1913. PUBLIC HEALTH. 17 already complaining of the large amount of "THE EVOLUlqON OF EPIDEMICS "* work and the large number of committees BvJ. T. C. NASH, M.D. (Edin.), D.P.H. (Camb.). (President of the Etstern Branch of the Society of which they are expected to attend. Medical Officers of Health.) The advocates for placing all sanitary Being a brief epitome or pr6cis of Chadwick Trust matters under the county councils would Lectures I., II. and III., on the Evolution of Epidemics. have us believe that the members of these councils have a much higher sense of duty than T HE evolution of disease implies and involves the members of rural district councils, but this the evolution of ideas of disease as well as certainly cannot apply to all county councils, of causes--the resultants being the labelled as, notwithstanding the permission given in the phenomena. Hence the importance of careful Local Government Act of i888 to appoint observation of phenomena objective and sub- medical officers of health, a cert~dn proportion jective, and of subsequent philosophic reasoning of county councils did not avail themselves of eoncerningsuch phenomena before pronouncing this privilege, and, indeed, only grudgingly a judgment. The history of disease should be appointed such officers when compelled to by traced back to broaden the outlook and the Housing and Town Planning Act of 19o 9. engender liberality of sentiment. Neither Chadwick nor Pasteur were medical DEFORmTIES.--\Vhen not due to tuberculosis men, but both played great pioneer parts in serious deformities are generally the result of preventive medicine, both making and recording infantile paralysis. The newer methods of modern observations and then applying philosophical surgery, such as muscle grafting, nerve grafting, induction. and tendon transplantation have extended the field of treatment of paralysis and deformities, My first lecture embraced a brief historical and in experienced hands often yield brilliant survey of some of the more remarkable results. Unfortunately, only a small percentage epidemics of the Middle Ages, obtained chiefly of crippled children at present can obtain admis- from the writings of Hecker and Creighton. sion into orthopaedic hospitals. The after cure There is almost total lack of contemporary of these cases is beset with numerous difficulties, walking or other apparatus is frequently needed. expert information--the medical men of the It is as a rule costly to obtain, and under the day being apparently galenically hide-bound wear and tear of school life is apt to get out of and lacking in independent philosophy. But order, and as growth proceeds not infrequently from ecclesiastical, municipal and other records becomes useless. It is clear that crippled children require more supervision and after-care than can we gather the striking fact that the Middle be bestowed under the present conditions. They Ages were years of great human misery and of are in many instances anaemic, weakly, ill-fed, cataclysmic natural phenomena, such as earth- and badly clothed, an easy prey to the first serious quake and flood. The lower classes were illness which may attack them. On leaving school, cast on the world without a trade, shut extremely indigent and their dwellings were in out from the ranks of unskilled labour by their a frightful condition of concentrated filth, as physical inability ~o compete with the able- recorded by Erasmus. The mud floors were bodied, left to themselves they go to swell the strewn with rushes, which, when impregnated ranks of the unemployed and destitute. On the with all manner of putrefying filth, were simply other hand, with proper treatment of the defect, and efficient after-care, they may become highly covered over with fresh rushes--covering over, skilled workmen and valuable members of society. bztt not removing, the ghastly mass of decombosing --Joseph Cates, M.D., D.P.H., Annual Re~bort, filth already there. In Britain, after " The Great Medical O~cer of Health, Lancaster. Plague of Cadwallader's time " in the middle of the 7th century (the exact nature of which APPOINTMENTS. is uncertain), the pestilences for the next seven JOIIN DEAN BUCItANS-N, M.B., B.Ch., B.A.O.R.U.[., centuries appear to be, according to Creighton, 1), P.II., Viet., has been appointed nledical officer of health ~,l" Lancaster. mainly the results of famine; but various \VJLLIAM ARNO'rT DICKSON, M.D., Ch.B., St. And., F.R.C.S., Edin., D.P.H., has been appointed tuberculosis periodical, sudden and fatal outbreaks, affecting el'fleer for Glouccstershire. monastic communities, were probably fresh ANDRE~V I,ESLIE D¥1-:ES, ~[.D. Edin., D.P.H. Lend., outbreaks of genuine plague. The feudal has been appointed assistant medical officer of health of the County Borough of Oldham. system was responsible for much misery. It RORY I~IcLAREN,M.I)., I).P.H., has been appoiatt~d a~is- is stated that in the reign of\Villiam Rufus the lant county medical officer of he'dth for Dorset. TIIOM.