mologies,
too, not so much of organs as of parts.

These memoirs (published in the _Annales du Museum d'Histoire
naturelle_, vols. ix. and x., 1807) dealt with the homology between
the bones of the pectoral fin and girdle in fish and the bones of the
arm and shoulder-girdle in higher Vertebrates, with the homologies of
the bones of the sternum, and with the determination of the pieces of
the skull, particularly in the crocodile. All Geoffroy's morphological
doctrine is found in them, but for the full expression of his views we
must take his chief work, the _Philosophie anatomique_, particularly
the first volume (1818). This volume contains, beside the important
"Discours preliminaire" and "Introduction" which we shall presently
consider in detail, five memoirs, which deal with the various bones
connected with the respiratory organs in fishes (the bones of the
operculum, of the hyoid, of the branchial arches, of the pectoral
girdle), and seek to discover their homologies with corresponding
bones in air-breathing Vertebrates.

"Can the organisation of vertebrated animals be referred to one
uniform type?" This is the question with which the _Philosophie
anatomique_ opens, the question to which the whole book is an answer.
But is it not generally acknowledged by naturalists that Vertebrates
are built upon one uniform plan, that, for instance, the fore limb may
be modified for running, climbing, swimming, or flying, yet the
arrangement of the bones remain the same? How else could there be a
"natural method" of classification?[87]

But the homologies so drawn repose upon a vague and confused feeling for
likenesses; they are not based upon an explicit principle. What general
principle can be applied? "Now it is evident that the sole general
principle one can apply is given by the position, the relations, and the
dependencies of the parts, that is to say, by what I name and include
under the term of _connections_." For instance, the part known as the
hand in man and generally as the fore foot in other Vertebrates, is the
fourth part in order in the anterior member, and its homologue can
always be recognised by this fact of its connections (p. xxvi.). The
principle of connections serves as a guide in tracing an organ through
all its functional transformations, for "an organ can be deteriorated,
atrophied, annihilated, but not transposed" (p. xxx.).

It is this principle which enables one to follow out in detail the
further