118 The Unity of the Organism 



the power the substances have, dependent upon temperature, 

 pressure, etc., to take up varying quantities of different sub- 

 stances, making them thus highly selective; and the ready 

 transformation of the substances back and forth from the 

 colloid to the crystalloid conditions to meet the needs of 

 the living cell.* 



Such expressions as those quoted from Hopkins (and 

 others of similar purport could be quoted from other au- 

 thors) it seems to me say merely this: The physical (in con- 

 tradistinction to the chemical) constitution of the living cell 

 is such as to enable it, as a complex unitary whole, to 

 accomplish the chemical transformations of substance and 

 energy which it is observed to accomplish. By its purely 

 physical properties, its spacial and energy magnitudes and 

 changes, the cell is primarily quantitative, while by its chem- 

 ical properties, its transformation of substances and ener- 

 gies, it is primarily qualitative. 



The physical principles implicated in organic phenomena 

 make of the cell an "organized laboratory," in Hopkins' 

 phrase, for bringing about "dynamic chemical events," 

 events, that is, which are qualitatively transformative. 



So our appeal as naturalists to physical chemistry for 

 help in interpreting the substances of which organisms are 

 composed is carrying us toward some such conception as to 

 their individ nation, apart from which we are obliged to con- 

 clude organic substance never exists, as that individuation 

 is dependent primarily on the chemical nature of the sub- 

 stance ; while the continued existence of individuals and 

 their genetic repetition is dependent primarily on the phys- 

 ical nature of the substance. 



This, I say, is the direction in which the evidence thus 

 far considered seems unmistakably to carry us. But we 



* See especially The General Physical Chemistry of the Cells and 

 Tissues, hy VV. Punli, in Physical Chemistry in the Service of Medicine, 

 translated by M. H. Fischer. 



