88 BACILLUS PESTIS BUBONIC^E 



centre, often presents the appearance of a diplo- 

 coccus or figure-of-eight bacillus. Some examples 

 of this polar staining can be seen in the figure. It 

 is lion- motile, occurs occasionally in short chains, is 

 frequently capsulated, and does not stain by Gram's 

 method. 



It can be cultivated on glycerine-agar and in 

 bouillon at 37 C. moderately well, but grows slowly 

 and without liquefaction on gelatine at 21 C. In 

 this medium typical thread-like colonies resembling 

 Proteus Vulgaris are produced (Klein). 



Preparation Fig. 92 is made from a young agar 

 culture, and shows an organism resembling that 

 from the tissues. In bouillon it assumes an almost 

 streptococcus form, and all cultures are very prone 

 to produce involution forms. 



Animals can be protected against inoculations of 

 the bacillus, and the blood serum of these immunised 

 animals is both protective and therapeutic. The 

 serum also appears to possess agglutinating proper- 

 ties similar to those described under B. Typhosus. 

 Protection can be afforded by the inoculation of 

 sterilised cultures, and, in man, vaccination by this 

 method has been very largely employed to secure 

 protection. 



