52 CIKCULATION OF THE BLOOD. 



in each case. All were taken at the same hour and with the subject in a sitting posture. 

 Dr. Guy found the pulsations of the heart in the fcfitus to be pretty uniformly 140 per 

 minute. At birth, the pulse is 136. It gradually diminishes during the first year to 

 about 128. The second year, the diminution is quite rapid, the tables of Dr. Guy giving 

 107 as the mean frequency at two years of age. After the second year, the frequency 

 progressively diminishes until adult life, when it is at its minimum, which is about 70 per 

 minute. It is a common but erroneous impression that the pulse diminishes in frequency 

 in old age. On the contrary, numerous observations show that at the later periods of 

 life the movements of the heart become slightly accelerated, ranging from 75 to 80. 



During early life there is no marked and constant difference in the rapidity of the 

 pulse in the sexes ; but, toward the age of puberty, the development of the sexual pecu- 

 liarities is accompanied with an acceleration of the heart's action in the female, which 

 continues even into old age. The differences at different ages are shown in the following 

 table, compiled from the observations of Dr. Guy : 



From 2 to 7 years 



" 8 " 14 " 



" 14 " 21 " 



" 21 " 28 " 



" 28 " 35 " 



" 35 " 42 " 



42 " 49 " 



49 " 56 " 



" 56 " 63 " 



" 63 " 70 " 



" 70 " 77 " 



" 77 " 84 " 



Influence of Digestion. The condition of the digestive system has a marked influence 

 on the rapidity of the pulse, and there is generally an increase in the pulse of from five 

 to ten beats per minute after each meal. Prolonged fasting diminishes its frequency by 

 from twelve to fourteen beats. Alcohol first diminishes and afterward accelerates the 

 pulse. Coffee is said to accelerate the pulse in a marked degree. It has been ascertained 

 that the pulse is accelerated to a greater degree by animal than by vegetable food. These 

 variations have long been recognized by physiologists. 



Influence of Posture and Muscular Exertion. It has been observed that the position 

 of the body has a very marked influence upon the rapidity of the pulse. Experiments 

 of a very interesting character have been made by Dr. Guy and others, with a view to 

 determine the difference in the pulse in different postures. In the male, there is a differ- 

 ence of about ten beats between standing and sitting, and fifteen beats between standing 

 and the recumbent posture. In the female, the variations with position are not so great. 

 The average given by Dr. Guy is, for the male standing, 81 ; sitting, 71 ; lying, 66 ; 

 for the female : standing, 91 ; sitting, 84 ; lying, 80. This is given as the average of a 

 large number of observations. There were a few instances, however, in which there was 

 scarcely any variation with posture, and some in which the variation was much greater 

 than the average. In the inverted posture, the pulse was found to be reduced about 

 fifteen beats. 



The question at once suggests itself whether the acceleration of the pulse in sitting 

 and standing may not be due, in some measure, to the muscular effort required in mak- 

 ing the change of posture. This is answered by the farther experiments of Dr. Guy, in 

 which the subjects were placed on a revolving board, and the posture changed without 



