CIRCULATION OF THE BLOOD 



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from the right auricle, and one by which the blood leaves 

 it through the pulmonary arteries and goes to the lungs. 

 The left auricle has four openings through which the 



n 



FlG. 63. Interior of the right auricle and ventricle. (Thornton's "Human 

 Physiology"): i, descending vena cava; 2, ascending vena cava ; 3, right 

 auricle; 4, semilunar valves; 5, 5', 5", tricuspid valve; 6, pulmonary 

 artery; 7, arch of aorta; 8, aorta; 9, large branches of the aorta; 10, left 

 auricle ; n, left ventricle. 



blood, returning from the lungs, enters. In the left 

 ventricle there are two openings; one between the 



