A STUDY OF THE SENSES 



301 



The portion of the second coat, which lies within the 

 sclerotic, is known as the cho'roid. It is richly supplied 

 with blood vessels, which run through meshes of connective 

 tissue, and its inner layers have a deep black color, which is 

 due to dark granules of pigment much like those described 

 in the skin (p. 235). In the region where the transparent 



Scl 



FIG. 137. Diagram of the Eye. 



c = cornea. ON = optic nerve. 



Ch = choroid coat. PE = pigment beneath retina. 

 CP ciliary process. R = retina. 



fc = yellow spot. Scl = sclerotic. 



I = iris. spl = suspensory ligament. 



L = lens. VH = vitreous humor. 



cornea begins, this middle layer of the eye separates from 

 the outer coat, turns inward, and forms the colored portion 

 of the eye which is known as the iris (Greek iris = rain- 

 bow). In the center of the iris is a circular perforation, the 

 pupil, through which the rays of light pass into the interior 

 of the eyeball. If one comes suddenly from a dark into a 

 light room, one sees that the size of the pupil is large, but 



