Metabolism Experimental Infection 575 



as it dies quickly when kept dry at 37 C., but remains alive 

 for months when kept dry at 19 C. Sunlight kills it in a 

 few hours. A temperature of 70 C. is invariably fatal in 

 a short time. 



Metabolism. The bacillus develops under conditions of 

 aerobiosis and anaerobiosis. In glucose-containing media 

 it does not form gas. No indol is formed. Ordinarily the 

 culture medium is acidified, the acid reaction persisting for 

 three weeks or more. 



Experimental Infection. Mice, rats, guinea-pigs, rab- 

 bits, monkeys, dogs, and cats are all susceptible to experi- 

 mental inoculation. During epidemics the purely herbiv- 

 orous animals usually escape, though oxen have been 

 known to die of the disease. When blood, lymphatic pulp, 

 or pure cultures are inoculated into them, the animals be- 

 come ill in from one to two days, according to their size and 

 the virulence of the bacillus. Their eyes become watery, 

 they show disinclination to take food or to make any bodily 

 effort, the temperature rises to 41.5 C., they remain quiet 

 in a corner of the cage, and die with convulsive symptoms 

 in from two to seven days. If the inoculation be made 

 intravenously, no lymphatic enlargement occurs; but if it 

 be made subcutaneously, the nearest lymph-nodes always 

 enlarge and suppurate if the animal live long enough. The 

 bacilli are found everywhere in the blood, but not in very 

 large numbers. 



Rats seem to suffer from a chronic form of the disease, 

 and sometimes can be found to have encapsulated caseous 

 nodules in the submaxillary glands, caseous bronchial glands, 

 and fibroid pneumonia months after inoculation. In all 

 such cases virulent plague bacilli are present. This matter 

 is important to the epidermiologist. 



According to Yersin, an infiltration or watery edema 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 enlarged, 

 the former often presenting an appearance similar to that 

 observed in miliary tuberculosis. Sometimes there is uni- 

 versal enlargement of the lymphatic glands. Bacilli are 

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

 eruptions may occur during life, and upon the inner abdom- 

 inal walls petechiae and occasional hemorrhages may be 

 found. The intestine is hyperemic, the adrenals congested. 



