6 THE ORIGIN OF LIFE 



been previously subjected. Or when by repeated 

 heating and cooling they can be made to disappear 

 and reappear again. If those which appear after the 

 first sterilisation when two substances are brought 

 together are entirely different from any which had pre- 

 viously existed therein before sterilisation was carried 

 out, there can be little doubt that spontaneous genera- 

 tion in some form had actually taken place, or at any 

 rate heterogenesis, for which Dr. Charlton Bastian 

 has fought so persistently and for so many years. 



Of this we propose to discourse in this book ; 

 whilst the results we have arrived at give us no small 

 reason to believe that the continuity of living and 

 not living substance, as familiarly understood, is a 

 matter which cannot be passed over without pause. 



The ancient philosophers like Aristotle believed 

 that motion constituted life. And in regarding Life 

 as mode of Motion, however inadequate that idea (in 

 its ultimate simplicity) may really be, we have been 

 guided by a somewhat similar conception, the notion 

 kept before our mind being, not motion in all its 

 simplicity, for the mere state of motion does not 

 constitute life, but motion in some particular form. 

 Life being, so to speak, a specialised motion, and all 

 its manifestations accompanied by a particular kind, 

 or kinds, of molecular interchange. It is a series of 

 fermentations and thus also a series of catalytic 

 actions and interactions, a catalytic action being 

 a molecular change or series of chemical changes, 

 brought about by the presence of some substance 

 which apparently takes no part in the chemical 



