* THE RECOVERY FROM DEPRESSION 487 



though not to their mutual exclusion. The metabolism of the 

 nerve cell is its function on the constructive side, and its function 

 determines its structure. This is no critical objection, as will 

 appear, but the establishment of the place of one specialized type 

 of cell in respect to a generalization for the senescence of all cells. 

 The primary conditions of senescence in the nerve cell are solely 

 functional, whether excitation to an ultimate exhaustion or 

 depression to the minimum, and structural changes are secondary 

 and dependent thereupon. 



In terms of the preceding discussion, natural senility becomes 

 a quantitative process. Heretofore, in discussing this senility, 

 the reservation of a qualitative side has been made to explain 

 the loss of recuperative power. In ignorance of the relation be- 

 tween growth and function, and hence with a tacit admission of 

 some inherent growth impulse in deference to the common idea 

 that was inevitable. But with the newer light on growth and 

 function involving the same substances in a functional growth, 

 the basis of this kind of senility becomes quantitative, that is, 

 after the usury of a life-time, certain primary materials are con- 

 sumed, decline of growth occurs and senile activity takes place 

 on a different quantitative level. Thus the senile deviation of 

 the nucleus-plasma relation from the norm represents a difference 

 in the quantitative reciprocal interchange of the same metabolic 

 materials. The quantitative principle which holds all through 

 life does not change for a natural end result of that life. 



That senility of depression is quantitative in respect to the 

 same metabolic materials as in the norm is more self-evident. 

 Depression physiologically (Verworn, '96) and cytologically (Dol- 

 ley, '14) is the quantitative opposite of activity, a lower level 

 instead of a higher level of metabolism. Senility of depression 

 is only a further reducement of reciprocal interchange which be- 

 comes permanent, as was emphasized in the objective descrip- 

 tion. It is the quantitative opposite of natural senility (see 

 schema under recovery with permanent disorganization). The 

 upset in favor of the nucleus opposes the upset in favor of the 

 plasma, but senile function in both is subserved by the same 

 materials. Hence either type of senile cell not only functions in 



