38 NATURAL BODIES. 



or taking up particles of their own structure, and throwing them off. 

 The actions of composition and decomposition are constant whilst life 

 persists ; although subject to particular modifications at different pe- 

 riods of existence, and under different circumstances. 



Again : the inorganic and organized are alike subject to changes 

 during their existence ; but the character of these changes, in the two 

 classes, differs essentially. The mineral retains its form, unless acted 

 upon by some mechanical or chemical force. Within, all the particles 

 are at rest, and no internal force exists, which can subject them to 

 modification. There is no succession of conditions that can be termed 

 ages. How different is the case with organized bodies ! Internally, 

 there is no rest ; from birth to death all is in a state of activity. The 

 plant and the animal are subject to incessant changes. Each runs 

 through a succession of conditions or ages. We see it successively de- 

 velope its structure and functions, attain maturity, and finally decay. 



Characteristic differences likewise exist in the external conformation 

 of the beings of the two divisions, as well as in their mode of increase. 

 Inorganic bodies have no covering to defend them ; no exterior enve- 

 lope to preserve their form ; a stone is the same at its centre as at 

 its circumference; whilst organized bodies are protected by an elastic 

 and extensible covering, differing from the parts beneath, and inservient 

 to valuable purposes in the economy. 



Every change to which an inorganic body is liable must occur at its 

 surface. It is there that the particles are added or abstracted when 

 it experiences increase or diminution. Increase for growth it can 

 scarcely be termed takes place by accretion or juxtaposition, that is, 

 by the successive application of fresh particles upon those that form 

 the nucleus ; and diminution in bulk is produced by the removal of 

 the external layers or particles. In organized substances, increase or 

 growth is caused by particles deposited internally, and diminution by 

 particles subtracted from within. We see them, likewise, under two 

 conditions, to which there is nothing similar in the mineral kingdom 

 health, and disease. In the former, the functions are executed with 

 freedom and energy ; in the latter, with oppression and restraint. 



7. Termination. Every body, inorganic or organized, may cease to 

 exist, but the mode of cessation varies greatly in the two classes. The 

 mineral is broken down by mechanical violence ; or it ceases to exist 

 in consequence of modifications in the affinities, which held it concrete. 

 It has no fixed duration ; and its existence may be terminated at any 

 moment, when the circumstances, that retained it in aggregation, are 

 destroyed. The vegetable and the animal, on the other hand, carry 

 on their functions for a period only which is fixed and determinate for 

 each species. For a time, new particles are deposited internally. The 

 bulk is augmented, and the external envelope distended, until maturity 

 or full developement is attained ; but, after this, decay commences ; the 

 functions are exerted with gradually diminishing energy; the fluids 

 decrease in quantity ; and the solids become more rigid, circumstances 

 premonitory of the cessation of vitality. This term of duration is 

 different in different species. Whilst many of the lower classes of ani- 



