Clinical or animal tests of the asserted intestinal antiseptics have hitherto given equivocal results because it is impossible, on the one hand, to predict the course of any intestinal infection, or, on the other hand, to determine what effect, if any, was produced by administration of the medicament. It therefore seemed unwise to undertake this line of investigation until the more direct laboratory bacteriologic methods had been exhausted. Consequently the investigator checked, in the first place, the phenol coefficient of one of the Trimethol preparations and then also determined its “penetrability” coefficient. Although by both methods Trimethol was found to be a germicide, the results did not indicate any remarkable potency or other properties suggesting that the drug possessed special therapeutic value. From the results obtained it appeared inadvisable to proceed further with the work until more definite evidence of the nature and of the value of the substance should be at hand. The report of the bacteriologic investigation follows: THE BACTERIOLOGIST’S REPORT “I have made no attempt to study the effects of internal administration of Trimethol on the intestinal flora. The methods available at the present time of enumerating the numbers of _viable_ bacteria in the feces are probably not accurate within 100 per cent. and the precision of such determinations is equally variable. The physiologic factors involved are so complex that they would appear to make a really valuable assay a question of many months’ careful study. If it were possible to administer known amounts of Trimethol, as such, the problem might be worth while; inasmuch as the available reactive substance is not at present quantitatively assayable, this phase of the investigation barely seems practicable. “‘Trimethol Syrup,’ as such, appears to be about 10 per cent. as efficient in its germicidal value as carbolic acid. If the assay, 3/4 m. Trimethol per drm. (as the label indicates), is correct, the substance would appear to possess germicidal merit provided enough could be administered, if it is not influenced by passage through the stomach. “A package containing four four-ounce bottles labeled ‘Trimethol, A Non-Toxic Germicide SYRUP Representing 3/4 m. Trimethol per drm., Alcohol 1-1/2 per cent.’ was received at the laboratory Dec. 15, 1916. Later a smaller package containing, according to the label, 100 Trimethol tablets, each 5 gr., representing 1-1/4 m. Trimethol, was received. The tablets were apparently chocolate coated. “Two separate series of tests were made upon the syrup. (_a_) PHENOL COEFFICIENT, using the method outlined in _Bulletin No. 82_, Hygienic Laboratory, Method of Standardizing Disinfectants With and Without Organic Matter. (_b_) A PENETRABILITY COEFFICIENT by the method of Kendall and Edwards, _Journal of Infectious Diseases_, 8, 250.