INTRODUCTION.] 



PHYSIOLOGY. 



• 



light being given out. Thirdly, the food you take 

 is not burnt in a separate part of your body, in a 

 furnace like that of the engine set apart for the 

 purpose. The food becomes part and parcel of your 

 body, and it is your whole body which is burnt, bit by 

 bit. 



Thus it is the food burning or being oxidized within 

 your body, or as part of your body, which enables you 

 to move and keeps you warm. If you try to do 

 without food, you grow chilly and cold, feeble, faint, 

 and too weak to move. If you take the right quantity 

 of proper food, you will be able to get the best work 

 out of the engine, your body \ and if you work your 

 body aright, you can ke*^p yourself warm on the 

 coldest winter day, without any need of artificial 



fire. ' ■"''.'-■' ■■■ ::'■' ■■\.:\, 



5. But if this be so, in order to oxidize your food, 

 you have need of oxygen. The fire of the engine 

 goes out if it is not fed with air as well as fuel. So will 

 your fire too. If you were shut up in an air-tight room, 

 the oxygen in the room would get less and less, from 

 the moment you entered the room, being used up 

 by you; the oxidation of your body would after 

 a while flag, and you would soon die for want of 

 fresh oxygen (see Chemistry Primer, p. 14). 



You have, throughout your whole life, a need of 

 fresh oxygen, you must always be breathing fresh air 

 to cairy on in your body the oxidation which gives 

 you strength and warmth. 



6. When a candle is burnt (Chemistry Primer, p. 6) 

 it turns into carbonic acid, and water. When wood 

 or coal is burnt, we get ashes as well. If you were to 

 take all your daily food and dry it, it too would burn 



