330 HEAD AND NECK 



The maxillary division is composed entirely of sensory 

 fibres. It runs anteriorly in relation to the lower and lateral 

 part of the cavernous sinus, and, after a short course within 

 the cranium, makes its exit through the foramen rotundum. 

 Near its origin it gives off a fine meningeal branch to the dura 

 mater of the middle fossa of the cranium. 



The ophthalmic division is the smallest of the three branches 

 of the trigeminal nerve, and, like the maxillary, it is com- 

 posed entirely of sensory fibres. It passes anteriorly in the 

 lateral wall of the cavernous sinus, and ends, close to the 

 superior orbital fissure, by dividing into three terminal branches. 

 As it traverses the sinus it is accompanied by the oculo- 

 motor and trochlear nerves, both of which occupy a higher 

 level. Like the other two divisions of the trigeminal nerve, 

 the ophthalmic nerve gives off a meningeal branch. This 

 small twig passes into the tentorium cerebelli. 



The terminal branches of the ophthalmic division of the 

 trigeminal nerve are the naso-ciliary, the lacrimal, and the 

 frontal. The naso-ciliary, as a rule, takes origin first ; the 

 lacrimal is given off soon after ; and then the stem of the 

 nerve is continued onwards as the frontal These three 

 nerves enter the orbit through the superior orbital fissure. 



Nervus Oculomotorius (Third), Nervus Trochlearis (Fourth), 

 and Nervus Abducens (Sixth). It has been noted already 

 that the oculo-motor nerve pierces the dura mater within the 

 small triangular area, in the middle cranial fossa, which 

 lies immediately anterior to the crossing of the attached 

 and free margins of the tentorium (p. 210). It has been noted 

 also that the trochlear (fourth) nerve pierces the dura mater 

 in the posterior fossa under the free margin of the tentorium. 

 Both now proceed anteriorly in the lateral wall of the cavern- 

 ous sinus. The oculo-motor nerve occupies the highest 

 level, then comes the trochlear nerve, and immediately 

 below that the ophthalmic division of the trigeminal nerve. 

 They therefore present a numerical order from above down- 

 wards. The abducent nerve, which pierces the dura mater 

 in the posterior fossa, at the lower and lateral part of the 

 dorsum sellae, curves round the lateral side of the internal 

 carotid artery, and then passes anteriorly more directly within 

 the cavernous sinus than the others (Fig. 130). 



The oculo-motor, trochlear, and abducent nerves during 

 their course in the cavernous sinus receive communica- 



