THE EYE. 35 



behind. It is seen to be made up of inner cir- 

 cular fibres and longer fibres which radiate from 

 these. When the pupil lessens, it is by the cir- 

 cular fibres contracting, but when it widens it is by 

 the radiating fibres contracting. What we have to 

 do in the darkened stable is to see that the ' pupil' 

 diminishes and enlarges freely. For this purpose 

 we cover the eye with our hand to darken it for 

 half a minute or so when we expect the * pupil' 

 will dilate ; then we place the candle close to the 

 back of the hand that is covering the eye and sud- 

 denly remove the hand and watch the pupil con- 

 tract, which it ought to do from the glare of the 

 light being too much for the eye. In a darkened 

 stable, and a candle held away from the eye, you 

 will still see the pupil widening and narrowing, 

 which is, of course, a sign that it is in good order 

 and capable of acting as a curtain and keeping out 

 bright glare which dazes the animal. It widens 

 and admits all light possible when there is not 

 much light to spare. When the pupil is very 

 widely open it gives the eye a glassy appearance, 

 and should this condition be permanent, as you will 

 have seen it, no doubt, the disease called Amaurosis, 

 gutta Serena, or glass-eye is present, and the eye is 

 worthless. It may be from disease of the brain. 



Instead of being fixedly open, the pupil may be 

 fixed and quite immoveable and closed, or nearly 

 so. This serious flaw arises in this way. When 

 violent inflammation seizes the eye and attacks the 



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