202 DYSENTERY, HOG AND CHICKEN CHOLERA. 



It produces gas copiously, but no indol. 



Vitality. It withstands drying for a long time. Its ther- 

 mal death-point is 54 C. 



Pathogenesis. It is intensely pathogenic for every labor- 

 atory animal, death being preceded always by a rise of 

 temperature, and postmortem lesions affecting chiefly the liver 

 and kidneys are seen. Sometimes the lesions are found in 

 the intestines and Peyer's glands also. The bacillus is found 

 in all the organs. Artificially swine are inoculat ^ with dif- 

 ficulty. 



Immunity in animals has been produced by Salmon and 

 Smith by injections of gradually increasing doses of cultures 

 of this bacillus. De Schweinitz has isolated from cultures 

 of the bacteria pure toxic substances with which he has been 

 able to produce immunity. By subcutaneous inoculations 

 with these toxins in cows he was able to develop in their 

 blood-serum an antitoxic substance capable of protecting ani- 

 mals from the disease. The serum of infected animals has a 

 remarkable agglutinating power; with a dilution of 1 to 

 10,000, agglutination can be obtained in an hour. 



CHICKEN CHOLERA. 

 Bacillus Choleras Gallinarum. 



History. This bacillus was observed by Perroncito, in 

 1878, and described by Pasteur. 



The cause of the disease known in fowls as chicken cholera 

 is due to a short, broad bacillus, with rounded ends, occurring 

 singly or united to form filaments. 



This bacillus stains in a peculiar way with the anilin dyes, 

 its two poles being markedly stained, whereas the centre of 

 the bacillus is scarcely stained at all, giving it very much the 

 appearance of a micrococcus, which it was at first believed 

 to be by Pasteur. It does not stain by Gram's method. 



Biology. It produces no spores and is non-motile. It is 

 easily killed by heat and drying. It grows on all ordinary 

 culture-media. On gelatin in two days the cultures appear to 

 the naked eye as small white points ; under the microscope 



