114 



Litmus. 



For te.sts made with litmus see under Reduction experiments and 

 in various other parts of this paper. 



REDUCTION EXPERIMENTS. 



Methylene Blue. 



The reducing tendencies of Ps. liyacinthi and other organisms were 

 tested on methylene blue in Dunham's solution (1 per cent peptone and 

 0.5 per cent sodium chloride in distilled water). To each 100 c. c. of 

 the Dunham's solution, which was made from Witte's peptonum siccum, 

 was added 2 c. c. of a solution of 50 mg". of methjdene blue in 50 

 c. c. of distilled water. The residts obtained are expressed briefly in 

 the following table, each organism grew in the medium, but as there 

 was no repetition of the experiment some of the statements may be sub- 

 ject to revision: 



Table VII. — F,ffe.ct of Ps. hyacinthi, etc., on methylene blue in salted j)epione water. 

 Experiment begun March 21. Color of fluid, bright blue. 



Species. 



Reduction. 



Effect of 

 shaking. 



Color at close 

 of experi- 

 ment. 



Dura- 

 Precipitate. ^0°,?' 



ment. 



1 



Ps. hyacinthi (2 

 tubes). 



Distinct (within a few 

 days), and long con- 

 tinued. Mar. 27, about 

 one-third and one-half as 

 blue as checks. Apr. 11, 

 one-thirtieth and one- 

 fiftieth as much color as 

 in checks. Apr. 18, still 

 nearly reduced. Ps. hya- 

 cinthi has a marked effect 

 on methylene blue in this 

 solution, and for a long 

 time. Apr. 25, color be- 

 gins to return. May 2, 

 as much, and nearly as 

 much, color as in checks. 



Color returns 

 quickly and 

 is blue. 



Bright blue. 

 Does not 

 deepen on 

 shaking. 



Not stained 



56 days. 



Ps. campestris 



Distinct (within few days). 

 Mar. 30, one-half as blue 

 as check. Apr. 11, one- 

 fiftieth as blue as check. 



Color deep- 

 ens rapidly 

 on shaking. 



Green. Does 

 not change 

 on shaking. 



do 



BO, 



Ps. stewarti 



None. (Observations on 

 Mar. 24, 27, 30; Apr. 6, 11. 

 18, 25; May 2, 16.) Fee- 

 bly but distinctly cloud- 

 ed in March, then clear. 



No change . . . 



Bright blue. 

 Same color 

 throughout 

 progress of 

 experiment 

 as on start. 



Deep blue . 

 Not stained 



Do. 



B. p y c y a n e u s 

 pericarditidis (1 

 tube). 



Distinct (on Mar. 30) . Apr. 

 6. Fluid uniformly pale 

 greenish instead of bright 

 blue; distinctly unlike 

 Ps. hyacinthi and Ps. 

 campestris; thev are 

 paler than this tiibe but 

 rapidly deepen their col- 

 or on shaking, whereas 

 this does not change 

 much even on prolonged 

 shaking. Apr. 11, about 

 one-fifth the color re- 

 main.s. Apr. 25, one-sixth 

 as much color as in check 

 tubes. 



Does not 

 change 

 much even 

 on long 

 shaking. 

 Fluid uni- 

 formly pale 

 greenish. 



Green. Does 

 not change 

 on shaking. 



Do. 



