File:The human body and health - an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools (1908) (14586516967).jpg

Identifier: humanbodyhealthe00davi (find matches)
Title: The human body and health : an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools
Year: 1908 (1900s)
Authors: Davison, Alvin, 1868-1915
Subjects: Physiology Hygiene
Publisher: New York : American Book Company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ks. It causednearly 100,000 deaths in the United States in the year1905. Structure of the Skin. — The skin is composed of twolayers, known as the cuticle^ or epidermis^ and the cutis, ortrue skin. The cuticle consists of epithelial cells, the sev-eral upper layers of which have no nuclei and are flat.The deeper cells are cubical. No blood vessels or nervesare present, but every square inch is pierced by a hundredor more tubes leading from sweat glands. Under a mag-nifying glass, the mouths of these appear as minute pitsarranged in rows on the little ridges in the palm of thehand. The cells on the surface of the epidermis are be-ing constantly shed, while new ones are being developedfrom the lower layers. In caterpillars, crabs, frogs, andsnakes the cells on the surface of the skin hold together STRUCTUUE OF THE HKIN 179 and are shed in one entire mass. The use of the epider-mis is to prevent injuries to the more delicate structuresbeneath and to keep germs from entering the tissues.
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Fig. 115. — Section through the skin, a, dead epidermis; c?, live epidermis:all below is the derma or true skin, ar, artery seen dividing into capillariesagain uniting to form a vein ; e, sweat glands; /, fat cells; n, nerve endings. The cutis^ or derma^ lies beneath the epidermis andconsists of a tough elastic network of fibers mingled witha few cells. In it are numerous capillaries and the end- 180 THE EXCKETOKY SYSTEM ings of nerves, some of which are acted on by heat, someby cold, and others by touch. The skin is bound to theunderlying muscles and fatty tissue by a loose elasticconnective tissue. Use of the Skin. — The epidermis prevents injury to themore delicate structures beneath. Touching the nakednerve endings would cause pain, and contact with roughmaterial would destroy them and break the delicate wallsof the blood capillaries. This may be observed on any rawsurface. The dry and liorny nature of the epitheliumexcludes germs and poisons with which the body frequentlycome

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