THE ARTERIES 175 



original incision made in performing the operation, and above the seat, 

 when the end of the artery may be secured and ligatured. Near its 

 termination {i.e., just before it splits up into the large and small meta- 

 carpal arteries) this artery is also in an exposed position, and is liable to 

 be accidentally injured and even ruptured in such wounds as are caused 

 by " spiking " the inner aspect of the limb when unsuccessfully clearing 

 a fence. In these cases when the artery is divided the proximal end is 

 retracted beneath the flexor muscles, and if unable to reach it from the 

 original wound an incision should be made at the seat of median 

 neurectomy, where no difficulty will be experienced in applying a 

 ligature. 



The Small Metacarpal Artery. — From the point of bifurcation of the 

 posterior radial artery this vessel takes a vertical course down the Hmb 

 on the inner aspect of the knee. It occupies a superficial position, being 

 outside the fibrous carpal arch, where it is placed behind the correspond- 

 ing vein. Just below the knee the artery curves outwardly and passes 

 almost transversely across the subcarpal or check ligament to anastomose 

 with a small artery which descends through the carpal sheath from the 

 supracarpal arch. By this anastomosis is formed what is known as the 

 subcarpal arch. From this arch four to six vessels are given off. They 

 are as follows : 



I. The Internal Dorsal Interosseous Artery. — From the arch this vessel 

 passes under the internal metacarpal vein, and emerges from between this 

 vein and the internal small metacarpal bone. It winds round the latter 

 just below the head, and then descends along the groove formed anteriorly 

 between the large and inner small metacarpal bones. The first portion 

 of the artery runs almost transversely, whilst that portion in the groove 

 mentioned is disposed vertically. From the bend of the vessel a small 

 branch is detached which runs transversely and terminates in the skin 

 covering the upper portion of the large metacarpal bone. 



2. The External Dorsal Interosseous Artery. — This leaves the arch and 

 passes outwards beneath the external metacarpal vein, winding round the 



