555 



Chapter 111. 

 decline of the system. 



To follow minutely the various steps by which 

 Nature conducts the individual to its state of ma- 

 turity, would engage us in details incompatible 

 with the limits of the present work. I shall only 

 remark, in general, that during the period when 

 the body is intended to increase in size, the powers 

 of assimilation are exerted to prepare a greater 

 abundance of nourishment, so that the average 

 supply of materials rather exceeds the consump- 

 tion ; but when the fabric has attained its pre- 

 scribed dimensions, the total quantities furnished 

 and expended being nearly balanced, the vital 

 powers are no longer exerted in extending the 

 fabric, but are employed in consolidating and per- 

 fecting it, and in qualifying the organs for the 

 continued exercise of their respective functions, 

 during a long succession of years. 



Yet, while every function is thus maintained in 

 a state of healthy equilibrium, certain changes are 

 in progress which, at the appointed season, will 

 inevitably bring on the decline, and ultimate de- 

 struction of the system.* The process of consoli- 



* It would appear from the researches of De Candolle, that the 

 vegetable system is not, like the animal, subject to the destructive 

 operation of internal causes ; for the agents which destroy vegetable 

 life are always extraneous to its economy. Each individual tree is 

 composed of an accumulation of the shoots of every successive year 

 since the commencement of its growth; and although, from the 

 continued deposition of lignin, and the consequent obliteration of 



