FLEXOR LONGUS POLLICIS. 233 



neath the annular ligament, are in relation superficially with the superficial 

 palmar arch, and palmar fascia ; and deeply with the tendons of the deep 

 flexor and lumbricales. 



The FLEXOR CARPI ULNARIS arises by two heads, one from the inner 

 condyle, the other from the olecranon and upper two-thirds of the inner 

 border of the ulna. Its tendon is inserted into the pisiform bone, and base 

 of the metacarpal bone of the little finger. 



Relations. By its anterior surface with the fascia of the fore-arm, with 

 which it is closely united superiorly. By its posterior surface with the 

 flexor sublimis digitorum, flexor profundus, pronator quadratus, and ulnar 

 artery, veins, and nerve. By its radial border with the palmaris longus, 

 and in the lower third of the fore-arm with the ulnar vessels and nerve. 

 The ulnar nerve, and the posterior ulnar recurrent artery, pass between 

 its two heads of origin. 



Deep layer. 



Flexor profundus digitorum, 

 Flexor longus pollicis, 

 Pronator quadratus. 



Dissection. This group is brought into view by removing the fiexoi 

 sublimis, and drawing aside the pronator radii teres. 



The FLEXOR PROFUNDUS DIGITORUM (perforans) arises from the upper 

 two-thirds of the ulna and part of the interosseous membrane, and termi- 

 nates in four tendons, which pass beneath the annular ligament, and be- 

 tween the two slips of the tendons of the flexor sublimis (hence its desig- 

 nation, perforans), to be inserted into the base of the last phalanges. The 

 tendon of the index finger is always distinct from the rest, the other three 

 tendons being more or less intimately connected by the cellular tissue and 

 tendinous slips. 



Four little muscular fasciculi, called lumbricales^ are connected with 

 the tendons of this muscle in the palm. They will be described with the 

 muscles of the hand. 



Relations. In the fore-arm. By its anterior surface with the flexor 

 sublimis digitorum, flexor carpi ulnaris, median nerve, and ulnar artery, 

 veins, and nerve. By its posterior surface with the ulna, the interosseous 

 membrane, the pronator quadratus, and the wrist joint. By its radial 

 border with the flexor longus pollicis, the anterior interosseous artery and 

 nerve being interposed. By its ulnar border with the flexor carpi ulnaris. 

 In the hand : its tendons are in relation superficially with the tendons of 

 the superficial flexor; and deeply with the interossei muscles, adductor 

 pollicis, and deep palmar arch. In the fingers : the tendons of the deep 

 flexor are interposed between the tendons of the superficial flexor and the 

 phalanges, and give attachment to vincula accessoria. 



The FLEXOR LONGUS POLLICIS arises from the upper two-thirds of the 

 radius, and part of the interosseous membrane. Its tendon passes beneath 

 the annular ligament, to be inserted into the base of the last phalanx of 

 the thumb. 



Relations. By its anterior surface with the flexor sublimis digitorum, 

 flexor carpi radialis, supinator longus, and radial artery and veins. By 

 its posterior surface with the radius, interosseous membrane, pronator 

 quadratus, and wrist joint. By its ulnar border it is separated from the 

 flexor profundus digitorum by the anterior interosseous artery and nerve 

 20* 



