the perfection and longevity of the species.

Let us therefore trace the effects of these changes on the human body.

During the winter, the prevailing cold acts as a universal sedative and
tonic, soothing the nervous excitement and sensibility, allaying the
activity of the circulation, moderating the functions of the skin, and
diminishing the various secretions.

As the Spring opens, the sun gains daily in influence, generating a
gradually increasing atmospheric warmth. The body therefore becomes
subject from this heat to a reactive effect, during which the nervous
sensibility and circulation are gradually re-excited, the blood is more
equally diffused towards the surface and extremities of the body, and
the secretion by the skin is increased.

If the cold of winter were to continue unmitigated from year to year,
without the genial influence of summer, the human race, as is apparent
in polar regions and upland mountainous districts, would degenerate into
dwarfishness.

If the heat of summer were continually maintained the whole year round,
a tendency to degeneracy of the race would be also observed, as we see
in tropical latitudes. It is in the medium betwixt these extremes, where
a moderate and regular winter cold is succeeded by a mild, genial summer
temperature, that the species approaches most to perfection in stature,
health, strength, and longevity.

In observing also the influence of day and night on the constitution,
there is a sedative effect produced in the morning before the sun is up,