508 



BONES OF THE HAND. 



Although thu perfect prehensile hand is pecu- 

 liar to man and the Quadrumana, the inferior 

 segment of the anterior extremity will be found 

 to possess many interesting analogies through- 

 out the mammiferous series. On this point we 

 refer to the articles OSSEOUS SYSTEM (Comp. 

 Anat.) and SKELETON. 



JOINTS OF THE HAND. 



Joints of the carpus. The bones consti- 

 tuting each row of the carpus are firmly con- 

 nected by strong ligaments, so that their com- 

 bined surfaces form one extended surface 

 adapted to the radius, or to the metacarpus, or 

 to each other. Thus the union of the superior 

 articular surfaces of the upper carpal row con- 

 stitutes the convex surface that contributes to 

 the formation of the wrist-joint, whilst the 

 united inferior articular surfaces of the same 

 row are adapted to the united superior surfaces 

 of the inferior carpal row. Again, the inferior 

 articular surfaces of this last row enter into the 

 formation of the carpo-metacarpal joints. 



The several articulations of each row are 

 strengthened by two sets of ligaments, one on 

 the palmar, the other on the dorsal surface of 

 the joints, palmar and dorsal ligaments; they 

 extend transversely from one bone to the other. 

 The palmar ligaments are considerably stronger 

 than the dorsal. The synovial membranes 

 which exist in these small articulations are 

 merely offsets from the large synovial mem- 

 brane which is interposed between the two 

 rows of the carpus. 



In the articulation between the scaphoid and 

 lunar bones, as well as in that between the 

 lunar and cuneiform, we observe a remarkable 

 h'bro-cartilaginous lamina interposed in the 

 whole extent of each articulation from before 

 backwards, although not extending over the 

 entire articular surfaces. These laminae are 

 readily seen on opening the radio-carpal joint 

 in the interval between the bones above men- 

 tioned ; they are attached to the palmar and 

 dorsal ligaments by their anterior and posterior 

 extremities. When dissected out they will be 

 found to be wedge-shaped, the thick edge being 

 directed towards the wrist-joint, and adherent 

 to the synovial membrane of that joint. These 

 lamina; are described by most anatomists as 

 ligaments, under the name of inlerosseous liga- 

 ments. Of their nbro-cartilaginous nature, 

 however, 1 have no doubt from repeated and 

 careful examinations ; they may therefore be 

 more correctly denominated interosscous Jibro- 

 cartilages. Feeble interosseous ligaments exist 

 on either side of the os magnum between it 

 and the unciform on one side, and the trapezoid 

 on the other; they are best seen when these 

 bones are torn from each other. 



Articulation of the two rows of carpal bones 

 In each other. The superior articular surfaces 

 of the four bones composing the inferior carpal 

 row are adapted to the inferior articular surfaces 

 of the scaphoid, lunar, and cuneiform bones. 

 The head of the os magnum and the superior 

 articular surface of thu unciform bone form a 

 prominent convexity, which is received into a 

 deep concavity formed on the ulnar side by the 

 cuneiform bone, on the radial side by the 



scaphoid, and in the centre by the lunar bone; 

 whilst external to the projection of the os mag- 

 num, a superficial oblong concavity receives the 

 convexity on the inferior and outer surface of 

 the scaphoid. Thus the line of this articulation 

 has somewhat of the course of the roman S 

 placed horizontally, o>. That part of the arti- 

 culation which is to the ulnar side, then, par- 

 takes more of the nature of enarthiodia or ball 

 and socket joint, while that to the radial side 

 is arthrodia with almost plane surfaces. 



This articulation is strengthened in front by 

 an anterior or palmar ligament which is of 

 considerable strength and thickness. Most of 

 the fibres of this ligament are attached inferiorly 

 to the palmar surface of the os magnum, 

 whence they diverge to be inserted into the 

 scaphoid, lunar, and cuneiform bones; some 

 few fibres extend from the trapezoid and trape- 

 zium to the scaphoid, and from the unciform 

 to the cuneiform. Behind we find a dorsal 

 ligament, also strong, although much less so 

 than the palmar. This ligament extends 

 obliquely from the bones of the first row to 

 those of the second, but is stronger on the ulnar 

 than on the radial side. The extent and con- 

 nexions of both these ligaments are best seen 

 when the joint is opened, by cutting through 

 the dorsal ligament to view the palmar, and 

 vice versa. The ligaments called lateral by 

 some anatomists are merely the continuation of 

 the lateral ligaments of the wrist-joint ; nor do 

 those described by Cruveilhier under the name 

 of glenoid ligaments deserve to be separated 

 from the anterior and posterior, of which they 

 constitute that portion most intimately connected 

 with the anterior and posterior notches of the 

 hollow cavity in which the head of the os mag- 

 num is lodged. 



In opening this joint in the manner already 

 described, it will be seen how extensive is its 

 synovial membrane. It extends some distance 

 on the palmar and dorsal surfaces of the neck 

 of the os magnum, and sends two processes 

 between the bones of the first row (between 

 the scaphoid and lunar, and the lunar and 

 cuneiform), and three processes between those 

 of the second row, (one on each side of the 

 os magnum,) and one between the trapezium 

 and trapezoid. 



Motions oj' the carpal articulations. An 

 examination of the dissected carpus will at 

 once show how limited are the motions between 

 any two of the carpal bones of each row. The 

 movement of one row upon the other, however, 

 is more extensive, but only in the direction of 

 flexion and extension, the former being con- 

 siderably greater in consequence of the less 

 resistance of the dorsal ligaments. Solidity 

 and strength, a power of resistance to violence 

 which might easily occasion fracture, were the 

 carpus one solid bone, are gained by the num- 

 ber of small bones of which it is composed, 

 the arthrodial form of its articulations, and the 

 strong ligaments by which the motions of these 

 joints are restricted. 



Articulation of the pisiform bone. The 

 pisiform bone is so little connected with the 

 mechanism of the carpus that its articulation 



