Schantyr, ignoring the cocci, describes three bacilli which cause three different diseases (distemper, abdominal typhus, and typhoid), but the distinctions are not clear nor generally accepted. Lignieres and Even, in Argentina, and dealing with the more susceptible high bred dogs (fox terriers, great Danes and carlins), found constantly in the blood of the dog, in the early stages of the disease, a long, delicate bacillus, nonmotile and easily stained in aniline, but not by Gram’s method. Inoculated on the Guinea pig it shortens, approximating rapidly in successive passages to a cocco-bacillus, and assumes the general characters of Lignieres’s _pasteurella_. Different bacteria may be found in the lungs, bronchial and nasal mucus, tears and vesicles. Lignieres’s _pasteurella_ is inoculable on the Guinea pig, mouse, rabbit, and dog, producing the symptoms of local or general infection. Two centigrammes, subcutem, in the _Guinea pig_, produced a local œdema, disappearing in four or five days and securing immunity. Five cc. subcutem proved fatal in 48 hours; intraperitoneal in 24 hours. In the _rabbit_ 1cc., subcutem, caused local œdema for 2 days and hyperthermia (104°) for 3 days; 1cc. intravenously, caused fever for 3 weeks, diffluent blood and hæmorrhagic lesions in lungs, liver, kidneys, bowels, spleen, and serosæ. In the mouse, 4 to 8 drops, subcutem, caused œdema, and recovery or death in 2 to 4 days. In such cases the microbe was found in pure cultures in the blood or inoculated tissues. Inoculations of the pure cultures on dogs produced in different cases, gastro-enteritis, pneumonia, pleuro-pericarditis, and arthritis, in various combinations. If the animal survives it is immune. Grown on _peptonized bouillon_, _neutral_ or _slightly alkaline_, the bacillus forms, in 24 hours, small granular colonies which fall to the bottom, leaving the liquid clear. The addition of serum renders this more abundant without causing opacity. On _pancreatic_ bouillon the growth is very free without indol. On _gelatine plates_ there are fine punctiform colonies, transparent, but becoming white and opaque in 8 or 10 days. Similar colonies form in stab and streak cultures. The gelatine is not liquefied. Cultures in _milk_ cause neither coagulation nor acidity. There is little or no growth in hay tea, on potato, nor in vacuum. The cultures have the peculiar odor of the pasteurella.