ACTION OF THE HEART. 109 



life, acts from seventy to seventy-five times in a minute. The 

 frequency of the heart's action gradually diminishes from the 

 commencement to near the end of life, but is said to rise again 

 somewhat in extreme old age, thus : 



In the embryo the average number of 



pulses in a minute is . . 150 



Just after birth. 



During the first year, 



During the second year, 



During the third year, 



About the seventh year, 



About the fourteenth year, the average 



number of pulses in a minute is 

 In adult age, .... 

 In old age, ..... 

 In decrepitude, .... 



from 140 to 130 

 130 to 115 

 115 to 100 

 100 to 90 

 90 to 85 



85 to 80 



80 to 70 



70 to 60 



75 to 65 



In persons of sanguine temperament, the heart acts some- 

 what more frequently than in those of the phlegmatic ; and in 

 the female sex more frequently than in the male. 



After a meal its action is accelerated, and still more so 

 during bodily exertion or mental excitement; it is slower 

 during sleep. The effect of disease in producing temporary 

 increase or diminution of the heart's action is well known. 

 From the observation of several experimenters, it appears 

 that, in the state of health, the pulse is most frequent in the 

 morning, and becomes gradually slower as the day advances : 

 and that this diminution of frequency is both more regular 

 and more rapid in the evening than in the morning. It is 

 found, also, that as a general rule, the pulse, especially in the 

 adult male, is more frequent in the standing than in the sitting 

 posture, and in the latter, than in the recumbent position ; the 

 difference being greatest between the standing and the sitting 

 posture. The effect of change of posture is greater as the fre- 

 quency of the pulse is greater, and, accordingly, is more 

 marked in the morning than in the evening. Dr. Guy, by 

 supporting the body in different postures, without the aid of 

 muscular effort of the individual, has proved that the increased 

 frequency of the pulse in the sitting and standing positions is 

 dependent upon the muscular exertion engaged in maintaining 

 them ; the usual effect of these postures on the pulse being 

 almost entirely prevented when the usually attendant muscular 

 exertion was rendered unnecessary. The effect of food, like 

 that of change of posture, is greater in the morning than in 

 the evening. According to Parrot, the frequency of the pulse 

 increases in a corresponding ratio with the elevation above the 

 sea ; and Dr. Frankland informed the author, that at the 



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