Treatment: gastric and intestinal disinfection—copperas, mineral acids, carbolic or salicylic acids, aromatics, quinine, naphthol, tar, phenic acid subcutem. _Definition._ A febrile hemorrhagic septicæmia of chickens and other fowls (pigeons, ducks, geese, parrots, etc.) communicable to certain rodents and other animals, and characterized by a short incubation, rapid progress, great prostration, violent diarrhœa usually greenish, and a high mortality (90 to 95 per cent.). _History, Geographical distribution._ It is quoted as prevalent in Lombardy in 1789, in East India in 1817, in France in 1825, and generally in Europe and America in the last half century. The _losses_ from the ravages of this disease are far greater than the average value of the individual animal would lead one to suppose, but with domestic fowls numbering 300,000,000 and a yearly egg crop bordering on a billion dozens it may well be called enormous. _Bacteriology._ Chicken cholera is caused by a very small ovoid bacterium (B. Choleræ gallinaceæ) about 0.3 to 1.8μ long, as found in the blood and tissues of the fowl. It has the general characters of the groups which cause hemorrhagic septicæmia, thus: 1. It fixes, above all at the poles, the ordinary anilin colors; 2. It is decolorized by the methods of Gram and Wiegert (iodine solutions); 3. It grows on gelatine without liquefying it; 4. It produces acute septicemic lesions; 5. It tends to polymorphism when grown under different conditions. In the peritoneum of the guinea pig it forms cocco-bacilli tending in acute and violent cases to diplococci. Fed to rabbits it appears in the fæces as a minute bacillus. Even the mode of staining causes a difference in appearance. Fixed in alcohol-ether, and then stained in Ziehl’s phenated preparation, coloring is polar, and the central area clear. If in place of Ziehl’s fluid, hot fuchsin solution is used warm for ½ a minute, bacillus or cocco-bacillus is shown (Lignieres). It is nonmotile, though some observers have been misled by Brownian movements. There are no flagella. In old bouillon cultures short chain forms are met with. No spores are formed.