BACTERIA PATHOGENIC FOR ANIMALS. 165 



serum, but only appear in the viscera some time after death, 

 when spores have developed. 



The animals are usually infected through wounds on the 

 extremities ; the stalls or meadows having been dirtied by the 

 spore-containing blood of animals previously dead of the dis- 

 ease. " Rauschbrand" is the German name; " Charbon symp- 

 tomatique," the French, from the resemblance in its symptoms 

 to anthrax. 



Immunity. Rabbits, dogs, pigs, and fowls are immune by 

 nature, but if the bacilli are placed in a 20 per cent, solution of 

 lactic acid, and the mixture injected, the disease develops in 

 them. The lactic acid is supposed to destroy some of the 

 natural resistance of the animal's cells. 



When a bouillon culture is allowed to stand a few days, the 

 bacilli therein lose their virulence, and animals are no longer af- 

 fected by them. 



But if they are placed in 20 per cent, lactic acid and the mix- 

 ture injected, their virulence returns. 



Immunity is produced by the injections of these weakened 

 cultures, and also by some of the products which have been ob- 

 tained from the cultures. 



Bacillus of Chicken Cholera. (Pasteur.) 



Syn. Micrococcus cholera gallinarum. Microbe en hull. Ba- 

 cillus avicidus. Bacillus of fowl septicaemia. 



Origin. In 1879 Perroncito observed this cocci-like bacillus 

 in diseases of chickens, and Pasteur, in 1880, isolated and 

 reproduced the disease with the microbe in question. 



Form. At first it was thought to be a micro- 



"R^Tr* QO 



coccus, but it has been seen to be a short rod 

 about twice as long as it is broad, the ends 

 slightly rounded. The centre is very slightly 

 influenced by the aniline colors, the poles 

 easily, so that in stained specimens the bacil- 

 lus looks like a dumb-bell or a figure-of-eight. 



,,,. . ., . Chicken cholera 



(Microbe en hint.) in blood 1000 x . 



Properties. They do not possess self-move- (Frankei and 

 ment ; do not liquefy gelatine. Pfeiffer.) 



Growth. Occurs at ordinary temperature, requiring oxygen 

 for development. It grows very slowly. 



