18 Can Science Explain Life? 



cautiously because it has never been proved that 

 amino acid molecules exist as such in proteins, 

 even in peptide combination. As will be ex- 

 plained in the subsequent chapters, they probably 

 originated as torn-off fragments which became 

 dislodged from the fabricated protein structure 

 during hydrolysis, and whether the dislodged 

 fragments are of one size or another may depend 

 not only on the chemical structure of the protein 

 but also on the nature of the hydrolyzing agent. 

 There is, in fact, only very little justification for 

 employing the molecular concept at all in our con- 

 sideration of proteins. The molecular theory was 

 invented for the explanation of the definite and 

 sometimes simple proportions by weight or vol- 

 ume in which certain substances react, but the ex- 

 periments on which the molecular theory were 

 based did not include experiments with proteins, 

 the combining proportions of which are neither 

 definite nor simple. Those proteins which are 

 soluble in water may consist, not of particles, but 

 of fibrous networks as is evidenced by the opal- 

 escence and stringyness of their solutions and by 

 many of their other physical and chemical proper- 

 ties, whereas those which required special re- 

 agents to dissolve them were probably trans- 

 formed chemically during the process, so that 



