SPONTANEOUS GENERATION 207 



clear that the proposal to fill or to replace those 

 gaps which we now see no more is the course 

 which men of science at the present day would find 

 most fruitful to adopt. 



It is therefore by the artificial synthesis of 

 highly complex compounds, and the artificial pro- 

 duction of cells from them, that progress seems to 

 us to lie most hopefully in view. And apart 

 altogether from the artificial synthesis of these 

 compounds, given the substances, provided they 

 have been properly sterilised, the artificial syn- 

 thesis or construction of cells from them is a step 

 onward in the right direction. 



We have shown how it is that the action 

 of certain salts under certain conditions on gelatin- 

 ous substances can give rise to the formation 

 of such cells — of cells which have all, or at 

 any rate most, of the properties which are 

 associated with vital processes. We see how it is 

 that by the action of radio-active bodies the efi"ects 

 if carefully attended to can show a still more 

 approximate imitation of the vital processes which 

 of their own accord present themselves in nature. 

 We see that the process of metabolism, not confined 

 to living protoplasm alone, is a phenomenon of 

 as wide an application as it is of wide significance, 

 and that it can take place in certain circumstances 

 under the action of radio-active bodies. 



The formation of such cells by the action of salts 

 on gelatinous media is the result of a highly com- 

 plex molecular process. These cells are produced, 



