38 



[Vol. 10 



GARDEN 



left in the closed arm. Inoculation was made in the 



manner, using invigorated 



room 



o 



C. Gas production took 



kept 



but 3 of the cultures (Exp. "B", table v) as was evidenced by the 

 accumulation of from 1 to 8 or 9 per cent of a gas in the closed 

 arm. Only very slight increases in the volume of the gas present 

 occurred after the end of the first week. During the first 4 to 

 6 days there was just about as much growth in the closed arm 

 of the tubes as in the open arm. 



Still another test of the gas-producing capacity of the black- 

 leg strains was made, using agar shake cultures. Small amounts 

 of gas were produced by all the strains tested (Exp. "C", table 

 v), as was evidenced by the development of a greater or less 

 number of bubbles in the medium. 



The appearance of gas bubbles in 1-day-old glucose agar slant 

 cultures suggested the use of this type of test. A 0.75 per cent 

 meat extract agar was used. The reaction of this medium was 

 not adjusted. To this was added 1 per cent of the carbohydrate 

 to be investigated. The medium was melted, cooled to 42° C, 

 and inoculated with 3-mm. loops of invigorated broth cultures. 

 The inoculum was thoroughly mixed and the medium aerated 

 by a vigorous rolling between the hands. The cultures thus made 

 were set aside in a vertical position to cool and were incubated at 

 27-28° C. In this type of culture it was found that there was 

 little increase in the volume of gas produced later than the sec- 

 ond day after inoculation, as evidenced by the number and size 

 of the bubbles. 



In following up this line of experimental work it was later 

 determined that when agar shake cultures were sealed with 

 paraffin a somewhat greater volume of gas was demonstrable, as 

 evidenced by the increased number and size of the bubbles in 

 the medium. What is even more significant: It was found 

 that the cultivation of a particular strain (or strains) in the 

 presence of a certain carbohydrate increased its powers to fer- 

 ment that carbohydrate with the production of gas. In this 

 way certain strains which at first produced gas very weakly, if 

 at all, were "trained up" to ferment the particular carbohydrate 

 in question more vigorously, as was evidenced by the produc- 

 tion of larger and larger volumes of gas. 



Diastatic action. — Absent. 



