Under normal conditions we daily lose a certain amount of water and also of gaseous and solid products, among them many harmful ones, through the invisible and insensible perspiration of the skin. That such a process does actually take place is proved by our personal observation and by the disagreeable feeling produced in cold and damp weather by the checking of such perspiration. We can even be seriously affected if by disease or by extensive burns a large portion of the skin be destroyed, thus abolishing this insensible perspiration.
The invisible and insensible perspiration can become visible and sensible when either its evaporation into the air is checked, as in the case of tight-fitting clothing, such as a rubber overcoat, or when the temperature of the medium around the body is raised. Both conditions can be fulfilled by fur clothing, for which reason its use as wearing apparel is to be deprecated.
When in a state of perspiration we should take special care that the passage of the perspiratory products into the air shall not be impeded by any means. Fur garments are not so unsuitable for old people in whom the perspiratory functions of the skin are much diminished. We have, in this connection, observed an old lady of 76 sitting at the dinner table, close to an overheated fireplace, and wearing a large fur collarette, in which she felt quite comfortable. As frequently mentioned in this book, in old age there is a degeneration of the thyroid gland to a greater or lesser degree, and consequently a lowering of the temperature of the body and a diminution of the functions of the skin, which is dry and rarely perspires.
When the temperature of the medium which surrounds the body is raised to a high degree, the capillaries of the skin are widened and more blood circulates through them; thus also more blood is conveyed to the sudorific glands, and naturally more water is then excreted by them, and at the same time also more of the solid and harmful products. According to Camerer, the sweat contains in each 100 grammes 50.6 g. ashes, 10 g. fat, and 10 g. nitrogenous matters, of which 30 per cent. is urea and 75 per cent. is ammonia. Uric acid was also found in the sweat of healthy people, but Magnus-Levy found it missing in gouty patients. By frequent sweating procedures the hygienic conditions of the skin can be promoted, and especially so in individuals whose skin is generally dry and inactive. In those who perspire much too freely, however, after several procedures of this kind the overactivity of the sudorific glands can be diminished. After very free perspiration the condition of the skin will be improved, and then we will note the disappearance of certain skin diseases, such as psoriasis in hot summer weather.
Habitual excessive perspiration can, however, impair the skin through the elimination of harmful products, although the skin is, to a certain extent, protected by the greasy matters secreted through the sebaceous glands. Likewise we can also note the loss of hair in persons perspiring very much about the head and more particularly in those parts where the sudorific glands are situated, such as the forehead and temples. This is most frequently observed in those who have dry hair, in whom accordingly there is a diminution of the functions of the sebaceous glands. In persons who wear fur caps and whose head is always covered, we most frequently find bald heads, especially if they have a tendency to perspiring about the head. For this reason it is also more reasonable never to wear hats if we desire to retain as long as possible the natural ornament of the head.
We can cause abundant perspiration by all the various means by which the temperature of the body is raised. In such cases more blood comes to the periphery of the body, and thus also to the sudorific glands. The essential factor is the widening of the capillaries, and this can be produced not only by agencies influencing the body from without, such as hot air or a vapor bath, but also by agencies from within the body which act on the vasomotor centers and thereby cause a widening of the capillaries, such as certain drugs like salicylates, and also organic preparations like thyroid extracts; mental emotion will also cause such an occurrence. Salicylates are excellent drugs for producing abundant perspiration, and are also less dangerous than pilocarpine. After the use of the former and very free perspiration, we notice an improvement in the symptoms of gout, for reasons we will give later.
Of the different baths which are used to induce perspiration we award the preference to electric light baths, where we obtain a double advantage, for we can unite the advantages of perspiration with those of the influence of light upon the body. We are able to prepare such a bath so that the chemically active rays (see chapter on the advantages of sunshine) are obtained. Not only is a very abundant perspiration produced (indeed sometimes about a liter of sweat can be removed from the body in from twenty to twenty-two minutes), but also the processes of oxidation can be augmented. As a consequence we often note a great diminution of fat in persons with a superabundant accumulation of this substance. When in such baths blue light is used and the blue rays are acting in overwhelming quantity, the condition of the nervous system can be influenced in a very favorable way, and especially can excited conditions be calmed. It is also probable that by such sweating procedures toxic products, which are deleterious to the nervous system, can be removed. Perspiration can also be caused by bodily movement through exercise. In such cases, as proved by physiological experiments, impulses are sent to the vasomotor centers, which result in a widening of the capillaries through the excitation of such centers. Thus sweating is created by fast walking, running, and frequently also by horseback riding, and by various kinds of sports, such as cycling. In all these cases it is essential, however, to change the clothes and underwear which we have worn when perspiring, and to take a bath; for the possibility is not to be denied that a part of the toxic products which adhere to the skin after such sweating exercises may be re-absorbed, although we are not in a position to give exact experiments to prove such a supposition.
Taking a bath and using soap and brush, and creating a friction until there is a red reaction of the skin, may then prevent the danger of catching cold, but after such a bath it is most important not to leave with a hot, red skin and opened pores, but to cause their contraction by a quick cold douche, continued at intervals until the skin is cooled and the pores thereby contracted. An energetic friction of the skin must follow before leaving the bathing place.
