134 ESSENTIALS OF BACTERIOLOGY. 



of infection. The bacilli are found in great numbers in the 

 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 synip- 

 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 add 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 huit. Ba- 

 cillus avitidus. Bacillus of fowl septicaemia. 



Origin. In 1879 Perroncito observed this 

 FIG. 73. cocci-like bacillus in diseases of chickens, and 



*> * Pasteur, in 18SO, isolated and reproduced the 



*<^ ' disease with the microbe in question. 



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

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

 Chicken cholera auout twice as long as it is broad, the ends 

 bacillus. slightly rounded. The centre is very slightly 



influenced by the aniline colors, the poles 

 easily, so that in stained specimens the bacillus looks like a 

 dumb-bell or a figure-of-eight. (Microbe en huit.) 



Properties. They do not possess self-movement ; do not 

 liquefy gelatine. 



