SYSTEMATIC AND DESCRIPTIVE. 25! 



begin to be visible after about twenty-four hours. 

 Examined with a low-power, and a small diaphragm, 

 these colonies have the following characteristics. 

 They appear as little masses, granular, and of a 



FIG. 84. COVER-GLASS PREPARATION OF THE EDGE OF A DROP OF MEAT 

 INFUSION, containing a pure cultivation of comma bacilli, with (a) spirilli- 

 form threads, X 600 [after Koch]. 



very faintly yellowish-red tinge, which have lique- 

 fied the gelatine, and sunk down to the bottom 

 of the resulting excavations (Fig. 86). 



j. nr. 



FIG. 85. COLONIES OF COMMA BACILLI ON NUTRIENT GELATINE, 

 NATURAL SIZE [after Koch]. 



In test-tubes of slightly alkaline nutrient gelatine 

 (10 per cent.), the appearance of the growth 

 is very striking. It commences to be visible in 



