318 MUSCLES AND FASCIJ3. 



which are inserted one on either side of the base of the first phalanx of the thumb, 

 the outer portion being joined with the Abductor, and the inner with the Adductor. 

 A sesamoid bone is developed in each tendon as it passes across the metacarpo- 

 phalangeal joint. 



Relations, By its superficial surface, with the palmar fascia. By its deep sur- 

 face, with the Adductor pollicis, and tendon of the Flexor carpi radialis. By its 

 external surface, with the Opponens pollicis. By its internal surface, with the 

 tendon of the Flexor longus pollicis. 



The Adductor Pollicis (fig. 173) is the most deeply seated of this group of 

 muscles. It is of a triangular form, arising, by its broad base, from the whole 

 length of the metacarpal bone of the middle finger on its palmar surface ; the 

 fibres, proceeding outwards, converge, to be inserted with the innermost tendon of 

 the Flexor brevis pollicis, into the ulnar side of the base of the first phalanx of 

 the thumb, and into the internal sesamoid bone. 



delations. By its superficial surf ace, with the Flexor brevis pollicis, the tendons 

 of the Flexor profundus and Lumbricales. Its deep surface covers the first two 

 interosseous spaces, from which it is separated by a strong aponeurosis. 



Nerves. The Abductor, Opponens, and oiiter head of the Flexor brevis pollicis, 

 are supplied by the median ner/e; the inner head of the Flexor brevis, and the 

 Adductor pollicis, by the ulnar nerve. 



Actions. The actions of the muscles of the thumb are almost sufficiently indi- 

 cated by their names. This segment of the hand is provided with three Extensors, 

 an Extensor of the metacarpal bone, an Extensor of the first, and an Extensor of 

 the second phalanx ; these occupy the dorsal surface of the forearm and hand. 

 There are, also, three Flexors on the palmar surface, a Flexor of the metacarpal 

 bone, the Flexor ossis metacarpi or Opponens pollicis, the Flexor brevis pollicis, 

 and the Flexor longus pollicis; there is also an Abductor and an Adductor. 

 These muscles give to the thumb that extensive range of motion which it pos- 

 sesses in an eminent degree. 



ULNAE REGION. 



Muscles of the Little Finger. 



Palmaris Brevis. Flexor Brevis Minimi Digiti. 



Abductor Minimi Digiti. Opponens Minimi Digiti. 



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

 ment on the ulnar side of the hand. It arises by tendinous fasciculi, from the 

 annular ligament and palmar fascia ; the fleshy fibres pass horizontally inwards, 

 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 inti- 

 mately 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 an expansion of the tendon of 

 the Flexor carpi ulnaris ; and terminates in a flat tendon, which is inserted into 

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



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. By its inner 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 tip of the unciform process of the unciform 

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

 the first phalanx of the little finger, with the preceding. 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. 



