364 AGRICULTURE ON THE PACIFIC SLOPE 



the stomach, intestines, liver, and kidneys lie below 

 the diaphragm. 



What becomes of the air after it enters the lungs? 

 The windpipe divides into finer and finer branches 

 (bronchial tubes); the very finest of these end into 

 little air sacs with very thin walls in which are very 

 fine tubes. The blood in these tubes take up the oxy- 

 gen from the air sacs, just as the cells of the leaf take 

 it up from the air in the air chambers of the leaf. At 

 the same time that the blood takes up oxygen from 

 the air, it gets rid of carbon dioxide by giving it off and 

 letting it escape into the air sacs. When the breath 

 is blown into limewater it turns the limewater milky 

 from the carbon dioxide in it. 



What is the blood? Ask the butcher to get you some 

 blood. At first it is liquid, but it soon becomes like 

 jelly. This is due to a protein (fibrin) in the blood 

 which coagulates in the same way that white of egg 

 does when heated (see page 351). This is why a wound 

 stops bleeding; were it not so, we might bleed to death 

 from a pin prick. 



The red color is due to very small disk-shaped bodies, 

 the red corpuscles. It is these which take up the oxy- 

 gen and carry it to all parts of the body, and give it 

 up to the parts which need it. 



There are also white corpuscles in the blood. When- 

 ever a wound is made these white corpuscles gather at 

 the spot, and it is thought that they attack and devour 



