SUPERFICIAL DISSECTIONS 15 



As its name implies, this muscle is a flexor of the knee. Its nerve 

 supply is derived from the musculo-spiral. 



The Ulnar Accessorius (23). — The origin of this muscle from the 

 olecranon process of the ulna is seen. The muscle is placed between 

 that just described and the flexor metacarpi medius. It disappears 

 between these two muscles and becomes more deeply seated where it 

 joins the two remaining heads of the flexor perforans, to be followed by 

 a common tendon, which disappears through the carpal sheath. The 

 tendon will be described with the inner aspect of the limb. 



The Flexor Metacarpi Medius. — Only the posterior origin of this 

 muscle which is attached to the olecranon process is represented in the 

 plate (the anterior head arises from the inner condyle of the humerus). 

 Both heads unite, and their common tendon is attached to the upper 

 border of the pisiform bone. This muscle is a flexor of the knee, 

 and is supplied by the ulnar nerve. 



The Arteries 



No vessels appear in the plate representing the upper half of the 

 limb. Just above the knee joint the interosseous artery of the forearm (27) 

 appears from beneath the extensor pedis muscle. It runs down the 

 limb at first on the extensor metacarpi obliquus and then on the radius, 

 being ultimately distributed superficially on the front of the knee. 



Running along the edge of the perforans tendon is the outer of the 

 two small unnamed arteries (35), which descends from the subcarpal arch 

 in front of the plantar nerve. It becomes lost towards the middle of 

 the metacarpus. 



The External Digital Artery (43). — This arises from the division of 

 the large metacarpal artery just above the fetlock. It appears between 

 the suspensory ligament and perforans tendon, and runs vertically across 

 the fetlock between the plantar nerve behind and the external digital 

 vein in front. It follows the course of the posterior digital nerve, and 



