294 ORIENTAL PLAGUE chap. 



had been originally derived from the bubo of a fatal 

 case of bubonic plague in a man in Cardiff in 1901. The 

 strain had been kept up in the laboratory by continued 

 subcultures till the commencement of this year, when it 

 was used for infecting rats. A trace of an agar culture of 

 recent date (forty-eight hours at 37° C.) inoculated into a 

 superficial incision of the skin of a rat caused typical 

 fatal plague within three days. The culture actually used 

 in the experiments to be described here was derived from 

 the spleen of a rat dead on March 23, 1904, which rat 

 had been cutaneously inoculated on March 20, 1904. In 

 all our tests, of a forty -eight hours old agar culture — 

 copious growth over the whole of the sloped surface 

 (6 centimetres by 2 centimetres) — an emulsion was made 

 with sterile distilled water. The emulsion was a strongly 

 turbid fluid. A single platinum loop of this emulsion 

 spread over a sloped agar surface brought forth innumer- 

 able colonies of the B. pestis. In all instances to 5 cc. 

 of the disinfectant contained in a sterile test tube, 5 

 drops (from a definite drop bottle) of the plague emulsion 

 were added and well shaken, and after the required time 

 of exposure cultures were made ; in all instances three 

 loops of the medicated fluid being spread out over a 

 sloped surface of gelatine or agar, or added to nutrient 

 broth, as the case might be. The culture tubes were then 

 incubated at 21° C. (gelatine), or at 37° C. (agar or broth), 

 and inspected from time to time until for some days no 

 further change was noticeable. Amongst the several 

 dozen cultures thus made, in no single instance was there 

 any accidental or stray microbe observed ; the tubes 

 contained either no growth at all, or they contained 

 colonies of the B. pestis in pure culture only, in varying 



