The condition designated septicaemia of mice is a laboratory disease which Koch produced by inoculating the house mouse with one or two drops of putrid fluid. The animal in a certain proportion of cases (about a third) becomes ill in about twenty-four hours, and dies in two or three days, with symptoms of an acute specific fever. The blood is then found loaded with .small bacilli (shown in Fig. 143, a, p. 348), many of which are in the leucocytes of the blood. The bacilli are very small, and they are stained by the ordinary agents. They have been cultivated on nutrient media, and animals have been infected by inoculation. House mice and white mice, pigeons, sparrows, and rabbits are susceptible, but it is peculiar that field mice, although so like house mice, are not. Fowls and guinea-pigs are also insusceptible. In rabbits the result is not septicaemia, but an inflammation of the subcutaneous tissue, like erysipelas.