MOVEMENTS OF THE HAND AND FINGERS. 



177 



The kind of movement which, is allowed between the several carpal and metacarpal bones 

 is best illustrated by placing the hand in such a position that the weight of the body is 

 rested upon the open palm. The metacarpal range, which naturally is concave towards the 

 palm, is flattened ; and the interosseous and palmar metacarpal ligaments are thus tightened, 

 while a slight separation of the opposed surfaces of the bones takes place ; so also the palmar 

 carpo-metacarpal ligaments are tightened, and both palmar and interosseous ligaments of the 

 second range of carpal bones. The convex part of the os magnum and unciform bone, fitted 

 in these circumstances into the concavity of the first range, is a little wider than the part 

 usually in contact with it ; and thus, while the bones of the second range are separated from 

 the palmar side, those of the first range are pressed still more apart from the distal aspect. 

 The whole arrangement secures elasticity. The fourth and especially the fifth metacarpal 

 bones are not so tightly bound to the carpus as the second and third, and can therefore be 

 moved to some extent forwards (opposition), thus making the hand narrower and deepening 

 the hollow of the palm : these bones move in this way very distinctly in shutting the hand, 

 so that the back is then rendered more convex, and the tips of the fingers are brought more 

 closely together. At the interphalangeal articulations the only movements allowed are 

 flexion and extension, while over-extension is prevented by the ligamentous structures in front 

 of the joints. At the metacarpo-phalangeal articulations of the fingers abduction and adduc- 

 tion are also allowed, chiefly in the extended position. In the articulation of the metacarpal 

 bone of the thumb with the trapezium all kinds of angular movement are allowed, but owing 

 to the shape of the articular surfaces the movement of flexion is accompanied by a certain 

 amount of rotation of the metacarpal bone on its long axis, by which the thumb is turned 

 towards the fingers, thus giving rise to the so-called opposition. The metacarpo-phalangeal 

 articulation of the thumb allows of only a limited amount of flexion and extension. 



III. THE ARTICULATION'S OF THE PELVIS. 



ARTICULATION OF THE PELVIS WITH THE LAST LUMBAR VERTEBRA. The 

 fifth lumbar is united to the first sacral vertebra by anterior and posterior ligaments 

 of the bodies, capsular ligaments of the articular processes, ligamenta subflava of 



Fig. 204. ARTICULATIONS OP THE 



PELVIS AND HIP-JOINT, SEEN FROM 

 BEFORE. THE ANTERIOR HALF 

 OF THE CAPSULAR LIGAMENT OF 

 THE LEFT HIP-JOINT HAS BEEN 

 REMOVED, AND THE FEMUR RO- 

 TATED OUTWARDS. (Allen Thom- 

 son.) i 



1, 1, anterior common ligament 

 of the vertebrae passing down to the 

 front of the sacrum ; 2, ilio-lumbar 

 ligament ; 3, anterior sacro-iliac liga- 

 ment ; 4, placed in the great sacro- 

 sciatic foramen, points to the small 

 sacro-sciatic ligament ; 5, a portion 

 of the great sacro-sciatic ligament ; 

 6, anterior ligament of the symphysis 

 pubis ; 7, obturator membrane ; 8, 

 capsular ligament of hip-joint ; the 

 figure is placed on its ilio-femoral 

 band ; 9, upper part of the divided 

 capsular ligament of the left hip-joint 

 near the place of its attachment to 

 the border of the acetabulum ; 10, 

 placed on the os pubis of the left 



side^above the transverse ligament of the acetabular notch. The head of the femur is withdrawn 

 partially from the socket, so as to show the interarticular ligament stretched from the transverse 

 ligament. 



the arches, interspinous and supraspinous ligaments, and by an inter vertebral disc y 

 all of which are similar to those between the vertebras above. It is also attached 

 to the pelvis by two other ligaments, as follows. 



The lateral lumbo-sacral ligament is a variable fasciculus, passing from the 



