492 THE MUSCLES AND FASCIA. 



tendons of the flexor muscles, and the branches of the median and ulnar nerves, 

 and on each side it gives off a vertical septum, which is continuous with the 

 interosseous aponeurosis and separates the lateral from the middle palmar group 

 of muscles. 



The lateral portions of the palmar fascia are thin, fibrous layers, which cover, 

 on the radial side, the muscles of the ball of the thumb, and, on the ulnar side, the 

 muscles of the little finger ; they are continuous with the dorsal fascia, and in the 

 palm with the central portion of the palmar fascia. 



The Superficial Transverse Ligament of the Fingers is a thin, fibrous band 

 which stretches across the roots of the four fingers, and is closely attached to the 

 skin of the clefts, and internally to the fifth metacarpal bone, forming a sort of 

 rudimentary web. Beneath it the digital vessels and nerves pass onward to their 

 destination. 



Surgical Anatomy. The palmar fascia is liable to undergo contraction, producing a very 

 inconvenient deformity known as "Dupuytren's contraction." The ring and little fingers are 

 most frequently implicated, but the middle, the index, and the thumb may be involved. The 

 proximal phalanx is drawn down and cannot be straightened, and the two distal phalanges 

 become similarly flexed as the disease advances. 



The Muscles of the Hand are subdivided into three groups : 1. Those of the 

 thumb, which occupy the radial side ; 2. Those of the little finger, which occupy 

 the ulnar side ; 3. Those in the middle of the palm and between the interosseous 

 spaces. 



Radial Region (Figs. 315, 316). 

 Muscles of the Thumb. 



Abductor pollicis. Flexor brevis pollicis. 



Opponens (Flexor ossis metacarpi) pollicis. Adductor obliquus pollicis. 

 Adductor transversus pollicis. 



The Abductor pollicis is a thin, flat muscle placed immediately beneath the 

 integument. It arises from the ridge of the os trapezium and annular ligament, 

 and, passing outward and downward, is inserted by a thin, flat tendon into the 

 radial side of the base of the first phalanx of the thumb, sending a slip to join the 

 tendon of the Extensor longus pollicis. 



Relations. By its superficial surface, with the palmar fascia ; by its deep 

 surface, with the Opponens pollicis, from which it is separated by a thin apo- 

 neurosis. Its inner border is separated from the Flexor brevis pollicis by a narrow 

 cellular interval. 



The Opponens pollicis is a small, triangular muscle placed beneath the 

 preceding. It arises from the palmar surface of the trapezium and annular 

 ligament, passes downward and outward, and is inserted into the whole length of 

 the metacarpal bone of the thumb on its radial side. 



Relations. By its superficial surface, with the Abductor pollicis ; by its deep 

 surface, with the trapezio-metacarpal articulation ; by its inner border, with the 

 Flexor brevis pollicis. 



The Flexor brevis pollicis is much larger than either of the two preceding 

 muscles, beneath which it is placed. It consists of two portions, outer and inner. 

 The outer and more superficial portion arises from the trapezium and outer two- 

 thirds of the annular ligament, and passes along the outer side of the tendon of 

 the Flexor longus pollicis, and, becoming tendinous, has a sesamoid bone developed 

 in its tendon, and is inserted into the outer side of the base of the first phalanx of 

 the thumb. The inner and deeper portion of the muscle is very small, and arises 

 from the ulnar side of the first metacarpal bone, and is inserted into the inner side 

 of the base of the first phalanx with the Adductor obliquus pollicis. A sesamoid 

 bone is developed in the common tendon of insertion. 



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



