FLEXOR MUSCLES OF WRIST AND FINGERS. 225 



Among the varieties that have been observed in its mode of termination are insertion, 

 partial or complete, into the fascia of the forearm, into the tendon of the flexor carpi ulnaris 

 and the pisiform bone, into the scaphoid, and into the muscles of the little finger. 



The palmaris longus muscle with the central portion of the palmar fascia are derived from 

 a superficial flexor of the fingers, which has become reduced in association with the greater 

 development and differentiation of the flexores sublimis and profundus digitorum. 



The flexor carpi ulnaris, the innermost muscle of the superficial group, arises 

 by two heads, the one of which forms the hindmost part of the common tendon from 

 the inner condyle of the humerus, while the other is attached to the inner side of the 

 olecranon, and to the posterior border of the ulna for the upper twcT-thirds of its 

 length, by an aponeurosis which is inseparably connected with the investing aponeu- 

 rosis of the limb. The muscular fibres, passing downwards and forwards from this 

 long line of origin, terminate in a tendon which descends along the anterior margin 

 of the muscle, and is inserted into the pisiform bone : this tendon is prolonged by 

 means of the pisi-metacarpal and pisi-uncinate ligaments to the fifth metacarpal and 

 unciform bones, and a small band passes to the anterior annular ligament. 



Relations. This muscle rests on the flexor profundus digitorum. The ulnar nerve and 

 the posterior ulnar recurrent artery pass between the two heads of origin, and the nerve is 

 then covered by the muscle as far as the wrist, as are also the ulnar vessels below the middle 

 of the forearm. 



Varieties. An additional slip of origin from the inner side of the coronoid process is 

 often present. Partial insertion into the annular ligament, the fourth or the fifth metacarpal 

 bone, has also been observed. 



The epitrochleo-aneonciix is a small muscle frequently present, arising from the back of 

 the inner condyle, and inserted into the olecranon ; it lies over the ulnar nerve, from which 

 it receives a twig. It is generally represented by a band of transverse fibres in the fascia. 



The flexor sublimis digitorum or flexor perforatus, the superficial flexor 

 of the fingers, is a broad flat muscle placed behind the preceding muscles. It arises 

 by a thick strong head from the inner condyle and the fibrous septa common to it 

 and the other muscles, from the internal lateral ligament, and from the inner margin 

 of the coronoid process ; and by a thin flat portion from the anterior oblique line 

 and part of the anterior border of the radius. It is divided inferiorly into four parts, 

 ending in as many tendons, which pass to be inserted into the second phalanges of 

 the four inner digits. These tendons pass under the annular ligament of the wrist 

 in pairs, the anterior pair consisting of those for the middle and ring fingers, the 

 posterior of those for the index and little fingers. 



In the palm of the hand the tendons diverge, and each, accompanied by a tendon 

 of the flexor profundus, enters a fibrous sheath which binds both tendons down to 

 the palmar surface of the phalanges. Opposite the first phalanx the tendon of the 

 flexor sublimis divides into two parts, which fold closely round the tendon of the 

 deep flexor, and are reunited by their margins behind it : the two portions of the 

 tendon thereafter separating, pass to be inserted one on each side into a ridge at the 

 middle of the lateral border of the second phalanx. 



The arrangement of the tendons of the flexor sublimis digitorum beneath the annular 

 ligament corresponds to a division of the muscle into two layers, which can be readily 

 separated almost up to the origin from the internal condyle. The superficial layer springs 

 from the condyle by a tendinous lamina which forms part of the common tendon : its fleshy 

 mass is divided below into two bellies, from which the tendons to the middle and ring fingers 

 proceed : the middle finger part receives the radial head, while the ring finger tendon is 

 joined by a slip from the deep division of the muscle. The deep layer has the construction 

 of a digastric muscle : it has a broad origin, for the most part by fleshy fibres, from the 

 internal condyle, the anterior band of the internal lateral ligament, and the inner margin of 

 the coronoid process, as well as from the deep surface of the tendon of the superficial layer 

 and the adjacent margin of the condylar tendon of the flexor carpi ulnaris : the fibres form 

 a conical belly, which terminates in a flat-cylindrical tendon above the middle of the forearm. 



