568 PHYSIOLOGY OF THE EYE OF THE HORSE. 
becomes comparatively slow, and now and then it appears to 
remain quite stationary; for as soon as the cataract has formed, 
the inflammation generally begins to decline. There are, 
however, some exceptions to this. 
It seems now to be a well ascertained fact, that not only does 
the inflammation permanently leave the eye with cataract, but, 
should the other eye have remained free from the disease, it is in 
less danger of being attacked. Under such circumstances, 
therefore, a cataract is hailed as a favourable omen. This is 
partly explained on the principle of sympathy, which is known 
to have great influence in ophthalmic pathology: indeed, this 
circumstance has been weighty enough for the artificial destruc¬ 
tion of one eye to be recommended in this disease, in order to 
preserve the other. 
A lenticular cataract may be firm, fluid, or milky in consist¬ 
ence : the first is the common variety among horses. 
Opacities of the Cornea .—We sometimes meet with two kinds 
of opacity upon the cornea, and it is of importance that we 
should be able to distinguish between them, because one is very 
often removable, and the other never is. The permanent opacity 
is the result of that change of interstitial texture which is one of 
the sequelae of specific ophthalmia. It has a yellow or brown 
tinge when it first makes its appearance, but afterwards it changes 
to a diffused muddiness over the whole cornea. 
We must take care, however, not to confound this with the 
turbid condition of the cornea resulting from vascular distention 
and concomitant efiPusion. The latter is one of the symptoms of 
ophthalmia itself. It is only present with the inflammatory 
action; the other is a sequela of it, remaining the same in the 
interval of remission, and consisting, in fact, of an organic change 
in the corneal texture. The former opacity has a cloudy appear¬ 
ance ; this is a conjunctival affection. It is evidently superficial 
on a lateral glance at the eye, and moreover distinguishable from 
the other by its remarkable white aspect; and still more certainly 
when we can obtain information as to its origin. 
Should appearances denote inflammatory action, that should 
be first subdued by proper antiphlogistic treatment, for it some¬ 
times happens that with the subsidence of inflammation the 
opacity disappears. Should that, however, not turn out to be 
the case, we may make use of some escharotic or stimulating 
application, in order to exite increased vascular action afresh, 
and thereby arouse that of the absorbents. Farriers are very 
fond of blowing finely powdered glass into the eye, whicli 
simply operates as a mechanical agent: calomel similarly used 
has a like effect. Sulphate of zinc may often be used to advan- 
