154 



OUR BODIES AND HOW WE LIVE 



artery, for instance, near the wrist, 

 or the temporal artery, just over 

 the temples, a slight throbbing 

 pressure on the finger will be felt. 

 This pressure, which comes and 

 goes at regular intervals, corre- 

 sponds to the beats of the heart. 

 It is called the pulse. 



Let us learn the reason for it. 

 When the left ventricle contracts, 

 the blood is forced into t"he arter- 

 ies and their walls are suddenly 

 distended. This wave of disten- 

 sion, or pulse, can be felt in all 

 the large arteries. 



In a grown person the pulse beats 

 about seventy-two times a minute. 

 In children the pulse is quicker 

 than in adults. In old age the 

 pulse is slower than in adult life. 



By feeling the pulse with a skilled 

 touch it can be told whether the 

 heart beat is too fast or too slow, 

 strong or weak, regular or irregular. 

 Thus, the pulse is a most important 

 ~ .- T * guide to the doctor, for it may tell 



FIG. 95. The Infenor Vena fc> < ' 



Cava and the Superior him many things about the condi- 



Vena Cava, with their tion of his patient. 

 Connecting Veins. 



A, inferior vena cava, cut off just above the hepatic veins : , superior vena cava, cut 

 off just below the junction of the innominate veins ; C, right and left innominate 

 veins ; Z), left internal jugular vein. The veins, known as azygos, with some of 

 their main branches, are shown. These veins connect the superior vena cava and 

 the inferior vena cava. 



