Steady State Potential Differences in the Early Development of Amblystoma *

The development of instruments and technics in recent years has made possible considerable increase in our information concerning electrical phenomena associated with living organisms. Though still little studied, this is true of those bioelectric phenomena, noted by DuBois-Reymond in the frog skin in 1843, which maintain a relatively steady state and change only slowly, as well as of those better known phenomena, commonly called action currents, which are defined by the instruments used to detect them as rapidly changing states. Steady state differences of electrical potential (p.d.) have been found in virtually every living membrane, cell, tissue, and organism which has been explored, although some p.d.'s are at the lower limit of the sensitivity of available instruments. One of the earliest objects of study after the design of the Burr-Lane-Nims microvoltmeter4 which made possible dependable and reproducible determinations at high sensitivity, was the developing embryo.2' 8 A notable feature of the results of these exploratory investigations was the wide scatter of points and the necessity of statistical treatment. Since these determinations represented spot readings of a galvanometer, a natural development was the application of continuous recording, for significant changes in potentials with alterations in the state of the organism may well pass unnoticed in discontinuous data. However, such methods have not yet been applied, so far as is known, to the problem of embryology. And yet a very considerable interest would obviously attach to a continuous record of the electrical output of the developing organism. Information on the course of steady state potentials through the mitotic bursts of cleavage, the determination of axial organs, movements of materials and differentiation of cells, should bear importantly on the question of the origin, nature, and influence of this type of bioelectricity.