Sweat Gland

Arthur C. Custance, Ph.D.

In the Sweat of Thy Brow

Scripture has very little indeed to say about sweating, but what it does say is remarkably significant. This significance is only apparent when one has learned something about the intricacies of the sweating mechanisms physiologically considered.

Hence a very large part of this paper is occupied with things physiological. But several interesting lines of thought develop in the process with respect to the relationship between man and the animals, and between fear and pain.

By reason of its consideration of other forms of sweating than that elicited by heat, such as emotional and mental sweating, this paper may serve an incidental purpose, namely, to introduce any reader unacquainted with the subject to the possibilities of research from a number of different points of view both physiological and psychological.


1. Animal Human Sweating

2. Sweating of Fallen Man

3. Uniqueness of the Brow

Appendix: A Guide to Scientific Literature


First published in 1962 under the title The Meaning of Sweat as Part of the Curse

Included in
The Flood: Local or Global? published in 1977 by Zondervan Publishing Company

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1. Animal and Human Sweating

Most of us object to sweating - particularly when others do it!   Even the word itself is distasteful. Yet it is an absolutely vital function of the normal healthy body, and ectodermal displasiacs - those unfortunate individuals who have impaired or inactive sweat glands - are in a most dangerous situation.   The slightest exercise or a rise in environmental temperature above what is called the "comfort zone" will endanger their lives very rapidly indeed.   The resulting elevation of body temperature can occur in a very few minutes and reach fever heights, and there is absolutely nothing they can do about it except by using artificial cooling devices.   In childhood such people (fortunately rare) have to be watched continually.

So efficient, on the other hand, is the thermoregulatory mechanism of sweating in normal people that we seldom experience more than slight discomfort over a wide range of environmental temperatures, a fact which enables man to live anywhere on the earth.   Indeed, for something like twenty minutes a man can survive temperatures as high as 260 degrees F - high enough to broil a steak in the same cubicle with him, provided the air is absolutely dry so that all his sweat is evaporated.

Under normal circumstances, the sweating mechanism is centrally regulated in the body through the hypothalamus.   This "human thermostat," as Benzinger has called it, is so finely adjusted that a rise of only 0.01 degrees C in what is termed the deep body temperature results in a compensatory increase in thermal sweating for evaporative cooling equal to 1/1000 of a Calorie per minute.   So, as Kuno (probably the world's greatest authority in this field) has said, a man is beautifully equipped physiologically to prevent any rise in body temperature.

Thermal sweat is one of the purest body fluids, containing less than 1 percent of substances other than water.   It is completely odourless unless bacteria are allowed to grow in it.   It can be copious indeed, and the weight loss via this avenue may be considerable without any injury to the subject.   I have myself lost four pounds in one hour on a treadmill in our own laboratories!   Since one gram of water evaporated removes 0.58 Calories of heat from the body, this hourly rate was ridding me of close to 1,000 Calories.   In a crude kind of a way, this is equivalent to the heat energy of a good meal, all within one hour!   Indeed, because the body produces this fluid secretion so readily during exercise, it can become a serious hazard in the Arctic: while dry clothing may be warm, wet clothing most certainly is not.   Dr. Paul A. Siple of Antarctic renown pointed out to me the paradoxical truth that on this account the only way to keep warm in the Arctic is to keep cool!

But in what way is man unique in this respect? Don't animals sweat profusely - horses, for example?   In spite of appearances to the contrary, animals are not equipped by nature as man is to achieve thermoregulation by sweating.   The literature on this subject is voluminous.   I have in my files a bibliography of at least three thousand works dealing with sweating, and this does not include a comparable literature to be found in other languages such as German, Russian, and Japanese.   Sweating seems like such a simple, straightforward phenomenon; in reality it is a highly complex subject.   Let us consider very briefly what we know about it, more particularly with reference to humans, drawing in part upon the thousands of experiments we have performed in our own laboratories over the past years, using soldiers as subjects.

