THE LANCET, JANUARY 9, 1897.

A Lecture

ON

THE SPREAD OF PLAGUE. Delivered before the Epidemiological Society on Dec. 18th, 1896,

BY JAMES CANTLIE, M.B. ABERD.,

F.R.C.S. ENG.,

substances, and the mucous membrane was red and inflamed towards the pyloric end; (2) the liver was much enlarged and congested and contained ova of tænia and distoma: (3) there was congestion at the base of the lung present in about 40 per cent.; and (4) glandular enlargement was present in 30 per cent. of those examined. There is no doubt now that the disease in the rat and man | are identical. The bacillus of plague has been met with in every case of rat disease of this description where it has been searched for. The infection of the rat is raised from being a mere popular belief into one of scientific precision, and we must now accept the rat at any rate as one animal

LECTURER ON APPLIED ANATOMY, CHARING CROSS HOSPITAL MEDICAL liable to plague. Whether the rat is affected previously to,

SCHOOL; LATE OF HONG-KONG.

(Concluded from page 7.)

coincidently with, or subsequently to, man being attacked is open to question. Is the disease amongst rats a forerunner of its outbreak in man, and, if so, are they a means of infection? These are, of course, two separate questions.

WHAT has been termed the "miasmatic" method of method of infection bears distinctly upon the maintenance and epidemicity of plague. Miasmatic infection implies a soilbred disease-a disease existing, as we assume malaria does, in the earth itself, in the water, or in some particular form of fermenting or decomposing material in which the germ finds a nidus. In a neighbourhood so infected the disease is endemic, as manifested by the fact that again and again the disease recurs-that after a few months of seemingly complete disappearance the disease crops up and runs a more or less severe course. The time of its disappearance may be merely one of hibernation, or the climatic conditions may be unsuited to the activity or the evolution of the bacillus of the disease; but when a sufficiency of time elapses or the requisite quantity of heat, moisture, and whatever else is necessary to the growth of the bacilli are attain-subsequently extended the rat mortality was most marked. able the revival of its infective power is speedily manifested. Whilst comparing malaria and plague as miasmatic disease it is not to be inferred that there is any bearing in the relation of the one to the other. In fact, Dr. Mouchard, writing from Yunnan, cites the cases of Mentz, a town on the hills, and Manhao, a town on the river 3600 feet lower. In the former plague is endemic, but in Manhao malaria is so great a scourge that the Mentz muleteers refuse to spend the nights in the town.

sioner, North West l'rovinces, India, who made excellent Surgeon-Major S. J. Thomson, Deputy Sanitary Commisreports on the outbreaks in Ghurwal and Kumaon in 1886 and again in 1888, writes as follows: "A fact mentioned in the Hong-Kong epidemic by Dr. Cantlie is the great mortality amongst rats. This is also most marked in the case of outbreaks of matra-mari, a hill plague; but I should of the disease amongst human beings. So well is this add that it is generally observed before the appearance recognised by the people that they will sometimes vacate their villages for fear of an outbreak of matra-mari when once this rat mortality has become distinctly noticeable." In Canton, Dr. Rennie writes that "from districts of the city where the diseases had lasted for some time rats entirely disappeared; but in other parts to which plague So convinced were the Chinese of the power of the rat to infect that certain officials took steps to have all the dead rats collected, and at one gate as many as 22,000 rats were collected by May 8th, which, taking into consideration the date of the outbreak, must imply that the collection was made in a few weeks. The Times of India, Sept. 30th, 1896, contains the following: contains the following:-" It was known more than a month ago to all the people of Mandvi (the district in Bombay where plague first broke out in September, 1896) and to all the municipal sweepers in the district that the rats were dying in thousands all over the districts. They were found dead and dying almost everywhere and in places where dead rats were never found before. The children amused themselves every morning by throwing them from the staircases into the streets and gulleys. The great rat mortality only became known recently and yet what a volume of information was it capable of conveying if it was only rightly used. It is universal history that rat and plague mortality go together; the merest tyro in hygiene knows the fact," &c. The rat therefore seems to be infected before the human being; and the fact of dead rats being found about the house during the plague epidemic is a true warning that the inmates of the house will in all probability be affected. How is the rat infected? 1. Experiment proves (a) that the rat is inoculable and dies from a disease identical with bubonic plague in man; the inoculation of both the blood and inflammatory fluids of the plague-infected is effective; and further, a pure cultivation injected hypodermically also sets up signs and symptoms of rat plague and causes death within a few days; and (7) that supplying the animal with Rats.-On all hands rats are reputed to behave peculiarly plague-infected food, whether flesh or cultivated germs, causes and with a wonderful constancy. Before, or it may be plague in rats. How does the rat in his natural state become during, an epidemic of plague, or before the individuals infected; by inoculation? We cannot assume that every rat in any particular house in an infected locality are stricken, the rats leave their haunts and seek the interior has a scratch or open wound by which it is infected. It is more likely he inbales or inbibes the poison either as a miasm of the house. They seem careless of the presence of in concentrated form or he ingests it with his food. It may man and run about in a dazed way with a peculiar be both forms of infection are at work; and, further, it must limping jerk or spasm of their hind legs. They are not be forgotten that rats are cannibal in their habits, and frequently found on the bedroom floor, or on the tables, but direct contagion must play a large part, if not the major not unfrequently their death is known by the putrefactive part, in, the general infection of their tribe. That it is odour of their decomposition arising from beneath the some general infection and not a chance inoculation is flooring. So pertinent has this rat affection become, manifested by their sudden and simultaneous seizure-a that during the epidemic in Macao in 1895, the Chinese seizure so sudden that scores of dead and diseased rats will and Portuguese left their houses when the diseased be found in a single house of any size within a few hours. rats invaded their premises. The cause of the rats' behaviour An interesting observation in connexion with the Calcutta is undoubtedly disease, and the symptoms tally wonderfully affection is "that although Calcutta was believed to be the with plague symptoms of man. Dr. Rennie examined seat of plague and the plague bacillus was pronounced to them carefully in Canton and noted the following post-have been proved in six cases no rats died." mortem appearances: (1) the stomach was distended and filled with particles of food, sand, and indigestible No. 3828.

