n] Circulation of the Blood. \:\ 



movements of the heart itself, that is of the ventricles. When, 

 in the beginning of the inquiry, he 'first gave his mind to 

 vivisections ' he found the task of understanding the ' motions 

 and uses of the heart so truly arduous, so full of difficulties ' 

 that he began to think with Fracastorius (a Veronese doctor 

 of the middle of the sixteenth century (1530) and more a poet 

 than a man of science), " that the motion of the heart was only 

 to be comprehended by God." But the patient and prolonged 

 study of many hearts of many animals shewed him that " the 

 motion of the heart consists in a certain universal tension, both 

 of contraction in the line of its fibres, and constriction in every 

 sense, that when the heart contracts it is emptied, that the 

 motion which is in general regarded as the diastole of the heart 

 is in truth its systole," that the active phase of the heart is not 

 that which sucks blood in, but that which drives blood out. 

 Ccesalpinus alone, as we have seen, of all Harvey's forerunners 

 had in some way or other dimly seen this truth. Harvey saw- 

 it clearly and saw it in all its consequences. It is, he says, the 

 pressure of the constriction, of the systole, which squeezes the 

 blood into and along the arteries, it is this transmitted pressure 

 which causes the pulses ; the artery swells at this point or 

 that along its course, not in order that it may suck blood into 

 it, but because blood is driven into it, and that by the pressure 

 of the constricting systole of the heart. 



With this new light shining in upon him, he was led to 

 a clear conception of the work of the auricles and the ventricles, 

 with their respective valves. He saw how the vena cava, 

 on the one side, and the vein-like artery, the pulmonary veins 

 on the other side, empty themselves into and fill the ventricles 

 during the diastole, and how the ventricles in turn empty 

 themselves during the systole, into the artery-like vein, the 

 pulmonary artery on the one side and the great artery or 

 aorta on the other. And this at once led him to a truer 

 conception of the pulmonary circulation than was ever 

 grasped by Servetus or Columbus. On the old view, only some 

 of the blood of the right ventricle passed through the septum 

 into the left ventricle ; the rest went back again to the tissues ; 

 and it was this ' some ' only which Servetus and Columbus 



