CHAP. Ill CHARACTER OF BACILLUS 25 



lucent. About the end of the week their maximum 

 growth is reached (Fig. 5). As with other species, so 

 also here, when the colonies of the surface are placed 

 at great intervals they grow much larger than when 

 they are near together. Those that develop in the 

 depth of the gelatine plate are very small as com- 

 pared with those growing on the surface, and remain 

 minute round dots, whitish in reflected, brownish in 

 transmitted light. The gelatine is never liquefied by 

 the growth. 



Sub-cultures made of a colony on the surface of 

 gelatine as streak-cultures, — i.e. when with the end of 

 a platinum wire a colony is touched and is then 

 drawn in a line over the surface of the gelatine, — show 

 after one or two days along the line of inoculation 

 a narrow, grey, translucent band. This band rapidly 

 broadens, and remains flat, and possesses a crenated 

 margin. After a week its breadth is 5-10 millimetres 

 and more, it is flat, thin, translucent, dry, smooth, and 

 possessed of a satiny or fatty lustre ; the margin is 

 slightly thicker than the middle, translucent, and 

 plicated. In stab-culture the line of inoculation — 

 the stab — becomes visible after a day or two as a 

 grey line. Under a glass it is composed of minute 

 spherical dots. On the upper surface of the stab 

 a thin, translucent, whitish-grey film gradually spreads 

 over the gelatine with irregular margin, which in 



