22 Can Science Explain Life! 



justified in assuming, without further proof, that 

 this difference in chemical structure between pro- 

 teins and polypeptides would not be sufficient 

 to explain the subsequent formation of diketo- 

 piperazines when proteins are subjected to hy- 

 drolysis. That diketopiperazines are not nor- 

 mally present in most proteins is also evidenced 

 by the fact that neither pepsin, tripsin, nor erepsin 

 will split the diketopiperazine ring. 



But regardless of whether or not the diketo- 

 piperazine ring is present in proteins, it appears, 

 from biological considerations, that neither the 

 simple polypeptide structure nor the unaltered 

 diketopiperazine rings are adequate for the pur- 

 pose, either singly or in juxtaposition. Neither 

 of these structures shows any tendency to grow 

 spontaneously by assimilation of amino acid mole- 

 cules, or to divide spontaneously into daughter 

 structures which either possess or acquire the 

 same specific structural organization as the par- 

 ent. The persistence with which living organisms 

 will devour every bit of food material within 

 reach and invade the entire earth's surface with 

 their progeny shows that they must possess within 

 the chemical structures of their tissues some con- 

 trivance which is definitely superior to ordinary 

 chemical forces and which can function in a man- 



