SPIRILLUM OF ASIATIC CHOLERA. 373 



color of milk to which neutral litmus tincture has been 

 added is changed to pink after thirty-six or forty-eight 

 hours at body temperature. 



Its growth in peptone solution, either that of Dun- 

 ham (see Special Media) or the one preferred by Koch, 

 viz., 2 parts Witte's peptone, 1 part sodium chloride, 

 and 100 parts distilled water, is accompanied by the 

 production of both indol and nitrites, so that after 

 eight to twelve hours in the incubator at 37° C. the 

 rose color characteristic of indol appears upon the 

 addition of sulphuric acid alone. (See Indol Eeac- 

 tion.) 



(What does the presence of nitrites in these cultures 

 signify ?) 



In peptone solution to which rosolic acid has been 

 added the red color is very much intensified after four 

 or five days at 37° C. 



Its growth on potato of a slightly acid reaction is 

 seen after three or four days at 37° C. as a dull,whitish, 

 non-glistening patch at and about the site of inocula- 

 tion. It is not elevated above the surface of the potato, 

 and can only be distinctly seen when held to the light 

 in a particular position. Growth on acid potato occurs, 

 however, only at or near the body temperature, owing 

 probably to the acid reaction, which is sufficient to pre- 

 vent development at a lower temperature, but does not 

 have this effect when the temperature is more favorable. 

 On solidified blood-serum the growth is usually said to 

 be accompanied by slow liquefaction. I have not suc- 

 ceeded in obtaining this result on Loeffler's serum, nor 

 have I detected anything characteristic about its growth 

 on this medium. 



The temperature most favorable for its growth is 

 17 



