406 THE MUSCLES AND FASCIA. 



There are also three flexors on the palmar surface a flexor of the metacarpal 

 hone, a flexor of the proximal, and a flexor of the terminal phalanx ; there is also 

 an Abductor and two Adductors. The Abductor pollicis moves the metacarpal 

 bone of the thumb outward ; that is, away from the index finger. The Flexor 

 ossis metacarpi pollicis flexes the metacarpal bone that is, draws it inward over 

 the palm and at the same time rotates the bone, so as to turn the ball of the 

 thumb toward the fingers, thus producing the movement of opposition. The 

 Flexor brevis pollicis flexes and adducts the proximal phalanx of the thumb. The 

 Adductores pollicis move the metacarpal bone of the thumb inward ; that is, to- 

 ward the index finger. These muscles give to the thumb its extensive range of 

 motion. It will be noticed, however, that ir. consequence of the position of the 

 first metacarpal bone, these movements differ from the corresponding movements of 

 the metacarpal bones of the other fingers. Thus extension of the thumb more 

 nearly corresponds to the motion of abduction in the other fingers, and flexion to 

 adduction. 



12. Ulnar Region (Fig. 243). 



Palmaris brevis. 



Abductor minimi digiti. Flexor brevis minimi digiti. 



Opponens (Flexor ossis metacarpi) minimi digiti. 



The Palmaris brevis is a thin quadrilateral muscle placed beneath the integu- 

 ment on the ulnar side of the hand. It ai'ises by tendinous fasciculi from the 

 annular ligament and palmar fascia ; the fleshy fibres pass inward, to be inserted 

 into the skin on the inner border of the palm of the hand. 



Relations. By its superficial surface, with the integument, to which it is 

 intimately adherent, especially by its inner extremity ; by its deep surface, with 

 the inner portion of the palmar fascia, which separates it from the ulnar vessels 

 and nerve, and from the muscles of the ulnar side of the hand. 



The Abductor minimi digiti is situated on the ulnar border of the palm of the 

 hand. It arises from the pisiform bone and from the tendon of the Flexor carpi 

 ulnaris, and terminates in a flat tendon, which divides into two slips ; one is 

 inserted into the ulnar side of the base of the first phalanx of the little finger. 

 The other slip is inserted into the ulnar border of the aponeurosis of the Extensor 

 minimi digiti. 



Relations. By its superficial surface, with the inner portion of the palmar 

 fascia and the Palmaris brevis ; by its deep surface, with the Flexor ossis meta- 

 carpi minimi digiti ; by its outer border, with the Flexor brevis minimi digiti. 



The Flexor brevis minimi digiti lies on the same plane as the preceding muscle, 

 on its radial side. It arises from the convex aspect of the hook of the unciform 

 bone and anterior surface of the annular ligament, and is inserted into the inner 

 side of the base of the first phalanx of the little finger. It is separated from the 

 Abductor at its origin by the deep branches of the ulnar artery and nerve. This 

 muscle is sometimes wanting ; the Abductor is then, usually, of large size. 



Relations. By its superficial surface, with the internal portion of the palmar 

 fascia and the Palmaris brevis; by its deep surface, with the Opponens. The 

 deep branch of the ulnar artery and the corresponding branch of the ulnar nerve 

 pass between the Abductor and Flexor brevis minimi digiti muscles. 



The Opponens (Flexor ossis metacarpi) minimi digiti (Fig. 234) is of a triangular 

 form, and placed immediately beneath the preceding muscles. It arises from the 

 convexity of the hook of the unciform bone and contiguous portion of the annular 

 ligament; its fibres pass downward and inward, to be inserted into the whole 

 length of the metacarpal bone of the little finger, along its ulnar margin. 



Relations. By its superficial surface, with the Flexor brevis and Abductor 

 minimi digiti; by its deep surface, with the Interossei muscles in the fourth 

 metacarpal space, the metacarpal bone, and the Flexor tendons of the little finger. 



