7O RALPH S. LILLIE. 



injury, but disorganization and death folio .v further reduction 

 unless food is restored. A similar loss of living substance through 

 the destructive metabolism inseparable from the life-process 

 takes place in all cells, although its rate and its possible limits 

 vary in the different cases apparently because of the unequal 

 resistance of different structural elements to regression of this 

 kind; thus in higher animals the loss during starvation is great 

 in voluntary muscle and small in the heart and nervous system. 

 In all cases the specific structural material appears subject to a 

 certain continual breakdown of this kind; even when the non- 

 nitrogenous food-supply is ample for energy-requirements it is 

 found impossible to reduce the nitrogen metabolism the index 

 of destruction of protein, the specific structure-forming substance 

 below a certain well-defined minimum. This can only mean 

 that the structural or organized material is subject to continual 

 destruction, and that maintenance involves its continual replace- 

 ment. This process of replacement is specific, in precisely the 

 same sense in which the growth-process is specific. We must 

 therefore recognize that maintenance involves the activity of 

 specific chemical and structural synthesis in the same sense as 

 does growth. When the construction of organized substance 

 balances destruction there is equilibrium the condition corres- 

 ponding to nitrogenous equilibrium in higher animals; any excess 

 of construction leads to growth, of destruction to regression. 

 We see once more that what is essential to continued life is the 

 specific synthetic activity of the protoplasm; when this ceases, 

 life ceases. Claude Bernard expresses this necessary dependence 

 of life upon synthetic or creative processes in the phrase, "life 

 is creation." It is clear that the process of specific creative 

 synthesis which lies at the basis of heredity is inherent in the 

 life-process in all of its forms. The problem of heredity is not a 

 problem to be dealt with by itself; it becomes identical with the 

 most fundamental problem of general physiology, the problem of 

 how living protoplasm is synthesized from non-living matter. 1 



1 All of this is clearly recognized by Claude Bernard; cf. "Lecons sur les phe- 

 nomenes de la vie," Vol. 2, p. 517, where he summarizes his general view as follows: 

 "The synthetic action by which the organism thus maintains itself [i. e., by a 

 combination of chemical and formative synthesis] is at bottom of the same nature 

 as that by which it repairs itself after it has undergone mutilation, or still further, 



