48 EX VIRIBUS VIVIMUS. 



decay, and in other cases only remotely so. It 

 is the influence of expenditure on longevity which 

 really gives rise to that complication which led us to 

 distinguish normal and absolute potential longevity. 

 (See antea, p. 25.) Expenditure, which was pointed 

 out as increasing more rapidly than the means of 

 supplying the loss it involved, and thus limiting 

 natural life, may be increased greatly or diminished 

 in organisms according to their requirements, and 

 may be so far diminished as never actually to allow 

 that period of balance and the subsequent one of 

 decay, which we saw occurred in one group of organ- 

 isms, to come on in another. 



Expenditure is of two kinds — that involved in the 

 wear and tear of obtaining and assimilating food, 

 and generally carrying on the life, and that involved 

 in the propagation of the species by the elaboration 

 or separation of living portions of the parent organ- 

 isms. We may distinguish these as — (1) personal, and 

 (2) generative expenditure ; and we may affirm, that 

 by diminishing or increasing either of these, you 

 favour or antagonize longevity. This follows de- 

 ductively from the conclusions arrived at with regard 

 to the relation of organic structure to longevity. 

 Expenditure of either sort uses up the matter of life, 

 and hastens on the period of natural decay. It is 

 observable that these two forms of expenditure are 

 naturally, inter se, antagonistic, on the old principle 

 that ' one cannot have a pie and eat it.' If personal 



