HEART AND BLOOD VESSELS 205 



food and to carry away the waste. The more active tin- 

 process of circulation, the more perfectly is this object 

 accomplished. It is the common experience that the 

 heart beats more rapidly, the lungs work harder, and the 

 body becomes warm after a few minutes of vigorous 

 exercise. These changes have a decidedly beneficial 

 effect upon building up the body and removing tin- 

 wastes. 



In most kinds of work only one set of muscles is used. 

 This set gets a full supply of blood, but others get less 

 than a full supply and so they get too little food and ac- 

 cumulate too much waste. Every one should, at some time 

 in the day, take exercise in the open air which will bring 

 all his muscles into play. If it is enjoyable exercise, tin- 

 effects upon the mind react favorably uj)on the body. 

 This is the advantage of such exercises as skating or 

 baseball. In the winter it often requires real effort to 

 force oneself to leave a warm room and to go out for ex- 

 ercise, but if one is properly clothed, cold air has a bracing 

 effect not obtained at any other time of year. 



Fainting. — Fainting is due to an insufficient supply of 

 blood in the brain. This lack of blood may arise from 

 several causes, but the most common is some disturbance 

 of the digestive processes, which causes the heart to beat 

 too slowly. A fainting person should be placed flat on 

 his back, if possible, with his head slightly lower than the 

 rest of his body, and should be given plenty of fresh air. 

 A dash of cold water in the face, or a bottle of ammonia 

 held to the nostrils, is often helpful in restoring conscious- 

 ness. 



TJie Effect of Drugs and Alcohol. — "The flow <>f tin- 

 blood is modified by various drugs, some causing the blood 

 to flow more rapidly, others more slowly. Coffee cans. - 

 the heart to beat harder and at the same time causes some 



