FLEXOR SUBLIMIS DIGITORUM 315 



Variations. — The palmaris longus is very variable. It may be double, and it is often absent. 

 The fleshy belly is suiuetimes below, and the tendon in part or entirely above. It may take an 

 additional head fmrn the radius or the onronoid proces-s. Its insertion may be into the fascia of 

 the forearm, the flexor carpi ulnaris, tlie short muscles of the little finger, or one of the carpal 

 bones. 



4. FLEXOR CARPI ULXARIS 



The flexor carpi ulnaris — named from its influence upon the wrist and its 

 position — is a thick sheet of muscular fibre, somewhat fusiform in shape, which 

 wraps round the convex ulnar border of the forearm. 



Origin. — First head: (1) by the common tendon from the lower part of the 

 front of the internal condyle; (2) the deep fascia of the forearm; and (3) the septa 

 which intervene between the muscle and the palmaris longus and flexor sublimis 

 digitorum. 



The second head : from the inner surface of the olecranon process, and the 

 upper two-thirds of the posterior border of the ulna. 



Insertion. — The upper surface of the pisiform bone, beyond which fibres are 

 continued to the unciform process and the front of the base of the fifth metacarpal 

 l)one. 



Structure. — The origin of the upper head is tendinous, and that of the lower is 

 partly fleshy, partly aponeurotic; the aponeurosis from the posterior ridge of the 

 ulna being common to it with the flexor profundus digitorum and the extensor carpi 

 ulnaris, and being closely blended with the deep fascia of the back of the forearm. 

 The two heads are united by a fibrous arch under which passes the ulnar ners'e. 

 From this tendinous and bony origin the fleshy fibres pass doAvnwards and forwards 

 in a penniform manner to be inserted into the posterior aspect of a tendon which 

 appears on the front of the muscle a little above the middle of the foreann, and 

 becomes free just above the wrist-joint, where it lies superficial and internal to the 

 anterior annular ligament. 



Nerve-supply. — From the inner cord of the brachial plexus (through the 

 eighth cervical and first thoracic nerves) by filaments from the ulnar nerve which 

 enter the deep surface of the muscle above the middle of the forearm. 



Action. — (1) To flex the wrist. The pisifonn bone assists this action by lifting 

 the line of the tendon a little from the metacarpal bone, much as the patella assists 

 the quadriceps femoris. (2) It assists somewhat feebly in adduction of the wrist. 

 (3) It helps in the flexion of the elbow. 



Relations. — Superficially, the deep fascia and superficial veins; deeply, the 

 flexor sublimis and profundus digitorum, the ulnar vessels and nerve. At the 

 elbow the posterior ulnar recurrent artery with the ulnar nerve passes between the 

 two heads of this muscle. Near the wrist the ulnar artery lies along the outer 

 border of the tendon. 



Variations. — Its insertion sometimes extends to the anterior annular ligament, and occasionally 

 it sends a sHp to the base of the fourth metacarpal bone. 



Second Layer 

 The second layer consists of one muscle — the flexor sublimis digitorum. 



FLEXOR SUBLIMLS DIGITORUM 



The flexor sublimis digitorum — named from its action as a flexor of the fin- 

 gers, and from its position in relation to the deep flexor {mhlin^ix ^ superficial) — 

 is a fusiform sheet, with two heads above, and dividing into four tendons below. 



Origin. — The first head arises from d) the front of the intemal condyle by 

 the common tendon; (2) the intermuscular septum which separates it from the 

 muscles of the first sheet; (3) the internal lateral ligament; and (4) a tubercle at 

 the upper part of the inner border of the coronoid process of the ulna. 



