i THE ESSENTIAL CAUSE 3 



inasmuch as Yersin's account is all throughout consistent, 

 whereas Kitasato's earlier account appears somewhat at 

 variance with his later statement, and it is for these 

 reasons that an undesirable confusion has arisen in the 

 minds of some later observers. Thus Aoyama ( Centralblatt 

 f. Bakter. und Parasit. xix. 481), while confirming 

 Yersin's B. pestis as the microbe of plague, denies to 

 Kitasato's bacillus this same claim. We shall show that 

 Kitasato's bacillus of his later account is the B. pestis, but 

 under a modification, being a different type of the plague 

 microbe. 



As mentioned just now, bacteriologists in all countries 

 who have had the opportunity of becoming acquainted 

 with, and who have carefully investigated the nature and 

 character of B. pestis in man, and in the rat, affected with 

 plague, have confirmed Yersin's and Kitasato's discovery, 

 that the B. pestis is the specific microbe of Oriental 

 plague. 



The distribution of the B. pestis in the affected body, 

 both of man and the rat, under natural conditions, is 

 subject to certain slight variations, which are dependent, 

 in a large measure, on the various forms under which 

 plague declares itself. We proceed to consider in detail 

 these variations. 



I. In Man 



(A) Pestis bubonica. — The most common form, as 

 admitted on all sides, is the bubonic form, i.e. the one 

 associated with conspicuous swelling and inflammation of 

 the lymph glands, with oedema, haemorrhage, and inflamma- 

 tion of the subcutaneous tissue around the glands ; both 

 together forming a painful, large, more or less soft " bubo." 



