382 



THE MUSCULAK SYSTEM. 



thick-walled bursa separates the tendon of the triceps from the posterior ligament 

 of the elbow-joint and the proximal end of the olecranon. 



The muscle is superficial in almost its whole extent. The long (scapular) head is concealed 

 at its origin by its relation to the teres muscles, between which it passes. 



The subanconaeus is a small muscle occasionally present. It consists of scattered fibres 

 arising from the distal end of the posterior surface of the humerus, deep to the triceps, and 

 it is inserted into the posterior ligament of the elbow-joint. 



Nerve-Supply. The several heads of the muscle are supplied separately by branches of the 

 radial nerve. The lateral head receives fibres from C. (6.) 7. 8. ; the long and medial head from 

 C. 7. 8. The medial head has a double supply. One nerve enters its proximal part, another (ulnar 

 collateral nerve of Krause) enters the distal part of the muscle. 



Actions. The triceps is the extensor muscle of the elbow -joint. The long head also acts as 

 an adductor of the humerus at the shoulder-joint. 



The chief action of these muscles (excepting the coracobrachialis) is on the elbow -joint, 

 producing along with other muscles flexion and extension. The flexor muscles are much more 

 powerful than the extensors. 



Table of Muscles acting on the Elbow-Joint. 



FASCI/E AND MUSCLES OF THE FOREARM 

 AND HAND. 



Fasciae. 



The superficial fascia in the forearm presents no exceptional features. On 

 the dorsum of the hand it is loose and thin ; in the palm it is generally well 

 furnished with fat, forming pads for the protection of the vessels and nerves. It is 

 closely adherent to the palmar aponeurosis and to the skin, especially along the 

 lines of flexure. 



M. Palmaris Brevis. The palmaris brevis is a quadrilateral subcutaneous 

 muscle which lies in the medial side of the hand, under the superficial fascia. It 

 arises from the medial border of the thick central portion of the palmar aponeurosis 

 and from the volar surface of the transverse carpal ligament of the wrist, and is 

 inserted into the skin of the medial border of the hand for a variable distance. It 

 covers the ulnar artery and nerve, branches of which supply it. Its action is to 

 wrinkle the skin of the medial border of the hand, and by raising up the skin and 

 superficial fascia, to deepen the hollow of the hand. 



The deep fascia of the forearm and hand is continuous above with the deep 

 fascia of the arm. In the proximal part of the forearm it is strengthened by 

 additional fibres around the elbow ; in front, by fibres from the lacertus fibrosus 

 (semilunar fascia) of the biceps ; behind, by the fascial insertions of the triceps ; and 

 laterally, by fibres derived from the humeral epicondyles in relation to the common 

 tendons of origin of the flexor and extensor muscles of the forearm which in part 

 take their origin from them. It is attached to the dorsal margin of the ulna, and 

 affords increased attachment to the flexor and extensor carpi ulnaris and the flexor 

 digitorum profundus muscles. Above the wrist the volar part of the fascia is 

 pierced by the tendon of the palmaris longus, and by the ulnar artery and nerve. 

 At the wrist it gains attachment to the bones of the forearm and carpus, is 

 greatly strengthened by addition of transverse fibres, and constitutes the transverse 

 carpal and dorsal carpal ligaments. 



Ligamentum Carpi Transversum. The transverse carpal ligament (O.T. 

 anterior annular ligament) is a band about an inch and a half in depth, continuous, 

 proxirnally and distally, with the deep fascia of the forearm and the palm of the 



