138 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' n is the German name ; " Ckarbon xi/inj>- 

 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 knit. Ba- 

 cillus avicidus. Bacillus of fowl sejrticcemia. 



FIG. 78. 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- 

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



Chicken cholera a b ou t twice as long as it is broad, the ends 



in blood 1000 X. T i ,1 j j rru . 1-1 ,1 



(Frankei and sn g nt v rounded. The centre is very slightly 

 Pfeiffer.) 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. 



