STRUCTURE OF BIRDS. 41 



The most external muscle, of which a portion is seen along 

 and behind the ulna, is the flexor carpi ulnaris^ 1 6, which has 

 already been described. 



22. The next muscle is the extensor carpi ulnaris, which arises 

 from the lower extremity of the outer condyle of the humerus, 

 runs along the middle of the fore-arm, with the ulna imme- 

 diately behind, and terminates in a long slender tendon, which 

 passes over a pulley at the extremity of the ulna, and is in- 

 serted into the posterior edge of the radial metacarpal bone. 

 Its action is to extend the hand, and when extended, to bring 

 it upwards. It is not by any means an adductor of the hand, 

 as stated in several books. 



23. Extensor primi digiti arises from the outer condyle of 

 the humerus, runs along the fore-arm parallel and anterior to 

 the last, and forms a very slender tendon, which, passing over 

 that of the next muscle, goes to be inserted into the base of the 

 bone of the first finger, which it draws upward and backward. 



24. Extensor digitorum arises from the outer condyle of the 

 humerus, and from the anterior edge of the ulna and the pos- 

 terior edge of the radius ; its tendon passes over the wTist joint, 

 and runs along the radial metacarpal bone to be inserted into 

 the last phalanx. Sometimes several slips are given off by this 

 tendon. Its action is to pull the hand or pinion upwards and 

 outwards. 



25. Extensor carpi radialis hrems arises also from the inner 

 condyle, and from nearly the whole length of the inner edge 

 of the radius, and is inserted by a slender tendon into the pro- 

 minence at the base of the metacarpal bone near that of the 

 extensor carpi radialis longior, 15, already described, and w^hich 

 is the muscle on the anterior edge of the fore-arm. 



There now remain the small muscles on the hand. 

 The first finger, g^ has three muscles. 



26. Flexor primi digiti arises from the base of the radial 

 metacarpal bone, and is inserted into that of the first finger, 

 wdiich it draws dow^n wards. 



27. Adductor primi digiti arises from the metacarpal bone, 

 and is inserted along the inner or posterior edge of that of the 

 first finger, which it draws toward the next. 



