264 ORIENTAL PLAGUE chap. 



ditions, decanted, sealed, and sterilised at the same time) 

 I have generally inoculated four rats, each being made 

 to receive subcutaneously 10 cc. of the finished product. 

 Except in the earliest experiments, white rats, half to 

 full grown, have been employed, as I find these highly 

 susceptible to plague, much easier to handle, and less 

 liable to accidental and spontaneous death than the brown 

 (wild) sewer or house rat. 



Eight to ten days (on occasion twelve days) after this 

 injection with the prophylactic the prepared rats, together 

 with two fresh or unprepared rats, are injected with living 

 plague culture, in amount sufficient to cause death from 

 typical plague in both controls, while permitting the 

 prepared rats to remain (if protected) alive. As a result 

 of my experience in the above sense of a considerable 

 number of brews of the prophylactic on a considerable 

 number of rats, I am prepared emphatically to maintain 

 that 10 cc. of the HafTkine prophylactic is capable of fully 

 protecting a rat (half-grown to adult) against a subsequent 

 injection of a dose of living plague culture that acts 

 lethally without fail on control rats. And a similar 

 experience was obtained in association with M. HafTkine, 

 when he and I tested on rats the prophylactic brought 

 by him from Bombay, viz. those which received an 

 injection of 10 cc. of the prophylactic withstood sub- 

 sequent infection with living culture of B. pestis. 



It is not necessary to detail all the above experiments 

 that were made on the rats with the prophylactic prepared 

 by me here in London. I have already given their general 

 purport, and I therefore proceed to describe the equally 

 satisfactory results which I obtained with the sterilised 

 bacillary bodies from the prophylactic, as also the results 



