404 M. R. SMIRNOW 



in five of the eight organisms in the first culture tube, and prac- 

 tically none thereafter. Dextrin, on the other hand, showed 

 the greatest variation in its effect upon the different strains 

 of B. coll. Strain no. 1 gave no indol throughout the experiment; 

 both nos. 5 and 6 gave a single trace in the first culture but none 

 thereafter, whereas no. 7 gave a trace in each sub-culture up 

 to the tenth, at which time the experiment was discontinued. 

 Maltose and mannite appear to have a more pronounced in- 

 hibitory effect upon indol formation than either glucose, lactose 

 or saccharose and would stand intermediate between them and 

 galactose. 



Experiments were undertaken to determine the permanency 

 of this change in biological activities using the same technique 

 as previously described. The bacteria, after being carried 

 through the carbohydrate peptone media for at least seven 

 transfers, were then inoculated into plain peptone, making suc- 

 cessive transfers until three consecutive positive indol tests 

 were obtained. 



By referring to Table XI, the most striking difference is seen 

 between the action of glucose and dextrin. In the case of glu- 

 cose the indol reaction reappeared only in the cases of B. coli nos. 

 1, 2, 5 and 7, and the cholera spirillum, the others remaining 

 negative up to the tenth transfer in plain peptone, at which 

 time the experiment was discontinued. For some unexplained 

 reason, the re-appearance of the property of indol formation 

 was slower and less marked in this set of experiments than on 

 previous occasions. When contrasted with the action of dex- 

 trin, a marked difference is seen. This substance permits a 

 prompt return of the indol producing property in the first trans- 

 fer of the different strains of bacteria used, with the exception 

 of B. coli nos. 1 and 2, and the cholera spirillum. Inasmuch 

 as this peculiarity was evident in each of the sugars, it would 

 appear that it was not due to the carbohydrate, but to a pos- 

 sible greater susceptibility on the part of these strains of bac- 

 teria. B. coli nos. 3, 4, 5, 6 and 7 gave positive indol tests on 

 the third or fourth transfers quite uniformly in all sugars except 

 glucose as already mentioned. It may be concluded that dex- 

 trin acts entirely unlike the other carbohydrates, having, in 



