THE HEAT OF THE BODY 



119 



water before handling. Test the strength of each cloth. Which 

 cloth holds together the best? 



Burning Test. Using the five kinds of cloth, light each piece 

 separately. Notice the odor and rapidity of burning. Repeat 

 the test, holding strip 

 of moist blue litmus 

 paper in the smoke 

 given off by the cloth. 

 What happens? Do 

 the same with moist 

 red litmus paper. What 

 happens? Sum up all 

 your observations in 

 your workbook. 



\\ool fibers 



Cottoia fibers 



flax fibers 



silk fibers- 



What These Ex- 

 periments Show. 



Wool fiber because of 

 its scales gives gar- 

 ments their rough 

 texture. When such 

 fibers shrink, as they 

 may when passing 

 from hot to cold 

 water or to water 



containing such a substance as lye, the scales cause the 

 fibers to stick close together. Wool undergarments ab- 

 sorb moisture and allow it to evaporate slowly. This 

 prevents rapid loss of body heat. Cotton underwear 

 leaves an excess of moisture on the skin and the mois- 

 ture may evaporate rapidly, thus chilling the body. The 

 twist in the cotton fibers serves the same purpose as the 

 scales on the wool : it gives spring and elasticity to 

 the material. Cotton fabrics are harder than wool, and 

 there are fewer air spaces in cotton materials than in wool, 

 hence cotton garments permit heat to escape more rapidly 

 from the body. Linen fibers have little elasticity and 

 hence the fabrics manufactured from them do not shape 



