REACTIONS IN LIVING MATTER 



To separate substances from each other by 

 filtration or by shaking with suitable liquids is one 

 of the daily tasks of the chemist. We must 

 expect analogous processes to occur regularly 

 in living cells. When nitrations are to be quickly 

 finished, we have to use filters which have a large 

 surface. In living protoplasm this condition is 

 very well fulfilled by the foam-like structure, which 

 affords an immense surface in a very small space. 

 We have been told that fine membranes form the 

 meshes of the network in protoplasm. These 

 membranes have the function of filters. We know 

 already that they are not permeable for every 

 substance. On the contrary they dissolve and let 

 certain substances pass through, whilst others 

 are retained. In this way a most perfect separation 

 is reached which may be compared with our best 

 filtering contrivances. I may add that by ad- 

 sorption the plasma membranes retain numerous 

 substances, which process is quite analogous to 

 precipitation and elimination from other reactions. 



Finally, we have to mention the importance of 

 procedures of mixing in chemical reactions. In 

 ordinary laboratory practice mixing is carried 

 out by stirring. In living cells there could not be 

 any better contrivance for stirring or mixing than 

 the streaming of protoplasm. There are many 

 considerations which render it very probable that 

 the real purpose and use of the streaming of proto- 

 plasm is the performing of this function. 

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