viii AGGLUTINATION OF B. PESTIS 237 



day ; the other, No. 28, died of plague on the ninth 

 day. 



(3) September 12. — Guinea-pig No. 35 was sub- 

 cutaneously injected with 100 cubic millimetres of living 

 plague emulsion mixed with 100 cubic millimetres of 

 blood serum. At the same time 100 cubic millimetres 

 of the same emulsion were injected into a control guinea- 



The guinea-pig No. 35 died of plague on the fifth 

 day ; the control guinea - pig died of plague on the 

 seventh day. 



From this series confirmation of the previous result is 

 obtained, viz. that even after several injections of living 

 cultures into the peritoneum of the guinea-pig no appreci- 

 able amounts of germicidal substances are present in the 

 blood of the protected animal. 



Seeing, then, that no germicidal effect can be produced 

 with the blood serum of guinea-pigs repeatedly injected 

 with living culture, it was not to be expected that a 

 positive effect could be produced with the blood serum of 

 guinea-pigs repeatedly injected with the Haffkine pro- 

 phylactic. But, nevertheless, experiments as to this were 

 actually made, as follows : — 



Guinea-pig No. 5, already mentioned (p. 218) as 

 having been injected subcutaneously with Haffkine's pro- 

 phylactic on seven separate occasions, furnished blood 

 serum which was tested for the presence of germicidal 

 substance twelve days after the fourth injection, and 

 again fourteen days after the sixth injection. The result 

 in both instances was negative. 



Guinea-pig No. 7, referred to at p. 219 as having 

 been injected intraperitoneally on eight separate occasions 