~S HF~NIeY lh.:~ToX, M.D., 13.Ch., B.A.0. Dub., incubus of excessive tribute apparently led to 1). P.II., has been appointed tubcrculosis officerfor ChcM]h'e. famine through no less remarkable a cause than Wigan Education Authority have unanimously decided h, appoint MRS. ALICE S'raLKER, M.B., Ch.B., D.P.H., to a refusal to cultivate the land. Such times of the position of assistant school medical officer and assistant * President's Address at Annual Meeting of the Eastern Counties tuberculosis officer. Branch of the Society of Medical Officers of Health. 18 PUBLIC HEALTH. OCTOBER, misery and lawlessness, with barbarous in- of visitations of disease which in the course of vasions by Scots and Celts, civil wars, baronial ages have appeared in divers forms, renders cruelties and predations, all contributed to the clearer our insight into the nature of disease. dire famine of 1143, when people ate the flesh We are, therefore, naturally in a better position of dogs and even the raw garbage of herbs and to trace evolutionary factors than our prede- roots. Better times followed in the reign of cessors, though our successors again will have Henry II. A five years'famine in II93-97was the advantage of us. accompanied by a pestilential fever; and In the evolution of medical science two dis- famine and pestilence prevailed again in 12o3 tinct tendencies diametrically opposite are in and after the hard frosts of 12o5. In 1256-59 evidence :-- famine was accompanied by remarkable scarce- (1) A tendency to differentiate as distinct ness of money, owing to the exactions of King affections diseases which had been in- and Pope, so that even men of good position cluded under one common designation ; felt the pinch of hunger. The last of the great (2) A tendency to determine a persistency famines was in 1315. A new chapter in the of type running through a long series history of English epidemics was opened by of disorders of various designations. the advent of the Black Death in 1348. Variation in the birth-rate and death-rate is England was, however, singularly free from the only the most obvious and numerically precise epidemics of "ergotism" which raged in of a whole series of variations in vital phe- France in the I4th century, probably due to nomena, such, for instance, as the apparition rye-bread being but little eaten in England as and vanishing of leprosy in mediaeval Europe. compared with France. Comparisons may be drawn between leprosy Let us for a moment refer to the astonishing and pellagra--another disease with profound psycho-pathies or neurotic epidemics of the disorder of the nerves--and as regards the Middle Ages, more particularly the dancing causation of both these diseases there are two manias, which illustrate how, in crowds, camps of opinion, according as to whether it is "ideas, sentiments, emotions, and beliefs pos- held that the cause of each is something sess a contagious power as intense as that of noxious in the dietary or not. microbes" (Le Bon, " The Crowd," p. 128). It is conceivable that a common saprophyte " The convulsions in the most extraordinary may, under different evolutionary conditions, manner infuriated the human frame, and excited such as semi-putrid fish on the one hand or the astonishment of contemporaries for more semi-putrid vegetable on the other, under than two centuries" (Hecker). Something of varying conditions of season and light, become the sort may still be seen in connection with a lepra bacillus in the one case or a pellagra devilworship or other heathen rites. Wretched- micro-organism in the other. It is, however, ness and want, combined with superstition and equally likely that the somewhat similar unusual excitement, had apparently much to nervous symptoms in leprosy and pellagra may do with these extraordinary disorders, which be the results of interaction between susceptible gradually became mitigated under military tissues and two quite distinct organisms. conditions. Apart from superstition, however, Recent research suggests that both leprosy men's minds were everywhere morbidly sensi- and pellagra are insect - borne diseases. tive through frightful calamities and pestilences Ravbitschek's and Charlton Bastian's observa- of a magnitude rarely known in these days. tions illustrate the enormous evolutionary Even decided sceptics were so vulnerable to importance of light and heat in the production these influences that they were subdued by a of primordial life. poison, the effects of which they had ridiculed, When studying the history of plague in and which was in itself inert. Hysterias were England I remarked that the I5th century common, and women (especially in Italy) led theory that bubo-plague was due to a cadaveric idle, lonely and miserable lives, and so were poison fitted in with both Pettenkofe's ground peculiarly susceptible to ecstatic attacks water fluctuation influences and the most excited by the delights of music, which fur- recent rat theories, as regards the causation of nished a magical means of exorcising their plague. Plague came in Europe in the age of melancholy. feudalism and of walled towns with a cramped From the preceding remarks, it becomes unwholesome manner of life and inhabited evident that a knowledge of contemporary spots of ground choked with the waste matters circumstances which attended the development of generations. Plague as an entity was 1913. PUBLIC HEALTH. 19

