454 SA OTERIOL OGY. 



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 begins. The dying comma 

 bacilli become altered in appearance and assume the 

 condition known as " involution-forms." (See Fig. 76.) 

 When in this state they take up coloring-reagents very 

 faintly or not at all, and may lose entirely their charac- 

 teristic 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 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 by Schottelius ' 

 in the following method devised by him for the bac- 

 teriological examination of dejections from cholera 

 patients : 



In dejections not examined immediately after being 

 passed it is often difficult, because of the large num- 

 ber of other bacteria that may be present, to detect 



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



