108 



EXPERIMENTAL PHYSIOLOGY 



the lens, a black, ridged membrane (the ciliary process) ; the 

 jelly-like mass that fills the body of the eye {vitreous humor) ; 

 the three layers of the wall of the eyeball — outer (sclerotic) ^ 

 middle (choroid), inner (retina). 



Note that the optic nerve pierces the two outer coats and 

 spreads out to form the retina. Remove the vitreous humor 

 and notice the soft, whitish retina. Tear this out with the 



rp' 



Fig. 51. — Cross Section of the Eye: Con, conjunctiva; Sc, sclerotic; C, cornea; A, 

 aqueous humor; /, iris; L, crystalline lens; Cm, ciliary muscles and ligament; 

 CP, ciliary process; V, vitreous humor; Ch, choroid; R, retina; O, optic nerVe. 



forceps and note its consistency and thickness. Under this 

 observe the color and luster of the choroid coat. When 

 this is torn out, the interlacing blood vessels are seen passing 

 from one layer to the other. 



LXXI. — ^Action of the Eye. 

 Apparatus. — Model of eye. 

 Directions. — Construct a model of the eye as follows: 



