— i) = about 3/4, and the other factors=io as before. Hence ^^= 5^3 = 8*65. Thus, while the parasite index of the 200 people actually examined is 50%, that of the 800 people in the village may be anything from 5o+8"65% to 50-8-65%; that is, from 58-65% to 41-35%. Suppose, however, that in the same village we had examined only 40 persons (as a recent Indian writer recommends) and had found plasmodia in 20. Then the percentage of error — 5n/i9==2i-8, and the parasite index of the village will not be 50%, as the unwary student might imagine, but anything between 71-8% and 28-2% — a very ambiguous result. Yet we are often asked to accept important theories on figures like these. The following square roots may be useful : — Square root of 2=i*4i Square root of 12 = 3-46 3=1-73 13 = 3-60 5 = 2-24 14 = 3-74 6 = 2-45 15 = 3-87 7 = 2-64 „ 17 = 4-12 8 = 2-83 „ 18 = 4-24 , 10 = 3-16 19 = 4-36 11 = 3-32 „ 20 = 4-47 The error tends to be larger when the percentage of objects belonging to the particular class is near 50% of the total number of objects examined, than when it is a low or high percentage. We must therefore examine, for example, more leucocytes to obtain the percentage of mononuclears than to obtain that of eosinophiles ; and more people if the parasite 3i] AGE AND THE MALARIA INDEX 235 or spleen index is near 50% than if they are very small or very large. (9). Variation of the malaria index according to age. — It is now generally accepted that amongst the natives of a per- manently malarious locality the signs of infection — parasites, fever, enlarged spleen — are generally much more frequently found in children than in adults. From this we infer that the individual can acquire natural immunity against the disease. So far as I can ascertain, this fundamental law was first discovered and stated by C. W. Daniels as the result of his study of a large number of autopsies in British Guiana [1895]. He found that the frequency, not only of simple enlargement of the spleen, but also of the malarial pigmenta- tion of the organ, varied from age to age. Both enlargement and pigmentation were absent in the bodies of infants less than one month of age ; became more and more frequent in bodies of children up to five years of age, in about 80% of whom they occurred ; and then became progressively less frequent with advancing age. These results were obtained from 1,289 autopsies on natives of the colony or of other malarious places — mostly negroes and East Indians. But different figures were recorded from 205 autopsies on persons, chiefly negroes, who were born in non - malarious places, and had come to the colony in early adult life. In nearly all of these the symptoms occurred shortly after arrival, and then fell in frequency with age, but never to so low a figure as in the case of the natives. The following are the curves for the negroes and East Indians. (See page 236). Daniels remarked, " It is, I think, clear from these figures that malaria is, amongst those exposed (to it) from childhood, a disease of early life. ... In adult life, amongst them, it is rare ; whilst amongst persons of the same race, but not exposed in childhood, it is common in adult life. This, it seems to me, can point to only one conclusion, viz. : that immunity is acquired by a class (that is, natives) in the course 3i] AGE AND THE MALARIA INDEX 237 of exposure to the infection in this district for some twenty years ; and, from the evidence of its frequency (evidence persisting for variable periods, in some cases for years), that this immunity is probably acquired by previous attacks." Daniels also observed that the spleen is frequently found to be enlarged, and very much enlarged, without showing any pigmentation at all, and inferred from this that there might be some other cause besides malaria for the enlargement. In my study of kala-azar [1899] I came to the erroneous conclusion that it was nothing but severe chronic malaria. Arguing from Daniels's observations, I thought that the un- pigmented enlargement of the spleen in this disease was due to numerous previous attacks of malaria followed by partial immunity and natural elimination of the pigment (plasmodin). Kala-azar is now known, of course, to be caused by another parasite ; but I still think that the pigment may be eliminated in cases of malaria after the parasites have died out — thus explaining its absence from old malarial enlargements. A little later, R. Koch observed that the parasites can usually be found more frequently in children than in adults, and suggested the examination of the blood for measuring malaria. His figures are given principally in his third Report [April 1900]. At Stephansort, out of 734 persons the parasites were found in 157, or 21-4%. In Kaiser- Wilhelm-Land, at Bogadjim, out of 22 children of under five years, the parasites were found in 13, or 59^ ; while none were found in 86 persons of over five years in age. At Bongu, out of 19 children under five years, the parasites were found in 12, or 63^; out of 17 children from five to ten years, in 4, or 24% ; and out of 39 persons from ten to forty-five years, in none (note, large error of random sampling). Almost at the same time, Christophers and Stephens published similar figures regarding studies in the Gold Coast [June 1900]. They state that in four places the parasite index found by them was 90, 75, 71 and 23% among " babies" ; 57, 50, 238 MALARIA IN THE COMMUNITY [Sect. 75, 20% among children up to eight years; 28, (?), 30, (?)% in children up to twelve years ; while children over twelve years showed parasites very rarely. They give no actuals. During the same year, Annett, Button and Elliott made a survey of the parasite index in ten places in Nigeria [1902]. The collected results were as follows : — Ages O-I 1-2 2-3 3-4 4-5 5-6 6-7 7-8 No. examined n 46 49 47 41 23 30 25 No. infected . 10 29 31 24 20 8 2 II Percentage 27 63 63 51 49 35 7 27 Ages 8-9 9-10 10 + 0-5 5-10 10 + Total No. examined 16 14 40 220 108 40 363 No. infected . 4 •^ 4 114 27 4 145 Percentage 25 14 10 52 25 ID 40 The figures agree well with those of pigmented spleen rates given by Daniels. There is a curious drop at the 6-^ age. The authors' tables are well compiled ; but the numbers for the separate localities are too small to furnish definite results, Panse [1902] gives the following figures for Tonga, East Africa : — Ages . o-\ i-i I 2 3 4-5 6-7 ^^^^" Adults Total o - - J t J / grown. No. examined 16 9 25 20 28 48 84 314 1,683 2,227 No. infected .6 6 22 17 25 34 52 125 258 545 Percentage • 37 67 88 85 89 71 62 39 15 25 Craig gives for Camp Stotsenburg, Philippines [1909] : — Ages 1-5 5-10 10-15 Adults Total No. examined .... 40 54 53 45 192 No. infected .... 30 20 13 28 91 Percentage • • ■ • 72 37 24 62 47 Similar figures are furnished by various authors, but the number of children examined is generally too small to yield reliable results. Often only percentages, which are, of course, almost useless, are given. The comparative frequency of enlarged spleen in children has been known for a long time — certainly in India; but much more exact work on the subject remains to be done. Craig well remarks [1909] that there are certain "rules 3i] AGE AND THE MALARIA INDEX 239 governing immunity." In heavily infected localities, where nearly all the natives are probably infected and re-infected in childhood, nearly all the survivors must be partially immune in adult age. On the other hand, where only a smaller propor- tion of the natives become infected in childhood, many of the remainder may be attacked for the first time at later ages. This must be especially the case where there are seasons, such as a sharp winter or a hot dry season, during which infection ceases. I notice, for instance, that the law of Daniels is not much insisted upon by Italian workers. From these considerations an important deduction, exactly opposite to the common opinion, may be drawn. Where there is much malaria, so many of the native adults will be immune that few of them should show signs of infection ; and, conversely, where the adults are frequently attacked, the amount of malaria should be comparatively slight. In other words, if the malaria index amongst adults (parasites, fever, splenomegaly) is high, the malaria rate of the locality is probably low ; and where the adult hidex is low, the rate is probably either high or low. If, there- fore, a considerable number of adults are coming to hospital with fever or enlarged spleen, we should believe, not that the malaria rate of the population is usually high, but that it is usually low — comparatively, of course. If malarial immunity were complete, and if every one were infected in childhood, no one would be ill afterwards. For example, if many soldiers in a regiment are attacked, we may infer that they have not been recruited from very malarious districts. Unfortunately, however, we are not sure {a) how far immunity derived from a single infection protects against subsequent infec- tions, and {b) how far immunity against one species of parasite protects against other species. Thus many partially-immune adults may suffer from short attacks of fever due to re-infection, especially by parasites of a species different to the one to which they have become habituated. Practically, therefore, for the purpose of the measurement of 240 MALARIA IN THE COMMUNITY [Sect. malaria, it is best to consider only the malaria index among children. Among adults the malaria index cannot yield very definite results : if high, it indicates that the malaria rate is comparatively low ; if low, that the malaria rate is either very high or very low. The study of large numbers of children is required to establish the age at which the malaria index is highest. Most of the figures suggest that that age is between one and three years. Similar studies are required to determine the age of maximum average spleen, and of maximum enlarged spleen. (lo). Determination of the inoculation rate. — According to section 26, the malaria rate of a locality is the percentage of the people who, at the moment of enquiry, contain plasmodia. But as many of these people must have been inoculated weeks, months or years previously, the malaria rate does not directly inform us as to what is going on at that moment — it instructs us regarding the past rather than the present. We may wish to know how many people are actually being inoculated during the week, month or year of observation ; and if we can ascer- tain this we can obtain a measure of the actual nialariousness of the locality at the moment when we are investigating the malaria in it. This could be ascertained experimentally if we could dis- tribute throughout the population a large number of healthy, non-immune immigrants, and could then observe accurately how many of them become infected within a given period : or if we could observe a large number of non-immune immigrants, and learn how long, on the average, they remain healthy. Such studies can sometimes be made with adults ; but, unfortunately, Nature herself is always carrying out the experiment for us by providing a constant influx of non-immune babies, and we have only to ascertain the proportion of them which have become infected within a week, month or year after birth. In his original article [1895], Daniels stated that in 43 infants who had died under one month after birth pigmentation 3i] THE INOCULATION RATE 241 of the spleen could not be found ; that it occurred in I2"5% of 16 infants of one to six months of age, in iiy of 14 infants of six to twelve months, and in 50% of 1 1 infants of one to two years of age. From these figures we gather that in British Guiana at that time the chances were small that infection should occur within one month, and increased by about 2^ roughly for every month after birth — so that the chances were that about 50% of all newcomers would become infected in two years. Meanwhile, however, immunity would tend to reduce the cases. Of course, with such small actuals, the error of random sampling is very large. R. Koch in his third Report [1900] states that in nine localities in Java, the parasites were found in 6y, or 11^, out of 619 infants of under one year examined ; and in 47, or 8"i^, out of 574 children of over one year of age. The infantile malaria index can easily be obtained by the parasite test or spleen test, or both combined, and, with large actuals, will give a good direct measure of the inoculation rate. But it will be still more useful if compared with rates calculated according to sections 27 and 28. As before, let p be the total population, and m and m^ the proportion of infected persons at the beginning and the end of the enquiry respectively. Then at the beginning of the enquiry there were nip infected persons and {\—iii)p healthy ones. Now let rnip be the number of infected persons who recover during the enquiry — suppose that r=\l^ and that the enquiry lasts one month; and let I{i—m)p be the number of healthy persons who become infected during the enquiry. Then by section 28, equation 4, m^p = mp + /( I — in)p — rmp or, /( I — m)p = in^p — mp + rmp Thus suppose that, in a village of 1,000 people, there were 250 infected persons at the beginning of the month and 300 infected persons at the end of it. Then, obviously, though 50 infected persons recovered during the month, there was Q 242 MALARIA IN THE COMMUNITY [Sect. nevertheless an increase of 50 infected persons at the end of it; so that 100 healthy persons must have become infected during the month. That is, I{\ — ni)p — \oo. Here I={nt~^ — m-\-rin)j{i—m), and is the inoculation ratio; that is, it gives the proportion of people, healthy or unhealthy, inoculated during the enquiry. In the above example /= 10/75 = 0'i33. Out of the 750 originally healthy people in the village 100 were newly infected, and out of the 250 previously infected people 33 were reinfected {Imp gives the number of reinfections); so that altogether 133 persons out of 1,000 were inoculated during the month. The inoculation rate of the village was /x 100= 13*3%; that is, the chances of a new- comer in the village, or of a new-born child, becoming infected during the month was as 13*3 to 100. From equation i of section 27, we might infer roughly that there were about 106 Anophelines to each person in this village. In fact, on comparing that and the following section, we see that /= b^saint. The fractions m, m^, I and r are connected by the equation m^ = m + I{i—m) — rm; and if we can ascertain any three of them we can calculate the fourth — which enables us to com- pare observed and calculated estimates. If the malaria is static, so that nt-^ = m, then I{i—vi) = rm. We may now esti- mate / from the infantile malaria index, w from the general malaria index, and r from statistics, and check our results by comparison. Suppose, for example, that r= 1/5 a month, and that 4% of the infants are infected in a month ; then the general infection rate of the locality should be about i6-6%. Comparing these figures with observed estimates, we shall probably arrive nearer to the truth than if we had relied on calculation or observation only. (11). Practical conclusions. — Having considered the various methods of measurement which may theoretically be adopted, it remains for us to select the best ones for practical use. A. First suppose that we wish to form an Actual Estimate 31] PRACTICAL CONCLUSIONS 243 of the Malaria Rate ; that is, of the percentage of people who contain plasmodia at the moment of observation. We may employ {a) the parasite index, {b) the spleen index, and {c) the combined methods. {a) The parasite index gives exact information only as to the lowest proportion of infected persons. The proportion of those who contain plasmodia in numbers too few to be found during the time allotted for the test may be very considerable, and has not been correctly estimated. The test requires a skilled observer, and the expenditure of so much time that it can be applied only to com- paratively few people. The error of random sampling is therefore generally very large. {b) The spleen index (by palpation only) can be quickly ascertained, by almost any intelligent person, for large numbers of people — so that the error of random sampling may often be reduced nearly or really to zero. A certain proportion of infected persons have no palpable enlargement of the spleen, and possibly in others with palpable enlargement (especially with great enlargement) the parasites may have died out in consequence of immunity ; but by the penultimate paragraph of (2), these two sources of error (amounting to say 20% each) will tend to annul each other, so that the spleeji index should be a nearly correct measure of the true malaria rate. Quinine, local conditions and other diseases (especially kala-azar) may affect the spleen index, but in most countries probably only to a small extent. Percussion of those who show no palpable enlargement will reveal a greater proportion of cases ; but with this test the infected non-spleen ratio will not be balanced by the non-infected spleen ratio — so that percussion may give a ratio further 244 MALARIA IN THE COMMUNITY [Sect. from the truth than that given by palpation alone. Percussion will also demand more time and skill. (c) The combined methods (on the same persons) will yield a greater malaria index than each method by itself — often a much greater one than that given by the parasite index by itself, and a considerably greater one than that given by the spleen index. If, how- ever, Laveran, Thayer, Mannaberg and others are right in their opinion that some enlargement of the spleen can be detected by percussion in almost all infected persons, then the combined parasite index and spleen index (by palpation alone) can yield little more information than that given by a careful spleen rate ascertained by percussion. The combined method will, however, require much more time, and will give no exact information regarding the non-infected spleen ratio. Subject to correction, then, I conclude that, as a general rule, the spleen index (obtained by palpation only) is by far the best method of measurement. It requires no great skill ; it can often be applied to almost all the people in a place ; and it should yield by itself a very correct measure of the actual malaria rate. As a rule, local conditions, race and other diseases are likely to cause a percentage of error far smaller than that due to the insufficient random sampling which must almost always attend the laborious estimation of the parasite index (the advocates of which frequently overlook this important point). But of course, in the presence of other widespread causes of splenomegaly (kala-azar or some unknown cause), the spleen index by itself will not be so reliable. Practically, therefore, it comes to this, that we must avoid two principal sources of error, (a) the possibility that the local splenomegaly may be due to other causes than malaria, and ih) the great error of insufficient random sampling. For the former purpose we must first satisfy ourselves, by the study 3i] PRACTICAL CONCLUSIONS 245 of hospital records (especially of autopsies), by consultation with local physicians, and by the blood examination of selected cases, that the local splenomegaly is really due to malaria. For the second purpose, if the first point is established, we should rely upon a large spleen census. The time required for a laborious study of the parasite index will generally be much better spent in extending the spleen census so as to avoid large error of sampling ; and the combined method will only occasionally be required for some special purpose, such as ascertaining the infected non - spleen ratio, or the infantile malaria index. We must, of course, always consider the season, the time allotted for the work, the amount of assistance available, and the population and area to be examined. For large populations the parasite index becomes almost impossible. Not the least advantage of the spleen index is that it can be applied equally well to a population of any size. B. TJie actual infantile malaria rate. — This is especially valuable by (10) for determining the inoculation rate. It can often be obtained among infants on estates and factories, in soldiers' families, and in many villages. As, however, infants up to one or two years of age are not always very numerous among small populations, and the information required is important, it is generally advisable and possible to use com- bined methods for examining them. The ages should be obtained as accurately as possible for each month for two years, and the infants examined as regards spleen, parasites, fever, anaemia and history of illness. The information obtained should be compared with the formula at the end of (10). If we assume, as argued above, that the general spleen index practically coincides with the general malaria rate, and denote the spleen ratio by S and the infantile ratio by /, then the formula becomes S^^S-^l{\-S)-rS 246 MALARIA IN THE COMMUNITY [Sect. If 5^ = 5, r=i/S a month, and / is a monthly infantile rate, then we should have /=5/5(i-5). It is, of course, best to examine, if possible, all the infants and to compare their numbers at different ages with the numbers given by, or calculated from, the last census of the population. C. Comparative estimates from time to time or place to place. — For these we adopt the same methods according to the same principles. But we can now often utilise the valuable information given by the attendances at hospitals and dispen- saries (5). That is, we obtain the ratio of attendances for malaria to attendances for all causes, and compare them from time to time or place to place. Remember that, for comparative estimates, ratios of indices should, ceteris paribus, be equivalent to ratios of actual rates — which makes the task much easier. The conduct of the malaria census will be referred to in connection with the whole campaign (section 40). 32. The Mortality and Cost of Malaria. — A little considera- tion will convince the reader of the difficulty of this part of the subject. The term malarial death-rate should mean the percentage of persons who die of malaria. Such rates can easily be obtained in the case of plague, cholera and other diseases in which the cause of death can be generally assigned with certainty ; but malaria is a benign and protracted disease which is often complicated and terminated by other maladies, such as pneumonia, infantile diarrhoea, dysentery, ankylostomiasis, and so on ; and it is often, perhaps usually, impossible to say whether death has not been due as much to one of these complications as to the original infection. Even with troops and prisoners the cause of death in such cases is often ascribed to one or the other cause on the evidence of the most predominant symptoms at the end. Even if we admit the correctness of the diagnosis as regards 32j MORTALITY OF MALARIA 247 deaths in hospital, still the hospital case mortality is no correct guide to the total case mortality, because only the more acute cases among the general population come to hospital at all. Probably the great majority of malaria deaths occur among the children of the poor, and in the tropics these are seldom brought to hospital, or even attended by medical men. The fact that in most tropical countries the cause of death is not necessarily certified by medical men adds still more to our difficulties. Indeed the so-called malaria death-rates given in many statistics are not even worth looking at. The parasites of malaria cause death in two ways : (a) by direct action, and (d) by enfeebling the constitution. Deaths by direct action probably occur only in " pernicious attacks." Celli (section 20 (6) ) records that 330 pernicious attacks occurred in 33,507 cases — about 1%, and of these probably only a fraction were fatal. W. H. Deaderick collects many useful facts in his text- book [1909], and gives records of case mortality amongst them. Out of 5,109,001 cases collected from twenty-five writers, 148,055 or 2-89% died (I judge that these were mostly severe cases treated in hospital). Out of 27,039 cases of perm'a'ous malaria, recorded by thirty observers, 7,205, or 2&6'y^ died. Out of 6,037 cases of blackwater fever (one of the most pernicious forms), 1,268, or 21% died. In India for 1907 we have the following figures (combining intermittent and remittent fevers) : — Strength. Admissions. Deaths. Malarial mortality%. Case mortality%. European troops . 69,332 10,662 14 •020 •13 Native troops 126,392 28,432 84 •066 •30 Prisoners 93.264 17,841 88 •094 •51 The highest malarial mortality here given, that of the prisoners, may be put at about i/iooo; but we can see at once that this is sure to be too low an estimate for a large general population. Troops and prisoners live in cleanly sur- roundings, are well housed, well fed, well treated in hospital, 248 MALARIA IN THE COMMUNITY [Sect. and (still more important) are all adults. Moreover, in my experience, medical men rarely attribute death to malaria alone unless there are no very marked complications. The rate amongst a large, poor, general population, including children, is therefore likely to be several times greater. But we have no figures to indicate the difference. As just mentioned, the deaths attributed in public statistics to malaria are generally worthless in the tropics, as they are not even certified to by medical men. They are often much too high, because the perplexed registrar has no other cause to give when dysentery, cholera, fits or debility fail him. For example, in Mauritius the deaths attributed to malaria con- stituted 14 per mille, or about half of the total mortality. In 1899, however, the medical certification of deaths was enforced in two districts of the island — with the result that the mortality ascribed to malaria fell in them at once from 45^ of the total deaths to only 25^. From this we calculate that quite 20^ of the general mortality was wrongly ascribed to malaria. But even with this correction many sources of error remain. Is there no better criterion of the true malarial death-rate.? In most civilised countries to - day the total death - rate is correctly reported : we may therefore obtain useful information by comparing the total mortality in various areas which differ in possessing or not possessing malaria, but which are alike in other respects. Take, for example, Mauritius (malarious) and the neighbouring Seychelles Islands (not malarious). n- •,• f Population Mauritius ^ ^ ^ , I Death-rates Seychelles] P^P"';^^^^" I Death-rates Difference For the seven years 1897 to 1903 the mean death-rate in the Seychelles was only lyi per inille against 347 in Mauritius. If the whole of this great difference is to be ascribed to malaria 1904 1905 1906 Means 387,395 386,128 383,206 385,576 32'2 40 "6 40'o 37-6 20,418 20,767 20,976 20,720 i6-i 15-0 i6-5 15-9 i6-i 25-6 23-5 217 32] MORTALITY 249 alone, we must suppose that the true malarial death-rate in Mauritius may average something like 20 per mille per annum or more — that is, a mortality exceeding the total mortality from all causes in the Seychelles and in most British towns. The figures are accurate, the deaths being carefully registered both in the Seychelles and in Mauritius, and the islands have a very similar climate. But in the mountainous Seychelles there are few or no Anophelines as in Mauritius. The population of the former, however, is of negro origin, and in the latter of Indian origin and much more dense. The following are some figures for ten other neighbouring islands of the Indian Ocean — all not malarious. The popula- tions were those of the census taken in 1901, and the death- rates were the averages for the following five years. Rodrigues, 3,437. I9'3; ^i^go Garcia, 526, 27-0; Agalega, 327, 31-2; Peros Banhos, 184, 24-0; Coetivy, 143, 36*4; Salomon, 119, 32*0; Six- Islands, 117, 29-0; St Bratidon, ?,y, 55*3; St Jean de Nove, 75, i6'0 ; Eagle Island, 74, 43-0. Total population, 5,134. Average death-rate, 31-5. Owing to the smallness of the population in the lesser islands the statistical error is large; but the mortality in some of them, in spite of the absence of malaria, appears to be as great as that of Mauritius. There is, however, an important difference. In Mauritius, the Seychelles and Rodrigues good medical attendance is available, but this, I understand, is not the case in the other islands, where syphilis, beri-beri, infantile tetanus, bowel complaints, ovarian and uterine diseases abound, and deaths in child-birth are common. Excluding these islands, therefore, the difference as regards the mortality between Mauritius with malaria, and Rodrigues and the Seychelles without it, remains a striking one. The large malarious island of Reunion (negroid popula- tion) has a mortality similar to that of Mauritius. The entry of malaria into Mauritius in 1866 is interesting in this connection (section 30 (21)). All deaths in the island have been registered since 1831. In the thirty-six years from 250 MALARIA IN THE COMMUNITY [Sect. 183 1 to 1866, the average death-rate was 35*3 per mille in a population varying from 93,000 in 1831 to 365,000 in 1866. In the next five years the death-rates were 120*5, 567, 35'0, 22*6 and 44' i respectively; and in the forty years from 1867 to 1906 they averaged 357 — almost the same as before the entry of malaria. Thus, apparently, while the disease caused a great increase of mortality for two years after its entry, it has caused no increase whatever since then ! In my report [1908], however, I have discussed this anomaly. As Dr Meldrum suggested, the extraordinary low mortality of 1870 was possibly due to the death from malaria of many persons in 1867 and 1868 who would otherwise have died in 1870. The high death-rate before the entry of malaria was probably due to many epidemics of measles, small-pox, relapsing fever and cholera, and to the immaturity of medical and sanitary practice in those days. Since the entry of malaria there have been few of such epidemics, and medical and sanitary practice have greatly improved, while vaccination has been rendered compulsory — so that the death-rate should have fallen to the low level found in Rodrigues and the Seychelles. Hence we may perhaps assume that it has not fallen because of malaria. In other words, the disease has counterbalanced all the successes of medical science against other maladies. The late Dr Meldrum, Director of the Meteorological Observatory in Mauritius, and an experienced statistician, study- ing the monthly death-rates from all causes in Mauritius before and after the entry of malaria, observed that they differed in an important particular. Before the malaria entered they remained roughly the same from month to month ; after it entered the curve rose markedly during the malarious months. In the Seychelles and Rodrigues the monthly rates still remain uniform as in Mauritius before malaria entered. The following table gives the population and number of deaths. S2J M( aRTALI TY 251 Average population. Januar)'. February. March. April. May. June. Seychelles. 1901-04 19,442 31 28 27 30 26 33 Mauritius. 1861-66 345,275 1,003 936 987 920 972 898 1870-89 353,958 790 809 1,005 1,043 1,118 1,059 1904-06 376,974 1,012 981 1,307 1,314 1,357 1,262 Average population. July. August. Sept. Oct. Nov. Dec. Seychelles. 1901-04 19,442 30 23 26 27 26 25 Mauritius. 1861-66 345,275 970 971 947 970 910 967 1870-89 353,958 1,004 893 783 759 718 740 1904-06 376,974 1,597 1,284 1,125 1,089 1,285 909 In the first two lines the monthly deaths are fairly uniform ; in the latter two they are lowest in November or December, before the malaria season, and highest after that season. Meldrum also enunciated another law based on the careful study of Mauritian statistics, namely, that the highest death- rate generally occurs about two months after the heaviest rain- fall. But the figures for other countries show that there may be many disturbing factors — heat, cold and epidemics. Never- theless, Meldrum's laws should be used, together with other data, in the study of local malaria death-rates [1881, 1890], We should endeavour to ascertain the average ordinary mortality, exclusive of epidemics, during the non - malarious months, especially those just before the commencement of the increase probably due to malaria. The difference between this average and the total mortality during what we have reason to suppose are the months of malarial mortality should give some rough indication of the amount of the latter, S. R. Christophers has recently suggested [1910] that rises in the total mortality, 7ninus other epidemics, should indicate epidemics of malaria. They should also indicate endemic variations. But of course in all such studies an accurate knowledge of local circumstances — climate, rainfall, other diseases — is required. So far as I can see the only method by which we can hope 252 MALARIA IN THE COMMUNITY [Sect. to ascertain the increase in the general mortality really due to malaria would be to undertake a careful comparison of the death-rates and spleen rates over a large area and for a con- siderable period. The task would be a suitable one for all Health Departments, and ought to have been performed long ago — if only to determine that fundamental question, the actual amount of mischief caused by the disease. In 1898 I proposed to undertake such a survey in Mauritius, and collected a number of figures from the sugar estates [1898]. Unfortunately, the death-rates could not be obtained for the period during which the spleen rates were taken ; and other fallacies invalidated the data. In section 22, however, the rates are given for the various districts of the island. The healthiest district, Moka, showed a spleen rate of 4-4% and a death-rate of only \%"] per milk, while Black River had a spleen rate of 567% and a death-rate of 39*5% (on the estates). This again suggests — as we saw from a comparison of Mauritius and the Seychelles — that malaria, when severe, may actually double the general mortality. But before accepting such an appalling estimate I should like to see the subject worked out step by step — I should like to know for several countries and races the rise in the mortality step by step for every rise of 10% in the spleen rate. Until this is done we remain merely in the clouds of medical conjecture. What precisely is the economical loss to the community caused by malaria ? — From the preventive point of view this is perhaps the most important question before us ; because, obviously, it governs the question of the expenditure which may be demanded for the anti-malarial campaign. In order to answer it we must know {a) the real malarial mortality ; {b) the constantly sick rate (section 31 (6)); and {c) the local values of human life and labour at various ages and in various social classes. Considering the importance of the theme, I had hoped to give here a detailed estimate ; but I find that the data are quite insufficient. We do not know even the real death-rate, 32] COST 253 much less the death-rates at various ages ; and the values of life and labour vary so much that different estimates must be prepared for each country. Many such estimates have been attempted. I will mention here as an example only one by Dr Bolton, Medical Officer of the Immigration Department of Mauritius (because I have already given so many statistics of that colony). There are about 39,CX)0 adult male coolies on the sugar estates, of whom about 15% are incapacitated by malaria for three months in the year. That is, more than 500,000 days' work is lost annually. The day's work is worth 1/4 rupee to coolies and 5/4 rupee to the planter ; so that the coolies lose about 125,000 rupees and the planters about 625,000 rupees per annum, or 750,000 rupees altogether. Besides the males there are about 8,000 women working on the estates, and, at the same rate, these lose 108,000 days' work, worth 21,000 rupees at 0"20 rupees a day. Similarly, outside the estates, there are 30,000 Indian coolies, earning 0*5 rupees a day ; and these lose about 20,250 rupees a year. Thus the workers lose about 166,250 xn^ees per annum, and the employers considerably over 650,000 rupees. With hospital and other expenditure Dr Bolton estimates that malaria costs Mauritius, with its population of 383,000, about 1,000,000 rupees a year (a rupee is about 1/15 pound English) — that is, about 2*6 rupees per head. Enhance- ment of wages, cost of invaliding, and loss of market are not considered. Similarly, L. O. Howard estimates that malaria costs the United States $100,000,000 a year (section 41). See also section 65 (9). CHAPTER VI PREVENTION 33. List of the Possible Preventive Measures. — One advantage of the malaria formula given in section 28, equation 4, is that it enables us not only to name the various preventive measures, but also to obtain some quantitative estimate of their relative utility. Suppose that an anti-malaria campaign is contemplated in any locality, and let m be the proportion of infected persons at the beginning of the campaign, and m^ be the proportion at the end of a given period. Then by the formula ■)n^ — in + U'-saii^ i — m)ni — rm. Hence m will be less than m^, that is, the malaria will be reduced, if we can make suitable modifications in the factors b, J, a, /, V. Such modifications can be made in various ways, as follows : — The biting factor, b, represents the average proportion of Anophelines which succeed in biting individuals. We have roughly estimated it at 1/4. Obviously, if we diminish this fraction we shall diminish the malaria in the locality. This can be done in many ways. The use of ordinary mosquito-nets, of wire-gauze to the windows and doors of houses, oi punkas and fans (which drive away the insects), of culicifuges, that is, substances which, when applied to the skin, tend to keep them off, and even the use of smoke, woollen clothing and bed cover- ings, must all tend to have the desired effect. But, of course, if we hope to reduce the malaria throughout a considerable 254 Sect. 33] POSSIBLE MEASURES 255 population, such measures must be adopted by a sufficiently large number of people. No appreciable effect will be pro- duced on the general malaria rate if only a few persons take the trouble to use them, because d expresses the average pro- portion of insects which succeed in biting. The next factor in the equation is s, which denotes the proportion of insects that succeed in maturing the parasites, and which we have generally taken at about 1/3. This factor depends principally upon the species factor of the local Anophelines (section 30 (11)). Certain species certainly suc- ceed in maturing the parasites more easily than others do, and, moreover, it has been suggested that certain foods inhibit the growth of the organisms in the insects, while cold also does the same thing. I fear that we are unable to modify this factor by itself. The next factor, a, denotes the number of different Anophelines to each person, and can be modified by any of the measures adopted for mosquito reduction ; that is, the adult insects may be killed by hand, or by various culicicides, or perhaps by the introduction of enemies, such as certain bats or birds. Or the larvae may be destroyed in numbers of ways, such as emptying out the water containing them or applying larvicides of various kinds, or introducing certain fish or beetles. Or the breeding of the insects may be checked by removing water suitable for their larvae or the weeds in which they often flourish. Or the locality may be rendered unsuitable for a given species of Anopheline by doing anything to modify the conditions which that species loves, such as removal of forest or undergrowth. Lastly, reduction of the biting factor, b, may tend to reduce the total mosquito density, according to section 29 (7). The factor i denotes the average proportion of infected persons whose blood contains the sexual forms. This can be modified to a certain extent by the careful treatment of the patients — though we must remember that quinine does not 256 PREVENTION [Sect. have much influence on the crescents when these are once produced (sections 23 and 65). The factor r denotes the average proportion of infected persons who recover during a given period, and this can certainly be very largely modified by suitable treatment of the sick. It is true that certain authors declare that quinine does not have much effect on relapses (section 23), but in the opinion of a majority of observers early and continued medication certainly produces marked results. Such treatment of persons who have had declared symptoms of the disease should be called case reduction ; but we should observe that a similar treatment may be commenced in persons before they have had any symptoms at all. That is to say, all persons in a locality may take quinine continuously on the chance that they may have happened to have become infected without their know- ledge, and in the hope of checking the parasitic invasion at its very outset. This method of dealing with the disease should be called quinine prophylaxis. For case reduction we treat the sick, for quinine prophylaxis the healthy. It will therefore be observed that we have many preventive measures against malaria ; but the ones given do not close the list. Another important measure is that of segregation. Instead of destroying the local mosquitos or their breeding- places we may segregate ourselves or a number of people from their haunts ; and, obviously, this will have the same effect upon the segregated people. Or we may segregate ourselves or a number of people from the infected area by removal to any locality where the original malaria ratio in is less. The reader will now do well to suppose various values for the factors in the equation and then to calculate that of m^ on these suppositions. Suppose, for instance, that the malaria ratio has been remaining at the static limit of one-half, so that by section 28, equation 4, the number of Anophelines, a, should be about T] to each person. Now suppose that a is reduced to one-half: then m^ falls from 1/2 to 9/20. Next, suppose that 34] BED-NETS 257 b is reduced to one-half: then m^ falls to 17/40 — a slightly lower figure, because the factor b in the equation is squared. Lastly, suppose that r is increased by proper treatment to twice the previous recovery rate of 1/5 : then m^ becomes 4/10 — which is still lower. But if we increase the recovery rate we are likely also to decrease the proportion of persons with gametids in their blood, /. Suppose that if the first is doubled the latter will be halved : then m^ falls from 1/2 to 7/20. Lastly, suppose that several of the factors are changed simultaneously — for example, reduce a and i to 1/2 and double r: then m^ falls to 13/40.^ This subject will be discussed again in section 39, but the reader should familiarise himself at once with the ideas involved in order to understand the following matter. Many of the measures were first named and discussed in my little book called " Instructions for the Prevention of Malaria Fever," and my series of articles in the British Medical Journal, both published anonymously in the autumn of 1899. The principles then laid down by me have since then been repeated in many papers and text-books. We now proceed to examine them in detail. 34. Protection against the Bites of Mosquitos.— (i) Port- able bed -nets. — The bed -net was well known to the ancients under the name oi conopeum (section i). It is now used almost everywhere in the tropics by those who can afford it, and adds greatly to the comfort of life, apart from the prevention of malaria. Long before the connection between malaria and mosquitos became known. General Outram of Indian fame, and Emin Pasha of African fame, and others, attributed their immunity from the disease to their care in the use of the net. In fact, when I went to India in 1881, it was a common saying amongst sportsmen, planters and many residents in that country, that the way to keep off malaria was to use a net under all circumstances. ^ Or we can use the static formula, section 28, equation 7. 258 PREVENTION [Sect. But the net must be used properly, and the following rules carefully attended to: — (a) Not a single rent or hole in the net must be allowed. If there is one, mosquitos, which spend the whole night in exploring every inch of the net in the hope of reaching the sleeper, are sure to find it and enter. Not only should there be no rent or hole, but the net should be so hung that no aperture for entry is left. Thus it should always be hung inside the poles provided for the purpose, and tucked continu- ously all round under the mattress. It should not be hung outside the poles, because then it cannot be tucked in satisfactorily in the manner mentioned ; and it should not be allowed to hang down to the floor unless heavily weighted, because then it is apt to be blown up by the wind, thus allowing insects to enter. Moreover, if it is hung down to the floor, insects which are hiding under the bed during the daytime will often be included. The servant should be instructed to let down the net before dark in the evening, and to see that no mosquitos are inside. If mosquitos do find entry, it is always due merely to carelessness. (d) Do not have any opening for the purpose of entering the net. Such openings are often used in Europe and allow the insects to go to bed with the sleeper. When entering, one should lift the lower edge of the net from the mattress as little as possible and slip in with a twisting movement, so as to exclude stray mosquitos which may have been hovering round outside. If possible, use a large bed and a large net in order to avoid the hands, knees and elbows being pushed against the gauze during sleep, and thus being bitten through the net by mosquitos outside. If no large bed and net are available, this contingency 34J BED-NETS 259 should be guarded against by sewing a loose valance of gauze round the lower part of the net, about 9 inches (23 cm.) above the upper surface of the bed, the valance being tucked under the mattress together with the net. (c) The thread of the netting should not be too thick, as if it is so it will exclude air. The mesh should be neither too small nor too large, the general size fixed being about eighteen threads to the inch (seven to the cm.). No part of the net should be made of any closer texture, as this is quite unnecessary and excludes the air. For example, where, as in India, punkas swing over the bed all night, a top of calico merely excludes the breeze and adds to the discomfort of the sleeper. Of course, where sand- flies i^Siinulidae) are present, the whole net must be made of closer texture, such as muslin or cambric. These insects inflict worse tortures than mosquitos do, and have also been proved to carry a particular kind of fever. The netting should always be white to permit the easy detection of insects. {d) In the great heat of the tropics, the manner in which the net is hung is very important. If it is arranged in thick or loose folds it will exclude the cooling breeze. The net should always be stretched as tight as possible in every direction, in order to allow the air to pass freely through it. In fact, those who complain that they cannot sleep under a net because it stifles them nearly always neglect this precaution. A tightly-stretched net with a thin thread excludes very little breeze. For this reason the pattern of net is important. In my opinion much the best nets are the square ones which are used almost throughout India, and which are capable of being stretched in the manner described. Nets which are bunched up 26o PREVENTION [Sect. at the top and hung from a single rope are much more close and uncomfortable for the sleeper ; but there is a good pattern which contains a circular hoop a yard or two above the bed, permitting the necessary tight stretching. (e) Many patent patterns are advertised, and nearly all of them are good ones. Different patterns are required for fixed domiciles and for travelling. The traveller needs a portable pattern which can be set up very quickly in any locality where he may require to sleep. Bedsteads with attached nets are also on the market, and can generally be obtained locally. Special patterns have been suggested for soldiers and others who have to bivouac in the open air. I generally carry a small square netting which can be hung inside the berths on board ship, because shipowners are still barbarous enough not to exclude mosquitos by wire-gauze at the ports (section 46). (2). Portable mosquito-proof rooms. — These are simply large nets, generally square and capable of holding the entire bed, together with a small table and chair, and perhaps a rotatory fan. Several special patterns are on the market. They are very useful for travellers. Entirely mosquito-proof tents have also been advertised, and should certainly be always used in warm climates. The one difficulty about such structures con- sists in the arrangements for entering ; but in my opinion it is not advisable to provide a special door for doing so, as one can always creep in under the lower edge of the net. (3). Fixed mosquito-proof rooms. — These are found in several colonies, and consist of a wire - gauze chamber supported by wooden uprights fixed in the floor. The mode of entry is by means of a self-closing door. The wire-gauze is in one respect preferable to the cotton netting, as it allows more breeze to enter, but on the other hand mosquitos which have entered cannot be so easily detected against the darker thread of the 34] SCREENING 261 wire. Of course, such chambers are constructed within the ordinary rooms of a house, or in the veranda. I have long advocated the use of them, during very hot weather, either in the open or on the roof of the house. (4). Mosquito proofing of windows and doors. — This has been long in use in the Southern States of America, and has been much advocated by French and ItaHan writers on malaria. The net may be of cotton, but this, of course, soon rots away, so that wire-gauze is always better. I am very strongly in favour of this method of protection, which I have seen in use in Lagos, Panama and elsewhere. It adds greatly to the comfort of life in the tropics. It excludes not only mosquitos, but flies, moths and other insects, bats and birds. It also excludes the glare of the sun during the day, and the damp exhalation rising after heavy tropical showers. At the same time it allows the breeze to enter almost unimpeded. The mesh of the net should be the same as that used for bed-nets. The wire may be either of " tinned iron " or of copper or brass. Roughly speaking, the price of the former is about twopence a square foot and of the latter about three- pence a square foot in British colonies. Some years ago a number of tests were carried out by the Crown Agents for the Colonies on behalf of the British Colonial Office, showing that tinned iron soon rots away in consequence of damp. But I once saw in Lagos a greenhouse covered in entirely with tinned iron wire-gauze which had remained quite sound for more than five years, even in that warm damp climate.^ The question how the gauze should best be applied to the windows has been much discussed, especially by Laveran [1907], who gives many diagrams and pictures. As a matter of fact, the question has generally to be decided according to the form of the windows already existing in a house. The problem is an easy one with sliding sashes. In such cases I advocate that the wire-gauze be permanently nailed, with nails ^ See also sections 46 and 55. 262 PREVENTION [Sect. of the same metal (in order to prevent galvanic rust), outside the window ; that is, if the shutters are hung inside. For French windows, which open outwards on hinges, the problem is much more difficult, because if the wire-gauze is fixed inside, the windows cannot be opened. Many types are adopted in such cases, but they are not always satisfactory. Movable wire- gauze frames which require trouble to put up are sure to be neglected by servants. In my opinion it is best in such cases to refit the windows so that they can be made to open inwards, and then to fix the wire-gauze outside, or vice versa. Further details are better left to the intelligence of the reader. In climates which are never cold, the glass of the windows can be replaced entirely by wire-gauze, thus simplifying the problem. Doors afford another problem. The Italians have long advocated double swing doors with a protected entry, but this is necessary only where the insects abound very much. Automatic swing doors generally suffice. Of course, in order to protect a room or a house completely, every possible orifice, including key-holes, chimneys and chinks round doors and windows should be properly closed or guarded ; but the details are so numerous that it is useless to give them in writing. Wurtz [1907] states that a solution of commercial silicate of potassium in its own volume of water, if painted several times with a brush, without drying between the coats, upon a piece of ordinary cotton netting stretched on a window-frame or elsewhere, will make the netting much stronger and more resistent to water or fire. The painting can be done in five minutes. The solution dries in an hour. The mesh should be large, as the interstices are partially filled by the solution. In this manner cotton netting can be utilised for window and house protection. The suggestion is a very good one and might be developed further. (5). Mosquito proofing of verandas. — This adds largely to the expense of protecting houses, but is, of course, a very great addition to comfort. A large part of the Meteorological 34] CULICIFUGES 263 Observatory in Mauritius was proofed in this manner at the cost of several thousand rupees, and the measure is much adopted in Panama and elsewhere. A much less costly procedure is to protect a single corner of the veranda. This was insisted upon by Sir William MacGregor in Lagos, and is now adopted in that colony. Something of the kind should always be used, as people must have somewhere to sit in during the evening. (6). ProteMon for the hands and feet. — In 1898 many writers advocated protection of this nature. It was suggested that whole armies should go on the march with veils over their faces and thick woollen gloves — a rather difficult suggestion for the tropics. The Italians have dealt with this matter at considerable length, and Laveran quotes and figures the pro- tection given to Japanese soldiers in Formosa and Manchuria. Special boots to protect the ankles have also been recommended. Personally, I think that such means of protection are too uncomfortable for general use, and I much prefer a hand fan (mentioned presently). (7). Medicinal protectives. — Many attempts have been made to find protective applications to the skin. Oil of lavender, of eucalyptus, petroleum, ammonia, powdered sandal-wood, and many patent fluids have been recommended to me for the purpose, but when I have recommended them to others, I have not always received favourable reports regarding them. Laveran [1907] mentions numerous statements on the subject regard- ing sulphur, petroleum, a mixture of tar and oil, and quassia. Vaseline (100 parts), naphthaline (10 parts), camphor (i part) has been recommended ; but he adds that his own experiences were unfavourable with such substances. Fermi and Lumbau [1900] tested many substances without marked success. Celli [1901] states that the old custom of hanging bags containing garlic or camphor round the neck originated in their protective effect against mosquitos. We should observe that experiments on the point must 264 PREVENTION [Sect. be very exact to be convincing ; that the effect of volatile substances is sure to be transient ; and that the use, even of successful protectives, can only be exceptional, as when mosquitos are very numerous, because few people will ever be persuaded to smear themselves constantly with them, and because they would probably affect the skin after a time. Such protectives do not come at present within the domain of practical sanitation. (8). Constant movement. — As a general rule (but not always), mosquitos bite only when their victim remains quiet. Hence I have formed the habit, when in danger of being bitten, of maintaining constant small movements of the hands, feet and head. I find this, together with the use of a hand fan, far preferable to the employment of hot gloves, thick clothing or inunctions. (9). Fans and punkas. — A palm leaf can be purchased almost anywhere in the tropics for a penny, and serves not only to drive away mosquitos, but also to keep the body cool. Fans rotated by electricity or small hot air engines are now frequently used in the tropics by those who can afford them. Punkas consist of a board or canvas stretched upon a wooden framework, hung by one edge from the roof, and swung backwards and forwards by means of a rope or pulley worked by hand labour or (in barracks and hospitals) by machines. The constant movement and the current of air prevent mosquitos biting even a sleeping person. Probably the alternating movement has a better effect for this purpose than the uniform movement of a rotatory fan. The punka should not consist merely of a pole with a fringe of cloth hung from it, because the yielding fringe gives no current of air. (10). So7ue results. — Perhaps the first example of the utility of ordinary bed-nets was cited by myself [22nd July 1899]. In October 1898 a company of the "Boys' Brigade" of Calcutta went to live for one week in a house in Barrackpur Park, near 35] RESULTS OF PROTECTION 265 the River Hoogly. The three officers and a friend slept in bed-nets, but thirteen boys did not. The officers and their friend remained well ; but all the boys, together with a sister of one of them, were attacked a few days later. The first boy attacked, died. Mosquitos were very numerous. Three native servants (without nets) also suffered. In 1899 also many experiments were made on the Italian railways by screening stations and houses of employees. The results were summed up as follows by Celli [1902]. Out of 4,363 completely protected persons, r9^ became infected and 2i'i% had relapses. Out of 5,165 incompletely infected persons 3*3^ became infected and 20^ had relapses. Out of 802 persons protected only during sleep iO'9^ became infected. The local fever index was 40-60^, or even more. Laveran [1907] quotes an experiment among Japanese troops in Formosa, of whom, out of 646 unprotected men, there were 285 cases of malaria, and out of 115 protected men there were none ; and also cites several similar small experiments in Corsica, Algeria, Holland and Senegal. In nearly all of these cases, however, quinine as well as protective screening was used. The experiment of Sambon and Low (section 7) served a useful purpose at the time in advertising the mosquito theory, but there was no very strong scientific evidence that the subjects would have been infected during the experimental period, even without the protection. Further experiments should be performed in order to ascer- tain the effect of mechanical protective measures alone. 35. Mosquito-reduetion. — This can be effected {a) by direct destruction of mosquitos or their larvae, and {b) by rendering houses or localities less suitable for them or for the breeding of them. (i). Destruction of adults by hand. — Large numbers of mosquitos can be destroyed in houses by a very simple device — a small hand-net. This is made for a shilling or two by 366 PREVENTION [Sect. tying a piece of flexible cane or other wood or wire in the form of a loop, to which a bag of white netting about i8 inches deep (4"5 decimetres) is attached. The net must be white and not green, in order to enable us to see the captured insect through the mesh. Any one can easily secure his persecutors by means of it, and thus obtain respite for some time. Sir William MacGregor employed a boy to kill mosquitos in this manner in his house in Lagos in 1901. In lofty rooms a long-handled net may be required to catch the insects under the roof. Colonel Gorgas and Mr Le Prince advocate (sections 42 and 43) the employment of men for this purpose and give examples. I think that every householder should possess such a net and should instruct his servants to use it regularly. The same thing should be done in hospitals, barracks, military camps and jails. Much more could be accomplished by this simple method than has yet been attempted. Boys become very expert at catching mosquitos. The offer of rewards of a penny for fifty Anophelines may quite possibly lead to a large slaughter by village children. Probably, for unit of cost and trouble, more mosquitos can be killed by hand than by fumigation. (2). Fumigation. — This method has long been employed, especially in Italy and the United States. The discovery of the carriage of yellow fever by Stegomyia calopus gave great stimulus to it for sanitary purposes. In yellow fever it is absolutely necessary that every Stegomyia which has bitten the patient should be killed for fear lest it may infect other persons ; and this is rendered easier because the yellow fever patient remains infective only for three days, and because vS. calopus is a domestic insect. But destruction of adults is not so useful for the prevention of malaria, because patients continue to be infective at irregular periods for a long time, and because the carriers are often wild insects (section 29 (4)) 35] DESTRUCTION OF MOSQUITOS 267 which may remain only an hour or two in houses. Hence the expensive and troublesome process of fumigation is not much employed in malaria prophylaxis. Celli and Casagrandi made experiments with many sub- stances [Celli, 1901]. Thick tobacco smoke and chloroform appear to be the best, and have been known for a long time. Sulphur dioxyde, hydrogen sulphide, coal gas, formaldehyde, kill in one to two minutes (but, curiously enough, acetylene gas seems to be quite innocuous). Fumes of pyrethrum powder causes apparent death in five minutes and actual death in eight hours. Numerous agents for the destruction of insects in greenhouses are on sale and are equally effective against mosquitos. Boyce [1909] describes very thoroughly, and with good illustrations, the methods of fumigation practised against yellow fever in America. His recommendations have already been given (section 12). In India fumigation is seldom used : and it would be difficult to apply in the thatched mud huts or leaf shelters of the poor. But I think that destruction by hand could be employed more than it is. Mosquito-traps were also described in sections 12 and 60. Wells, cellars, privies, stables and dark rooms are natural traps in which the insects often congregate in large numbers and can easily be destroyed. (3). Introduction of 7iatural enemies. — Bats, birds, lizards, dragon flies and other flies are known to catch mosquitos ; but whether their presence makes any marked effect on the number of the insects is another question, which, so far as I know, has not been studied. It has been known for a long time that small fish devour the larvae ; and indeed the larvae were used for feeding the fry of British trout introduced into India, in my memory, before 1890. Fish, however, vary greatly in their liking for the larvae. Thus in Mauritius the small gold fish which abound in ornamental waters eat them, but not voraciously. On the 268 PREVENTION [Sect. other hand, I saw in India in 1890- 1899 minnows which would devour a dozen or more in a few seconds and would visibly swell after the meal. The waters of Panama contain a minute fish, less than an inch long, which is equally fond of them, and which thrives in quickly running streamlets. The same is true of the common small fish at Ismailia. On the other hand, large fish often disdain such small prey. I saw a ditch in Calcutta full of small fish and also absolutely thick with mosquito larvae ; and have observed fish and larvae living together in rice fields. Boyce [1909] well describes the larvicidal propensities of Girardinus poeciloides, popularly called " millions," a minute fish probably allied to the one which abounds at Panama. Mr C. Kendrick Gibbons in 1905 attributed to it the immunity of Barbados from malaria. The people keep these fish even in water receptacles, of which Boyce examined sixty without finding larvae. The Imperial Department of Agriculture in Barbados has introduced millions into Jamaica, St Kitts and Antigua. Further references to larvae-eating fish will be found in Chapter VII I.i Tadpoles, Notonecta (the water boatman), and the larvae of several insects eat mosquito larvae ; and indeed the latter are often cannibals. This part of the subject is of great importance and is now receiving considerable attention. Obviously, the success of the measure must depend largely upon the habits of the local malaria carriers — whether they breed mostly in perma- nent pools where fish and their other enemies also can live, or whether they abound elsewhere, as in evanescent rain-water pools. The question depends entirely upon the local con- ditions and requires local study. No cheaper and better anti-malaria measure than the ^ J. Chaytor-White suggests the importation of "millions" into India [1910]. He reproaches me for not recommending the measure for Mauritius. This was due to oversight, and the fish are being introduced. 35] ENEMIES OF MOSQUITOS 269 extermination of Anophelines by natural enemies could be conceived or devised — were such a thing possible. It may be possible in some places ; while for other places we may not be able to find the suitable enemy. Unfortunately, experience proves that animals and plants often survive, even in large numbers, the introduction of their most deadly enemies ; they succeed in finding some refuge or other, and a state of com- mensalism is finally arrived at. For example, Anophelines abound in the Panama Canal Zone in spite of the fish referred to. It is only the academical hygienist who believes that any measure which suggests itself is sure to be practically useful. It may often happen, too, that the expense of main- taining the " enemy " will be greater than that of removing the breeding water entirely. Nevertheless, we should seek what allies we can find.^ It has often been observed that parts of India where M. rossii, which seem not to carry plasmodia, abounds are comparatively free from malaria. Quite possibly it may tend to crowd out other species, thus reducing them below the malaria-bearing limit, although it does not exterminate them entirely. Experiments on this point are much required, and I have suggested them tentatively for Mauritius. The comparative freedom of large tracts where the conditions appear to be favourable must be due to some cause. If we can ascertain the factor we may be able to introduce it else- where (section 30 (10) and (u)). H. Marcus Fernando, in a suggestive paper just to hand [1910], points out that though Colombo, Ceylon, is surrounded by low-lying grass fields, subject to periodic inundations, it is practically immune from malaria. This he attributes to swarms of minnows and other enemies of mosquitos. He states also that very hot dry seasons are often followed by much malaria, simply because they tend to destroy the aquatic enemies of the larvae. These views accord exactly ^ See also section 54. 270 PREVENTION [Sect. with those already expressed in section 30 (i), (6) and (10). So also rice fields are often not malarious — as in Madras town. (4). Destruction of larvae — The methods employed depend on where the larvae are found. For small movable receptacles of water, such as broken bottles and crockery, empty tins, flower - pots, gourds, old buckets and tubs, fire-buckets, fallen palm leaves, etc., emptying out suffices for the moment. But such articles ought to be collected in suitable dust-bins, and the laws regarding the proper deposition of rubbish ought to be strictly enforced. Oiling. — This method, long known,^ was first elaborated as a public health measure in my reports on Sierra Leone [1899]. It is employed wherever the previous methods are inapplicable, or where the water is required for use, or where more permanent measures cannot be adopted at the time — that is, for water butts, metal cisterns of drinking water, wells, garden cisterns, washing waters, cesspits and so on. The method has now become familiar to all. The oil is poured on the water and broken up so that it quickly forms a thin film all over the surface. The larvae and pupae are no longer able to keep the surface by surface-tension and quickly drown — Laveran thinks that the oil chokes the breathing tube [1907]. The oil may be poured on the water out of a tin or kettle, or by means of a special syringe. For small pools, I advocated that each man engaged on the work should be provided with a tin of oil, and a bunch of rag tied to the end of a stick. The rag is dipped in the oil, which is now " painted," on the surface of the pool — but such details are unimportant. It is best to use the cheapest oils in the local market. Refined petroleum spreads rapidly and well, but evaporates quickly. Crude petroleum is cheaper and makes a much more lasting film. For Ismailia I recommended an equal mixture of the two. Celli [1901] said that 0"i c.cm. was the minimum amount required per square metre of surface, but Fermi ^ Howard [1893] and Nuttall[ 1 899]. 35] POOLS AND HOLES 271 and Lumbau [1900] require 5*0 c.cm., and others various amounts. Experiments in vitro are of little use ; and the amount required depends on the quality of the oil, the heat of the sun, the amount of vegetation, dSris, etc., and should be determined locally. Logan Taylor and I found crude creosote to be very useful in Sierra Leone ; it is more deadly, but also much more expensive than crude petroleum. For killing larvae in drinking waters, Strachan recommended me to use eucalyptus or juniper oil. For pools it is advisable, and indeed sometimes necessary, to remove vegetation before applying the oil. My brother, E. H. Ross, described an automatic oiler for cess-pits at Port Said, and Gorgas and Le Prince mention " cotton waste " soaked in oil. Celli and Casagrandi [Celli 1901] and others describe experiments with many substances. Aniline dyes are active destroyers. Gallol and Green Malachite kill to a certainty in solutions of 0'Oi25/iooo and O'25/iooo, and a mixture called " larvicide " appears to be very effective. They diffuse them- selves continuously in water, are not volatile, and do not poison men, cattle, or crops. Celli says that larvicide costs from 12 to 56 lire for destroying larvae in 10,000 cubic metres of water. It is said to have little action on the pupae. Oiling should also be used for the tins of water placed under the feet of tables and meat-safes in order to exclude ants ; and for saucers under water bottles, flower-pots and filters. Small pools of water on the ground, especially those which form after heavy showers, or in rocks along the margin of streams, or in gutters, open drains, and stone water-channels, can often be quickly brushed out, water, larvae, and all, by means of a broom. Holes m rocks and trees are best dealt with simply by filling up with earth or gravel as a temporary measure, or with concrete as a permanent one. Plants which breed mosquitos should be removed if possible. In Mauritius, Bilbergia splendida^ a wild pine-apple with a 272 PREVENTION [Sect. gorgeous flower, was planted in most of the gardens and kept the houses supplied with innumerable Scutomyia notoscripta Skuse, until the wiser inhabitants rooted them up during and after my visit. Cut bamboo stems should be cut again flush with the next knot, or with the ground. Unfortunately, mosquitos often breed in palm trees and sugar cane — in which case I can recommend nothing but grease being applied at the off-shoot of the leaves. The householder has often to determine whether he will sacrifice his plants to his comfort. It is mostly the Qilicines which breed in such situations. Rain-water gutters along the eaves of houses are best dealt with by boring a small hole in the most dependent part of the gutter where the water stagnates. Heavy old metal cisterns, etc, not worth removal, can often be treated in the same manner, (5). The screening of breeding waters, — We now proceed to consider methods for rendering localities or houses less suitable for mosquitos or for their breeding. We will deal first with what I call " minor works." Mosquitos, more especially the Culicines, breed very much in collections of water, such as water - butts, cisterns, wells, cess - pits, etc., which cannot be dispensed with, and which should be so protected that the insects cannot lay their eggs in them. At the same time it is often necessary to ventilate the water. For this purpose we should apply covers which are so scrupulously well fitted that no insect can enter, and at the same time protect the ventilating orifice by wire-gauze. In many countries tubs are used outside houses to collect rain-water from the roof, A wooden top should be closely fitted and a hole of about 6 inches or more in diameter should be cut in it. Nail down a piece of wire-gauze on the outside of the orifice. The pipe which brings the water from the roof discharges over the orifice, so that the water flows directly into the barrel, being drawn out by a tap below. Similar devices can be employed for cisterns, but if these are made of metal and have badly fitting covers, considerable 35] WELLS AND CESS-PITS 273 difficulty is often experienced in making the proper arrange- ments, which must be left to the reader. The subject of wells is of great importance in the tropics, as they are often the only source of drinking water. For the usual hygienic reasons the people should never be allowed to lower buckets and ropes into wells, as this frequently leads to serious defilement of the water. In my opinion every well should be furnished with a closely fitting cover, the water being drawn by means of a pump of some kind. But in order to ventilate the water, a hole protected by strong wire- gauze should be cut in the cover. I have seen excellent wells of this kind in several localities, notably at Bathurst, Gambia. Cess-pits are frequently used, especially in French possessions, and are ventilated by long pipes which discharge at the roofs of the houses. We observed at Ismailia that Culicines were breeding in large numbers in these pits, though they were entirely closed except for the ventilating shafts, down which adults found entrance and exit. To prevent this it is necessary only to protect the ventilation with strong wire -gauze. In badly-made cess-pits there are other orifices by which the insects can enter. These should be done away with as much as possible. If they cannot be completely filled up, the pits must be regularly oiled by some method (section 53). (6). Dealing with breeding-holes. — I have already mentioned that holes in trees and rocks should be filled with concrete, that is, with a mixture of Portland cement and sand or gravel. The best mixture for the locality should be determined by local engineers. Two men must work together, one carrying concrete and the other laying it into the holes. Mosquito breeding-holes in trees are sometimes very difficult to find, men or boys having to climb the trees for the purpose. Hence, when they are found their position should be marked on the tree by a conspicuous patch of paint for future identification. Inexperienced persons are apt to think that such work is altogether too much for human weakness to accomplish, but s 274 PREVENTION [Sect. as a couple of men can generally fill fifty holes a day, it is not long before most of the breeding - places round houses are disposed of. In many cases, moreover, the water in such holes can easily be liberated by cutting. If concrete is not available, earth, gravel, or stones often suffice perfectly for a considerable period. A little trouble guided by common sense is all that is required. Garden cisterns often occasion much difficulty. Water is required for irrigating plants, and is often allowed to stagnate for weeks in the cisterns. The best way to deal with them is to direct that not too many of these cisterns be allowed to remain, so that those which are permitted to do so shall be in constant use. The frequent agitation of the water by the gardener generally suffices to check mosquito-breeding in it. The gardener should be instructed to deal with his irrigation water in such a manner as not to cause breeding of mosquitos. Here, again, details can be better left to the reader. Irrigation pits are often employed for cultivation, and are found to contain Anophelines, which live especially in the presence of grass and vegetation occurring at the edge of the water. These are often difficult to deal with, as the people occasionally require the water. If possible, they should be filled in, but if this is not possible, we can often render them unsuitable for larvae by dragging out the weeds and " backing up" the margin of the pit by filling with large stones, the owners being instructed to prevent the new growth of vegetation, A gang of men will deal in this manner with a number of such pits in a day. Borrow pits, that is, pits from which earth has been taken for building purposes, are found everywhere, and are not always easy to deal with. They may often be filled up with ordinary town rubbish, but this should be ultimately packed into them closely and covered with a layer of earth. In some places they can be filled up at greater expense with stones brought from a distance, if such are available. Where 35] BORROW-PITS 275 they cannot be filled up, the best plan to deal with them is by the method just suggested for irrigation pits. Where no stones can be obtained, and where the water cannot be drained away, our only resource is to deepen the bed. Make the banks " steep-to " all round, and clear away all the vegetation, leaving the water as before. Such places are particularly suitable for the introduction of natural enemies of larvae ; but they must be examined from time to time to see whether they are really free from mosquitos. A number of small questions of this nature are apt to rise in connection with cultivation, and must be left to the ingenuity of the director of the works. Railway companies often cause much trouble by their borrow pits along the course of railways, and they continue to do so in spite of the protests of medical men. This is a point which should always be taken note of by the Government of the colony, who should insist upon the borrow pits being so made as to allow the water to run off. I know that in absolutely flat country this is difficult, if not impossible ; but in such cases much can be done by making regular pits without marshy borders, and by insisting that these shall be kept free of vegetation, and shall be stocked with fish, etc. Built conduits and drains. — By this I mean water-courses and drains which run through masonry. In the course of time the masonry is apt to wear away, thus leaving breeding-holes. These holes can be dealt with by rebuilding, or by filling with concrete. (7). Training the banks of streams, rivers and lakes. — The word " training " is one used by engineers to signify rendering banks more regular or solid. Untrained streams and lakes are apt to spread over the ground beyond their margins, and to cause innumerable small breeding-pools, and the object of the training is to check this tendency. The director of the work must be guided by circumstances how this can best be done. In many places the water may be deepened, the earth 276 PREVENTION [Sect. taken from the bottom being used to build up a steep bank. In other places large stones may be arranged along the margins. Everywhere the streams should be so dealt with as to allow the water to run freely, and above all, weeds should be dragged out of the water, while the banks are rendered as " clean " and permanent as possible. The Forest Department in Mauritius " canalised " a stream in this way, at the cost of only 0*37 rupees a running foot for both banks.^ While the rough training is in progress, holes in neighbouring rocks may be filled in with cement. Cattle often cause much trouble by leaving holes in muddy banks in which Anophelines breed with readiness. This problem is attacked in Panama by a rule that cattle be allowed to water only at fixed spots which are properly pre- pared by cobble-stones to prevent such breeding. Exactly similar measures are required for rivers and lakes, but the works involved for them must often be taken under the heading of major works. Irrigation canals and irrigation works in general must be attended to on the same principles. It is often stated that irrigation is not compatible with mosquito reduction. This is quite untrue, because in Ismailia at the present day we have an example of the opposite. Ismailia, though built in the desert, is now a well-watered garden without mosquitos. Nothing but attention to the small details which I have mentioned is required, and the expense of the work is very small. Idleness always finds an excuse. Small marshes can frequently be dealt with quite easily by these simple means, that is, merely by clearing the natural lines of drainage. Our mosquito gangs in Mauritius, consisting merely of Indian workmen, made short work of considerable areas of marsh in this manner. Only common sense is required ; but, of course, in other instances major works by drainage have to be performed in order to give a final outlet to the water. Temporary marshes (section 30 (i)) can be attacked on the same principles. * See pp. 166 and 450. 35] MARSHES 277 (8). Major works. — I divide all works for the reduction of mosquitos into two classes, namely {a) such as we have hitherto dealt with, which can be performed by any intelligent persons, and should be called minor works ; and {b) those which require the advice of an engineer, and which should be called major zvorks. Naturally, major works generally require a greater expenditure of capital than minor works, though this does not imply that they are always more ex- pensive in the long run. As a general rule, I think, major works need not be undertaken until minor works have failed, unless expert advice to the contrary is given. Marshes are of two kinds, those in which the natural outlets for the water are sufficient but have become choked by vegeta- tion, cultivation, or other small obstructions, which can usually be removed by minor works ; and those in which the natural outlets are insufficient and require deepening. For adequate dealing with the latter, levels must be taken and extensive works, directed by an engineer, are generally demanded. Marshes may be caused not only by insufficient outlet, but by excessive inlet. The water in a marsh may not come merely from rainfall over the marshy area, but from streams or drainage from beyond. Thus marshes are very apt to occur at the base of hills, small or large, the rainfall upon which runs out and stagnates on the plain. We must there- fore consider whether we should increase the outlet or decrease the inlet ; whether we should cut channels across a marsh in order to free the water in it, or carry intercepting trenches round it in order to remove the incoming waters. In many cases, especially in marshes due to periodical inundations by streams and lakes, the problem of how best to deal with them can be solved only by an expert. The marsh may be («) drained away, {b) filled up, or {c) converted into an open lake too deep to breed mosquitos. Estimates must be prepared, and the engineers have to select the best plan. Marshes difficult to deal with are often formed by roads, 278 PREVENTION [Sect. railways, houses, irrigation canals, ill-managed water conduits and standpipes, and even by badly-made drains. The form of drain to be employed often requires careful thought. Drains may be (a) open channels cut in the soil ; (d) open channels flanked with stone or concrete ; (c) channels filled with large stones at bottom and gravel above (rubble drains) ; or (d) various kinds of subsoil piping. All major works require to be constantly kept in repair by minor works, that is, after the major work is done, there must be a constant expenditure for what engineers call " maintenance." Though it may be quite possible to treat a given breeding surface by minor works only, yet the expense of this may be so great that it will exceed the interest on the money laid out for clearing the area by a major work plus the expense of maintenance. In all these matters the advice of the local engineers should be sought. But this does not mean that the advice of the director of the anti-malarial campaign should be disregarded. They must work together. For instance, M. Watson notes (section 57), that open channels are quite effective in the lowlands of his district, because the local carrier will not breed in them ; but piped drains are required in the uplands where the carriers breed in any open water-course.^ Obviously the habits of the local carriers should always be carefully ascer- tained and considered, because this is likely to diminish largely the cost of their reduction. Engineering works made in ignorance or in defiance of this knowledge may do more harm than good. For example, I think that most of the malaria in Freetown, Sierra Leone, was due to the badly-made drains ; and I have seen much malaria caused by other works constructed without regard to their possible evil sanitary consequences. A whole book could be written on drainage of the soil as a ^ Compare sections 42 and 43. 35] VEGETATION 279 preventive of malaria — the history of the subject alone would fill many pages. The reader will find further details in the next chapter. (9). Trees. — Vegetation has long been known to affect malaria. In some places it seems to have a bad effect, and in others a good effect. Probably this depends largely upon the habits of the local carrier. We quite understand that certain mosquitos prefer wooded country, while others like the open. Thus M. Watson finds that in his district one of the most important measures consists simply in clearing the jungle to a considerable distance round habitations. On the other hand, it has been sometimes claimed that trees round habita- tions exclude mosquitos breeding in marshes beyond. Suggestions were made some time ago that eucalyptus trees would have the effect of drying up the soil, and that their odour is inimical to mosquitos. Consequently many plantations of eucalyptus were made in Italy, Mauritius, India and elsewhere, but the results have been quite indefinite, as might be supposed. I certainly think that eucalyptus tends to dry up the soil, but whether it does so sufficiently to check mosquito-breeding is another matter. The cost of making plantations will generally exceed that of minor works. It is well known that trees exhale a great amount of damp, which is always favourable to mosquitos and unfavourable to men. On the whole, then, I am strongly of opinion that many trees should not be allowed in the proximity of houses or in the middle of towns in the tropics. In addition to giving out moisture they exclude the breeze and increase the heat, because the amount of shade thrown by them scarcely compensates for the cooling effect of wind. In the case of houses surrounded by considerable grounds, trees are pleasant and beneficial at a distance from the house. As already mentioned, moreover, trees are almost sure to breed Culicines in holes in their trunks and principal branches, I therefore think that every tropical country should possess strict rules empowering the health 28o PREVENTION [Sect. department to control the growth of trees within, say, lOO metres of houses. In Port Louis, Mauritius, the Mayor, Dr Laurent, very wisely made a great reduction in the forestation. In the same place much discussion has occurred regarding what are called the " river reserves." By an old law the forest department insists upon maintaining a belt of trees in the neighbourhood of each of the streams for the purpose, partly of preserving the streams, and partly of maintaining the rainfall, forests being found to increase the number of rainy days, a thing which is very useful for various kinds of cultivation. On consideration I was very doubtful as to the effect of such river reserves, but suggested that in the neighbourhood of towns and villages they should be kept scrupulously free from undergrowth. As a general rule undergrowth is favourable to subdomestic and wild species of Anophelines, which, after leaving houses where they find their food, like to take refuge in thick vegeta- tion. Personally, I prefer houses surrounded by open lawns rather than by thick shrubberies. In a house occupied by Major Fowler and myself in Mauritius, and surrounded by trees, the Scutomyia notoscripta was a pest by day, while C. fatigans was equally troublesome by night. In the barracks of the European troops, however, situated in an open grassy maidan a few hundred yards away, these insects were not nearly so numerous. Many similar experiences might be cited. (lo.) Houses. — Without making any general attack on the numbers of mosquitos in a locality, they can be reduced in dwellings simply by the manner in which the house is built. As a general rule Anophelines much prefer dark damp houses, especially with wooden or mud walls and thatched roofs, and surrounded by thick vegetation. Lofty houses built of stone, with large windows and plenty of ventilation, are not so haunted by Anophelines, though they may sometimes be full of Culicines. 36] HOUSES 281 I am sure that the colour of the walls is a very important detail. No mosquitos seem to like white walls and ceiling, especially if there is plenty of light (Nuttall [1901]). Europeans called upon to live in the tropics are very apt to bring with them their ideas of house decoration, and English ladies especially like to furnish their drawing - rooms with numbers of beautiful curtains, pictures and stuffed chairs, all of which harbour the insects. This method of decoration is rather barbarous at the best, and is quite inappropriate for warm climates. Curtains especially check the breeze which is so cooling to the inmates and so unpleasant for mosquitos. The whole subject of houses in the tropics requires very careful consideration. The housing of the poor is often simply disgraceful. The building laws, if any, are generally evaded, with the result that the mass of the people have to live in the most miserable shanties made of wood, palm leaves, and often of old kerosene oil tins. In every malarious country a committee should be appointed to consider the whole of this housing question^ especially with a view to excluding mosquitos and malaria. Good houses suitable for the poor could easily be designed, and building laws could be made in order to enforce their construction by degrees. The same remarks apply to tropical cities, where the native quarters are generally in a dreadful condition. There is no reason which I can see why houses in the tropics should not be as well built as those in temperate climates. This, however, is a question of scientific administration in opposition to those forms of administration which we meet with too often in the world. 36. Prevention by Treatment. — It used to be said that prevention is better than cure, but we are now finding that cure is one of the best methods of prevention. In all parasitic diseases, one way to remedy the disease is to destroy the parasites in the patients, who then cease to spread them to other persons. This has been undoubtedly the case with 282 PREVENTION [Sect. ankylostomiasis, and will prove to be the case with other parasitic diseases. The history of prevention by treatment in malaria is a long one : Laveran [1907] gives many interesting details. After the mosquito theory was established, Koch was the first to call marked attention to this method. He suggested that all patients, especially children, should be carefully treated with quinine. His principles were immediately tried in Italy and in various German possessions (sections 49, 51); and in Pro- fessor Celli's contribution to this book, an admirable account will be found of the use of the method with more recent extensions given by the Italians themselves. Equally good results are quoted by other contributors to Chapter VII, where many practical details are given. As stated in section 33, treatment affects the malaria equation partly by increasing the recovery factor r, and also by reducing the proportion of infected persons with gametids in their blood i. It thus modifies two of the factors. Treat- ment of the sick only should be called case reduction ; and treatment of those who have not yet shown symptoms, but who may have become infected unknown to themselves, should be called quinine prophylaxis. We should always understand that quinine does not really prevent infection. I presume that the protospores may be inoculated into a person whether he is taking quinine or not, but that they will not thrive in the former case — see negative cases 5 and 6 in section 1 5.^ We should also understand from section 23 that quinine, whether used for case reduction or for prophylaxis, should be continued for a long time. The drug does not have a very lethal effect on the gametids, at least those of the malignant parasites, when these are once formed ; but it certainly tends toward destroying the other forms. The Italians insist that it does not have much effect upon relapses, but, for reasons given in section 23, I doubt ^ And section 65 (5). 36] PREVENTION BY TREATMENT 283 whether they are right on the point, and am inch'ned to think that the inadequacy of the treatment has been to blame for the recurrences of fever. This point is made clearer by some of our cases recently studied in Liverpool by enumerative methods. On the whole, there is no doubt whatever that a continuous and sufficient use of quinine will tend largely to reduce the malaria ratio. Another point must not be forgotten. For public health work cases cannot be treated with the elaboration of detail employed in hospital practice. All we can do is to recommend a general line of treatment for the public ; and, in fact, the people must become their own physicians. It is idle, therefore, under these circumstances, to suggest complicated scales of dosage and the use of various preparations. I have always taught, in entire agreement with Professor Celli,^ that daily dosage is much the best for public health work. He insists strongly that physiological immunity of the patients against the drug is much more quickly arrived at by daily dosage than by intermittent dosage — and I have always found the same. But there is a still stronger reason for daily dosage. If we order quinine every few days, the patient is apt to put off the evil hour until to-morrow — he complains that he has much work to do to-day, or that he has indigestion, or is not feeling very well. When to-morrow comes other excuses may be found. Then the patient is attacked with fever and finally decides that the quinine treatment is of no use. Personally, I recommend that quinine should be given invariably once a day, either just before the morning meal or at bedtime. With regard to dosage, I do not advise quantities which will disgust the people with the drug. It is perhaps better to use amounts which will prevent the disease only in a percentage of people, than to cure all of them at the expense of making them all ill. CelH recommends 40 centigrams of the bisulphate, hydrochlorate, or bihydrochlorate for adults and young persons ; ^ See section 49, p. 417. 284 PREVENTION [Sect. 20 centigrams of the same salts or 30 centigrams of the tannate for children ; and in every case administered in the agreeable form of comfits or of chocolates. But he increases the dose to 50 or 60 centigrams for adults in the presence of very severe malaria. I have generally recommended 5 grains (33 centi- grams) for adults, and much similar doses for children. It has, of course, been shown that children can take quinine in larger doses than adults ; but, on the other hand, I doubt whether such larger doses are really necessary for them, and the vomit- ing which is frequently caused in young children by the larger doses is apt to alarm mothers. In fact we have to take the greatest care not to impose too great a burden on the people whom we wish to persuade into anti-malarial courses. In India quinine is generally administered for public use in the form of powders wrapped in papers. I think that this is a bad method, partly because the taste is so very apparent in powder, and also because much of it is wasted. I recommend freshly-made pills or tablets, coated in a suitable manner. If these are swallowed in milk or in water just before a meal, the taste of them does not remain in the mouth for more than a few seconds. Personally, I always take the drug thus in preference to chocolates, etc., in which the bitterness seems to me to be rather increased than diminished by contrast to the sweetness of the preparation. Small children can generally be bribed to take a pill by giving them some small sweet afterwards. The experiments on the absorption and elimination of quinine (section 23) cannot be accepted as having answered the question as to which is the best salt for use in treatment or prevention. For this purpose accurate observations by enumerative methods, such as we are now adopting, must be carried out at length. The only answer to the question can be obtained by finding exactly how many parasites are killed by a given dose. I have usually recommended the more soluble salts, because a greater quantity is likely to be found in the blood at a given moment ; the insoluble salts are certainly 36] SEGREGATION 285 absorbed very well, but probably not so suddenly as to produce a maximum poisoning effect on the parasites. On the other hand, the insoluble salts are likely to keep the blood more continuously impregnated with the drug, and may therefore be more useful for general prevention. Pending such researches, it cannot be said that one salt is much more efficacious than another ; and the salts selected must depend upon the local price, and the local facilities for making up any forms useful for administration. The sulphate is certainly the most generally used in British possessions, but the Italians have lately insisted very strongly upon the tannate, which certainly has great advantages, being nearly tasteless and comparatively cheap. Euquinine is more expensive, and is generally prescribed in doses of 50 centigrams for adults and 25 centigrams for children. Arsenic was used long ago for prophylaxis by Tommasi- Crudeli, but has now been abandoned in Italy. We are making further experiments with atoxyl and methylene blue. It would be most useful if some drug could be found which affects crescents more definitely than quinine does. Various other agents, including serum of cattle, have been tried, but the experiments will have to be repeated by enumerative methods. Segregation. — On going to West Africa in 1899, after service in India, I was much struck by the fact that Europeans in the former country are not segregated as they are in the latter. In India the British officials and troops are nearly always housed in separate locations commonly called cantonments, so that they are frequently spared infection derived from neighbouring crowded native quarters. But in Freetown, Sierra Leone, the ofificials were oblisred to live almost in the midst of the native population, even ladies being housed in rooms under which native shops existed. I called attention to this immediately, and attributed much of the large death-rate amongst Europeans to it. The idea was elaborated by Stephens and Christophers, who added the important consideration that native children are 286 PREVENTION [SECT. the principal sources of the parasites, and J. E, Button strongly recommended segregation for Bathurst. Others opposed the idea, because they thought it would be wicked for the Europeans to live apart from their coloured brethren. At this time the advisibility of reducing mosquitos was much disputed on the ground that the insects diffuse themselves in all directions from a breeding centre, just as particles of gas diffuse themselves from a generating bottle — which is, of course, not the case. At the same time segregation was much urged as an alternative measure ; but I pointed out [1904] that both the measures depend upon the same principle — namely, that mosquitos do not diffuse themselves without limit from a centre. That is, I suggested the principles of random scatter given in section 29 (14). Obviously, if mosquitos spread to great distances, local drainage will not reduce their numbers, and, equally certainly, segregation will not enable us to avoid them. If this were the case, mosquitos infected in native villages would be able to travel to such distances that segregation would be useless. Happily, however, this is not the case, and therefore both segregation and mosquito reduction remain valid. We may segregate ourselves from the proximity either of many infected persons or of breeding - places. S. P. James [1903] removed a number of people from a locality in which Anophelines abounded to one in which they were more scarce. In October 1901, seventy-eight children belonging to these people showed malaria parasites in 56%. In August 1902 they were all moved into tents about 600 metres from the nearest pool — no Anophelines now being found in the tents. The result was that not a single case of fever occurred among the adults, and that on 24th October the height of the fever season, parasites were found only in one out of twenty-five children examined — and this without treatment of any kind. Their spleen rate had also decreased from 75% in April 1902 to 60% in October 1902 — the splenomegaly evidently dis- appeared much more slowly than the parasite index. 37] MEASURES FOR PERSONAL PROPHYLAXIS 287 As proof of the good effect of segregation from infected persons, I think that I may safely quote the case of the Indian cantonments, where malaria is certainly much less rife than in the crowded native quarters in the neighbourhood. Similar segregation has recently been carried out in Sierra Leone, where a special quarter has been provided for officials at some distance from Freetown — owing, I believe, largely to my advice given previously. I look upon segregation as a most important measure for preserving the health of European officials, not only against malaria, but against many other diseases. It should always be adopted until sanitation in general arrives at a much higher degree of development in the tropics than it has hitherto attained. 