154 
THE CANALIS VACIFKRUS. 
an inch wide and three quarters long, of this beautiful structure 
from its most prominent lateral part. The cartilage is about one- 
fifth of an inch in thickness ; and when the piece described is 
raised from its place by the point of the knife, it will be found 
to have an exceedingly slight attachment by a few points to the 
thin membrane below. On the entire removal of this piece of 
cartilage we obtain a fine view of the large veins forming the 
plexus spoken of above ; they are lying or hanging loosely in an 
open space, of size sufficient to contain a hazel-nut without dif¬ 
ficulty or much compression of the bloodvessels, and consequent¬ 
ly capable, during the violent exertions of the horse, of permit¬ 
ting them to dilate greatly, and receive, as in a reservoir, the 
blood which must be forced upwards. There certainly is no organ 
in any animal which has such an obvious demand for a provision 
of this kind against sudden rupture, since the foot of the horse 
(itself a most vascular and sensitive structure, and richly supplied 
with bloodvessels) may be otherwise said to be enclosed in a 
tightly-fitting horny box, which precludes any lateral extension 
of the vessels themselves; and although the veins are anasto¬ 
mosed in a beautifully intricate manner, and there are no valves 
below the fetlock joint to cause any impediment to a free return 
of the venous fluid, yet it is probable that these precautions 
would have proved insufficient (even supposing the foot was per¬ 
mitted its natural action by expansion shoeing), had it not been 
for the bounty of nature in providing this reservoir within the foot 
itself. Mr. B. Clark has observed that this cavity is largest on 
the inner side of the foot where the circulation is always greatest. 
It is most appropriately placed in a part of the foot which is 
ordinarily free from pressure, and securely protected by the over¬ 
hanging arch of the cartilage, so that this part is seldom prima¬ 
rily injured. But if the cartilage receives a violent blow, or 
from any cause leading to high inflammatory action of the foot 
generally, the infundibulum becomes the seat of the highest ex¬ 
citement, which frequently causes the death of a portion of the 
cartilage covering the part. The disease is then called a quittor, 
and for which the best remedy is skilful extirpation of the dis¬ 
eased portion of cartilage. 
There are many other considerations which force themselves 
upon the mind respecting this newly-discovered structure; but, 
lest this paper should extend too far, I forbear them for the pre¬ 
sent. 
