84 INTRODUCTION. 



vessels and completely inorganic, like horns, hoofs, and other 

 parts of the skin, do not undergo any other change of colour 

 than that produced by the fading of their tints from long ex- 

 posure to the weather, or that caused by the abrasion or fall of 

 the extremities of their filaments, when a fresh surface of a dif- 

 ferent colour is exposed. Many birds attain the permanent 

 colours of their plumage at their first moult, while others take 

 four or five years before they acquire their full dress. On this 

 subject various misstatements have been made by authors, 

 some of which I shall endeavour to rectify, when opportunities 

 occur, in describing the species in which the appearances al- 

 luded to are most prominent. 



Those who may be desirous of prosecuting the anatomy of 

 birds will find it advantageous to consult more especially Cu- 

 vier's Lecons d' Anatomic Comparee ; Carus's work on the same 

 subject ; the article Birds, by Macartney, in Rees' Cyclopaedia ; 

 Dr. Granfs Outlines of Comparative Anatomy; the article 

 Aves, by Mr. Owen, in Todd's Cyclopaedia of Anatomy and 

 Physiolog}^ and Dr. Milne Edwards' Elemens de Zoologie ; 

 of the details in some of which I have occasionally availed my- 

 self in drawing up these observations, although in no case have 

 I set doMTi any thing that I have not seen and examined in 

 nature for myself. It is necessary to remark, however, that no 

 progress can be made in comparative anatomy without repeated 

 and varied dissections ; and that to derive the full advantage 

 from zoological descriptions, it is requisite to have the bird 

 treated of, or at least its skin or its portrait, at hand for inspec- 

 tion. Above all modes of acquiring a knowledge of birds, that 

 is to be recommended in which nature is chiefly consulted, 

 and books, especially those composed of critical disquisitions 

 respecting names and classifications, referred to only on rare 

 occasions. If one should know the structure and habits of a 

 species, although he should be ignorant of its name, or rather 

 its half-dozen names, — for it must be a rare bird indeed that 

 has not in the present improved state of science at least as many 

 as a German princess, — he may consider himself more fortunate 

 than if he had learned to distinguish a dozen species in a 

 museum. 



