THE -HEART A DOUBLE PUMP 99 



heart. That explained, too, why the valves in the veins 

 of the neck were set with their mouths downwards — 

 towards the heart. The veins therefore could not be 

 channels for conveying blood outwards to nourish the 

 tissues, as everyone then believed. 



What, then, were the valves of veins for ? The valves 

 led towards the heart ; it, too, was hung with valves. 

 He set himself to study how they were set and shaped, 

 and how they worked in the hearts of all kinds of animals. 

 A very ordinary belief served as a magnetic needle to 

 guide him in his inquiries. It was simply this : Nature 

 is a perfect designer, and therefore every part of the 

 human body and animal machine had been given the shape 

 that best fitted it for the work it had to do. Shape was 

 a clue to function. If we could not explain every detail 

 of a part of the human body, then we had not found out 

 its true use ; that was the touchstone Harvey applied to 

 the structures in the human body. The manner in which 

 the valves of the heart were set guided him as to the 

 direction in which the blood must flow. Even then he 

 was often puzzled to find an explanation for the use of 

 certain parts of the heart. So he watched it at work 

 while it was still living, and after observing hard for 

 fourteen years was at last able to explain the use of its 

 various parts. It turned out to be a more wonderfully 

 contrived pump than any yet conceived by the inventive 

 brain of man. 



We can best understand what Harvey discovered in 

 these fourteen years of studious inquiry if we attend the 

 College of Physicians in London in 161 6 and listen to 

 him as he gives his first course of anatomy lectures. 

 The college now looks out on Trafalgar Square, but in 

 Harvey's time it was hid in Amen Corner, near St Paul's. 

 The lad we saw set out from the King's School, Canter- 

 bury, has grown into a man of slight build with a quiet 

 courteous bearing, a delicately cut, studious counte- 

 nance, bearded in the Jacobean manner, a man taking his 

 subject — but not himself — seriously. He is 37 years 

 of age, has married a daughter of the king's physician, 



