THE HEAT OF THE BODY. 487 



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

 ductors. 



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 con- 

 gested ; this within limits is a protective physiological pro- 

 cess, but if excessive it readily passes into the diseased state 

 known as inflammation. When hot, therefore, the most 

 unadvisable thing to do is to sit in a draught, throw off the 

 clothing, or in other ways to strive to get suddenly 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 return in a very much colder 

 evening; and if his clothes be not such as to prevent a sud- 

 den surface chill, will get off 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 

 persons, especially of the female sex, often thus acquire far 

 more serious diseases. When sudden changes of temperature 

 are at all probable, even if the prevailing weather be warm, 

 the trunk of the Body should be always protected by some 

 tolerably close-fitting garment of non-conducting material. 

 Those whose skins are irritated by anything but linen should 

 wear immediately outside the under-garments a jacket of 

 silken or woollen material. In mid-winter comparatively few 

 people take cold, because all then wear thick and noncon- 

 ducting clothing of some kind. 



