FASCLF OF THE UPPER LIMB. 229 



The flexors arising from the inner condyloid eminence of the humerus, and the 

 extensors arising from the outer condyloid eminence, are most advantageously situated 

 for acting on the other joints over which they pass, when the position of the elbow- 

 joint is such as to keep them most on the stretch ; but when flexion of those other 

 joints is either completed or opposed, they have also some effect, though not great, 

 upon the elbow-joint itself. 



Thejlexores sublimis and mofundus and the lumbricales muscles are the flexors 

 respectively of the second, third, and first phalanges. The lumbricales, while they 

 flex the first phalanx, at the same time, by virtue of their connection with the extensor 

 tendons, extend the other phalanges, thus causing the fingers to pass through the 

 movement which they undergo in making the hair-stroke in writing. They are 

 assisted in this action by the interossei. 



When the thumb is opposed to the other fingers, the metacarpal bone is drawn 

 forwards, not only by the opponens muscle, but also by the abductor, and by the flexor 

 brevis, acting when the first phalanx is flexed, or when it is fixed by the extensor 

 primi internodii. The precise action of the abductor is to draw the thumb forwards 

 and outwards. The extensor ossis metacarpi is entirely an abductor, as indicated by 

 the name given to it by Albinus. The extensor primi internodii likewise is an 

 abductor as well as an extensor of the first phalanx. The extensor secundi internodii 

 extends both phalanges and draws the metacarpal bone directly backwards. The 

 adductor and the inner fibres of the flexor brevis adduct the thumb. A combination 

 of the actions of the different muscles in succession produces circumduction. 



The little finger is withdrawn from the others by its abductor, as the ring-finger is 

 withdrawn from the middle finger by the fourth dorsal interosseous muscle ; and the 

 abductor, acting with the long flexors, likewise assists the flexor brevis in keeping the 

 first phalanx firmly down in grasping. 



The palmaris longus has but little action, and that is exerted in tightening the 

 palmar fascia. The palmar is brevis increases the hollow of the hand by pulling on 

 the integument on the inner side, so as to increase the hypothenar prominence. 



FASCIAE OF THE UPPER LIMB. 



The superficial fascia covering the muscles which pass from the trunk to 

 the shoulder and upper limb, forms a complete investment of the upper part 

 of the trunk, being continuous with that of the neck superiorly, and with 

 those of the abdomen and hip inferiorly, and extending from the shoulder 

 and over the arm, forearm and hand, so as to cover the whole limb. In the 

 subcutaneous tissue of the upper limb bursse are usually found placed over 

 the acromion, the olecranon, and the knuckles. 



The superficial fascia of the pectoral region encloses the mammary 

 gland, covering it both in front and behind, and sending strong septa iu 

 between its lobes. Processes likewise extend from the investment of the 

 gland between the masses of fat forwards to the skin and nipple, and these, 

 from the support which they afford to the gland, have been named by Sir 

 Astley Cooper ligamenta suspensoria. (" On the Anatomy of the Breast," 

 London, 1840.) 



The superficial fascia of the arm is most distinct opposite the bend of the 

 elbow, where the superficial veins contained within its laminae are numerous 

 and large. In the palm of the hand, on the contrary, the subcutaneous 

 tissue forms a firm connecting medium between the skin and a strong 

 aponeurosis named the palmar fascia : it consists of a network of fibres pass- 

 ing between those two structures, dividing the subcutaneous fat into small 

 granules, so as to prevent the skin from shifting to any considerable extent. 



Of the deep fascice the following parts require special notice. The costo- 

 coracoid membrane is a distinct layer of firm fascia whose strongest fibres, 

 distinguished sometimes as the costo-coracoid ligament, extend from the 

 coracoid process to the first rib at the origin of the subclavius muscle, and 



