Studies on the Electrical Potentials of Living Organisms. I. Base-lines and Strain Differences in Mice *

With the development of the vacuum-tube microvoltmeter by Burr, Lane, and Nims4 and the elimination of many sources of error in the determination of bioelectric potentials, a new impetus has been given to the study of the direct current potential gradient of living organisms. Earlier investigators, as well as those of the last year or so, have assumed some causal relationship between the potentials observed and some biological or chemical process such as metabolism, hydrogen ion shifts in local or generalized areas, muscular or neural activity, alterations of hormonal levels, growth involving mitotic activity, etc. Changes in potential have been observed during ovulation in the rabbit (Burr, Hill, and Allen'; Reboul, Friedgood, and Davis'") and in the cat (Greulich and Hill9), during the growth of chick and amblystoma embryos (Burr and Hovland2 3), during the development of cancer in mice (Burr, Smith, and Strong7' 8), associated with menstruation and ovulation in women (Burr and Musselman5; Burr, Musselman, Barton, and Kelly6), and in the cestrus cycle and with the injection of theelin in rats (Rogers"' 12). With the exception of the last-mentioned study, experiments have dealt with phenomena produced by the animal itself, and it has not been possible to proceed very far with an analysis of the specific factors which might have been instrumental in producing potential changes. It seemed advisable, therefore, to produce experimentally certain changes in the organism in order to isolate those factors which might be responsible for the shifts of potential. Before any reliable conclusions could be drawn, however, it would be necessary to determine the range and constancy of the base-line of a normal unanesthetized animal. This paper reports the study of such a base-line.