xxiv : INTRODUCTION. 
therefore feel indebted. These details I had resolved to pre-. 
sent to you, because I have thought that no perfect knowledge 
of the affinities of species can be obtained until their internal 
organization is known. I believe the time to be fast approach- 
ing when much of the results obtained from the inspection of 
the exterior alone will be laid aside : when museums filled with 
stuffed skins will be considered insufficient to afford a know- 
ledge of birds; and when the student will go forth not only to 
observe the habits and haunts of animals, but to procure spe- 
cimens of them to be carefully dissected. 
When I commenced the present volume, I expected that it 
should contain descriptions of all the species represented in 
the fourth volume of my Illustrations; but, on proceeding, I 
found that, even without Episodes, which I have been obliged 
to exclude, in order to make room for anatomical notices, of 
more interest to the scientific reader, I could not include more 
than the usual number of one hundred species. In the fifth 
and concluding volume, the printing of which has already be- 
gun, you will find Descriptions of upwards of a hundred spe- 
cies, many of which are new to science, together with Lists 
illustrative of the geographical distribution of birds, an Ap- 
pendix containing additions and corrections, and, finally, a 
Synopsis of the Birds of North America, methodically ar- 
ranged, with generic and specific characters. 
JOHN J. AUDUBON. 
Epinsuren, Ist November 1838. 
