mater and enters (lie posterior end of inc outer wall of the cavernous sinus. In the 

 wall of the cavernous sinus it forms communications with the cavernous plexus 

 of the sympathetic Mid by a small filament with the ophthalmic division of the 

 fifth nerve. It gradually ascends, as it passes forwards in the outer wall of the 

 Finns, and, beyond the middle of the sinus, it crosses the outer side of the trunk of 

 the OCUlo-motOT nerve and gains a higher [Misition. At the anterior end of the sinus 

 the nerve enters the orbit above, the external reel us and immediately turns inwards 

 between the periosteum of the roof and the levator palpebnc superioris. At the 

 inner border of the n of of the orbit it turns forwards to its termination, and enter- 

 the orbital or superior surface of the superior oblique muscle to which its til. res are 

 distributed. 



Kit;. 700. DIAC;U\M> < i SECTIONS THHOI-OH THE Ouic.ix OK THE FOURTH XF.RVE. (Stilling.) 

 (The upper figure is an oblique section, the lower is a coronal section.) 



IV 



CERERIil 



\rrr.Krs OF 



TROCHLEAR KERVE 



MEDIAL LOKOITUDJXAL 

 FASCICULUS 



RATHE 



[j>^ AQUJSDUCTL'S CEREBRI 



LATERAL 1. EM K ISC US 



The Central Connections of the nucleus of the trochlear nerve are similar to those of the 

 oculo-motor .save that its cells probably do not send fibres which connect with the facial nerve. 



The trochlear is peculiar in that (1) it is the sin.-illest of the cranial nerves; (2) it is the 

 only nerve having its superficial attachment upon the dorsal aspect of the encephalon; (3) it 

 is the only cranial nerve whose fibres undergo a total decussation, and (4) in that it terminates 

 in a muscle of t lie side of the body opposite that in which it has its origin. Gaskell has suggested 

 that this latter condition has probably been brought about, phylogenetically, by the transference 

 of the muscles which have carried their nerves with them. 



. THE FIFTH PAIR THE TRIGEMINAL NERVES 



Each fifth or trigeminus nerve is the largest of the cranial nerves with the exception 

 of the optic, and it possesses both a sensory and a motor root. The fibres of the sen- 

 sory root spring from the cells of the semilunar (Gasserian) ganglion, which cor- 

 responds with the ganglion on the dorsal root of a spinal nerve, and those of the 

 motor root issue from the side of the pons, close by the side of the entering fibres of 

 the sensory root. 



The semilunar (Gasserian) ganglion is a semilunar mass which lies in Meckel's 

 cave, a cleft in the dura mater above a depression in the inner part of the upper sin ; 

 of the pet nms portion of the temporal bone. The convexity of the ganglion is turned 

 forwards, and from it three large nerves, the ophthalmic, the maxillary, and the 

 mandibular. are given off. From the concavity, which is directed backwards, springs 

 the sensory or afferent root of the fifth nerve. The inner end of the ganglion is in 

 close relation with the cavernous sinus and the internal carotid artery at the foramen 

 lacerum, and the outer end lies to the inner side of the foramen ovale. The surf. 

 of the ganglion are striated, due to bundles of fibres traversing them. The upper 



