446 Veterinary Medicine. 



electric light without the slightest contraction of the pupil. The 

 pupillary reflex to light is entirely lost. In the slighter cases 

 ■(amblyopia) there remains some slight response of the iris to 

 light but always far short of the normal. The widely dilated 

 pupil admits a flood of light, and in the absence of cataract, lights 

 up the chamber of the vitreous to an unusual degree. The blue 

 or yellowish reflection of the tapetum is very striking, and led to 

 the obsolete names of gutta serena and glass eyes. Sometimes 

 the disease is unilateral and at others bilateral. In case it is 

 unilateral there is a strong presumption that the causative lesion 

 is in the affected eye or in the optic nerve in front of the chiasma. 

 In the bilateral cases it is more likely to depend on disease of the 

 brain or some more distant organ. 



Certain important indications are to be drawn from the expres- 

 sion of the face, the position of the head and ears and the mode 

 of locomotion. In all blind animals the face is without expres- 

 sion. The dilated pupils give no suggestion of mind looking 

 through them, they have on the contrary an uniform stony stare. 



There is no sense of fire or life, but the face is like a dull sculp- 

 tured mass. The immobile face finds a sharp contrast in the 

 alertness of the ears, which may be carried one forward, and 

 another back, but fixed and yet ready to turn to catch every 

 sound. In the horse the head is usually carried a little to one 

 side for the same reason, and with the nose elevated {star-gazer^ 

 and nostrils dilated. The ox inclines to carry the head low, 

 while the dog keeps his nose near the ground to guide himself 

 by the sense of smell. All blind animals are disposed to move 

 slowly and carefully, and the horse acquires a habit of high 

 stepping to avoid stumbling. 



A common and important test where both eyes are equally 

 affected and cannot be contrasted with each other, is to strike the 

 lower part of the face with the hand and immediately threaten to 

 repeat the blow. If the animal can see, it will seek to jerk the 

 head out of the way as soon as the hand is raised for the second 

 blow, while if blind there will be no such movement provided 

 the motion of the hand has not been such as to induce a current . 

 of air on the face. 



Lesions. Blindness, or the general symptoms of amblyopia or 

 amaurosis, may attend on the atrophy of the retinal fibres in con- 



