558 APPLICATION OF METHODS OF BACTERIOLOGY 



It does not grow in an atmosphere of carbonic acid, but 

 is not killed by a temporary exposure to this gas. 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 development 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 development 

 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. 

 93.) 



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 development under these cir- 

 cumstances does not, however, last longer than two or 

 three days; degeneration and death begin, and the other 

 organisms gain the ascendancy. This fact has been taken 

 advantage of in the bacteriological diagnosis of cholera. 



In connection with his experiments upon the poison 

 produced by the cholera organism Pfeiffer 1 states that in 

 very young cultures, grown under access to oxygen, there 

 is present a body that possesses intensely toxic properties. 

 This primary cholera-poison stands in very close relation 

 to the material composing the bodies of the bacteria them- 



1 Zeitschrift fur Hygiene und Infektionskrankheiten, Bd. xi, S. 393. 



