CHARTER XII 



THE EVOLUTION OF MANKIND 

 AND ITS FUTURE 



1. The Orthogenesis of Protein Molecules 



The denaturation or the structural change of proteins appears to 

 proceed without stopping in so far as the change-inducing agents are 

 present as seen in the change of phage by formalin. The process is 

 compared to the gradual alteration of the genes by environmental 

 factors. It is worthy of note, however, that the velocity of the process 

 or the velocity constant, if calculated as a monomolecular reaction, 

 tends to become smaller as the reaction proceeds. It is reasonable to 

 regard the process as a monomolecular reaction, but if calculated as 

 a bimolecular reaction the decreasing rate of the velocity constant is 

 lessened, and therefore the writer attributed this phenomenon to the 

 infection of denaturation, that is, he considered that the denaturation 

 •was autocatalytically accelerated by the transmission of denaturation 

 from the protein undergoing denaturation to other intact molecules 

 (61). Frequently, however, the decrease in the progress is so manifest 

 that it cannot be explained even by this assumption and there seems 

 to exist still another cause to lessen the velocity. 



At present the writer believes that this must be based upon the ten- 

 dency of the protein to recover its original structure, that is, upon the 

 reversibility. As previously discussed, protein denaturation sometimes 

 proceeds in oscillation like a physical phenomenon. This is interpreted 

 as resulting from the competition between the effort of the protein 

 to recover its original structure and that of denaturating agent to 

 promote the change. If so, the velocity of the change would be the 

 more lessened as the change progresses the more, since the repulsive 

 force or reversibility should become stronger Avith the progress of the 

 change. This appears actually the case. As every one knows an 

 elastic substance can be bent easily at first, but further bending may 

 become difficult on account of the increase in the force to spring back 

 to the original shape. Protein molecules can be looked upon as such 

 an elastic substance. 



In Figs. 36 and 37 the progress of inactivation of rennin respec- 

 tively by its antiserum and tannin is illustrated (91). In both cases 



