494 APPLIED BIOLOGY 



energy can be transformed from one form into another 

 without loss, or reducing the amount of energy in the uni- 

 verse; that is, energy cannot be destroyed. The total 

 amount of energy in the universe is always the same. 



Another important discovery is that energy is not now 

 being created anywhere. The most wonderful machines 

 can do nothing but transform energy. For example, the 

 steam-engine is a machine for changing heat energy into 

 motion or kinetic energy. A water-wheel changes the poten- 

 tial energy of water stored at an elevation into motion. A 

 watch changes into motion the energy stored in a wound-up 

 spring. An electric-battery changes the energy stored in 

 chemicals into electricity. And so we might go through the 

 whole list of known physical changes in the universe, and in 

 each case find evidence that transformation of energy, and 

 not destruction and creation, is constantly occurring in the 

 universe. Science has found no positive evidence concerning 

 either creation or destruction of energy in all its forms. 



The facts regarding changes of energy are now embodied 

 in the Law of Conservation of Energy, which is, that energy 

 can be transformed from one form into another, but cannot 

 be created or destroyed. 



One of the most interesting phases of science study is that 

 of the changes of energy as presented in the science of physics. 

 The law of conservation of energy has numerous practical 

 applications in machinery. For example, a physicist would 

 never spend his time in trying to invent a " perpetual- 

 motion machine," for that would be completely opposed to 

 the established law of conservation of energy. 



417. Energy of the Human Body. This is manifested 

 externally in the form of heat, and muscular and nervous 

 activity. The source of this energy is the stored or potential 

 energy of food, and numerous experiments have demonstrated 

 that the law of conservation of energy applies to the human 

 body (and all other living things), just as it does to a steam- 



