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.