37. Selection of Measures for Personal and Domestic Prophylaxis. — The various preventive measures have been described in the previous sections as briefly as possible, because much more information is given in the important contributions to this book contained in the following chapter. But we must now discuss exactly an important matter, namely, the relative values of these measures for use under various circumstances. The preventive measures themselves are now well known and are described in all the text-books ; but mere description is not enough, as it is always difficult to employ every one of the measures, and both the individual and the health officer may be called upon to select the most feasible ones. We have to examine, first, the measures most appropriate for the indi- vidual — that is, for private persons, heads of houses, factories, institutions, ships, and so on ; and, secondly, the much more complicated problem of the selection of methods for public prophylaxis. (i). Self -protection of Europeans in the tropics. — I have had experience on this point during many years and in many different countries, and have only once been infected, and that at a time when we did not know how the infection is produced. 288 PREVENTION [Sect. I always rely upon the possession of four articles, namely, a good bed-net, costing about eight shillings, a small hand-net for catching mosquitos, costing about one shilling, a palm leaf fan, costing one penny, and a bottle of quinine. With these articles the chances of becoming infected are reduced enormously — especially if a little common sense and care are added to the stock. I cannot speak too highly for the ordinary bed-net, if used as directed in section 34 (i). Anophelines almost always bite at night. If the number of bites received by two individuals, one of whom always sleeps in a bed-net, while the other does not do so, could be strictly estimated, I think it would be found that the latter receives only about 10% of the number of bites inflicted upon the other. When a person is walking about in the day or in the evening he is not nearly so accessible to any species of mosquito as when he lies still and unconscious in sleep. It is therefore almost certain that the large majority of inoculations occur during sleep, and hence, obviously, protection during sleep will prevent a very large proportion of them. Moreover, I have frequently found that persons who despise bed-nets, as many sportsmen, soldiers, planters and others are apt to do, are very prone to suffer from malaria. So are those who use bed-nets carelessly. After service in India, where most people are wise enough to guard themselves in this manner, I was much struck by the negligence on this point of Europeans in West Africa. There can be little doubt that the comparative good or bad health of Europeans in many parts of the world depends very much on the intelligence which they display in this matter — which seems such a small one to thoughtless people. Fortunately, the public have now been awakened, and I have even heard of several shipping and business firms who are wise enough to hold their employees responsible for becoming infected, unless they can show that they have used every precaution. This would be a very good plan to adopt generally, even by governments and military authorities. 37] MEASURES FOR PERSONAL PROPHYLAXIS 289 Next to the bed-net, I attach most value to the small palm leaf hand-fan ; as stated above, I much prefer the use of it to thick gloves, mosquito-boots, etc. Here again the more manly, but often more unwise person, is apt to despise the suggestions of common sense. The small hand-net is almost equally valuable. If I sit down to write or read, I am generally visited at once by a number of hungry suitors, and I like to take the precaution of catching and killing the lot before proceeding to my task. In fact I am not ashamed to confess that I take both a hand- net and a hand-fan to bed with me, in order to deal with any stray mosquito which may enter with me ! Protected by these humble means, I do not often have recourse to quinine. In most places in the tropics where large numbers of Europeans are called upon to live, the continuous use of quinine is scarcely demanded. For example, in the Indian cantonments, or the principal towns and settlements in other tropical countries, the chances of infection are too small to compensate for the discomforts caused by the drug, even when given in the best form and in the best way. It is, how- ever, another matter when one is obliged to sleep in places of high endemicity ; and here we should always use the drug. Medical men can often be guided also by the great prevalence of Anophelines ; and in fact many of the general public are now beginning to recognise these dangerous insects by their attitude and the spots on their wings. If exposed in this manner, or if I think that I may have been bitten by infected mosquitos, I take the drug daily for about a fortnight in doses of between 5-10 grains (1/3 to 2/3 grammes). I know that this will not absolutely insure destruction of any protospores which may have entered, but I trust to luck that this has been the case. Anyway, I think that the inoculated germs have been so much reduced in numbers that (for certain reasons of my own) I think they are not likely to produce a very severe illness, T 290 PREVENTION [Sect. even if they do reach the fever h'mit. Then also I am otherwise protected by netting. How far we should recommend what some may consider to be reprehensible carelessness for the general public is another question. The medical man does not always adopt for him- self the advice which he gives to his patients ; and I therefore prefer to leave further details under this head to the reader. The European in the tropics must be told that he cannot insure himself against infection to an absolute certainty, however careful he may be. By bad luck he may be bitten when least expecting it, and by good luck he may escape altogether, just as the soldier may receive or escape the fatal bullet in battle. Other precautions remain to be mentioned. If we can select our place of residence, we should, of course, never live in proximity to native locations, or to marshes, or in old tumble-down thatched houses, or (very frequently) in dirty hotels. One does not therefore always welcome the hospitality of residents, however well meaning it may be. For travellers it is most important to recommend that they shall not go and live inside village houses ; they should always endeavour to pitch tents, both for themselves and for their followers, in appropriate country at some distance. Of course travellers should always be provided with mosquito-proof tents, both for themselves and for their men, (2), Domestic precautions. — The head of a house should enforce the various personal measures for the whole of his family on the lines just given. He should also try to screen a portion of his house. In many places this will be difficult, because in the tropics at least occupiers do not own their own houses and owners are generally averse to paying for such screening. But it does not cost much to screen a small corner of a veranda for sitting in. Next to nets, I advocate the more general use of punkas or fans. A comparison of the life of Europeans in India with it in many other tropical countries will force us to admit their 37] CHILDREN AND TROOPS 291 great value. Malarial infection of Europeans is very rare in Indian cantonments, where they use punkas almost day and night, but it is common enough among planters, who are apt to neglect them. I really think that punkas prevent some- thing like 50 to 70% of infection. Moreover, they keep the body cool and vigorous, while without them we remain covered with perspiration and tormented by mosquitos all day long. So convinced am I of the value of punkas or fans for general hygienic reasons that I would advocate the use of them even in places where every mosquito has been banished. The question of prevention for European cJiildren in the tropics is of the greatest importance. The difficulty of rearing them is due, I think, partly to the great heat, partly to malaria, and partly to various entozoa and other diseases. Those who can afford screening and punkas should therefore employ them for their children at whatever cost. If they cannot afford them, they should not bring their children to the tropics. The habitual use of prophylactic quinine is seldom seen among European children in the tropics, and I doubt whether it can be generally recommended. In fact, if such use is actually required, the place should be considered too malarious for children. Of course it is another matter if children have already become infected. (3). Troops on service. — The amount of baggage allowed is always very small, but the last article to be dispensed with should be the bed-net. In my opinion the military authorities should make all efforts to provide every man with one, because the cost due to loss of strength in consequence of invaliding from malaria must always be vastly in excess of that of the purchase and transport of nets. The disease has caused well- known disasters to troops, as in the British Walcheren expedi- tion and the French expeditions in Madagascar (section 60). On the other hand, the American troops in the Philippines used nets and admitted their great value. Where the authorities fail in providing them the wise soldier will do well to follow the old maxim of " self-help." A daily quinine ration of say 5 grains 292 PREVENTION [Sect. every morning should also be insisted upon, together with the rigorous use of nets. I scarcely think that gloves and veils, such as Laveran figures as used among the Japanese troops, are so urgently demanded — at least in the tropics, where they would be nearly intolerable. The Medical Department has the care of choice of proper bivouacs and quarters.^ (4). Ships. — I always carry a net which can, if required, be hung over the bunk. Ships in the tropics often delay for hours or days in port, and are frequently visited by swarms of mosquitos. Of course, all ships owned by companies who possess any degree of humanity and intelligence should be invariably screened against mosquitos in the manner shown by Dr Wolferstan Thomas (section 46). Quinine should be always given to the crew on arrival at the first malarious port, and for at least one month after leaving the last one, if the voyage lasts so long. The great mistake of stopping the drug on departure from the malarious coast is often, indeed generally, made. Many of our nautical patients in Liverpool give histories of having been attacked for the first time when nearing the British coast — that is, their infections had been received weeks previously, but had been suppressed by the drug until the use of it was abandoned. (5). Hospitals and asylums. — Here quinine cannot be given without interfering with the treatment of the various kinds of disease present. The superintendent must see to it that mosquitos are not being bred within the hospital premises ; but unless mosquito reduction has been adopted for a con- siderable radius outside the institution, screening should be adopted as well. Hospitals with crowded, unprotected wards furnish the worst examples of congregate sleeping (section 28 (3)), so favourable to the mosquito transference of several diseases. For example, dengue prevailed greatly in an un- protected hospital in the Philippines, while it was absent from a protected one ; and I have frequently found filariae and ^ See destruction of adult mosquitos, p. 362. 37] BARRACKS 293 Plasmodia in hospital mosquitos. In fact the dangers are so great that it is perhaps better to advise that every hospital should be screened whether mosquito reduction is carried out or not. A mosquito - infested hospital is a most disgraceful thing. The miserable defenceless people it contains are in- fected in the very place where they have come to be cured, and there is no excuse for it. (6). Barracks. — Unless mosquito reduction can be rendered very thorough, the best plan is perhaps to employ screening as well. Probably most of the inoculations occur at night, largely in consequence of the congregate sleeping usually adopted in barracks. The cost of death and invaliding of soldiers is probably far in excess of that of screening. Bed-nets are now being often used or advocated, even for native soldiers ; and I have heard of several cases where officers have helped their men to purchase them. But surely it is the duty of the military authorities to provide screening instead. Enormous sums are frequently wasted on the erection of new barracks — sums which would have sufficed to screen all the barracks in a country. The neglect on this point is simply marvellous. In one case, known to me personally, a serious epidemic of malaria occurred because the authorities were disputing as to who should pay for the hooks required to hang the bed-nets (already purchased !). Several of the men died, and a number were invalided at a cost which afterwards sufficed to drain the whole neighbourhood. Punkas pulled by machinery have long been in use in many military hospitals and barracks in India. Unless screening is very perfect, great care must be taken to complete the extermination of the parasites in infected soldiers. In any case this is necessary in order to maintain the effec- tive fighting strength, because soldiers " soaked " with malaria are only a source of expense in war. I doubt whether the six weeks' treatment used in India is quite sufficient.^ Of course a large proportion of the infections among troops ^ See H. H. Johnston, Brit. Med. Journ., 15th August 1908. 294 PREVENTION [Sect. are often contracted outside barracks. The question then becomes one of public prophylaxis (section 39). The quarters of officers and families should, in my opinion, be always screened unless mosquito reduction is very perfect. In the old days, in British possessions, large areas round barracks were kept strictly under the cantonment authorities, who refused to allow the general populace to live in them. Unfortunately, owing to the pernicious sentimental outcries which are proving so destructive to vigour and prosperity, this wise rule is now tending to fall out of use ; filthy huts spring up close to the barracks ; the troops become heavily infected with malaria and other diseases ; and the nation which gives way to this brainless folly has to pay much more for its military service, and may have to pay still more, some day, for military defeat. (7). Prisons. — The prisoners are taken from the lowest populace, and are being constantly changed as sentences expire. Hence large numbers of them are infected outside, and the principal measure is case reduction. In addition to this, screening or mosquito reduction, or both, should be adopted according to circumstances. (8). Schools. — Boarding schools are scarce in malarious countries. Day schools give a most valuable opportunity, not only for dealing with malaria by case reduction, but also for measuring it ; but this matter is part of the general plan of campaign (section 40 (6)), (9). General rules. — In all matters of domestic prophylaxis it is wise to remember the following rules (which cannot be repeated too often) : — {a) unless there is strong prima facie reason to believe that cheap measures must fail, always begin with them before attempting more expensive ones ; and {h) do not adopt any measure until careful examination has proved the necessity for it. For example, I have seen and heard of expensive screening being installed {a) where a little mosquito brigade work would have cleared the mosquitos entirely, and {b) where most of the infections were really being acquired outside. 38] SANITARY AXIOMS 295 38. General Sanitary Axioms. — Before we consider the complex subject of public malaria prevention, it is advisable to state the following series of propositions regarding the pre- vention of all diseases. (i). Widespread diseases, especially endemic diseases, cause much pain, sorrow, expense and loss of prosperity to the people. (2). Next to the maintenance of the State, it is the duty of scientific governments to investigate their mode of propagation, and to endeavour to control them. (3). For economic reasons alone, governments are justified in spending for the prevention of such diseases a sum of money equal to the loss which the diseases inflict upon the people. (4). The amount of money spent on the prevention of various diseases should, ceteris paribus, be proportioned to the amount of sickness and mortality caused by each. (5). It is the duty of governments to make and to enforce ordinances required for the prevention of diseases ; and of the people to submit to them. (6). Cete7'is paribus, that sanitary measure is the wisest which causes the public the least inconvenience. (7). Ceteris paribus, that measure is the most practicable which can be carried out by governments without making any demands at all on the thoughts, efforts or compliance of private persons. (8). Ceteris paribus, that measure is the most economical which confers, for unit of cost, the widest benefits on the public. (9). For the prevention of diseases on a large scale a suit- able expert organisation is always required. (10). It is always advisable to carry out accurate and repeated measurements of the prevalence of the disease which we propose to prevent ; of the cost of the adopted measures ; and of their results. 296 PREVENTION [Sect. Written out in this manner these statements appear trite enough ; but in my experience every one of them is forgotten in actual administration. Thus few persons remember the first axiom — until they themselves are taken ill. Few governments really attend to the second one. Scarcely any one has con- ceived the simple idea contained in the third, and it is the rule to grudge spending a hundred pounds for a disease which costs thousands. Dramatic diseases interest many, while common ones are forgotten ; and the remaining axioms are too often overlooked even by those who direct or discuss sanitary work. 39. Selection of Measures for Public Prevention.— From the fundamental reasoning in sections 28 and 33, and also from general experience in many countries during the last ten years, we are now probably justified in making the following state- ments : — That malaria can be completely extirpated in a locality by the complete adoption of any one of the three great pre- ventive measures, namely, protection, mosquito reductioti, and treatment. That is to say, if every person in the community could be fully guarded against mosquito bites, or if every Anopheline could be banished, or if every infected person could be thoroughly treated from the beginning of his case, then each of these measures ought to suffice by itself to banish the disease entirely. Moreover, if we could use two of the measures, or all of them, the result would be still more assured. But, obviously, it will never be possible in any general community to adopt or to enforce any one of these measures completely. Thus, however carefully mosquito-nets or screening are used, many people will still continue to be bitten occasion- ally, so long as the mosquitos are allowed to remain. Again, however carefully we may destroy every mosquito which we can catch, or every larva, or remove the principal breeding- places, still, a few insects and breeding-places are sure to escape us. Thirdly, however strongly we may urge suitable treatment of all infected persons, a few are sure to resist it, and to 39] MEASURES FOR PUBLIC PREVENTION 297 spread the disease if any Anophelines are left. Hence, though theoretically possible, the complete use of any one of the measures is not really practicable. Fortunately, however, we can see by careful consideration of the principles laid down in section 28 that complete eradica- tion of malaria may still be possible by the adoption of each measure by itself, even if that measure is not completely given effect to. By that section we see that the static malaria (section 30) will tend to vanish, not only if all the factors of the equation are rendered absolutely prohibitive, but also if they are reduced to a certain figure ; that is, if the new infections can no longer keep pace with the natural recoveries. This important and encouraging law has been well exemplified in Great Britain, from which the disease has entirely disappeared owing to partial and indeed almost unconscious agencies, as described in section 30 (21). Lastly, we can understand from the same reasoning that a partial adoption of any one of the measures, though it may not banish malaria absolutely, is still likely, or indeed certain, to make some reduction in the disease provided that the other factors remain unchanged. All these truths still continue to apply if we adopt not one single measure, but several combined. Thus it may well be that an extremely partial application of two of the measures will produce results as good as a less partial application of one of them would have done ; and this fact may help us to do the work much more economically. Thus the head of a sanitary department who intends to carry out a large campaign is fortunately able to avail himself of several measures or combination of measures, by any one of which his purpose may be effected. But he has to consider means as well as objects : his duty to his Government demands that he should spend as little money as possible, and his duty to the people demands that he should not trouble them too much. Still more important, the various measures are more or 298 PREVENTION [Sect. less practicable according to a number of local conditions, all of which must be carefully considered by him before he comes to a decision. In practical sanitary politics, therefore, the mere enumeration and general description of the various measures are quite insufficient, and we are obliged to discuss with great care their relative values under different circumstances. The reader can assure himself still further of this, by studying the numerous contributions given by the most eminent men in the following chapter. He will see that different measures are being adopted in different countries. In some countries, especially Panama, Egypt, Durban and the Federated Malay States, mosquito reduction is the principal measure. In others, especially Italy, Greece and the German and French possessions, prevention by treatment is the favourite remedy ; and in other places combined measures are in use. In fact there has been much discussion upon this point during the last ten years ; some urge one measure and some urge others — each being guided by his own experience in his own malarious country. The truth is that all the measures are good and useful, and that each is most suitable under certain circumstances. The subject is evidently a complex one. I will try to make the issues as clear as possible by supposing at first that each measure is to be adopted by itself alone. Protection (section 34) requires the use of bed-nets, screen- ing, fans and some other devices. It demands an entire concurrence of the people who are to be protected. Probably no government can force the public to protect themselves. Although the rich may be quite willing to do so by bed-nets or screening, the poor will generally refuse the expense incurred. The cost of a good bed - net is, for instance, equal to the monthly pay of a day labourer in India. The cost of screen- ing a house completely is often more than a tenant cares to incur, and the house owner generally refuses to undertake it for tenants who occupy their houses on short leases (as gener- ally happens in the tropics). Punkas and fans are scarcely 39] PROTECTION 299 practicable for the poor, and medicinal culicifuges are of little value. In most countries the poor, especially in rural districts, are badly housed in huts which are everywhere permeable to mosquitos. To protect such houses by any known means will generally cost as much as rebuilding the whole house. Even if the state would be willing to provide every householder with a bed-net for himself and his family, it would still have to make arrangements for the constant repair of them, while they would often remain unused. We can scarcely expect that poor families, living crowded together in a single chamber, will ever exert themselves to use mechanical protection in a careful way. But even with the most complete protection of houses, people will still be subject to being bitten out-of-doors. This, however, is to look at the subject only from the darker side. As already stated, even a partial protection is quite likely to have an immense effect on the malaria. Even if only a proportion of the people could be persuaded to use an)- care in protection, doubtless the new infections would be reduced so much that the static malaria might either disappear entirely or become very small. It is, therefore, most advisable to urge pro- tection as strongly as possible ; to advocate suitable housing for the poor ; and to post notices for the information of the public regarding the dangers of being bitten by mosquitos. We see, then, that the measure of general protection against mosquitos is scarcely capable of more than a very partial adoption by the public. As a Government measure it is opposed to the seventh sanitary axiom given above. Although it possesses what some governments may consider to be an advantage, namely, that it does not make direct demands upon their own finances, it may yet be in the end more costly to the public than other measures. In most countries the number of houses is equal to about 1/4 or 1/5 of the total population — that is to say, the houses are very numerous. The cost of screening each house or of providing all the innates with mosquito-nets will therefore mount up to a very large sum. Thus in a city 300 PREVENTION [Sect. of 30,000 inhabitants, there are hkely to be 6,000 houses, and if the average cost of screening each house amounts to only £1, the total cost, including that of maintenance, will be very large. I doubt whether any form of screening for the poor will not depreciate at the rate of 50% per annum. It may therefore happen that the total cost will greatly exceed that of mosquito reduction or treatment. Even if it does not exceed that of mosquito reduction, the advantages of the latter are so great that it would be preferable to adopt it (if it is feasible). So much for protection as a general measure ; but it is often decidedly called for under special circumstances, as for isolated houses in the country, especially in proximity to marshes ; and for hospitals, barracks, prisons, hotels, travellers' rest-houses, tents, ships, river-boats, and so on. For general prophylaxis, especially in crowded localities, Anopheline reduction has many great advantages, which I have often pointed out. Practically, Anopheline reduction may be generally merged into the wider measure of mosquito reduction, which costs little more to effect and adds greatly to the benefits obtained. It is essentially the radical measure, which tends to remove not only the carriers of the disease but also a continual source of annoyance to the public. As mosquitos are known to carry other diseases, namely, yellow fever, filariasis, and almost certainly dengue, mosquito reduction will probably do much more even than to reduce malaria. To the practical hygienist it has still greater claims for consideration, especially because it conforms perfectly, not only with the eighth sanitary axiom, but also with the sixth and seventh — which is not the case with some of the other measures. For example, a government or municipality can maintain men for the purpose of removing breeding - places without causing any trouble at all to the populace. A certain amount of legislation is required to control obstinate people who sometimes refuse out of wilfulness to allow sanitary agents into their premises ; but beyond this it is generally advisable for the authorities to do everything as 39] MOSQUITO REDUCTION 301 regards mosquito reduction for themselves. No one is asked to believe in the mosquito theory, or to take drugs, or to protect himself and his family with bed-nets, or to put screens to his windows. Nor does mosquito reduction cause much or any inconvenience to the public (axiom 6). Occasionally cultivation in proximity to towns must be controlled, and pits, cisterns, wells, etc., used for irrigation must be dealt with ; but compensa- tion for any harm done must be paid for by the authorities, and, where mosquito reduction is generally feasible, only a small proportion of the people are affected in such matters. Lastly, mosquito reduction has the advantage (which is not always recognised) that it compels the sanitary authorities always to maintain a minute inspection of the area under their care, compels cleaning of all premises, removal of waste water, proper maintenance of roads, and so on (section 35). 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 may depend every- where on the nature of the soil, the slope of the ground, the rainfall, the vegetation, the existence of marshes, the character of the drainage and of the sanitary department already in use, and so on. Quite possibly, although the necessary expenditure is really within the capacity of the local budget, the authorities may not think so at the moment, so that the health officer is left powerless to adopt this measure. The advantage of mosquito reduction, that it can be carried out entirely by the state, has a corresponding disadvantage, namely, that the state imagines that it alone pays for the work. In a perfect govern- mental machine, the state could immediately call for increased taxes in consequence of any work of absolute public necessity ; but in this very imperfect world, the public is apt to be rather blind in these matters, and the state is afraid of arousing hostility, even by saving people's lives. At the same time it is proper to note over and over again that mosquito reduction often really does not cost as much as some pretend. The 302 PREVENTION [Sect. figures for Ismailia and the Federated Malay States include large items in excess of the actual anti-mosquito campaign, that is, items for general drainage, for building sites or cultivation purposes ; and those for Panama are so mixed that wc cannot exactly extricate the cost of this measure by itself^ Moreover, by the general principles of section 28, malaria may be com- pletely reduced even by a partial reduction of the Anophelines below the necessary limit (which I have roughly estimated to be about 40 different Anophelines per head per month) ; and it may be partially reduced even by a smaller reduction of the insects. In fact the small measures under the head of minor works generally cost but very little, and though they may not suffice for complete mosquito reduction, are still likely to do much good, especially if combined with other precautions. Prevention by treatment also has many advantages. In every locality, even if every mosquito can be banished, a number of cases are likely to continue to suffer from relapses for many months, and these always require careful treatment. Hence case reduction should always be adopted as much as possible, whether the other measures are used or not. Such case reduction can hardly come within the sixth and seventh sanitary axiom, because no inconvenience or trouble is inflicted on the people by gratuitous treatment of their sickness. Another great advantage is that the measure can be com- menced, even on a somewhat large scale, by medical men, without making any immediate large demands on the public purse. As shown in Italy and Greece, the mere sale of quinine at cost price by Government produces an excellent effect, if the people are intelligent enough to use it. Moreover, medical men who are now best acquainted with the whole theory of malaria, are precisely those who carry out this measure. In fact their practice actually receives some benefit by it, at least at first ; they are accustomed to the use of drugs, and they find no difficulty in urging their patients to take quinine. ' Col. Gorgas says $2"o a head (secLion 42). 39] BY TREATMENT 303 Unfortunately, all this does not apply in many countries in which the number of qualified medical men is very small. In many other countries the natives object entirely to our forms of treatment, and rebel even against quinine. Still further, many people are afraid of admitting the existence of domestic illness amongst their children, or will not take the trouble to treat them at all. Others, again, refuse to buy quinine, even at the cheapest rates, or cannot afford the time to attend hospitals or dispensaries for it, so that inefficient doses are frequently taken, with the result that the patients become sceptics as to the value of the drug, and advise their friends against it. In fact, these practical difficulties are so great that, as I stated in my Mauritius report, we are obliged in the tropics to distribute the drug gratis from house to house if we wish to obtain any material benefit from it. Lastly, if we propose to confine ourselves only to case reduction, that is, to the treatment of the sick, we have to distinguish the sick from the healthy, which generally can be done only by medical men, or by qualified assistants at the cost of considerable and continued labour. This trouble is saved if the public can be persuaded to adopt not only case reduction, but also quinine prophylaxis — that is, the treatment of persons who have not yet shown signs of illness, but may possibly have become infected. Unfortunately, if there are difficulties in the way of treating the sick, there are sure to be still greater difficulties in the way of persuading healthy persons to take any form of quinine continuously. Poor and ignorant natives, and indeed many other people, object strongly to this course. Some say that they would actually prefer the occasional chance of malaria to a continued certainty of dyspepsia. It is true that if quinine is given daily in small doses it produces much less physiological effect ; but in the majority of persons it always does produce some slight inconvenience. Busy people, hard-worked labourers or mothers of families tend to rebel very much against any continued 304 PREVENTION [Sfxt. medication. We know in Europe how much people are apt to protest against vaccination — a single simple operation causing scarcely any discomfort, and protecting for years against a dangerous and disfiguring disease ; how much more, therefore, will people be apt to protest against a medicine which must be taken daily for months during the malaria season, even if they are not affected by the disease. Of course, persons who remain infected, specially children, always continue to be a danger to their neighbours, and for this reason alone a complete reduction of malaria by treatment must always be difficult, unless the authorities have such power that they can actually force the drug down the throats of the people. This is often possible in the case of soldiers, employees of companies, or coolies on plantations, but scarcely for the general public. On the other hand, we may rest assured, though complete case reduction is seldom practicable, that the partial measure is certain to do much good. Because we cannot force all the people to take quinine, that is no reason why we should not persuade as many as possible to do so. Segregation, either from marshes or from infected persons, should not be looked upon as a measure of general public prevention, as it is applicable only in a few cases. Next, let us compare the measures two and two — at the risk of repetition. First, suppose that we have to deal with an ideal country where all the measures are equally feasible, and will cost the same sum of money — a thing which, of course, never happens. Protection is evidently at a disadvantage compared with mosquito reduction. It will never entirely prevent the bites of mosquitos ; nets and screens always require some trouble to keep in order, and certainly add somewhat to the heat- often so unbearable in the tropics. On the other hand, mosquito reduction, if sufficient, removes at once an incubus, a veritable plague — we breathe, move and sleep freely, our children are safe, our verandas and gardens open to us. 39] COMPARISONS 305 Now, compare protection with prevention by quinine. The former guards us not only against all mosquito-borne diseases, but against constant personal annoyance ; the latter, only against malaria. Nets and screens cause no dyspepsia, no ringing in the ears, and no daily trouble with the children. I think that every one will prefer freedom both from mosquitos and from dyspepsia to the inflictions of both. Hence protection has great advantages. But, in spite of this, the sick must still be treated. Mosquito reduction has all the advantages of protection and more, and is therefore greatly preferable (under our hypothetical conditions) to quinine. But, nevertheless, the sick must still be treated. Ideally, therefore, mosquito reduction is by far the best measure. Protection is next, and quinine last. Now, let us consider the measure from the point of view of cost and feasibility. The cost of protection must obviously vary according to the number of houses, which can be roughly ascertained by dividing the population by about four or five. In Mauritius at the census of 1901 the population was 373,336, and there were 93,031 houses, so that there were about 4*25 persons to each house on the average. Probably the cost of protecting a single house there would be quite £1 on the average, as a very low estimate, amounting to ^^93,031 (about 1,500,000 rupees) for the whole island. Besides this, repairs and renewals of the screens and nets would probably amount to quite 2$/^ of the original cost at a low estimate; so that after the first installation of the protection an annual cost of ;^23,ooo (350,000 rupees) would have to be incurred for the mechanical work of supervision. This, of course, is a very rough estimate, and quite possibly more than £1 would be required to protect each house on the average, because many of the poorest houses are little better than shelters of mud and thatch. Regarding the feasibility of protection, I repeat that it cannot be forced by Government on the people except as U 3o6 PREVENTION [Sect. regards employees of planters, railway companies, etc. Officials cannot, therefore, have any resource except to persuade and to keep on persuading, and even then only a proportion of the people would adopt the measures. For anything like general protection the Government would probably have to supply most of the cost — which we have seen will be very considerable. Of course, in Europe and the United States, where the people have reached a higher degree of prosperity than in most tropical countries, this measure is more likely to be adopted by the general public ; but even in them the very poor and the agricultural classes are likely to cause great difficulties. It can, therefore, scarcely be said that general protection, or even protection of a percentage of houses, is an easy and cheap measure. Observe, also, that the cost of it is likely to vary according to the number of houses. Notes on the cost of mosquito reduction have just been made. For Mauritius, which contains 705 square miles (1,924 square kilometres) and a population of 534 persons to i square mile, I estimated that a general mosquito reduction in inhabited areas, especially in towns, would cost, for minor works alone, the sum of ;^5,6oo (83,910 rupees) per annum. For making this estimate I relied upon figures given to me by the Medical Department, who suggested the number of workmen which would be required for each village, plantation, town and district, and the sum includes funds for the director, and travelling expenses. But it does not include the cost of the major measures, that is, the drainage of large marshes, and dealing with such waters as require the advice of an engineer (section 35 (8)). This cost was estimated in Mauritius by the Public Works Department at a capital expenditure of about ;^42,ooo (630,000 rupees), but I advised that these major works should be undertaken only where the minor works might be found, after experience, to be ineffective. For the reasons already given it is almost impossible to furnish any general estimate for mosquito reduction anywhere. 39] COMPARISONS 307 The cost depends upon the number of major works required, the price of labour, the price of expert supervision, the local laws, and the local efficiency of administration. It is very difficult to extricate from the accounts of various campaigns the money expended on mosquito reduction alone. In the town of Port Said, however, where there is very little rainfall and where a complete Culicine reduction has been carried out, the cost has been about 5d. per head of population per annum (section 53). I have already stated that mosquito reduction has the great advantage that it can be carried out by Government alone with- out reference to the people. Labourers can be employed to treat Anopheline waters or to clear away Culicine waters from the backyards of houses, without causing any real trouble to the public. It is not necessary for Government officials to go about persuading householders to do this or that, or for medi- cal men to examine large numbers of individuals, and so on. On the other hand, mosquito reduction may just possibly be essentially unfeasible in places where the breeding waters are such that they cannot be removed for any cost that can be afforded by the local funds ; and this is, of course, a question upon which it is impossible to make general statements. As a broad rule the cost of mosquito reduction must always tend to vary according to the area of the country treated. [X It is often thought, especially by medical men, that the cost of prevention by treatment is almost nil. We write pre- scriptions, which cost us nothing and which are made up by the dispenser ; and we often seem to think that a similar prescrip- tion can be given, at the same small cost, to a whole nation. But the cost is sure to be very considerable. For Mauritius in addition to the mosquito reduction, I prescribed a very partial scheme of prevention by treatment, costing 30,cxx) rupees for the quinine alone, 3,600 rupees for its preparation and despatch, and 6,000 rupees for the services of five quinine dispensers, amounting to ;£'2,640, or 39,600 rupees, per annum. 3o8 PREVENTION [Sect. This was without the salary of a director and cost of office, etc., and it was proposed that the quinine should be distributed gratis, but chiefly in intensely infected localities. Here again the cost must always depend largely upon the local conditions. A highly civilised and prosperous people will take the drug readily, where a very ignorant, poor, coloured population will require the utmost amount of persuasion. Thus we have to pay not only for the amount of the drug used, and for its preparation and despatch, but also for an agency which will distribute it to the people and will persuade them to use it properly. We are very apt to forget this last and very costly item. Think for a moment of the position of the very poor in malarious villages and towns. The occupant of each house is generally obliged to go to his labour extremely early in the morning. His wife has her household duties and her children to attend to. What time have they to obtain the drug at local dispensaries which may perhaps be miles distant ; and, very often, what money have they to purchase it near at hand .? Moreover, neither the man nor the woman has time to force the medicine down the throats of the younger children. The same difficulties recur day after day and week after week, perhaps during the whole of the malaria season, and even beyond it. Meanwhile patients rebel against the medicine, just as much as those who care for them rebel against the necessity of fetching it, and soon there is very apt to be a general rebellion. This has been strongly felt already in many localities, where pre- vention by treatment has been much practised ; and in fact it was for this reason that my advice was sought both at Ismailia and in Mauritius. Dr Malcolm Watson has also made some important remarks under this heading (section 57). In my Mauritius report I laid down that for most tropical countries the only effective way of giving quinine is {a) to give it gratis, {b) to give sufficient quantities to last each patient for one or two weeks or more, and {c) to distribute it actually from house to house. Now all this must cost the state a very 39] COMPARISONS 309 considerable sum. As a matter of fact a large number of fully- qualified medical men, and also qualified assistants, must be employed to carry out this distribution ; and we must remember that the salary of a fully qualified medical man is as much as the wages of about fifty coolies (at least in India), and the salary of a reliable qualified assistant may amount to as much as the cost of five to ten coolies. Regarding the feasibility, independent of cost, we must again remark that this measure does not accord with sanitary axioms 6 and 7. The cost will tend to vary according to niiniber of population. To sum up — protection is evidently a personal or domestic measure which cannot be forced by any government on the people, unless the former is willing to supply the nets or screens to the poor — the cost of which would probably largely exceed that of mosquito reduction, at least in towns. But protection should always be adopted for public buildings and isolated houses, such as railway stations, rest-houses, and houses on estates. I think that it might also be used, even at the cost of supplying netting, for villages in proximity to large marshes which cannot be drained without great expense. At the same time it should always be urged on the public by means of lectures, pamphlets and placards, which cost Government almost nothing, and certainly have a good effect. Practically, therefore, for public prophylaxis we are called upon to choose between mosquito reduction and quinine. Ideally the advantages of mosquito reduction are simply over- whelming — so much so that I urge it should be universally adopted in all towns i?i the tropics^ as a part of a general crusade against vermin of every description. The relief caused by removal of the mosquito pest is great enough to compensate for the small cost involved (in towns) even if the insects do not carry any disease. Practically, however, our choice is often limited by the financial position of the place and time. To familiarise him- 3IO PREVENTION [Sect. self with the question the reader will do well to recall to his memory various localities which are well known to him. Suppose, for illustration, that malaria were to break out in London round Hyde Park in consequence of an obstruction to the drainage to the Serpentine river. Can we suppose for a moment that the authorities would not at once under- take Anopheline reduction by removing this obstruction ? Would not this be much cheaper and almost infinitely more convenient than to force people to screen their houses or to take quinine, while the hypothetical mosquitos are allowed to remain as numerous as before ? Precisely the same answer must be given in the case of most cities, towns and even large villages in the tropics. But now take another extreme case, and suppose that the disease were to break out in any large rural area in Europe, such as among the bogs and lakelets of Connemara. What practical hygienist would urge mosquito reduction here, with the immense cost involved, merely for the benefit of a few scattered farm - houses. The appropriate measures would obviously be protection and quinine, as a general rule ; but even here, we might occasionally find villages in which the Anophelines breed in a few local waters which can be removed at a smaller expense than would be involved in the other measures. In fact, between the two extreme cases suggested, there are innumerable instances where either of the measures or both may be used, and where the director must use his own judgment. The cost of reduction of Anophelines tends to vary with area, and not with population. It does not matter much whether the area is crowded with houses or not ; though, if anything, density of population, necessitating well - paved streets and the removal of agriculture, will tend to cheapen the cost per unit of area. Thus roughly, the cost of Anopheline reduction for a square mile of densely-crowded city or town is likely to be actually less than that of the Anopheline reduc- tion for a square mile of uninhabited wilderness. In the former 39] COMPARISONS 311 case the expense will benefit a large number of human beings, and in the latter case only the birds and beasts. On the other hand, the cost of case reduction and quinine prophylaxis must vary directly, not with area, but with popula- tion. It will be vastly greater in a crowded square mile than in a square mile containing only a few cottages. Therefore evidently mosquito reduction is called for by every considera- tion in the case of crowded areas, and, on the other hand, quinine tends to be the more proper ipeasure amongst a scattered population, where Anopheline reduction would be too expensive for the local funds. This is, of course, a general rule, exceptions to which must be carefully considered by the director himself. Much thoughtless matter has been written on this point. For instance, it has been stated that because quinine has proved so beneficial in Italy, it is also the appropriate measure for all malarious countries. But the success of quinine there does not prove that mosquito reduction might not have been equally successful, possibly even at the same cost. I do not say that this is the case, but it might be so. Moreover, the conditions in Italy and elsewhere may be extremely different. Italy possesses a temperate climate which admits of mosquito-breed- ing only during a few months of the year, so that there is plenty of time for the treatment of old cases during the non- malarious months. Italy is also a highly civilised country with an intelligent white population, amongst whom there are numbers of medical men who speak their own language, and who add to their practice by the treatment of cases of malaria. Lastly, in Italy malaria occurs principally in rural areas, that is just where quinine is rationally called for. What more natural than prevention by treatment in it. But in many other countries the.se conditions do not obtain ; malaria abounds in towns ; the population is ignorant and often stupid ; there are very few qualified medical men ; infections occur nearly all the year round ; and the cost of maintaining medical men and 312 PREVENTION [Sect. dispensers for quinine distribution may, in urban areas, far exceed that, not only of Anopheline reduction, but of mosquito reduction in general. We really must not apply rules suitable for one country to all other countries. We have to consider each case on its own merits. Protection is a measure for individuals, mosquito reduction for local governments and municipalities, guided by their sani- tary departments, and prevention by treatment for doctors. It is not to be wondered at that the last named are so fond of the last measure ; they are acquainted with drug giving, but often not acquainted with public health matters, drainage and general municipal polity. They naturally tend to select quinine, and often very wisely so. In many cases, however, it would have been a wiser policy to have adopted the larger measure from the first. Up to the present we have considered each measure separ- ately ; but in many cases, probably in nearly all, it may be better to adopt a combination of several measures partially carried out. In fact, practically it nearly always comes to this. As previously stated, the complete adoption of any one measure is generally impossible ; we cannot remove every mosquito, nor can we treat every case. Possibly a partial mosquito reduction combined with a partial case reduction will produce the same amount of malaria reduction at much less cost. In other words, we remove what breeding waters we can remove without great expense, and we treat as many of the infected persons as possible. At the same time we urge protection upon the populace and adopt various methods under different local conditions. The proper policy is not the protection policy, nor the mosquito reduction policy, nor the quinine policy, but an opportunist policy which uses any weapon it can. It is sometimes stated that this opportunist policy will cost more than the specialised policy ; but this does not follow at all. Ultimately we have to frame our measures according to local feasibility. 4o] FIRST STEPS 313 40. Conduct of the Campaign. — Up to the present most of the anti-malaria campaigns have been due to the intelHgence and energy of individuals ; but it must be the desire of all — and certainly this book has been written in the hope of it — that similar work should now be attempted in every civilised malarious country. This has not hitherto been done, because often neither governments nor health departments have known how to commence and to organise their efforts. I propose now to make some suggestions on the point. They are based upon the scheme proposed by me for Mauritius, after careful con- sultation with the capable medical profession of that colony. They are tentative suggestions, and alterations of detail may be required under other conditions, and even in Mauritius ; but I hope that, with such alterations, the general scheme will prove applicable to most malarious countries, especially in the tropics. (i). First steps. — Whether the campaign is to be a large or a small one, the authorities must begin by educating not the public, but themselves, regarding the simple but often ignored axioms of section 38. The following points must also be remembered : — {a) In most places the campaign can never cease — the disease can seldom be extirpated once and for ever, until civilisation has reached a much higher state. We should be prepared for the fact that malaria reduction must become a permanent part of the general sanitary campaign. {J}) Unless the work is to be a pretence it cannot be attempted without expense. Perhaps the ideals of the third and fourth axioms cannot be reached — but they must be remembered. Rarely can we destroy so redoubtable an enemy without some goldshed. But every penny spent is likely to save pounds both to Government and to the public. Moreover, though the war may never cease, the cost of it is 314 PREVENTION [Sect. likely to diminish with good administration, and especially with success. (c) Public instruction must always be given, but, except perhaps in very civilised states, it is not likely to be entirely effective by itself. The individual may take quinine, use nets, or prevent breeding in his premises, but he cannot force his neighbours to do so, nor can he clear the surrounding country or drain the marshes. Only the better educated classes are likely to attend to sanitary advice. The great public is an infant for which everything must be done by the nurse. The poor are too poor, the idle too idle, the busy too busy, to concern them- selves much with sanitary injunctions. Neverthe- less, instruction costs the state little and may occasionally reach the small percentage of the wise. (d) Sanitation is a form of war. It requires not only money and effort, but also thought, organisation and discipline. (2). Appointment of a directory. — This being the case the first thing to do is to appoint a commandant. For a small campaign in a town or district, the proposer of it, whether he be an administrative, sanitary or medical officer, had better appoint himself (without salary) and then proceed to collect what army he can in the form of sanitary inspectors, medical assistants and even policemen. He can then begin to ask for funds. But this is personal effort ; and for larger areas Govern- ment should appoint a special officer in the Sanitary Department. His pay and status must depend upon the area to be dealt with. He should be thoroughly acquainted with the subject and also with general sanitary administration — a medical man, or possibly an entomologist or engineer, or for very large areas an administrative officer. For entire countries I advocate the construction at once of a Malaria Bureau as part of the general Sanitary Department — 4o] DIRECTORY 315 that is, a director with a trained "malariologist," an entomologist, a sanitary engineer, and a statistician as subordinates, and a suitable office. The bureau will collect information and co- ordinate efiforts throughout the country, will carry out inspec- tions, give advice, examine results, and publish reports. Those who have no acquaintance with public affairs may think that this is an extravagant suggestion. In 1904 I mooted the idea for India through the Secretary of State. In that country malaria has been officially estimated to cause about 1,000,000 deaths annually. Government spends enormous sums on plague, which has a smaller mortality and much smaller morbidity ; but a mere cipher on malaria. My suggestion was not accepted, and not even a director was appointed. Hence the efforts made there have been, in my opinion, too discon- tinuous for success (section 59), and much of the money spent has possibly been wasted. The head of the Sanitary Department must often himself direct the anti-malaria work. He will do well to begin at once by collecting a permanent special staff. This will cost money ; but it will save much more which is otherwise likely to be wasted on inexperienced efforts. Public work is permanently successful only if directed by officials who are permanently interested in its success. Local enthusiasts perform great services in originating campaigns, but they alone cannot maintain them for ever. General anti-malaria work is now sure to be commenced in most civilised countries, and it is high time that governments should prepare for this by providing the necessary adminis- trative nucleus. (3). Anti-malaria Leagues, under the presidency of high officials, consisting of numbers of medical men and influential persons, with a central office and local branches, should be started at once — have been, in fact, already started in many places. They serve to interest the public, to disarm opposition, and to enlist active allies. To them should be entrusted the 3i6 PREVENTION [Sect. dissemination of information regarding the disease by the well- known methods of placards, pamphlets, postcards and lectures. Personally, I think it wise not to demand a general subscription for membership, as this tends to limit the list, but to ask for donations from Government and wealthy individuals in order to pay for the printing and other small expenses of the League. Unfortunately, there is a distinct danger that the Government, as soon as the League has been formed, will attempt to shift responsibility on to it. It is not often that the League will be able to do the whole work. Its duty lies principally in arousing public attention as regards protective measures and quinine. It can seldom undertake extensive mosquito reduction or much quinine distribution. Lastly, as soon as the novelty wears off, the efforts of the League may tend to slacken. (4). Legislation. — The next thing required is to reconsider the local Government and municipal sanitary regulations in order to take power to deal with mosquitos and other details. This is largely a lawyer's matter, as most regulations are so framed that they may be interpreted in various ways. The Government will do well, therefore, to call together a committee to consider the subject thoroughly. Certain clauses are given as examples in section 64. It is easy to overrate the import- ance of legislation in the campaign. The experienced health officer depends upon it as little as possible ; but it is, never- theless, occasionally useful to control objectors and other foolish people. Thus, in Egypt my brothers found it better to ignore such persons rather than waste time over compulsion, and my experience has always been the same. The trouble and expense of bringing recalcitrants to book is greater than what is incurred in doing the work by departmental agency. The wise health officer seeks to trouble the public as little as possible, and the amateur one as much as possible. Laws protecting indentured coolies should be carefully revised in the same sense, though this is seldom necessary. All this costs nothing, but requires considerable time to effect in consequence of the unavoidable and 4o] THE MALARIA SURVEY 317 often unnecessary discussions which arise. I apprehend that these discussions will now become shorter, because every colony is adopting the required legislation. See especially R. Boyce's book [1910] and sections 59 and 64. A serious difficulty in the way of all sanitary improvement lies in the inadequacy of punishment often given by legislators for sanitary contraventions. These are too small to be deterrent. Endless petitions are allowed ; and the time of the Sanitary Department, 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 stringent discipline exerted ; and the public themselves have become thankful for it. Sanitary discipline is like that of the sick-room, against which only the most foolish patient rebels — to his own cost. I would, therefore, strongly advise the Government which determines upon a general war against malaria to tighten up the reins in this matter. (5). The pj'eliminary malaria survey. — The necessity for repeated measurements of malaria is quite obvious. Without them we cannot {a) make any estimate of the expense which might theoretically be incurred for prevention by axioms 3 and 4, and {b) determine the exact effect of the measures which are taken. Thus, the authorities will not feel the necessity for the demands made on them, nor the value of the work done, and the whole campaign may tend to collapse. This happened in 1899 in Sierra Leone, where the authorities disliked a malaria survey because they feared that it would alarm the public. 3i8 PREVENTION [Sect. Hence, while the League is being formed, the Director will do well to spend some months in making his preliminary- measurements according to the principles given in sections 31 and 32. Maps being obtained, the local total death-rates for as many years as possible should be carefully scrutinised and compared with the attendances for malaria at hospitals and dis- pensaries — the results being entered in the maps and registers. This will cost nothing, but will yield information regarding both local distribution and general prevalence which will be invaluable for testing the success of future measures. At the same time the measures proposed in next sub-section to be adopted in schools, including registration of enlarged spleen, should be commenced. It is now also advisable to make, if possible, a general " spleen census," That this can be done on a large scale at little expense has been proved in Mauritius and Ceylon, where 31,022 and 92,258 children respectively were examined (section 22). Of course, the work cannot be done entirely by the Director himself. Orders should be issued to Government medical officers to undertake it, each for his own district, and the help of all medical men, of trustworthy assistants and dis- pensers, and of large employers of labour should be solicited. Travelling expenses must occasionally be paid, and I think that fees ought to be allowed under certain circumstances, as the gratuitous services of medical men are too often demanded as it is. The Director should set the example by examining as many children as possible, and he must, of course, register all the results. The season during which the spleen census is taken is important. In the middle of the malaria season the figures are probably very variable ; so that it would be better to select a time before or after that season. I advise between one and two months before the commencement of the season, or a period within about one month after the end of it — in the hope of obtaining the minimum and maximum spleen indices y 4o] MEASURES IN SCHOOLS 319 respectively. In fact, for the first year I advise that the census be taken twice, namely, at the periods mentioned. Of course, it is not necessary or possible that all the children should be examined on the same day, but I think that the work ought to be done within about one month. (6). Measures in schools. — From this point the actual campaign commences, and the first principle requiring attention is that the cheapest measures should first be set in train. The Director will be able to do much at little cost with various public institutions according to the principles laid down in section 37. Schools, if they exist, furnish an admirable opportunity for large-scale work. In most countries the schools are either maintained entirely by Government or are given what are called "grants in aid," or at least licences. This enables Government to maintain a close control over the health of the children, and the Director to use the schools for his great purpose. Two uses can be made of them, {a) by the treatment of children with fever or enlarged spleen, and {b) for the repeated measurement of malaria. Both measures are especi- ally suitable for children since they are the principal homes of the parasites. I advise as follows : — (i). That every school be visited once a quarter by a suitable medical officer (who may, if necessary, be paid for the work). (2). That at this examination the medical officer shall select all children with enlarged spleen, or with fever at the time of his visit, and should enter their names in a register kept by the schoolmaster. (3). That at the same time the medical officer shall advise the schoolmaster as to the treatment to be given to the child during the next three months. (4). After the inspection the medical officer should report to the Malaria Director the number of children found to show signs of malaria, and the latter should incorporate the facts in his statistics. 320 PREVENTION [Sect. (5). At the next inspection the medical officer should observe the number of newly-infected children and those who have become cured, and should again report the facts to the Malaria Director. (6). The schoolmaster should give the medicine to the children as ordered by the medical inspector. (7). Quinine may also be advised for the children who are not suffering from fever or enlargement of the spleen, but no compulsion should be used to force them to take it. (8). The Medical Department should supply quinine in freshly-made pills or tablets, in appropriate doses, to each school. This may be done gratuitously for the schools of the poor, but I think that payment should be demanded in some cases. Different doses should be put up in different canisters, and sweets may be allowed for small children. (9). The medical inspector may stop the drug, if in his opinion it disagrees with a child. I do not advise here as to the amount of the drug, which I think had better be left to the medical officer. A useful plan is for the schoolmaster to give the medicine when the child first comes to school in the morning. It may not be considered advisable to dose the children every day during the whole three months, though this may perhaps be done at certain times. Perhaps the first fortnight of each month ought to suffice, at least for a trial. During the malaria season the drug may be given more continuously, and during the non-malarious season, less so. (7). Measures on estates, factories, etc. — There are generally large numbers of children in connection with the above, and these may be managed in exactly the same manner as children in schools. Estates often have their own medical officers, who should be directed to keep the registers, to give the quinine, and to report every quarter to the Malaria Director. The 4o] MEASURES ON THE ESTATES 321 latter will thus possess an excellent standing record of the state of health upon each estate or factory. In addition to this adults on estates and factories must also be continuously treated if they are sick. The defect has generally been that they are given doses only for a day or two, thus necessitating their frequent presence at the dispensary, a thing which causes endless trouble both to dispensers and to patients. It is much better to give sufficient quinine to last for a week, or fortnight, or more, according to section 36. Whether quinine should be used for prophylactic purposes depends upon the severity of the local endemicity, the possi- bility of reducing Anophelines, and the judgment of the Director (see especially section 57). Whether quinine is to be supplied gratis to plantations, etc., depends upon the local labour regulations. (8). Other quinine distribution. — I suggest the following steps in accordance with section 36 : — (i) A number oi quinine dispensers, who are duly qualified dispensers, should be appointed under the Malaria Director. (2) Each dispenser should be stationed at a convenient centre within an area allotted to him, and should spend the whole of his time in house-to-house distribution of quinine to those who he thinks require it. (3) He should be provided with a small portable case, to be carried by himself, containing a day's supply of quinine in the form of pills or tablets, put up in canisters of different doses. (4) He should be provided with a uniform, or at least an official badge, and a written authority stating his duties. (5) Every day he should visit a number of houses allotted to him, (6) On coming to a house he should offer the quinine X 322 PREVENTION [Sect. gratis to all persons who suffer from fever or enlargement of the spleen. He must not demand nor take any payment whatever, either for medicine or for his advice. (7) He may give the drug to any person who demands it, in doses sufficient for a week or a fortnight, if he thinks that that person is infected or is in imminent danger of becoming infected. (8) He may also examine children for enlargement of the spleen, if permitted to do so by the occupiers of the houses, and shall keep a record of the number in which he finds this symptom. (9) The quinine dispensers should be well instructed in their duties, and in a knowledge of malaria in general. They should furnish a report every month to the Malaria Director. (10) The Malaria Director will be well advised to send these men most frequently to the most intensely infected areas, and utilise them also, if necessary, for providing vermifuges and sulphur ointment to the very poor. The cost of this will be but small and the advantage great. In addition to the quinine dispensers, I advised in my report [1908] that a change should be made as regards the distributing of quinine to out -door patients of hospitals and dispensaries. It is quite insufficient to give patients only a few doses for a few days. Enough should be given for a fortnight or more. In Mauritius we found that one dispenser could visit 200 houses a week, and giveaway about 3-3 lbs. (about 1,200 grammes) of quinine to about 650 sick, or nearly 3 grammes to each. I must again remark that to be really useful the drug must simply be poured out in unlimited quantities. A certain amount may be sold, but stinginess in this particular tends merely to defeat the main object in view. Government quinine may 4o] MOUSTIQUIERS 323 be distinguished by a certain colour, as done in India ; authorities should guard against the possibility of their quinine being subsequently retailed to purchasers or even exported ; but too many precautions 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. The cost of collecting money for small sales, and of sending in reports of exact amounts distributed, really exceeds the cost of wastage, unless this is allowed entirely without any limit. Government must, I fear, face a certain loss from leakage, but this should be looked upon as an unavoidable part of the general cost of the campaign. (9). Appointment and instruction of vioustiquiers. — We now turn to mosquito reduction. The first necessity, an absolute one, is for the Director to have a number of subordinates well trained in a knowledge of mosquitos. In Mauritius we called these men moustiquiers. They were paid about 25 rupees a month, and were mostly of Indian extraction. The men should be carefully selected for intelligence and reliability by the Director himself, and should be formed into a class to be trained by him personally. It will be found that they learn their work in a surprisingly short time, and generally take great interest in it. Each man should be taught how to catch adult mosquitos, and how to find larvae in all possible breeding- places ; also how to fill up holes in trees and rocks, and to direct the gangs of workmen required for clearing pools and streams, etc. The appointment should be made with a view to permanency, with a scale of increasing salaries, and, if possible, with a promise of pension. This is obviously an economical principle, because after a year or so moustiquiers become highly experienced in their work. After he is trained, each man should be allotted a given district, consisting either of town or of village, or of open country, according to the judgment of the Director. The duties of the moustiquiers will consist in ascertaining all the breeding-places in his district, in guiding the works of the malaria gangs, and in making occasional 324 PREVENTION [Sect. reports to the Director. Oral reports generally suffice. It may be advisable to appoint head moustiquiers to superintend larger areas. Each moustiquier should be provided with a white enamelled pan or sieve for finding larvae in water. These men are essential for a continued campaign against mosquitos. They are, so to speak, the local eyes of the Director. Without them there will be no permanence in the measures, because directors and superintending medical officers may change from time to time, while the staff of moustiquiers will be permanent. In fact, many campaigns have failed because this fundamental point was overlooked. The number of moustiquiers will depend upon the amount of work allotted to each. I suppose that one man can super- intend quite lo square miles of area, except in crowded towns. If the campaign is to include Culicine reduction, more men will be required for towns. Moustiquiers are exposed to considerable risk of infection. Care must be taken of their health, and they must be provided with bed-nets. The Director can send his most reliable men to outlying stations and plantations in order to report to him as to mosquito breeding there, and also in order to instruct managers, head- men of villages, and so on — a thing which he cannot always do himself. (lo). Malaria gangs for minor works. — The moustiquiers do not do manual labour, which is entrusted to workmen of the class usually employed for gardening and engineering works. The duty of these workmen should be to train small pools, to keep street gutters, surface drains, roadside ditches and channels, margins of ponds and streams clear of weeds and obstructions ; to carry out rough canalisation of streams, to deepen or " back-up " breeding - ponds ; to fill or oil other waters ; to fill holes in rocks and holes in trees ; to cut under- growth ; and to deal with house waters which breed Culicines (section 35). 4o] GANGS AND OFFICES 325 From our experience in Mauritius I advised that the work- men be formed into gangs of about three or four men each. One of the men should be appointed the headman of each gang, with extra pay, and should be responsible for the work of the gang. This extra pay is an inducement for the work- men to remain in such employment, which, like that of moustiquiers, requires considerable training for economical working ; and it is astonishing how much trained men will do in a given time. It is impossible to state how many gangs will be required for a given area. This will depend entirely upon the local conditions. In Mauritius I thought that one gang could manage about 4 square miles as a very rough average, and the cost of each gang was about 50 rupees (;^3'3) a month. The gangs are to be superintended by the moustiquiers, or by special headmen if necessary ; but the Director must frequently examine the work done. It may also be frequently feasible to put the gangs under enthusiastic local medical officers, or district officers, or members of the Anti-malaria League, subject, of course, to the final authority of the Director. (11). Local offices. — All this organisation — dispensers, moustiquiers and malaria gangs — will require a number of local offices where the men can be given instructions, paid, supplied with medicines, oil, tools and impliments, etc. Generally, as the whole organisation is under the Medical Department, it will be better to make local dispensaries the headquarters of each local malaria administration ; but, of course, this question depends upon conditions. I do not think it is necessary to appoint a special clerk at each dispensary. Perhaps the sanitary inspector's office may be more convenient than the dispensary in many cases. (12). Major works. — Here the fundamental principle of 35 (8), namely, that of minor works before major works ^ must always be remembered. It is folly to commit the state to a 326 PREVENTION [Sect. large expenditure where a small one may suffice. At the same time it may sometimes be more economical to do the major work at once. Hence, at an early stage of the campaign, the Director should obtain rough conjectural estimates of the cost of all major works that may be required. Exact estimates can only be obtained from the Public Works' Department at considerable cost, incurred for accurate surveying and skilled advice ; but Government will generally be able to ask its engineers to prepare the rough estimates by mere inspection of the localities concerned. These rough estimates are now borne in mind by the Malaria Director, who shapes his policy accordingly. Of course, major works will generally demand not only a considerable capital outlay, but also an annual expenditure for maintenance. Government always finds a considerable difficulty in obtaining the former item, which may require loans and the consent of higher authorities. The Director should, therefore, generally not make such demands until he is con- vinced by the unsuccessful result of minor works during several years that the expenditure is absolutely necessary ; unless he and the Public Works' Department consider that money will thereby be saved in the end. The important question as to who is to pay for drainage of marshes on private property often arises ; and I was asked in Mauritius to advise upon the point. I first enquired officially whether 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 their property. In reply I was informed that in the opinion of the Law Officer, marshes could not be held to be nuisances in the statutory sense of the word ; and that legislation had been proposed but presented many difficulties. The answer seems to me to depend upon {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 4o] MAJOR WORKS 327 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 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 required by the Medical Department ; and if it is proved that the marsh is actually causing sickness, or, in the opinion of the Medical Department, is likely to cause sickness ; then I think that he (the owner) may be forced to do the work. As a matter of fact a marsh in a malarious country is a nuisance, 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 clean 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 immedi- ately 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 Government will often feel it more fair to pay at least a part of the expense. At the same time, legislation to compel defaulting owners should certainly be passed. Precisely similar difficulties often occur in connection with water-ways, drains, polluted rivers, and especially irrigation channels ; and I think they may generally be met on the same principle. (13). The annual malaria report. — I think it is most essential that a report upon the work done should be submitted to Government every year. It should be prepared by the Malaria Director, and should commence with a detailed statement of the measurement of malaria for previous years as well as for the year under review. It should then describe the measures 328 PREVENTION [Sect. taken, the number of men employed, and the cost ; and should conclude with remarks upon the results obtained. This report will enable Government to judge whether or not value is being received for the money spent. Officials are apt to dislike the trouble incurred, but it is a necessary one. In British possessions, one often finds a single per- functory annual report on medical matters, and we should compare such with those excellent monthly reports issued by the Americans for the Panama Canal Zone. (14). Cost. — I will content myself by giving the approximate estimate which I prepared for Mauritius [1908]. Items Rs. per annum. 1. Salary of the Malaria Authority .... 6,000 2. Salaries of 5 Quinine Dispensers (say) . . 6,000 3. Salaries of 15 Moustiquiers .... 4,560 4. Salaries of 109 gangs (327 men) .... 65,400 5. Cost of quinine (say) 30,000 6. Preparation and despatch of quinine (say) . . 3,600 7. Office of Malaria Authority (say) . . . 1,500 8. Implements, etc., for gangs (say Rs. 50 a gang) . 5,45© 9. Travelling expenses for staff (say) . . 2,000 10. Margin for possible calls 10,490 Total 135,000 This amounts to ^9,000 per annum for a population of 375,400 (1906), or 0-36 rupees per head per annum, and r2% of the total revenue. The estimate was an " outside one." The number of gangs of men was determined, not by myself, but by the Medical Department, and many suppose that it is considerably in excess of the actual requirements. In fact, I have since heard that the whole work can probably be done at much less cost My whole scheme has, however, been held over pending the final settlement of the financial position of the Colony. This has only just been effected (1910), and I hear that the scheme will now be proceeded with. In addition to the above annual expenditure, we had to 4o] COST 329 consider the major works. A rough conjectural estimate for these was prepared by the Public Works Department, and was put at 630,000 rupees for capital expenditure, together with 42,300 rupees for annual maintenance. But, as I have said, I hope that experience will prove that little of this will really be called up. Critics of my report have complained that such expenditure, though it may be possible for Mauritius, will be altogether too vast for other countries. The total revenue of Mauritius is 9,915,863 rupees, of which 749,827 was allotted to the Medical and Health Department and to quarantine. Hence the proposed malaria expenditure amounted only to i"2// of the total revenue, and to 18^ of the medical and sanitary revenue; while the disease causes 1/3 of the total sickness, and costs the colony about 1,000,000 rupees a year (section 32). The sum of about one- third of a rupee per head of population is scarcely too much to pay for all the advantages, not only of malaria reduction, but of very considerable mosquito reduction, and general " cleaning up." Moreover, I may note again that the malaria gangs can be largely utilised for general sanitary purposes, and for perform- ing many useful offices during the non-malarial season. On the whole I am quite convinced that this expenditure would be a very small one for any population, compared with the benefits obtained. Of course, the Malaria Director will have to prepare similar estimates before he engages large numbers of men. Unfortun- ately, it is always impossible to state without trial how many gangs are required for a given area. Thus, the Director is almost forced to commence with the most populous areas, and especially with the most malarious ones. He must point out these difficulties to the Government, and must do the best he can. (15). Remarks. — Amateurs are fond of advising that all practical measures should be postponed pending the carrying 330 PREVENTION [Sect. out of detailed researches upon the habits of the Anophelines, the parasite rate of localities, the effect of minor works, and so on. In my opinion this is a fundamental mistake. It implies the sacrifice of life and health on a large scale, while researches which may have little real value, and which may be continued indefinitely are being attempted. As a matter of fact, the campaigns at Havana, Panama, Ismailia, and the Federated Malay States, were all commenced before the local carriers were definitely incriminated and their habits studied. We already know the broad general principles that these carriers breed in more or less stagnant waters, and that protection and prevention by treatment are valuable. More exact knowledge of the habits of the carriers is certainly often very valuable, because it enables us to deal more economically with them ; but, if the principle of minor works before major works is remembered, we need not wait for the full development of such studies. Moreover, the Medical Director will be able to carry out such researches much more effectively by the aid of his moustiquiers and quinine dispensers than by himself in a long preliminary survey during which the people are allowed to continue dying. In practical life we observe that the best practical discoveries are obtained during the execution of practical work, and that long academical discussions are apt to lead to nothing but academical profit. Action and investigation together do more than either of these alone. I strongly advocate a generalised campaign in preference to one which deals only with a few spots. The former is likely to be more economical in the end, and the latter is more likely to dishearten the authorities and to waste money. At the same time financial considerations will almost always demand stronger efforts in the larger, more populous, and most malarious localities — at least to begin with. But the Director must always hold in mind and prepare for extension to every part of his domain. In conclusion, I believe that anti - malaria work can be 4o] REMARKS 331 effected for little cost in all malarious countries, and will soon be attempted everywhere. The success of it depends, not so much on profuse expenditure, as on the intelligence, enthusiasm and energy of those who are responsible for sanitary affairs. He who undertakes the work must remember that he is a soldier in one of the greatest of crusades, which has for its object the conquest of the tropics for humanity. CHAPTER VII SPECIAL CONTRIBUTIONS By Professor L. O. HOWARD Chief of the Bureau of Entomology, Department of Agriculture^ Washington, D. C, United States 41. Anti-malaria Work in the United States.— Beginning with 1900 and gradually increasing in amount year by year, a great deal of anti-mosquito work, more or less well planned, has been done in different parts of the United States ; but, looking over the entire field, it is astonishing to note how little of this work has been done with a direct sanitary object in view. The sanitary point has been held constantly in mind in the operations conducted under the United States Govern- ment in Cuba, on the Isthmus of Panama, in Porto Rico, and in the Philippines, but in the United States, while malaria is prevalent in large regions, such work as has been done has been instituted for the most part with the sole idea of relieving localities from the nuisance of mosquitos, thus not only render- ing living conditions more agreeable, but increasing the value of real estate. In fact, one of the best bits of work done was accomplished by means of a large sum of money presented by a wealthy man whose object was not primarily the improved health of the people of the region, but bettering the condition of his high-priced race-horses, which were suffering from the abundance of mosquitos. Nevertheless, what anti - mosquito work has been done naturally has resulted in improved con- ditions in health in localities included within the scope of operations. A great deal of valuable drainage work has been done in the past few years in the salt marsh region of the North 332 Sect. 41] LONG ISLAND 333 Atlantic coast, and there is one instance of this upon the Pacific coast, with the direct idea of doing away with the salt msCrsh mosquitos, several species of which occur in such localities, all having unusual power of flight, and being able to proceed inland for many miles, thus annoying the inhabitants of a large extent of country. In America Anop/icles mosquitos are rarely found in these salt marshes, and, in fact, there is but one record of the finding of Anopheles larvae in such locations in the United States. One of the first operations of this kind was conducted by the wealthy owners of Center Island, off the north coast of Long Island in Long Island Sound. This led to some- what elaborate work under the organisation known as the North Shore Improvement Association, which included simple operations over a considerable distance along the north shore of Long Island, and in the vicinity of Oyster Bay. In the course of this work the breeding - places of Anopheles were studied and mapped, and especial effort was made to destroy them. These operations took place in 1902 and 1903, and have been reported at length in a small volume published by the Association. Later, some excellent work was done at Lawrence, Long Island, which demonstrated the feasibility of controlling the salt marsh mosquitos by relatively simple and comparatively inexpensive ditching operations. These opera- tions were continued for four years at an annual expense of something more than one thousand dollars per year. The work in the early part of this short period of years was usually started here and there by intelligent and up-to-date citizens, citizens' associations, city improvement societies, and women's clubs. The California work, taken up in 1905, was done under the auspices of the Burlingame Improvement Club. Excellent anti-mosquito work was begun as early as 1900 on Staten Island, New York, by the Richmond County Club. Admirable community work was taken up during 1901 and 1902 by certain New Jersey towns, notably South Orange, 334 ANTI-MALARIA WORK IN THE UNITED STATES [Sect. Elizabeth, Montclair, Monmouth Beach and Summit, and a little later independent work was begun in Greater New York under Dr Lederle, which included the mapping of all mosquito breeding - places within the city limits. Independently, the health officers of Brooklyn, Jamaica and the Brinx began efficient work, while the summer resorts of Arverne and Wood- mere reduced the mosquito supply by intelligent operations. At Willets Point, New York, intelligent and efficient work was carried on on a small scale. In Massachusetts interesting and important work was done at Brooklyn and at Worcester. In Brooklyn the Board of Health first considered the work in August 1901, and in September all the breeding-places of Anopheles and other mosquitos were treated. In 1902 all pools, ponds, ditches and other breeding - places, including catch-basins, were located on the town map, the approximate areas were determined, and the number of catch - basins ascertained ; breeding-places of Culex and A nopkeles respectively were determined, and also places where both species were breeding together — this being done in order to ascertain the proper intervals for treatment — that is, whether every two weeks or every three weeks. Public dumps and other places where accidental receptacles of water might be found were located on the maps. Light fuel oil was used on all breeding- places. At Worcester the work was of the most interesting kind. Dr William M'Kibben and Dr C. F. Hodge started the crusade. Breeding-places were mapped and photographed, and public lectures were given. The school children of the several grades were interested, and were organised into searching parties. Many breeding-places were filled up, and others were treated with kerosene. The prevalence of malaria in Worcester was pointed out by those engaged in the crusade, and the relation between mosquito breeding-places and the houses where malaria patients lived was shown. A map was prepared showing the exact distribution of malaria in the city, and photographs 4i] BALTIMORE 335 were made showing the character of the breeding - places of the malarial mosquito. It is probable that these Worcester efforts to interest the school children were the first made in this direction, although the idea was carried out to a much greater extent later in San Antonio, Texas, under Dr J. S. Lankford. Other early work was carried on at Pine Orchard and Ansonia, Connecticut, and Old Orchard Beach in Maine, and on the campus of the Michigan Agricultural College in Michigan. At Atlanta, Georgia, the Sanitary Department used a large amount of kerosene in the stagnant pools and the swampy places around the city, and warned the citizens to watch their rain barrels and to keep their gutters open. A great many pools of water were drained. In Savannah some work was done, and the number of mosquitos was reduced very considerably. At Talladega, Alabama, under the direction of Dr B. B. Simms, anti-mosquito work was commenced early in 1902, and carried out systematically. St Louis took up the work early in 1903, and the Municipal Assembly made an appropriation for supplies. The Health Department, however, was hampered for lack of men and little work was done. Many of these and other efforts were spasmodic and only temporary in their effect ; even the boards of health in some instances lost interest. An excellent example of the difficulties encountered by intelligent citizens was shown in the city of Baltimore. Intelligent individuals pointed out very early that a large part of the mosquito supply of the city could be easily handled, and year after year, in public press and before the Board of Health and the City Council, these persons con- tinually agitated the subject of anti-mosquito and anti-malarial work. Finally, in 1907, Mr George Stewart Brown, a member of the City Council, succeeded in getting an appropriation to start the work for that year. Much of this money was expended in extensive advertising in the street cars, etc., but the remainder was expended very efficiently, though necessarily 336 ANTI-MALARIA WORK IN THE UNITED STATES [Sect. with only partial results, by organising a gang of men to drain and fill up the pools in the vacant lots around the suburbs. Next year the appropriation was reduced, and only this gang of men was continued. During 1909 no appropriation was made, the gang of men was dropped, and the whole question was abandoned. It should be stated, however, that before the appropriation was made an ordinance was passed by the City Council requiring every householder to remove, screen with wire-netting, or keep covered with oil all standing water around his premises, but it seems that no real attempt was ever made to enforce this ordinance. Of course such an attempt could hardly be successful at first without the aid of an especial appropriation for the purpose, and at the present time the ordinance seems to be a dead letter. It is pleasing, in the face of so much of this sort of thing, to note a well-directed and rather large-scale bit of work with a direct anti-malarial bearing which was begun at an early date, and that is the work on Staten Island under Dr A. H. Doty, the health officer of the port of New York. Staten Island, lying in New York Harbour, had had a rather unenviable reputation on account of the great number of mosquitos present and the continued presence of malaria. It was largely on account of the latter condition that Dr Doty began his investigation in 1901. He soon found that there were two factors to deal with in this work, namely, the inland mosquitos and the salt marsh mosquitos. In the extermination of the inland mosquitos, the section of Staten Island which was known to contain many cases of malaria both in the acute and chronic forms was selected for experimental work. This section consisted of a basin or low- land about a mile square, containing about one hundred small dwelling-houses some distance apart. Within its boundaries were a large number of stagnant pools varying in size from ten feet in diameter to an acre or more in area. A house-to- house visit showed that at least 20% of the inhabitants of this 4i] STATEN ISLAND 337 district were suffering with some form of malaria, and in the immediate vicinity of every house were found typical breeding- places in the shape of old tinware, rain-water barrels, cisterns, cesspools and ground depressions, many of which contained larvae. For the purpose of detecting the presence of adult Anopheles, glass tubes fitted with cotton plugs were distributed among the occupants of these houses with the request that the mosquitos found in the house at night be captured and placed in the tubes. In the collection were found many Anopheles. These were particularly numerous in tubes coming from a small group of houses. In one of the latter was found a family con- sisting of five persons, all of whom showed the acute or chronic form of malaria. Dr Doty himself secured live mosquitos from the interior of this house. On the first evening five were captured, and all but one were Anopheles. On the second evening twenty-two were collected, and of these more than one \\2\{-w^xt. Anopheles. In the house on the opposite corner was found a patient suffering from an acute attack. In the beginning considerable difficulty was found in detect- ing the breeding - places of the Anopheles, but this became easier as the inspections became more thorough. For instance, in a group of two or three houses close together a number of Anopheles were captured, but their breeding - place could not be found for some time. Finally, in the backyard of one of the houses, overgrown with weeds, was discovered a very large metal receptacle filled with Anopheles larvae, and with many adults in the immediate vicinity. This receptacle was almost entirely covered by underbrush. After this experience the men employed learned to make the closest possible search, and to find probably every breeding- place. The island was then divided into small districts, which were visited by mosquito corps consisting of five men, one of whom was a sanitary police officer connected with the New York City Department of Health. The equipment of the mosquito Y 338 ANTI-MALARIA WORK IN THE UNITED STATES [Sect. corps consisted of a large waggon provided with spades, rakes, hoes, scythes, and petroleum oil. A house-to-house inspection was made in each district. House owners or tenants were required to remove from about the premises all receptacles which might act as breeding-places, or to protect them. Rain- water barrels and cisterns were covered with wire-netting, all roof gutters were repaired, and pools of water were covered with petroleum. In certain instances orders were sent to the owners of property containing depressions in the soil to fill them in or drain them. If these orders could not be enforced, the mosquito corps returned every ten days or two weeks and applied more petroleum. Copies of a circular of informa- tion were delivered so far as possible to each house on Staten Island by police officers, and this educational campaign brought about valuable co-operation on the part of the public. In 1905 the details of this work were presented to the Department of Health of the city of New York, and the city government granted an appropriation for the drainage of the swamp land along the entire coast of the island. With the aid of this appropriation, ditching was carried on somewhat in the same manner in which it has been carried on in New Jersey. Down to the present time between 800 and i,0CXD miles of ditches have been dug. The swarms of mosquitos soon practically disappeared, window screens were discarded, and meals were served upon the verandas of the hotels. With the malarial and other inland mosquitos the work was carried on in the manner above described, not only in the built-up portion of the island, but also in the open spaces between the small and scattered settlements. During the past two years cases of malaria on Staten Island are becoming practically unknown, and for the past year Dr Doty has been unable to secure any Anopheles, whereas, in the beginning of the investigation they were found almost everywhere on the island. The statistics of the Department of Health indicate the decrease of malaria from 1905 on. Prior to 1905 malaria 4i] RESULTS OF DR DOTY'S WORK 339 was not regularly reported, but the number of cases was surely very much greater than that reported in that year. Since 1905, however, they are stated to be as follows : — 1905, thirty-three cases ; 1906, fifty-four cases ; 1907, four cases ; 1908, six cases ; 1909, five cases. The work of exterminating malarial mosquitos has been necessarily slow, as the area involved is considerable, the island being about 16 miles long and 4 to 6 miles wide, probably containing over eighty thousand inhabitants in large areas between the various towns. The expense of the operations down to the present date has been about $50,000 ; this, of course, includes the expense of the extensive drainage operations in the salt marshes. Dr Doty, in addition to being the Health Officer of the Port of New York, is a Commissioner of Health of New York City, and he carried out this work in his capacity as a municipal officer, and not as a State official. Earlier and very much smaller pieces of work have previously been described by the writer in "Mosquitos" (New York, 1901), including the work done by Dr W. N. Berkeley in a small town near New York City during the summer of 1900, and the work done at Chaptico, Maryland, by the Rev. William Brayshaw, in both of these cases the work being directed primarily against malaria. Later, some excellent work was instituted through the combined action of the boards of health of Cambridge and Belmont, Massachusetts, to improve the sanitary conditions of the cities of Cambridge and Somerville, and the towns of Arlington and Belmont, at the inspiration of Mr W. L. Underwood, a member of one of the boards of health. This was effectively carried out at an expense of S600 without assessment upon land-holders. In 1903 some extensive work was done at Newport, Rhode Island, at the expense of a single property holder, and the following year the Citizens' Association of Flushing, Long Island, took up the problem, and with the assistance of the 340 ANTI-MALARIA WORK IN THE UNITED STATES [SECT. Board of Health extensive drainage operations have been carried on, but are not yet completed. In 1903 the American Mosquito Extermination Society was founded, and took an active part in interesting the people of the United States in the mosquito crusade. It was founded for the purpose of educating the public, of bringing about legislation, and of securing co-operation and exchange of ideas. It held its first anti-mosquito convention i6th December 1903, and continued its organisation, publishing several bulletins, finally disbanding in 1907 in consideration of the fact that the objects of its existence would be taken over by the National Drainage Association. In 1903 and 1904 work against mosquitos was undertaken by the state entomologist of Connecticut, Dr W. E. Britton, who made careful mosquito surveys over the whole state, and he published in his Annual Report for 1904 a careful and well- illustrated article devoted to showing how the mosquito nuisance can be abated. The largest-scale work taken up in the United States, how- ever, has been carried on by the state of New Jersey, and this is the first of the United States to take official action in this direction. This work was instigated by Dr John B, Smith, the state entomologist, under whose direction it has been carried on, and resulted largely from his discovery of the exact habits of the salt marsh mosquitos. An admirable state law was passed carrying a very considerable appropriation. The law provided for a survey at the request of the board of health of any city, town or township, which should map all mosquito breeding- places, and provided that the board of health must, after the survey, proceed to abolish the breeding-places. The law provides further that if the necessary cost of the work shall equal or exceed the value of the land without increasing its taxable value the board may apply to the director of the work, who may, if he deems the matter of sufficient public interest, contribute from the state funds to the cost of the necessary 4i] NEW JERSEY 341 work, providing that not more than 50% of the amount shall be contributed in any case. Under this appropriation and during the past three years much admirable work has been done upon the salt marshes of the New Jersey coast. In all 25,192 acres of marsh land have been reclaimed by 3,633,974 feet of ditching, and this includes a shore line of nearly 70 miles. Other work has been done also, more specifically against inland mosquitos, including Anopheles. The work that was done in New Orleans during the yellow fever outbreak of 1905 was an object lesson to the people of the United States. This work was so thorough that it resulted in the reduction of the numbers of the yellow fever mosquito to a minimum, and at the same time sensibly decreased the numbers of Anopheles. This work, while carried on originally under the United States Public Health and Marine Hospital Service, has been continued by the city Board of Health, and the example of New Orleans in this direction has been slowly followed by other southern cities. The city of San Antonio, Texas, has the honour of instituting and carrying forward a large-scale effort to educate the children in the public schools, which is worthy of rather specific mention on account of its widespread application. In November 1903 there were a few cases of yellow fever in San Antonio which caused several deaths, and an inexcusable interruption of commerce that cost hundreds of thousands of dollars. In the effort to allay the panic, the existence of yellow fever was denied, not only by persons having business interests in the city, but by many medical men as well. Very many adults not only denied the existence of the fever in the city, but denied the relation between the mosquitos and the fever. Perhaps the majority of the adults seemed too old to learn ; and to the enlightened physicians it appeared that it was impossible to begin education at the wrong end of life. The Chairman of the Sanitary Committee of the School Board (Dr J. S. Lankford) grasped the happy idea that if the 342 ANTI-MALARIA WORK IN THE UNITED STATES [Sect. children were properly educated, sanitary matters in the future would be much better attended to. He suggested to the Board that it would be valuable to educate all of the school children of the city in prophylaxis and make sanitarians out of them all. The School Board heartily approved of the proposition, and the campaign was at once begun to educate the children on the subject of Insects as Disease Carriers. The best recent medical literature on the subject was procured and furnished to the teachers, and a circular letter was sent to them outlining a proposed course and offering a cash prize for the best model lesson on the subject. Teachers became deeply interested in the subject. A crude aquarium, with eggs and wrigglers, was kept in every schoolroom, where the pupils could watch them develop ; and large magnifying glasses were furnished in order that they might study to better advantage. The children were encouraged to make drawings on the blackboard of mosquitos in all stages of development ; lessons were given and compositions were written on the subject. Competitive ex- aminations were held, and groups of boys and girls were sent out with the teachers on searching expeditions to find the breeding-places. Rivalry sprung up between the 10,000 public school children of the city in the matter of finding and reporting to the Health Office the greatest number of breeding-places found and breeding-places destroyed. Record was kept on the blackboards in the schools for information as to the progress of the competition, and great enthusiasm was stirred up. In addition to these measures, a course of stereopticon lectures was arranged, grouping the pupils in audiences of about one thousand from the high school down, and, in Dr Lankford's words, " It was an inspiring sight to watch these audiences of a thousand children, thoughtful, still as death, and staring with wide-open eyes at the wonders revealed by a microscope. It seemed to me that in bringing this great question of preventive medicine before public school children we had hit upon a power for good that could scarcely be over-estimated." The result of 4i] COST OF MALARIA 343 this work, it is pleasing to say, was a decided diminution in the number of mosquitos in San Antonio. There was some opposition among the people, but the movement on the whole was very popular. One result of this work was that while there had previously been from fifty to sixty deaths a year from malarial trouble, the mortality was reduced 75^ the first year after this work was begun, and in the second year it was entirely eliminated from the mortality records of San Antonio. In organising community work against mosquitos, the school children hereafter must be counted upon as most important factors. Almost every child is a born naturalist, and interest in such things comes to them more readily than anything else outside of the necessities of life. They are quick-witted, wonderfully quick-sighted, and as finders-out of breeding-places they cannot be approached except by adults of the most especial training. One of the first steps that a community should take is, therefore, the encouragement of the interest of the children in the public schools. I fear that it will appear from what precedes that, consider- ing the economic loss existing in the United States through malaria, which has been estimated by the writer at surely not less than S 100,000,000 per year (see Bulletin No. 78, Bureau of Entomology, United States Department of Agriculture), nothing like the competent work has been done that should be done, or really that should have been done in the past eight years, within the territorial limits of the United States themselves. While very many sections of the country that were originally extremely malarious have been practically freed from malaria by the drainage of swamp areas, undertaken not as a measure of sanitation but in order to add to the supply of arable land, it is nevertheless seen that the conditions of improved civilisation have brought about steadily increased opportunities for Anopheles to breed, and this increase in the number of breeding - places and kinds of breeding - places is constantly growing. The introduction of irrigation into many 344 ANTI-MALARIA WORK IN THE UNITED STATES [Sect. portions of the western country has resulted in the introduction of malaria, and these operations are going on with a very rapid increment. Moreover, in regions which are not dry and which need no irrigation, the construction of mill-dams, the excavation of stone quarries, the building of railroad embank- ments and many other operations which follow rapidly increas- ing populations have resulted in the multiplication ol Anopheles, and in many instances the introduction of malaria has been followed by its rapid spread through extended regions. On the whole, under such conditions it would not be surprising if malaria were increasing rather than decreasing in the United States, and the mosquito crusade is bound to become an extremely important matter within the next few years. References on Anti-malarial Work in the United States. American Mosquito Extermination Society. Mosquito Brief. 