Staining 



at the center, so as to resemble a dumb-bell or diplococcus. 

 The bacilli sometimes appears vacuolated, and nearly all 

 cultures show a variety of involution forms. Kitasato has 

 compared the general appearance of the bacillus to that of 

 chicken-cholera. 



Involution forms on partly desiccated agar-agar not 

 containing glycerin are said by Haffkine to be characteris- 

 tic. The microbes swell and form large, round, oval, pea- 

 or spindle-shape or biscuit-like bodies which may attain 

 twenty times the normal size and in growing gradually lose 

 the ability to take up the stain. Such involution forms 

 are not seen in liquid culture. 



Fig. 166. Bacilli of plague and phagocytes, from human lymphatic 

 gland. X 800 (Aoyama). 



Ogata * states that while Kitasato found the bacillus in the 

 blood of cadavers, Yersin seldom found it in the blood, but 

 always in the enlarged lymphatic glands; that Kitasato 's 

 bacillus retains the color when stained by Gram's method; 

 Yersin's does not ; that Kitasato's bacillus is motile, Yersin's 

 non-motile; that the colonies of Kitasato's bacillus, when 

 grown upon agar, are round, irregular, grayish-white with 

 a bluish tint, and resemble glass-wool when slightly mag- 

 nified; those of Yersin's bacillus, white and transparent, 



* "Centralbl. f. Bakt. u. Parasitenk.," June 24, 1897, Bd. xxi, Nos. 

 20 and 21. 



