320 PATHOGENIC BACTERIA. 



Upon potatoes no growth occurs at ordinary tempera- 

 tures. When the potato is stood away for a few days in 

 the incubator, a scanty, dry, whitish layer develops. 



Kitasato found that mice, rats, guinea-pigs, and rabbits 

 are all susceptible. When blood, lymphatic pulp, or pure 

 cultures are inoculated into them, the animals become ill 

 in from one to two days, according to size. Their eyes 

 become watery, they begin to show disinclination to take 

 food or to make any bodily effort, the temperature rises 

 to 41.5 C., they remain quietly in a corner of the cage, 

 and die with convulsive symptoms in from two to five 

 days. 



According to Yersin, an infiltration can be observed 

 in a few hours about the point of inoculation. The 

 autopsy shows the infiltration to be made up of a yellow- 

 ish gelatinous exudation. The spleen and liver are en- 

 larged, the former often presenting an appearance much 

 like an eruption of miliary tubercles. Sometimes there 

 is universal swelling of the lymphatic glands. Bacilli are 

 found in the blood and in all the internal organs. Very 

 often there are petechial eruptions during life, and upon 

 the inner abdominal walls there are occasional hemor- 

 rhages. The intestine is hyperemic, the adrenals con- 

 gested. There are often sero-sanguinolent effusions into- 

 the serous cavities. 



Kitasato found that pigeons were not susceptible. 

 Animals fed upon cultures or upon the meat of others 

 dead of the disease became ill and died with typical 

 symptoms. When he inoculated animals with the dust 

 of dwelling-houses in which the disease had occurred, 

 some died of tetanus, one from plague. Many rats and 

 mice in which examination showed the characteristic 

 bacilli died spontaneously in Hong-Kong. 



Yersin showed that flies also die of the disease. Mace- 

 rating and crushing a fly in bouillon, he not only suc- 

 ceeded in obtaining the bacillus from the medium, but 

 infected an animal with it. 



Yersin found that when cultivated for any length of 



