102 THE HUMAN BODY. 



source of the work done and the heat given off is the oxida- 

 tion of coal in a furnace, (7) Chemistry teaches us that just 

 the same amount of energy or work power is given off when 

 an ounce of any given substance is oxidized, whether the 

 oxidation occurs rapidly or slowly. (8) Chemistry also 

 teaches us that many oxidations, or burnings, occur in the 

 presence of water, and that in them just the same amount 

 of energy is set free as if the oxidation occurred in dry air. 

 (9) In our bodies substances are burnt slowly at a low 

 temperature and in the presence of moisture : in tliis burn- 

 ing energy is set free which the body uses for performing 

 its necessary work. (10) In the burning which the tissues 

 undergo while they work they are used up and destroyed. 

 (11) To compensate for the destruction of tissue which 

 accompanies and provides the power for every action of 

 the body, material must be taken into it from outside, 

 which will restore or repair the oxidized tissues. (12) 

 Such substances taken into the body from outside are 

 called foods, and the constant oxidation of the body which 

 is necessitated by the performance of the functions essen- 

 tial to life, requires a supply of food from the outer world, 

 if life is to be maintained. (13) The body of a healthy 

 person has in it at any moment a certain reserve of oxid- 

 izable matters, which we may call stored-up food. The 

 most important of these reserve foods is fat. A fat man 

 can accordingly bear starvation longer than a lean one un- 

 der similar circumstances. 



(7) The amount of energy given off when a substance is oxidized 

 at high or low temperatures; (8) The teachings of chemistry with 

 reference to oxidations in the presence of moisture ; (9) The con- 

 ditions under which substances are oxidized in our bodies ; (10) The 

 changes which oxidized tissues undergo ; (11) Why we need to 

 take material from the outer world into our bodies ; (12) What is 

 meant bv food; and why \v need foods ; (13) What are reserve 

 foods. Illustrate. 



