68 THE DATA OF BIOLOGY. 



This exceptional instance, however, will scarcely be held to 

 obscure that broad distinction from inorganic processes, 

 which organic processes derive from the combination among 

 their constituent changes. And the reality of this distinction 

 becomes yet more manifest when we find that, in common 

 with previous ones, it not only marks off the living from the 

 not-living, but also things which live little from things which 

 live much. For while the changes going on in a plant or a 

 zoophyte are so imperfectly combined that they can continue 

 after it has been divided into two or more pieces, the com- 

 bination among the changes going on in a mammal is so 

 close that no part cut off from the rest can live, and any con- 

 siderable disturbance of one function causes a cessation of the 

 others. Life, therefore, as we now regard it, is a com- 

 bination of heterogeneous changes, both simultaneous and 

 successive. 



Once more looking for a characteristic common to these 

 two kinds of vital action, we perceive that the combinations 

 of heterogeneous changes which constitute them, differ from 

 the few combinations which they otherwise resemble, in re- 

 spect of definiteness. The associated changes going on in a 

 glacier, admit of indefinite variation. Under a conceivable 

 alteration of climate, its thawing and its progression may be 

 stopped for myriads of years, without disabling it from again 

 displaying these phenomena under appropriate conditions. 

 By a geological convulsion, its motion may be arrested with- 

 out an arrest of its thawing ; or by an increase in the in- 

 clination of the surface it slides over, its motion may be 

 accelerated without accelerating its rate of dissolution. 

 Other things remaining the same, a more rapid deposit of 

 snow may cause an indefinite increase of bulk ; or, conversely, 

 the accretion may entirely cease, and yet all the other actions 

 continue until the mast, disappears. Here, then, the combina- 

 tion has none of that definiteness which, in a plant, marks 

 the mutual dependence of assimilation, respiration, and cir- 

 culation ; much less has it that definiteuess seen in the 



