DIOPTRIC MECHANISMS OF THE EYEBALL 



615 



INNERVATION OF THE INTRINSIC MUSCLES OF THE EYE 



The eyeball is supplied by the short ciliary nerves, which come 

 from the lenticular or ciliary ganglion and passing forwards pierce the 

 sclerotic coat about half-way between the anterior and posterior poles 

 of the eyeball. The lenticular gan- 

 glion has three so-called roots, by 

 which it is connected with or receives 

 fibres from : 



(1) The third or oculo-motor 

 nerve, by the ' short root.' 



(2) With the sympathetic plexus 

 lying in the cavernous sinus, and, 

 through the fibres lying on the 

 internal carotid artery, with the 

 cervical sympathetic nerve. 



(3) With the nasal branch of the 

 ophthalmic division of the fifth nerve 

 by means of the ' long root.' 



The eyeball is also supplied by l.c 

 the two long ciliary nerves (Fig. 276) 

 which come direct from a branch of 

 the ophthalmic division of the fifth 

 nerve and pass forwards on to the 

 eyeball, piercing the sclerotic coat 

 in front of the point at which this 

 coat is penetrated by the short 

 ciliary nerves. There are thus three 

 nerves by means of which the 

 activity of the muscular fibres form- FlG - 276 - 

 ing the ciliary muscle, the sphincter, 



-Is 



8.C 



sym 



Nerve-supply to the eyeball. 

 (After FOSTER.) 



lenticular ganglion with its three 



and the dilatator iridis can be in- roots, viz. : r.b, radix brevis or short 

 , . , , . j , , root ; r.l, radix longus or long root ; 



fluenced, viz. the third nerve, tne 5//m> sympathetic root ; V. opth. oph- 

 fifth nerve, and the sympathetic thalmic division of F nerve ;/// oc.m, 



. J . .. oculo-motor nerve ; //, optic nerve ; 



nerve. On exciting the root OI the i tCf i ong ciliary nerves ; s.c, short 



third nerve we obtain : ciliar y nerves - 



(a) Constriction of the pupil. 



(b) Contraction of the ciliary muscle, i.e. spasm of accommoda- 

 tion. 



The same effects are produced by stimulating the lenticular ganglion 



or the short ciliary nerves. 



Excitation of the long ciliary nerves of the ophthalmic division of 

 the fifth nerve, or of the Gasserian ganglion, causes dilatation of the 

 pupil, but is without influence on the ciliary muscle. 



