At last one day he came up from his laboratory with a triumphant face. His joy was such that tears stood in his eyes. I have never seen a more radiant expression of the highest and most generous emotions than emanated from his countenance. 'I should never console myself,' he said while embracing us, 'if a discovery such as my assistants and I have just made were not a French discovery.' * * * * * And with the clearness which is the charm of this powerful mind, he related to us the most recent discoveries of his laboratory. In neutralised chicken infusion the splenic microbe can no longer be cultivated at a temperature of 44 or 45 degrees. Its cultivation, on the contrary, is easy at 42 or 43 degrees; and in these conditions the microbe produces no spores. At this latter temperature, therefore, and in contact with pure air, we can maintain a culture of filamentous parasites of splenic fever, deprived of all germs. In some weeks the crop dies--that is to say, when this culture is sown in fresh broth the sterility of the broth remains complete. But during the preceding days life exists in the cultivating liquid. If after two, four, six, or eight days of exposure to the air and to heat, the contagium is tried upon animals, its virulence is found to be continually changing with the time of its exposure to the air, and, consequently, it represents a series of attenuated contagia. From the moment when the formation of the spores of the splenic fever bacillus is prevented, all becomes substantially the same as in the case of the microbe of fowl cholera. Moreover, as in the cholera microbe, each of these states of attenuated virulence can be reproduced by cultivation. Finally, splenic fever not being recurrent, each of these splenic fever microbes constitutes a vaccine for the more virulent microbe. In order to apportion the virulence of the vaccine to the species it is desired to vaccinate, it must be tried on a certain number of individuals of the same species. If some vaccinated animals are inoculated with the virulent virus, and none of them perish, the vaccine is good. Among individuals of the same species, however, the difference of receptivity is in general great enough to make it prudent, and even necessary, to have recourse to two vaccines, one weak and the other stronger, with an interval of from 12 to 15 days between the two inoculations. * * * * *