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rather viewed as a substance per se, liable to many diseased conditions which medical art sought to cure either by experimental external applications, as ointments, lotions, &c., or by the internal administration of drugs, to act through the digestive process. No organ, in fact, has been more misunderstood, neglected, and ill-used, than the skin. It has been blistered, scarified, punctured, and tortured in almost every conceivable way, yet Drug-Medication is still deplorably at fault as regards the possession of specifics for the various diseases considered proper to the skin itself!
The revival of Hydropathic practice naturally led to greater attention being bestowed on skin functions; but it was not until the establishment of the Hot-air Bath that the real value of the skin attracted the attention it, so eminently deserved. It is by the proved amenability of that organism to the soothing yet stimulating and nourishing influences of heat that the great remedial virtues of the Bath, judiciously administered, are brought into action and are enabled to operate. This truth is now so well established that it is already producing, as we shall see, revolutionary changes in medical practice.
The Skin considered in relation to Animal Heat-Its susceptibility of being made a Curative Agent in Disease.
WE must further consider the human skin, in its relation to the natural temperature of the body, and as susceptible of being influenced by artificial Heat, for its peculiar organism in these respects makes it the most powerful and active medium for preserving health, preventing disease, and restoring impaired bodily functions.
The possession of a definite amount of inherent Heat, by all living organizations, is absolutely necessary for the performance of vital actions-in other words, for the performance of those functions which are essential to life. As such actions require to be performed uniformly and regularly, nature has wisely provided that the degree of Heat necessary to their performance should be maintained at an equally uniform and regular standard for every species of animal. All living organizations, therefore, have an inherent independent temperature peculiar to themselves, and which is not perceptibly affected by the temperature of the surrounding atmosphere.
As to the mode in which this animal Heat is produced, different theories have been advanced; but as our purpose is not to follow speculative opinions, but to deal with well-ascertained facts, it is sufficient to state there is a general concurrence among physiologists, that animal Heat in man is produced by the combinations of the fluids and solids of the body in the process of Nutrition, although in what precise manner those combinations are effected is not positively determined. It is known, however, that as Nutrition is necessary for all the organs of the
body, so is it a function appertaining to all to appropriate and assimilate a sufficiency of Nutritive particles to supply their own wants. This process of Nutritive combination, incessantly going on, has the effect of disengaging-for the purpose of elimination from the system-an amount of carbon or waste, and by union of which with the oxygen of the air we inspire carbonic acid is formed, and in this chemical process an evolution of caloric is necessarily produced. It matters not how this union. or combination takes place, or what other hidden agencies may be at work, the result is the generation of animal Heat, which we know is essential to the performance of the functions of life, and we also know that the requisite amount of heat is produced and maintained at a uniform standard within the body itself.
Now, the temperature of the human body is habitually maintained at a standard of 98°, which is called blood heat. Though some exceedingly slight deviations from the standard, attributable to individual idiosyncrasies may be occasionally observed, it appears very surprising at first sight, that, save in disease, this temperature never otherwise varies-that the human body maintains the same degree of warmth, the same standard of Heat in every latitude, and under every atmospheric variation. It is the same, whether exposed to the frozen climate of the polar regions, or to the burning atmosphere of the torrid zone-the same with the thermomoter at 309 or 1008 below the freezing point, as at 100° or 2009 above it.
It may seem extraordinary that such extreme variations of temperature could possibly be endured by man, when it is considered that if the temperature of his blood was raised above the normal standard of 98° to 112°, or reduced below it to 60°, death in either cases would inevitably ensue. But man, peculiar degree and to a marvellous extent, possesses the powerof enduring extreme natural variations of atmospheric temperature, and of artificial also. Although water boils at a temperature of 212°, and his own body is maintained at a normal standard of 98°, he can endure habitual exposure to an artificial
temperature of dry air as high as from 300° to 600°. Of this many instances may be noticed. Carpenter says:
Many instances are on record of heat of from 250° to 280° being endured in dry air for a considerable length of time, even by persons unaccustomed to a particularly high temperature; and persons whose occupations are such as to require it, can sustain a much higher degree of heat, though not perhaps for any long period. The workmen of the late Sir F. Chantrey have been accustomed to enter a furnace in which his moulds were dried, whilst the floor was red-hot, and a thermometer in the air stood at 360°; and Chabert, the 'Fire-king,' was in the habit of entering an oven, whose temperature was from 400° to 600°.”—Human Physiology, third edition, par. 888.
Men engaged in various branches of manufacturing industry, such as in Iron-foundries, Glass-houses, Ore-smelting, &c., are habitually exposed for lengthened periods to degrees of Heat ranging from 200° to 300°, and even higher, which they are able to sustain regularly without any detriment to health,
Now the explanation of this is simple, and serves to illustrate the admirable organism of the skin as adapted to act beneficially as a curative medium in disease. The temperature of the surface of the skin is regulated by Exhalation and Evaporation. There are, as we before observed, a vast number of glandulæ spread over the inner surface of the cutis vera or true skin, for the purpose of secreting an aqueous fluid for Exhalation. Whatever the temperature of the atmosphere may be above the normal standard, in a degree corresponding therewith is the stimulating action on the secreting glandule of the skin. At high temperatures the secretions are proportionably excited. Exhalation is copious. Evaporation takes place rapidly, and thus the skin surface is kept moist and cool. Such is the provision Nature has made to enable man to bear without injury such elevated temperatures as we have noticed.
It follows, therefore, that the capacity of the human body to endure high temperatures with impunity must be measured by the powers of Exhalation and Evaporation its cutaneous organism possesses. Because, were the skin torpid or paralysed so as not to secrete and exhale sufficently, the action of the
heat on the skin surface would become unbearable, and if the atmosphere was so charged with moisture that it could contain no more, the transuded perspiration could not, of course, be evaporated, and consequently, as vapour scalds at 120°, death by scalding would result.
Thus, for example, water boils at 2120, when what we call "steam" is formed, but all the coal in England, if heaped into one monster fire, could not raise the temperature of water one degree above 212°, as long as the steam is allowed to pass away by evaporation or otherwise. And just so with the human body. Man can endure a temperature of 300° or 600° with impunity for a time, provided his skin organism acts freely, and the perspiration that exhales to the surface is freely evaporated, but not otherwise.
In further illustration of this important function of the skin we may adduce a very simple experiment that has been repeatedly verified, though apparently of so marvellous a character as likely at first to excite general incredulity. A man can sit, with complete impunity, in a Hot-Air Bath raised to a temperature sufficiently high to bake bread or cook a beefsteak! Erasmus Wilson testifies that he sat without the slightest inconvenience in a Bath at 240°, that is 28 degrees above the boiling water point. And he says, "if I had had bread, or meat, or eggs with me, they must necessarily have. been cooked at that Heat." Now why is a beefsteak or mutton chop cooked in a Hot-Air Bath, the high temperature of which the human body can endure with perfect impunity-nay pleasure? Simply because the human skin acts in the manner we have described, so as to keep the temperature of the body at the normal standard by the Exhalation and Evaporation of its superabundant Heat. Not so, however, with the beef or mutton: It has ceased to be living matter, and has thus lost its preservative properties. Consequently the Heat gradually penetrates into and permeates the whole substance, thereby effecting the chemical change known as baking or cooking. Thus we have exemplified how remarkable the difference is in the action of Heat on living and dead organic matter.