THE LABORATORY OF THE ÉCOLE
NORMALE.
VARIOUS STUDIES. HYDROPHOBIA.
Since the day when a minister told Pasteur, that there were not 1,500 francs in the budget to allow for the expenses of his laboratory, science has obtained a little more consideration. At the present time she has nothing to complain of: her sovereignty is recognised; her schools are becoming palaces; she has an amply sufficient civil list: she is rich enough, in short, to pay for her researches. M. Pasteur's laboratory has had its full share of the well-bestowed generosity of the State. The municipal council of Paris even wished to attach vast dependencies to this laboratory. The old garden of the ancient Collège Rollin was placed at the disposal of Pasteur; who at once hastened to build stables for lodging horses attacked by glanders, stalls for sheltering splenic fever sheep, and kennels for the reception of mad dogs. But, while taking advantage of these hospitable premises, Pasteur still retained, in the basement of his laboratory in the Rue d'Ulm, a whole population of animals under experiment. Isolated in round cages which impart some sense of security, are the rabid dogs; some attacked with furious madness, biting their bars, devouring hay, uttering doleful howls which those who have once heard can never forget; others carrying the germ of this terrible disease, still fawning with a humble look of tenderness, as if imploring attention. Hens and chickens pass their heads through the wooden bars of their coops. From time to time a cock from the bottom of his den crows 'a gloomy dawn.' Rabbits eat peaceably, while little families of guinea-pigs cluster together, and at the least alarm utter a frightened cry. All these animals are destined to be shortly inoculated. Each morning a round of inspection is made in this little hospital of condemned animals. The dead are taken out, carried to one of the upper rooms, and placed on the dissecting-boards.
It is also to such boards that living animals are fastened when it is necessary to experiment upon them. Certainly when one sees a dog lying with a forlorn look, its feet tied, its body trembling from fright, on the point of undergoing, though in full health, a bloody operation, one cannot suppress the feelings of pity. But a single visit to a physiological laboratory suffices to reveal vivisection in its only and true light; that of the interest it offers to science, and the results it may have in store for the benefit of humanity. Moreover, in Pasteur's laboratory, every dog subjected to vivisection is chloroformed. The persons who take up the controversy about vivisection are careful that the outside world shall see only the suffering and anguish of the animal, where the solution of a problem should be the object kept in view. Would the English physiologist Harvey have discovered the circulation of the blood, if he had not practised vivisection on deer in the park of Charles I.? Would Claude Bernard have been able, without vivisection, to demonstrate the glycogenic function of the liver? If Pasteur had not sacrificed some fowls and sheep, would the great scientific fact of the attenuation of virus have been discovered? If 500 dogs had to perish, what would that be, compared with the discovery tomorrow of the cause of hydrophobia, and of the means of protecting humanity against this frightful scourge?
On one occasion, in presence of a large assembly, Pasteur made an experiment on atmospheric oxygen. He placed under a glass bell a bird, which in a short time, after having consumed the oxygen contained in the bell, gathered itself up into a ball, opened its beak, and shut its eyes, as if it were going to die. At this moment Pasteur introduced a second sparrow, which, passing directly from the ordinary air into the bell, without any gradual preparation, immediately fell, asphyxiated. There was a little exclamation of horror and a movement of pity in the audience. While the first sparrow, which had gone through the ordeal unharmed, was set free, and gradually revived, Pasteur turned towards the assembly and said—
'I never had the courage to kill a bird in sport, but when it is a question of experiment I am deterred by no scruple. Science has the right to assert the sovereignty of its aims.'
But to return to the animals of the laboratory: From the little white mice, which hide themselves in a packet of wadding, to the dogs which bark furiously in their iron cages, all are devoted to death. But it is not only the inmates of the laboratory which daily succeed each other upon the operating and dissecting tables. From divers parts of France, hampers full of fowls which have died of cholera, or of some other disease, are sent to Pasteur. Here is an enormous basket packed with straw containing the dead body of a pig which had died of measles. This fragment of lung, packed in a tin box, belonged to a cow which died of peripneumonia. Other packets are still more precious. Since Pasteur went to Pauillac two years ago, to watch for the return of a ship which was to bring back some passengers attacked with yellow fever, he sometimes receives from a distant country a bottled dose of vomito negro.
