“The former method compares the viability of naked germs in a 1 per cent. carbolic acid solution as a standard, with various dilutions of the germicide to be tested. The latter measures the relative diffusibility and germicidal power of carbolic acid and various dilutions of the germicide to be tested upon Bacillus coli suspended in 1.2 per cent. agar which is molded in cylinders of one centimeter diameter after infection with the organism.
“The first method—phenol coefficient—possesses advantages and disadvantages which are well known and need no mention here. It is worthy of notice, however, that as the death rate of the bacteria increases during the progress of the test, it becomes increasingly difficult to maintain a uniform suspension of living organisms so that each loopful removed shall exactly represent the developmental potentiality of the residual organisms.
“The second method theoretically covers the possibility because all the organisms are immobilized and are exposed to the germicide in direct proportion to its diffusibility until the center of the agar mass is reached, where the residual viable bacteria are presumably located. Inasmuch as the penetrability of an intestinal mass is involved in a discussion of intestinal germicides, the propriety of utilizing this ‘penetrability coefficient’ in this connection is obvious, in spite of its patent shortcomings.
“It is unnecessary to discuss the technique—the standard broth mentioned in the Hygienic Bulletin, a temperature of 70 F., a standard 4 mm. loop and careful attention to dilutions (using distilled water) were all observed. The various dilutions of Trimethol Syrup were made with accurate volumetric pipettes, measuring flasks and distilled water was used as a diluent.
“The results of several determinations, using Trimethol Syrup from three separate bottles, were in sufficient accord to warrant the statement that a dilution of 1⁄10 of Trimethol Syrup was equivalent to a 1⁄100 dilution of carbolic acid, using Bacillus typhosus as the test organism. Both solutions—the Trimethol and phenol—killed the organism in the interval between 71⁄2 minutes and 10 minutes’ exposure. That is to say, our observations indicate that under standard conditions as defined above, a 10 per cent. solution of Trimethol Syrup is equivalent in germicidal powers, as defined by the phenol coefficient to a 1 per cent. solution of phenol. Naturally, no predictions can be drawn from these observations indicative of the value as an intestinal germicide of Trimethol itself.
“The Penetrability coefficient resulted as follows: A 5 per cent. solution of phenol killed Bacillus coli, suspended uniformly throughout a cylinder of 1.2 per cent. agar in the interval between 60 and 90 minutes. A 1 per cent. solution of phenol killed the same organisms under the same conditions in the interval between two and one half and three hours. An undiluted solution of Trimethol Syrup killed the organisms in the interval between two and one half and three hours. A 10 per cent. solution (nine volumes of distilled water to one volume of Trimethol Syrup) failed to kill the organisms in four hours. It would appear that undiluted Trimethol Syrup has the same combined penetrability and germicidal value as a 1 per cent. phenol solution.
“The Phenol coefficient: A 10 per cent. solution of Trimethol Syrup in distilled water (nine volumes of distilled water to one volume of Trimethol Syrup) possesses the same germicidal power as a 1 per cent. solution of carbolic acid. This coefficient takes no cognizance of the actual amount of Trimethol as such—it merely indicates the relative germicidal power of the Trimethol Syrup as sold.”
The preceding report shows that Trimethol Syrup has a phenol coefficient of 1⁄10, and, assuming Trimethol Syrup contains the amount of Trimethol declared, the substance Trimethol would have a phenol coefficient of 81⁄3 instead of 40, as is claimed. According to Kendall and Edwards’ method, the penetrability-germicidal value of the syrup is equal to a 1 per cent. solution of phenol.