230 ORIENTAL PLAGUE chap. 



receiving 8 or 10 cc. ; that is to say, two full-grown 

 animals received each 10 cc, other two half-grown 8 cc. 

 in each instance. 



On February 5 one of the small animals was killed 

 and its blood serum tested (dilutions 1 : 20 and 1 : 10), 

 with negative result in one hour. 



It follows from these experiments that injection into 

 rats of Haffkine's prophylactic in amount more than 

 sufficient to protect them against a fatal dose does not 

 cause the production in their blood of any agglutinins. 



14. In this experiment three rats were subcutaneously 

 injected with the filtrate of Haffkine's prophylactic, each 

 animal receiving 10 cc. on November 21 and other 10 cc. 

 on December 31. 



Their blood serum was tested on February 2 (dilu- 

 tion 1:20 and 1:10), with completely negative result. 

 This result was to be expected, considering that the 

 injection of the prophylactic as such did not in previous 

 experiments produce agglutinins. 



The results, then, of the numerous experiments here 

 described can be thus summarised : — 



1. The blood of rodents (guinea-pigs, rabbits, rats) 

 which have been repeatedly injected with large masses of 

 the sterilised bodies of B. pestis possesses the power of 

 agglutinating a duly prepared emulsion of the B. pestis. 

 Especially in rabbits is this manifest. 



2. The same agglutinating action is observed with 

 respect to the blood of rodents which having been injected 

 with sub -fatal doses of living plague bacilli had as a 

 consequence been affected with the disease and recovered 

 from it. 



3. The increase in agglutinating action of the blood of 



