TEE GLOBE OF THE EYE. 



927 



The Membranes of the Eye. 



A. Fibrous Membranes. 

 ' 1. The Sclerotic (Fig. 502, h). 



The sderoHc is a white, very solid iiiembrane, forming in itself about four- 

 fifths of the external shell of the eye. 



Its exteniaJ face, in relation with the recti muscles and adipose tissue, receives 

 posteriorly — thougli lower than the middle — the insertion of tlie optic nerve, 



Fig. 602, 



THEORKTIC.^L SKCTION OF THE HOPSF.'S F.YK 



1, Orbital arch ; 2, l.idirymal gland. <i, Optic nerve; 6, scJprotic ; c, < horoid ; d, rptina; e, cornea, 

 / /, iris; g, h, ciliary ligament an<l processes given off by the choroid, thousjh rrpre.^ented as 

 isolated from it, in order to indicate their limits more clearly; i, insertion of the cilijiry processes 

 on the capsule of the crystalline lens; j, crystalline lens; k, crystalline capsule; /, vitreous 

 humour; m. n, anterior and posterior chambers; o, theoretical indication of the membrane of 

 the aqueous humour; p, p, tarsi ; q q, fibrous membrane of the eyelids; r, elevator muscle of 

 the upper eyelid; s s, orbicularis muscle of the eyelids; t t. skin of the evelids ; u, conjunctiva; 

 V, epidermic layer of this membrane covering the cornea ; x, postpri<T rectus muscle ; r/, superior 

 rectus muscle; z, inferior rectus muscle; w, fibrous sheath of the orbii (or orbital membrane). 



which passes through it and the choroid to form tlie retina. Its internal face is 

 loosely united to the choroid by vessels, nerves, and connective tissue. 



In front, the sclerotic shows an elliptical opening, the greatest diameter of 

 which is transversal, while its border — bevelled on the inner side — is closely 

 united to the circumference of the cornea. The substance of this membrane is 

 traversed by numerous vessels and nerves, and is not of the same thickness 

 throughout ; at the back, around the entrance of the optic nerve, it is thickest ; 

 it then diminishes gradually towards the larger axis of the organ, and afterwards 

 increases until it meets the cornea. 



Structure. — The sclerotic is wholly composed of fasciculi of connective 



