304 VETERINARY BACTERIOLOGY 



the organism is particularly evident in smears from tissues or 

 blood. 



Isolation and Culture. The organism may be isolated directly 

 from infected lymph-glands in pure culture. It has been ob- 

 tained from the blood, but this is not usual. Growth occurs 

 readily on most culture-media. The colonies on agar are delicate, 

 drop-like, with center somewhat granular and thicker than the 

 uneven, slightly granular margin. Growth on other media does 

 not differ markedly from that described for other members of this 

 group. Growth occurs scantily or not at all on potato. One 

 character that has been described and has been found useful in 



Fig. 123. Bacillus peslis (Wherry). 



diagnosis is the " stalactite " formation in broth covered with 

 oil and allowed to remain without being disturbed. Under these 

 conditions long delicate threads are produced which hang from the 

 oil and resemble the stalactites found in caves. 



Physiology. The organism is aerobic and facultative anaerobic. 

 The optimum growth temperature is between 25 and 30, but 

 growth occurs both above and below these temperatures. It is 

 easily destroyed by desiccation, heat, light, and disinfectants. 

 Dextrose broth is acidified, but no gas is produced. Indol is not 

 formed. 



