S42 jdiinial of Agriculture, Victoria. [11 Dec. 191 i. 



Case No. 4. — A bay light mare, aged 15 years, full sister to No. 3, 

 and with foal at foot. She was also bred by the owner. Both eyes in 

 this ca.se are affected with cataract of at least three years' standing, and 

 the mare is totally blind in both eyes. Two foals have been bred from 

 her since .she became l)liiid. but up to tlie present their eyes appear to be 

 normal. 



The foregoing cases are all the property of one owner. 



Case No. 5. — Bay medium draught mare, aged 4 years, belonging to 

 a brother of the owner of the preceding cases, who resides in the same 

 neighbourhood. This mare also has well marked cataract in both eyes. 

 She is in no way related tO' the others, though bred in the district. Her 

 sire and dam still survive, and belong to the district, but there has been 

 no opportunity for examaning them, so the statement has to be accepted 

 that their eyes have not been noticed to be wrong in any way. 



It will be as well here to give some information as to what the con- 

 ditions met with really are. To begin with, a short reference \yill be 

 made to the structure of the normal eye, the various parts of which are 

 indicated in Fig. i. This represents the normal horse's eye, seen on 

 section from front to back. The eye is made up as follows : — 



A. Tlie cornea or watch glass — front of the eye. This is exposed to view when 



the lids are naturally open and is normally quite clear to allow the light 

 to pass into the deeper portions of the eye. 



B. The front chamber or cavity behind the cornea which -3 filled with trans- 



parent fluid which transmits light and preserves the shape of the front 

 of the eyeball. 



C. The iris or inside curtain of the eye pierced by an elliptical opening, the 



pupil, which enlarges or reduces in diameter according to the strength 

 of light passing through. 



D. The elliptical open space in the centre of the iris, called the pupil. 



E. The lens of the eye — a bi-convex structure; jelly-like and transparent — 



through which the rays of light are bent to concentrate on the back 

 curtain and nerve of the eye. 



F. Main cavity of eyeball filled with thin transparent jelly-like fluid which 



transmits light and preserves the shape of the larger back portion of the 

 eyeball. 



G. Retina or back curtain of the eye, which receives the impressions of light 



or objects and transmits them by the optic nerve to the brain. 



H. The optic nerve which carries impressions to the brain. 



I. Outermost coat — the sclerotic or "while of the eye"" — covering the whole eye- 

 ball, except the front transparent portion. 



J. The middle coat of the eyeball — the choroid — which lines the inside of the 

 " white of the eye "' and is joined to the iris in front. 



K. Eyelids. 



A study of the foregoing details will enable the reader to more readily 

 understand the nature and situation and peculiar characters of the 

 affections. 



In case No. x , the appearance of the eyes, already described, is very 

 suggestive of a blighting process having in some way affected the primi- 

 tive eye substance at an early period in its development. This process, ap- 

 parently, while not destroying the actual elements of the eye, has seriously 

 interfered with their natural growth and development to such an extent 

 that the jjortion which represents the " white of the eye," besides assum- 

 ing a fleshy character, has grown at a greater rate than that which should 

 ultimately have become the transparent front of the eye. The result of 

 this is that the former has closed in on the latter, .so as to pinch it up 

 and shut it out of its proper place. 



Though totally blind, the foal is growing quite satisfactorily and 

 manages tO' get along surprisingly well. It seems also to be sensible to 

 the contrast between lightness and darkness, though, curiouslv enough, 

 when moving about, it invariablv turns in circles to the right. 



