142 



RELATION OF HEAT TO COMFORT 



year round, regardless of the temperature of our sur- 

 roundings. How does the body maintain this con- 

 stant temperature? The temperature of the body is 

 regulated largely by means of the activity of the 

 sweat glands. Beneath the surface of the body are 

 tiny blood vessels, many of them surrounding the 

 sweat glands. As the temperature of the air around 

 the body increases or when muscular activity is in- 

 creased through exercise or work, the blood is heated. 

 This increases circulation and thus causes the blood 

 vessels to expand; this change in turn stimulates the 

 sweat glands to secrete more perspiration. The evap- 

 oration of more perspiration cools the skin, and the 

 cooling of the skin in turn cools the blood. In this way 

 the body maintains an even temperature. 



What is the scientific reason for wearing different 

 kinds of clothing in different seasons of the year? 

 Clothing does not furnish heat to the body. Heat is 

 obtained in the body by oxidation of the food that 

 we eat. Clothing simply helps the body to retain or 

 lose heat. 



The value of clothing is generally considered from 

 two standpoints : its ability to conduct heat from the 

 body and its power of absorbing moisture. In win- 

 ter our problem is to find clothing that is a poor con- 

 ductor of heat but that will absorb large quantities of 

 moisture. Woolen clothing is widely used for winter 

 wear because it possesses both of these qualities. Since 

 air is a very poor conductor of heat, clothing for 

 winter wear is generally woven so as to contain much 

 air. Do you know why a cotton blanket seems warmer 



than a cotton sheet? In sum- 

 mer linen and cotton fabrics 

 are worn next to the skin be- 

 cause their fibers are better 

 conductors of heat and also 

 because they give up mois- 

 ture to the air quickly, there- 

 by giving a cooling effect to 

 the skin. 



What are the sources of 

 the different types of fibers 

 used for making clothing? 

 The fibers from which cloth- 

 ing is made may be obtained 

 from plants or animals, or 

 they may be produced arti- 

 ficially from inorganic matter. The principal fibers 

 used in this country are cotton, wool, linen, silk, and 

 rayon (artificial silk). 



Cotton is obtained from the cotton plant. The fruit 

 or boll (see Fig. 223) of the cotton plant contains 

 seeds, each of which has fine, white, twisted hairs 

 clinging to it. These fibers enable the wind to dis- 



Int emotional News Photos, Inc. 

 FIG. 223. COTTON BOLL 



tribute the seeds over a wide territory in much the 

 same way as dandelion and milkweed seeds are dis- 

 tributed. These fibers are the raw cotton. The cotton 

 is picked and the seeds are removed by a machine 

 called the cotton gin. Then the fibers are pressed 

 into bales and shipped to cotton mills where they 

 are woven into cloth. More than eight billion square 

 yards of cotton goods are manufactured and used in 

 this country annually. 



International A' ews Photos, Inc. 



FIG. 224. PICKING COTTON 



Cotton fibers are treated and woven in a large 

 number of ways, producing many varieties of cotton 

 fabrics. Each variety is sold under a different name 1 

 such as gingham, calico, flannel, muslin, denim, per- 

 cale, organdie. 



Wool is obtained from sheep. Sheep raising is car- 

 ried on extensively in this country as well as in South 

 America and Australia. The wool is clipped from the 

 animals generally once a year, and then shipped to 

 mills. Here it is sorted, cleaned, and dried. Then it 

 is carded or combed and spun into yarn from which 

 woolen cloth is made. 



If you examine wool under a microscope you will 

 see that it is composed of many cells overlapping each 

 other, which give it a rough, scaly appearance. This 

 characteristic of wool makes it finer and softer than 

 other fibers as the scales of the fibers mat together. 



Linen is a fiber of vegetable origin. Linen fibers 

 are obtained from the inner bark of the flax plant. This 

 plant is cultivated extensively in Ireland and to a lesser 

 extent in other European countries. Irish linen is gen- 

 erally considered to be the best. 



1 Farmers' Bulletin No. 1449, U. S. Department of Agricul- 

 ture, March, 1926, lists and describes about a hundred varieties of 

 standard cotton fabrics. The bulletin can be obtained from the 

 U. S. Department of Agriculture for five cents. 



