Nothing is more striking than the rapid inflation and almost immediate putrefaction of animals which have succumbed to splenic fever. Of all the vibrios ready to pass from the intestinal canal into the network of mesenteric veins which surround the canal those which seem to take the foremost place are the septic vibrios. These specially merit the name of vibrios of putrefaction, from the very putrid gases which result from their action upon nitrogenous and sulphurous substances. The others diffuse themselves more or less slowly in the blood, but the septic vibrio takes almost immediate possession of the dead body. Already after twelve or fifteen hours, the blood of the diseased animal, which at the time of its death and during the first following hours contained exclusively the parasite of splenic fever, harbours at one and the same time both the bacillus of splenic fever and the septic vibrio. Then occur the very curious effects arising from the anaerobic nature of these vibrios, and their opposition to the bacillus of splenic fever, which is exclusively aerobic. Diffused in blood deprived of oxygen gas, the splenic bacillus soon perishes. In its place are to be found amorphous granulations deprived of all virulence. The septic anaerobic vibrio, on the contrary, finds itself after death in the most favourable conditions for its life and development. Not only does it penetrate into the blood by the deep mesenteric veins, but also into the liquids which ooze out of the abdomen and muscles. From the antagonism existing between the physiological peculiarities of the splenic bacilli and the septic vibrio, it results that if, in order to inoculate an animal capable of contracting the fever, a drop of blood be taken from one that has just died of it, and if the operation is performed during the first few hours after death, it is certain to communicate to that animal splenic fever, and splenic fever only. If, on the other hand, the operation is performed after a greater number of hours--say, between twelve and twenty, according to the season of the year--then the inoculation of the blood will communicate, at one and the same time, splenic fever and septicæmia--acute septicæmia, as it may be called, because of the rapid inflammatory disorders that the septic vibrio causes in the inoculated animal. The two diseases may be developed simultaneously in the inoculated animal, but generally one precedes the other. The septic contagium is the quickest in its action; it generally causes death before the splenic fever has had time to develop itself and to produce appreciable effects.