216 POSTERIOR BRACIIIAL REGION. 



carpi pollicis, extensor primi internodii, extensor secundi internodii, 

 extensor indicis, posterior interosseous artery and nerve, wrist joint, 

 metacarpal bones and interossei muscles and phalanges. By its 

 radial border with the extensor carpi radialis longior and brevior. 

 By the ulnar border with the extensor minimi digiti, and extensor 

 carpi ulnaris. 



The Extensor minimi digiti (auric ularis) is an off-set from the 

 extensor communis, with which it is connected by means of a ten- 

 dinous slip. Passing down to the inferior extremity of the ulna it 

 traverses a distinct fibrous sheath, and at the metacarpo-phalangeal 

 articulation unites with the tendon derived from the long extensor. 

 The common tendon then spreads out into a broad expansion which 

 divides into three slips to be inserted as in the other fingers into the 

 two last phalanges. It is to this muscle that the little finger owes 

 its power of separate extension ; and from being called into action 

 when the point of the finger is introduced into the meatus of the 

 ear, for the purpose of removing unpleasant sensations, or producing 

 titillation, the muscle was called by the older writers " auricularis." 



The Extensor carpi ulnaris arises from the external condyle and 

 from the upper two-thirds of the border of the ulna. Its tendon 

 passes through the posterior groove in the lower extremity of the 

 ulna, to be inserted into the base of the metacarpal bone of the little 

 finger. 



Relations. By its superficial surface with the fascia of the fore- 

 arm, and posterior annular ligament. By its deep surface with the 

 supinator brevis, extensor ossis metacarpi pollicis, extensor secundi 

 internodii, extensor indicis, ulna, and wrist joint. By its radial bor- 

 der it is in relation with the extensor communis digitorum, and 

 extensor minimi digiti, and by the ulnar border with the anconeus. 



The Anconeus appears to be the continuation of the triceps : it 

 arises from the outer condyle, and is inserted into the olecranon and 

 triangular surface on the upper extremity of the ulna. 



Relations. By its superficial surface with a strong tendinous apo- 

 neurosis derived from the triceps. By its deep surface with the elbow 

 joint, orbicular ligament, and slightly with the supinator brevis. 



Deep Layer. 



Supinator brevis, 

 Extensor ossis metacarpi pollicis, 

 Extensor primi internodii pollicis, 

 Extensor secundi internodii pollicis, 

 Extensor indicis. 



Dissection. The muscles of the superficial layer should be 

 removed, in order to bring the deep group completely into view. 



The Supinator brevis cannot be seen in its entire extent, until the 

 radial extensors of the carpus are divided from their origin. It 

 arises from the external condyle, from the external lateral and orbi- 

 cular ligament, and from the ulna, and winds around the upper part 



