214 MUSCLES OF THE UPPER LIMB. 



brachial artery. Its inferior tendon is in contact with the supinator brevis, and the 

 fibrous expansion is stretched across the brachial artery and median nerve. 



Occasionally a third head, arising from the humerus in more or less close connection 

 with the brachialis anticus and the insertion of the coraco-brachiali*, is added to the 

 biceps muscle : this head lies generally on the outer side of the brachial artery, and 

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

 extending downwards from the biceps to the intermuscular septum over the inner 

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

 Anatomy of the Arteries," &c., p. 270, pi. 57.) 



The brachialis anticus muscle (brachiaeus interims) arises from the lower 

 half of the anterior surface of the humerus. At the upper part of its 

 origin it embraces the insertion of the deltoid by two angular fleshy pro- 

 cesses; it extends downwards to the capsule of the elbow-joint, and 

 inwards to the internal supracondyloid ridge and 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. 



This muscle projects at each side of the biceps, and supports the brachial artery 

 and median nerve. Fibres have been found to pass inwards from it, over the brachial 

 artery, to the internal intermuscular septum. 



The triceps extensor cubiti, occupying the whole space behind the humerus 

 and intermuscular septa, 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 intervening 

 between that tendon and the most prominent part of this process. The 

 middle or long head (musculus anconeus longus) arises from the lower 

 part of the glenoid cavity and an adjoining rough portion of the inferior 

 border of the scapula, by a tendon which spreads over the sides of the 

 muscular structure proceeding from it. The muscular fibres from this 

 source descend and form the middle and superficial part of the common 

 mass, presenting a flat vertical tendon on their surface inferiorly. The 

 external head (m. anconeus brevis) takes origin by tendinous and fleshy 

 fibres from the humerus along a line extending from the insertion of the 

 teres minor, downwards on the outer border of the humerus as low as 

 the musculo-spiral groove; from this line of origin its fibres, which are 

 comparatively short, descend obliquely to be inserted into the tendon of 

 the middle part. The lowest fibres of this head are bound down by a slight 

 aponeurotic arch over the extremity of the musculo-spiral groove, and below 

 their inferior margin other fibres are found arising from the external inter- 

 muscular septum and the surface of the humerus behind ; but these last 

 pass to be inserted more deeply than into the tendon of the middle part of 

 the muscle, and are rather to be considered as belonging to the muscular 

 mass which forms the internal head. The internal or deep head (m. an- 

 coneus internus), the shortest of the three, commences in a narrow pointed 

 part behind and below the tendon of insertion of the teres major, and 

 arises from the whole posterior surface of the bumerus below the musculo- 

 spiral groove, from the internal intermuscular septum in all its length, 

 and from the inferior portion of the external septum ; some of its lower 



