294. DISEASES OF THE HORSE, 
strength and vigor is protective; whatever contributes to weakness 
and poor health is provocative of the disease in the predisposed 
subject. 
Symptoms.—The symptoms vary according to the severity of the 
attack. In some cases there is marked fever, and in some slighter 
cases it may be almost altogether wanting, but there is always a 
lack of vigor and energy, bespeaking general disorder. The local 
symptoms are in the main those of internal ophthalmia, in many cases 
with an increased hardness of the eyeball from effusion into its 
cavity. The contracted pupil does not expand much in darkness, nor 
even under the action of belladonna. Opacity advances from the 
margin, over a part or whole of the cornea, but so long as it is trans- 
parent there may be seen the turbid, aqueous humor with or without 
flocculi, the dingy iris robbed of its clear, black aspect, the slightly 
clouded lens, and a greenish-yellow reflection from the depth of the 
eye. From the fifth to the seventh day the flocculi precipitate in the 
lower part of the chamber, exposing more clearly the iris and lens, 
and absorption commences, so that the eye may be cleared up in ten 
or fifteen days. 
The characteristic of the disease is, however, its recurrence again 
and again in the same eye until blindness results. The attacks may 
follow one another after intervals of a month, more or less, but they 
show no relation to any particular phase of the moon, as might be 
inferred from the familiar name, but are determined rather by the 
weather, the health, the feed, or by some periodicity of the system. 
From five to seven attacks usually result in blindness, and then the 
second eye is liable to be attacked until it also is ruined. 
In the intervals between the attacks some remaining symptoms 
betray the condition, and they become more marked after each suc- 
cessive access of disease. Even after the first attack there is a bluish 
ring around the margin of the transparent cornea. The eye seems 
smaller than the other, at first because it is retracted in its socket, and 
often after several attacks because of actual shrinkage (atrophy). 
The upper eyelid, in place of presenting a uniform, continuous arch, 
has, about one-third from its inner angle, an abrupt bend, caused by 
the contraction of the levator muscle. The front of the iris has 
exchanged some of its dark, clear brilliancy for a lusterless yellow, 
and the depth of the eye presents more or less of the greenish-yellow 
shade. The pupil remains a little contracted, except in advanced and 
aggravated cases, when, with opaque lens, it is widely dilated. If, 
as is common, one eye only has suffered, the contrast in these respects 
with the sound eye is all the more characteristic. Another feature is 
the erect, attentive carriage of the ear, to compensate to some extent 
for the waning vision. 
