CH. xiv. DOUBLE CIRCULATION OF THE BLOOD. 113 



FIG. 13. 



NECK 



FtlCHT 



LEFT 



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

 artery 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 corner 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 Diagram of Heart and Blood-vessels 



the Chamber a, from Which it first <* f, Lower chambers of the heart, 



called ventricles, b d, Upper 



Started, and the Whole rOUnd be- chambers of the heart called 



. auricles. The arrows and num- 



gins again. The first j ourney of bers show the course of the blood - 

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

 culation, and the second journey through the lungs is called 

 the pulmonary 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 1619, and at last published a small book on the 



