98 THE ENGINES OF THE HUMAN BODY 



patients has time to spare, and this Harvey determined to 

 devote to settling certain doubts which had arisen in his 

 mind during the time he dissected and studied in Padua. 

 Mark the way he proceeds to settle his doubts ! He sets 

 aside one of the rooms of his house for dissections — the 

 dissection of animals, for at that time the human body 

 itself was but seldom opened. He knew that the bodies 

 of warm-blooded animals were constructed on the same 

 plan as the human body. Hence he set to work and 



A. B. C. 



Fig. 27. 



A, A swelling on a vein indicating the presence of a valve within it. 



B, The vein laid open, showing the valves partly open. 



C, Showing the valves shut. 



dissected all kinds of animals. He looked very carefully 

 at the valves of the veins and found them to be effective 

 traps, shutting instantly when a current of blood or of 

 water was made to flow outwards — the direction which 

 Fabricius thought the blood took in life. He made the 

 veins of his own arm swell by tying a ligature round its 

 upper part ; when he milked these swollen veins towards 

 the hand he noticed that the blood refused to pass a 

 valve ; the valves were competent in living as well as in 

 dead veins. He saw that the valves were set so as to 

 allow the blood to pass in but one way — towards the 



