236 BACILLI OF THE HEMORRHAGIC SEPTICEMIA GROUP 



cause them to appear like filaments. Involution forms are also liable 

 to present themselves early in a similar manner even on favorable 

 media. 



The plague bacillus is decolorized by Gram's method. When 

 grown in the animal body the bacillus possesses a capsule, which, 



FIG. 127 



Postmortem smear from the spleen in a case of bubonic plague, showing polar staining. 

 (Author's preparation.) 



FIG. 128 



FIG. 129 



Postmortem smear from a case of plague 

 pneumonia, showing polar staining. 

 (Author's preparation.) 



Cover-glass preparation from a twenty- 

 four-hour-old agar plague culture, stained 

 with dilute carbol-fuchsin, showing very 

 small bacilli, with rounded ends. (Author's 

 preparation.) 



however, is difficult to demonstrate unless thin spreads are prepared 

 and fixed with great care in alcohol. There is nothing characteristic 

 in the capsule, so its exhibition will not assist in the microscopic 

 diagnosis. The bacilli are not motile, do not possess flagella, nor 



