Volume 2

Health lectures for the people.

Date:
1883-1892
Catalogue details

Licence: Public Domain Mark

Credit: Health lectures for the people. Source: Wellcome Collection.

    67/600 (page 55)
    bringing close to the surface of the body a great extent of blood- vessels, just as in mountainous Scotland there is a much greater superficial area for streams and water-courses than if our country- were a level plain. There are also networks of vessels surrounding the glands and hair roots. The blood-vessels are not equally full at all times. They contract under the influence of cold, and dilate when heat or irritants are applied. They are still further emptied of their contents when they are constricted in consequence of contractions of the involuntary muscular fibres in the true skin. The effect of nervous influence also upon them is great. The flush of shame, the pallor of fear are caused by opposite conditions of these vessels effected directly through the nervous system. As fluids are very good conductors of heat, we have in such an extensive system of blood-vessels, so near the surface and communicating with all parts of the body, a ready channel for applying heat to, or of abstracting it from the system. There is another extensive system of vessels- -the lympJiatics. These accompany the blood- vessels more or less closely. The latter convey to the skin the requisite nourishment, but the lymphatics are associated with them in conveying from it waste material produced in the performance of its functions. If the skin is healthy the waste products are normal, but if the functions of the skin are inter- fered with, these products may be morbid, and sometimes are hurtful to the system. If with an ordinary pocket lens we examine the point of one of the fingers we may observe on the ridges of the skin a number of small dark spots (fig. 3). These are the orifices of the sweat glands. With the unaided Fis;. 3. Magnified view of the point of one of the fingers showing ridges and furrows. The round spots are the openings of sweat glands.