MUSCLES AND FASCIA OF UPPER EXTREMITY 155 



of the extensor minimi digiti tendon; this fourth is 

 the smallest tendon, and receives muscular fibers as 

 far as the wrist. 



Opposite the metacarpophalangeal joints the tendons 

 are bound down by transverse fibers from the front 

 of the joint, ligamenta dorsalia; inserted into the base 

 of the last phalanx. 



Extensor minimi digiti arises from the superficial and 

 deep fascia of the forearm, from the orbicular ligament, 

 from the septa between it and common and ulnar exten- 

 sors; its tendon is in a groove between the radius and 

 ulna, and splits into two on the back of the hand, the 

 outer being joined by a slip from the fourth common 

 extensor tendon, and both parts end on the little 

 finger, like the other extensor tendons. 



Extensor Carpi Ulnaris (Ulnaris Externus). Origin, 

 common tendon, orbicular ligament, septa, fascia of 

 the forearm, which is connected with the elbow- 

 joint capsule, and anconeus. Insertion, tuberosity of 

 the base of the fifth metacarpal. A bursa is under 

 its tendon of origin in one-fourth of the cases. 



Anconeus fills the space between the triceps and 

 extensor carpi ulnaris; is flat and triangular, covered 

 by fascia connected with the triceps ; arises by a narrow 

 tendon from a fossa on the inner and posterior part 

 of the external condyle; upper fibers are transverse, the 

 rest pass obliquely down and into the radial aspect of 

 the olecranon and adjacent upper third of the ulna. 



DEEP LAYER. Supinator Brevis. Origin, external 

 lateral ligament, orbicular ligament, supinator ridge, 

 oblique line of the ulna, and for a short distance on 

 the outer border of the ulna from the fascia covering 

 it, which is connected with the external condyle; it 

 regularly consists of two layers separated by the 

 posterior interosseous nerve; the superficial one rises 

 by aponeurotic fibers, the other by muscular. The 

 fibers pass sling-like around the upper part of the 

 radius to be inserted into a third of its length, limited 



