384 THE MUSCULATURE 



the forearm and hand is too complex a subject to be briefly summarised. The phylogeny of the 

 forearm flexors and the pahnar musculature has been studied by McMurrich. In his papers a 

 summary of the Uterature on the subject may be found. 



FASCI.E 



The fasciae and the general relations of the musculature of the forearm and hand may be 

 followed in the cross-sections fig. 366. 



The tela subcutanea contains a moderate amount of fat in the upper part of the forearm. 

 This grows less in amount as the wrist is approached. On the back of the hand it contains 

 little fat. In the palm and on the volar surface of the fingers a moderate amount of fat is 

 embedded between dense vertical bundles of fibres which unite the skin to the fascia. Except 

 on the volar surface of the hand and on the backs of the terminal phalanges, the tela is but 

 loosel}' united to the underlying fascia. 



The bursa subcutanea olecrani lies over the dorsal surface of the olecranon. Subcutaneous 

 bursce are also frequently found over the knuckles (b. subcutaneae metacarpophalangeae 

 dorsales) and the proximal joints of the fingers (b. subcutaneae digitorum dorsales). 



The antibrachial fascia encloses the muscles of the forearm in a cylindrical sheath, composed 

 in the main of cii'cular fibre-bundles, but strengthened by longitudinal and obhque bundles 

 extending in from the epicondyles of the humerus, the olecranon, the lacertus fibrosus of the bi- 

 ceps, and the tendon of the triceps. The fascia of the forearm is attached to the dorsal surface 

 of the olecranon and to the subcutaneous margin of the ulna. Above, it is continued into the 

 fascia of the arm; below, into the fascia of the hand. From the antibrachial fascia in the upper- 

 half of the foreai-m a fibrous septum extends between the radio-dorsal and the ulno-volar 

 muscle group to the radius. In the radial septum below the elbow a branch of communica- 

 tion extends between the superficial and deep veins of the arm. That part of the fascia over- 

 lying the radio-dorsal group of muscles is much denser than that covering the volar group, 

 except where the latter is strengthened by the lacertus fibrosus. In addition to the main 

 radial septum other septa descend between the underlying muscles from the antibrachial 

 fascia. These septa are best marked near the attachment of the muscles to the humerus. 

 Here the fascia is firmly fused to the muscles. 



Dorsally the antibrachial fascia is strengthened at the wrist by transverse fibres which 

 extend from the radius to the styloid process of the ulna, the triquetrum (cuneiform), and 

 pisiform, and give rise to the dorsal ligament of the carpus (posterior annular ligament). From 

 this ligament septa descend to the radius and ulna and convert the grooves in these bones into 

 osteo-fibrous canals which lodge the tendons of the various muscles extending to the wrist and 

 hand. 



On the back of the hand there is spread a fascia composed of two thin fascial sheets between 

 which the extensor tendons are contained. Between the tendons these sheets are more or less 

 fused. On the backs of the fingers the fascia blends with the extensor tendons and the associated 

 aponeurotic expansions from the interosseous and lumbrical muscles. Between the fingers 

 it is continued into the transverse fasciculi of the palmar aponeurosis. At the sides of the hand 

 the fascia is continued into the thenar and hypothenar fasciae. Each dorsal interosseous 

 muscle is covered by a special fascial membrane which is separated by loose tissue from the 

 fascia investing the extensor tendons. 



Fig. 366, A-H. — Transverse Sections through the Left Forearm and Hand. 



H. Transverse section through the first phalanx of the middle finger, diagrammatic, with the 

 cavity of the synovial sheath of the flexor tendons distended. 

 The regions through which these sections pass are indicated in the diagram, c and d in the 

 diagram show the regions through which pass sections C and D, fig. 362 (p. 375). 



1. Aponeurosis palmaris. 2. Arteria radialis. 3. A. ulnaris. 4. Bursa bicipito-radialis. 5. 

 Discus articularis. 6. Ligamentum carpale dorsale. 7. L. carpi transversum. 8. L. 

 carpi volare. 9. Fascia antibrachii. 10. Musculus abductor pollicis brevis. 11. M. 

 abductor poUicis longus — a, tendon. 12. M. abductor digiti quinti. 13. M. adductor 

 polhcis. 14. M. anconeus. 15. M. biceps, tendon. 16. M. brachialis, tendon. 17. M. 

 brachio-radialis — a, tendon. 18. M. extensor carpi radialis brevis — a, tendon. 19. M. 

 extensor carpi radialis longus — a, tendon. 20. M. extensor carpi ulnaris. 21. M. ex- 

 ten.sor digitorum communis — a, tendon for second finger; b, tendon for the third finger; c, 

 tendon for fourth finger; d, tendon for fifth finger; e, digital aponeurosis. 22. M. extensor 

 digiti quinti proprius. 23. M. extensor indicis proi)rius. 24. M. extensor pollicis brevis 

 — a, tendon. 25. M. extensor pollicis longus — a, tendon. 26. M. flexor carpi radialis — 

 a, tendon. 27. M. flexor carpi ulnaris — a, tendon. 28. M. flexor digitorum profundus — 

 a, tendon for second finger; b, tendon for third finger; c, tendon for fourth finger; d, tendon 

 f<jr fifth finger. 29. M. flexor digitorum subliinis — a, tendon for second finger; b, tendon 

 for third finger; c, tendon for fourth finger; d. tendon for fifth finger. 30. M. flexor digiti 

 quinti brevis. 31. M. flexor poUicis brevis. 32. M. flexor i)ollicis longus — a, tendon. 

 33. M. interossei dorsales. 34. M. interossei volares. 35. M. lumbricales. 36. M. op- 

 poneris pollicis. 37. M. opponens digiti quinti. 38. M. palmaris brevis. 39. M. palmaris 

 longus — a, tendon. 40. M. pronator quadratus. 41. M. pronator teres. 42. M. supi- 

 nator. 43. N. cutancus antibrachii lateralis. 44. N. medianus. 45. N. radialis — a, 

 deep radial nerve; b, superficial radial nerve. 46. N. ulnaris. 47. Os capitatum 

 (magnum). 48. Os hamatum (unciform). 49. Os lunatum (semilunar). 50. Os meta- 

 (•ari)alc, I. 51. Os mctacarpale, II. 52. Os metacarf)alc, ill. 53. Os metacarpale, IV. 

 54. Os metacarpale, V. 55. Os niultanguluin majus (trai)ezium). 56. Os naviculare. 

 57. Ossa sesamoidea of fifth digit. 58. Kadius. 59. Ulna. 60. Vagina fibrosa (tendon- 

 sheath) of the long digital flexors. f'»l. Vagina fibrosa (tendon-sheath) of the flexor 

 pollicis longus. 62. Vagina fibrosa (tendon-sheath in digit). 63. Vena cephalica. 



