Metabolic Products 627 



yellowish-brown growth takes place. Sometimes the color 

 is quite dark, and chocolate-colored potato cultures are not 

 uncommon. 



Bouillon. In bouillon the growth which occurs at the 

 temperature of the incubator is quite characteristic, and 

 very different from that of the cholera spirillum. The 

 entire medium becomes clouded, of a grayish-white color, 

 and opaque. A folded and wrinkled pellicle forms upon the 

 surface. 



Milk. When grown in litmus milk, the original blue 

 color is changed to pink in a day, and at the end of another 

 day the color is all destroyed and the milk coagulated. 

 Ultimately the clots of casein sediment in irregular masses, 

 from the clear, colorless whey. 



Vital Resistance. The organism, like the cholera 

 vibrio, is very susceptible to the influence of acids, high 

 temperatures, and drying. The thermal death-point is 

 50 C., continued for five minutes. 



Metabolic Products. The addition of sulphuric acid to 

 a culture grown in a medium rich in peptone produces the 

 same rose color observed in cholera cultures and shows the 

 presence of indol. When glucose is added to the bouillon, 

 no fermentation or gas-production results. The organism 

 produces acids and curdling enzymes. 



Pathogenesis. The organism is pathogenic for animals, 

 but not for man. Pfeiffer has shown that chickens and 

 guinea-pigs are highly susceptible, and when inoculated under 

 the skin usually die. The virulent organism is invariably 

 fatal for pigeons. W. Rindfleisch has pointed out that this 

 constant fatality for pigeons is a valuable criterion for the 

 differentiation of this spirillum from that of cholera, as the 

 subcutaneous injection of the most virulent cholera cultures 

 is never fatal to pigeons, the birds only dying when the 

 injections are made into the muscles in such a manner that 

 the muscular tissue is injured and becomes a locus minoris 

 resistenti<B. When guinea-pigs are treated by Koch's 

 method of narcotization and cholera infection, the tem- 

 perature of the animal rises for a short time, then ab- 

 ruptly falls to 33 C. or less. Death follows in from twenty 

 to twenty-four hours. A distinct inflammation of the intes- 

 tine, with exudate and numerous spirilla, may be found. 

 The spirilla can also be found in the heart's blood and in 

 the organs of such guinea-pigs. When the bacilli are intro- 



