THE HUMORS OF THE EYE. 



419 



reaction, and weighs about four grains. The anterior 

 chamber is bounded in front by the cornea, behind by the 

 anterior surface of the iris. The posterior chamber is 

 limited in front by the iris, behind by the suspensory 

 ligament and ciliary processes. 

 In the foetus a delicate mem- 

 brane, the membrana pupil- 

 laris, is stretched across the 

 pupil. It becomes absorbed 

 about the seventh month. 



The vitreous humor is in- 

 closed in a sac called the 

 hyaloid membrane. It fills 

 the posterior four-fifths of the 

 eyeball. It is transparent, 

 albuminous, and slightly 

 gelatinous. Anteriorly it is 

 concave, and accommodates 

 the crystalline lens. A leaflet 

 of the hvaloid membrane 



ii 



passes to the margin of the 

 lens, forming its suspensory 

 ligament. The interval be- 

 tween this and the lens forms 

 a canal, the sinus of Petit. 



T , 1 . FIG. 181. LAYERS OF THE RETINA. 



Ill the ICetUS Vei'V dellCate Pi, hexagonal pigment cells : St. rods Hnd 



cones: Le. external limiting membrane ; SuK. 

 external nuclear layer ; augr external granu- 

 Iar i aver . inKi internal nuclear ; ingr, internal 

 granular: Ggl. ganglionic nerve-cells : O, fibres 



f i> tic : Li -,i.^T al mitinf f '"T" 



brane: Rk. hbres of Muller; K, nuclei; Sg, 

 i\ i j_i_ r spaces for the nervous elements. 



nmg through the centre of 



the vitreous is the canal of Stilling, foimed by the hya- 



loid membrane. 



The crystalline lens is a biconvex, plastic body, in- 

 vested by a capsule. It is placed behind the pupil, and 

 rests in a depression in the vitreous humor. In front it 



PVf frmrirl tVimnrrVirmf 

 die lOllllCl UllOUgllOUl 



1 . , _-. 



the vitreous humor. Run- 



