100 



THE SKELETON OF THE HORSE 



proximal extremity unites with the shaft before birth, the distal extremity toward 

 the middle of the second year. The small metacarpal bones ossify from two cen- 

 ters, one of which is for the proximal extremity. Their distal ends are cartilaginous 

 at birth. Fusion of the middle part of the shaft with the large metacarpal bone is 

 common. 



THE PHALANGES 

 The First Phalanx 

 The first phalanx (Phalanx prima) ^ is a long bone, and is situated between the 

 large metacarpal bone and the second phalanx. It is directed obliquely downward 

 and forward, forming an angle of 50 to 55 degrees with the horizontal plane in well- 

 formed liml)s. It consists of a shaft and two extremities. 



Distal end of small iniid- 

 carpal hone 



Distal end of large metacarpal hone 

 Proxunid end of first phalanx 



Proximal sesamoid hone 



Disteil end of first phalanx 

 Proximal end of second phalanx 



Distal sesamoid hone 



Fjxti nsor proces 



vd surface 



Dorsal groove 

 A ngle 



Distal border of third phalanx 

 Fig. 7S. — Skeletox of Digit axd Distal Paut of Metacarpus of Horse; Lateral View. 

 1-7, Eminences and depregsion for attachment of ligaments. Cartilage of third phalanx is removed. 



The shaft (Corpus) is wider and much thicker above than below, and presents 

 two surfaces and two borders. The dorsal surface is convex from side to side and 

 smooth. The volar surface is flattened, and bears a triangular rough area, bounded 

 b>' ridges which begin at the proximal tuberosities and converge distally; this area 

 furnishes attachment to the distal sesamoidean ligaments. The borders, medial 

 and lateral, are rounded and have a rough area or a tubercle on their middle parts. 



The proximal extremity (Extremitas proximalis s. basis) is relatively large. 

 It bears an articular surface adapted to the distal end of the large metacarpal bone, 

 1 This bone is also called the large pastern bone or os suffraginis. 



