MUSCLES OF THE FORE EXTREMITY 331 



is there surrounded by a synovial membrane; continuing downwards, it 

 becomes inserted into the head of the inner small metacarpal bone. 



Action. — To flex the knee-joint. 



Flexor Metacarpi Medius (Middle Flexdr of the Metacarpus or 

 canon). — Situated beliind the fore-arm to the outer side of the preceding 

 muscle. It is divided above into two parts, the posterior of which is the 

 smaller. 



Origin. — By its anterior and larger division from the internal condyle 

 of the humerus immediately behind the internal flexor. By its posterior 

 division from the upper and posterior part of the point of the elbow 

 (olecranon). 



Insertion. — Into the upper border of the pisiform bone. 



Action. — To bend the knee. 



Flexor Metacarpi ExternuiS (External Flexor of the Metacarpus or 

 canon). — Placed on the outer and posterior part of the fore-arm. 



Origin. — From the point of the ridge on the outer and inferior extremity 

 of the humerus. 



Insertion. — By two tendons — (l) a broad flat one into the upper border 

 of the pisiform bone; (2) a short round one into the head of the external 

 small metacarpal bone. The latter passes over a groove and through a 

 synovial sheath on the outer surface of the pisiform bone. 



Action. — To bend the knee. 



Flexor Pedis PerforatUS. — Superficially placed behind the lower 

 arm. 



Origin. — From a ridge on the inner and inferior part of the humerus 

 by a tendon common to this muscle and the flexor pedis perforans. 



Insertion. — About the middle third of the radius the tendon of this 

 muscle is joined by a strong band of fibrous tissue (superior check ligament). 

 Its tendon then passes behind the knee, where it is enclosed in the carpal 

 sheath, and, coursing its way downwards, ultimately divides into two short 

 branches, which become inserted into the posterior upper border of the 

 small pastern bone (second phalanx). 



Action. — To flex the pastern and the knee. 



Flexor Pedis Perforans. — This muscle is situated behind the lower 

 arm, with which it is in contact. It is composed of three unequal portions 

 — the humeral, the ulnar, and the radial. The humeral is much the largest 

 of the three, and constitutes the chief bulk of the muscle. 



Origin. — It arises (l) from a ridge on the inner and inferior part of the 

 humerus; (2) from the upper and posterior part of the ulna; (3) from the 

 posterior surface of the radius. 



Insertion. — The three portions unite and form one common tendon. 



