56 Hounds 



The eyeballs are lodged in bony sockets, the upper 

 segment of the orbital circle being completed by a 

 ligament and not by bone, as in the horse, etc. 



Each eyeball is composed of three tunics, named 

 from without to within as follows : 



{a) The Sclerotic coat. 

 {b) The Choroid coat. 

 {c) The Retina. 



{a) The Sclerotic Coat. — This forms the white 

 portion of the eyeball and is composed of a tissue 

 known as white fibrous. In its normal condition 

 the most minute blood-vessels can be seen passing 

 here and there over its surface from the border of 

 the eye, but when the eye is irritated these minute 

 thread-like blood-vessels become injected, sometimes 

 so much that the whole eyeball becomes blood-shot. 



At the back of the eyeball the optic nerve (nerve 

 of sight) pierces the organ and expands on the inner 

 surface of the retina. 



The front central portion of the eyeball is trans- 

 parent, circular, and composed of muscular layers 

 of cells. It is called the cornea, and is fitted into 

 the sclerotic like a watch-glass into its rim. 



It is this portion of the eye that is commonly the 

 seat of opacity. Either through injury or disease, 

 thus, a spot upon the cornea will interfere with the 

 proper admission of the rays of light into the interior 

 of the eye. 



