INTRODUCTORY 



23 



finger has been elongated to form a long, rigid rod, strengthened at 

 the base by that portion of the third finger which in ourselves con- 

 tributes to form the '' palm " of the hand. In the bird's palm there 

 are but two bones, forming the base of the second and third fingers 

 respectively. 



The bird's wing folds in a peculiar manner, so as to form a more 

 or less Z-shaped rod, the humerus, or upper arm, forming the top of 

 the Z, the fore-arm the downstroke, and the hand the base of the Z. 



When extended, each 

 of these divisions, or seg- c c. 



ments, will be found to 

 support a series of long, 

 broad feathers. Those on 

 the hand are known as 

 the primaries, and those 

 on the fore-arm as the 

 secondaries, while those 

 on the upper arm are 

 sometimes described as 

 the tertiaries. These last 

 form a double series, one 

 attached to the upper and 

 one to the under surface 

 of the humerus, or upper 

 arm-bone, and their pur- 

 pose is to close the gap 

 which would otherwise be 



left between the wing and the body during flight — a gap which, indeed, 

 would make flight well-nigh, if not quite, impossible in birds which, like 

 the Albatross, have a long humerus. Above the *' quill " or '' flight " 

 feathers — the primaries and secondaries — will be found a number 

 of rows of smaller feathers, which can be divided into several distinct 

 series. These are the ** coverts," and are known respectively as 

 the major, median, minor, and marginal coverts. Of the first and 

 second series — the major and median coverts — there is, of each, 

 but a single row ; while the minor and marginal coverts number 

 several rows each. Some of these smaller coverts have, for clearness' 



Fig. 9.— Wing of a Bird, showing the Flight 

 Feathers and some of the Coverts. 



