HINTS FOR HEALTH.
["A very old and active correspondent," Tim Tobykin, has furnished us with the following interesting extracts from Dr. Rennie's Treatise on Gout and Nervous Diseases, just published. 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 actually true to a certain extent. By early retirement to rest, the sedative effect on the constitution, to an extent such as to disturb the functions, is escaped.
If we connect these two influences, the annual and diurnal successions of cold and heat, in their joint effect, we find, that about, or a little after the summer solstice, the influence of the sun being at its maximum, the nervous sensibility, heat, circulating excitement, and cutaneous secretions of the body, are also at their maximum. The temperature of the day and night differ so little, that the sedative effects of evening and morning are not sufficient to restore the frame by soothing the sensibilities, overexcited and irritable from the previous warmth. Whence the languor and irritability felt in summer, when the heat is long continued, and the nights are spent in restlessness and anxious oppression. Exhaustion and relaxation of the frame are the consequence.
As the autumnal equinox verges on, the mornings and evenings get cooler in relation to the mid-day heat; and about the equinox, the difference in the temperature of mid-day and midnight is at its maximum. We have therefore a powerful sedative effect in the morning, which braces and invigorates the body; a powerful reactive effect at mid-day, which rouses and stimulates the actions and sensibilities of the frame; and again towards evening a sedative effect, from the increasing cold reaching its maximum at midnight.
As the season passes on from the Equinox towards the winter solstice, the heat of the sun daily diminishes, and the cold gains a daily preponderance. The sedative effect on the body goes on progressively increasing, being less and less counteracted by any genial influence from the solar heat at mid-day; whence the gloom and depression so universally experienced by the nervous in November and December, which is more and more felt till the shortest day. So soon as the minimum of solar influence and maximum of sedative effect on the body has passed over, the sun gradually acquires more of meridian influence, and a daily increasing ascendancy over the prevalent cold. The human constitution at the same time is subject to a proportionate reactive disposition; which reaction is felt most at noon, and it daily becomes more and more apparent till the vernal equinox, when we have the difference betwixt the meridian and midnight temperature again at a maximum. We have daily a powerful sedative effect in the morning, a powerful meridian reaction, which again subsides into a sedative condition on the access of the evening. This daily effect on the constitution is exactly similar to that at the autumnal equinox, only it occurs under different circumstances. In autumn it is connected with departing heat and progressively increasing cold; in Spring it is connected with progressively diminishing cold and advancing heat. After the vernal equinox, the difference in the meridian and midnight temperature gradually diminishes; the daily sedative effect at morning and evening becomes less and less apparent as general atmospheric warmth prevails, till towards the summer solstice, the general effect on the constitution is stimulation and excitement by atmospheric heat.