CH. XIV. DOUBLE CIRCULATION OF THE BLOOD. 



n 



RICHT 



returns by the lower vein, while the blood of the upper 

 arteiy is returning by the upper vein, and both streams pour 

 into the right upper chamber of 

 the heart, b. 



The blood has now made one 

 round, but it does not stop here. 

 It escapes through some valves 

 down into the lower chamber c ; 

 out of the right top comer of 

 which it starts again in the direc- 

 tion of arrows 8 and 9, and passes 

 through the lungs, returning by 

 the lung- veins, ox pulmonary veins 

 as they are called, in the direc- 

 tion of arrow 10, back into the 

 left top chamber of the heart, d. 

 From there it passes down into 

 the chamber a, from which it first 

 started, and the whole round be- 

 gins again. The first journey of 

 the blood round the whole body is called the general cir- 

 culation, and the second journey through the lungs is called 

 the pulmonaiy circulation ; when Harvey had traced these 

 two journeys he had proved the double circulation of the 

 blood. 



Although this discovery as stated here appears very 

 simple, yet it took Harvey nineteen years to trace the blood 

 through all the channels of the body, before he felt quite 

 certain that he had hit upon the truth. Meanwhile he had 

 returned to London, and had been made physician at St. 

 Bartholomew's Hospital. Here he taught his theory in his 

 Lectures of 16 19, and at last published a small book on the 



Diagram of Heart and Blood-vessels 

 front. 



a c. Lower chambers of the heart, 

 called ventricles, h d. Upper 

 chambers of the heart, called 

 auricles. The arrows and num- 

 bers show the course of the blood. 



