THE HEART 169 



drinker feels a desire for more alcohol and so forms a 

 habit of its use. While a little alcohol may make a man 

 feel better, yet the strength and endurance of his heart 

 is really diminished. Alcohol is like a whip which makes 

 the heart beat harder for a- time but leaves it less able 

 to do its work in the future. Its blow is pleasant at the 

 time it is given, but it is all the more harmful because 

 it is enjoyed. 



296. Effects of continuous drinking". The derangement 

 of digestion and assimilation resulting from long-continued 

 drinking impairs the nutrition of the whole body, includ- 

 ing the heart. Drinkers confound the absence of fatigue 

 with strength itself. 



297. Effects x>f tobacco upon the heart Tobacco used 

 in any form is a direct poison to the heart's muscle and 

 causes it to beat with less strength. When a large amount 

 is used, it poisons the nerves of the heart and hinders their 

 harmonious action. Then the heart will beat irregularly, 

 and there will be palpitation on slight exertion, so that 

 hard physical exercise becomes an impossibility. The 

 trouble may be only an inconvenience, so that the person 

 cannot engage in violent exercise ; but in its severe forms 

 it may be the cause of death. 



SUMMARY 



1. The blood is kept in constant motion by a double 



muscular pump, called the heart. 



2. The heart contains two pairs of cavities, each con- 



sisting of an auricle and ventricle. 



3. Between each auricle and ventricle there is a valve 



which permits blood to flow into the ventricle, but 

 keeps it from flowing back. 



