disharmonies . . . which will strive to restore the disturbed harmonies . . . Once 

 this harmony is disturbed anywhere, even if only very slightly, the activity of 

 the whole is disturbed and the entire system begins to be destroyed." 



Extreme differentiation, connected with a loss of the cells' ability to divide 

 and of the protoplasm's to be restored, is considered by S. I. Metal'nikov as 

 also explaining the loss of the ability to regenerate among higher animals. 

 This loss leads to death: "If man possessed the same ability to regenerate his 

 amputated extremities or his head that we find in many worms and insects, if 

 he could restore his damaged intestine as do holothurians, then, of course, 

 neither death nor old age would be terrible to him" (1917). 



S. I. Metal'nikov also wrote such fundamental works as "The Problem of 

 Immortality in Contemporary Biology" and "La Lutte contre la Mort" (1937). 



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