OSTEOLOOIA AYIUM. 



INTRODUCTION. 



CHAPTER I. 



Birds, or the class Aves, observes Professor Owen*, " form the best characterized, most 

 distinct and natural class in the whole animal kingdom — perhaps even in organic 

 nature. They present a constancy in their mode of generation and in their tegumentary 

 covering which is not met with in any other of the vertebrate classes. No species of 

 bird ever deviates like the cetacea among mammals, and the serpents among reptiles, 

 and the eels among fishes, from the tetrapodous type of formation which so peculiarly 

 characterizes the vertebrate division of animals." 



This constancy to a type renders the distinctive differences between the members of 

 the class less dissimilar than those constituting the other classes of vertebrate animals ; 

 probably, also, it is from this cause that the osteology of birds has been so much 

 neglected. This apparent similarity, however, is not so great as might be supposed by 

 the casual observer of a collection of skeletons ; and the deeper the study of them is 

 proceeded with, the more distinct will appear the characters which distinguish the 

 different groups. 



It is not my intention in the following pages to advocate any particular system of 

 arrangement, let it be binary, tertiary, quinary, or called by any other name with which 

 the fancy of its author may invest it. Not that I disbelieve that a system exists in 



* Cyclopedia of Anatomy and Physiology, edited by Dr. Todd, p. 265. 



