FORMATION OF ORGANIC SUBSTANCES 111 



bulk of the organic compounds present in petroleum have 

 been formed secondarily by alteration of the constittient sub- 

 stances of plants or animals ^vhich at some time inhabited the 

 Earth. 



A proof of this is afforded by the recognition in petroleum 

 of numerous compounds which are characteristic of living 

 organisms. These include porphyrins and quinolines and 

 also a number of other compounds of nitrogen, sulphur, 

 phosphorus and oxygen whose nature suggests that they are 

 biogenic. The optical activity of several of these compounds 

 is also that characteristic for living organisms. The isotopic 

 composition of petroleum suggests the same, for the ^^c : ^-c 

 ratio is very close to that which we find in living organisms. ^^ 

 Finally, the manner in which petroleum deposits are distri- 

 buted in sedimentary formations has also convinced many 

 geologists that their origin is biogenic. 



Summing up all the evidence at our disposal, we may 

 conclude that, under natural conditions, the conversion of 

 carbon from its inorganic to its organic compounds is only 

 effected by the agency of living beings. 



This conclusion set an enormous obstacle in the path of 

 solving the problem with which we are concerned. It appeared 

 necessary to assume that the first organisms to develop on 

 the Earth must have been autotrophs — that is, beings capable 

 of satisfying their own nutritional requirements from in- 

 organic compounds; organic substances were held to have 

 appeared on the Earth only as a result of the activity of living 

 organisms. 



We find this point of view expressed by the overwhelming 

 majority of authors around the beginning of the present 

 century when they wrote about the primaeval forms of life 

 which w^re the original inhabitants of the Earth. The 

 ' biophores ' of A. Weismann,-^ the ' biococci ' of S. Meresch- 

 kowsky'* and E. Minchin,^' the primaeval organisms of F. 

 Allen,"" H. Osborn,^'' V. Omelyanskii,"' W. Francis" and 

 others — all these hypothetical living beings must have arisen 

 all of a sudden, being formed directly from inorganic com- 

 pounds and have forthAvith proved capable of constructing 

 the materials of their bodies out of such compounds. 



Many botanists, for example van Tieghem'° in France and 



