ARTICULATIONS OF THE ANTERIOR LIMBS. 199 



by the small sigmoid cavity of the ulna and the ligaments which complete it. The inferior 

 extremity also rolls on the ulnar facet in describing a similar movement, and the internal 

 tuberosity of this extremity is carried forwards. 



In the movement of pronation, this tuberosity is brought inwards, and the anterior face of 

 the radius comes forward by an opposite mechanism. 



The inferior bone of the anterior limb being articulated in a hinge-like manner with the 

 radius, it follows this bone in its rotatory movements, the anterior face of the metacarpus 

 looking outwards during supination and forwards in pronation. 



The radio-ulnar articulation in Man resembles that of the Dog and Cat, the articular 

 surfaces only being larger and the movements more extensive. In supination, the palmar face 

 is turned forward, and the radius, situated on the outer side of the ulna, is in the same direction 

 as the latter. In pronation, on the contrary, the palmar face of the hand looks backwards, and 

 the radius — remaining outwards in its upper part — crosses the ulna in front in such a manner 

 that its lower extremity is placed witliiu the ulna. 



4. Articulations of the Carpus (Figs. 129, 130) 



Preparation. — After removing the tendons surrounding the carpus, the ligaments cbmmon 

 to all the carpal articulations can be studied. The anterior and posterior membraniform 

 ligament can tben be removed, and the ligaments proper to each row, as well as those uniting 

 the two rows, and these to adjoining bones, can be dissected. Some time is required for this 

 dissection, which is not difficult. 



These comprise : 1. The articulations uniting the carpal bones of the first 

 row to each other. 2. The analogous articulations of the second row. 3. The 

 radio-carpal articulation. 4. The articulation of the two rows with each other. 

 5. The carpo-metacarpal articulation. 



Articulations which unite the Bones of the First Row to each 

 other. — These bones, four in number, are joined by the diarthrodial facets on 

 their lateral faces, and form small arthrodial articulations.^ They are maintained 

 in contact by six ligaments, three anterior, and three interosseous. The anterior 

 ligaments are small flattened bauds carried from the fourth bone to the first, 

 from the first to the second, and from that to the third. The first, placed 

 outside rather than in front of the carpus, is covered by the external lateral 

 ligament and the inferior tendon of the external flexor of the metacarpus ; the 

 others adhere to the capsular ligament. The interosseous ligaments are implanted 

 in the grooves of insertion which separate the diarthrodial facets. One of them, 

 derived from the common superior ligament, unites the first to the second bone. 

 The two others, situated between the three last carpal bones, are confounded 

 with the corresponding anterior ligaments. 



Articulations uniting the Carpal Bones of the Second Row. — 

 These are arthrodial articulations, like the preceding, but numbering only two. 

 They are fixed by two anterior and two interosseous ligaments. One of the 

 anterior ligaments joins the first bone to the second, and strongly adheres to the 

 capsular ligament ; the other is entirely covered by the lateral internal ligament, 

 and attaches the two last bones to each other. Of the two interosseous ligaments, 

 the second alone is confounded with the corresponding anterior ligament. That 

 which is situated between the two first bones is separated from the anterior 

 hgament by one of the diarthrodial facets between these bones. 



Radio-carpal Articulation. — The inferior extremity of the radius, in 

 becoming united to the upper row of carpal bones, constitutes a diarthrosis 

 which, from the nature of the movements it permits, may be considered as 

 an imperfect hinge- joint. 



' The facet uniting the supercarpal to the first bone is not situated on one of its faces, but 

 rather on the anterior part of its circumference. 



