STUDIES ON THE CORRELATION BETWEEN METABOLIC GRADIENTS, ELECTRICAL GRADIENTS, AND GALVANOTAXIS. I

Abstract

1. The idea is advanced that differences of potential in organisms; particularly the permanent differences which exist along the main axis of animals, are due to differences in metabolic rate at different regions, the region of highest metabolic rate being the most negative in the external circuit, most positive in the internal circuit. It is further suggested that internal potential differences account for the galvanotactic response, in many animals at least. Data are presented in various groups of animals to show the correlation between metabolic differences, electrical differences, and galvanotactic orientation. 2. In the sponges; Leucoselenia and Grantia, the oscular end has usually a higher metabolic rate than, and is electronegative (galv.) to, the basal end. 3. In the colonial hydroids tested the apical hydranths and levels of colonies have a higher metabolic rate than, and are electronegative (galv.) to, basal hydranths and levels. In the one species tested the apical end of the hydranth is cathodic. 4. In the hydromedusæ tested the metabolic rate and electronegativity (galv.) are greatest in the manubrium, next in the tentaculate margin, next in the subumbrellar surface, and least in the exumbrella. So far as tested, manubrium and tentacles are cathodic. 5. In the ctenophore, Pleurobrachia, the metabolic rate and the electronegativity (galv.) are highest at the aboral pole and decrease toward the oral pole. No galvanotactic response was obtained. 6. In Planaria maculata anterior and posterior ends have a higher metabolic rate than the middle; the anterior end is electronegative (galv.) to posterior levels. In a current a U-shape is assumed with anterior and posterior ends directed toward the cathode, middle toward the anode. In a polyclad worm anterior and posterior ends and margins were found to be electronegative (galv.) to the middle regions; the galvanotactic response was similar to that of Planaria. 7. In annelids anterior and posterior ends have a higher metabolic rate than the middle and are electronegative (galv.) to it. In Nereis, after being kept in the laboratory, anterior and posterior ends are electropositive (galv.) to the middle. When placed in the current, all oligochætes tested turn their anterior ends toward the cathode, and the larger forms also bend their posterior ends toward the cathode, the body assuming a U-shaped posture. Nereis, in which the two ends are positive (galv.), assumes the same posture, but with the ends facing the anode. 8. In frog tadpoles the posterior end has the highest metabolic rate and is electronegative (galv.) to anterior levels. In a current they orient with posterior end directed toward the cathode, anterior end toward the anode. 9. It thus appears that so far as our tests have proceeded that regions of higher metabolic rate are externally negative, internally positive, to regions of lower metabolic rate, and that when placed in a current animals direct those parts positively (int.) charged toward the cathode and those parts negatively (int.) charged toward the anode.