Infection of, and by, animals. In support of plague being a soil-bred-a a miasmatic-disease is the fact, so often announced, that rats are invariably affected. From Canton, Hong-Kong, Macao, Pakhoi, Yunnan, from hills in the north-west provinces of India, and, most recently of all, from Bombay the observation is constant, definite, and most pointed. The first time particular notice is taken of the death of rats in connexion with plague is in Mr. Rocher's report on the Yunnan plague, some twenty years ago. The Chinese firmly believe the poison emanates from the soil; so far is their conviction carried that they estimate with mathematical precision its gradual rise above the ground. The graduation is estimated by the successive animals that are attacked. The sequence is affected apparently by the height of the animal's breathing apparatus from the ground, the small animals being the first seized and the larger or more elevated animals the last to be attacked. Rats, poultry, pigs, dogs, goats, sheep, cows, buffaloes and last of all man as being the tallest of these is their scale of infection. This is not to be taken seriously but the infection of some of these animals is undoubted.

1 Brit. Med. Jour., Sept. 8th, 1894.

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This was

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regarded as a peculiar and, shall I say, an unprecedented condition, but the explanation is simple enough. The rats did not die, as true plague did not exist in Calcutta, the cases of fever with bubonic swellings being found to be minus a toxic bacillus. This is in accordance with all previous experience. The Calcutta form of disease is benign and no record of rats dying during its prevalence has ever been made. Are we to doubt our belief in the diagnostic value of the bacillus or admit a new disease into our category-a benign polyadenitis? It may be we are called upon to do neither, for we have evidence to show that non-virulent forms of the bacillus can be cultivated and that a bacillus can be found in the soil and cultivated which behaves like the non-thinned their numbers in Pakhoi, and the latter would have virulent bacillus extracted from true plague cultures. These points will be discussed later. 2. An observation by Dr. Thomson in the North-West Provinces of India is worth recording. "In these hill tracts the huts are usually double storeyed, the upper storey being occupied by human beings, and the lower by cattle, goats, &c. It is the custom of the villagers to store the grain in pits under the floors of the huts, and the soil is very foul from the excrement of animals NO. The theory among the people is that the rats eat the grain which is often musty. Most of these bill people are very poor and would consume such grain, which is their principal food, even when musty and clearly affected with -fungoid disease." It is some widespread source of infection by which the rat is infected. Dr. Rennie tells us that the places from which the exodus takes place are left without a rat to be seen.

