272 BUREAU OF ANIMAL INDUSTRY. 



refracted, perfect vision would not be restored, and the animal would 

 be liable to prove an inveterate shj^er. If perfect blindness continued 

 by reason of pressure on the nerve of sight, no shying would result. 



PALSY OF THE NERVE OF SIGHT, OR AMAUROSIS. 



Causes. — The causes of this affection are tumors or other disease 

 of the brain implicating the roots of the optic nerve, injury to the 

 nerve between the brain and eye, and inHannnation of the optic nerve 

 within the eye (retina), or undue jn-essure on the same from dropsical 

 or inflammatory effusion. It may also occur from overloaded stom- 

 ach, from a profuse bleeding, and even from the pressure of the 

 gravid womb in gestation. 



Symptoms. — The symptoms are wide dilatation of the pupils, so as 

 to expose fully the interior of the globe, the expansion remaining the 

 same in light and darkness. Ordinary eyes when brought to the 

 light have the pupils suddenly contract, and then dilate and contract 

 alternately until they adapt themselves to the amount of light. The 

 horse does not swerve when a feint to strike is made unless the hand 

 causes a current of air. The ears are held erect and turn quickly 

 toward any noise, and the horse steps high to avoid stumbling over 

 objects which it can not see. 



Treatment is only useful when the disease is symptomatic of some 

 removable cause, like congested brain, loaded stomach, or gravid 

 womb. When recoveiy does not follow the termination of these con- 

 ditions, apply a blister behind the ear and give one-half dram doses of 

 nux vomica daih'. 



TUMORS OF THE EYEBALL. 



A variety of tumors attack the eyeball — dermoid, papillary, fatty, 

 cystic, and melanotic— but perhaps the most frequent in the horse is 

 encephaloid cancer. This may grow in or on the globe, the haw, the 

 eyelid, or the bones of the orbit, and is only to be remedied, if at all, 

 by early and thorough excision. It may be distinguished from the 

 less dangerous tumors by its softness, friability, and great vascularity, 

 bleeding on the slightest touch, as well as by its anatomical structure. 



STAPHYLOMA. 



This consists in a bulging forward of the cornea at a given point 

 by the saccular yielding and distension of its coats, and it may be 

 either transparent or opaque and vascular. In the last form the iris 

 has become adherent to the back of the cornea, and the whole struc- 

 ture has become filled with blood vessels. In the first form the bulg- 

 ing cornea is attenuated; >in the last it may be thickened. The best 

 treatment is by excision of a portion of the iris so as to relieve the 

 intraocvdar pressure. 



