THE FREQUENCY OF IMPULSES IN THE NERVE FIBERS TO THE NICTITATING MEMBRANE OF THE CAT

Abstract

The contraction of the nictitating membrane of the cat was studied in relation to the frequency of stimulation of its preganglionic and of its postganglionic nerve fibers. No consistent difference between the 2 cases was found. This does not support the hypothesis that the frequency of impulses in the postganglionic neurones differs from that in the preganglionic neurones. The extent of contraction increases with increase of frequency up to 25 or 30 per sec., and remains constant for higher frequencies, except that with stimuli which are only slightly supramaximal and at the higher frequencies, the contraction may be submaximal from the start or fall from maximal to submaximal. In fatigued preparations this effect may be obtained even with stronger stimuli. Theoretical explanations are suggested.