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If not from grain or from inoculation, whence comes the poison. From the soil? Dr. Rennie found sand and indiKestible material in the contents of the dead rats' stomachs. May this sand have been the source of infection? I kept guinea-pig on soil from the grave of a plague patient who had been dead for two months; the guinea-pigs were not infected, but perhaps the earth had hardly had time to become infected. If the poison is miasmatic and emanates from the soil as a gas or cloud the rat in his close stifling quarters is exposed to a concentrated inhalation. I have already mentioned the soldiers employed in digging out the filth from plague dwellings being seized and the infection was presumed to be brought about by the intensity of the virus. Therefore, we cannot presume that the rat can be infected by a miasm merely. Of the three forms of infection discussed we may safely lay aside inoculation. We may hesitate over the infection by fungoid grain, but although the musty grain would render the disease endemic it could not account for an epidemic spreading to districts where the grain is sound, unless we assume the rat is the carrier. We are left, therefore, either with actual consumption of poisoned material or the concentrated emanation from an infected soil as the means of introduction into the rat's economy.

Snakes.- Dr. Thomson remarks2: "Moreover, when rats are thus dying dead snakes also are said to be found about the site in unusual numbers " Later he remarks: "The snakes eat the rats." From the North-Western Provinces of India we also have record of snakes being affected during plague outbreaks. The snake is not observed as one of the animals affected in the list given by the Chinese, but the infection is natural and the infection through their consumption of the rat is feasible. The possibility, however, of direct miasmatic infection must not be lost sight of.

Dogs. In the Chinese Customs Medical Gazette in the fortyseventh and forty-eighth issues we read that dogs died during an epidemic of plague. The observer ascribes it to the dogs eating the flesh of human beings or any other animal dead from plague. In the same paper it is described that in Yunnan the dying are removed out of the houses to repose in the streets in accordance with Chinese customs, and that those dead and dying from plague are found outside the dwellings or even outside the town walls. He has, moreover, seen the dogs eating the flesh of those dead from plague. In Hong-Kong we had no special mortality amongst dogs, nor have Canton or Macao anything to say on the subject, but the dead were better cared for than in Yunnan and no dog could get at them. It would seem as though the dog were infected by eating the flesh. In the places mentioned such an opportunity was not afforded him, but in the town of Mentz, Yunnan, the custom as to the disposal of the dying seems to explain the infection of the dog.

2 Brit. Med. Jour., Sept. 8th, 1895, p. 560.

Pigs. It is even more important to ascertain whether or no the pig is infected. Pork is largely consumed by Chinese; and, moreover, Europeans in the East seldom or never eat Chinese fed pork. The Chinese died from plague, whilst the Europeans enjoyed an immunity from the disease; nothing: seems more conclusive than that pork was the infecting food. Moreover, most of the pork brought to the HongKong market comes from Pakboi, a town where plague has been endemic for years. The first point to be settled is Does the pig suffer? Not as a rule. The pigs from Pakhoi showed no falling off in numbers, and they were not sickly the former condition would have obtained bad plague been found out when they reached Hong-Kong, where careful inspection of all food supplies is made. Dr. Mouchaud writes that the pigs died in Yunnan, and he states that we saw on some roads dogs and pigs feeding undisturbed on corpses which no one cared to bury. These animals fell victims to their greed and succumbed to the scourge." Further, plague has been produced in the pig experimentally, all of which goes to prove that pigs die from plague after consumption of corpses dead from plague and inoculation; but that pigs are not primarily liable to plague in the same way as rats and pigeons seems conclusively shown. Oxen, sheep, and goats are not known to be subject to a disease allied to plague, nor are they affected by any fatal malady during the time plague is epidemic. As regards sheep, Custaldi states that plague in Kurdistan was preceded by a fatal epizootic among sheep; that they had plague, however, is not stated.

Jackals are known to be subject to the disease in Yunnan. They are more prone than either dogs or pigs to consume exposed human bodies, and therefore are very likely animals to be affected, ·

Pigeons.-Dr. Surveyor, in a private letter to me dated Nov. 13th, 1896, Bombay, asks: "Did you notice any mortality amongst pigeons from this disease?" In reply I have to state that I did not, nor did any observer in China, so far as I know. draw attention to the infection of pigeons. If stored grain is the source of infection it is easy to imagine that pigeons would be perhaps one of the most likely species of birds to be affected, and it but draws attention to the disease of grain still more pointedly than before. Several observers in India are most decided in their statements as to the grain source of the disease, and that the rat and pigeon are the sufferers seems to point somewhat in that direction. On the other hand, it must be remembered that the ordinary barnyard fowls are not (except in the London Plague of 1111 A‚Ð., and it is so long ago that it may be discounted), so far as we know, struck down by any disease resembling plague, so that, although the grain origin of the disease may be worth investigating, we cannot turn towards it with any a priors hopes of elucidation. It will be seen at once that the infection of birds will render the possibility of the rapid spread of plague on its appearance in isolated districts easily explainable. It is not comfortable news that we have a winged distributor of plague.

