CHAPTEE Y. 



JISEASES OF THE EYE. 



The Membrana nictitans, Simple Ophthalmia, Conjuntivitis, Inflammation of the 

 Conjunctiva, Specific Ophthalmia, Periodic Ophthalmia, Moon Blindness, 

 Cataract, Lenticular Cataract, Capsular Cataract, Interstitial Cataract, Spu- 

 rious Cataract, Amaurosis, Glass Eye, Gutta Serena, Glaucoma, Lacerations 

 of the Eyelids, Disease of the Lachrymal Passages, Foreign Bodies in the Eye, 

 Worms in the Eye. 



A very marked peculiarity of the eye in the horse is what is called 

 the Membrana nictitans or Haw, which is situated in the inner corner 

 of the eye. The haw has two principal uses : first, by moving backwards 

 and forwards it wipes off the dust or other extraneous particles which 

 may lodge on the surface of the eye; and secondly, by protruding for- 

 ward, when the eye is drawn back on the approach of danger, it guards 

 the cornea, to a certain degree, from any accidental blow. Its motion 

 may be said to be involuntary, because it is forced over the eye mainly by 

 the withdrawal of that organ into its socket. 



This peculiarity of structure renders it very difficult to perform on 

 the eye of the horse many of those delicate operations which are so useful 

 in human surgery for the relief of various ocular diseases. With some 

 trouble, however, the eye may be got at. It is necessary, in the first 

 ' instance, to catch and retain the haw by a hook. The operator must 

 frequently touch, or threaten to touch, the eye; and though for. some 

 time it will be drawn back at each threat, yet at last the retractor muscle 

 will be wearied out, and certain operations may then be performed. This 

 practice is adopted with success in India in cases of worm in the eye. Of 

 late years, chloroform has been used in operations on the eye. The 



