212 Descriptive Zoology. 



side, so when the wing is struck against the air, the resist 

 ance presses the vanes together in one continuous layer, 

 through which the air cannot pass. The result is that a 

 strong " push " is made against the air, and by reaction the 

 bird is propelled upward or forward according to the direc- 

 tion of the wing stroke. In seeking the muscle that raises 

 the wing, one would naturally look on the dorsal surface in 

 the region of the shoulder ; but, oddly enough, the muscles 

 that raise the wings are also on the breast. Every one has 

 noticed in the well-cooked breast of a bird that the meat of 

 the breast separates into two parts, the outer part being 

 large and flat, the pectoral muscle just described. Inside 

 of this, lying in the angle between the body of the breast- 

 bone and the keel, is a slender muscle, somewhat triangu- 

 lar in cross section. This is the subclavian muscle. At 

 its anterior end it narrows into a tendon, which passes 

 up through a hole left between the bones that make the 

 shoulder; the tendon then turns and is attached to the 

 upper (dorsal) surface of the arm bone (humerus). When 

 the subclavian muscle shortens, this tendon acts as a pulley, 

 and elevates the wing. In raising the wing it is desirable 

 that there should be as little resistance as possible. This 

 condition is secured ( i ) by the convex outer surface of the 

 wing; (2) by the fact that pressure on the outside of the 

 wing separates the quills and allows the air to pass through 

 with very little resistance. 



The Legs and Feet. The pigeon is a model flier. It 

 uses the feet but little, hence the legs and feet are small 

 and weak. Heavy legs and feet would be to the pigeon a 

 useless burden. The hind limb consists of three parts, 

 thigh, leg, and foot. The true heel is some distance from 

 the toes, where we cut off the foot in dressing a bird. The 

 part between the toes and the heel, usually covered with 



