DISEASES OF THE EYE. 255 



(pressed on the upper lid while the thumb depresses the lower one. In 

 cases in which it is desirable to examine the inner side of the eyelid 

 further than is possible by the above means, the upper lid may bo 

 drawn down by the eyelashes with the one hand and then everted 

 over the tip of the forefinger of the other hand, or over a probe laid 

 flat against the middle of the lid. Where the interior of the eye must 

 be examined it is useless to make the attempt in the open sunshine or 

 under a clear sky. The worst cases, it is true, can be seen under such 

 circumstances, but for the slighter forms the horse should be taken 

 indoors, where all light from above will be shut off, and should be 

 placed so that the light shall fall on the eye from the front and side. 

 Then the observer, placing himself in front of the animal, will receive 

 the reflected rays from the cornea, the front of the lens and the back, 

 and can much more easily detect any cloudiness, opacity or lack of 

 transparency. The examination can be made much more satisfactory 

 by placing the horse in a dark chamber and illuminating the eye by 

 a lamp placed forward and outward from the eye which is to be exam- 

 ined. Any cloudiness is thus easily detected, and any doubt may be 

 resolved by moving the lamp so that the image of the flame may be 

 passed in succession over the whole surface of the transparent cornea 

 and of the crystalline lens. Three images of the flame will be seen, 

 the larger one upright, reflected from the anterior surface of the eye; 

 a smaller one upright, reflected from the anterior surface of the lens ; 

 and a second small one inverted from the back surface of the lens. 



So long as these images ai;e reflected from healthy surfaces they 

 will be clear and perfect in outline^, but as soon as one strikes on an 

 area of opacity it will become diffused, cloudy, and indeflnite. Thus, 

 if the large upright image becomes hazy and imperfect over a partic- 

 ular spot of the cornea, that will be found to be the seat of disease 

 and opacity. Should the large image- remain clear, but the small 

 upright one become diffuse and indefinite over a given point, it indi- 

 cates opacity on the front of the capsule of the lens. If both upright 

 images remain clear while the inverted one becomes indistinct at a 

 given point, then the opacity is in the substance of the lens itself or in 

 the posterior part of its capsule. 



If in a given case the pupil remains so closely contracted that the 

 deeper parts of the eye can not be seen, the eyelids may be rubbed 

 with extract of belladonna, and in a short time the pupil will be found 

 widely dilated. 



DISEASES OF THE EYELIDS. 



Congenital disorders. — Some faulty conditions of the eyelids are 

 congenital, as division of an eyelid in two, after the manner of hare- 

 lip, ahnormally small opening between the lids, often connected with 

 imperfect development of the eye, and closure of the lids hy adhesion. 



