104 MANtjAt OF NATURB STtJDY. 



entrance of veins and departure of arteries, dis- 

 tinguishing between those of the pulmonary sys- 

 tem and those of the systemic. The heart may 

 be represented as a pump, forever receiving blood 

 from the lungs and body, and continually pumping 

 it again to various parts of the system. (See third 

 year work.) 



Color of blood ? When a finger is cut, what is 

 the great natural process that stops the flow of the 

 blood ? (Clotting.) What is the use of blood to 

 the system ? How does it create heat ? How does 

 it promote growth and repair waste ? 



"Blood, then, is a very wonderful fluid.' * * * 

 But you will not wonder at it when you come 

 to see that the blood is the great circulating market 

 of the body, in which all the things that are wan- 

 ted by all parts, by the muscles, by the brain, by 

 the skin, by the lungs, liver and kidneys, are 

 bought and sold. What the muscle wants it buys 

 from the blood ; and so with every other organ and 

 part, as long as life lasts, this buying and selling 

 is forever going on, and this is why the blood is 

 forever on the move, sweeping restlessly from 

 place to place, bringing to each part the things it 

 wants, and carrying away those with which it has 

 done. When the blood ceases to move, the market 

 is blocked, the buying and selling cease, and all 



