20 ON THE CLASSIFICATION OP BIRDS. 
outvmrd organisation. The study of the first is not so 
essential to the zoologist as that of the last ; and, al- 
though both are intimately connected, tliey may be, 
and have been, pursued separately. It is, for instance, 
by no means necessary for the clear understanding of 
the ruminating quadrupeds, that the naturalist should 
be informed that they possess more stomachs 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 ivere he 
to neglect the study of the external anatomy of these 
beasts, and disregard the form, direction, and substance 
of their horns, the size and situation of their teeth, and 
other parts of their external anatomy, he would be ut- 
terly 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 of structure of the body, and all its various 
members, is comprised under the head of external ana- 
tomy ; and it is from the various modifications and 
appearances which these parts assume, that the ornitho- 
logist is capable of drawing such discriminating charac- 
ters 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 be able to classify those native birds which, from 
being common, might be procured for dissection ; hut 
thousands of others must he left undetermined : and 
after all, however elaborate might be his system, it would 
be utterly useless for practical puq)oses,and unintelligible 
to all but professed anatomists. It has generally hap- 
pened, that those who have attached so much fancied 
importance to the internal anatomy of animals, have 
been but very imperfectly acquainted with the habits 
and economy of the animals themselves; and thus, while 
we have had the most minute details of their internal 
conformation, we have been left in comparative igno- 
rance of those especial purposes for which each particular 
structure was intended : just as if we described, with 