To begin with, we sweat for a number of different reasons, and this allows us to classify the reaction under at least six headings.   There is thermal sweating which enables us to maintain a safe body temperature.   There is mental sweating, whose function is only partially understood but which is always found to parallel quite exactly the level of mental effort.   Emotional sweating, as the name implies, occurs in response to excitement, fear, anxiety, and a multitude of other disturbed states.   The omission of pain in this list of stimuli to emotional sweating is intentional; we shall discuss why subsequently.   Another form of sweating is termed gustatory, resulting from the ingestion of highly spiced foods; its function is not clearly understood.   There is also that reaction known as cold sweat, defined as a form of thermal sweating elicited by a non-thermogenic stimulus.   It has been found to be a very dependable index of motion sickness.   Finally there is sexual sweating, which is well established in animals and for which there is some evidence in humans.   Undoubtedly other distinct types of sweating will be discovered in time, but these at least are known to be highly specific.

The specificity of these types of sweating is not only associated with their innervation - that is, their relationship to the central nervous system - but also their location on the skin surface; briefly the situation is as follows: thermoregulatory sweat glands are distributed over the whole body surface except in a few restricted areas.   Mental sweat glands are limited to the palms and soles, and more specifically to what are appropriately termed the contact points in these areas.   Emotional sweat glands are found in the armpits, technically known as the axillae.   Gustatory sweating is limited almost entirely to the facial area immediately surrounding the mouth.   Cold sweating occurs over the whole body surface involving the thermoregulatory glands.   Sexual sweating appears to be limited chiefly to the axillae, with some representation around the nipples and possibly in the pubic region.

While these areas can be mapped with some measure of exactitude and labeled for the type of sweating which is characteristic of each, there are complications because in certain areas two different types may be found.   Thus, in the palmar region sweating is elicited by mental stimuli such as occur when doing arithmetic, for example, and by emotional stimuli such as fear.   There is, however, no response in spite of all appearances to the contrary to thermal stimuli per se.   In the armpits sweating is elicited by emotional stimuli primarily, but also to some extent by thermal ones.

For those who have not studied physiology, it may help for me to point out that there are two kinds of regulatory processes in the body: those which we can control to some extent (moving the eyes, the limbs, etc., and regulating the breathing), and those over which we have virtually no control (dilation of the pupil, alterations in the condition of the blood vessels relative to the volume of flow, movements of the intestinal tract in digestive processes, heart rate, etc.).   It is difficult to be exact because some of these processes can be brought under control by training and others continue automatically until we decide to do something about them.

However, a further division is made within the group of processes over which we have no control whatever under normal circumstances.   As a class these processes are called "autonomic" since they are self-regulating. Within this autonomic system there are those processes which prepare the body for flight or fight (called "sympathethic") and those which prepare the body for recovery and restoration (called "parasympathetic").   Quite simply, the first class of activities includes an increased pulse rate and breathing rate, dilation of blood vessels leading to the muscles, dilation of the pupils, and a virtual cessation of digestive processes.   The blood supply to the skin and to the digestive system is reduced.   These preparatory and facilitative reactions are beautifully suited for the end in view, namely, to sharpen vision and to provide the muscles with maximum energy and more rapid removal of waste.   One further process which occurs at the same time is the appearance of sweat in the palms and soles.   Everyone is aware that dry hands reduce tactile sensitivity and frictional contact.   The moistening of the hands provides better touch sense and grip: both facilitate action.

When the occasion for flight or fight is passed, the body at once sets about restoring itself.   Since, in the previous condition, it was essential to divert the blood to the muscles, a process facilitated by reducing the blood supply to the intestinal tract, the body did not waste food which had been ingested by allowing it to pass on through, but held it back so that the energy available in the food could be extracted when the time came for transfer to the blood.   In the restoration period, the blood is once more supplied freely to the intestines and digestion is resumed.   Blood is also diverted from the muscles to the skin surface in order to carry the body heat, elevated by increased metabolic activities, to the surface   for cooling.   This cooling process is assisted by the outbreak of sweat, which by means of evaporation removes the heat from the blood before it is returned once more to the heart.   Thus thermal sweating is associated with recovery and restoration. Or, to put it in more technical language, mental and emotional sweating are sympathetic in origin, whereas thermal sweating is parasympathetic.

Animal and Human Sweating   continues ...
 

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Arthur Custance
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by Arthur Custance