366 DISEASES OF THE HOESE. 



tive accuracy, as when the vessels which supply the posterior extremi- 

 ties 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 upon his 

 being permitted to rest. There is an increase of the difficulty, how- 

 ever, and, though he 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 was too pain- 

 ful 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 mani- 

 fest 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 pre- 

 pared 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 com- 

 pared 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 appears to the feel hard, 

 more or less cordy, and pulseless, or giving a sensation of fluttering, 

 as of a small volume of blood with a trickling motion passing through 

 a confined space, the difference between the sides will make the case 

 plain. The first will be the full flow of the circulation through an 

 unobstructed channel, the other a forced passage of the fluid between 

 the thrombus and the coats of the artery. In such a case the prog- 

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