CHAPTER X. 



THE VASCULAR SYSTEM CONTINUED: THE GENERAL CIRCULA- 

 TION; THE PULSE AND ARTERIAL PRESSURE; VARIATIONS 

 IN THE CAPILLARY CIRCULATION. 



The general circulation of the blood. At each beat of the 

 heart the contraction of the ventricles drives a certain quantity 

 of blood, probably amounting to four 

 ounces, with great force into the 

 aorta and pulmonary artery. The 

 aorta delivers this supply of blood 

 from the left ventricle, through its 

 branches, to the capillaries in all 

 parts of the body, except the lungs. 

 In the capillaries, the blood is robbed 

 of oxygen and other constituents 

 necessary for the life and growth 

 of the tissues, is loaded with car- 

 bonic acid and other waste matters, 

 and is returned by the superior and 

 inferior venae cavse to the right side 

 of the heart. From the right side 

 of the heart, the blood is conveyed 

 by the pulmonary artery to the 

 capillaries in the lungs, where it 

 receives a fresh supply of oxygen 



and gives Up the carbonic acid with LATION. A, aorta; P, pulmonary 



. i T i artery; 0, O, auricles; V, V, ven- 



which it has become loaded during tricles / /, intestines ; F, liver ; 



its circulation through the body. l ?^'%?* 



Thus a double circulation is COn- hepatic veins ; 6, portal vein ; 7, 8, 



stantly and simultaneously going 

 on, the artery from the left side of veins. 



109 



FIG. 82. DIAGRAM OF CIRCU- 