Everywhere, on the work tables, are to be seen tubes filled with blood, microscope slides carrying little drops. In the stoves are ranged the cultivating flasks, which resemble little flasks of liqueur. The point of a needle dipped into one of these flasks is sufficient to cause death. Enclosed in their glass prison, millions upon millions of microbes live and multiply.
It is really a curious spectacle this workshop of research and discovery. How numerous and varied are the subjects which are being studied, and with what energy and patience does Pasteur attack them! It is not only to the most dreaded diseases that he has applied the germ theory. He has extended it to certain common disorders. Everything to him is a subject for experiment. In May 1879, a person who was working in the laboratory was troubled with boils, which reappeared, as usually happens, at short intervals, sometimes on one part of the body, sometimes on another. Pasteur, whose mind was constantly dwelling on the part played by microscopic organisms, asked himself if the pus of the boils did not contain a parasite, the presence and development of which, and its accidental transport here and there in the body, might be the cause of the local inflammation and of the formation of the pus. The constant reappearance of the evil would be thus accounted for.
The pus of the first boil, which was situated on the nape of the neck, was collected in great purity; some days afterwards, the pus of a second boil, then of a third boil, was collected. The pus, or the blood-stained lymph of the red swelling which preceded the formation of the pus, were sown in a sterilised infusion, and each time a microbe, formed of little spherical points connected in pairs, frequently united in small clusters, was seen to develop itself. The cultivating liquid was sometimes infusion of fowl, sometimes of yeast. In the infusion of yeast the little grains are suspended in pairs throughout the liquid, which is uniformly thickened with them. In the fowl infusion, the grains are united into little clusters, which cover the sides of the vessels, the liquid remaining clear as long as it is not shaken.
New observations were made upon a series of boils, in the case of a man sent to Pasteur by Dr. Maurice Raynaud. The same parasite was again found—a unique parasite, distinct from all others. At the Hospital Lariboisière, a woman whose back was covered with boils, offered another opportunity for experiment, and with the same result. It appears certain, then, that every boil contains a microscopic aerobic microbe, and that to it are due the local inflammation and the consequent formation of pus.
When guinea-pigs or rabbits are inoculated with the cultivating liquids, little abscesses are formed, which, however, quickly disappear. As long as the cure of these little abscesses is not quite completed, one can extract from them the microscopic organism which has formed them. When the little parasite is sought for in the general blood of those attacked with boils it is not found. The cause of this, no doubt, is that an aerobic parasite has always some difficulty in developing itself in the blood. The blood corpuscles appropriate, and do not willingly give up to a foreign organism, the oxygen which they require. There is a struggle for life, and in the struggle against the boils the victory is not doubtful. It might be thought, then, that the little organism of boils does not exist in the blood, but there is no doubt that if, instead of a small drop of blood, one could put several grammes or more into cultivation fruitful results would follow. The little parasite is no doubt conveyed by the blood at one time or other. It is transported from a boil, in the process of development, to another point of the body, where it may be fortuitously arrested, there to cultivate itself and form a new boil.
'It is to be wished,' said Pasteur, 'that a patient would submit to a number of punctures on different parts of the body, distant from boils already formed or in process of formation, and that with the blood thus taken from the general circulation a multitude of cultivations might be carried on. I am persuaded,' he added, 'that, among these cultivations, we should find some fruitful in the little organism of the boils.'
