466 BACTERIOLOGY. 



It does not grow in acid media, but flourishes best in 

 media of neutral or slightly alkaline reaction. It is so 

 sensitive to the action of acids that at 22 C. its devel- 

 opment is arrested when an acid reaction equivalent to 

 0.066 to 0.08 per cent, of hydrochloric or nitric acid is 

 present. (Kitasato.) 



Under artificial cultivation the maximum develop- 

 ment of this organism is reached in a comparatively 

 short time ; after this it remains quiescent for a period, 

 and finally degeneration or involution begins. When in 

 this state they take up coloring-reagents very faintly or 

 not at all, and may lose entirely their characteristic 

 shape. (See Fig. 76.) 



When present with other bacteria, under conditions 

 favorable to growth, the comma bacillus at first grows 

 much more rapidly than do the others ; in twenty-four 

 hours it will often so outnumber the other organisms 

 present that microscopic examination might lead one 

 to regard the material under consideration as a pure 

 culture of this organism. Its conspicuous develop- 

 ment under these circumstances does not, however, last 

 longer than two or three days ; degeneration and death 

 begin, and the other organisms gain the ascendency. 

 This fact has been taken advantage of in the bacteriolo- 

 gical diagnosis of cholera. 



In connection with his experiments upon the poison 

 produced by the cholera organism Pfeiffer * states that 

 in very young cultures, grown under access of oxy- 

 gen, there is present a body that possesses intensely 

 toxic properties. This primary cholera-poison stands 

 Zeitscbrift fur Hygieneund Infektlonskrankheiten,Bd. xi. S. 393, 



