CIRCULATION 



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thin- walled vessels called capillaries. These capillaries 

 unite and form veins. Thus the blood is continually flow- 

 ing from the heart 

 through the arteries and 

 capillaries into the veins 

 and back to the heart. 



As a rule the arteries 







are below the surface of 

 the body, where they 

 are protected, but if the 

 finger is placed on the 

 wrist or the side of the 

 face near the ear, an 

 artery can be felt 

 through which the blood 

 is pulsing. The veins 

 can be seen in the back 

 of the hand and a pin 

 piercing the body any- 

 where will break open 

 some of the capillaries 

 and cause blood to ooze 

 out. The capillaries 

 spread throughout the 

 entire tissue of the body 

 and supply with food 

 and oxygen the different living cells of which the body is 

 composed. 



The heart is a muscular force pump composed of four 

 chambers, two auricles and two ventricles. It is shaped 

 somewhat like a pear and is situated almost directly be- 

 hind the breastbone. The blood coming back from the 

 veins flows into the right auricle, a chamber with rather 

 flabby walls. From here, it passes through a valve into 



THE CIRCULATORY SYSTEM. 

 Notice that the veins (white) are out- 

 side of the arteries (black). 



