TRIGEMINAL NERVE. 



68 3 



V. TRIGEMINAL NERVE. 



The trigeminal nerve (Fig.. 242) arises, like a spinal nerve, by two roots (Fig. 

 241). The smaller, anterior, motor root originates as a bundle of neurites from 

 the motor nucleus of the trigeminus (nucleus masticatorius and locus coeruleus, 

 Fig. 241, 5), rich in large cells, on the floor of the fourth ventricle close to the 

 middle line, some of the fibers coming from the opposite side. 'From the cortical 

 motor center of the cerebrum fibers from the opposite side pass through the cerebral 

 peduncle to this nucleus. In addition, the descending root furnishes motor fibers. 

 This root (5,,,) extends 

 from the anterior quad- 

 rigeminate body later- 

 ally along the aqueduct 

 of Sylvius downward to 

 the point of exit of the 

 nerve. The large sen- I- olf. 



sory, posterior root re- 

 ceives fibers (i) from 

 the gray matter of the 

 sensory nucleus of the 

 trigeminus (5 t ) , situ- 



IV. trocJi. 

 V. try. 



VI. aid. 



VII. fac. 



VIII. acust. 



IX. glossph. 



X. vag. 



XL access. 

 XII. hypgl. 



II. opt. 



01; > ^LI- ///. ocm. 

 ated to the side of the 

 motor nucleus, and the 

 analogue of the poste- 

 rior horn. (2) From the 

 gray matter of the pos- 

 terior horn of the spinal 

 cord down to the sec- 

 ond cervical vertebra. 

 These fibers give off 

 collaterals to the ori- 

 gins particularly of the 

 hypoglossal and facial 

 nerves, participate in 

 the reticular formation 

 and enter the white 

 posterior column and 

 then, as the spinal or 

 ascending root, the sen- 

 sory branches of the 

 trigeminus. (3) From 

 the cerebellum (unde- 

 cussated) fibers passing 

 through the crus were 

 described by Meynert. 



The origins of the 

 sensory root are con- 

 nected with the motor 

 nuclei of all of the 

 nerves arising in the 

 medulla oblongata, with 

 the exception of the 

 abducens. This fact explains the various reflex effects. 



The thick trunk appears laterally between the fibers of the pons; then its 

 posterior root forms the Gasserian ganglion (Figs. 242 and 243) at the apex of the 

 petrous bone. In the ganglion the bipolar ganglion-cells are actually the seats of 

 origin of the sensory root. Filaments of the sympathetic from the cavernous plexus 

 pass to the Gasserian ganglion. Then the nerve divides into its three large branches. 



The first, or ophthalmic, division (Fig. 243, d) receives sympathetic 

 (vasomotor) fibers from the cavernous plexus, then passes through the 

 sphenoidal fissure into the orbit. Its branches are: 



i. The small recurrent nerve, which gives off sensory branches to the 

 tentorium cerebelli. To it are added fibers from the carotid plexus of the 

 sympathetic as vasomotdrs for the dura mater. 



CV 1 



FIG. 



242. The Cerebral Nerves, / to XII (according to Schwalbe): JR. 

 island of Reil; h, hypophysis; th, optic thalamus; c, c, corpora albicantia; 

 gm, gl, mesial and lateral geniculate bodies; py, pyramid; ov, olivary 

 body; CTi, first cervical nerve. 



