Abstract
In cultures, bacteria break down sugar into fatty acids, alcohol, lactic acid, methane, hydrogen and carbon dioxide. We have determined the amounts of the fatty acids occurring in human stools with various diets and under the conditions of constipation or catharsis. 1 Since lactic acid is produced in cultures in large amounts, this work was undertaken to answer the question whether lactic acid is present in stools in amounts comparable to those found for volatile fatty acids.
The isolation of lactic acid from stools could be carried out by extracting with ether or if a suitable precipitant were found which would free the filtrate from interfering substances, the filtrate might be directly oxidized. By means of the mercuric sulphate precipitation of West, 2 one can obtain from stool water clear filtrates practieally free from nitrogen and almost free from interfering substances. 3 The filtrate from the mercury precipitation must be further treated by the usual copper sulphate and lime precipitation. Applying the method of Friedemann, Cotonio and Shaffer, 3 we found that the amounts of oxidizable material in such filtrates is small as shown by the fact that 100 cc. of filtrate, representing from 5 to 10 gm. of stool, require in the lactic acid apparatus less than 50 cc. of 0.01 N potassium permanganate to show a permanent excess of permanganate. As a matter of fact, there was obtained only 0.2 to 0.5 mg. of sulphite binding substance from the above mentioned amount of material.
To obtain filtrates that do not give a biuret test, we found it necessary to use 2 volumes of a 30% mercuric sulphate solution in 10% sulphuric acid to one volume of stool.
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