104 THE UPPER EXTREMITY 



One of these is incorporated with the common origin from the 

 medial epicondyle; the other springs from the medial border 

 of the olecranon of the ulna, and likewise by an aponeurotic 

 attachment from the posterior border of the same bone in 

 its proximal two-thirds. Fibres are also derived from the in- 

 vesting fascia and the intermuscular septum on its lateral side. 

 The two heads of origin of the flexor carpi ulnaris bridge 

 across the interval between the medial epicondyle of the 

 humerus and the olecranon, and between them the ulnar 

 nerve is prolonged distally into the forearm. The tendon 

 appears upon the volar border of the muscle, and is inserted 

 into the pisiform bone. The flexor carpi ulnaris is supplied 

 by the ulnar nerve. It is a flexor and adductor of the hand 

 and a flexor of the elbow. 



M. Flexor Digitorum Sublimis. The flexor sublimis re- 

 ceives this name from its being placed upon the superficial 

 aspect of the flexor profundus. For the most part it lies 

 deeper than the other superficial muscles (Fig. 41). It is a 

 powerful muscle which arises from the medial epicondyle of 

 the humerus by the common tendon, but it also takes origin 

 from the ulnar collateral ligament of the elbow- joint, from 

 the medial margin of the coronoid process of the ulna, the 

 volar surface of the radius (Fig. 43, p. 108), and the fascial 

 intermuscular septa in relation to it. The radial head of 

 origin is a thin fleshy stratum which is attached to the 

 volar border of the radius from its proximal extremity to a 

 variable distance distal to the insertion of the pronator teres 

 muscle. Four tendons issue from the fleshy mass. These 

 enter the palm by passing under cover of the transverse carpal 

 ligament, and go to the four medial digits. Their insertions 

 will be seen later on, but in the meantime note that at the 

 wrist, and for a short distance above it, they are enveloped 

 by the vagina mucosa previously mentioned, and also that as 

 they pass behind the transverse carpal ligament they lie in 

 pairs the tendons to the ring and middle fingers being placed 

 on the volar aspect of those for the index and little fingers. 

 The flexor digitorum sublimis is supplied by the median nerve. 



Dissection. The ulnar artery" and at the same time the ulnar and 

 median nerves should be followed in their course through the forearm. 

 The artery in the proximal part of its course lies very deeply, but its 

 relations can be fully studied and its branches traced by simply slitting up 

 the intermuscular septum between the flexor digitorum sublimis and the 

 flexor carpi ulnaris. 



