Resting membrane potential in chick muscle cells during ontogeny

Resting membrane potentials were recorded from developing thing muscle cells of the chick at different stages from the third day of incubation. During the early stages the membrane potentials were lower than in the adult animal. No significant changes in potentials were observed until after the fifteenth day. There was a marked increase between the fifteenth and nineteenth days, and the membrane potential reached values comparable to those of the adult. In a study of the concomitant morphological development, the increase in membrane potentials was found to coincide with the transformation of the majority of the cells from myotubes to myocytes.