712 EXAMINIJVa FOE SOUNDNESS. 



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 eye, 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, we should 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, we 

 should 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. We may also 

 regard the eye from one side, while holding the taper to the 

 front. To further test the condition of the lens, we may hold the 

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

 of the flame that are to be seen in a healthy eye; the first and 

 brightest being reflected from 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 ohs.tructed when the 

 light falls on the lopacity. 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 as it re- 

 quires 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, we may employ a magnifying glass. If it is necessary 

 to dilate the pupil, we may place in the eye a drop or two of 

 liquor atropice sulphatis (p. 601). 



