ACTION OF THE HEART. 319 



also commenced in 12 seconds. In the Fowl, the former period was 6 sec- 

 onds, and the latter Gi ; in the Rabbit, the first was 4, and the other 4.V sec- 

 onds. From such experiments, it seems evident that the rapidity of the 

 circulation is underrated, in any estimate that we found upon the capacity 

 of the Heart, and its number of pulsations in a given time; and it is diffi- 

 cult to see how the two sets of facts are to be reconciled. According to 

 Hering, the rapidity of the circulation diminishes with age; and Vierordt 

 has shown that with increased frequency of the heart's action there is in 

 general an increased rapidity of the circulation, at least in the higher Ver- 

 tebrata. Still it by no means follows that an increase in the frequency of 

 the heart's action in a particular animal should be always accompanied by 

 an increased rapidity in the current of the circulation ; in point of fact, the 

 experiments of Heriug 1 show that, in the Dog and Horse, when inflamma- 

 tory or febrile conditions, such as Pericarditis, are set up, a much longer 

 period is occupied in the passage of the blood than before. 



248. The number of contractions of the Heart in a given time is liable to 

 great variation, within the limits of ordinary health, from several causes; 

 the chief of these are diversities of Age, of Sex, of Stature, of Muscular 

 exertion, of the activity of the Respiratory process, of the condition of the 

 Mind, of the state of the Digestive system, and of the Period of the day. 



a. Putting aside the other causes of uncertainty, the following table may 

 be regarded as an approximation to the average frequency of the Pulse, at 

 the several Ages specified in it, taking equal numbers of Males and Females : 



Beats 

 per minute. 



In the foetus in utcro, . . 140-150 

 Newly-born infant, . . . 130-140 



Beats 

 per minute. 



From the 7th to the 14th ye;ir, . 80-90 

 From the 14th to the 21st'year, . 75-85 



During the 1st year, . . . 115-130 From the 21st to the 60th year, . 70-75 



During the 2d year, . . . 100-115 Old age, 2 75-80 



During the 3d year, . . . 95-105 ' 



b. The difference caused by Sex appears from the inquiries of Dr. Guy, 3 

 to be such that the pulse of the adult Female is more frequent than the 

 pulse of the adult Male, at the same mean age, by from 10 to 14 beats in a 

 minute. 



c. The influence of Stature is affirmed by Volkmaun to be tolerably well 

 defined. The pulse being cceteris paribas less frequent as the stature is 

 greater; so that if the pulse of a man of 5i feet high were 70 per minute, 

 that of a man of 6 feet would be 66.7, and that of a man of 5 feet 73.8. 



d. The effect of Muscular Exertion in raising the pulse is well known; as 

 is also the fact, which is one exemplification of it, that the pulse varies con- 

 siderably with the posture of the body. The amount of this variation has 

 been made the subject of extensive inquiry by Dr. Guy; and the following 

 are his results. In 100 healthy Males, of the mean age of 27 years, in a 

 state of rest, the difference between standing and sitting was 10 beats, or 

 about th of the whole number of beats per minute; the difference between 

 sitting and lying was 5 beats, or yV^h f the whole; and the difference be- 

 tween standing and lying was 15 beats, or th of the whole. In 50 healthy 

 Females of the same mean age, the difference between standing and sitting 



1 Archiv f. Phys. Heilk., 1853, t. xii, p. 133. 



2 The rise in the average frequency of the pulse in very advanced life, contrary to 

 the prevalent notion, has been determined by the observations of Levret and Mitivie 

 (De la Frequence des Fouls chez les Alienes), Dr. Pennock (Amer. Journ. of Mod. 

 Sci., July, 1847), and Prof. Volkmann (Op. cit., p. 427). 



3 Guy's Hospital Reports, vol. iii, p. 312; and Cyclop, of Anat. and Physiol., vol. 

 iv, Art. Pulse. 



