ACTION OF THE HEART. 481 



The more recent experiments of Yolkmann 1 have led him to nearly the same 

 conclusion; notwithstanding that he has pointed out certain fallacies in Pois- 

 seuille's method. The force which the walls of the Heart must exert, in order 

 to impart such a pressure to the blood which they propel, is properly estimated 

 by multiplying the pressure of blood in the aorta by the ratio between the area 

 of that trunk and the surface of a plane passing through the base and apex of 

 the left ventricle ; which method of computation would make it about 13 Ibs. 



511. 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 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 utero . 140 150 



Newly-born infant . . 

 During the 1st year . - [ ..< 

 During the 2d year 

 During the 3d year 

 From the 7th to the 14th year 

 From the 14th to the 21st year 

 From the 21st to the 60th year 

 Old age 2 . n tv ; V . 



130140 



115 130 



100 115 



95 105 



80 90 



75 85 



70 75 



75 80 



l>. The difference caused by. Sex is very considerable, especially in adult age; 

 it appears from the inquiries of Dr. Guy, 3 that the pulse of the adult Female 

 exceeds in frequency the pulse of the adult Male, at the same mean age, by from 

 10 to 14 beats in a minute. 



c. Many of the observations upon the effect of Stature upon the pulse are 

 invalidated by the neglect of other conditions in making them ; it is affirmed by 

 Volkmann, however, that a tolerably definite ratio exists, 4 the pulse being, caeteris 

 paribuSy less frequent as the stature is greater, so that if the pulse of a man of 

 5J 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 considerably 

 with the posture of the body. The amount of this variation has been made the 

 subject of extensive inquiry by Dr. Gruy ; and the following are his results. In 

 100 healthy Males, of the mean age of 27 years, in a state of rest, the average 

 frequency of the pulse was, when standing 79, when sitting 70, and when lying 

 67 per minute. Several exceptions occurred, however, to the general law; and 

 when these were excluded, the average numbers were, standing 81, sitting 71, 

 and lying 66 ; so that the difference between standing and sitting was 10 beats, 

 or l-8th of the whole; the difference between sitting and lying was 5 beats, or 



1 "Die Hamodynamik nach Versuchen," CHAP. vn. 



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 Leuret and Mitivi6 (" De la 

 Frequence des Pouls chez les Alienes"), Dr. Pennock (" Amer. Journ. of Med. 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.," 

 Art. "Pulse." 



4 With his usual zeal for formularization, Volkmann expresses this ratio, as deduced from 

 a large number of observations, by the ratio p : p f =h^ : A| ; p being the rate of the pulse, 

 and h the height of the body. Or. in other words, the ratio is that of the ninth root of the 

 fifth power of the height. Surely mis is riding a hobby to the death. 



31 



