THE EXCITABILITY OF FROG MUSCLE WITH PARTICULAR REFERENCE TO ITS LATENT ADDITION

Abstract

With a view to indicating that the a excitatory state in muscle is not of a special nature it is shown that the [alpha] strength-duration curves are of the same form as those detd. for nerve and other tissues except that in about 2/3 of all cases the rheobase appears to be slightly too low. In latent addition, the a excitatory state following an inadequate stimulus subsides exponentially at a rate which is related to the excitability in the same way as the subsidence rate in nerve is related to the nerve''s excitability. In both tissues the subsidence as measured directly is 2-3 times as fast as it appears to be from the strength-duration curve. The refractory period is at least as short as that of nerve so the [alpha] chronaxie is usually long compared to the refractory period. There is no reason, however, to consider this as having any bearing on the problem at issue. The [alpha] excitability evidently differs from others in the rates of its reactions rather than in its fundamental nature and any conclusions about excitability drawn from its study will probably be valid.