354 



APPLIED ANATOMY. 



The External Set. The thenar or thumb eminence has four muscles, the 

 abductor pollicis, opponens, flexor brevis, and adductor. This latter is usually divi- 

 ded into two parts called the adductor transversus and adductor obliquus (Fig. 368). 



The flexor brevis has two heads, an outer and an inner. The outer head 

 is inserted into the base of the proximal phalanx on its outer side along with the 

 abductor. The inner head, called by some the first volar interosseous, is inserted 

 into the inner side along with the adductor; between the two heads runs the tendon 

 of the long flexor of the thumb. The opponens inserts into the outer anterior border 

 of the shaft of the first metacarpal bone. 



The Internal Set. The little finger, like the thumb, has abductor, oppo- 

 nens, and flexor brevis muscles, but no adductor. There is, however, a short 



Four dorsal interosseous 

 muscles 



Three palmar inter- 

 osseous muscles 



The two medial 

 (inner) lumbricales 



The two lateral 

 (outer) lumbricales 



FIG. 367. Showing the mode of insertion of the interosseous and lumbrical muscles. 



muscle, the palmaris brevis, which is superficial to the palmar fascia and, passing 

 transversely across the hypothenar eminence, inserts into the skin. It makes a 

 dimple on the ulnar side when the hand is hollowed. The abductor and flexor brevis 

 minimi digiti muscles insert on the ulnar side of the proximal phalanx, hence when 

 they contract they tend to hollow the hand, as does also the opponens minimi digiti, 

 which inserts on the ulnar side of the fifth metacarpal bone. 



SURFACE ANATOMY OF THE HAND. 



The hand is twice as long as it is broad. The length of the middle finger from 

 the metacarpophalangeal joint to its extremity is equal to the distance from the 

 metacarpophalangeal joint to the radiocarpal joint. If the hand is turned with the 

 palm up, the thumb diverges from the median line at an angle of 40 degrees. The 



