1923] 



JENNISON — POTATO BLACKLEG 35 



As was stated in an earlier paragraph, the several students of 

 the blackleg bacillus differ in their published observations and 

 conclusions as to the gas- and acid-producing capacity of differ- 

 ent isolations of this parasite. This fact is clearly shown in the 

 tabular summary presented herewith (table vi). 



The results of the writer's fermentation studies are briefly 

 summarized in table iv. The data presented here lead to the con- 

 clusion that the several strains of the organism studied (except 

 No. 191) are similar and that all produce small quantities of gas 

 and considerable acid from dextrose, lactose, and sucrose, but 

 no acid or gas from glycerin or potato starch. 



In the course of his studies the writer determined that some 

 of the strains at hand produced gas and acid from fructose, galac- 

 tose, and maltose as well (compare with results of quantitative 

 experiments on carbohydrate consumption). 



Among other things, it was determined that the gas-producing 

 function of the blackleg bacillus varies, depending upon (1) oxy- 

 gen relations, (2) the length of time cultivated in the presence of 

 a sugar, (3) the composition of the culture medium, etc., more 

 than upon the particular strain or strains of the organisms under 

 observation. In one experiment (Exp. "A", table v) only the mi- 

 nutest volumes of gas collected in the closed arm of 3 of the tubes 

 (lactose) out of a total of 90 inoculated (30 of lactose alone). In 

 this set 1 per cent of the carbohydrate was added to Dunham's so- 

 lution (the reaction was not adjusted) and distributed in fermen- 

 tation tubes. The tubes were heated in streaming steam until the 

 air dissolved in the solution had been expanded and driven out. 

 The bubble which collected in the top of the closed arm of the 

 tubes was carefully tilted off before the set was autoclaved. Small 

 bubbles found in the closed arm of 2 of the tubes upon removal 

 from the autoclave were tilted off. Invigorated cultures were used 

 for inoculation, and this was accomplished in the usual manner 

 as soon as the culture medium was cooled. The cultures were 

 incubated at 27-28° C. A feeble to moderate growth developed 

 in the closed arm of all tubes containing glucose, lactose, and su- 

 crose, also in tubes under observation containing fructose, galac- 

 tose, maltose, but not in closed arms of tubes containing glycerin, 

 dextrin, and potato starch. Under the circumstances it may 

 be concluded that the strains of the blackleg bacillus under ob- 

 servation grow anaerobically only when they obtain sufficient 