1904. American Mosquito Extermination Society. Bulletins 1-2, 1904 -1906. {Bulletin i is issued by the National Mosquito Extermination Society.) American Mosquito Extermination Society. Yearbook for 1903- 1905, con- taining the proceedings of the ist and 2nd anti-mosquito convention. Edited by Henry Clay Weeks and Edward Hagaman Hall. New York, 1 904- 1 906. Britton, W. E. & H. L. Viereck. — Report on mosquito investigations. (Fourth report of the State entomologist of Connecticut Agr. Coll. Exp. Station for the year 1904, pp. 253-310, pi. X.-XVII.) Chase, H. Lincoln & J. Albert C. Nyhen.—" Abatement of the Mosquito Nuisance in Brooklyn." (Reprint from the Journal of the Mass. Assoc, of Boards of Health, Boston, 1902- 1903, vol. xii. pp. 190-203, Jan. 1903. Reprint is 14 pages.) Doty, Alvah H. — "The Mosquito: Its Relation to Disease and Its Extermination." New York, 1908. 26pp. (Reprinted from the New York State Journal of Medicine, May 1908.) Doty, A. H.— "On the Extermination of the Mosquito." New York, 1906. lopp. (From the American Journal of the Medical Scietices, Feb. 1906.) 4i] REFERENCES 345 Doty, A. H. — " The Use of Sulphate of Copper alone, and its Combination with Lime, for the Destruction of Mosquito Larvae, as a Deodorant, and as a Disinfectant." New York, William Wood & Co., 1905. 12pp. (Reprint from the Medical Record^ 21st Jan. 1905.) Howard, L. O. — "Economic Loss to the People of the United States through Insects that carry Disease." Washington, 1909. 40pp. (U.S. Dept. of Agr. Bureau of Entomology, Bulletin No. 78.) Howard, L. O. — " Mosquitos : how they live ; how they carry disease ; how they are classified ; how they may be destroyed." New York, M'Clure, Phillips & Co., 1901. xv. 241pp. Lankford, J. S. — " Public School Children and Preventive Medicine." New York, 1904. 9pp. (Reprinted from the New York Medical Journal for loth Dec. 1904.) M'KiBBEN, William W. — "Malaria and Mosquitos of Worcester. A Year's Observations on the Habits of Culex and Anopheles." Boston, 1903. 9pp. (Reprinted from the Boston Medical and Surgical Journal^ vol. cxlix. No. 25, pp. 665-669, 17th Dec. 1903, and No. 26, pp. 704- 708, 24th Dec. 1903.) North Shore Improvement Association. Reports on plans for the extermi- nation of mosquitos on the north shore of Long Island between Hempstead Harbour and Cold Spring Harbour. New York, 1902. 124pp. North Shore Improvement Association. Report of the Association's experts, Frank E. Lutz and William W. Chambers, upon the work of mosquito extermination during the summer of 1902. New York, 1902. 26pp. QUAYLE, H. J. — "Mosquito Control." (Univ. of California, College of Agr. Agr. Exp. Station, Bulletin No. 178, 1906.) Smith, John B. — Report of the New Jersey State Agricultural Experiment Station upon the mosquitos occurring within the state, their habits, life history, etc. Trenton, 1904. 482pp. Smith, John B. — Report on mosquito investigations. (In Reports of the Entomological Department, New Jersey Agri. Coll. Exp. Station, for the years 1902- 1908.) By Colonel W. C. GORGAS, United States Army Chief Sanitary Officer, Isthmian Canal Commission, Panama 42. Malaria Prevention on the Isthmus of Panama.— The Panama Canal extends diagonally across the Isthmus of Panama from south-east to north-west, a distance of 42 miles from shore to shore. Commencing on the South Sea at Panama it runs up the valley of the Rio Grande river to Pedro Miguel, then across the divide to Bas Obispo, and from there down the valley of the Chagres to Colon. Roughly, about two - thirds of this distance is broken and mountainous, and one - third low and swampy. About one - fourth of the population lives in the lowlands and three-fourths in the highlands. Before coming to Panama in 1904 the Army Medical Corps had had very little experience in dealing with malaria on a large scale in rural districts. The mosquito work established by the Army medical officers in the city of Havana in 1901 had not only gotten rid of yellow fever but also of malaria. This work has now been going on in Havana for the past eight years, part of the time under Army medical officers, and part of the time under Cuban officers, and is the most successful example of municipal malarial work that I know of The following table shows the decrease of malaria under these measures, and at the present time, its practical extinction : — 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 170 203 202 240 201 207 450 811 910 909 Mosquito work commenced February of this year, 1901. 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 (to July) 325 151 87 51 44 32 26 23 19 2 Sect. 42] DRAINAGE 347 Ronald Ross's work at Ismailia was the only example at this time that I knew of, pertaining to successful anti-malaria work in rural districts. At Panama our anti - malarial work is principally rural, located for 47 miles along the line of the railroad between Panama and Colon. The railroad in general follows the line of the canal. In this distance we have a population of about eighty thousand living within a half a mile of the railroad, and occupying some thirty villages and camps, and more or less isolated houses scattered between. In this article I shall describe the sanitary organisation as it existed in July 1908. This strip of 47 miles along the railroad is divided into eighteen districts, each district in charge of an inspector. The inspector's duties consist in the carrying out of the sanitary work of the district, and for this purpose he had at his disposal, on an average, about fifty men. The anti-malarial work con- sists in the order of its importance, of: — (i). Drainage, (2). Brush and grass cutting. (3). Oiling. (4). Use of larvicide. (5). Prophylactic quinine. (6). Screening. (7). Killing mosquitos in quarters. Drainage. — He is required to drain and do away with all pools within, approximately, 200 yards of all villages, and 100 yards of all individual houses. For this purpose we con- sider subsoil-drainage by far the most effective and economical ; second, open concrete ditches ; and, third, open ditches. The porous subsoil pipes give a perfect anti - malarial drainage. Besides doing away with all breeding-places, they enable you to use a horse - mower on the ground so drained, and thus much cheapen the cost of subsequent grass cutting. We use the open concrete ditch in localities where 348 MALARIA PREVENTION ON ISTHMUS OF PANAMA [Sect. subsoil drainage is not practicable, such as flat places where the fall is not sufficient, and small natural rills where the volume of water is too large for subsoil drainage, etc. The objection to this style of ditch as compared with the subsoil is that it requires supervision for the purpose of keeping it free. Any obstacle in the ditch will make a small collection of water, which in this warm climate will breed mosquitos at any time of the year. Open ditches we only use when the occupancy is going to be temporary, not more than two years. While the first cost is smaller than in either of the other class of ditches, the ultimate cost is very large. In a locality such as Panama, vegetation grows so rapidly that the ditches have to be cleared out at least once a month, and when clean they will breed larvae unless treated with larvicide. We pay our inspectors from one hundred and twenty-five dollars per month to one hundred and seventy-five, and thus get, in general, an educated intelligent class of men. We have attached to the department an inspector of sufficient engineering education to lay out the ditches, but the local inspector is entirely responsible for their execution. In general, it is the character of work such as the farmer does through our country, and any man of ordinary intelligence is capable of carrying it out. But for its anti-malarial success it is important that the man in charge should have a good knowledge of the breeding habits of the species of mosquitos in his neighbourhood. Brush and grass cutting. — The inspector is required to keep the tropical undergrowth cut off within 200 yards of villages and 100 yards of isolated houses. Within this area the grass must be kept less than a foot high. I consider this scarcely less important than drainage. Brush and grass shelter the adult mosquito, and they will reach a habitation from distant breeding-places by short flight, if they have the continuous protection of brush, whereas the Anopheles will not cross a cleared area of 100 yards. 42] OTHER MEASURES 349 Oiling. — We use oil where drainage is either impracticable or too costly, such as the edges of swamps, edges of streams, etc. In a large construction work such as this, temporary pools are constantly being formed. The oil should be of such consistency that it will spread readily, but not so thin that it will evaporate too rapidly. For this purpose we use crude oil thinned with larvicide. Larvicide. — There are many places, such as the grassy edge of ponds, or of streams, in which the Anopheles larvae love to breed, and where oil will not spread. In such places we use a poison which mixes in the water and which we denominate larvicide. We have done a good deal of experi- menting to get an effective and, at the same time, cheap larvicide. Mr Le Prince gives the formula in his paper. We use per year about 4,500 barrels of oil and about 1,900 barrels of larvicide. Prophylactic quinine. — We consider quinine taken for pro- phylactic purposes an exceedingly important measure against malaria. Quinine is given gratis to any one applying to any one of our dispensaries. We have at various points along the line 21 dispensaries. It is placed on all hotel and mess tables. But we place most reliance on our quinine dispenser. In each district we have a man attached to the dispensary who is known as the quinine dispenser. He spends the day visiting the various squads of negroes at work. He offers everybody in the squad quinine. He gives it to them as they prefer, either in pill or solution. We do not attempt to use compulsion in the matter. Last year we used 3,200 pounds of quinine. Two- thirds of this was given to employees. On an average about half of our force gets a prophylactic dose of quinine each day. Screening. — We insist upon all Government buildings being so screened as to keep them mosquito-proof The details of screening are very important. It should always be under the supervision of a sanitarian who understands these details. As the sanitary work progresses, screening becomes less and less 350 MALARIA PREVENTION ON ISTHMUS OF PANAMA [Sect. necessary. In the older stations, such as Ancon or Culebra, I doubt if screening is now necessary. The country has been so thoroughly drained that there are very few mosquitos, though we still insist upon the screening just as carefully as we did when mosquitos were bad. Killing mosquitos in quarters. — When a locality has been recently occupied, and the general sanitary work has not had time to effect malaria, or when malaria is bad from other causes, we attempt to kill the infected mosquitos. As daylight comes on, the Anopheles, when she has had her fill of blood, will not in general leave the building where she has fed, but will seek some dark corner in which to spend the day. Taking advantage of this we have a man go around and kill all the mosquitos he can find in the building. In this way most of the infected mosquitos are killed before they become infectious. This method is particularly efficacious in tents and small buildings. It is surprising what results can be obtained by this method in properly selected cases. Cost. — The total cost of sanitation on the Isthmus ^ for the past five years has averaged annually about three dollars and a half per capita for the whole population on the strip. During that time this population has averaged 100,000. As the general result of this expenditure our death-rate for the total population on the Zone has fallen from a maximum of 6772 per thousand in July 1906 to 2r52 in December 1909. The rate for 1905 was 49-94 ; 1906—48-37 ; 1907—33-63 ; 1908—24-83 ; 1909— 18-19. The death-rate among employees for disease has fallen from a maximum of 62-15 i^i July 1906 to 10-13 in December 1909. Of the yearly expenditure of $3-50 per capita, I estimate that $2-oo per capita is spent on mosquito work. This expenditure has accomplished the total eradication of yellow fever. The last case on the Isthmus occurred in Colon in May 1906. It has reduced the deaths from malaria in the total ^ Wages are high in Panama. — R. Ross. 42] RESULTS 351 population from a maximum of i6'2i per thousand in July 1906 to 2"58 per thousand in December 1909. Among employees it has reduced the deaths from malaria from a maximum of ii"59 per thousand in November 1906, to r23 per thousand in December 1909. The admission rate among employees has fallen from a maximum of 1263 per thousand in July 1906 to 191 per thousand in December 1909. The admission rate per thousand for malaria among employees has been as follows: 1904, 125; 1905, 514; 1906, 821; 1907, 424; 1908, 282; 1909, 215. Wherever, in this article, I have used the expression so many per thousand for a month, I mean on the basis of a year. If I say the death-rate was ten per thousand for July, 1909, I mean that if the number of deaths and population had continued the same for the year that they were for July the rate would be ten per thousand per year. I think that the mosquito work already done at Ismailia, Havana, Panama, and other places has demonstrated that malaria can be controlled and eventually banished from even the worst places in the tropics, and this at no very great expense. I think that the individual farmer can go anywhere into tropical countries and be free from malaria if he will drain the land and clear brush within a hundred yards about his house. And in addition screen his house so carefully that mosquitos cannot gain access. This will not cost him anything like as much as he expends in protecting himself against the cold of Dakota or Manitoba. Notes by R. Ross. — Dr H. R. Carter, the distinguished discoverer of "extrinsic incubation" in yellow fever, and until recently Director of Hospitals in the Panama Canal Zone, writes me a letter from which I am permitted to quote the following : — " Independently of the general results as shown in the general statistics, there have been some — a number — of beautiful examples of the results of anii-Anopheles work : Caballo Viego, falling from an admission rate of 1675% per week to 3% within two months ; Porto Bella from 10-12% to 3% and finally to 1-5% ; Juan Grande the same ; La Boca exceedingly bad in 1905, and in 1907 the least malarial station in the Isthmus; Carroval, bad in 1905 and considered almost uninhabitable 352 MALARIA PREVENTION ON ISTHMUS OF PANAMA [Sect. 42 in French times, one of the most healthful places from 1906 on. It was beautiful work. Not all 'beer and skittles' by any means, but beautiful work all the same. It is work, however, that depends absolutely on the perfection of its details ; like aseptic surgery." See also Dr Carter's article [1909] for a brief but clear analysis of the subject. S. T. Darling, M.D., has kindly informed me that the Panama Anophelines which carry malaria are A. {Cellia) albimanus ; A. {Cellia) argyrotarsis ; A . pseudopunctipennis ; and A. tarsimaculata. See also his papers [1909, 19 10], and Section 65 (4). By J. A. LE PRINCE, C.E.A.M. Chief Sanitary Inspector, Panama Canal Zone 43. Anti - malarial Work on the Isthmus of Panama ; Technics. — As we approach the tropics, where the rate of. growth of vegetation and rainfall increases, the cost of main- taining open ditches and keeping them free from Anopheles larvae increases considerably. In the north the greater part of the rainfall occurs at a season of the year when mosquito life is dormant. Well-made surface ditches will need very little attention, and those having a fair grade will often be dry during the greater part of the Anopheles breeding season. Here we have conditions that are different, and which are very favourable to the development of mosquito life. Our rainy period lasts for seven or eight months. The ground remains wet for many days at a time, and the dense vegeta- tion prevents evaporation of surface water to a large extent. Most of our ditches contain water continuously throughout the wet season and well into the dry season. It is not un- usual to have rain or showers occur during twenty-six days out of thirty. Such conditions keep the vegetation in open ditches growing rapidly, and are favourable to the develop- ment of growths of algae. The latter play a prominent part in the development of Anopheles larvae. If the ditches are not kept free from vegetation, Anopheles larvae will generally be found, and the number thereof seems to increase when algae are present. It is necessary to have as few ditches as we can possibly get along with. The flatter the ditch the more the likelihood of it becoming a propagation area. Also, as we know that the larvae have the habit of collecting in 353 z 354 ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. still water, or in water having a low velocity, it is necessary to keep the ditches of uniform cross-section and free from obstructions. If this be not done larvae from up-stream will probably find safe resting-places at points lower down. At times, when all other insect life has been washed down-stream, these larvae may be seen clinging to the bank of the ditch. In connection with open ditches, it should be stated that hard showers of short duration are a temporary help in that they clean out the ditches and remove all larvae. Very often, however, hard rains will practically ruin a ditch and make regrading necessary. A most important source of Anopheles on the Isthmus is the seepage water ^ that outcrops on hill- sides or on low ground near the foot of a hill. Such productive areas may last for short or long periods, and may occur at irregular intervals. If the quantity of seepage water be small it may not be noted. In case it occurs near a settlement, such an area, even though small, may and often does become the cause of a large increase in the previously low malarial sick-rate ; and, moreover, extra attention will probably be given to anti-malarial work at more distant points, while the real source of the trouble may have escaped attention. Sub-drainage is far superior to open ditches in every way, and should be used whenever conditions are favourable therefor. It is much more economical and better than the application of larvicide under such conditions as exist here, for it is always possible, even with the most careful inspection, for numerous small wet areas to be missed. The practice here is to cut off seepage water by means of intercepting ditches containing drain tile. In all cases locations and plans of such ditches should be made at the height of the rainy season, when the worst conditions occur. If this is not done errors will surely be made, and during extra long rainy periods seepage water will occur on the up- hill side of the tile line. Ditches for sub-drainage must be ^ /.^., Water which oozes out. — R. Ross. 43] TECHNICS OF DRAINAGE 355 cut to true grade, and should be made as narrow as possible so as to reduce the amount of cover stone needed. The tile should be laid to true grade with open joints of about 1/8 inch, and then be covered with stones corresponding to field stone of about 4 to 6 inches in diameter. The dirt from the trench must be placed on the downhill side of the tile line to prevent it washing back into the ditch. When the soil uphill from the ditch is covered with vegetation the space between the cover stones does not fill up. Water will find its way into the tile line through the joints. We find that the flow of water in drain tile thus laid always carries such fine silt and sand as enters through the joints of adjacent sections, provided the grade is about 1% for 6-inch tile and not less than one half of 1% for lo-inch tile, when there is no loose soil above the line of the ditch. Special care should be taken to have the outlet of the tile kept clear at all times. When tile drains are located and laid properly they are the most economical method of draining for anti-malarial work, and the cost of maintenance is very small. Some drains laid three and a half years ago have not cost one cent for maintenance since installation. Due to washouts, erosion, necessity of frequent regrading, cleaning, removal of vegetable growth, algae, etc., the cost of maintaining open ditches is often expensive and necessarily continuous. If such mainte- nance costs are or will be excessive, and conditions such as grade, character of soil, etc., are unfavourable for sub-drainage, we make the ditches the shape of a flat " V," and line them with flat stone laid in just sufficient cement mortar to hold them together, leaving sufficient weep holes near the rounded floor to take care of ground water. Frequently here the cost of maintaining an open ditch for two or three years will be more than that of lining the ditches permanently with flat stone. Near some of the camps such lining of ditches costs from 25 to 50 cents per running foot, and as the same ditches cost previously about 25 cents per foot per year to maintain. 356 ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. the advantage of the permanent work is self-evident. Stone- lined ditches are very seldom sources of Anopheles. Filling is sometimes necessary in low lands that cannot be drained, and under certain circumstances it should be accomplished, providing the cost is not prohibitive. A large number of Anopheles larvae may occur on flat lands where water collects in small quantities in numerous places. Although much of the water may evaporate, and the breeding - places dry up before the larvae can develop into adults, yet what usually happens is that a sufficient number of the small wet places remain, which, taken together, will produce during the rainy season sufficient adult mosquitos to keep a near-by settlement well supplied. All very small as well as large wet places that are not thoroughly dry during a period of ten days need attention. Evaporation of the surface-water can be largely increased by the removal of the vegetation. In fact, in many such areas we find that the larvae develop only when the grass and vegetation are sufficiently high to retard evaporation. Where the water continues to remain after the removal of all vegeta- tion it will often be necessary to apply larvicide. In case the breeding areas cover a large territory, the transportation and proper application of the larvicide may cost several times more than the larvicide itself Then it becomes necessary to use some form of concentrated larvicide in order that the labourers may employ nearly all of their time in applying it rather than in its transportation. After much unsuccessful experimenta- tion with commercial larvicides it was found that a mixture of carbolic acid, resin and caustic soda has very satisfactory larvicidal properties and acts promptly. It meets the con- ditions that we have to contend with fairly well. It costs less than one-half of the best commercial larvicide w^e could obtain, and the latter was apparently not standardised. One part of this mixture placed in five thousand parts of water containing mosquito larvae will kill them all in less than five minutes. 43] LARVICIDE 357 When one part is applied to eight thousand parts of water containing larvae, the same will be killed in thirty minutes. The method of preparing it is as follows : — Crude carbolic acid, containing about 1 5% of phenol, is heated to 212 degrees F., finely pulverised resin is added, and the mixture kept boiling until the resin is all dissolved. Caustic soda is then added, and the solution kept at 212 degrees F. for about ten minutes, or until a perfectly dark emulsion without sediment is obtained. The mixture is thoroughly stirred from the time the resin is added until the end. As the composition of crude carbolic acid varies greatly, the proportion of ingredients of the larvicide will vary, and it is necessary to have small experimental lots made in the laboratory, and tested before the batch of larvicide for use in the field is manufactured. The average mixture is about as follows : — 300 gallons crude carbolic acid ; 200 lbs. resin ; 30 lbs. caustic soda. The larvicide costs us about 14 cents a gallon. In lagoons, ponds and lakes near settlements we get rid of the vegetation so far as possible, and at the edges where the water is shallow, and in other places where larvae occur, we destroy them with this larvicide. When numerous small particles of dead vegetable matter that are washed into lakes or ponds are collected by the wind, the Anopheles lays her eggs in amongst this debris^ and it must be removed. In long running streams and open ditches where anti- malarial work is being done crude petroleum may be used, and it is more effective when applied automatically. Should the quantity of running water be small, so that not much oil is needed, then a handful of cotton waste tied in a bundle is soaked in oil for a day, and then placed near where the water outcrops. The water passing by this waste becomes covered with a very thin film of oil. The waste gives off an oil film for about ten or fourteen days, and is then resoaked in oil and used aerain. For larger bodies of water having a fair 358 ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. velocity, drip cans or drip barrels are used, and should be located 2 feet above the water surface to break up the oil drops as they fall. They are made as follows : — A piece of metal similar to that of a flat wick lamp that holds the flat wick is fastened to the barrel or can near its base. This wick chamber is made somewhat larger than the wick, so that the wick may fit it loosely when saturated with fuel oil. The space inside the barrel, between the wick chamber and the bottom of the barrel, is filled with a solution of caustic soda or larvicide. As the oil passes along the wick it comes into contact with the caustic soda, and is " cut " or rendered thinner. This prevents the wick from becoming clogged by the thick fuel oil. The wicks seldom clog, but in case such occurs some larvicide is dropped on the wick. This cleans it, and makes it as serviceable as before. Adult Anopheles may persist near settlements when it is supposed that all that is possible has been done toward their eradication. Near the seashore the larvae of some species of Anopheles occur in water that is quite brackish. All brackish water should be considered as capable of supporting Anopheles larvae until the contrary is proved to be true. Also mud from above which the water has recently disappeared should be looked on with suspicion, and treated when it supports mosquitos. Many small muddy areas may contain no mosquito life, but if the larvae are present in some small spots, the sum total of such possible places, most of which are hidden by the grass and not easily seen, is worthy of consideration. The adults that may develop therefrom in rainy periods are often numerous. Larvae may only be present in one or more particular parts of a large possible breeding-area, and a superficial inspection thereof will be misleading. Dipping with a cup is a very unsatisfactory way to determine the presence of larvae. Even when larvae cannot be dipped up from a small shallow body of water, if the same is stirred up the larvae will often appear promptly at the surface. When no larvae can be seen it does 43] DESTRUCTION OF LARVAE 359 not always mean that none are present. We use the larvicide appHcation method to determine the presence or absence of larvae to a large extent. When applying strong solutions of larvicide at the edges of a large body of water it is noticed that the larvae appears to lose all sense of direction. Very few reach the clear water, and nearly all that do so die soon afterwards. Our labourers are supplied with knapsack sprayers for distributing larvicide, and a labourer can take enough larvicide along with him to last for several hours of spreading. The cost of spreading a dollar's worth of crude oil by hand often amounts to two dollars or more. So far as we can determine not much malaria is actually contracted by labourers while outside on the work. In fact we have no case on record where a person has been bitten on the Isthmus by an Anopheles when the person was exposed to the direct rays of the sun. Although we think very little infection is conveyed during working hours out in the sunlight, we do know that it is a common occurrence for persons to be bitten in the daytime by Anopheles when both are inside of buildings. We have noted that a person indoors may be bitten several times in a period as short as ten minutes, and that Anopheles while indoors will take blood at any time between daylight and dark, as well as at night. In connection with the prevention of malaria, the destruction of adult Anopheles in barracks, tents and other crowded quarters is certainly worthy of attention. The screening of buildings is of importance. To keep the screening intact and effective is quite a problem where ignorant labourers are concerned. A screened building is far superior as a preventative measure to the use of mosquito bars over each cot. The latter, as used by labourers, is generally of little value. The American housewife on the Isthmus is interested in keeping the screened doors closed in order to keep out mosquitos and flies. The children and wives of American employees have been particularly free from malaria, and in fact do not contract malaria 36o ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. on the Isthmus as often as they would in many parts of the United States. During February of 1907 a census of American women and children then in the territory between Bohio and Balboa was taken. There were 552 women and 345 children present. Some of them had come to the Isthmus in 1904 and 1905, but the greater part in 1906. The malarial sick-rate in 1905, 1906 and 1907 was very much higher than it is to-day. Among the 897 women and children, 82% had not had malarial fever between the time they arrived here and up to the time the census was taken. During the same period some of the labourers' camps had a 10% malarial hospital sick-rate per week. Of the American children on the Isthmus in February 1907, 90% had not yet had malaria. At Bohio, where the houses were not screened, there were seven American children and seven American women in February 1907. Three of the women and three of the children had had malarial attacks since arrival at Bohio. A temporary camp consisting of tents was established at Cocoli during April 1908. Anopheles breeding-places occurred on all sides, and we could not possibly get rid of them without considerable expenditure of funds. The size of the camp did not warrant much expenditure. Adult Anopheles were very numerous about the camp, and thirty or more could be counted in a single tent in the daytime. A watchman was employed to kill off all mosquitos seen in the tents during the daytime. This watchman kept on the go from tent to tent. All mosquitos in the tent were within reach, which was a very important advan- tage. No work was done by the watchman after 5 p.m. At first Anopheles were so numerous that a tent could not be left for a half-hour without some coming in. The near-by breeding- places were oiled in order to reduce the number of adults, but many remained. The destruction of adults began loth April 1908, and between that time and 24th August 1908 there were seventeen cases of malaria at Cocoli, which would mean only a little over i^ of the force were sick with malaria during each 43] DESTRUCTION OF ADULTS 361 period of seven days. The camp was abandoned on 24th August 1908. This was a lower sick-rate than had occurred at other camps where anti-malarial work had been carried out for quite some time, but at Cocoli we were killing adult mosquitos, and the other places were not. As this work resulted so successfully it has since been carried out at labourers' barracks at various stations, and has undoubtedly been an important item in the marked decrease of the malarial rate that has occurred during the past year. Recently some six hundred Anopheles (mostly albipes) were collected alive in various camps where the adult Anopheles are being systematically destroyed daily in barracks. They were examined by Dr S. T. Darling, Chief of the Board of Health Laboratory, and not a single one showed malarial parasites. It seems fairly evident that we catch most of the Anopheles between the time they first enter the barracks and the time when they should become infective. The catching of adults in the buildings which have high walls or in dark rooms is a much more difficult proposition than their destruction in low tents, where all can easily be seen and reached. It would be a large advantage to have the interior of buildings painted a light colour or white- washed so that Anopheles could be readily seen when resting on the walls. We now use test-tubes containing cotton wool and chloroform to destroy adults resting on walls, etc. It is quieter than the slapping method, and very few mosquitos are frightened away. At the base of Diablo Hill is a swampy area about two miles long and a half a mile wide. It cannot be drained at the present time. From the top of the hill to the water-line is about 200 yards. In June of 1908 several hundred United States Marines were stationed at Camp Diablo, and remained on this hill for about six or eight weeks. The conditions affecting malaria, such as drainage, etc., were then the same as they are to-day. While the Marines were in the camp their malarial sick-rate 362 ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. was 2^ per day, or 14% per week. Since that time a string of railroad cars in which the labourers of the railroad construction gang sleep was located near the foot of the hill, and between the swarap and the camp formerly occupied by the Marines. During the past thirty weeks an average of forty-four Anopheles per day have been destroyed each morning in these cars. They were caught in chloroform tubes as above described. It takes the labourer thirty minutes each morning to do this work. The cost is 5 cents per day, or 30 cents per week, and the destruc- tion is carefully performed by a competent man. From the first week in May 1909 to 30th November 1909, which is the rainy season, only four cases of malaria have occurred among the forty labourers sleeping in these cars, or about one man in 300 men working for a period of seven days, although they were more freely exposed to the Anopheles than the Marines had been. This work of destruction of adults in quarters costs so little that undoubtedly it will be of value in all malarial districts where house tenants are interested in the prevention of malaria. It will be of special importance where an army is in camp, or where railroad camps are established in malarial districts, as with proper care the sick-rate could by this means be kept far below what it would otherwise be. On the Isthmus we consider such work as supplementary to the drainage and other anti- malarial measures. It should be noted that most of the labourers' camps in the Canal Zone are located near native towns, and undoubtedly a large percentage of what malaria we do have is contracted by our labourers spending their evenings at, or living at the native settlements. Nevertheless, in spite of continuous topo- graphical changes, constant rains, native villages and numerous other difficulties, the malarial sick-rate is being steadily and systematically decreased year after year. The decrease of adult Anopheles to be found at the camps is equally noticeable. Several years ago it appeared that the malarial sick-rate would always be much higher during the rainy season than in 43] RESULTS AT HAVANA 363 the dry season, but during the past two years the Department of Sanitation have been able to control the situation to such an extent that at some of the larger settlements there has been no appreciable increase in the number of malarial cases during the wet season as compared with the dry season. It is of interest to note that this has occurred in those districts where during previous years the increase of malaria closely followed the increase of rainfall. This is very encouraging, considering that such results have been obtained where the settlements are scattered over large areas. With regard to the destruction of adult Anopheles in dwell- ings it should be stated that malaria cannot always be controlled by this means only, although it was fairly successful at Diablo and Cocoli. The colour of the house walls, height of the ceiling, the amount of light in rooms and the number of hiding-places, etc., effect the percentage of adults that may be destroyed. Again, if persons living in houses that are inspected daily visit houses that are not so treated, or are infected elsewhere, the results will not be as satisfactory as where their camp is iso- lated as was the case at Cocoli and at Diablo. Drainage and eradication of breeding-areas is the all-important work in an anti - malarial campaign. The catching of adults should be considered as supplementary to drainage, screening, application of larvicide, etc. At Havana we relied exclusively on drainage and filling. Most of the natives there do not like to take quinine. Malaria at Havana has practically been eradicated. Data relating to charts showing reduction of malaria in the Canal Zone. — Chart No. i shows the percentage of all Canal employees (malarial cases only) that were sent to the hospital each month from 1906 to 1909 inclusive. Attention is invited to the fact that the sick-rate is always lowest about May or at the end of the dry season. That the malarial sick - rate would advance rapidly in former years with the arrival of the wet season June, July and August. This advance has been materially checked. Compare the wet season record of 1909 (June to December) with the same period of the previous years 364 ANTI-MALARIAL WORK ON ISTHMUS OF PANAMA [Sect. and with the dry season of 1909 (January to May). The successive yearly reductions are a fair index of the value of the anti-malarial work. The successive months are plotted one half inch apart, horizontal measurement.^ The percentage malarial sick-rate is plotted on the vertical lines, on a scale of two inches vertical measurement, equals i^. If the force employed consisted of 40,000 men, and 500 of them are sent to the hospital with malaria during a month, then the rate on Chart No. i for that month would be plotted as r25^. Chart No. 2 is a record of malarial cases among employees at Porto Bello. The percentage sick-rate for each week plotted. This was a new camp that was opened up a few weeks before anti-malarial work started. At all newly opened camps the malarial rate runs high, as compared with areas where anti- malarial work is being done. Without doubt the rate would remain high if no anti-malarial work were done. Note that preventive work at Porto Bello started 21st March 1908, and that the rate from then to June averaged, say, about 3^ per week. Or, over 12^ of employees were sent to hospital per month (malarial cases), and many of the labourers remaining at work were not in physical condition to do as much work as they are capable of doing to-day. That during this same period, among employees in the Canal Zone, the monthly sick- rate (malaria only) was not much over i^. (See Chart No. i.) About 600 men are located at Porto Bello, Chart No. 3 is a record of malaria at Gorgona. Present population 2,000 employees. Compare years 1908 and 1909 with the previous years. No large increase of malaria occurs in the wet season (June to December) during the last two years. Anopheles are now seldom found in barracks, which indicates that they are not numerous. Note the effect of the wet season on the malaria rate for 1906, and absence of same for wet seasons of 1908 and 1909. In Charts No. 2 and No. 3 the weekly sick-rates are given. ^ The accompanying charts are reduced. — R. Ross. 43] RESULTS AT PANAMA 365 For instance, during the week ending 6th January 1906 a number of the employees at Gorgona (Chart No. 3) were sent to the hospital whose cases were diagnosed as malaria. This number consisted of 274^ of the entire working force living at Gorgona during that week. The dates of the ending of each week for which the percentage sick-rate is plotted are given. These percentages show only the malarial sick-rates and not the other hospital cases. In connection with Chart No. i it should be stated that in the early days it was difficult to get the malarial patients from among the ignorant labourers to go to the hospital, and so the actual sick-rate at that time was higher than what has been recorded. At the present time the labourers go voluntarily to the hospital when they feel sick. Note that during seven months of 1906 the rate was above 6%; that during 1907, for ten months, the rate was below 5%. In 1908, during eleven months, the rate was below 4%. In 1909, the rate was below 3%. The highest monthly rate during the wet season of 1909 was a little over 2//, as compared with 4%, 5% and 10% respectively for the wet season of the years 1908, 1907 and 1906. Refer again to Chart No. 2, relating to malaria at Porto Bello. During December of 1909 the number of rainy days was twenty-seven out of thirty-one. The rainfall was 45*03 inches for November and 58'i7 inches for December 1909, as against 4173 and 2572 inches respectively for November and December of 1908. Such conditions of rainfall mean a large increase in the number of possible Anopheles areas. As shown on the chart, no increase of malaria occurred due to the increased wet area accessible to Anopheles. This is a good illustration of the results of anti-malarial work performed under severe conditions when the work might at first sight appear to be almost impossible to accomplish. From 1st November 1908 to 2nd January 1909, 5% of the force were sent to hospital with malaria. From 31st October 1909 to 1st January 19 10, during the period of heavier rainfall, only 3'26% of the force were hospital malaria cases. JanJ laio- to ■a > o r > w ^ > H o ITI > o (/I w on OJ C/J 1 ^ H ?> H r O > K ^ O > 2 > > H M O ?a O O ^ S o o o o '^ ?3 O > O •z f^ > N By Sir RUBERT BOYCE, F.R.S. Professor of Pathology, University of Liverpool 44. Malaria in the West Indies. — There is no doubt that malaria has markedly decreased throughout the West Indies. This statement can be verified by comparing the current health reports with those furnished by the Surgeon-Generals when the various islands were garrisoned. The factors which have brought about this diminution are the same as those which have, in more recent time, operated in towns like Bombay, New Orleans, Rio, etc., and which at a still earlier period led to the disappearance of malaria from a large portion of Europe. It may now be stated that malaria as an endemic disease is limited to the country districts throughout the islands, and that it ceases at the outskirts of the principal towns, in a few instances penetrating into a centre of population along the banks of some neglected marsh or stream. In the principal towns the swampy ground which almost invariably surrounded the early settlements has now all been reclaimed, and in its place well-planned streets have appeared. Properly-graded roads and concrete drains are the rule rather than the exception. Since the year 1850 a considerable pro- portion of the larger towns received the immense advantages of a pipe-borne water-supply, derived from reservoirs or rivers outside the towns. This system at once did away with the old-time wells, and abolished, or greatly decreased, rain-water barrels and storage tanks. These improvements, coincident 369 2 A 370 MALARIA IN THE WEST INDIES [Sect. with the progress of prosperity and the appreciation of the laws of hygiene, have together brought about the cessation of malaria and yellow fever as endemic diseases in the chief towns. Therefore it is to the country districts, and on the plantations, that the student must look for the survival of malaria in its endemic form. And there is no doubt that it does still so survive throughout the Antilles, as an analysis of the Registrar-General's or the Medical Officer's Mortality Returns abundantly proves. Unfortunately, it is very difficult to estimate accurately the total sickness and mortality rates from malaria in the various islands ; in many instances the causes of death in 50^ or more of the cases is not definitely stated. And, of course, as is well known, although the anaemia of malaria may have had the chief share in producing lowered vitality, yet the actual cause of death is registered as perhaps bronchitis or consumption, as the symptoms of these affections were the more obvious ones from which the patients suffered during illness. Efforts are now being made, however, to make more accurate estimates of malaria by the employment of more perfect methods of diagnosis, such as spleen rates and blood examinations. Grenada. — Population, 68,253. Capital, St George's ; popula- tion, 5,198. Malaria is still prevalent in the country districts, and is endemic and imported. In No. i District in St George's Parish 681 cases and 22 deaths were recorded in 1906, and 317 cases and 12 deaths in 1907. In No. 6 District 1,119 cases were reported in the same year. The malaria is due to the breeding of Anophelines in certain swampy lands and puddles, and, in the wet season, perhaps also to the presence of water-holding epiphytes upon the shade trees on the cocoa plantations. Preventive Measures : — I. Introduction of pipe-borne water. This was the first step which led to the reduction of Anophelines in the 44] GRENADA, ST VINCENT 371 towns of St George's, Gouyave and Grenville by doing away with numerous barrels and odd water containers. 2. Road-making and street drainage in the towns. 3. Government and medical officers throughout the colony making returns of all anti-malarial measures under- taken in their respective districts. 4. 1st April 1909. — The fish " millions " were introduced into the colony with the object of stocking ponds and large collections of water. 5. The Public Health Ordinance of 1907 prohibited the keeping of stagnant water unless protected, oiled or stocked with fish, and all odd receptacles were to be removed. 6. In 1902 and 1905 further ordinances were promulgated, declaring mosquito breeding - places in and about human habitations to be a statutory nuisance. 7. The more careful cultivation on the cocoa estates has led to better drainage, and a diminution of malaria on the estates. 8. Considerable attention is now paid to entomology. St Vincent. — Population, 47,548. Capital, Kingstown ; population, 4,547. Malaria for the most part confined to small, swampy districts in the country. The Medical Officer's returns show 525 cases in 1907, and 281 cases in 1908. Prophylaxis : — 1. Pipe-borne water has led to great diminution of water barrels and odd receptacles and wells. 2. Construction of side drains and roads. 3. Removal of odd receptacles from yards, and better sanitary supervision. 4. A nti-larval meastires — 1901. — Measures promulgated against stagnant water, unless oiled, screened or stocked with fish. 372 MALARIA IN THE WEST INDIES [Sect. igoQ. — New Public Health Ordinance, with provision against stagnant water and mosquito larvae. 5. The late Dr Branch was a keen entomologist, and did much to get rid of breeding-grounds of mosquitos. Sf Lucia. — Population, 50,000. Capital, Castries. There is still a small amount of malaria, due to a few low- lying, swampy patches which persist near Castries. Prophylaxis : — 1. Introduction of pipe-borne water brought about a great reduction in the number of breeding-places. 2. Better roads and side drainage undertaken from 1890- 1900. 3. Energetic anti-mosquito drainage and bush clearing operations undertaken by Major Hodder. 4. Anti-mosquito laws. — In 1906 the Colonial Secretary commenced a vigorous systematic campaign against mosquitos, by causing careful returns to be made of all insect -carried diseases and of the breeding-places of mosquitos. In 1907 regulations were framed dealing with stagnant and waste water. In 1909 a vigorous house-to-house campaign amongst mosquitos was started. Fines have been regularly enforced from 1907 against all who, after caution, refuse to get rid of mosquito larvae. Trinidad. — Population, 336,769. Chief Town, Port of Spain ; population, 70,000. General death-rate for 1908, 10 per milk. Total deaths from malaria, 71 in 1908. Total amount of malaria small. Upon the estates, however, malaria is responsible for more than half of the gross sickness rate amongst the indentured labourers. 44] TRINIDAD, BRITISH GUIANA 373 Prophylaxis : — 1. Pipe-borne water-supply. — This system was first intro- duced into the Port of Spain as far back as 185 1, and has since then been largely extended throughout the Port of Spain. To it must be ascribed the abolition of endemic yellow and malarial fevers, for it at once did away with the necessity of the numerous water barrels, cisterns, wells and odd receptacles of all descriptions, which in the old days were the breeding-places of the mosquitos. 2. The construction of well - graded roads and concrete drains everywhere within the vicinity of the town. 3. Concreting backyards, removal of rubbish and bush. 4. Education. — Systematic training of the sanitary inspectors, schoolmasters and others throughout the colony. 5. Entomology. — The establishment of a strong entomo- logical department to study the breeding-places of mosquitos. 6. Anti - larval laws. — In 1907 regulations were made against stagnant water and larvae, enforcing the screening or oiling or fish stocking of stagnant water which could not be got rid of In 1909 a new Draft Ordinance was prepared strengthen- ing these regulations, and numerous fines have been inflicted for contravention of the Mosquito Bye-laws. British Guiana. — Population, 278,328. Capital, George Town. Colony intersected by innumerable water trenches, swamps and canals. Malaria, the principal disease of the colony. In 1907 the deaths from malaria were 301. Prophylaxis : — 1. Construction of good roads and drains. 2. Pipe-borne water-supply to George Town not completed. 3. Fish stocking of all waterways. 374 MALARIA IN THE WEST INDIES [Sect. 4. Education, and training of sanitary inspectors, teachers, schools, etc. 5. Sanitary supervision, removal of odd water receptacles. 6. Drainage Ordinance. — In 1907 Bye-laws were intro- duced enforcing proper drainage in George Town ; later these were extended to the country districts. Vat Screening. — In 1907 an Ordinance was introduced to render compulsory the screening of vats, and this law was enforced in 1909. 7. The distribution of quinine. Barbados. — Population, 199,542. Chief town, Bridgetown. It is stated on good authority that there are no Anophelines present in this island. Malaria is not endemic ; imported cases of malaria are common amongst the labourers returning from Panama. The absence of Anophelines is attributed to the very porous nature of the soil throughout the island, which prevents the formation of puddles. The ponds which are met with are all apparently stocked with " millions." In Bridgetown the streets are well drained and kept flushed. Water-supply. — An abundant and excellent pipe-borne water-supply was introduced into the colony many years ago, and has since been extended. It strikes at the root of endemic yellow fever by putting an end to the innumerable odd water receptacles which were everywhere abundant. In 1909 a vigorous anti-mosquito compaign was started, and the Anti-stagnant Water Ordinance of 1909 was rigorously enforced. Sanitary inspection was increased, and a general cleansing and removal of all odd water receptacles carried out. The Bahamas. — In 1905 measures were adopted against mosquito-carried diseases, and in 1907 anti-larval regulations were enacted, and screening, oiling or fish stocking of stagnant water enforced. Quinine was also distributed. 44] JAMAICA, BRITISH HONDURAS 375 The Northern Islands. — In 1904 vigorous action was com- menced against mosquitos. Jamaica. — Population, 639,491. Capital, Kingstown. Anti-malarial measures in Jamaica. — In October 1909 a special commission was appointed to investigate and to take measures to remedy the conditions which gave rise to malarial fever in different parts of the island of Jamaica. The Com- mission consisted of the Colonial Secretary, P. C. Cork, Arch- bishop Nuttall, the Superintending Medical Officer, Dr Kerr, Dr Turton and Dr Graham, and Messrs Gideon and Hart. Mr Isaacs was made Official Secretary of the Commission. The objects of the Commission were to ascertain the breed- ing-places of Anophelines, and to suggest the carrying out of remedial and preventive measures ; also to conduct investiga- tions and to take evidence if necessary. The Commission had power to expend up to ;^500. British Honduras. — Chief town, Belize ; country very swampy. Prophylaxis : — 1. Anti-mosquito work was commenced in 1905, and has been kept up with marked success. 2. A mosquito destruction Ordinance was passed in 1906. Owners of property were compelled to screen, oil or stock with fish all collections of water. 3. Drainage and filling - in operations have also been started. Bush clearing was enforced. By W. T. PROUT, M.B., C.M.G. Lately P.M.O. Sierra Leone 45. Malaria in Jamaica.— The chief factors which influence the prevalence and distribution of malaria in Jamaica are, first, the physical configuration of the island, and second, the methods of cultivation, which are necessitated by the requirements of its forms of agriculture. The centre of the island is occupied by a lofty chain of mountains trending generally east and west, from which spurs are thrown off running north and south, with intermediate fertile valleys : while the coast is occupied by flat alluvial land of vary- ing extent. From the mountains a number of streams, some of considerable size, rush precipitously down till they reach the lower plains, where they frequently form extensive grass-grown swamps and open into the sea by a series of shallow, sluggish mouths, in all of which malaria-carrying mosquitos breed in great abundance. Moreover, it is naturally in the alluvial plains that the staple industries of the island, namely, banana and sugar plantations, are carried on. In the north-eastern portion, where the land is almost entirely under banana cultivation, there is a heavy rain- fall, and the soil is stiff" and clayey. In consequence, the banana Sect. 45] MORTALITY AND MORBIDITY 377 plantations have to be deeply trenched for the purpose of subsoil drainage, and the trenches, unless properly graded and kept clear of grass and weeds, afford suitable breeding-grounds for Anophelines. In the south and south-eastern parts of the island different conditions obtain. The rainfall is small, and irrigation, both on banana and sugar estates, is imperative. Here again the canals, unless properly supervised, are a prolific source of mosquitos. Among minor factors may be mentioned the ponds formed by surface drainage, invariably grass-grown, and used sometimes as the water-supply of a village, and more frequently as cattle ponds ; and the shallow, earthen, weed-covered gutters along the sides of the streets of the villages and towns. General malarial death- and sick-rates. — Although the exten- sive prevalence of malaria in certain districts of Jamaica has long been recognised, and its seriousness as affecting not only the general health and the death-rate of the community, but the agricultural development of the colony, was fully appreci- ated by the medical profession, yet, apparently from the apathy of the laity, no attempt appears to have been made to make an accurate malarial survey of the island, and preventive measures were practically non-existent. In the latter part of 1908, how- ever, an expedition from the School of Tropical Medicine of Liverpool visited the island, and, thanks to the active co-opera- tion of the Government and of the Island Medical Service, a systematic though limited survey was made, and much useful information was obtained. The following statistics are mainly taken from one of the reports of the expedition by myself {Ann. Trop. Med. Ill,, No. 4, 17th November 1909). The total malarial deaths for the whole island for a period of ten years amounted to 34,695, which is equivalent to a malarial death-rate of 4*4 per 1,000. The general death-rate during the same period was 22*5. The average percentage of malarial to total deaths was 197, representing nearly one-fifth of the total deaths. 378 MALARIA IN JAMAICA [Sect. A summary of the statistics is given in the following table :- AVERAGE DEATH-RATES, ETC., FOR THE DECENNIUM ENDING 30TH APRIL 1907. Average death- Average death- Average death- Average percent- age of malarial deaths to total deaths. Parish. rate from rate from rate from malaria. other causes. all causes. St Thomas . 6-5 i8-5 25*0 26-1 St Catherine 6-2 19-4 25-6 24-4 Westmorland 5-9 15-8 217 277 St Mary 5-9 i8-o 23-9 24-6 Clarendon . 5*3 15-2 20'5 23-8 Portland 5-3 19-3 24-6 2 1 '9 St James 4-8 17-1 21*9 22-3 Hanover 4-8 19-5 24-3 19-9 St Andrew . 4-0 23-9 27-9 i4'6 St Ann . 3-4 14-5 17-9 19-4 Trelawny 3'4 20-8 24-2 14-4 St Elizabeth 2-9 15-6 i8-5 15-8 Kingston 2-4 26*3 287 8-6 Manchester . 1-6 14-8 i6"4 I0"0 Whole island . 4*4 i8-i 22-5 197 But the prevalence of malaria is really much greater than is indicated by the death-rate, for of the admissions to the Govern- ment hospitals of the colony, it is found that at least one-third are due to malaria, and the malarial sick-rate shows a marked increase of recent years. Year. Total admis- sions from all causes. Total deaths. Death- rate per cent. Malarial admissions. Malar- ial deaths. Malarial death- rate per cent. Percentage of malarial to total admissions. 1904-05 1 905-06 1906-07 1907-08 16,103 17,856 21,555 21,837 669 563 661 830 37 31 3-06 3-8 4,827 6,285 7,113 7,510 89 88 99 121 1-8 1-4 1-3 1-6 29-9 35-1 32-9 34-3 Total . 77,351 2,723 ... 25,735 397 Average 19,337 680 3-5 6,433 99 1-5 33-2 45] COST AND SPLEEN-RATES 379 It is calculated that the cost of the maintenance and treat- ment of the malarial cases alone amounts to over j£6,^oo per annum. On banana and sugar estates the loss of time through illness, mainly malarial and therefore preventable, amounted to sixteen out of every hundred working days, per coolie labourer employed ; while among the constabulary, a picked body of men, it is estimated that there is a loss of nearly four thousand days' service per annum from the same cause. T/ie spleen rate. — That the endemic index of the island is high is shown by the results of the examination of the spleens of children. Among 2,036 children examined in all parts of the island, 536 were found to have enlarged spleens, a spleen rate of 263^. But if the mountainous centre of the island were to be excluded, and places on the littoral only taken, the spleen rate would be found to be much higher, and in certain localities rises as high as 80%. The following table summarises the results of the splenic survey : — No of Spleens.^ Total No. Average spleen. Parish. children examined. I 3 6 9 of enlarged , ^^^^ spleens. 1 Portland . . St Mary . . St Thomas St Catherine . St Elizabeth . Kingston . . Westmorland . Trelawny . . St Ann . . . Manchester . Chapelton . . 291 398 44 212 249 220 278 189 69 42 44 112 216 27 156 195 197 255 187 69 42 44 152 158 10 48 47 23 17 2 26 '72 'I 7 7 5 I I I I 179 182 17 56 54 23 23 61-5 457 38-5 26-4 21.2 10-4 8-2 ro6 2-5 2-1 2-3 1-6 i'5 1-2 r2 1-03 ro ro ro Total . 2,036 1,500 457 73 6 536 26-3 12 A complete splenic survey, in order to obtain an accurate idea of the distribution of malaria, is one of the first steps to be taken in any anti-malarial scheme. 1 See section 31 (4). 38o MALARIA IN JAMAICA [Sect. Anti - malarial measures. — To diminish this extensive pre- valence of malaria the following measures have been recom- mended as being particularly applicable to the requirements of Jamaica : — 1. To make the harbouring of mosquito larvae in com- pounds a punishable offence. 2. To keep all margins of rivers and swamps in the neigh- bourhood of towns free from grass and weeds. 3. The application of crude kerosene where possible. 4. The screening of wells, tanks, etc. 5. The cementing of gutters in towns. 6. The gradual reclamation of swamps. 7. Screening of public hospitals, police stations and coolie barracks, 8. Prophylactic administration of quinine to police, coolies, school children and the general public. 9. Education in sanitation and hygiene, all of which would be under the supervision of a central anti-malarial organisation. As already stated, up to the beginning of 1909 little in this direction has been done. Small quantities of quinine had been distributed to estates for prophylactic purposes, but had not been given systematically and continuously ; a few isolated efforts at swamp reclamation had been made by private individuals, and one police station had been made mosquito- proof, but there was no concerted or systematic effort to stamp out malaria. As a result, however, of the attention which was drawn to the subject by the expedition from the Liverpool School, probably assisted by a severe outbreak of malaria which occurred in the spring of 1909, public interest appears to have been awakened, and in the autumn of that year the first steps were taken to deal with the disease in an organised and systematic manner. His Excellency the Governor appointed a Com- mission, consisting of the Colonial Secretary, the Archbishop 45] MEASURES ADOPTED 381 of the West Indies, the Chief Medical Officer, and other medical men, to enquire into the subject, and to take such steps as appeared to be urgently necessary. A series of public lectures have been given, which has done much to spread a knowledge of the disease in different parts of the island ; a new Public Health Ordinance has been passed ; steps have been taken to train sanitary inspectors in the recognition of the breeding- places of Anophelines, and in anti-mosquito measures ; and, most important of all, in February 19 10 a sum of ^^"5,000 was voted to carry out the various measures necessary. So that now we may consider that the anti - malarial campaign in Jamaica has been fully started, and the outlook for the gradual extinction of malaria in the island is distinctly hopeful. By H. WOLFERSTAN THOMAS, M.D, CM. (M'GiLL) Of the Liverpool School of Tropical Medicine Research Laboratories, Manaos, North Brazil 46. Malaria in the Amazon Regrion, and the Protection of Ships. — (i). Malaria prevails throughout the Aiiiaao?i region. The chief industry of this part of South America is rubber, and the immense trade requires a large number of men to collect the crop. The conditions under which they work cause many privations and expose them to infection. The old say- ing that every kilo, of rubber represents the loss of a life is an exaggeration but there is an enormous mortality amongst the " caucheros " who work in the interior. In the vast territory watered by the Amazon River three places of importance occur, which serve as the commercial centres for the up-river traffic of the interior. Iquitos, 2,200 miles from the mouth of the Amazon, is the only large town in Peru on the eastern side of the Andes. Manaos, on the Rio Negro, some 900 miles distant from the mouth of the Amazon River, and Para, which lies near the mouth, are in Brazil, and possess the only hospitals for the accommodation of the up-river patients. No attempts have been made by the states of Amazonas and Para to create any hospitals along the rivers in the interior of the rubber districts. They are very necessary, but their establishment is hindered by reason of the enormous expenses involved. Iquitos has no pipe-borne water-supply, and the drainage is of the most primitive character. Extensive swamps extend in and about the town, but no attempt has been made to fill them. 382 Sect. 46] MANAOS 383 Cellia albimana ^ and Cellia argyrotarsis abound. The majority of the cases appear to have contracted malaria up-river. The cities of Manaos and Para receive many cases of malaria from the interior, and consequently their death-rates are unduly high. Both cities suffer from the return of the infected rubber- collectors, who go and live in the suburbs along the swamps ; they either neglect all treatment, or take an insufficient amount of quinine, and, living in a state of poverty and misery, they lie in their mud huts exposed to the bites of numerous mosquitos. Their blood contains many gametes, and they therefore serve as infecting agents for the Anophelines that feed on them. Their presence is a menace to the community, as they may cause most virulent epidemics of malignant types of the disease. Manaos is intersected by many creeks and swamps. Those in the centre of the city are completely filled ; but, on the outskirts of the city proper, certain creeks and swampy areas still form foci of malaria. In the suburbs extensive swamps exist, and very severe forms of malaria prevail. A modern system of drainage and water-supply exists, and has done much to mitigate the evils. COMPARISON OF MALARIA INDEX OF CHILDREN IN SUBURBS AND CITY ^ Swamps r Apparently healthy in \ Ailing Suburbs \_ Average both classes City swamps .... Children living along swamps \ in suburbs . . . . j Children living along swamps \ on outskirts of city . . J Spleen-rate. 0-5 years. 36-23 46-82 43 "o? 12-94 5-10 years. 4274 45-83 44'36 35-86 43-82 24-85 Blood-rate. 0-5 years. 48-93 51-80 50-61 29-23 5-10 years. 50-00 57-14 52-60 48-78 51-64 40-13 1 Newstead, R., and Thomas, H. Wolferstan : " The Mosquitos of the Amazon Region," v^Mwa/j Trop. Med. and Parasitology, vol. iv. No. i. " Thomas, H. Wolferstan: "The Sanitary Conditions and Diseases prevailing in Manaos, North Brazil, 1905-1909," Annals Trop. Med. and Parasitology, vol. iv. No. I. 384 MALARIA IN THE AMAZON REGION [Sect. The state and municipal authorities are gradually destroying the Anopheline breeding-places within the city. Free advice and medicines are given to the poor, but no steps have been taken to organise a campaign against the hordes of Cel. albiinana and argyroiarsis, which, especially the former, are the carriers of malaria throughout the whole of the Amazon region. At Porto Velho on the Madeira River, a railway is being constructed to connect Bolivia and Brazil. Several attempts have been made to build this line, and each time malaria has raged amongst the workmen. A most virulent form of fever occurs which has at times incapacitated 50% to 80^ of the total working force. The difficulties in combatting the disease are great, and are increased by the possibilities of importing yellow fever from Manaos, Serpa or Pard. The line is in the interior, through virgin forests and large swamps ; an organised attack on the lines of the anti-mosquito campaign of Panama and Xerem in South Brazil would facilitate the progress of the undertaking. A graphic account of some of the past unsuccess- ful attempts is recorded by Craig.^ Belem or Para possesses a pipe-borne water-supply. The swamps are numerous above the outskirts of the city. In 1909 the authorities were influenced to undertake the filling of much swampy land, and to institute free distribution of quinine. A most serious outbreak of malaria occurred amongst the poorer inhabitants living in the outskirts of the city, along the swamps of the Marco de Legua, Pedreira and Canudos, etc. A medical commission ^ traced the outbreak to the arrival in Para of many labourers who had returned in an infected condition from the Madeira-Mamore railway and Alcoboca works. These people went to the outskirts, and, living in a state of squalor, they remained untreated, and quickly infected the numerous Ano- phelines of the locality. Practically every one in the district 1 Craig, Neville B. : " Recollections of an Ill-fated Expedition to the Head- waters of the Madeira River in Brazil." (Lippencott. ) - Relatorio apresentado pala commissao nomeada para debellar a epidemia de pialmudismo, reinante no Marco de Legua, Pedreira e Canudos. Belem. Imprensa official do Estado do Para, 1909. 46] PARA 385 suffered from malaria. Free clinics were opened, and in four months nearly 13,000 people were treated with quinine; the very severe cases were sent to the hospital. Endeavours were made to have all patients with enlarged spleens confined in the hospitals, or screened from mosquitos. Mosquito-nets were lent and all gametocyte carriers were energetically treated with quinine. A brigade was formed to fumigate the dwellings of badly-infected individuals, and a general purgation of the sur- rounding yards and houses was made. Measures were taken to drain and fill the pools and swamps of the most heavily infected districts, and as many breeding-places as possible were destroyed. A great and general improvement was noted after a few months. The number of infections and the number of Anophelines diminished, and it is to be hoped that these satis- factory results will encourage the authorities to continue their efforts. The expenses were about ^9,500, which was expended on clinics, hospital accommodation, drugs, draining and filling of pools, swamps, etc. The inhabitants of the Amazon region take very little care to avoid contracting malaria. They frequently neglect to take quinine, or discontinue it after a few days of treatment. The labouring-class Brazilian hardly ever uses a mosquito-net, and, unfortunately, Europeans are prone to follow their example. In Iquitos, the Peruvian labourer generally protects his bed, not because of malaria, but for relief from the swarms of Mansonia titillans and Culex fatigans, which are veritable pests ; this helps to account for the less pronounced infection of the Peruvian. All through the Amazon region, where large engineering works have been undertaken, the old familiar story has been repeated. Not only has money been wasted, but many lives have been sacrificed by the neglect of the promoters to realise the dangers of malaria and Anophelines. The astute commercial man has still to learn that it is cheaper as well as quicker to organise a scientific force to combat malaria or yellow fever, and to have such a force in operation before any attempt is made 2 B 386 MALARIA IN THE AMAZON REGION [Sect to import labourers and commence the work. The Federal authorities insert clauses regarding quinine prophylaxis, screen- incr, etc., in the contracts with the concessionaires, but these clauses are frequently neglected. Many important engineering works are certain to be undertaken in the opening up of the country in North Brazil, and an endeavour should be made to prevent the serious loss of life which has hitherto occurred. The sanitary authorities of both the Amazon and Pard states are alive to the necessity of combatting the disease by extermina- tion of the Anophelines. (2). Protection of ships. — Very little attention has been devoted to the protection of the crew and passengers of steamers navi- gating regions where malaria prevails. On some steamers mosquito-nets have been provided for the bunks, and a few wire-screened doors for the outside cabins, wheel-house and chart-room. These are inadequate, as they do not protect the entire living quarters of the passengers and crew. The screening of a steamer is a difficult undertaking. Four facts must always be remembered. (i) That the navigation and working of the ship should not be interfered with. (2) That the scheme of screening shall be as simple as possible. Elaborate designs are certain to fail, as they cause much trouble and inconvenience to those on board. The members of a crew or even passengers will neglect to carry out complicated methods of closing doors and port-holes. (3) That the maximum amount of air shall be available. In the tropics the closeness of the atmosphere does not encourage the average individual to reduce the ventilation by the interposition of wire-gauze screens. I have seen on a steamer plying to the Pacific large screened wooden frames, designed to fit in the port- holes, but so massively constructed that the cross diameter was reduced nearly one-half It is hardly 46] PROTECTION OF SHIPS 387 to be expected, since so much air and light is cut off, that the crew will make use of the screens. (4) That an endeavour should be made to screen the vessel in sections, so that if mosquitos succeed in obtaining an entry, they can only circulate in that part of the ship and can be hunted down and destroyed, Mosquitos generally board a ship when it is moored near the shore or is hugging the banks, and they quickly find their way to the saloons and living quarters of the crew. All parts of a ship which communicate with the danger zone, i.e.y the open deck, should be protected. The doors should be screened, and where there is much passing to and fro between a protected area and the danger zone, a second door should be placed some 3 or 4 feet away, thus forming a vestibule, and allowing one door to be closed before the other is opened. All doors should be provided with spring-locks which catch easily, and a strong door-spring to ensure a rapid and tight closing of the door. If the storm-doors are left on, care should be taken that the knobs do not impinge upon the wire screens and so tear or fray the gauze. The ventilators leading to the cabin, alleyways, etc., should be screened at the ceiling vent. Through the courtesy of the Booth Steamship Company the plans of a vessel specially screened against mosquitos are shown. The ship is designed for use in ocean and river-trade, in a district severely infected with malaria and Anophelines. The port of call is far up-river, and is notorious for the severity of the malarial infection. It is the outcome of the experience gained by Dr Melville Davidson, Medical Superintendent of the Company, to whom I acknowledge my indebtedness. All the port-holes of the steamer are provided with removable screened frames, which are so adapted that the port-hole can be closed and screwed down without necessitating the withdrawal of the screens. The frame of the screen consists of a metal hoop, on which gauze is tightly stretched and soldered, The 388 MALARIA IN THE AMAZON REGION [Sect. frame is provided with rigid bayonet catches, which are so arranged that they sHp easily into the ordinary port, and a half turn of the screen is sufficient to lock it. All the ventilators, as is seen in the drawings (figs. 1-4), are screened by a most simple and efficient arrangement. Ordinary circular moulding is fastened on the ceiling around the vent pipe ; the moulding has a deep groove, into which fits a round metal frame covered with wire-gauze ; the screened frame is retained in position by three small buttons, so that it can be instantly applied or removed. The screen doors have light wooden frames and panels of wire-gauze. They are provided with spring-locks and strong coiled wire door-springs. By reference to the accompanying plan (figs. 5, 6) it will be seen that the arrangement of the screening is quite simple and yet adequate. The screened port-holes and doors are outlined in black. The only entrances to the saloon, chart-room, captain's cabin, pantry and bath-room, are through a screened door on the port side, another on the starboard side, and a third at the foot of the stairs leading from the wheel-house. The outside cabins are all shown with screened doors and port-holes. Further aft, and isolated by the steam-steering gear, are the cabins of the doctor and hospital. On the main deck the entrances on the port and starboard sides through which the crew must pass to their work are screened. On the starboard side there are two sets of screened doors along the alleyway. These are provided because the ash- discharger is open to mosquitos and therefore constitutes a danger zone. On the port side this extra screening is un- necessary, as in the river only one ash-shoot will be used. A study of the plan will show that the only unscreened parts of the ship communicating with the interior are the engine-room, stoke-hole and galley. Theoretically, these sections should be screened, but two factors must be taken into account, viz., the intense heat of the places, which is always accentuated in the 8.S. "VINCENT." ON OF SHIP SHEWING MOSQUITO TION TO DOORS AND PORTS. -f i:-H-- u^4s- Fi^.r TbFojce' Page. 388. SKETCH SHEWING MOSQUITO PROTECTION FOR DOORS, VENTILATORS AND PORTS. S.S. "VINCENT." • « DOORS AND PORTS 7V> Voc» Fbge 3/III. SKETCH SHEWING MOSQUITO PROTECTION FOR DOORS, VENTILATORS AND PORTS. S.6. "VINCENT." DOOR, PORT AND VENTILATOR Fiq.3. FiAj.2. Method of »ttachin4 wire-gauil sciiken to frames. DOORS AND PORTS. 1^.4. ToFace'FkLge'388. 6.S. "VINCENT." PART SECTION OF SHIP SHEWING MOSQUITO PROTECTION TO DOORS AND PORTS. Mg.1. To Face Page 3S8. BOAT DECK •i I I ,^ r^ ^ ^g^^ 1 ^ ^ I "757 " ' ^Ts. m f^ A . ^ -Fig 5. POOP s, BRIDGE DECK -f-i/G^ ^ Tc Face Page 3(t8. 46] PROTECTION OF SHIPS 389 tropics, and the coal-dust, that would cake and block the meshes of the screen, and thus restrict the inlet of air. The wheel- house is unprotected, as screening would be impossible when navigating a river. Provided the screening is not disturbed very few mosquitos should be able to gain an entry, and adequate regulations can be made to prevent such acts as the taking off of a port-hole screen or tying back a door. For port-holes an 18 mesh should suffice, and the gauge of wire need not be thicker than 32 or 30. For doors which are liable to be roughly used, a heavier gauge wire is necessary. The mode of application of the wire-gauze is important. The gauze should not be tacked on to the frame. A far better method is to have a deep groove running around the panel (fig. 3), and a rod either of wood or metal of a size slightly smaller than the groove. The wire-gauze is laid over the entire panel and the rods driven into the grooves. This makes the wire taut and the tension is equally distributed. All strands of the mesh are fastened securely, which is not the case with gauze fastened down by tacks. Over the rod a neat strip of moulding can be fixed, which finishes off the panel and can be easily removed. The great advantage of this method is that it is a comparatively simple matter to take off the strip of moulding, remove the rods, and substitute another piece of gauze. This method is extensively used all through the United States. Excellent arrangements for large private yachts and even passenger steamers can be devised. I have seen nearly the whole of the bridge deck enclosed with ordinary mosquito- netting. The top was made of tarpaulin stretched on robes, and the sides were made of gauze. At sunset the sides were let down, and from fifteen to thirty people were able to dine and sleep in comfort. The expense is not so great, and is amply compensated for by the relief from mosquitos.^ ^ Messrs John Holt & Co. have recently screened an entire ship for West Africa. — R. Ross. 46] PROTECTION OF SHIPS 389 tropics, and the coal-dust, that would cake and block the meshes of the screen, and thus restrict the inlet of air. The wheel- house is unprotected, as screening would be impossible when navigating a river. Provided the screening is not disturbed very few mosquitos should be able to gain an entry, and adequate regulations can be made to prevent such acts as the taking off of a port-hole screen or tying back a door. For port-holes an 18 mesh should suffice, and the gauge of wire need not be thicker than 32 or 30. For doors which are liable to be roughly used, a heavier gauge wire is necessary. The mode of application of the wire-gauze is important. The gauze should not be tacked on to the frame. A far better method is to have a deep groove running around the panel (fig. 3), and a rod either of wood or metal of a size slightly smaller than the groove. The wire-gauze is laid over the entire panel and the rods driven into the grooves. This makes the wire taut and the tension is equally distributed. All strands of the mesh are fastened securely, which is not the case with gauze fastened down by tacks. Over the rod a neat strip of moulding can be fixed, which finishes off the panel and can be easily removed. The great advantage of this method is that it is a comparatively simple matter to take off the strip of moulding, remove the rods, and substitute another piece of gauze. This method is extensively used all through the United States. Excellent arrangements for large private yachts and even passenger steamers can be devised. I have seen nearly the whole of the bridge deck enclosed with ordinary mosquito- netting. The top was made of tarpaulin stretched on robes, and the sides were made of gauze. At sunset the sides were let down, and from fifteen to thirty people were able to dine and sleep in comfort. The expense is not so great, and is amply compensated for by the relief from mosquitos.^ 1 Messrs John Holt & Co. have recently screened an entire ship for West Africa. — R. Ross. By Dr OSWALDO GONgALVES CRUZ Director of the Institute of Manguinhos 47. Prophylaxis of Malaria in Central and Southern Brazil. — Several anti-malarial campaigns have been carried on under the technical direction of our Institute, all of which have been crowned with the most complete success. They were undertaken in the following chronological order : — (i) In the construction of the Itatinga Railway, Santos. (2) In the work of damming the Rivers Xerem and Mantiquira, for the water-supply of the city of Rio de Janeiro. (3) At the time of the extension works of the Brazilian and Northern of Minas Railway, (4) During the survey work for the Bahia and Espirito Santo Railway. (5) During the construction of the North West of Brazil Railway. (6) In the suburbs of the city of Rio de Janeiro in con- nection with the prophylaxis of yellow fever. The most important campaigns were conducted by Drs Carlos Chagas, Arthur Neiva and Gomes de Faria, Members of the Institute; and Dr Carlos Chagas (1906- 1907- 1908) had already written on some of them, he being among us the first to organise a scientific campaign against malaria. The prophylactic formulae adopted by the Institute com- prised the following : — (i) Prophylaxis by quinine exclusively, adopted when the treatment had to be applied to a moving population 390 Sect. 47] QUININE 391 and one not remaining any length of time in a particular zone (railway construction). (2) Preventive administration of quinine, isolation of the persons infected with gametes, in infirmaries fitted with wire-gauze, and unrelaxing treatment of those infected. This system was adopted when the persons already infected had to reside for some time in the infected zone with healthy persons, and where the work was done more slowly. (3) The same measures as above, together with systematic sulphur disinfection of infected dwellings. Prophy- laxis adopted when the staff remained for a longer period in the infected zone, and where it was not possible to carry out prophylaxis by means of larvicide. (4) Indirect prophylaxis by war on mosquitos. Let us see more in detail how these prophylactic systems were carried out among us. The first prophylactic formula. — This was put into execution with success in the surveys for the South of Bahia Railway, by Drs Mauricio de Abreu and F. Soledade, of the General Board of Public Health. The process consisted in the daily administration of 50 centigrammes of hydrochlorate of quinine. It was compulsory, and the medicine was administered by the doctors themselves, who saw that the patients swallowed the capsule. In this case, as the persons never remained long in the same place, the dose of quinine given was always prophy- lactic, which is not the case when the persons remain for a long time in the same infected places, as we shall see later. In the special case, the results were most complete ; not one of the persons subjected to the regime fell sick, whereas others who accompanied the party, without belonging to it, and who would not submit to the same prophylaxis, were attacked by malaria. The second prophylactic formula. — Here the process followed out included : — 392 MALARIA IN CENTRAL AND SOUTHERN BRAZIL [SECT. (i) The preventive administration of quinine, in the dose of 50 centigrammes every three days, (2) The isolation of the persons infected with gametes, in infirmaries protected by wire-gauze during the hours the Anopheles sting, being subjected to strict treat- ment until the gametes disappear. (3) Early and radical treatment of persons infected for the first time and not themselves infectious (this was done without isolation), in order to prevent them becoming infectious to mosquitos by the formation of gametes. Dr Neiva, who was entrusted with the carrying out of the quinine prophylaxis on a large scale (among some 3,500 work- men at Xerem), observed that among those treated with quinine cases of first infection began to appear and increase rapidly. He was able to verify these positively by excluding the cases of reappearance noted after the beginning of the campaign. Satisfied that the dose of quinine was not sufficient to guarantee the prophylaxis, he proceeded to administer it at intervals of two days ; after some time, fresh cases of first infection began to appear, and these were only really stopped when he commenced to administer the quinine in a daily dose of 50 centigrammes. It is interesting to note that among the persons thus treated with quinine an outburst of malaria occurred when they dis- continued the use of quinine, even though the practice had been continued after leaving the infectious malarial zone ; and to prevent such attacks it became necessary to continue the use of quinine for a long time, and repeat treatment at intervals. Stranger still, persons who, after leaving the malarial zone, went to reside in places which were certainly not infected, where they continued the use of the quinine (50 centigrammes daily) for a month, as soon as they abandoned this preventive were attacked by malaria. Such persons had remained for fourteen months in the infected zone without ever suffering any attack of fever. When under the action of quinine they 47] DESTRUCTION OF ADULTS 393 had no fever, but harboured plasmodia in the system. Dr Neiva, in view of his observations, admits that during the quinine prophylaxis the plasmodia become gradually accustomed to the quinine and immune against t/it's pot'son, giving rise to a family able to resist the quinine, and similar to the families of trypanosoma which defy atoxyl. Subsequent to this interest- ing observation of Dr Neiva's (made in October 1907) several other authors have referred to analogous facts.^ The occurrence of the new infections could not be attributed to the inefficient administration of the quinine. This was com- pulsory, and was administered by trustworthy persons, the infections being found to exist in persons who undoubtedly had taken the prescribed doses. The second item of the prophylactic formula under con- sideration is intended to destroy the gametes in circulation, which prevents the infection of the mosquitos, which, as we know, can only occur when there are gametes in the periphery. This result was obtained by the daily and continuous adminis- tration of 50 centigrammes of quinine. It was proved by the microscope that after a time it was no longer possible to recognise the existence of gametes, whether of the benign or of the malignant (tropical) tertian. When the parthenogenesis of the gametes occurred, following on excessive work or heavy rains, i gramme of quinine was given daily, as a rule by intramuscular injection. It should be noted that no scabs appeared after the injections. The above shows the necessity of carrying on the anti- malarial campaigns by persons capable of making the utmost use of the assistance furnished in such cases by the microscope. T/ie third prophylactic formula. — Dr Carlos Chagas, in his studies on the epidemiology of malaria, and on the biology of the Anopheles responsible for the transmission of the trouble within the zones, found that there were dwellings constituting regular hot-beds of malaria, and that such houses were invaded ^ Incubation retarded by quinine is well known. — R. Ross. Sect. 47] DESTRUCTION OF LARVAE 395 at night by the Anopheles, which stayed there till dawn, some withdrawing to the woods, whence they returned the following night, others remaining concealed in the dark damp places of the huts. These infected mosquitos caused the permanently infected condition of these dwellings. The opinion that malaria is a disease commonly infectious in houses finds a perfectly feasible basis in arguments relating to the biology of the Anopheles, and in numerous facts arising from careful observation. In view of this Dr Chagas resolved to make systematic cleansing by sulphur vapours in such dwellings, and thus succeeded in sterilising these centres of infection. These measures were always accompanied by quinine prophylaxis. But as an experiment Dr Chagas ascertained that the treatment of dwellings by sulphur was sufficient to prevent the infection of the persons who passed the night in such deadly centres of malaria, and who were not subjected to the action of quinine. The fourth prophylactic formula. — This consists of indirect war against malaria by the destruction of the larvae of the Anopheles. This prophylactic system was tested at Rio de Janeiro, when the prophylaxis of yellow fever was carried out in the metropolis of Brazil. One part of the war on mosquitos was begun by drying up all temporary deposits of water, the destruction of the larvae in natural deposits by means of the cultivation of larvae - devouring fish {Girardinus caudi- maculatus), by the protection of indoor water - cisterns from mosquitos, the petrolising of large sheets of water, the destruc- tion of the Bromelias epiphytes, etc. The results obtained were very favourable, as may be seen by an examination of Table No. i, which we give below. In Table No. 2 is given the complete result of the anti-yellow fever campaign. The malaria figures do not show the same decrease as those for yellow fever, because in the table for malaria the cases existing in the urban hospitals, where 396 MALARIA IN CENTRAL AND SOUTHERN BRAZIL [Sect. patients were received from rural zones not influenced by the prophylactic campaign, appear. TABLE II. TABLE OF MORTALITY BY YELLOW FEVER IN RIO DE JANEIRO FROM 1872 TO 1909. 1872 1873 1874 1875 1876 1877 1878 1879 1891 1892 1893 1894 1895 1896 1897 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 16 23 122 3 156 102 138 50 3 8 79 15 201 6 30 510 57 51 1,006 4 371 27 524 28 22 99 42 13 32 133 2 3 6 SI 168 319 ID 420 227 496 67 13 9c 208 28 351 18 39 719 103 357 1,290 57 1. 