CH. IX] OF TRANSMUTATION 127 



at 37° C. after plating. The filtrate was then inoculated with 

 a 48 hours' growth of B. typhosm isolated from the stool of a 

 carrier " " and a week later plated out on bile salt neutral 

 red lactose agar. Two or three colonies were examined. One 

 gave the typical reactions of B. typhosus but two other 

 colonies failed to agglutinate with typhoid serum and cor- 

 responded in their reactions to B. faeccdis alecdigenes. One 

 week later the latter organism alone was found and it 

 persisted unchanged for several months afterwards. 



Criticism. The same criticism applies to this experiment. 

 The original strain was not grown from a single organism. 

 "A particle," we are told, of the growth was added to the 

 solution, sufficient to yield 480 million bacteria to each cubic 

 centimetre. The purity of such a strain cannot be guaranteed. 

 The original culture was derived from a stool and it is said 

 to have yielded an organism closely resembling B. faecalis 

 alcaligenes. The experiment was however repeated twice 

 over with a laboratoiy strain with the same result — a fact 

 which considerably discounts this objection. The new strain 

 might, again, be regarded as a variant of the original B. 

 typhosus which, as a result of growth under conditions 

 inimical to its vitality, had suffered a loss of power with 

 respect to its fermenting properties and also its property of 

 agglutinating with typhoid serum. Its other agglutinative 

 characters were not examined, but a similar organism obtained 

 in the same manner from a laboratory strain was found to 

 possess slight power of absorbing agglutinins from antityphoid 

 serum. The new strain was, however, further tested (" culture 

 33 " page 242) by being alternately passed through the peri- 

 toneal cavity of a guineapig and subcultured on agar. In one 

 experiment, after the 3rd passage, the peritoneal fluid removed 

 at the end of 6 hours contained B. coli, but the fluid removed 

 at the end of 12 hours contained not B. coli but the new 

 strain of B. faecalis alcaligenes which had been injected. 



Only three passages were made — the investigation, that is 

 to say, was not persisted in long enough to decide whether 

 the new strain was capable of reverting or not. 



The recovery of B. coli after the 3rd passage Major 



