MODERN CONCEPTION OF PROTOPLASM. 31 



matter acts in virtue of its peculiar organisation, of which we can form 

 only a hypothetical conception, and can give no scientific explanation. 



One general idea, however, the study of structure has suggested, 

 which the conclusions of physiologists corroborate. This idea is — that 

 a cell consists of a relatively stable living framework, and of a changeful 

 content enclosed by it. 



Now, many physiologists regard the framework as the genuine living 

 protoplasm, and the contents as the material upon which it acts. " The 

 framework is the acting part, which lives, and is stable ; the content is 

 the acted-on part, which has never lived, and is labile, that is, — in a 

 state of metabolism or chemical transformation." This view naturally 

 leads those who adopt it to regard protoplasm as a sort of ferment 

 acting on less complex material which is brought to it, which forms 

 the really changeful part of each cell. It may be recalled that the 

 strange characteristic of a ferment is that it can act on other substances 

 without being itself affected by the changes which it produces, and that 

 it can go on doing so continuously with a power which has no direct 

 relation to its amount. In these respects, therefore, living matter 

 resembles a ferment. 



Somewhat different, however, is another idea, — that the protoplasm 

 is itself the seat of constant change ; that it is constantly being unmade 

 and remade. On the one hand, more or less crude food passes into 

 life by an ascending series of assimilative or constructive chemical 

 changes, with each of which the material becomes molecularly more 

 complex and more unstable. On the other hand, the protoplasm, as 

 it becomes active or a source of energy, breaks down in a descending 

 series of disruptive or destructive chemical changes ending in waste 

 products. 



The former view, which considers protoplasm as a sort of ferment, 

 restricts the metabolism to the material on which the protoplasm acts. 

 The second view regards protoplasm as the climax or central term of 

 the constructive and disruptive metabolism. 



It may be, however, that there is no such substance as protoplasm, 

 and that vital phenomena depend upon the interactions of several com- 

 plex substances. 



Generalising from his studies on colour sensation, Professor Hering 

 was led to regard all life as an alternation of two kinds of activity, 

 both induced by stimulus, the one tending to storage, construction, 

 assimilation of material, the other tending to explosion, disruption, dis- 

 assimilation. 



Generalising from his studies on nervous activities, Professor Gaskell 

 was led to regard all life as an alternation of two processes, one of 

 them a running down or disruption (katabolism), the other a winding 

 up or construction (anabolism). 



All physiologists are agreed that in life there is a twofold process of 

 waste and repair, of discharge and restitution, of activity and recuper- 

 ative rest. But there is no certainty as to the precise nature of his 

 twofold process. 



