DISEASES OF THE EYE. 
By James Law, F. R. C. V. S., 
Formerly Professor of Veterinary Science, etc., Cornell University. 
We can scarcely overestimate the value of sound eyes in the horse, 
and hence all diseases and injuries which seriously interfere with 
vision are matters of extreme gravity and apprehension, for should 
they prove permanent they invariably depreciate the selling price to 
a considerable extent. A blind horse is always dangerous in the sad- 
dle or in single harness, and he is scarcely less so when, with partially 
impaired vision, he sees things imperfectly, in a distorted form or in 
a wrong place, and when he shies or avoids objects which are com- 
monplace or familiar. When we add to this that certain diseases of 
the eyes, like recurring inflammation (moon blindness), are habitu- 
ally transmitted from parent to offspring, we can realize still more 
fully the importance of these maladies. Again, as a mere matter of 
beauty, a sound, full, clear, intelligent eye is something which must 
always add a high value to our equine friends and servants. 
STRUCTURE OF THE EYE. 
(Pl. XXII.) 
THE EYEBALL. 
A full description of the structure of the eye is incompatible with 
our prescribed limits, and yet a short description is absolutely essen- 
tial to the clear understanding of what is to follow. 
The horse’s eye is a spheroidal body, flattened behind, and with its 
posterior four-fifths inclosed by an opaque, white, strong fibrous 
membrane (the sclerotic), on the inner side of which is laid a more 
delicate, friable membrane, consisting mainly of blood vessels and 
pigment cells (the choroid), which in its turn is lined by the ex- 
tremely delicate and sensitive expansion of the nerve of sight (the 
retina). The anterior fifth of the globe of the eye bulges forward 
from what would have been the direct line of the sclerotic, and thus 
forms a segment of a much smaller sphere than is inclosed by the 
sclerotic. Its walls, too, have in health a perfect translucency, from 
which it has derived the name of transparent cornea. This trans- 
parent coat is composed, in the main, of fibers with lymph interspaces, 
274 