To sum up our knowledge, we find that pigs, dogs, raus, snakes, jackals, and pigeons are affected by a fatal malady, whilst plague is epidemic amongst human beings. Pigs and dogs are believed to be attacked only after consumption of plague flesh. Snakes by the swallowing of rats, and possibly jackals, are infected in the same way. None of the purely herbivorous animals, horses, donkeys, oxen, sheep, goats, or rabbits, are attacked. It is the flesh-eating animals which are the sufferers. Of course, the rabbit, guinea-pig, and a number of animals can be inoculated experimentally or made to consume plague-diseased food, but no herbivorous animal acquires it by the natural processes of infection. If it is by consumption of flesh that animals are infected, how do human beings get it? The animals affected seem to become infected from flesh: the snake from the rat, the jackal, pig, and dog from eating the flesh of persons dead from plague but how does the rat become infected? Could we find that out we should likely know how man is infected. One animat missing in the scale is the cat; if rats perish from plague surely the mortal enemy, the cat, would be diseased. Perhaps the instinct of the cat teaches it to avoid the diseased rat. [In Hong-Kong during 1894 many cats died in a peculiar way the chief symptom being paralysis of the hind legs.]

In the discussion about the rat infection it must never be forgotten that if we take it for granted that the disease attacks rats before human beings become victims, we must consider the questior, "Has the rat ailment to do directly

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bubo may precede the fever, the patient suffering no inconvenience even. Such a case is that recorded from Calcutta, where the patient, a boy from Bombay, had had for fifteen or twenty days before developing fever a swelling in either groin. Subsequently he developed the ordinary symptoms of plague and the diplococcus was found in his blood." These two cases are sufficient to show that fever or plague may exist and the patient not be aware of it, and that glands may be affected for, a fortnight before the disease declares itself in the usual way by headache, fever, and prostration. The onset of the disease, therefore, even during a plague epidemic, may not be so definite as we should like to believe, and as yet we have no charts recording the condition of the patient between the time of exposure and the invasion.

malignant variety. 3. At the present moment in Calcutta there is reported to be a form of fever with glandular swellings, and also a form of glandular swellings without fever, and it is further stated that these are constantly met with in medical practice in Calcutta. 4. In 1890 the variety of idiopathic buboes, of glandular swellings with fever, and of mumps met with in Hong-Kong before referred to was not. followed until four years afterwards by plague. These records go to prove:-1. That long periods of time may intervene between the prevalence of specific glandular swellings and the outbreak of malignant plague. 2. That glandular swellings may exist for nine years before: malignant. plague appears, and continue for years after it has disappeared. 3. That independent outbreaks of glandular swellings (pestis minor) may come and go and no plague supervene.

The latest evidence we have from Calcutta is conflicting in the extreme. We have it to hand on trustworthy evidence that people are suffering from fever with glandular enlarge..... ment, that the disease is regarded as pestis ambulans-a mild bubonic plague-and that the diplo-bacteria of plague are found in the blood. We have hitherto regarded the presence of the bacillus in the blood as the one token of the disease being malignant in type; but we have now contrary evidence to consider, and if we are to accept it, we must believe that specific glandular swellings in the plague belt may be caused by a detinite bacillus, and at the same time admit a varying degree of malignancy to that bacillus. Professor Cunningham-a most competent observer-declares that the bacillus found in the Calcutta cases is non-infective, and that probably it is not the same bacillus as that described by Kitasato in 1894. This is stated in the face of positive evidence by careful observers which cannot be set aside thoughtlessly. Time alone will answer this question. In the meantime, however, it is feasible to suggest that there may be but one bacillus, and that according to its state of development, or in consequence of its evolution,. different types of the disease may prevail in the human body, each associated with a definite train of symptoms, characterised in the one by glandular swellings merely and in the other by a toxic infection of extreme intensity.

