THE CIRCULATION. 113 



beats. These follow each other not only with great 

 regularity, but with great rapidity. The average number 

 in an adult man is about seventy-two in a minute. But 

 the heart is a susceptible organ, and many circumstances 

 affect its rate of action. Heat, exercise, and food will 

 increase its action, as cold, fasting, and sleep will decrease 

 it. Posture, too, has a curious influence; for if while sit- 

 ting, the beats of the heart number seventy-one; standing 

 erect will increase them to eighty-one, and lying down 

 will lower them to sixty-six. 



26. The modifying influence of mental emotions is very 

 powerful. Sudden excitement of feeling will cause the 

 heart to palpitate, or throb violently. Depressing emotions 

 sometimes temporarily interrupt its movements, and the 

 person faints in consequence. Excessive joy, grief, or fear, 

 lias occasionally suspended the heart's action entirely, and 

 thus caused death. The rate of the heart-beat may be 

 naturally above or below seventy-two. Thus it is stated 

 that the pulse of the savage is always slower than that of 

 the civilized man. Bonaparte and Wellington were very 

 much alike in their heart's pulsations, which were less than 

 fifty in the case of each. 



27. Activity of the Heart. The average number of 

 heart-beats during a lifetime may be considered as at the 

 rate of seventy-two per minute, although this estimate is 

 probably low ; for during several years of early life the rate 

 is above one hundred a minute. In one hour, then, the 

 heart pulsates four thousand times ; in a day, one hundred 

 thousand times ; and in a year, nearly thirty-eight million 

 times. If we compute the number during a lifetime, thirty- 

 nine years being the present average longevity of civilized 

 mankind, we obtain as the vast aggregate, fourteen hun- 

 dred millions of pulsations. 



26. Mental emotions ? Sudden excitement ? Excessive joy ? The heart-beat 

 rate ? Bonaparte and Wellington ? 



27. Average number of heart-bears? In one hour ? Year? Lifetime? 