endemic in Britain for more than 300 years, One thing, however, that was not touched although probably all the records of " pestes" by the sanitary policy of the day was the dis- were not outbreaks of bubonic plague. After posal of the dead, and the old city churchyards 142o it became more and more a disease of the became scandalously overcrowded and the towns. Parliament was frequently adjourned earth incapable of effecting oxidation of the from Westminster on account of the infection bodies. in London. "Change of air" meant more Plague was prevalent both in Scotland and than it means now. Ireland also throughout the Tudor period, Between 15oo and 1521 plague appears to which closed with a severe epidemic at Stam- have been regularly prevalent in London, ford, which began in I6~2. A severe outbreak especially severe in I513-I 5. Yearly references in Scotland in 1568 gave occasion to the first occur again from 1526-1532. The first known treatise in English upon the subject by a reference to the London Bills of Mortality is Dr. Skene of Aberdeen. made in 1532, the first weekly bill showing 99 The last period of plague in England, from deaths in the City from plague, and 27 deaths 16o3 to its extinction iu i666, was as fatal as from other causes. In I539, parish registers of any known. the births, marriages and deaths began to be In my second Chadwick Lecture I suggested kept. By this means we can henceforth trace that in comparing the "sweating sickness" the existence of epidemic disease which might of the later Middle Ages with modern influenza not have been suspected. Curiously, the reigns we gain an insight into evolution in thoughts of Edward VI. and Mary, full of trouble as and ideas as well as in actual disease processes. they were in other ways, furnish hardly a single The "sweat" type of disease was first recorded record of plague ; but a very severe epidemic in England in I485, and the attacks were of occurred in London in 1563, more particularly in dramatic suddenness and fatality ; the progress the latter half of the year, reaching an average of the " sweat" in i529 was noted as " like of 1,35 ° deaths a week from plague in Septem- an influenza, reversing the order of its usual ber-the total mortality in 33 weeks was direction." 16,586, or an average of abont 5o0 deaths a Its first introduction into England was sup- week. The most probable determining factor posed to be through the mercenary troops from of this sharp outbreak was the re-accumulation Rouen who accompanied Henry VII. They of a susceptible population during a non- were natives of a region in which a sweating epidemic interval of a dozen years, the incidence sickness had long been indigenous. Influenza rate rapidly falling when once this non-immune is essentially a protean disease, showing pabulum was exhausted, but never quite dis- changes of type, which gave rise to many appearing. Very little sanitary provision was different titles at different times, including made, until in 1518 a quaint form of notification " stop gallant," " new acquaintance," "jolly was required in Oxford. The first plague order rant," "la grippe," "hot ague," "catarrh," etc. of which the text is extant was issued in the The persistency of fundamental types in thirty-fifth of Henry VIII. (1543), and provided disease, in spite of well-marked variations-the for notification, quarantine, destruction of in- evolutionary results of environment--is really fected straw, etc. A clause provided for the remarkable. A noteworthy peculiarity of in- cleansing of streets, etc., and there were special fluenza is its tendency to relapse, thus clauses relating to dogs and beggars. In the differentiating it from the majority of well- light of present-day knowledge we may surmise defined infectious diseases, where one attack that dogs and beggars harboured infected fleas. confers, as a rule, a high degree of immunity Queen Elizabeth ordered bonfires in the against further attack. In March, i9o6 , in a streets in the evening to consume " the corrupt paper on " Evolution in Relation to Disease," airs." An unfortunate order, dated September I suggested that some well-recognised diseases 3oth, 1563, attempted to shut up the foul air of had become largely specialised types, through infected houses. This was apparently revoked evolutionary factors on certain fairly definite in January, 1564, when a more sensible order lines (fairly defined for each special type) required a general cleansing and airing of houses, gradually influencing the life processes of some bedding and the like. A most essential means common ancestral