44 CRITICISM 'OF MECHANISTIC THEORY 



imperfect observation, and has long been 

 abandoned. We now know that all cells 

 are formed by division of pre-existing cells, 

 and that the problem of the process of cell- 

 growth and cell-nutrition is not one which 

 we have at present any prospect of solving 

 in a mechanistic direction. Nor is it any 

 better with the problems of secretion and 

 absorption. Thanks to the work of Ludwig 

 himself, of Heidenhain, and a host of other 

 investigators, we now know far more than 

 was known at the middle of last century 

 about secretion and absorption ; but their 

 'mechanism' is further away than ever. 

 When Johannes Miiller suggested that the 

 processes of secretion and absorption are 

 akin to the processes of growth he was 

 doubtless far nearer the truth than his 

 immediate successors : for secretion and 

 absorption are evidently only phases of the 

 many-sided metabolic activity which we 

 designate by the name of cell-life. We have 

 made great progress in learning how many- 

 sided, and how orderly, this cell-life is, but 

 none at all in explaining how this life is 

 ordered and maintained. 



