Now—and I appeal to the good sense of my readers—would it be better to efface the suffering of those rats, those guinea-pigs, those rabbits, and return to the olden times when the mortality in lying-in hospitals was often 40 per cent. (it is to-day, 0.02 per cent.!)? Must we condemn Lister and Pasteur as great criminals because they dared to inoculate microbes into a few rabbits and bring about in those unfortunate animals—they would have died a long time ago even without that—experimental ailments in order to ward off malignant diseases from thousands and thousands of human beings?
The second discovery which I shall mention is that of the infectiousness of tuberculosis. Thousands and thousands of doctors had had tuberculous patients under their care. Three thousand years ago, Hippocrates described tuberculosis with as much precision as could be done to-day. Illustrious physicians in every land had tried to analyse the nature of this terrible disease and to unravel its cause; nevertheless, they were unable, from clinical observation alone, to prove what is to-day quite commonplace knowledge, viz., that tuberculosis is infectious. In 1864, a French doctor, Villemin, conceived the simple and ingenious idea of inoculating rabbits with the tuberculous matter found in the lungs of consumptive patients. These rabbits became tuberculous; they died in a few weeks with tuberculous granulations in lungs and liver. It was thus demonstrated that tuberculosis was infectious. Later on, in 1878, Koch discovered that the active agent of this infection is a special microbe. But, however important may be the discovery of the microbe of tuberculosis (the tubercle-bacillus of Koch), the essential dominating fact is that tuberculosis is infectious.
As soon as this great fact became known, a profound revolution occurred in social hygiene, in the treatment and in the prevention of this terrible evil. We know now the consumptive man carries in his lungs and sputum the germ capable of developing the same evil in others; consequently we know how to preserve ourselves against tuberculosis. We must purify or destroy the habitations wherein consumptives have lived, burn or carbolise all the sputum, make spitting in public places a punishable offence, take sanitary measures against unhealthy meat, defend our children against contaminated milk—in a word, we are armed against a disease, the sole and unique cause of which, as experimentation alone has taught us, is infection.
Formerly it was believed that diseases were due to a sort of divine anger, or, what amounts pretty much to the same thing, to certain imperceptible epidemic exhalations stretching over whole populations, or attacking isolated individuals, striking like an exterminating angel, as his fancy chose, such or such an unhappy victim. A sort of will or caprice, governed only by chance, was exercised in relation to this disease, and man was powerless, because he was unarmed against chance. He did not even think of it. He resigned himself to being ill, and waited for the disease, without doing anything to fight against it, benumbed under a kind of Oriental fatalism. The doctor shook his head, bore testimony to the evil, and confined himself to prescribing inefficacious treatments which were only, according to a celebrated saying, a long meditation on death.
But the times have changed; there is no longer any fatality in tuberculosis; there is imprudence, there is error, there is vice, and, specially, social vice. We may almost say that, if there are still consumptives in our midst, it is because of our defective social institutions. We leave innumerable populations steeped in misery, seven or eight individuals living in the same infected hovel. In the slums of our large cities, swarms of infants are to be found morally and materially perverted by misery. Therefore, if consumption still exists, it is our own fault; it is no longer as it was in olden times, when we knew not, because now we know. The plague can be battled with; and if it still has so much power left, it is because we have not the courage to apply to public and individual hygiene the treatment science has definitely shown us should be applied. To foresee is to know; and now that we know, we must not forget that it is to experimenters, and to experimenters alone, that we are indebted for this great benefit.
Moreover, however imperfect our defence against tuberculosis may still be, it is by no means nil; great progress has been made; the mortality has decreased in a considerable proportion. During the last twenty-five years, it has decreased by about 25 per cent., and notably in England, where the laws of public hygiene, energetically upheld by the good sense of the people, are strictly applied, the mortality has diminished by 50 per cent. This is only a beginning, and the near future will bring about the complete extermination of the disease.
Now, honestly, I ask if the rabbits which Villemin sacrificed weigh more in the scales of universal progress, and even in public morality, than the three millions of individuals who, by progress in hygiene, have been preserved from an early and painful death. I estimate at a high price the life and the sufferings of fifty rabbits, but, at the risk of appearing a barbarian, I prefer, to these fifty rabbits, the three millions of young people who have been saved by Villemin's discovery, and the millions which it will still save.
All the more so, inasmuch as experimental studies on tuberculosis have not only preserved men; they have also preserved animals. Thanks to Koch, there is now a very simple way of recognising if an animal is or is not tuberculous. Koch was able to extract from tubercle bacilli, a substance which he has called tuberculin. At first he thought tuberculin cured the disease; but this was an error. Subsequent experiments showed that tuberculin exercised quite a different action to that of healing. It has the property, when injected in small doses into a tuberculous animal, of provoking an intense fever, whilst it produces no reaction whatsoever in a normal animal. If, therefore, tuberculin is injected into every animal in the cattle shed, we can feel sure—and this is impossible otherwise—that such or such animals are tuberculous or healthy. All cows that show a rise in temperature after an injection of tuberculin are tuberculous; the others, on the contrary, are in good health.
Thus the sanitary inspection of stables and cattle-sheds can be carried out thoroughly; and we are now able to protect not only men but also animals from the disease of tuberculosis.