SPAVIN 79 



brought out. After exercise the lameness disappears. There is, then, a 

 pecuHar similarity between these cases in this respect and navicular 

 disease. " It is a supporting leg lameness, and in consequence the 

 quarter is carried low, and in the trot the quarter sinks a little." * Incom- 

 plete extension of the joints below the hock leads to pressure being placed 

 almost entirely on the toe, so that the shoe at the toe becomes worn. 

 As a later result of inaction at the heel we find the foot becomes more 

 upright and blocky, and the frog atrophies and is carried up out of 

 function. When the animal is turned sharply towards the sound side 

 there is obviously greater pressure thrown upon the inner aspect of the 

 affected limb, and this tends to accentuate the lameness, on account of 

 the pain to which the animal is subjected. It is usual to apply what is 

 known as the spavin test. This consists in forcibly flexing the affected 

 hock for about a minute, and then causing the animal to move on 

 suddenly. This causes the lameness to be more apparent. Too 

 great stress, however, must not be attached to this test, since most 

 horses will move off stiffly afterwards, particularly if the test be severely 

 applied. 



The seat should be carefully palpated, and an attempt be made to 

 locate the grooves and ridges which we have described. There is no 

 difficulty in coming to a conclusion when a marked exostosis is present, 

 but there is much greater difficulty when the external indication is simply 

 a filling up of the grooves and a levelling of the surface. In such cases 

 the hock should be compared with the hock of the other limb, and a 

 reasonable diagnosis made if the grooves on the sound limb are even 

 slightly more distinct. In connection with this method of comparison 

 it should be mentioned that animals with odd hocks are not infrequently 

 met with in which there is an enlargement on one hock at the seat of 

 spavin. This enlargement is usually due to an abnormally large ridge on 

 the cuneiform magnum ; and although to the sight there would appear to 

 be an enlargement on the seat of spavin which not infrequently attains 



* Macqueen. 



