The Skin : Part 1

Hygienic Physiology: with Special Reference to the Use of Alcoholic Drinks and Narcotics
by Joel Dorman Steele, Ph.D.

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A protection from the outer world, it is our only means of communicating with it. Insensible itself, it is the organ of touch. It feels the pressure of a hair, yet bears the weight of the body. It yields to every motion of that which it wraps and holds in place. It hides from view the delicate organs within, yet the faintest tint of a thought shines through, while the soul paints upon it, as on a canvas, the richest and rarest of colors.

The Skin is a tough, thin, close-fitting garment for the protection of the tender flesh. Its perfect elasticity beautifully adapts it to every motion of the body. We should learn hereafter that it is more than a mere covering, being an active organ, which does its part in the work of keeping in order the house in which we live. It oils itself to preserve its smoothness and delicacy, replaces itself as fast as it wears out, and is at once the perfection of use and beauty.

1. Structure of the Skin

Cutis And Cuticle. - What we commonly call the skin - viz., the part raised by a blister - is only the cuticle nor gives rise to pain, neither suffers from heat nor feels the cold.

The cuticle is composed of small, flat cells or scales. These are constantly shed from the surface in the form of scurf, dandruff, etc., but are as constantly renewed from the cutis below.

Under the microscope, we can see the round cells of the cuticle, and how they are flattened and hardened as they are forced to the surface. The immense number of these cells surpasses comprehension. In one square inch of the cuticle, counting only those in a single layer, there are over a billion horny scales, each complete in itself. - Harting.

Value of the Cuticle. - In the palm of the hand, the sole of the foot, and other parts especially liable to injury, the cuticle is very thick. This is a most admirable provision for their protection. By use, it becomes callous and horny. The boy who goes out barefoot for the first time, "treading as if on eggs," can soon run where he pleases among thistles and over stones. The blacksmith handles hot iron without pain, while the mason lays stones and works in lime, without scratching or corroding his flesh.

The Complexion. - In the freshly made cells on the lower side of the cuticle, is a pigment composed of tiny grains. In the varying tint of this coloring matter, lies the difference of hue between the blonde and the brunette, the European and the African. In the purest complexion, there is some of this pigment, which, however, disappears as the fresh, round, soft cells next the cutis change into the old, flat, horny scales at the surface.

Scars are white, because this part of the cuticle is not restored. The sun has a powerful effect upon the coloring matter, and so we readily "tan" on exposure to its rays. If the color gathers in spots, it forms freckles.

2. Hair And Nails

The Hair and the Nails are modified forms of the cuticle.

The Hair is a protection from heat and cold, and shields the head from blows. It is found on nearly all parts of the body, except the palms of the hands and the soles of the feet. The outside of a hair is hard and compact, and consists of a layer of colorless scales, which overlie one another like the shingles of a house; the interior is porous, and probably conveys the liquids by which it is nourished.

Each hair grows from a tiny bulb, which is an elevation of the cutis at the bottom of a little hollow in the skin. From the surface of this bulb, the hair is produced, like the cuticle, by the constant formation of new cells at the bottom. When the hair is pulled out, this bulb, if uninjured, will produce a new one; but, when once destroyed, it will never grow again. The hair has been known to whiten in a single night by fear, fright, or nervous excitement. When the color has once changed, it can not be restored.

Wherever hair exists, tiny muscles are found, interlaced among the fibers of the skin. These, when contracting under the influence of cold or electricity, pucker up the skin, and cause the hair to stand on end. The hairs themselves are destitute of feeling. Nerves, however, are found in the hollows in which the hair is rooted, and so one feels pain when it is pulled. Therefore the insensible hairs become wonderfully delicate instruments to convey an impression of even the slightest touch.

Next to the teeth and bones, the hair is the least destructible part of the body, and its color is often preserved for many years after the other portions have gone to decay.

The Nails protect the ends of the tender finger, and toe, and give us power more firmly to grasp and easily to pick up any object we may desire. They enable us to perform a hundred little, mechanical acts which else were impossible. At the same time, their delicate color and beautiful outline give a finish of ornament to that exquisite instrument, the hand. The nail is firmly set in a groove (matrix) in the cuticle, from which it grows at the root in length and from beneath in thickness. So long as the matrix at the root is uninjured, the nail will be replaced after any accident.

3. The Mucous Membrane

Structure. - At the edges of the openings into the body, the skin seems to stop and give place to a tissue which is redder, more sensitive, more liable to bleed, and is moistened by a fluid, or mucus, as it is called. Really, however, the skin does not cease, but passes into a more delicate covering of the same general structure, viz., an outer, hard, bloodless, insensible layer, and an inner, soft, sanguine, nervous one. Therefore every part of the body is wrapped in a kind of double bag, made of tough skin on the outside, and tender mucous membrane on the inside.

Connective Tissue. - The cutis and the corresponding layer of the mucous membrane consist chiefly of a fibrous substance interlaced, like felt. It is called connective tissue, because it connects all the different parts of the body. It spreads from the cutis, invests muscles, bones, and cartilages, and thence passes into the mucous membrane. So thoroughly does it permeate the body, that, if the other tissues were destroyed, it would give a perfect model of every organ. It can be seen in a piece of meat as a delicate substance lying between the layers of muscle, where it serves to bind together the numerous fibers of which they are composed.