THE CIRCULATION III 



become tightly contracted and send the blood to the in- 

 terior of the body. It accumulates there and may cause 

 such congestion of the mucous membrane of the nose, 

 throat, windpipe, or lungs, that inflammation ensues. A 

 cold is an inflammation of the mucous membrane of part 

 of the air passages. Rapid cooling off from a heated 

 condition, especially if one is in a profuse perspiration, 

 may cause the same results ; or, exposure to moderate but 

 continuous cold without exercising may bring on a cold. 

 Sitting on the damp ground, sitting with damp feet, sitting 

 for a long time in a cool draught, or going thinly clad in cool 

 weather, may cause a cold; only foolish persons think 

 they are so hardened as to withstand such risks without 

 injury. Persons who pay attention to their feelings and 

 instincts can detect the beginning of any such derange- 

 ment of the circulation, and prevent trouble by timely 

 prudence. 



191. A person may be in the habit of coddling himself 

 by living in overheated rooms, or by wearing too warm 

 clothing and by constant use of mufflers on going out ; his 

 surface nerves thus become so delicate ^nd the blood vessels 

 of the surface so relaxed, as to insure taking cold on every 

 accidental or unavoidable exposure. A better plan is to 

 keep the house cool, the thermometer standing at 65 or 

 70, sleep with open windows, take cool baths, and keep 

 warm when out of doors by walking or exercising briskly. 

 Thus the blood vessels are toned up, the circulation is made 

 vigorous and steady, and the person is better fitted to with- 

 stand the ordinary conditions of life without disease con- 

 tinually recurring owing to deranged or weak circulation. 

 Any process of " hardening to cold " that is not accom- 

 panied by vigorous exercise, is a risk to the health. 



192. The reciprocal action of the blood vessels of the skin 

 and the internal organs is sometimes illustrated when a 

 person drinks freely of cold water. There is a sudden 