But whilst Dr. Maurice Raynaud gave Pasteur the means of studying boils, Dr. Lannelongue enabled him to investigate that serious disease of the bones and marrow called 'osteomyelitis.' In February 1880 that skilful surgeon, who has published a highly esteemed work on osteomyelitis, and on the possibility of its cure by trepanning the bone, followed by washings and antiseptic dressings, conducted Pasteur to the Hospice Trousseau. A little girl twelve years of age, attacked with this cruel malady, was about to be operated upon. The right knee was much swollen, as was also all the leg to below the calf, and a part of the thigh above the knee. After having chloroformed the child, Dr. Lannelongue made a long incision below the knee, from which pus flowed abundantly. The bone of the tibia was laid bare for a considerable length. Three trepanning perforations were then made in the bone, from each of which the pus issued in great quantities. Pasteur carefully collected, with all the conditions necessary to the preservation of their purity, the pus of the exterior and the pus of the interior of the bone, and, returning to his laboratory, he examined them attentively. The direct observation, by a microscope, of the two specimens of pus was extremely interesting. It was obvious that they contained, in large quantities, an organism like that of boils, in pairs of two or four, and also in parcels, some with a clearly defined outline, others scarcely visible, and with very faint outlines. The external pus showed an abundance of pus globules, but that of the interior did not show any. It was like a paste entirely composed of microbes, so numerous and fertile that, in less than six hours after sowing them in the cultivating liquid, the development of the little microbe had commenced, and was rendered visible to the naked eye by a slight but general turbidity of the liquid.
Its close resemblance to the organism of the boil might lead to the assertion that they are identical, if it were not known how great are the physiological differences that may exist between microscopic parasites of the same appearance and the same dimensions.
I.
As Pasteur advanced in these studies, he found at the Academy of Medicine some fellow labourers, who being keenly interested in such researches did all they could to promote them. Thus M. Villemin, the chief medical officer of the Val de Grâce (who had with so much sagacity discovered the contagion of tuberculosis) when typhoid fever was raging in Paris two years ago, never allowed a case of the fever to pass through his hands without informing Pasteur, who habitually went himself to collect specimens of the blood of those who had died. How numerous were the drops of blood thus enclosed in little tubes, and how frequent the attempts at cultivation, as yet without result, in the hope of finding the cause of a disease which claims so many victims! There is another malady to which Dr. Hervieux especially called Pasteur's attention, and by which so many women are attacked—puerperal fever. He went with M. Hervieux to the Maternity Hospital, to visit a woman under his charge who had contracted puerperal fever some days after her confinement. By means of a pin a prick was made in the forefinger of the left hand, which had been washed previously with dilute alcohol and carbolic acid, and dried with singed linen. The drop of blood taken in this way was sown in an infusion of fowl. For some days the cultivation remained sterile. Next day blood was taken from a fresh puncture, and this time it proved fertile. The woman died three days after. The blood, therefore, already at the time when Pasteur had taken it, three days at least before death, contained a microscopic parasite capable of cultivation. Eighteen hours before this woman died, some blood taken from the left foot had been sown, and, like the former, it had proved productive; but—and this fact deserves to be noted—while the first productive cultivation only contained a microbe resembling that of boils, the other cultivation contained long flexible chaplets clustered together like tangled strings of beads.
At the post-mortem examination of this woman large quantities of pus were found in the peritoneum and the uterus. This pus was sown with all due precaution. Some blood taken from the basilic and femoral veins was likewise sown. It was everywhere easy to recognise the long chaplets in little tangled parcels, and always without admixture of other organisms, except in the cultivation of the peritoneal pus, which, besides the long strings of grains, showed also the little pyogenic vibrios to which Pasteur had already assigned the name of the pus organism.
From the Maternity Hospital Pasteur went to the Hôpital Lariboisière, where he had been informed that another woman had just died of the same fever. From a puncture in the peritoneum he collected some pus which was found there in great abundance. He sowed this, as well as some blood taken from a vein in the arm. The culture of the pus furnished the long strings of grains and the little pyogenic vibrio. The culture of the blood exhibited only the long strings quite pure.
Pasteur made many other observations of the same kind in cases of puerperal fever. He arrived at the conclusion that, under the name of puerperal fever, diseases of different symptoms were classed, but which all appear to be the result of the invasion of common organisms, which develop themselves on the surface of wounded parts, and from thence spread themselves, in one form or another, by the medium of the blood or of the lymphatics, over different parts of the body. Here the various morbid symptoms are determined by the nature of the parasite and the general constitution of the patient. Pasteur is convinced that, with the possible exception of cases where, by the presence either of internal or external abscesses, the body, before confinement, contains microscopic organisms, the antiseptic treatment ought to be infallible in preventing puerperal fever from declaring itself. The employment of carbolic acid may be of great service; but its smell, and often the melancholy association of ideas which it awakens, might render it unsuitable for women in labour. There is not the same objection to concentrated solutions of boric acid, which, at the ordinary temperature, contain from thirty to forty grammes of acid to one litre of water.
