THE ANTERIOR RADIOULNAR REGION 



475 



its commencement, it increases in size, and terminates in a tendon which forms 

 rather more than the lower half of its length. This tendon passes through a canal 

 on the outer side of the annular ligament, runs through a groove in the os trapezium 

 (which is converted into a canal by a fibrous sheath, and is lined with a synovial 

 membrane), and is inserted into the base of the 

 metacarpal bone of the index finger, and by a slip 

 into the base of the metacarpal bone of the middle 

 finger. 



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 teres 

 and the radial vessels; by its inner border, with the Pal- 

 maris longus above and the median nerve below. 



The Palmaris longus (m. palmaris longus} (Fig. 

 356) is a slender, fusiform muscle, lying on the 

 inner side of the preceding. It arises from the in- 

 ner 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 upper part of the annular ligament, to end in 

 the central part of the palmar fascia and lower part 

 of the annular ligament, frequently sending a tendi- 

 nous slip to the short muscles of the thumb. This 

 muscle is often absent, and is subject to very con- 

 siderable variations; it may be tendinous above 

 and muscular below; or it may be muscular in the 

 centre, with a tendon above and below; or it may 

 present two muscle bundles with a central tendon; 

 or, finally, it may consist simply of a mere tendinous 

 band. 



Relations. By its superficial surface, with the deep 

 fascia. By its deep surface, with the Flexor sublimis digi- 

 torum. Internal/i/, with the Flexor carpi ulnaris. Exter- 

 nally, 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 (m. flexor carpi ulnaris} 

 (Fig. 356) lies along the ulnar side of the forearm. 

 It arises by two heads, connected by a tendinous 

 arch, beneath which pass the ulnar nerve and 

 posterior ulnar recurrent artery. One head (caput 

 humerale) arises from the inner condyle of the 

 humerus, by the common tendon; the other (caput 

 ulnare), from the inner margin of the olecranon 

 and from the upper two-thirds of the posterior border of the ulna, by an aponeu- 

 rosis, common to it and the Extensor carpi ulnaris and Flexor profundus digi- 

 torum; 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, and is 

 prolonged from this to the unciform and fifth metacarpal bones by the pise- 



FIG. 356. Front of the left forearm. 

 Superficial muscles. 



