But to return to the animals of the laboratory: From the little white mice, which hide themselves in a packet of wadding, to the dogs which bark furiously in their iron cages, all are devoted to death. But it is not only the inmates of the laboratory which daily succeed each other upon the operating and dissecting tables. From divers parts of France, hampers full of fowls which have died of cholera, or of some other disease, are sent to Pasteur. Here is an enormous basket packed with straw containing the dead body of a pig which had died of measles. This fragment of lung, packed in a tin box, belonged to a cow which died of peripneumonia. Other packets are still more precious. Since Pasteur went to Pauillac two years ago, to watch for the return of a ship which was to bring back some passengers attacked with yellow fever, he sometimes receives from a distant country a bottled dose of _vomito negro_. Everywhere, on the work tables, are to be seen tubes filled with blood, microscope slides carrying little drops. In the stoves are ranged the cultivating flasks, which resemble little flasks of liqueur. The point of a needle dipped into one of these flasks is sufficient to cause death. Enclosed in their glass prison, millions upon millions of microbes live and multiply. It is really a curious spectacle this workshop of research and discovery. How numerous and varied are the subjects which are being studied, and with what energy and patience does Pasteur attack them! It is not only to the most dreaded diseases that he has applied the germ theory. He has extended it to certain common disorders. Everything to him is a subject for experiment. In May 1879, a person who was working in the laboratory was troubled with boils, which reappeared, as usually happens, at short intervals, sometimes on one part of the body, sometimes on another. Pasteur, whose mind was constantly dwelling on the part played by microscopic organisms, asked himself if the pus of the boils did not contain a parasite, the presence and development of which, and its accidental transport here and there in the body, might be the cause of the local inflammation and of the formation of the pus. The constant reappearance of the evil would be thus accounted for.