ANCONEUS 311 



cause of the rapid movements of the lower end of the forearm which are made use 

 of in tin-owing and striking. 



Acting from below, the trice})s will extend the upper arm upon the forearm, as 

 in the use of the parallel l)ars, and in many other gymnastic exercises. 



Relations. — The long head lies behind the subscapularis, teres major, and latis- 

 simus dorsi, in front of the teres minor, witli the dorsalis scapula vessels upon its 

 posterior, and the posterior circumflex vessels and the circumflex nerve upon its 

 anterior border. Lower down, the posterior surface of the muscle is only separated 

 from the integuments by the deep fascia; in front lie the brachialis anticus, brachio- 

 radialis (supinator longus), extensor carpi radialis longior, and coraco-brachialis, 

 with the superior and inferior profunda vessels and the ulnar and musculo-spiral 

 nerves. A small bursa intervenes between the tendon and part of the olecranon 

 process. The muscle is also in relation with the shoulder- and elbow-joints. 



Variations. — The internal head .somethues arises as high as the greater tuberosity. An addi- 

 tional slip is occasionally received from the capsule of the shoulder-joint, the coracoid process, or 

 the tendon of the latissimus dorsi. A sli]) of muscle is frequently separated from the lower 

 border of the internal head, and, passing from the inner condyle to the olecranon, bridges over 

 the ulnar nerve. 



2. ANCONEUS 



The anconeus is described with the Muscles ox the Back of the Foeearm 

 (page 327). 



MUSCLES OF THE FOREARM 



The muscles of the forearm are enveloped by a strong deep fascia which is con- 

 tinuous with that of the upper arm. It is thickest upon the posterior aspect, where 

 it is attached to the sides of the triangular posterior surface of the olecranon, and to 

 the Avliole of the posterior ridge of the ulna. Below the internal condyle it receives 

 the broad band of the bicipital fascia; and behind, the aponeurotic insertion of the 

 triceps. In the bend of the elbow it is pierced by a communicating vein. On the 

 outer side and back of the forearm the deep fascia has numerous connections with 

 the longitudinal ridges on the lower ends of the radius and ulna. It also becomes 

 much thickened by the addition of transverse bands, so as to form the posterior 

 annular ligament, which passes from the outer border of the lower end of the 

 radius, inwards and at the same time a little downwards, to the ulnar border of the 

 ear})us, where it is attached to the inner sides of the pisiform and cuneiform bones. 

 On its anterior surface this ligament is attached to the ridges upon the back of the 

 lower extremity of the radius, and so forms canals through which pass the tendons 

 of the long muscles upon the radial border and posterior surface of the forearm. 

 The ligament is also in contact with the lower end of the ulna, which it binds in its 

 place, much in the same manner as the head of the radius is held in position by 

 means of the orbicular ligament, but it has no insertion into this bone. 



In the front of the Avrist the deep fascia forms a thin layer, which overlies the 

 anterior annular ligament. The latter is sometimes described as a thickening of 

 the same fascia, but really it is continuous with a thin aponeurosis which separates 

 the first and second layers of the muscles of the forearm shortly to be described. 

 It is a strong band of fibrous tissue, which stretches transversely from the pisiform 

 l)one and unciform process on the ulnar side of the carpus to the scaphoid and the 

 trapezium on the radial side. 



MUSCLES OF THE FRONT OF THE FOREARM 



The muscles upon the front of the forearm form four planes or layers: the first 

 two layers having their origins from the front of the internal condyle; the last two 

 from the liones of the forearm alone. 



