454 NERVOUS SYSTEM. 



SECT. III. NERVUS MOTOR OCUL1. 



The Nervus Motor Oculi, or third pair, having reached from 

 the basis of the brain to the external side of the cavernous si- 

 nus, is placed there within and above the optic nerve and the 

 sixth pair; it then changes its direction, and penetrates through 

 .the sphenoidal fissure into the orbit, on the outer side of these 

 nerves, and below them. 



The motor oculi divides, in the sphenoidal fissure, into two 

 branches, one above the other. The first crosses over the op- 

 tic nerve and the nasal branch of the ophthalmic, having some 

 anastomoses with the latter, and then distributes its filaments 

 upon the rectus superior muscle; some of them also penetrate 

 the latter to get to the levator palpebrse. The second branch 

 is much larger than the first. It passes between the optic nerve 

 and the rectus inferior muscle, and is subdivided into three 

 fasciculi: one for the rectus internus muscle; another for the 

 rectus inferior; and a third, which is the longest and the small- 

 est, for the obliquus inferior muscle. The latter fasciculus, not 

 far from its root, gives off a filament, which, going along the 

 external margin of the optic nerve, runs into the posterior 

 margin of the lenticular or ophthalmic ganglion, and is its short 

 root. 



The Lenticular Ganglion is situated on the outer side of the 

 optic nerve, in the orbit of the eye, and is about a line in dia- 

 meter, being flattened. Two nerves concur to form it: the 

 branch just alluded to, from the motor oculi, and one from the 

 ophthalmic branch of the trigeminus. From this ganglion 

 arise the most of the ciliary nerves; which, as stated, are about 

 twenty in number, and go to the choroid coat of the eye and 

 to the iris. 



SECT. IV, NERVUS TROCHLEARIS. 



The Nervus Trochlearis, or fourth pair, having got into its 

 canal in the cavernous sinus, as it goes along the internal mar- 

 gin of the ophthalmic nerve, receives there a small filament 



