PHYSIOLOGY OF THE EYE OF THE HOPvSE. 567 
do, or are apt to think we do, hasten the departure of inflamma¬ 
tion, and ward off or mitigate some of its consequences ; but an 
experienced practitioner is too well aware of the liability to, 
and indeed the certainty of, a relapse, to repose any faith in a 
truce so obtained, and therefore his ordinary advice to his 
owner is to dispose of his horse during the interval of remission. 
Knowing therefore, as we do, that such horses are constantly 
changing owners, it is a qualification of the first importance to 
us in practice, to be able to discriminate between an originally 
sound eye and one that has been attacked by this malady. 
Vision may possibly be unimpaired in the latter, but we are not 
to suffer ourselves to be deluded by the transient appearance of 
health. 
Cataract is an opacity, partial or complete, of the lens or its 
capsule, or both. The specific opthalmia, just described, has too 
frequent a tendency to terminate in cataract, which, as it never 
appears, as it does in the human subject—a disease distinct 
and independent of the active inflammation of ophthalmia—can 
hardly be said to merit a separate place among the diseases of 
the horse. 
There is in the cataract of horses, independent of the opacity 
of the lens, generally much derangement of the internal parts of 
the eye. The iris sometimes adheres to the lens, at other times 
to the cornea, and in some cases its pupillary opening is so 
reduced by contraction as to render the cataract hardly per¬ 
ceptible. This internal derangement, therefore, greatly prevents 
any benefit being derived from the operation of couching in 
veterinary practice; added to which, a horse so operated on 
would be under the necessity, in order to reap any advantage 
from the operation, to wear glasses ever afterwards. In addition 
to this would be the difficulty of so steadying the eye as to be 
enabled to perform the operation without wounding the iiis or 
retina. The adhesions formed would also render much internal 
violence necessary, in order to the extraction of the lens and dis¬ 
organization has also usually proceeded far beyond the lens, and 
its capsule: unless, therefore, we can perform miracles as well 
as operations, and restore all these altered parts to their former 
state of health, we had better never think of purchasing a cata¬ 
ract-knife. 
The appearance of the disease is a grey or white speck, 
perceivable through the centre of the pupil, and which slowly 
and gradually enlarges until it quite blocks up the aperture. 
The growth of the incipient speck, during the time that the 
organ is suffering from ophthalmia, is commonly rapid; but as 
soon as the inflammatory action has su])sidcd, its progress 
