The locus of the action of veratrin in the sciatic nerve of the frog.

In a former paper 1 it has been pointed out that if the end of a sciatic nerve is immersed in a veratrin solution there results, after a widely variable latent period, spontaneous muscle twitchings in the gastrocnemius. If, at this time, the sciatic nerve is sectioned between the point of immersion in the veratrin solution and attachment to the muscle, the writing lever falls to the base line. It has also been shown that direct stimulation of the gastrocnemius, when the nerve is immersed, elicits a contraction with delayed relaxation. The question arises as to whether some of the veratrin solution actually travels along the nerve fiber to the muscle by capillarity and thus functionally affects the muscle fibers. If this should be the case, the wide range of latency might be accounted for by rapidity of transmission or length of nerve. Moreover, with this conception of the phenomenon, a nerve-block applied between the supply of veratrin and the muscle should not inhibit muscular twitchings due to chemical stimulation by veratrin, nor characteristic contracture of the muscle, following direct electrical stimulation. In order to test this theory experiments were made with nerve muscle preparations of the frog arranged as previously described 1 and using the same concentration of alkaloid solution. An ethyl chloride nerve-block (Gebauer's ethyl chloride) was employed between the veratrin container and the muscle.

If the nerve-block be applied before the nerve is immersed in veratrin solution, direct stimulation of the muscle elver a period of 45 minutes results in normal contractions. If, after the nerve has been immersed in veratrin and the muscle twitchings have begun, the nerve-block is now applied, the writing lever returns at once to the base line.