486 DAVID H. DOLLEY 



of this relation is the elaboration of chromatin, finally displayed 

 as the chromidial apparatus, the immediate source of functional 

 energy. The nerve cell is devoted solely to function, and its 

 whole series of anabolic processes is directed to the above 

 specific end. That cell having been shown to have no function 

 other than irritability, one needs go no farther than a basis for 

 that property. Hence it follows that the constructive metab- 

 olism of the nerve cell is its function in respect to the potential 

 energy involved in any functional act — that energy is stored as 

 chromidial apparatus. 



But the various shifts in the nucleus-plasma relation which 

 subserve functional states, changes in size and in size relations, 

 are merely the outward token of the inward chemistry of chro- 

 matin anabolism, objectively to be interpreted as phases of the 

 reciprocal relation. So far then, structure depends on function. 

 Further, this relation of structure to function unquestionably 

 goes deeper. For in a study of the development of the nerve 

 cell, unfortunately yet unpublished save in abstract ('16), the 

 evidence from volumetric relations at least indicates that non- 

 divisional growth back to a very early period of development 

 is a functional growth. So far as this goes, the development of 

 structure for the nerve cell depends thus further on function. 

 The statement of Child ('15, p. 44) therefore unequivocally 

 applies to this special case: (The nerve cell) "constructs itself 

 by function." The development of the nerve cell (growth in 

 mass), the maintenance of its status quo in maturity and its pos- 

 sible functional hypertrophy depend thus on a common property 

 of function. Moreover, just as immediate function is quanti- 

 tative in respect to the normal metabolic level, so the volumetric 

 evidence indicates that the lasting effect of function is quantita- 

 tive. For example, the functional hypertrophy is an absolute 

 increase of materials in the same proportion. 



It follows immediately from this conception with reference to 

 senility that in a cell so highly specialized for function that all 

 other properties are lost, whatever may be true of less speciahzed 

 cells, there is no necessity of distinguishing between structural 

 and functional causes of senescence, as Conklin ('13, '14) does. 



