77 



words, there was no growth in the oxygen- free vacuum; and 9 days' 

 exposure to it while not killing all of the organisms probably killed 

 many of them, since subsequent growth in the air was distinctly 

 retarded. 



Cultures of J-*s. stewarti and of Bacillus amylovoms were also 

 exposed to this vacuum. Bacillus amylovorus was inoculated on ordi- 

 nary slant beef extract peptone agar. On this substratum, which 

 probably contained a little muscle sugar, it made a slight but distinct 

 growth. The check tube developed promptly, and made a good white 

 growth the whole length of the streak. The growth in vacuo was 

 about one-tenth to one-fifteenth as much as in the air. The 4 check 

 tubes of Ps. stewarti (2 coconut, 2 potato) developed a distinct buff 

 yellow -growth within 48 hours. The 4 tubes in vacuo made no growth 

 whatever during the 9 days' exposure, and after removal to the air 

 growth in each one was even more distinctly retarded than in case of 

 Ps. hyacinthi. 



(2) The second test was made in the same manner as the first, except 

 that the vacuum was not so complete and the remnant of oxygen was 

 not removed. The experiment was begun March 8, and the seal was 

 broken March 20. The mercury in the cistern barometer was down to 

 3 inches when the jar was sealed, and the vacuum kept quite well. 

 The temperature during the experiment was 16° to 25'-' C. (mostly 20° 

 to 22° C). 



Four organisms were tried in this jar, Ps. liyacinthi., Ps. campestris., 

 Ps. stewarti^ and Bacilkis carotovorus. The media used were carrot 

 (stock 402), alkaline beef broth (stock 382), coconut (stock 412), and 

 potato (stock 406). All of the check tubes but one made a "feeble" 

 to "good" growth within 48 hours, and all showed a "good growth" 

 at the end of the third day except one tube of Ps. hyacinthi on potato, 

 which lagged and was doubtful, but which 2 days later showed the 

 typical yellow growth over about 4 sq. cm. The tubes in the vacuum 

 were distinctly different. On the fifth day Ps. hyacinthi showed some 

 growth on coconut and potato, but it was not as yellow as in the air. 

 The same was true of Ps. campestris and Ps. steivarti. Each showed 

 some growth, and neither was as yellow as in the checks. On the 

 eighth day the mercury stood at 3f inches, and none of the potato 

 cylinders were grayed. The condition on the twelfth day (March 20), 

 when the seal was broken, and on subsequent days, was as follows: 



Ps. hyacinthi: 



(a) Carrot. — March 20, no visible growth (there was no check upon this tube); 

 March 23, no growth; March .31, no growth; April 5, a smooth, wet-shining, trans- 

 lucent growth now covers the whole exposed surface of the carrot, and the precipi- 

 tate is yellow; April 17, slime and fluid distinctly acid. 



(b) Beef broth. — March 20, fluid clear, precipitate very slight (2 mm. broad), 

 colorless; no rim, no pellicle, iio zoogloeee; March 23, feebly clouded; March 31, well 

 clouded. 



