from the sum of the animal heat, and thereby diminishes stimulation. In
the cessation of excitement and sensibility that ensues, the whole vital
actions are moderated, existing irritation is soothed; and in the same
manner as sleep recruits the wasted powers, so does cold restore and
invigorate the nerves when overstimulated, and in fact promotes the tone
and vigour of the whole body; when again a warmer atmosphere succeeds a
colder, the animal heat increases in its sum, the surface of the body is
re-excited, nervous sensibility returns, and a reaction of the
circulation takes place; so that the blood diffuses itself in greater
abundance towards the remote and superficial parts of the body, and the
secretions are also promoted.

Alternations of cold and heat therefore in healthy constitutions within
certain limits, are salutary; promoting, on the one hand, the vigour and
tone of the body; on the other, the due activity and excitement of the
various functions.

The temperature occasioned by day and night, and also those more
progressive and slow alternations of heat and cold, on the large scale,
attending the annual revolution of the seasons, are a natural provision
admirably adapted to effect these objects as described; constituted as
our bodies are, such a constant and regular succession of heat and cold
is just such as the necessities of the human frame require. The
alternations of day and night, of winter and summer, are far from being
merely incidental and unimportant circumstances in the general
adaptation of the earth to man's constitutional wants; neither do they
bear reference solely to the productions of the earth for his use. They
exert a continual and direct influence on his constitution, calculated
to aid the vigorous and healthy performance of the various functions of
the body each in its due degree and order, and they conduce mainly to