84 A SCIENTIFIC APPROACH 



quite obvious to us that Pfliiger oversimplified the compli- 

 cated phenomenon of the metabolism of living protein. It 

 is, however, of interest in connection with the problem we 

 are studying, that Pfliiger built up his original theory of the 

 origin of life on this basis. If the cause of all vital phenomena 

 lies in special groups of atoms, the cyanogen-containing 

 radicals of proteins, then, he argued, it is clear that the 

 whole solution of the problem of the origin of life resolves 

 itself simply into a solution of the question of how these 

 radicals arose. How was cyanogen formed on the primaeval 

 lifeless Earth? Pfliiger wrote : 



In this connection organic chemistry provided us with a very 

 significant fact, namely that cyanogen and its compounds are 

 formed at incandescent temperatures when the necessary nitro- 

 gen-containing compounds are brought into contact with glowing 

 carbon or when mixtures of the substances are raised to white 

 heat. Thus nothing could be clearer than the possibility that 

 cyanogen compounds might be formed at a time when the earth 

 was partly or wholly in a fiery or incandescent state. Life arose 

 from fire and its foundations were laid at the time when the 

 earth was a fiery incandescent globe. 



This theory was very progressive for its time and played 

 a positive part in the history of the development of our 

 ideas concerning the origin of life in so far as it included 

 an attempt to explain the primary development of organic 

 substances. However, the hypothesis on which it was based, 

 namely that the vital characteristics of protoplasm could be 

 attributed to the presence of cyanogen or some other radicals 

 in the composition of the proteins, was found to be false and 

 was later refuted. 



It must be noted that at the end of last century and 

 the beginning of the present one opinions, which were very 

 widely held, associated life and all its properties, not with 

 protoplasm in its entirety but with particular hypothetical 

 ' living molecules ' or molecular complexes the chemical 

 reality of which was far more problematical than that of the 

 cyanogen-containing radicals of Pfliiger's ' living protein '. 



The biological literature of those times is very rich in 

 different complicated names which were thought out to 



