THE CIRCULATION 169 



36. The Pulse. With each contraction of the left side of 

 the heart, the impulse causes a wave-like motion to traverse 

 the entire arterial system. If the arteries were exposed to 

 view, we might see successive waves speeding from the heart 

 to tlifli smallest of the branches. The general course of the ar- 

 teries is as far as possible from the surface. This arrangement 

 is certainly wise, as it renders them less liable to injury the 

 wounding of an artery being especially dangerous. It also 

 protects the arteries from external and unequal pressure, by 

 which the force of the heart would be counteracted and wasted. 

 Accordingly, we generally find these vessels close to the bones, 

 or hiding behind the muscles and within the cavities of the 

 body. 



37. In a few situations, however, the arteries lie near the 

 surface; and if we apply the finger to any of these parts, 

 we shall distinctly feel a throbbing motion taking place in 

 harmony with the heart-beat. This is part of the wave-motion 

 just mentioned, and is known as the pulse. All are familiar 

 with the pulse at the wrist, in the radial artery ; but it is not 

 peculiar to that position, for it may be felt in the carotid of 

 the neck, in the temporal at the temple, and elsewhere, espe- 

 cially near the joints. 



38. Since the heart-beat makes the pulse, whatever affects 

 the former affects the latter also. Accordingly, the pulse is 



FIG. 42. THK FORM OF THE PULSB 



a good index of the state of the heajth, so far as the health 

 depends upon the action of the heart. It informs the physi- 



11. The Beating of the Pulse. "According to experiments made in 

 Paris, the pulse of a lion beats forty times a minute ; that of a tiger, 



86. Successive undulations from the heart ? Course of the arteries ? Protection of the 

 arteries ? General location of the arteries ? 



37. Where do the arteries lie ? If we apply the finger ? Pulse? Where felt? 