'Would it not be very useful,' said Pasteur one day, when developing his ideas and observations before the Academy of Sciences, 'to place always by the bedside of each patient the concentrated and warm solution of boric acid, with compresses to be very frequently renewed, after having been soaked in the solution, these applications being begun immediately after the confinement? It would also be prudent, before using the compresses, to put them into a hot-air stove, at a temperature of 150 degrees, which is more than sufficient to kill all the germs of common organisms.
'I have,' he added, 'represented the facts as they have appeared to me, and I have hazarded the interpretation of them; but I do not disguise from myself that, in the domain of medicine, it is difficult to withdraw oneself entirely from a pre-existing subjective bias; neither do I forget that the medical and veterinary studies are foreign to myself: therefore I earnestly desire judgment and criticism. While I am little tolerant of frivolous contradiction or of prejudice, despising as I do that vulgar scepticism which would erect doubt into a system, I honour that militant scepticism which makes doubt the basis of a method, whose motto is "More light."'
Since these ideas have penetrated further into practice; puerperal fever, I was told lately by a distinguished medical man, is hardly known in the Maternity Hospital. The employment of a solution of one to a thousandth of corrosive sublimate, which is one of the best antiseptics, gives excellent results, and keeps off all danger. May it not be permitted to hope that puerperal fever will soon disappear in the same way that purulent infection has disappeared in hospitals, since the introduction of Lister's dressings?
II.
In 1882, a new malady occupied the attention of the laboratory of the École Normale, a malady the name of which was not even known in Paris, but which made great ravages in the country—namely, swine fever (rouget). Here, again, it is a microbe which causes the disorder. This microbe was first perceived by Thuillier, in a little commune of the Département de Vienne, when examining the blood and humours of pigs which had died of the fever. Experiments were at once set on foot in the laboratory, with the view of proving that the microbe was really the cause of the disease. The microbe was cultivated in a sterilised infusion of veal. This cultivation was passed on to a succeeding one, a small drop of the preceding cultivation being always taken for seed. Inoculations from these last cultivations produced the fever in certain breeds of pigs. The proof was thus given that the microbe was really the origin of the disease.
Pasteur then, accompanied by Thuillier and a young assistant, M. Loir, went, in his turn, to study the disease in the Department of Vaucluse. He remained more than a month in the canton of Bollène, in the house of a veterinary surgeon, M. Maucuer, who took him to all the pigsties in the arrondissement. After having had recourse to the oxygen of the air to attenuate the virulence of the microbe, Pasteur made some experiments in vaccination. Some pigs which had been vaccinated remained in the canton of Bollène, under the supervision of M. Maucuer, the owners having pledged themselves to keep their vaccinated pigs for at least a year. In the ensuing September, when swine fever raged everywhere in the canton of Bollène and in the arrondissement of Orange, not a single vaccinated pig was attacked. 'They are all flourishing,' wrote M. Maucuer. An address of thanks was sent to Pasteur by the municipal council of Bollène.
But, notwithstanding these happy results, the question of the application of vaccines to different breeds requires still further investigation, before the vaccination of pigs can become general.
Soon afterwards a method, different from that of the atmospheric oxygen, for weakening the virulence of the fever virus, was tried in the laboratory.
