Diseases of the skin : a manual for practitioners and students / by W. Allan Jamieson.

  • William Allan Jamieson
Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: Diseases of the skin : a manual for practitioners and students / by W. Allan Jamieson. Source: Wellcome Collection.

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    finer shades of expression. More important as regards the well- bein- of the body are the involuntary muscles. These are not directly under the influence of the will, but contract and relax in response to alterations of temperature, or to mental states, as fear which causes their contraction, and blanches the face- or shame, leading to their relaxation, which permits an overfilling of the vessels of the skin, and the tell-tale blush appears. . Those involuntary muscles are arranged m various ways. Some obliquely, which, when they contract, compress the com- ponent parts of the skin together and make it thinner. Some lenothwise, at the bases of the papillae: these check or regulate the'outflow of perspiration. Some to the hair glands, embracing the sebaceous follicles : these, when they shorten, make the hairs stand up and squeeze the oil from the oil glands, thus prevent- incr it from drying up, and so choking the apertures. ° When the surface of the body is exposed to cold, these little muscles contract in all directions, and, aided by the muscular fibres of the blood-vessels themselves, which act m concert, lessen the amount of blood in the skin. The production of sweat is at the same time diminished, and the evaporation from the surface being reduced, the natural heat of the body is main- tained. When, on the contrary, we are exposed to heat, either from the sun's rays, or, what is practically the same tiling, when we exert ourselves and thus become warm, these muscles relax, allow more blood to flow to the surface, the sweat glands act with increased energy, the surface becomes moist, and this dampness in drying cools clown the exterior, and maintains the uniform temperature of health. Implanted in the skin at various depths are three species ot glands. One of these provides sweat or perspiration, another an oily material, and a third hair. The sweat glands consist partly of a coiled-up tube lined with secreting cells, and placed deep down in the subcutaneous areolar tissue, among the fat cells ; partly of a long duct also
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