THE TORE EXTREMITY. 209^ 



Flexor metacarpi internus. It arises from tlie internal 

 surface of the inferior extremity of the humerus, where it 

 is attached to a slightly prominent ridge, j^asses over the 

 caj)sular ligament of the elbow- joint, to which it is firmly 

 attached, and runs downwards along the internal margin of 

 the posterior surface of the radius covering the radial artery y 

 vein, and nerve. It then runs through a synovial sheath 

 behind the knee, and becomes inserted into the head of the 

 inner small metacarpal bone. This sheath is strengthened ex- 

 ternally by a fibrous band reflected from the internal surface 

 of the annular ligament, which superiorly blends with the 

 stipe7'ior siisiDensory ligament, a dense white fibrous tissue 

 band running from the posterior part of the inferior ex- 

 tremity of the radius to the perforans and the perforatus 

 tendons. This septum is broad superiorly, but inferiorly 

 grows narrow, and separates the tendon of flexor metacarpi 

 internus from those of the perforatus and the perforans. 

 Opposite the superior part of this reflection a small branch 

 runs from the radial artery to become superficially placed 

 on the inner surface of the limb, the small metacarpal, 

 which anastomoses with the recurrent branch of the large 

 metacarj^al, and gives off the medullary artery of the large 

 metacarpal bone. The annular ligament of the knee 

 terminates below in a definite band of white fibrous tissue 

 at the inferior part of the middle third of the internal 

 surface of the inner small metacarpal bone ; between this 

 bandand the remainder of the ligament the inyier metacarpal 

 vein passes to gain the cutaneous surface of the limb, and 

 from it the superficial radial vein arises, which passes 

 upwards to the superficial brachial vein. 



Flexor metacarpi medius is situated posteriorly to flexor 

 metacarpi internus. It is broad superiorly, where we see 

 some of its tendinous fibres running transversely from the 

 point of the ulna to get a firm insertion into the capsular 

 ligament of the elbow-joint, and into the inferior part of 

 the ridge running upwards from the inner condyle of the 

 humerus. Under this part run the ulnar artery, vein, and 

 nerve. The ulnar nerve proceeds down the back of ih& 

 limb at first underneath ulnaris accessorius, and then about 

 opposite the inferior part of the middle third of the radius 

 passes under the tendon of that muscle to gain the inner 

 surface of flexor metacarpi externus. The postero-superior 

 part of flexor metacarpi medius blends with ulnaris acces- 



14 



