DISEASES OF CATTLE 423 



watery substance, and has a tendency to spread widely and deeply. 

 If it spreads superficially upon the cornea, the transparency of this 

 membrane is lost; if it proceeds deeply and penetrates the anterior 

 chamber of the aqueous humor, this fluid escapes, the iris may pro- 

 lapse, and the lens and the vitreous humor become expelled, thus 

 producing a destruction of the whole organ. 



Treatment. It is of the greatest importance, as soon as an ulcer 

 appears upon the cornea, to prevent its growing larger. The cor- 

 roding process must be converted into a healthy one. For this pur- 

 pose nothing is more reliable than the use of solid nitrate of silver. 

 A stick of nitrate of silver should be scraped to a point; the animal's 

 head should be firmly secured; an assistant should part the lids; if 

 necessary the haw must be secured within the corner of the eye and 

 then all parts of the ulcer should be lightly touched with the silver. 

 After waiting a few minutes the eye should be thoroughly washed 

 out with a very weak solution of common salt. This operation gen- 

 erally has to be repeated once more at the end of three or four days. 

 If healthy action succeeds, the ulcer assumes a delicate fleshy tint, 

 and the former redness around the ulcer disappears in proportion as 

 the ulcer heals. 



In superficial abrasions of the cornea, where there is no distinct 

 excavation, this caustic treatment is not needed. The eye should 

 be bathed with sulphate of zinc, 30 grains to half a pint of soft 

 water, several times a day, and protected against exposure to cold air 

 and sunlight. Excessive ulceration sometimes assumes the form of 

 fungous excrescence upon the cornea, appearing to derive its nour- 

 ishment from loops of blood vessels of the conjunctiva. Under these 

 circumstances the fungoid mass must be cut away, and the wound 

 cauterized with the nitrate of silver, or else the eye will soon be 

 destroyed. When ulcers of the cornea appear indolent, with a teii- 

 ency to slough, in addition to the treatment already prescribed, tonic 

 powders should be given twice a day mixed with the feed ; powdered 

 copperas, gentian, and ginger, equal parts by weight. Dose, one 

 tablespoon i ul. 



CATARACT. 



In cataract the crystalline lens becomes opaque and loses its 

 transparency, the power of refraction is lost the animal can not see. 



Causes. Cataract generally arises from a diminution (atrophy) 

 or other change in the nutrition of the lens ; it may occur as a result 

 of inflammation of the deep structures of the eye. Cataract may be 

 simple, or complicated with amaurosis, adhesions, etc. 



Symptoms. It is known by the whiteness or loss of transpa- 

 rency of the lens, although the pupil dilates and contracts. Sight 

 may be totally lost ; however, evidence is usually manifested that the 

 animal distinguishes light when brought out of a darkened stable. 

 For the most part the formation of cataract takes place slowly, the 

 cases in which it originates very quickly being but few. 



Treatment. There is only one method for the treatment of 

 cataract a surgical operation for the removal of the lens; but this 



