

viii AGGLUTINATION OF B. PESTIS 231 



these " prepared " animals is not in a direct ratio to the 

 amount of material injected, or to the number of the 

 different injections. It appears to go on increasing up 

 to a certain degree, and then to decrease or be lost 

 entirely. 



4. The repeated administration of Haffkine's pro- 

 phylactic into guinea-pigs, when injected subcutaneously, 

 produced no agglutinin in the blood ; whereas the 

 repeated intraperitoneal injection of the prophylactic 

 into guinea-pigs appears to have produced agglutinin 

 which, however, was soon lost, even during continuance 

 of "treatment." 



5. In the rabbit, on the other hand, the repeated 

 injection (intravenous, less when subcutaneous) of 

 Haffkine's prophylactic did produce agglutinins at one 

 or another stage, although on the whole such production 

 was uncertain. 



6. In the rat the repeated injection subcutaneously of 

 Haffkine's prophylactic failed to produce agglutinin. 



7. The repeated injection (in whatever way) of the 

 filtrate of Haffkine's prophylactic into rodents (guinea- 

 pigs, rabbits, rats) failed to produce agglutinins. 



Besides the experiments on agglutinins above sum- 

 marised, investigation has been made of the power of the 

 blood serum of guinea-pigs and rabbits, and in a few 

 instances also of rats, previously immunised in various 

 ways, in inhibiting the action of the living B. pestis, 

 when such serum along with a lethal dose of plague was 

 injected into a susceptible or unprepared animal. In 

 other words, account having been given of the agglutina- 

 tion or test in vitro, what follows will deal with Pfeiffer's 

 test or the test in corpore. 



