THE OPHTHALMIC BRANCH OF THE FIFTH. 59 1 



the metor nuclei of all the nerves arising from the medulla oblongata, with the exception of 

 the abducens. This explains the vast number of reflex relations of the fifth nerve. The thick 

 trunk appears on each side of the pons (fig. 428), when its posterior root (perhaps in connection 

 with some fibres from the anterior) forms the Gasserian ganglion, upon the tip of the petrous 

 part of the temporal bone (fig. 429). Fibres from the sympathetic proceed from the plexus caver- 

 nosus to the ganglion. The nerve divides into three large branches. 



I. The ophthalmic division (fig. 429, d) receives symjmthetic fibres (vaso-motor 

 nerves) from the plexus cavernosus ; it passes through the superior orbital fissure 

 [sphenoidal] into the orbit. Its branches are : 



1. The small recurrent nerve which gives sensory branches to the tentorium 

 cerebelli. Fibres the vaso-motor nerves for the dura mater proceed along with 

 it from the carotid plexus of the sympathetic. 



2. The lachrymal nerve gives off (a) Sensory branches to the conjunctiva, the 

 upper eyelid, and the neighbouring part of the skin over the temple (fig. 429, a) ; 

 (b) true sensory fibres to the lachrymal gland (?). Stimulation of this nerve is said 

 to cause a secretion of tears, while its section prevents the reflex secretion excited 

 through the sensory nerves of the eye. After a time, section of the nerve is followed 

 by a paralytic secretion of tears (Herzenstein and Wolferz), although the statement 

 is contested by Reich. The secretion of tears may be excited reflexly, by strong 

 stimulation of the retina by light, by stimulation of the first and second branches 

 of the trigeminus, and through all the sensory cranial nerves (Demtschenko) ( 356, 

 A, 6). 



3. The frontal (/) gives oft' the supratrochlear, which supplies sensory fibres to 

 the upper eyelids, brow, 'glabella, and those which excite the secretion of tears 

 reflexly; and by its supraorbital branch (6), analogous branches to the upper- 

 eyelid, skin of the forehead, and the adjoining skin over the temple as far as the 

 vertex. 



4. The naso-ciliary nerve (nc), by its infratrochlear branch supplies fibres, 

 similar to those of 3, to the conjunctiva, caruncula, and saccus lacrimalis, the 

 upper eyelid, brow, and root of the nose. Its ethmoidal branch supplies the tip 

 and alse of the nose, outside and inside, with sensory branches, as well as the upper 

 part of the septum and the turbinated bones with sensory fibres, which can act as 

 afferent nerves in the reflex secretion of tears ; while it is probable that vaso-motor 

 fibres are supplied to these parts through the same channel. (These fibres may be 

 derived from the anastomosis with the sympathetic (?).) The naso-ciliary nerve 

 gives off the long root (I) of the ciliary ganglion (c), and 1 to 3 long ciliary nerves. 



The ciliary ganglion (fig. 429, c), which, according to Schwalbe, perhaps belongs 

 rather to the third than the fifth nerve, has three roots (a) the short or oculomo- 

 torius (3 see 345) ; (b) the long (I), from the naso-ciliary ; and (c) the sympa- 

 thetic (s) sometimes united with b, from the carotid plexus. The short ciliary 

 nerves (t), six to ten in number, proceed from the ganglion, along with the long 

 ciliary nerves, to near the entrance of the optic nerve, where they perforate the 

 sclerotic coat and run forwards between it and the choroid. 

 Ciliary Nerves. Physiologically, these nerves contain : 



1. The motor fibres for the sphincter pupillae and the tensor choroideae from 

 the root of the oculomotorius ( 345, 2, 3). 



2. Sensory fibres for the cornea, which are distributed as excessively fine fibrils 

 between the epithelium of the conjunctiva bulhi ; they perforate the sclerotic. 

 These fibres cause a reflex secretion of tears (N. lacrimalis) and closure of the 

 eyelids (N. facialis). Sensory fibres are supplied to the iris (pain in iritis and in 

 operations on the iris), the choroid (painful tension when the ciliary muscle is 

 strained), and the sclerotic. 



3. Vaso-motor nerves for the blood-vessels of the iris, choroid, and retina. They 

 arise in part from the sympathetic root, and the anastomosis of the sympathetic 