saprophytic organism, more for controlling plague was the institution of particularly in its environmental relation to "searchers" for cases and contacts. These man in various countries. In this way special- "searchers" became a regular institution in 1578. ised varieties of a common ancestral protoplasm, 20 PUBLIC HEALTH. OCTOBER, or germ, would be evolved, and under similar "Dunn's disease," may be further evolutionised environmental conditions would naturally tend forms of reactive phenomena due to special to breed pure, and produce fairly specific toxins environmental conditions. The old term giving rise to fairly specific reactive phenomena "morbilli," or "measles," covered, no doubt, in human animal tissues, rendering diagnosis what is now differentiated as scarlet fever and simple. diphtheria. In 19o6 I referred to certain bac- Two diseases of very stable specific type, teriological evidence suggesting that both viz., measles and smallpox, illustrate what is scarlet fever and diphtheria may be fairly meant by specific disease, but, strange to say, specifically evolutionised conditions arising although measles is so constantly with us, and from one common parental saprophyte under smallpox is generally so distinctive, and is yet slight variations in environment. As regards common enough in various parts of the world, measles, undoubted restraining influence can no causal germ has yet been definitely recog- be exercised on the disease by steps taken by nised for either disease. Certain other the education and health authorities acting in "specific" diseases have been found to be due close conjunction, preferably through one to the life-processes within the blood and common medical officer versed in public health tissues of higher forms of life than mere and state or preventive medicine, as well as in bacteria. I need only mention malaria as an general medicine. The diagram on the wall example of such As regards smallpox it appears shows clearly the control obtained over measles to have been known in China since I2oo B.c., in Southend-on-Sea since I912,when I acquired and in Europe since the 6th century. Until early school notification of measles, which has recent times it was characterised by the ever since been kept up. enormous areas affected and the malignant type In the course of the I9th century public of the disease. One of the oldest known medical opinion gradually became intolerant of over- works on the subject is by an Arabian physician crowding and the grosser insanitary conditions --Rhazes--in the ioth century, who quotes of towns. Towns and villages entered on a extracts from an Egyptian physician who period of unparalleled growth to meet the new practised in the 7th century. In the same industrial conditions which followed the intro- century smallpox appears to have been known duction of factories, and the country districts in Ireland, but not to have been recognised in sent the best of their young manhood into the England until the Ioth century. The first towns to meet the demands for labour. People known English work on smallpox dates only had not yet learnt the dangers of aggregation from the end of the I6th century. In pre- and the consequent soil-polluting, water- vaccination days smallpox in Great Britain polluting, atmosphere-deteriorating and insect- showed a periodic intensity of prevalence every contaminating collections of refuse. These three, four, or five years, but during the latter conditions bred sickness and consequent half of the I9th century, since vaccination was poverty, and sanitary administration was made compulsory in I85 I, only one wide-spread evolved from an enquiry into these conditions. epidemic occurred in 1871-72 , when smallpox In Norfolk, a sparsely populated county, one overran Europe and America; but it must be wonders why, with so much available space, clearly remembered that vaccination was not villages should have their cottages crowded the only measure in force, and compulsory together with inadequate yard or garden space. notification, disinfection, isolation, " following The cure of such faults transmitted from our up" of contacts throughout the incubation of ancestors will naturally take time, public the disease, all assisted in limiting the spread energy, and public thought. Medical officers of of infection and widening out the inter-epidemic health need the unstinted support of public periods. opinion in order to propose the strong and The striking resemblance in many of the radical measures necessary to deal with the phenomena of smallpox and of measles make evils so clamant. the latter disease one of peculiar interest at this To Chadwick, as a pioneer in recognising juncture, and it is not outside the bounds of that overcrowding is the greatest factor in the possibility that an original saprophyte evolu- evolution of epidemic diseases, we owe a tionised on different lines, tending specifically boundless debt of gratitude. to measles on the one hand and to smallpox on I dealt in my third Chadwick Lecture with the other. Such diseases as rubella, the so- the present-day scientific evidences of evolution. called "Fourth disease," and the so-called Many medical scientists who do not profess to 1913. PUBLIC HEALTH. 