METHODS 101 



solved 1 , whereas in reality it simply passed from one 

 colloid stale to another colloid state in equilibrium with that of 

 the stomach cells. This new way of looking at things 

 explains quite naturally a paradox that has been the 

 occasion of many an odd explanation. 



" Why does not the gastric juice digest the walls of the 

 stomach ? " 



The answer is direct : 



" Because the gastric juice's work is to bring the colloid 

 states of the ingesta into equilibrium with the stomach cells, 

 whereas the stomach cells are naturally in equilibrium with 

 themselves." 



In the same way astonishment is felt that the venom of 

 scorpions and serpents should be inoffensive to themselves. 

 The notion of physical assimilation explains it all. 



Physical assimilation, in certain cases, is carried on both 

 inside and outside the living protoplasm ; but it is not 

 wonderful that, for the most part, it should be much stronger 

 inside the active cells and be exercised in the surrounding 

 medium with an intensity decreasing in proportion to the 

 distance from the centre of activity. For this reason we are 

 obliged in many cases, in order to procure certain diastases, 

 to triturate mechanically the cells which have produced them. 

 It is also possible that certain activities should become 

 localized inside the living cells and have no diffusion out- 

 side ; relatively to such activities our effective functional 

 analysis would be incomplete. 



The history of physical assimilation is very clearly summed 

 up in the phenomena which take place in an amoeba vacuole 

 (Fig. 4). The amoeba, which comes up for study again with 



1 When milk is digested by rennet its physical assimilation is 

 made known by a more solid state (curdled milk), and not by a 

 more liquid state. 



