2 REMARKS ON THE DIGESTIVE ORGANS. 



each other by imperceptible gradations, their external parts as 

 well as their internal organs being formed on the same plan. 

 The short strong conical bill, sharp-edged, pointed, and form- 

 ed for shelling or husking seeds, at once distinguishes the 

 Deglubitores ; but the bill of the Vagatores, although always 

 stronger than that of the Cantatores, is not very dissimilar. 



The general structure of the digestive organs of Birds has 

 been, it is hoped, rendered sufficiently intelligible to the reader, 

 to enable him to perceive that upon the modifications present- 

 ed by them may be founded an arrangement of the species, 

 genera, and families, more natural than any that can result 

 from the comparison of the external parts only. It is not by 

 any means assumed by the author that such an arrangement 

 has been elicited by him ; for a more intimate and extended 

 acquaintance with the organization of the birds of all countries 

 than he possesses is necessary to render an attempt to construct 

 a natural system successful. In the mean time he has not only 

 continued his observations on the birds of this country, but 

 has examined the digestive and respiratory organs of more than 

 two hundred species from North America, which were brought 

 him in spirits by JSIr Audubon. The results of this exami- 

 nation are recorded in the fourth and fifth volumes of the 

 Ornithological Biography of that enthusiastic ornithologist, 

 and, with the aid of the numerous sketches by which they are 

 illustrated, will enable any one desirous of obtaining a general 

 idea of the subject, to judge how far the forms, proportions, 

 and modifications of the organs in question may be useful in 

 indicating the affinities of the species. 



In the first volume of the present work, four very distinctly 

 defined varieties of the intestinal canal, including under that 

 title the entire alimentary tube, were exhibited as peculiar to 

 the four groups or orders of birds there described ; two other 

 forms were also presented in the plates, and a seventh is pro- 

 duced in the first part of this volume. As the subject appears 

 to be of great importance, and as I am desirous of throwing 

 as much light upon it as my opportunities and faculties enable 

 me to do, I shall here present a series of those forms which 

 seem to be most illustrative. 



