CULTURE OF THE CHOLERA SPIRILLUM. 321 



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 Reac- 

 tion.) 



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, whit- 

 ish, non-glistening patch at and about the site of inoc- 

 ulation. 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 tem- 

 perature, owing probably to the acid reaction, which is 

 sufficient to prevent development at a lower tempera- 

 ture, 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 

 succeeded in obtaining this result on Loffler's serum, 

 nor have I detected anything characteristic about its 

 growth on this medium. 



The temperature most favorable for its growth is 

 between 35° and 38° C. It grows, but more slowly, 

 at 17° C. Under 16° C. no growth is visible. 



It is not destroyed by freezing. When exposed to 

 65° C. its vitality is destroyed in five minutes. 



