PROPAGATION OF PHYSIOLOGICAL CHANGE 483 



anabolism and katabolism ; no very certain limit being placed 

 to the meaning of these terms. Alongside of the processes 

 leading to the formation of an unstable and highly complex 

 product were also processes leading to its destruction, and both 

 sets of processes were characteristic of the normal resting 

 state of living matter. Stimulation led to a new quantitative 

 relation between the two, so that momentarily the destructive 

 process was dominant. During the recuperative period 

 following excitement the constructive process was dominant 

 in its turn. 



More recently considerations introduced by Ehrlich, as 

 also the time relations of the oxidation process observed by 

 Hermann, have served to modify and harden this view. It 

 is on the one hand made clear that the destructive process 

 need not be postulated as overtaking more than a certain 

 fraction of the molecule, or, as it is expressed, no more than 

 certain of its side chains. On the other hand also the con- 

 structive process can be imagined as repeatedly recommencing 

 from a constantly surviving level of considerable perfection. 

 Verworn has therefore brought to our notice a certain stable 

 atom-complex, or nuclear group, to which more unstable 

 side chains are linked under pressure of ordinary chemical 

 and physical circumstance. In these and between these 

 side chains perpetual change occurs, which is exaggerated and 

 perhaps given a new direction by the incidence of stimulation. 

 Every act of " life " therefore has its basis in the chemical 

 changes taking place on the fringe and within the influence 

 of these residual nuclear molecules. This at least if certain 

 " enzymes " are allowed to play a part less definitely assessed, 

 and take a place in the molecule less definitely assigned. 



To satisfy the intimacy of intracellular life the conception 

 has been tentatively extended by a hypothesis first boldly 

 introduced by Pfluger. The residual atom-complexes are linked 

 together to form a giant nuclear molecule which occupies a 

 great share of the space within the cell, as for example the 

 whole of that process of a nerve-cell known as the core of a 

 nerve-fibre. In this way we have in front of us a schema 

 which clearly illustrates the conception that " life " is primarily 

 dependent upon chemical structure, and that all the expressions 

 of life are the outcome of chemical change. This conception has 

 indeed been welcomed as serving usefully to link together many 



