222 5IUSCLES OF THE UPPER LII\IB. 



by a tendon into the raclial border of the first phalanx of the thumb 

 at its base. 



The opponens pollicis muscle, placed behind the abductor, arises 

 from the annular ligament and from the os trapezium and its ridge, 

 and is inserted into the whole length of the metacarpal bone of the 

 thumb at the radial border. 



The fiexor "brevis pollicis muscle arises by two heads, a superficial 

 and a deep. The superficial head is attached to the outer two-thirds of 

 the annular ligament and to the trapezium : the dce]5 head is attached 

 to the OS trapezoidcs and os magnum, to the sheath of the flexor carpi 

 radialis, and to the sheath of the flexor carpi radialis, and to the bases of 

 the second and third metacarpal bones. From the superficial and deep 

 heads of origin two strong masses of fibres proceed, v;hich, becoming 

 tendinous, arc inserted into the sides of the base of the first phalanx of 

 the thumb ; the outer head is also joined by a considerable fasciculus 

 from the deeper origin ; the inner head is inserted conjointly with the 

 adductor pollicis. In each of the tendons of insertion a sesamoid bone 

 is developed, which plays over the grooved surface of the first meta- 

 carpal bone. The tendon of the long flexor lies between the heads of 

 origin, and grooves the surfiice of the muscle as it passes between the 

 tendons of insertion. 



The adductor pollicis muscle arises from the middle two-thirds of 

 the palmar surface of the third metacarpal bone, and is inserted into 

 the base of the first phalanx of the thumb along with the inner tendon 

 of the short flexor. 



]\IuscLE.s OF THE LITTLE FINGER. — The fleshy mass at the inner 

 border of the hand {hjipoihenar eminence) consists of three muscles 

 passing to the little finger. 



The abductor minimi digiti muscle arises by tendinous fibres from 

 the pisiform bone and the inserted tendon of the flexor cai'pi ulnaris, 

 mid is inserted into the base of the first phalanx of the little finger 

 ou the ulnar l)ordcr. 



The flexor brevis minimi digiti, separated o.t its origin from the ab- 

 ductor muscle by a small interval through which pass the deep palmar 

 branch of the ulnar nerve and the communicating branch of the ulnar 

 artery, arises from the front of the annular ligament, and from a tip of 

 the hooked process of the unciform bone, and is inserted into the base 

 of the first phalanx of the little finger, in connection with the preceding 

 muscle. This muscle is sometimes absent, or becomes incorporated with 

 the abductor. 



The opponeiis minimi digiti muscle arises from the annular ligament 

 and the unciform process, and is inserted into the ulnar border of the 

 litth metacarpal bone in all its length. 



The INTEROSSKOUS MUSCLES occupy the intervals between the meta- 

 carpal bones. They are seven in number, all of them more or less 

 visil)le fi'om the palmar aspect, and they are divided into two sets, viz.. 

 those which are best seen on the dorsal aspect of the metacarpus, and 

 those which are seen only in the palm. Their disposition is most easily 

 understood by reference to their action. 



The dorsal interossei muscles withdraw the fingers from the'middle 

 line of the hand ; they are four in number, each occupying one of the 

 spaces between the metacarpal bones, and are numbered from with- 

 out inwards. Each muscle arises from both the metacarpal bones 



