CHEMISTRY 227 



The instability of glucose and of all the 

 simple sugars is indeed exceptional in char- 

 acter, and the resulting processes are perhaps 

 far more intricate and numerous than in any 

 other similar case. However, this very case 

 is of exceptional physiological importance, be- 

 cause carbohydrates are the direct result of 

 that synthetic action of chlorophyll, 



6 C0 2 + 6 H 2 = C 6 H 12 6 + 6 2 , 



which is the source of all organic substances 

 and of all the energy of the organic cycle in 

 plants and animals. Carbohydrates, more- 

 over, are the chief constituents of plants and 

 the chief food of animals. 



Turning to this synthesis of carbohydrate 

 in the plant, we find much that is important 

 in the present study. The details of the 

 chemical transformation by which water and 

 carbonic acid and solar energy are changed 

 to sugars and oxygen still remain unknown, 

 in spite of many careful investigations. But, 

 at all events, it is possible to see that two 

 things must somehow be done in order to 

 accomplish the synthesis : — 



(1) Carbonic acid and water must be re- 

 duced. That is to say, oxygen must be sepa- 

 rated from both of these compounds so that 

 free valences may exist to unite carbon and 



