70 THE ORIGIN AND EVOLUTION OF LIFE 



grouping of the nineteen or more chemical elements which were 

 subsequently added. The creation of new chemical compounds 

 may have been analogous to the successive addition of new 

 characters and functions, such as we now observe through 

 palaeontology in the origin and development of the higher 

 plants and animals, resembling a series of inventions and dis- 

 coveries by the organism. 



Conceivable steps in the process were as follows: From 

 earth, air, and water there may have been an early grouping 

 of oxygen, nitrogen, hydrogen, and carbon, such as we witness 

 in the lowliest bacterial stages of life. Even those lifeless com- 

 pounds which contain neither hydrogen, carbon, nor oxygen, 

 make up but a very small percentage of the substance of known 

 bodies. The compounds of carbon, hydrogen, and oxygen 

 (C, H, 0)^ constitute a unique ensemble of fitness among all 

 the possible chemical substances for the exchange of matter 

 and energy within the life organism and between it and its 

 environment. As the higher forms of life are constituted to- 

 day, water and the carbon dioxide of the atmosphere are the 

 chief materials of the complicated life compounds, and also 

 the common end products of the materials yielding energy to 

 the body. Proteins are made from materials containing nitro- 

 gen in addition. 



Thus may have arisen the utilization of the binary com- 

 pounds of carbon and oxygen (CO2), and of hydrogen and 

 oxygen (H2O), to the attractive power of which Henderson- 

 has especially drawn our attention. It is this attractive power 

 of oxygen or of hydrogen or of both elements combined which 

 is now bringing, and in the past may have brought into the 

 life organism other elements useful to it in its various func- 



^ Henderson, Lawrence J., 1913, pp. 71, 194, 195, 207, 231, 232. 

 -Op. cit., pp. 239, 240. 



