40 INTRODUCTION. 



longus, and has a similar insertion. Another tendon also 

 passes to be inserted into the base of the radial metacarpal 

 bone, under that of the supinator radii longus. 



19. The JIea:or carpi radialis arises from the inner condyle 

 immediately below the origin of the pronator radii teres, and 

 concealed by the palmaris longus. Its fibres pass obliquely for- 

 wards along the lower and posterior edge of the radius, in con- 

 tact anteriorly with the pronator radii teres, and posteriorly 

 Avith the flexor digitorum. It is inserted fleshy along the pos- 

 terior edge of the radius. Its action is to draw the arm ob- 

 liquely downw^ards and forwards. 



20. Under these muscles is a shorter one which arises from 

 the posterior edge and lower surface of the ulna for two-thirds 

 of its length, and forms a short strong tendon, which passes 

 over the wrist joint, to be inserted into the base of the radial 

 metacarpal bone. Its action is to assist in extending the hand 

 and brinofincr it into a line with the cubitus. 



A thin fleshy muscle extends obliquely forwards from the 

 outer edge of the ulna, in nearly its whole length, to be inserted 

 along two-thirds of the lower surface of the radius. It is a 

 pronator of the radius, which, although fixed when the wing is 

 extended, has considerable motion when bent, in which case 

 it tends to elevate the hand. This muscle is analogous to the 

 pronator^ radii quadratus. 



21. The most anterior muscle of those that come from the 

 inner or posterior part of the lower extremity of the humerus is 

 the pronator radii te?'es. It arises from the upper part of the 

 inner condyle of the humerus, at a considerable distance up 

 the arm, by a tendinous origin, passes obliquely outwards, in 

 contact first w^ith the insertion of the biceps flexor cubiti, then 

 on the same or anterior side of the fore-arm with the extensor 

 carpi radialis longior, and on the other side with the flexor 

 carpi radialis ; and is inserted into tvT^o-thirds of the length of 

 the radius. Its action is to bend the fore-arm obliquely down- 

 wards and inwards. 



The small muscles on the hand may be described afterwards. 

 Let us now turn to the upper surface of the cubitus, seen in 

 Fig. 2, Plate III. 



