DISEASES OF THE EYES. 245 



or acetates of {/Otassa or sDda). Those that present increased 

 tension and hardness of the eyeball should be early treated by 

 irideclomy, which can, however, only be undertaken by the 

 surgeon. All cases should have a course of tonics (oxide of 

 iron, nux vomica, ginger) as soon as the violence of the fever 

 has abated, and should be submitted to a regimen calculated 

 to improve their condition so as to ward off a new attack. 

 Recovery from a particular attack may be expected in from 6 

 to 10 days, and this contributes to sustain the reputation of 

 such ridiculous resorts as knocking oat tlie wolf teeth, and 

 such injurious ones as cutting out the haw (hooks). 



CATARACT. 



This is the most constant result of internal ophthalmia, 

 though it may occur from other causes, such as diabetes or 

 urremia. The condition is opacity of the lens, and may be 

 recognised as a white speck, or a white (leecy cloud filling, in 

 the worst cases, the whole of a v/idely dilated pupil. It is best 

 seen with the animal looking out of the stable door, and with 

 a dark background. A still more satisfactory examination can 

 be made with a lighted taper in a dark room. Three images 

 of the taper are reflected (i) from the surface of the eye 

 (cornea) ; (2) from the anterior surface of the lens, and (3) 

 from the posterior surface of the lens. The two anterior are 

 upright, the posterior is inverted. If either of the two posterior 

 images is changed into a diffused white haze in passing over 

 any pait of the pupil, it implies an exudation into that part of 

 the lens — a cataract. Haziness of the large anterior image is 

 only caused by opacity of the cornea. 



Treatment. — Newly formed cataracts will sometimes clear up, 

 by absorption, under such treatment as is adopted for inflam- 

 mation, but the rule is that an opacity of the lens once found 

 is permanent. In cattle and sheep the lens may be extracted 

 or depressed as in man, but in the horse such an operation 



