120 SPECIFIC OPHTHALMIA. 



affected or almost lost, and yet the horse has been pronounced sound by very fail 

 judges. The eye must be exposed to the light, and yet under the kind of shelter 

 whic h has been already described, in order to discover the defect. The pupil of the 

 horse is seldom black, like that of the human being, and its greyish hue conceals the 

 recent or thin film that may be spreading over the lens. 



Confirmed cataract ii. the eye of the horse admits of no remedy, for two obvious 

 reasons : the retractor muscle draws the eye back so powerfully and so deeply into 

 the socket, that it would be almost impossible to perform any operation ; and, could 

 an operation be performed, and the opaque lens removed, the sight would be so 

 imperfect, from the rays of light not being sufficiently converged, that the horse 

 would be worse to us than a blind one. The man who has undergone the operation 

 of couching may put a new lens before his eye, in the form of a convex spects^le ; 

 but we cannot adapt spectacles to the eye of the horse, or fix them there. 



Since the publication of the first edition of " The Horse," some controversy has 

 taken place with regard to the occasional appearance and disappearance of cataract 

 without any connexion with the common moon-blindness. Mr. Clay deposed in evi- 

 dence, that cataracts might be formed in a fortnight or three weeks that he had 

 known many instances in which they had been completed in less time, and without 

 any previous apparent disease of the eyes ; and that he had detected them when the 

 owners had not the slightest suspicion of disease in the eye.* 



Mr. Cartwright adds, that he has known two sinul-r cases. The first was of a 

 horse that had two cataracts in each eye two of them of the size of a large pin's 

 head, and the other two treble that size. There was no vestige of former inflamma- 

 tion ; and the person who bred him said that he never had been subject to inflamma- 

 tion of the eye. In December 1831, these cataracts were plain enough; but in the 

 autumn of 1832, they had completely vanished. 



In November 1832, Mr. Cartwright saw a five-years old mare, and detected a cata- 

 ract in the right eye, of the size of a coriander seed. He advised the owner to get 

 rid of her, thinking that she would go blind ; but, being a useful animal, he kept her. 

 In August 1833, Mr. Cartwright saw her again. The cataract had disappear**! and 

 the eyes were perfect, t 



That excellent veterinarian, Mr. Percivall, had a somewhat similar case. A gen- 

 tleman brought a horse one morning to the hospital, in consequence of its having fallen 

 in his way to town, and grazed his eyebrow. On examining him carefully, the cornea 

 was partially nebulous, and a cataract was plainly visible. Neither of these defects 

 was sufficient to attract the notice of any unprofessional observer, and both were 

 unconnected with the slight bruise produced by the fall. The owner was told that 

 the corneal opacity might possibly be removed ; but as for the cataract, he might 

 regard this as beyond the reach of medicine. He returned with his horse on the fifth 

 day, saying that the physic had operated well, and that he thought the eye was as 

 clear as ever. Mr. Percivall examined the eye, and could discover no relic either of 

 the conical opacity or of the cataract. 



The opinion respecting cataract is therefore essentially modified. It is not necessa- 

 rily the result of previous inflammation, although in the great majority of cases it is 

 so, nor does it always lead to blindness. Still it is a serious thing at all times, and. 

 although existing in the minutest degree, it is unsoundness, and very materially lessen* 

 the value of the horse. 



" Were I asked," says Mr. Percivall, " how the practitioner could best distinguish 

 a cataract of the above description from that which is of orcfinary occurrence, and 

 known by us all to constitute the common termination of periodical ophthalmia, I 

 should say that the unusually lucid and healthy aspect which every other part of the eye 

 presents is our best diagnostic sign ; the slightest indication, however, or the slightest 

 susn : cion of prior or present inflammation, being a reason for coming to a different 

 conclusion. As to the period of time a cataract of this species, supposing it to be 

 membranous,, would require for its formation, I should apprehend that its production 

 night be. as its disappearance often would seem to be, the work of a very short inler- 

 al, perhaps not mon than five or six days." As to tho cause and treatment of it 



Veterinarian, il. vii. D. 41. t Ve ;erinarian, vol. vii. p. 44. 



