206 MUSCLES OF THE TPrEE LIMB. 



little above the bend of the elbow, the muscle suddenly becomes 

 narrower, and is continued into the flat rounded tendon of insertion. 

 This tendon, slightly twisted upon itself as it descends, is inserted into 

 the rough posterior margin of the tuberosity of the radius, gliding on 

 the anterior smooth surface of that process by the intervention of a 

 synovial bursa From the inner side of the lower part of the muscle 

 and tendon a strong flat aponeurotic band, called the semilunar fascia^ 

 passes downwards and inwards, and becomes blended with the deep 

 fascia of the forearm over the pronator radii teres. 



lielatlonK. — Concealed above by the deltoid and pectoralis major muscles, the 

 biceps fonns in the rest of its extent the prominence of the front of the arm. It 

 rests in its upper part on the humerus, and in its lower on the brachialis anticus, 

 and by its inner margin is in contact in its upper half with the coraco-brachialis, 

 in its lower with the brachial artery. Its inferior tendon is in contact with the 

 supinator brevis. and the fibrous expansion or semilunar fascia is stretched across 

 the brachial artery and median nerve. 



Yarict'u'x. — The biceps is one of the most variable muscles in the body. Among 

 the most frequent of its varieties are, 1st, the greater than usual separation of 

 its glenoid and coracoid portions, and 2nd, the increase in the number of its 

 heads of origin. The last occurs most frequently by a slip which forms a third head 

 arising from the humerus, in more or less close connection with the brachialis 

 anticus and the insertion of the coraco-brachialis, and being inserted into the 

 under surface of the semilunar fascia so as to form a tensor of that fascia : this 

 head lies generally on the outer side of the brachial arter3\ and has sometimes 

 been found covering it. A muscular band has also been observed extending 

 do viTi wards from the biceps to the intermuscular septum over the inner condjde 

 of the humerus, and passing over the brachial artery. (R. Quain. " The Anatomj' 

 of the Arteries," &c.. p. 270, pi. 57.) A thiixl head has also been observed passing 

 from the outside of the humerus (brachio-radialis of W. Gmber). and sometimes 

 from the bicipital groove, or great tuberosity. Occasionally the long head does 

 not reach the glenoid part of the bone, but stops short in the bicipital groove. 



The brachialis anticus muscle arises from the lower half of the ante- 

 rior surface of the humerus. At the upper part of its origin it embraces 

 the insertion of the deltoid by two angular fleshy processes ; it extends 

 downwards to the capsule of the elbow-joint, and inwards to the internal 

 supracondylar ridge and the intermuscular septum in its whole extent ; 

 on its outer side it is separated from the external ridge and septum in the 

 greater part of its length by the supinator longus, and only arises from 

 it for a short distance at its upper end. It is closely adherent to the 

 ligament in front of the elbow-joint, and terminates below in a thick 

 mass which is inserted into the rough triangular surface on the front of 

 the coronoid process of the ulna. 



Helationx. — This muscle lies immediately behind and projects at each side of 

 the biceps. It supports the brachial artery and median nerve. Fibres have 

 been found to pass inwards from it, over the brachial artery, to the internal in- 

 termuscular septum. 



^'aricti(■.t. — This muscle is subject to considerable variation. The most frequent 

 of these consist in its subdivision into two or sometimes more parts ; its union 

 with neighbouring muscles, svich as supinator longus, pronator teres or biceps ; 

 insertion of a slip from it into the semilunar fascia ; and occasionally into the 

 radius. 



The triceps extensor cubiti muscle occupies tlie whole posterior 

 brachial region. It consists superiorly of three portions or heads which 

 are united lower down in a common mass, the tendon of which is 

 inserted into the posterior and upper part of the olecranon, a bursa inter- 



