erely
in our own behalf, but for the benefit of others. If we discharge the
obligations of our trusteeship, we shall enjoy present strength,
usefulness, and length of days; but if we fail in their performance,
then inefficiency, incapacity, and sickness, will follow, the sequel of
which is pain and death. Let us, then, prove worthy of this generous
commission, that we may enjoy the sweetest of all pleasures, the
delicious fruitage of honest toil and faithful obedience.

* * * * *

PART I.

PHYSIOLOGY.

CHAPTER I.

BIOLOGY.

In this chapter we propose to consider Life in its primitive
manifestations. _Biology_ is the science of living bodies, or the
science of life. Every organ of a living body has a function to perform,
and _Physiology_ treats of these functions.

_Function_ means the peculiar action of some particular organ or part.
There can be no vital action without change, and no change without
organs. Every living thing has a structure, and _Anatomy_ treats of the
structures of organized bodies. Several chapters of this work are
devoted to _Physiological Anatomy_, which treats of the human organism
and its functions.

The beginning of life is called _generation_; its perpetuation,
_reproduction_. By the former function, individual life is insured; by
the latter, it is maintained. Since nutrition sustains life, it has been
pertinently termed _perpetual reproduction_.

LATENT LIFE is contained in a small globule, a mere atom of matter, in
the sperm-cell. This element is something which, under certain
conditions, develops into a living organism. The entire realm of nature
teems with these interesting phenomena, thus manifesting that admirable
adjustment of internal to external relations, which claims our profound
attention. We are simply humble scholars, waiting on the threshold of
nature's glorious sanctuary, to receive the interpretation of her divine
mysteries.

Some have conjectured that chemical and physical forces account for all
the phenomena of life, and that organization is not the result of vital
forces. Physical science cannot inform us what the beginning was, or how
vitality is the result of chemical forces; nor can it tell us what
transmutations will occur at the end of organized existence. This
mysterious life-principle eludes the grasp of the profoundest
scientists, and its presence in the world will ever continue to be an
astonishing and indu