40 INNERVATION. [CHAP. XVII. 



its axis, along which it runs to the interior of the eye, in a canal of 

 fibrous tissue. This branch then radiates to supply the retina, and in 

 the foetus sends forwards a twig to the lens. It is accompanied 

 everywhere by corresponding veins. 



Other nerves are distributed to the eye, which are connected with 

 the nutrient and other actions of the eyeball. These are derived 

 from the ophthalmic division of the fifth, from the third pair, and 

 from the sympathetic. It is remarkable, however, that all these 

 nerves, with two exceptions, between their origin and their dis- 

 tribution in the globe of the eye, meet in a small ganglion situated 

 on the outer side of the optic nerve, called the ophthalmic or len- 

 ticular ganglion. This body is usually considered a portion of 

 the cephalic division of the sympathetic; it is connected with the 

 superior cervical ganglion by a long branch which ascends from the 

 carotid plexus along the carotid artery, and enters the orbit. A 

 long nerve from the nasal branch of the ophthalmic division of the 

 fifth also joins this ganglion at its superior and posterior angle, and 

 a short thick branch from the third nerve joins the ganglion at its 

 inferior posterior angle. From the anterior angles of the ganglion 

 thus formed, proceed two bundles of delicate nerves, from twelve to 

 sixteen in number (ciliary nerves'), which, after having pierced the 

 sclerotic at its posterior third, pass between that tunic and the 

 choroid, and are distributed chiefly to the ciliary muscle and iris, 

 but also to the cornea 



From the nasal branch of the ophthalmic there proceed two long 

 nerves, called long ciliary nerves, which do not form any connexion 

 with the ophthalmic ganglion. These nerves pass off in company, 

 but soon separate from each other, one going to the inner, the other 

 to the outer side of the eyeball; they penetrate the sclerotic, and 

 accompany the other ciliary nerves in their distribution to the ciliary 

 muscle and iris. 



The eye is moved by six muscles, four straight and two oblique. 

 The former arise from the margin of the optic foramen, at the apex 

 of the orbit, and are inserted into the sclerotic near the cornea, 

 above, below, and on each side, The superior oblique arises with 

 the recti, but has its direction changed by a pulley of fibrous tissue 

 at the upper and inner part of the margin of the orbit; whence it 

 passes backwards, outwards, and downwards, under the superior 

 rectus muscle to the sclerotic behind the transverse median plane of 

 the globe, between the superior and external recti. The inferior 

 oblique arises from the lower part of the margin of the orbit, 

 about its inner third, and passing backwards, outwards, and up- 



