SELECTED PAPERS 



animals do not represent isolated phenomena but are, on the con- 

 trary, also encountered among quite remote groups of organisms. Is 

 it not edifying that immeasurably small amounts of vitamin B-12, for 

 example, which protects man from the horrors of pernicious anemia, 

 may, under certain conditions, also determine the well-being of a 

 small flagellate? 



In the course of extended studies concerning the manner in which 

 vitamins and growth factors exert their favourable effect on the be- 

 haviour of such diverse organisms it has become clear that they are 

 partly components of fundamentally important catalytic systems that 

 operate in cellular metabolism. Understandably, this has raised the 

 question how cells can get along and perform their normal vital 

 functions without growth factors in their food. Almost imperceptibly 

 this has led to an important new notion, to the effect that those cells 

 that do not require growth factors have certainly not renounced the 

 use of those convenient tools, but differ from the growth factor-requir- 

 ing ones in that they are capable of synthesizing the agencies in ques- 

 tion themselves. 



The fact that a sulphur bacterium that has developed at the ex- 

 pense of such simple inorganic substances as sulphur, oxygen, and a 

 few salts appears to be a veritable storehouse of numerous vitamins 

 that are indispensable for human nutrition provides food for thought. 

 Given the absolute dependence of human health on a continuous 

 supply of these vitamins, there is every reason for paying homage to 

 the puny microbe that needs these substances just as much, but man- 

 ages to manufacture them practically from the elements. Consequently 

 the unity in the material basis for life does not express itself only in the 

 comparable composition of the proteins of all living organisms, but 

 obviously the same catalytic systems are employed by green plants, 

 animals, and microbes, for the performance of their normal functions. 



The far-reaching similarity in material composition of individual 

 living entities, together with the earlier discussed unity in the multi- 

 farious energy-yielding processes, evidently provide a not-to-be-under- 

 rated support for the evolutionary theory which, in its broadest for- 

 mulation, holds that life is one and continuous, both in space and in 

 time. I must refrain from discussing the developments that have led 

 to the evolutionary theory; a few remarks may here be launched. 



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