21 believe in the special creation of ordinary animal bacillus correspond in generations to a genera and species each after his kind, as geological epoch in the history of the human suggested in the First l-~ook of Moses, yet race," and pointed out that experiments proved paradoxically believe in the absolute specificity that as regards environment in the matter of of epidemic diseases, and disease germs, as temperature, atmosphere, pabulum, and other descending from, and always reproducing their physical conditions, minute micro-orqanisms are like, in unchanged form. exquisitely sensitive to changes of a degree so A considerable minority have expressed a slight, that they are inappreciable to more more philosophical breadth of view, insisting highly-organised--that is more specialised-- on the application of the laws of evolution to creatures. Sir W. J. Collins, in his paper on disease processes. The present lecturer also " Specificity and Evolution in Disease" many can claim to have made several contributions years previously, had remarked, " It is reason- on evolution in relation to disease and disease able to believe that in organisms whose cycle germs since I9Ol ; and Professor R. T. Hewlett may be less than an hour, and whose rate of was one of the earliest of bacteriologists to propagation is incalculable, that evolution must trace biological affinities between two forms of be powerfully at work." Remy expressed in bacteria which are looked upon by the specifi- 19oo his conclusions from a large number of cists as absolutely distinct and unconnected experiments, that the difficulty of isolating the with each other. I refer here to what are typhoid bacillus from fluids in which it had known as Klebi-L6ffler and Hoffman bacilli. been existing with bacillus coli was not due to The present-day scientific evidences of evolu- the disappearance of the typhoid bacillus, but tion in relation to disease may be gathered to modifications in biological characters. from :-- When a specific bacillus is pushed too far by (a) Field work epidemiology--based on the absolute specificist, he has to invent new painstaking investigation and accurate names for bacteria giving rise to symptoms clinical observation apart from labora- almost, or quite, alike, but differing slightly in tory aid. some one or two chemico-physical properties. (b) Systematic, day-to-day bacteriological Baerthlein's recent experiments show that observations in the laboratory from bacterial mutations occur regularly, but infected mucous membranes, or dis- suddenly, under defined environment ; the charges, or the blood, or otherwise; changes being transmitted to following genera- not neglecting, as is too often the case, tions under the same conditions--the mutations the study of natural conditions and affecting the morphological, biological, and symbiotic relationships. serological relations of the bacteria. Some (c) Philosophical logical deductions based bacteria, such as B. typhosus, have several on (a) and (b). mutative forms~but all such forms tend to Two important phenomena stand out and return to the original form when the biological mark the evolution of the organic world : One environment is made as like the original con- is the actual existence of different species, their ditions as possible. differentiation in groups, the increasing com- Drs. Thiele and Embleton concluded from a plexity of organisms, their evolution from the number of experiments that the pathogenicity lowest to the highest forms--the other is the of bacteria is largely an evolutionary process, adaptation of living things to the conditions due to environmental conditions in the tissues and necessities of their environment. of a susceptible animal. No biologist will ever again consider natural Mr. Sidney Turner, M.R.C.S., F.L.Z., in selection as the only fa=tor. Roux's theory of 1894 tersely defined zymotic disease in general functional stimulation beginning with embryonic as life in the wrong place. life in more highly organised creatures, affords In dealing with biological problems we have a solution of the difficulties which exist in to do with complicated historical processes explaining the hereditary transmission of related to a far-reaching past, and hence only acquired characters in higher forms of life. to be approximately estimated. Hence we have As regards bacteria, howeverl I wrote in 19Ol to proceed by induction, with proportionate that "organisms of the most primitive type confidence from the accumulation of detailed pass through many generations in the course observations. The figures given by individual of a few hours, so that a few days or a week of observers are too few to permit of general con- ordinary time might in the life history of a clusions from them. Those given by the 9,2 PUBLIC HEAL TH. OCTobER,

