260 BACTERIOLOGY. 



authors, be detected ; but this is by no means constant 

 or frequent. 



This organism grows under artificial conditions very 

 slowly, and frequently not at all. 



When successfully grown upon the different media it 

 presents somewhat the following appearance : 



On gelatin it grows very slowly, if at all, probably 

 owing in part to the low temperature at which gelatin 

 cultures must be kept. If development occurs it appears 

 as minute whitish or blue-white points on the plates. 

 These very small colonies are round, finely granular, 

 sharply circumscribed, and slightly elevated above the 

 surface of the gelatin. The growth is very slow and no 

 liquefaction of the gelatin accompanies it. 



If grown in slant or stab cultures the surface devel- 

 opment is very limited ; along the needle-track tiny 

 whitish or bluish-white granules appear. 



On nutrient agar-agar the colonies are almost trans- 

 parent ; they are more or less glistening and very deli- 

 cate in structure. On blood-serum development is more 

 marked, though still extremely feeble. Here it also ap- 

 pears as a cluster of isolated fine points growing closely 

 side by side. 



A growth on potato is not usually observed. When 

 grown in milk it commonly causes an acid reaction with 

 coincident coagulation of the casein. Some varieties, 

 especially non-virulent ones, do not coagulate milk. 1 It 

 is not motile. 



It grows best at a temperature of from 35 to 38 C. 

 Under 24 C. there is usually no development, but in 

 a few cases it has been seen to grow at as low a tem- 



i Welch, loc. cit. 



