346 DISEASES OF THE EYES. 



to such an extent, that the cornea booomes opaque, and the horse 

 loses the sight of the involved eye. 



Respecting the ability of a worm to insert itself between the 

 lens and the iris, we may see that in Fig. 140 there is a space shown 

 between these two structures, which has been made merely for 

 clearness sake; but it is probable that during life, the margin of 

 the pupil remains usually in contact with the lens, unless when the 

 pupil is dilated. At the same time, the contact is loose enough 

 to allow the worm to wriggle itself between the lens and iris. The 

 use of belladonna in the treatment of the inflammation of the eye, is 

 to prevent the iris, at the edge of the pupil, from permanently ad- 

 hering to the lens, which, if it remained in contact with the lens, it 

 would be apt to do, owing to the adhesive nature of the in- 

 flammatory exudation. The use of atropine (the active principle 

 of belladonna) obviates the risk of adhesions being formed, by 

 causing the radiating muscular fibres of the iris to contract, and, 

 thus, to draw the margin of the pupil away from the lens. 



TREATMENT.— The moment we have found out what is the 

 matter with the eye, we should proceed to remove the jDarasite ; 

 for the longer it stays in the eye, the more harm, as a rule, will it 

 inflict on that organ. The usual manner of operating is as 

 follows; the only instrument required being a Grsefe's or Beer's 

 cataract knife. Vet.-Captain Appleton recommends a large suture 

 needle, because it readily punctures the cornea, and is not liable 

 to hurt the iris, on account of its curved shape. If none of these 

 instruments be available, we may use a fine-pointed lancet, the point 

 being guarded by thread wrapped round the blade, so as to leave 

 about a quarter of an inch bare. The horse should be cast on the 

 side opposite to that of the affected eye, and in such a manner that 

 there will be a good light on the part. A truss of straw should 

 be placed under his head, which sihould be steadied and kept down 

 by the assistance of a couple of men. The horse should be put 

 under chloroform, or the surface of the eye and haw {inemhrana 

 nictitans) rendered insensitive by placing on it a few drops of a 

 10 per cent, solution, in water, of the hydrochlorate of cocaine 

 about teii minutes before making the incision. I would also 

 advise the use of a solution of atropine (p. 601). Before operating, 

 it is well to wash the eyelids and skin around the eye with warm 

 salt water (a teaspoonful of salt to a pint of water). The hands 

 and lancet should be thoroughly disinfected (p. 70). The opera- 

 tor should kneel down behind the horse's poll, and holding 

 the lancet between the finger and thumb, while resting the hand 

 close to the eye and keeping the i:>oint of the instrument almost 

 touching the eye at the spot where it is intended to puncture, 



