THE HEAT OF THE BODY 269 



While clothing is designed to prevent too rapid radia- 

 tion of heat from the surface, it should still permit the 

 evaporation of perspiration, for an accumulation of mois- 

 ture uf)on the skin may expose one to dangerous chills. 



396. Fabrics of wool have been found to possess more 

 fully than any other materials the qualities desired for 

 clothing. They are so light and porous as to admit of 

 sufficiently free evaporation and the circulation of air ; 

 and as wool is a bad conductor of heat, it retains the heat 

 of the body, while it holds in its meshes a considerable 

 quantity of air, which is also a nonconductor of heat. In 

 variable climates, such as that of our Northern states, it is 

 wise, at least for those in delicate health or especially 

 sensitive to changes of temperature, to wear wool next 

 the skin at all seasons. The gentle friction of woolen 

 garments against the skin tends to prevent clogging of 

 the pores, to promote even circulation, and in general to 

 keep the surface in a healthy condition. 



397. Silk is less valuable than wool in preserving heat 

 and permitting evaporation, though better than cotton oi- 

 lmen. It may be worn next the body when wool causes 

 irritation of the skin. 



398. Linen is less useful than other materials for the 

 innermost garments, as it quickly becomes saturated with 

 moisture. Cotton, being more porous, answers the purpose 

 better. In respect to all these materials the weaving of 

 the fabric has much to do with its value for clothing. 

 Closely woven cloth of hard-twisted threads should not be 

 chosen for underwear, but rather that of soft, loosely 

 twisted fibers, loosely woven. 



399. Fur is indispensable in the coldest climates, as it 

 retains better than anything else the bodily heat. But it 

 prevents the evaporation of perspiration, and should not 



MACY'S PHYS. 17 



