CLOTHING. 459 



of the Body be exposed so that currents of air can freely 

 traverse it much more heat will be carried oif (under 

 those usual conditions in which the air is cooler than the 

 skin) than if a stationary layer of air be maintained in con- 

 tact with the surface. As every one knows, a "draught" 

 cools much faster than air of the same temperature not in 

 motion. All clothing, therefore, tends to keep up the 

 temperature of the Body by checking the renewal of the 

 layer of air in contact with it. Apart from this, however, 

 clothes fall into two great groups; those which are good, and 

 those which are bad, conductors of heat. The former allow 

 changes in the external temperature to cool or heat rapidly 

 the air stratum in actual contact with the Body, while the 

 latter only permit these changes to act more slowly. Of 

 the materials used for clothes, linen is a good conductor; 

 calico not quite so good; and silk, wool, and fur are bad 

 conductors. 



Whenever the surface of the Body is suddenly chilled 

 the skin-vessels are contracted and those of internal 

 parts reflexly dilated ; hence internal organs tend to 

 become congested, a condition which readily passes into the 

 diseased state known as inflammation. When hot, therefore, 

 the most unadvisable thing to do, is to sit in a draught, 

 thro\v oif the clothing, or in other ways to strive to get sud- 

 denly cooled. Moreover, while in the American summer it 

 is tolerably safe to wear good-conducting garments, and few 

 people take cold then ? this is by no means safe in the 

 spring or autumn, when the temperature of the air is apt 

 to vary considerably within the course of a day. A person 

 going out, clad only for a warm morning, may have to re- 

 turn in a very much colder evening; and if his clothes be not 

 such as to prevent a sudden surface chill, will get oif lightly 

 if he only " take" one of the colds so prevalent at those 

 seasons. In the great majority of cases, no doubt, he suffers 

 nothing worse, but many persons, especially of the female 

 sex, often acquire far more serious diseases. When sudden 

 changes of temperature are at all probable, even if the pre- 

 vailing weather be warm, the trunk of the Body should 

 be always protected by some tolerably close-fitting garment 



