jer-falcon's wing. 30o 



unsweiing to the palm of the hand, extend from II, 

 the wrist joint, to III, the knuckle joint; and this 

 also consists of two portions, extending the whole 

 length, and united at both extremities. From the 

 knuckle joint at III to the point at 1, answers to the 

 fingers in the human hand. The fore-finger, from III 

 to 1, consists of two phalanges soldered together. 

 The distal phalanx forms the tip of the wing, and 

 terminates at 1. This phalanx consists of only a 

 single bone. This bone consists of a longer thickened 

 portion, the fore-finger ending at 1, and a shorter, the 

 second finger, ending at 2, with a thinner portion of 

 bone between them. The second phalanx, which is 

 broad and flat, is marked by oblique thickened portions 

 ending at 3 and 4, and answering to the third and 

 fourth fingers, only the whole is one plate of bone, 

 thickened and strengthened by the oblique ridges 

 terminating at 3 and 4, which proceed from a thick- 

 ened portion continued along the other side. 



It will be seen that all the bones in this wing which 

 have moveable joints are very much enlarged at their 

 extremities; and that, with the exception of the joint 

 at the head of the humerus, one part only of which 

 is seen, as the socket in which the shoulder joint 

 moves is not shown in the figure, have their motions 

 chiefly in one direction or plane only. 



When the wing is extended, the upper process of 

 the head of the humerus is brought considerably 

 within the centre of motion of the shoulder-joint. To 

 it the tendons of the muscles v^hich raise the wing 

 are attached, and its projection, increased beyond the 

 centre of motion, gives the lever power, by means of 

 which these muscles act. The muscle which depresses 

 the wing, or gives the stroke in flying, has its tendon 

 attached to the under side of the flattened portion of 



