THE SIMPLER ORGANISMS 85 



In order to understand the energy involved it is necessary 

 to take into account the attraction of the atoms. Carbon 

 and oxygen have strong mutual affinity, and combine to- 

 gether in carbon dioxide to produce a very stable compound. 

 In the above reaction the carbon is separated from the 

 oxygen, and this requires the expenditure of energy — the 

 energy of the sun. In overcoming the strong affinity of 

 carbon and oxygen for each other, this energy disappears, 

 being rendered potential in the separated atoms: it will 

 reappear in like amount whenever these reunite. It is readily 

 measurable in terms of heat. The heat produced by com- 

 bining twelve grams of carbon with thirty-two grams of 

 oxygen (an ounce and a half of these two elements) is suffi- 

 cient to raise the temperature of a kilogram (over two 

 pounds) of water from the freezing to the boiling point, 

 and in the separation of like quantities of these elements 

 whether in the electric furnace or in the green leaf, a like 

 amount of energy is rendered potential. 



It is easy to demonstrate that starch is formed by 

 chlorophyl -bearing protoplasm only in the presence of sun- 

 light. It is not difficult by proper chemical means to 

 determine the composition of the sugar or starch formed, 

 but it is impossible to follow its formation by direct obser- 

 vation: hence it must be borne in mind, the above equation 

 is a theoretical explanation, based on knowledge of the 

 behavior of the chemical elements, of the nature of the com- 

 pounds in the food and in the products of the plant, and of 

 the observable phenomena of its nutrition. If so great 

 difficulties attend the explanation of the first step in the 

 synthesis of organic substances, it will be readily appreciated 

 why the succeeding steps involving the manufacture of 

 proteins, are little understood. A purely theoretical ex- 

 planation of the production of asparagin, one of the simplest 

 of organic nitrogen compounds, of wide distribution in green 

 plants is that of the following equation : 



