THE WRIST AND HAND 



1433 



Deeper are the articular synovial sacs, five in number: — (1) Between the 

 interarticular cartilage and the head of the ulna; (2) between the radius and the 

 interarticular cartilage above, and the navicular and lunate and triquetrum 

 below; (3) between the greater multangular and first metacarpal bone; (4) be- 

 tween the pisiform and the triquetral bone; (5) between the two rows of carpal 

 bones, sending two processes upward between the three bones of the upper row, 

 and three downward between the four of the lower row; these three processes being 

 also continued below into the medial four carpo-metacarpal and three inter- 

 metacarpal joints. 



Beneath the palmar aponeurosis covering the thenar eminence are the following structures: — 

 Superficial volar artery, abductor pollicis brevis, opponeus poUicis, radial head of short flexor, 

 tendon of long flexor, ulnar head of short flexor, first volar metacarpal arteries, metacarpal bone 

 of the thumb, with the tendon of the flexor carpi radialis and greater multangular. 



Beneath the central part of the palmar aponeurosis are the superficial arch and its digital 

 branches; the ulnar and median nerves, with their branches; the flexors, superficial and deep, 

 with their synovial sheath; and the lumbricales; then a layer of connective tissue (the only 



Fig. 1152. — Diagrams Illustrating the Insertions of the Extensor, Lumbrical and 

 Interosseous Muscles of the Right Hand. A, Index finger. B, Middle finger. C, Ring 

 finger. D, Little finger. 1L,2L,3L,4Ij, Lumbricales. 1D9, 2D9, 3D9, 4D9, dorsal interossei. 

 1P9, 2P9, 3P9, palmar (volar) interossei. EC, Extensor communis digitorum. E9, Extensor 

 indicis proprius. EMD, Extensor digiti quinti proprius. AMD, abductor digiti quinti (Willan : 

 Anat. Anz. Bd. 42, 1912.) 



structure, together with the deep layer of fascia over the interossei, which prevents matter pent 

 in by the palmar aponeurosis from making its way back out through the dorsum), the deep 

 arch, the interossei, and the metacarpal bones. 



In the hypothenar eminence under the fascia are part of the ulnar artery and nerve, the ab- 

 ductor and flexor brevis digiti quinti, the opponens, the deep branch of the ulnar artery and 

 nerve, and the fifth metacarpal bone. 



The back of the wrist and hand. — The dorsal carpal (posterior annular) liga- 

 ment has already been described. On the lateral side is the so-called 'snuff-box 

 space' {tabatiere anatomique of Cloquet), a triangular hollow, bounded toward the 

 radius by the long abductor and short extensor of the thumb, and toward the 

 ulna by the long extensor. The navicular and greater multangular, vnih. their 

 dorsal ligaments, form the floor. In the roof lie the radial vein and branches of the 

 radial nerve. More deeply is the artery, folloTNang a line from the apex of the 

 styloid process to the back of the interosseous space. 



The different tendons have already been given. Between the first two metacarpal bones is 

 the first dorsal interosseous muscle, which forms a fleshy projection against the radial side of 

 the index metacarpal, when the thumb and index are pressed together. On its palmar aspect 

 is the adductor pollicis. Wasting of the former muscle is a ready indication of injury or disease 

 of the ulnar nerve. 



