THE CRANIAL OR ENCEPHALIC NERVES. 711 



which receive these fibres, are in conmunication with several cranial nerves, 

 particularly the pneumogastric, glosso-pharyngeal, facial, and auditory. 



Semilunar or Gasserian ganglion. This ganglion, which receives the 

 sensitive root of the trigeminus, is crescent shaped, its concavity being 

 turned backwards and inwards. It may be said to be imbedded in the 

 nbro-cartilaginous substance which in part closes the occipito-spheno- 

 temporal hiatus, and divides it into several particular foramina. Its 

 superior face is covered by the dura mater, and sends a number of filaments 

 to that membrane. 



The Gasserian ganglion is not continued by a single trunk, but imme- 

 diately gives rise to two thick branches, one of which leaves the cranium 

 by the foramen ovale an opening formed by the above-named hiatus; 

 while the other is lodged in the external fissure in the intercranial face of 

 the sphenoid bone, and passing along it as far as the entrance to the supra- 

 phenoidal foramina, bifurcates. 



Hence it results that the trigeminus is divided, even at its origin, into 

 hree branches : two superior the ophthalmic branch of Willis, and the 

 uperior maxillary nerve, commencing by the same trunk ; and an inferior, 

 which constitutes the inferior maxillary nerve. . 



Motor or small root (Figs. 337, 338). This is a flattened band which 

 emerges from the pons Varolii, at the inner side of the principal root. Its 

 ibres may be easily followed to the interior of the pons Varolii, and in their 

 Lirection they comport themselves like those of the large root, by becoming 

 confounded with the substance of the antero-lateral fasciculus of the 

 medulla oblongata. Leaving the pons, this root passes forwards on the 

 nferior face of the Gasserian ganglion, which it crosses in a diagonal 

 manner outwards, and beyond which it intimately unites with the fibres 

 of the inferior maxillary nerve. The superior maxillary nerve and the 

 ophthalmic branch do not receive any fibres from it. In the fifth pair, then, 

 t is only the inferior maxillary nerves which are at the same time sensitive 

 and motor, and are real mixed nerves. 



A. OPHTHALMIC BRANCH (Fig. 335, 1). This is the smallest of the 

 ;hree divisions furnished by the Gasserian ganglion, and proceeds by a 

 ;runk common to it and the maxillary nerve, which will be described here- 

 after. This branch enters the smallest of the large suprasphenoidal 

 foramina, along with the common and external oculo-motor nerves, and 

 in the interior of this bony canal divides into three ramuscules, which reach 

 ;he bottom of the ocular sheath by the orbital hiatus. 

 These ramuscules are : 



1. The frontal or supra-orbital (supratrocldear) nerve. 



2. The lachrymal nerve. 



3. The nasal or palpebro-nasal nerve. 



1. FRONTAL NERVE (Fig. 335, 4). This is a flat, voluminous branch 

 placed on the inner wall of the ocular sheath, and proceeding nearly parallel 

 with the great oblique muscle of the eye to the supra-orbital foramen, into 

 which it passes along with the artery of the same name. Undivided before 

 its entrance into this orifice, immediately after its exit from it, it separates 

 into several ramuscules, which meet the anterior auricular nerve, and are 

 expended in the skin of the forehead and upper eyelid. 



2. LACHRYMAL NERVE (Fig. 335, 3). This is composed of several 

 filaments, which ascend between the ocular sheath and the elevator muscles 

 of the eyelid and superior rectus, to enter the lachrymal gland. One of 



