588 ButtETIN 167 



11. Acids produced.- — Hydrogen sulphid. Tubes of nu- 

 trient broth were prepared and inoculated in the ordinary way 

 and in each, including controls, was suspended a strip of filter 

 paper thoroughly moistened with lead acetate solution. Blacken- 

 ing of the paper after a suitable incubation of the cultures in- 

 dicated the presence of hydrogen sulphid. The following strains 

 gave this reaction constantly, CXV, CXL, Ps. tenuis. With 

 strain CXV it was in evidence in 2 days; with Ps. tenuis and 

 CXL, in 5 to 6 days. A slight reaction was observed in tubes 

 of LI and a doubtful trace occasionally in Ps. putrida, CXII, 

 and CXLV. 



12. Alkalies produced. — Ammonia was indicated by Nes- 

 sler's reagent in nitrate broth cultures of all strains (c. f. page 



579)- 



13. Crystals. — Crystals of magnesium ammonium phos- 

 phate were formed in Cohn's solution by Ps. alba, Ps. longa and 

 strain LI. 



14. Diastasic action on potato starch. — Broth cultures of 

 the 13 strains were tested for diastasic action upon potato starch 

 after incubation periods of varying duration. The results were 

 negative. 



15. Anaerobiosis. — Pyrogallic acid oxygen absorption meth- 

 od : Freshly prepared agar slants were placed in a liter Novy 

 jar containing 15 grams of pyrogallic acid. Just before seal- 

 ing about 200 cc. of a 1% sodium hydroxid solution was added. 

 After 10 days incubation in the sealed jars a slight growth 

 with fluorescence was apparent in strains Ps. alba, Ps. flito- 

 rescens, Ps. longa, Ps. mesenteric a, Ps. tenuis, CXII, CXL. 

 CXLV, CXLVIII, XXXVI, and LI. No growth resulted 

 with Ps. putrida, or CXV ; however, normal growth occurred 

 in tubes of the latter two strains soon after they were removed 

 from the jar. 



Carbon dioxid method. — Carbon dioxid was produced from 

 washed and boiled marble and hydrochloric acid in a Kipp gen- 

 erator and purified by passing successively through solutions of 