351 41 731 33 90 170 64 41 64 142 7 13 9 953 168 385 1,405 74 331 226 471 46 23 335 253 58 483 89 29 281 297 301 1,019 35 130 169 273 26 27 598 210 51 304 37 128 539 142 187 169 1,026 960 1,404 410 108 135 1.978 695 86 141 1,002 445 37 20 255 287 204 91 78 61 69 64 16S 178 151 99 7 8 23 59 6 8 6 14 I 165 244 395 40 60 81 "5 25 12 300 68 65 74 18 116 97 109 600 147 172 305 104 136 17 36 37 154 24 10 64 3 83 69 104 147 12 23 54 58 14 8 III 15 57 23 61 38 421 35 141 114 77 37 6 78 25 28 17 131 10 4 61 I 4 3 37 41 4 18 43 18 13 I 69 12 44 9 I 50 27 22 190 14 73 14 51 20 3 65 II 9 14 79 9 4 26 18 16 383 I 37 7 166 102 3.659 829 1,292 3.476 282 1,176 974 1.625 257 863 445 1-449 137 747 2,156 719 4.456 4.312 825 4.852 818 2,929 159 1,078 731 344 299 984 584 48 289 42 39 4 Table No. 3 shows the results obtained in the campaign undertaken at the time of the damming of the Rivers Xerem and Mantiquira for the water-supply of the city of Rio de Janeiro. The region through which canalisation work had to 47] BRAZILIAN ANOPHELINES 397 be extended was so devastated by malaria that 95^ of the men employed in the work were attacked, the mortality being so heavy that the Government was obliged to abandon the first attempt. Work could not be resumed until the special prophylactic service for malaria had been organised, with the result that in a few months the works were completed and the city of Rio de Janeiro provided with an abundant supply of drinking water. In the malarial zones of Brazil the following species of Anopheles are found : — Cydolepteron mediopunctatuin (Theob, Lutz), Cydolepteron interniedimn (Chagas), Cellia argirotarsis (Theob), Cellia albiniana (Wied), and Arribalzagaia pseudoma- culipes (Chagas). These are undoubtedly the transmitters of malaria, as was experimentally shown by the characteristic forms of evolution of the Plasmodium in them. The following species are suspected of transmitting the malaria, so far as can be judged by epidemiological studies: — Myzomyia lutzi (Theob), Cellia braziliensis (Chagas), Myzorhyn- chella lutzi (Cruz), Myzorhynchella parva (Chagas). As to the habits of the Anopheles, Dr Chagas noticed that as a rule they suck only at certain hours, at nightfall, when they come in swarms, or in the early hours of the morning. They disappear entirely during the day and night, at which time, therefore, there is no danger of men being infected by the contaminating mosquitos, or of the mosquitos being infected by sick persons with gametes. An exception to this rule is the Cellia braziliensis (Chagas), which attacks for preference during the day and in the sun, which fact shows the necessity of studying the Anopheles fauna of the region in which it is proposed to start an anti-malarial campaign. Further details as to the Brazilian Anopheles and their relations with malaria may be found in the works of Dr A. Neiva, lately published (1909). In dealing with the organisation of the systematic prophy- 398 MALARIA IN CENTRAL AND SOUTHERN BRAZIL [Sect. 47 laxis against malaria a knowledge of the existence of the Myzoniyia lutzii (Theob.) in the region is deserving of special attention. This mosquito, which appears to be responsible for the transmission of malaria in the regions where there are no swamps, lives in the waters found in the Bromelias epiphytas (Lutz, 1902), and is so small that it can pass through the wire- gauze of 1*5 mm. mesh, usually employed for protection of houses. For this further reason it is advisable to study the Anopheles fauna of the region before proceeding to instal mechanical prophylaxis of malaria. Finally, it should be mentioned that the quinine prophy- laxis has been carried out without the slightest inconvenience to the persons subjected thereto^ there being a large number of people who have used daily 50 centigrammes of hydrochlorate of quinine for the last two years and ten months without showing the slightest bad effect from the employment of this medicine. Further, the phenomena of noises in the ears, etc., are not observed when the quinine is administered at meal times. No cases of hoemoglobinuria have been observed following on the administration of the quinine, and the few cases (8) of this morbid nature observed disappeared with the quinine treatment. BIBLIOGRAPHY 1902. Dr Ad. Lutz.— " Forest Mosquitos and Forest Malaria." Central- Blatt ficr Bakt. etc., ist pt. orig. vol. xxxiii. p. 282. 1906-7. Dr Carlos Chagas. — " Prophylaxis of Malaria." Brazil-medico, year xx. pp. 315-337 and 419 ; year xxi. p. 151. 1908. Dr Carlos Chagas.— A paper on " Malarial Prophylaxis." Zeit- schrift fiir Hygiene und Insect krank. vol. Ix. p. 321. 1908. " Prophylaxis of Malaria." Paper read at the 6th Brazilian Congress of Medicine and Surgery. In Revista Medica de Sao Paulo., No. 19, year xi. p. 391. 1909. Dr Arthur Neiva.—" Contribution to the Study of Diptera." Observations on the biology and organism of Brazilian Anopheles, and their relations with malaria. Proceedings of the Oswaldo Cruz Institute, vol. i. p. 69. Table 3. di^JiL-lWlli:ii..i.-^:^-- \To face page 398. By IAN MACDONALD, M.D, Edin, M.D., Paris Huelva, Spain 48. Malaria in Spain. — Among the countries of Europe, Spain has always suffered severely from malaria, and the records of history show that it swept over her with the virulence of plague. In September 1283, when Philip the Bold of France besieged and took Gerona, his army was almost destroyed by pernicious fever, and he himself succumbed to an attack at Perpignan. In this epidemic, according to Dormese, great importance was attached to " some flies which caused death by their bites," Of its ravages in the Peninsula no better picture has been given us than that of Johnson in 1771, "the attack of Carthagena is yet remembered, where the Spaniards from the ramparts saw their invaders destroyed by hostility of the elements ; poisoned by the air and crippled by the dews ; where every hour swept away battalions ; and in the three days that passed between the descent and the embarkation half an army perished." From historical data, it is clear that the greater number of Spanish authors up to the eighteenth and first half of the nineteenth century in many cases con- founded malaria with the whole group of infectious diseases. In these times one Spanish clinician, Ludovic Mercado, physician to Philip II and Philip III, stands apart from the rest, for in 1608 he differentiated pernicious intermittent fevers of tertian type in the midst of the pathological chaos around him. In 1783 Masdevall described the lamentable effects of malaria in Lerida and the devastation it caused among the French troops massed in Cdceres. He pointed out the relation 399 400 MALARIA IN SPAIN [Sect. between fever and the pools left by rivers and after rains, and remarked that the greater number of cases were always found amongst those who worked in the sun and who slept at night in the open air. He completes those accurate observa- tions by recommending the use of Peruvian bark for the cure of the disease. In the first years of the nineteenth century (1800- 1805) several papers appeared on the value of quinine in epidemics of yellow fever, and Nelson in one of his last letters to Lady Hamilton, writes of " the dreadful effects of yellow fever at Gibraltar, and in many other parts of Spain." Though Stegomyia fasciata, the carrier of yellow fever, exists in the cities of Southern Spain, from a study of the symptoms, and course of this fever and the therapeutics employed by these authors, it is clear that they were dealing with severe types of summer autumn fever with hepatic symptoms. In 1888, discussions began in Spain as to the validity of Laveran's great discovery, and till 1896 the best paper on the parasite was that of Thin and Marshall, who accurately described the types of fever met with in Southern Spain. But the hypotheses of Laveran and Manson, at that date passing from theory to fact in the researches of Major Ross, received no support from these investigators ; for their con- clusions are thus presented in a well-known text-book (1899): " The observations of Thin and Marshall go to show that in the province of Huelva at all events telluric conditions are the permanent factor in infection, that the plasmodium is not usually conveyed by water, and that there is no evidence of the mosquito being an intermediary host." After the publica- tion of Professor Ross's early papers, in the summer of 1899 we began to investigate malaria in the same province, over an area of 60 miles, extending from the Rio Tinto mines in the foot hills of the Sierra Morena to the coasts around the town of Huelva. In the hills it would be difficult to find a 48] WORK AT HUELVA 401 more arid district, where water appeared to be completely wanting-, for the vegetation within a three-mile radius had been destroyed by the fumes of sulphur smoke. It lies 320 metres above the sea- level, and the soil is chiefly ironstone. Hardly any rain falls from May to October (fever season), with the exception of rare thunder-storms. The aspect of the country is that of undulating hills covered with low brush-wood beyond the smoke area. The valleys in winter are often filled with roaring torrents. In summer these streams dry up, leaving pools, varying in size from about 3 ft. in diameter to the size of a plate or saucer. The district is dotted over with small villages which are situated on the slopes of the hills. The whole area was more or less malarious, but certain villages were notoriously unhealthy, and it was a curious fact that the lowest lying village was the healthiest, though the moving of earth for mining operations went on at its very doors. Yet half a mile off, where most of the British employees lived, fever was frequent. In September 1899, we showed that, so far from mosquitos being scarce owing to the presence of sulphur smoke, they abounded in the district ; and in the paludic villages Anopheles maculipennis was often the only mosquito to be found in the houses. In the Province of Huelva we differentiated the following varieties of mosquitos : Anopheles maculipennis^ Anopheles superpictus Grassi, Myzotnyia superpictus Blanchard, Stegomyia fasciata, Culex phytophagus, Culexpipiens, Ctdex penicillaris {Grathamia penicillaris Rondani), Culex spathipalpis {Theobaldia spathipalpis). In south Spain A. maculipennis is the chief carrier of malaria. A. superpictus is not often met with ; we have only found it in three or four districts. We have always found that the abundance oi Anopheles m any district is in relation to the extent of malaria. Since then, repeated observations in many places in the South of Spain have always shown us the same conditions in fever districts. Whether the town is in the hills or on the 2 C 402 MALARIA IN SPAIN [Sect. plains, the dried - up water-course is always there, the pools sometimes covered with algae. In the hills the water is often running slowly. In the Sierra we have found Anopheles larvae in rocky pools devoid of vegetation, but as a rule they contain algae, at the edges of which the larvae swarm. The difficulty of seeing the larvae of Anopheles compared with those of Culex is of course well known ; and in some cases a careful examina- tion is needed before concluding that there are none in the pool. In the hills, if a muddy pool and a clear one existed side by side, we constantly noted the preference of Anopheles for the limpid water. As a general rule we have not found larvae in artificial collections of water — only very occasionally in old barrels and iron tanks on a railway line. In mining districts here, dams are often believed to be a source of malaria. We have not yet found larvae in such collections of water, but have often demonstrated them in the ravines within 50 metres of the dam. The adult insects in winter and spring hibernate here in stables, hen-houses and pig-styes, where they can always be found until the end of May or the beginning of June. After that time they are also found in the houses. The course of the epidemic season of the malaria in Spain confirms, as elsewhere, the strict relation there is between the human infection of the previous year (winter relapses, cahectics, children) and the infection of the mosquito in June and July, the beginning of the fever season. Our dissections showed that the percentage of the infected mosquitos in June was only 7%, while towards the end of July and in August it rose to 18%. Of Anopheles captured in stables, etc., none were found infected. We frequently found red larvae of Hydrachnides fixed on the insects, and sections of some Anopheles which died rapidly in captivity were examined by Laveran and were found to contain a fungus in the wall of the stomach and in the coloemic cavity, which possibly may be pathogenic for the insect. For infection experiments, we fed A. viaculipemiis on fever 48] OTHER PARTS 403 cases, and weak hematine gave us good results in staining the zygotes. Sometimes no infection of the insect took place, or the zygotes failed to reach maturity. We felt that such variations were probably due to the diet of the mosquito, and a note by Sehoo of Holland confirmed this ; for he pointed out the importance of avoiding acid fruit in the food of insects under infection experiments, and when we fed them on melons the growth of the zygotes was uninterrupted. The role then of Anopheles in Spain admits of no doubt • and the mosquito has never been found wanting in malarial districts in the fever season when searched for by competent observers. These investigations were confirmed elsewhere in Spain by Huertas and Mendoza in the province of Caceres, and by Pittaluga in Catalonia (Barcelona), Valencia, Madrid, and the Balearic Isles, where he found A. maculipennis, A. psendopictus, A. superpictus and A. bifurcatus. In 1903 Pittaluga collected the investigations up to date on malaria in Spain, and from the papers of different writers in that volume some idea was obtained of the extent of malaria in modern Spain. His map gives a good idea of its distribution. Though exact data are difficult to obtain, it is quite apparent that the disease still reigns with great severity in the Peninsula. In 1900 there were 4,703 deaths from malaria in Spain in a population of 18,300,000, which is a malarial mortality of 0*25 per milk. In relation to the general mortality of 536,716 (29-3 per mille), this represents 1/114 of the general mortality, or 9 per 1,000 of the cases of death. In 1898 and 1899, when the troops came back from Cuba, the malarial mortality rose immediately, and probably gave in each of these years a mortality of not less than 8,000 per annum. The following figures from a railway company give a further idea of the ravages of malaria in Spain to-day. In 1902 12,746 employees were treated medically or surgically, and of these 1,904 were malaria patients. Five deaths were directly attributable to fever 404 MALARIA IN SPAIN [Sect. and the company lost 14,275 days' work in consequence of the disease. On certain divisions of the line this company keeps a double personnel to alternate every fifteen days, and the employees themselves call one notoriously unhealthy area " Little Cuba," where their doctors admit that the mortality is equal to that of tropical countries. After these researches some stimulus was given to prophy- laxis, but, so far, in Spain it has only been undertaken by a few companies and private individuals. In a country where typhus last year raged in her capital, and the isolation hospital is unknown in her provinces, sanitation is only in its infancy^ In the city of Badajoz in 1899, in one street 500 people were attacked by malaria, and the supply of quinine ran short in the town. Yet no municipality has yet organised a scheme of prophylaxis. Through the kindness of Dr Varela we are enabled to submit the following figures from the Madrid, Zaragoza, and Alicante Railway, where protection of the railway servants' houses by wire-gauze, and the administration of quinine, are the methods employed, and have given a gradual but steady diminution in the cases of fever : — 1901-1902 no protection 631 cases 1903-1904 with protection 306 „ 1905 „ „ 190 „ In Rio Tinto, supported by a company which recognises the importance of the health of their staff, we initiated measures of prophylaxis, on a small scale, which have been continued under the direction of Dr Russell Ross, the chief medical officer, with eminently satisfactory results. The English staff of this compan)', with their wives and families, number about 170 persons. They live in a group of thirty houses, in close proximity to the ravines where Anopheles pools are found. A few years ago in the malarial season each house had its fever patient, and the place was notoriously unhealthy. The 48] RIO TINTO 405 pools are now filled up or drained away ; and, where it is impossible to remove the water completely, narrow channels are made by which a rapid flow is maintained, and stagnation prevented. Simple open drains have been laid in the bed of some water-courses. The use of nets is recommended, and some families have their houses protected by wire-gauze. The effect on the number of mosquitos has been marked, for now they are hardly ever seen. Hen-roosts and places harbouring domestic animals are smoked out once a week by a mixture producing sulphurous acid gas. The diminution in the cases of malaria may be seen by reference to the following table which we owe to the kindness of Dr Ross : — Cases of acute malaria 25 2 O o I The attack on the Anopheles pools has recently been extended to the ravines round the workmen's villages, where gangs of men under supervision drain away and fill in the pools. The improvement in the health of the people has been most marked. In former years departments with 2,0(X) men at times had hundreds incapacitated by fever, and difficulty was sometimes found in maintaining the service. Now, though some cases still occur, fever never rages to the extent it did formerly. Villages which were recognised as hot-beds of malaria, and consequently avoided by the workmen, have been rendered comparatively healthy again. The cost of these measures in Rio Tinto and its environs is less than £\Q0 per annum ; but costs are lessened by assistance given by the various departments of the mine. Ten years ago there was a yearly despatch of 1,225 oz. of quinine; it is now reduced to 900 oz., though there is an increase of 50% in the number of workmen. Cases of illness 1896 . no prophylaxis 89 1906-07 61 1907-08 1908-09 prophylaxis 64 78 1909-Ioj 80 By Professor ANGELO CELLI Director of the Institute of Hygiene, University of Rome 49. The CampaigTi against Malaria in Italy.^— In my report to the International Congress, held at Brussels,^ I described how a Society for the study of malaria in Italy had arisen, and stated that it had initiated its work for the purposes of know- ing better and vigorously combating this grave scourge of our country. I have much pleasure now in noting summarily the results obtained from 1903 till to-day. Since Ross's discovery was confirmed and consolidated by the work of some of our members, and later by many other workers, we have continued to work in the scientific and practical fields. In the scientific field we have made researches on the etiology, physio-pathology, epidemiology and prophylaxis of malaria. In the practical field we have introduced new and improved prophylactic measures into medical use, legislation and the habits of the people. In order to keep within the narrow limits assigned to me, I can note only the following facts : — ^ Owing to pressure of work, Professor Celli has asked me to take for his contribution to this book his article in the Journal of Tropical Medicine for 1st April 1908 (trans- lated by Dr John J. Eyre), with special additions. The editor of the Journal has kindly permitted this. — R. Ross. 2 Septime Section. " Hygiene Coloniale, Deuxieme Question : Prophylaxie de la Malaria," vol. viii. , Bruxelles, 1903, and Giornale della R. Soc. ital. d'/giene, Milan, 1903. 406 Sect. 49] QUININE AND MORTALITY TABLE 407 FIG. I. — MORTALITY FROM MALARIA AND THE CONSUMPTION OF QUININE IN ITALY. I Annual number of deaths from malaria from 1887 (upper part). ^ Kilograms of quinine imported by private measures from 1 89 1 onwards. ^ Kilograms of State quinine sold yearly from 1902 (lower part). 4o8 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. I.— The Principles of Epidemiology By our researches it has been demonstrated and confirmed in different ways that : — (i) Man is the only source at present known of malarial infection. (2) Not only infants, but also children and adults, are the bearers of the infective germs. (3) The recurrences, sometimes obstinate, in spite of every kind of treatment, are the most marked characteristic of every form of malarial fever. They maintain the contagion between the healthy and the diseased from one epidemic year to the next, and are one of the main causes which regulate the local and annual variations of the malarial epidemics. (4) As the indication of an epidemy, it is necessary to take into consideration : — (a) The infantile malarial morbidity and the relative splenic enlargement: this splenic index, as it is named by Christophers and Stephens, may be easily ascer- tained, but is neither exact nor exclusive ; moreover, it does not suffice, when alone, to indicate the intensity of an epidemic, (^) The morbidity in the whole population or in some classes of it (country people, miners, soldiers, railway employees). (c) The recurrent cases which are more or less obstinate. (d) The numerical relation between the aestivo-autumnal and the mild tertian fever cases. (e) The more or less severe clinical features and complica- tions (haemoglobinuria). (/) The manifestation of domestic epidemics or of sporadic cases. (£■) The total or absolute mortality related to the whole population (relative mortality), or the one related to 49] GENERAL PRINCIPLES 409 the number of the infected individuals (pernicious- ness or lethality from malaria), (/z) Demographic indications, especially the excess of deaths over births and the following depopulation and desolation which are but too sad a characteristic of malarious lands. When we take into account all these indications, we may every year not only exactly establish the course of epidemics in our districts, but also precisely compare our observations with the international ones. An historical description of epidemics in these last years, by making use of the above - mentioned indications, would be possible only for small, well - circumscribed and thoroughly studied areas. Therefore we must generally content ourselves with the mortality index, and, so far as possible, with the morbidity index too. (5) The severe tertian, the mild tertian, and the quartan have each a special type of epidemy ; that is to say, the first is aestivo-autumnal proper, the second is the only one which presents itself in the spring, the third is principally autumnal. (6) The Anopheles are never wanting where the fevers exist, but their quantity is not always in direct proportion to the intensity of the epidemy ; in fact, it is frequently in inverse proportion. On the other hand, there may be plasmodia and Anopheles without malaria developing itself, even when malarial patients arrive there from other places, or some autochthonous or sporadic case of fever manifests itself there. Plasmodia and Anopheles may therefore persist, and, notwithstanding this, the malaria may become attenuated and disappear. (7) The number of Anopheles infected is always small, even in the places and months most affected by the fevers. The hereditary transmission of the infection from mosquito to mosquito has not been demonstrated up to now. (8) Various annual epidemic types exist, namely : — 4IO THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. {a) The South of Italy type, with great predominance of the aestivo-autumnal parasites, with virulence gener- ally exalted. {b) The North of Italy type, with more or less predominance of the parasites of the mild tertian and the initiation of this in the spring. (c) The North of Europe type, with the absolute pre- dominance of the mild tertian and the precocious development of the epidemy in the spring. In Hungary, Greece and Russia epidemic types like those observed in Italy are met with, (9) The mortality from malaria in the whole of Italy from 1887 onwards {cf. fig. i, upper part) has been subject to regular periodic oscillations, with a maximum every five or six years. This periodic course is most marked in the most malarious regions — namely, from Latium downwards, and in the islands {cf. fig. 2), while in the rest of Central and North Italy the progressive descent without notable variations is manifest. The morbidity also from malaria in the Rome hospitals is subject to periodic oscillations which in the last fifteen years have reached their maximum every five years. No relation has been as yet established between the meteoro- logical conditions and the annual and periodic epidemic oscilla- tions, which would seem to be due more to general biological properties inherent in the specific parasites themselves than to climatic reasons. (10) In the study of the malarial epidemics, besides infected men and Anopheles, it is necessary to take into consideration also other predisposing or immunising causes of biological or organic {x), physical or local {y), economic or social {s) origin. Although they are unknown in their intimate mechanism of action, nevertheless they have undoubted influence both on man and on Anopheles, and hence they may stimulate or impede the development of a malarial epidemy. Therefore, for the primary, very simple equation: Malarial man-\- Anopheles = epidemy of 49] TABLE OF RESULTS 4" malaria, we must substitute this other : Malarial man ■'r Anopheles + x,y, 5 = epidemy of malaria.^ (ii) The above-mentioned facts show that the problems of NUMBER OF DEATHS 887 BST 89 90 91 92 93 94 95 96 97 98 99 900 01 02 03 04 05 06 07 08 itooo 500 lOOOO 500 9000 500 8000 500 7000 500 6000 500 5000 500 4000 500 3000 500 2000 500 lOOO 500 O • t 1 • A — — — A iL 1 i • ^ r V J\ ^ =y> • T. ^ j V S y \. • ^i -\ \l 4 \ V u, 1 \ • ' \'< — ^ \ \ \^ \ /\ \ \ « |a "^ v> A i 1 \ '^ \ f t \ \ ^V* V y \ \ N • V \^ -.- ../ • \ s... -> ,^ \ \ \ "\ N k ..^ N. •»• r»»« '••• "- ... '•♦. ^ v^- '••. '•.. ^ ••• ... ... "N *s > — _ ■"l- • *•• >■• FIG -^ —MORTALITY FROM MALARIA IN THE REGIONS OF ITALY BEFORE AND AFTER THE STATE QUININE. Latium and South Italy. - - - Sicily and Sardinia. , t i \ Central Italy (excluding Latium and North Italy). the epidemiology and prophylaxis of malaria cannot be con- sidered from a narrow point of view. II._The Measures for Combating Malarial Epidemics Our first attempts were directed to the destructmi of the mosquitos by physical and chemical means. The laboratory 1 Compare section 28. — R. Ross. 412 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. experiments were encouraging. Later attempts, with great perseverance, were carried out by Galli-Valerio and by J. Rochaz de Jong, by biological means (animals and plants which kill mosquitos or impede their development). On carrying this into practice on a large scale one meets with many difficulties owing to which, at least among us, with so many extensive marshes and so much intensive culture, one cannot succeed, save in exceptional cases and by long and assiduous work, in destroying malaria by means of the destruction of mosquitos. Nevertheless, to the old and reliable methods of the campaign against malaria, namely, draining and agrarian sanitation^ our efforts were directed. The hygienic effects of the sanitation by drainage already carried out were studied. The result was that on large extensions of land the best drainage sanitation very frequently failed to drain off all the water or to give it sufficient velocity to impede the aquatic life of Anopheles. Frequently, also, the deficiency of the neglected state of the complementary drains and of the discharging canals helped to maintain the anophelism. Consequently, very often the drainage improvement is not synonymous with sanitation, to which one will arrive in time, when the agrarian sanitation supervenes, which, therefore, must be the necessary complement of the drainage improvement. Both, however, as we shall see, can, and should, be facilitated and shortened — with incalculable saving in health and time — by means of the medical, mixed, or at least the quinine prophylaxis. In its turn the agrarian sanitation helps to improve the conditions of life of the worker by better housing, alimentation, work and clothing. These coefficients, together with improved medical assistance and the consumption of quinine, have led after a long time, and now lead more quickly, to the sanitation of a territory, even where paludism, with the relative anophelism, still exists, and even can usefully exists inasmuch as it helps to render, by the utilisation of the waters, the agriculture more prosperous. 49] MEASURES COMPARED 413 Keeping away infected mosquitos from the person and frotn the house is another mode of protecting oneself from malaria, which is directly derived from the new theory. However, if man on whom this scourge weighs should wish to free himself from it only by the mode which is directly derived from the theory of the Anopheles, that is, by the destruc- tion, or at least by the keeping away of these insects, who knows how long he would have to wait ? We refer to the difficulties met with by us in our campaign in endeavouring to destroy the mosquitos. A quicker and, within certain limits, a more easy method is to prevent them biting one by keeping them away. But only the minor part of the population, namely, the richer and, therefore, the least attacked, can enjoy this benefit. In fact, in order to prevent the bites of mosquitos one requires, above diW, proper clothing, which frequently is wanting, and owing to the great heat cannot be supported ; thus, also, the gloves and masks for protecting the uncovered parts of the body are very inconvenient, and prevent one working. Odours, ointments, and washes containing culicidal sub- stances, which, according to our researches and those of others, are many, have a very restricted action in closed spaces, and little or no action in the open air. On the other hand, he who can live in some kind of habita- tion, with all the openings protected with wire - netting to prevent the entrance of mosquitos, can thus, as a rule, preserve himself from malaria. This method, which was first adopted by us in 1899, by our advice is coming more and more into use in the houses along the railways, as shown from the subjoined table. This mechanical prophylaxis has been adopted in the Custom-house officers' barracks. It, however, is not equally practicable for soldiers. Unfortunately, owing to the first cost and that of repair, it 414 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. is an expensive prophylaxis ; besides, it presupposes a special hygienic education in those who inhabit the protected houses, and that they should retire there during the most dangerous hours of the day, things which are very far removed from the mode of life to which our peasants are accustomed. TABLE I Mechanical Prophylaxis along the Adriatic Railways Percentage attacked Percentage of WITH FEVER. CONTROLS attacked. Year. Persons protected. Recurrent. Primary. Min. Max. 1899 24 20 20 96 _ 1900 27 5-5 7-5 n 92 I901 5,165 3-3 20-2 20 96 1902 5,851 lOI 2" 12 81 1903 8,230 22-5 4-6 10 32 1904 12,378 87 2-0 10 27 Fortunately, much easier and quicker results can be obtained, when one wishes it, by the proper administration of quinine. It is very well known that quinine is a truly sovereign remedy, both for disinfecting the blood of malarial patients and for provoking an artificial medicamental immunity. But this very powerful weapon with a double edge has not been well managed by others; whereas in our hands it has constantly increased in value, not only for the curative treatment, but also for the preventive treatment of malaria. There is no doubt that this remedy acts in inverse pro- portion to the degree of development of the malarial parasites in the blood-stream ; that is to say, it acts best against the sporozoites directly they are inoculated, and least against the forms destined to maintain the recurrent fevers, and little or not at all against the sexual forms destined to propagate the species. We have thus proved over and over again that some 49] PREVENTION BY TREATMENT 415 fevers are pertinacious in recurring in spite of the abundant and protracted use of quinine, either alone or associated with the so-called reconstituents (iron and arsenic). In fact, these latter drugs, under whatever form and in whatsoever way administered, have no value as direct anti-malarial remedies. It follows from this that even the best treatments in the pre- epidemic period do not succeed in preventing, as Koch thought they would, the development of malaria in the following summer. Therefore, by the quinine treatment alone to extirpate malaria from an extensive locality is much more difficult than one would a priori imagine. In any case, it must be the work of long duration, that is to say, treating in every period of the year, day by day, energetically and assiduously, every case of malarial fever. Quinine, however, is the best remedy for the radical treatment of malaria, even latent and recurrent. The essential thing is to continue the treatment for a long time with great patience and perseverance ; and the secret of success is to administer the quinine in the most agreeable and therefore also the most tolerable form. Besides, it is better, when possible, to call in the aid of other means pre-eminently beneficial, such as alimentation, habitation, clothing and moderate work. Since, therefore, the latent and recurrent infections cannot be prevented, much less eradicated, // is necessary to do every- thing to prevent completely the malarial infection itself. The quickest and best results regarding the preventive treat- ment are obtained by quinine administered for this purpose. To establish firmly the scientific and practical basis of this preventive treatment of malaria has been, since 1900, one of the principal tasks we have undertaken. Thus, by degrees, with the assistance and control of able collaborators, we have come to the following conclusions : — {a) That quinine, provided it be administered daily, is in average and even therapeutic doses better tolerated, and for a longer time than a priori one could have believed ; that is to 4i6 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. say, after the first two or three days it no longer produces the least singing in the ears, and is not only completely innocuous, but also acts as an aid to nutrition and as a tonic to the digestive apparatus and muscles, thereby increasing the appetite and the power of work. (b) Quinine taken daily is always present in the blood, and thus prevents instead of producing the phenomena of quininism. Further, there is not, perhaps, another example of a remedy so perfect, nor one which so rapidly establishes itself, and can be prolonged for a long time (up to five or six months), and yet can be interrupted when desirable without any disturbance, and without, although the organism is habituated to the small and average doses, diminishing the curative efficacy of the large doses when they are necessary. {c) But if quinine be given at intervals longer than three days the phenomena of quininism present themselves every time ; in consequence the method of intermittent administration, namely, every four days (Ziemann), every five (Plehn), every seven to ten (Koch), although recommended by these able workers, is not preferable to our continuous and daily method. The administration at intervals of every two or, at the utmost, of every three days (Sergent) may be in some cases employed. Longer intervals are not to be recommended, owing to the disappearing of quinine from the blood three days after the administration. {d) Intolerance to the salts of quinine insoluble in water, if they be administered in average doses daily, is met with in very few persons, and up till now we have never observed the haemoglobinuria which the intermittent method and the relative large doses have not succeeded in preventing. {e) Intolerance very exceptionally manifests itself if a salt insoluble in water, such as tannate of quinine, be given. This salt is slowly absorbed, especially in the intestine, by the work of the bile and of the pancreatic juice, and it is perhaps for this reason that it has the value of being generally atoxic, even in 49] QUININE 417 persons who have a special idiosyncrasy for haemoglobinuria towards the salts soluble in water. By reason of this ordinary atoxicity, as well as the absence of bitter taste, it is specially indicated for young children, and for those adults who show intolerance for the other salts or suffer from malaria com- plicated by gastro-intestinal disturbances. (/) According to Mariani and Giemsa also, quinine proper that is, in the basic state, is absorbed, and acts very well. Con- sequently, the solubility or not in water of a preparation of quinine, or its administration with the stomach full or empty, do not in the least deserve that importance which has been and is attributed to them. (^) An essential coefficient of true tolerance is to administer it in an agreeable form ^ hence the forms of comfits or chocolates which we have persistently proposed for the various salts of quinine. (Ji) He who takes quinine every day, and therefore has always a supply of quinine in the blood-stream, can undergo with impunity inoculations of blood full of malarial parasites, and can expose himself with little or no danger to the bites of infected mosquitos.^ (f) Arsenic and iron do not display any protective anti- malarial action, either experimentally or chemically demonstrable. These are the scientific and practical facts on which we have based the method of preventing new infections, and of reducing the recurrences by means of the daily administration of quinine in average doses, namely : — 40 centigrams of the bisulphate, hydrochlorate or bihydrochlorate of quinine for adults and young persons ; 20 centigrams of the same salts, or 30 centigrams of tannate of quinine for children ; and in every case administered in the agreeable form of comfits or of chocolates. These, especially, owing to the sugar and cocoa have overcome the dread and prejudice against the prophy- lactic use of quinine. ^ See end of section 16 and section 65. — R, Ross. 2 D 4i8 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. In districts with very severe malaria the above doses are increased to 50 or 60 centigrams for adults and young persons, and one can or must substitute the bisulphates for the bihydro- chlorate of quinine. In districts with mild malaria the indicated preventive treatment of children may be given on alternate days. The efficiency of our method is demonstrated by the follow- ing figures, which show the rapidly increasing number of persons who, in virtue of the work of our members from year to year, have benefited by this preventive treatment. TABLE II Quinine Prophylaxis in Italy Year. Number of persons treated for I to 5 months with preven- tive quinine. Attacked by fevers. Locality. Persons treated. Percentage of control. Total. Percentage. Min. Max. 1900 1901 1902 1903 1904 1905 1906 1907 1908 116 538 3,055 19,021 52,690 59,340 110,804 100,816 102,572 52 30 335 932 4,262 3,458 7,115 4,192 5,780 IO-3 5-5 77 5-6 8-0 5-8 6-4 4T 57 63 20 12 38 8 9 9 60 81 90 80 82 50 Agro Romano and Pontine Marshes. ,, ,, ,, ,, ,, ,, Various parts of Italy. ,, ,, ,, ,, ,• ,, ,, ,, In its turn Table III demonstrates that in the Agro Romano, which has been the birthplace of this prophylaxis, owing to the initiative of our Society, the Red Cross Society and the rural doctors of the communes of Rome, while the number of immunised continually increased from 1900 onwards, the cases of primary fevers and of all malarial ailments treated by the Red Cross diminished, Further, the Rome hospitals 49] QUININE 419 admitted a much smaller number of cases in the years 1902- 1904, barely felt the usual quinquennial recrudescence of 1905, and admitted a minimum number of cases in 1906. TABLE III Quinine Prophylaxis in the Agro Romano 1900. 1 901. 1902. 1903. 1904. 1905- 1906. 1907. 1908. Prophylaxis in the Agro 79 1,176 3,8S3 17.506 29,693 38,429 42,726 34.927 33.808 Romano Primary infections treated 1,716 1,263 764 320 162 250 129 166 127 by the Red Cross Society (17) (13) (7) (2) (1-34) (1-52) (0-7) (i'44) (1-62) Malarial patients treated 3.751 2,366 2,581 1.547 1,406 839 576 371 437 by the Red Cross Society (,V) (26) (20) (") (10) (51) (3-4) (3-2) (2-0) Malarial patients admitted 6,t86 4.725 2,750 2,461 2,991 3.991^ 2.513 2,486 2.748 into the Rome hospitals 1 Year of periodic epidemic recrudescence The figures in parentheses are the percentages. The unanimous agreement of both the doctors and patients during these last years have convinced us more and more that this daily quinitie treatment diminishes notably the recurrence^ causes the perniciousness to disappear^ prevents cachexia, and very frequently the primary infections, and at least reitders the fevers milder and more readily curable by simply increasing the quinine for a few days to the therapeutic dose and then returning to the prophylactic dose. Hence it is that from the Agro Romano, where we made our first experiments, the daily use of quinine, which is as necessary as daily bread in the districts and months of malaria, has to-day extended to every malarious province of Italy, and it is extending more and more among the rural populations, the State employes living along the railways, and in the Army. Its further extension to those who need it is a question of time, that is, of education and organisation. Inasmuch as, in order to convince oneself of its value, it is sufficient to try it, he who has done so proclaims its value and goes on using it ; and thus by entering gradually into the habits of the country people, it acquires a wide field of beneficial action, especially among the 420 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. very numerous persons who, being without any kind of habita- tion, are compelled to live and work in insalubrious places. TABLE IV The Malaria in the Army Year. Number of men. Total number of cases. Recurrent cases. Primary cases. Observations. 1901 1902 1903 1904 1905 1 1906 1907 1908 189,848 199,253 206,468 210,637 204,745 211,718 202,320 216,679 49,94 36,52 24,14 19,21 23,00 18,94 12,46 8,04 17,85 12,71 13,90 12,66 7,76 5,19 6,28 6,49 9,05 6,30 4,50 2,85 Initiation of quinine prophylaxis Continuation of quinine prophylaxis ,, ,, ,, Quinine prophylaxis becomes extensive 1, ,, I, „ ,, ,, ^ Year of periodic epidemic recrudescence. It is certain that it is much better to be able to live in protected houses, and to make preventive use of quinine. It is precisely this mechanical and chemical or mixed prophylaxis which is to-day in use along our railways, and is obligatory for TABLE V Malaria along the Adriatic Railways Days of mean Mean of days Year of cases of duration of of illness lost Observations. malaria. cases of malaria. per person. 1888-1905 69-92 7-88 5-48 Without prophylaxis. 1902 44'93 6-99 3-12 Mechanical prophylaxis. 1903 30-32 6-25 1-89 ,, ,» 1904 33-10 7-53 2-48 ,, ), 1905 39'44 ' 7-64 3-01 ,, ,j 1906 27-65 7.09 3-39 Mixed prophylaxis. 1907 22-70 8-58 2-41 M ^, 1908 15-79 9-67 3-17 " ." 1 Years of periodic epidemic recrudescence, 49] RESULTS 421 the contractors of public works, and is gradually extending also among the rural administrations. TABLE VI Malaria among the Custom-house Officers Year. Number of Custom- House officers. Cases of fever verified. Percentage. Observations. I 900-02 1903 1,738 1,035 222 65-30 1273 Without prophylaxis. Mechanical prophylaxis. 1904 1905 1,714 1,721 209 187 12-19 10-86 " " Mechanical prophylaxis and beginning of 1906 1,614 1x8 7-31 quinine prophylaxis. Mechanical and chemical prophylaxis. 1907 1908 1,642 1,511 7Z 73 4-50 4-83 ,, ,, „ » Thus in Italy (where we have employed it from 1899), Algeria and Russia, it has been proved to be the most suitable method for guaranteeing health and the power of work to man even in the most desolate malarious regions. On consulting Tables V and VI it appears that the mean percentage of the cases of malaria along the Ex-Adriatic railways has diminished from 69-92 to 15-79, and the mean of the days of illness from 5-48 to 3-17, owing to the gradual introduction first of the mechanical and later of the mixed prophylaxis. Similarly, amongst the Custom-house officers the percentage of malaria has fallen from 65-30 to 4"83%. From all this one can conclude that by the triple alliance of the doctor, drainage and agriculture, it is possible to thwart the most formidable enemy of our country. It is necessary, however, for the doctor to proceed with the vanguard, systematically protecting man from the fevers and 422 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. enabling him, therefore, to live and work well even in the most unhealthy places, and thus break that old vicious circle by means of which man could not live on the land because it was malarious, and it could not have been rendered healthy because man was unable to live on it. III. — Legislation Concerning Malaria {a) Laws on State quinine. — These laws were drafted by us on a very solid experimental basis, and were introduced into our sanitary legislation as soon as their necessity and practicability were demonstrated. The following laws were promulgated as follows : — That of 23rd December 1900 (State quinine on sale to the public at a minimum price) ; that of 2nd November 1901 (the right of workers of every kind to have gratuitously the State quinine for the treatment of the fevers from the communal doctors at the expense of the respective employers) ; that of 22nd June 1902 (concession at a low price of the State quinine to the communes, charitable institutions, and to those who desire or have to distribute it gratuitously to the workers) ; that of 25th February 1903, Article 3 (the right of the poor to have quinine with other drugs given them gratuitously by the communes or by the charitable institutions) ; and finally, that of 19th May 1904 (the right of workers of every kind to have it gratuitously also for prophylaxis). These laws, demanded by new social duties, necessarily must have clashed with many private interests. Parliament had the notable merit of passing them with wonderful solicitude and agreement. But even when the first law was promulgated, we saw that making it was easy enough, but that the difficulty rested in applying it. We therefore had to watch that these laws, which were the synthesis of our experience, were properly applied. It is to be noted also that every fiscal question having been 49] LEGISLATION 423 set aside, the net profits of the great State administration (see Tables V and VII) went entirely to lessen the causes of malaria. Further, one can loudly proclaim that our legislation on State quinine has not only a scientific^ but also a vioral and social purpose, inasmuch as it recognises that malaria is a calamity connected with agricultural work ; and it wisely imposes upon the employers the duty of preventing the damage by giving the preventive quinine gratuitously to the workers, and of com- pensating them by giving the curative quinine also gratuitously ; and to the relatives of employees in public works it assures, besides, the payment of an indemnity in cases of death from the pernicious fevers. In our anti-malarial legislation the mechanical prophylaxis is obligatory solely for the State employees, including the railway servants who inhabit the places where malaria is most severe. To the private persons who wish to adopt it for their dependents the State accords premiums, which are deducted from the profits of the sale of the State quinine (see Table VII). (^) Laws regarding drainage. — Several times we have urged that our antiquated laws in drainage should be harmonised with the modern, scientific and practical views. We have succeeded already in introducing new principles of anti - malarial hygiene as a guide in the planning and execution of these works. Formerly it was believed that the only, or at least the best, mode of combating the fevers was sanitation by drainage, and consequently, in the supreme interests of public health, expense was no object. And, in fact. New Italy has spent or allotted upwards of 500,000 lire for this purpose, which works out at no less than 420 lire (^16, i6s. 8d.) for every hectare (2a. ir. 35p.) drained.^ To-day, however, for less cost, namely, with good quinine and healthy houses well defended from mosquitos, we can protect man from malaria. 1 Compare section 57.— R. Ross. 424 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. At the present day we know how to spend much better than in the past these many millions for drainage, which, if well employed, would, without doubt, render the land, at present barren and deserted, definitely prosperous and healthy. (c) Laws on agrarian sanitation. — Our first anti-malarial campaign in the valley of the Aniene has clearly shown that reoccupation of many large areas, left uncultivated owing to malaria, can now be easily accomplished ; and that the labourers can be kept healthy whilst at work by the application of modern prophylactic and curative measures. This experiment of ours has inspired several others to adopt the sanitation of the Agro Romano, and has enabled us to encourage and direct, with the sound advice of the medical hygienist, the great undertakings of colonisation arising in different parts of Italy, and destined to become economic successes. IV. — Contribution to the Organisation of the Campaign against Malaria We invite, above all, the Government to set the good example of applying the new methods of the anti-malarial prophylaxis to all the workers directly and indirectly depending on it. At present the majority of those living in the midst of malaria reap the benefit of the new laws which protect them from this disease. Also among the soldiers, sailors and carabineers the new prophylaxis, especially the chemical, has been extending from year to year. The benefit of the gratuitous quinine has been extending likewise among our emigrants who depart or return suffering from malaria. To many Italians also who live outside Italy in malarial regions it has been, and is, distributed by the Ministry of Foreign Affairs, through the consuls and benefit societies ; and to make it better known and appreciated, gifts of quinine 49] DEMONSTRATION CAMPS 425 have been offered and accepted by other States which, Hke Italy, are fighting against malaria. Directly the above-mentioned law of 19th May 1904 was promulgated, with admirable zeal and disinterestedness our members started what are called demonstration camps for quinine prophylaxis ; and we have become more and more convinced that nothing is better than these for overcoming the apathy and the prejudices of our people, who, living for ages in malarious places, if they have not proved it, will not believe it possible to protect themselves so easily, or to limit the damage which they are accustomed to suffer, and to believe comes from heaven. We have likewise made, and continue to make, a wide propaganda of the new theories and laws concerning malaria. Of manifestoes, handbills, bulletins, reports, extracts from the laws and regulations, our Society has distributed, or helped to distribute, about 2,000,000 copies in all. For this purpose we make use also of the National Associa- tion of Parish Doctors, the Ordini del sanitaria the Unione Magistrate Italiana, the Associazione dei .Professori di Cattedre AmbiUanti di Agricoltiira, the Lega NazionaU, and the various local Leagues of peasants and miners, the Camera di Lavoro, and the medical and lay Press. Public lectures and conversazioni also in dialect, repeated explanations and demonstrations, have not been neglected by our members, especially by the doctors and medical students. Finally, we are indebted to the local anti - malarial com- mittees which we are endeavouring to organise throughout the whole of Italy for an active propaganda by means of facts, publications, lectures, etc. V. — General Results The following figures enable us to believe and hope that our labours have not been in vain : — 426 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. TABLE VII State Quinine and Mortality from Malaria Consumption of State Mortality from QUIN INE. malaria. Net profits of administration of State quinine Financial Kilograms Solar Total in lire. year. sold. year. deaths. 1895 16,464 1896 14,017 1897 11,947 1898 11,378 1899 10,811 1900 15,865 1901 13,861 1902-3 2,242 1902 9,908 34,270 1903-4 7,234 1903 8,513 183,039 1904-5 14,071 1904 8,501 183,382 1905-6 18,712 1905 7,838 293,395 1906-7 20,723 1906 4,871 462,290 1907-8 24,351 1907 4,160 700,062 1908-9 23,635 1908 3,463 769,809 From the foregoing table it appears that the annual con- sumption of State quinine has progressively increased from 2,242 to about 23,000-24,000 kilograms, and that in these seven years the mortality from malaria has progressively diminished four-fifths. This intimate relation between the progressive increase of one and the progressive diminution of the other cannot honestly be ignored or denied. In fact, from 1887 to the end of 1895 upwards of 15,000 persons died annually from malaria. From 1896 to 1902 an attenuation began (see fig. i), but still 13,000 in media died annually, a mortality which was much augmented by that of the period of the recrudescence in 1900. On the contrary, owing to the introduction and the continuously increasing diffusion of the State quinine, the mortality from year to year has rapidly 49] kESULTS 45^ fallen to less than 4,000 victims, and the characteristic periodic recrudescences have no longer presented themselves. Now, who can deny to-day that quinine is not the sovereign remedy, and that only those die from malaria who do not take it in time and in sufficient quantity ? This was, and undoubtedly is, one of the principal causes of the very high mortality in the poorest regions of Italy, because they are the most malarious, and they are the most malarious because they are the poorest. Well, the lessened mortality from malaria in these regions (see fig. 2) proves to us that the sovereign remedy is used more and more among the poorest, and thus our legislation has begun to reach its high social aim, namely, to break that old vicious circle of poverty and malaria. If one considers, besides, that in the above period the importation of quinine into Italy by private means remained more or less the same (see fig. i, middle part), consequently the consumption of the " private " quinine has not diminished, while that of the State now equals it, and thus the total consumption of quinine is almost doubled (see fig. I, middle and lower parts). Regarding the efficacy of sanitation by drainage, which necessarily proceeds very slowly, there is little to hope. Also to the spontaneous diminution of the epidemy, one can only assign that value which, according to fig. 2, must be cal- culated on the basis of the preceding years. It is certain that, owing to the State quinine, which is now legally at the disposition of all, no person ought to die from malaria, and many fewer persons ought to contract it. We remember, however, that from the Maremma downwards, including the Mezsogiorno and the islands, very severe malaria has reigned undisputed for centuries ; and during the five years that our special legislation has been in vogue, and in spite of the efforts of the administrative powers, there are still many communes which do not furnish quinine in sufficient quantities, 428 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. not even for the treatment of the fevers ; and for prophylaxis very few workers receive it regularly and sufficiently. We are, however, at the dawn of the redemption of Italy from this scourge, and in these years of study and struggle^ our Society, one can say without boasting, has helped to indicate a relatively easy path to the desired goal, and has removed some of the many obstacles to success. Be this as it may, after having taken a notable part in the international researches into the cause and propagation of malaria ; after having studied its epidemy, improved the methods for combating it, and introduced new ones ; enriched the patrimony of the pathological knowledge; prepared new laws and endeavoured to improve the old ones ; defended the new theories and laws in order to make them more readily enter into the customs of the people, and enlarged the sphere of action for all Italy, we have the serene consciousness of having performed a useful duty towards our country. And we cannot but be delighted that outside Italy, and following our example, other attempts are being carried out, that anti- malarial campaigns are being initiated, and that other societies or leagues similar to ours have been formed in Algiers, Corsica, Greece and Russia, while scientists of all nations visit and appreciate our work. Besides, our anti-malarial legislation has not only been imitated by Austria, and by France for Corsica and Algiers, but has also been wholly adopted by Portugal, Greece, Bulgaria, Argentina. . . . All this enables us to foresee the formation of an international alliance against this universal epidemy, as has been formed already against other epidemics.^ 1 From 1893 to July 1909, we had at disposal for our work only about 90,000 lire. '^ On the unanimous proposal of the reporters Ross, Ruge, Galli-Valerio, Savas, and Celli, section vii. of the Fourteenth International Congress of Hygiene and Demography adopted by acclamation the following resolutions : — "The Hygienic Congress urges upon Governments of malarious countries a more active campaign against malaria by means of all the methods proposed by the reporters to the Congress on this subject, and particularly advises : "(i) The sale by Government of good and cheap quinine on the basis of the Italian law ; "(2) The appointment of special medical commissioners by the Governments of 49] CONCLUSIONS 429 VI. — Conclusions The campaign against malaria should be conducted, two measures acting concurrently : — (A) The one directed (a) to destroy, or at least (d) render inoffensive, the mosquitos which inoculate man with the parasite. (B) The other directed to destroy (a) with specific means, (d) with general means, these parasites in the human blood. (A — a) The extinction of mosquitos can be obtained by physical, chemical and biological means. Frequently, however, in the open country, the extinction is interfered with by the extent to which the reproduction of these insects is assured in Nature ; and while, therefore, it requires money and organisa- tion, it can have practical application only in limited districts, and assisted, where possible, by better and more extensive drainage. On the other hand, sanitation by drainage, while it also requires time and money, which fails in getting rid of all the surface water or in putting it in movement, does not succeed in removing the local conditions necessary to the life of the mosquitos, and even when it can succeed agriculture is frequently opposed to it, as in warm climates the surface water is utilised for the cultivation of rice, etc. Hence it is that sanitation by drainage by itself alone is not always efficacious in eradicating malaria from extensive territories. {A — U) It is relatively more easy in definite circumstances to render the mosquitos inoffensive, even in the most dangerous seasons and places, by keeping them away from persons and houses with both chemical and mechanical means {mechanical prophylaxis^. Be this as it may, when one desires to, and can adopt any means whatever directed against the mosquitos, one must never tropical malarious countries to direct anti-malarial measures and lo superintend the collection of the malaria statistics for those Governments." 430 THE CAMPAIGN AGAINST MALARIA IN ITALY [Sect. forget that in many parts of the world the Anopheles are always present, and nevertheless vialaria either has disappeared or has become, or tends to become, attenuated. {B — a) The destruction of the malarial parasites in the human blood, as is well known, can be obtained by means of the specific remedy, quinine. However, it is certain that this acts in inverse proportion to the stage of development of the parasites, and hence it is that the forms destined to assure the conservation and propagation of the species resist most, and that instead the sporozoites resist but slightly. Therefore, more easily and more readily than with the curative use, one obtains the specific internal disin- fection by means of the preventive use of quinine, and of its preparations soluble or not in water, administered in the most agreeable form, and preferably in average doses daily (40 centi- grams per die), or in days very near one another, in order to establish a perfect mithridatism. With this preventive treatment extended in the epidemic period to the greatest possible number of inhabitants of a malarious zone, and with in every season the most assiduous and prolonged quinine treatment of the malarial patients, one will see the primary infections immediately reducing themselves to the minimun, the recurrents reducing themselves much, and the pernicious cases and the cachexia disappearing, and thus from year to year the diminution of the epidemy among the respective populations will become more manifest even where the paludal and the local anophelic state remains. But to reach all this on a large scale it is indispensable that the State itself should manufacture the quinine preparations in order to sell them at the miiiimum price or to distribute them gratuitously, and always in the more agreeable form (comfits or chocolates, etc.). Hygienic education, with the continuous popular propaganda and anti-malarial sanitary organisation, will do the rest. Especially, then, with the quinine prophylaxis (eventually coupled with the mechanical) one can immediately, where and 49] CONCLUSIONS 431 when one desires it, keep man healthy even on very unhealthy land, and thus render possible, or at least more easy and prompt, the drainage and agricultural works necessary for the definite sanitation of even very vast districts. {B — b) Thus more promptly and without the mortality of earlier times we can arrive to-day at the agrarian sanitation^ and colonisation of malarious disti'icts, or establish those general means, namely, improving the alimentation, clothing, housing, education of man, which in every period of civilisation augments the organic resistance against the malarial parasites, and by this means more easily subdue malaria, even in the places where anophelism may not become extinct. Evidently neither of the above-mentioned series of measures for combating malaria exclude one another, but can mutually help one another, and ought to be adopted together in practice. By const. SAVAS Professor of Hygiene, University of Athens. Physician to H.M. the King of Greece. President of the Greek Anti-Malaria League I 50. Anti- Malaria Measures in Greece.^ — Greece is one of those countries which are very severely scourged by malaria. The information, collected by the Anti-Malaria League from all the mayors of the kingdom, and from a great number of physicians, proves that the average number of cases of the disease throughout the kingdom is 29%, or, in other words, out of a total population of 2,631,952 inhabitants, an average of 770,0CK) are affected by the disease every year. It happens, however, that in some years the number of cases is far heavier. Thus, for example, according to the statistics of the League, in the year 1905 more than half the inhabitants of the country were affected by malaria, and over 6,000 died of the disease. Of the 69 provinces of the kingdom, 19 show a number of cases equal to over 40% of the number of inhabitants, and of 445 communes only 29 are free from the disease, whilst the remainder are affected in a greater or smaller degree, especially in the cases of 59 communes with a percentage of 41 to 50%, 33 with 51 to 60%, 23 with 61 to 70%, 18 with 71 to 80%, and 2 with 81 to 90% ; or 135 communes (nearly one-third of the total number) with a percentage of over 40%. In years of epidemic it happens that in many communes the whole of the inhabitants are attacked by malaria. The cause of this great frequency of malaria is not only climatological, but is also due to the existence throughout the 1 Given in English by the author. — R. Ross. Sect. 50] PREVALENCE 433 country of numerous marshes and torrent beds. According to the information collected at my request by the Government, there are in Greece 639 marshes, each of an area above one stremma (1,000 square metres), which cover together from 84,657 to 87,903 hectares, or 846-879 square kilometres. As the whole kingdom of Greece covers an area of 60,000 square kilometres, these marshes occupy an extent varying between 1/68 and 1/72 of the whole surface of the kingdom. In addition to these marshes Greece is full of small marshes of under 1,000 square metres in extent, and of torrent beds which owe their existence to the widely - spread deforestation of the mountains, due to repeated forest fires during the long period of Turkish domina- tion, as well as during the Seven Years' War of Independence. These torrent beds are full of small pools which ^xo. par excellence nurseries of Anophelines, and consequently the chief cause of malaria in Greece. Malaria is at its height in Greece during the months of July, August and September, and commences to decline in October and November; but relapses continue throughout the winter (from December to March), and with the first heat of May the disease recommences its baleful activity. Malaria has from prehistoric times been the scourge of Greece. The classical description of the disease in the works of Hippocrates is well known. Information concerning malaria during the decline of ancient Greece is lacking, and it is only after the birth of modern Greece that descriptions of the spread of the disease again appear. Notwithstanding the fact that these descriptions are short and rare, it is to be gathered there- from that the disease was widely prevalent, especially at the commencement of the establishment of the new state, when the cultivation of the land had not made much progress. How- ever, after the reinstatement of law and order the population increased, villages and towns sprang up, the cultivation of the land spread more and more, and measures began to be taken with the object of draining many of the smaller and some of 2 E 434 ANTI-MALARIA MEASURES IN GREECE [Sect. the large marshes, and of regulating the beds of the torrents. By these measures, and at the same time by the application of more careful medical treatment and the wider use of quinine, malaria commenced to decline, and there is no doubt that the disease is now not only less common, but also less virulent than formerly. This relative amelioration is not, however, due to a systematic campaign against this disease, but to the above- mentioned causes which came about, so to say, automatically with the progress of civilisation. The methodic and systematic fighting of malaria only commenced when, in January 1905, I founded the Anti - Malarial League, which laid the first scientific and practical basis of the campaign against malaria, and met with an extremely favourable reception in all parts of the country. We propose hereinafter to give a concise description of the general measures which have been taken by the Government and by the League, as well as of those special sanitary operations which have been executed either by the Government or by the League or by different com- panies. The general measures include the popularisation of the ideas now prevalent regarding the manners in which malaria is caused and repressed, and the undertaking of the supply and sale of quinine by the Government. II Propagation of scientific knowledge concerning malaria. — Two years previous to the foundation of the League I issued a pamphlet. Instructions for Use in Combating Malaria, which was printed at the cost of the Government and distributed in thousands amongst all the physicians, engineers and mayors of the kingdom. On the establishment of the League, one of its first cares was the publication of a small pamphlet of sixteen pages containing short instructions regarding the 5o] PUBLIC INSTRUCTION 435 causes and prevention of malaria. Forty - five thousand of these pamphlets have been distributed amongst not only all the local authorities, but also many of the educated inhabitants, especially the schoolmasters, who have been instructed by the Ministry to explain the questions to their pupils. Last year, too, the Government printed 300,000 copies of a leaflet containing the decalogue of malaria. This leaflet was dis- tributed amongst the pupils of the schools, who, after the teachers had explained the instructions to them, were told to give them to their parents. At the same time of late years the daily press and the periodicals of the whole country have repeatedly published illustrated articles on the part of members of the League respecting the causes and prevention of malaria. In addition, some hundred of the leading physicians of the country were invited to Athens by the League. These gentlemen remained for two days in Athens, and consulted with the chief members of the League regarding the ways and means of combating malaria in Greece, and heard us explaining the latest scientific discoveries in this connection. On their return to their homes they acted as apostles of the anti-malaria movement, both amongst the other local medical men, the authorities and the people, visiting the chief malarious districts of the country, and both pointing out the absolute need of the preventive use of quinine, searching out the small pools which serve as nurseries of Anophelines, and applying, wherever possible, the various sanitary measures recommended in the work of Professor Ronald Ross, " Mosquito Brigades," which has been translated into Greek, and printed at Govern- ment expense and distributed gratis. The importance of combating malaria and the manner of so doing have repeatedly been explained to the engineers and heads of the Agricultural Schools, and especially to school- masters, whenever they have been assembled for educational purposes by the Government inspectors. The League has also approached the rich landowners, 436 ANTI-MALARIA MEASURES IN GREECE [Sect. furnishing them with printed instructions and pointing out the necessary sanitary measures in connection with the pools on their estates, and urging them to disseminate and apply general measures for the prevention of malaria. Conjointly with measures for the popularisation of the methods of combating malaria, the League has also attended to the collection of local information concerning the disease. Official Health Statistics are issued in Greece only in the case of the twelve chief towns of the kingdom, the population of which together amounts to 430,000, and they are confined to the number of deaths, whilst with regard to the frequency of disease and the mortality in the rest of the kingdom no official statistics are to be had. We have consequently deemed it right to apply for information to all the physicians of the country regarding the number of cases of malaria in the districts in which they practise. This information refers to the periods of the commencement, the height and the decline of the disease, to the ascertainment of the percentage of cases among the inhabitants, both absolute and relative to past years, and to certain other questions. We succeeded in collecting information of this kind relating to five years. Several of the physicians drew up at the same time lengthy reports concern- ing malaria in their provinces, and respecting the marshes in the district, with the measures by which the disease may be stamped out. At the request of the League the Government instructed all the local mayors to submit reports as to the number of cases in each commune, and the marshes existing therein. A complete epidemiological chart of the frequency of the malaria in Greece was thus drawn up. This plentiful material was published by the League in three bulky volumes, which also contain the results of a similar work undertaken in the island of Crete by our League. We are of the opinion that the collection of information of this kind is not merely valuable for the sake of the information itself, but also in that it incites physicians, mayors, engineers and people generally 5o] STATE QUININE 437 speaking to turn their attention to the spread of the disease and the detriment caused thereby, keeps them in continual intercourse with us and the question always on the tapis, undoubtedly resulting in measures being taken with a view to combat the disease. III The State Quinine. — In view of the splendid results achieved in Italy by the assumption by the Government of the provision and sale of quinine, the League has recommended a similar measure for Greece. We were also induced to take this view by the fact that considerable abuse took place in connection with the sale of quinine, which is sold in Greece not only by chemists but also by grocers. This quinine not only is some- times of bad quality, but is often adulterated with foreign substances, besides which it is far from rarely sold underweight to customers, whilst, to crown all, it is sold at a very high price, so as to render the frequent use of quinine by the poorer classes beyond their means. As a means of putting a stop to these abuses the League appealed to the Government and the Chamber, setting forth the harm done by malaria, and at the same time pointing out the means of remedying the evil, the foremost of which is considered to be the undertaking by the Government of the provision and sale of quinine. At the same time the League published the report, which was sent at our request by the Liverpool Tropical School, followed by a draft of a bill concerning quinine, together with an explanatory report, and finally a translation of the Italian laws regarding the combating of malaria. The Chamber refused to accept the principle of a monopoly of quinine proposed by the League, and on the 15th of December 1907 passed a bill similar to the Italian quinine law. According to this the Government acquires the right to order and to sell any of the salts of quinine recommended 438 ANTI-MALARIA MEASURES IN GREECE [Sect. by the Royal Sanitary Council. The order is given by the Minister of Finance on the basis of tenders (except in case the quinine is purchased from foreign State institutions), and fixed upon on each occasion by the Sanitary Council. The sale of quinine is made by the Chemical Laboratory attached to the Ministry of Finance, by the Public Treasuries, post and telegraph offices, educational functionaries, and by other authorities chosen by Royal Decree. The State sells quinine at cost price. It is sold retail to the public by chemists, grocers and other merchants, who derive a small profit therefrom. In the case of bisulphate of quinine the law demands that the retail price per gramme shall not exceed lo lepta (centimes). The price of other salts of quinine is fixed, as occasion arises, by Royal Decree. The importation and sale of quinine is not prohibited by this law, but such commercial quinine will be examined chemically at the custom houses, and will only be allowed to enter provided the quality is equal or superior to that of the State. Heavy penalties are prescribed for persons selling State quinine or the commercial article at prices above that fixed, adulterating or selling adulterated quinine, smuggling quinine into the kingdom or selling quinine underweight. The law also obliges such communes as are severely scourged by malaria to enter in their budgets an amount destined for the purchase of State quinine to be distributed gratis to the poor of the commune. After the publication of this law Greece requested the Italian Government to supply the requisite amount of quinine out of that prepared for the latter. The Italian Government was kind enough to consent, and the Greek Government now receives from Italy bisulphate and hydrochlorate of quinine in tablets of o-20 gramme, packed in boxes containing ten glass tubes, each of five tablets. The contents of the box, together with the price and the above-mentioned penalties, are printed on the outside label. The glass tubes are wrapped in paper containing full instructions for the use of the quinine, in which, so] STATE QUININE 439 in the case of adults, the dose prescribed is five tablets (i gramme) per diem for a week, followed by two tablets per diem during the following two months. The inhabitants of marshy districts are recommended as a preventive measure to take two tablets every day from the end of May to the beginning of November. The proper dose for children is also given in these instructions. Besides these tablets the Italian Government supplied phials for hypodermic injections, con- taining a solution of quinine made up' according to the prescription of Gaglio (phials of i gramme solution contain 0'40 hydrochlorate of quinine and 0'20 ethyl urethane). These injections have an alkaline reaction, and are painless, whilst they cause neither necrosis nor callosity, and are very easily absorbed. We were also supplied with chocolates of tannate of quinine, each double chocolate containing 0'85 gramme of tannate of quinine, or 0'30 gramme of pure anhydrous quinine (cioccolattini). This State quinine, which is sold, not only by chemists, but also by merchants of every kind, found its way with astonish- ing rapidity all over the kingdom. Ten thousand kilogrammes of quinine in tablets and 60,000 boxes of chocolates were sold in the first year after its introduction, which ended in September last. This is a large quantity if it be remembered that the average sale of quinine by merchants during the previous seven years amounted to 6,000 kilogrammes, and that besides this State quinine, a further amount of quinine derived from other sources was sold by retailers. The quantity thus sold is not yet known to us. The League has especially endeavoured, by means of various publications and by circulars addressed to physicians, to promote as much as possible the preventive use of quinine. We are, however, afraid that the achievement of this object will be difficult, as the majority of people will only take quinine after being attacked by malaria. We have now given a description of the general measures 440 ANTI-MALARIA MEASURES IN GREECE [Sect. employed against malaria, and shall next describe a few of the sanitary measures undertaken in certain districts of the country. IV Anti-malaria measures in the plain of Marathon. — After endeavouring by every means to popularise the knowledge of the mode of fighting malaria, the League considered it to be its duty to provide a practical example, by undertaking at least one definite work of the kind, with the object of con- vincing people of the efficacy of the measures recommended. It was also necessary for the conditions, which are indis- pensable for the achievement of such work in Greece, to be studied on the spot. With this object in view Marathon v/as chosen as the field of action. The plain of Marathon lies on the east coast of Attica, at a distance of 30 kilometres from Athens, and is 11 kilo- metres in length. It is famous in connection with the battle fought in 490 B.C. between the Greeks and Persians, and con- tains a few villages, amongst which is that of Marathon, the capital of the commune. The northern part of the plain is traversed by a torrent which runs close to the villages of Marathon and Bey, whilst at the north-east extremity of the plain there are extensive marshes. The following villages and hamlets are situated in this plain : — the village of Marathon with 1,200 inhabitants; that of Bey with 150 inhabitants, at a distance of i kilometre from Marathon ; that of Lower SouH with 160 inhabitants, at a distance of 5 kilometres; besides these, eight hamlets are scattered over the plain, with 173 inhabitants in all. The total population of the plain thus amounts to some 1,680 souls, most of whom are engaged in agriculture and vine-growing, and a few in poultry and stock farming, and thus spend the greater part of their time in the so] MARATHON 441 plain, returning to their houses to spend the night, with a very few exceptions. The inhabitants of the plain of Marathon are extremely subject to malaria. An examination, conducted in October 1906, of the pupils of the local school, show that 100% suffered from an enlarged spleen. In May 1907, 1,216 persons were examined, and 1,031, or 8479^, suffered from fever during the previous summer. These observations coincide with the reports of the Marathon doctors, one of whom put the number of cases of malaria in 1906 at 90%, and the other at 80%. Owing to the great prevalence of malaria the inhabitants, at the commencement of our work of sanitation, were pale and sallow, and their skin dried up, whilst they appeared exhausted and incapable of work owing to frequent attacks of fever. In many cases the spleen was enormous, and reached the pubic symphysis. According to the evidence of the local physicians the mortality was very great, not merely among the children, but also among adults, whilst death occurred not only from pernicious fevers, but to a great extent from pneumonia, which is one of the commonest diseases of the place. Mortality was so common amongst adults that three-fifths of the inhabitants had been married a second time, whilst persons of over sixty years of age were rarely found, whereas longevity is common in the healthy villages of Greece. Throughout the whole plain of Marathon stagnant waters were found in the bed of the torrent, which flows near the two villages, in the two large marshes, and in small pools between the two marshes. In this stagnant water we invariably found larvae of Anopheline mosquitos. Both in the bed of the torrent and the houses of the villages of Marathon and Bey the Anopheles superpictus was especially noticeable, whilst in the marsh of Lower Souli a large number of larvae of Anopheles claviger'^ was found, together with a small number of bifurcatus, and ^ A. rnaculipennis Meig. 442 ANTI-MALARIA MEASURES IN GREECE [Sect. in the houses of this village a large number of Anopheles claviger was remarked. In the other marsh, which is situated at some distance from the villages, repeated examination brought to light a very small number of the larvae of Anopheles supeipictus and claviger. In all the other distant pools through- out the plain only Anopheles claviger was discovered, but in large quantities. The chief source of the malaria in the villages of Marathon and Bey was therefore concluded to be the adjacent torrent, and that of the village of Lower Souli, the neighbouring marsh. The inhabitants of the hamlets in the plain were, of course, infected by mosquitos from the other pools. The first larvae of Anopheles were remarked, in the case of the year 1907, at the end of April, and in 1909 at the commencement of May. The work of sanitation was carried on at Marathon during three successive years, and only during the summer and the commencement of the autumn. In the year 1907 we com- menced on 1st May and continued until November, whilst in 1908 and 1909 we carried on operations from ist June to 20th October. The staff engaged in this work was composed in 1907 of one physician and one medical student as assistant, both despatched from Athens for the purpose, whilst in 1908 we employed one physician and two medical students, and in 1909 only one physician without any assistant. The physician and his assistants were installed in a small house in the village of Marathon, where they set up a microscopical laboratory, and a pharmacy which included a certain number of absolutely indispensable drugs besides quinine. Patients received advice and treatment gratis. Only sufferers from malarial diseases were admitted, all other applicants being referred to the village physicians. The work was performed in the following manner : — In the first place, the names of the inhabitants of the villages were entered in a special register, together with their age, and any enlargement of the spleen stated, as well as, in many cases, 5o] MARATHON 443 the result of the microscopical examination of their blood. The inhabitants were next divided into as many sections as there were physicians of the League, and each of these doctors took care of the inhabitants who fell in his section. Patients complaining of attacks of malaria were examined as regards both their spleens and blood, and, if proved to be so suffering, were subjected to the proper treatment as described below. As a means of facilitating our work several lectures were given by our physicians to the people, and by the teachers to their pupils, explaining the plan of the League to render healthy the plain of Marathon, and other related details. At the commencement of our work the peasants showed some dis- trust. Later on, however, when they were convinced of our good intentions, they willingly agreed to undergo the treat- ment proposed by us, and showed considerable gratitude at being liberated from the terrible scourge which had from time immemorial tormented their country. We proceeded in the work of sanitation, firstly by destroying the larvae in the torrent bed, and secondly, by administering quinine, which was purposely distributed in a different manner in each of the three years. In order to prevent the development of Anophelines in the torrent bed the water thereof was drawn off in a narrow channel so as to produce a more rapid flow, whilst all pools were treated every ten days with petroleum, which generally is provided by the Government, mixed with tar, at a minimum price for the purpose of destroying locusts. In this part of our work we received valuable aid from the teacher of the village, who indefatigably attended to the carry- ing out of this measure with the help of his young pupils. The quinine was given therapeutically throughout the three years, and preventively only during the first and the second year. Sulphate and hydrochlorate of quinine were given thera- peutically to patients of ten years of age at the rate of i to I'S grammes per diem for eight successive days,jn the case of those who had suffered one or more attacks, or in whose blood 444 ANTI-MALARIA MEASURES IN GREECE [Sect. parasites were detected. Children under ten were treated therapeutically with a quantity of quinine proportionate to their age, z>., from eight to ten years of age, o*8o gramme, from six to eight, 0'6o, and from four to six, 040 gramme. Children under four were given tannate of quinine either in powder or in chocolate ; during the first year the sulphate or hydrochlorate of quinine was given in wafers, and during the two remaining years in the shape of tablets. In addition to the therapeutic employment of quinine during the first year we also used the drug preventively. With this object we gave out quinine to all the inhabitants, irrespective of whether they suffered from fever or not, according to the method of Koch as modified by the Italians; i.e., i gramme of quinine per diem for two successive days in the week to those above the age of ten, and a proportionate quantity to the children, i.e., 075 gramme in the case of those aged from eight to ten, 0*50 in the case of those aged six to eight, and 0'25 gramme to those of four to six. In the case of infants below the age of four they were given euquinine or chocolate with tannate of quinine. The quinine was given out to the pupils every Thursday and Friday at the school, and every Saturday and Sunday to the other peasants. It must, how- ever, be confessed that this preventive method did not prove to be practically applicable, as the peasants, healthy men in other respects, who worked on week-days in the fields, found such large doses very annoying, owing to the con- sequent singing in the ears and other discomfort, especially on Sundays, the only day in the week on which they can rest and amuse themselves. These large doses also hindered them in their work during the week. Several of the pupils suffered so much from giddiness and drowsiness after taking quinine that they were unable to attend to their lessons. Out of the 1,680 inhabitants only 1,544 went through this preventive treatment in 1,252 cases. Unfortunately, all would not continue a regular course, but the figures given hereunder so] RESULTS 445 show the results of the preventive treatment according- to the length of application. Of Gj persons who took quinine during 21-24 weeks none were attacked by malarial fevers. Of 145 persons who took quinine during 16-20 weeks 30 were attacked, or 20'6%. Of 220 persons who took quinine during 11-16 weeks 103 were attacked, or 48*6^. Of 820 persons who took quinine irregularly during i-io weeks 464 were attacked, or 56'5%. It follows, therefore, that out of 1,252 persons taking quinine only 597, or 47'6%, suffered from malaria. It must here be added that in the surrounding villages, which were not included in our sphere of action, malaria was prevalent to a very great extent, so that we may consequently consider that, without our inter- vention, we should have had the usual number of cases of malaria at Marathon too, or from 80 to 90%, if not more. An investigation carried out in May 1907 showed 57^ of enlarged spleen out of 125 pupils of either sex, and of 39/^ out of 752 adult inhabitants. After the conclusion of the sanitary work, or at the end of October, an examination of 1 10 pupils showed only 35^ with enlarged spleens, and of 509 adults, 25/^. The proportion of cases of enlarged spleen was therefore less at the end of the summer season, thanks to the sanitary measures, without which, it will be easily understood, it would certainly have been greater. In the whole district under our control one person died of pernicious fever and three persons of blackwater fever. All three were treated by the local physicians. In 1905, according to information furnished by the doctors, seven persons died of malarial diseases. During the summer of 1908 we changed the manner of giving out quinine, and adopted the Italian preventive system ; ix.y between ist June and 20th October we gave out every day two tablets (0"40 gramme) in the case of persons above the age of ten, and one only (0*20 gramme) in that of children below 446 ANTI-MALARIA MEASURES IN GREECE [Sect. the age of ten down to the age when swallowing the tablets was not possible. In the case of infants unable to swallow the tablets we gave chocolate with tannate of quinine, as furnished by the Italian Government. As, however, we only had a small stock of these, we confined their use to the cases of twenty-six infants, and for a short period only. It may therefore be said that the preventive method was not applied in the case of infants of under three years. Out of 1,306 inhabitants of the villages of Marathon and Bey only fifty-six (4'28%) suffered from malaria during the whole summer. If, however, we deduct from these two pregnant women, who took no quinine from fear of causing a miscarriage, twenty-one children, who only took quinine irregularly owing to the lack of " cioccolattini," one who came infected from Athens, one who suffered from urticaria owing to the use of quinine, and one of the local doctors, who refused to undergo the preventive treatment, together with four persons who were infected at the commencement of our work, there remain only twenty-six cases of malaria, and the percentage is reduced to i'99%. It is to be remarked that in the surrounding villages the malaria was very severe. There died only one child of those who regularly took quinine, of a disease which the local doctor who was attending it described as pernicious fever, without, however, parasites being discovered in either of two examinations which were made of the blood. With regard to the examination of the spleen of the pupils this showed an enlarged spleen in 3 1 to 43% at the beginning of June, and 7'40% at the end of October. This method of giving out quinine was welcomed by the inhabitants, who both remarked the beneficent results and experienced no ill-effects, and showed great willingness in adopting it. During the third and last year of our work at Marathon (the summer of 1909) we neither took measures against the so] COST 447 larvae of the Anopheles^ neither did we give out quinine for preventive treatment, but confined ourselves to the therapeutic employment of the drug, according to the Austrian treatment adopted in Dalmatia. We therefore gave out quinine only to those who had suffered distinct attacks of malaria, and whose blood contained the parasite. The quinine was given out in the following way : — one gramme of State quinine every day for a week, followed by 0*40 gramme every day for two months, to patients of the age often and above. In the case of children from eight to ten years of age, o*8o gramme every day ; from six to eight, 0'6o gramme ; from four to six, 0*40 gramme in each case for a week, followed by 0*20 gramme every day for two months. In the case of children below the age of four years State chocolate with tannate of quinine was given. The result of this treatment was, that out of the 1,312 inhabitants only 176, or I3"4i%, suffered from malarial attacks, attested by microscopic examination of the blood. The fifteen infants which were treated therapeutically with cioccolattini only suffered a single attack in each case. Examination of the spleen after the termination of the sanitary work showed enlargement in I4'48^, while at the commencement of January it amounted to 2"67^. During the whole summer two children died of malignant fever, according to the diagnosis of the local doctors, which, however, was conducted without a microscopical examination of the blood. The quantity of quinine expended in these three sanitary campaigns at Marathon amounted to an average of I5"6 grammes for each inhabitant in 1907, 32'3 grammes in 1908, and 5 '6 grammes in 1909. The total expense ^ during 1907 reached Drachmas ( = Francs) 5,715 — or an average of Drs. 370 for each patient under- going the preventive treatment. In 1908 the amount expended reached Drs. 6,736 — or Drs. 5"i5 per head; whilst in the year ^ Including pay of the medical men. 448 ANTI-MALARIA MEASURES IN GREECE [Sect. 1909 Drs. 2,226 were spent, or an equivalent of Drs. 1*69 for each of the inhabitants. It consequently appears that the Italian system is more expensive than the other methods. We gather the following conclusions from our three years' work at Marathon. The Koch preventive method seems likely to meet with considerable difficulties in our country ; that of Celli, in combination with the destruction of the larvae of the Anopheles^ gives excellent results, and is an ideal method of combatting malaria. Nevertheless, that method is not easily applicable in every part of the country, as it requires continual superintendence of an expert in order to oblige the inhabitants to continue taking quinine every day during the whole summer, and for a series of years, until a permanent cure is effected. It can, however, be employed with excellent results in the army and the navy, in the prisons, railway and other companies, in mines, in villages forming private property, and, generally speak- ing, everywhere where there is a single authority, with the power of enforcing that method willy-nilly upon those under it. Throughout the rest of the country, however, which is in- habited by independent people, who regulate at will their life and diet, it is difficult for the Italian method to be introduced. Those, however, who have suffered from fever and have taken quinine at irregular intervals without being able to throw off the disease, will be gladly surprised to see the favourable results which are produced by the methodical use of quinine such as applied by us at Marathon during the third year of our work : and so recovering their shaken faith in the drug, they will most probably end by adopting the Italian preventive method. V Sanitary work at Laurium. — A work of a similar nature was undertaken during the summer of 1909 by the Greek Laurium Mines Company, the employees of which suffer ex- cessively every summer and autumn from malaria. This work so] LAURIUM AND ATHENS 449 was confined to the preventive treatment with quinine, as in excavating the mines numerous large hollows are formed in the soil, and these being filled with water and serving as nurseries of Anopheles, it becomes impossible, owing to their large extent, to destroy the larvae. Every miner was provided with two tablets (o'40 gramme) of State quinine per diem from the commencement of May to the end of October. The result of this treatment was that out of 480 miners only 28 (5"8%) were attacked by malaria, whereas in each of the foregoing years, 1 906-1 908, from 30 to 40% suffered from fevers. That this good result is due to the use of quinine may be seen from the fact that, of 75 miners who failed to take quinine regularly, 34 were attacked by malaria. VI Sanitary work in Athens. — In the city of Athens the two suburbs which suffer most severely from malaria are those of Pankrati and Batraconesi, where, before the year 1900 the percentage of cases fluctuated between 25 and 30%, and from 1901-1906 it reached 49%, and even as high as 92%, as will be seen in the following table. This excessive prevalence of malaria was due to the small pools in the bed of the river Ilissos, which were found to be full of larvae of Anopheles superpictus. As a means of coping with this situation, the League re- quested the Government to undertake certain sanitary works in the bed of the Ilissos, and, as a matter of fact, in the summer of 1906 the Government carried out the work in question, which consisted chiefly in levelling the inequalities in the river-bed, and in drawing off the water by means of a narrow channel where the development of Anopheles was hindered by the rapid flow of the water. In 1906 the work was but slowly conducted, and consequently the influence upon malaria was slight, as shown by the table given below. During 2 F 45° ANTI-MALARIA MEASURES IN GREECE [Sect. 50 the second year, 1907, the percentage of cases of malaria in the Pankrati fell to 2 or 3%, and in the Batraconesi, where the work was carried out later in the season, it fluctuated between 25 and 30%. In the summer of 1908 the work of sanitation commenced at the proper time in the Ilissos, and as a result the number of cases of malaria fell to 1%. In 1909 the work was also carried out in due time and the cases fell to o-66%. It is to be remarked that no preventive use of quinine was resorted to, and so the satisfactory results are entirely due to the work carried out in the bed of the Ilissos. Comparative Table of the Cases of Malaria among the Children in the Pankrati and Batraconesi Suburbs Before the adoption of the sanitary measures {Pezopoulos and Cardamatis) Percentage In the summer of 1901 out of 280 children 260 were attacked . 92*85 „ „ „ „ 1902 „ „ 200 „ 160 „ „ . 8o-oo „ 1903 » » 235 „ 192 „ „ . 8170 „ 1904 „ „ 180 „ 89 „ „ . 49-09 „ 1905 „ „ 200 „ 185 „ „ . 92-50 ?) It During the five years 1,095 886 80-90 After the adoption of the sanitary measures {Cardatnatis) In the summer of 1906 out of 301 children 177 were attacked, „ „ „ )5 1907 ?) „ 345 ') 73 )' J5 „ „ „ » 1908 „ „ 300 „ 8 „ „ „ ,, » » 1909 » ,> 300 „ 2 „ „ Percentage 58-80 21-15 2-66 0-66 BANKS OF THE ILISSOS, ATHENS, UNTRAINED. BY DR CARUAMATIS. KANKS OF THE II.LSSOS, TRAINED. KV DR CARDA.MATIS. [ To face page 450, By Dr Professor CLAUS SCHILLING Late Medical Officer of the German Colonial Office, at Togo, West Africa Abteilungsleiter im Institute fur Infektionskrankheiten, Berlin. 51. The Prevention of Malaria in German Possessions.— When Germany began colonising, she found herself face to face with the problem of developing the raw material of the territories she had occupied, making it accessible to trade and civilisation. The development arrived at in these twenty-six years has not been such as to render the colonies able to dispense with the support of the mother-country. The empire has also to make it her care to improve the health conditions of those under her protection. But the science of Hygiene is able to obtain only by slow degrees the place due to it in the work of colonisation, conducted on economical principles. It requires the greatest energy on the part of the doctors to obtain what is necessary from the very slender means at the disposal of the authorities. Of the tropical colonies of Germany — viz. : East Africa, Kamerun, Togo, and the north of South-west Africa, New Guinea, the Carolines, and Samoa in the South Seas — only the two last-named are free from malaria ; in all the others it is, next to small-pox, the most widespread of diseases. The following summary gives information as to the frequency of malaria amongst the natives. 451 452 PREVENTION IN GERMAN POSSESSIONS [Sect. TABLE I. Age IN Years. Up to Up to Up to Up to Up to Up to Up to I. 2. 5- 10. 15- 20. SO. New Guinea : Bogadjim (Koch) . 80 1 41 '6 Bongo (Koch) 100 46-1 23-5 Gazelle peninsula (Demp- 1 wolff) .... 19 32 22 I 8 12 East Africa : Tanga (Panse) 48 88 79 45 i5'3 Dar - es - Salaam : Indians (OUwig) .... 29-6 32-5 29-3 i6-i Dar - es - Salaam : Negroes (Ollwig) .... 390 40-8 20'I 7-6 Kamerun : Duala (Plehn) . 94 92 85 5° Togo : Anecho (Schilling) . 88-8 71-5 74-0 1 68-0 16 -6 1 The percentage of those examined found to contain parasites. It is evident from this table, amongst other things, that the development of immunity in malarial districts is by no means of equal extent. It is evidently connected with the frequency of infection by stings from infected Anophelines. In spots where no decided alternation between the rainy and the dry season takes place {e.g., New Guinea) there is also constant opportunity for fresh infection and for re-infection. This point is to be taken into consideration in a plan of malaria prophy- laxis. The table is so far of interest as showing that active immunity in malaria by no means sets in with certainty {e.g., in Duala, only in 50% of the natives who had been exposed at least for ten years to the infection without a break). The chances, therefore, of acquiring active immunity fluctuate between 13:1 and i:i during a sojourn of from ten to fifteen years in dangerous malarial districts. The practical unimport- ance of the objection, that malaria prophylaxis interrupts this active immunity, may be considered as proved by this com- putation, SI MALARIA INDEX IN TANGA 453 Diagrarils 1 and 2 show a comparison of the value of micro- scopic examination of the blood and palpation of the spleen. They show that in Tanga, East Africa, the two curves of Diagram i. Malaria index in Tanga (Panse). Number of those examined, — — Parasites found. - - - - Spleen enlarged. the spleen rate and the positive results of blood examination correspond approximately, so that the latter could replace the former. But in Anecho it was only in children between two 454 PREVENTION IN GERMAN POSSESSIONS [Sect. and five years' old, that palpation of the spleen produced higher results than examination of the blood ; whereas in later years the spleen tumour quickly subsides, even where malarial infection exists. So that if the spleen tumour is to be made use of as an indicator of the malarial index of some special locality, the relation between spleen tumour and condi- 50 years. Malaria index in Anecho (Schilling). Number of those examined. Parasites found. Spleen enlarged. tion of the blood must be first of all ascertained by comparative examination, which must then be taken into consideration in the computation. To introduce individual therapeutics only on the basis of spleen palpation is not feasible, according to Patise's and my own examinations. Pause, for instance, found that in a positive condition of the blood the spleen tumour was absent, 5i] PRELIMINARY MEASUREMENT 455 7 children under 2 years, in 14% of those examined. 52 „ „ 5 „ 28 31 » .. 