d become emancipated from vegetation--_Florae
liberti, et libertini_!" In insects we first find the distinct
commencement of a separation between the muscular system, that is, organs
of irritability, and the nervous system, that is, organs of sensibility;
the former, however, maintaining a pre-eminence throughout, and the nerves
themselves being probably subservient to the motory power. With the fishes
begins an internal system of bones, but these are the results of a
comparatively imperfect formation, being in general little more than mere
gristle. In birds we find a sort of synthesis of the powers of fish and
insects. In all three, the powers are under the predominance of
irritability; but sensibility, which is dormant in the insect, begins to
awaken in the fish, and, though still subordinate, is quite awake in the
bird, of which no better proof can be given than its power of sound, with
the rudiments of modulation, in the large class of singing birds, and in
some others a tendency to acquire and to imitate articulate speech. The
next step of ascent brings us to the _mammalia_; and in these, including
beasts and men, the complete and universal presence of a nervous system
raises sensibility to its due place and rank among the animal powers.
Finally, in Man the whole force of organic power attains an inward and
centripetal direction, and the "apex of the living pyramid"becomes a fit
receptacle for Reason and Conscience.

* * * * *

It is much to be regretted, that the estimable Author did not live to put
a finishing hand to this Essay; but the part completed involves
speculations of so interesting a nature, and presents such striking marks
of deep and original thought, that the Editor, to whose hands it was
committed, did not feel himself justified in withholding it from the
judgment of the public.

PHYSIOLOGY OF LIFE.

Introduction.

When we stand before the bust of John Hunter, or as we enter the
magnificent museum furnished by his labours, and pass slowly, with
meditative observation, through this august temple, which the genius of
one great man has raised and dedicated to the wisdom and uniform working
of the Creator, we perceive at every step the guidance, we had almost
said, the inspiration, of those profound ideas concerning Life, which dawn
upon us, indeed, through his written works, but which he has here
presented to us in a more pe