. A manual of practical hygiene. opic absorption beingat least double in proportion to its weight,and quadruple in proportion to its surface. This property of hygroscopically absorb-ing water is a most important one. Duringperspiration the evaporation from the sur-face of the body is necessary to reduce theheat which is generated by the the exercise is finished, the evapora-tion still goes on, and, as already noticed,to such an extent as to chill the dry woollen clothing is put on afterexertion, the vapor from the surface of thebody is condensed in the wool, and gives
. A manual of practical hygiene. opic absorption beingat least double in proportion to its weight,and quadruple in proportion to its surface. This property of hygroscopically absorb-ing water is a most important one. Duringperspiration the evaporation from the sur-face of the body is necessary to reduce theheat which is generated by the the exercise is finished, the evapora-tion still goes on, and, as already noticed,to such an extent as to chill the dry woollen clothing is put on afterexertion, the vapor from the surface of thebody is condensed in the wool, and gives outagain the large amount of heat which had be-come latent when the water was a woollen covering, from this causealone, at once feels warm when used during sweating. In the case of cottonand linen the perspiration passes through them, and evaporates from the ex-ternal surface without condensation ; the loss of heat then continues. Thesefacts make it plain why dry woollen clothes are so useful after Fig. 97.—Wool x 2S5. 1 Pettenkofer gives (Zt. fur Biol., Band i., p. 185) some experiments showing the hy-groscopic power of wool as compared, with linen. He shows that linen not only absorbsmuch less water, but parts with it much more quickly ; thus, to cite one experiment^ 78 PRACTICAL HYGIENE. In addition to this, the texture of wool is warmer, from its bad conduct-ing power, and it is less easily penetrated by cold winds. The disadvantageof wool is the way in which its soft fibre shrinks in washing, and after atime becomes smaller, harder, and probably less In the choice of woollen underclothing the touch is a great guide. Thereshould be smoothness and great softness of texture ; to the eye the tex-ture should be close ; the hairs standing out from the surface of equallength, not long and straggling. The heavier the substance is, in a givenbulk, the better. In the case of blankets, the softness, thickness, and close-ness of the pile,
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Keywords: ., bookcentury1800, bookdecade1880, booksubjecthygiene, bookyear1883
