412 



COLLEGE ZOOLOGY 



e.c 



ecj 



serves as a protective covering. In front of the lens (L) the 



sclerotic coat forms a transparent area called the cornea (c). 



Beneath the sclerotic coat is the middle coat or choroid (Cti) ; 



this is supplied with blood vessels and contains a great deal of 



black pigment (P.E) 

 which prevents light 

 from entering except 

 through the cornea. 

 The choroid coat is 

 separated from the 

 sclerotic coat and perfo- 

 rated just in front of the 

 lens; the opening is the 

 pupil, and a part of 

 the choroid surrounding 

 the pupil is the iris (I). 

 The inner coat, the 

 retina (R), is the most 

 important, since it is the 

 sensitive layer, being an 

 expansion of the optic 

 nerve (O.N). It lines 

 the cavity back of the 

 lens. The lens (L) is 

 biconvex and trans- 



Scl 



parent. It is attached 



FIG. 351. Diagrammatic horizontal section 

 of the eye of MAN. c, cornea; Ch, choroid 

 (dotted) ; C. P., ciliary processes; e.c, epithelium 

 of cornea; e.cj, conjunctiva; f.o, yellow spot; 

 7, iris ; L, lens ; O.N, optic nerve ; os, ora 

 serrata; o-x, optic axis; p.c.R, anterior non- 

 visual portion of . retina ; P.E, pigmented 

 epithelium (black); R, retina; sp.l, suspen- 

 sory ligament; Scl, sclerotic; V.H., vitreous to the c h O roid Coat by 

 chamber. (From Parker and Haswell, after 



Foster and Shore.) ' a suspensory ligament 



(sp. I) , and separates the 



small anterior cavity, filled with a fluid called aqueous humor, 

 from the large posterior cavity, filled with a jelly-like substance 

 called vitreous humor (V.H.). 



The eye is like a camera in certain respects. With the aid 

 of the lens an image is formed on the sensitive retina of the 

 objects in front of the cornea. The eye is accommodated for 



