45° PATHOGENIC BACTERIA. 



growth in bouillon and in peptone solutions is accompa- 

 nied by the production of indol. 



The spirillum is pathogenic for mice, guinea-pigs, and 

 canary birds. 



Spirillum Weibeli. — This spirillum (Fig. 103) was found 

 in 1892 by Weibel in spring-water which had a long time 



Fig. 103. — Spirillum Weibeli, from agar-agar; x iooo (Itzerott and Niemann). 



before been infected by cholera. It is short, rather thick, 

 and distinctly bent, often forming S-shaped figures. 



The colonies before liquefaction sets in are described 

 as pale-brown, transparent, circular, and homogeneous. 

 Liquefaction is much more rapid than in cholera, and 

 causes the borders of the colonies to become irregular. 

 In the centre of each colony a little depression is ob- 

 served. 



In gelatin puncture-cultures the growth is rapid, be- 

 ginning first upon the surface, where a large flat, saucer- 

 shaped liquefaction, extending to the sides of the tube, 

 forms. Scarcely any growth takes place in the puncture, 

 but the superficial liquefaction, separated by a horizontal 

 line from the normal gelatin, descends slowly. 



Upon agar-agar a grayish-white layer is formed. 



No growth has been obtained upon potato. 