10 » 51 5 .. ,,15 n 80 Without examination of the blood, all these persons would have been deprived of quinine therapeutics. As regards the frequency of differetit forms of malaria, the following table for Dar-es-Salaam, 1908- 1909, gives information. TABLE II. There were found " Rings." 1 Tertians. Quartans. Crescents. In April- June 1908 . 1,039 28 122 121 In July-Sept. „ . . 1,184 50 115 173 In Oct.-Dec. „ . . 567 13 87 132 In Jan. -March 1909 • 594 40 138 165 In reference to mortality amongst children^ in consequence of malaria, Steuber states that before the introduction of pro- phylaxis in places on the coast, of the total number of deaths amongst children under four years, 44% in Dar-es-Salaam, 57% in Lindi, and 25% in the higher situated Tabora, were due to malaria. On the introduction of malaria prophylaxis into German colonies, the principle was laid down that it should always be preceded by a statement of the so-called endemic index ; that is to say, by ascertaining what percentage of the inhabitants of one place were infected by malaria at the time. The researches, whenever possible, were extended over various quarters of the town, in order to discover what parts were seriously threatened. In doing this, it turned out, moreover, that not all parts of the population were equally attacked by the disease, or were equally predisposed to it. (See Tables — Indians and Negroes in Dar-es-Salaam.) Further, it is essential that the examinations of the population be repeated at different seasons of the year. ^ By this are meant the ring forms of all three kinds of parasites, which could not be distinguished one from the other, and were not accompanied by the characteristic forms of division, or by gametes. 456 PREVENTION IN GERMAN POSSESSIONS [Sect. It is specially important with children of a year old, whether they have already gone through a rainy, i.e., a malarial period, or not. In the German colonies the first place is given to fighting malaria with quinine. In Stephansort, in New Guinea, Robert Koch for the first time adduced positive proof that in a perfect hot-bed of malaria it is possible to reduce this disease to a minimum, nay, make it disappear altogether, and this by the exclusive aid of quinine. Thus, on the island of Brione (Istria), Frosch, under Koch's superintendence, carried on a struggle against malaria in the years 1901 - 1902. At the beginning of the campaign in December 1900 there were 63 = 48% of the inhabitants infected with malaria. In the first nine months of the struggle, 22 cases in all occurred amongst labourers, drawn from regions free from fever ; from that time, in the next fourteen months, there were no fresh cases of infection at all, and only nine relapses ! ^ The fight against malaria is therefore twofold, consisting, (i) in the treatment of the sick, and (2) in the destruction of the parasites that have already made their way into the human organism — the "prophylaxis" proper. If the solution of these problems can be brought about, malaria must disappear. Individual prophylaxis can be practised according to an empirical scheme which has proved useful ; thus I have found that in the worst fever regions, on marches and expeditions, the dose of one gramme of quinine every fifth and sixth day is sufficient to guard against fever. Other authors recommend other methods ; as to the value of the separate schemes, the last word has not been said. But it is certain that individual quinine prophylaxis is able to prevent the outbreak of malaria infection, and, on the other hand, that the use of the drug may be left to the patient himself, under the control of the doctor. It is a different thing with the general part of the fight, with ^ This work does not belong to my present subject. I mention it here because it prepared for and completed the experiment of Stephansort. 5i] STEPHANSORT 457 the treatment of the persons infected : the latter can only be detected by the doctor or by a staff specially trained for the purpose, and their treatment must be individualised. The fight against malaria by this method can therefore only be begun and carried out under medical supervision. In the year 1900 Koch found about 734 persons in Stephansort, New Guinea, 157 of whom harboured malaria parasites ; 240 Chinese with 63 infected, 209 Malayans with 53 infected, and 264 Milanesians with 157 infected were examined. In the beginning the infected persons were treated with one gramme of quinine, until the parasites had disappeared from the blood ; from that date, for two months, every eighth and ninth day one gramme of quinine each was given. The result was a striking one, as appears from the number of patients admitted to the hospital. January . February March . April May June 24 admitted on account of malaria. 13 2 3 I Koch emphasises that the months of January to May are notorious as being specially dangerous, and that also in the year 1900 the rainy season lasted right on into June. Never- theless they succeeded in reducing malaria morbidity to a very slight amount, more especially as the cases of illness from it which had occurred from April to June were only relapses and not fresh cases of infection. And this success was obtained through the rational usage of quinine. It does not make any difference to the importance of this proof, even if one admits that the conditions were rather favourable in Stephansort — being here the case of plantation labourers living far from their own homes and under complete control — and that the success was lost with the time as the control slackened. The proof I mentioned was given, and nothing more has been intended. 458 PREVENTION IN GERMAN POSSESSIONS [Sect. It was only natural that Koch's experiments in Stephansort were copied in the other German colonies and adapted to local conditions. In German South-west Africa, the northern tropical districts of which suffer badly from malaria, Vagedes has undertaken to make practical use of Koch's ideas ; because for those districts, where numerous small collections of water such as those which occur in footprints of cattle, horses and wild animals, serve as breeding-places for Anophelines, and where mosquito preven- tion by means of wire-gauze, screening the native huts, cannot be spoken of, quinine treatment and prophylaxis are the only possible methods. In Franzfontein and the surrounding settle- ments, Vagedes found 30% to 75^ of the inhabitants infected with malaria. Every eighth and ninth day, ninth and tenth day, and every ninth, tenth and eleventh day respectively the infected adults were given one gramme at a time ; the children correspondingly less. Certainly, it was not un- important that quinine was given whenever possible in the form of hydrochloride in solution, and only in rare cases in wafers. In children, who easily rejected the solution, sub- cutaneous administration was adopted. This treatment was continued from two to three months. The results were very satisfactory. In Franzfontein, with its fixed and therefore regularly-treated population, the percentage of infected persons decreased from 79^ to 9^ ; out of 165 persons only 7 new infections and 4 recidives occurred. In Tumamas ^7% ^^id in Canas 30^ of infected persons were found at the beginning of the campaign. In the course of the following rainy season the settlements were free from malaria. Koch's ideas of anti - malarial measures have been also applied to Dar-es-Salaam. Dar-es-Salaam, at the time when Ollwig began his activities as director of the anti-malarial brigade, was a town of 12,000 to 15,000 inhabitants. The population consisted of Europeans (officials and officers stationed there for periods of one and 5l] DAR-ES-SALAAM 459 a half years, and merchants with engagements of longer periods), Indians, Goanese, Arabs and Negroes. The Europeans live partly on the peninsula facing north - east, and partly in the districts near the harbour. The Indians live in the adjacent blocks of houses situated more inland, and the native town is grouped around these. The larger portion of the town is surrounded by a depression where water remains for long periods through the dry season, and which renders the cultivation of rice possible. Along the shore wells spring up and form ditches and ponds. The town is therefore surrounded by a ring of water - collections which offer most favourable breeding-places to Anophelines. The abolition of these water-collections, the land-level being but little higher than the sea-level at high tide, would have involved very great technical difficulty, and consequently would have been most expensive. Other measures, such as oiling of single water-collections with petrol, did not — as was to be expected — affect the number of Anophelines infecting the houses. Ollwig first tried to establish the malaria index based on microscopic examination of the blood. Palpation of the spleen does not appear to have been practised. Ollwig accepts as a sign of malarial infections also the basophile granulation of the red blood corpuscles, if he could find no other cause (anaemia due to ankylostomiasis) for its appearance.^ For this purpose the town was divided into twenty blocks, and the inhabitants of these quarters were regularly examined without exceptions. Owing to the fixedness of the Indian and Goanese population, this examination could be fairly well carried out; in the Negro quarters, however, this was an extremely difficult task, as they continually change their domiciles from village to town and vice versa. Therefore in the following table the Negroes mentioned have undergone a single examination. 1 Due to other causes. — R. Ross. 46o PREVENTION IN GERMAN POSSESSIONS [Sect. From the table, in the column devoted to " first examina- tions," the malaria index is given fairly accurately, and shows that spontaneous immunisation in adults does not occur to any appreciable extent, and that therefore the treatment with quinine was justified also in the case of adults. TABLE III Children Children Children A^..U, First up to I year from I to 5 years over 5 years examined infected examined infected examined infected examined infected Indians examinations 27 8=29% 62 20 = 32% l8l 53 = 29% 650 105 = 16% and 1 Goanese Later examinations 75 2=27% 211 28 = 13% 415 23=5-5% 1,702 82=4'8% First examinations 26 9 = 34% 94 45 = 47% 288 74=26% 3.338 238=7-6% Negroes < Later exammations 42 8 = 19% 169 55=33% 627 99 = 15% " 1 The " first examinations " were made in August, September and November 1901, and January to March 1902 ; the "later examinations" from March 1902 to March 1903 — therefore after i"5 year's campaign at most. On the contrary, compared to Dar-es-Salaam the malaria index of some villages further inland appeared rather high : of children up to one year of age, 77*5% were infected ; of children up to five years of age, 57'3% ; of children above five years of age, 3 1 '9%; of adults, 217%. The anti-malarial measures were limited to quinine treat- ment of all persons who were found infected, as well as those, naturally, who put themselves at the disposal of the doctor. OUwig gave adults, at first on three consecutive days and later on every fifth and sixth day, one gramme quinine muriate ; after nine days' interval again three quinine days, and so on for two and a half to three months. Children were given a corresponding quantity of the drug in solution and a lump of 5i] DAR-ES-SALAAM 461 sugar afterwards ; adults, mostly in form of tablets. One can see it was a question of a purely therapeutic anti-measure, and not one of prophylaxis. Many of the details in Ollwig's interesting report (one and three-quarter years after the anti-work) cannot be referred to here, and only the "facit" is drawn as resulting from Table III. In one school (not referred to in the table) they were successful in reducing the number of infected persons from 21*0% (August 1901) to 3-5% (March 1903). Amongst the Indian population from July 1901 to June 1902, 410 cases, from July 1902 to May 1903, 210 cases of malaria, came to the knowledge of the medical officer. It may be noted here that the Indians gradually gained confidence with the medical officer ; and so in the first half of the period more infections remained unobserved than in the second half. In the Negro children, on the contrary, the results, though noticeable, were not so favourable (decrease from 34% to 19%). This can easily be understood because the Negro population is subject to constant fluctuations, and it is only seldom possible to continue the after-treatment long enough. Statistics of adult Negroes have been omitted from Ollwig's report ; the 7'^% of infected adults are of little importance in proportion to the 26-40% of the children. Ollwig proves in his report that the reduction in the malarial morbidity can have been caused neither through climatic factors nor through other possibly adopted measures. The periods of rain and the numbers of Anophelines were not less during the time of the observation than previously, and the work of assainment and petrolisation of the water-collections have been practised so irregularly and to such a slight degree that these measures cannot have had great influence upon the large differ- ences in the numerical value. Ollwig rightly emphasises that only a very small staff — one medical officer, one nurse, one European and five coloured assistants — has been necessary for this successful struggle. 462 PREVENTION IN GERMAN POSSESSIONS [Sect. It is to be regretted that Oil wig did not calculate the total cost, as this calculation would have shown how cheap this method of anti- malarial measures is in comparison to other methods. Up to 1908 the number of native assistants never exceeded half a dozen, besides three to four Europeans, by whom 15,627 natives were examined microscopically and treated with quinine. Subsequently anti-malarial work was continued in Dar-es- Salaam. For this work only one medical officer was available, whose time was greatly occupied with quarantine and other administrative work ; the staff of assistants was not much aug- mented either. Ross-Ruge's method of blood examination (the so-called thick film method) was adopted, and this method made it possible to discover even quite isolated parasites. The consequence was a remarkable increase in the positive cases since October 1907, and for this reason the numerical values given in Table V, before and after that date, are not to be compared with each other " without further consideration." Other methods of anti - malarial measures could not be practised except to a very slight degree, as the money provided by the Government was just enough for quininisation. In some houses mosquito-proof rooms — such as verandas — have been arranged ; the petrolisation of water - collections could naturally yield but little success. In Tanga, the most important seaport next to Dar-es-Salaam, the anti-malarial work, according to the example of the capital, was not taken up until 1905 (Table IV). Besides one medical officer only three to four nurses understanding microscopical examination of the preparations were available. In addition to microscopical findings, tumours of the spleen decided the need of treatment. This treatment was commenced with one gramme doses in adults, and correspondingly lower doses in children, on two consecutive days per week, and was continued for three months. In all cases an enormous decrease of splenic tumours (from 1,040 to 1,042) and distinct improvement in 51] TANGA 463 the general condition have been stated. Only in very rare cases this cure did not sufifice to cause the parasites to disappear. TABLE IV 1905-06 i All persons with tumour of the spleen or mal. parasites in blood, were treated with quinine for 3 months. Negroes Indians Children Adults. Children Adults. June-Aug. (before quinine treatment) 49 "6% 12 "4% 54'o% 13-8% Jan.-March (after quinine treatment) 24-6% 5-3% 29-5% 3 "9% 1906-07 A In June, July, and Aug. all nations became quinine prophylactically May-July 84-0% 14-9% 87-1% i8-3% Dec. -March 30-0% 6-1% 3i'3% 4-6% 1907-08 1907 April-June i8-3% 12-6% July-Sept. i6-i% 9-5% Oct. -Dec. i4"o% 7-5% 1908 Jan.-March I2'0% 6-8% 1908-09 As the year before April-June 668 170=24% 2,025 295 = 14% July-Sept. 755 181 = 24% 1,879 272=18% Oct.-Dec. 601 121=20% 2,100 258=14% 1909 Jan.-March 846 208=24% 2,23s 532=23% 1 The population in Tanga being smaller and much more fixed than in Dar-es-Salaam, the result during the first year was more satisfactory. From March to June 1906, however, the number of infections increased threefold, which is explained by the extraordinary amount of rain during that time. In the course of the following dry season the index sunk to the level 464 PREVENTION IN GERMAN POSSESSIONS [Sect. of the previous year. In 1907 to 1909, apparently another rise in the cases of malarial infection occurred in Europeans at Tanga ; but this is due to numerous immigrations from further inland, the people in case of infection having the opportunity to get to the hospital in Tanga by means of the recent rail- way extension. Among the settled white inhabitants of the city of Tanga the malaria morbidity has gone back from 37% to 35y/ of the total strength. Drainage of the town, petrolisation — though not quite general — of water-collections, and deforestation of numerous uncultivated pieces of land, were undertaken simultaneously ; also many Europeans' houses were provided with wire - gauze protection. The increase of malaria during 1908 to 1909 {vide Table V) may be due to the hospital being more generally used by the patients from the district, which is more and more frequented by Europeans, and by people employed in the construction of the railway. In Dar-es-Salaam itself malaria has diminished to such a degree among the whites settled there in the European quarter, that individual quinine-prophylaxis is no longer regarded absolutely necessary ; rather, numerous officials have passed the whole of their one and a half years' time of service without taking quinine, and without once contracting malaria. Many, however, continue the quinine prophylaxis. In the other settlements in East Africa, where medical officers and officials are stationed, no proper anti-malaria work is practised to any appreciable degree. From a general report on infected Europeans who have been treated by the medical officers, it can be concluded that, both together, the anti - malarial measures and the individual prophylaxis in Dar-es-Salaam as well as in Tanga have been a success, 51] RESULTS TABLE V 46s Europeans in Dar-es-Salaam. Strength, Dar - es - Salaam (town), (Iststarke) Morbidity, malaria and blackwater fever in the district of Dar-es-Salaam Mortality, malaria and black- water ..... 1902-03. 1903-04. 1904-05, 1905-06. 1906-07. 1907-08. 3" 377 380 657 851 897 ^ 166 168 141 355 287 268 I S3 -3% 44 "5% 37'i% 54-0% 337% 29-8% 7 3 4 6 6 1908-09. 743 342 46 '0% • Europeans in Tanga. Strength, Tanga (Iststarke) . (town), Morbidity, malaria and black- water fever, in the district of Tanga ..... Mortality, malaria and black- water ..... 95 148 192 205 211 222 c no 61 178 156 128 206 ^"5-8% 41-2% 87-5% 76-1% 6o-6% 92-8% 2 2 5 6 3 2 258 203 787% 1 Vide page 464. The reports on the garrison (Table V«) were the most accurate ones, as the majority of recorded infections were observed by a medical officer. The statements about " civil persons " (Table Nb) are far less precise, only a small number of the malaria infections among them coming to the knowledge of the doctor. The figures showing the morbidity here have therefore been stated far too low, but, as these conditions do not change from year to year, it is quite permissible to compare the different years with each other. With the coloured population matters are entirely different (Table VI). The percentage value in itself is here not standardised, as it was impossible at the repeated examina- tions to find always the same persons who had been treated with quinine. In addition to those there were persons who had come into town meanwhile, and who had been treated with quinine only insufficiently or not at all. Some other 2 G t^ o On CO S-S 4 00 UO T)- "^ o O M M CO o H vd 9 o ^"1 NO o c^ IT) o 00 o ^ o m ;r o o PI M ON w "iS- o o CO i ? ON M 0\ eo O (N O C4 NO H 00 ON ^ w < o 2 9 N < o H w H c« < o g, w sj? w 8 ^ 8 W CO On M g en a, o li 0^ 0) H tl On M o H M ' N d\ 2 < ON 00 ON 00 H o - ^ ^ ^ H CO N o CO Di 9^ M °2 1^ ID 5; 00 ^ O IH w as H o ON 00 O N ON M M 15 o s NO ON < < On 00 M H M CO t^ 2 <; lO < ON On 00 CO N M 2 °- " Tj- rt. •i- On 5-S fO : NO On CO CT) '-' • 5 'c rt u u > .5 E rt S o ^ o o E 01 n! «; D S 3 ^ v^ •o T3 " o w "o to M t/i ^ U] ^ c ? 5. ro "^ N e< I vO 00 ►-4 0) 0 OnOO B -^t^f^ M ■'d- 00 NO N On iri On On ro NO Cn U-) ri- r^ uo 00 NO to N T3 O O > J5 ro N N -T n" ro n" ro s ■35 '55 "K (U 4J -0^ ■ S r<-)NO On u-1 ^S S^ S^S^S^ >^ ^5^5^ t^ ro NO N 1:^ ■* n Tj- « 10 o -i t.» u-i N r^ ONOO NO M H IH 0\ On '^ X hT I-.* i-i Tl-vo M VO "^ VO "1 Aug. -Sept. (after the rainy season), Nov. -Dec. (short rainy season). 3 •r" CJN ^ J 'On u 3N . - d " >—> •f ON ►», . ■ ON £."90 d" *ii a, < 2" >N «• '. 2" CTj.i ^ -^ !^ Si c .2 "O J) (U trt ->-. lU 9 rG w childr ives h: phylac e a we for thr ngst t J ni -^ 9 "S^ - cu Ui M 3 rainy season th( ndians and na en quinine pr Iry year. Twi lie of quinine, istributed am >N.S a, 3} ^ 3 J 3 J w ■3 "^ S ^8 C i) S (U u ^'X r S'^ . a-. 2 11 a, . »-( > .. =^ ring the of the been gi cally. c c^ -S c« (U 0) c n. tJJo § § 2.S "S '5 cr '3 cr 3 3 J2 1/3 Q Q < ^ < ^ ^ :=! u-i . ■ c 5 NO U5 1) •S c •3 s !i ^ r^ P^=S " o! - ci ^ "3^ ••a U3 11 Nt-l rt ^--( ■1- S op a tn r; 1 ^1 0) rt iS a> 11 3 ^.S 1 is 3 1 3 W3 Q |Q Q Cfi O) ^ t«. 00 ON 9 »i^ v6 t^ 06 ON ON ON ON t-H " " Sect. 5i] KAMERUNS 469 the infected persons. But the statistician, as well as the practitioner in the midst of his work, comes to the conclusion, that a simple diminution does not suffice, and that this diminu- tion is very fluctuating and strongly influenced by incalculable factors. It is, therefore, the keen ambition of the medical officers in Dar-es-Salaam to obtain the means necessary for conducting anti-mosquito measures in the surrounding districts of the town. At present, engineers are engaged on surveying the town and surrounding districts in order to work out, on the basis of these measures, a plan for the abolition of ditches and other Anopheline breeding-places. (2). Kameruns. — This German territory had, and has partly up to this day, a very bad reputation as a hot-bed of fever. In 1896-1897 the malaria morbidity in Duala, the most important seaport, amounted to about 391% ; in certain months as many as 70% of the Europeans became infected ; about 48^ of the Europeans acquired blackwater fever ; and the total mortality caused by tropical diseases altogether amounted to about 8^ (Table VII). TABLE VII Malaria among the European troops in Kamerun. Strength (Iststarke) igoo-oi. 1901-02. 1902-03. 1903-04. 1904-05. 1905-06. 1906-07. 1907-08. 91 85 71 87 84 92 89 Cases of malaria X 340 = 370% 114= 162% 104= "9% 131 = 165% 131 = 1-^2% 87 = 97% Deaths due to malaria Cases of blackwater fever 20 18 21 23 8 13 9 Deaths due to black- water fever . 2 2 3 ... I Official statistics for the Kameruns are very incomplete, in consequence of the scattered nature of the single stations. The capital Duala is situated on a relatively favourable spot, z>., on the brink of the rapid Kamerun River, about 470 PREVENTION IN GERMAN POSSESSIONS [Sect. 6 to 12 metres above its highest level. Here was therefore given the possibility greatly to reduce the number of Anophelines through rainwater conductors and a regular system of drainage of several swampy places. In the latter years Ziemann has worked in connection with the local Government with great energy at the amelioration of the general hygienic conditions. The territory of the town itself has been planned, and cleared of all superfluous bush ; and by means of straitly made roads the wind is given free passage. Sewers effect rapid drainage of all rainwaters. A sanitary brigade supervises the accurate and continued adherence to the specified measures. The brigade extends its surveillance also over the surrounding districts ; hollows in the neighbouring wood, from where the Anophelines swarmed to the town, were drained or filled up, and if this was not practicable, Saprol was poured over the water surface at regular intervals. Great credit is to be given, however, to the Government medical officers for their work of furthering quinine prophylaxis. It was as early as the close of the last century when F. & A. Plehn recommended prophy- lactic use of quinine, and since then the value of this method, together with general hygienic improvements, has found full recognition with the majority of settlers. Also mosquito-proof houses are recommended and used as an anti-malarial measure, although this method is rendered much more difficult by the humid climate which soon destroys the wire-gauze. The benefit resulting from the above measures can be easily seen from the figures indicating the malaria morbidity for Duala alone : — 1900-01. ^87% 1901-02. ■30% 1902-03. 77% Number of inhabitants 'j District Duala . J 1902-03. 142 1903-04. 152 1904-05. 164 1905-06. 183 1906-07. 260 1907-08, 300 Hospital frequented by Hospital for malaria . 187 83 158 S3 163 83 151 68 185 89 213 74 Malaria percentage . 44'4 53-6 50-9 45 'o 48-1 347 51] TOGO 471 In spite of the increase of the European population to double its previous strength, the number of severe cases of malaria treated in hospital had, with slight fluctuations, remarkably diminished. It must be admitted that under such measures also the malaria among the natives is bound to diminish. At the policlinic, quinine is distributed gratis to all natives ; the number of those who received quinine in 1907- 1908 was 820. The treatment of so many infected people in one place is sure to lower the possibility of infection for the Anophelines and consequently the malarial infections in man. The number of Europeans in the other settlements in Kamerun is too small, and is also subject to too many changes, to allow the possibility of deducting any conclusions about the value of certain anti-malarial work. The favourable effect of the malaria prophylaxis, and especially the individual quinine administration (prophylactic), together with general improvement in hygienic conditions, is evident anywhere. The same holds good for the territory of Togo, with its three important places : Lome with about 6,000, and Anecho and Palime with about 3,000 inhabitants each. The two former places are situated on a line of dunes directly at the sea, and landwards spreads a so-called lagoon. During the dry season, from October to April, there is so little malaria in Lome that Dr Kriiger (no reference) recommends to suspend the quinine prophylaxis during that time. When, however, in April or May the rainy season commences, the malarial infections soon reappear, for the innumerable little hollows in the bed of the richly vegetated lagoon now fill up, and the Anophelines rapidly increase. At places with such pronounced "malaria seasons" the quinine prophylaxis must be given first consideration. In Togo it is religiously practised by many Europeans, though not by all, as in 1 907- 1 908 still 99 infected Europeans required medical attendance, 61 of whom, however, contracted the disease "in 472 PREVENTION IN GERMAN POSSESSIONS [Sect. the bush," The work of a mosquito brigade is making for the diminution of the gnats {Stegomyid) within the town and surrounding districts, whilst drainage of the lagoon has only just been decided upon. (3). German South-west Africa. — This territory has badly suffered from disturbances, so that no precise statistics exist for this time. In 1907- 1908 about 3,000 soldiers were sent home, and about 3,400 Europeans remained in March 1908. Among the latter occurred 507 cases of malaria with one death, and 4 cases of blackwater fever, one of which with lethal exitus. The malaria is more general in the north of the protectorate which projects into the tropics and possesses a pronounced rainy period, the rainfall measuring from 400 to 700 mm. per annum (December till May). During this short period the Anophelines multiply enormously in the numerous puddles and pools, even in the footprints of horses and wild animals and the leaf-axils of certain plants. As water is there a question of great economical importance, petrolisation is not practicable, as, for instance, in the case of watering-places for cattle. The only measure to be taken into consideration seems to be fumigation. During 1906-1907 a proper quinine prophylaxis — every fifth and sixth, respectively eighth and ninth day a O'5-ro gramme dose — was practised under the supervision of the local medical officers in the following stations : Namutoni, Zesfontain, Grootfontain, Waterberg, Outjo, Otavi and Omaruru. The result was a very unfavourable one : i r6 to 90% of the persons treated suffered from malaria ; in four stations more than 75%. The reason for this non-success has not been quite explained, as since 1907 no further report has been published. In many places it has been stated that the quinine tablettes were not quite soluble ; and it is probable that the form of malaria in question was of the most virulent type, against which the quinine was but of little use. The infection was mostly very slight. It will be necessary to continue exact observations for many 5i] SOUTH SEAS 473 years before one can possibly determine for what reason the quinine prophylaxis has failed just here. At the time any judgment upon this single observation would be premature. (4). The German possessions in the South Sea. — The colonies in these regions are relatively small, and so is the number of Europeans. Only few medical officers are in practice there, and consequently the statistic material can add but little to what has been said above. It is worth mentioning that Koch found only quartana on the " French Islands " (Bismarck-Archipel), and only tropica in Maty. Some groups of islands are completely free from malaria. The results of anti-malarial measures in the German Colonies can be briefly stated as follows : — 1. The simplest and cheapest method has been found to be quininisation. 2. With carefully - practised and well-supervised quinine- therapy and prophylaxis it is possible to exterminate malaria even in very badly-infected places. 3. Individual prophylaxis with quinine suffices in suscept- ible persons (Europeans) to prevent with great certainty an outbreak of malaria. According to the probability of infection in a certain place, this prophylaxis must be increased or diminished. 4. Anti - malarial measures in the form of quinine treat- ment of infected persons have led to a decrease in the malaria morbidity, wherever they have been practised regularly, and for a sufficiently long period. 5. The steadier the native population of a place, the easier it will be to find out all infected people and treat them thoroughly. 6. Quinine must be distributed gratis, and directly offered to the natives. 7. The treatment of infected persons with quinine, according 474 PREVENTION IN GERMAN POSSESSIONS [SECT. 51 to Koch, is sufficient to keep the malaria on a low level among the natives in tropical towns. 8. The treatment of the natives with quinine together with individual prophylaxis leads to a remarkable decrease in the malaria morbidity among Europeans. 9. In many cases quininisation alone will not suffice to reduce the morbidity to a degree which is desirable in the politico-economic interest. 10. Which one of these three anti-malarial measures, quinin- isation, mechanical protection, and anti - mosquito measures, is the most important can only be decided upon according to the local conditions. Par le Dr EDMOND SERGENT (Alger) 52. Campagrnes Antipaludiques en Territoire Fran(?ais. — Le paludisme n'existe plus en France que sur de rares points ou il s eteint d'ailleurs peu a peu : la Vendee, la Sologne, la Camargue. La culture intensive succedant a de grands travaux d'assain- issement agricole, I'accroissement du bien-etre et de I'instruction generale peuvent expliquer en partie ce recul du paludisme sur le territoire de la mere-patrie, mais il est difficile d'en preciser retrospectivement d'une fa^on parfaite toutes les causes. La survivance des Anophelines au paludisme dans la France entiere est un fait tres net qui montre que le paludisme peut disparaitre sans que son vecteur soit extermine. Malheureusement la France, grande puissance coloniale, a dans ses possessions d'au dela les mers un ennemi toujours present dans le fleau paludeen. L Campagnes a^itipaludiques en Algerie. — La plus belle de ces colonies a vu son sort longtemps discute, non seulement pour des raisons politiques diverses, mais surtout a cause de son insalubrite qui, croyait-on, devait en rendre a jamais le sejour impossible aux races europeennes, Alger etait occupe en 1830, et en 1841 le General Duvivier, un heros de la conquete, ecrivait la phrase fameuse : " Jusqu'a present, les cimetieres sont les seules colonies toujours croissantes, que I'Algerie presente."^ C'est en Algerie que le Professeur A. Laveran devait decouvrir, en 1880, I'agent de la fievre paludeenne et etablir ainsi sur une base reellement scientifique 1 etude de cette affection en 1 General Duvivier, "Solution de la Question de I'Algerie." Paris, 1841, p. 4, Cette solution, c'etait I'evacuation, p. 49. 475 476 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. meme temps qu'il ouvrait un nouveau chapitre de la microbi- ologic, celui des microbes pathogenes Protozoaires.^ C'est aussi en Algerie qu'un autre medecin militaire : F. C. Maillot, des 1834, apportait de I'ordre dans la determination des fievres continues des pays chauds, et, malgre de vives attaques de I'ecole broussaisienne, demontrait d'une facon definitive quelles sont les regies, jusqu'alors insoupconnees, qui doivent presider a la medication quinique.^ Deux chimistes frangais, Pelletier et Caventou, avaient rendu possibles les beaux travaux de Maillot en isolant I'alcaloide du quinquina. C'est a Maillot que I'Algerie doit d'etre devenue frangaise ; et le Dr Battarel a pu dire qu'il a complete de la facon la plus heureuse la formule du Marechal Bugeaud : ense et aratro en y ajoutant : et quina. L' Algerie etait devenue habitable, mais le progres normal de I'assainissement y est lent. Encore a present, beaucoup trop de vies et d'energies y sont consumees du fait du paludisme. C'est pourquoi, a I'annonce de la belle decouverte de R. Ross, sur le role des moustiques dans I'etiologie paludeenne, I'lnstitut Pasteur de Paris envoya, en 1902, une mission antipaludique, dont les essais furent poursuivis d'abord sur les reseaux de Chemin de Fer. Mais des 1904 M. le Gouverneur - General Jonnart demanda a M. Roux, Directeur de I'lnstitut Pasteur de Paris, d'etendre ces essais aux localites les plus paludeennes de toute I'Algerie ; il leur temoigna une precieuse sollicitude, et les appuya constamment de sa haute autorite. Territoire. — L'Algerie occupe une surface approximative de 300,000 kilometres carres. La partie habitable figure un parallelogramme allonge de Test a I'ouest entre le Sahara et la Mediterranee. Sur le bord meme de la mer surgissent des chaines de montagnes dirigees egalement, d'une facon generale de Test a I'ouest et dont les sommets depassent rarement 2,000 ^ A. Laveran, " Traite du Paludisme." Paris, 2eme ed., 1907. 2 Le Professeur Trolard a reuni un certain nombre des oeuvres de Maillot dans un ouvrage de 260 pages. Paris, 1894, chez Doin. 52] LOCAL CONDITIONS 477 metres. Entre ces montagnes ou entre leurs contreforts s'ouvrent des vallees et des plaines (vallees de la Seybouse, de la Soummam, du Cheliff, plaines de la Mititdja, de la Macta, Hauts Plateaux), qui constituent autant de regions distinctes par leurs caracteres de geographie physique. La faune, la flore, la climatologie sont ceux du bassin mediterraneen. Une assez etroite bande littorale limitee au Sud par la ligne qui correspond aux chutes d'eau minima annuelles de 40 cm. represente la partie colonisable par les Europeens. Plus au Sud c'est le steppe, pays des Nomades, du mouton et du chameau. Plus au sud encore c'est le desert du Sahara, a climat continental, et qui s6pai-e davantage I'Algerie de I'Afrique que la mer ne la separe de I'Europe. En raison de la faible hauteur des montagnes et de I'absence des neiges eternelles, le regime des cours d'eau {oued en arabe) est essentiellement torrentueux. Les marecages des plaines basses et les mares subsistant en et6 dans le lit des oueds sont les principaux gites a- Anophelines. Habitants. — Sur ce vaste espace habitent (recensement de 1906) 5,231,850 ames, dont 729,960 Europeens et 4,501,890 indigenes, les premiers agglomeres surtout dans les villes et les villages, les seconds epars dans la campagne. Les indigenes, tous de race blanche : Arabes ou Berberes arabises dans les plaines, Berberes dans les montagnes ou le desert (Kabyles de la grande et de la petite Kabylie, Chaouias de I'Aures, Touareg du Sahara), possedent souvent ainsi que je I'ai montre avec mon frere, une certaine immunite relative centre I'hematozoaire du paludisme, qui leur permet d'heberger ce mJcrobe dans leur sang peripherique, sans presenter de symptomes morbides (exactement comme les populations negres de I'Afrique d'apres ce qu' avaient deja vu R. Koch, Stephens et Christophers). Cet etat d'immunite relative ou de paludisme latent est tres dangereux pour la collectivite car ces " porteurs d'hemotozo- aires" qui souffrent peu, eux-memes, en etat normal, de leur 478 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. infection, sont toutefois susceptibles d'infecter a tout moment les Anophelines. Les sujets exposes au paludisme sont done en premier lieu les colons immigrants, et les indigenes provenant de regions saines. Le degre de danger couru par eux depend surtout du voisinage d'indigenes en etat de paludisme latent, car il y a des Anophelines partout en Algerie, sauf dans les grandes villes. Le peril pour les colons etablis dans une exploitation provient de ce que I'infection ne reste pas unique, mais est suivie, en regie, de reinfections successives qui se produisent avant que I'immunite relative ait pu etre acquise. Les Europeens qui resistent a ces reinfections presentent ensuite, comme les indigenes, une immunite relative coexistant avec un paludisme latent. Anophelines. — Les Anophelines de I'Afriquedu Nord actuelle- ment connus sont :^ — Anopheles maculipenms Meigen, I'espece la plus repandue. On le trouve partout sauf dans les villes ; il habite le littoral, les plaines, les montagnes, les vallees, le steppe, le Sahara. En moyenne 4% sont infectes dans les pays paludeens. A. algeriensis Theobald, espece vicariante de H. bifurcatus espece sylvane, farouche. On le trouve aussi infecte par des sporozoites de Plasmodium. Pyretophorus myzomyifacies Theob. et Serg. Vallees des regions accidentees. On le trouve egalement infecte par des sporozoites de Plasmodium. Pyretophorus sergenti Theob. Lisiere des Steppes et du Sahara. Pyretophorus chaudoyei Theob. (etudie par A. Billet), Sahara. Une premiere epidemic de tierce benigne apparait au printemps, la tierce maligne predomine en ete et en automne. La quarte se montre surtout en automne et surtout dans certaines contrees. 1 Voir Annales Institut Pasteur, t. xix., 1905, pp. 246 sq. ; t. xx., 1906, p. 248. C. R. Soc. Biologic, pp. 246, 1905, p. 499. F. V. Theobald, " Monograph of Mosquitos" (iv. tomes), London. 52] INDIVIDUAL PROPHYLAXIS 479 Mesures prophylactiques. — Nous les classons dans I'ordre suivant : — A EloigJiefnent des gites a Anophelines Eloignement du Reservoir de virus B Grandes mesures antilarvaires Petites mesures antilarvaires . Mesures centre les adultes C Quininisation preventive . Quininisation curative D Defense mecanique personnelle Defense mecanique collective . Ces diverses mesures, partant de principes divers pour aboutir au meme but, sont utilisables a des degres differents selon que Ton se trouve dans I'un de ces trois cas : — (i) Prophylaxie antipaludique d'un particulier. (2) „ „ d'une collectivity. (3) » » del'Etat. (i). Prophylaxie dun particulier. — Dans les nombreux voyages que nous avons faits a travers les regions les plus paludeennes de I'Algerie, nous sommes restes toujours indemnes du paludisme en observant les precautions suivantes : — Autant que possible, passer la nuit loin des agglomerations indigenes et des gites a Anophelines. Prendre tous les jours une dragee de 0*20 centigrs. de bichlorhydrate de quinine (enrobee dans 0'30 centigrs. de sucre), pendant tout le temps que Ton passe en pays infecte, et pendant 15 jours apres la rentree en pays sain. Parfois, en pays tres palud6en, nous prenions 0*40 centigrs. par jour, une dragee a chaque repas. Enfin nous n'avons jamais dormi en pays paludeen, soit la nuit, soit a I'heure de la sieste, sans notre moustiquaire portative que nous emportons toujours dans nos bagages et que nous montons tou- jours nous-memes. Un certain nombre d'ofificiers, de fonctionnaires ou de colons contraints a traverser des regions fievreuses ont adopte la pratique de ces mesures de preservation personnelle. Celle 48o ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. qui est le plus frequemment observee est la quininisation preventive. (2). Vne collectivite (compagnie de chemins de fer, exploita- tions agricoles, minieres, grandes administrations) doit eviter d'installer ses postes, ses gares, dans le voisinage des gites a Anophelines et des agglomerations indigenes. Le Service antipaludique en Algerie est consulte en principe chaque fois que I'on construit une ligne de chemin de fer et que Ton fonde un nouveau village de peuplement europeen. On a pu faire prevaloir parfois le choix de certains emplacements moins exposes que d'autres a la contagion paludeenne. Les collectivites (agents de chemins de fer et des Services publics, troupes, ouvriers agricoles, mineurs, etc.) peuvent dtre facilement soumises a une quininisation preventive par les petites doses journalieres. II est bon dans ces cas de faire tenir un registre des prises de quinine pour que Ton sache bien comment est absorbe le medicament. Enfin ces collectivites peuvent etre egalement protegees par les grillages metalliques poses aux ouvertures des habitations : defense tnecanique collective. C'est la un procede de luxe qui coute fort cher et ne peut etre propos6 qu'en faveur de personnes d'un niveau social assez eleve pour prendre soin de leur confortable. Nous tachons de rendre cette defense mecanique le plus automatique possible, pour demander tres peu d'attention et de bonne volonte aux occupants des habitations, C'est ainsi que nous faisons etablir les volets a I'interieur des fenetres de facon a ce que le grillage des fenetres soit exterieur a tous les battants, et, par consequent, n'ait pas besoin d'etre perce de lucarnes pour le maniement des verrous, crochets au fleaux destines a assujetir les volets. Si les volets sont exterieurs, par exemple dans les maisons deja construites que Ton veut grillager, nous preferons pour les grillages les chassis a guillotine dont la fermeture est automatique. Fig 1. 1". C. MAILLOT. I'lG. 4. GITE A AN01'Ili:i.INK DANS UNE OASIS SAIIAKIKN'MC. Fig. 5. par (/rs y/yy/lh'h's CULEX (CULICINEI Comment on se prole<(c contrc to Paludisme cow.uc>T Dime iiu pmnUU D'lllE IVTIE IW ^ Le* AQopbete« en piquant dt-s Bt-vmux, suf-nl. avi-r !<■ unu. Ic microbe de la fi^vre. qu'iia peuvi^ut fa&uLin mocalcr &ux autr<^ pHraonnta qu ils piqueot. Poor ^Tiier ies fi^vp.-s palud6«nDes. tl fBot dune m proi^:gt^r ooiitr« !«• Moustiques r.->mme l^^ Wtv^b de ceux-cj vivent duis lV«u sUgnanb- dus mar«*. de* M&n^m, etc.. il fkul uL(u>i>J<.i ■■. i iTmn-s ^utDfrs. tfic . <>u. 8i oeU e«\ impossible. en p4troler la Barfice loua la« quinxe jour» eu ♦•U; i 10 ~ H.- p.'lrol*- par mfttre OMT* de •urfar* de»u). Lea lir»e« sont aaphyiitea par ie p^irole qnelU* Aspir-nl en Ten»ni r-^pirer «i U surfac* oe«1 p«a 9)^r de dftruirv t>~>ult« liv lar- Mousbque*. on se proWKo i-onlre !«»« HouiUquci kJulw* qui s>'>ni AclOA dr« aymphea, en ^amis*«ni \f\ purtea . U« rt>D(>tn« ti Ifs ouverliir«a d*« chemin^^«. de gnkl«K(.-« i-n toile metklliqur de 1,5 i 2" de lsr^<-ur de tOftille. 11 «at hon uiiui de pr*odrv pn'v«Qti*enu-Dt de la quiniDc (30 oenUj{r«mni<-« par jour pour un adulu.-). Ci-iu> fatbtc doae. priar rt^gniti^rvmfol WuB k^a joura. iih fati^fue pas. ••i »'11*» no( tffiiAi-- llCi. o. .SA.Ml'I.l-. CHART FuK PUBLIC IN.STKLCTION. [ To face page 480. 52] MAJOR MEASURES 481 (3). Le role de t&tat dans la prophylaxie antipaludique peut etre compris ainsi : Execution des gr-andes mesures antilarvaires : — Canaux de dessechement, grandes plantations dans les marais, reboisement des montagnes, petits barrages dans les hauts bassins, regular- isation des cours d'eau, surveillance des barrages, reservoirs, etc. Mais ces enormes travaux, qui coutent tres cher, ont toujours un but principal d'assainissement agricole ; I'hygiene antipaludique ne peut intervenir ici qu'a titre accessoire, pour appuyer tel projet, contre-indiquer tel autre. D'ailleurs ces grandes mesures antilarvaires ne sont pas completement efficaces par elles-memes ; elles ne font que rendre possibles les petites mesures antilarvaires et surtout la bonification agricole. Celle-ci, en drainant et en permeabilisant le sol, en supprimant les moindres mares, en utilisant toute I'eau des pluies et toute I'eau des sources, aboutit, en poursuivant un but purement cultural, a un resultat reellement antipaludique. Nous avons souvent constate qu'un grand canal de desseche- ment est surpeuple de larves d'Anophelines, tout comme le marais qu'il remplace. Mais le marais etait inaccessible, tandis que des deux berges du canal on peut atteindre et detruire les larves d'Anophelines. Cet exemple montre bien ce que sont, a notre sens, les petites mesures antilarvaires. Dans le canal dont il s'agit, les larves reapparaitront constamment, quoiqu'on fasse, car il aura toujours de I'eau, puisque c'est son office de drainer I'eau des couches superficielles du sol. D'autre part il viendra toujours des Anophelines femelles pondre sur cette eau tran- quille, car si loin que Ton recule les limites des mesures anti- larvaires, elles ne pourront pas englober toute I'Afrique du Nord. Par consequent les mesures de destruction des larves devront etre repetees indefiniment sur les parties du canal voisines de lieux habites (dans un rayon de un kilometre et demi) et c'est la le principal caractere des petites mesures antilarvaires : de n'avoir qu'une efficacite temporaire. Elles 2 H 482 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. tiennent purement et simplement en 6chec la pullulation des larves pendant le temps ou elles sont mises a execution. On a done interet a maintenir indemnes de larves les environs d'une agglomeration importante, mais il faut evidemment que la valeur economique du groupement a defendre soit assez grande pour justifier les depenses engagees. II est une autre utilite des petites mesures antilarvaires, c'est celle de supprimer temporairement les vecteurs de la contagion et, par suite, d'empecher pendant ce temps les reinfections. Elles permettent ainsi la guerison des anciens infectes, que Ton aide, d'autre part, par la quininisation curative. En resume, a mon sens, les petites mesures antilarvaires auront pour but, non pas seulement d^eviter les infections des indemnes, vtais aussi de permettre la guerison des anciens infectes. Le type des petites mesures antilarvaires est presente par les faucardements des eaux stagnantes repetes, suivant les besoins, 2 ou 3 fois par an, et les petrolages, renouveles tous les quinze jours (tous les 8 jours au Sahara). Mais les minimes artifices, qui rendent impossible la vie des larves dans les aquariums parfois tres reduits qui leur suffisent, peuvent etre varies a I'infini. Je citerai comme un exemple typique le procede suivant que nous avons applique deja souvent. Soit une source, une fontaine, un abreuvoir, dont I'eau d'ecoulement forme des gites intarrissables et permanents. Nous faisons creuser, au lieu d'un seul canal, deux petits canaux d'ecoulement fermes a leur origine par une vanne. On laisse I'eau s'ecouler par un seul canal pendant huit jours : les oeufs y sont pondus, les larves naissent, se developpent. Au bout de huit jours nous baissons la vanne de ce canal et ouvrons I'autre : les larves qui ne sont meme pas encore arrivees a la nymphose meurent sur la boue qui seche au fond du canal abandonne par I'eau. Ainsi, sans aucune surveillance, cinq minutes de travail toutes les semaines suffisent a empecher tout developpement des larves dans cette eau d'ecoulement. Les mesures contre les adultes telles que les fumigations de 52] QUININE 483 poudre de pyrethre ou de soufre, la pulverisation de poudre de pyrethre ou de petrole, les trous-pieges de Blin, jouent un role tres secondaire dans la lutte antipaludique. C'est au contraire la quininisation airative que I'Etat peut appliquer en grand et faire servir le plus efficacement a I'assainissement d'une region en Algerie. Nous dirons d'abord que dans notre pratique nous organisons la quininisation curative exactement comma la quininisation preventive. II faut, en effet, reserver aux m^decins le traitement des fievreux, vraiment medical, c'est a dire celui qui procede par des fortes doses. D'autre part, il est bien plus commode d'avoir une technique unique qui s'applique aussi bien aux sujets indemnes qu'aux anciens infectes dans un pays oil le paludisme est aussi commun. Enfin la comparaison des index endemiques par la palpation des rates avant et apres les campagnes antipaludiques nous demontre la reelle efficacite des petites doses journalieres longtemps repetees. D'ailleurs on sait que meme les petites doses de quinine sufifisent a faire disparaitre les parasites du sang peripherique bien avant la guerison totale de I'infection palud6enne. Les individus ainsi " blanchis," alors meme qu'ils ne sont pas encore gueris, sont deja rendus inoffensifs pour la collectivite. Au moment oii les procedes de la quininisation preventive et curative sont mis en ceuvre de plus en plus dans tous les pays paludeens, on nous permettra de rappeler que depuis longtemps en Algerie, a la suite de Maillot, les medecins civils et les medecins de I'armee ont preconise et applique ces deux sortes de quininisation. Je citerai, parmi les experiences les plus nettes, celles de Sezary^ et celles de Cornebois.^ Sezary ecrit en 1891 : "J'ai fait prendre du ler Juillet au ler Decembre, tous les jours, a Tun des repas 1 5 centigrammes de quinine, quelquefois 20, mais jamais davantage. Avec cette dose infime, j'ai maintenu, depuis deux ans, en divers centres, 1 "Prophylaxiede la Malaria par la Quinine." Alger, Jourdan, i6 pp., 21 Octobre 1891. 2 " Contribution a I'Etude de la Prophylaxie de la Malaria par la Quinine." These tnedecine, Montpellier, 1894, 484 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. tres malsains, des families entieres en parfait etat de sante, au milieu de voisins toujours malades. Et non seulement les acces disparaissent, mais I'appetit augmente, les couleurs du visage, Tembonpoint reviennent, en un mot, c'est I'apparence de la sante parfaite . . . tantis qu'autour de ces personnes tout le monde subit les influences facheuses du milieu." Cornebois arrive en 1894 exactement aux memes con- clusions : " L' Administration de petites doses quotidiennes de quinine a pour resultat de prevenir, soit I'invasion, soit le retour du paludisme." Les medecins de I'armee emploient depuis longtemps en Algerie la quininisation reguliere preventive, et les resultats dependent du soin qu'on apporte a observer leurs prescriptions. Le Service antipaludique en Algerie emploie des dragees lenticulaires roses de bichlorhydrate de quinine, semblables a celles de I'Etat italien et contenant vingt centigrammes de sel comprimes et enrobes dans trente centigrammes de sucre. Nous faisons distribuer une dragee par jour aux adultes (deux dragees dans les regions tres paludeennes) ou bien trois dragees tous les deux jours, ou tous les trois jours. Pour assurer une exacte administration de la quinine, eviter tout abus et tout accident, nous croyons necessaire de faire distribuer les dragees par des quininisateurs, agents des services publics ou personnes de confiance, chargees temporaire- ment de ces fonctions pendant I'ete, moyennant retribution. Les quininisatrices sont encore plus precieuses que les quininisa- teurs, a cause de leur facile acces aupres des femmes musulmanes. Le quininisateur distribue lui-meme aux moments fixes : tous les jours, ou tous les 2 jours, ou tous les 3 jours, la quinine aux personnes inscrites sur un registre ad hoc. II fait ingerer les dragees en sa presence et note les prises sur son registre. Nous evaluons les resultats de cette quininisation par la comparaison des index endemiques avant et apres la campagne. En regie generale ce sont les index spleniques que nous relevons, et, nous ne quininisons, d'habitude, que les agglomerations ou 52] QUININE 485 rindex splenique depasse, au printemps, 15%. Lorsqu'on le peut, on releve aussi I'index hematologique. La quininisation en grand par I'Etat est rendue difficile en Algerie par le fait que ce pays est soumis comme la France europeenne a la loi de Germinal an XI qui donne aux Pharmaciens le monopole de la vente de la quinine. II a fallu done que le Gouvernement G6n6ral de I'Alg^rie negocie avec les Pharmaciens de la Colonie une entente aux termes de laquelle les drag^es de bichlorhydrate de quinine vendues au public, sous des marques de garantie speciales, sont soumies a un tarif particulier, aussi has que possible quoique laissant un benefice aux Pharmaciens. Ceux-ci approvisionnent de ces dragees des depots de quinine confies a des agents des Services publics autorises a revendre, au prix marque, les dragees au public. D'autre part les Pharmaciens delivrent ces dragees au Service antipaludique, pour la quininisation du Reservoir de virus, sans prelever de benefice. En somme cette entente, si elle donne ses fruits, mettra a la disposition du public, dans toute I'Algerie, de la bonne quinine, a bon marche, sous une forme agreable, et permettra a I'Etat d'entreprendre avec le moins de frais possible la quininisation publique de I'enorme Reservoir de virus constitu6 par des millions d'indigenes, en majorite indigents. Si nous voulons resumer le mode d'action de I'Etat Algerien dans la lutte antipaludique nous dirons que ses efforts princi- paux portent sur la reduction du Reservoir de virus forme par les indigenes anciens infectes. Cette reduction du Reservoir de virus est poursuivie par la quininisation par petites doses quotidiennes, et elle est facilitee, acceleree dans toutes les localites ou la chose est possible, par I'organisation de petites mesures antilarvaires. Le service antipaludique a institue des campagnes anti- paludiques exp6rimentales dans trois champs de demonstration : un par departement : Montebello (Alger), Tourville (Oran), Mondovi (Constantine). D'autre part il subventionne et aide 486 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [SECt. les campagnes locales organisees suivant les memes principes par les medecins collaborateurs residant dans des villages fievreux et dirige les mesures prises sur les reseaux des chemins de fer, dans les immeubles administratifs. Enfin il propage les connaissances nouvelles sur I'etiologie et la prophylaxie du paludisme. (Une ligue algerienne centre le paludisme, fondee en 1903 par les Prof. Moreau et Soulie se livre egalement a la vulgarisa- tion des decouvertes recentes sur I'etiologie et la prophylaxie du paludisme.) Resultats. — Nous resumons ci-dessous les resultats constates dans les champs de demonstration du Service antipaludique. lis donnent une idee des resultats obtenus par les diverses campagnes menees ailleurs. (i) Departenient d' Alger.— Montebello (mesures antilarvaires et quininisation). Avant la campagne : — En 1904 75 infectes, 12 indemnes, il se produit 11 leres infections. Apres la campagne : — En 1905 44 anciens infectes, 36 indemnes, il se produit o lere infection. „ 1906 21 „ „ 71 „ „ „ o „ „ 1907 13 „ „ 65 „ „ „ o „ „ „ 1908 20 „ „ 54 „ „ „ o „ „ „ 1909 18 „ „ 68 „ „ „ o „ „ Depuis le debut de la campagne (1905) il y a eu a Monte- bello 10 naissances. Aucun de ces enfants n'a eu le palu- disme jusqu'a present. Le fait est unique dans I'histoire de Montebello. Localites du voisinage, non defendues, pouvant servir de temoins : — En 1905 9 Personnes indemnes, 8 premieres infections. ,, 1906 29 cas graves de premiere invasion (i mort par acces pernicieux). „ 1907 7 personnes indemnes, 4 premieres infections. „ 1908 3 personnes indemnes, i cas de premiere invasion. )> 1909 5 personnes indemnes, 2 cas de premiere invasion. 52] ORAN, SAINTE LEONIE, CONSTANTINE 487 (2) Departement dOran. — Tourville (mesures antilarvaires et quininisation). Avant la campagne: — En 1905 Sur 82 enfants, 58 grosses rates (707%). Apres la campagne : — En 1906 Sur 113 enfants, 26 grosses rates (23%). Sur 900 habitants I Ire infection. „ 1907 Sur 65 enfants, 4 grosses rates (6'i%). Sur 1000 habitants 1 Ire infection. „ 1908 Sur 148 enfants, 5 grosses rates (3'3%). Sur 1000 habitants o Ire infection. „ 1909 Sur 188 enfants, 8 grosses rates (4"2%). Sur 973 habitants o Ire infection. Depuis le debut de la campagne (1906), il y a eu a Tourville 106 naissances. Deux enfants seulement se contaminerent (i en 1906, I en 1907). Sainte Leonie. — (Mesures antilarvaires et quininisation — celle-ci defectueuse). Avant la campagne : — En 1905 Sur 30 enfants, 15 grosses rates. „ 1906 Sur 49 enfants, 18 grosses rates (36%). Sur 300 habitants 2 Ires infection dont une mortelle. Apres la campagne : — En 1907 Sur 60 enfants, 16 grosses rates (25%). Sur 300 habitants o Ire infection. „ 1908 Sur 78 enfants, 10 grosses rates (12%). Sur 300 habitants 2 Ire infection. ,, 1909 Sur 127 enfants, 7 grosses rates (4"i%). Sur 346 habitants o Ire infection. Localites du voisinage, non defendues, pouvant servir de temoins : — En 1906 14 personnes indemnesj 14 premieres infections. „ 1907 2 „ „ 2 „ „ dont une mortelle. „ 1908 I personne indemne, i premiere infection. „ 1909 I ,, » I ,, (3) D^partement de Constantine. — Mondovi (mesures anti- larvaires et quininisation). 488 ANTIPALUDIQUES EN TERRITOIRE FRANgAIS [Sect. Avant la campagne : — En 1906 Plusieurs cas d'hemoglobinurie et plusieurs cas de premiere invasion chez les nouveau-nes. Apres la campagne : — En 1907 Sur 773 personnes 3 cas de premiere invasion. „ 1908 „ 1300 „ 2 „ „ „ » 1909 » 1300 „ 2 „ „ „ L'index endemique de Mondovi : — En automne 1906 est de 78"8% » » 1907 „ „ 42-5% » » 1908 „ „ 32-6% » » 1909 „ „ 28-5% Localites voisines, pouvant servir de temoins : — En 1907 19 cas de premiere invasion. „ 1908 Nombreuses rechutes graves. „ 1909 Sur 260 personnes, 2 cas de premiere invasion. Penthievre. — (Mesures antilarvaires et quininisation). Apres la campagne : — En 1907 Sur 200 Europeens 2 cas de premi&re invasion (benins). „ 1908 ,, 200 „ I cas benin de premiere invasion. „ 1909 „ 200 „ o cas de premiere invasion. L'index endemique de Penthievre : — En automne 1907 est de 40 % » » 1908 „ „ 32-1% .1 » 1909 ,, „ 23-5% Localites voisines, temoins de Penthievre : — En 1907 I cas de premiere invasion. „ 1908 Cas de paludisme nombreux. „ 1909 Sur 260 personnes. 2 cas de premiere invasion. En 1909 ont ete distribues, en dehors des champs de demon- stration, 450 kilos de dragees de quinine, par les medecins col- laborateurs du Service antipaludique, qui avec un zele et un desinteressement dont on ne saurait trop leur savoir gre, ont ajoute a leurs occupations professionnelles la charge de com- 52] TUNIS 489 battre repidemie la plus repandue, sinon la plus grave actuelle- ment, en Algerie. Budget de la lutte antipaludique en Algerie. — Depuis plusieurs annees, les campagnes antipaludiques coutent au Gouvernement General environ cinquante mille francs par an : Personnel permanent (avec frais de deplacement) environ 16,000 francs. Personnel temporaire (quininisateurs) : de 3,000 a 4,000 francs. Achat de quinine: de 18 a 20,000 francs. Petites mesures anti- larvaires : de 13 a 15,000 francs. La defense mecanique est payee par chaque administration competente. Le budget total de I'Algerie est de cent millions de francs environ. II. Campagnes antipaludiques en Tunisie. — La Tunisie, qui continue, a Test, I'Algerie, nourrit sur 100,000 kilometres carres 1,800,000 habitants dont 1,600,000 indigenes. Comme en Algerie, presque toutes les regions basses et arrosees, les plaines marecageuses, les vallees parsemees de sources sont frapp^es par le paludisme au printemps (epidemie de tierce benigne) et en ete et automne (fievre maligne estivo- automnale). Certaines regions presentent de la quarte. Les Anophelines signales sont: Anopheles maculipennis Meigen, Anopheles algeriensis Theobald, PyretopJiorus cJiaudoyei Theobald. C. Nicolle, apres une premiere experience de lutte anti- paludique en 1903, obtint la creation d'un service antipaludique rattache a I'lnstitut Pasteur de Tunis, et qui fonctionne regu- lierement depuis Janvier 1907, sous la direction technique de Husson.^ Ce service a pour but principal de defendre contre le paludisme les centres de colonisation en enseignant aux colons les dangers qu'ils courent et les precautions a prendre pour les eviter et en renseignant I'administration sur les mesures prophylactiques d'ordre general ou local qu'elle seule peut entre- prendre. En consequence, des tournees sont faites dans un but ^ Voir Archives de V Institut Pasteur de Tunis, depuis 1906, et Bulletin de la Soc. de Pathol. Exotiq., t. i.., 1908, p. 385 sq. 490 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. de propagande et d'organisation dans les localites les plus malsaines : il faut citer en particuHer les defenses organisees sur les reseaux des chemins de fer et dans des compagnies d'exploitation des phosphates, les reglements elabor6s pour la declaration obligatoire du paludisme dans la ville de Tunis. Pour un certain nombre de localites les conditions exactes du paludisme ont ete determinees. Pour propager les principes de la lutte antipaludique, des distributions sont faites de brochures, d'affiches. Enfin le service antipaludique ainsi que le gouvernement tunisien distribue gratuitement des dragees de quinine. Le privilege des pharmaciens n'existant pas en Tunisie, pays de protectorat, I'Etat a pu y organiser la vente de la quinine. Un arrete du 15 Juin 1909 charge les debitants de tabac de la vente de la quinine dont ils s'approvisionnent a I'entrepot des Monopoles. Le minimum d'approvisionnement et le prix de vente sont reglementes. II s'agit du chlorhydrate de quinine en dragees de 20 centigrammes. Sur les lignes de chemins de fer, ou les mesures sont bien prises et surveillees, on constate I'assainissement reel de gares et maisonnettes auparavant fort paludeennes. Dans les centres de colonisation, ou I'intensite du paludisme est plus difficile a mesurer exactement, on constate les progres de I'education du public, et une amelioration souvent tres nette de I'etat paludeen. Budget. — Le Budget officiel de I'antipaludisme monte a quelques milliers de francs (appointements et frais de tournee du Directeur du service, achat de quinine, publications de propagande). III. Canipagnes antipaludiques en Corse} — Territoire. — La Corse est une ile allongee du Nord au Sud sur 200 kilometres de longueur et une largeur maxima de 90 kilometres. Une chaine de montagnes dirig^e selon le grand axe Nord-Sud est separee ^ Les renseignements qui suivent m'ont ete tres aimablement communiquees par le Dr Thiers, president de la Ligue Corse contre le Paludisme, que je remercie tres vive- ment de sa grande obligeance. 52] CORSICA 491 de la mer a Test par une plaine longue de 150 kilometres et large de 6 a 20 kilometres. Cette plaine orientale couvre 190,000 hectares, pres du quart de la superficie de I'Tle. Elle est toute entiere infectee de paludisme, a type estivo-automnal. Population. — Le Dr Thiers estime a 40,000 le nombre des habitants qui subissent annuellement les atteintes du paludisme (sur un chiffre total de population qui n'atteint pas 300,000 ames) pour le departement tout entier. Anophelines. — L'espece dominante est Anopheles maculipennis Meigen. Mesures adoptees. — L'Etat n'a encore pris aucune mesure importante en Corse. Ce fut le Professeur A, Laveran qui, en 1901,^ prit I'initiative de conseiller la creation d'une societe locale pour I'assainissement de ce pays. Une ligue corse contre le paludisme fut fondee en 1902 par le Dr Battesti, et depuis la mort de ce regrette savant, elle est presidee par le Dr Thiers. L'action des devoues Societaires est surtout morale, elle consiste d'abord en une oeuvre de diffusion dans le departement de brochures de vulgarisation, envoi de cartes postales, pose d'affiches mettant en garde contre la piqure des moustiques, conseils sur la facon de prendre la quinine, renseignements sur la facon d'organiser la production mecanique, installation et entretien de quelques maisons protegees, destinies a servir de modele.^ La Ligue a obtenu des pharmaciens que ses adherents puissent se procurer la quinine au prix de quinze centimes le gramme, prix bien inferieur aux prix en cours auparavant. Elle a decide la Compagnie des Chemins de Fer departementaux d'abord, les diverses Administrations de I'Etat ensuite, a 1 Bull. Ac. Midecine : " Sur la Prophylaxie du Paludisme en Corse," 24 Decembre 1901 ; et " Assainissement de la Corse," 7 Octobre 1902. Voir Battesti: "Ligue Corse contre le Paludisme." Campagne 1902. Bastia 1903. " La 2eme Campagne de la Ligue Corse contre le Paludisme." Annee 1903. Bastia 1903. 2 Voir la communication des Drs Thiers a Stefani au) Congrh de V Alliance (£ Hygiene Sociale. Lyon, Mai 1907. 492 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. adopter les toiles metalHques et la prophylaxie quinique dans les localites reputees paludeennes. Resultats obtenus. — Au point de vue moral, I'opinion publique en Corse e=t avertie, a I'heure actuelle, des dangers et des causes du paludisme, ainsi que des moyens d'y remedier. Au point de vue pratique la morbidite a diminue en certains points bien surveilles : elle est tombee parfois de 50% a 12^, mais il ne s'agit que des cas de premiere invasion, les recidives sont encore aussi nombreuses. C'est que le zele des medecins qui dirigent la lutte antipaludique et des Chefs d' Administration n'est pas toujours seconde par la bonne volonte des interesses eux- memes. La question du paludisme devrait constituer une des principales preoccupations de la Commission gouvernementale chargee actuellement d'etudier les moyens du relevement economique de la Corse. Budget. — Les cotisations des Societaires ont subventionne I'ceuvre de la Ligue Corse ainsi qu'une somme de 3,000 francs que lui attribua le Professeur Laveran sur des fonds mis a sa disposition par la caisse des recherches scientifiques. IV. Campagnes Antipaludiques dans les Colonies Francaises. — Le Ministere des Colonies a public en 1903 des Instructions concernant les meswes a prendre contre les maladies endeniiques, epidemiques et contagieuses. Mr le Medecin Inspecteur General Kermorgant y consacre 22 pages a la hygiene antipaludique.^ II revient en 1906 sur cette question dans un article sur "La Prophylaxie du Paludisme." ^ Sur ses instructions, I'etude des Culicides fut poursuivie dans toutes les colonies Frangaises et montra, entre autres choses, que les seules colonies exemptes de paludisme: la Nouvelle-Caledonie et Tahiti, sont en meme temps indemnes d'Anophelines.^ Mais on constate surtout des essais individuels de grillages des habitations. Et d'autre part, depuis longtemps, I'initiative ^ Voir Annexe aux Annales cf Hygiene et de Medecine Coloniale, 1 903. - Ann. (T Hyg. et Midec. Colon., t. ix., 1 906, pp. iS-46. ' Je remercie vivement Mr le Medecin Inspecteur General Kermorgant des renseignements qu'il a bien voulu me communiquer. 52] RlfeUNION, MADAGASCAR 493 de prescrire de la quinine preventive dans les pays paludeens ou en expeditions coloniales est laissee aux medecins.^ Les renseignements que nous avons pu recueillir parmi les documents publi6set au Ministere des Coloniessont lessuivants: — La Reunion. — He de 2,500 kilometres carres et 170,000 habi- tants infectee depuis 1867 par le paludisme. Deux especes d'Anophelines : Myzorhynchus coustani et Pyretophorus costalis. En 1902 le Colonel Sordoillet, commandant sup6rieur des troupes edicta des reglements, qui furent bien appliques dans la population militaire, pour la quininisation preventive et curative, I'emploi obligatoire des moustiquaires et la destruc- tion des moustiques dans le voisinage des postes et casernes. La mortalite autrefois assez elevee dans les statistiques militaires devient nulle en 1904 et 1905, alors que la mortalite dans la population civile subissait une progression importante. Apres le depart de cet officier superieur, les mesures ne furent pas aussi bien surveillees et les atteintes de paludisme recommencerent.^ Madagascar. — Un decret du 20 Octobre 1905 autorise le Gouverneur-General de Madagascar a prendre par voie d'arret^ toutes les dispositions necessaires pour que les sels de quinine soient mis a la disposition de tous et au plus bas prix possible. Le Professeur A. Laveran fait emettre en 1904 un voeu par I'Academie de Medecine pour que les casernements militaires de Madagascar soient proteges par des toiles metalliques.' Afrique occidentale franqaise. — Senegal. — Le Dr Thiroux qui, apres le Dr Marchoux a specialement etudie le paludisme du Senegal, rapporte* les mesures prises pour assainir en 1904- 1905 la ville de Saint-Louis (20,000 habitants). ^ Voir A. Laveran, " Traite du Paludisme." 2° ed., 1907. A. Billet, "La Lutte contre la Malaria en France et dans les Possessions Fran^aises en 1903." Atti. de Soc. per gli Studi delta Ma/aria, t v., 1904, p. 287. * J. J. Vassal, " Le Paludisme a I'lle de la Reunion." Atti. de Soc. per gli Studi delta Malaria, t. viii., 1907, p. 19. ^ Bull. Acad. Midec, " Seance du 8 Mars 1904," pp. 183-190. * A. Thiroux et L. d'Anfreville, " Le Paludisme au Senegal pendant les Annees 1905- 1906." J. B. Bailliere, 1908. 57pp. PI. en couleurs. 494 ANTIPALUDIQUES EN TERRITOIRE FRANCAIS [Sect. Les Aiiophelines du Senegal sont : — Pyreiophorus costalis, Myzomyia funesta, MyzorJiyyichus paludis, Cellia pharoe^isis, Cellia squamosa. On proceda au remblaiement des marais de la pointe nord de la villa de Saint-Louis, des marais du faubourg de Sor. Pour ces derniers, on a install^ un systeme de drainage, avec siphons s'ammorcant d'eux-memes a maree basse et ne fonc- tionnant plus a maree haute. On procede a des petrolages dans la ville de Saint-Louis ; quelques essais de defense mecanique ont ete tentes. La ligne du chemin de fer de Saint - Louis a Dakar a toutes ses gares et ses logements d'employes proteges par des toiles metalliques. Territoires des Rivieres du Sud. — Le Dr Le Moal appliqua en 1905 ^ les mesures antilarvaires a I'assainissement de Conakry (900 habitants) batie sur I'ile de Tumbo, une des villes les plus paludeennes d'Afrique. II y organisa des brigades a moustiques qui eurent pour mission de remblayer les bas- fonds, de drainer les marais, de petroler les mares. Haut- Senegal et Niger. — Le Dr Boufifard^ conseille, avec examples a I'appui, pour I'Europeen la cure quinique preventive (dose quotidienne de 25 centigrs. augmentee en cas de danger special) prolongee deux semaine apres le retour en pays sain. II y joint I'usage de la moustiquaire individuelle. II estime par contre la quininisation des indigenes impossible dans ces pays et croit les mesures antilarvaires susceptibles de diminuer le paludisme chez les Negres. II trace un pro- gramme des travaux a executer suivant que les agglomerations indigenes sont en plaine ou en montagne. Enfin I'Adminis- ^ Le Moal, "Campagne Antipaludique a Conakry en 1905." Ann. Hyg. et Mid. Colon., t. ix., 1906, pp. 550. Voir aussi du meme auteur : " Etude sur les Moustiques en Afrique Occidentale Fran9aise, Role Pathogene-Prophylaxie." Ibidem, 1906, pp. 181-219. 2 Bouffard, " Prophylaxie du Paludisme chez I'Europeen dans le Haut-Senegal et Niger." Bull. Soc. Path. Exot., t. ii., 1909, No. i, pp. 34-39. "Prophylaxie du Paludisme chez I'lndigene dans le Haut-Senegal et Niger." Jbidem, t. ii., 1909, No. 2, pp. 84-87. 52] INDOCHINA 495 tration peut agir efficacement en choisissant d'apres les regies de I'hygiene antipaludique remplacement des villages. Indochine. — Comme pour Madagascar, un decret autorise le Gouverneur - General a delivrer aux indigenes de la quinine p-ratuitement ou a tres bon marche. By H. C. ROSS, M.R.C.S., L.R.C.P. Director of the Royal Southern Hospital Researches, Liverpool Lately in the service of the Egyptian Public Health Department 53. Mosquito Reduction in Egrypt.— Before considering the history and details of the several campaigns started and in progress in Egypt, it w^ill be better to discuss briefly the local conditions which affect a sanitary measure of this nature. Egypt owes its very existence to the Nile. Were it not for that river Egyptian territory would merely be a part of the desert. Except on the Mediterranean Coast in the winter months, rainfall is a negligible quantity ; so that stagnant pools of rain-water like those found in the tropics are unknown. The only natural collections of water in the country are the Nile, the two Bitter Lakes through which the Suez Canal passes, a fresh -water lake — derived from the Nile — at the Oasis of the Fayoum, and two shallow sea-water lakes near the Mediterranean Coast. The Nile itself flows through Egypt without receiving a single tributary. Although the natural collections of water are so few, Egypt may be defined as a veritable marsh surrounded by desert. The marsh is, of course, confined to the narrow limits of the basin of the Nile, and the water is the most valuable asset of the country. Canals and irrigation channels are everywhere, and the native spends his existence baling the water either out of the Nile itself, or from the canals, or from wells, on to the soil itself In consequence, if there are few natural collec- tions of water, the country is riddled with puddles and artificial breeding-places for mosquitos. The peculiar cosmopolitan nature of the population must 496 Sect. 53] LOCAL CONDITIONS 497 be mentioned. The term " native " refers to the local subject, and it is used in contradistinction to the Europeans, many of whom, so far as their instincts regarding sanitation are con- cerned, are not very superior to the native. Almost every nationality finds a home in Egypt, and foreign countries do not appear always to send their best subjects when Egypt is singled out as a settlement for them. The native himself is fairly easily led, especially the lower classes ; but when he becomes educated, especially in Europe, he is inclined to form ideas for himself which are not always of the best ; and it is then frequently necessary to do more than to invite him to accept reforms. The upper classes of Europeans are similar to European colonists found elsewhere ; with this exception, that they take less patriotic interest in Egyptian affairs than they would if they were living in a colony of their own country. The low-class Europeans, the low-class Greeks or Italians, who form a large percentage of the population, are a very difficult community to deal with, and the Levantine may be regarded as being neither native nor low-class European. A brief consideration of the Government of Egypt and the laws in force regarding sanitation is necessary. The ostensible Government of Egypt is complex. Egypt is Turkish territory, ruled by His Highness, the Khedive. There is a Council of Ministers, and the interests of European subjects are safe- guarded by the Consuls-General and Consuls. Laws which affect natives can be passed by the Council, but important measures which affect Europeans have to be sanctioned by the country or countries concerned. The British Agent has under him several British officials who are supposed to act as advisers to the native ministers, but who, in reality and quite openly, have charge of the several Government Departments. He is practically the autocrat of the country. The only laws with which we are immediately concerned are those which govern sanitation, and they are few in number. 2 I 498 MOSQUITO REDUCTION IN EGYPT [Sect. The Government is under a difficulty with regard to them because, although they can be enforced with the native, the procedure with Europeans is more difficult owing to the " Capitulations." In the event of epidemics of certain specified diseases, such as plague, cholera, etc., stringent measures can be adopted with reference to native individuals and habitations. In the case of Europeans, however, it is necessary to invoke the co-operation of their Consuls, which involves delay. There is a sort of Factories Act which is applicable to natives and Europeans alike ; it necessitates the passing by the Government of the plans of new " unhealthy establishments," and it allows existing ones to be inspected. Unfortunately, this measure is very elaborate, not well suited to the conditions found in Egypt, and usually considered almost to be unworkable by the inadequate staff at the disposal of the Director-General of the Public Health Department. The native and Levantine are so cunning that they succeed frequently — and I speak from personal experience — in evading this law ; and the punish- ments, especially those given in the mixed courts to Europeans, are so lenient that it often pays the individual to ignore the law and suffer the small penalty. So far as sanitation is concerned, the Capitulations enjoin that no official may enter the house or property of a European subject unless he has obtained permission either from the subject himself or from his Consul. In considering all sanitary reforms this has to be taken into account ; the Consuls sometimes, though not often, are unwilling to assist, and officials in Egypt usually complain that the Capitulations obstruct their efforts. In fact, this has become a tradition, and if any new effort fails, the Capitulations are usually blamed. There can be no doubt that the measure is an obstacle, though not such a serious one as is made out, and to this point I shall again refer. Other questions will be mentioned in the description of the several campaigns, which will now be taken seriatim, in the order in which they were started. 53] ISMAILIA 499 Ismailia. — At the present day Ismailia is a sleepy little town picturesquely situated on the shores of Lake Timsah. De Lesseps intended it to be one of the greatest ports in the world. When the Suez Canal was opened, and the venture an assured success, it was determined to make Ismailia a model city, a thriving port, and the headquarters of the Suez Canal Company. With this end in view, the Company acquired the control of a large piece of land on the northern shore of Lake Timsah, a small sea-water lake through which the Canal passes, placed in the centre of the isthmus of Suez, There the offices of the Company were built, surrounded by the houses of its employees ; and the largest shareholder, the Khedive Ismail Pasha, built himself a magnificent palace. Villas were erected overlook- ing the Canal, and gardens were planned and parks marked out. All the ships in transit of the Canal stopped there, and passengers were to land, and cargo to Egypt was transshipped. Then there was boating, bathing free from sharks, shooting, and every inducement both for work and play. Ismailia, though young, was very healthy, being situated in the desert and isolated from other towns. It was completely under the con- trol of the Company, who spared no expense to make it a model town free from insanitary native huts or unsightly modern flats and hotels. The Government Offices of the district were situated there, with the Courts, and the town soon began to prosper. De Lesseps' intention was on the highroad to fulfilment when, owing to ignorance, a false step was made. The town was supplied with fresh water by a shallow canal which connected it with the Nile. The canal was built in 1877, and replaced the old system of transport of water by camel, which was in vogue during the early years of the Suez Canal construction. The water in this canal, which was deepened in 1882 to allow the passage of canal boats trading between Cairo and Ismailia, was laden with a rich silt from Abyssinia, and it was used to irrigate the desert and the marked-out parks and 500 MOSQUITO REDUCTION IN EGYPT fSECT. gardens, with the result that a veritable oasis was formed. Trees were planted, and the gardens grew apace under the influence of the irrigation. But the water was not properly- controlled, and much of it ran to waste, forming shallow marshes and ponds in and about the town. With the marshes came the mosquitos ; and with the mosquitos came the fever ; and with the fever came the — downfall. In the days of its salubrity, Ismailia had progressed very rapidly, rising to a population of 10,000 ; but when the fever appeared, all progress stopped and decadence took its place. Nearly 2,000 cases of malaria were treated every year, but probably many more occurred. Men, both Europeans and natives, were unable to work, children were always ill, the death-rate increased, while the birth-rate fell. Every one was down with fever, and trade was soon at a stand- still. The Government offices were closed and were ultimately moved to Port Said ; the tribunals were transferred to the neighbouring towns of Zagazig and Mansurah, and the Suez Canal Company were, in 1900, left to face the question whether the town should be abandoned, or whether the disease could be prevented. In 1877, when malaria first appeared in Ismailia, 300 cases occurred from August to December. The next year there were 400 cases ; and the annual sick-rate remained at about this figure until 1885. The disease then became worse, and in 1891 nearly 2,500 cases were recorded. Acting on the old assumption that the disease is caused by a miasm, the Canal Company made several efforts to combat it by partially draining the marshes, and probably these efforts prevented the epidemic reaching extreme dimensions. The discovery of the trans- mission of malaria by mosquitos was not completed until 1899. In 1902 the Company resolved to take further advice. They sent a medical officer to Italy to make enquiries about the anti-mosquito measures being conducted there, and then they invited my brother. Major Ross, to go to Ismailia to advise them. He arrived at the Suez Canal on 12th September 1902, 53] ISMAILIA 501 in company with Sir William MacGregor, the Governor of Lagos, who wished to study the malaria at Ismailia with him. The first measure to be recommended by Major Ross was the extermination of mosquitos, which was immediately put into effect, the Company bearing the entire expense. The main breeding-places for mosquitos were found to be shallow irrigation pools and puddles in the gardens and yards, where Anopheline larvae were taken. Each house has its cesspool, according to the general rule in Egypt, for there are no properly instituted sewerage arrangements in the country, and all sewage passes directly into the "fosse" under the house. The fresh-water canal, which brings drinking - water from the Nile and which passes through the town, does not harbour mosquitos. There the water is running, and fish are plentiful ; but a short distance away from the town a marsh was formed by leakage from the canal, and here larvae were found. Rigorous measures were adopted ; the marsh was drained and the pools were filled up. A mosquito brigade was formed, which consisted of a European foreman and two natives. Their duty was to visit every house once a week, and to treat the cesspools with petroleum. Irriga- tion canals and channels were cleared of reeds, and the water made to flow swiftly. When a certain garden had received its proper supply of water, the flow was stopped and the water allowed to soak in. All the work was systematic; each breeding-place was visited and treated on a certain day in each week, which was kept up throughout the year. Similarly, all water vessels, tubs, and flower vases were emptied. A penalty was imposed on the inhabitants if they did not report untreated collections of water to the authorities. No expense was spared to make the new sanitary measure a success. There is one difference between the Ismailia campaign and the others which must be mentioned. The Capitulations did not form an obstacle there. The laws at Ismailia were the same as those elsewhere, but the Canal Company made short work of the Capitulations, for practically all the inhabitants, whether 502 MOSQUITO REDUCTION IN EGYPT [Sect. European or native, were employees of, or dependent on the Company, and if they objected to the visits of the brigade, they could be either dismissed or have their salaries cut. Instituted by their President, Prince d'Arenberg, the Suez Canal Company can well be proud of the result of the anti- mosquito work at Ismailia. Last year not a single new case of malaria occurred there, and the disease has been stamped out. Ismailia affords a striking example of the great commercial importance of malaria prevention. When De Lesseps decided that the headquarters of the Canal should be at Ismailia, he, of course, did not appreciate the possibility of invasion by malaria, I believe that his decision was due to the presence of the large natural harbour afforded by Lake Timsah, where a fleet of ships could anchor to take in coal and provisions on their way through the Canal, without obstructing the transit of other ships. It is true that all coal has to be imported from Europe, but in spite of the fact that Ismailia is nearly 50 miles from the Mediterranean, the presence of the natural harbour there was so important, that the extra expense which would have to be incurred in bringing the coal through the 50 miles of canal was hardly taken into consideration. In fact it paid the Canal Company to insist on all coal being brought to Ismailia, because dues were obtained for its transit. Commercially, everything was in favour of Ismailia being made the headquarters of the Canal. The point is an interesting one, for De Lesseps' great commercial proposal was disposed of by malaria. For years the Company tried to force ships to coal and land passengers at the fever-stricken town, but now they have been compelled to relinquish the natural harbour, and to build an artificial one at Port Said (which requires, and always will require, incessant dredging) at an outlay of many millions. Even natural assets of enormous commercial value, such as this harbour in the greatest shipping highway of the world, fail utterly in the face of a comparatively small epidemic of malaria. The artificial harbour at Port Said has been built, and Ismailia has dwindled 53] ISMAILIA 503 into insignificance, at a cost which probably can never be estimated. The results of the anti-malaria work are well known. Accurate figures, showing the number of severe cases of malaria which had occurred before the mosquito work was started, had been kept, and these could be compared with those obtained afterwards. Every employee of the Company is obliged to go to a doctor when ill in order to obtain a certificate of absence, so that all cases were easily recorded. But there must have been a number of cases of early and slight fever, in which the malaria parasite would not be in evidence, and which would not necessitate the patient lying up ; and besides, there were those cases which occurred in persons who were not employed by the Company, and also many native women and children, who will not go to doctors. But the results which are given by Dr Pressat are very interesting. Years. Cases. Years. Cases. Years. Cases. 1877 300 1888 1,400 1899 1,545 1878 4CK) 1889 1,450 1900 2,284 1879 500 1890 1,900 1901 1,990 1880 4CX3 1891 2,590 1902 1,551 1881 450 1892 2,050 1903 214 1882 480 1893 1,750 1904 90 1883 550 1 1894 1,100 1905 37 1884 9CX3 1895 1,350 1906 No fresh cases. 1885 2,000 1896 1,150 1907 No fresh cases. 1886 2,300 i 1897 2,089 1908 No malaria contracted in Ismailia. 1887 1,800 ; 1898 1 1,545 And now, although cases of malaria are occasionally intro- duced into the town from the villages situated higher up the fresh-water canal, such as Mahsammah, Nefiche, and Tel el Kebir, yet the disease never spreads there because the Ano- phelines are absent, and there is no longer any necessity for taking quinine. The chief difficulty and source of expense at Ismailia was that of the initial control of the irrigation, and the drainage and S04 MOSQUITO REDUCTION IN EGYPT [Sect. filling up of the marshes which surrounded the town. And even now, in the autumn, mosquitos find their way there from marshes situated to the west above the town, there being no habitations between. These marshes would cost much to drain or fill — an unnecessary expense. The number of mosquitos in- troduced into the town from this source is so small that it may well be ignored, and there is but little chance of their becoming infected, as there are now no cases of fever in the town. The cost of the permanent works, including the filling up with sand and the drainage of the marshes, pools, and the control of the irrigation, was 50,000 francs (;^2,ooo). The annual cost of the regular work of clearing streams, ponds, and of keeping the gardens clear of mosquito larvae is 7,800 francs. And the oiling of the cesspools and the general work of the mosquito brigade is 10,500 francs. Of this sum, 5,300 francs are spent annually on oil, and 5,2CO francs on salaries and other incidental expenses. Thus the cost of the regular annual work is now i franc 90 centimes per head of population per year ; at first it was 2 francs 30 centimes. The total annual cost is now about ;i^i,ooo per year. And for this sum, after an original outlay of iJ^2,ooo, Ismailia is kept healthy and free from fever. But the work must always be kept up, though the cost of it will gradually decrease. As in Port Said, if the mosquito brigade stops work for a week, the mosquitos return. The men require constant supervision. M. Doyen, of the Suez Canal Company, is to be heartily congratulated on the way the work progresses, for the town continues free from malaria. But Ismailia has never recovered the blow that malaria dealt it, for natives now call it " El turba e'nadeefa " (the clean tomb). Port Said. — Port Said was a much more difficult problem than Ismailia. The town is larger, with a very cosmopolitan population of 50,000 inhabitants. It is built on a triangular spit of land bordered by the Mediterranean, the Suez Canal, and the shallow sea-water lake of Menzalah. The price of 53] PORT SAID 505 land is considerable, as the town cannot expand, with the result that high buildings containing residential flats are being erected everywhere. The soil consists of sand, and the subsoil water, which is really sea-water, can be found at a depth of about a metre. Port Said may be said to be built on a sand-bank. All the drainage from the houses passes into cesspools usually placed under the floor. Owing to the height of the subsoil water, these cesspools are frequently too small to be adequate, and overflow as a common result. They are con- tinually being emptied at great expense, which falls on the landlords, who are not too willing to carry out this duty. It may be imagined, therefore, that before the mosquito campaign was started, that is, before any proper systematic sanitary administration was instituted, Port Said was one of the most insanitary places. Many of the houses had basements, and the cesspools were bricked reservoirs built in among the rooms contained in them. When the cesspools became full, they frequently burst, and the sewage passed into the rooms which formed the basement. I have often seen shops and dwellings with only a wooden flooring separating the living rooms from the sewage, and more than occasionally one used to see persons living in a room with the sewage oozing up through the floor. Without exaggeration, one can say that a few years ago Port Said was famed for being one of the most disgusting " holes " on the face of the earth. Crime was rife, every one looked ill, and it was openly said that all the scoundrels in the world collected there. In fact, little more than ten years ago it was hardly safe to walk in the streets at night. The population is largely European, to a far greater proportion than in most other Egyptian cities ; and owing to the Capitulations, the Government police officials could not enter the European houses, and knew little of what was going on. But the filth and general insanitation were almost inde- scribable. Sewage used frequently to be seen trickling down the pavements from the overflowing cesspools, and puddles of 5o6 MOSQUITO REDUCTION IN EGYPT [Sect. faecal matter formed in the roads. Sometimes the stench was such that certain houses and corners were deliberately avoided by pedestrians. Mosquitos bred in the sewage and then bit the inhabitants. The authorities could do little or nothing owing to the Capitulations (so they said). Consuls would be approached by means of endless correspondence and red tape. Sometimes a little improvement was effected, but usually nothing was done. Fever was rife and mortality very high. It was dangerous then, as in Cairo now, to keep a European child in Port Said during the summer months. I have seen an infant's face so covered with mosquito bites, that I thought it was suffering from confluent small-pox. The whole place was a " sink of iniquity," a statement which, I think, will be confirmed by any person who passed through the Suez Canal a few years ago. But the mosquito campaign has changed all that. Practically speaking, the Capitulations have vanished. Sanitary inspectors, on the plea of mosquito destruction, now enter every house, and every dwelling-room if necessary, in the town. Everything is known and reported to the police should occasion require it. And the remarkable thing is that no one appreciates this reform more than the Europeans themselves, even the lowest class Levantine. Children are healthy, trade has increased, and crime and vice have been reduced to a minimum. In fact, Port Said now resembles a quiet seaside watering-place. The history of the reform — and it is well worth recording — is a remarkable one. Towards the end of 1905 my brother, E. H. Ross, then a surgeon in the British Navy, was appointed Medical Officer of Health to the town by Sir Horace Pinching, the Director-General of the Public Health Department. The new officer, appreciating the results obtained at Ismailia, owing to the advice of our brother, R. Ross, saw that similar measures would effect far greater results at Port Said. It was true that there was no epidemic of malaria as at Ismailia, but Anophelines had been found in many places, and malaria did undoubtedly occur. Cellia pharoensis and Anopheles ptaculi' 53] PORT SAID 507 pennis, both malaria-propagating mosquitos, were found breed- ing in puddles and cesspools. Moreover, the ubiquitous Culex fatigans and Stegomyia fasciata were a positive nuisance. Every one was bitten day and night. The cesspools were full of larvae. E. H. Ross reported as follows : — " In Port Said, only those who lived in the town before 1906 can realise the misery caused by this pest. Quite apart from the fever, the constant irritation of the mosquito bites, and the persistent manner with which the insects used to attack one, both during the day and night, nearly drove one mad. I have seen clerks in offices arranging mosquito-nets over their desks in the daytime, hanging them on to the gas brackets, and the native workmen in laundries covering their naked feet and legs in paper to prevent themselves being bitten. A certain amount of immunity against the irritation is produced in time, and certain individuals feel the effects of the venom less than others, but they are bitten for all that. Then the heat of the mosquito- net at night. Every time one moved in one's sleep, and threw off any bed-clothes that the heat would allow, one was liable to touch the net with a hand, arm or leg, and to be bitten through the net. And the persistent scratching and the dis- turbed sleep — these things have to be experienced to be realised. I have estimated that a mosquito-net makes a difference of three degrees Fahrenheit when there is any wind, for it keeps out any air that there is. How well I remember the many evenings sitting at the laboratory table, trying to dissect mosquitos, trying to investigate their interior economy, while they in their turn were doing their utmost to investigate me, nibbling my ankles, raising wheals on my wrists and neck, and making all work impossible. At all events I think that they had the best of the bargain. And then, how often in a fit of rage one has chased them with a fly-wisk, or stalked them with a candle, making oneself hot with the exertion of numberless futile attempts, until driven to bed and the refuge of the mosquito-net, hot and in a bad temper." It was clear that, in spite of the possibility of there not being very much malaria at Port Said, the general prevalence of mosquitos probably caused illness, and my brother grasped that an attempt at their destruction could only bring good results and might lead to the general cleaning up of the town. 5o8 MOSQUITO REDUCTION IN EGYPT [Sect. He therefore made enquiries as to how much fever there was which could be attributed to mosquitos. Formerly, a fever of mild type, which used to affect whole households and which lasted for two or three days, was common in Port Said ; some- times it was called dengue and sometimes influenza. Quinine was beneficial in some cases. Malaria did occur, a fact which was proved by Dr Cufifey, the Medical Officer of the English Hospital. Anophelines were sought for and found, but not in very great numbers, although they were breeding in many parts of the town. An examination of 480 children showed that 162 were suffering from anaemia and splenic enlargement, and, out of 136 children examined in the hospital wards, 10 were found with malarial cachexia. Dengue was also prevalent, and came in epidemics from other parts of Egypt. This disease is said to be conveyed by Culex fatigans, which is a very common mosquito throughout Egypt. Then there was the disease known as Simple Con- tinued Fever, which seems to infect schools and factories. Unfortunately, there were no reliable statistics. Diseases are supposed to be notified in Egypt, but doctors do not obey the regulation, which is not properly enforced. Natives do not usually consult doctors, and patients are frequently not seen until death. The Public Health Department thinks that a cursory examination of a dead body, with a rough speculation of the disease from which the person suffered, is sufficient to form an idea of the diseases prevalent in Egypt. Statistics are published, but they are quite worthless ; the only reliable data, therefore, are the number of registered deaths. In 1904 the number was 1,450; in 1905, 1,208 ; in 1906, 1,199; and in 1907, 1,412. The actual population was unknown, and although a census has been taken recently, it is not accurate. The absence of reliable figures is the most unsatisfactory part of anti- mosquito work in Egypt, except at Ismailia. As in subsequent campaigns, two steps were necessary at the outset : to estimate the cost and obtain the necessary funds, 53] PORT SAID ^6g and to arrange a scheme to overcome the Capitulations. To estimate the cost a house-to-house examination was made. At first it was decided to treat only the European quarter, which lies to the east of, and is distinct from, the native quarter. The European quarter was chosen because it contained more mosquitos ; and if the work there was successful it would be a good example to the natives who, especially the Mahomedans, are suspicious of innovations. Moreover, this was the first campaign in which the Capitulations formed a difficulty, and the starting of the campaign in the European quarter formed an experiment which demonstrated how effectually that difficulty could be overcome. I wish to lay stress upon this point, for the Capitulations in Egypt have defied the greatest administrators, yet a junior official in the Egyptian Public Health Department succeeded, by instituting the mosquito campaign at Port Said, in showing how easily this obstacle to reform can be overcome. My brother reports as follows : — "Beginning at the easternmost end, namely, at the street bordering the canal, every house and garden in the European quarter was visited seriatim. Street by street the examination was made, and the number of permanent water collections, such as cesspools, flooded cellars, fountains, water tubs, counted, with a note as to the number of square metres water surface they contained. The number of days required to make this examination from east to west and from north to south by one person was also noted, and then an allowance of half a litre of mixed equal parts of crude and refined petroleum allowed for each square metre of water surface per week. This gave the amount of oil required to destroy the mosquito larvae in all the water in the town every week, and the estimate was therefore multiplied by fifty-two, as the work has to be repeated every week during the year, some mosquitos breeding during the winter as well as during the summer months. Then by a simple calculation it was determined that it would require a gang of workmen, containing five men under the charge of a foreman, to apply the oil to all permanent collections of water in the European quarter every week ; and therefore one mosquito brigade would be required to get rid of the mosquitos in this part of the town. The price of oil in Port Said is as follows : — 5IO MOSQUITO REDUCTION IN EGYPT [Sect. crude oil in tins containing i8 litres (4 gallons) is 8 piastres per tin, and refined oil is 1 1 piastres per tin. To the cost of the amount of oil required per year, then, it was necessary to add the yearly wages of the five workmen at 6 piastres per day each (is. 3d.), and the foreman at L.E. 5 per month. The purchase of an oil barrel on wheels, five buckets, five half-litre tin measures, overalls for each workman, and allowing for small repairs to the equipment, etc., the estimate of the cost of the campaign in the European quarter was obtained per year. The estimate amounted to L.E. 800, but the actual cost for the first year was L.E. 719 (L.E. = about 21 shillings). " The estimate had been made and the money subscribed, and it remained only to obtain the necessary official permission to enter the houses of all foreign subjects from the various consuls, so that the work would not be hindered by the domicile clause of the Capitulations. In order to obtain this permission, we advertised in every direction, spoke to all influential persons and made people interested, and then when the Governor wrote officially to all the consuls, they unanimously consented to assist us in every way, and gave the sanitary authority of the town permission to enter the houses of their subjects for the purpose of ' disinfection and for killing mosquitos ' ; and each consul appointed a prominent member of his community, to whom any difficulty could be referred without officially disturbing the consulate concerned. We, on our part, undertook to supervise the work carefully, as the workmen had to enter every house once every week, and to take all reasonable precautions to ensure their honesty. And in this respect it is noteworthy that although the work has now been in progress without interruption for three years, there has not been a single charge of dishonesty upheld against the workmen, nor has there ever been occasion to appeal to the consular delegates. " The preliminaries had taken two months, but everything was ready for a start early in May 1906. Many good authorities had said that it would be found impossible to clear the town, or a portion of it, of the mosquitos which infested it ; even as they say that it will be impossible to clear Cairo to-day. But it was determined to try. A gang of five men were engaged. They were all natives of good character who lived in and had families in the town. A Greek foreman was found who could speak all the necessary languages, which include Arabic, English, French, Italian, Greek and Turkish. An iron barrel, capable of holding 300 litres, fitted to wheels to enable it to be pushed about the streets, was bought, and each workman was given a bucket, a half-litre measure, and a broom-stick, 53] PORT SAID 5" while the foreman was armed with a note-book. This was the equipment for the European quarter ; and the following routine was instituted. The quarter was subdivided into six equal portions, one for each week-day. Work begins every Monday morning at the Governor's house, and one member of the brigade visits every house allotted to him that day. Every house is numbered, and is placed in the charge of one work- man, who is responsible for the mosquitos, or the absence of them, in that house. On Tuesday morning at seven o'clock the brigade begins where it left off on the Monday evening ; and so on, until the whole of this part of the town is com- pleted by Saturday night at the Governor's house again. Thus every house in the quarter is visited by the same workmen at the same hour of the same day every week, and the tenants know when to expect him, and can complain to the foreman if he doesn't come regularly. Each workman fills his bucket with mixed crude and refined oil from the oil - cart in the street. When he arrives at the house allotted to him he asks the tenants if they have been annoyed by mosquitos during the week. If the answer is in the negative, he enters the house with their permission, and pours a small quantity of oil down each water-closet and sink. He mounts to the roof, where in Port Said the wash-houses are usually situated, and empties out all tubs and basins containing water. He examines the kitchens and servants' rooms in each flat, for any collection of water which they may contain. Householders are now quite used to this weekly visit, for the men are well known, and it serves to remind the tenants to see that the workman carries out his duties properly ; and at the same time they are advised to empty out all water in which mosquitos are likely to breed, as in flower-vases and in suchlike utensils. The workman then descends to the basement, where he examines carefully every cellar for any water or sewage, and he then opens the cesspool of the building and pours into it that amount of oil, allowing now, after three years, a quarter of a litre for each square metre of water surface it contains, as nearly as possible. The oil on the surface of the cesspool water is then well stirred with the broom-stick, so that it may spread everywhere evenly. Lastly, he visits the garden and examines the fountain and the water-taps, flower- pots, and the yard if there is one ; and then, when finished, he goes on to the next house allotted to him, repeating the process while refilling his bucket from the oil-cart in the street.