552 PATHOGENIC BACTERIA. 



bonic Plague" (Government Printing Office, Washington, 

 D. C. , 1900), finds it convenient to divide plague into {a) 

 bubonic or ganglionic ; (b) septicemic ; and (c) pneu- 

 monic forms. Of these the bubonic form is most frequent 

 and the pneumonic form most fatal. 



The infection usually takes place through some periph- 

 eral lesion, but may occur by inhalation of the specific 

 organisms. 



The bacillus of bubonic plague (Fig. 126) seems to 

 have met an independent discovery at the hands of 



•« r* 1 ■*■•%. 



Fig. 126. — Bacillus of bubonic plague (Yersin). 



Yersin and Kitasato in the summer of 1894, during the 

 activity of the plague then raging at Hong-Kong. There 

 seems to be but little doubt that the micro-organisms 

 described by the two observers are identical. 



The bacillus is short and thick — a cocco-bacillus, as 

 some call it — with round ends. Its size is small {zft in 

 length) and its form is subject to considerable variation. 

 It not infrequently occurs in chains of four or six or 

 even more, and is occasionally encapsulated. It shows 

 active Brownian movements, which probably led Kitasato 

 to consider it motile, while Yersin did not. Gordon ! 

 found that some at least of the bacilli have flagella. It 



1 Centralbl. f. Bakt. u. Parasitenk., Sept. 6, 1897, Bd. xxii., Nos. 6 and 7, 

 p. 170. 



