"A man leaves his village for Paris to make a name for himself, and he returns only when bad luck or inability sends him back. And then it is only every four years that there is a 'concours' for admission. In four years what will be my moral and intellectual condition? How should I support this exile of four years? Imagine the effect that four years of isolation in the mountains will produce. But this is not all. Besides this ostensible end that I have pursued since I left my village, I have my special work that I can carry out only in Paris. Without having overwhelmed you with the details of medicine, you know that it is about to undergo a revolution that will transform it. Until now it has been taught officially, in pathology, that the human organism carries within itself the germ of a great many infectious diseases which develop spontaneously in certain conditions; for instance, that tuberculosis is the result of fatigue, privations, and physiological miseries. Well, recently it has been admitted, that is to say, the revolutionists admit, a parasitical origin for these diseases, and in France and Germany there is an army looking for these parasites. I am a soldier in this army, and to help me in these researches I established a laboratory in the dining- room. It is to the parasites of tuberculosis and cancers that I devote myself, and for seven years, that is, since I was house-surgeon, my comrades have called me the cancer topic. I have discovered the parasite of the tuberculosis, but I have not yet been able to free it from all its impurities by the process of culture. I am still at it. That is to say, I am very near it, and to-morrow, perhaps, or in a few days, I may make a discovery that will be a revolution, and cover its discoverer with glory. The same with the cancer. I have found its microbe. But all is not done. See what I must give up in leaving Paris." "Why give all this up? Could you not continue your researches in Auvergne?"