^ ^ In Port Said, mosquitos do not breed in the drinking-water cisterns, as the filtered water contains no food for the larvae. We have therefore been able to ignore house cisterns. 512 MOSQUITO REDUCTION IN EGYPT [Sect. " But should the tenants complain of the presence of mosquitos, and the workman find that the cesspool is full, or that the cellars contain water, he at once informs the foreman, and they both begin a careful search for the mosquito larvae. The foreman reports at the Public Health Office every morning at noon, and details the presence of mosquitos, and whether the larvae have been found or not. He also reports on the sanitary condition of the streets dealt with, and the houses examined that day, and states whether any cesspool requires pumping out, or whether any cellar has water in it, in which case the proprietor of the house is dealt with by the Sanitary Inspector, and an extra foreman is sent down to find the mosquito larvae, when they cannot be found by the brigade. " Ultimately, when the mosquito larvae have been found — and they can always be discovered if carefully sought after, either in the house itself or on the premises — some are put into a bottle and examined. If there are any nymphs, it is known that the eggs have been laid for more than seven days, and therefore the workman responsible for the house has neglected to oil the water in which they were found, and he is punished. But more often it is found that the proprietor of the house is at fault, and the mosquitos have reappeared because he has neglected to have the cesspool pumped out ; and in con- sequence of its being full it has overflowed or has burst, and the sewage has collected in the cellars, and there the mosquitos were breeding. In this case the proprietor is written to and is warned to empty the cesspool without delay, or he will be sued and fined in the Courts ; for there is a law which enables us to do this. Every cesspool in the town has been fitted with a movable iron door, so that access can be obtained to its interior when desired. We persuaded the proprietors of all the houses to put these in, for we found that there are some cess- pools into the farthest corners of which the oil cannot reach when poured in through the water-closets and sinks, or even through the door. This is probably due to solid sewage float- ing on the surface of the water and preventing the oil spreading evenly. In such places the oil is well stirred with a broom- stick to make it reach all parts ; but if this fails also, then we have had recourse to the automatic oilers described in the Annals of Tropical Medicine for June 1907, and they have been most successful for the purpose, though even when these are in use the cesspools containing them must be carefully examined every week in case the oiler becomes clogged. This is recognised by the presence of male and female mosquitos in the cesspool after ten days have passed since the clogging. S3] PORT SAID 513 " This is the routine which has been followed ever since its institution in the European quarter, and which has been since copied exactly in the native quarter. It has undergone no modification, except that the amount of oil used weekly has now been reduced considerably. " The work in the European quarter was begun in the first week in May 1906, and by the end of July, the mosquitos in this part of the town were sensibly diminished. The summer was very hot and damp, but we were able to rest in the after- noons without being bitten by Stegomyia. By the end of August mosquitos had been reduced greatly ; and in many parts of the European quarter mosquito-nets were no longer required. But it was found that we were using an enormous amount of oil, nearly 3,000 gallons of equal parts crude and refined oil per month. This was because of the sewage in the cellars. It was therefore determined to try to reduce the amount of water in these cellars permanently, so as to economise the oil. There were then 400 cellars in the town flooded with sewage, having a total of 7,296 square metres water surface. " This condition of insanitation was due to the following peculiarity of the place. The subsoil water (sea-water) is only a metre below the ground-level, as the whole spit of sand, on which Port Said is built, is reclaimed from the sea. Owing to the small area reclaimed, the ground-rent is very high, and in consequence many large buildings, of often four and five and even six stories, have been erected, and divided into flats and suites of offices. These houses have been built with basement cellars. In every building the portion of the cellars situated under the main entrance hall has been shut off by brick walls from the cellars to form the cesspool, into which all the house drains discharge. These cesspools were supposed to be sealed except for a ventilating shaft, but were, in the majority of instances, badly built and leaky. The result was that the sewage was passing into the adjoining basement cellars as fast as it poured into the cesspool. Once in the cellars it did not rapidly soak into the sand forming their floor, as at that level the sand was already saturated with the subsoil water. So that we found when we began our campaign, that in the 400 large buildings the whole basement constituted the cesspools, and in them mosquitos, flies, cockroaches, and other insects were breeding in myriads. These cellars were also swarming with rats and were the cause of the perpetual smell of sewage which assailed one even in the street." Towards the end of 1906, people in the European quarter 2 K 514 MOSQUITO REDUCTION IN EGYPT [Sect. were beginning to discard their mosquito curtains and life was becoming more bearable, and, as was anticipated, the natives began to ask why their quarter was not treated also. In response to their request, therefore, a campaign was started in the native quarter in January 1907. A fresh brigade was formed, and the campaign was conducted on precisely similar lines to that in the European quarter. The results at Port Said have fully compensated for the cost of the undertaking. When I was in Port Said for several months in the spring of 1908, I never saw a single mosquito — a marvellous contrast to my experience in the same town ten years before. Mosquito curtains are never used now by the inhabitants, and no precautions whatever are required to be taken against being bitten.^ The following table gives the cost of the campaign, the Egyptian Pound being equivalent to about twenty-one shillings. Year. Amount of oil used. Total cost. 1906 European quarter only, May to December . , . 14,296 gallons. L.E. 384768 1907 European and native quarters for the whole year . . 41,120 gallons. L.E.i,i76"275 1908 Both quarters. 12 months. Cellars filled up . . 31,670 gallons. L.E.i,023'463 It will be noticed that the amount of oil used, and therefore the cost of the work, diminishes every year, and this should be expected. Should the present cesspool system of sewage dis- posal ever be replaced by drainage, the amount of oil required will become very small, and the size of the gangs could be reduced, for there would be less work to be done. But the cost of the campaign has been trifling compared with the beneficial results to the community. Everybody has been delighted with the results, fevers have declined, and the children have become healthy. The streets no longer smell as they did, and the place has improved in every way. The ^ In 1902 Sir W. MacGregor and I were " devoured alive " by Stegomyia in Port Said. During three visits in 1907 and 1908 I did not see a single mosquito. — K. Ross. 53] PORT SAID 515 absolute disappearance of mosquitos is a most remarkable thing, and is probably unique in history ; yet if the brigades become slack, the gnats reappear in a few days. The inhabitants now complain at once if mosquitos appear, and their breeding-places are then looked for. They will always be found in the im- mediate neighbourhood. But the general effect on the town is the most striking example of the efficacy of the sanitary measure. Officials of the Government enter every house unmolested ; they know all that is going on, and, in consequence, vice has been greatly reduced. Port Said is no longer a "sink of iniquity." The streets are safe ; there is less prostitution there than in any town in Egypt ; gambling dens have disappeared ; all is known in spite of the Capitulations. If a cesspool bursts or over- flows, the landlord has to remedy the defect, or he has to stand the abuse of his tenants owing to the return of the mosquitos. Moreover, he is promptly sued by the Government. The consuls themselves, far from obstructing, now assist the authorities in every way. It is right to mention that the Suez Canal Company, through its President, Prince d'Arenberg, have placed a large sum of money for the maintenance of this campaign at the disposal of the Egyptian Government. This campaign at Port Said is perhaps the most successful which has ever been started, and any one who is able to com- pare Port Said in the old days with the present state of affairs will, I am sure, eulogise the work which has been done. A great deal remains to be done, however ; but the mosquito campaign has paved the way for it, and has shown that with a little perseverance sanitary reform in Egypt is not nearly so difficult as is usually made out. There can be no question that drainage is the next thing required at Port Said. The present cesspool system is quite inadequate, and it should be replaced by proper sewerage as quickly as possible. A scheme has been drawn up and passed. 5i6 MOSQUITO REDUCTION IN EGYPT [Sect. 1 believe ; and I have heard that the Suez Canal Company have offered to advance the necessary funds for it. It is difficult to appreciate, therefore, why it has not been undertaken. The Egyptian Government itself appears to be doing very little for Port Said, but the least it might do is to accept the Canal Company's offer and drain the town. At present negotiations are on foot between the Government and the Company regard- ing the latter's concession, and I suppose that the health of Port Said has suffered for this delay. The drainage will be expensive, for it will have to be done on the artificial pumping system, there being no *' fall " at Port Said. Still, drainage there is almost more necessary than at Cairo. If the place were properly drained, the expenses attached to the mosquito campaign would be reduced almost to a negligible quantity. Cairo. — Cairo is a very much larger city than Port Said. It contains an estimated population of more than half a million, the European element being smaller than that of either Port Said or Alexandria. The town is situated on the east bank of the Nile, at the apex of the delta of the river. Facing Cairo, on the other side of the river, there is the town of Ghizeh, and between the two, on an island, there is the residential suburb of Ghezireh. Cairo proper can almost be divided into two portions — the native to the east and the European to the west — by the old canal, now filled in to form a tramway, called the Khalig. Suburbs extend to the north and south, but the city itself is compact, and, for its population, does not cover a very great area. Owing to the fact that the Govern- ment owns most of the surrounding land and will not part with it cheaply, the price of land is exorbitant, and in conse- quence there is great overcrowding, with the erection of high buildings containing residential flats (in this city, with its almost tropical climate). Cairo is infested with mosquitos. To destroy them through- out the city would be a stupendous, but not impossible, task, and it would involve an expenditure of about ^20,000 annually. 53] CAIRO 517 It is true that in the winter months the gnats are not so numerous, but in the summer and autumn the pest is as bad as in many tropical places. Like Port Said, Cairo is built on a lake of subsoil water. The Nile water, of course, is not confined between the banks of the river. In fact, the underground river is much larger than the Nile itself, and it flows directly beneath the city of Cairo. The height of the subsoil water, therefore, varies with the height of the Nile, and in the months of September and October, when the Nile at Cairo is in flood, it frequently happens that the basements of the houses are filled with water. Every house, native or European, has its cesspool, which leads directly into the subsoil water ; and for centuries past all the sewage of the city has passed directly into this under- ground lake and has saturated the soil all round. The cess- pools of the houses built by Europeans are called " percolating pits." They are commonly built immediately beneath the houses, and they vary in size according to the uses put to them. Their bases are deficient in bricks and are formed by the porous earth only. Every cesspool dips into the subsoil water, and bricks are removed from the walls in places to facilitate the percolation of the sewage into the surrounding earth. It can veritably be said that the land on which Cairo is built is sodden with sewage. Nearly all the pits are ventilated by short intake and long uptake shafts carried up to the roofs of the houses, and it is by means of these pipes that mosquitos gain access to the cesspools. A few of the more modern houses are fitted with "fosses morass," which are, in reality, modified liquefying tanks. Some of them are made on a fairly satisfactory basis, but usually they are pre- tences, and are nothing more than rather elaborate percolating pits. The native cesspool is, if possible, more insanitary. It consists of a long trough dug in the earth under the house. Stone flags form its roof, and one of these flags, having a hole 5i8 MOSQUITO REDUCTION IN EGYPT [Sect. in it, is used as the closet. No water flushing arrangement is employed, and fluid soon soaks into the earth. For this reason mosquitos do not breed so readily in the native as in the European cesspools, and consequently they are not so numerous in the native as in the European quarter of the city. Both classes of cesspool have to be pumped out from time to time, and conservancy carts form an important, if not an ornamental, portion of the Cairo traffic. The pumping out process is an expensive item for the landlord, and is a lucrative business conducted, not by the Government, but by private enterprise. On the plea of expense landlords frequently neglect to cause the cesspools to be emptied until the last moment. At present there are no drains. For the last three years the Government has made a special drainage department for the construction of sewerage. I have heard that the plans of the scheme have already been passed. In the meantime, when the soil is turned up in any part of the town for the purpose of making the foundations of new buildings, the stench is usually indescribable, for the subsoil water is soon reached, and that water is practically sewage. Moreover, these excava- tions form fruitful breeding-places for mosquitos. The water-supply of Cairo is derived from shallow wells placed below the town, a source which has given rise to con- siderable controversy. In the native quarters, almost every house has its own well, which is bored close beside the porous cesspool. The water in the well is that which has usually percolated in from the neighbouring cesspit. The natives prefer this or the Nile water, which, of course, is polluted, to that supplied from the wells at Rod el Farag. When cholera broke out some years ago, many of the wells were filled up, but they have nearly all been reopened. In all the cesspools, wells and other collections of water which riddle the city, mosquitos, cockroaches, and all sorts of vermin thrive. The human mortality is enormous, especially the infantile mortality. The figures supplied by the Public Health Department are 53] CAIRO 519 unreliable (as I know, for I have assisted to compile some of them). The actual population is unknown, many deaths are probably never reported, and sickness is not usually notified. All deaths are supposed to be registered, the diagnosis usually being made by a brief inspection of the dead body. Doctors will not notify disease, because they say that it ruins their practice. Landlords prefer to knock holes in the sides of their cesspools and allow the sewage to flood their cellars and basements rather than go to the expense of having them pumped out. The water-supply is not the best obtainable, the streets are not properly cleaned, and enormous heaps of dung and rubbish have been allowed to accumulate for years past on the outskirts of the city. Many of the streets are not metalled ; which perhaps is a good thing, for the rough surface acts as a sponge for the stale urine which would otherwise collect in puddles. Dung and street refuse are used as fuel generally ; and large collections of this rubbish are kept for this purpose on the roofs of the " Turkish Baths." Nearly all the dogs have been destroyed owing to outbreaks of rabies, and mangy cats have taken their place as natural scavengers. Hordes of flies, which breed in the dung and rubbish, abound everywhere, and are nearly as great a nuisance as the mosquitos. Without exaggeration, Cairo may be described as a city which is hardly fit for habitation, and at present it must rank with Moscow, Pekin and Hankow as being one of the most insanitary spots in the world. Since the mosquito campaign. Port Said is a health resort compared with it. The common mosquitos found are Culexfatigafis, Stegomyia fasdata, and a species of Anopheline called Cellia pharoensis. They breed in the cesspools, wells and ornamental fountains. The natives love fountains, and their houses always contain large numbers of water vessels of all sorts and sizes. Fevers are undoubtedly rife. Typhoid broke out in one or more of the principal hotels each season when I was in Cairo ; for it must be remembered that Cairo is a favourite 520 MOSQUITO REDUCTION IN EGYPT [Sect. resort in the winter. The typhoid is probably propagated by the vegetables, which are usually washed in old canals, or even cesspools, by the natives when they bring them into the town. Some years ago a scheme was made to prevent this washing, which is done to make the vegetables glisten and look fresh for the market ; but the Government would not adopt it. Dengue, which is probably propagated by Culex fatigans, occurs in epidemic form every year. Malaria exists in Cairo, but it is only of the mild tertian and quartern types. Following on some questions which were asked in the House of Commons last year, a controversy arose in the Press in Egypt regarding the incidence of the disease. One paper said that it did not exist. But it does. Only last summer an outbreak occurred at Ghezireh, and according to the Statistical Report of the Public Health Department for 1908, twenty-nine deaths occurred in Cairo alone from the disease. The Senior Medical Officer of the Egyptian Army reported an outbreak at Zeitoun and Abbassieh (suburbs of Cairo) on 3rd November 1907 (Letter No. 411). I have myself seen cases of malaria, and have taken Anophelines frequently, especially at Ghezireh. Probably the incidence of the disease is far greater than is commonly supposed. Several other diseases, such as Simple Continued Fever, are confounded with it. Elephantiasis, also conveyed by Culicines, is a common complaint, and victims are frequently seen begging in the streets. A real estimate of the incidence of malaria has never been made. Last year a small spleen census was taken among some children, but the result was vitiated by the discovery of a disease, provisionally called " Endemic Cirrhosis of the Liver," which occurs among them. Still, malaria exists, and other fevers too ; which is sufficient ground for the institution of a campaign, apart from the other great sanitary benefits conferred by these undertakings. At one of the campaigns, also, that at the Police School, figures have been obtained, 53] CAIRO 521 which I shall quote later, and they demonstrate amply the beneficial results which would accrue from general mosquito reduction. Cairo is visited annually by thousands of English and American tourists, who live in palatial hotels, and who cannot realise the real state of affairs. From a superficial visit, Cairo is a most picturesque city ; but let them go off the beaten tracks into the depths of Boulac, Saida Zenab, and Bab el Sharia, districts which visitors do not often see, and they will then appreciate the insanitary precipice whose brink they visit. The first mosquito campaign in Cairo was started by a few English residents in the district of Kasr el Dubarra in 1904 or 1905. Only a few houses were treated (by the residents themselves), and although a reduction in the number of mosquitos resulted, the campaign soon lapsed owing to the fact that many of the breeding -places were overlooked. In the meantime. Sir Horace Pinching, K.C.M.G., Director- General of the Egyptian Public Health Department, who was very pleased with the work of my brother, E. H. Ross, at Port Said, gave me an appointment as probationer in that Service, for which I abandoned the Medical Service of the British Navy — in the hope of having better opportunities for scientific and sanitary work. In the autumn of 1906, His Excellency Mansfield Pacha, then the Commandant of the Cairo City Police, suggested to me that an experimental campaign should be instituted privately in the Muski district near the police headquarters. Most of the necessary funds were provided by the police, and Mansfield Pacha used his influence to get subscriptions from the other residents whose property was to be treated. The campaign included the build- ing of the Mixed Tribunals, the Opera House and the Esbekieh Gardens. This campaign is an interesting one, for the whole area involved was very small, about half a square mile of densely-populated buildings situated right in the heart of the city, where the houses were, if possible, more infested by 522 MOSQUITO REDUCTION IN EGYPT [Sect. mosquitos than elsewhere. The result was remarkable, for in three months the mosquitos had practically disappeared from the area treated, whereas all round they remained as bad as ever. Every cesspool was oiled once a week with a mixture of refined and crude petroleum in equal parts. All water vessels were overturned and dried out. In the Opera House the audience could watch the performance in comfort owing to the mosquito campaign, whereas if any one crossed the street to one of the uncampaigned houses, he would be pestered by hundreds of insects. This campaign proved the point that mosquitos will not migrate far from their original breeding - places. We received no opposition whatever from the inhabitants, in spite of the fact that the majority of them were Europeans, and incidentally hasheesh and gambling dens were discovered and reported to the police. Early in 1907 a new campaign was started in Kasr el Dubarra by myself under the orders of Sir H. Pinching. This district is bordered by the Nile and contains the best residential houses in Cairo, including the British Agency. It is right to mention that this campaign was restarted largely at the instigation of Lady Cromer, who suggested that it might be instituted on scientific lines by a responsible official ; not by private enterprise, like the first attempt in 1904. Sir Horace Pinching ordered the funds to be provided after a rough estimate of the cost had been prepared. The next step was to obtain permission from the residents themselves to allow us to enter their houses. It was considered preferable to obtain permission from individuals rather than from their consuls, because at that time some of the consuls in Cairo were not on very friendly terms with the Government. Letters printed in several languages were sent to the residents, and a large number were soon answered giving permission. The European residents never appeared to object when they appreciated that they would have nothing to pay — a point which was clearly stated in the printed letters. Curiously 53] KASR EL DUBARRA 523 enough, the only persons who objected were the natives who had no right to refuse. We could, of course, have entered the houses of the local subjects without their permission, but E^ypt is governed by a diplomatic administration rather than by a scientific one, and it seemed more diplomatic to treat both native and European alike. The objectors were called upon and the campaign explained to them. Lady Cromer came to the rescue, and was indefatigable in calling and seeing personally many of those who refused to allow us to enter their houses, and allaying their suspicions. By the end of January the campaign was in full swing, the brigade consisting of a European foreman and two native labourers. In about three months, when the mosquitos ought to have been reappearing owing to the return of the hot weather, the residents noticed that their houses remained practically free, in spite of the fact that the pest was assuming its usual pro- portions in the other uncampaigned parts of the city. One by one the objectors asked that the campaign might be instituted in their houses, for they began to realise the benefit of it. For instance, one of the gentlemen who objected to the campaign at the outset was a native prince. His palace, therefore, was not entered. After a few months his neighbours began to complain that the mosquitos from his house annoyed them ; and he, on entering their houses, remarked on the reduction of the number of gnats. Suddenly a polite letter was received asking for a visit from the brigade, and the letter was followed by a visit from the objector himself, who implored us to destroy his mosquitos. From instances such as this we learnt that it is better to ignore objections to the visits of a brigade rather than to endeavour to persuade people. Let the campaign be continued in the houses of others ; after a short time I think that it will be found that all objections will disappear. The following October, when the mosquitos ought to have been at their worst, Kasr el Dubarra enjoyed comparative 524 MOSQUITO REDUCTION IN EGYPT [Sect. immunity from them, and at the Semiramis Hotel, which is in the district, visitors and tourists could sleep without mosquito curtains, the only place of this nature in Cairo where this has ever been done. At the beginning of 1907, on the initiative of Sir H. Pinching and Major Elgood, a small campaign was also started by me in the Police School at Cairo. This school contained about five hundred students, recruits for the Police Force in Egypt, and it was established in an old palace in the Abdin quarter of the city. The palace is a very large building sur- rounded by a garden. It is built on the native plan in the shape of a quadrangle with a large courtyard in the centre. It was infested with mosquitos, from which the students suffered greatly. The ceiling of the school hospital, which formed part of the building, used to be black with the gnats, a sight I have never seen before. Like many of these native palaces, there were more than seventy latrines, all of the native pattern, which communicated with large cesspools under the building. These cesspools were not ventilated, and the only access to them was through the closets themselves which led directly into them. In the garden there were the inevitable fountains, and a sort of pond which was used for irrigation purposes. Oil used to be poured down most of the latrines ; others were sealed up. The pond and fountains were emptied. The number of mosquitos was greatly reduced in a very short time, and before I left Cairo a year later, they had practically disappeared. Major Elgood, the Commandant of the school, then kindly undertook to supervise this campaign, and when, at a later date, the school was moved to new buildings at Abbassieh, a fresh campaign has been started there by him with most successful results. The year before this campaign was started, 26 to 27^ of ^he. personnel were admitted to hospital suffering from various forms of fever, including dengue and simple continued fever (probably some were cases of malaria). After the campaign had been in progress for some time, the 53] HELUAN 525 fever showed a decline, thus — June 1908 to June 1909, the incidence of fever fell to 7"2%. The average number of the personnel is about five hundred. In a paper describing this campaign/ Major Elgood gives the following figures : — Year 1907-1908, eighty-eight cases of dengue occurred. During the year 1908- 1909, when the campaign was in progress, the number of cases fell to six. In March 1907 a campaign was started at Heluan by myself under the orders of Sir H. Pinching. The initial procedure was similar to that adopted at Kasr el Dubarra. Heluan is a town built in the desert about 15 miles to the south of Cairo. It is famed as a health resort owing to its hot sulphur springs and dry, invigorating climate. There are many hotels and sanatoria, and the town itself is a growing one considerably larger than Ismailia. The reason why Sir H. Pinching ordered the campaign to be started at Heluan was because malaria existed there. Anophelines had been taken, and examination of blood-films taken at random from native children demon- strated benign parasites ; an examination which had been made sometime previously by Dr Dreyer of the Public Health Department. A new brigade was formed, and all the water collections and cesspools were treated with petroleum. Mosquitos were found to be breeding in some pools of sulphur water, which had collected in some places owing to overflow from the sulphur wells. It seems that after this water has been allowed to stand for some time, the sulphur precipitates, and the larvae of mosquitos (including these of Cellia pJiaroensis) will then thrive in it. An attempt was made to drain this surplus water, which will be an expensive undertaking. In the meantime, as much of it as possible was oiled. Heluan was famed almost as much for its mosquitos as it ^ "Some Account of the Preventive Measures taken "against Mosquitos at the Police School, Cairo," by Major 1*. G. Elgood. Cairo Scientific Journal^ No. 34, vol. iii., and Brit. Med. Journ., i6th Oct. 1909. 526 MOSQUITO REDUCTION IN EGYPT [Sect. was for its sulphur baths ; even in the winter months one was being bitten night and day. Nearly all the gardens have fountains, but unlike the houses in Cairo, the cesspools are usually to be found in the garden or courtyard. Stegomyia breed freely in the fountains, which were therefore stocked with fish. Some householders objected to oil being poured into the fountains because it is unsightly, and it was found that a common variety of Nile fish ( Tilapia nilotica) is very hardy and will keep small collections of water free from larvae. The cesspools are constructed very deeply in Heluan, as the subsoil water, especially in the east and north of the town, can only be found at a considerable depth. There are not many water- closets, and the result is that some of the cesspools are dry except in " pockets " which have formed in the earth. To reach these " pockets " with oil, it was frequently necessary to send a man down into the cesspool itself. In this case a rule was made that a lighted candle was previously lowered to test for the presence of poisonous gases — an important precaution against accident. The results of the campaigns in Cairo and Heluan may be summed up together, for in every case it was practically the same. The number of mosquitos began to diminish perceptibly in about three months ; and in Heluan, in six months, people were sleeping without mosquito curtains. Even those people who were inclined to doubt the possibility of ridding districts of Cairo of mosquitos, had to admit that the destruction of the pest is not only a possible, but really an easy problem. In September 1907 Dr Dreyer again examined blood-films from some children in Heluan, and found that very few parasites could now be demonstrated. No cases of dengue occurred there during the autumn of the same year, although an epidemic of the disease was in progress in other parts of Egypt, Apart from the prevention of disease, however, mosquito campaigns are valuable measures to be adopted in a country like Egypt, for they bring the officials who organise them more 53] RESULT 527 in touch with the inhabitants, who, consisting largely of natives, are inclined to mistrust those set above them. Mosquito brigades are constantly visiting the houses, and when the inhabitants appreciate that something is really being done for them, they take an interest in the work, and ultimately further this and other sanitary reforms. When I left Egypt in January 1908 there was no one who objected to the visits of the mosquito brigades, nor were there any complaints that any member of them had abused the privileges conferred on European subjects by the Capitulations. In fact, the Capitulations put little real difficulty in the way of sanitary reform. Europeans and their consuls are fully alive to the possibilities of scientific measures properly carried out ; and if Europeans and even natives are assured that efforts to improve sanitation are made con- scientiously, I believe that they will forego, as has been proved by the mosquito campaigns, the one privilege which they prize, namely, an immunity against interference by Government officials. The difficulty caused by the domicile clause of the Capitulations, which is used as a cloak for nearly all adminis- trative sins, vanishes in the face of a mosquito campaign. The experience gained in Cairo and Heluan proves conclusively that mosquito destruction is a desirable measure to be adopted in Egypt, and it is remarkable that this fact was not appreciated before. Unfortunately, Sir Horace Pinching, who had been so sympathetic towards this work, retired in the autumn of 1907 from his post of Director-General of the Department. His successor immediately told me that he did not consider it necessary for me to continue the work, and he treated me in such a manner that I was obliged to resign my appointment in the Department. At the same time my brother, E, H. Ross, was also threatened in my presence with dismissal. It will therefore be understood that since these events the Government has become lethargic about anti-mosquito measures. 1 have heard that mosquitos have returned in the parts campaigned 528 MOSQUITO REDUCTION IN EGYPT [Sect. in Cairo ; and at Heluan, and even Port Said, the pest is reappearing. I have seen frequent complaints in the Egyptain newspapers that the campaigns have been allowed to fail, and I fear that for the time being mosquito destruction has fallen into disrepute in Egypt. From my experience of the Public Health Department, I think that the Government does not appear to appreciate its responsibility regarding sanitary administration. A visit to Cairo will show that nearly all improvements are made by private enterprise. When a new town is started, such as Heliopolis Oasis, it is started by a company. The most modern buildings in the city itself, erected for the public, have been built by His Highness, the Khedive, on his own private property. Yet the Government owns nearly all the vacant land round the city, and it refuses to part with it. The result is that the city is becoming overcrowded, with an enormous death-rate. Calculated on the 1907 census, the death-rate of Cairo was, for 1908, 39"23 per 1,000, and for 1909, 44*9 per 1,000. In an article published in the British Medical Journal on loth April 1 910, which describes the state of the sanitation of Cairo, it is stated that 28*2% of the infants born in Cairo die during the first year of life ; and 48'5%, or nearly half, of the children born will, if the present death-rate continues, die before they reach the age of sixteen years. When I was in Cairo, in certain districts in the Saida Zenab quarter, known as El Mardi and El Sakkia, Government properties, the death-rate reached 20^, and yet the Government will not allow the city to expand, and appears to await a rise in the value of the property before it will part with it. My personal opinion is that the fault is due to the fact that the country is governed almost by amateurs. The sanitary officers are not bound to obtain Public Health Diplomas, and it seems to me that many of the higher Government offices are placed in the hands of friends and relatives of existing officials, apparently without regard as to qualification. I have shown that the laws are difficult to enforce. There is no building 53] REMARKS 529 law whatever ; anybody can build any hovel he pleases. Few reports are published from the Public Health Department, and officials under the present regime are not permitted to print the results of their work for the benefit of their successors. Mosquito extermination, however, is bound to be undertaken seriously in Egypt under more competent management. For the time being, perhaps, it will remain in abeyance, but it is a measure which is so certain in its results and so far-reaching in the good which it does, that before long, I think, it will be generally demanded by the public. It is nauseating to live in Cairo in the summer and to be bitten persistently by insects which breed in excrement. Mosquito destruction is an un- pleasant though a simple problem. It must be continued unremittingly, or the gnats will return ; but the cost of the campaign will fall to a certain extent after the initial destruction of the pest. I hope that the work will be started throughout Cairo, for I know that the results will be greater than were ever anticipated. By ANDREW BALFOUR, M.D, B.Sc, F.R.C.P. Edin., D.P.H. Camb. Director, Wellcome Research Laboratories, Gordon College, and Medical Officer of Health, Khartoum 54. The Campaign at Khartoum. — In the pre - Dervish days Khartoum must have been a hot-bed of mosquito Hfe. This is apparent from the evidence of Sir Rudolph Baron von Slatin, who states that mosquitos were very prevalent during this period, and from that of Father Ohrwalder of the Austrian Mission, who asserts that he was sometimes driven to go and stand up to his neck in the Nile in order to avoid the attentions of the winged hordes. That malaria was also present cannot be doubted. Schweinfurth speaks of the unhealthiness of the place in a manner which leaves little doubt but that one of the chief causes of the high mortality which obtained at certain periods was malarial fever. It is believed that its evil reputa- tion was one of the reasons which induced the Mahdi to abandon its site altogether, and, with that empirical wisdom which often characterises the native, to found Omdurman on a spot where the river banks are not bold and terraced but shelving, and consequently free from pools at low Nile. Some four years after the new city had come into being, a survey of the conditions as regards mosquito prevalence was made. This disclosed the fact that three genera, represented by three species, were constantly present, namely, in order of frequency, Culex fatigans, Stegoniyia calopus and Pyretophorus costalis. Malaria was found to exist, and it was shown that infection could be acquired locally, while numerous cases were always being brought into the town by steamers coming from the highly malarious regions to the south. It was towards the close of 530 Sfxt. 54] BREEDING-PLACES 531 1903 that anti-mosquito measures were instituted and a small mosquito brigade established. These measures have continued in force ever since, and the brigade has been constantly employed ; for one of the chief points elucidated by the work is the absolute necessity for its continuity. In a place like Khartoum it is essential to carry out preventive measures year in and year out, and two mottoes most suitable for those in charge might well be " Weary not in well-doing," and " Do not put overmuch trust in the native inspector." In this brief note we are only concerned with the single species of Anopheline which constitutes itself a danger to the town, and may omit any detailed account of the work in connection with the two other species of Culicid mentioned ; but it is well to point out that in practice these latter cannot be neglected. Mosquito prevention measures must be general, and it is very often the operations against Culex or Stegomyia which lead to the discovery of invasion or threatened invasion by Pyretophorus. P. costalis, then, is the malaria carrier of the Northern Sudan, and so far as Khartoum is concerned its breeding-places were found to consist of: — (i) Pools left by the falling Blue Nile. These are found for the most part in the sand-banks which appear in the river's bed, but may also occur in the sloping and terraced banks as the river falls. (2) Garden tanks. (3) Bath-waste pits. (4) Permanent garden pools, (5) Sakia pits, as used in irrigation work. (6) Irrigation channels and pools formed by leaking " gudwals," as the large and small canals are termed. The only large area of irrigated land is at Khartoum North. (7) Wells. (8) Rain-water collections. 532 THE CAMPAIGN AT KHARTOUM [Sect. (9) Household water collections, such as water stored in barrels. These are not at all common. (10) Water collections on steamers, provided these be exposed to the light, i.e., in boiler trays, cisterns, etc. (11) Chance water collections, as in old barges and leaky boats where speedy water evaporation is prevented. One or two of these breeding-places merit a few words of explanation. The soil in some parts is what is termed "weep- ing." It contains a large quantity of salt. Hence if gudwals are constructed of this soil the water dissolves out the salts, and leakages soon result, pools form, and, despite the fact that the water is brackish, P. costalis readily lays her eggs in such collections. This mosquito is very rarely found in wells, but its larvae have once been encountered in a well 70 feet in depth. This is so peculiar that one wonders if they had not been accidentally introduced. Rain-water collections are rare in Khartoum, but occasionally the summer is compara- tively wet, and then pools and puddles may persist for some time. They are not commonly utilised as breeding - places by P. costalis. This Anopheline is not often found breeding out on the river steamers, but has been known to do so, and may be introduced into Khartoum as imagines both by steamers and by native boats. Recently a species of Nyssorhynchus has been apparently introduced in this manner. It is worth noting that since operations were started cases of malaria locally acquired in Khartoum have never once occurred with- out the presence of Anophelines in or near the town being demonstrated. The chief methods of prevention and reduction put in force may be tabulated as follows : — (i) Systematic inspection. (2) Notification of cases of malaria. (3) The issue of warning notices and distribution of information. (4) Petrolage. 54] DETAILS OF MOSQUITO REDUCTION 533 (5) Filling in of pools and abolition of water collections such as garden tanks, bath-waste pits, etc. Also the screening of cisterns. (6) The introduction of fish into water channels. (7) The piping and covering of raised water channels to prevent leakage through their banks. (8) The imposition of fines. (9) General legislation as regards borrow pits, irrigation, engineering work, and the provision and maintenance of dry zones. All three forms of malaria used to occur in Khartoum. Benign tertian was the most common, malignant next, while quartan was rather infrequently encountered, though it has been found to be much commoner than was at first supposed. Quite a large number of cases harbouring crescents annually come into the town from the Upper Nile and the Bahr-el- Ghazal Province. Some of these measures call for a little further notice. The inspection must be thorough and the native inspector must be controlled by trained and reliable British sanitary inspectors. The town is divided into sections, each of which is in charge of a native who has no sooner completed his round than he begins again. In this way, if he does his work properly the inspector should visit every house and every water collection in his district at least once a week. The British inspectors are responsible for the whole town, and often combine mosquito work with house-to-house inspection. Areas bordering on the river, the point of danger, are in charge of the most experi- enced men, and a special native inspector is detailed for steamer and boat work. Khartoum has a population of some 16,000; Khartoum North, of about 25,000; and there are in all at the present time three British sanitary inspectors^ and seven native inspectors. Of these one British and two native inspectors are responsible for Khartoum North, where with ^ Mosquito prevention is, of course, only a part, though an important one, of the work of these inspectors. 534 THE CAMPAIGN AT KHARTOUM [Sect. the exception of some pools on a sandy island there are no river pools, the banks being high and steep, and, where there are scarcely any gardens, the only dangerous area, so far as P. costalis is concerned, being a large stretch of irrigated land and certain small irrigation channels which are apt to leak and form pools. The dockyard is situated at Khartoum North, and the steamers require constant attention, but more for Culex and Stegomyia than for Pyretophorus. When necessary, extra men are employed filling in river pools ; and if these happen, as at present, to exist in sand-banks opposite the so-called British Barracks, the services of the British troops tenanting these latter are at once solicited, and never in vain. Notification has proved of great value. It stimulates enquiry and has often led to the discovery of breeding-places when such would otherwise have been missed. Here are types of the warning notices inserted at intervals in the local press, especially during the winter when the Nile is falling, and again during the brief rainy season in August and September. SANITARY NOTICES "The attention of householders and others is again called to the necessity of properly emptying and drying out zeers and other vessels holding water at least once a week, in order to prevent mosquitos find- ing breeding-places. Persons pro- ceeding on leave are especially requested to see that this is done before premises are left vacant. Any one found harbouring mosquito larvae or pupae on his premises is liable to be punished in accordance with Town Regulations ; and in future stringent action will be taken to put an end to this nuisance and danger to health. It is not enough to instruct servants to carry out these measures. There must be personal supervision. Five minutes per week is no great tax on the time of any one." " Householders are urgently re- quested to give immediate notice to the Sanitary Inspector at the Mudiria if they find themselves troubled by mosquitos or note their presence. Any one found harbour- ing larvae or pupae on his premises is liable to be fined ; and stringent action will be taken, as malaria- carrying species are at present endeavouring to obtain a footing in the town." 54] ANTI-LARVAL MEASURES ON STEAMERS 535 The regulations as regards steamers are of practical interest and are also given below. When carefully followed the results have been excellent. " I. Before leaving Khartoum the bilge water in the various sections should be oiled by pouring petroleum on the surface of the water and stirring well with a stick. A film will then form on the surface, which prevents access of air to the mosquito larvae and pupae, and so kills them. Eggs deposited by mosquitos on this oil film will not develop, and many of the females themselves will be killed. Roughly, about one half-pint of oil should be devoted to each section. A little experience soon shows how much or how little oil is needed to form a proper film. In addition, the water in the trays under the boilers should be examined, and, if necessary, oiled. " A cup or wide-mouthed bottle can be used for collecting water for examination. The vessel should be quickly but gently dipped under the surface and lifted out without spilling any of the contents. For somewhat inaccessible places a tin with its bottom replaced by wire-gauze mesh and attached to a stick is useful. The larvae are then found wriggling on the gauze. Such a collecting dish is easily made and answers well. It should be examined in a good light. It is to be remembered that any standing water collections will harbour mosquito larvae, and attention should therefore be paid to the water-closet cisterns, zeers and tanks. " 2. During the voyage, opportunity should be taken to re- oil the bilges wherever possible. This should especially be the case before starting on the return journey. Wood holds are usually at fault. The difficulty can be got over by empty- ing these in rotation, so that the water in the hold can be got at and oiled once in every fortnight. Special attention should be directed to zeers when these are used for storing bottles of drink. All zeers should be emptied out at least once a week during the voyage. " 3. The thing to be avoided is returning to Khartoum with mosquitos on board. If this is done, wells and water collections in the town which have been cleared at trouble and expense are liable to become reinfected. This has happened repeatedly, so that it is very important that steamers should arrive clean and free. It is well to have all bilge water emptied on arrival, and all steamers lying up should be inspected and treated in the manner described. Similar precautions are required as regards barges, sandals, launches and any vessel on which there is stagnant water. 536 THE CAMPAIGN AT KHARTOUM [Sect. "Note. — It has been proved that mosquitos, as a rule, will not stay for any length of time on a steamer if they are prevented from breeding out on board. Consequently, such preventive methods are effective, as has been demonstrated on several occasions ; and there is no excuse, in most instances, for steamers reaching Khartoum with their bilge water, etc., full of larvae and pupae, and their cabins full of adult mosquitos. " Sometimes it has been found advisable to employ sulphur squibs when there were many adult insects in the holds." A little space may be devoted to the introduction of fish which has been successfully employed in the irrigation channels at Khartoum North and, as will be seen, elsewhere in the Sudan. A zealous and interested official some time ago suggested the introduction of the small " millions '" fish {Girardinus poecil- loides) from Barbados to cope with larvae in swamps, irrigation channels, large pools and like collections of water. The question was referred to me, and I found myself opposed to the idea, partly because I know the difficulty of transporting these fish, and the possibility that they might not take kindly to new surroundings, and partly because, like the proud Syrian of old, I was tempted to reply : " Are not Abana and Pharpar, rivers of Damascus, better than all the waters of Israel ? " In other words, one was of opinion that there was no use going outside for what might very well be obtained at home. I knew that Captain Flower, Director of the Zoological Gardens at Ghizeh, employed young " Bulti " {Tilapia niloticd) in the tanks of the aquarium at Ghezireh, and found them most efficient in keeping the water free from mosquito larvae, and it was reason- able to suppose that many Nile fish were effective, especially as it is found that when fish are present in any pool left by the falling river, mosquitos do not breed out therein. There were two points, however, requiring attention. If any water collection is stocked with fish, these latter are apt to be speedily cleared out by natives or birds, such as king-fishers, which are very plentiful. Moreover, as is explained later, fish 54] LARVIVOROUS FISH 537 which attain any size are not suitable for use on irrigated land. Hence, it was desirable to find a small and greedy fish which would offer no temptation to the native, which could be used in irrigation channels, and which, though not immune from the depredations of fish-loving birds, yet was so prolific, or could be used in such numbers, as to make these ravages of little account. The type of fish desired was that known in India as the Chilwa {Chula argentea), which is said to be more efficient than " millions," as not only does it devour the larvae but, being a surface-feeder and an eager fly-taker, it is deadly to the adult mosquito, especially to the female intent on egg- laying. As Mr Harold King, our entomologist, was going up the White Nile in the Floating Laboratory on a voyage of discovery, I asked him to take every opportunity of studying the question. Mr King is an excellent field-naturalist, and admirably fitted to carry out such an investigation. His report, which I append, will be found of interest and value, and it would appear that in Cyprinodon dispar we have obtained the fish we require. This, as Mr King remarks, remains to be proved, but the following letter, kindly sent me by the Acting Manager, Sudan Plantations Syndicate, in whose irrigation channels the fish are being tested, is at least promising : — "Dear Sir, — In reply to your favour of the 19th inst. I have examined the small canal into which the fish have been introduced. " The canal is about thirty metres long and about half a metre deep, and the opening to the larger canal is closed with gauze- wire netting to keep other fish out. Although the still water is now lying twenty-five days there are no signs of mosquito larvae. " The fish are alive and seem to feed on flies on the surface of the water, and are most active in the early morning. — Yours faithfully, Alex. MacIntyre." Like Mr King, I ha\'e fed Ophiocephalus obscurus {vide infra) on the larvae of Pyretophorus costalis, and noted how the 538 THE CAMPAIGN AT KHARTOUM [SecT. latter were devoured before ever they reached the bottom of the jar. The following is Mr King's report : — "While on the White Nile, between the dates of 17th April and 19th July, I carried out some investigations with Nile fish with a view to ascertaining what species, if any, were likely to be of value in controlling mosquitos by feeding on their larvae. In most of the swamps, where mosquito larvae abounded, shoals of small fish of various species also occurred, but from the fact that the two throve together it was evident that the fish were not likely to be of very much use. Numbers of these fish were captured, placed in jars and offered mosquito larvae, but with one exception they refused them until they had passed one or more days without food. The exception was a fish found in a khor between Gebel Ahmed Aga and the river. In this khor very few mosquito larvae could be found — a search of nearly two hours resulted in less than a dozen specimens being taken — but there were present numbers of the young fry which has been identified by Mr G. Boulenger of the British Museum as Ophiocephalus obsairus. " This fish feeds greedily on mosquito larvae, thrives well in captivity and in stagnant water, and appears to be an ideal fish for the purpose for which it is wanted, except in one respect, viz., size. When full grown it attains a length of 35 centimetres. As fry, inhabiting shallow waters such as are found in swamps and river-spills, this fish would no doubt prove of value, for it is in just such places that mosquitos breed. On the other hand, though the fish would flourish in large irriga- tion canals, and the fry could reach the smaller gudwals on irrigated land, the latter are frequently so constructed that the young fish on increasing in size could not regain the parent canals and would perish. Hence this species of fish is not likely to be an economical means of dealing with mosquito larvae in such situations. " Some thirty specimens of 0. obscurus are still living in a jar in the Laboratories. " During May, I met Mr Butler, superintendent of game preservation, who told me of a small fish — Cyprinodon dispar — which lives in Khor Arbat, about twenty-two miles from Port Sudan. He very kindly furnished me with some notes on its habits, and recommended that it should be given a trial as it appeared to him to be likely to give good results. He further said that, while no mosquitos are noticeable in the vicinity of 54] LARVIVOROUS FISH 539 that khor, they are plentiful near other similar khors where C. dispar does not exist. " Accordingly, on 6th September, I left for Khor Arbat and, having spent three days there, returned to Khartoum on 12th September. There were myriads of the fish in the khor, but at first I had considerable difficulty in persuading them to live in captivity. Eventually, I found that while, if placed in jars nearly full of water, most of them died within twelve hours, yet if given only about two inches of water over a layer of sand they could be transported fairly easily. One hundred and one living specimens reached Khartoum, and were there offered mosquito larvae, which they took readily. This, however, is not conclusive proof that C. dispar feeds on mosquito larvae in its wild state, as the specimens had been unfed for two days when the larvae were given them, none being obtainable at Khor Arbat. " As these fish did not thrive in jars I wrote to Mr Maclntyre, Acting Manager of the estate at Zeidab, belonging to the Sudan Plantations Syndicate Ltd., asking him if he would allow them to be placed in a gudwal on the Company's estate for purposes of experiment. This he readily agreed to ; so that on 19th September I took those that were still alive — about seventy in number — to Zeidab, and the following morning liberated them in a short length of gudwal which Mr Maclntyre very kindly had filled with water. This gudwal is not used, at present, for agricultural purposes, and the pipe connecting it with the canal has been netted to prevent other fish gaining access. This was done in order that the C. dispar might be given every chance of establishing themselves before being subjected to the possible ravages of other and larger fish. " The specimens liberated at Zeidab were all immature, as it was found that partially-grown fish withstood captivity better than did adults. " When full grown, C. dispar attains a length of 8 centimetres, and in all stages appears to prefer shallow water. " Should the gudwal in which these fish were liberated remain free from mosquito larvae during the coming year, while similar gudwals in the immediate vicinity serve as breeding-places for these pests, I think sufficient proof of their value will have been obtained to justify an effort being made on a larger scale to establish C. dispar throughout all the gudwals on the Sudan Plantations Syndicate Ltd.'s estate, and on other similar farms where great difficulty is experienced in controlling mosquitos." As regards legislation the following irrigation rules, imposed 540 THE CAMPAIGN AT KHARTOUM [Sect. on all who take up land with a view to cultivation on a large scale, may be quoted with advantage. They are of very great importance both from the sanitar}' and the economic standpoint. " I. Irrigation channels should be constructed on a higher level than the surrounding land, so that when the flow of water in them ceases they may drain dry. "2. They should be constructed of such material and in such a manner as to prevent leakage. " 3. Their banks and beds should be kept in good repair, and the beds even, to prevent the formation of pools. "4. 'Dead ends' of irrigation channels should be reduced to the smallest size compatible with efficiency, so that water will not stagnate in them. " 5. Vegetation should be periodically cleared out of the channels. " 6. Sluices should be constructed so that there is no leakage to form stagnant puddles. " 7. Where possible, fish should be introduced, and kept in the main channels to destroy the larvae. " 8. Lands where water is apt to stand should have proper surface drainage. " 9. Crops, such as sugar-cane, rice and others which require to stand in water, should not be grown within half a mile of any town or village. " 10. If an engine or pump should happen to break down, particular care should be taken to deal with stagnant pools, and petroleum should be used when necessary. "II. Cases of malarial fever, and any prevalence of mosquitos, should be notified to the governor of the provinces by the manager of the concession." The above is a brief outline of the measures adopted and the work accomplished. What has been the result? It is difficult to give comparative statistics, as we do not know how much malaria used to be locally acquired in Khartoum ; but we do know that P. costalis used to be fairly common, especially at certain times of the year ; while now it is wholly absent during many months, and if it does invade the town its breeding operations are usually quickly checked, it does not multiply, and soon disappears. As a direct consequence locally acquired malaria has become very rare. One cannot 54] RESULTS 541 wholly trust the notifications, but they afford considerable indication of how matters stand, and, so far as Egyptian and British troops are concerned, are trustworthy. Here, then, are the locally acquired cases for the past few years. Year Civil Egyptian British population, military troops Oct. to Sept. About 3,000 men (One battalion) inclusive. most of them about 600 men very susceptible changed annually, to infection. 1904-05 Seven cases in all. Not stated according to population attacked. Unsatisfactory notification. 1905-06 2(?) ? 8 1906-07 441 1907-08 210 1908-09 142 1909-10 2 ... 4 (to date) (i6th January 1910) It is very rare for a British official or European resident to acquire malaria in Khartoum itself, while I should say that owing to increased trade and communication more cases are now imported than was previously the case. There can be no doubt that if operations were suspended Khartoum would speedily regain, if not its old evil notoriety, at least a certain measure of the same. At the time of writing there is a good deal of malaria in the neighbourhood of the town, i.e., in villages a couple of miles to the north, in one part of Omdurman, and at various places along the White Nile. Anophelines now, as previously, are endeavouring to obtain a footing in the town, and have been blown into it by the wind or brought into it by boats. As a result, we have had a few cases, mostly in British soldiers who were wont to wander out to the east of their quarters towards a part of the river where there are extensive sand-banks and many pools, some 2\ miles from the centre of the city. Had operations not been in force I am very certain that this year would have witnessed an epidemic ; for conditions seem specially favourable to the propagation of P. costalis at present, and, as stated, there is much malaria 542 THE CAMPAIGN AT KHARTOUM [Sect. 54 in the neighbourhood. A measure which has had good effects is to put any dangerous area out of bounds for British troops. One may conclude by stating that Khartoum is a favour- able place for carrying Professor Ross's methods into effect ; and that they have met with marked success, and doubtless will continue to do so, provided the work is carried out con- tinually, thoroughly, consistently and with intelligence, that the influence of immigration is borne in mind, and that legisla- tion provides for the control of irrigation and the regulation of irrigated areas. By Dr L. BOSTOCK District Surgeon, Komatipoort, Transvaal 55. Malaria in South Africa. — British South Africa as a whole does not suffer much from malaria. Along the east coast, in Portuguese East Africa, Swaziland and Zululand, the disease is common enough, and occasional outbreaks occur in a few parts of the Cape Colony and Natal. A recent outbreak in Durban assumed serious proportions. In the Transvaal the disease is endemic in the Low Veldt, in the east and north of the country ; and the type is severe, bilious, remittent and haemoglobinuric forms being common. Owing to paucity of population in these districts the disease attracted little attention until the building of the Pretoria-Delagoa Bay railway line, when the heavy death-rate forced the disease upon the public notice. No effort was, however, made to combat the disease until I was appointed District Surgeon here, and com- menced to make representations to Government on the sub- ject in 1903. The work was started in 1904, and immediately its results were obvious in a greatly reduced sick-rate. The Railways thereupon instructed me to make a fever survey of the main line and the Barberton branch, and to make recom- mendations for each station. I obtained the assistance of the Government Entomologist, the late Mr C. B. Simpson, for this survey, and our recommendations, being promptly carried out, resulted in a considerable reduction of fever along the line. 543 544 MALARIA IN SOUTH AFRICA [Sect. Every station and ganger's cottage from Komatipoort to Waterval Onder was dealt with, local measures for mosquito reduction carried out, and all railway quarters in the Low Veldt made mosquito-proof We were compelled to rely chiefly on the latter method of fever prevention, owing to the small number of persons concerned, and the great amount of work necessary to deal with the breeding-places along the Crocodile River, which runs parallel to the line. All small breeding- places in the immediate neighbourhood of the stations were dealt with. To the Central South African Railway belongs the credit of first efforts to combat malaria in the Transvaal, and since 1905 the apathy of the public and the authorities has been gradually overcome. The results obtained by the Central South African Railway proved a powerful argument, and now the value of anti-malarial measures is fully recognised by private residents and the different Government departments who have officials in this part of the Transvaal. Practically every private resident in this town has now a mosquito-proof bedroom ; and in the country many farmers have also adopted this precaution. Mosquito-proof quarters are being provided for all police posts in the Low Veldt, and also for the officials of the Government Game Reserve, which lies north of the Crocodile River. The Colonial Secretary's Department have now arranged to issue free quinine in all fever districts in the Transvaal to all indigent whites and all natives ; the Barberton municipality have lately taken up the subject ; and a League has been founded for the purpose of carrying on the anti-malarial campaign throughout the district. Anti- malaria methods employed at Komatipoort. — Anti- malarial work was commenced at Komatipoort in 1904, the cost being borne by the Central South African Railways. The town is rather unfortunately situated, in the angle between the Crocodile and the Komati Rivers. Along both rivers are fe-,> -^ I. AN EXCELLENT TVl'E OF MOSQUITO-I'KOOK HOL'SE AS lUILT HY THE TRANSVAAL GOVERNMENT. The residence of Major Hamilton, Warden of the Sabi Government Game Reserve. \'ie\vs of front and iiack of house. A SHOOTING CAMP ON THE LOW" VELDT. Portable folding mosquito-proof beds. 2. AN EXAMPLE OF ROUGH BUT EFITCIENT MOSQUITO PKOOFLNG IN THE VELDT. A hut at Sabi Bridge, Game Reserve. Transvaal, fornierl}- occupied by the Warden, Major Hamilton. AN AFRICAN " RONDHAVliL," AS MOSQUITO-PKOOF SLKEPING-QUAKTF.RS. 3. AN l.\(.l-.MiH .1 lUKA. A military block house, Ijought as it stood after the war, converted by addition of door and \vindo.\s into a very comfortable niosiiuito-proof bedroom. TWO-ROn.\rF.I1 WOOD AXn iron- house with MOSQUITO-I'ROOF vf.raxda. As built by the C.S.A.R. for temporary quarters at the Sabi Uridj^e, Selali Railway. Cost about ;/,i8o. 4. A GOOD EXAMl'l.E UF .MoSQUFro-l'Kool HuL'SF. The Customs quarters, Komatipoort. ^fb^'"^ 5. JOINT OFFICKS OF THE WlTWATEKSKANl) XATIVK LAIiOUK ASSOCIATION, AND THE PORTUGUESE DEPARTMENT OF EMIGRATION AT RESSAXE GARCIA, PORTUGUESE EAST AFRICA. Natives receiving their passes tiirough tlie sliding window in the netting. (The tear is in the photo film, not in the netting.) 55] KOMATIPOORT 545 backwaters, pools and inlets, with dense vegetation in parts, and below the junction lie some acres of broken, rocky ground holding innumerable small pools. The worst breeding-place of Anophelines, however, was a swamp running parallel to the railway and opposite the station. The swamp was fed by a small spring and surface drainage, and by the waste water from the pump and engine sheds. It consisted of about two acres of ground only, but the whole of it was a network of small pools amongst thick reeds and rank vegetation. Anopheline mosquitos were breeding here in great abundance, and it was decided to obliterate this swamp entirely. A brick and cement drain was cut through the centre to carry off the water supply which maintained it. The ground was cleared, all pools filled in, and the surface evenly graded from each side down to the drain to carry off the rainfall. The reclaimed ground was planted with banana trees and eucalyptus, and absorption of water by these has sufficed to keep the area perfectly dry, and the former swamp is now, on a small scale, a town plantation. Efficient treatment of the main rivers was im- possible on the score of expense ; but the portions of them within half a mile of the town were dealt with by filling in some pools by rubble and cement, and, a mosquito gang having been organised, larger pools were treated with paraffin. These methods proved in practice to be most satisfactory. Only partial reduction of mosquitos had been attempted, but it was subsequently found most difficult to discover any specimens of Anophelines within the town area. At the same time all railway servants' quarters were made mosquito-proof, and the reduction of fever cases was marked and immediate. The following table is taken from a report on the subject made to the General Manager of the Central South African Railway in December 1905. 2 M 546 MALARIA IN SOUTH AFRICA [Sect. 1903 1904 1905 212 396 55 230 341 42 277 405 43 281 320 33 207 192 60 40 20 175 61 10 209 80 63 3S 4 18 191 41 28 217 20 25 9 8 (to 7th Dec.) Cases of malarial fever among Central South African Railway employees — Komatipoort — Kaapmuiden section : — January . February March April May June July August September October . November December The above figures are gross details, and represent each case counted for every day of illness, that is, they are " days lost " by the whole of the railway staff. The actual daily average of the number of sick during March 1905 is i"38, against a similar average for the same month in 1904 of i3"o6. The work of proofing the quarters was begun in June 1904. Portuguese East Africa. — With the exception of the town and district of Lourenco Marques nothing has been undertaken, but the Portuguese authorities have taken up the subject with great energy in the town of Lourenco Marques, with the result that the town, once extremely unhealthy, is now comparatively free of the disease. The Municipal Health Officer, Dr Amaral Leal, has con- trolled the work, while the Government Entomologist, Mr C. W. Howard, has carried out an investigation of the local mosquito problem. Their methods have been the draining of a swamp, which was the chief breeding-ground ; organisation of anti - malarial sanitary measures ; appointment of special sanitary inspectors, with power to inspect all houses and com- pounds, and to enforce the carrying out of their instructions ; the treatment of all breeding - places ; and the netting of Government offices and quarters.^ ^ In speaking of anti-malarial measures in Louren9o Marques, I should like to put on record the great service rendered on this subject by A. W. Bayly, Esq. , the 55] SOUTH AFRICAN MOSQUITOS 547 All offices and quarters on the Portuguese railway between Komatipoort and Lourenco Marques are now mosquito-proof. Mosquitos. — The following is a list of the mosquitos which are prevalent in this Colony. The larger number of them were collected at Nelspruit in the season of 1904- 1905. Anophelina. Nyssorhynchus pretorietisis. Pyretophorus cincrcus. Myzorhynchus mauritianus. Do. nianhalli. Do. maculipalpis. Do. costalis. CULICINA. Culex bostocki. Culex transvaleiisis. Culex sitnpsoni. Culex 7nmuius. Culex theileri. Culex bifoliata. Culex hirsutipalpis. Culex salisbrunensis. Culex fatigans. Stegomyia fasciata. Culex tigripes. Stegomyia simpsoni. In addition to these there are a dozen other species of rare genera, which as far as we know as yet are of but little or no economic importance. In the early part of the season the commonest Anopheles mosquito at Nelspruit is P. cinereus, and later in the season N. mmirilianus and N. maculipalpis. The former is much more abundant than the latter, especially in March and April, It seems that the abundance of these last two mosquitos is quite parallel with the abundance of fever. While all of these may carry fever, the two latter are, in our opinion, the most important agents of transmission. Stegomyia fasciata is by far the most abundant mosquito in the Low Veldt. It is followed by C. simpsoni, C. hirsutipalpis, and S. simpsoni in order of abundance. — From Bostock and Simpson [1905]. I have obtained from Mr Howard, the Chief of the Ento- mological Section of the Agricultural Department, Lourenco Marques, the attached report on the Anophelines for the Province of Mozambique. proprietor and editor of the Lourenco Marques Guardian. He was among the first householders in the town to make his house mosquito-proof, and has spared no trouble to extend a knowledge of the subject by constant references to it in his paper. 548 MALARIA IN SOUTH AFRICA [Sect. 55 Report by C. W. HOWARD, Esq., B.A., F.E.S. Chief of the Entomological Section, Department of Agriculture for Mozambique Distribution of Anophelines in Mozambique In my collections in Lourengo Marques District, Gazaland, and about the Zambesia, I have taken several Anophelines. The commonest is Pyretophorus costalis. It seems to be distributed all along the coast, and is without doubt the principal carrier of malaria. I have always found it wherever I found people suffering from malaria. It is very abundant in the flats about Lourenco Marques, breeding even in the brackish marches along the shores of the bay. Careful notes were made of this mosquito last season, and it was found that its increase and decrease almost exactly coincided with the rise and fall of malaria cases in town. They seem to hibernate over the dry season, in such places as grass huts and stables, although, if favourable places exist, they ma}'- breed throughout the year in sheltered localities. This, how- ever, seems to be the exception. The same mosquito is also very abundant along the Zambesia and about Quelimane. Another Anopheline fairly common on the coast is Alyzor- hynchus niauritianus. I have taken this on the Limpopo and Maputo rivers, but not about Lourenco Marques. It frequents houses in company with P. costalis, but not in such large numbers. NyssorJiynchiis pretoriensis also occurs along the coast. My specimens seem to have been taken from Lourenco Marques District. An apparently new species of Anopheles also occurs here, and is now being named by Mr Knab of Washington. Of mosquitos other than Anophelines our commonest species along the coast are : — Stegomyia calopus Mey., our com- monestmosquitonexttoCy^^//^a«J^ Scutomyia sugens Wied. Stegomyia sitnpsoni Theob. Culex luteolateralis Theob. Culex univittatus Theob. Grabhainia durbanensis Theob. Culex transvaalensis Theob. Taeniorhynchus aurites Theob. Matisonia uniformis Theob. Culex theileri Theob. Culex fatigans Wied. Common everywhere. Culex thalassius Theob. Eretmapodites n. sp. Heptaphlebomyia simplex Theob. By p. MURISON, M.D., B.Sc, D.P.H. Medical Officer of Health, Durban 56. Epidemic of Malaria in Durban, 1905-1907. — Malaria broke out in Durban during January 1905, and the number of cases rapidly increased until the cooler autumn weather set in. The following table shows the monthly notifications : — Summer. Autumn. Winter. January. February. March. April. May. June. July. 12 85 612 1,084 1,877 497 135 Some parts of Zululand are so unhealthy from the presence of malaria that they are uninhabitable. In Durban, malaria has been a compulsorily notifiable infectious disease since 1902, and as a result an average of seventy cases were notified per annum, as existing in the borough. All these cases were found on enquiry to have contracted the disease elsewhere, and had come to Durban to recuperate. No definite information, either from professional or lay persons, can be obtained to show that malaria had ever existed as a local infection within the borough of Durban previous to 1905. Within a fortnight of the 1905 outbreak every medical man in Durban had recognised many cases. The borough of Durban consists somewhat roughly of a triangle, one side being bounded by the Indian Ocean, another by the waters of Durban Bay, and the base is formed by a range of low hills, in extent about 6 miles, which stretches from one end of the borough to the other. From the base of these hills to the water's edge there is a plain, being about 549 550 EPIDEMIC OF MALARIA IN DURBAN [Sect. i^ miles in greatest width, and probably averaging about 15 feet above high-water mark. All classes of houses are to be found on this plain. Chiefly along the base of these hills, this flat area is at its lowest level, and contains many swampy areas, some of quite small size, others extending to scores of acres. The slope of the hills (Berea) extend to, roughly, about a mile from the plain to their summit, and on this gradual rising ground have been erected dwellings of all classes. The notifications received during the first few months distinctly localised malaria into many areas, and these were found to be always in close proximity to swampy or water- logged lands. When malaria broke out, I decided to rigidly follow the teachings of Professor Ronald Ross, and this has been adhered to throughout. It was recognised from the beginning that in order to cope with the disease both temporary and permanent measures were necessary. The permanent improvements were to consist of such work as (i) The drainage of surface and water-logged and swampy areas. The cutting of new watercourses and the extension of old ones. (2) The filling in of swampy areas, pools, etc., and the levelling and grading of land to enable stormwater to flow towards some drain or watercourse. Such measures naturally removed for all time the pools and swamps necessary for the larvae stage of mosquito development. Since 1905 the borough has expended on this class of work approximately ^80,000. The temporary measures consisted of the formation of a mosquito brigade, whose work was to consist of dealing immediately with all pools or areas of swampy lands which were the habitat of mosquito larvae by means of larvicides such as paraffin and disinfectants. We discovered that the crudest and cheapest disinfectants 56] MEASURES ADOPTED 551 were the best for larvae destruction, and we used disinfectants where pools were shallow, or where reeds existed in considerable numbers. We found it not only cheaper but more efficient to use disinfectant under such circumstances. One part of disinfectant to five thousand parts of estimated water in the pool was found to be effectual. Paraffin was used where pools were deep, and where an unbroken film could be formed. Many substances were tried as larvicides, and some mechanical ingenuity was shown by those in charge of the work in endeavouring to improve the process of application of the larvicides. As permanent improvements are carried out, the area of temporary measures was naturally reduced, and it may be stated that the only part of the borough of Durban requiring any temporary measures now is practically confined to that part known as the Eastern Vlei. It was also recognised that the education of the inhabitants of the borough regarding the natural history of malaria was a necessary auxiliary aid in the work of prevention. We believed that a much more whole - hearted assistance would be more readily obtained if some facts regarding the disease were freely spread about so that the rationale of the work and the orders required to be carried out by householders were more clearly understood and appreciated. Hand - bills dealing with malaria prevention were left at all houses in which cases of malaria had been notified to exist, and in some areas these hand-bills were left at every house. Lectures and magic lantern demonstrations were given by me to societies, institu- tions, schools, etc. ; and I feel sure these lectures and demonstra- tions were a potent agent for good in our campaign. The mosquito brigade consisted of two Europeans and about fifty Indians. Every swampy part where larvae could breed out being treated every ten days or thereby, so as to render their development impossible. Present position. — In 1907 the number of freshly - infected 552 EPIDEMIC OF MALARIA IN DURBAN [Sect. cases were very few in number. From a circular issued to all the medical practitioners of Durban (for we had stopped compulsory notification of the disease owing to the excessive cost in 1906), the total number of cases would probably be less than a hundred. At the same time, immediately outside the borough, every household, European and coloured, was down with the disease, and the deaths amongst Indians in particular were enormous. This, in my opinion, was a brilliant object lesson as to the efficiency of the preventive measures employed within the borough. Durban can be invaded from the neighbouring country from both ends, the swampy lands here being continuous. On the reverse slope from Durban of the Berea hills the descent to the Umgeni Valley is fairly steep. This valley was saturated with malaria in 1907, but no invasion of the borough took place from this direction. The hill (500 feet) seems to act as an effectual barrier. At each end of the ridge, however, where invasion did occur, an area or zone was formed, in which permanent and temporary measures were carried out as efficiently and quickly as possible. Fresh cases which occurred in the borough in that year were almost wholly confined to these areas. Government recog- nised the necessity for dealing with the excessive sickness and mortality in the area lying in contiguity to our borough, and started an anti-malarial movement towards the end of the season, but too late to be of any practical benefit for that year. In Durban during 1908 permanent improvements were still carried out and temporary measures maintained. No cases occurred within the borough. Outside the borough, where the disease had been rampant the previous year, and where no preventive measures of any kind were being taken, no fresh cases of malaria occurred. The disease seemed to have suddenly left Durban County. The measures which have been carried out in Durban in order to exterminate malaria have added very much to the comfort of life, as well as to the salubrity of the town. Water 56] RESULTS 553 tanks and cisterns which were an adjunct of every house, although rendered quite unnecessary owing to the bountiful supply of water introduced into Durban, were still retained in position full of water, probably more through apathy than anything else. These were all ordered to be removed by the Sanitary Department. These tanks did not form breeding- places for Anopheles^ but Culex developed in them in great numbers. With the vigilance which is still being maintained, Durban may be said to be at present practically free from mosquitos of any kind. In fact, the presence of a few mosquitos in a house is at once communicated to the Sanitary Department in order that the nuisance may be abated. Contrasted with the existing state of matters five years ago, I can only describe it as marvellous, and no people ought to be more grateful to Professor Ross of Liverpool than the inhabitants of Durban, both for the practical benefits resulting from his brilliant researches into the etiology of malaria, and for the effectual preventive measures he so simply enunciated, and which have been demonstrated and proved in this borough. By MALCOLM WATSON, M.D., D.P.H. Chief Medical Officer Estate Hospitals Association Late Senior District Surgeon, Federated Malay States Medical Service Abstract by R. Ross 51. The Prevention of Malaria in the Federated Malay States. — The contribution to this book sent by Dr Watson contains a full and vivid description of his enthusiastic, large and successful campaign, carried out during the last nine years. Unfortunately, it is too long for insertion here ; but owing to the interest of Sir Frank Swettenham, G.C.M.G., and a number of Rubber Companies, it will shortly be published as a separate book. I will here attempt to give only a brief abstract. The campaign was conducted chiefly in the State of Selangor. The climate is warm and humid; the mean rainfall is 80'4 inches; and the country was originally covered with thick jungle, and belonged to a number of independent states. Owing, how- ever, to the efforts of Sir Frank Swettenham, these states were amalgamated into a Federation, since when there has been much progress in the country. By reason of its products and its good Government, it is now a comparatively wealthy and prosperous one. The history of malaria prevention in it dates from 1901, and is concerned {a) with prevention in the towns, and {b) with prevention in the district. (i). Towns. — The two principal towns are Klang and Port Swettenham. In 1901, Klang, situated on the river of that name, contained 3,576 inhabitants, occupying 293 houses. The area of the town was about 290 acres, of which 22 acres were swamps, 25 acres virgin jungle, and 80 acres dense secondary growth, 30 to 40 feet high. Owing to the humidity mosquitos 554 Sect. 57] PORT SWETTENHAM 555 bred in vast numbers all the }-ear round. During that year the author says that the outbreak of malaria reached terrible proportions. Nearly every one was attacked, and many died. The whole population was demoralised, and when, in November, the death-rate rose to the equivalent of an annual death-rate of 300 per mille, the Chinese suspended business. In the mean- time, however, Watson resolved to make a determined stand against the disease, and after consideration decided to adopt my proposals for mosquito reduction. In this he was warmly supported by Dr E. A. O. Travers, State Surgeon, by the Government, the Sanitary Board, and the people. The requisite money was voted ; the marshes were rapidly drained, chiefly by contour drains which cut off the inflow. The author says, " I must confess that I by no means expected the success which as a fact followed the works. I had the feeling that perhaps a 20 or 30% reduction might be obtained in the hospital returns . . . indeed I was prepared for a total failure of the works. ... I record these feelings that they may encourage others who may be disinclined by the apparent magnitude of the task from attempting to combat this disease." The success was, however, complete and lasting. Port Swettenham is situated on the river five miles from Klang. It was founded in 1895 in order to provide a port for ocean-going steamers. The country was covered with low- lying mangrove swamp frequently flooded by the sea. There were few inhabitants and few cases of malaria, but Watson observed that new arrivals quickly became affected. The place was practically a mangrove swamp in which about 15 acres had been cleared. On the 15th September 1901, the port was formally opened and the Government population and coolies connected with the shipping were transferred to it. Immediately afterwards " malaria assumed an epidemic character. In less than a month the 180 loading coolies were so decimated by disease that the remainder refused to live any longer at the port and returned to Klang." Freshly-imported coolies deserted. 556 PREVENTION OF MALARIA IN MALAY STATES [Sect. Out of 176 Government servants, 118 were attacked between the loth September and 31st December. Ships came in and could not discharge their cargoes. The outbreak was so bad that the High Commissioner ordered the closure of the port until it could be made more sanitary. In the meantime Watson had recommended measures similar to those taken at Klang, and a special commission appointed by Government adopted them. " Within six weeks the work of the port was proceeded with without great difficulty. An area of about 100 acres was bunded and drained and freed from jungle." The results were immediate and decisive. The author had kept careful hospital statistics, including returns of all cases in individual houses, from facts known to him in his capacity as District Surgeon. The figures are given in a series of papers by him and Dr Travers {Journal of Tropical Medicine^ 15th September, i6th November, ist December 1903, ist April 1905, 2nd July 1906). I attach the following abstract from my paper [1907]. I . Cases of Malaria admitted to Klang Hospital front 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 1902 1903 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 . . 1900 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 Children examined . . 173 87 298 Children infected . . i i loi November and December 1905 Children examined . . 119 76 247 Children infected 59 57] KLANG 557 5. Sick Certificates and Sick Leave Granted to Government Employees (Numbering 176 in 1901 and 281 in 1904) Years . 1 901 1902 1903 1904 1905 Certificates . 236 40 23 14 5 Days of leave 1,026 198 72, 71 30 Since 1905 the figures have not been accurately kept, but children examined at Klang show evidences of malaria as follows : — 1906, out of 142 children, i infected 1907 „ „ 71 ,. 3 >, 1908 „ ,,455 >, 13 » 1909 „ „ 463 „ 17 „ These are extraordinarily small percentages, considering that the district surrounding Klang was not fully treated. Mean- time, the population of Klang had risen to an estimated total of 5,745. The results at Port Swettenham were not so permanent. The population spread into an undrained area, with the result that there was an outbreak in 1906. The cause of this was rapidly identified and removed by drainage. The cost at Klang for the five years 1901 to 1905 amounts to $35,818 (the Malay dollar appears to equal 2s. 4d, British money). Watson says that " much money was spent in filling which could have been avoided had the town not been burdened by the legacy of its old brick drains," and there was other considerable waste. He adds that the drainage should have cost about £2 per acre, or about iJ^Soo instead of ^3,000. " Thousands of acres in the neighbourhood have been cleared of malaria at this cost, and I can see no reason why Klang could not have been similarly dealt with at a similar cost," but of course many mistakes are made in first attempts. At Port Swettenham the cost amounted to $52,364. In addition to this capital expenditure there was an annual one of ;^270 for maintenance at Klang, and of ^^140 at Port .Swettenham. In the former 332 acres (134 hectares), and in the latter no 558 PREVENTION OF MALARIA IN MALAY STATES [Sect. acres (45 hectares) have been dealt with. The total cost was about £v2 per head of population for the whole five years together. The author says that in Klang " not one single grain of quinine was given to any of the population, except to those who were actual patients from malaria, in hospital or in my official or private practice." It should be observed that all this work was done before the species of carrier had been exactly identified. (2). District. — The local Anophelines were identified by Dr G. F. Leicester in his Culicidae of Malaya in 1904. There are nine species, of which, according to Watson, two are certainly carriers. One of these, Mr Newstead tells me, is certainly Myzorhynchus umbrosus, though the genus is not quite certain, and the other is Nyssorhynchus willmori. The former breeds all over the country, and the latter only in the hilly tracts in quickly running streams. The former can be entirely removed by ordinary open drainage channels ; the latter require subsoil pipe drainage, as it will breed with facility in the open channels. Watson's account of the extensive malaria campaign in the district is a fascinating one, but as it is concerned with numbers of scattered rubber plantations, each of which has to be dealt with separately, the history is much too detailed to be given here, though that history is an example of what can be done in rural areas under the worst conditions by all the measures, especially by drainage. I therefore content myself with giving his conclusions and some of his remarks. The former are as follows : — "(i) That both flat and hilly land in Malaya is, before open- ing, very malarious, and that blackwater fever has been found in both. "(2) That hundreds of square miles of the flat land in Malaya have been freed from malaria simply by draining, and by felling the jungle. " (3) That the cost of these rural anti-malaria measures in 57] CONCLUSIONS 559 Malaya (where labour is dear) is about ;^3 an acre, being £2 to drain and £\ to fell the heavy virgin jungle. This expenditure at the same time is the first step in agriculture, and under it the land has acquired a considerable increased value. "(4) That this freedom from malaria coincides with the disappearance of an Anopheline {M. umbrosus) which breeds in undrained jungle, and does not breed in open earth drains when kept clear from weeds, and flowing. "(5) That certain hilly land intersected by ravines, both open and drained, is as malarious as when first opened. "(6) That the continuance of malaria here is due to N. wilhnoriy which breeds in ravine streams, which cannot be driven from them despite the utmost care of keeping these streams free from weeds, and which cannot be completely washed out of the ravines even by the heaviest tropical showers. " (7) That quinine given regularly greatly reduces the sick- and death-rate of those exposed to malaria. " (8) That doses of less than six grains daily are of little value if the malaria be intense — say where the spleen rate is 75% or more. "(9) That when given in lo-grain doses on six days out of seven, or in 20-grain doses when a coolie has fever, or is in such bad health that he does not feel inclined to work, between 20 and 30% of those taking the drug will still be found with parasites in their peripheral blood. "(10) That the use of quinine can therefore never result in the abolition of malaria, or even make any material reduction in the liability to infection in a malarious ^ locality. "(11) That mosquito-proof houses have a value; but the attempt to discover a satisfactory mosquito-proof coolie house ended as an inconclusive experiment. "(12) That not only for urban, but for rural districts, anti- malaria sanitation should be based on mosquito reduction, if this be a physical possibility." ^ ? Intensely malarious. — R. Ross. 56o PREVENTION OF MALARIA IN MALAY STATES [Sect. The author has many additional remarks to make, of which 1 here note the following : — (i) There was conclusive evidence that the construction of roads increases the malaria in Malaya by obstructing drainage. (2) In the flat land removal of jungle within a radius of about half a mile from plantations suffices to remove malaria, as proved by many experiences over a distance of about 50 miles, but this does not suffice in the hilly land, where malaria is carried by Nyssorhynchiis wilbnori. (3) As shown by examination of large numbers of children, proximity to jungle greatly increases the malaria rate. (4) He says, " We never seem to hear that a place always remains unhealthy, and never improves as time goes on. This is because, after a time, the population of an unhealthy place consists almost entirely of those who have acquired a certain amount of immunity. New people have practically ceased to come to it, and so the health seems to improve. But it only wants new arrivals to come in numbers to start a severe epidemic of malaria." (5) The introduction of a large number of Tamil coolies has greatly increased the malaria rate in certain plantations. This is due to the principles laid down in section 30 (17 and 18). (6) Regarding quinine prevention, he makes the following further remarks. On one estate fifty-six coolies were found to have parasites, though they were getting 6 to 8 grains of quinine, with double doses when they were ill. Of these 75% were apparently in the most perfect health, while 87% were in good health and fit for work. The author says that this " clearly demonstrated that, while keeping the malaria in check, so that the coolies can carry on their work, three years' administration of the drug had entirely failed to eradicate the disease. That the estate is really as unhealthy as ever is shown by the visitors to it who contract malaria in about ten days . . . finally, out of 19 N. willmori captured in the lines, 4, or 21^, had malaria, 2 with zygotes, i with sporozoits and i with both zygotes 57] QUININE AND DRAINAGE 561 and sporozoits." The author further examined an estate in which 10 grains of quinine were given in the most thorough and systematic manner to each adult who worked, and 20 grains to those who did not work, and 5 grains daily to children, with double doses when they were ill. The blood of 29 children was examined, and the parasites were found in 276% of these ; while out of 125 adults the parasites were found in 18-4%, giving a total of 20% infected out of 1 54 persons. The author observes that quinine has little effect on the gametids ; that patients die even after 40 grains of quinine daily, and repeats my teaching regarding the persistence of the sporids (Chapter IV) ; but adds : " If, as has been shown, the immunity from malaria produced by quinine leaves the patient infective while he is acquiring the immunity, then it will be impossible, in the presence of many Anophelines, and in the presence of many new arrivals (such as newly-born children), ever to eradicate malaria by quinine. It follows, too, that if drainage be an alternative, even though much more expensive, drainage must be the method which should be adopted. Even if the community possesses no money for drainage, money might be borrowed with which to carry out the works, and at the end there would be an asset to show for the expenditure. Borrowing, however, would be impossible if the object were to buy quinine. It must not be forgotten, too, that the administration of quinine in effective doses is by no means an inexpensive method. To give 10 grains daily to one thousand people, without any extra to those who actually have pyrexia, for ten years would cost about ;!