OSCILLOGRAPHIC STUDIES ON THE SPINAL TRACT OF THE FIFTH CRANIAL NERVE

Abstract

By means of the oscillograph, tactile impulses were traced into the spinal tract of the 5th nerve of the cat. Impulses originating in the ophthalmic division of the trigeminal were recorded as far as the caudal part of the first cervical segment, those from the maxillary area as far as the rostral part of the first cervical segment and those from the mandibular area were followed to the junction of the medulla and cord. Synchronous action potentials evoked electrically from a large branch of each of the divisions of the 5th nerve were recorded from the spinal tract and traced to approximately the same levels as given above. These potentials were easier to trace than the random tactile responses but could not be detected an appreciable distance below the levels mentioned. Physiological evidence is presented to support previous anatomical findings regarding the relative position of the 3 trigeminal divisions within the spinal tract. The ophthalmic fibers assume a ventral position, the mandibular fibers a dorsal position, and the maxillary fibers an intermediate position. Each division remains relatively independent throughout its course. The action potential evoked electrically consisted of 1 or 2 waves each of which had one or more crests. The first wave was complete within 2 msec. and very likely resulted from activity in first order neurones. The 2d wave started at about 2 msec, lasted to as long as 4-5 msec, and evidenced activity in 2d or higher order neurones.