ANTERIOR BRACHIAL REGION. 385 



annular ligament, runs through a groove in the os trapezium (which is converted 

 into a canal by a fibrous sheath, and 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 tied 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 Polli- 

 cis 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, and 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 the 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 presents many varieties. Its 

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

 at either extremity ; or the Palmaris 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, terminating, 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 sur- 

 face, with the Flexor Digitorum Sublimis. Internally, with the Flexor Carpi 

 Ulnaris. Externally, with the Flexor Carpi Radialis. The median nerve lies 

 close to the tendon, just above the wrist, on its inner and posterior side. 



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 mar- 

 gin of the olecranon, by an aponeurosis from the upper two-thirds of the pos- 

 terior 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 in tying the vessel 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, and the ulnar vessels and nerve below. 



The Flexor Digitorum Sublimis (Perforatus) is placed beneath the preceding 

 muscles, which therefore must be removed in order to bring its .attachment into 

 view. It is the largest of the muscles of the superficial layer, and arises by 

 three heads. One head arises 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 (Fig. 157). 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 and little fingers. The 

 tendons diverge from one another as they pass onwards, and are finally inserted 

 25 



