The Mirror, 1828.07.05, issue No. 321 | Page 7

These, however, are but a
portion of our correspondent's selections; and as they are written in a
popular style and appear to be equally applicable to the welfare of all
classes, they will doubtless be acceptable to our readers. We are not
friendly to the introduction of purely professional matters into the
pages of the MIRROR, but the following extracts are so far divested of
technicality as to render their utility and importance obvious to every
reader.]
CLIMATE, LOCALITY, AND SEASONS.
I shall first inquire, says Dr. Rennie, what are the effects of climate on
healthy constitutions, as respects heat, cold, moisture, and vicissitudes;
including also the diurnal and annual revolutions.

Cold applied to the body acts as a direct sedative. It diminishes the
nervous sensibility, represses the activity of the circulation, detracts
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
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, a
reactive tendency promoted towards noon under the solar influence,
and again towards evening this reaction is repressed by the sedative
effect of the evening cold; and this sedative effect is at its maximum at
midnight. Hence those who sit up late feel unusually chilly and
depressed towards midnight, partly owing to exhaustion from want of
sleep, but chiefly from the total absence of solar influence in the
atmospherical temperature. In regular habits this sedative effect is
never thoroughly experienced; for before midnight, the constitution,
enveloped in warm blankets, has experienced the reaction arising from
the accumulation of heat in bed. Whence the common remark, that one
hour's sleep before midnight is worth three after that hour, is