24 GENERAL HISTORY OF BIRDS. 



the trunk, the mandibles, wings, tail, and feet, and these parts have, by 

 descriptive ornithologists, been divided up into certain regions, areas, and 

 special characters in great detail. In fact the description of the topographical 

 anatomy of the exterior of an ordinary bird would occupy far more space 

 than the writer has at his command in this place, and to give the barest sketch 

 of our present knowledge of this subject would demand many pages. 



Morphological or anatomical descriptions of the mandibles of different 

 species of birds in the world, their feet, external anatomy of the eye and ear, 

 special growths and variations of parts, wattles, and the general development 

 of the ptilosis would furnish material for a small volume. Some of these 

 structures will be briefly referred to again further on, but for the present the 

 skeleton will be first considered, after which a short account will be given of 

 the other systems of a bird's anatomy. 



THE SKELETON. 



To gain a complete understanding of the skeleton of a bird, one should study 

 its development in the chick, and follow it through its various stages to the 

 adult. This applies particularly to the skull, which is made up of various 

 bones that are for the most part only separate in early life, being as a rule largely 

 fused together when the individual comes to maturity. This process is more 

 or less tardy in the ostrich-like birds, but in them, as in all other members of 

 the class, the skeleton is conveniently divided for the purposes of study into 

 the skull; the skeleton of the trunk or body; the skeleton of the limbs or 

 members; and finally, any special ossifications. Another not unusual division 

 is that of the axial skeleton^ and the appendicular skeleton^ the first includ- 

 ing the skull and trunk, and the latter the limbs. In the study of birds, 

 a knowledge of the anatomy of the skeleton is of the utmost importance. 

 It is not only the framework of the bird itself, but is likewise the framework 

 of the science of ornithology. To avian anatomy it is what the frame is to a 

 house or a ship, for to it are attached all the other parts of the structure, or 

 within it are harbored the organs and the vital machinery. In a natural 

 classification of birds, a knowledge of the skeleton is absolutely essential as it 

 furnishes the majority of characters having taxonomic value. Of all parts of 

 the skeleton, no portion possesses the importance and interest that the 

 skull does, — that beautifully fashioned object in bone, that not only in 

 birds, but throughout the vertebrata, has been one of the knottiest problems 

 the morphologist has had to solve. But there is a rich literature upon the 

 subject now, and ever ready at the student's hand. An easy skull to study is 

 that of the common fowl, for much has been written upon it. In this type, 

 at the end of the first year of its existence, it has passed through all the embry- 