^i,900. Such a sum, if lent by a government to a community at a reason- able rate of interest, would free a very large area from malaria if drainage methods suitable to the local Anophelines were employed. And in ten years the community would have nine years of prosperity and health in which to repay the loan. In the case of many small villages, it would probably be possible to eradicate the breeding-places of Anophelines, where they are in the midst of the community, at a mere fraction of the 2 N 562 PREVENTION OF MALARIA IN MALAY STATES [Sect. 57 money which would be required to dose the population effec- tively with quinine, even for a year. While for other com- munities the cost of drainage would be relatively much less than in the case of the smaller ones, since the same expenditure would protect a relatively larger number of people " (section 39). (7) The author carefully compares the conditions in Italy with those in his country. The reason for the freedom of the hills in Italy from malaria is that the principal carrier there is a pool breeder and not a stream breeder. The attitude of the Italians to quinine is due to local conditions, drainage being difficult in many malarious localities there, especially along the coast. But as regards the tropics, the author adds : " To me it seems only the vision of a dream that any organisation will ever induce a whole tropical population to take quinine in the doses required by the Italians. And when it is further con- sidered that the population, even when taking this quinine, would still be infectious, the policy of spending money on quinine for an indigenous population, where drainage is possible, appears to me indefensible either on medical or financial grounds" (section 39). (8) The author also discusses malaria in India, and criticises the statements of James and Christophers {^Lancet, 20th June 1909). He does not agree with them that "prevalence of Anophelines, though always important, is by no means in every case the most important factor to be considered," or that the Italian measures are most suitable in India. He states that the Malayan experiences should apply also to India, and adds : " The logical conclusion therefore seems to me that quinine can never do more than give a temporary relief to India, and that the factor to be dealt with is the Anopheles^ and that measures must be aimed at it — not only in towns, but also in rural districts." For N. willmori he advises closed subsoil drains. By Dr T. TAKAKI Director of the Medical School, Chief of the Sanitary Bureau, Government of Formosa 58. Prevention of Malaria in Formosa.— (i). Brief sketch oj Formosa. — The island of Formosa, which came under Japanese rule in 1895, lies between Lat. 21° 45" and Lat. 25° 37" N., and between Long. 119° 18" and 122'^ 6" E., comprising an estimated area of 13,434 square miles. The following are the numbers of the population, according to the latest investigation : — Formosans 3>036,855 Aborigines ........ 120,254 Japanese ........ 83,229 Foreigners (including Chinese) . . . . 12,151 Total Deaths. Per 1000. 104,622 100-9 102,853 111-9 102,232 114-5 Total population 3,225,589 Malaria prevails over nearly all localities of the island, and the deaths caused by malaria in 1906- 1908 are given below. ^ Deaths ''^^''- from Malaria. 1906 10,562 1907 iijOiS 1908 11,714 Statistics only for the years 1906- 1908 are given above, no available ones being obtainable for the preceding years. It must be remembered that there are still about 1,800 native practitioners of the Chinese school in the island, whose service is scarcely to be depended upon. \2). Mosquitos which carry the parasites. — Seven species of 563 (2) An. (3) An. (4) An. (5) An. (6) An. (7) An. (8) An. 564 PREVENTION OF MALARIA IN FORMOSA [Sect. Anophelina are known to be in existence in Formosa, with an additional one recently discovered ; they are as follows : — (i) Anopheles {Myzorhynchus) sinensis Wied. {Myzomyia) listoni Liston. {Mj/z.) rossii Giles. (Myz.) species, from Taito. {Nyssorhynchus) annulipes Walk. {Nys^ maculatus Theobald. {^Nys.) fuliginosus Giles. {Cellid) kocJii Donitz. Of these, the first two species have been found to be the medium of malaria. According to the announced result of experiments made by the late Dr Kinoshita and Dr Miyajima and others, Anopheles sinensis has the power of developing the Plasmodium vivax of tertian fever, but not the Plasmodium, praecox of aestivo-autumnal fever ; while Anopheles listoni is host of PI praecox, its cysts growing upon the mosquitos' intestinal wall. In other words, tertian fever is transmitted by Anopheles sinensis, and aestivo-autumnal fever by An. listoni. Anopheles rossii being recognised as an innoxious species, no cyst of Plasmodium can be found growing in its body by process of infecting experiments. The pathogenical importance of other Anophelines are not yet clearly defined. In the order of the extent of prevalence. Anopheles sinensis^ the tertian fever carrier, comes first ; and next comes An. listoni^ a much smaller but extremely dangerous species. An. rossii is mostly found in the middle and south of Formosa, its sphere of influence in the north being limited to 24° N. The newly- discovered Anopheles from Taito (on the east coast) was like- wise collected in the southern part. The remaining three species of Nyssorhynchus are met with in the mountainous districts. The newly- discovered An. kochi has been obtained in Keelung, which lies 18 miles north of Taihoku. S8] MEASURES AND RESULTS 565 (3) Preventive measures adopted. — A. By the general improvement of sanitary conditions in towns and in the country, as, for instance, by the construction of properly macadamised and paved roads, the discontinuance of the use of the drink- ing-water mixed with sewage, the facilitating of the carrying off of rain-water and drainage, and so on. B. Protection from mosquito attacks by means of wire- gauzed shutters and windows, and mosquito-nets, etc., etc. This means is chiefly adopted by the garrison troops here. C. Prophylactic administration of quinine after R. Koch. D. Thoroughgoing post-malarial treatment. (4). Results. — As a marked result of the above-mentioned public measure A., Taihoku and Taichu, which formerly used to be malaria-stricken places, are now found completely cleared of the dreaded disease. As to the merit of the mechanical measure B.^ reference may be made to the uniformly improved health condition among the troops of Formosa. The measure of screening the barrack windows, etc., with wire-gauze was first resorted to by the garrison here in the summer of 1909. The following Table shows its result : — TABLE I. Year. Malaria cases Malaria deaths per 1,000 soldiers. per r.ooo soldiers. 1897 2724-3 17-3 1898 2493-9 19-3 1899 235 1 '0 23-9 1900 2345'5 20-7 1901 1768-2 II-5 1902 1 1427 7-1 1903 4608 1-7 1904 213-8 i-i 1 90s 145-0 3-1 1906 280-3 2-1 1907 528-1 2-1 1908 498-3 13 566 PREVENTION OF MALARIA IN FORMOSA [Sect. The unusual increase of the number of malaria-affected soldiers in the last year is accounted for by the fact that in the said year many soldiers fell victims to malaria during the big campaign against the savages, and that the sick - rate adopted by the Army was rather too high. As a result of the medicinal measure C, the experiment made at Kosenpo may profitably be referred to. Kosenpo is a village lying in the southern mountainous districts, the majority of whose inhabitants are camphor collectors. In April 1907 malaria prevailed terribly in this locality, especially among Japanese new-comers, so that 30^ of the Japanese residents proved to be malaria patients. From July 1907 R. Koch's gramme-prophylaxis began to be systematically used under the direction of the late Dr Kinoshita. The people were administered quinine hydrochlorate in pastil, in pro dosi vo for adult, every nine and ten days successively. The pro- phylaxis was strictly conducted under care of the police officials from July to November 1907, and from January to October 1908. The reduction of both malaria-morbidity and malaria-mortality will clearly be seen from the following Table II. (5). Estimated cost incur-red for the prevention of malaria. — No estimated costs for the prevention of malaria can be given, as they differ according to various circumstances. Note by R. Ross.— By the kindness of Professor Dr Kitasato, Dr M. Miyajima of his Institute for Infectious Diseases at Tokio has suppHed me with the malaria statistics of the Imperial Japanese Army, serving in Japan, China, Chorea and Manchuria, as given by the Medical Bureau of the Army. The totals for three years are as follows : — Years. Total Patients. Total Deaths. Malaria Patients. Malaria Deaths, 1906 77,lc>o 749 2,717 10 1907 104,266 636 4,863 9 1908 114,794 646 4,666 7 296,060 2,631 12,246 26 Dr Miyajima says that in Japan itself the parasite is almost exclusively P. vivax, but that the other species occur in Formosa and the Loo Choo Islands. The largest number of malaria cases were in Formosa and in Chorea (5,348 and 1,974 cases respectively in the three years). 58] RESULTS TABLE II. 567 A/TnntVi Japanese Malaria Malaria Malaria cases Malaria deaths IVi (J 1 1 L i 1 ■ Inhabitants. cases. deaths. per 1,000 Japanese. per 1,000 Japanese. 1906 Jan. 314 Unknown Unknown Feb. 211 51 I 265-4 4-74 March 387 105 I 271-3 2-58 April 502 165 I 328-7 1-99 May 741 256 2 345-5 2-70 June 754 394 I 522-5 1-33 July 836 408 7 488-0 8-37 Aug. 1,006 593 9 589-5 8-95 Sept. 984 503 12 5II-2 I2-20 Oct. 1,094 659 6 602-4 ■5-48 Nov. 1,229 579 14 471-1 11-39 Dec. 1,364 Average Population 496 5 363-6 3-67 Total 785-2 4,209 59 5,361-8 75-14 1907 Jan. 1,494 329 I 220-2 067 Feb. 1,435 244 I 170-0 0-70 March 1,508 172 3 II4-I 1-99 April 1,626 220 135-3 May 1,708 243 I 142-3 0-59 June 1,806 274 2 I5I-7 i-ii * July 1,487 208 I 139-9 0-67 * Aug. 1,588 141 2 88-8 1-26 * Sept. 1,604 76 I 47-4 0-62 * Oct. 1,625 46 I 28-3 0-62 * Nov. 1,668 75 2 45-0 1-20 Dec. 1,665 Average Population 116 2 69-7 1-20 Total I,6oi-2 2,144 17 1,338-1 10-61 1908* Jan. 1,669 102 6ri * Feb. 1,668 60 I 36-0 060 * March 1,675 44 26-3 * April 1,674 58 34-6 * May 1,883 92 48-9 * June 1,918 127 66-2 * July 1,898 169 89-0 * Aug. 1,933 152 78-6 ■x- Sept. 1,949 168 2 86-2 1-03 * Oct. 1,829 183 2 lOO'I 1-09 Nov. 1,282 169 3 I3I-8 2-32 Dec. 1,258 Average Population 143 I 113-7 0-79 Total 1,719-2 1,467 9 8i8-2 5-23 (* indicate prophylacted months.) By RONALD ROSS, D.P.H., F.R.C.S., D.Sc, LL.D., F.R.S., C.B. Major Ind. Med. Serv. {t-et.) President, Society of Tropical Medicine and Hygiene ; Professor of Tropical Medicine, University of Liverpool and Liverpool School of Tropical Medicine 59. Notes on Some Other Works. — It is impossible to give within the limits of this book a full account of all the campaigns which have been commenced, or even to mention some of them ; but I think that brief notes on the following works should be added. (i). India. — In section 7 I described my own work in India up to the publication of a report [1899] in which I suggested my proposals for mosquito reduction. By this time I had left India ; and no notice was taken of the report, except that several medical men wrote against the idea. They pointed out that Anophelines breed in rice-fields, and so on, near canton- ments, and therefore thought that the task of banishing them would be impossible. They evidently failed to understand my arguments, and had no idea of the economical principle laid down in axiom 3 of section 38. At this time many persons were writing up the recent discoveries. Unfortunately, some of them were not personally acquainted with the tropics, and few of them had any know- ledge whatever of practical tropical sanitation. It was almost impossible to make them understand my proposals ; but some of them clamoured for a formal experiment to test them in the field. I was very averse from this suggestion. Success would demand a long and patient enquiry, requiring an exact preliminary survey of the amount of malaria and the number of mosquitos present, followed by equally exact measurements of these quantities made on frequent occasions. Now it will be seen from Chapter V how difficult it is to measure malaria 568 Sect. 59] INDIA 569 exactly, and how much more difficult to obtain any direct enumeration of the Anophelines. Moreover, failure might be due, not only to the impracticability of my proposals, but also to want of enthusiasm or care in those who were appointed to test them. Thus failure, or at least an indecisive result, was very probable, and would have a disastrous effect upon anti-malaria work for many years. I thought it would be much better to allow local authorities to attempt the work quietly in the ordinary course of sanitation, and not as a formal test experiment ; and this was actually done since 1902 in Havana, Ismailia, the Federated Malay States, and elsewhere. But my critics could not be got to understand the bad policy of their suggestions, and consequently the so-called test experiment was commenced at Mian Mir, near Lahore, Punjab, India. The place was a most unsuitable one ; almost flat, with an impervious subsoil and watered by irrigation, mosquito reduction was not easy in it. Moreover, it was a military cantonment containing scattered barracks, from which statistics of the local malaria rate could hardly be compiled, since the troops and their followers were frequently being changed from other stations ; while, lastly, the place was scarcely a town, that is, a locality which was most appropriate for mosquito reduction. In fact, the selection of the place showed how little the subject was understood at that time. Mian Mir was examined by the Malaria Commission of the Royal Society in 1901, but without any exact estimates of the amount of malaria or the number of Anophelines. In April 1902, however, practical operations were at once commenced, evidently on the model of my suggestions for Sierra Leone, and were continued for that and the following year. For 1902 the operations were reported upon by S. P. James [1903], and for the following year by S. R. Christophers [1904]. The former reported very doubtful success, and the latter practically denied the feasibility of mosquito reduction. Their reports were, however, exhaustively criticised by myself in a paper 570 NOTES ON SOME OTHER WORKS [Sect. [1904], to which no reply has been given; and also by Sewell [1904], Giles [1904], and others. No one who is acquainted with the nature of scientific evidence can imagine for a moment that this experiment gave any proof of anything connected with the subject. The measurements of malaria were of the most inadequate nature, and were based upon the most insufficient random sampling — while in some cases the number of children examined was not recorded (section 31 (8)). The enumeration of mosquitos was evidently of an equally casual nature, the authors not having been able to devise any accurate method. Neither report was well written, and the second one was worded so confusedly that almost anything might be inferred from it. Both reports claimed that the mosquitos increased in spite of the reduction measures. This is, of course, possible to a certain extent (section 29 (8)) ; but it is otherwise mathematically impossible, and the statement suggests only that the authors' methods were inaccurate. As no exact enumeration of the mosquitos had been made before the operations, the total result of the work could not be determined. In fact the reader who is interested in exact work will do well to compare these reports with Chapter VI, if only to learn what not to do as regards the measurement of malaria and of mosquitos, and the conduct of a campaign. It has been frequently claimed by several Indian writers on the prevention of malaria, that the operations at Mian Mir were carried out merely to determine the practical feasibility of mosquito reduction for a reasonable cost in India. Even this claim cannot be accepted. During the first year (1902) only 7,216 rupees were expended for dealing with an area of 4 square miles containing numbers of troops, and of this sum, 5,364 rupees were spent on bricking, lining and plastering a single watercourse, leaving only 1,851 rupees, or about £120 for the rest of the work. This is hardly a convincing ex- penditure for a test experiment. The life of a single soldier 59] INDIA 571 costs more. It will scarcely be believed that in the second report of the experiment, designed, as has been declared, for the express purpose of providing official information for the whole of India, no accounts whatever of the cost incurred were vouchsafed ! In fact, the whole affair was conducted on un- practical and unscientific lines. It proved nothing at all, and its only effect was to retard anti-malaria work in that and other countries for years. Since 1904 the military authorities at Mian Mir undertook much more patient and useful work there, with the apparent result of a considerable reduction in malaria — see especially H. D. Rowan [1908]. At the Bombay Medical Congress of 1909, however, S. P. James described how, during a recent visit to Mian Mir, he had found no reduction, either in the malaria or in the number of mosquitos. His statements were immediately controverted by five administrative medical officers (see Lancet, 3rd July 1909). James stated that out of ten men of the Gloucester regiment, who had been taking quinine regularly, and who were selected by him at Mian Mir " more or less at random," he found parasites in no less than eight — an enormous percentage. The commandant of the regiment, however, informed me at Bombay shortly afterwards that his regiment had not suffered much from malaria at that time. Many local campaigns have been commenced in India, and will be found mentioned in the Annual Sanitary Reports, in the Proceedings of the Malaria Conference [1910], and in a recent publication by W. G. King [1909], and elsewhere. I have received many private communications regarding these, from which I gather that they have not been given much encourage- ment from headquarters, that the organisation has not been sufficient to ensure continuity, and that the necessary measure- ments of malaria have been quite inadequate. There is no doubt that the general policy of a clique in India has been opposed to mosquito reduction, and has not been very keenly interested in any other form of malaria campaign. A 572 NOTES ON SOME OTHER WORKS [Sect. party in that country has been advocating quinine on the Italian model, and appears to have persuaded the Government that it will cost nothing, while mosquito reduction must always be enormously expensive. Personally, I would welcome any measure that is effective, but apparently not even the quinine method has been fully pushed in that country. Experience will, I think, prove to the Government of India that no anti - malaria campaign can be conducted without expense ; that each measure has its proper sphere of action ; and that quinine may not always cost less than other measures. Up to the present the work in India seems to me to have been wanting both in intelligence and in leadership, in spite of the 1,000,000 deaths a year officially attributed to malaria there. In October 1909 an Imperial Malaria Conference was held at Simla. It was not, I think, arranged in a perfectly satisfactory way. Engineers and several good workers on the subject appear not to have been called. Nevertheless, the conclusions of the Conference simply confirmed my proposals, especially as put in my Mauritius report. I hope that the Conference will mark the beginning of a new era in India. C. A. Bentley has recently published a report on malaria in Bombay [19 10]. A. G. M'Kendrick had found a splenic index of 629/8325 = 7*5%, and the author one of 3075/21,517 = I4"3//. The local carrier is Nyssorhynchus stephensi, which, unlike most Anophelines, breeds readily in deep wells, cesspits, cisterns and salt water. The author recommends a campaign against it (not including other mosquitos) chiefly by means of strict legislation aimed at the removal or protection of such waters by householders, and does not appear to advocate any special municipal organisation. Such legislation is certainly a necessary preliminary and easy to suggest ; but in practice the cost of the numerous inspections and summonses required to enforce it is apt to exceed that of doing the work by departmental agency, as hygienists well know (axioms 6 and 7, section 38). Nevertheless, municipalities like the idea, because 59] HONGKONG 573 it appears at first sight to put them to no expense. We generally observe two things about tropical municipalities — the excellence of their sanitary laws and the completeness with which the public ignores them. Which is the cheaper in the end, {a) to make one inspection and then do the work, or {b) to make many inspections, worry the householder, issue several summonses, be finally forced to do the work, and then try to recover the cost in the law courts? We must always remember this question, and endeavour to arrange a proper balance between the respective obligations of the householder and the municipality. (2). Hongkong. — One of the earliest and best of the campaigns in British territory. The city of Victoria, usually called Hongkong, runs for nearly 5 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 2 to 5 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 crranitic. 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 larvae. 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 [1901], who undertook an exhaustive study of the mosquitos and their breeding-places. He examined over 32,000 specimens, of which he found about 4^ to be Anophelines, and in November advised an active anti-malaria campaign by drainage, 574 NOTES ON SOME OTHER WORKS [Sect. clearing of jungle, "training" of the nullas, the use of wire- gauze, oiling pools, and quinine prophylaxis. As seen by his excellent papers [1900- 1903], his recommendations were not of a general nature, but were particular, practical and exact. These recommendations were rapidly acted upon by the Government. Since 1901 all the nullas or watercourses 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 else- where by training watercourses, 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 [1901], 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 Francis Clark [1906]. Dr Thomson informs me that before estimating them it is necessary to remember that malaria can never become extinct in Hongkong owing to the fact that some three thousand to four thousand 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. Nevertheless, the figures show a rapid diminu- tion both in the admission and in the death-rates. Malaria Statistics in two large Hospitals Years . 1897 1898 1899 1900 1901 1902 1903 1904 1905 Admissions 1021 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 . . 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 Admissions % . 32 "'^^ 25 19 31 42 44 19 18 11 12 Deaths from Malaria Years . . 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 Population . 239,419 377,850 Total deaths . 533 554 530 546 555 574 425 300 301 285 Deaths in city (Chinese only) 290 302 280 218 242 281 189 152 90 87 59] CANDIA 575 The official sanitary reports give similar figures. The improvements have, of course, varied much in different localities. Thus in 1900 the western end of Bonham Road used to be one of the worst districts. Now, in 1905, it is reported not to have sent a single case to the Government Civil Hospital [1900-1905]. 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 i^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. Figures for subsequent years have not been obtainable. (3). Cafidta, Crete. — The accounts of this excellent campaign, conducted in connection with the British troops in Crete, will be found in successive numbers of the Journal of the Royal Anny Medical Corps. The town of Candia, containing 21,000 inhabitants, is situated on the seashore of a semicircular plain bounded by hills. The rainfall is heavy, and the ground is traversed by many streams, which become torrents in winter and nearly dry in summer. Two of them have marshy margins near the sea. The houses of the town are of the Oriental type and contain many wells. The troops are accommodated in quarters to the west of the town and close to it, and suffered considerably from malaria. Apparently as early as 1902 Lieutenant-Colonel J. V. Salvage, R.A.M.C. [1904], commenced to examine into the distribution of Anophelines and to destroy the larvae by drainage, or by closing or oiling the wells, or putting fish into them, and expressed himself hopefully regard- ing the result. In March 1903 Major C. J. MacDonald arrived in Crete and continued the work [1905]. He gives many very interesting details. Works of a permanent nature were attempted, and quinine prophylaxis and mosquito-nets insisted upon. The first results were as below : — 576 NOTES ON SOME OTHER WORKS [Sect. 59 Years . Strength . Admissions Rate % I90I 1902 1903 564 460 410 ,540 1,084 227 273 236 55 The admissions include simple continued fever, together with malaria, in order to avoid error due to diagnosis. Major MacDonald attributes the fall to the measures taken. In 1905 Captain R. A. Cunningham, R.A.M.C, adds a third article [1905], in which he stated that the fall in the malaria rate had continued, and was only 30% in 1904 compared with the 55% of 1903. The mosquitos were so few that it is almost un- necessary to use a net at night. In 1905 there were 246 admissions, or a rate of 387%. Many men become infected on guards and outposts. By Colonel C. H. MELVILLE Royal Army Medical Corps, Professor of Hygiene, Royal Army Medical College, London 60. The Prevention of Malaria in War. — Part I. The Lessons of History. — The history of malaria in war might almost be taken to be the history of war itself, certainly the history of war in the Christian Era. Even in Europe up till at least the middle of the nineteenth century all armies in the field were liable to attacks of this class of disease, as witness the French and Austrian armies in the campaign in the north of Italy in the year 1859. It is probably the case that many of the so-called camp fevers, and probably also a consider- able proportion of the camp dysentery, of the wars of the sixteenth, seventeenth and eighteenth centuries were malarial in origin. In our own army, as the writings of Pringle and Monro teach us, the various campaigns in the Low Countries were marked by severe outbreaks of paludal fevers, culminating in the epidemic that wrecked the ill-fated Walcheren expedition just one hundred years ago. It would be out of place here to do more than mention these earlier histories, but the Walcheren disaster merits more than passing notice, for several reasons. In the first place, it occurred in comparatively recent years. There must be men still alive who can remember having seen and spoken to survivors of the expedition, some, at least, of whom must have carried the marks of their sufferings to the grave. In the next, the close proximity of the scene of action 577 20 578 THE PREVENTION OF MALARIA IN WAR [Sect. to our own shores struck even contemporaries with a sense of the reaHty of the disaster. These two characteristics tend to make this outbreak one of peculiar interest ; but there are others of even greater value than interest, which bear very closely on the question of prevention of malarial fevers in campaigns of the present day. Of these the first is that the locality selected for the debarkation of the troops was one notoriously unhealthy on account of malarial fevers. Already, in 1747, the force landing in Zealand had suffered to such an extent from this cause that, according to Sir John Pringle, some of the battalions in South Beveland and Walcheren had but 100 men fit for duty, being less than one-seventh part of their whole number. Another experience repeated in the expedition of 1809 was that the men-of-war which lay at anchor in the channel between South Beveland and Walcheren, even during the worst period of the distemper, were not affected with either flux or fever, but enjoyed the most perfect health. In the light of our present-day knowledge this coincidence is easy of interpreta- tion ; but the practical lesson to be drawn was clear, or should have been clear, even in 1809, namely, that on a malarial coast troops should not be landed from the transports until all steps are ready for an immediate advance. It was the preliminary delay under the walls of Flushing that laid the army of Lord Chatham open to the first onslaughts of disease. An early advance into the comparatively higher ground of the interior would undoubtedly have done much to check the disease. In the second place, the season of the year selected for the expedi- tion was notoriously the most unhealthy of the year. And this fact also was on record. Sir John Pringle wrote as follows in the year 1765 : "The epidemics of this country may therefore be generally dated from the end of July, or the beginning of August, under the canicular heats : their sensible decline, about the first falling of the leaf; and their end, when the frosts begin." Here, again, the lesson was as plain as the warning. If a force has to land in a malarious locality, then the unhealthy season 6o] WALC KEREN, 1809 579 should be carefully avoided. How long it took before that lesson was learnt the records of our earliest campaign in Ashanti, and the experiences of the French in Madagascar, show only too clearly. And lastly, there was no selection of the men. Davis, who was appointed to attend the troops on their return to England, in his " Scientific and Popular View of the Fever of Walcheren " (p. vii.), alludes to the fact that the troops consisted of " numbers of young men unaccustomed to fatigue and the hardships of a military campaign." It may be accepted as one of the most important points in the conduct of a campaign in a malarial locality that the men should be seasoned soldiers, free from the taint of previous severe malarial infection, but accustomed by experience to the proper camp discipline essential to the prevention of paludal diseases. The expedition left the shores of England on the 28th July 1809, and disembarked in Middleburg and Walcheren on the 29th and 30th of the same month. The siege of Flushing was at once undertaken, and this place surrendered on the 15th. Up till that date, with the exception of the men killed in action, there had been no deaths in the force of 17,000 men, and though the medical authorities on the spot were justifiably anxious, in view of the medical history of the locality, the general public were far from sharing in this apprehension, " observing that the notion of the unhealthiness of Walcheren being so great that it ought not to be garrisoned by British troops, was too absurd to deserve much notice ; as it might probably be as unhealthy as Romney marsh, or the hundreds of Essex." ^ This was on the 23rd August, but " a different impression was felt in Walcheren, for as early as the 25th it appears, by a letter from the expedition, that the interruption to active operations which had then taken place from the rapidity with which the disease was spreading had caused much regret." - By the 29th August there were 3,000 men in hospital out of a total of about 25,000 men. Early in September there 1 Davis, p. xi. ^ Ibid. p. xi. 58o THE PREVENTION OF MALARIA IN WAR [Sect. were upwards of 7,000 men in the different hospitals, and by the 14th it was estimated that out of a strength of 15,000 in Walcheren, 10,000 were actually sick, the deaths then averaging at from 25 to 30 per day. The repatriation of the troops to England had already begun, and "about the 13th they began to arrive at Deal, where soon after the mortality in one hospital amounted to 14 in one day . . . indeed the mortality among those who first arrived in England was greater, comparatively, than at the same period even in Flushing, for there the whole daily mortality, though seldom less than 50, for some time previous to the 12th had never on any one day exceeded 100."^ At the latter place, " on the 23rd of September, the sick report included 218 officers, 382 sergeants, 190 drummers and 9,046 privates."^ From that date the fever subsided. On the 26th there were 9,798 in hospital, and on the 30th 8,600, and though the army was disabled and vanquished, its invisible enemy gradually slackened its pursuit, and the " remnant of an army " returned to England on the 23rd December, having faced fifteen days' fighting with 247 casualties, and two months' fever with more than 4,000 dead. And how about the wounded in this appalling struggle.? Years afterwards the men who survived still showed in shattered constitutions the results of the in- eptitude which planned, and the inefficiency which led the expedition of 1809. The expedition to Walcheren is one of the most striking instances of the part that epidemiology should play in strategy. There were, on political and military grounds if on no other, doubts as to the advisability of attacking the French in the Low Countries. The known unhealthiness of Zealand should have been recognised, and should have acted as the decisive factor. In whatever part of the French dominions a British force had been landed at that season of the year, the neighbourhood of Walcheren was the last that should have been selected. ^ Davis, p. xvii. * Ibid. p. xviii. 6o] ASHANTI, 1864 581 In no other campaign during the " Great War " did malarial fevers play so commanding a role as in the expedition of 1809, though it is true that both in Estremadura and before Cuidad Rodrigo, the army under Sir Arthur Wellesley suffered notably from this type of disease. The chiefinterest, however, of paludism attaches historically in the nineteenth century to campaigns in the tropics, and as this will undoubtedly be even more the case in years to come, I do not propose to refer in this brief sketch to any other class of enterprise. And I will further limit myself to a consideration of two of our own expeditions to Ashanti, and to that of the French to Madagascar in 1895, since these present typical instances of small wars where success or failure depended not on the bravery of the men, or the tactical skill of their leaders, but entirely on the amount of forethought paid to the problems of disease at home, and to the translation of that forethought into terms of energetic action on the spot. Passing over the earlier unsuccessful, or only partially successful campaigns of 1822, 1824 and 1833 in Ashanti, I shall begin with that of 1864. Of this expedition the late Surgeon-General Gore (sanitary officer with the expedition of 1873) writes (" Medical History of our West African Campaigns," p. 10) : " It can scarcely be called a war, as an enemy was never seen, or a grain of powder expended ; our troops were defeated by disease, much of which was preventable." He goes on: "In August of the former year (1863), the right wing of the 4th West India Regiment landed at Cape Coast Castle. Preparations were at once commenced for the future advance. Stores were collected and paths cut, these operations lasting until December, during the continuance of which the men suffered much from dysentery, remittent and intermittent fever." This point is worth noting. One of the most essential pre- cautions in the case of tropical campaigns is to see that the collection of stores is carried out in anticipation of the landing of the expeditionary force. The campaign, as already stated, 582 THE PREVENTION OF MALARIA IN WAR [Sect. was a fiasco. By the end of March one quarter of the strength was in hospital, and by the middle of May all the members of the original force at Prahsue were relieved. The admissions in 1864 amounted to over 1,600, and the deaths to a fraction under 60 per 1,000. It must be noted, too, that these troops were not Europeans, but black troops from the West India regiments. Of 60 European officers 35% succumbed to the effect of disease. The lessons of this campaign were not, however, lost. Early in 1873 the Ashantis made one of their periodical inroads into the Gold Coast Protectorate. Owing to the scanty numbers and scattered distribution of the British garrison, our men were confined to the defence of the posts held by them. A small reinforcement of Marines was despatched from England, and reached Elmina, the most seriously - threatened post, by the 1 2th June, inflicting on the next day a serious repulse on the enemy. Affairs remained in statu quo, the enemy becoming somewhat less active, but still maintaining a threatening attitude, until, in September, an attack on the boats of the Rattlesnake demonstrated that sterner measures must be taken to deal finally with them. Sir Garnet Wolseley arrived from England on the 2nd October, and at once began the erection of wooden huts, and the enlistment of native artificers, labourers and porters, as well as the enrolment of local levies and regiments under specially - selected officers, " it having been thought that with European organisation and guidance Ashanti armies might well be successfully encountered by Africans of other races." ^ The first blow was struck on the 14th October, when a force advanced from Elmina and captured and burnt the village of Essaman, with but trifling loss. As a result of this blow the Ashantis prepared to retreat to their own country, but Sir Garnet decided that to complete their punish- ment a force containing a strong European contingent should be sent into Ashanti territory. In spite of well-founded apprehension as to the consequences of employing European 1 A.M.D. Report, 1873, p. 232. 6o] ASHANTI, 1873 583 troops in the climate of the West Coast, it was decided that a force corresponding to the requirements formulated by General Wolseley should be despatched, it being considered, as a result of the experience of campaigns in low-lying, swampy districts of other tropical countries, that " there was a season of comparative healthiness corresponding to the driest season of the year, and that in this, with suitable precautions and limitations, Europeans might undertake field service in the Gold Coast country."^ Pending the arrival of the European force operations were undertaken with the troops at hand with a view to clearing the enemy from the territory of the Protectorate, and facilitating the advance of the punitive force as far as the banks of the Prah. Sites were selected between the base at Cape Coast and the river named, for the formation of camps, temporary barracks being erected at these places. In all, eight such sites were fixed, the average distance between one camp and the next being a fraction over nine miles. The object in view was to ensure that " the troops were to march into stationary camps, and to reach the Prah — the second base of the expedition — as little fatigued as possible, so that the force might start thence with the men in the highest state of efficiency, and strike the intended blow before it was materially reduced by sickness." ^ Eventually, the first detachment of European troops landed on the I St January 1874, and the whole strength was assembled and the river crossed on the 21st. Some rather smart fighting occurred at Amoaful on the 31st January, and again outside Coomassie on the 4th February. The city was entered that same evening, and burnt and evacuated on the 6th. The entire force, with the exception of some of the irregular corps, recrossed the Prah by the 14th February, that is, within three weeks of the date of first crossing it. The 42nd Highlanders, which was the first regiment to land, was also the last to leave. The period that elapsed between landing and embarkation was eight ^ A.M.D. Report, 1873, p. 236, 2 jUfi^ p_ 246, 584 THE PREVENTION OF MALARIA IN WAR [Sect. weeks all but one day. The admission rate was 58 per 1,000 for European rank and file, and the death-rate i8"2 per 1,000, Five British officers and 13 men were killed in action, while 21 and 40 of these two classes respectively died of disease. This striking contrast between the two campaigns of 1864 and 1874 deserves to be noted. The keynotes of success in the latter case were careful preliminary preparation, and swift and rapid execution. Failure in the former expedition was due to " unselected men, under officers many of whom had already suffered from illness, not especially well equipped or cared for, remaining in the field at a bad season, and languishing in inaction month after month." ^ The only other historical instance on which I shall dwell is the French campaign in Madagascar in 1895. The necessity for an expedition to Madagascar was recognised in the late months of 1894, but already for a year prior to the actual parliamentary sanction for the despatch of a force, the Naval and War Departments had had such a possibility under con- sideration, and the former had, with commendable forethought, caused reconnaissances to be made of the possible points of disembarkation, and of the best lines of advance. In August 1894 an inter-Departmental Committee was formed at the Foreign Office, in which the two departments already named and the Colonial Office collaborated in the production of a joint report on the geographical and military situation, with suggestions as to the composition of the expeditionary force, and the various measures to be adopted to meet the grave difficulties presented. There was in fact no want of pre- paratory consultation. About the middle of November it was decided to entrust the execution of the plans to the Ministry of War, and accordingly a fresh commission was formed, of an advisory nature, which sat at the War Office under the direction of the Chief of the General Staff, and was presided over by General Duchesne, specially selected for the chief command of 1 A.M.D. Report, 1837, p. 237. 6o] MADAGASCAR, 1895 5^5 the expeditionary force. On this commission all departments concerned were represented, and a second commission entrusted with a fuller consideration of details was also appointed. Meanwhile time passed. It was necessary to start active operations by May at the latest, and in fact the advance guard of the expedition landed at Majunga twenty-four days before the last-named commission completed its work. Even so the War Office was by no means independent in its management of affairs. Diplomatic arrangements still remained under the Foreign Office, while the troops available came partly under the Ministry of Marine, partly under the Colonial Depart- ment, and partly under the War Office. As one result of the complication of authority and responsibility the force was compelled to march for forty-three days through a malaria- infested country, instead of proceeding by steamer, though the necessity for the latter expedient had been recognised, and arrangements to that end begun. Transport being deficient and unsuitable, the troops were forced to advance in heavy marching order, in spite of the heat. Medical equipment was left behind, and even quinine was often not to be had. No special hutments were provided, and Malagasy huts had to be utilised even at the very base.i " From the ist to the 24th March the troops were almost entirely occupied in disembark- ing '>nateriel, in building shelters and making roads, work made all the more laborious by the lack of native labour, and the heavy rain." Just as there was no lack of forethought at home, so there was no lack of energy at the front. Unfortunately, the divorce between the two was complete. Eventually the supply of water at Majunga ran short, the apparatus for distillation being insufficient, and an advance had perforce to be made. One company of engineers that left Majunga 225 strong, arrived at Suberbieville with only 25 worn-out men still effective. It is unnecessary to prolong this narrative. Reynaud gives in his excellent " Considerations 1 Reynaud, p. 312. 586 THE PREVENTION OF MALARIA IN WAR [Sect. Sanitaires sur I'Expedition de Madagascar," a detailed account of the misfortunes that continued to befall the expedition. From Suberbieville a flying column was despatched to Antan- anarivo, which it reached on the 30th September after incredible exertions, leaving ten per cent, of its strength on the road. The French soldiers christened this column " la colonne Marche- ou-Creve," a not inappropriate expression for a force where to fall out meant mutilation and death at the hands of a cowardly enemy. And yet many fell out and remained to die of starva- tion, worn out with suffering and illness. And as Dr Reynaud reminds us, this was the march of a conquering army, not a precipitate flight before a victorious enemy, but the culminating point of an expedition, the details of which had been carefully thought out. The last remnants of this unfortunate army left the shores of Madagascar on the 28th December, leaving behind them 4,498 dead out of the combatant force alone. Amongst the auxiliaries it was estimated that there were 3,000 deaths, whilst as regards non-combatants the numbers are beyond calculation. The proportion of deaths amongst the combatants was equivalent to 320 per 1,000 of strength, due almost entirely to malarial fevers and their sequelae. The deaths in action were 13, and in addition there were 88 men wounded. The causes of this disaster were the antitheses of those which led to our success in Ashanti in 1874 — confused councils, divided authority, and delayed execution. Part II. Practical Measures. — We now come to the im- portant question of the prevention of malarial diseases in war. I propose to discuss this subject under two heads. First, the measures to be adopted in anticipation of the opening of hostilities, and secondly, those to be carried out during the actual progress of active operations. Measures to be adopted in anticipation of the outbreak of hostilities. — Before actually detailing these, it is necessary to insist on their enormous importance, It is not going too far 6o] PRACTICAL MEASURES 587 to say that the success of any tropical campaign depends infinitely more on the administrative measures taken in the preparation for the expedition than on the courage and fighting capacity of the troops engaged. The success of the Ashanti campaign of 1874 was ensured in Pall Mall before ever Sir Garnet Wolseley left England, and the fate of the French expedition to Madagascar in 1895 was decided in Paris and not at Majunga or Suberbieville. The only serious problem in a tropical campaign is disease. This has been proved time and again. No soldier will for a moment pretend that either in Burma or Ashanti the fighting was of a serious nature, and the same is true of the French army in Madagascar. The only obstacle to be feared was disease, and most importantly malaria. Now there is this difference between a human enemy and disease. The former may alter his plans at the last moment, and our plans may have to be changed accordingly. But disease does not alter its laws. As far as we know or can guess at those laws we are able to calculate confidently on their regularity, and our plans can be fixed accordingly. It is almost a platitude to say that the success of any tropical campaign is settled as much in Whitehall as on the actual spot. An ill-provided, ill-thought-out expedition can only end in disaster, however brave the soldier, and however skilled his commander. On the other hand, but little military skill and no extraordinary amount of courage is necessary to enable a small picked force of healthy Europeans, armed with modern weapons, to march through the territory of the most powerful savage tribe in the tropics. But what is necessary is that the objective should be clear, the means exactly proportioned to the end, and all things necessary provided before the start is made. It was an observance of these principles that made the Ashanti campaign of 1874 a brilliant success, and neglect of them that turned the French expedition to Madagascar in 1895 into a dismal failure. The composition and strength of the force sent is an 588 THE PREVENTION OF MALARIA IN WAR [Sect. important consideration. One of the greatest initial mistakes made by the French Government in 1895 was sending too large a force, and one in which the proportion of Europeans was unduly great. As already stated, the military foe is the one least to be feared in a tropical campaign. Locally raised troops drilled and officered by Europeans should be capable of meeting their own tribesmen, undrilled, unofficered and poorly armed. A stiffening of Europeans is necessary, but no more.^ General Gallieni, in his " Deux Campagnes au Soudan Francais," lays down this principle very clearly. " Taking into account," he says, " the unhealthiness of the climate and the peculiarly trying conditions that characterise our campaigns in the Soudan, I did not wish to encumber myself with too large a force of Europeans. I contented myself with a strong company of Marine infantry. In action this body would be available as a reserve to the native troops. The right class of soldier for the Soudan is the Senegalese rifleman." The following are the numbers respectively of Europeans and natives employed in some of our campaigns : — Abyssinia: 3,655 Europeans, 9,833 natives, Ashanti (first expedition, 1 868), 2,284 Europeans, 2,377 black troops. Ashanti (second expedition, 1874), 1,050 Europeans, 2,050 black troops. It will be noted that the disastrous expedition to Ashanti in 1868 was the only one in which there was an equality in numbers between the two classes. In Madagascar in 1895 the French had 11,000 European soldiers to 3,800 natives (two battalions Algerians, one battalion Malagasys, and one battalion Haussas). It may be definitely laid down that those branches of the service not immediately concerned in fighting should be composed entirely of natives, sufficient Europeans only being sent to superintend their work. This rule applies to the Engineers, the Supply and Transport Departments, and to ^ Reynaud, p. 247. 6o] SELECTION OF MEN 589 a great extent to the Medical Department. Men actually engaged in nursing the sick should be European, but cooks (with a few picked exceptions) and the general duty section generally should be replaced by natives. The composition of the force should be such that no fatigues and no unnecessary non-combatant duties should be imposed on Europeans. The next point to be thought of is the selection of the men to form the force. These should be carefully picked. All men with a previous history of severe or repeated malaria should be excluded. As regards rank and file this rule should be absolute. No man whose blood contains, or probably con- tains, the malarial plasmodium should be allowed to proceed on the expedition, partly in his own interests, but mainly in those of his comrades. As regards officers, and more particularly those who possess special qualifications for em- ployment, some latitude must be given. In such cases three or four examinations of the blood should be made, and if Plasmodia are not found, a previous malarial history need not exclude. If plasmodia are present, the value of the individual as a strategical or tactical factor must be balanced against his potential danger as a disease centre. With an educated man occupying a tent by himself the danger is obviously not so great as in the case of a comparatively uneducated private soldier sleeping amongst his comrades. No young soldiers should be sent. Not because there is, as far as we know, any special predisposition connected with immaturity, but because the less tough a man is, the less able he is to withstand the hardships and privations inseparable from tropical active service, and, therefore, the more likely he is to break down, and consequently lower his powers of resistance. It must be remembered that in a malarious country a man with Plasmodia in his blood is just as much a focus of infection as a small-pox patient would be in a barrack-room at home. Any man, therefore, who is likely to break down is a danger to his comrades, and should be rejected. The made soldier 590 THE PREVENTION OF MALARIA IN WAR [Sect. has the further advantage that he is more knowledgeable as regards the thousand details that make the difference between comfort and discomfort, which in the tropics is almost equiva- lent to saying health and disease, than the raw youngster. He knows better how to cook, how to rig up rough shelters, what to eat, drink and avoid, and, generally, how to look after himself. Syphilis, of course, should exclude, unless the man has special qualifications. Some German authorities advise that all men should be tested prior to embarkation, to see whether or no they possess any special intolerance to quinine — a somewhat meticulous precaution. An absolute intolerance of this drug is rare, as a matter of experience. The next point to be considered is the selection of the theatre of war, and more especially the selection of the line of advance into the enemy's country, and the base of operations. As regards the first named, naturally not much can be done by the sanitarian. If the enemy inhabits a malarial country, or the key of the strategical situation lies in a district where these diseases are rife, the fact has to be faced, and made the best of when the time comes. Still the Walcheren expedi- tion is a notable instance where the epidemiological factor should have been given decisive weight. As regards the line of advance and the base of operations the case is different. One of the most important duties devolving on the Intelligence Department, in connection more particularly with campaigns in the tropics, is the collection of information as regards the health conditions of the country to be invaded. If a preliminary reconnaissance is feasible, a specially-selected medical officer should be entrusted with this duty. He should, if possible, be acquainted with the country already, but most certainly he should have a thorough practical knowledge of malarial prevention and of tropical entomology. He should ascertain the spots most suitable for landing troops, and note the possi- bilities in the way of systematic malarial prevention possessed by each. He should, at the same time, draw up schemes for 6o] SELECTION OF SEASON 59i such work, giving an estimate of time necessary for its com- pletion, number of labourers required, and so on. His recon- naissance should be pushed as far up the line of projected advance as possible, and he should select sites for camps and posts, temporary and permanent. It must be kept in mind that dealing, as we mostly are in these cases, with a savage foe, the first energies of the force should be directed, not against the human enemy, but against the far more intractable and deadly insect foe. Superiority in armament should be more than sufficient to cancel the tactical defects, if any, of a position selected primarily on sanitary grounds. More especially would this be the case if the base were situated (as in the majority of cases it will be) on a coast where the fire from the fleet can be made available to assist the force on land. It would be a mistake, however, to suppose that there need necessarily be any conflict between the sanitary authorities and the staff of the expedition. A good military site is in most cases elevated, and free from immediate obstruction to the view. The post, therefore, will be more or less elevated, and the surrounding jungle must be burnt or cut down, both important points as regards the prevention of malaria. Proximity to drinking-water must not be allowed to overrule the importance of avoiding as far as possible all mosquito- breeding grounds. The place being fixed, the next point in order of importance is time. Here greater latitude is allowable, and it must be at once stated emphatically that only the most urgent political necessity, the rescue, for instance, of a beleaguered garrison, can justify the despatch of a European force to a malarious country at the unhealthy season of the year. As an instance of this may be noted the Ashanti war of 1873. The first inroad of the Ashantis took place in May of that year, but though the various threatened posts were reinforced as necessary, the first actual blow was not struck by Sir Garnet Wolseley till the 14th October. The Ashanti expedition of 592 THE PREVENTION OF MALARIA IN WAR [Sect. 1864 shows equally well the results of neglecting this obvious precaution. It is necessary to insist on this point. The expedition in 1864 was undertaken in the unhealthy season — March to June — and the mortality and sickness, almost entirely from malaria, were so great that the entire enterprise collapsed. Malaria was just as rife on the coast in 1873 as in 1864; the mortality among the Marines in the interval between May and October of the former year, whilst Wolseley was waiting for the auspicious moment to strike his blow, was I7'30 per 100, greater, as Sir Anthony Home (A.M.D. Report, 1873, p. 225) points out, than that of the army in Walcheren : whilst that of the expeditionary men after October was only 3" 14%- It must be remembered that scientific prevention of malaria, as we now understand the term, was as little known in 1873 ^^ it had been nine years earlier. The striking difference in the incidence of disease in the two expeditions was due, in great part, to the careful selection of the season in which active operations were carried out. The question of housing of troops is most important. For this purpose portable mosquito-proof houses should be provided. These can be constructed of any material, but probably some of the modern fire-proof compositions (Eternit, etc.) would be found the most convenient. These should be provided in sufficient numbers to house all European details left at the base throughout the progress of active operations, with a margin of 10 to 20%. This is essential. No European should be made to sleep exposed to the attacks of mosquitos for a single night, where this risk can by any possible means be avoided. If the force is kept, as regards Europeans, within reasonable limits, there should be no difficulty in this respect. Any barracks of this nature sent out should be shipped on the transports carrying the troops, and it ought to be laid down that no men should be landed in advance of their barracks. If the line of advance is easy and well known, and if transport is easily procurable, then huts for Europeans should be sent 6o] RATIONS, CLOTHING, NETS, FANS 593 forward to the first camps on the Lines of Communication, especially those likely to be occupied permanently, as in Ashanti in 1873- 1874. If the correct view of the class of campaign be clearly recognised, which is, that the contest is one not so much with man as with disease, and that the defensive measures necessary should be directed not against the attack of a human foe, but against those of tropical insects, it will be realised that the provision of adequate shelter against these pests is as essential as the provision of adequate shelter against the fire of a civilised enemy in a European war. The best type of hut or barrack is one raised on piles from the ground, much like the pattern of bungalow used in Burma, Rations. — The scale of rations should be liberal. The meat would perforce need to be in most cases preserved, and probably biscuit would have to take the place of bread. In this case a liberal supply of antiscorbutics in the form of lime-juice, pickles, jam or preserved fruit should be supplied. A special issue of coffee, cocoa or tea should be arranged to be served out to men on night duty. It is unnecessary to say that alcoholic stimulants, in excess of the ordinary service occasional issue, are not demanded. Clothing. — The ordinary field service kit would be sufficient, with the addition of gloves and veils for use after dark. The Japanese mosquito-bonnet might be adopted. Special equipment. — For hospitals mosquito-netting should be issued, and the same applies to the details left at the base. It is doubtful in how far it is any use issuing squares of curtain to men actually in the field, since the use of it in camp life is difficult. It would at least be a harmless precaution. Some form of mechanically operated fan should be supplied for use in hospitals and offices at the base. The motive power can be supplied either by electricity, or by a small gas or hot air engine. Such fans not only aid in ventilation, but they also assist in keeping off mosquitos. Instruction of men. — All officers and men taking part in Z P 594 THE PREVENTION OF MALARIA IN WAR [Sect. the expedition should be carefully instructed in the causation and pathology of malarial fevers, as well as of other tropical diseases. The important part played by insects should be pointed out, and special emphasis should be laid on the fact that the causation of these diseases is not of an esoteric nature, but the mere commonplace result of the bite of a commonplace insect. The miasmatical theory dies hard, and it is not easy to get the lay intellect to realise that disease is not caused by some mysterious power of induction possessed by some intangible emanation. The period occupied or spent on board ship can profitably be utilised for this instruction. We now come to the period of active operations, and the first point to be considered is the base of operations. Amongst the instructions to Sir Garnet Wolseley in 1873 it was laid down that if the use of European troops became imperative everything should be prepared in anticipation, and not a man be landed before the moment for advance into the interior arrived. The accommodation for troops at the base need not therefore be large, and may be limited to that for the details left there on duty, with a small margin. Measures directed against the breeding-grounds of the mosquito, which should have been, as already stated, drawn up by the special medical officer entrusted with the preliminary survey of the base, must be carried out as in cantonments in time of peace. A specially selected medical officer should be placed in charge of these operations with executive and disciplinary powers, a step that has been proved to be so effective by the officers of the United States Army in Cuba and elsewhere. This officer should be provided with an ample supply of native labour, and such number of European subordinates, preferably N.C.O.s of the Royal Army Medical Corps, as the size of the locality demands. Any parsimony in this direction may have serious results. Presumably, the base will not be in the immediate vicinity of a native village. Nothing but the most urgent strategical necessity can justify such ^ 6o] THE BASE 595 selection. In addition, all native establishments must be encamped or hutted at a distance from the European lines. Their defence and discipline must be ensured by appropri- ately situated outposts, electric lights and barbed wire fencing being used to assist in these and prevent desertion. The guns of the fleet can, of course, assist in defence. It may be neces- sary to erect a base hospital, but patients should be retained there only so long as to permit of rest prior to embarkation. Two hospital ships should be used on any tropical expedition. Of these one would always be available for the reception of sick coming from the front, whilst the other was carrying its passengers to the nearest healthy port or island. It is essential to insist that there is no difference between the conditions at the base, and the conditions of any canton- ment during ordinary peace time. Everything that is possible in the latter case is possible in the former, and should be carried out with the same thoroughness and the same careful organisation. The subject of prevention of malaria in canton- ments is treated of elsewhere, so more need not be said here. The important point, and this cannot be too often repeated, is that undivided responsibility should be given to one man, and that authority of equal extent should go hand in hand with the responsibility. So only can success be hoped for in the war against malaria. Leaving the base of operations, the force now proceeds on its mission. Detachments will no doubt be made from time to time of small bodies to hold fortified posts on the Lines of Communication. These detachments may have to remain stationary for the greater part of the campaign, and in their case regular anti-mosquito measures must be undertaken, as far as possible on the same lines as at the base, or in canton- ments in peace time. The proximity of a native village will necessarily be avoided as far as possible. Where the tactical situation necessitates such proximity, the village, if deserted, must be destroyed by fire directly the permanent occupation 596 THE PREVENTION OF MALARIA IN WAR [Sect. of the post is decided on. If still inhabited some trouble may arise, but it would be preferable to forego some minor tactical advantage than to run the great risk of disease that such a situation entails. If the tactical considerations are paramount, then the inhabitants should be, if possible, evicted, fresh shelters being built for them at a little distance, and any necessary compensation paid. The site could then be, as already recom- mended, cleansed by fire. Since it may be accepted that the mosquitos already existent in the neighbourhood of the post are infected, it would be advisable to adopt the method origin- ally suggested by Nuttall {^Journal of Hygiene^ 1902, vol. ii. p. 73) of constructing mosquito-traps from small boxes, lined inside with some dark material. Dr Blin, Principal Medical Officer of Conakry, utilised a similar method in Dahomey in 1905 {Archiv. fur Schiffs — und Tropefi Hygiene^ Bd. xiii., 1909, p. 645). He noticed there that the adult insects were in the habit of sheltering them- selves during the hot hours of the day in the burrows of the land crab, and in holes between the roots of mangroves. He accordingly caused small holes to be dug in the ground about 16 inches deep, at a somewhat acute angle to the surface. These holes were so situated as to be protected from direct sun- light, and were, if properly placed, invariably crowded with mosquitos. These insects remained in their shelters until 4 P.M. as a rule, and accordingly between 2 and 3 p.m. on each day the holes were burnt out by means of a small torch, consisting of a stick about 5 feet long, at the end of which a piece of rag or tow, soaked in petroleum, was fixed. Such a torch will burn for about ten minutes, and one will suffice to burn out fifteen to eighteen holes if in close proximity to each other. A well-trained native can attend in this manner to one hundred mosquito-traps in a day. The cost is trifling, 3 litres of oil are sufficient for five hundred torches. Fresh holes must be dug once a fortnight, as the old ones become saturated with oil. As far as possible all permanent posts 6o] THE MARCH 597 should be provided with mosquito - proof huts, and in their absence mosquito-netting should be supplied to the men. Night duties should be reduced to a minimum, and sentries relieved every hour, or even oftener. The very fullest use should be made of mechanical appliances, barbed wire entangle- ments, searchlights, etc., with a view to lessening the strain on the sentries. Hot coffee, cocoa, or tea should be freely avail- able for all men exposed to the night air. On no account should fatigues, which can be performed by natives, and for which natives are available, be carried out by Europeans. The question of the prophylactic use of quinine will be discussed later. With regard to moving bodies of troops, which do not occupy any one camp for more than forty-eight to seventy- two hours, it is obvious that measures directed against the breeding-grounds of the larvae can be of no avail. Before any such measures can have effect the force will already be many marches away. The defence therefore limits itself to the pro- tection of the men from the adult mosquito, and to preventing the access of the latter to the exposed surfaces of the body, or, as a last resort, to rendering individuals immune to the Plas- modium by the use of quinine. The former can be achieved by the use of mosquito-veils and gauntlet gloves by men on night duty, and, doubtfully, by the use of mosquito - netting when asleep. Unless a man is provided with some sort of framework whereon to support the curtain, it is doubtful in how far this precaution is of use. Obviously a complete set of poles for mosquito-curtains cannot be carried by each man. The issue of a couple of yards of netting to each member of the force is at the same time a precaution that may with advantage be adopted. The use of essential oils for the purpose of anointing the exposed surfaces of the body has much to recommend it. It causes less dis- comfort than that entailed by the obstruction to respiration when veils are worn. There is at the same time less hindrance 598 THE PREVENTION OF MALARIA IN WAR [Sect. to the vision, and the hands are less hampered in the manipula- tion of the fire-arm than is the case with gauntlet gloves — important points in the case of sentries. Kerosene or paraffin oil, everywhere procurable in the tropics, serves this purpose as efficiently as any of the more elegant aromatic oils. Last of all we come to the prophylactic use of quinine. When it is impossible to control the breeding of mosquitos, or to protect oneself from the bites of the adult mosquito, then it is necessary to have recourse to the prophylactic administration of quinine. But it must be premised that such a system of prevention of malaria is a confession of failure. Success may be difficult, or even impossible, under the many vicissitudes of campaigning in tropical jungles when troops are constantly on the move. Success may be difficult, but it should not be impossible, under conditions such as prevail at a properly selected and administered base of operations. The prophylactic administration of quinine should not therefore be looked upon as anything but a last resort, or a merely temporary expedient in the case of troops living under settled or comparatively settled conditions. The prevention of disease by the adminis- tration of drugs is as unscientific as the treatment of disease by relief of symptoms only. Both courses may, under certain conditions, be imposed on us by the force majeure of circum- stances, but neither should be deliberately chosen as the chief method of defence, either in sanitation or therapeutics. The administration of quinine has this great drawback, that each individual has to be protected separately. The total mass of disease in the country is in no way affected. Every new- comer is still exposed to the risk of infection, just as much as his predecessors, and each such person must be protected. On any scientific system of sanitation the disease should be attacked, not after it has infected the patient, but before. Measures directed to the latter end protect the individual, not the community, whilst true sanitation aims at protecting the individual as an item merely in the community. If quinine 6o] QUININE 599 is administered, I lean personally to the German method of giving two large doses on two consecutive days, lo to 15 grains, according to the idiosyncrasy of the individual. As a matter of practical administration this should be done once a week, on Mondays and Tuesdays, or any other days, but the same days of the week should be adhered to throughout. The dose is less likely to be omitted in such a case. By Major C. E. P. FOWLER Royal Army Medical Corps, Gibraltar 61. The Prevention of Malaria among Troops under Peace Conditions. — The vast importance of malarial fever can be appreciated by a glance at the following table, from which it will be seen that out of a total strength of European troops serving at home and abroad of 215,467 there are admitted to hospital each year 19,092 patients suffering from this affection. The average constantly sick reaches the large total of 653'03, which means that a number equal to the ordinary strength of a regiment is always hors de combat owing to this disease. EUROPEAN TROOPS AT HOME AND ABROAD. AVERAGE STRENGTH, 215,467. Malaria. 1908. Gross Admissions to Hospital. Deaths. Invalids. Average Constantly sick. 19,092 47 197 653-03 1908. Ratio per i ,000 88-6 0"2I 1-87 3-07 1903- 1907. Ratio per 1,000 64-4 0-13 2-39 2-47 The next table shows the incidence in some of the countries where malaria is most rife, and a comparison is here given of the effects of the disease during 1908 and the five previous years. 600 Q 8 •J^OIS XlJUBJSUOQ r" 00 NO l-O CO lO nO CO 00 *^ 00 ■* CO -* (S t^ CO CO nO N '-' o t^ (S Tf 00 nO •spqBAUi CO NO Lr> ON On On u O NO '^ o NO ,^ C» 2 CO M ►- M ON t^ NO '^ 00 1^ cs CO CO '-' vO I^ ^ t^ NO u~» NO ■JfOIS iCnUBJSUOQ i U1 r D t-^ NO CO — t^ CO i ''' CO CO ■nI- «— 1 o o 00 § 1 rj {S H NO CO l-O TJ- CS oo •^ o On 0.- : CO M 01 CO "^ O o 4^ QJ •sqjBaa CO ^ ir^ CO ►-< • o a 1 '"' M vO LO CO r-^ 00 NO ■snoissiuipy — NO CO :^ 0^ u-i NO O •^ i-n CO CO ON ON cs ON i-r\ C^ ON •JJOIS XlJU-EJSUOO CO CO CO ON NO On CI NO CO r^ •oj^ aSBjaAV o NO CO O c< CO •SpilBAUJ • : vO 2 t^ u~i Cl NO •sqjBsa • CO r^ CO ro ON r^ '^ 00 On LTl NO CO qBjidsoH CO CO CO CI N ri CO NO ojut suoissiiupv vo" 00 o O 3" '^ 00 CO CO CI r^ •qiSnajjs 3SBJ3AY o ^ ■^ U-1 NO oo O CO cT CO Cl o 30~ NO 1 1 l/l * c o a! 0- n o '•S < in cti G '-5 u 3 O CO H 1 U ex 03 u S a 3 a C _o U 1 6o2 PREVENTION OF MALARIA AMONG TROOPS [Sect. During 1908 malaria gave the largest gross number of admissions and therefore the highest admission rate per 1,000 of any disease on the nomenclature. This fact alone must point out the transcendent importance to the military sanitarian of finding some means of lessening the disease and saving the enormous waste entailed by the loss of service of our soldiers and sacrifice of public money through inefficiency. On looking at the table it will be seen that Western Africa heads the list under nearly every column of ratios per 1,000. The West Coast has always held a bad record for malaria, and this disease can be said to cause from 50% to 60% of the total admissions, invaliding and average constantly sick for all diseases at the stations in this command. The West Indian troops suffer almost as severely as the European, but the West African regiments are much less susceptible. The country which costs us most dearly is India, where we can see how terribly heavy the toll of sickness caused by malarial fever is. The figure for 1907 was a great improvement on that for the ten years previous, but, unfortunately, 1908 was a wet year, fever was prevalent amongst the native popula- tion, and, in consequence, the figure again rose, in spite of all efforts to diminish it. INDIA. APPROXIMATE STRENGTH OF BRITISH TROOPS, 70,000. Malarial Incidence. Year. Admissions. Deaths. Invalids, 1898. 28,382 50 485 1899. 16,579 36 246 1 900. 19,445 62 190 1901. 18,217 35 418 1902. 15,367 45 245 1903. 17,037 35 244 1904. 12,112 23 259 1905. 7,947 10 126 1906. 12,601 22 136 1907. 10,662 15 274 1908. 16,763 35 62 6i] STATISTICS 603 It should be noted that since 1903 a large number of men, averaging from 4,000 to 5,000 each year, are treated in barracks. Amongst the native army of India malaria is also very prevalent. During the last ten years the average strength of these troops has been 124,523, of whom 34,074 have been each year admitted to hospital, to say nothing of those treated in barracks and not coming on the returns. Having thus briefly outlined the incidence of malaria at some of the various stations of British troops, there is now to be considered what means of prevention can best be employed to counteract such serious losses. In the first place, it must be presumed, when formulating any means of prevention, that readers are believers in the part played by the mosquito in the transference, spread and maintenance of the malarial parasite, and have absolute faith in the formula of " No mosquitos, no malaria." It would appear mere waste of words to make such a statement at the present day, were it not that experience has shown how even now there are people, including members of the medical profession, who still retain doubts of the mosquito being the sole carrier of the malarial parasite. All recom- mendations here made will be based entirely on the proved facts of malarial transference by the aid of certain varieties of Anophelines. In formulating the measures of prevention most applicable to troops, it must always be remembered that the soldier cannot be thought of in his position as a unit only ; there also has to be taken into consideration the inhabitant of the country in which the soldier is residing. It may be stated, as a general axiom, that if the native suffers from a certain disease, it will almost necessarily follow that, unless extraordinary precautions are taken, the soldier will inevitably suffer from a like com- plaint. The soldier is largely dependent for his health on that of the community around him. Therefore it comes to this in many cases, that to check malaria amongst the troops it will be necessary at the same 6o4 PREVENTION OF MALARIA AMONG TROOPS [Sect. time to lessen it amongst the surrounding inhabitants. Thus the question can be seen to be a much wider one than would at first appear. Preventive measures may be divided into : — 1. General measures of prevention. 2. Personal measures of prevention. I. The general measures of prevention are such as will be undertaken by the State, Local Government, or Community at large. As a rule they involve a considerable expenditure of capital, as well as a large amount of thought, trouble and probable legislation by those in power. For these reasons obvious means of cutting short malarial incidence have been on more than one occasion allowed to lapse, or only very in- adequately provided for by Local Government officials. Failure must necessarily follow ; and though the authorities may endeavour to make a scape-goat of the means recommended, the blame lies entirely at their own door. In other instances financial considerations alone must block the way to improvement ; and in certain of our colonies it is a question for serious debate whether the necessary funds should not be provided temporarily by the Imperial Exchequer. It is heart-breaking to look on the results of malarial havoc, knowing at the same time that this could be controlled, were power and money employed to the best advantage ; and yet neither can be obtained. These general measures can be dealt with but briefly in this section, but reference must be made to them as affecting the population surrounding the troops, on whose health the latter are so largely dependent. At the present time there are two schools of opinion. One relies mainly on the destruction of the larval mosquito ; the other, believing that such a desideratum is without the range of possibility, affirm that quinine dosage forms the mainstay of prevention. The first school, relying chiefly on larval destruction, looks 6i] MEASURES 605 upon quinine as a valuable aid certainly, but not to be placed upon the same footing as the destruction of the primary agent, except in certain cases where larval destruction is almost hope- less. The second school base their preventive measures primarily on quinine dosage, and hold that if the malarial parasite is prevented from remaining in the human blood-stream by the administration of quinine, then it is impossible for the mosquito to become infected. In every country where malaria is present there is some diversity of opinion on which of these methods chief reliance should be placed. This matter will be dealt with fully in other sections, so that no further reference will be made to it here, save to mention, as a general statement, that in the majority of our possessions larval destruction is the one of primary importance and trial. A. The General Measures may therefore be cited as follows : — (i) Larval destruction. (2) Segregation of the soldier. (3) General quinine treatment. (i). Larval destruction, under this heading, means the elimination of all spots where the Anophelines may find a home or a suitable breeding-place, from which it can reach barracks, cantonments or other sites where troops may be quartered. The question at once arises : What is the probable or possible flight of one of these insects? A reply of fact and not of theory it is impossible to furnish. Some years ago many authorities would have judged the probable limit of flight at a few hundred yards, but facts have arisen since then, showing that mosquitos under favourable climatic conditions can and will travel several thousands of yards from their breeding-place to their feeding-ground. To lay down a precise distance of safety is quite impossible, but a reasonable limit, within which no breeding-spot should be allowed around barracks, may be 6o6 PREVENTION OF MALARIA AMONG TROOPS [Sect. quoted at 2,000 yards or thereabouts. Now many of our barracks abroad are built on small plots of ground belonging to the War Department, but the land closely adjoining may be quite without their jurisdiction ; the consequence being that the Military Authorities have no power to enforce the abate- ment of evils existing on the ground of neighbouring tenants. At the present day no barracks should be built in the tropics or sub-tropics on ground which does not include the control of an area of 2,000 yards' radius from it as the centre of a circle. Unless this plan is carried out the troops occupy- ing the barracks must of necessity be exposed to all dangers arising from a neglected condition of the surrounding area, as well as the risk of being infected with other diseases from which the inhabitants living on this ground may be suffering. Many examples of barracks situated in this faulty position might be quoted from our Colonial garrisons. When the State or War Department owns or controls the land around barracks, it is incumbent upon them to place this ground in such a condition that it shall not act as a breeding-spot for mosquitos. If such a land is not their property, and is forming a favour- able source of origin for Anophelines, it is essential that the ground should be purchased, in order to gain complete control over it. The purchase may involve great expense, but this would probably soon be covered by the saving effected in the improved sick-rate of the troops. (2). Segregation of the soldier. — This has been referred to under the previous heading. It may be stated fairly con- clusively that the wider the separation of the soldier from the native inhabitants the better will be his health. The barracks that have been carelessly placed in the midst of native towns, or that have become encroached upon and surrounded by native houses, will show a far heavier incidence of disease than barracks standing in isolated positions. The reservoir of the malarial parasite is to be found chiefly in the children of the 6i] CANTONMENTS 607 native inhabitants. An infected village with a high spleen rate amongst its children will contaminate any camp or settle- ment within a wide distance of its site. Such a condition of things exists in numbers of our garrisons abroad. Take the case of so many of our Indian stations. The barracks may have originally been placed at a reasonable distance from the native town, but a bazaar has been allowed to grow up alongside them for the use of servants and others serving on or trading with the troops. Many of these Sudder Bazaars contain several thousands of inhabitants. Malaria or any other disease from which they may suffer must inevitably spread to the troops. Again, within the Indian cantonment, until quite recently the native was allowed to grow any sort of crop, and to do practically whatever he wished with the ground rented. The consequence was, and still is, in some places, that rice fields existed within quite a short distance of barracks, to say nothing of other crops requiring an abundance of moisture, which so generally means neglected ditches and the formation of small marshes. The outcry against the continuance of such a state of things has often been raised, but is invariably met by the answer that if such crops are done away with, the cantonment funds would disappear and financial ruin ensue. It is the duty of the State to insist on an abatement of such dangers; and if in any case its continuance cannot be stopped, then the troops should be moved and the station evacuated. Until the State can appreciate the enormous losses involved by the sickness of our soldiers from malaria and its sequelae, it is almost hopeless to expect works to be taken in hand, which must appear to the authorities to involve a large expenditure of capital without any evident financial return. (3). General quinine treatment. — By this is meant quinine treatment of the general population of the country in districts around the location of troops. This lies outside the measures to be undertaken by the Military Authority, who would only 6o8 PREVENTION OF MALARIA AMONG TROOPS [Sect. be in a position to advise and not insist on such a campaign of defence. It would mean action on the lines of the Italian school, and will be fully dealt with in another section. The military forces would benefit very greatly, as the chief source of their contamination, namely, the native children, would be brought under treatment, and their capability of spreading the parasite by acting as reservoirs materially lessened. B. Personal Meastires of prevention must now be considered. These are such as can be carried out by units themselves and will involve no great initial expense, as is so often the case with the general measures. The various means employed may be enumerated as follows : — (i) The attack on Anopheline larvae in their breeding spots. (2) The defence against the adult Anopheline. (3) The segregation of malarial patients, and their protec- tion from the Anopheline mosquito. (4) Segregation from the native. (5) The administration of quinine. (i). It is one of the first duties of an officer commanding a barrack or cantonment to see that the same is kept in a clean and sanitary condition. It must also be the duty of this officer to see that the place under his control in a malarious country is in such a state that mosquitos will be unable to find any breeding spots on its area. If he does not himself under- stand or appreciate the hygienic importance of this order, he must be compelled to do so by a higher authority, and be made to accept the advice of experts who have made a special study of the subject. The attack on mosquito larvae can best be carried out by the formation of " mosquito brigades," or " working gangs," consisting of men especially trained to such work. These men may be either soldiers or natives of the country. It 6i] MOSQUITO REDUCTION 609 is not considered that the former are suitable for these duties. Soldiers are wont to despise such employment, and think it beneath their dignity to carry it out. In addition, there is always the likelihood of their being continually changed and taken for other duties, just at a time perhaps when their services are most urgently required. It must also be borne in mind that the heaviest work will come just at the most trying season of the year, when the weather is intensely hot and perhaps saturated with moisture. In a tropical country soldiers should certainly not be employed. It remains, then, to rely on the native. It has been found in practice that, if the proper class of native is selected, he is capable of being trained very efficiently to the work ; but of course he will always need the supervision of Europeans. The number of these men required v/ill vary in accordance with the size and conditions of the barracks, cantonment or War Department ground. Experience has shown that it is better to divide up the men into separate units or working gangs, rather than have a number of men engaged indis- criminately. A convenient working gang would consist of a head man with two or three underlings. The head men should be selected for their special aptitude in the work and should receive more instruction than their underlings, in order that they in their turn may be able to impart the information received. All the men employed must be given a general insight into the causation of malaria and be taught the life history of the mosquito. They must know the different species, both of the larvae and adults, together with their habits. They must also receive a course of instruction in the best means of dealing with casual water, in ditching and rough draining. These men should be under the direct control of the medical or other officer appointed in charge of malarial work, and he will be responsible for their instruction. Different ways of working the gangs can be arranged as best suits the individual place. For instance, the station may be 2Q 6io PREVENTION OF MALARIA AMONG TROOPS [Sect. divided up into six different areas, and a gang made responsible for each ; or gangs can be employed on one of these areas for a day in each week. Again a gang may be appointed to each regiment or unit, and a man, preferably a N.C.O., made respon- sible for its working. The general duties of these gangs will be shortly as follows : — The exploring and examining of all ground around the barracks or cantonment ; the collection of all tins, pots, pans, or other rubbish capable of holding water ; the cutting and removal of all waste vegetation, brushwood and scrub ; the clearing and grading of ditches, the filling up of holes and hollows, the draining away of casual water and small marshes ; the examination of water-tanks, water- butts, wells and cess-pools ; the search for plants and holes in trees retaining water ; the treating with paraffin-oil, tar or other larvicide of all water that cannot be disposed of or properly protected. It is advisable that attention should be paid, not only to the Anopheline larvae, but also to those of Culex and Stegomyia, as the destruction of the two latter, which are usually the more domestic species and therefore more in evidence as nuisances, will show the inhabitants of the station that something is being done. Besides, in many places, these mosquitos are a veritable pest, the Stegomyia by day and the Culex by night, and their destruction is worth some outlay, if only to obtain increased comfort. When dealing with these larvicidal operations, the question of the station or cantonment irrigation is certain to arise. Where a canal supply is in force, as in many parts of India, it is well- nigh impossible to act efficiently on the Anopheline larvae, unless such irrigation is stopped. The main canal, as it passes through the cantonment, is broken up into numberless small channels for the distribution of the water. These generally become little better than rough and neglected gutters, over- grown with vegetation, and allowing the water to stagnate. Small patches of marsh or water-logged soil are often formed 6i] MECHANICAL PROTECTION 6ii by the side of these channels from leaking or overflowing of their banks. These will form ideal breeding spots for most varieties of the Anophelines. On the other hand, it has to be recognised that if irrigation is cut off, the cantonment will be turned into a desert. Irrigation from wells is by no means so objectionable. The supply of water is limited by the labour necessary to raise it from the well, and therefore only a sufficient quantity to irrigate the crops themselves is drawn. Water seldom stands wasting in channels or sides, so that the Anophelines have little opportunity of finding any breeding pools. A medical officer should be detailed for each station or cantonment to look after all malaria work, and he should be placed in charge of all the working gangs to direct and super- vise their operations. At the headquarters of each district or province a medical officer possessing special knowledge on the subject of malaria should be appointed. It should be his duty to travel from place to place, to supervise the work being carried on, and to advise as to future procedures. All reports on malaria from the out-stations should be submitted to him, in order that he may collect the various details, and be in a position to form a reliable opinion on the efficiency or otherwise of the different measures of prevention. (2). The defence against the adult Anopheline. — The means at disposal are mosquito-proof houses and mosquito-curtains. In Europe, or even in a sub-tropical climate it is easy to lay down rules and carry them out as regards the use of the above means. The matter resolves itself into one only of expense for their provision. In the tropics the situation is far different. Here the most prominent question is : Will the troops or others make use of such means if they be provided? or even it may be asked : Can they be allowed to do so .? To those who have experienced hot weathers on the plains of India this point is one that is only too vividly appreciated. To 6i2 PREVENTION OF MALARIA AMONG TROOPS [Sect. expect any one to remain under a mosquito-net during the day or night-time of the hot weather, or even to remain in a room, the windows of which are blocked by wire -gauze netting, is scarcely reasonable. Existence would be unbearable, and in all probability sacrificed to an attack of heat apoplexy. Un- fortunately the use of mosquito - curtain and punka is incom- patible, at least for the soldier. Mosquito - proof rooms and powerful electric punkas or fans might be borne. In many parts of India, for five or even six months of the year, punkas are a necessity of existence, and therefore curtains cannot be made use of It is impossible to lay down definite rules in regard to this question. In each district or station the various points will have to be taken into consideration in a common- sense manner, and corresponding recommendations made. Mosquito - curtains should undoubtedly be provided for all soldiers in a malarious locality, and they should be made to use them if the climatic conditions permit. The form of curtain varies. The bell pattern is the cheaper, more easily managed and hung, but does not allow the same air-space within it. This appears a minor point in the sub-tropics, but is soon appreciated under tropical conditions. The old pattern square shape is now again being used on this account, but the obstruction to ventilation and air movement becomes very great when each bed in a barrack room is fitted with these curtains. Men must always be instructed in the best method of hanging them, otherwise they are worse than none at all, and act simply as traps. In many cases it has been found that although curtains are provided, the men are not in the habit of using them when on guard or attached duty, and consequently become infected. The provision of wire-gauze for all doors, windows and ventilators in a barrack - room is one of theoretical excellence, but one of great practical difficulty. The expense, both initial and recurring, is of some magnitude, and constant watch must be kept on the proper fitting and closing of the openings ; otherwise the soldier is 6i] SEGREGATION 613 sure to remove what he will consider are useless obstructions to the breeze. In certain isolated and dangerous positions, where a small number of men are on duty, the employment of this method is undoubtedly a sound one, but as a general preventive measure it has not been taken up for our garrisons. As regards the destruction of the adult mosquito but little can be done. The majority of the Anophelines are night feeders, and as a general rule will leave a room before day- light. There are some varieties, however, which will remain a certain time after engorgement, and can be found in the dark corners of rooms. Various means have been devised for killing off these insects by fumigation, such as the burning of sulphur, formalin or other chemicals. These methods are of but little use in the tropics, where it is most difficult to render a room in any way fume-tight. The safest procedure consists of the regular sweeping out of all dark corners, removal of unnecessary hangings, and thorough cleanliness. Many so-called specifics have been brought forward, purporting to ward off the attacks of mosquitos when smeared on the skin, such as soaps, ointments, oils, etc. Some of these are excellent, whilst their virtue lasts, but the latter is very evanescent, and few of them are found to be efficient for more than about half an hour. (3). The segregation of malarial patients and their protection from Anophelines. — This is a most important matter and one that has been much neglected up till very recently. It was customary to place patients suffering from malaria in any ward with other patients not yet infected, no provision being made or even thought of to prevent infection being carried from one to the other. In consequence, many men who were in hospital for some trivial complaint became infected with the parasite during their detention. At the present day it is understood that a patient suffering from malaria is a danger to his non-infected neighbour, and he should, therefore. 6i4 PREVENTION OF MALARIA AMONG TROOPS [Sect. be placed in a separate ward, and provided with curtains, or if these cannot be borne, then the ward must be rendered impervious to the entrance of the mosquito. In any station where malaria is prevalent, these precautions are essential. A ward containing malarial patients unprotected from the attacks of the Anopheline carrier, is a grave potential danger to the surrounding community, and should not for one moment be tolerated. (4). Segregation from the native. — The importance of this has been referred to previously under general measures of preven- tion, when insistence was laid on the advantages to be derived in separating soldiers entirely from the native houses and population around. It must not be forgotten that the soldier may still easily contract the disease by visiting places or towns, where malaria is rife amongst the inhabitants, and it is very necessary to do everything in one's power to prevent such excursions, more especially after dark. When troops attend camps of exercise or are on the march through a malarious country, the encampments should always be placed as far as possible from any native village or from any spots where infected mosquitos are likely to be prevalent. The same advice can be given as regards shooting-trips, on which the officer often, and the soldier occasionally, proceed. Native guides will always try to induce a party to pitch their encampment in close proximity to a village or water of some kind, for obvious reasons of supply. This should not be allowed, but the very opposite plan adopted. The use of nets for soldiers when on the march is almost impossible, crowded as they are together in small tents, but for the officer it is quite a simple matter to carry a small bell-shaped net and sling it up from the tent wall or branch of a tree at night. On shooting-trips during the malarious season a net should invariably be carried. It is very light and easily packed, if the supporting ring is hinged to fold over. (5). The administration of quinine. — This drug must be 6i] QUININE 615 employed for the soldier as for the general population, namely, to (a) cut short the actual attack, (d) prevent relapses, (c) prevent the infected acting as reservoirs and potential spreaders of the parasite, (d) act as a prophylactic agent. (a) The various methods of administering quinine as a curative agent will be dealt with in other sections, so that further reference to this point will not be made. The treatment of the soldier differs in no way from that of a man in civil life, and army medical officers have now a free choice of any method which they may select. (3) It may be taken for granted that, if a patient has been infected with the malarial parasite and suffered from an attack of fever thereby, it will require a period of probably three, certainly two months continuous and rigid treatment, before the parasite is rendered more or less inactive. To say that it is destroyed is not possible, however energetic the treatment may be. The failures of quinine to prevent so-called relapses are not generally failures in the true sense, as the recrudescence of the attacks is in the larg-e majority of such cases due to a re-infection. This is the reason why it is so extremely difficult to cure a patient when he still continues to reside in a malarious locality. Within the last few years the importance of the after-treatment of all soldiers affected with malaria has been appreciated by army medical officers, and nowadays every care is taken to carry on continuous treatment over a period of several months and to record results. It may be presumed that the blood of every suspicious case of fever now admitted to a military hospital will be examined for the malarial parasite, 6i6 PREVENTION OF MALARIA AMONG TROOPS [Sect. and that the diagnosis of malaria will never be made unless a positive result is found. When a malarial patient is discharged from hospital, some such scheme as the following may be employed. The man is given a paper, telling him on what days he must attend for doses of quinine. A duplicate of this order is kept by one of the hospital staff, whose duty it is to give the paper, note the dates of attendances, and report any failure to do so. The raison d'etre of continued treatment should always be briefly and reasonably explained to the patient, in order that he may grasp the importance of taking quinine regularly, not only for his own sake but in the interest of his comrades. The treatment must be enforced ; but as a general rule there is not much difficulty in making a soldier who has once had an attack of malaria realise that it will be to his benefit to continue treatment. Every facility must be given to him for obtaining the necessary doses. There is some variance of opinion as to the best method of giving the drug. For soldiers the most suitable plan is perhaps the administration of lo or 15 grains of the sulphate or its equivalent on two successive days every week or on three successive days every ten days over a period of three months. During this time the blood should occasionally be examined for the presence of para- sites and the treatment modified if necessary. {c) To prevent the infected acting as reservoirs of the parasite : Treatment for this object is in reality bound up with that mentioned for the prevention of relapses. If the latter do not occur, it is improbable that many or in fact any gametes are 6i] QUININE 617 circulating in the patient's blood. Similar lines of giving quinine can therefore be recommended. {d) As a prophylactic agent : On the use of quinine for this object there is a considerable diversity of opinion, and the latest military reports are not by any means favourable to any definite conclusions of the benefit ensuing from its administration, (A.M.D. Report, 1908, India.) However, there has been undoubted evidence of beneficial action exerted by its use, and it is therefore the duty of the medical officer in charge of troops to administer the drug whenever malarial conditions are widely prevalent. It must always be remembered that positive results, as the outcome of quinine in prophylactic dosage, are most difficult to estimate. Negative results are declared only too vividly ; and a few of the latter as facts far outweigh any estima- tions of the former as theories. In considering the results, it should be also brought to mind that a large proportion of the cases admitted to hospital, probably more than 50% in some stations, are relapses, and that the administration of quinine may greatly lessen the number of such relapses, quite apart from any action in preventing fresh infections. The difficulties encountered in carrying out an efficient prophylactic issue are very great. The soldier is extremely suspicious, when forced by order to undergo such a dosage, and will often do every- thing in his power to evade it. Considerable tact must always be employed in order to win over his confidence. In any case the drug must be taken by order, and in the presence of the medical officer or other reliable person. An issue to volunteers only soon resolves itself into a farce. The drug may be given in solution, or in the 6i8 PREVENTION OF MALARIA AMONG TROOPS [Sect. form of pills or tabloids. Solution has the advantage that it is always at hand and easily made up, but the taste is of course extremely disagreeable to most people. Pills are convenient, but take some time to make, and do not keep well under conditions of heat or moisture. Tabloids are really the most useful form, and given as a preventative only, they are unlikely to pass through the intestine unchanged. The uncoated form should be used. As regards this, there is a note in the A.M.D. Report, 1908, to the following effect. " As is usual the men disliked the quinine parades, and many adopted every means they could to avoid swallowing the dose ; tabloids of quinine were found unsuitable, since many men kept them in their mouths until the parade was dismissed, and then threw them away. Hence, quinine in solution was administered, and each man had to shout out his regimental number immediately after- wards to prove that the dose had been swallowed." The above is one typical instance of resentment at com- pulsory treatment, and points out how extremely difficult it must be to rely entirely on the results of quinine prophylaxis under military conditions. As regards the dose, there is some difference of opinion. A daily administration of 5 grains cannot be recommended for soldiers, owing to the trouble it involves in the parading, etc., of the men. In India during 1908, where in 53 out of 58 plains stations quinine was given as a prophylactic during the malarious season, in the majority of the cases 10 to 15 grains were used on two consecutive days in each week. This seems to be as good a method as can be recommended. One most important point not yet referred to is the instruc- tion of the soldier and others in the causation and spread of malaria. 