THE NERVOUS REGULATION OF THE HEART 981 



aorta and heart cavities, is not yet fully made out. The reflex slowing of the 

 heart often fails to accompany rise of blood -pressure. Thus the rise in blood- 

 pressure and the increased filling of the heart associated with muscular 

 exercise are attended by an increased pulse-rate. 



THE PULSE-RATE IN MAN 



The normal pulse-rate in man is about 72 per minute. It is largely 

 influenced by bodily movements. The pulse-rate varies considerably with 

 age. The following Table represents the average pulse-rate in man at 

 different ages : 



Age in years Pulse-rate per minute 



. . 136 



5 . . 88 



10-15 . . 78 



15-60 . . 68-72 



It must be remembered that marked differences in pulse-rate may be 

 found in different individuals without having any pathological significance. 

 Thus pulse-rates of 30 per minute and 120 per minute have been observed in 

 men who were otherwise perfectly healthy. The pulse-rate is raised by 

 warmth and diminished by cold applied to the surface of the skin. It is 

 also increased somewhat by the taking of food. The act of swallowing causes 

 a reflex quickening of the rate by inhibition of the tonic vagus action. 



