232 JOHN T. MYERS 



Another field in which bacterial sulphur metabolism may be of 

 importance is in soil bacteriology. The part played by sulphur 

 here is little understood. Lipman, McLean and Lent (1916) 

 suggest that sulphur oxidation in soils may have an effect on the 

 availability of mineral phosphates as plant food. 



Again a number of workers have attempted to apply hydrogen 

 sulphide formation to water analysis, the assumption being that 

 the amount of hydrogen sulphide produced when water is planted 

 in a suitable medium is proportional to the degree of pollution. 

 Schardinger (1894) seems to have first suggested this possi- 

 bility. He observed that when water polluted with fecal ma- 

 terial was added to peptone solution and incubated, it produced 

 a characteristic odor, and that it blackened a strip of lead ace- 

 tate paper which was suspended over the liquid. Dunham in 

 1897 suggested the following method for the detection of pol- 

 luted water. Sterilize 10 cc. of an aqueous solution of 10 per cent 

 peptone and 5 per cent sodium chloride in a plugged Erlenmeyer 

 flask. To this flask add 90 cc. of the water under examination, 

 suspend a strip of filter paper impregnated with lead carbonate 

 over the mixture, and incubate for twenty-four hours at 37°C. 

 Dunham maintained that the colon bacillus and the organisms 

 of putrefaction readily multiply and cause the production of 

 hydrogen sulphide which discolors the lead carbonate paper. 



Redfield (1912) studied the effect upon the speed and amount 

 of hydrogen sulphide production when different factors were 

 varied. Among the conditions investigated were the effect of 

 using filtered and unfiltered peptone solutions, the effect of the 

 concentration of the peptone, of the type of inorganic salts added 

 to the peptone solution, of the concentration of various salts 

 added to the medium, of the kind of bases and acids used in ad- 

 justing the initial reaction of the medium, and of the relation of 

 the final reaction of the culture to the amount of hydrogen sul- 

 phide production. As a result of his work Redfield suggests the 

 following method for the detection of polluted water : 



Bring 700 cc. of tap water to a boil and add 300 grams of Witte pep- 

 tone and 75 grams of potassium chloride. Maintain a gentle heat and 



