CHAPTEE VI. 



CIRCULATION OF THE BLOOD IN THE ARTERIES. 



Physiological anatomy of the arteries Course of blood in the arteries Elasticity 

 of the arteries Contractility of the arteries Locomotion of the arteries and 

 production of the pulse Form of the pulse Sphygmograph Pressure of 

 blood jn the arteries Hemodynamometer Cardiometer Differential cardio- 

 meter Pressure in different parts of the arterial system Influence of respi- 

 ration on the arterial pressure Effects of hemorrhage Rapidity of the cur- 

 rent of blood in the arteries Instruments for measuring the rapidity of the 

 arterial circulation Variations in rapidity with the action of the heart Ra- 

 pidity in different parts of the arterial system Arterial murmurs. 



IN man and in all animals possessed of a double heart, 

 each contraction of this organ forces a charge of blood from 

 the right ventricle into the pulmonary artery, and from the 

 left ventricle into the aorta. We have seen how the valves 

 which guard the orifices of these vessels effectually prevent 

 regurgitation during the intervals of contraction. There is, 

 therefore, but one direction in which the blood can flow in 

 obedience to this intermittent force ; and the fact that in the 

 smallest arteries there is an acceleration in the current coin- 

 cident with each contraction of the heart, which disappears 

 when the action of the heart is arrested, shows that the ven- 

 tricular systole is the prime cause of the arterial circulation. 



This part of the physiology of the circulation is not as 

 simple as we might at first be led to suppose. The arteries 

 have the important function of supplying nutritive matter to 

 all the tissues, of furnishing to the glands materials out of 



