164 EQUINE ANATOMY. 



At the point of entrance of the optic nerve, there is an oval 

 point i inch in diameter, where all nerve elements are absent; 

 this is the blind spot. 



FIG. 26. 



THEORETICAL SECTION OF THE HORSE S EYE. 



a, Optic nerve; b, Sclerotic; c, Choroid; d, Retina; e, Cornea; /, Iris; g, h, Ciliary 

 circle (or ligament) and processes given off by the choroid, though represented 

 as isolated from it, in order to indicate their limits more clearly; z", Insertion of 

 the ciliary processes on the crystalline lens; /, Crystalline lens; k, Crystalline 

 capsule; /, Vitreous body; m, n, Anterior and posterior chambers; o, Theoretical 

 indication of the membrane of the aqueous humor; p, p, Tarsi; q, g, Fibrous 

 membrane of the eyelids; r, Elevator muscle of the upper eyelid; s, s, Orbicularis 

 muscle of the eyelids; t, t, Skin of the eyelids; , Conjunctiva ; v, Epidermic layer 

 of this membrane covering the cornea; x. Posterior rectus muscle; y, Superior 

 rectus muscle; z. Inferior rectus muscle; w, Fibrous sheath of the orbit (or or- 

 bital membrane). 



HUMORS. 



These are the aqueous and vitreous 'humors, and crystalline 

 humors. 

 The Aqueous humor fills up the space lying between the 



