530 APPLICATION OF METHODS OF BACTERIOLOGY 



2 parts of Witte's peptone, 1 part of sodium chloride, and 

 100 parts of distilled water, is accompanied by the produc- 

 tion 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 Reaction.) 



(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 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 inoculation. 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 prevent development at a lower temperature, 

 but does not have this effect when the temperature is more 

 favorable. On solidified blood-serum 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. Below 

 16 C. no growth is visible. 



It is not destroyed by freezing. When exposed to 65 C. 

 its vitality is destroyed in five minutes. 



It is strictly aerobic, its development ceasing if the supply 

 of oxygen be cut off. 



