112 ORIGIN AND NATURE OF LIFE 



an end-to-end affair, so that a row of carbon 

 atoms eighteen long instead of six, is obtained, 

 with the acid group at one end. It is obvious 

 what a huge molecule nature constructs when 

 she produces a fat ; it is also clear on what 

 a simple basis it is achieved by simple redupli- 

 cation between these very simply constructed, 

 large moleculed, fatty acids and the glycerine 

 molecule. 



Setting aside the smaller differences at the 

 ends of the linkages, and where unions of the 

 big groups occur, it is obvious that the oft- 

 repeated structure in the carbohydrate is the 

 carbon atom united to a hydrogen and a 

 hydroxyl group, while in the fat it is a carbon 

 atom with two hydrogen atoms. Nature is 

 always engaged building up carbohydrate 

 into fat, because it is a more valuable store- 

 house of energy, and, weight for weight, 

 gives out twice as much heat, or other form 

 of energy to the body. What is the simple 

 process by which it is accomplished ? By 

 input of energy a HO group is taken away, 

 and a hydrogen atom put in its place. 

 This means discharge of oxygen and replace- 

 ment by hydrogen. The chemist calls such 

 a process reduction. Reduction is Nature's 

 plan for building up these organic bodies, 

 and so saving up energy for later use " while 