After such a bath we shall experience a sensation of great comfort, and shall feel much lighter and fresher. Such baths should be taken frequently, at least once a week, and if we are very desirous of keeping a youthful appearance for a long time, even more frequently. In stout people, however, it is necessary for such baths that the muscles of the heart be not degenerated; and also that there should be no serious affection of the heart valves or of the blood-vessels, if baths of a very high temperature and lasting a considerable time are indulged in.
In cases of chronic intoxication and such like diseases of metabolism, such as gout, and in cases of old age, perspiration induced by very hot baths, providing the circulatory system is in good condition, should be tried and given often if the results prove satisfactory, as we thus obtain the benefit of the bath and also of the perspiration.
The sweat baths should not exceed 15 to 20 minutes in duration unless they are well borne, when a few more minutes may be added. In old people cold douches should not be resorted to, but directly after the bath they should be put to bed, which should have been previously warmed by hot-water bottles. In persons where the processes of oxidation are diminished and the skin very inactive, as is the case with many aged people, such baths give very excellent results.
Sweating improves the functions of the kidneys in a much greater degree than those of the skin. By insensible perspiration water is eliminated, together with certain harmful solid products which otherwise would make their way through the kidneys; this occurs much more so when the perspiration is greatly increased by sweating processes. In such cases about a liter of water can pass through the skin daily, and in addition a considerable part of the nitrogenous end-products of metabolism and of common salt. It has been discovered by Professor Hermann Strauss[238] that in a liter of sweat, under favorable circumstances, fully six grammes of common salt can be removed from the body. Leube once found 2.31 grammes of chlorides in 800 grammes of sweat.
Of nitrogenous bodies, according to Strauss, about 2 grammes can be removed through the skin daily, and according to Professor von Noorden[239] only 1 gramme. Leube discovered, about thirty years ago, that the amount of nitrogen in the urine was 2 grammes less on such days as sweating processes had been used than was usual on other occasions. Kovesi and Roth-Schulz found 29 grammes of nitrogen and 29 grammes of common salt in the sweat of patients suffering from Bright’s disease. Strasser and Blumenkranz found, after electric light baths, a considerable increase in the elimination of common salt up to 18 grammes, 4 grammes more than had been ingested. Nitrogenous bodies have also been eliminated in larger quantities than have been introduced, as has also more water. This has been proved in experiments on the effects of bathing, in which people with diseased kidneys have been used as the subjects. In these cases the elimination of common salt and nitrogenous products is certainly greater than in normal individuals. Still there can be no doubt that with such, by perspiration and bathing, an increased elimination of these products can be obtained.
The experiments of Roth-Schulz and Kovesi are most interesting. These authorities discovered, and before them H. Strauss, that the sudorific glands of nephritic patients when in increased activity can secrete a liquid that is more concentrated than the blood. Thus a compensatory action can be obtained. They hold that, through sweating, from 10 to 20 per cent. of the solids in the urine can be eliminated through the skin.
It is also most important that they discovered a reduction in the molecular concentration of the blood, which, as we know, is increased in nephritic conditions. The frequency of sweating processes for persons suffering from affections of the kidneys is all the more indicated because such persons, generally, have a pale and very dry skin, the temperature of which is, as a rule, diminished.
To this great amelioration of the kidney functions by perspiration is also due the fact that gouty patients are much relieved after frequent sweatings. As already mentioned we attribute gout to an alteration of the tissues of the kidneys, by which uric acid is retained. By diverting the end-products of the nitrogenous bodies to the skin and relieving the kidneys of a part of this strain, we may also improve their condition and thereby the gouty element. At the same time, in consequence of these procedures, the excretion of urine has much increased; and this has been going on for several days, not only after the bath, but after the sweating. By such an increased diuresis the condition of gout can also be much improved, as everything that improves the kidneys improves that.
From the observations of Haig, the elimination of uric acid is rendered more difficult by reason of the presence of common salt; the increased elimination, therefore, through the skin must necessarily be more advantageous in the case of gouty people.
There can be no doubt that sweating processes are of great benefit, not only to the kidneys, but also to the other organs, such as the liver.
We also generally observe perspiration in all processes of infection or intoxication, and it may therefore be regarded as a probable species of self-defense of the human body against the attacks of microbes or other toxic products, for it would seem that by this means nature desires spontaneously to get rid of the various toxic matters. Indeed, when we treat fever with salicylates we are assisting nature to this end, for we thus create perspiration. As already mentioned in Chapter III, persons with a dry skin, who perspire but rarely, have less protection from infectious diseases than others. Thus everything supports the theory that the various toxic products, including those from microbes, are eliminated by perspiration. Many years ago we tried to find microbes in the sweat of typhoid fever patients in the St. Pierre Hospital in Brussels, but as has been found in the bacteriological laboratory of the Institute Solvay, the cultures that formed were due to a pollution of the perspiratory products with foreign microbes. The efforts of other authorities have also failed up to now to discover, by exact research, the presence of microbes in sweat, as expressive of their elimination through sweating. But, even if not supported by exact evidence, we feel inclined to believe that by perspiration in abundance a number of toxins of bacterial origin can be eliminated from the blood, because in feverish ailments, after great perspiration, as in the case of pneumonia, a great improvement takes place in the condition of the patient. In former times bleeding gave similar results, perhaps in a greater degree; but in the present day sweating has superseded this.
To the hygiene of the skin through bathing we would wish to add, before concluding this chapter, that carbonic acid baths may also give good results, as they cause a better circulation of the blood through the skin, which gets red. Such baths are also excellent preventatives against arteriosclerosis.