CHAPTER III 

 CIRCULATION OF BLOOD IN THE VESSELS 



Circulation of blood in the arteries Physiological anatomy of the arteries Locomotion of the 

 arteries and production of the pulse Form of the pulse Pressure of blood in the arteries 



Pressure in different arteries Influence of respiration Influence of muscular action, etc. 



Influence of hemorrhage, etc. Rapidity of the current of blood in the arteries Circula- 

 tion of blood in the capillaries Physiological anatomy of the capillaries Pressure of blood 

 in the capillaries Rapidity of the capillary circulation Relations of the capillary circula- 

 tion to respiration Causes of the capillary circulation Influence of temperature on the 

 capillary circulation Circulation of blood in the veins Structure and properties of the 

 veins Valves of the veins Pressure of blood in the veins Rapidity of the current of 

 blood in the veins Causes of the venous circulation Influence of muscular contraction 



Influence of aspiration from the thorax Uses of the valves of the veins Conditions 

 that impede the venous circulation Circulation in the cranial cavity Circulation in erec- 

 tile tissues Derivative circulation Pulmonary circulation Circulation in the walls of 

 the heart Migration and diapedesis Rapidity of the circulation Phenomena in the 

 circulatory system after death. 



IN man and in all animals with a double heart, each cardiac contrac- 

 tion forces a charge of blood from the right ventricle into the pulmonary 

 artery and from the left ventricle into the aorta ; and the valves guard- 

 ing the orifices of these vessels prevent regurgitation during the intervals 

 of contraction. There is, therefore, but one direction in which the blood 

 can flow in obedience to this rhythmic action ; and the fact that even in 

 the smallest arteries there is an acceleration in the current coincident 

 with each contraction of the heart, which disappears when the action of 

 the heart is arrested, shows that the ventricular systole is the cause of 

 the arterial circulation. The supply of blood regulates, to a considerable 

 extent, the processes of nutrition and has an important bearing on the 

 general and special functions ; and the various physiological processes 

 necessarily demand considerable modifications in the quantity of arterial 

 blood furnished to parts at different times. The force of the heart, how- 

 ever, varies but little within the limits of health ; and the conditions nec- 

 essary to the proper distribution of blood are regulated almost exclusively 

 by the arterial system. These vessels are endowed with elasticity, by 

 which the circulation is considerably facilitated, and with contractility, 

 by which the supply to any part may be modified independently of the 

 action of the heart. 



50 



