204 MUSCLES OF THE UPPER LIMB. 



wards when it is raised . and rotate it outwards or inwards when hanging by the 

 side. The teres major rotates the raised humerus inwards, the teres minor out- 

 wards : acting together, they assist in depressing the arm. The deltoid muscle 

 superficially, and the supra- and infraspinatus muscles, the teres minor and sub- 

 scapularis, more deeply, afford important protection to the shoulder-joint, and by 

 their tension prevent displacement of the head of the humerus. 



MUSCLES AND FASCIiE OF THE UPPER ARM. 



FASCiiE. — The aponeurosis of the arm is composed chiefly of 

 transverse fibres, held together by others having an obhque or longitu- 

 dinal direction ; it is thin over the biceps muscle, stronger where it 

 covers the triceps, and particularly dense as it approaches the outer and 

 inner condylar eminences of the humerus. It is pierced on the inner 

 side of the limb by the basilic vein, below the middle of the arm. 

 It is attached to the shaft and condylar eminences of the humerus by 

 the two processes next to be described. 



The external and internal intermuscnlar septa are two fibrous 

 partitions which bind the aponeurosis of the arm to the humerus, and 

 with which the neighbouring muscles of the arm are intimately con- 

 nected. The external intermuscular septum extends upwards from the 

 outer condylar eminence along the outer lateral ridge to the insertion 

 of the deltoid, from which it receives tendinous fibres. It is pierced 

 from behind forwards by the muscnlo-spiral nerve and superior pro- 

 funda artery. The internal septum, much stronger, extends along the 

 ridge from the inner condylar eminence to the insertion of the coraco- 

 brachialis muscle. It is traversed from before backwards by the ulnar 

 nerve, and by the inferior profunda and anastomotic arteries. 



At the bend of the elbow the aponeurosis is closely connected with 

 the periosteum covering the condylar eminences of the humerus and the 

 olecranon process of the ulna ; and it is strengthened by tendinous 

 fibres sent from the triceps and biceps muscles. 



Mut^CLES. — The coraco-brachialis muscle, elongated in form, arises 

 from the tip of the coracoid process of the scapula, between the pector- 

 alis minor and the short head of the biceps, with which latter it is for a 

 sliort distance conjoined by an intermediate tendon. The lower part of 

 the muscle is directly inserted into the inner border of the humerus near 

 its middle, in a linear impression of from two to three inches in length, 

 between the origin of the triceps and the brachialis anticus. Higher 

 up its fibres are found inserted into a tendinous band which is prolonged 

 upwards to the liead of the humerus, forming a sling over the latissimus 

 dorsi. 



lichitions. — This muscle is usually pierced by the musculo-cutaneous nerve ; 

 its outer border is in contact with the biceps muscle, and its inner with the 

 brachial ai-terj% by which it is crossed obliquely near its insertion. It lies in 

 front of the tendons of the subscapularis. latissimus dorsi, and teres major, and 

 is covered by the deltoid and pectoralis major muscles. 



VarUii/'.i. — This muscle has been showai by various authors to be subject to 

 considerable varieties, which seem to indicate, according to Wood, that it con- 

 sists typically of three parts : viz., 1, a superior short one rising from the coracoid 

 process, or near it, and running over the capsular ligament, to be inserted close 

 below the small tuberosity of the humerus : 2. a second corresponding most 

 nearly to that usually described in human anatomy, of middle size, and placed 

 between the first and third ; 3, a third which is the longest and most superficially 

 placed, and descends to the inner condyle, or near it, and in many instances is 



