586 



Plaffue 



sipelas cocci, and contained zooglea attached to the sides and at 

 the bottom of the tube of nearly clear fluid. 



Haffkine* found that when an inoculated bouillon culture is 

 allowed to stand perfectly at rest, on a firm shelf or table, a char- 





Fig. 231. — Bacillus pestis. Highly virulent culture forty-eight hours old, from 

 the spleen of a rat. Unstained preparation (Kolle and Wassermann). 



acteristic appearance develops. In from twenty-four to forty- 

 eight hours, the liquid remaining limpid, flakes appear underneath 

 the surface, forming little islands of growth, which in the next 

 twenty-four to forty-eight hours grow into a jungle of long stalactite 



Fig. 232. — Bacillus pestis. Involution forms from a pure culture on 3 per 

 cent, sodium chlorid agar-agar. Methylene-blue (Kolle and Wassermann). 



like masses, the liquid remaining clear. In from four to six days 

 these islands become still more compact. If the vessels be dis- 

 turbed, they fall like snow an.d are deposited at the bottom, leaving 

 the liquid clear. 



Colonies. — Upon gelatin plates at 2 2°C. the colonies may be 

 observed in twenty-four hours by the naked eye. They are pure 

 * "Brit. Med. Jour.," June 12, 1897, p. 1461. 



