276 



PHYSIOLOGY 



CHAP. 



from the nasal branch of the ramus ophthaluiicus of the 

 trigeminus, a motor root from the oculo-motor, and afferent and 







KM-. 114. A. ;u-t flies ol the chiiriiid and iris, lateral vif\v ; H, veins of thf el,., mid, lateral vif\v. 

 ( I'l.itn Auiold.) a, optic nerve ; b, part of sclerotic left behind ; c, region of ciliary muscle : 

 d, iris ; 1, posterior ciliary arteries piercing sclerotic and passing along choroid ; 2, one of thf 

 ]"ii_: ciliary artei ies ; ::, anterior ciliaiy ait cries; 1, 1. two trunks of the venae vorticu^ae at 

 the place whi'ic they leave the choroid and pieiee the scleia. 



ell'crent roots from the plexus cavernosus of the sympathetic. 



The long and short ciliary nerves are given off from the ganglion 



and sympathetic plexus, 

 and penetrate by the pos- 

 terior part of the sclera in 

 12-20 little bundles to the 

 eye, run across its posterior 

 surface, and are ultimately 

 distributed to the ciliary 

 body, iris, and cornea (Fig. 

 116). 



II. From the physio- 

 logical standpoint two 

 parts must be distinguished 

 in the structure of the eye- 

 ball : the retinal portion of 

 the inner coat, containing 

 the expanded termination 

 of the optic nerve, on which 

 the specific function of the 

 eye as the peripheral organ 

 of vision depends, and the 

 of the eye, which constitute a complicated dioptric 



8 



Fio. 115. Nerves of the orbit, lateral view. Reduced J. 

 (Sappey.) The rnmus externus is divided and tinned 

 back. 1, optic nerve ; 2, trunk of third nerve ; 3, its 

 superior division to the levator palpebrae and rectus 

 superior ; 4, its lower and longer branch to the 

 interior oblique ; 5, sixth nerve joined by branches 

 of the sympathetic ; 6, Gasserian ganglion ; 7, 

 ophthalmic nerve ; 8, its nasal branch ; 9, ciliary 

 ganglion ; 10, its short, 11, long, 12, and sympathetic 

 roots; 13, short ciliary nerves; 14, supra-orbital 

 nerve. 



other parts 

 system. 



This physiological distinction 

 development of the eye 



logical 



is sanctioned 

 (for which 



by the embryo- 

 see Text -books of 



