112 ORIENTAL PLAGUE chap. 



On several occasions I have tested for the Board 1 the 

 efficacy 'of the HafFkine plague prophylactic. This was 

 done on rats, for the reason that Professor Haffkine and 

 I had ascertained that subcutaneous injection of 10 cc. of 

 his prophylactic fluid is uniformly efficacious in pro- 

 tecting a full-grown rat against a subsequent injection 

 of a large (multiple fatal) dose of virulent culture of 

 B. pestis. The samples of prophylactic fluid tested 

 comprised a batch prepared by Professor HafFkine in 

 Bombay and a batch prepared by me in London. 



A number (ten) of rats 2 were injected subcutaneously 

 in the groin with plague prophylactic, 10 cc. per 

 animal. 



All these animals appeared on next and subsequent 

 days lively and fed well; but all exhibited tumour in 

 the groin. After three weeks, during which time the 

 animals remained quite well, the initial tumour having 

 for some days completely disappeared, all of them were 

 inoculated cutaneously with the tissue of the bubo of 

 a rat that had died in three days of typical acute plague 

 after inoculation with culture of L.P. I. 8 The juice of 

 this bubo was crammed with B. pestis. At the same 

 time, and with the same material, one control rat was 

 inoculated also cutaneously. This control rat died within 

 three days with typical plague ; but all the " protected " 

 rats appeared lively and feeding well, and they remained 

 so. At the end of the week these animals, being 

 seemingly normal, were killed. On post-mortem examina- 



1 Report of the Medical Officer of the Local Government Board, 1903-1904, 

 p. 371 and passim. 



2 In all these experiments tame (white) rats were used, for reasons which 

 were stated on a former page, viz. that white rats are highly susceptible to plague, 

 are easier to be kept in cages, and easier also to handle. 



3 London Plague of 1896. 



