Cultivation 



527 



is plentiful and where a distinct 

 shaggy pellicle is formed. From the 

 deeper growth, fine filaments extend 

 from the puncture into the sur- 

 rounding gelatin, with a beautiful 

 arborescent effect (Fig. 161). 



Liquefaction progresses from 

 above downward until ultimately 

 the entire gelatin is fluid and the 

 growth sediments. 



Agar-agar. Upon agar-agar 

 characteristic appearances are few. 

 The growth takes place along the 

 line of inoculation, forming a gray- 

 ish-white, translucent, slightly 

 wrinkled layer with irregular edges, 

 from which curls of bacillary threads 

 extend upon the medium. When 

 the culture is old, the agar-agar 

 usually becomes brown in color. 

 Spore-formation is luxuriant: 



Bouillon. In bouillon the an- 

 thrax bacillus, because of its marked 

 affinity for oxygen, grows chiefly 

 upon the surface, where a thick felt- 

 like pellicle forms. From this, fuzzy 

 extensions descend into the clear 

 bouillon below. After a few days 

 some wooly aggregations can be seen 

 in the bottom of the tube. In the 

 course of time the growth ceases 

 and the surface pellicle sinks. If, 

 by shaking, it is caused to sink 

 prematurely, a new, similar surface 

 growth takes its place. Spore-for- 

 mation is rapid at the surface. 



Potato. Upon the potato the 

 growth is white, creamy, and rather 

 dry. Sporulation is marked. 



Blood-serum. Blood-serum cul- 

 tures lack characteristic peculiari- 

 ties; the culture medium is slowly 

 liquefied. 



V 



Fig. 1 6 1. Bacillus an- 

 thracis ; gelatin stab cul- 

 ture, showing character- 

 istic growth with com- 

 mencing liquefaction and 

 cupping (from evapora- 

 tion) at the surface of 

 the medium (Curtis). 



