7S OSTEOLOGY. 



at about one-third from the top by the medullary or nutrient 

 foramen. On each side of this surface is a vertical ridge, to 

 which the small metacarpals are attached. 



The proximal exti-etnity presents a smooth surface, formed by 

 three continuous articular facets, one large and flat, on which 

 the OS magnum rests ; the second, very small, on the postero- 

 internal border, articulates with a portion of the trapezoid ; and 

 the third, which articulates with the unciform, and occupies the 

 whole external border, is bevelled off from within outwards, and 

 divided by a deep furrow into two portions. In front of the 

 large articulation, towards the intero-anterior portion of the 

 head, is a roughened prominence for the insertion of the 

 extensor metacarpi magnus tendon ; and at the posterior part 

 of the head a roughened surface, from wljich the suspensory 

 and check ligaments originate, and on each side tw^o facets, 

 divided by furrows, articulate with the small metacarpal bones. 



The distal extremity, widest from side to side, and convex 

 from before backwards, presents an articular surface, consisting 

 of two condyles joined by a prominent semicircular ridge, the 

 whole of which articulates with the os suffraginis below, and 

 the two sesamoid bones behind. Each of the condyles, the 

 internal being slightly the larger of the two, presents a depression 

 on its side for the insertion of the lateral ligament. Thus the 

 large metacarpal bone articulates superiorly with the trapezoid, 

 magnum, and unciform, laterall}'- with the small metacarpals, and 

 inferiorly with the os suffraginis and the two sesamoid bones. 



OSSA METACARPI PAEVA. 

 (Fig. 17. 10.) 



The small metacarpal, or splint bones, tuberous in form at the 

 carpus and tapering distally, are attached to the large bone, one 

 on each side of its posterior surface, by ligaments in the young 

 animal, and by ossification in most grown up, and in all old 

 animals. They vary somewhat in length in different animals, 

 but are usually about two-thirds of the length of the cannon, the 

 internal being generally the largest. 



The base, or head, of each bone is turned upwards, its superior 

 surface being articulatory, and assisting to form the carpal-joint. 

 The internal one possesses two articular facets, one large and flat, 

 on which the trapezoid rests, and the other small and bevelled 



