480 



THE MUSCLES AND FASCIAE. 



of the metacarpal bone of the index finger, and by a slip into the base of the 



metacarpal bone of the middle 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 surf ace, with the deep fascia and the integument; 



by its deep surface, with the Flexor subliniis 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 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 passes over the annular 

 ligament to end in the palmar fascia, frequently 

 sending a tendinous slip to the short muscles of 

 the thumb. This muscle is often absent ; or it 

 may be tendinous above and muscular below ; or 

 muscular at both extremities of a middle tendon. 



Eelations. By its deep surface, Avith the Flexor 

 sublimis digitorum ; internally, Avith 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 con- 

 nected by a tendinous arch, beneath which pass 

 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 which arises also from the upper two- 

 thirds of the posterior border of the ulna, in com- 

 mon with the Extensor carpi ulnaris and the Flexor 

 profundus digitorum ; other fibres spring from the 

 septum between it and the Flexor subliniis digito- 

 rum. The fibres terminate in a tendon which occu- 

 pies the anterior part of the lower half of the 

 muscle, and is inserted into the pisiform bone, and 

 is prolonged from this to the fifth metacarpal and 

 unciform bones by the piso-metacarpal and piso- 

 uncinate ligaments and to the annular ligament. 

 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 superficial surface, with the 

 deep fascia, with which it is intimately connected 

 for a considerable extent ; by its deep surface, 

 with the Flexor sublimis digitorum, the Flexor 

 profundus digitorum, 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 sublimis digitorum (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 super- 

 ficial layer, and arises by three heads. One head arises from the internal condyle 



FIG. 306. Front of the left forearm. 

 Superficial muscles. 



