526 PROTOPLASM 



prussic acid (hydrocyanic acid, HCN) or the closely related and 

 interconvertible compound that chemists call cyanogen, CN. 

 These are the compounds that form when a hot mixture of the 

 three gaseous elements oxygen, hydrogen, and nitrogen is allowed 

 to cool slowly. At a somewhat later stage of the cooling, another 

 chemical reaction occurred. Hydrogen gas and oxygen gas 

 combined to form water, or perhaps at first steam, while the 

 earth was too hot for any liquid water to exist, which would 

 later condense to water. Prussic acid gas is soluble in water. 

 Accordingly, the primitive ocean must have absorbed consider- 

 able amounts of this material. The water would also dissolve a 

 small amount of the carbon monoxide gas. In this ocean of 

 dilute prussic acid overlaid by an atmosphere containing large 

 amounts of carbon monoxide gas, the first constituent of living 

 matter possibly arose. Protoplasm contains large amounts of 

 proteins. These, and therefore protoplasm itself, can be broken 

 down into the simpler nitrogenous constituents, the amino acids. 

 The amino acids, of which the simplest is glycocoll, contain carbon, 

 hydrogen, oxygen, and nitrogen. It is certainly more than a coin- 

 cidence that this compound, glycocoll, may be produced in the 

 laboratory by a succession of chemical reactions among the three 

 substances which we have seen were present in the primeval ocean 

 — prussic acid, carbon monoxide, and water. During the millions 

 of years that were to elapse before the period when we find actual 

 traces of life in the rocks, there was ample time for simple nitro- 

 genous substances such as glycocoll to undergo changes and 

 combinations — to be built up into more complicated forms and 

 ultimately into substances similar to protoplasm. While the 

 individual steps cannot be traced, it is possible that by some such 

 path as the one outlined by Free did organic matter first arise 

 on earth. 



While carbohydrate or protein may have been formed under 

 high temperatures, it is probably not so likely a method as the 

 one followed by the plant. There is also the possibility that the 

 path along which living matter developed may have been other 

 than any of the hypotheses so far given; for example, sugar may 

 have been formed by the combination of free carbon and water 

 instead of by the reduction of carbon dioxide in water; or, again, 

 if a hydrocarbon was the first organic substance formed, it may 

 have arisen through the combination of free carbon and hydro- 



