24 THE SURGICAL ANATOMY OF THE HORSE 



removed in order that the important structures lying beneath it might 

 be displayed. 



The artery again appears in the plate about three inches above the 

 knee (39), where it is found between the tendons of the internal and 

 middle flexors of the metacarpus. It descends between these two tendons, 

 and just above the carpus it divides into the large and small metacarpal 

 arteries. 



The Large Metacarpal Artery (41). — This is much the larger of the 

 two terminal divisions of the posterior radial artery. It continues the 

 course of the latter vessel in a vertical direction, and disappears within 

 the carpal sheath. Near its origin from the posterior radial it gives off a 

 branch (42), which passes backwards behind the radius, and anastomosing 

 with the terminal branch of the ulnar artery, forms the supracarpal arch. 



The large metacarpal artery is again visible in the plate (52), where it 

 leaves the carpal sheath. It runs down the metacarpal region between 

 the internal metacarpal vein, which ascends in front of the artery, and 

 the internal plantar nerve. Just above the fetlock the vessel disappears 

 by passing outwardly, and whilst so obscured from view it divides into 

 the external and internal digital arteries. 



The Sjnall Metacarpal Artery (43). — This is very much smaller than 

 the vessel just described. From the point of bifurcation of the posterior 

 radial artery it takes a downward course, outside the fibrous arch which 

 encloses the carpal sheath. Below the knee the artery passes outwardly 

 and disappears to contribute to the formation of the subcarpal arch. This 

 latter arch is formed by the small metacarpal artery and a small artery 

 which descends from the supracarpal arch, and it is placed across the 

 back of the limb between the subcarpal and suspensory ligaments. 



The Internal Dorsal Interosseous Artery (49). — In the plate this vessel 

 makes its appearance between the internal metacarpal vein and the inner 

 small metacarpal bone. It comes from the subcarpal arch, and winds 

 round the small metacarpal bone just below the head of the latter, 

 passing under the internal metacarpal vein. The vessel then runs down- 



