534 



PATHOGENIC BACTERIA. 



be circular and rounded, or irregular. They are said 

 rarely to reach a greater diameter than 2 mm. The gela- 

 tin is not liquefied. There is nothing distinctly charac- 

 teristic about the appearance of the colonies. 



Upon agar-agar the superficial colonies attain a diam- 



Fig. 119. — Ulceration of the intestine in a typical case of swine-fever 

 (Crookshank). 



eter of 4 mm. and have a gray translucent appearance with 

 polished surface. They are round and slightly arched. 



In gelatin punctures the growth takes the form of a 

 nail with a flat head. There is nothing characteristic 

 about it. The growth in the puncture shows it to be an 

 optional anaerobe. 





