entire skeletons are found, there is great difficulty in
discovering their distinguishing characters, as these are chiefly
founded upon their hairs and colors and other marks which have
disappeared previous to their incrustation. It is also very rare
to find any fossil skeletons of quadrupeds in any degree
approaching to a complete state, as the strata for the most part
only contain separate bones, scattered confusedly and almost
always broken and reduced to fragments, which are the only means
left to naturalists for ascertaining the species or genera to
which they have belonged.

"Fortunately comparative anatomy, when thoroughly understood,
enables us to surmount all these difficulties, as a careful
application of its principles instructs us in the correspondences
and dissimilarities of the forms of organized bodies of different
kinds, by which each may be rigorously ascertained from almost
every fragment of its various parts and organs.

"Every organized individual forms an entire system of its own,
all the parts of which naturally correspond, and concur to
produce a certain definite purpose, by reciprocal reaction, or by
combining towards the same end. Hence none of these separate
parts can change their forms without a corresponding change in
the other parts of the same animal, and consequently each of
these parts, taken separately, indicates all the other parts to
which it has belonged. Thus, as I have elsewhere shown, if the
viscera of an animal are so organized as only to be fitted for
the digestion of recent flesh, it is also requisite that the jaws
should be so constructed as to fit them for devouring prey; the
claws must be constructed for seizing and tearing it to pieces;