INTESTINAL OR COLON-TYPHOID GROUP 



273 



The optimum growth temperature is about 37; it grows also, 

 but more slowly, at room-temperature. The thermal death- 

 point is 58, with ten minutes exposure. The organism will 

 remain viable for several days when dried. Gas and acid are 



produced in dextrose broth. The gas formula is 



TT 



reverse of that of B. coll. Lactose and saccharose are not fer- 

 mented, and no growth occurs in the closed arm of the fermentation 

 tube containing these sugars. Indol is not ordinarily produced. 



Fig. 113. Bacillus cholera suis, showing flagella (deSchweinitz, Bureau Animal 



Industry). 



It will be noted that there are no physiologic differences between 

 the B. enteritidis and B. choleroe suis. 



Pathogenesis. It should again be emphasized that the B. 

 chokrce suis is not the primary cause of hog-cholera, but that it 

 is a secondary invader of importance, and may be occasionally 

 the primary cause of disease in hogs, but this disease probably 

 would possess, according to Dorset, Bolton, and McBryde, a low 

 degree of contagiousness. 



Experimental Evidence of Pathogenesis. Some differences in 

 virulence have been observed in cultures obtained from different 

 sources. Rabbits succumb to septicemia in five to eight days 



18 



