420 A MANUAL OF ANATOMY 



arch, the inner one being single and the other three compound, for the suppl} 

 of the inner three and a half fingers. It should be noted that the digita 

 arteries, in passing to the fingers, lie over the interosseous spaces and super 

 ficial to the digital nerves. About the centre of the palm the inner arterj 

 will be found to be reinforced by a communicating branch from the deeply 

 placed innermost palmar interosseous, and the outer three arteries, close tc 

 their points of bifurcation, will be found to be joined each by a palmar inter 

 osseous artery. The possible presence of a large median artery joining th< 

 superficial palmar arch is to be borne in mind. 



The median and ulnar nerves are next to be dissected in the palm as far a; 

 the roots of the fingers. The median nerve, after emerging from beneath th( 

 anterior annular ligament, will be found to present an enlargement, and thei 

 to break up into outer and inner divisions. The outer division is to be showi 

 giving off a muscular branch which supplies the abductor poUicis, opponeni 

 pollicis, and superficial head of the flexor brevis pollicis, and then to arrang< 

 itself into three single digital nerves to both sides of the thumb and outer sid< 

 of the index finger, the last branch giving a twig to the first or outermos 

 lumbricalis muscle. The inner division furnishes two compound digital nerves 

 each of which divides near the clefts of the fingers into two branches for th( 

 supply of the contiguous sides of the index and middle, and middle and rinj 

 fingers. The compound digital nerve to the cleft between the index anc 

 middle fingers will be found to give a twig to the second lumbricalis, and tha 

 to the cleft between the middle and ring fingers communicates by a cros! 

 branch with the compound digital branch of the ulnar nerve to the clef 

 between the ring and little fingers. 



The ulnar nerve is next to be dissected as far as the fingers. Its divisioi 

 into a superficial and deep branch is to be shown, the latter accompanying 

 the profunda artery between the abductor, and flexor brevis, minimi digiti 

 The superficial division will be found to supply the palmaris brevis anc 

 then to divide into two digital nerves — an inner single to the inner side o 

 the little finger, and an outer compound for the supply of the contiguous side: 

 of the little and ring fingers. The digital arteries and nerves are now to b« 

 followed along the sides of the fingers, where the nerves will be seen to b< 

 superficial to the arteries, and to present minute swellings, called Paciniar 

 bodies. In dissecting the digital nerves on the outer side of the index fingei 

 and both sides of the thumb the arteria radialis indicis and the two branche; 

 of the arteria princeps polhcis are to be shown. 



The sheaths of the flexor tendons are now to be examined. The strong 

 almost cartilaginous, vaginal ligaments over the first and second phalanges art 

 to be noted, and the weak membrane opposite the interphalangeal joints, with 

 its obliquely-decussating fibres, is to be shown. The sheath being opened, the 

 synovial lining is to be studied, and the insertions of the superficial and deep 

 flexor tendons are to be examined. In connection with the synovial lining 

 the vincula accessoria tendinum are to be displayed, namely, the ligamenta 

 longa and ligamenta brevia. The sheath of the tendon of the flexor longus 

 pollicis is to be examined in a similar manner. The relations of the synovial 

 sheaths of the flexor tendons on the digits to the great palmar bursa are to be 

 carefully studied. 



The thenar muscles are now to be dissected. The most superficial is 

 the abductor pollicis, and beneath this is the opponens pollicis. The super- 

 ficial head of the flexor brevis pollicis lies internal to the opponens pollicis 

 and close to the outer side of the tendon of the flexor longus pollicis, anc 

 the adductor obliquus pollicis is close to the inner side of that tendon. Th« 

 adductor transversus pollicis lies beyond the obliquus, from which it is separ 

 ated by the radial artery. The deep head of the flexor brevis pollicis ii 

 difficult to show. It Ues deeply, and arises from the inner side of the base o 

 the first metacarpal bone, and it joins the adductor obliquus pollicis. A larg< 

 bundle of fibres should be looked for passing from the adductor obliquui 

 pollicis to the superficial head of the flexor brevis pollicis, and in each of thesi 

 muscles at its insertion a small sesamoid bone will be met with. The medial, 

 nerve will be found to supply the abductor, opponens, and superficial head O 



