ANTERIOR BRACHIAL REGION. 307 



in size, and terminates in a tendon which forms the lower two-thirds of its struc- 

 ture. This tendon passes through a canal on the outer side of the annular liga- 

 ment, runs through a groove in the os trapezium, converted into a canal by a 

 fibrous sheath lined by a synovial membrane, and is inserted into the base of 

 the metacarpal bone of the index-finger. The radial artery lies between the 

 tendon of this muscle and the Supinator longus, and may easily be secured in 

 this situation. 



Relations. By its superficial surface, with the deep fascia and the integument. 

 By its deep surface, with the Flexor sublimis digitorum, Flexor longus pollicis, 

 and wrist-joint. By its outer border, with the Pronator radii teres, and the radial 

 vessels. By its inner border, with the Palmaris longus above, the median nerve 

 below. 



The Palmaris Longus is a slender fusiform muscle, lying on the inner side of 

 the preceding. It arises from the inner condyle of the humerus by the common 

 tendon, from the deep fascia, and intermuscular septa between it and the adjacent 

 muscles. It terminates in a slender flattened tendon, which is inserted into the 

 annular ligament, expanding to end in the palmar fascia. 



Variations. This muscle is often absent; when present, it exhibits many varieties. Its fleshy 

 belly is sometimes very long, or it may occupy the middle of the muscle, which is tendinous at 

 either extremity ; or it may be muscular at its lower extremity, its upper part being tendinous. 

 Occasionally there is a second Palmaris longus placed on the inner side of the preceding, termi- 

 nating, below, partly in the annular ligament or fascia, and partly in the small muscles of the 

 little finger. 



Relations. By its anterior surface, with the deep fascia. By its posterior surface, 

 with the Flexor sublimis digitorum. Internally, with the Flexor carpi ulnaris; 

 Externally, with the Flexor carpi radialis. 



The Flexor Carpi Ulnaris lies along the ulnar side of the forearm. It arises by 

 two heads, separated by a tendinous arch, beneath which passes the ulnar nerve, 

 and posterior ulnar recurrent artery. One head arises from the inner condyle of 

 the humerus, by the common tendon ; the other, from the inner margin of the 

 olecranon, by an aponeurosis from the upper two-thirds of the posterior border of 

 the ulna, and from the intermuscular septum between it and the Flexor sublimis 

 digitorum. The fibres terminate in a tendon, which occupies the anterior part of 

 the lower half of the muscle, and is inserted into the pisiform bone, some fibres 

 being prolonged to the annular ligament and base of the metacarpal bone of the 

 little finger. The ulnar artery lies on the outer side of the tendon of this muscle, 

 in the lower two-thirds of the forearm ; the tendon forming a guide to the opera- 

 tion of including this vessel in a ligature in this situation. 



Relations. By its anterior surface, with the deep fascia, with which it is 

 intimately connected for a considerable extent. By its posterior surface, with the 

 Flexor sublimis, the Flexor profundus, the Pronator quadratus, and the ulnar 

 vessels and nerve. By its outer or radial border, with the Palmaris longus, above; 

 with the ulnar vessels and nerve, below. 



The Flexor Digitorum Sublimis is placed beneath the preceding muscles; these 

 therefore require to be removed before its attachment is brought into view. It 

 is the largest of the muscles of the superficial layer, and arises by three heads. 

 One from the internal condyle of the humerus by the common tendon, from the 

 internal lateral ligament of the elbow-joint, and from the intermuscular septum 

 common to it and the preceding muscles. The second head arises from the inner 

 side of the coronoid process of the ulna, above the ulnar origin of the Pronator 

 radii teres. The third head arises from the oblique line of the radius, extending 

 from the tubercle to the insertion of the Pronator radii teres. The fibres pass 

 vertically downwards, forming a broad and thick muscle, which divides into four 

 tendons about the middle of the forearm; as these tendons pass beneath the 

 annular ligament into the palm of the hand, they are arranged in pairs, the anterior 

 pair corresponding to the middle and ring fingers ; the posterior pair to the index 



