FORMATION OF ORGANIC SUBSTANCES IO9 



This transition seems, moreover, to have been the first and 

 most important stage in that development of matter which 

 led up to the emergence of life. Therefore, in approach- 

 ing the problem with which we are concerned, we should 

 first of all clarify our ideas on the following question : What 

 were the natural conditions during the formation of the 

 Earth or in the early stages of its existence which led to the 

 emergence of the hydrocarbons and their simplest deriva- 

 tives? For these are the carbon compounds from which 

 there could later arise all those other extremely complicated 

 organic stibstances which form the material basis of life. 



Comparatixely recently, about twenty or thirty years ago, 

 that first step on the path towards the origin of life seemed 

 to be quite inaccessible to serious study. The majority of 

 scientists of the late nineteenth and early twentieth centuries 

 were firmly convinced that under natural conditions organic 

 substances could only arise by biogenesis, i.e. through the 

 agency of living beings. To some extent they were echoing 

 .early vitalistic views from the time of Berzelius, but their 

 attitude was mainly based on extensive and reliable observa- 

 tions of nature. 



These observations show quite definitely that at present 

 the overwhelming bulk of organic substances arises on the 

 surface of the earth as a result of photosynthesis. Green plants, 

 by means of the energy of sunlight, use an inorganic car- 

 bon compound (carbon dioxide) to synthesise all the organic 

 stibstances necessary for their life and growth. Animals obtain 

 these substances from plants, either eating them as such or 

 maintaining themselves on the bodies or residties of plant- 

 eating creatures. The same sources of nourishment serve 

 for those other macro- and micro-organisms which are classed 

 as parasites and saprophytes. 



Almost until the end of the nineteenth century photo- 

 synthesis was regarded as the exclusive source of all the or- 

 ganic substances on the Earth. Summing up the extensive 

 factual information on photosynthesis which had already 

 accumulated, K. Timiryazev, in his famous book The life of 

 plants,^ pointed out that the green leaf should be regarded 

 as " a unique natural laboratory in which organic substance 

 is prepared for both the plant and animal kingdoms ". 