Pasteur had proved that viruses are not morbid entities, that they can assume numerous forms, and especially physiological properties, dependent on the medium in which they live and multiply. The virulence belongs to living microscopic species, but is at the same time essentially modifiable. It may be weakened or intensified, and each of these states is capable of being made permanent by culture. A microbe is virulent in an animal, when it has the power of swarming in the body of that animal, after the manner of a parasite, and of producing, by the renewal of its own life, disturbances which cause disease and death. If this microbe has lived in any species of animal—that is to say, if several times over it has passed from the body of one individual into that of another of the same kind, without having been subjected to any sensible exterior influence during its passage—we may consider that the virulence of this parasite has reached a fixed and maximum state for the individuals of that race. The splenic fever parasite pertaining to sheep, for instance, varies little from one subject to another or from one year to another in the same country; this must be attributed, doubtless, to the fact that, in its successive passages through the sheep, the habit of the parasite to live in sheep has, so to speak, attained a definite state. It is thus with the virus of the Jennerian vaccination. But the virulence of a virus which is not at its maximum may be essentially modified by its passage into a succession of individuals of the same race. It will be remembered how, when Pasteur and his assistants wished to increase progressively the virulence of the virus of chicken cholera and splenic fever, so as to bring them at last to their maximum intensity, these viruses were first inoculated into young subjects, and from them successively into older ones.
'The Academy remembers, without doubt,' said Pasteur in a recent communication, 'that, some time ago, we discovered a microbe virus in the saliva of hydrophobia. This microbe, though very virulent for rabbits, is shown to be harmless for adult guinea-pigs, but it kills rapidly guinea-pigs only some hours or days old. In following out this inoculation from young guinea-pigs, we have seen the virulence increase, and easily arrive at the point of causing death to older guinea-pigs. There was even at last a marked difference in the lesions. The increase of virulence, by successive passages through individuals of one race, was clearly shown.
'But the new and unexpected result that I wish to point out to the Academy consists in this: that the microbe, after having increased its virulence by successive passages through the bodies of guinea-pigs, shows itself to be less virulent in relation to rabbits than it was before.
'In these new conditions, it gives to the rabbit a disease which is spontaneously curable; and, moreover, having once gone through the malady, the animal becomes refractory in regard to the microbe which is deadly to rabbits. From this arises the all-important consequence, that the habit of living in one species (the guinea-pig) at a definite corresponding degree of virulence, can change this virulence in relation to another species (the rabbit), so much diminishing its effects as to cause it to become a vaccine for this latter species.
'The importance of this result cannot fail to be perceived by everyone, for it contains the secret of a new method of attenuation, which can be applied to some of the most virulent viruses. We will give an example and an application of it.
'If a pigeon be inoculated in the pectoral muscle with the microbe of swine fever, the pigeon dies in an interval of six or eight days, after having shown the apparent exterior symptoms of fowl cholera.
'When a second pigeon is inoculated with the blood of the first, a third with that of the second, and so on in succession, the microbe acclimatises itself to the pigeon. The symptoms of forming itself into a ball, and of somnolence, which are the habitual characteristics of the disease, appear in a much shorter time than with the first pigeons of the series. Death likewise comes on more rapidly. Finally, the blood of the last pigeons exhibits much more virulence in the pig than even the most infectious products of a pig that has died of what is called spontaneous fever.
'The passage of the swine fever microbe through rabbits leads to quite a different result. Rabbits inoculated with the infectious products of a pig that has died of the fever, or with the cultivations of them, are always made ill and most frequently die.
'When the virus is inoculated from rabbit to rabbit, the microbe acclimatises itself to the rabbit. All the animals die, and death comes in a very few days. The cultures of the blood of these rabbits in sterilised media become progressively easy and more abundant. The microbe itself changes its aspect somewhat, grows rather larger than in the pig, and appears in the form of an 8, without the filiform lengthening out characteristic of certain other cultures.'
'When pigs are inoculated with the blood of the last rabbits, and the results compared with those obtained from the first of the series, it is found that the virulence has been progressively diminishing from the first rabbit to the following ones. Very soon the blood of the rabbits ceases to cause death in the pigs, though it renders them ill. On recovery they are proof against the deadly swine fever.'
III.
