82 ANATOMY. 



with that of the wrist -joint through an opening in the triangular fibro cartilagt 

 which separates the head of the ulna from the wrist-joint, and acts as one of 

 the ligaments of this articulation, which are 3, viz. 



Anterior Radio-ulnar. Posterior Radio-ulnar. 



Triangular Interarticular Fibro- cartilage. 



Describe the Wrist-joint. It is chiefly an enarthrodial articulation, though 

 incapable of rotation, and is formed by the lower end of the radius and the tri- 

 angular fibro-cartilage, with the scaphoid, semilunar, and cuneiform bones of the 

 carpus. Its Arteries are the anterior and posterior carpal from both the radial 

 and ulnar, the anterior and posterior interosseous and ascending branches from 

 the deep palmar arch. Its Nerves are derived from the ulnar; it is lined by a 

 synovial membrane, and has 4 ligaments, viz. 



External Lateral (radio-carpal). Anterior. 



Internal Lateral (ulno-carpal). Posterior. 



Describe the Carpal Articulations. They are in 3 sets, (i) between the 

 bones of the first row, (2) between the bones of the second row, (3) between 

 the 2 rows of bones. 



(1) The scaphoid, semilunar, and cuneiform bones are connected together 

 by 2 Dorsal, 2 Palmar, and 2 Interosseous Ligaments. The pisiform bone 

 has a separate capsular ligament and synovial membrane and 2 fasciculi 

 connecting it with the unciform and the 5th metacarpal. 



(2) The 4 bones of the second row are connected together by j Dorsal, 3 

 Palmar, and 3 Interosseous Ligaments. 



(3) The 2 rows of bones are united by a Dorsal, a Palmar, and 2 Lateral 

 Ligaments, the last named being continuous with the lateral ligaments of 

 the wrist-joint. 



Describe the Carpo-metacarpal Articulations. That of the thumb with the 

 trapezium is an enarthrodial joint, having a Capsular Ligament and a separate 

 synovial membrane. The 4 inner metacarpal bones form 4 arthrodial joints 

 with the adjacent carpal bones by 6 Dorsal, 8 Palmar, and 2 Interosseous Liga- 

 ments, irregularly disposed. 



Describe the Synovial Membranes of the Wrist. They number 5, and are 

 situated as follows, viz. 



The First, or Membrana Sacciformis, between the head of the ulna, the sig- 

 moid cavity of the radius, and the triangular interarticular fibro-cartilage. 

 The Second, between the lower end of the radius, the triangular fibro-carti- 

 lage, and the scaphoid, semilunar, and cuneiform bones of the carpus. 

 The Third, between all the carpal bones except the pisiform, and between 

 the bases of the inner 4 metacarpal bones ; but it extends only halfway 

 into the 2 intervals between the 3 proximal bones of the carpus. 



