292 PA THOGENIC BA CTERIA. 



In bouillon and peptone solution the addition of dilute 

 sulphuric acid produces the red color of nitro-indol. 



It is said that cultures grown at a temperature of 22 C. 

 phosphoresce in the dark. 



The spirillum seems to be pathogenic for guinea-pigs 

 when introduced into the stomach according to Koch's 

 method for cholera. 



Spirillum Danubicus. This organism (Fig. 90) also 



FIG. 90. Spirillum Danubicus, from an agar-agar culture; x 1000 (Itzerott and 



Niemann). 



much resembles cholera. It was first isolated by Heider 

 in 1892. In appearance it is rather delicate and decidedly 

 curved. It is often united in sigmoid and semicircular 

 forms, and exhibits long spirals in old cultures. It is 

 actively motile, each organism presenting a terminal 

 flagellum. 



The growth upon gelatin plates is rapid. Small light- 

 gray colonies, resembling those of cholera, but exhibit- 

 ing a dentate margin, are observed. The growth in 

 gelatin punctures also much resembles cholera, and the 

 agar-agar growth can scarcely be distinguished from it. 



The potato growth has a distinct yellowish-brown 

 color. 



Milk is coagulated in three or four days. 



