172 ZOOCHEMICAL PROCESSES. 



The case is very different when physical forces act under 

 organic conditions, or when motion occurs in organised bodies, 

 for here we find a tendency to persistence ; everything that 

 is brought into the line of direction of these concurrent forces is 

 impelled to similar motion, and although a temporarily prepon- 

 derating force may be antagonised, equilibrium will not be induced ; 

 for equilibrium is rest, and in rest there is no life, and in equili- 

 brium there is death. 



If we may be permitted to bring prominently forward some 

 few causes from the sum of the conditions under which physical 

 forces act in the motion of living beings, there are three character- 

 istic points which appear especially to challenge our attention. 

 The question arises how this persistence of motion, which can only 

 be maintained under purely mechanical conditions, can exist inde- 

 pendently of vital stimuli. We are acquainted with a number of 

 purely chemical motions or processes which require for their 

 accomplishment a certain duration of time, or, in other words, a 

 longer interval, to equalise all the conditions of affinity than 

 is required for the usually instantaneous effects of chemical 

 affinity. We need only refer to the solution of fibrin in nitre- 

 water, to the decomposition of alcohol by caustic alkalies, to 

 the formation of numerous compound ethers (Liebig*), and more 

 especially to the processes of fermentation and putrefaction. In 

 the meanwhile, notwithstanding the occasional constancy of all 

 these chemical motions, they differ in a very marked manner 

 from orgariico-chemical actions in living organisms. Thus in fer- 

 mentation and putrefaction we observe that the chemical motion 

 exhibits a tendency towards the simplification of the radical a 

 tendency to equilibrium ; in these decompositions there are always 

 produced more fixed combinations and more persistent bodies, 

 until at length there are formed either undecomposeable radicals or 

 their most constant combinations, upon which equilibrium or rest 

 follows. We perceive no tendency of this kind towards equilibrium 

 in chemico-vital motion ; for here one motion is produced only in 

 order to call forth some other motion, the object of the metamor- 

 phosis being merely to effect a new change. The molecular motion 

 itself is thus maintained by motion, and gives occasion to new 

 motion ; a substance undergoing metamorphosis gives origin to a 

 new substance, which in its turn becomes the source of new 

 motion, that is to say, new substances are formed by chemical 

 activity which are not characterised by their constancy, as in 

 putrefaction and decay, but are distinguished by their marked 

 * Ann. d. Ch. u. Pharm. I3d. 65, S. 350. 



