948 ARTERIAL THROMBOSIS. 



The disease generally develops insidiously, attention being first 

 directed to it by the attacks of lameness, but when large vessels 

 are blocked other well-marked symptoms are present, like dyspnoea, 

 sweating, and cramp in the affected groups of muscles. The 

 thrombosed vessel never again becomes clear, though collateral 

 circulation is sometimes established, and gradual improvement 

 follows, hi other cases the lameness increases, in consequence of 

 the increase of the thrombus. 



Symptoms. The intermittent lameness, which soon disappears 

 with rest, but always returns on movement, is characteristic. Its 

 severity and extent depend on the position and size of the thrombus 

 or thrombosed vessel. Blocking of the femoral artery is immediately 

 followed by loss of function in the iliac-psoas and tensor fascia lata, 

 which it supplies with blood. Lameness is, therefore, most marked 

 whilst the limb is being advanced. The forward stride is retarded 

 and shortened, and the limb dragged, the reason being that these 

 actions are normally performed by the muscles named. 



Thrombosis of the external iliac artery, which supplies the glutei 

 and quadriceps femoris, produces a " supporting leg lameness," 

 which closely simulates crural paralysis. The animal is unable to 

 stand on the limb, because at every attempt the joints become flexed. 

 Paralysis of the glutei is followed by loss of balancing power, and 

 when double-sided by rolling to and fro of the hindquarters. In 

 obstruction of the caudal arteries the tail hangs limply. Horses 

 with double-sided iliac thrombosis rapidly lose control of both 

 hindquarters when galloped. The hind limbs approach one another 

 more and more closely, the hoofs are planted on the ground just along- 

 side of one another, and finally the animal comes to the ground with 

 the hindquarters first. 



A rare condition was described by Haas. When first examined the 

 horse showed symptoms of thrombosis of the left iliac artery. Fifteen 

 minutes later, when again moved, the lameness seemed transferred to 

 the light limb. On post-mortem examination there was found extending 

 into the left iliac artery a thrombus, which, however, could easily be carried 

 by the blood-stream into the right. Haas saw thrombosis of the posterior 

 aorta in a cow. Strebel saw a cow which was only capable of standing 

 for a few moments at a time. On post-mortem the cause was found to be 

 thrombosis of the left iliac artery. Proeger saw thrombosis in a cow in 

 consequence of endocarditis. 



In bilateral thrombosis, or in thrombosis of the aorta, these 

 symptoms are combined, and may become so severe that the animal 

 is unable to support the hindquarters, even when at rest. Such eases 

 often show dyspnoea, tumultuous action of the heart, cramp in the 



