13 A TEXTBOOK OF PHYSIOLOGY 



mencement. For chlorophyll, which now acts as the transformer, is 

 itself one of the most complex of known organic substances, and could 

 not have been the first organic substance to be evolved from inorganic 

 matter. In considering the origin of life, therefore, the start must be 

 made in a purely inorganic world without a trace of organic matter, 

 either plant or animal. 



Recently it has been shown that, when dilute solutions of colloidal 

 ferric hydroxide, or the corresponding uranium compound, are exposed 

 to strong sunlight, or to the ultra-violet rays of a quartz mercury arc, 

 there are synthesized the same organic compounds which are at present 

 formed as the first stage in the process of organic synthesis by the green 

 plant namely, formaldehyde and formic acid. Taking the view that 

 the earth arose from a gaseous nebula, it may be assumed that at first, 

 as the planet cooled down, only elements were present, at a lower 

 temperature binary compounds formed, next simple crystalloidal salts 

 arose. Then, by the union of single molecules into groups of fifty or 

 sixty, large molecular colloidal aggregates appeared. As these non- 

 diffusible or colloidal aggregates increased in complexity, they also 

 became more delicately balanced in structure and labile that is to say, 

 they were easily destroyed by sudden changes in environment, but, 

 within certain limits, were peculiarly sensitive to energy changes, and 

 could take up energy in one form and transform it into another. These 

 labile colloids took up water and carbon dioxide, and, activated by 

 the sunlight, produced the simplest organic structures. Next these 

 simpler organic structures, reacting with themselves, and with nitro- 

 genous inorganic matter, continued the process, and built up more 

 and more complex, and also more labile, organic colloids, until finally 

 these acquired the property of transforming light energy into chemical 

 energy. By the continued action of this " law of molecular complexity " 

 life originated. Such an origin of life was no fortuitous accident, and 

 the same processes are still guiding life onwards to higher evolution 

 in a progressive creation. 



