THE POKE EXTREMITY. 211 



Radialis accessorius arises from the posterior surface of 

 the middle third of the humerus inclined to its outer side ; 

 its fibres become inserted into the perforans tendon, in 

 blending with the superior suspensory ligament above and 

 "behind the knee. 



Ulnaris accessorius runs to the same insertion, after 

 arising from the posterior part of the olecranon in common 

 with flexor metacarpi medius. Its muscular portion covers 

 the ulnar nerve and is covered by the faschia of the arm. 



On examination of the external surface of the arm we 

 find that the faschia of the arm blends anteriorly with the 

 fibrous band of extensor metacarpi magnus, which runs 

 from flexor brachii. Supero-externally its fibres converge 

 to form a white tendinous band (which contains some yel- 

 low elastic fibres, and to which levator humeri and pectoralis 

 transversus are attached). This, superiorly, is firmly at- 

 tached to the inferior extremity of the ridge running down- 

 wards from the external tubercle of the humerus, passes 

 over and binds down humeralis externus in its course over 

 the external surface of the humerus, and posteriorly runs 

 to become attached to the ridge passing upwards from the 

 ■external condyle of the humerus, inferiorly it blends with 

 •caput medium. 



Extensor metacarpi magnus at its superior attachment 

 to the ridge running upwards from the external condyle of 

 the humerus, blends with extensor pedis. It is also at- 

 tached by a strong tendon to the anterior part of the cap- 

 sular ligament of the elbow- joint, thus separating humerali* 

 •externus from that ligament. Between the upper part of 

 this muscle and humeralis externus runs the spiral nerve, 

 which after meeting the spiral artery and vein and their 

 small accompanying nerve at the front of the joint proceeds 

 with them down the front of the limb under the muscles. 

 At the upper part of the front of the knee its tendon is in 

 contact with extensor metacarpi obliquus, which passes over 

 it in its course from without inwards and downwards, and 

 is separated from it by a bursa. Passing then through the 

 central one of the three grooves at the anterior part of the 

 inferior extremity of the radius, and through a special 

 channel in the annular ligament of the knee, where it is 

 lubricated with synovia, the tendon of this muscle becomes 

 inserted into the j)rominence on the antero-superior part of 

 the large metacarpal bone, slightly inclined to the inner side. 



