684 TRIGEMINA.L NERVE. 



2. The lacrimal nerve gives off (a) sensory branches to the conjunc- 

 tiva, the tipper lid, the adjacent skin of the temple (Fig. 243, a) ; (6) true 

 secretory fibers to the lacrimal gland. Accordingly, irritation of the 

 nerve excites the secretion of tears, while division causes paralytic flow 

 of tears. The secretion can be excited reflexly by the irritation of strong 

 light and by irritation of the first and second branches of the trigeminus, 

 and even of all of the sensory cerebral nerves and some of the nerves of 

 the trunk. The reflex center for the secretion of tears is situated in 

 the optic thalamus. 



3. The frontal nerve (f) gives off, through its supratrochlear branch, 

 sensory fibers to the upper lid, the brow, the glabella, and fibers reflexly 

 stimulating the secretion of tears; and, through its supraorbital branch, 

 analogous fibers to the upper lid, and the skin of the forehead and of the 

 adjacent temple to the vertex. 



4. The nasociliary nerve (n c), through its infratrochlear branch, 

 supplies fibers analogous to those just mentioned to the conjunctiva, the 

 lacrimal caruncle and sac, the upper lid, the brow, the root of the nose. 

 Its ethmoid branch supplies the tip and the alae of the nose exter- 

 nally and internally with sensory fibers and also the anterior portion of 

 the septum and the lower turbinates with tactile fibers (which also in 

 part excite reflexly the flow of tears) and perhaps also with vasomotor 

 fibers, which may possibly arise through anastomosis with the sym- 

 pathetic. From the naso-ciliary branch arise also the long roots (Fig. 

 243) of the ciliary ganglion (c) and the first, second, and third long ciliary 

 nerves. 



$ The ciliary ganglion (Fig. 243, c), which really belongs rather to the 

 third than to the fifth nerve, has three roots: (a) the short root, from the 

 oculomotor (3), (b) the long root (1) from the nasociliary, and (c) the 

 sympathetic root (s) from the carotid plexus, occasionally united with 

 b. From the ganglion there arise between six and ten short ciliary nerves 

 (t), which, together with the long ciliary nerves, penetrate the sclera near 

 the entrance of the optic nerve and pass forward between this and the 

 choroid. They contain: 



1. The motor fibers for the sphincter muscle of the pupil and the 

 tensor of the choroid from the oculomotor root. 



The oculomotor root is connected in the ciliary ganglion by terminal ramifica- 

 tions with dendrites of the ganglion-cells (not the sympathetic and those of the 

 trigeminus). After division of the oculomotor nerve, degeneration of its libers 

 takes place only into the ciliary ganglion, but not further in a peripheral direction. 

 Small doses of nicotin paralyze the oculomotor nerve from its origin to the ciliary 

 ganglion and this portion rapidly loses its function after death, while the ciliary 

 nerves that cause contraction of the pupil retain their irritability for a considerable 

 time. 



2. Sensory fibers for the cornea, which are distributed by means of 

 most delicate filaments throughout the epithelium ; and for the bulbar con- 

 junctiva, which penetrate the sclera. These stimulate also reflexly 

 the flow of tears (lacrimal nerve) and closure of the eyelids (facial nerve). 

 The iris, which is the seat of pain in the presence of inflammatory 

 processes and as a result of operation; the choroid, which is the seat of 

 painful tension on contraction of the tensor of the choroid; and the 

 sclera also receive sensory fibers. 



^3. Vasomotor nerves for the vessels of the iris, the choroid, and the 

 retina. These, however, are derived in part only from the sympathetic 



