The accommodation curves of nerve and nerve fiber, with special reference to the "breakdown of accommodation," and the effects of veratrine, guanidine and aconitine upon them.

Abstract

1. Accommodation curves of whole nerves and single nerve fiber muscle preparations of a Japanese toad were measured by exponentially increasing currents. With whole nerves, the bending of accommodation curves was found in about 40% of all determinations, and in two such cases changes of site and manner of muscle contractions were observed.2. In single nerve fiber muscle preparations, the strict linear relationship, between current strength and time-constant of current rise was obtained.3. These results give us the conclusion that the bending of the accommodation curve was produced by excitations of other nerve fibers which have a higher threshold and a slower accommodation.4. Veratrine, guanidine and aconitine, in appropriate concentrations, lower the threshold and decrease the minimal current gradient Of the nerve fiber.