STRUCTURE OF BIRDS. 85 



Some ingenious writers have attempted to show that a know- 

 ledge of the internal structure of animals is not essential to the 

 zoologist, who, it is said, may get on remarkably well, and 

 form the most natural arrangements, by attending merely to 

 the exterior. The views of such persons are not likely to find 

 much favour in the eyes of those wdio have studied animals as 

 organized beings, and who do not remain satisfied with inspect- 

 ing their surface.* Zootomy regards the entire structure of ani- 

 mals, which must be examined in all their parts, before the 

 zoologist can arrange them according to their affinities. The 

 study of their interior must in fact form the basis of all arrange- 

 ment ; and although many natural groups may be formed by 

 attending exclusively to the exterior of animals, it is only be- 

 cause their internal organization is presumed to be similar. 

 The external parts afford an index to the internal ; and if we 

 find a bird having a short hooked bill and curved claws, w^e 

 shall not be WTong in inferring that it has a wide oesophagus 

 and a large membranous stomach. The great divisions of 



* As affording a sample of the once prevalent, but now declining, notions of 

 this class of ornithologists, who, although they boast of being in advance in the 

 matter of the manufacturing of genera, subgenera, and names, are yet at least a 

 century behind in every thing that relates to structure. I may adduce a portion 

 of the 24th paragraph of Mr. Swainson's " Natural History and Classification 

 of Birds.'^ " Comparative anatomy regards two distinct portions of the structure 

 of an animal, — its inivard and its ontivard organization. The study of the first 

 is not so essential to the zoologist as the last ; and, although both are intimate- 

 ly connected, they may Ise, and have been, pursued separately. It is, for in- 

 stance, by no means necessary for the clear understanding of the ruminating- 

 quadrupeds, that the naturalist should be informed that they possess more sto- 

 machs than any other animal ; nor is it essential to his object of defining and 

 classifying them, that he should know which species ruminate their food, and 

 which do not. But were he to neglect the study of the external anatomy of 

 these beasts, and disregard the foi'm, direction, and substance of their horns, 

 the size and situation of their teeth, and other parts of their external anatomy, 

 he would be utterly unable to proceed ; nay, more — he would be scarcely able 

 to define what difference there was between an ox and an elephant. As with 

 quadrupeds, so with birds. The form and structure of the body, and all its va- 

 rious members, is comprised under the head of external anatomy ; audit is from 

 the various modifications and appearances which these parts assume, that the 

 ornithologist is capable of drawing such discriminating characters as enable him 

 to form clear conceptions of their respective peculiarities. Were he, on the 

 other hand, to make their internal anatomy the basis of his system, he might 



