770 



THE NEKVOUS SYSTEM. 



superior cerebellar arteries, the nerve pierces the dura mater beside the posterior 

 clinoid process, in a small triangular space between the free and attached borders 

 of the tentorium cerebelli. Beneath the dura mater the nerve courses through the 



Diaphragma sellae 

 Fossa hypophyse 



Sphenoidal sinus 

 Sphenoid bone 

 Internal carotid artery 



Internal carotid artery 

 Trochlear nerve 

 Oculo-motor nerve ,' 



Optic nerve 



I Ophthalmic artery 



Anterior clinoid process 

 Trochlear nerve 



Frontal nerve 



Lacrimal nerve 



Oculo-motor nerve 

 (superior division) 



Naso-ciliary nerve 



Oculo-motor nerve 

 (inferior division) 

 Abducens nerve 

 Maxillary nerve 



Abducens nerve 



Cavernous sinus 



Ophthalmic nerve 



Maxillary nerve | 



Mandibular nerve 



Foramen ovale 

 ' Mandibular nerve 

 Motor root of trigeminal nerve 



FIG. 645. DELATIONS OF STRUCTURES IN THE CAVERNOUS SINUS AND SUPERIOR ORBITAL FISSURE. 



lateral wall of the cavernous sinus, and enters the orbit through the superior 

 orbital fissure and between the two heads of the lateral rectus muscle. As it 

 enters the orbit it divides into upper and lower branches, separated by the naso- 

 ciliary nerve. 



Branches. The 

 superior branch of the nerve 

 supplies two muscles of 

 the orbit the superior 

 rectus and the levator 

 palpebrse superioris. 



The inferior branch 

 passes forwards, and after quadr ? g eS 

 giving branches to the 

 medial and inferior recti, 

 ends in the inferior oblique 

 muscle. The short root of 

 the ciliary ganglion arises 

 from the terminal branch 

 which goes to the inferior 

 oblique muscle. 



Frenulum veli 

 Anterior medullary velum 



Thalamus 



Brachium 

 quadrigeminum 



Trochlear nerve 



Lateral lemniscus 

 Brachium 

 conjunctivum 

 Pedunculus cerebri 



Lingula 



FlG. 646.- 



-DORSAL SURFACE OF THE MID-BRAIN, to show the origin 

 of the trochlear (fourth) nerve. 



Communications. 1. In the cavernous sinus the oculo-motor nerve communicates with 

 the cavernous plexus on the internal carotid artery. 2. In the cavernous sinus it also 

 receives a slender communication from the ophthalmic division of the trigeminal nerve. 

 3. The short root of the ciliary ganglion passes upwards from the branch of the nerve 

 which supplies the inferior oblique muscle. 



NERVUS TROCHLEARIS. 



brain. It arises at tne side 01 the Jrenuium veil irom tne anterior end 01 tne 

 anterior medullary velum, just behind the corpora quadrigemina. It is extremely 

 slender, and of considerable length. Passing round the cerebral peduncle, the 

 nerve appears at the base of the brain behind the optic tract, in the interval 

 between the cerebral peduncle and the temporal lobe of the brain. Continued 

 forwards to the base of the skull, it pierces the free border of the tentorium cerebelli 

 postero-lateral to the oculo-motor nerve, and proceeds forwards in the lateral wal) 

 of the cavernous sinus, to the superior orbital fissure, lying between the oculo- 



