Such structure and habits make it not surprising that the alimentary canal of many birds contains only a scanty intestinal flora. Parrots, for instance, which are remarkably long-lived birds, harbour very few microbes in the intestine. The small intestine contains almost none, the rectum so few that the fæcal matter appears to be formed of mucus, the waste of the food, and only a very few microbes. M. Michel Cohendy, who has examined the intestinal flora at the Pasteur Institute, was unable to isolate more than five different species of microbes living in the alimentary canal of parrots. Even in birds of prey which feed upon putrid flesh, the number of microbes in the intestine is remarkably limited. I have investigated the case of ravens which I fed on flesh which was putrid and swarming with microbes. The droppings contained very few bacteria, and it was specially remarkable that the intestines had not the slightest smell of putrefaction. Although the opened body of a herbivorous mammal, such as a rabbit, gives off a strong smell of putrefaction, the body of a raven with the digestive tube exposed has no unpleasant smell. This absence of putrefaction in the intestine is probably the reason of the great longevity of such birds as parrots, ravens, and their allies. It might be said, however, that the long duration of life in birds is due to the organisation of these animals, rather than to the scantiness of their intestinal flora. To meet this objection, it is necessary to turn to the case of cursorial birds.