EXTRACT XLIV.c. 



ON THE PHYSIOLOGICAL PROCESS KNOWN AS 

 "AGEING," OR INVOLUTION. 



WE have already " trenched on this ground," but still 

 think that it requires " turning over," in order that it 

 may yield "something more of a crop" to repay the 

 expenses of labour. 



" Ageing " is a natural process due to the co-operation 

 of dynamic and material factors on definite physiological 

 lines, and characterised by the evolution of a regular 

 succession of tableaux vivanfs, or living " tell tales," each 

 indicating a difference from the other in physical features 

 and physiological peculiarities sufficient to mark the stage 

 of development and age attained by its subject in his or 

 her passage " from the cradle to the grave." The process 

 thus viewed reveals the great physiological truth that the 

 limits of life as represented in the usual experience of 

 " the longest liver/' or where and when senile decay 

 takes possession of the organism and closes the life scene 

 by involution are laid in and constituted respectively by 

 the two great periods of almost purely systemic nerve 

 control, and the combined early and late periods of 

 nervine control actuated by the influence of sympathetic 

 nervine energy dominant during the almost entire abey- 

 ance, on the one hand, and final exhaustion, on the other, 

 of systemic nerve energy. 



Between the periods of pre- and post- sympathetic 

 nerve control in the systemic period of innervation of 

 the organism, we witness the continuous evolution of 

 the representative phenomenon of "age" or "ageing" 



2 H 



