DISEASES OF THE EYE. 



By Dr. JAMES LAW, F. R. C. V. S., 



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 saddle 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 commonplace or familiar. 

 When we add to this that certain diseases of the eyes, like recurring 

 inflammation (moon blindness), are habitually transmitted from parent 

 to offspring, we can realize still more fully the importance of these mala- 

 dies. 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. 



THE EYEBALL. 



A full description of the structure of the eye is incompatible with our 

 prescribed limits, and yet a short description is absolutely essential to 

 the clear understanding of what is to follow. 



The horse's eye is a spheroidal body, flattened behind, and with its 

 posterior four-tifths inclosed by an opaque, white, strong fibrous mem- 

 brane (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), and that in its turn is lined by the extremely 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 trayisp are nt 

 cornea. This transparent coat is composed, in the main, of fibres with 

 lymph interspaces, and it is to the condition of these and their conden- 

 sation and compression that the translucency is largely due. This may 

 be shown by comjiressing with the fingers the eye of an ox which has just 



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