79 



that in check tube. March 23, a very thin, pale buff-yellow growth covers 4 to 5 

 sq. cm; the slime is very pale yellow for the amount of growth; the potato in the 

 air begins to gray. March 31, growth feeble. 



Growth in Hydrogen. 



Two tests were made in hydrogen. The gas was prepared by the 

 action of zinc on c. p. sulphuric acid dissolved in distilled water (acid 1 

 part, water 9 parts). It Avas produced in quantity in a Kipp generator 

 and was freed from impurities by passing it through strong solutions 

 of argentic nitrate, potassium permanganate, and sodium bA'drate. It 

 was finally allowed to bubble through a jar of distilled water and then 

 passed into the culture chamber. This zinc was certified to be free 

 from arsenic and subsequent tests did not reveal an}^ of this substance. 

 To facilitate the removal of air, the gaseous contents of the well-luted 

 bell jar was pumped out before allowing the hydrogen to enter. The 

 jar was then repeatedly pumped out and refilled with the hydrogen, so 

 that only a trace of oxygen could have remained. During the prelimi- 

 nary trial exhaustions, leaks were of course discovered in various places 

 and were waxed or screwed tight. At the beginning of each experi- 

 ment everything was gas tight and remained so until its close (16 days). 

 The exposures were in a large Novy jar. At the close of each experi- 

 ment the tightness of the seal was demonstrated by the fact that when 

 the -i clamp screws were loosened hydrogen passed out through the 

 broad vaselined rubber joint (with a slight sound) in hundreds of tiny 

 branching whitish rivulets and then air began to pass into the jar in 

 the same curious way. 



(1) The first experiment Avas begun June l-i and closed June 30. 

 The temperature during this period was the ordinary room tempera- 

 ture of Washington (usually 25^ to 30^ C. in June). The inocula- 

 tions were all into test tubes, using in case of each tube and of each 

 organism one 2-mm. loop of cloudy beef broth 3 days old. The cul- 

 ture media tested were potato (stock 519), +15 beef broth (stock 473a), 

 and +15 nutrient slant agar (stock 516), i. e., media well adapted to 

 these organisms. Various bacteria were tested. The observations 

 on opening the jar June 30 (sixteenth day) and on subsequent days 

 are given Ijelow: 



Ps. hyacinth i: 



(a) Potato. — June 30, no growth. July 2, no growth; plenty of water in the tube. 

 July 5 (end of fifth day), doubtful; there seems to be feeble clouding and a slight 

 growth on the potato out of the water. July 9, distinct feeble, pale-yellow growth; 

 potato grayed; fluid feebly browned. July 16, a thin, yellow, typical growth covers 

 a portion only of the exposed potato; there is also a small amount of yellow pre- 

 cipitate; fluid abundant; a marked retardation of growth. 



(b) Beef broth. — June 30, clear; no growth. July 2, clear. July 5, no growth. 

 July 9, not cloudy; July 16, clear; no grf)wth. 



(c) Agar. — June 30, no growth. July 2, no growth. July 5, no growth. July 9, 



