the functions of the skin are seriously interfered with," says Miller, in his Organic Chemistry, "it usually happens that derangements, more or less serious, either of the kidneys or of the lungs occur." And just as that interference is permitted to continue-in proportion as it is perniciously prolonged-so will functional derangements of the internal organism be intensified and rendered organic and incurable.

Dr. Copland, in his edition of Richrand's Physiology, refers to cases that came under his own observation which remarkably illustrated the vital functions of the skin. "The lungs," he says, "were partly destroyed from an imposthume, and the side of the chest was consequently contracted." Nevertheless, he found that the cutaneous functions increased so as to supply the deficiency caused by impaired lung-action. All subsequent experience has tended to establish the potent agency of the skin, not only as an assistant to the Lungs," but also to the whole excretory organism; for it is a well-established fact that there is an anatomical connection between the mucous membrane which lines our internal organism, and the external mucous membrane, or true skin, which covers the whole body. As Carpenter remarks, "the general term Mucous Membrane may be applied to that great system of membraneous expansions, which forms the external tegument or skin-the lining of the internal cavities whose walls are continuous with it, or Mucous Membrane proper and the prolongation of this into the secreting organs, forming the tubes and follicles of the glands."* Hence, Erasmus Wilson has observed, that "the lungs are nothing but a bit of skin turned in, just as the internal surface of the lung would become skin if it were exposed externally."

Unfortunately, however, medical practitioners have not heretofore properly understood the functions of the skin, and, therefore, did not seek to make them available as sound physiology and pathology now dictate. The skin was not regarded as supplying a medium through which deranged internal organism could be easily reached and remedially acted on, but was

* Human Physiology, 2nd edit., par. 176.

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.

CHAPTER VIII.

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 100o 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, in a peculiar degree and to a marvellous extent, possesses the power of 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:

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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 glandulæ 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