3S4 A MANUAL OF ANATOMY 



border, of the ulna, by an aponeurosis common to it, the flexor 

 profundus digitorum, and extensor carpi ulnaris. 



Insertion. — ^The pisiform bone. From the tendon of insertion 

 two prolongations are given off, known as the pisi-uncinate and pisi- 

 metacarpal ligaments, the former being attached to the anterior 

 border of the hook of the unciform bone, and the latter to the front 

 of the base of the fifth metacarpal. The tendon also gives off 

 laterally a band to the anterior annular ligament. 



Nerve-supply. — The ulnar nerve, which is a branch of the inner 

 cord of the brachial plexus, its fibres being derived from the eighth 

 cervical and first thoracic. 



The fibres are directed downwards and forwards, and terminate 

 on the posterior aspect of the tendon which appears about the 

 centre of the forearm. 



Action. — (i) To flex and adduct the wrist-joint, and (2) to flex 

 feebly the elbow- joint. 



The ulnar nerve and posterior ulnar recurrent artery pass between 

 the two heads of the muscle. 



Second Layer. — Flexor Sublimis Digitorum (flexor perforatus) — 

 Origin. — The upper part arises from (i) the internal epicondyle ; 

 (2) the intermuscular septum between it and the first layer ; (3) the 

 internal lateral ligament of the elbow-joint ; and (4) the tubercle 

 on the inner margin of the coronoid process of the ulna. The 

 lower part, broad and thin, arises from the anterior oblique line of 

 the radius. 



Insertion. — By four tendons into the sides of the second 

 phalanges of the four inner fingers, at their centre and on their 

 anterior aspect. 



The muscle in the lower part of the forearm is replaced by four 

 tendons which pass beneath the anterior annular ligament in pairs. 

 The tendons of the anterior pair are for the middle and ring 

 fingers, whilst those of the posterior pair are for the index and little 

 fingers. In this situation, as well as for a little above the wrist, and 

 as low as about the centre of the palm, they are invested, along with 

 the deep flexor tendons, by the great palmar bursa, to be afterwards 

 described. In the palm the four tendons diverge, and each is accom- 

 panied by a tendon of the flexor profundus digitorum, which lies 

 beneath it. At the commencements of the digits each pair of tendons 

 enters the sheath on the palmar aspect of a finger, which binds them 

 to the first and second phalanges. Towards the distal end of the first 

 phalanx the flexor sublimis tendon splits into two parts to allow the 

 flexor profundus tendon to pass through. The two divisions of the 

 superficial tendon are folded round the deep tendon, and unite 

 beneath it at the proximal end of the second phalanx. Beyond this 

 point the superficial tendon is grooved to support the deep tendon, 

 and then divides into its two parts of insertion. The sheath and its 

 accessories will be afterwards described. 



Ntrve-supply. — The median nerve. 



Action. — (i) To flex the second phalanges of the four inner fingers ; 



