EXAMINING THE EYES. 723 



waistcoat or shirt front, should be carefully excluded ; for it would 

 be apt to cause the production in the eye, of white images, the 

 appearance of which might interfere with the accuracy of the 

 observer's scrutiny. The plan of examining the sight in the open 

 air, while shielding the eye with the top of a black hat from the 

 reflection of white objects, is far too rough a procedure by which 

 to arrive at correct results. While covering one eye with the hand, 

 and bringing the light close to the other ©ye, and then drawing it 

 away, we should see if the pupil of the eye which is being examined 

 contracts or dilates in a natural manner; that no part of the iris 

 is adherent to the lens ; and that the power of contraction and 

 dilatation is the same in both eyes. Each eye should be examined 

 separately ; for one may be completely blind from amaurosis, and 

 yet its pupil may obey the stimulus of light applied to the sound 

 eye, although insensible to that falling on its own retina. While 

 making this experiment, observe if the corpora nigra (the small 

 brownish-black balls which are to be seen, principally, on the upper 

 margin of the pupil) are regular; for it sometimes happens that 

 one or more of them become torn away from the iris, and may 

 consequently affect the vision. The cornea should be carefully 

 examined, to see if there are any scars or opacities on it ; and, 

 while holding the candle or lamp a little to one side, and raised 

 or depressed as the case may require, look through the pupil, and 

 try to detect on the lens or its capsule any speck, the existence of 

 which should be sufficient to cause the rejection of the horse for 

 cataract. Regard the eye from one side also, while holding the 

 taper to the front. To further test the condition of the lens, hold 

 the light a little to one side of the eye, and look for the three 

 images of the flame that are toi be seen in a healthy eye ; the first 

 and brightest being reflected fro'm the cornea; the second and 

 largest from the front surface of the lens ; and the third, which is 

 small, dim, and placed upside-down, from the back of the lens. If 

 the flame be slowly moved from one side to the other, the first 

 two images will follow the direction of the candle, while the third 

 and reversed one will go the opposite way. If a cataract be 

 present and complete, the third image will be absent ; if it be only 

 partial, the view of the third image will be found to be obstructed 

 when the light falls on the opacity. The ophthalmoscope might 

 frequently be used with benefit in the examination of the eyes of 

 the horse. As its description is beyond the limits of this work, 

 and it requires practical instruction to attain facility in its use, I 

 need not further allude to it here. In cases of doubt as to the 

 condition of the lens, employ a magnifying glass. If it is necessary 

 to dilate the pupil,, place in the eye a drop or two ofMiquor atropice 

 sulphatis (p. 613). 



46* 



