A Treatise on Anatomy, Physiology, and Hygiene Part 42

The oil-tubes are sometimes called the _se-baceous folli-cles_.

[Ill.u.s.tration: 4. A small hair from the scalp, with its oil-glands. The glands (A) form a cl.u.s.ter around the shaft of the hair-tube, (C.) These ducts open into the sheath of the hair, (B.) All the figures, from 1 to 4, are magnified thirty-eight diameters.]

631. What is said of these tubes in the eyelids? In the ear? In the scalp? What are these glands sometimes called?

_Observation._ Among the inhabitants of cities, and especially in persons who have a torpid state of the skin, the contents of the oil-tubes become too dense and dry to escape in the usual manner. Thus it collects, distends the tube, and remains until removed by art. When this impacted matter reaches the surface, dust and smoke mix with it, then it is recognized by small, round, dark spots. These are seen on the forehead, nose, and other parts of the face. When this matter is pressed out, the tube gives it a cylindrical form. The parts around the distended tubes sometimes inflame. This const.i.tutes the disease called, _"acne punc-tata."_

632. The PERSPIRATORY APPARATUS consists of minute cylindrical tubes, which pa.s.s inward through the cuticle, and terminate in the deeper meshes of the cutis vera. In their course, each little tube forms a beautiful spiral coil; and, on arriving at its destination, coils upon itself in such a way as to const.i.tute an oval-shaped, or globular ball, called the _perspiratory gland_.

633. The opening of the perspiratory tube on the surface of the cuticle, namely, "the pores," is also deserving of attention. In consequence of its extremity being a section of a spirally-twisted tube, the aperture is oblique in direction, and possesses all the advantages of a valvular opening, preventing the ingress of foreign injurious substances to the interior of the tube and gland.

634. "To arrive at something like an estimate of the value of the perspiratory system, in relation to the rest of the organism, I counted the perspiratory pores on the palm of the hand, and found 3528 in a square inch. Now each of these pores being the aperture of a little tube about a quarter of an inch long, it follows, that in a square inch of skin on the palm of the hand there exists a length of tube equal to 882 inches, or 73 feet. Surely such an amount of drainage as seventy-three feet in every square inch of skin--a.s.suming this to be the average for the whole body--is something wonderful and the thought naturally intrudes itself, What if this _drainage_ be obstructed?

What is said of the retention of the unctuous matter in the oil-tubes?

632. Of what does the perspiratory apparatus consist? 633. What is peculiar in the opening of the perspiratory tubes on the surface of the cuticle? 634. How many perspiratory pores did Dr. Wilson count upon a square inch of skin on the palm of the hand?

[Ill.u.s.tration: Fig. 116. A perspiratory gland from the palm of the hand, magnified forty diameters. 1, 1, A twisted tube composing the gland. 2, 2, The two excretory ducts from the gland. These unite to form one spiral tube, that perforates the cuticle, (3,) and opens obliquely on its surface at 4. The gland is imbedded in cells filled with fat, which are seen at 5, 5.]

What does fig. 116 represent?

635. "Could we need a stronger argument for enforcing the necessity of attention to the skin? On the pulps of the fingers, where the ridges of the sensitive layer of the true skin are somewhat finer than in the palm of the hand, the number of pores on a square inch a little exceeded that of the palm; and on the heels, where the ridges are coa.r.s.er, the number of pores on the square inch was 2268, and the length of the tube 567 inches, 47 feet.

636. "To obtain an estimate of the length of tube of the perspiratory system of the whole surface of the body, I think that 2800 might be taken as a fair average of the number of pores in the square inch; and consequently, 700, the number of inches in length. _Now, the number of square inches of surface in a man of ordinary height and bulk is 2500; the number of pores, therefore, 7,000,000; and the number of inches of perspiratory tube is 1,750,000; that is, 145,833 feet, or 48,611 yards, or nearly TWENTY-EIGHT miles!_"--_Wilson._

Give other computations in this paragraph. 635. What is said of the number of these pores on the pulp of the fingers? On the heels? 536.

What is an average number of pores and length of tube of the whole surface of the body? Give the summary of the number of pores, and number or inches of perspiratory tube.

CHAPTER x.x.xII.

PHYSIOLOGY OF THE SKIN.

637. The skin invests the whole of the external surface of the body, following all its prominences and curves, and gives protection to all the organs it encloses, while each of its several parts has a distinct use.

638. The cuticle is insensible, and serves as a sheath of protection to the highly sensitive skin (_cutis vera_) situated beneath it. The latter feels; but the former blunts the impression which occasions feeling. In some situations, the cuticle is so dense and thick, as wholly to exclude ordinary impressions. Of this we see an example in the ends of the fingers, where the hard and dense nail is the cuticle modified for the purpose referred to. Were the nervous tissue of the true skin not thus protected, every sensation would be so acute as to be unpleasant, and contact with external bodies would cause pain.