But in the midst of these investigations undertaken by Pasteur, there is one which is paramount over all the others, one on which for three years all his efforts, as well as those of his pupils, have been concentrated, and this is Hydrophobia. Mysterious in its incubation, alarming in its symptoms, Pasteur's attention had for a long time been drawn to it, when in 1880 he finally attacked it. Besides the attraction which an obscure problem had for him, he felt that if he succeeded in discovering the probably microbean etiology of such a disease, he would carry all minds with him into the current of these new ideas. He had been very often struck, if not with the opposition, at least with the prudent and circumspect reserve, shown in the examination of his doctrine, by a considerable number of physicians who, possessed by the idea that the moral element could cause modifications in the symptoms and development of a malady in man, are not disposed to recognise the least assimilation between human diseases and those of the animal species. No doubt the emotional qualities, grave family cares, the terror of approaching death, the dread of the great unknown, may modify the course of the evil in man, may aggravate it, even hasten it; but, whilst recognising—for never was there a man more a creature of sentiment than he—what there is of deep truth in this opinion, Pasteur could not help thinking that the first origin, the cause of every contagious malady, is physiologically the same in the two groups, and that our bodies, notwithstanding our superior moral qualities, are exposed to the same dangers, to the same disorders, as the bodies of animals.
To overcome these resistances, it was necessary, as in the great experiments on splenic fever, to attack a disease common both to men and animals—one in which experimentation, the only, but great, strength of Pasteur, was supreme. Hydrophobia offered these conditions.
Again, it was Dr. Lannelongue who introduced Pasteur to his first case of hydrophobia. On December 10, 1880, a child of five years old, who had been bitten in the face a month previously, was dying in the Trousseau Hospital. Devoured at the time by a raging thirst, and seized with a horror for all liquids, he approached with his lips the spout of a closed coffee pot, then suddenly started back—the throat contracted—a prey to such fury that he insulted the nursing sister who was attending on him. He was at the same time attacked by aerophobia to a prodigious degree. At a certain moment, the heel of one of his feet protruded from the bed. An assistant blew on it. The child had not seen the assistant, and the breath of air was so light as to be almost imperceptible. The poor child flew into a rage, and a violent spasm seized him in the throat. The next day delirium began, a frightful delirium. The frothy matters which filled his throat suffocated him.
Four hours after his death, the mucus from the palate of the child was collected. It was diluted with a little water, and two rabbits were inoculated under the skin of the abdomen. The rabbits perished in less than thirty-six hours. The saliva of these dead rabbits also transmitted the disease to fresh rabbits. Did it not seem as if one had got hold of an inoculation of hydrophobia? Such was in fact the conclusion of Dr. Maurice Raynaud, who, having been informed, at the same time as Pasteur, of the illness of the child, had made, on his own account, some experiments on rabbits. His rabbits were dead. Already a year previously M. Maurice Raynaud had announced the transmission, by the saliva, of rabies from man to rabbits. 'We are, then, in the presence of a new fact of this kind,' he said, 'and we really believe, until a proof to the contrary is given us, that these latter rabbits died of hydrophobia.'
With his habitual prudence, and trusting more to the results of experiment than to medical observation alone, Pasteur was not in a hurry to form such positive conclusions. He began by doing what Dr. Maurice Raynaud had neglected to do. He examined with the microscope the tissues and the blood of the rabbits inoculated in the laboratory; he discovered, both in those that were dead, and in those which were on the point of death, the presence of a special microbe, easily cultivable in a pure state and of which the successive cultures caused the death of other rabbits. Invariably, the same microbe appeared in the blood. As one or two days sufficed to cause death, hydrophobia could not have had time to make its appearance. Pasteur, moreover, found this same microbe in the saliva of children who had died of common maladies, and even in the normal saliva of healthy adults. It was a new microbe, causing a disease unknown up to that time. To Pasteur it seemed, in the case of the experiments made with the mucus from the child's palate, to be simply an accompaniment of the rabic virus.
