Limbs : Upper Limb 101 



At birth the ends of the bones are cartilaginous, and also the tubercle of the radius : 

 the coronoid process has been formed as part of the shaft of the ulna. 



The additional epiphysial centres appear first in the radius, perhaps on account 

 of it being the direct supporting bone for the hand. 



The " growing ends " are distal, and in these centres appear, in the radius early 

 in the second year, and in the ulna about the sixth or seventh year. They unite with 

 the shaft between eighteen and twenty-one, the ulnar head joining a year or two 

 before the lower end of the radius. 



The upper ends begin to ossify, in the radius about the sixth year, and in the ulna 

 during the tenth year, and unite between seventeen and twenty, the ulnar fusion again 

 preceding that in the radius. 



The centre for the radial tubercle appears about twenty and joins a few years 

 later. There is frequently an additional centre for the tip of the olecranon : observe 

 in the figure that the olecranon centres do not correspond with the whole of the descrip- 

 tive process (Fig. 78). 



Occasional centres have been described for the two styloid processes. The centre 

 in the head of the radius has been said to be formed by the junction of several small 

 ones, but this is probably not a correct interpretation of the observations. 



The above account can be taken as representing the normal history of ossification 

 in the male, but for the female there seems to be a marked modification in the direction 

 of earlier appearance of epiphysial centres at the growing ends of the bones : thus 

 in the radius the lower centre is found six months earlier than in the male, while that 

 in the ulna is a year earlier. 



HAND. 



The skeleton of the hand consists of twenty-seven bones arranged in three divisions 

 or groups. The proximal part, carried by the Radius, is the Carpus, consisting of 

 eight small irregular bones arranged in two rows, proximal and distal : the distal row 

 supports the metacarpus, a set of five long bones numbered from without inwards, 

 articulating by their bases with the bones of the distal (or second) row of the carpus, 

 and carrying on their distal rounded extremities, or heads, the proximal parts of the 

 skeleton of the digits : this is composed of three phalanges in each finger numbered 

 from the metacarpal as first, second, and third (or ungual) phalanx respectively, but 

 the thumb only possesses two phalanges. Certain " sesamoid " bones are also normally 

 found in the hand, but these do not belong to the bony skeleton, being modifications 

 in tendons or ligaments. 



CARPUS. The constituent bones are closely applied to one another and firmly 

 secured in their rows by strong ligaments, so that the carpus as a whole forms a strong 

 bony and fibrous mass, concave on its palmar aspect and convex dorsally : the flexor 

 tendons of the fingers occupy the concavity. 



There are four bones in each row. These are shown, somewhat diagrammatically, 

 in Fig. 82, and are named as follows : First row : (i) Scaphoid (or Navicular), (2) Semi- 

 lunar, (3) Cuneiform, (4) Pisiform. 



Second row : (5) Trapezium, (6) Trapezoid, (7) Os Magnum, (8.) Unciform. 



Each of these bones, with the exception of the pisiform, articulates with its neigh- 

 bours in its own row, and in addition with bones above and below it. The articula- 

 tions can be followed in the figure, where it can be seen that every one of the elements 

 articulates with its neighbour, on both sides save in the case of the marginal bones ; 

 but the other contacts are rather more complicated than this. 



