POLYPEPTIDES AND PROTEINS 233 



chemical and the purely biological definitions. For example, 

 they argue as follows: if the process of organic-chemical 

 transformation in the waters of the primaeval ocean could 

 have given rise to protein-like polymers of amino acids, then 

 the same processes must have led to the formation of ' living 

 protein molecules '. In what the specihc ' life-conferring ' 

 structure of these molecules consists and how it coidd have 

 arisen seems to be something of an inessential detail from 

 this point of view ; this structure might even have been 

 formed as a result of purely fortuitous combinations of groups 

 of atoms which remained imchanged during the reproduc- 

 tion and multiplication of these molecules in all succeeding 

 generations. The perpetrators of arginnents of this sort do 

 not, however, notice that their approach to a solution of the 

 problem in hand is purely formal and verbal in character and 

 that what they regard as a detail constitutes the very essence 

 of the question. 



It seems to us that the problem of the primary develop- 

 ment of proteins should be formulated in a different way, as 

 follows: the numerous and varied proteins which \ve can 

 now isolate from living organisms in crystalline form as 

 individual chemical compoinids (various enzymes, hormones, 

 viruses, etc.) have definite structures which are highly specific 

 to each of them and ^vhich are extremely well adapted to the 

 fulfilment of those vitally important functions which they 

 stibserve in living protoplasm (in metabolism, in reproduc- 

 tion, etc.). Substances of this kind only arise nowadays as 

 components of living bodies and there can be no doubt that 

 the specific structures w^hich they now exhibit reflect the 

 earlier evolution of these bodies and are the result of the 

 prolonged development of living organisms.^* 



The main point of the qtiestion is w^hether compoimds of 

 this kind could arise outside living material, primarily, on 

 the basis of the thermodynamic and kinetic laws which \\ere 

 explained in the preceding chapter of this book, or whether 

 this required new laws of a higher order. To give a satis- 

 factory answer to this question it is necessary to give at least 

 a short account of what is now know^n of the chemical struc- 

 ture of the actual proteins which have been isolated from 

 living things and to try to understand which are the specific 



