24 



The growth in the streak cultures was better than in the stabs. Even 

 on the best gelatin and when large loops of fresh fluid cultures were 

 used the streaks came up rather slowly, i. e. , in 3 to 5 days, at 18"^ to 

 24° C. When 2 weeks old, these streaks were usually 2 to 3 mm. 

 wide and 4 to 5 cm. long. The growth was pale yellow, not very 

 dense, finely granular under Zeiss X 6 aplanat, and often fine crenulate- 

 serrate along the margins. The streaks were made with a medium - 

 sized oese (2 mm. diameter), and the germs did not show much tend- 

 enc}^ to spread beyond the original streak. 



In streak cultures on stock 205 a much better growth was obtained 

 than with concomitant cultures of Ps. cmnpestris^ Ps. 2>^^^^^<^oli^ oi' 

 Bacilhis tracheijphilus. In 14 days, at 22° to 24° C , the streaks were 

 about 2 mm. by 5 cm. with fine crenuhite-serrate margins; the surface 

 was very pale yellow and finely granular under Zeiss aplanat. There 

 was no liquefaction at this date, but 6 weeks later all of the gelatin 

 (10 c. c.) was fluid except a little in the bottom of the tubes and in the 

 extreme top of the slant, and there was a moderate amount of pale 

 yellow precipitate. During this period the tubes were in a cool box 

 at approximately 20° to 24° C. 



Some interesting results were obtained with the malic acid gelatins. 

 They did not inhibit growth, as fluids of the same grade of acidit}^ 

 would have done, and in the +36 gelatin growth was not retarded. 

 In the +48 and +54 gelatin growth was slightly retarded at first, and 

 in the depths of the latter it was never as vigorous as in the less acid 

 media, the separate colonies in the lower parts of the stabs always 

 remaining smaller. After a time, however, the growth in the upper 

 part of the stab and on the surface of the +48 and +54 gelatin out- 

 stripped that in the +36. On the fifth day there was most growth in 

 the +36 gelatin and least in the +54. On the eighth day the retarding 

 influence was still idsible in the +54 gelatin. Subsequently it was 

 overcome except in the depths. Two other interesting differences 

 were observed. In 56 days, at 17° to 20° C, there was no liquefac- 

 tion whatever in the +36 gelatin, and the color of the organism was a 

 very pale yellow. In the -f 48 and +54 gelatins, on the contrary, the 

 surface growth was bright yellow, and liquefaction set in at the end of 

 the third week, involving the upper ~)ne-third of the 10 c. c. of gelatin 

 in the course of the next 10 or 12 days. At the end of 56 days two- 

 thirds to three-fourths of the gelatin in these tubes had liquefied. 



A repetition of the tests with the +36 gelatin gave no different results. 

 In 40 days, at 8° to 20° C. (mostly under 15°), there was no liquefac- 

 tion and no bright yellow color, although the stab was well developed 

 and the surface growth was 7 by 8 mm. in breadth. Additional cul- 

 tures in the +48 and +54 gelatin 3nelded no new or different results. 

 After 40 days there was an abundant l)right-yellow growth, and the 

 upper one-third of the gelatin was liquefied to the walls. The remain- 



