MATTER AND ENERGY 79 



ones energy becomes kinetic; it may appear, 

 for example, as heat or motion. In the case 

 we are considering, it is possible to determine 

 with accuracy the energy the oil contains, or, 

 in other words, the heat produced by its 

 combustion ; this amount of heat is conceived 

 as kinetic energy ; and if it were possible, by 

 a synthetic process, so to combine the carbon, 

 hydrogen, and oxygen as to re-form the olein, 

 the same amount of energy would have to be 

 expended as was liberated by decomposition. 

 In any such system of operations the sum of 

 the energy at the close would be the same as 

 at the beginning. 



38. Chemical Substances. We are now in 

 a position to consider from the chemical 

 point of view, the matter of which the body is 

 composed. The chemical elements in living 

 matter have been referred to in section 7. 

 These elements are combined to form chemi- 

 cal compounds, divided into organic and 

 inorganic. Organic compounds are again 

 classified into nitrogenous and non-nitrogen- 

 ous. The nitrogenous are the more important ; 

 they are necessary for the constitution of 



