THE DISCOVERY OF THE 

 CIRCULATION OF THE BLOOD 



THE CIRCULATION OF THE BLOOD 



IF you place the finger of one hand lightly on the outer 

 side of the front part of your other wrist you will feel 

 a throbbing. This throbbing is called the pulse, and 

 has been known and observed by medical men for 

 thousands of years. The throbbing or pulsation is 

 caused by the expansion of a tube or blood-vessel of a 

 special type known as an artery. The expansion of 

 the artery at each pulsation or beat of the pulse is caused 

 by blood being forced into the artery by the special pump 

 known as the heart. 



From the heart arises a great artery, the aorta, into 

 which the blood is pumped. The aorta is provided with 

 valves at the point at which it arises from the heart. 

 These valves are so arranged that they prevent any return 

 of blood to the heart. The blood, therefore, when once 

 forced into the aorta can move in one direction only, 

 namely, away from the heart. 



Now the aorta has many branches and, as the blood 

 moves away from the heart, it enters them. These 

 branches in their turn have yet smaller branches. The 

 arteries go on branching until they get so small that they 

 cannot be seen except with a microscope. Through all 



