68 THE ARTISTIC ANATOMY OF ANIMALS 



of tendons, which shghtly alter its appearance ; so that it is 

 the principal base of this part of the fore-limb. Its posterior 

 surface is flattened. The superior extremity of this metacarpal 

 presents plane surfaces, variously inclined, with which the 

 bones of the inferior row of the carpus articulate. On the 

 anterior surface, and a little to the inner side, is found a 

 tuberosity, which is destined for the insertion of the anterior 

 extensor of the metacarpus, the hcmologue of the radial 

 muscles. The inferior extremity is formed by two condyles, 

 an internal and an external ; between which is found a 

 median crest. 



This extremity, the superior extremity of the first phalanx, 

 which articulates with it, together with two sesamoid bones 

 — ^the great sesamoids — which are situated on its posterior 

 surface, collectively form the region which from its rounded 

 outlines is called the ball. 



With regard to the rudimentary metacarpals, external 

 and internal, to which some authors give the name of fibulcB, 

 they are applied to the sides of the posterior surface of the 

 principal metacarpal. They are elongated bones, of which 

 the superior extremity, which is a little thickened, is called 

 the head ; the lateral bones of the second row of the 

 carpus partly rest on the heads of these. They become 

 more slender as they descend, and terminate opposite 

 the inferior fourth of the principal metacarpal. Each ends 

 in a slight swelling, to which the name button has been 

 given. The internal one is the better developed. 



The rudimentary metacarpals are vestiges of atrophied 

 digits, as will be explained further on. 



The single finger of the horse consists of three phalanges. 

 The first phalanx, which is directed obliquely downwards 

 and forwards, corresponds to the constricted region situated 

 below the ' ball,' and known as the pastern. It is flattened 

 from before backwards ; its anterior surface is convex trans- 

 versely, while the posterior surface is plane. Its superior 

 extremity is moulded on the inferior extremity of the 

 principal metacarpal, and its inferior extremity, which is 

 smaller, presents a trochlea with which the second phalanx 

 articulates. This is also directed downwards and forwards. 



