of the cornea, the injury may lead to ulceration that may
penetrate more or less deeply and leave a breach in the tissue which, if
filled up at all, is repaired by opaque fibrous tissue in place of the
transparent cellular structure. Pus may form, and the cornea assumes a
yellowish tinge and bursts, giving rise to a deep sore which is liable
to extend as an ulcer, and may be in its turn followed by bulging of the
cornea at that point (staphyloma). This inflammation of the conjunctiva
may be simply catarrhal, with profuse mucopurulent discharge; it may be
granular, the surface being covered with minute reddish elevations, or
it may become the seat of a false membrane (diphtheria).

_Treatment._--In treating external ophthalmia the first object is the
removal of the cause. Remove any dust, chaff, thorn, or other foreign
body from the conjunctiva, purify the stable from all sources of
ammoniacal or other irritant gas; keep the horse from dusty roads, and,
above all, from the proximity of a leading wagon and its attendant cloud
of dust; remove from pasture and feed from a rack which is neither so
high as to drop seeds, etc., into the eyes nor so low as to favor the
accumulation of blood in the head; avoid equally excess of light from a
sunny window in front of the stall and excess of darkness from the
absence of windows; preserve from cold drafts and rains and wet bedding,
and apply curative measures for inflammation of the adjacent mucous
membranes or skin. If the irritant has been of a caustic nature, remove
any remnant of it by persistent bathing with tepid water and a soft
sponge, or with water mixed with white of egg, or a glass filled with
the liquid may be inverted over the eye so that its contents may dilute
and remove the irritant. If the suffering is very severe, a lotion with
a few grains of extract of belladonna or of morphia in an ounce of water
may be applied, or, if it is available, a few drops of 4 per cent
solution of cocaine may be instilled into the eye.

In strong, vigorous patients benefit will usually be obtained from a
laxative, such as 2 tablespoonfuls of Glauber's salt daily, and if the
fever runs high from a daily dose of half an ounce of saltpeter. As
local applications, astringent solutions are usually the best, as 30
grains of borax or of sulphate of zinc in a quart of water, to be
applied constantly on a cloth, as advised under "Inflammation of the
eyelids." In the absence of anything better,