DISEASES OF THE HORSE. 265 



ULCERS OF THE CORNEA. 



These may be treated with nitrate of silver lotion of twice tlie 

 strength used for opacities. Powdered gentian, one-half ounce, and 

 sulphate of iron, one-fourth ounce daily, may improve the general 

 health and increase the reparatory power. 



INTERNAL OPHTHALMIA (iRITIS, CHOROIDITIS, AND RETINITIS). 



Although inflammations of the iris, choroid, and retina, the inner, 

 vascular, and nervous coats of the eye, occur to a certain extent inde- 

 pendently of each other, 3^et one usuallj^ supervenes upon the other, 

 and, as the s^^mptoms are thus made to coincide, it will be best for 

 our present purposes to treat the three as one disease. 



Causes. — The causes of internal ophthalmia are largely those of the 

 external form only, acting with greater intensity or on a more suscep- 

 tible eye. Severe blows, bruises, punctures, etc., of the eye, the 

 penetration of foreign bodies into the qjq (thorns, splinters of iron, 

 etc.), sudden transition from a dark stall to bright sunshine, to the 

 glare of snow or water, constant glare from a sunny window, abuse 

 of the overdraw check-rein, vivid lightning flashes, drarfts of cold, 

 damp air; above all, when the animal is perspiring, exposure in cold 

 rain and snowstoims, swimming cold rivers, also certain general 

 diseases like rheumatism, arthritis, influenza, and disorders of the 

 digestive organs, maj' become complicated by this affection. From 

 the close relation between the brain and eye — alike in the blood ves- 

 sels and nerves — disorders of the first lead to affections of the second, 

 and the same remark applies to the persistent irritation to which the 

 jaws are subjected in the course of dentition. So potent is the last 

 agency that we dread a recurrence of opthalmia so long as dentition is 

 incomplete, and hope for immunity if the animal completes its 

 dentition without any permanent structural change in the eye. 



Symptoms. — The symptoms will vary according to the cause. If the 

 attack is due to direct ph3'sical injury the inflammation of the ej^elids 

 and superficial structures may be quite as marked as that of the interior 

 of the eye. If, on the other hand, from general causes, or as a compli- 

 cation of some distant disease, the affection may be largely confined 

 to the deeper structures, and the swelling, redness, and tenderness 

 of the superficial structures will be less marked. When the external 

 coats thus comparatively escape the extreme anterior edge of the 

 white, or sclerotic, coat where it overlaps the border of the transparent 

 cornea is in a measure free from congestion, and, in the absence of 

 the obscuring dark pigment, forms a whitish ring around the cornea. 

 This is parth^ due to the fact that a series of arteries (ciliary) passing 

 to the inflamed iris penetrate the sclerotic coat a short distance behind 

 its anterior border, and there is therefore a marked difference in color 



