THE PULSE. 223 



into capillaries; before the next heart-beat occurs they pass 

 on into these minute vessels as much blood as the aorta re- 

 ceived during the preceding ventricular systole; consequently 

 they shrink again during the pause, just as a piece of rubber 

 tubing with a small hole in it, when overfilled with water, 

 would gradually collapse as the water flowed out of it. The 

 next beat of the heart again overfills and expands the arteries, 

 and so on; at each heart-beat there is a dilatation of the 

 arteries due to the blood sent into them from the ventricle, 

 and between each beat there is a partial collapse of the ar- 

 teries, due to their emptying blood into the capillaries. 



What may be learnt from the Pulse, The pulse being 

 dependent on the heart's systole, "feeling the pulse" of 

 course primarily gives a convenient means of counting the 

 rate of beat of that organ. To the skilled touch, however, 

 it may tell a great deal more; as, for example, whether it is 

 a readily compressible or "soft pulse," showing that the 

 heart is not keeping the arteries properly filled up with 

 blood, or tense and rigid ("a hard pulse"), indicating that 

 the heart is keeping the arteries excessively filled, and is 

 working too violently, and so on. In healthy adults the 

 pulse rate may vary from sixty-five to seventy-five a minute, 

 the most common rate being seventy-two. In the same in- 

 dividual it is faster when standing than when sitting, and 

 when sitting than when lying down. Any exercise in- 



Into what do the final arterial branches open? How much blood 

 is sent into the capillaries during a cardiac period? What change 

 takes place in the bulk of the arteries during the interval between 

 two ventricular contractions? Illustrate. What happens in the 

 arteries during each heart-beat? Why? What during each heart 

 pause? Why? 



How may we conveniently count the rate of heart-beat? What 

 does a soft pulse indicate? A hard pulse? What is the most com- 

 mon pulse rate in health? Within what limits may it vary? How is 

 it influenced by the positbn of the body? 



