J SHORT MUSCLES OF THE HAND. 329 
It is the most superficial muscle of the thenar eminence, and conceals partially 
the opponens, and the superficial portion of the flexor brevis pollicis. 
The opponens pollicis arises beneath the preceding muscle from the annular 
ligament and the ridge on the trapezium. Extending downwards and outwards, it 
is inserted into the whole length of the first metacarpal bone on its anterior sur- 
face. The muscle is superficial along the outer border of the abductor pollicis. 
The flexor brevis pollicis consists of two parts. a. The superficial part of the 
muscle arises from the anterior annular ligament, and is inserted into the outer side 
of the base of the first phalanx of the thumb, a sesamoid bone being present in the 
tendon of insertion. This part of the muscle, partly concealed by the abductor 
pollicis, is superficial in the interval between that muscle and the tendon of the 
flexor longus pollicis. 
b. The deep part of the muscle (interrosseus primus volaris) arises from the 
ulnar side of the base of the first metacarpal bone, and-is inserted into the inner 
side of the base of the first phalanx of the thumb along with the adductor 
obliquus pollicis. This little muscle is deeply situated in the first interosseous 
space, in the interval between the adductor obliquus pollicis and the first dorsal 
interosseous muscle. It may be regarded as homologous with the palmar interossei 
muscles, with which it is in series. 
The adductor obliquus pollicis arises from the anterior surfaces of the trapezium, 
trapezoid, and os magnum, from the tendon of the flexor carpi radialis, and from 
the bases of the second and third metacarpal bones. It is inserted by a tendon, in 
which a sesamoid bone is developed, into the inner side of the base of the first 
phalanx of the thumb. At its outer border a slender slip separates from the rest 
of the muscle, and passing obliquely beneath the tendon of the flexor longus pollicis, 
is inserted into the outer side of the base of the first phalanx along with the 
superficial part of the flexor brevis pollicis. 
The adductor obliquus pollicis lies on the ulnar side of the tendon of the flexor 
longus pollicis, internal to the thenar eminence. It is covered by the flexor tendons 
of the thumb and fingers, and conceals the radial artery and the deep part of the 
flexor brevis pollicis. At its inner border the radial artery (deep palmar arch) 
appears between it and the adductor transversus pollicis. 
The adductor transversus pollicis arises from the front of the third meta- 
carpal bone, in its lower two-thirds. Triangular in form, it is directed outwards, 
to be inserted into the inner side of the base of the first phalanx of the thumb along 
with the adductor obiquus. Lying beneath the flexor tendons, this muscle con- 
ceals the interossei muscles of the first two spaces and the radialis indicis and 
princeps pollicis arteries. Its upper border is separated from the adductor obliquus 
pollicis by the radial artery (deep palmar arch). 
MUSCLES OF THE LITTLE FINGER. 
The abductor minimi digiti (m. abductor digiti quinti) arises from the pisi- 
form bone and the tendon of the flexor carpi ulnaris, and is inserted into the inner 
side of the base of the first phalanx of the little finger. It les superficially upon 
the opponens and flexor brevis minimi digiti. 
The opponens minimi digiti (m. opponens digiti quinti) arises from the 
anterior annular ligament and the hook of the unciform bone, and is inserted into 
the whole length of the fifth metacarpal bone along its inner margin. 
It is concealed by the previous muscle, and may be pierced near its origin for 
the passage of the deep branches of the ulnar artery and nerve. 
| The flexor brevis minimi digiti (m. flexor digiti quinti brevis) arises from 
the anterior annular ligament and the hook of the unciform bone, and is inserted 
— along with the abductor into the inner side of the first phalanx of the little 
finger. 
This muscle is placed external to the opponens and abductor, and is separated 
_ from the latter by the deep branches of the ulnar artery and nerve. It may be 
_ reduced in size, absent altogether, or incorporated with either the opponens or 
abductor minimi digiti. 
