21 



trace of typhoid serum of a prepared rabbit, just like a 

 similar gelatine culture of the laboratory B. typhosus kept 

 and tested for control. 



Subcultures from the Drigalski plate in the different media 

 (neutral red broth, litmus milk, MacConkey fluid, lactose 

 litmus peptone, shake gelatine, phenol-broth, Proskauer and 

 Capaldi I and II) are made ; if there were any doubt about 

 a colony, further similar subcultures are made in each 

 series of oysters from the Drigalski plates of the first and 

 last oyster, and occasionally in addition from one or the other 

 in the middle of the series. Intraperitoneal injection of 

 guinea-pigs with a given dose (J-^o or ^ ess ) ^ a ^4 hours' 

 old agar culture was practised for testing the virulence of 

 the microbe, generally only of the first and last oyster of the 

 series from which the microbe was recovered, and in all cases 

 it was found to have retained its full virulence. 



EXPEEIMENT I. 



Clean Burnham Oysters. These were obtained from one 

 of the foremost oyster shops in the City. The oysters were 

 thoroughly cleaned on the outside of the shell, and one was 

 used for a preliminary test by means of a Drigalski plate for 

 the presence of B. coli and for that of blue colonies, the rest 

 were placed in a clean wooden tub * in 2000 c.c. of clean sea 

 water. The tubs used were oval in shape and could hold 

 easily 12-16 natives in one layer ; the sea water was always 

 sterilised by heat (90-100 C.), and after cooling well and 

 repeatedly shaken up with air. As a matter of routine we 

 always prepared the 2000 c.c. of sterile sea water the day 

 previous to using it. Having ascertained after 24 hours' 

 incubation at 37 C. by the Drigalski plate that the test 

 oyster was clean, we now proceeded to infect twelve of the 



* Each tub after having been used was well brushed under the hot 

 water tap, and was then kept filled with the hot water 80 C. for some 

 time (hours). This process was, as a rule, repeated on two or even three 

 subsequent days. In the later experiments the tubs were even " steamed " 

 before being used again. 



