Intramuscular propagation of sensory impulses

There is now overwhelming evidence of different kinds that in the Pacinian corpuscle there is no detectable propagation of impulses in the nonmyelinated ending, either antidromic (Diamond, Gray & Inman, 1958a) or orthodromic (Diamond, Gray & Sato, 1956; Diamond, Gray & Inman, 1958b; Loewenstein, 1958; Loewenstein & Rathkamp, 1958). Another point that seems to have been established is that the after-effects of an antidromic impulse on the ending are similar to those of an orthodromic one (Diamond et al. 1958a). This was shown clearly earlier in the sensory cell of the crayfish stretch receptor (Eyzaguirre & Kuffler, 1955). If direct evidence could be obtained these properties would probably also be found in other visceral and somatic sensory receptors. However, at present it is only possible to obtain indirect evidence in these receptors. Such evidence, which happens to be conclusive in the present instance, has been obtained in muscle stretch receptors of the cat and is presented in this paper. The essence of the experiments lies in the procedure for determining intramuscular conduction time accurately. This has been described briefly already (Paintal, 1958). The basis of this procedure rests on the assumption that recovery of the ending following an antidromic impulse is identical with that following an orthodromic one. The experiments have shown that this assumption is correct.