STRUCTURE OF BIRDS. 39 



As these muscles are numerous, it is expedient to describe 

 them in the order in which they are seen in the two views. 



Fig. 2, Plate III, represents the lower face of the wing. In it 

 are observed the following muscles. 



15. Extensor metacarpi i^adiaUs longm\ or supinator radii lon- 

 gus. It is the muscle seen on the fore edge of the cubitus. It 

 arises from the outer condyle of the humerus, fleshy and penni- 

 form, runs along the anterior edge of the fore-arm, and ter- 

 minates in a tendon, which is inserted into the protuberance 

 on the head of the radial metacarpal bone, anterior to the first 

 digit. Its action is to bend the arm and extend the hand, or 

 bring it into a straight line with the cubitus. The insertion 

 of the biceps cubiti is between the head of this muscle and that 

 of the pronator radii teres. 



16. Of the muscles that arise from the inner condyle, the 

 first or most external is the flexor carpi ulnaris^ which comes 

 off by a tendon from the lowest i3art of the condyle, passes 

 along the inner and posterior side of the ulna, in contact with 

 the bases of the cubital quills, and on the anterior side with 

 the palmaris longus, and is inserted by a short tendon into the 

 projecting point of the ulnar carpal bone, analogous to the os 

 pisiforme. Its action is to bend the hand, or bring it back to- 

 wards the fore-arm. 



17. The palmaris longus arises from the inner condyle of the 

 humerus, immediately above the flexor carpi ulnaris, and, cover- 

 ing the flexor carpi radialis, runs superficially over the flexor 

 digitorum, and is inserted partly into the base of the posterior 

 carpal bone, partly into the fascia which covers the lower sur- 

 face of the metacarpus, partly into the ulnar carpal bone, and 

 sends an extremely slender tendon along the radial metacarpal 

 bone and the first phalanx, to be inserted into the base of the 

 second phalanx. Its action is to bend or adduct the hand, and 

 at the same time extend the digit. 



18. T\iQ flexor digitorum is a small muscle arising under the 

 palmaris longus from the inferior and posterior surface of the 

 ulna, along four-fifths of its length, the upper fifth excepted. 

 Its fibres pass obliquely forwards, and it sends off a very long 

 tendon, which runs anterior and parallel to that of the palmaris 



