260 OMENTAL PLAGUE chap. 



and then injected intraperitoneally ; and injection in 

 this way was repeated in the same amount on May 22 

 and on June 5. The animal was then injected intra- 

 peritoneally with small doses of living culture on eight 

 separate occasions. Finally, on December 28, it was 

 injected subcutaneously with an ordinary lethal dose of 

 living culture. The animal remained alive, but it 

 developed a fair bubo, which suppurated and healed up 

 in about a fortnight. 



On May 15, 1901 — a year, that is, after the first 

 injection — it was injected, for the thirteenth time, sub- 

 cutaneously with an ordinary lethal dose of plague 

 material. The animal remained alive and fairly lively, 

 and it fed well, but it again developed a bubo in the 

 inguinal region which extended on to the thigh and 

 became nearly as big as a pigeon's egg. This bubo 

 suppurated by the end of a week, and had not quite 

 healed by the end of a fortnight. 



This is by no means an isolated instance as regards 

 the guinea-pig. I have had several such cases in 

 1896-1897 (see my Eeport to the Local Government 

 Board), and I have quite a number of similar in- 

 stances in the present investigation. All show that 

 a high degree of immunity in the guinea-pig does not 

 exist even after a good many previous injections of 

 sterilised and also living plague bacilli. The animals 

 acquire no doubt a certain resistance against fatal in- 

 fection, but this resistance does not prevent the develop- 

 ment of a well-marked bubo with living bacilli in the 

 early stages. 



In view of this experience, it was not to be expected 

 that the injection of the Haffkine prophylactic could 



