PROXIMATE DEFINITION OF LIFE. 69 



mutual dependence of the chief animal functions : no one of 

 which can be varied without varying the rest : no one of 

 which can go on unless the rest go on. It is this definiteness 

 of combination which distinguishes the changes occurring 

 in a living body from those occurring in a dead one. Decom- 

 position exhibits both simultaneous and successive changes, 

 which are to some extent heterogeneous, and in a sense com- 

 bined ; but they are not combined in a definite manner. They 

 vary according as the surrounding medium is air, water, or 

 earth. They alter in nature with the temperature. If the local 

 conditions are unlike, they progress differently in different 

 parts of the mass, without mutual influence. They may end in 

 producing gases, or adipocke, or the dry substance of which 

 mummies consist. They may occupy a few days, or thousands 

 of years. Thus, neither in their simultaneous nor in their suc- 

 cessive changes, do dead bodies display that definiteness of 

 combination which characterizes living ones. It is 



true that in some inferior creatures the cycle of successive 

 changes admits of a certain indefiniteness that it may 

 be apparently suspended for a long period by desiccation or 

 freezing ; and may afterwards go on as though there had 

 been no breach in its continuity. But the circumstance 

 that only a low order of life permits the cycle of its changes 

 to be thus modified, serves but to suggest that, like the pre- 

 vious characteristics, this characteristic of definiteness in its 

 combined changes, distinguishes high vitality from low vital- 

 ity, as it distinguishes low vitality from inorganic processes. 

 Hence, our formula as further amended reads thus : Life is 

 a definite combination of heterogeneous changes, both simul- 

 taneous and successive. 



Finally, we shall still better express the facts, if, instead of 

 saying a definite combination of heterogeneous changes, we 

 say the definite combination of heterogeneous changes. As 

 it at present stands, the definition is defective both in allow- 

 ing that there may be other definite combinations of hetero- 

 geneous changes, and in directing attention to the hetero- 



