322 BACTERIOLOGY. 



It is strictly aerobic, its development ceasing if the 

 supply of oxygen is cut off. 



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 devel- 

 opment is arrested when an acid reaction equivalent to 

 0.066 to 0.08 per cent, hydrochloric or nitric acid is 

 present (Kitasato). 



In cultures, the development of this organism 

 reaches its maximum relatively quickly, then remains 

 stationary for a short period, after which degeneration 

 begins. The dying comma bacilli become altered in 

 appearance and assume the condition known as " involu- 

 tion forms." (See Fig. 61.) When in this state they 

 take up coloring reagents very faintly or not at all, and 

 may lose entirely their characteristic shape. 



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 would lead one 

 to think that the material under consideration was a 

 pure culture of this organism. This, however, does not 

 last longer than two or three days ; they then begin to 

 die, and the other organisms gain the ascendency. This 

 fact has been taken advantage of by Schottelius' in the 

 following method devised by him for the bacteriological 

 examination of dejections from cholera patients : 



In dejections that are not examined immediately 



1 Deutsche med. Woohensohrift, 1885, No. 14. 



