THE HEART A DOUBLE PUMP 105 



it became swollen beyond the ligature ; he opened an 

 adjacent artery, the blood spurted with each beat from 

 the end next to the heart. 



Then Harvey approached the crisis of his argument. 

 He found that the left ventricle of a man's heart held 

 2 oz. of blood, without being at all distended, but in 

 order not to exaggerate the work that the heart performed 

 as a pump, he counted on only half the load being dis- 

 charged at one stroke. Now, if the left ventricle dis- 

 charges but 1 oz. into the aorta at each beat, and beats at 

 seventy times a minute, then in 10 minutes it will have 

 discharged 700 oz. — 44 pints of blood, — which is not only 

 more than the aorta and all the arteries could hold, but 

 two or three times more than would fill all the vessels of 

 a man's body. He was certain of his facts, certain that 

 every part of the human machine was shaped to serve 

 a definite purpose. What, then, became of the blood 

 pumped into the aorta ? How was it that the veins were 

 kept so constantly filled ? There was only one possible 

 explanation, he maintained, and that was that there must 

 exist channels or pores between the arteries and the veins, 

 and that the blood must flow in a circle from arteries to 

 veins. The heart was, therefore, a double pump which 

 kept up the circular flow of blood. Harvey saw these pores 

 or communications only with the eye of faith ; not one 

 of his hearers believed that such passages existed. 



These were famous lectures which Harvey gave in 1 6 1 6 

 at the College of Physicians of London. He became 

 the King's physician. At the battle of Edgehill he sat 

 under a hedge with the royal princes watching a royal 

 progress which led towards the scaffold. He remained 

 all his life long a patient, careful student of living things, 

 dying in 1657 — during the days of the Commonwealth — 

 in his 78 th year. Four years after his death Malpighi, 

 a great Italian anatomist, by means of the microscopes 

 he had learned to use, saw the channels which actually 

 lead from the arteries to the veins — the channels which 

 Harvey knew of although he had never seen them. 

 They have exceedingly delicate transparent walls, and 



