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Oxidation-reduction studies of saliva have been neglected, possibly due to the rapid drift toward a negative potential under in vitro conditions at room temperatures. To the writer's knowledge only 3 references appear in the literature. Pincus (1) first reported the marked reducing properties of saliva as demonstrated by the reduction of methylene blue and dichlorphenol-indophenol to the colorless form within a few seconds. Appleton (2) indicated the need for studying the oxidizing and reducing properties of saliva. He observed that the ability of saliva to reduce methylene blue varies with the individual and may even be absent. Aerobic bacterial flora of the mouth may partially account for the reducing power of saliva. It should be pointed out that bacterial dehydrogenases in the presence of suitable substrates could easily account for a low Eh and especially the reduction of methylene blue. Wessinger (3) made a few tests with an electrometer by placing saliva in a sample cup and testing in vitro at room temperatures, but found that the potential drifted rapidly to the negative scale, even under paraffin oil. He found no correlation between the potentials and pH and concluded that no accurate data on oxidation-reduction activities of saliva were obtainable.The general field of oxidation-reduction is growing rapidly in biology, but the drifts in biological systems have caused great difficulties in obtaining consistent results. Good reviews of the literature are found in Elvehjem and Wilson (4) and Michaelis (5). The purpose of this paper is to report the temporary oxidation-reduction activities of saliva immediately after spitting, and to determine whether or not consistency of data is obtainable. Repeated oxidation-reduction tests were made in this laboratory while studying the hydrogen-ion concentration of the same sample of saliva (6). METHODSThe procedure was that used by Eisenbrandt (6) for determining the pH of saliva. A pH-Eh meter was utilized with a gold-plated platinum electrode which was substituted for the glass electrode used in determining the pH of saliva. This instrument was identical to the one used by Wessinger (3). Unstimulated saliva was collected within the closed mouth until about 5 ml. had accumulated; then it was spit into the sample cup and tested immediately. Only a fraction of a minute was required to switch electrodes, adjust the instrument and obtain the potential readings at temperatures averaging 28°C. Consequently both pH and Eh readings were obtained within 1 minutes after filling the sample cup with saliva. The tests were entirely in vitro.

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