106 



ESSENTIALS OF B A CTERIOLOG! Y. 



FIG. 53. 



Growth. Develops at ordinary temperatures on all nutrient 

 media that have an alkaline or neutral reaction. They are 

 facultative anaerobic. 



Colonies, gelatine. After 24 hours, small white points which 

 gradually come to the surface, the gelatine being slowly .lique- 

 fied, a funnel-shaped cavity formed holding the colony in its 

 narrow part, at the bottom, and on the fifth day all the gelatine 

 is liquid. If the colonies of three days' growth are placed under 

 microscope they appear as if composed of small bits of frosted 

 glass with sharp irregular points. 



Stab Culture. After 30 hours a growth can be distinguished 

 along the needle track, and on the surface a little cavity has 

 been formed, filled up by a bubble of air, and this liquefaction 

 proceeds until on the sixth day it has reached the sides of the 

 tube, tapering, funnel-shaped to the bottom of the tube. After 



several weeks the spirilla 

 are found in little collec- 

 tions at the bottom of the 

 fluid gelatine. In eight 

 weeks the bacilli have 

 perished. 



Agar. Stroke cultures. 

 A shiny white layer lasts 

 many months. 



Potato. A yellow honey- 

 like transparent layer, if 

 the potato is kept at ani- 

 mal heat. 



Bouillon. A wrinkled 

 scum is soon formed in 

 bouillon. They live well 

 and grow in sterilized milk 

 and sterilized water, re- 

 maining virulent in the 

 latter for many months. 



In ordinary water, the bacteria present are destructive to the 

 comma bacillus, and they die in a few days. 



Staining. They are colored well with watery aniline solu- 



Cholera dejections upon a damp sheet, a.- 

 Formed bacilli. 600 diameters. (Koch.) 



