lameness: its causes and treatment. 391 



thrombosis. 



There are certain forms of lameness which are very peculiar 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. 



Sym/ptoms. — ^Thrombi 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 

 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 



