296 PATHOGENIC BACTERIA. 



The colonies which form upon gelatin are circular, 

 have smooth borders, and look very much as if bored out 

 with a tool. They have a brown color and are finely 



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FIG. 94. Spirillum aquatilis, from an agar-agar culture; x 1000 (Itzerott and 



Niemann). 



granular. In gelatin puncture-cultures the growth occurs 

 almost exclusively at the surface. 



The agar-agar cultures are similar to those of cholera. 



Scarcely any development occurs in bouillon. By the 

 growth of the organism sulphuretted hydrogen gas is 

 produced. 



The spirillum does not grow at all upon potato. 



Giinther did not find the organism to be pathogenic. 



Spirillum Terrigenus. This species, also discovered 

 by Giinther, was secured from earth. It generally occurs 

 in a slightly curved form, but sometimes is spiral. It is 

 actively motile and has a terminal flagellum. 



The colonies, which appear in twenty-four hours, are 

 small, structureless, and transparent, and later take on a 

 4 ' fat-drop ' ' appearance. 



Upon agar-agar a thin white coating is formed. Milk 

 is coagulated by the growth of the organism. No indol 

 is produced. 



The organism does not stain by Gram's method, and 

 is said not to be pathogenic for guinea-pigs or for mice. 