Varieties. It is not my intention to mention merely the varieties of symptoms which predominate at any one time or throughout any one epidemic, but to draw attention to varieties which are so pronounced in their character as to justify the belief that whilst dealing with this subject we are actually attempting to bring in line under one heading diseases which may be even separate species. The commonly accepted types are these: (1) abortive (or larval) plague; (2) typical plague; and (3) fulminant plague. The two latter are so well understood and have been so largely and fully dealt with elsewhere that there is no advantage in recapitulating what can be read in any text-book; but I wish to draw attention to the first-named. The abortive form is sometimes styled larval, ambulatory, or pestis minor. The names partly declare the character of the disease and create a condition so apart that it has at all times been separately described. It is at the same time so indefinite in its duration, so unstable in its relation to malignant plague, and so uncertain in its onset and departure that up to the present no scientific precision has been assigned to the relationships. As long ago as the year 1666, when plague ravaged London, we have it on the authority of Sydenham that "at times tumours may break out without either fever or any important symptoms. Those to whom this happens may walk about in public as usual and attend to the common duties of life. Foderè, writing of plague in 1820, observes: "In the Levant and in the Marseilles epidemics of 1820 cases were to be seen which were not ushered in by any The bacillus. The bacteriology of plague began_with alarming symptoms and where the natural functions were the advent of Kitasato from Tokio during the Hongundisturbed and where buboes and carbuncles appeared Kong epidemic of 1894. On June 14th, 1894, Kitasato without fever or only with slight fever, or the buboes went demonstrated the bacillus, which was confirmed afteron to a healthy suppuration more or less prompt, or even wards by Dr. Yersin of the Pasteur Institute in Saigon, disappeared and went on to resolution without the help of working in an independent manner. The bacillus has art, without any inconvenience, and with a perfect integrity been variously described as (1) a diplococcus; (2) diploof all the functions. This state is comparable to benign coccus enclosed in a delicate capsule; and (3) a short. small pox, during which children play together and walk in bacillus with the ends somewhat rounded and a clear space the streets without any precautions, no care being taken of or band in the centre. Professor Woodhead writes:their treatment and yet terminating favourably. It is the "The size varies considerably according to the staining benign plague of authors which is observed when the method employed, the organism appearing rather smaller in disease commences and when it is at its end, though the watery gentian violet solution than in the glycerine it is rarely seen in the middle period, which is entirely fuchsin solution. It is plain that the size of the capsule and devastating, but it is not less plague and it no less its staining capacity valy very considerably, and it is quite merits the attention of physicians and magistrates." Again, possible that this appearance of a capsule is like that which is in all recent epidemics in Tripoli, Mesopotamia, and sometimes met with around the bacillus of anthrax stained in Astrakan non-fatal, mild bubonic disease occurred both special solutions in that it may be simply a refraction from before and after the epidemic. We have it on the authority the albumin from the constricted bacillus due to the drying of Dr. Dickson that in Mesopotamia, previously to the mani- and other processes of preparation." In the figures drawn by festation of plague, glandular swellings free from fever pre- Woodhead an organism was met with in some specimens vailed. All this evidence seems to indicate a close con- which seems to indicate a development after death. nexion between benign and malignant polyadenitis; but we last statement may be the most important of all, and its have some evidence of the separate existence of the two confirmation will be anxiously looked for during the present diseases. 1. In Mesopotamia Tholozan records: (a) that outbreak in India. It may be the first step towards a knowmild non-fatal bubonic plague existed from 1856 to 1865, ledge of the life-history of the bacillus in the same manner during which period (nine years) no malignant type was as the flagella of the plasmodium malaria are found to observed; and (b) that after the epidemic of malignant develop in the field of the microscope some half hour after plague (1866-67) passed over the same form of mild plague removal from the body. Dr. Yersin undertook some exexisted. Did it exist during the epidemic? This is not known, periments to test the truth of the infection of the soil, the for it is not likely that persons suffering from so mild an results of which elucidate the toxic nature of the bacillus. ailment would present themselves for treatment to foreign He found (1) that a bacillus in some respects resembling medical men at a time when all swellings were viewed with in its appearance that met with in the human body was suspicion. There is, therefore, no evidence to show that found in the soil of Hong-Kong during the plague epidemic; the two diseases did not co exist seeing that it existed❘ (2) that the bacilli of the soil and body occasionally behaved nine years before and perhaps as long afterwards. similarly in culture experiments; and (3) that the culture. The present belief is that the mild develops into the specimens of soil bacilli were, however, innocuous, possessing malignant type, and when that subsides it is once more no virulence when injected into mice or guinea-pigs. deprived of its malignancy and becomes benign. We have Dr. Yersin further found that in his cultures of human no evidence of any disease behaving in such a manner to plague bacilli there were microbes of different virulence, such an extent as claimed for plague. 2. In Calcutta six some mildly powerful and some altogether powerless to inyears ago an outbreak of mild, non-fatal plague occurred infect either mice or guinea-pigs. Dr. Lowson, in conjuncthe fort amongst the troops, but it was not followed by the

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tion with Dr. Takaki, Dr. Kitasato's assistant, found a