This microbe of the saliva is very easily cultivated in sterile infusions—that of veal, for example—and successive cultures can be made in the usual way. The virulence continues. Could the virulence be attenuated, asked Pasteur, by the action of the oxygen of the air? This would, by a new example, go to establish the generalisation of the method of attenuation by oxygen. The attempt succeeded. When care is taken, as with the attenuation of the fowl cholera contagium, not to allow more than some hours' interval to elapse between one cultivation and the succeeding one, the virulence of the successive cultivations of the microbe of the saliva is preserved in some sort indefinitely. In other words, if it be arranged that the cultures succeed each other every twelve hours, the rabbits inoculated from the last cultures die as quickly as those inoculated from the first. Thuillier had had the patience to make, in this manner, eighty cultures in contact with air, and eighty cultures in a vacuum; the microbe of the saliva being both aerobic and anaerobic. The eightieth culture killed as quickly as the first. But by allowing the successive cultures to remain for some time in contact with the air, before passing from one culture to the following one, the virulence of the cultures becomes enfeebled. Thus, then, as in fowl cholera, attenuated cultures of the microbe can be obtained. Unlike what happens with cholera, however, the cultures of the microbe of the saliva, exposed to the contact of air, perish very quickly. Two or three days of keeping suffice for the parent cultivation to lose all virulence. The seed, taken in any quantity from it, does not fertilise a new cultivation. But, before perishing, this culture passes through very different degrees of progressively weakened virulence, and it is easy with these cultivations to render rabbits ill without causing their death. Once cured, they resist all inoculation which would be mortal for others. The oxygen of the air is manifestly the transformer of this virulent virus into vaccine virus; for, if the virulent blood or cultivations remain inclosed in their tubes, sealed from all entrance of the air, they retain not only for some hours, but for months, their life and their original virulence.
But though these results were as new as they were unexpected, and though one cause of confusion in the study of this terrible problem was removed, yet these first researches were not marked by any progress in the etiology of hydrophobia. The question remained wholly unsolved.
Impatient with the length of time required for the incubation of the disease, and with the obligation of waiting whole months for the result of an experiment, when the subject demanded such numerous ones, Pasteur began to seek some means of producing hydrophobia with certainty and of making it appear more rapidly. Notwithstanding the assertion of a professor of the veterinary school at Lyons that the saliva of the rabid dog alone contained the virus of the disease, and that he had failed in every attempt to inoculate, whether with the substance of the brain or with the spinal marrow of rabid dogs; Pasteur, with due care as to purity, introduced under the skin of some rabbits and some dogs, divers parts of the brain of a dog which had died in a rabid state. Hydrophobia declared itself in both dogs and rabbits, with a duration of incubation about equal to that which followed the ordinary bite of a dog. Although it was necessary still to submit to this long uncertainty with regard to the incubation, one great result was obtained: hydrophobia could be inoculated with other matter than saliva. Not only is the saliva always impure, containing a saliva microbe, which is endowed with a special virulence of its own, but it presents other inconveniences. It is necessary, in these researches, to have a supply of material constantly at hand. Now, the saliva loses its rabic virulence in twenty-four hours. The existence of the rabic virulence in the brain substance placed, on the contrary, at the disposal of the experimenter, an abundance of the virus, in a state of great purity and capable of long preservation.
The idea then occurred to Pasteur and his assistants, to inoculate the virulent rabic matter in its pure state under the dura mater on the surface of the brain of a dog. Why not carry the virus, said Pasteur, directly to the place of its activity and development? After having trepanned the skull of a chloroformed dog, a little bit of the medulla of an animal which had died of hydrophobia was deposited on the surface of the brain. As soon as the influence of the chloroform was dissipated, the dog recovered its healthy appearance. It ate its food that same evening. But after some days the symptoms of hydrophobia appeared. The animal became dejected and restless; it tossed its litter about, refused all nourishment. A doleful, sharp howling was the first indication of the rabic voice, which is but one long cry of suffering and appeal, mingled with barkings from hallucinations. The stomach became depraved; the dog swallowed hay and straw. It soon grew furious, agitated with violent convulsions; finally, after a last fit, it died. During all this time there was great rejoicing in the laboratory. They were at last in possession of a method for singularly shortening the period of incubation, and for communicating the disease with certainty. The experiments were multiplied; all the dogs which were trepanned, and which received on the surface of the brain a little of the medulla of the rabid animal, succumbed to the disease, with very rare exceptions, within a period of twenty days. Did not the method pursued demonstrate, among other things, that hydrophobia is a disease of the brain; that the seat of the rabic virus, far from being exclusively in the saliva, belongs, above all, to the cerebral matter?
