284 ORIGIN OF STRUCTURES AND FUNCTIONS 



between the theory and the analytical evidence is less satis- 

 factory. A. L. Bounce considers that the specific arrange- 

 ment of the amino acids during the formation of a protein 

 is determined, not by triads, but by diads of nucleotides 

 (Fig. 26). 



These suggestions certainly still require a lot more experi- 

 mental work, but many biologists and physicists are now 

 attracted to them. Owing to the attractiveness of the matrix 

 theory some authors are trying to resurrect the earlier theory 

 of the ' living molecule ', though it is no longer the protein 

 molecule which plays this part, for it is now quite clear that 

 this needs complicated systems for its biosynthesis. The part 

 has now been assumed by the molecule of nucleic acid, the 

 formation of which has not yet been studied. 



In the scientific literature of to-day concerning nucleic 

 acid its individual molecules are endowed with the ability to 

 ' reproduce themselves ', to ' divide ' and to ' multiply ' just 

 as were the molecules of protein yesterday. However, experi- 

 ence with the latter teaches us that we should regard with 

 caution such a priori and highly simplified ideas.* 



It is first necessary to understand clearly that, in the 

 process of the biosynthesis of proteins, nucleic acid (especially 

 RNA) does not act as an independent entity, it is only a part 

 of a complicated apparatus. Without this apparatus nucleic 

 acid cannot synthesise protein on its own. This is indicated 

 by all the facts concerning the biosynthesis of proteins and, 

 in particular, by the experiments which we have already 

 discussed involving the very gentle disruption of the struc- 

 tures of isolated fragments of bacterial protoplasts deprived 

 of their envelopes simply by a slight lowering of the con- 

 centration of sucrose in the surrounding solution. When this 

 happens, there is no detectable chemical alteration in the 

 nucleic acids, they remain just as they were but the synthesis 

 of protein is arrested. This is because it requires not merely 

 the intramolecular structure of nucleic acid but also the 

 larger-scale structure of the formed elements of the proto- 

 plasm on which are ' assembled ' the enzymic systems which 

 determine the order and harmony of the energetic and syn- 



* For a criticism of these views see C. C. Lindegren.204 — Author. 



