METABOLISM 51 



the electricity generated by which affords us light, 

 heat, and such chemical analyses and syntheses as 

 are involved in cooking. In all these transformations 

 of one kind of energy into another, though much is 

 wasted in manipulation, none is lost ; in other words 

 all can be accounted for. This conception, that 

 the sum of energy in the universe is constant and 

 merely changes its form from one kind to another, 

 is one of the great generalizations of natural science, 

 and is known as the " Law of the Conservation of 

 Energy." 



Chemistry teaches us also that the more complex 

 " organic " compounds are built up of relatively 

 few kinds of atoms; but these are combined and 

 recombined into groups of higher and higher orders, 

 an absorption of energy taking place with every 

 combination, until a huge aggregate results, the 

 potential energy of which is enormous. Thus, a mole- 

 cule of a simple sugar, dextrose (CeHisOe), may be 

 combined with another molecule of a similar sugar 

 to form a new sugar of a higher order, cane-sugar 

 or sucrose (C^H^On). 1 In this reaction a mole- 

 cule of water is subtracted. More molecules may be 

 added to the combination over and over again, like 

 keys on a keyring, if the molecule of water is each 

 time removed. With every such combination there 

 is an addition to the amount of potential energy 

 accumulated in the molecule, and of course this 

 energy must be supplied from without. Usually 

 its source is the heat of the alcohol or gas flame which 



1 C 6 H 12 6 + CsHx^e = CuH^On + H 2 O. 



