I am not sure that the feeling, of which the doctrine to which I have
referred is the full expression, does not lie at the bottom of the
minds of a great many people who yet would vigorously object to give a
verbal assent to the doctrine itself. However this may be, the main
point is that sufficient knowledge has now been acquired of vital
phenomena, to justify the assertion, that the notion, that there is
anything exceptional about these phenomena, receives not a particle of
support from any known fact. On the contrary, there is a vast and an
increasing mass of evidence that birth and death, health and disease,
are as much parts of the ordinary stream of events as the rising and
setting of the sun, or the changes of the moon; and that the living
body is a mechanism, the proper working of which we term health; its
disturbance, disease; its stoppage, death. The activity of this
mechanism is dependent upon many and complicated conditions, some of
which are hopelessly beyond our control, while others are readily
accessible, and are capable of being indefinitely modified by our own
actions. The business of the hygienist and of the physician is to know
the range of these modifiable conditions, and how to influence them
towards the maintenance of health and the prolongation of life; the
business of the general public is to give an intelligent assent, and a
ready obedience based upon that assent, to the rules laid down for
their guidance by such experts. But an intelligent assent is an assent
based upon knowledge, and the knowledge which is here in question means
an acquaintance with the elements of physiology.

It is not difficult to acquire such knowledge. What is true, to
a certain extent, of all the physical sciences, is eminently
characteristic of physiology--the difficulty of the subject begins
beyond the stage of elementary knowledge, and increases with every