ANTERIOR HUMERAL REGION, 



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line, and by means of its extensive origin can carry the arm forwards or 

 backwards, so as to range with the hand a considerable segment of a large 

 circle. The arm, raised by the deltoid, is a good Fig 120 * 



illustration of a lever of the third power, so common 

 in the animal machine, by which velocity is gained 

 3t the expense of power. In this lever, the weight 

 ;hand) is at one extremity, the fulcrum (the glenoid 

 cavity) at the opposite end, and the power (the in- 

 sertion of the muscle) between the two, but nearer 

 to the fulcrum than to the weight. 



Anterior Humeral Region. 



Coraco-brachialis, 

 Biceps, 

 Brachialis anticus. 



Dissection. These muscles are exposed, on the 

 removal of the integument and fascia from the ante- 

 rior half of the upper arm, and the clearing away of 

 the cellular tissue. 



The CORACCKBRACHIALIS, a name composed of its 

 points of origin and insertion, arises from the cora- 

 coid process in common with the short head of the 

 biceps ; and is inserted into a rough line on the 

 inner side of the middle of the humerus. 



Relations. By its anterior surface with the deltoid, and pectoralis 

 major. By its posterior surface, with the shoulder joint, the humerus, 

 subscapularis, teres major, latissimus dorsi, short head of the triceps, and 

 anterior circumflex vessels. By its internal border with the axillary and 

 brachial vessels and nerves, particularly with the median and external 

 cutaneous nerve, by the latter of which it is pierced. By the external 

 border with the short head of the biceps and brachialis anticus. 



The BICEPS (bis xs<paXa/, two heads) arises by two tendons, one the 

 short heady from the coracoid process in common with the coraco-brachi- 

 alis ; the other the long head, from the upper part of the glenoid cavity. 

 The muscle is inserted by a rounded tendon, into the tubercle of the ra- 

 dius. The long head, a long slender tendon, passes through the capsular 

 ligament of the shoulder joint enclosed in a sheath of the synovial mem- 

 brane ; after leaving the cavity of the joint, it is lodged in the deep groove 

 that separates the two tuberosities of the humerus, the bicipital groove. 

 A small synovial bursa is interposed between the tendon of insertion, and 

 the tubercle of the radius. Jit the bend of the elbow, the tendon of the 

 biceps gives off from its inner side a broad tendinous band, which protects 

 the brachial artery, and is continuous with the fascia of the fore-arm. 



Relations. By its anterior surface with the deltoid, pectoralis major, 

 superficial and Aeep fascia and integument. By its posterior surface the 



* The muscles of the anterior aspect of the upper arm. 1. The coracoid process o f 

 the scapula. 2. The coraco-clavioular ligament (trapezoid), passing upwards to the 

 Bcapular end of the clavicle. 3. The coraco-acromial ligament, passing outwards to the 

 acromion. 4. The subscapularis muscle. 5. The teres major; the triangular space 

 above this muscle is that through which the dorsalis scapulee vessels pass. 6. The 

 coraco-brachialis. 7. The biceps. 8. The upper end of the radius. 9. The brachialis 

 anticus ; a portion of the muscle is seen on the outer side of the tendon of the biceps 

 10. The internal head of the triceps. 



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