OBSERVATIONS ON SOUNDNESS. 667 
present. It amounts to unsoundness, of course, but it 
seldom interferes with the usefulness of the animal. 
Opacity of the lens assumes such a variety of forms, that 
it will be necessary to merely state that cataract in any stage 
is an unsoundness. 
The vitreous humour is that part of the structure of the 
visual organ but little understood by practitioners generally. 
That it is liable to disease there is sulfficient evidence, from 
the fact of its becoming at one time liquefied and at another 
solidified; in either case loss of vision is the result. 
It only remains that I should speak of the retina to com¬ 
plete the hastily thrown together remarks I have made upon 
the visual organ. This membrane, it will be remembered, 
consists of three layers—the external, or Jacobis membrane ; 
the middle, or nervous membrane; and the internal, or vas¬ 
cular membrane. The first is said by its discoverer to be a 
serous membrane, the nervous is the expansion of the optic 
nerve, and the vascular the ramifications of the arteria cen¬ 
tralis retina. When we take into account the three different 
structures, w^e need not feel much surprise at the complica¬ 
tion of its diseases and the want of success in their 
treatment. In the first place, should we meet with inflam¬ 
mation of the serous membrane, we can readily understand 
the effects and results of such a structure being inflamed; 
secondly, when nerve-matter partakes of inflammatory action, 
we must all be aw^are of the pain the patient has to endure; 
and lastly, if the vascular membrane is diseased, we can 
imagine what devastating influences may be expected; and 
to sum up the whole, let us imagine all these different struc¬ 
tures to be suffering from inflammation at the same time, 
to say nothing of other parts of the organ, we should 
not wonder at our efforts being without fruit, when, as 
surgeons, we are called upon to treat them. I need not, I 
am sure, state that any impairment of function of the retina 
will materially interfere with vision, and should be pro¬ 
nounced unsoundness. 
A question often arises as to the soundness of an eye 
whose lid h^ls been partially excised. These cases are always 
produced by injury, either from the bite of another horse or 
from being torn by a nail or some awkward instrument. I 
have had occasion to examine a good many of such cases 
as I have alluded to, and have in each observed that the 
eye is lachrymose. This it is which causes the purchaser 
to push his interrogations very close. I have never in 
any case heard of serious inconvenience; it is an eye^ 
sore certainly, and must be considered m the eye of the 
