An academic physiology and hygiene .. . and straightened out, itwould be about 1V of an inchlong. Careful computations havefixed the total number of thesweat-glands at nearly 2,400,000;and hence their united lengthwould be about two and a halfmiles. 12. In some parts of the skinthese glands are very numerous ;on the palms and soles there areabout 2,700 in each square inch, Fig. View of the and Qn ftit forehead about 1,250Epidermis, showing the Pores. in equal space. In other partsthey are less numerous; the cheeks have but 550 in asquare inch, while the neck and back have still f
An academic physiology and hygiene .. . and straightened out, itwould be about 1V of an inchlong. Careful computations havefixed the total number of thesweat-glands at nearly 2,400,000;and hence their united lengthwould be about two and a halfmiles. 12. In some parts of the skinthese glands are very numerous ;on the palms and soles there areabout 2,700 in each square inch, Fig. View of the and Qn ftit forehead about 1,250Epidermis, showing the Pores. in equal space. In other partsthey are less numerous; the cheeks have but 550 in asquare inch, while the neck and back have still the sweat-glands is a network of capillaryvessels, and from the blood in these vessels water andrefuse matter in the form of carbonic acid, fatty acids,ammonia salts, etc., are filtered into the glands and castout through their ducts. This water and these impuritiesconstitute the sweat, or perspiration. 13. Forms and Quantity of Perspiration. — The sweat-glandssecrete constantly, and under ordinary circumstances the. THE SKIN, CLOTHING, AM) BATHING. 28l sweat is given off in so small an amount that it docs notcollect in drops, but evaporai soon as it reaches the surface. This is called insensible perspiration^ because itis not perceptible by sight or by touch. It is only whenthe body is exposed to a high temperature or heated byexercise that the perspiration manifests itself to sight andtouch, and becomes what is termed sensible perspiration. 14. Though the glands are very small, their great num-ber gives a vast secreting surface, and their millions ofducts pour out fluid nearly equal in quantity to that sentout by the kidneys. The amount of perspiration within jiven time varies according to the temperature andmoisture or dryness of the air, amount of exercise, quan-tity and quality of food and drink, etc. Results of care-ful experiments agree, however, in placing the daily per-ation in the average person in good health at twopounds, or two pints ; and yet ha
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