BUILDING OF LIVING MATTER 109 



But this reduplication can evidently go on 

 so long as energy conditions in the reduplicated 

 molecule will allow of it. On paper a thousand 

 such reduplications could be set down easily, 

 and so theoretically a molecule as huge as 

 a world could be built up, but such a structure 

 has, in actual fact, a limit at which it breaks 

 down on account of instability. The exact 

 limit at which instability stops the process 

 is unknown to us, but this is the simple way 

 in which nature builds up starches in living 

 plants. Such starches possess at least thirty 

 to forty such groups, so simply joined together. 

 This is a good example of how this step 

 in the process of evolution towards life builds 

 up molecular structure, and it may be premised 

 here that such structural change is accom- 

 panied by great changes in the energy pheno- 

 mena of the matter forming the molecule. 



There are three great divisions of the 

 organic bodies built up by living plants 

 and animals, called carbohydrates, fats, and 

 proteins, respectively. These are the com- 

 monest, and build up the great bulk of the 

 living organisms. In addition to them there 

 are other indispensable things, as will be 

 seen later. It will, however, be sufficient here, 

 if we gain some idea of how these three great 

 classes are made up. 



