45 



or permanent amaurosis. If, in the course of intlamation, 

 if the retina pigment is deposited in the retina, it produces 

 night blindness — a condition that prevents the animal seeing 

 at night. Extreme sensitiveness of the retina, as observed 

 in Albinos and in some white horses, leads to day blindness. 

 In such cases, the pupil is so nearly or completely closed 

 that the animal can not see in clear sunshine, or when the 

 ground is covered with snow ; but during twilight, on cloudy 

 days, and at night vision is normal. Amaurosis sometimes 

 results from castration. 



Fig. 14. 



Amaurosis. — The pupil is greatlj- expanded, gray-blue in color and 

 the eye appears bright, glassy, very clear (after Armatage . 



In well established cases of amaurosis there is total blind- 

 ness; yet there are no opacities in any of the tissues or 

 humors of the eye. The eye is bright, clear, and perfectly 

 transparent. The animal steps high, stumbles over, and 

 runs against objects in its way. If, at a short distance, you 

 noiselessly threaten to strike it, there is no winking or 

 manifestations of fear. The ears are very sensitive to 

 sound, and the outer ears ar« constantly on the alert to 

 catch all noises. The pupil is expanded to its extreme limit; 

 the iris is immovable and insensitive to ligfht. Leailing the 

 animal from the dark into the light, or from the light into 

 the dark, does not change the size of the pupil or move the 

 iris; while in the normal eye the pupil ex[)ands in darkness 



