MYOLOGY i8i 



extensor of the fingers. It is necessary to add that it is most 

 prominently visible during supination, and that it tends to 

 be effaced during pronation. 



An analogous arrangement is met with in animals. But 

 the muscular prominence is formed by the united radial 

 extensors, and the fossette, because of the permanent pro- 

 nation of the forearm, is scarcely recognisable. Likewise, 

 with regard to the dog, we may say that it does not exist, 

 on account of the prominence which the epicondyle forms 

 in that animal (Fig. 73, 7). 



In connection with this prominence of the epicondyle, 

 it is interesting to add that this detail recalls the relief 

 which the same process produces on the external aspect of 

 the human elbow when the forearm is flexed on the arm. 

 We know that, in this case, the epicondyle is exposed,, 

 because the muscles which mask it in supination (long supi- 

 nator and long radial extensor) are displaced and set it free 

 during flexion. But, in the dog, as in other quadrupeds 

 besides, the forearm is, in the normal state, flexed on the 

 arm ; the latter being oblique downwards and backwards, 

 and the former being vertical. Further, the epicondyle is 

 well developed. 



The muscle with which we are now occupied, long and 

 vertical in direction, arises from the inferior part of the 

 external border of the humerus (there it is covered by 

 the anterior extensor of the metacarpus, from which 

 it is freed a little lower down) and from the external 

 and superior tuberosity of the radius. In the carnivora, 

 it arises from the epicondyle. Its fleshy body is fusiform 

 in shape, becomes tendinous in the lower half of the fore- 

 arm, and then divides into a number of slips, varying in 

 number according to the species ; this division is correlated 

 to that of the hand — that is to say, with the number of the 

 digits. Before reaching this latter, the common extensor 

 of the digits passes through the most external groove on 

 the anterior surface of the inferior extremity of the 

 radius. 



In the cat and the dog, the four tendons which result 

 from the division of the principal tendon go to the four last 



