79 



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

 s(|. cm; the aliwe is very pale yellow for the amount of growth; the potato in the 

 air l)egins to gray. March 31, growth feeble. 



Gkowtil in Hyokogex. 



Two tests were made in hydroo-cn. The *^as was prepared l)y 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 passint^ it through strong solutions 

 of argentic nitrate, potassium permanganate, and sodium hydrate. 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 any of this substance. 

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

 bell jar was pumped out before allowing the h^^drogen to enter. The 

 jar was then repeatedl}' pumped out and refilled Avith the hydrogen, so 

 that onU^ 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 screw^ed tight. At the beginning of each experi- 

 ment ever}' thing w^as gas tight and remained so until its close (16 da3\s). 

 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 4: clamp screws were loosened h^^drogen 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 was begun June 14 and closed June 30. 

 The temperature during this period was the ordinary room tempera- 

 ture of Washington (usualh^ 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 4T8a), 

 and 4-15 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 below: 



J*s. fnjfirhUlii: 



(a) PoUUo. — June 30, no growth. July 2, no growth; plenty of water in the tul)e. 

 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, yellowy 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 growth. 



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



