CHEMICAL PHENOMENA IN LIFE 



compounds when being digested by the leaves of 

 Drosera or by parasitic fungi are dissolved before 

 they enter further chemical reactions in the living 

 cells. Digesting is essentially identical with dis- 

 solving, or bringing into a liquid state. On the 

 other hand, the chemist knows how to save a 

 substance from chemical change by reactions, by 

 transferring it from the state of solution into a 

 solid state. This is what is called precipitation. 

 The solid insoluble deposit of the substance now 

 remains chemically unchanged. Metabolism in 

 plants employs the same means. Substances 

 which are to be stored up, such as starch, fat, 

 or protein bodies, are deposited in insoluble solid 

 form, ready to be dissolved and used whenever 

 wanted for the life process. Further substances 

 which are useless or even poisonous are easily 

 withdrawn from the complex of chemical reactions 

 in living protoplasm, and form a solid insoluble 

 deposit. For instance, oxalic acid is a wide- 

 spread product of oxidation in living cells which 

 has strong poisonous properties. Oxalic acid 

 immediately forms an insoluble compound when 

 calcium salts are present. In reality deposits of 

 oxalate of calcium are most common in plant 

 cells. We may then maintain that oxalic acid 

 is in this way withdrawn from active metabolism. 

 Resins and essential oils in quite a similar manner 

 are isolated and separated from the other reacting 

 substances in living protoplasm. 

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