115 



Tablk VII. — Effect of Ps. hyacinthi, etc., on metJu/lene hhie in salted peptone iruler. 

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



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

 4 categories: 



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

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

 JPs. hyacivthi. 



(2) As in 1. Ijut the final color of the fluid green. Ps. canipestris. 



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

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

 pericarditidis. 



(4) Reduction feeble or doubtful or absent. Final color of the fluid 

 blue. Bacterial precipitate stained deep blue. Ps. stewartl, B. coll., 

 B. amylovorus. 



Indigo Carmine. 



The reducing tendencies of Ps. hyacinthi and other organisms on 

 indigo carmine were tested in the same way as in case of methylene 

 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 foUowino- table: 



