viii AGGLUTINATION OF B. PESTIS 239 



tested on July 15, i.e. after the second subcutaneous 

 injection with Haffkine's prophylactic. 



100 cubic millimetres of plague emulsion mixed with 

 100 cubic millimetres of its blood serum |were injected 

 into guinea-pig No. 9. 



This animal, No. 9, died on the fourth day of typical 

 plague. 



The test was repeated on July 31, i.e. thirteen days after 

 the third injection of 10 cc. of Haffkine's prophylactic. 



100 cubic millimetres of plague emulsion mixed with 

 100 cubic millimetres of the blood serum were injected 

 into guinea-pig No. 23 ; and at the same time 100 cubic 

 millimetres of the emulsion alone were injected into 

 control guinea-pig No. 24. 



The control, No. 24, died on the eighth day, the other 

 guinea-pig, No. 23, died on the twelfth day. 



The test was repeated on August 26, again with 

 negative result. 



Babbit No. 5. — The blood serum of this rabbit was 

 tested on three different occasions — July 16, July 31, 

 and August 26. But, as was the case with rabbit 

 No. 3, the result proved negative in all three instances. 



As regards rabbits Nos. 3 and 5, the test on the last 

 occasion, viz. August 26, was altered in this way. In- 

 stead of mixing equal parts of plague emulsion and blood 

 serum, a double volume of blood serum was used, viz. 

 100 cubic millimetres of plague emulsion were mixed with 

 200 cubic millimetres of blood serum. The guinea-pigs 

 injected with the mixture died, notwithstanding, of typical 

 plague. 



From these experiments it follows that, as with the 

 guinea-pig so with the rabbit, neither repeated intra- 



