Part 19

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.