The hygiene of the skin / by J.L. Milton.

  • Milton, J. L. (John Laws), 1820-1898.
Date:
1890
    scarf-skin can, indeed, be artificially separated from each other, but in a state of nature they are inextricably con- nected, and those of the true skin are still more closely united. Perhaps this brief account will enable the reader to appraise, at its just value, the truth of the report about a late distinguished personage having one skin too few, such a state being simply inconceivable. The scarf-skin is so necessary to the true skin, and the entire membrane so necessary to the structures which lie below it, that life could not go on for twelve hours in the absence of either of them, and there is no other skin. This wonderful covering, without which man would be a hideous spectre, incapable of communicating with the ex- ternal world, is pierced in almost innumerable places for the passage of the sweat ducts. These lead from the sweat glands, small, roundish, yellow bodies seated on the under surface of the true skin and on the fat lying underneath, and open on the outer surface of the scarf-skin. The duct is a very fine elastic tube, which thus pierces both skins and opens by an orifice slightly wider than the tube itself \ at its lower end it is rolled up as a fine thread might be. Slender as the sweat duct is, it yet possesses three coatings, an invest- ment of connective tissue, a proper membrane, and an epithelial lining of cells. Some of the larger sweat ducts, e.g., those in the arm-pits, where they are found in great numbers, have a layer of plain muscular fibre cells between the two last coats. These larger ducts arise, too, from larger glands of more complicated structure than the others, and with semi-fluid contents. Though I have spoken of them as almost innumerable, their numbers could be ascertained by
    a rough computation; thus we can, with the aid of a plaster cast, find how many there are on a square inch of the skin, and the entire superficies of the skin could, of course, be measured in an individual case, supposing it were worth the trouble to do so. One author, taking as his starting point two separate square inches on different parts of the skin, computes the number of these tiny aqueducts at seven millions ; but inasmuch as the proportion of pores to a given surface varies in every part of the body, and as the same amount of surface would not be found twice in fifty people, it must be obvious that any such resultant might just as easily as not be wrong by some millions. Their great numerical extent can for all reasonable purposes be inferred from the statement that, according to one author there are upwards of 3,500 of them, but, according to a much more accurate writer, Krause, 2,800 in a square inch on the palm of the hand, where they are very densely set, and as many as 400 to 600 in the same amount of surface on the back and lower limbs, where they are most sparsely distributed. Beyond this, all attempts at calculation must be sheer waste of time, seeing that an average cannot be struck with even an approach to accuracy. These numerous tubes carry off both the visible perspiration, or sweat, and the invisible, called transpiration—a sort of perpetual but unseen and unheard breathing from the skin, which, though unnoticed, rids the system of a bulk of poisonous fluid, ranging from a pound and a quarter to three pounds and a half in the twenty-four hours, an average being 8 8 grains per minute, equal to a little over two pounds daily, or more than half as much again as passes off by the lungs. This B
    excretion is so contaminated with carbonic acid gas, that when a burning candle is introduced into the air of a vessel in which the hand or foot has been confined for an hour, the flame begins to burn dim, and Jurine found that air, kept for a time in contact with the skin, consisted almost exclusively of carbonic acid. M. Edwards considers that part of the water is carried off from the skin by mere physical evaporation, the same as would take place from a dead body, and that when the temperature of the air is not above 68 deg. Fahrenheit, the vital transpiration does not expel more than an eighth of the whole amount. Embedded in the lower part of the true skin we find little glands which secrete a suety fluid, known as sebum or sebaceous fluid, from the latin name for suet. These glands, especially numerous in the scalp, are groups of minute rounded bags, or sacculi, and, except in a few parts of the skin of no great extent, they all open into the sheaths of the hairs, by means of which they find their way to the surface, the largest of the glands sometimes emptying where the hairs are very small. The following is the constitution of this fluid :—In round numbers one-fourth is made up of fat, and one-fifth of phosphate of lime, a salt which enters largely into the composition of bones and the scurf of the horse's skin. The rest consists of what is called ozmazone, with traces of oil, watery extract, albumen (a substance analogous to white of egg), casein, and carbonate of lime. Traces of acetate of soda and chloride of sodium (common salt) are also found. In the midst of all this, the micro- scopist often observes, living apparently quite at its ease, a very minute eight-legged animal called the acarus, or
    steatozoon, of the follicles, from the hundred and thirtieth to the eightieth of an inch in length, and about the five hundredth of an inch broad. The reader may be interested to know how such a ques- tion, as the amount of fluid poured out by well-nigh count- less tubes scattered over a large and unequal area like that presented by the human frame, can be determined with accuracy, and a short narrative of the method employed will help to show the vast amount of labour and self-denial which have been directed to the investigation of physiology. The process was as follows :—A famous philosopher in his day, Seguin, shut himself up in a bag of gummed silk, tied above his head, and having an opening only for his mouth, provided with a copper mouthpiece. The edges of this opening were hermetically fixed round the mouth with a mixture of turpentine and pitch. He was then weighed in a very fine balance, and at the end of a certain time weighed again. All loss, except that from the lungs by the mouth, being thus prevented, it became possible to ascer- tain by this means how much the lungs threw off per hour. He was then weighed without the bag, and, after the expira- tion of a fixed period, the entire loss per hour was ascer- tained by another weighing. Subtracting the quantity given by the first experiment from that yielded by the second, the balance would represent the loss by the skin, and this observation was farther corrected by weighing all the other excretions together against the amount of food and drink. Notice has probably been taken of the statement that a sort of breathing goes on from the skin, and it is considered
    by some writers that this process maintains heat, and is, therefore, supplementary to the respiration carried on by the lungs; a supposition which they think is borne out by the fact that in many of the lower animals, the mingling of the oxygen of the atmosphere with their blood, which is so essential to life, is in a great measure effected through the skin. Animals, whose skins have been varnished over, have died rapidly and with blood imperfectly reddened. It has also been taught that perspiration reduces morbid heat of the skin, as when it occurs in fever; also that it enables men to support the excessively high temperature to which Blagden, Fordyce, and some observers have exposed them- selves in their experiments. The latter opinion seems to some extent based on a mis- conception. Perspiration in a feverish state ensues because the fever itself is lessened. As to the experiments of Blagden, it may be remarked that the exhaled fluid cannot act the only part in which it is likely to be useful, that of a non-conductor, and the heat, so far as it reaches the skin, must equally reach it whether in a perspiring state or not. But the fact is that the surface, in these trials, is in a great measure protected against the action of heat by thick non- conducting materials, and what is resisted seems to be non- effective by reason of the vital power; for the dead body is affected by heat just as a like mass of inorganic matter would be, and the exudation of fluid from its surface, when exposed to heat, would not prevent such a rise of the tem- perature as must soon prove fatal to life. The explanation of the relief afforded by perspiration I believe to be that given in the " Laws of Life " with reference to many facts