Chap, iv.] THE ORBIT AND EYE. 47 



and in haemorrhage into the vitreous, which often 

 follows injury, the blood may be derived from the 

 retinal vessels, since they run in the inner layers of 

 that membrane, or from the vessels in the ciliary 

 region. 



Nerve supply of the eye-ball. 1. The ciliary 

 nerves derived from the lenticular ganglion and the 

 nasal nerve pierce the sclerotic close to the optic nerve, 

 and pass forwards between the sclerotic and the 

 choroid, supplying those parts. They enter the ciliary 

 muscle, form a plexus about the periphery of the iris, 

 and then send fibres into the iris, which form a fine 

 plexus as far as the pupil. They send branches through 

 the fore part of the sclerotic to the cornea. Thus the 

 eye-ball obtains through these nerves its sensory fibres 

 from the nasal branch of the first division of the fifth, 

 its motor fibres for the ciliary muscle and sphincter 

 iridis from the third nerve, and many sympathetic 

 fibres, among which are those that supply the dilator 

 muscle of the iris. 2. The conjunctiva is supplied by 

 four nerves : above, the supratrochlear ; on the inner 

 side, the infratrochlear ; on the outer side, the lachry- 

 mal (all branches of the first division of the fifth) ; and 

 below by the palpebral branches of the second division 

 of the fifth. As the ciliary nerves pass forwards 

 between the choroid and the sclerotic, it will be seen 

 that they are readily exposed to injurious pressure 

 against the unyielding sclerotic in cases of increased 

 intraocular tension. 



The sensation of the globe itself is derived 

 solely from the first division of the fifth. In inflam- 

 matory affections of the globe, as in corneitis or iritis, 

 besides the pain actually felt in the eye, there is 

 pain referred along other branches of the first division 

 of the fifth. There is pain over the forehead along the 

 supratrochlear, supraorbital, and lachrymal branches 

 (circum-orbital pain), and pain down the side of the 



