ANATOMY OF THE EYE 17 



composed principally of capillaries; fifth, the lamina 

 vitrea, which is lined with a layer of pigment epithe- 

 lium. Late authorities claim that this pigment-layer 

 embryologically belongs to the retina. An absence of 

 black pigment on the posterior layer in the carnivora 

 affords a greenish-blue reflex, and is known as the 



Fig. 5. — Fundus oculi, seen on equatorial section of eyeball of horse: 

 I, Sclera; 2, choroidea; j, retina (loosened); 4, tapetum; 5, optic papilla; 

 6, optic nerve. (After Ellenberger, in Leisering's Atlas.) 



''tapetum lucidum." This reflex is noticeable in cats' 

 eyes in the dark. 



Because of the intimate association of the pigment 

 and circulatory layers of this body with those of the 

 ciliary body and iris, and from the likeness, as a whole, 

 to that of a grape when the sclera is stripped off, this 

 portion of the eye — the iris, the ciliary body, and the 

 chorioid — is known as the uveal tract or uvea. 



The retina is the internal coat or lining of the eye. 



