115 



Table VII. — Effect of Pa. hyacinthi, etc., on methi/lcue hlue in salted peptone water. 

 Experiment began March 21. Color of fluid, bright blue — Continued, 



Species. 



Reduction. 



wfff^ot nf Color at close 



TaiLt ^^^l^f- Precipitate. 



Dura- 

 tion of 

 experi- 

 ment. 



B. coli (1 tube) 



Doubtful. Soon heavily 

 clouded. Paler blue at 

 first (in March), then 

 doubtful. No reduction. 

 Possibly the paler blueon 

 start was due to the heavy 

 clouding. 



Does n o t 

 (• li a n g e . 

 Uniformly 

 blue. 



Blue. Does 

 not change 

 on shaking. 



Dark blue . 



Do. 



B. amylovorus (1 

 tube). 



Doubtful. No distinct re- 

 duction. Less clouding 

 than in B. coli. 



Does not 

 change. 



Blue. Does 



not change 

 on shaking. 



Deep blue. 



Do. 



From the above table the 6 organisms mentioned appear to fall into 

 4 categories: 



(1) Marked reduction, prompt reoxidation on shaking, final color 

 the same as at the beginning^i. e., pure blue. Precipitate not stained. 

 J^s. hyacinthi. 



(2) As in 1, but the final color of the fiuid green. J^s. catnpestris. 



(3) Distinct slow destruction of color. Color does not return on 

 shaking. Final color green. Precipitate unstained. B. pyocyaneus 

 pericarditidis. 



(tt) Reduction feeble or doubtful or absent. Final color of the fiuid 

 blue. Bacterial precipitate stained deep blue. Pa. stewarti^ B. coli., 

 B. cunylovoru^. 



Indigo Carmine. 



The reducing tendencies of Ps. hydcinthi and other organisms on 

 indigo carmine were tested in the same way as in case of meth^'lene 

 blue. The culture medium consisted of 100 c. c. of Dunham's solu- 

 tion, to which was added 2 c. c. of a solution of 500 milligrams of 

 indigo carmine in 100 c. c. of distilled water. The results obtained 

 are shown in the following table: 



