4 



LETTERS ON TREES. 



agency of its own vitality, as are ultimately incom- 

 patible with the longer continuance of life. Death 

 then follows as a matter of course. And those changes 

 are attended by a gradually increasing languor or 

 sluggishness in the vital processes, and by a corres- 

 ponding hardening and rigidity of the textures com- 

 posing the organism, — changes that constitute and 

 betoken the state to which the name of old age is 

 given ; a state which obtains uniformly when life is not 

 prematurely cut short, and is indicative of the approach 

 of death. 



7. Again, all organised bodies have an appointed 

 size or bulk of organism. Of lifeless inorganic bodies, 

 it cannot be affirmed that they possess any such pro- 

 perty, being larger or smaller, to any conceivable 

 extent, according as circumstances may determine. 

 It is otherwise, however, with animal and vegetable 

 organisms. These have naturally a fixed or standard 

 size to which they grow, and from which they never 

 greatly deviate. 



8. I have perhaps needlessly gone into these details 

 respecting this principle. But I have purposely done 

 so, and for this reason, that, while the principle is con- 

 fessedly one of the grounds on which the questions 

 before us proceed, and one which I hold to be unas- 

 sailable, no answer that may be given to the questions, 

 that is not in conformity with it, can be regarded as 

 satisfactory. 