639. The cuticle, also, prevents disease, by impeding the evaporation of the fluids of the true skin, and the absorption of the poisonous vapors, which necessarily attend various employments. It, however, affords protection to the system only when unbroken, and then, to the greatest degree, when covered with a proper amount of oily secretion from the oil-glands.

640. The cuticle is, originally, a transparent fluid, exuded by the blood-vessels, and distributed as a thin layer on the surface of the true skin. While successive layers are formed on the exterior of the true skin, the external cuticular layers are converted into dry, flattened scales, by the evaporation of their fluid contents. The thickness of the cuticle is formed mainly from these scales.

637-656. _Give the physiology of the skin._ 637. What is said of the skin? 638. Give a function of the cuticle. Does it vary in thickness on different parts of the body? Give examples. 630. Mention another use of the cuticle. 640. What is the cuticle originally?

641. The cuticle is, therefore, undergoing a constant process of formation and growth at its under part, to compensate for the wear that is taking place continually on its surface. A proper thickness of the cuticle is in this manner preserved; the faculty of sensation and that of touch are properly regulated; the places of the little scales, which are continually falling off under the united influence of friction and ablution, are supplied; and an action necessary, not merely to the health of the skin, but to that of the entire body, is established.

642. Whenever the cuticle is exposed to moderate and repeated friction, it becomes thicker and tougher, as may be seen in the cuticle of the lady's finger that plies the needle and in the hard or callous appearance of the hands of farmers masons, and other mechanics. This enables them to handle the utensils and materials used in their vocations without pain or inconvenience.

_Observations._ 1st. When the joints of the feet are subjected to moderate and continued pressure or friction, frequently one or more of the papill enlarge. This is accompanied with a thickening of the layers of the cuticle, which is termed a "callosity," or "corn." These thickened layers of the cuticle are broad at the top and narrow at the bottom, and the enlarged ma.s.s is conical, with the point innermost.

When pressed upon by a tight shoe, these sensitive papill cause pain.

How is the thickness of the cuticle mainly formed? 641. Describe the changes of this membrane. Show the necessity of this constant growth.

642. How does moderate and repeated friction affect the cuticle? Give examples. What is the benefit derived from having the cuticle thus changed? What is the result if the joints of the feet are subjected to moderate and continued pressure? What is the form of a "corn"?

2d. To remove these painful excrescences, take a thick piece of soft leather, somewhat larger than the corn; in the centre punch a hole of the size of the summit of the corn, spread the leather with adhesive plaster, and apply it around the corn. The hole in the leather may be filled with a paste made of soda and soap, on going to bed. In the morning, remove it, and wash with warm water. Repeat this for several successive nights, and the corn will be removed. The only precaution is, not to repeat the application so as to cause pain.

643. Let a person unaccustomed to manual labor, trundle the hand-cart, or row a boat, for several successive hours, and the cuticle upon the palms of the hands, instead of becoming thicker by use, is frequently separated from the subjacent tissues, by an effusion of serum, (water,) thrown out by the vessels of the true skin. Had the friction been moderate, and applied at regular intervals, instead of blisters being formed upon the inside of the hands, material would have been thrown out to form new layers upon the lower surface of the cuticle.

644. The cuticle is interesting to us in another point of view, as being the seat of the color of the skin. The difference of color between the blonde and the brunette, the European and the African, lies in the cuticle;--in the deeper, and softer, and newly-formed layers of that structure. In the whitest skin, the cells of the cuticle always contain more or less of a peculiar pigment, incorporated with the elementary granules which enter into their composition. In the white races, the pigmentary tint is extremely slight, and less in winter than in the summer season.

In the darker races, on the contrary, it is deep and strongly marked.

How can they be removed? What precaution is given? 643. Explain why those persons unaccustomed to labor, blister their hands in rowing a boat or performing ordinary manual employment for several successive hours. 644. In what other point of view is the cuticle interesting? In what part of it do we find the coloring matter?

645. The various tints of color exhibited by mankind, are, therefore, referable to the amount of coloring principle contained within the elementary granules of the cuticle, and their consequent depth of hue.

In the negro, the granules are more or less black; in the European of the south, they are amber-colored; and in the inhabitants of the north, they are pale and almost colorless.

646. Color of the skin has relation to energy in its action; thus, in the equatorial region, where light and heat are most powerful, the skin is stimulated by these agents to vigorous action, and color is very deep; while in the temperate regions, where light and heat are not so intense, the lungs, liver, and kidneys relieve the skin of part of its duties. The colored layer of the cuticle has been called the _rete mu-cosum_, (mucous coat of the skin,) and described as a distinct layer by many physiologists.

_Observation._ "The various coloring of the inner layer of the cuticle gives to some animals their varied hues; the serpent, the frog, the lizard, and some fishes have a splendor of hue almost equal to polished metal. The gold-fish and the dolphin owe their difference of color and the brilliancy of their hues to the color of this layer of the skin."