THE MECHANISM OF LIFE 487 



the relation of these two processes. Living substance is continuall)^ 

 performing both. Heiing believes that these processes, vi^hich 

 constitute the metabolism of living substance, " take place 

 simultaneously in all the most minute parts of the latter." 

 Hatschek has expressed a view differing from this, and emphasises 

 the difficulty of the idea " that the proteid molecule simultaneously 

 receives and gives off carbon." When only a single particle is 

 considered, it is very difficult to conceive this process, for the split- 

 ting-off and the regeneration of any groups of atoms by a molecule 

 exclude each other chronologically, and, when considered strictly, 

 although instantaneous, they are only able to take place in succession, 

 unless it is assumed that corresponding groups of atoms, separated 

 from the molecule at one place, are added to it at another place. 

 This latter idea Hering himself rejects, since he emphasises the 

 following : " We ought not to be misled into picturing living 

 substance as a mass that is at rest internally, while being 

 consumed upon one side and built up upon the other." If we are 

 unable to conceive the dissimilation and assimilation of the 

 minutest individual particle or biogen molecule as absolutely 

 simultaneous, within a larger quantity of living substance these two 

 processes can take place at the same time. In this latter case 

 there are always different molecules that are destroyed and rebuilt 

 at the same moment, for only the residue of the biogens already 

 present is capable of regeneration, and, vice versa, only the 

 complete biogen molecules already present are capable of 

 decomposition. 



If we consider the quantitative relation of assimilation to dissimi- 

 lation in a considerable mass of living substance, for example such 

 as is contained in a cell, we find it very variable, and even without 

 the influence of stimuli it changes within wide limits. This 

 relation of the two processes in the unit of time, which can be 



A ... 



expressed by the fraction — and will be termed, m brief, hiotonus, 



is of fundamental importance for the various phenomena of life. 

 The variations in the value of the fraction effect all changes in the 

 vital manifestations of every organism. 



The fraction — is merely a general form of the expression 



of biotonus. In reality, assimilation and dissimilation are not 

 simple processes; on the contrary, the events that lead to the 

 construction of the biogen molecule and the formation of the 

 decomposition-products are very complex and consist of many pro- 

 cesses closely interwoven. Hence, if we would express biotonus 

 in a specialised way, we must give the fraction the form 



«' + «i + a2 + "3+ • • • in which a, asj, a^, a^, etc., and d, d^, d^, d„, etc., 



d + dj+d2 + d^+ ... 



represent the partial processes that combine to form the whole. 



