Metabolism 589 



Rosenau* found temperature the most important factor, as it 

 dies quickly when kept dry at 37°C., but remains alive for months 

 when kept dry at i9°C. Sunlight kills it in a few hours. A tem- 

 perature of 7o°C. is invariably fatal in a short time. 



Metabolism. — The bacillus develops best under aerobic con- 

 ditions though it develops to a sUght extent also under anaerobic 

 conditions. In sugar-containing media it does not form gas. Acids 

 are formed from dextrose, lactose, galactose, mannite and maltose 

 but not from saccharose, sorbite, dulcite or inulin. No indol is formed. 

 Ordinarily the culture-medium is acidified, the acid reaction persist- 

 ing for three weeks or more. 



Ghon,t Wernicke,! and others who have studied the toxic prod- 

 ucts of the bacillus all inchne to the belief that it forms only 

 endotoxin. 



Kossee and Overbeck,§ however, believe that there is, in addition, 

 a soluble exotoxin that is of importance. 



Bielbnovsky || finds that broth, agar, and serum cultures of the 

 plague bacillus possess the property of hemolyzing the blood of 

 normal animals. The hemolytic power of filtrates of plague cultures 

 increase up to the thirteenth or fourteenth day, then gradually di- 

 minishes, but without completely disappearing. The hemolysins 

 are notably resistant to heat, not being destroyed below ioo°C. 



Experimental Infection. — Mice, rats, guinea-pigs, rabbits, and 

 'inonkeys are all susceptible to experimental inoculation. When 

 blood, lymphatic pulp, or pure cultures are inoculated into them, 

 the animals become ill in from one to two days, according to their 

 size and the virulence of the bacillus. Their eyes become watery, 

 they show disincUnation to take food or to make any bodily effort, 

 the temperature rises to 4i.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 bacilU are found everywhere in the blood, but not in 

 very large numbers. 



Rats suffer from both an acute septicemic and a chronic form of 

 the disease. In the former 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 yellowish gelatinous exuda- 

 tion. The spleen and liver are enlarged, the former often pre- 

 senting an appearance similar to that observed in miliary tuber- 

 culosis. Sometimes there is universal enlargement of the lymphatic 



* Bulletin No. 4 of the Hygienic Laboratory of the U. S. Marine Hospital 

 Service, 1901. 

 t Wien, 1898. 



t 'Tentralbl. f. Bakt.," etc., 1898, xxiv. 

 §"Arbeiten aus d. kaiserl. Gesundheitsamte," 1901, xvni. 

 II "Arch, des Sci. Biol.," Petersb., 1904. St. Tome x, No. 4. 



