THE NERVES. 383 



turcica, between pia mater and arachnoid, below the oculo-moto- 

 rius ; in the sinus cavernosus, on the outer side of the last nerve, 

 above n. ophthalm., united with it by means of several filaments ; 

 in the orbits, close under the periorbita, internal to ram.frontalis, 

 where it gives off filaments to the ram. lacrymalis. Branches : 

 ram. tentorii, from out of the sinus cavernosus backwards to sin. 

 transversus ; it comes, according to Arnold, from ophthalmicus. 



N. trochlearis, long and thin, supplies the obliquus superior, is 

 the n. respiratorius oculi, according to Sir C. Bell. 



634. V. N. trigeminus s. quintus, the Trifacial nerve. 



Origin : with two roots ; the larger posterior (ganglion) root, 

 from corp. restiforme (continuation of the posterior columns of the 

 spinal cord) ; the anterior, smaller root from the surface of the 

 pans, in the anterior lateral part of which, both (the small root 

 from within) become visible in a fissure, as they are united into a 

 trunk. Course : the trunk passes from the pons as a flat fascicu- 

 lus upwards, outwards and forwards, through a canal which the 

 dura mater forms with the superior border of the apex of the pe- 

 trous bone. Here the fibres of the posterior root (portio major) 

 separate and interlace, and form alone the ganglion Casseri, 

 whilst the anterior root (portio minor) passes away under the pos- 

 terior surface of the ganglion, and with the third branch of the 

 ganglion forms the n. maxillaris inferior. [The two portions of 

 this nerve are generally separated at their exit from pons Varolii 

 by a few of its fibres.] 



Ganglion Casseri, the semilunar ganglion, consists of soft gray 

 substance traversed by white fibres ; it is flat, convex in front and 

 externally, lies on the anterior surface of the apex of the petrous 

 bone, in a depression, firmly united with the dura mater. The three 

 following branches pass off" from its convexity : 



Ramus ophthalmicus. 



Ram. maxillaris superior, and 



Ram. maxillaris inferior. 



They diverge as they pass out, and the last is accompanied by the 

 small (motor) root of the n. trigeminus. From the Cass. ganglion 

 a few fibres pass to the tentorium and to the dura mater of the 

 petrous and sphenoid bone ; others to the plexus caroticus. 



635. Ramus I. trigemini s. N. ophthalmicus, 



the smallest and most superior of the three branches of gangl. 

 Casseri, passes forwards, outwards and upwards, on the outer wall 



