affected by the blocking up of the
posterior aorta or its ramifications.

The existence of thrombosis of the arteries of the hind leg may always
be suspected when the following history is known: The general health of
the animal is good, but symptoms of lameness in one of the legs have
been developed, becoming more marked as he is worked, and especially
when driven at a fast gait. But the disturbance is not permanent, and
the lameness disappears almost immediately after a rest. There is an
increase of the difficulty, however, and, though the animal may walk
normally, he will, when made to trot, very soon begin to slacken his
pace and to show signs of the trouble, and if urged to increase his
speed will become lamer and lamer; an abundant perspiration will break
out; he will refuse to go, and if forced he shows weakness behind, seems
ready to fall, and perhaps does fall. While on his feet the leg is kept
in constant motion, up and down, and is kept from the ground as if the
contact were too painful to bear. If undisturbed this series of symptoms
will gradually subside, sometimes very soon, and occasionally after a
few hours he will return to an apparently perfect condition. A return
to labor will lead to a renewal of the same incidents.

A history like this suggests a strong suspicion of a thrombus in an
artery of the hind leg, and this suspicion will be confirmed by the
external symptoms exhibited by the animal. The total absence of any
other disease which might account for the lameness, and a manifest
diminution of heat over a part or the whole of the extremity, when
compared with the opposite side or with any other portion of the body; a
sensation of cold attendant on the pain, but gradually subsiding as the
pain subsides, and the circulation, quickened by the rest, has been
reestablished throughout the extremity; all these are confirmatory
circumstances. Still, it is thus far only a suspicion, and absolute
certainty is yet wanting. To establish the truth of the case the rectal
exploration must be resorted to. The hands then, well prepared and
carefully introduced into the rectum, must explore for the truth, first
feeling for the large blood vessels which, divided at the aorta,
separate to supply the right and left legs. These must be compared in
respect to the pulsation and other particulars. The artery which is
healthy will, of course, exhibit all the proper conditions of that
state. On the other hand, if the vessel