THE FREQUENCY OP TtfE PULSE. jot 



In a condition of fasting and resting the pulse rate decreases slightly 

 during the day, up to 2 P.M., and is then slightly accelerated again. 



The seasons have little effect on the pulse rate. Coste, 1 in a period 

 of five years' examination, found his pulse to beat less frequently in the 

 summer, and more frequently in the winter. 



Change of position of the body, whether such change be brought 

 about actively or passively, has a marked effect on the pulse rate. In 

 one hundred men averaging 27 years in age, Guy 2 found the average 

 rate of pulse to be 



78-9 . . . Standing 



70-1 . . . . Sitting. 

 66 - 6 . . . Lying. 



After debilitating disease the change of frequency between the 

 horizontal and erect postures may reach 30 to 50 beats per minute. 3 

 Active movement has a very great effect on the pulse rate. The 

 frequency may, for example, be 100 when slowly walking, and rise to 

 150 on running as fast as possible. The exertion of climbing steps may 

 raise the pulse 58 per minute, and produce marked dicrotism. 4 After 

 a series of pendulum movements executed for a period of 30 seconds 

 by the right arm, which was loaded with a weight of 2 lb., the pulse rate 

 was noted to rise in one case from 82 to 156 per minute. When 

 active movements have been executed for a short period only, the 

 frequency quickly returns to normal, while if continued long the 

 pulse rate may subsequently remain increased for an hour or more. 

 Sleep lowers the rate of heart-beat slightly in adults, and markedly in 

 children. 



The pulse frequency is greater in women than in men, but this 

 difference almost disappears if men and women of equal stature are 

 compared. 



Large animals always have a slower pulse rate than small animals ; 

 thus elephants have a frequency of 25 to 30, and rabbits 150 ; and 

 tall men have as a rule slower rates than short men. The accelera- 

 tion in small animals is due to the fact that the surface exposure 

 is greater in these, in proportion to the cubic contents of the body ; 

 therefore, as the loss of heat is greater, and the metabolism more 

 rapid, a quicker circulation is required. Individual variations in 

 healthy men may be very great. It is said that Napoleon had a 

 constant pulse rate of 40. Eates of 20 and 26 have even been 

 recorded. On the other hand, a constant rate of 120 has been noted 

 in a healthy woman. 5 We can sum up from the above facts that 

 a small size of body, the female sex, muscular movement, hot food, 

 and rise of temperature of body, increase the pulse rate. In the 

 following table is shown the average pulse rate at different ages up to 

 20 years. The observations were taken in the resting and sitting 

 posture, and not immediately after food. 6 From 20 years onward the 

 rate remains practically constant; in old age there may be a very 

 slight increase. 



1 Nature, London, May 14, 1891. 



102. 



5 Milne-Edwards, " Lefons sur la phys. cornp.," 1859, tome iv. p. 89. 



6 Guy, loc. cit., p. 184. 



