LAMENESS: ITS CAUSES AND TREATMENT, 391 
THROMBOSIS. 
There are certain forms of lameness which are very pecutiar in 
their manifestation, and which to the nonprofessional mind must 
appear to belong to the domain of mystery or theory instead of oc- 
cupying a well-established position among the subjects of equine 
pathology. Yet they are no less susceptible of actual demonstration 
and of positive comprehension than many facts which, plain and 
familiar to the general understanding now, were once ranked among 
things occult and unsearchable. A thrombus, considered as a cause of 
lameness, may find a place among these understood mysteries. 
Cause.—Under certain peculiar conditions of inflammation of the 
blood vessels, and also in aneurisms, clots of blood are sometimes 
formed in the arteries and find their way in the general circulation. 
At first, while very small, or sufficiently'so to pass from one vessel to 
another, they move from a small vessel to a larger, and from that to 
one still larger, constantly increasing in size until at some given point, 
from their inability to enter smaller vessels, their movement is 
finally arrested. The artery is thus effectually dammed, and the clot 
in a short time cuts off completely the supply of blood from the parts 
beyond. This is thrombosis, and it often gives rise to sudden and 
excessive lameness of a very painful character. 
Symptoms—tThrombi may form in any of the arteries, and doubt- 
less have been the cause of many cases of lameness which could never 
be accounted for. If they exist in small arteries their diagnosis will 
probably fail to be made out with certainty, but when situated in 
the larger trunks a strong suspicion of their presence may be excited. 
In some cases they may even be recognized with possitive accuracy, 
as when the vessels which supply the posterior extremities are 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 gen- 
eral 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 
*sanimal 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 
