Page:Popular Science Monthly Volume 20.djvu/827

Rh represented it formerly in one of the plates of my work on the diseases of silk-worms. Little by little all connection between them disappears, and presently they are reduced to nothing more than germ-dust. If you make these corpuscles germinate, the new culture reproduces the virulence peculiar to the thready form which has produced these corpuscles, and this result is seen even after a long exposure of these germs to contact with air. Recently we discovered them in pits in which animals, dead of splenic fever, had been buried for twelve years, and their culture was as virulent as that from the blood of an animal recently dead. Here I regret extremely to be obliged to shorten my remarks. I should have had much pleasure in demonstrating that the anthracoid germs in the earth of pits in which animals had been buried are brought to the surface by earth-worms; and that, in this fact, we may find the whole etiology of disease, inasmuch as the animals swallow these germs with their food. A great difficulty presents itself when we attempt to apply our method of attenuation by the oxygen of the air to the anthracoid microbes. The virulence establishing itself very quickly, often after twenty-four hours, in an anthracoid germ which escapes the action of the air, it was impossible to think of discovering the vaccine of splenic fever in the conditions which had yielded that of chicken-cholera. But was there, after all, reason to be discouraged? Certainly not; in fact, if you observe closely, you will find that there is no real difference between the mode of the generation of the anthracoid germ by scission and that of chicken-cholera. We had, therefore, reason to hope that we might overcome the difficulty which stopped us by endeavoring to prevent the anthracoid microbe from producing corpuscle-germs, and to keep it in this condition in contact with oxygen for days, and weeks, and months. The experiment fortunately succeeded. In the ineffective (neutre) bouillon de poule the anthracoid microbe is no longer cultivable at 45° Cent. Its culture, however, is easy at 42° or 43°, but in these conditions the microbe yields no spores. Consequently it is possible to maintain in contact with the pure air, at 42° or 43°, a mycélienne culture of bacteria entirely free of germs. Then appear the very remarkable results which follow: In a month or six weeks the culture dies that is to say, if one impregnates with it fresh bouillon, the latter is completely sterile. Up to that time life exists in the vase exposed to air and heat, If we examine the virulence of the culture at the end of two days, four days, six days, eight days, etc., it will be found that long before the death of the culture the microbe has lost all virulence, although still cultivable. Before this period it is found that the culture presents a series of attenuated virulences. Everything is similar to what happens in respect to the microbe in chicken-cholera. Besides, each of these conditions of attenuated virulence maybe reproduced by culture; in fact, since the charbon does not operate a second time (ne récidive pas), each of our attenuated anthracoid microbes constitutes