. Kirkes' handbook of physiology . rd, downward, or inward. 4, The pupil becomes dilated,mydriasis. 5, The eye cannot accommodate for short distances. The Fourth Nerve, or Trochlearis. Origin. The fourth nervearises from a nucleus consisting of large multipolar ganglion cells situated THE FIFTH NERVE, OR TRIGEMINAL 551 ventral to the aqueduct of Sylvius, and the inferior corpus fibers from both sides sweep dorsally around the central gray matter, andreach the valve of Vieussens, where they decussate in the mid-line of the roof,then pass forward along the lateral aspect of the
. Kirkes' handbook of physiology . rd, downward, or inward. 4, The pupil becomes dilated,mydriasis. 5, The eye cannot accommodate for short distances. The Fourth Nerve, or Trochlearis. Origin. The fourth nervearises from a nucleus consisting of large multipolar ganglion cells situated THE FIFTH NERVE, OR TRIGEMINAL 551 ventral to the aqueduct of Sylvius, and the inferior corpus fibers from both sides sweep dorsally around the central gray matter, andreach the valve of Vieussens, where they decussate in the mid-line of the roof,then pass forward along the lateral aspect of the crus. The nucleus of thefourth nerve on either side is connected with those of the third and sixth nervesand with the optic reflex center previously described. Functions. The fourth nerve is exclusively motor, and supplies only thetrochlearis or superior oblique muscle of the eyeball. The Fifth Nerve, or Trigeminal. Origin. The fifth or trigeminalnerve resembles the spinal nerves in that it has two roots; namely, the larger nyiri. Fig. 385.—Section Across the Pons, About the Middle of the Fourth Ventricle, py, Pyramidalbundles; po, transverse fibers passing pou behind, and in front of py; r. raphe; , su-perior olive; , bundles of ascending root of V. nerve enclosed in a prolongation of the sub-stance of Rolando; VI, the sixth nerve; nVl, its nucleus; i//, facial nerve; , intermediateportion, nVH, its nucleus; VIII, auditory nerve, nVIII, lateral nucleus of the auditory. (AfterQuain.) or sensory, in connection with which is the Gasserian ganglion, and the smallor motor root, which has no ganglion, and which passes under the ganglion of thesensory root. The fibers of origin of the fifth nerve come from the floor of thefourth ventricle. The motor root arises to the inside of the sensory, about themiddle of each lateral half of the fourth ventricle. The sensory fibers,however, can be traced down in the medulla oblongata as far as the upper partof the cord. The m
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