460 PATHOGENIC BACTERIA. The organism is widely distributed in nature, being almost always present in garden-earth. It is also found in various dusts, in the waste water from houses, and sometimes in the intestinal canals of animals. When introduced beneath the skin this bacillus proves pathogenic for a large number of animalsmice, guinea- pigs, rabbits, horses, dogs, sheep, goats, pigs, calves, chickens, and pigeons. Cattle seem to be immune. Giinther points out that the simple inoculation of the bacillus upon an abraded surface is insufficient to pro- duce the disease, because the oxygen which is, of course, abundant there is detrimental to its growth. When an experimental inoculation is performed, a small subcu- taneous pocket should be made, and the bacilli introduced into it in such a manner as not to be in contact with the air. If the inoculated animal be a mouse, guinea-pig, or rabbit, in about forty-eight hours it sickens and dies. The autopsy shows a general subcutaneous edema con- taining immense numbers of the bacilli. In the blood the bacilli are few or cannot be found, because of the oxygen which it contains. The great majority of them occupy the subcutaneous tissue, where very little oxygen is present and the conditions of growth are therefore good. If the animal is allowed to remain undisturbed for some time after death, the bacilli spread to the circulatory sys- tem and reach all the organs. Brieger and Ehrlich have reported two cases of malig- nant edema in man. Both cases were typhoid-fever patients injected with musk, and developed the edema in consequence of impurity of the therapeutic agent. No case is reported, however, in which healthy men have been infected with the disease. Cornevin declares that the passage of the bacillus through the white rat diminishes its virulence, and that the animals of various species that recover from this milder affection are subsequently immune to the virulent organisms.