INFLAMMATION OF THE EYE. 49 



It is important to distinguish between such appear- 

 ances and those which are caused by a blow or external 

 injury. In the latter case, after the inflammation has 

 subsided, there is frequently left an opacity of the 

 external cornea, which sometimes extends over half 

 the eye. The internal parts of the eye, however, 

 will appear perfectly clear and free from disease; 

 also vision will only be interfered with by the opacity, 

 which on examination is discovered to be confined to 

 the conjunctiva. Sometimes, when the injury proceeds 

 from the lash of a whip, one or two white and opaque 

 streaks will be found upon the eye, the other parts 

 being perfectly clear. In old cases of this description 

 it is best to attempt nothing medicinally, for the in- 

 jury is established ; but when the case is recent, and 

 all sign of inflammation has subsided, the white place 

 may be lightly touched over with a stick of lunar 

 caustic, or an ointment may be used composed of 

 a grain of cantharides to an ounce of lard. 



The natural course of specific ophthalmia is to 

 involve the capsule covering the crystalline lens ; 

 either this or the lens itself may become wholly or par- 

 tially opaque. Such opacity is termed Cataract. The 

 effect of it is either imperfect vision or blindness — 

 irremediable blindness ; for if the operation for cata- 

 ract, which benefits the human being, were success- 

 fully performed, and the lens removed, the horse, not 

 being fitted to wear spectacles, could have no distinct 

 vision ; he would be deprived of that which refracted 

 the rays of light, and regulated the picture which is 

 impressed upon the retina. 



A very considerable change has lately taken place 



