INTRODUCTION. O 



The Margins of the mandibles are tlieir lateral 

 edges, wMcli meet when the bill is closed. In some 

 birds the margins of the npper mandible overlap 

 those of the lower, while in others the two edges 

 exactly meet ; the line thus formed by the meeting 

 of the mandibles is termed the Commissure. 



The commissure may be either straigld, as in the 

 Woodpecker ; festooned, as in the Sparrow-hawk ; 

 undulated, as in the Tanager; arched, as in the 

 Hoopoe; or angidated at its base, as in the Starling. 



The Upper Mandible is sometimes continued over 

 the forehead, so as to form a sort of helmet. In 

 rapacious birds and Parrots its base is covered with 

 a soft skin called the Gere. 



The Wing of a bird is constructed upon the same 

 general plan as the human arm, or the fore-leg of 

 quadrupeds, and when denuded of its feathers, it is 

 not difficult to perceive the relationship between 

 these apparently different organs. 



The Quill-Feathers of the wing are di\4ded into 

 three sets, distinguished as the primaries, the 

 secondaries, and the tertiaries. 



The Primaries are always the longest, and in 

 swift-flying bu'ds, like the Swallows, are of double 

 the length of any of the other quills : they are usually 

 nine or ten in number, sometimes eleven, and are 

 attached to the metacarpus, or those bones which 

 represent the hand of the human skeleton (3). 



The Secondaries are implanted in the cubit or 

 fore-arm, and are usually only half the length of 

 the primaries (3*). 



The Tertiaries are those attached to the upper 

 arm, or humerus. 



The origins of the quills are overlapped, and pro- 

 tected -by smaller feathers, arranged something like 

 the tiles of a house, and called the Wing-Coverts 



(1 r 1"). 



The power of flight possessed by any bird depends 



upon the arrangement, the proportionate size, and 



. the shape of the wings : hence it will be necessary 



B 2 



