Étude Oscillographique de la Paralysie Thermique du Nerf

Abstract

The phenomenon of thermal narcosis of nerve fibers has been studied comparatively on the nerves of the 2 European frogs, Rana tem-poraria and R. esculenta, whose temps. of paralysis differ by about 8[degree]C. The nerve of R. temporaria lost its excitability and conductibility at the remarkably low temp. of about 32[degree]C, which may be still lowered by K and by anesthetics. The fibers of the A group are differentially heat-sensitive, the [gamma] ones being the more resistant. The reversibility of the phenomenon is rapid and complete. The voltage curve of the action potential (spike and negative after potential) as a function of temp. shows no parallelism with the curve of the resting potential. Thermic narcosis coincides in the 2 spp. with the same fall of resting potential of 8-9 mV. The immediate cause of the loss of conduction, which is preceded by a slowing of its velocity, is presumably the rise of threshold of the fibers. At a time when conduction is abolished, a local cathodic response is still observed. The initial perturbation leading ultimately to paralysis is probably the thermic inactivation of the nerve enzyme mechanisms (according to expts. on the respiration of brain tissue of the 2 spp. of frog).