6i] INSTRUCTION 619 All such instruction should be given in a way which will appeal to the imagination, and the language used should be couched in the most popular style. Short descriptions of lantern slides are the very best means of imparting elementary knowledge of this kind. Each medical officer appointed to a division or district as an expert on malaria should be provided with a set of lantern slides and suitable lantern, and give short demonstrations in each station throughout his district. A full but elementary understanding of the cause of malaria and the role of the mosquito in its spread, will explain to the soldier the reason of many precautions which he may have failed to under- stand and thereby neglected. It will be found that the men are ready enough to receive such instruction, and become greatly interested in the subject, provided that the facts are placed in a simple and straight- forward manner before them. ^' 2. THE CAUSK Ul' llIK MALARIA A.\I().\(,ST TH1-: TK(JU1'S IN Till-; lU'TS. This stream was situated at a distance of 400 yards, and formed a most favourable breeding-ground for /-". coslalis. 3- ANoi'iiEi.iNK hkki-:i)1n(;-(;k()i;.\I) in a coi.oniai, cantoxment (Mal-ritil-s). (The Latanier, near Port Louis, Mauritius— the river of Paul and \'irginia. — R. Ross. 5. TIIK SAME FINISHKI). This stood intact after several floods. *■ 't *' ^ c \ ADDENDA 62. Sugfgrested Terminologry for the Phenomena of Cyto- gfenesis. — Several such terminologies have been proposed, among others by myself. That of F. Schaudinn is now extensively used, but has the defect of attempting to limit the word spore to the first genera- tion of daughter cells proceeding from the zygote, and the word schist only to subsequent generations. His merozoites are in fact spores, his spores merozoites : his spores are really produced by his schizogony and his schizonts by his sporogony. I think therefore that a more general system, in which each root is invariably used in a strictly defined sense, may still be proposed for consideration, briefly, as follows : — Schist =^z. division of the centrosome and nucleus only. Clast = a. division of centrosome, nucleus and cytoplasm only. Mere = 2L division of the whole cell. Spore = z. mere when more than two meres are produced at a time. Protoschists or protoclasts are the first schists or clasts produced in the dividing cell, z.w^ protomeres ox protospores the first meres or spores (starting with the zygote). Deutero- and trito-^ etc., for succeeding generations. Gametes = the sexual elements. Microgamete = sperm, macrogamete = oon. Zygosis — conjugation, and zygote = the resulting body. — g^^y = production by — e.g., parthenogeny, sporogeny. — genesis = production of- — e.g., spermatogenesis. — -//aj/i- = making of — e.g., gametoplasis. — phase = p\i2ise or cycle — e.g., gamophase (sexual cycle), agamophase (asexual cycle), schistophase, merophase, zygophase, etc. — cyte = di cell destined to produce — e.g., gametocyte. — phore = z. body actually producing — e.g., sporophore (sporulating body), spermatophore (flagellate body). — cyst^z. capsule containing — e.g., oocyst, clastocyst, 621 622 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. — id=3i body connected with, or belonging to, the phase of — e.g., merid, sporid, gametid. Also haematid (red corpuscle), leukid (white corpuscle), micrid (blood plate), etc. Descriptions should, I think, commence with the definite starting- point of the zygote. Thus I should describe the general cytogenesis (or biogenesis) of Plasmodium briefly as follows : — Zygosis occurs in the stomach of the mosquito. The zygote pene- trates into the stomach wall ; and after a short schistophase produces about eight to twelve protoclasts which, continuing schistogenesis, produce a large number of deuteroclasts. These, escaping from the cyst, become protospores ; which pass by route of the insect's salivary glands into the vertebrate blood, where each penetrates a haematid. Here the sporid, after another schistophase, produces six to thirty deuterospores, the sporophase being thus continued indefinitely. The gamophase commences (by stages not yet clearly seen) in the vertebrate blood. The oocyst has one oon, and the spermatocyte, say, four to six sperms ; but gametophoresis and zygosis do not occur until the blood is ingested by another Culicid.^ 63. Notes on the Malaria - bearing- Anophelines. — This section ought to have been placed in Chapter III, but has been relegated to the Addenda for the following reasons. Many works on malaria and on mosquitos give lists of the malaria-bearing Anophelines, but mostly without exact references to the literature in which the incriminating evidence was published. Hence early in 1910 I directed Mr W. R. Drawz, our Malaria Bibliographer (Tropical Diseases' Research Fund), to collect all the data which he could find ; but the work could not be completed in time for the earlier chapters of this book ; and he reports that even now, after several months' close search, some references have probably been overlooked. I am also much indebted to Mr R. Newstead and Dr J. W. W. Stephens, of the Liverpool School of Tropical Medicine, for their valuable assistance. (i) So far as we can find, the following is a complete list of the Anophelines which have been mentioned in various books and papers as being capable of carrying malaria : — (Note. — Only synonyms in small type.) A?topheles albimatia, Theobald (1901), vide Cellia albimana, (Wiedemann) (1821). Anopheles albimana, Wied., xnde Cellia albimatia, (Wiedemann) (1821). ^ I am indebted to Professors Myres and Postgate, University of Liverpool, for advice regarding the Greek roots. 63] ADDENDA 623 Anopheles albimanus, R. D., vide Cellia argyrotarsis^ (Robin-Desv.) (1827). Anopheles albitarsis, Arribalzagia (1901), vide Cellia argyrotarsis^ (Robin-Desv.) (1827). Anopheles algeriensis, Theobald (1903). Anopheles annulipes, Walker (1850), vide Nyssorhynchus annulipes, (Walker) (1850). Aitopheles arabiensis, Patton (1905). Anopheles barbirostris. Van der Wulp (1884), vide Myzorhynchiis barbirostris, {yzxi der Wulp). Anopheles bifurcatus, (Linn.) (1758). Anopheles bifurcatus, Meigen (1804), vide Anopheles maculipennis, Meigen (18 18). Anopheles chaudoyei. Billet {is not a spec), vide Pyretophorus chaudoyei, Theobald (1903). Anopheles claviger, Fabr. (1805), vide Anopheles maculipennis, Meigen (18 18). Anopheles claviger, Meigen (1804), vide Anopheles bifurcatus, (Linn.) (1758). Anopheles cohaesus, Donne. Anopheles costalis, Loew (1866), vide Pyretophorus costalis, (Loew) (1866). Anopheles crucians, Wiedemann (1828). Anopheles culicifacies, Giles (1901), vide Myzomyia culicifacies, (Giles) ($ non ^) (1901). Anopheles farauti, Laveran (1902). (Doubtful species.) Anopheles forniosaensis, Tsuzuki (1902) (? Genus Anopheles). Anopheles fuliginosus, Giles (1900), vide Nyssorhynchus fuliginosus, (Giles) (1900). Anopheles funesta, Giles (1900), vide Myzomyia funesta, (Giles) (1900). Anopheles funesta var. subuvibrosa, Theobald (1900), vide Myzomyia funesta, (Giles) (1900). Anopheles fujiesta var. umbrosa, Theobald (1900), vide Myzotnyia funesta, (Giles) (1900). Anopheles gambiae, Giles (1902), vide Pyretophorus costalis, (Loew) (1866). Anopheles grabhantii, Theobald (1901), vide Cycloleppteron grabhamii, (Theobald) (1903). 624 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. Anopheles gracilis, Donitz (1902), vide Pyretophorus cos talis, (Loew) (1866). Anopheles jamesii. Listen (non Theobald) (1901), vide Nyssorhynchus fuliginosus, (Giles) (1900). Anopheles jesoensis, Tsuzuki (1902), vide Myzorhynchus sinensis, (Wiedemann) (1828). Anopheles kawari, James-Liston (1901), vide Nyssorhynchus kawari, James-Theobald (1901). Ajtopheles kochii, Donitz (1901), vide Cellia kochii, (Donitz) (1901). Anopheles kumasii, Chalmers (1900), vide Mysojuyia funesta, (Giles) (1900). Anopheles leucopus, Donitz (1901), vide Nyssorhynchus fuliginosus, (Giles) (1900). Anopheles listoni, Giles (1901) (? ^ only), vide Myzoinyia ctdicifacies, (Giles) ( $ non (J) (1901). Anopheles listoni, Liston, vide Myzomyia listoni, Liston (non Giles) (1901). Anopheles lutzii, Theobald (1901), vide Myzomyia lutzii, Theobald (1905). Anopheles maciilipalpis, Giles (1902), vide Nyssorhynchus inacidipalpis (Giles) (1902). Anopheles maculipennis, Meigen (18 18). Anopheles martini, Laveran (1902). Anopheles metaboles, (Theobald) (1902), vide Nyssorhynchus stephensi, (Liston) (1901). Anopheles musivus, Skuse (1888), vide Nyssorhynchus annulipes, (Walker) (1850). Anopheles paludis, Theobald, vide Myzorhynchics paludis, (Theobald) (1900). Anopheles pharoefisis, Theobald (1901), vide Cellia pharoetisis, (Theobald) (1901). ? Anopheles picius, M'Donald, vide Myzomyia hispaniola, Theobald (1903). Anopheles pseiidopunctipennis, Theobald (1901). Anopheles punctipennis, Say (1823). Anopheles pursati, Laveran (1902). Anopheles quadrimaculatus, Say (1824), vide Anopheles jnaculipennis, Meigen (18 18). Anopheles rossii, Giles (1899), vide Myzomyia rossii, (Giles) (1899). 63] ADDENDA 625 Anopheles sinensis^ Wiedemann (1828), vide Myzorhytichus sinensis, (Wiedemann) (1828). Anopheles stephensi. Listen, vide Nyssorhynchus siephensi, (Listen) (1901). ? Anopheles superpictus, Grassi, vide Pyretophorus superpictus, (Grassi) (1900). Anopheles tarsimaculata, Goeldi (1905) (not Anopheles). Anopheles theobaldi, Giles, vide Nyssorhynchus theobaldi, (Giles) (1901). Anopheles treacheri, (? Daniels 1909). Anopheles trifurcatus, Fabricius (? date), vide Anopheles bifurcatus, (Linn.) (1758). Anopheles turkhudi, Listen, vide Myzomyia turkhudi, (Listen) (1901), Anopheles vagus, Donitz (1902), vide Myzomyia rossii, (Giles) (1899). Anopheles villosus, Reb.-Des. (1827), vide Anopheles bifurcatus, (Linn.) (1758). Anopheles vincenti, Laveran (1901). Anopheles walkeri, Theebald (1901), vide Anopheles bifurcatus, (Linn.) (1758). Arribalzagia maculipes, Theobald (1903). Cellia albimana, (Wiedemann) (1821). Cellia albipes, Theebald (1903), vide Cellia albimana, (Wiedemann) (1821). Cellia argyrotarsis, (Rob.-Des.) (1827). Cellia kochii, Donitz (1901). Cellia pharoensis (Theobald) (1901). Culex bifurcatus, Meigen (1804), vide Anopheles niaculipennis, Meigen (18 18). Culex hyemalis. Fitch, vide Anopheles punctipennis, Say (1823). Cycloleppteron grabhamii, Theobald (1903). Cycloleppteron mediopunctalus, (Lutz M.S.), Theobald. Myzomyia christophersi, Theobald (1902), vide Myzomyia listoni, Listen (non Giles) (1901). 2 R 626 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. Myzomyia culicifacies, (Giles) ( % non ^ ) (1901). Myzomyiafluviatilis, Christophers M.S. (1901), vide Myzomyia listoni, Liston (non Giles) (1901). Myzomyia funesta, (Giles) (1900). Myzomyia kispaniola, Theobald (1903). Myzomyia indica, Theobald (1901), vide Myzomyia culicifacies, (Giles) ( $ non $) (1901). Myzomyia listoni, Liston (non Giles) (1901). Myzomyia ludlowi, Theobald (1903). Myzomyia lutzii, Theobald (1905). Myzomyia nili, Theobald (1904). Myzomyia rossii, (Giles) (1899). Myzomyia turkhudi, (Liston) (1901). Myzorhynchus barbirostris, (Van der Wulp). Myzorhynchus coustani, (Laveran) (1902), Myzorhynchus mauritianus, (Grandpre) (1900). Myzorhynchus paludis, (Theobald) (1900). Myzorhynchus paludis var. similis, Theobald (1901), vide Myzorhynchus mauritianus, (Grandpre) (1900). Myzorhynchus pictus, Ficalbi (1899), vide Myzorhynchus pseudopictus, (Grassi) (1899). Myzorhynchus pseudopictus, (Grassi) (1899). Myzorhynchus sinensis, (Wiedemann) (1828). Myzorhynchus tenebrosus, Donitz (1902), vide Myzorhynchus mauritianus, (Grandpre) (1900). Myzorhynchus umbrosus, Theobald (1903), Myzorhynchus ziemanni. Von Griinberg (1902). Nyssorhynchus annulipes, (Walker) (1850). Nyssorhynchus fuliginosus, (Giles) (1900). Nyssorhynchus kawari, James-Theobald (1901). 63] ADDENDA 627 Nyssorhynchus maadipalpis, (Giles) (1902). Nyssorhynchus maadipalpis var. indiensis, Theobald (1903), vide Nyssorhynchus maculipalpis, (Giles) (1902). Nyssorhynchus maculatus, (Theobald) (1900). Nyssorhynchus stephensi, (Listen) (1901). Nyssorhynchus theobaldi, (Giles) (1901). Nyssorhynchus willmori, James (Theobald) (1904). Pyretophorus ardensis, Theobald (1905). Pyretophorus chaudoyei, Theobald (1903). Pyretophorus costalis, (Loew) (1866). Pyretophorus costalis var. melas^ Theobald (1903), vide Pyretophorus costalis^ (Loew) (1866). Pyretophorus Jeyporensis, Theobald (1903). Pyretophorus myzomyifacies, Theobald (1907). Pyretophorus sergenti, Theobald (1907). Pyretophorus superpictus, (Grassi) (1900). Stethomyia fragilis^ (Theobald) vide Anopheles treachtri^ (? Daniels) (1909). Stethoinyia nimba, Theobald. (2) I now add some notes on the species regarding which we have succeeded in finding some incriminating evidence. That evidence is of three degrees of value : — {a) experimental proof that certain individuals of a species are capable of developing all the stages of any or all the species of the human PIas?nodia, or of causing infection in man, or of both ; (b) proof that a species may contain some of the stages of the parasites (zygotes) ; and {c) apparent correla- tion between the numbers of a species and the local prevalence of malaria. Here (b) is not conclusive because, though the zygotes may develop to a certain degree in an insect, it does not follow that they come to maturity ; and {c) is not worth much because, as we showed in the case of Myzorhynchus mauritianus, a species may abound in a malarious locality, although the disease is really being spread by quite another one. Lastly, even {a) proves only that the variety concerned 628 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. in the experiments is culpable, because, for instance, we failed in infecting English A. maculipennts, which certainly carry in most other places. The reader should also note that the breeding-waters selected by larvae in some places need not necessarily be the same as those selected by the same larvae elsewhere. Anopheles algeriensis. — Ed. and Et. Sergent state that they found protospores in the salivary glands of the two individuals examined by them [1905]. They also state that a violent epidemic of malaria occurred in the villages of Thiers in Algeria, where it was not possible to find any other Anopheline except this one. Occurs in Algeria, and the Sergents say that it haunts les collines saheliennes^ and the plains of the littoral. Anopheles arabiensis. — Apparently incriminated by W. S. Patton [1905]. Literature not available. Protospores found in it. Distribu- tion : Arabia and Aden. See Stephens and Christophers [1907, p. 156]. Anopheles bifurcatus. — There are two species of Anophelines under the name of claviger, A. maculipennts Fabr. and A. bifurcatus Linn. Both appear to have been incriminated by the Italians by cultivation of the parasites in all their stages, and also by inoculation of healthy persons (see section 17, cases 2, 3, 4) ; but it is not always clear which species is referred to. We gather that A. maculipennis is the one concerned in the experimental inoculations, and generally in the cultiva- tions. But Bignami and Bastianelli also incriminated bifurcatus by cultivation. Grassi says [1901] that he found it much more difficult to work with bifurcatus than with maculipennis, owing to the small size of the former, but found zygotes in thirteen out of sixteen insects, and adds (page 121, German edition) that parasites were found in bifurcatus and maculipennis in the Maccarese district. Jansc6 also [1904, 1905 and 1908] gives experiments with A. claviger without stating which claviger he referred to ; but we gather that he was referring to maculi- pennis. Probably bifurcatus can be safely claimed as a carrier. It is generally distributed over Europe and North America. In England it is certainly the commonest of the three Anophelines, the other species being maculipettnis and nigripes. Grassi states that it occurs in forests and breeds in small collections of fresh water such as wells and in rot holes in trees ; that it occurs seldom in houses and stables, and that when one is bitten in forests it is generally by this species. It bites more quickly than A. claviger, and in the daytime, 63] ADDENDA 629 and enters habitations at night. Newstead says that it is the commonest Anopheline in the New Forest in England, where the larvae occur in large numbers in the shallow pools and in the cattle footprints. In the marshes of Cheshire it is also abundant, occurring chiefly in shallow, terrestrial waters, sometimes in company with the larvae of Culex. Anopheles formosaensis. — The generic position of this species has not yet been definitely fixed. Incriminated by J. Tsuzuki [1902], who followed completely the development of the malignant parasites in it, but did not inoculate man with it. Occurs in the whole island of Formosa. Tsuzuki apparently distinguishes two varieties, one of which is common in the north and the other in the south of Formosa. Anopheles maculipennis. — Incriminated by the Italians, see under A. bifurcatus ; also by A. Van de Scheer and Van Berlekom [1900J, by Schaudinn [1903], by Hirschberg [1904], Husson [1907], and by Jansco [1904, 1905, 1908], and others. The proof is by complete cultivation of the parasites, and also by inoculation of man by the Italians and by Jansc6. Common and generally distributed through- out Europe, including Russia and Scandinavia. It appears also to be generally distributed in the United States of America, and to be common in many parts of Canada. It is chiefly a domestic insect, found in houses, sheds, stables, and hen coops, etc. This habitat also obtains to a very large extent in Great Britain. The larvae occur chiefly in open terrestrial waters in marsh lands, in forests and boggy places. Theobald states that in Britain the food of both sexes is entirely vegetable. Ficalbi, on the other hand, says it is very trouble- some to man in Italy. A. psetidopunctipennis. — Incriminated by S. T. Darling [1910], who found zygotes in four out of thirty-one insects fed on cases of the malignant parasites, and also protospores in the glands of one insect. He thinks that it is only slightly concerned in the transmission of malarial fever in the Canal Zone. Occurs in Panama, Grenada and New Mexico. Darling says that it is one of the two commonest species in the Canal Zone, and breeds in most terrestrial waters. A. tarsimaculata. — Incriminated by S. T. Darling [19 10], who found zygotes in three out of five insects. Occurs in Panama and South America. It is doubtful if this species is referable to the genus Anopheles. 630 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. Cellia albimana. — Incriminated by S. T. Darling [19 10], who found zygotes in thirty-six out of fifty insects and protoclasts and protospores in three. Occurs in Panama, Brazil, British Guiana and in the West Indies. Theobald (vol. iii. p. iii) states that Dr St George Gray says that this Anopheline will bite at any time of the day or night ; that the breeding-grounds are extremely varied, such as collections of water, especially full of reeds ; and records also that he has found larvae in brackish water in a lagoon shut off from the sea. He states, however, that he has never found the larvae in water barrels or similar receptacles in towns. Darling [1909, 19 10] says that this and pseudo- punctipennts are the commonest mosquitos in the Panama Canal Zone, and breed in almost any terrestrial water. It carries both malignant and tertian malaria. Theobald, in his " Mosquitos of Jamaica," also mentions rivers and large swamps and irrigation water, etc., as breeding- places. Cellia argyrotarsis. — S. T. Darling [19 10] says that a zygote was found in one individual at Panama. Occurs in South America, the West Indies, Panama, but appears not to be an important carrier. From the records we gather that this is a less common species than C. albimana, to which it is very similar (possibly only a variety). Cellia pharoensis. — Newstead, Dutton and Todd [1907-1908] say that " malaria parasites were seen to develop in this mosquito at Boma." The insect was common at Ismailia, and has been reduced simultaneously with malaria by operations since 1902 (section 53). Pressat [1905] considers it to be malaria-bearing, but gives no evidence. Occurs in East, West, Central and Northern Africa. It is recorded also from Palestine. Theobald (vol. i., 1901) says that this mosquito occurs during the month of April in Mashonaland and during January in Egypt. I found the larvae in small swamps of almost fresh water caused by seepage from the fresh-water canal at Ismailia, also in an ornamental fountain and in water-cress beds. Not seen in sewage cisterns. Willcocks say that it is a domestic mosquito, both in the larval and adult stages. The adults enter houses in order to obtain blood. In the open the females bite most viciously at sunset. The water in which the larvae live may be brackish. Larvae, in various stages of development, placed in water containing i'78% common salt, die in less than twenty-four hours, but in water containing 1% common salt they live from two to three days, but become sluggish in their movements and appear to feed very little or not at all. 63] ADDENDA 631 Myzomyin cuUcifacies. — Incriminated by Stephens and Christophers [25th April 1902]. Experimentally it carries quartan as far as the protospores, and the other two species as far as the zygotes. In nature frequently found to be infected in 4-6% at Mian Mir, and in 8'6% at Ennur, near Madras. Widely spread in India, where it is one of the principal carriers. Breeds in pools in sandy river-beds, sluggish irrigation channels, ditches, muddy tricklets, edges of rivers, etc. Myzomyia fimesta.- — Proved by Ross, Annett and Austen [1900] to carry quartan (one out of five insects) and mild tertian (one insect) in West Africa. Further confirmed by Daniels [1900, p. 41] for malignant. Stephens and Christophers [1901] found what appeared to be this Anopheline in the Duars, in India, but Theobald subse- quently did not admit the identity. Also observed by Button and Todd, who report that malaria was seen to develop in it at Lusambo [1907]. Occurs in Central, Western and Southern Africa, Sudan and the Philippine Islands. Breeds in clear water in small springs and edges of streams and rivers. Daniels says it cannot thrive in stagnant waters, and that it may be found in marshes, but only where the water is kept fresh by springs during heavy rainfall. Stephens and Christophers say that it breeds in running waters, such as sluggish irrigation channels, ditches, etc. It frequents houses and does not leave them in the daytime. It feeds preferably at night, especially in the early hours of the evening, but also at other times, even in dayhght, both when free and in captivity. Myzomyia hispaniola. — Incriminated by Sergent brothers [1905], who dissected fourteen in 1904 without result, but in 1905 found protospores in one of three dissected. Occurs in Spain, Teneriffe, Algeria. The Sergents say that it abounds above all in valleys of hilly, broken regions, but that it is found at a distance of some kilometres in the plains in the debouche of these valleys, and add that this Anopheline is like algeriensis but is little domestic. It frequents houses only during the night, and does not remain after having bitten its victim. Myzomyia listoni. — Incriminated by Stephens and Christophers. In this species protospores were readily found in the Bengal Duars, but only in nature. Also by Kinoshita [1906], who says it can be infected from 50 to 98% in Formosa. Occurs in India, Japan, Federated Malay States, Inhabits running waters, swiftly - flowing 632 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect- streams, sluggish irrigation channels, ditches, muddy tricklets and edges of rivers. Myzomyia lutzii. — Lutz [1903] says that he is convinced that this mosquito carries malaria, but gives no further evidence. Oswaldo Cruz (section 47) suspects it. Occurs in Brazil, British Guiana. Lutz who paid considerable attention to the bionomics of this mosquito, states that it is found widely distributed in various places along the chain of mountains in the region of San Paolo and Santos. It breeds in Bromilaceous plants. Myzomyia rossii. — I failed in infecting this species in Calcutta in 1898-1899. Stephens and Christophers [1902] obtained experimentally quartan and malignant zygotes in a few individuals. Never found them infected in nature. They add that zygotes were found in nature by Captain James, but sporozoits never in nearly 1,000 dissected. W. T. de Vogel [1909] found zygotes in two insects bred from larvae grown in salt water (i'3%), but not in those bred in fresh water. C. A. Bentley also finds them in sea water; and failed to discover the parasites in 425 dissected. Occurs in India, Ceylon, Malay States, China, East Indies, Philippine Islands, and Java. Breeds in foul puddles near habitations, clean clear water puddles without much algae, and often turbid with suspended matter, boats and puddles near houses, shallow muddy rivers, rice fields and cultivation of all kinds. Theobald states that Mr E. E. Green {Tropical Agriculture, vol. xxvii. p. 84, 1906) considers that it is a malaria carrier in parts of Ceylon. He found the larvae breeding in a brackish lake at Batticaloa, and also in the cocoanut estates, in the small water holes used for watering young plants, and in chatties sunk at the roots of plants. I have often thought that the comparative healthiness of India may be due to the fact that this species ousts more dangerous ones. Vogel's suggestion is interesting.^ Myzomyia turkhudi. — Incriminated by Stephens and Christophers [1902]. Found to carry, experimentally, malignant tertian zygotes. Occurs in India ; and found in large pools in quarries, stony and shallow running waters. Myzorhynchus barbirostris. — Proved by Stephens and Christophers [1902] to develop malignant tertian experimentally. Their first experi- ments had been negative. Occurs in India, Malay Peninsula. Stated ^ See also section 65 (8). 63l ADDENDA 633 to have been found at Old Calabar (?). Breeds in running waters with much weed and algae, swamps, and deep water with much aquatic vegetation. Myzorhynchus sinensis. — Tsuzuki [1902] proved that the parasites develop in all stages in this mosquito and that it causes infection in a healthy man. Also that quartan parasites develop in many of these mosquitos ; but he did not infect man with this species of parasite. Kinoschita cultivated mild tertian parasites in seven out of sixteen mosquitos, but quartan only at low temperatures, and malignant parasites not at all. Occurs in Formosa, Japan, China, Federated Malay States. Habits not described. Myzorhynchus umbrosus. — Incriminated by Malcolm Watson. Ex- periments not mentioned, but certainly a carrier. Occurs in the Federated Malay States. Breeds principally in the flat country, but not in flowing water. Abounds in thick jungle which it will not willingly leave, so that removal of jungle round plantations reduces malaria (section 57). Nyssorhynchus annulipes. — Kinoshita [1906] developed malignant, only at high temperature without oscillations, in three out of five mosquitos. Occurs in South West Queensland, Australia, Formosa. Donitz says it occurs in the Bismarck Islands. Breeds both in fresh and in salt water (1,040 sp. gr.), and will live for a month on dates. Myzorhynchus fuliginosus.- — Incriminated by Stephens and Christo- phers [1902] and Adie [1903]. Stephens and Christophers say that it occurred in Mian Mir in small numbers, and think that it is not an active agent. They were able to infect it experimentally for malignant tertian (zygotes), in one case sixty-six medium and ten small zygotes. It developed also quartan up to zygotes, experimentally. Occurs in India, Federated Malay States. Breeds in puddles and pools with much algae, common in stream beds, water trickling over rocks and lakes with weedy margins. Giles and Liston say that as a rule this species prefers open water and sunlight. Nyssorhynchus niaculipalpis. — Stephens and Christophers found zygotes experimentally in this mosquito, which they called N. jamesii. Occurs in India, Mauritius, Mashonaland. Scarce in Mauritius. Breeding in marshes on sea coast, and at 1,400 feet above sea. Nyssorhynchus stephensi. — Stephens and Christophers [1902] 634 NOTES ON THE MALARIA-BEARING ANOPHELINES [Sect. developed zygotes of malignant tertian in it, experimentally. W. G. Listen [1908] at Bombay found 25% infected with malaria. C. A. Bentley, in the same city [19 10], found zygotes in 30 and protospores in 8 out of 404 dissections. Occurs in many parts of India. Breeds not only in open, clean terrestrial waters, but in deep wells, iron cisterns, filter beds, garden tanks, and even small vessels (section 59). Nyssorhynchus theobaldia. — Stephens and Christophers [1902] developed malignant tertian and quartan to zygotes, experimentally. Occurs in India and Aden Hinterland. Breeds in running, stony and shallow water with much weed and algae. Nyssorhynchus willmori. — Incriminated by Malcolm Watson (section 57). Details of experiments not given, but the insect appears to be certainly a carrier in the hilly land in the Federated Malay States. Also Daniels [1909]. Occurs in Federated Malay States, Kashmir, Ceylon. Breeds in rapidly running streams, and cannot be reduced by open drainage. The larvae were found in the clear puddles formed by a spring at a height of 4,800 feet in Kashmir (Theobald, vol. iii. p. 102). Pyretophorus chaudoyei. — Billet states that this mosquito occurs exclusively in places where there is much malaria in the Saharian Oases in Algeria. He had no opportunity of finding zygotes in the insects, but is sure that it is a carrier. Theobald (vol. iii. p. 70) says that protospores have been found in it. Occurs in Algeria, Touggourt in Algeria, and southern posts in Sahara. Breeds in water containing a higher percentage of salt than normal sea water. Larvae are found in little isolated pools or ponds, which under the influence of active solar radiation greatly increase in the percentage of salt, giving at the end of summer a percentage of 40 grammes per litre. (Foley and Yvermault, Bull. Soc. Path. Exot., 1908, i. iii. pp. 172-173.) Pyretophorus costalis. — Incriminated by Ross, Annett, Austen [1900] to carry all three species in 27 out of 109 insects. Also by Stephens and Christophers [1900] and by R. Ross in Mauritius [1908]. Common and widely distributed over the African continent, Madagascar, Reunion and Mauritius, but not in many neighbouring islands which are non-malarious. Breeds in stagnant terrestrial waters often without much weed. Appears to prefer the sea coast in Mauritius, but was found in marshes up to 1,700 feet, where, though scanty, it yet caused malaria. Breeds in pools in dried-up beds of hill streams, 63] ADDENDA 635 and in weedy margins, etc. In Mauritius prefers verandas to inner rooms, and bites in the open, especially after 11 p.m. Takes shelter from wind, but wanders far on windless nights. Pyretophorus niyzomyiafacies {?). — Incriminated by Ed. Sergent (section 52), who says that the protospores have been found in it. Occurs in Algeria, especially in broken, hilly valleys. Pyretophonis siiperpictus. — Grassi seems to think that it is a malaria carrier [German translation, p. 219, 1901], but apparently gives no evidence. Also Bignami and Bastianelli think that it is a carrier. Occurs in the South of Italy, Spain, Greece, Algeria, and (?) Africa and India. Carries Filaria immitis. This concludes the Anophelines regarding which we have been able to find any reliable experiments, but other species are mentioned as being possible or certainly carriers, but without giving the evidence. Thus Oswaldo Cruz (section 47) says that Cydoleppteroti mediopunctaium Theobald and Lutz, Cydoleppieron intermedium Chagas, and Arri- balzagia pseudomaculipes Chagas, " are undoubtedly carriers, as shown experimentally." C Daniels, in a letter to me of the 17th June, says that C. kochii is the constant in badly malarial suburbs in the Malay States, and is absent or scanty in other places. A. treacheri [Stethomyia fragilis Theobald) was the only mosquito which he could find in badly malarial jungles. He adds that it was difficult to make any experi- ments with these two species, as they will not live in confinement, and says : "The trouble with these, as with several other mosquitos, is that whilst you cannot absolutely include them because there is no positive proof (experimentally), you cannot exclude them because there is no negative proof (experimentally), and the circumstantial possible evidence is strong." Laveran mentions two species which he calls pursaii and martini as being carriers ; but the entomologists appear not to accept them as species. Obviously much more exact work requires to be done even on this point, which is so important for public prevention. C. S. Banks [1907] states in a lengthy paper that he cultivated Plasmodia in Myzotnyia ludlowii Theobald, a Philippine Anopheline which breeds in rivers and streams and also in sea water, and that he inoculated a healthy person by its means ; but certain points in his description suggest doubts as to the nature of the bodies which he considered to be malaria parasites. 636 EXAMPLES OF LEGISLATION [Sect. 64. Examples of Legfislation. — Notes on legislation have already been made in section 40 (4) and 59 (i). The object of such legislation is to give the Health Department power (a) to enter private premises (including houses, yards, gardens, lands and estates) in order to search for mosquitos, flies, rats and other annoying or dangerous vermin ; {b) to destroy such vermin when found ; and {c) to prevent the breeding of them. Another object is to compel owners or occupiers to take reasonable precautions against such breeding. But at the same time the rights and properties of the owners or occupiers have to be duly guarded. Most civilised malarious countries now possess Health Acts, more or less based upon precedent, and these contain clauses against "nuisances." But the word "nuisance" is not always defined so as to include the breeding of vermin. In such cases, then, it suffices merely to extend by act the definition of the word — if possible, to include all vermin as well as mosquitos. It was my duty in Mauritius to consider the local Ordinances carefully for this purpose ; and I drafted the following clauses, which were scrutinised and accepted by the Health Department and by the Procureur- General, and then submitted to Government. (The first clause here given was meant to be inserted in the definition of "nuisance" contained in the Health Ordinance already in existence) : — "All collections of water, rubbish, refuse, ordure, or other fluid or solid substances, and all other conditions which permit, or facilitate, or are likely to permit or facilitate, the breeding or multiplication of animal or vegetable parasites of men or domestic animals, or of insects or other agents which are known to carry such parasites, or which may otherwise cause or faciHtate the infection of men or domestic animals by such parasites. " It shall be lawful for any sanitary authority, or any person deputed by him in writing, to take immediate steps to destroy mosquito larvae on any premises where they may be found, and to take such action as may be necessary to render any pools or accumulations of water unfit to be breeding-places for mosquitos. "When such pools or accumulations of water lie on premises under the charge of a public body or corporation, they shall not be dealt with as above provided, unless due warning has been given in writing to such public body or corporation, and no action has, within reasonable delay — not to be less than twenty-four hours — been taken by them. In such cases the expenditure incurred shall be borne by such public body or corporation. "Any owner or occupier who shall object to pools and collections of water on his premises being dealt with as above provided, shall within twenty-four hours submit his reasons to the sanitary authority, 64] ADDENDA 637 who, after enquiry, shall order such action to be taken as he shall consider necessary to meet the provisions of this Ordinance. Should the objections be rejected, the measures originally ordered shall be carried out at the expen-^e of the said owner or occupier. " It shall not be lawful for any owner or occupier to allow mosquitos to breed on his premises, or to allow the presence on such premises of any receptacle in which water is kept or may collect, unless such receptacles are properly protected from access of mosquitos, or unless the water they may contain is treated in such a way as to prevent the breeding therein of mosquitos, nor shall such owner or occupier allow on his premises any conditions which may, in any way, be favourable to the breeding of mosquitos. " Trees on all premises shall be at all times kept freely lopped to the satisfaction of the sanitary authority by the owner or occupier, and no trees shall be allowed to grow within 10 feet from any dwelling- house. The sanitary authority may, in writing, direct the said owner or occupier to carry out the above provision within a reasonable delay, not to be less than forty-eight hours, and, in case of non-compliance, the trees shall be lopped or cut down at the expense of the owner or occupier.^ " It shall be lawful for the Director of the Health Department to make such regulations as may be necessary to carry out the provisions of this Ordinance. " It shall be lawful for the Director of the Health Department, in any case when the owner or occupier of any premises is liable for the expense of any measures carried out on his premises, to relieve such owner or occupier from the said expense, if, after enquiry, the Director is satisfied that such owner or occupier is not in a position to incur such expense. In such cases the expenditure shall be borne by Government." Clauses of penalties follow. Sir Rubert Boyce gives [19 10] the laws passed in several West Indian Colonies. From my experience (in 1896 I was a member of a committee which reformed the municipal laws in the station of Bangalore in India), I do not think that all of them are very good or practicable ; and Boyce admits that they have often become a dead letter. But I quote some of the clauses as examples. " The occupier or owner of any premises shall keep such premises free of stagnant water liable to breed mosquitos, and the presence of mosquito larvae in any collection of water, wherever situated, shall be sufficient evidence that such water is stagnant." Accepted in most of the colonies — a simple and inclusive clause. ^ Some specific provision ought to be made to enable the sanitary authority to fill up with concrete, or otherwise to treat, holes and hollows in trees which breed, or are likely to breed, mosquitos ; and also to compel owners to cut insanitary undergrowth. 638 NOTES [Sect. " The owner, or when required by the local authority, the occupier of every lot of land situate in a town or village district shall effectually drain the lot, and for that purpose shall (i) make such dams and drains on the lot as may be necessary for effectually draining the lot ; (2) fill up all irregularities on the surface of the lot, and adjust the surface thereof, and if necessary raise the level of the surface thereof, in such a manner (a) that the water received on the lot may flow into the drains without obstruction, (d) that no water can remain on any portion of the surface of the lot other than the drains, and (c) that the surface of the lot does not remain swampy. Provided that where the swampy state of any lot in any such district is occasioned by the main drains into which the drains of the lot discharge not having a sufficient outfall or a sufficient capacity to carry off all the water discharged into them, the owner or occupier of the lot shall not be liable under this section to raise the level of the surface of the lot if the level of such surface is as high as the average height of the level of the land surrounding such a lot for a distance of 20 roods (? 20 rods = 110 yards. A rood is a square measure); and provided that any owner may, with the consent of the local authority of the district in which the lot is situated, have a pond on the lot." George- town^ British Guiana. " All vats, tanks, or other vessels shall be screened with mosquito- proof wire-netting or other suitable material, so as to prevent the entrance into or exit of mosquitos from such vats or tanks or other vessels." British Guiana. Such regulations should, if possible, be included in the general Health Act, and not be left to the bye-laws of local bodies, which are often very incompetent. In my opinion British administration is generally much wanting in disciphne, and tends to neglect the health and lives of the people for the sake of antiquated notions about the liberty of the subject. 65. Notes. — I will conclude this book with some miscellaneous notes on points of interest which have been studied while it was in the press. (i). The thick-film process. — For ordinary microscopic preparations, I c.mm. of blood is spread out thinly over, say, 4 sq. cms. of area, and then examined either fresh or stained — at the cost of much time (section 18 (9)). Consequently I proposed the following method [1903]. A quantity of blood, say i c.mm., is spread over only about 1/4 sq. cm. of area, and allowed to dry. The haemoglobin is then washed out with water, and the residue, consisting of parasites, leukids, micrids and the stromata of the haematids, is stained by any appro- priate method. We can thus search i c.mm. of blood in about 1/16 65] ADDENDA 639 the time, or less, required for an ordinary preparation — but the parasites, especially P. vivax, are apt to be overlooked unless the observer trains himself in the work. Originally I washed out the haemoglobin with water and then fixed and stained the residue as usual; but later I obtained better results by washing out with eosin solution, washing this off, and then passing over a weak solution of methylene blue. R. Ruge, however, advocates the former procedure [1903], and L. Rogers [1908, p. 17] prefers first to fix and stain, and then to wash out the haemoglobin with a very dilute solution of acetic acid — which leaves the outline of the haematids without obscuring the view. All these methods are useful. Sediment and overstaining of the stromata are to be avoided, and the film should not be too thick. (2). Eniimerative methods. — Very rough ones are now in use. We count the number of parasites in a given number of fields of an ordinary preparation — giving an enormous possible error, because we do not know the amount of blood in each field. Or we count the number of parasites found near a given number of leukids, the latter being counted by a haemocytometer. Here the total estimate is the product of the two partial counts ; and if the errors contained in the latter are both positive or both negative (which should occur in half the estimations), the total error may again be enormous. Direct counting by the haemacytometer is far from easy in the case of small parasites, owing to the depth of the fluid examined. Since the beginning of this year (19 10), the Advisory Committee of the Tropical Diseases' Research Fund (Colonial Office) have granted considerable funds for the accurate study of cases of malaria in Liverpool, and Dr David Thomson and myself have commenced this study by elaborating improved " enumerative methods " based on my thick-film process. A measured quantity of undiluted blood is made into a thick-film preparation, and the total number of parasites con- tained in the whole of it is carefully counted. The quantity of blood used is measured by means of a graduated pipette or capillary tube. It is necessary that this tube should have a very fine calibre to allow a small quantity of blood, such as i c.mm., to occupy a sufficient length of the tube to permit of accurate measurements being made. Thus a tube of i8o/x in diameter, and of 4 cm. in length, will contain I'oiS c.mm. (say i c.mm.) of blood. Dr Wakelin Barratt points out that any one can make a suitable pipette by drawing out a fine capillary glass tube, measuring its calibre by the microscope, and calculating the length required to contain the given volume (area of 640 NOTES [Sect. circle = square of diameter x by o'7854, and area of ellipse = product of the two diameters x by the same figure). We are, however, making special tubes, measuring 1/4 c.mm. or more, Mr M. Greenwood, Jr., of the Lister Institute, informs me that the percentage of error is e% = 67"449 / Jn where n is the number of bodies actually counted in the measured quantity of blood. Thus the error=i% if we have counted 4,550 bodies, 2% for 1,138 bodies, 5% for 182 bodies, and 10% for 46 bodies. We must therefore always count enough bodies (parasites or leukids) to reduce the error to any required percentage. Hence the measured quantity of blood should be small when the parasites are numerous, and large when they are scarce. We should perhaps allow 5% error for the measurement of the blood, especially when very small quantities are taken. First sample should be rejected, and fixing before staining is demanded in order to avoid loss. The method is excellent for leukids. (3). Some results. — Applied to a case of sleeping sickness this method disclosed, besides other facts, a regular periodic rise and fall in the number of trypanosomes occurring every seven to eight days — a phenomenon apparently not previously detected {^Proceedings of the Royal Society, June 19 10). With twenty-five cases of malaria some of our results are, briefly, as follows : — When fewer than about 1,000 per c.mm., the sporids are not always numerous enough to cause marked rise of temperature (section 18 (8)). They may remain present in very small but detectable numbers during every day between relapses. A rise in their numbers to about 1,000 or more is generally accompanied by a febrile relapse and followed by a fall in haemoglobin. A fall in the number of malignant sporids may be followed by such an abrupt and high rise that the said fall cannot be due to the death of the parasites, but must be caused by their retire- ment from the peripheral blood — thus proving the hypothesis of Marchiafava and Bignami. Relapses may occur without a single crescent being found even after daily thick-film examinations made during twenty-nine days ; and the number of sporids counted during such relapses cannot be explained by parthenogenic reproduction, unless we suppose that each crescent can produce some hundreds of spores. A rise in the sporid curve is often followed after eight to ten days by a corresponding rise in the crescent curve, suggesting that the latter require this period for development from the former; but some- times no crescents at all are produced, even without quinine ; or else the gamogenesis commences or ceases suddenly. The rise of the 6s] ADDENDA 641 crescent curve may be very rapid and continuous. The fall may be equally rapid at first, but often alternates with short rises — suggesting continuous death and reproduction ; but later the fall tends to be more gradual. Quinine (even in 2 gramme daily doses in a boy), soamine and methylene blue had no very decisive effect on the crescents when once formed. The crescents have never numbered more than 1/8 the highest number of sporids. Of the latter (malignant), 300,000 was the largest number found per c.mm. G. C. E. Simpson, working with us, has demonstrated parallel fluctuations of urobilin in urine and faeces. Faradic and galvanic currents applied to the spleen did not increase the number of crescents in the peripheral blood, and X-rays to the spleen did not prevent a relapse. (Compare Chapter IV.) The method gives at the same time much more accurate diagnosis, and is useful for obtaining the parasite rate (section 51). (4). S. T. Darling has recently done some good enumerative work at Panama, partly pubUshed [1909] and partly just communicated to me by letter [1910]. He counted the number of crescents in patients (by comparison with leucocytes), fed Anophelines on them, and then counted the zygotes in the insects ; and estimates that the mortality of the parasites in the stomach cavity is 97% (section 18 (i)). A. albimana, bred in laboratory, weighed o"ooo8 grammes before feeding and o'ooi6 grammes after a moderate blood meal. He takes the average blood-meal to weigh about one milligramme, and from the number of gametids counted in the blood, he estimates the number which must have been ingested during the meal. This he compares with the number of zygotes actually found. For example, he estimated that one mosquito should have contained 1,632 zygotes after three feedings : but it contained only fifty. He thinks that fully half the ingested gametids are captured by leukids in the insect's stomach — as I showed in 1895. In one mosquito he found 168 zygotes. He concludes that if the gametids in a patient's blood are less than about 12 per c.mm. they will not be numerous enough to infect mosquitos. After experiments on " a number of patients," he thinks that 30 grains of quinine taken daily will reduce the number of crescents (section 23). We have seen, however, that the crescent curve may fall quite irregularly, and sometimes vary rapidly, without any quinine. At my suggestion my brother, E. H. Ross, recently carried out the following experiments at Port Said, in parts from which mosquitos have been entirely banished : 344 Culex fatigans, males and females, 2 S 642 NOTES [Sect. were liberated from bottles in houses free from mosquitos, and search was made to ascertain what became of them. Only 54, or 16%, were found, mostly dead, during the next day or two, after which the remainder disappeared entirely. Only three persons were bitten after the experiment — suggesting that the biting ratio (section 29 (3)) is very low, say 1/50. (5). We have found three more successful mosquito inoculations of man, bringing the number up to 38 (section 17). Case 36, J. Tsuzuki [1902]. — Source, benign tertian. One of many infected Myzorh. sinensis bit healthy subject in Sapporo, Jeso, Japan, which is free of malaria on 24th August (?) 1901. Fever and parasites on 31st August. Case 37. N. Jansco [1903]. — Source, malignant. A. daviger (? Meig.) bit subject on 6th December 1907 in Hungary. One gramme sulphate of quinine given on seventh and eighth day after inoculation. Fever and parasites on 18th December. Case 38. Ibid. — Same source and one A. daviger. Subject given same dose of quinine on eighth, ninth and tenth days after inoculation on 20th and 25th October (? year). Fever on 4th November and parasites on the 5 th. Jansc6 also records three interesting negative cases obtained at the same time. Case i received i gramme of quinine daily from the second to the fourteenth day after inoculation, and remained well during nine months' incubation. Case 2 received 1/2 gramme every morning on an empty stomach from ten hours before inoculation to the thirteenth day afterwards, and remained well during one month's observation. Case 3 received i"5 grammes quinine on fourth, fifth, ninth, tenth, fourteenth and fifteenth days after inoculation, and had no fever during one month's observation. M. Glogner [1905] records two cases which he thinks were due to inoculation during vaccination. (6). With reference to the attitude of Anophelines, Mr Theobald informs me that the only species known to him of which the larva suspends itself in water like a Culicine larva is Myzomyia azriki Patton, 1905 ; and that Myzomyia culidfades is the only one of which the adult has an abnormal attitude So far as he knows the larvae of all the species have no siphon. 65] ADDENDA 643 (7). Regarding the enumeration of mosquitos (section 29 (4)), I forgot to mention a method used at Panama and elsewhere which consists in keeping note of the number of breeding-places found from time to time. It is, of course, a very vague method, but has the advantage of being easily practised by the working gangs or moustiquiers. Such records give them no additional trouble and serve for a check upon their work. (8). A. Eysell in the Archiv. fur Schiffs und Tropai Hygiene, Band XIV., 19 10, argues that M. rossii is the same as the malaria bearing mosquitos of Kinoshita and also of Schiiffner. (9). Colonel W. G. King, the distinguished Sanitary Commissioner of Madras and Burma, informs me that from estimates which he has made regarding the cost of death and of sickness in India, he finds that the death of an adult costs Rs.20; of a child Rs.7 ; while a month's sickness of an adult costs Rs.9. and of a child Rs.4'5. As there are quite 1,000,000 deaths from malaria every year in India, with a corresponding amount of sickness, the total cost of the disease may be roughly computed from these figures. (10). Some time ago I asked Professor Karl Pearson to assist me with the calculations regarding the diffusion of malaria given in Chapter V of this book. He requested Mr H. Waite to undertake the work. Unfortunately Mr Waite was not able to complete his studies until this book was finished ; but I have now seen the proof of his paper — which I hope will appear in Biometrika. Mr Waite proceeds on the basis given in my report on Mauritius and in section 2 7 ; and it is very important to note that his general conclusions are the same as those obtained independently by me and given in section 28 ; that is to say, that the malaria rate in a locality will fall or rise to a definite stable figure depending upon the average proportion of Anophelines present. REFERENCES TO LITERATURE NOTED IN SQUARE BRACKETS 1697 Morton. " Pyretologia opera medica." Geneve, 1696. 1717 Lancisi. " De noxiis paludum effluviis, eorumqueremediis." Romae, Salvioni, 1717. 1753 Torti. "Therapeutice specialis ad febres quasdam perniciosas." Editio quarta-Venetiis. 1743, lib. V., cap. i. 1834 Maillot. " Memoire sur I'epidemie de Bone." Journ. hebdom. des progress des sc. and instit. me'dicales, 1834. 1847 Meckel (H.). "tjber schwarzes Pigment in der Milz und im Blute einer Geisteskranken." Allgem. Zeitschr. f. Psychiatrie, 1847, IV. pp. 198-226. 1854 Beauperthuy (Louis Daniel). Gaceta Official de Cujnand, Venezuela, 23rd May 1854. 1867 Binz. " iJber die Wirkung antiseptischer Stoffe auf Infusorien von Pflanzenjauche." Ccnfralbl.f. 7ned. IVi'ss., 1867, No. 20. Binz. " tJber Einwirkung des Chinin auf Protoplasmabewegung." Schultz^s Arch. f. mikr. A7iatomie, 1867, III. p. 383. 1878-9 Klebs (E.) and Tommasi-Crudeli (C.) "On the Nature of Malaria." R. Accad. d. Lincei, Roma, 1878-9 ; also, New Sydenham Soc, 1888, Vol. CXXI. 1880 Dochmann(A.). "Zur Lehre der Febris Intermittens." St Petersburg. Med. Woch., 1880, No. 20, 164 ; also, Virchow and Hirsch, Jahresber., 1880, II. 9 and 11. 1881 Finlay (Charles). Anales de la Real Acadeviia de Ciencias, 14th August 1 88 1. Meldrum (C). " Relations of Weather to Mortality." Mauritius, 1881. 1883 King (A. F. A.). "Insects and Disease — Mosquitos and Malaria." Popular Science Monthly. New York, September 1883. 1884 Gerhardt (C). " Uber Intermittensimpfungen." Zeitschr. f. klin. Med., 1884, VII. p. 372. 645 646 REFERENCES TO LITERATURE 1884 Laveran (A.). "Traite de fievres palustres." 8° Paris, Doin, 1884. 1885 Marchiafava (E.) and Celli (A.). "Nuove richerche suU' infezione malarica." Ann. d' Agricult., 1885, pp. 96-104; sXso Fortschr. d. Med.., 1885, III., Nos. II and 24. Arch, per le Scienze viediche, 1885, IX., No. 15. 1886 Celli (A.). "Acqiia potabile e malaria." Giornale della Societa italiana di igiene. Milano, 1886. Golgi (C). "Sulla infezione malarica." (? 15th November 1885?) Golgi, Opera Omnia., III. p. 989; also, Arch, per le Scienze mediche, 1886, X., 4, p. no. Ostler (W.). " An Address on the Haematozoa of Malaria." Phila- delphia Med. Times, 1886 ; also, Brit. Med. Journ., 1887, I. p. 556. 1889 Antolisei (E.) and Angelini (A.). "Due altri casi di febbre malarica sperimentale." Rif. Medica, September 1889, Nos. 226 and 227. Golgi (C). " Sul ciclo evolutivo dei parassiti malarici nella febbre terzana." Arch, per le Scienze mediche, 1889, XIII., 7, pp. 173-196. Gualdi (T.) and Antolisei (E.). "Due casi di febbre malarica speri- mentale." Rif. Medica, 1889, No. 225. Bull. del. R. Accad. med. di Roma, XV., 1888- 1889, p. 343. " Una quartana sperimentale." Rif. Medica, 13th November 1889, No. 264, pp. 1 580- 1 582. " Inoculazione delle forme semilunari di Laveran." Rif. Medica, 25th November 1889, No. 274, p. 1639. Kelsch and Kiener. "Traite des maladies des pays chauds." Paris, 1889. Bailliere et fils. 1890 Canalis (Pietro). " Studi sulla infezione malarica." Arch, per le Scienze mediche, 1890, XIV., i, pp. 75-110. Celli (A.) and Marchiafava (E.). "Sulle febbri malariche predomin- anti nell'estate e nell'autunno in Roma." Arch, per le Scienze mediche, 1890, XIV., 8, p. 177. Marino. " Dell'acqua dei luoghi malarici." Congresso med. Roma 1890 ; also, Rif Medica, 1890, No. 251, p. 1502. Meldrum (C). " Relations of the Mortality of Mauritius to the Rainfall, etc." Mauritius, undated (about 1890). Zeri (A.). " Acqua potabile e malaria." Atti della R. Accad. Med. di Roma, 1890, Anno XVI., Vol. V., Serie II. 1 89 1 Bein (G.). " Aetiologische und experimentelle Beitrage zur Malaria." Charitc-Annalen, 1891, XVI. ; also, Centralbl. f Bakt, 1892, XL, p. 203. NOTED IN SQUARE BRACKETS 647 1891 Calandruccio (S.). " Brevi contribuzioni alio studio della malaria." Atti delPAccad. Gioenia di Scienze Nattirali, Catania, Vol. X., Serie IV. Guttmann and Ehrlich. " tJber die Wirkung des Methylenblau bei Malaria." Berliner klin. IVoc/i., 1891, No. 39. Laveran (A.). " Du Paludisme et de son Hematozoaire." Paris, G. Masson & Cie., 1891. Mattel (Eugenio di). /?{/. Medica, 1891, No. 121, p. 544. 1892 Baccelli (G.) " Uber das Wesen der Malarinfektion." Deutsch. Med. Woch., nth August 1892, No. 32, p. 721. Davidson (A.). "Geographical Pathology." Edinburgh, 1892, Y. J. Pentland. Thayer (W. S.). Johns Hopkins Hosp. Bull., May 1892. 1893 Howard (L. O.). "An Experiment against Mosquitos." (Read on i6th August 1892, at a meeting of the Assoc, of Econom. Entomol. at Rochester, N. Y.) Insect Life, 1893, V., 12-14, 109-110, 199. 1894 Bastianelli (G.) and Bignami (A.). "Studi suU'infezione malarica." Bull, della R. Accad. med. di Roma, 1894. Mannaberg (J.). "Die Malaria Parasiten." Wien, 1893. (Transla- tion, 1894, New Sydenham Society.) Manson (P.). " On the Nature and Significance of the Crescentic and Flagellated Bodies in Malarial Blood." Bfit. Med. Journ., 8th December 1894, II., p. 1306. Sakharoff (N.) (Sacharow.) " Uber den Einfluss der Kalte auf die Lebensfahigkeit der Malariaparasiten." Centralbl. f. Bakt., 5th February 1894, XV., 5-6, p. 158. 1895 Daniels (C. W.). " Further Notes on a Series of Post-mortems in the Public Hosp., Georgetown, April 1893 to March 1895." The Brit. Guiana Med. Ann. and Hosp. Rep., 1895, pp. 50-79. Mattei (Eugenio di). " Contributo alio studio della infezione malarica sperimentale nell'uomo e negli animale." Arch, per le Scienze mediche, 1895, XIX., No. 4 ; also, Arch. f. Hygiene, 1895, XXII., 3, P- 191- Thayer (W. S.) and Hewetson (J.). "The Malarial Fevers of Baltimore. An Analysis of 616 Cases of Malarial Fever, etc." The Johns Hopkitts Hosp. Rep., 1895, V. 1896 Bignami (A.). " Le ipotesi sulla biologia dei parassiti malarici fuori dell'uomo." // Policlinico, 5th July 1S96 ; also. Lancet, 1896, II., pp. 1363, 1441. 648 REFERENCES TO LITERATURE 1896 Manson (P.). "The Life History of the Malaria Germ outside the Human Body." Brit. Med. Journ.., 15th, 21st, and 28th March 1896. North (W.). "Roman Fever." Sampson Low, Marston & Co., 1896. Ross (R.). " Observations on Malaria Parasites." Secunderabad, Deccan. Bi'it. Med. Journ.., ist February 1896. Ross (R.). " Some Experiments in the Production of Malarial Fever by Means of the Mosquito." (Read 30th October 1896.) South Indian Branch Brit. Med. Assoc, December 1896 ; also, Ind. Med. Gas. Ross (R.). " Some Practical Points respecting the Malaria Parasite." Indian Med. Gaz.., 1896, p. 42. 1897 Celli (A.) and Santori (F. S.). " Intorno alia siero-profilassi della malaria." Accad. medica di Roma, 1897. Duggam (C. W.). " The Parasite of Malaria in the Fevers of Sierra Leone." Medico-Chiriirg. Transactions., 1897, LXXX., p. 213. MacCallum (W. C). " On the Flagellated Form of the Malarial Parasite." The Lancet, 13th November 1897, II., pp. 1240-1241 ; d\so, Journ. oj Experim. Med., 1898, III., No. i. Marchoux (E.). " Le Paludisme au Senegal." Ann. de VInst. Pasteur, 1897, No. 8 ; also, Arch, de Med. nav., 1897, LXVIII., p. 288. Ross (R.) " Observations on a Condition Necessary to the Trans- formation of the Malaria Crescent." Brit. Med. Jourii., 30th January 1897, I., p. 251. Ross (R.). "On Some Peculiar Pigmented Cells found in Two Mosquitos fed on Malarial Blood." Brit. Med. Journ., 18th December 1897, II., pp. 1786-1788. Simond. " L'evolution des sporozoaires du Genre Coccidium." Ann. Institut. Pasteur, July 1897. 1898 Bastianelli (G.), Bignami (A.), and Grassi (B.). " Coltivazione delle semilune malariche dell'uomo nell' Anopheles claviger Fabr." (Sinonimo : Anopheles maculipennis Meig.). Inviata il : 28th November 1898. Atti. della R. Accad. del Lincei, 1898, VII., P- 313- Bignami (A.). " Come si prendono le febbri malariche. Richerche speriment." Bull, della R. Accad. med. di Roma, 15th November 1898 ; also, Lancet, 3rd and loth December 1898. Bignami (A.). " Sulla questione della malaria congenita." // Policlinico, 1898. NOTED IN SQUARE BRACKETS 649 1898 Bignami (A.). "Due casi di terzana estiva sperimentale." // Policlinico, 1898. Grassi (B.)- " Rapporti tra la malaria e peculiari insetti." Policlinico, 1st October 1898; also Rendic R. Accad. del Lincei^ 1898, VII., pp. 163-172. Grassi (B.) "La malaria propagata per mezzo di peculiari insetti. Rendic R. Accad. dei Lined, 1898, VII., pp. 234-240. Grassi (B.). " Rapporti tra la malaria e gli artropodi." Rendic R. Accad. dei Lincei., 1898, VII., pp. 314-315. Manson (P.). " Surgeon-Major Ronald Ross's Recent Investigations on the Mosquito- Malaria Theory." Brit. Med. Journ., i8th June, 1898, I. pp. 1575-1577- Manson (P.). "The Mosquito and the Malaria Parasite." (Read at the end of July.) Brit. Med. Journ., 24th September 1898, II., pp. 849-853. Ross (R.). "Further Observations on the Transformation of Crescents." Ind. Med. Gaz., January 1898, XXXIII., No. i. Ross (R.). "Pigmented Cells in Mosquitos." Brit. Med. Journ., 26th February 1898, I. Ross (R.). Report on a Preliminary Investigation into Malaria in the Sigur Ghat, Ootacamund. Ind. Med. Gas., April 1898, XXXIII., pp. 133-136, 170-175 : also, Transactions of the South Indian Branch Brit. Med. Assoc, February 1898. Ross (R.). Preliminary Report on the Infection of Birds with Proteosoma by the Bites of Mosquitos. Dated nth October 1898. Government Press, Calcutta. Ross (R.). Report on the Cultivation of Proteosoma, Labbe, in Grey Mosquitos. Government Press, Calcutta (dated 21st May 1898). Also Ind. Med. Gaz., November and December 1898. Thayer (W. S.). " Lectures on the Malarial Fevers." Henry Kimpton, London, 1898. 1899 Bastianelli (G.) and Bignami (A.). " Sullo sviluppo dei parassiti della terzana nell' Anopheles claviger." Atti d. Soc. per gli studi d. 7nala>ia, 1899, I., pp. 28-49. Daniels (C. W.). " On Transmission of Proteosoma to Birds by Mosquitos." Royal Society, i6th March 1899. Elting (A. W.). " ijber Malaria nach experimentellen Impfungen." Zeitschr.f. Klin. Med., 1899, XXXVI., 5-6, p. 491. 650 REFERENCES TO LITERATURE 1899 Grassi (B.), Bignami (A.), and Bastianelli (G.). " Ciclo evolutive delle semilune nell'Anopheles claviger ed altri studi sulla Malaria dall'ottobre 1898 al maggio 1899." Atti d. Soc. per gli studi d. malaria, 1899, I., pp. 14-27. Koch (R.). tJber die Entwickelung der malaria' parasiten." Zeitschr. f. hygiene, 1899, XXXII. Koch (R.). "Ergebnisse der wissenschaftlichen Expedition nach Italien zur Forschung der Malaria." Deiitsch. Med. Woch,, 2nd February 1899, XXV., 5, pp. 69-70. Nuttall (G. H. F.). "On the Role of Insects, Arachnids and Myriapods, as Carriers in the Spread of Bacterial and Parasitic Diseases of Man and Animals." Johns Hopkins Hospital Reports, 1899, VIII. ; also, Hygien. Rundschau, 1899. Nuttall (G. H. F.). "Die Mosquito-Malaria Theorie." Centralbl f. Bakt., 1899, XXV., No. 5, p. 161 ; 6, p. 209 ; 7, p. 245 ; 8, 9, p. 285 ; 10, p. 337 ; 24, p. 877 ; 25, p. 903 ; and XXVI., 4, 5, p. 140. Ross (R.). " Du Role des Moustiques dans le Paludisme." Ann. Inst. Past., 1899, No. 2, p. 136 {Acad, de Medecine, 24th January 1899). Ross (R.). Report on Kala - azar (dated 30th January 1899). Government Press, Calcutta, 1899. Ross (R.). "Extermination of Malaria" (dated i6th February 1899). Ind. Med. Gaz., July 1899. Ross (R.). "The Possibility of Extirpating Malaria from Certain Localities by a New Method." Brit. Med. Journ., ist July 1899, II., p. I. Ross (R.). " An Outbreak of Fever attributed to Mosquitos." Brit. Med. Jour?t., 22nd July 1899. Ross (R.). " Life History of the Parasites of Malaria." Nature, 3rd August 1899. Correspondent (R. Ross). "The Malaria Expedition to Sierra Leone." Brit. Med. Journ., 9th, i6th, 30th September and 14th October 1899. Ross (R.). " Malarial Fever : Its Cause, Prevention, and Treatment." Liverpool Sch. Trop. Med., Memoir I., 1899. 1899- Stephens (J. W. W.) and Christophers (S. R.). Reports to the 1903 Malaria Committee of the Royal Society, 1899-1903. 1900 Daniels (C. W.). "Development of Crescents in the Small Dark Anopheles prevalent in British Central Africa." Rep. Mai. Com, Royal Soc, 1901, Series V., pp. 41-44. NOTED IN SQUARE BRACKETS 651 1900 Fermi (C.) and Lumbau (S.)- " Befreiung einer Stadt von den Mucken." Centralbl. f. Bakt. I. Abt., 1900, XXVIII., pp. 179, 185. Gosio (B.). "La malaria di Crosseto nell'anno, 1899." Estratto dal : Policlinico, 1900, VI I -M. Grassi (B.). " Studi di uno zoologo sulla malaria." R. Accad. d. Lincei, 4th June 1900. Koch (R.). "Berichte iiber die Tatigkeit der Malaria expedition." Deutsch. Med. IVock., 1899, No. 27 5 iQoo, Nos. 5, 17, 18, 25, 34, and 46 ; also, Br/^. Med. Journ., loth February, 12th May, 30th June. Koch (R.). " Zusammenfassende Darstellung der Ergebnisse der Malaria Expedition." Deutsch. Med. JVoc/i., 1900, No. 49. Manson (P.). " Experimental Proof of the Mosquito - Malaria Theory." Bnf. Med. Joiirm.., 29th September 1900, II., pp. 949-951. Rees (D. C). " Experimental Proof of the Malaria-Mosquito Theory." Brit. Med. Journ.., 6th October 1900, II., pp. 1054-1055. Ross (R.), Annett (H. E.), and Austen (E. E.). Report of the Malaria Expedition of the Liverpool School of Tropical Medicine. University Press of Liverpool. Memoir II., February 1900. Scheer (A. van der) and Berdenis van Berlekom (J.). " Malaria and Mosquitos in Zealand." Ned. Tydschr. v. Ceneesk, 24th February and 14th July 1900; also Brit. Med. Jou7-n.., 26\.h. January 1901, I., pp. 200-202. Stephens (J. W. W.) and Christophers (S. R.). Reports to the Malaria Committee of the Royal Society, 1899-1903. Various Authors : Liverpool School of Tropical Medicine., Memoirs II., III., IV. ; and Royal Society Reports to the Malaria Com- mittee, 6th July and 15th August 1900. 1900- Thomson (J. C). " Malaria Prevention in Hong-Kong." Official 1903 Report, containing many letters. 1900- Reports on the Health and Sanitary Conditions of the Colony of 1905 Hong-Kong, 1900-1905. 1901 Billet (A.). " Sur la presence constante de I'hematozoaire de Laveran dans le paludisme en Algerie" (Constantine). Compt. Rend. Soc. Biol.., December 1901, LIII. pp. 1063-1065. Celli (A.). " Malaria according to the New Researches." Longmans, Green & Co., London, 1901. Ewing (J.). 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Nuttall (G. H. F.), Cobbett (L.), and Strangeways-Pigg (T.). "The Geographical Distribution of Anopheles in Relation to the Former Distribution of Ague in England." Journ. of Hygiene, January 1901, I., I, pp. 4-44. Rogers (L.). " The Seasonal Prevalence of Anopheles and Malarial Fever in Lower Bengal ; and the Practical Application of the Mosquito Theory." Journ. of Hygiene, October 1901, I., 4, pp. 407-421. Ross (R.). "First Progress Report of the Campaign against Mosquitos in Sierra Leone, with Letter by Daniels." Liverpool Sch. of Trap. Med., Memoir V., Part I, 15th October 1901. Ruge (R.). " Untersuchungen liber das deutsche Proteosoma." Centralbl.f Bakt, 1901, I. Abt., XXIX., 5, p. 187. Stephens (J. W. W.), Christophers (S. R.), and James (S. P.). " Note on the Occurrence of Anopheles funestus and Anopheles costalis in India." Ind. Med. Gas., October 1901, XXXVI., p. 361. Theobald (F. V.). " The Classification of Mosquitos." Journ. Trop. 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Atti, 1902, III., pp. 356-366. Celli (A.). " Stato palustre ed anofelico (paludisme) senza malaria." Atti della Soc. per gli studi d. malaria, 1902, III., pp. 115-145. Chalmers (A. J.). "A Theory to explain how Man and the Anopheles originally became infected with the Malarial Germ." Jou?'n. Trop. Med., 1st May 1902, V., 9, pp. 133-134. Button (J. E.). Report of the Malaria Expedition to the Gambia, 1902. Liverpool Sch. Trop. Med., Memoir X. Longmans, Green and Co., London, 1903. Maurer (G.). "Die Malaria Perniciosa." Centralbl. f. Bakt. Otig., 5th November 1902, XXXII., p. 695. Nuttall (G. H. F.) and Shipley (A. E.). "The Structure and Biology of Anopheles {A. tiiaculipemtis).'" Joiirn. of Hygietie, January 1901 ; April 1901 ; October 1901 ; January 1902 ; April 1903. Panse (O.). " Bie Malaria unter Eingeborenen in Tanga." Arch.f. Schiffs und Trop. Hyg., 1902, VI., 12, pp. 403-427. Ross (R.). " Mosquito Brigades, and how to organise them." George Philip & Son, London, 1902. 98 pages. Sambon (L. W.) and Low (G. C). Report on two Experiments on the Mosquito-Malaria Theory. Medico-Chirurgical Trans., 1902, LXXXIV. Schaudinn (F.). " Studien iiber krankheitserregende Protozoen. I. Cyclospora caryolytica Schaud., der Erreger der perniciosen Enteritis des Maulwurfs." Arbeit, a. d. Kais. Gesundh., 1902, XVIII., pp. 378-416. Schiiffner (W.). " Die Beziehungen der Malariaparasiten zu Mensch und Miicke an der Ostkiiste Sumatras." Zeitschr. f. Hyg. und Inf., 1902, XLL, p. 89. Schiiffner (W.). " Uber die Malariaparasiten im Anopheles an der Ostkiiste von Sumatra." Geneesk. Tydsckr. v. Ned. Ind., 1902, XLIL, pp. 8-13. 6S4 REFERENCES TO LITERATURE 1902 Stephens (J. W. W.) and Christophers (S. R.). Reports from India. III. "The Relation of Species of Anopheles to Malaria Endemicity.'' Further Report (received 25th April 1902). IV. "An Investiga- tion into the Factors which determine Malaria Endemicity." (Received 25th April 1902.) 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"The Thick Film Process for the Detection of Organisms in the Blood." Thomson Yates Reports, 1903, V., Part I. Ruge(R.)- Zur Erleichterung der mikroskopischen Malaria-diagnose. Deutsch. Med. JVoc/i., 19th March 1903, XXIX., No. 12, p. 205. Schaudinn (F.). " Studien iiber krankheitserregende Protozoen." II. "Plasmodium vivax (Grassi and Feletti), derErreger des Tertian- fiebers beim Menschen." Arbeit a. d. Kais. Gesundh., 1903, XIX., p. 169. Watson (M.). "The Effect of Drainage and other Measures on the Malaria of Klang, Federated Malay States." Journ. Trap. Med.., 16th November 1903, VI., 22, pp. 349-353; and ist December 1903, VI., 23, pp. 368-371. Travers (E. A. O.). An Account of Anti-Malarial Work carried out with Success in Selangor, one of the Federated States of the Malay Peninsula." Journ. Trop. Med., 15th September 1903, VI., 18, pp. 283-285. 1904 Boyce (R.). "The Anti-Malaria Measures at Ismailia." Liverpool Sch. Trop. Med.., Memoir, 1904, XII. Christophers (S. R.). 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Soc. per gli studi d. ynalaria, 1904, V., pp. 211- 258. Pressat (A.). " Prophylaxie du Paludisme dans I'lsthme de Suez." La Presse Medicale, 30th July 1904. 656 REFERENCES TO LITERATURE 1904 Rosenau, Parker, Francis and Beyer. Report of Working Party, No. 2. Yellow Fever Institute, May 1904. Government Printing OflSce, Washington, U.S. Ross (R.). "The Anti-Malaria Experiment at Mian Mir." Brit. Med. Journ.., 17th September 1904, II., pp. 632-635. Salvage (J. V.). " Preventive Measures against Malaria in Kandia, Crete." Journ. of the R.A.M. Corps., May 1904, II., 5, pp. 566-569. Sewell (E. P.). "The Results of the Campaign against Malaria in Mian Mir." Brit. Med. Journ.., 17th September 1904, II., pp. 635-637. Smith (F.) and Pearse (A.). "Fevers in Sierra Leone" (Mount Aureol), being a preliminary account of an enquiry into the causes of the continued prevalence of ill-health in an apparently favourably situated hill station." Journ. of the R.A.M. Corps, March 1904, II., 3, pp. 278-282. Schaudinn (F.). " Generations und Wirtswechsel bei Trypanosoma und Spirochaete." Arbeit, a. d. Kais. Gesundh.., 1904, XX., 3, pp. 387-438. Schaudinn (F.). " Die Malaria in dem Dorfe ' St Michele di Leme' in Istrien und ein Versuch zu ihrer Bekampfung." Arbeit, a. d. Kais. Gesundh., 1904, XXL, 3, pp. 403-475. Strachan (Henry). "Discussion on the Prophylaxis of Malaria." Part v., Brit. Med. Journ., 17th September 1904, II., pp. 637-639. 1905 Carducci (A.). " Sulla cura e sulla causa delle recidive nella malaria." Atti d. Soc. per gli studi d. malaria, 1905, VI., PP- 27-37- Cunningham (R. A.). " Malaria Fever in Candia." Journ. of the R.A.M. Corps, 1905, V., pp. 274-275. Glogner (M.). tJber zvvei Malariaimpfungen. Arch. f. Schiffs und Trop. Hyg., 1905, IX., 10, pp. 439-441- Goeldi (E. A.). Os mosquitos no Pari. Com 144 figuras no texto e 5 estampas chromolithographicas, Para, 1905, Estabel. Graph. C. Wiegandt. Jansco (N.). " Der Einfluss der Temperatur auf die geschlechtliche Generationsentwicklung der Malariaparasiten und auf die experi- mentelle Malariaerkrankung." Centralbl. f. Bakt. Orig., 1905, XXXVIII., p. 650. Jolly (J.) " Mosquitos and Fever in Susruta." Roy. Asiatic Soc, July 1905, p. 558. MacDonald (C. J.). "Crete as a Station, with a Mosquito Campaign conducted there in 1903." Journ. of the R.A.M. Co?ps, January 1905, IV., I, pp. 31-45. NOTED IN SQUARE BRACKETS 657 1905 Mannaberg (J.)- "Article on Malaria." NoihnagePs Encyclopedia. English edition, 1905. Modigliana (E.). " Cioccolattini al chinino di Stato. Assorbimento e eliminazione della chinina somministrata in forma di tannato." Am d. Soc. per gli studi d. malaria, 1905, \T., pp. 95-104. Patton (W. S.). " The Culicid Fauna of the Aden Hinterland." Journ. Bombay Nat. Hist. Soc, 1905, p. 623. Penton (R. H.). " Egyptian Army : The Malarial Campaign in the Soudan, 1904." Journ. of the R.A.M. Corps., May 1905, IV., 5, pp. 628-633. 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Medical News, 4th March 1905, LXXXVI., p. 425 1906 Clark (F.). "An Address on the Prevention of Malaria in Hong- Kong." Hong-Kong, 1906. Noronha & Co. Copeland (R. J.) and Smith (F.). " Malarial Fever contracted in Portsmouth." Journ. R.A.M. Corps, August 1906, VII., 2, p. 186. Craig (C). "Observations upon Malaria. Latent Infection in Natives of the Philippine Islands, Intracorpuscular Conjugation." Philippine Journ. of Science, 1906, I., p. 523. Craig (C). " Intracorpuscular Conjugation in the Malarial Plas- modium and its Significance." American Mediane, 1906, X., 24 pp. 982-986 ; and No. 25, p. 1029. 2 T 658 REFERENCES TO LITERATURE 1906 Kinoshita (K.). " Uber die Verbreitung der Anophelen auf Formosa und deren Beziehung zu den Malariakrankheiten." Arch. f. Schiffs imd Trop. Hyg-, 1906, X., 22, pp. 708-726. Pearson and Blakeman. "A Mathematical Theory of Random Migration." Drapers^ Company Research Me7noirs, University of London. Dulan & Co., London, 1906. Ross (R.). " Malaria in Greece." Journ, Trop. Med., 15th November 1906, IX., 22, p. 341. Ruge (R.). " Einfiihrung in das Studium der Malariakrankheiten mit besonderer Beriicksichtigung der Technik." 2nd edition, 1906. G. Fischer, Jena. Suez Canal Co. "Suppression du Paludisme a Ismailia." Ofiicial Report of the Compagnie Universelle du Canal Maritime de Suez, 1906. Travers (E. A. O.) and Watson (M.). " A Further Report on Measures taken in 1901 to abolish Malaria from Klang and Port Swettenham in Selangor, Federated Malay States." Jom-n. Trop. Med., 2nd July 1906, IX., 13, pp. 197-198. Ziemann (H.). "Malaria." Handbuch der Tropenkrankheiten, III., 1906, by Dr C. Mense. Leipzig, J. A. Barth, 1906. 1907 Banks (C. S.). " Experiments in Malarial Transmission by Means of Myzomyia ludlowii Theob." Philipp.Jourti. Science, 1907, II., B., pp. 513-536. Giemsa and Schaumann. " Pharmakologische und chemisch-physio- logische Studien iiber Chinin." Atxh. f. Schiffs und Trop. Hyg., 1907, XL, Beiheft, 3. Grosch. Med. Klin. No. 20. Husson ( ). " Etudes epidemiologiques et prophylactiques sur le paludisme en Tunisie." Aim. de Plnst. Past, de Tunis, 1907, p. 3. Jones (W. H. S.). " Malaria : a Neglected Factor in the History of Greece and Rome." Chapter by Dr G. G. Ellett and preface by R. Ross. Macmillan & Bowes, Cambridge, 1907. Laveran (A.). "Traite du Paludisme." Masson & Cie, Paris, 2nd edition, 1907. Nichols (F. P.). "The Effect of Large Drainage Works on the Prevalence of Malaria." Journ. 0/ the R. A.M. Corps, April 1907, VIIL, 4, pp. 343-360. NOTED IN SQUARE BRACKETS 659 1907 Ross (R.)- "An Address on the Prevention of Malaria in British Possessions, Egypt, and Parts of America." Delivered in Section VII. of the 14th Internat. Congr. of Hyg. and Demogr. held at Berlin, September 1907. Lancet^ 28th September 1907, II. pp. 879-887. Sergent (Ed. and Et.). "Etudes sur les hematozoaires d'oiseaux." Ann. de PInsL Past., 25th April 1907, XXL, 4, pp. 251-280. Stephens (J. W. W.) and Christophers (S. R.). " The Practical Study of Malaria and other Blood Parasites." 3rd edition, London, 1907. Wurtz (R.). " Silicatage des tulles employes pour proteger contre la piqure des moustiques." Revue de Med. ei d'Hyg. T7-op., 1907, IV., 4, p. 181. 1907- Newstead (R.), Dutton (J. E.), and Todd (L. J.). " Insects and other 1908 Arthropoda collected in the Congo Free State." Ann. of Trap. Med. and ParasitoL, 1907- 1908, I., p. 10. 1908 Bliiml (M.) and Merz (G. F.). " Schizogonie der Makrogameten." Arch. f. ScJiiffs und Trap. Hyg., 1908, XII., 8, pp. 249-255. Fowler (C. E. P.). " Malarial Investigations in Mauritius." London, 1908. Harrison & Sons. Also, _/ti«r«. TV^/. yI/^<^., 15th September 1909, XII., 18, pp. 273-275. Howard (R.). " Malarial Prophylaxis in Small Communities in Brit. Central Africa.' Journ. Trop. Med., ist January 1908, pp. 1-16, Jansco (N.), " L'etat du paludisme en Hongrie pendant les dernieres annees." Attid. Soc.per glistudid. malaria, 1908, IX., pp. 125-150, Koch(R.). " tJber meine Schlafkrankheits expedition." Berlin, 1908, D. Reimer. Liston (W. Glen). The " Present Epidemic of Malaria in the Port of Bombay." Journ. Bombay Nat. Hist. Soc, 15th November 1908, XVI 1 1., No. 4. Merz (G. F.) and Bliiml (M.). "Schizogonie der makrogameten van tertianaparasieten." (Onderzoekingen, verricht in het hospital te Koeta-Radja, September to December 1907.) Geneesk. Tydschr. v. Ned. Ind., 1908, XLVIIL, 2, pp. 194-204. Neumann (R. O.). " Die Ubertragung von Plasmodium praecox auf Kanarien-vogel durch Stegomyia fasciata, und die Entwicklung der Parasiten im Magen und den Speicheldriisen dieser Stechmiicke." Arch.f. Protistenkunde, 1908, XI 1 1., r, p. 23. Rogers (L.). " Fevers in the Tropics." Henry Frowde, Hodder and Stoughton, London, 1908. 66o REFERENCES TO LITERATURE 1908 Ross (R.). "Report on the Prevention of Malaria in Mauritius." London, 1908. Waterlow & Sons. Rowan (H.). " Mian Mir (Lahore Cantonment) : A Retrospect and Prospect." Jouf'ft. of the R. A.M. Corps, September 1908, XL, 3, pp. 229-242. Walter (A.), " On the Influence of Forests on Rainfall and the Probable Effect of ' Deboisement' on Agriculture in Mauritius." Mauritius, Storekeeper General's Printing Establ., 1908. 1909 Baermann (G.), " Uber Chinintod." (Central Hosp., Petoemboekan, Sumatra.) Muftch. Med. IVoc/i., 9th November 1909, No. 45. Boyce (Sir R.). " Mosquito or Man." John Murray, London, 1909. Carter (H. R.). " Notes on the Sanitation of Yellow Fever and Malaria from Isthmian Experience." Med. Rec, New York, loth July 1909. Christophers (S. R.) and Bentley (C. A.), "The Human Factor in Malaria." Transactions of the Bombay Medical Congress. The Times Press, Bombay, 1909. Craig (C F.) "The Malarial Fevers, Haemoglobinuric Fever and the Blood Protozoa of Man." London, 1909. J. & A. Churchill. Daniels (C W.). " Mosquitos in Federated Malay States." Daniels (C. W.) and Wilkinson (E.) "Tropical Medicine and Hygiene." London, 1909. John Bale, Sons and Danielsson. Darling (S. T.). "Transmission of Malarial Fever in the Canal Zone by Anopheles Mosquitos." Journ. Atneric. Med. Assoc, i8th December 1909, LI 1 1., p. 2051. Deaderick (W. H.). " A Practical Study of Malaria." Saunders & Co., Philadelphia, 1909. Easton (P. G.). " A Case of Malarial Fever contracted at Aldershot," foiirn. R.A.M. Corps, November 1909, XI 1 1., 5, p. 585. Efifertz (O.). " Malaria in Tropical America and amongst Indians." Janus, April 1909, p. 246. Genovese (F.). "II clima antico della Magna Grecia e la malaria attuale di Foca (Caulonia). Note storiche, profilattiche e demo- grafiche." Atti. d. Soc.perglistudid. malaria, 1909, X., pp. 461-481. Harrison (W. S.). " On the Cause of Relapse in Malaria." Joutn. of the R.A.M. Corps, December 1909, XIII., 6, pp. 647-649. Jones (W. H. S.). " Malaria and Greek History." Chapter on the history of Greek therapeutics and the malaria theory of Dr E. T. Withington. University Press, Manchester, 1909. NOTED IN SQUARE BRACKETS 66i 1909 King (W. G.)- Information supplied for the Simla Anti-Malaria Conference. Government Printing Office, Rangoon, 1909. Nardelli (G.)- " Sulla eliminazione della chinina per le urine in rapporto alle diverse dosi negli individui sani e malati." "Malaria," May 1909, I., 3, p. 146. Neeb (H. M.). "Parthenogenese der makrogameten van de tropica- parasiet." Geneesk. Tydschr. v. Ned. Ind., 1909, XLIX., 5, pp. 574-584; aXso, Jotirn. Trop.Med., ist April 1910, XIII., 7, pp. 98-102. Ross (R.). "The Campaign against Malaria." (Read at the meeting of the Royal Inst, of Great Britain, 7th May 1909.) London, William Clowes & Sons. Sandro (D. de). "Chinina nei diversi organi." Riforma Medica., Naples, 8th November 1909, XXV., 45, pp. 1233-1260. Vogel (W. T. de). " Myzomyia rossii als overbrengster der malaria." Geneesk. Tydschr. v. Ned. Ind.., 1909, XLIX., 5, pp. 585-595. 1910 Bentley (C. A.). " Malaria in Bombay." Government Central Press, Bombay, 19 10. Boyce (R.). " Health Progress and Administration in the West Indies." London, 1910. Murray. Cellia (A.). " Ancora del tannato di chinina nei casi di intolleranza d'altri preparati chinacei" (Nota 2a). "Malaria," January 1910, II., I, p. 45. Cellia (A.). " II tannato di chinina e le sue indicazioni per la profilassi e per la cura della malaria." "Malaria," March 1910, II., 2, pp. 92-103. Chaytor- White (J.). "The Propagation of Small Fish as a Means of Limiting Malaria." Proceedings of the Imp. Mai. Coft/.i Simla, 19 10. Christophers (S. R.). "A New Statistical Method of Mapping Epidemic Diseases in India, with Special Reference to the Mapping of Epidemic Malaria." Proceedings of the Imp. Mai. Conf, Simla, 1910. Darling (S. T.). " Factors in the Transmission and Prevention of Malaria in the Canal Zone." Afin. Trop. Med. a7id Parasitol., 1910, IV., 2. Fernando (H. M.). " Prevention of Malaria in Ceylon." Read at the Ceylon Branch, Brit. Med. Assoc, 19th March 1910. Simla Conference. Proceedifigs of the Imperial Malaria Conference held at Simla. Government Press, Simla, 1910. CONTENTS IN DETAIL CHAPTER I— HISTORY Section 1. Ancient Times, I. Egypt, i. Possible entry of malaria into Greece about 550 B.C., I. Knowledge of the ancients regarding malaria, 3. Ceylon, 6. 2. Early Modern Times, 6. Discovery of Cinchona, 6. Theory of Morton and Lancisi regarding the paludic miasma, 7. 3. Discovery of the Parasites, 8. Discovery of the paludic pigment. 8. Efforts to find the organism in marshes, 8. Laveran discovered the parasites, 9. Gerhardt successfully inoculated man, 9. Re- searches on the parasites, 9. 4. Speculations regarding the Mode of Infection, 10. Failure of infection experiments with marsh water, 10. Discovery of metaxenyof animal parasites, 11. Discoveries regarding Cucidanus elegans, Filaria inedinensis, Dipylidiuiii caninium, Filaria bancrofti^ and Piroplasma bigenium, 12. Conjectures of Nott, Beauperthuy, Finlay, King, Laveran, Koch, Manson, 15. 5. Researches regarding the Mode of Infection, 20. Negative researches on mosquito-transmission, 21. Final success, 23. Dis- covery of the full mosquito cycle, 25. 6. Confirmations and Extensions, 26. Koch, Daniels, Bignami, Bastianelli, Grassi and others, 26. 7. Recent History of Prevention, 29. Early studies on mosquitos, 30. First proposals regarding mosquito reduction, 31. Sierra Leone, 34. Later entomological work, 2,7- The quinine method, 37. The Royal Society Commission, and prevention in Lagos, Sierra Leone, Ismailia, Federated Malay States, Rio Janeira, Algeria, and else- where, 38. 8. Remarks, 43. Early neglect of anti-malaria measures, 43. Neglect of recent discoveries, 44. Cause of such neglect, 46. 663 664 CONTENTS IN DETAIL CHAPTER II. — SUMMARY OP^ FACTS REGARDING MALARIA. (SUITABLE FOR PUBLIC INSTRUCTION.) Section 9. The Parasites and the Fever, 49. 10. TheModeof Infection, 51. 11. Facts about Mosquitos, 54. 12. Personal Prevention, 58. 13. Public Prevention, 60. CHAPTER III.— THE FUNDAMENTAL OBSERVATIONS AND EXPERIMENTS 14. The Parasites cause the Disease, 62. Relations between the parasites and the illness, 62. 15. Experimental Blood Inoculations, 66. Short description of 51 successful cases and 6 important negative ones, 66. 16. The Parasites develop in Certain Mosquitos, 76. 17. Experimental Mosquito Inoculations, -]•]. Experiments on birds and 35 successful mosquito inoculations of man, 79. CHAPTER IV.— THE PARASITIC INVASION IN MAN 18. The Onset of the Invasion, 86. (i) The number of parasites in the mosquito 86. (2) The number of protospores in the salivary glands, 88. (3) How many protospores enter the human blood ? 88. (4) Further development of the protospores, 88. (5) The number of spores produced by each species of parasite, 89. (6) The onset of the invasion, 89. (7) The number of haematids in an average man, 90. (8) The lowest number of parasites required to produce the first illness, 91. (9) The time required to examine the blood microscopically, 91. (10) The period of incubation, 94. 19. The Further Progress of the Invasion, 98. (i) Increase of the parasites, 98. (2) The maximum number of parasites, 99. (3) Limitation of the invasion, 100. (4) The illness is due to a toxin, loi. 20. The Decline of the Invasion, 104. (i) The period of regular paroxysms, 104. (2) The appearance of sexual forms, 107. (3) The period of rallies and relapses, 108. (4) The parasites during the rallies, no. (5) Probable cause of the rallies and relapses, 115. (6) Frequency of the relapses, 118. CONTENTS IN DETAIL 665 Section 21. Average Duration of Untreated Infections, 122. 22. Enlargement of the Spleen and Liver, 127. Some hypotheses, 128. Kala-azar, 129. Spleen rates in Mauritius and Ceylon, 131. 23. The Effect of Quinine, 134. Absorption and eUmination, 134. Effect on the parasites, 137. Effect on relapses, 140. Administra- tion and duration of treatment, 141. 24 Summary, 143. CHAPTER v.— MALARIA IN THE COMMUNITY 25. Is the Infection caused otherwise than by the Anophelines? 145. Several questions discussed, 145. Does malaria come from the soil .'^147. Do other insects carry malaria? 149. Do the parasites enter the eggs of mosquitos ? 150. 26. Some Definitions, 151. Indigenous and imported cases, 151. The malaria rate, the malaria index, the inoculation rate, etc., 152. 27. Conditions required for the Production of New Infections in a Locality, 153. Analysis, 153. 28. Laws which Regulate the Amount of Malaria in a Locality, 156. Analysis, 156. Formulae, 159. Examples, 159. The limit of the malaria ratio, 161. 29. Laws which Regulate the number of Anophelines in a Locality, 164. (i) The output of mosquitos from marshes, 165. (2) The average life of the winged insects, 166. (3) The proportion of mosquitos which succeed in biting human beings, 167. (4) The number of Anophelines in unit of area, 169. (5) Variation of mosquito - density from place to place, 172. (6) Variation of mosquito-density from time to time, 172. (7) Variation of mosquito- density due to food, etc., 173. (8) Relation of mosquito-output to extent of breeding-surface, 173. (9) Flock-migrations of mosquitos, 176. (10) Visitation of ships, 176. (11) Transportation by ships and vehicles, 177. (12) Transportation by rivers and wind, 177. (13) Velocity and length of flights, 178. (14) The random-scatter of animals from a given point, 179. (15) Exceptions, 181. (16) Diminution of mosquitos round a central sterile patch, 182. 30. Explanation of Various Phenomena, 186. (i) Connection with marshes, 187. (2) Connection with soil, 189. (3) Connection with slope, 189. (4) Connection with vegetation, 190. (5) Connec- tion with rainfall, 191. (6) Connection with temperature, 192. (7) Connection with altitude, 192. (8) Comparative freedom of centre of towns, 194. (9) Effect of density of human population, 194. (10) The "regional factor," 195. (11) The species factor, 196. (12) The social factor, 197. (13) Possible effect of malaria 666 CONTENTS IN DETAIL Section on the Anophelines, 197. (14) Seasonal variation, 198. (15) Annual variation, 199. (16) Effect of imported cases, 201. (17) Isolated, super-malarious, or infra-malarious areas, 203. (18) Effect of mass migrations, 204. (19) Extraneous infection, 205. (20) Slow changes in endemicity, 206. (21) Examples : Mauritius, Ismailia, Clairfond, Britain, 209. (22) Possible errors in the study of endemicity, 214. (23) Remarks, 216. 31. The Measurement of Malaria, 217. (i) The parasite rate and index, 218. (2) The spleen rate and index, 220. (3) Combined parasite index and spleen index, 223. (4) Average spleen and average enlarged spleen, 225. (5) The fever rate and index, 226. (6) The constantly-sick rate and index, 229. (7) Malarial death-rates, 230. (8) Random sampling, 230. (9) Variation of the malaria index according to age, 235. (10) Determination of the inoculation rate, 239. (11) Practical conclusions, 242. 32. The Mortality and Cost of Malaria, 246. Difficulties, 246. Case mortality, 247. Malarial death-rate, 248. Meldrum's law, 250. Cost of malaria, 252. CHAPTER VI.— PREVENTION 33. List of the Possible Preventive Measures, 254. 34. Protection against the Bites of Mosquitos, 257. (i) Portable bed- nets, 257. (2) Portable mosquito-proof rooms, 260. (3) Fixed mosquito-proofrooms, 260. (4) Mosquito proofing of windows and doors, 261. (5) Mosquito proofing of verandas, 262. (6) Pro- tection for the hands and feet, 263. (7) Medicinal protectives, 263. (8) Constant movement, 264. (9) Fans and punkas, 264. (10) Some results, 264. 35. Mosquito Reduction, 265. (i) Destruction of adults by hand, 265. (2) Fumigation, 266. (3) Introduction of natural enemies, 267. (4) Destruction of larvae, 270. (5) The screening of breeding waters, 272. (6) Dealing with breeding-holes, 273. (7) Training the banks of streams, rivers, and lakes, 275. (8) Major works, 277. (9) Trees, 279. (10) Houses, 280. 36. Prevention by Treatment, 281. Treatment of the sick, 282. Quinine prophylaxis, 282. Segregation, 285. 37. Selection of Measures for Personal and Domestic Prophylaxis, 287. (i) Self-protection of Europeans in the tropics, 287. (2) Domestic precautions, 290. (3) Troops on service, 291. (4) Ships, 292. (5) Hospitals and asylums, 292. (6) Barracks, 293. (7) Prisons, 294. (8) Schools, 294. (9) General rules, 294. 38. General Sanitary Axioms, 295. CONTENTS IN DETAIL 667 Section 39. Selection of Measures for Public Prevention, 296. Comparison of the various measures, 296. 40. Conduct of the Campaig-n, 313. (i) First steps, 313. (2) Appoint- ment of a directory, 314. (3) Anti-malaria leagues, 315. (4) Legislation, 316. (5) The preliminary malaria survey, 317. (6) Measures in schools, 319. (7) Measures on estates, factories, etc., 320. (8) Other quinine distribution, 321. (9) Appointment and instruction of moustiquiers, 323. (10) Malaria gangs for minor works, 324. (11) Local offices, 325. (12) Major works, 325. (13) The annual malaria report, 327. (14) Cost, 328. (15) Remarks, 329. CHAPTER VII.— SPECIAL CONTRIBUTIONS 41. Anti-malaria Work in the United States, by Professor L. 0. Howard, 332. Center Island, Long Island, California, Staten Island, 333. Brooklyn, Worcester, 334. Staten Island, 336. Newport, 339. New Jersey, 340. New Orleans, San Antonio, 341. Cost, 343. References, 344. 42. Malaria Prevention on the Isthmus of Panama, by Colonel W. C. Gorgas, 346. Drainage, 347. Brush and grass cutting, 348. Oiling, larvicide, prophylactic quinine, screening, 349. Kill- ing mosquitos in quarters, cost, 350. Notes by R. Ross, 351. 43. Anti-malarial Work on the Isthmus of Panama— Technics, by Chief Sanitary Inspector J. A. Le Prince, 353. Surface ditches, 353. Sub-drainage, 354. Larvicide, 356. Cotton waste, 357. Detection of larvae, destruction of adults, 359. Results, 363. 44. Malaria in the West Indies, by Sir Rubert Boyee, 369. Grenada, 370. St Vincent, 371. St Lucia, 372. Trinidad, 372. British Guiana, 373. Barbados, 374. The Bahamas, 374. Jamaica, 375. British Honduras, 375. 45. Malaria in Jamaica, by Dr W. T. Prout, 376. General malarial death- and sick-rates, 377. The spleen rate 379. Anti-malarial measures, 380. 46. Malaria in the Amazon Region and the Protection of Ships, by Dr H. Wolferstan Thomas, 582. Iquitos 382. Manaos, 383. Para, 384. Protection of ships, 386. 47. Prophylaxis of Malaria in Central and Southern Brazil, by Dr Oswaldo G. Cruz, 390. The first prophylactic formula, 391. The second prophylactic formula, 391. The third prophylactic formula, 393. The fourth prophylactic formula, 395. References, 398. 48. Malaria in Spain, by Dr Ian Maedonald, 399. History, 399. Mosquitos, 401. Rio Tinto, 404. 668 CONTENTS IN DETAIL Section 49. The Campaign against Malaria in Italy, by Professor Angelo Celli, 406. (i) The principles of epidemiology, 408. (2) The measures for combating malarial epidemics, 411. (3) Legislation concerning malaria, 422. (4) Contribution to the organisation of the campaign against malaria, 424. (5) General results, 425. (6) Conclusion, 429. 50. Anti-malaria Measures in Greece, by Professor Dr C. Savas. 432. (i) Prevalence of malaria, 432. (2) Propagation of scientific knowledge, 434. (3) The State quinine, 437. (4) Marathon, 440. (5) Laurium, 448. (6) Athens, 449. 51. The Prevention of Malaria in German Possessions, by Professor Dr C. Schilling, 451. Various localities, 451. Kameruns, 469. German South West Africa, 472. South Seas, 473. Conclu- sions, 473. 52. Campagnes Antipaludiques en Territoire, Frangais, by Dr Ed. Sergent, 475. Algeria, 475. Tunis, 489. Corsica, 490. French colonies, 492. 53. Mosquito Reduction in Egypt, by H. C. Ross, 496. General considerations, 496. Ismaiha, 499. Port Said, 522. Heluan, 525. Conclusions, 527. 54. The Campaign at Khartoum, by Dr Andrew Balfour, 530. Mosquitos, 530. Methods, 532. Regulations regarding steamers> 535. Introduction offish, 536. Results, 540. 55. Malaria in South Africa, by Dr L. Bostock, 543. Komatipoort, 544. Portuguese East Africa, 546. Mosquitos, 547. Report by C. W. Howard on mosquitos, 548. 56. Epidemic of Malaria in Durban, 1905-1907, by Dr P. Murison, 549. Description, 549. Measures, 550. Present position, 551. 57. The Prevention of Malaria in the Federated Malay States, by Dr Malcolm Watson (abstract), 554. (i) Towns, 554. Results, 556. (2) District, 558. Conclusions, 558. Effect of roads, effect of jungle, introduction of coolies, quinine prevention compared with drainage, 560. 58. Prevention of Malaria in Fromosa, by Dr T. Takaki, 563. Pre- valence, mosquitos, 563. Preventive measures, results, 565, Cost, 566. 59. Notes on Some Other Works, by Professor R. Ross, 568. India, 568. Hongkong, 573. Candia, 575. 60. The Prevention of Malaria in War, by Colonel C. H. Melville, 577. (i) History, 577. (2) Practical measures, 586. 61. The Prevention of Malaria among Troops under Peace Con- ditions, by Major C. E. P. Fowler, 600. Statistics, 600. Larval destruction, 505. Quinine, 607. Protection, 611. Segregation, 613. Quinine, 614. CONTENTS IN DETAIL 669 ADDENDA Section 62. Suggested Terminology for the Phenomena of Cytogenesis, 621. 63. Notes on the Malaria-beaping Anophelines, 622. (i) Complete list of suspected Anophelines with synonyms, 622. (2) Notes on the incriminated Anophelines, 627. 64. Examples of Legislation, 636. 65. Notes, 638. (i) The Thick-film process, 638. (2) Enumerative methods, 639. (3) Some results, 640. (4) Recent work of S. T. Darling and E. H. Ross, 641. (5) Three more mosquito inocu- lations, 642. (6) The attitude of Anophelines, 642. (7) Counting of breeding-places. (8) M. rossii. (9) Cost of malaria in India. (10) Professor Karl Pearson and Mr H. Waite confirm result of section 28, 643. Horml) I n I M 1 For the treatment of malaria. Of exceptional purity and alkaloidal value. TRADE 6 i#W^ MARK fl I Qu i n I 1^ 1 1 s Famed throughout the world for its purity, accuracy, convenience and palatability» Supplied as follows : gr. 1/2, in bottles of 50 and 100 ; gr. 1, in bottles of 36 and 100 ; gr. 2, gr. 3, gr. 4, gr. 5, gr. 10, 0-1 gm., 0'25 gm. and 0-5 gm., in bottles of 25 and 100. Issued plain or sugar-coated, except gr. 10 and 0-5 gm., which are plain only. TRADE MARK 6 T| O M E ' ^^^'^^ 1 11 i :a © ^S Hi};) x\ n CD A.ttains a much higher standard of purity than required by the British Pharmacopoeia, Supplied in ** Compact Crystals '^ and ** Large Flake '* (the ordinary form), both being identical in composition. Issued in bottles and tins of convenient sizes. Prices and supplies of all B. W. & Co. 's fine Quinine Pro- ducts obtainable of Pharmacists in all parts of the world. BURROUGHS WELLCOME & CO., London New York Montreal Sydney Cape Town XX 190 Milan Shanghai Copyright yVlRE GAUZE MOSQUITO SCREENS CHRISTIE'S OXYDIZED BRONZE MOSQUITO GAUZE Strongest and most Durable Outlasts many renewals of any other quality BRASS AND GALVANIZED GAUZE for Windo'ws, Doors, etc. SAMPLES AND FULL PARTICULARS FROM GEORGE CHRISTIE, LTD. Q y LADYWELL WIRE WORKS GovAN, Glasgow Telegrams and Cables : "LADYWELL, GLASGOW." 231'^ 06 WM H^^lJli y^^^^^y U.C. BERKELEY LIBRARIES CD2535?5tl