HEREDITARY DISEASES OF HORSES. 589 
not likely to be productive of any bad effects, or to be 
hereditary. All such sounds occurring in the lighter breeds 
of horses must, however, be regarded with great suspicion. 
There are few diseases in which hereditary tendencies are 
so manifest as in that variety of deep-seated ophthalmia , or 
inflammation of the eye, recognised by veterinarians under 
the various titles of periodic, specific, or constitutional 
ophthalmia and moonblindness. In this disease the inflam- 
mation involves, to a greater or less degree, all the internal 
parts of the eye, exhibits a great tendency to effusion of 
lymph, often attacks only one eye at a time, but, on sub- 
siding in the one first affected, is very apt to appear in the 
other; always leaves the eye affected dim, weak, and sus- 
ceptible to a future attack, and is seldom entirely got rid of 
until blindness of at least one eye has been induced. The 
symptoms of this disease are usually tolerably well marked. 
The mucous membrane and its various appendages are 
inflamed ; there is copious secretion of tears, great pain and 
tenderness, and marked intolerance of light. The cornea 
becomes opaque and for some time intercepts the view of the 
parts within. The eyelids are nearly closed, and the eye- 
ball within when visible through the cornea soon loses its 
clear transparency, in consequence of the humours becoming 
of a muddy yellowish-brown colour from effusion of lymph . 
Febrile symptoms are present, and are greatly more intense 
than might be anticipated from the comparatively small size 
of the part affected. After two or three days there is often 
a remission in the intensity of the disease, the external parts 
being less inflamed and the dull muddiness of the cornea 
and interior gradually diminishing. A recurrence of the 
acute inflammation, or its transference to the previously 
sound eye, is always, however, much to be dreaded. Some- 
times the eye apparently recovers, and the superficial ob- 
server might consider it perfectly healthy, but the more 
experienced will find, on careful inspection, sufficient 
evidence that the organ has been the seat of disease, and 
that there still remains a change of structure which pre- 
disposes to subsequent attacks. The eye seems smaller than 
its fellow, and still remains intolerant of light ; the cornea 
is often dull, the margins of the pupil frequently uneven and 
ragged, and the movements of the iris impeded by adhesions ; 
the more deep-seated parts have a peculiar leaden appearance, 
and shreds of lymph may sometimes be observed floating in 
the aqueous humour, or imbedded in the crystalline lens or 
its capsule : the last condition constituting what is tech- 
nically called a cataract. This may vary much in size, being 
