BUBONIC PLAGUE. 



553 



is an aerobic organism. No spores are formed. It 

 stains well by the usual methods ; not by Gram's method. 

 When stained the organism appears darker at the ends 

 than at the centre, so as to resemble a dumb-bell ordiplo- 

 coccns. The bacilli sometimes appear vacuolated and in 

 old cultures show a variety of involntion-forms. Kitasato 

 has compared the bacillus to that of chicken cholera. 



In his studies of plague, Ogata 1 states that while 

 Kitasato found the bacillus which he described in the 

 blood of cadavers, Yersin seldom found his bacillus in 



Fig. 127. — Bacilli of plague and phagocytes; x 800. From human lymphatic 



gland (Aoyama). 



the blood, but always in the enlarged lymphatic glands. 

 Kitasato's bacillus retains the color when stained by 

 Gram's method; Yersin's does not. Kitasato's bacillus 

 is motile; Yersin's, non-motile. The colonies of Kita- 

 sato's bacillus when grown upon agar are round, irreg- 

 ular, grayish-white with a bluish tint, and resemble glass- 

 wool when slightly magnified; Yersin's bacillus forms 

 white, transparent colonies with iridescent edges. Ogata, 

 in the investigation of the cases that came into his hands, 



1 Centralbl. f. Bakt. u. Parasitenk., June 24, 1 897, Bd. xxi., Nos. 20 

 and 21. 