Registrar-General are perhaps of sufficient served to corroborate the evolution of patho- magnitude to enable allowances to be made for genic properties in micro-organisms, which errors of observation, etc., and yet to allow of constituted the thesis of my paper. broad inferences being drawn. These show As regards scientific evidences of evolution that in each succeeding decade the population from the bacteriological or laboratory side, is becoming more able to resist tuberculosis, Professor Greenfield observed an evolutionary an evolutionary factor of much importance. phase--in the modification of virulence of the Sir Hugh Beevor, Bart., in i9oo , showed so anthrax bacillus--which he communicated to regular a general diminution in rural phthisis the Royal Society in I88o. Ten years later, as to cause him to state that it was cogent Professor Sims \Voodhead stated that patho- evidence of the insignificance of case-to-case genic bacteria, grown under unusual conditions, infection. underwent changes either in the direction of Generally speaking, I consider that the losing power of developing in living tissues, or history of phthisis prevalence shows for tuber- of developing a virulent specific poison. Ite culosis, as for infective diseases as a whole, stated that modification of function, due to evidence that when a disease has been endemic delicate metabolic changes, would sooner in a community for a considerable period of be in evidence than coarser morphological years, it tends to lose its virulence and becomes modifications. of a milder type. Sir Douglas-Powell believes In a long series of experiments, Prof. Hewlett the infection is a distributed one rather than a and Miss Knight obtained connecting links person-to-person contagion, and thinks, as I between the Klebs-Lgffler bacillus 0f diphtheria also do, that the tubercle bacillus is evolution- and the pseudo-diphtheria bacillus. ised from a saprophytic streptothrix. In 19o6 I was able to state, from a large As regards the present- day scientific clinical, epidemiological and bacteriological evidences of evolution, the facts gathered from investigation of diphtheria between 1899 and (a) field-work epidemiological observation were I9O6, that from my own observations with cautiously stated by Sir R. Thorne-Thorne in frequent swabbings from numerous diphtheric April, 1878. His observations were chiefly in cases at various stages of the disease under connection with diphtheria outbreaks, and led daily observation, even morphological modifica- him, by induction, to conclude that the facts tions were often detectable in the course of a appeared to indicate a progressive development of few days (representing, of course, innumerable the broperty of infectious~ess. Dr. Roberts and generations of the organisms). Dr. Hubert Airy, about the same time, pointed Sir William Collins, in his paper entitled out that the laws of variation seemed to apply " Man v. the Microbe," gave quotations from in a curiously exact manner to many of the that most eminent of bacteriologists--the late phenomena of infectious diseases, and Dr. Airy, Professor Robert Koch--that to combat pesti- from a Darwinian point of view, insisted that lences successfully we must strike at the root of all forms of life, including disease-producing the evil, and direct sanitary measures to the bacteria, are undergoing slow but perpetual enviromneut of mankind, such as the destruc- changes in coaptation with the peripheral tion of vermin, the purification of water, the changes of the complex scenery of their prevention of contact between the infected and existence. the sound, to make our practice accord with In 1881 Sir William Collins urged the im- the latest discoveries of science, thus com- portance of applying the doctrine of evolution pletely justifying "the sanitary idea" of to the elucidation of the nature and origin of Chadwick, Benjamin Ward Richardson, Alfred specific diseases. In 1891 Colonel A. M. Davies, Carpenter, and other of the older pioneers in R.A.M.C., showed that Murchison's theory of public sanitation. the pythogenic or "de novo" origin of typhoid fever could be explained on the hypothesis of DIPHTHERIA IN A ggRDEEN.--Referring to a recent evolution of pathogenic properties on the part return showing an increase in the notifications of diphtheria Dr. Matthew Hay, the medical officer, of a previously saprophytic organism; and in states that no definite reason can be assigned for the discussion on my paper on " Evolution in the outbreak, which is not confined to Aberdeen. Relation to Disease," in 19o6 , Col. Davies gave In every part of Scotland diphtheria is prevalent, several instances from vegetable ~athology (in and has been so for the past few years. The only explanation that can be advanced is that some un- which the surrounding conditions are more known condition favourable to the epidemic is at under control than in the case of man) which present being experienced.