THE MUSCLES AND FASCIA OF THE HAND. 235 



forms between these two muscles are also met with. (Gruber, " Beobachtungen," Heft vi 

 and vii.) 



Nerves. The anconeus (7, 8c), supinator longus (6c), and extensor carpi radialis longior 

 (6, 7c) receive branches from the musculo-spiral nerve ; the remaining muscles of this group 

 are supplied by the posterior interosseous division of that trunk, the offsets for the extensor 

 carpi radialis brevior (6, 7c) and supinator brevis (6c) arising from the nerve before it pierces 

 the latter muscle, while those for the extensors of the digits, both superficial and deep (7c), 

 as well as the extensor carpi ulnaris (7c), are given off after it appears on the back of the 

 forearm. 



THE MUSCLES AND FASCIAE OF THE HAND. 



FASCIA. The fascia of the dorsum of the hand, a thin layer composed 

 mainly of transverse fibres, is prolonged downwards from the lower border of the 

 annular ligament over the extensor tendons, and blends with these on the ringers. 

 Deeper than the extensor tendons thin aponeuroses are stretched over the inter- 

 metacarpal spaces, being attached laterally to the bones, and covering the dorsal 

 interosseous muscles to which they are firmly adherent. 



The fascia of the palm consists of a central part, which is thick and strong, 

 and of two lateral portions, which are very thin and cover the eminences formed by 

 the short muscles of the thumb and little finger. The central portion is that 

 commonly referred to under the name of the palmar fascia. Consisting principally 

 of longitudinal fibres which are in largest part continued from the tendon of the 

 palmaris longus, others, however, springing from the front of the annular ligament, 

 it is narrow above and becomes expanded and thinner below. Here it divides into 

 four processes which pass to the bases of the several fingers, and join the com- 

 mencement of the digital sheaths, sending some fibres also to the integument at the 

 clefts of the fingers, and to the superficial transverse ligament. From the sides of 

 these processes, moreover, offsets are sent backwards to be attached to the transverse 

 metacarpal ligament opposite the lateral margins of the heads of the metacarpal 

 bones, and thus above each finger a short canal is formed, in which the flexor 

 tendons run. In the intervals between the processes some deeper transverse fibres 

 make their appearance, covering the lumbricales muscles and the digital vessels and 

 nerves. At the lower margin of the palm a superficial band of transverse fibres, 

 which stretches across the roots of the four fingers, being contained in the folds of 

 skin at the upper ends of the clefts, is known as the superficial transverse ligament 

 of the fingers. There is also deeply placed in the palm a thin layer of fascia which 

 covers the interosseous muscles, and dipping between them, is attached to the palmar 

 ridges of the metacarpal bones, while inferiorly it becomes continuous with the 

 transverse metacarpal ligament. From the deep surface of the palmar fascia a thin 

 septum is sent backwards -on each side between the flexor tendons and the thumb 

 and little finger muscles respectively, and these, joining the fascia covering the 

 interosseous muscles, complete a sheath in which the tendons are contained in their 

 passage through the palm. 



Cutaneous ligaments of the phalang-es. These are fibrous bands which pass from the 

 edges of the phalanges to the skin of the sides of the fingers, and serve the purpose of 

 retaining the skin in position during flexion of the joints. (Cleland, Journ. Anat., xii, 526.) 



MUSCLES. Besides the tendons of the long muscles and the lumbricales already 

 described, there are placed in the hand one superficial muscle called palmaris brevis, 

 the short muscles of the thumb and little finger, and the interosseous muscles. 



The palmaris brevis (fig. 235, 16) is a thin flat subcutaneous muscle, which 

 arises from the inner margin of the palmar fascia and the annular ligament ; its 

 fibres pass transversely inwards, and are inserted into the skin along the inner 

 border of the palm. 