Other results, in addition to this one, were not slow in revealing themselves. It was established that not only the brain, but the spinal marrow, along its whole length, may be rabic, and that the nerves themselves throughout their whole system, from the centre to the periphery, may contain the virus of hydrophobia. If there exists a microbe of hydrophobia, its medium of cultivation in the body is, par excellence, the brain, the spinal marrow, and the nerves. It was also established that there were localisations of virus in certain parts of the mucous system, and that the very considerable differences of rabic symptoms which exist in different cases of hydrophobia, must be sought for in this fact. At the moment of death the medulla oblongata is always rabic. Finally, it was established that hydrophobia could be given (and almost as rapidly as by trepanning) by inoculating rabic nervous matter into the circulation of the blood by a vein.
In presence of such facts it is easy to account for what takes place in the case of a bite from a mad dog. The circulation of the blood carries the virus to the surface of the brain, or to the surface of the spinal marrow; there it houses itself in particular spots, and, little by little, invades the nervous matter. This last would be progressively attacked throughout, if death from the medulla oblongata did not almost always supervene before the propagation of the virus can become general.
The saliva glands are often rabic, doubtless because the virus oozes into them, little by little, from the nerves which enter these glands. Thus may the presence of this virus be explained in the saliva of mad dogs, where, at all times since the disease was first known, it has been found to exist. When the first point attacked by the virus is the spinal marrow, or certain portions of it, a general paralysis often precedes death. In this case the howling and biting symptoms are for the most part absent, and the dog continues to be caressing until it dies.
In a thesis written by M. Roux, Pasteur's laboratory assistant, last July, we read the following:—'If we examine with care a little of the pulp taken freshly from the brain of a rabid animal, and compare it with the same substance from the brain of a healthy animal, it is difficult to distinguish any difference between the two. In the rabic pulp, however, besides the granulations which are found in profusion in the healthy pulp, there seem to exist little grains of extreme minuteness, almost imperceptible even with the strongest microscopes. In the cephalo-rachidic liquid so limpid in appearance, it is possible with great attention to detect similar little grains. Can this be the microbe of hydrophobia? Some do not hesitate to affirm that it is. For ourselves, as long as the cultivation of the microbe outside of the organism has not been effected, and that hydrophobia has not been communicated by means of artificial cultures, we shall abstain from expressing a definite opinion on the subject.'
But the grand problem in regard to hydrophobia is, not so much the isolation of the microbe, as the finding of a means of preventing this frightful disease.
Even now the experiments are in full swing. Biting dogs and bitten dogs fill the laboratory. Without reckoning the hundreds of mad dogs that have died in the laboratory during the last three years, there never occurs a case of hydrophobia in Paris of which Pasteur is not informed. Not long ago a veterinary surgeon telegraphed to him, 'Attack at its height in poodle-dog and bull-dog. Come.' Pasteur invited me to accompany him, and we started, carrying six rabbits with us in a basket. The two dogs were rabid to the last degree. The bull dog especially, an enormous creature, howled and foamed in its cage. A bar of iron was held out to him: he threw himself upon it, and there was great difficulty in drawing it away from his bloody fangs. One of the rabbits was then brought near to the cage, and its drooping ear was allowed to pass through the bars. But, notwithstanding this provocation, the dog flung himself down at the bottom of his cage and refused to bite.
Two youths then threw a cord with a slip loop over the dog, as a lasso is thrown. The animal was caught and drawn to the edge of the cage. There they managed to get hold of him and to secure his jaws; and the dog, suffocating with fury, his eyes bloodshot, and his body convulsed with a violent spasm, was extended upon a table and held motionless, while Pasteur, leaning over his foaming head, at the distance of a finger's length, sucked up into a narrow tube some drops of the saliva. In the basement of the veterinary surgeon's house, witnessing this formidable tête-à-tête, I thought Pasteur grander than I had ever thought him before.