VIII 



AGGLUTINATION OF B. PESTIS 



229 



Haffkine's prophylactic, 10 cc. subcutaneously injected) 

 and were then injected with more than an ordinary fatal 

 dose of living culture of the plague bacillus, developed a 

 distinct bubo which suppurated. This after some days 

 healed completely, and the animals' blood tested along 

 with salt emulsion of gelatine culture showed in a con- 

 spicuous degree agglutination (dilutions 1 : 20 and 1 : 40) 

 in ten minutes. I have had occasion to repeat this 

 experiment on other rats which had passed through a 

 non-fatal attack of plague, and have been able fully to 

 confirm it. 



12. In this experiment three rats were injected sub- 

 cutaneously with Haffkine's prophylactic, each animal 

 receiving 10 cc. : — 



As was ascertained from the experiments carried out 

 in conjunction with Prof. HafFkine in 1899, a single 

 injection of 10 cc. of this prophylactic into rats suffices 

 to give them protection against an otherwise fatal dose of 

 living plague. In the present instance no further injection 

 beyond the above 20 cc. was employed. The blood serum 

 of one of the rats (after the animal had been killed) was 

 tested (dilution 1 : 20) on January 30, and it showed no 

 distinct agglutination within one hour. 



13. Four rats were injected on December 31 sub- 

 cutaneously with Haffkine's prophylactic, each animal 



