42 PROTOPLASMIC ACTION AND NERVOUS ACTION 



cited general rule, and indicate clearly that the physico- 

 chemical conditions determining functional activity are 

 in close relation to those determining metabolic synthesis 

 and growth. 



Claude Bernard has pointed out that in any living 

 system a relation of this kind must exist if the system 

 is to persist and retain its normal properties under 

 varying conditions of activity.^ All activity involves a 

 certain breakdown of organized structural material, as 

 well as of energy-yielding compounds like sugar; hence 

 a return to the normal or resting condition after stimula- 

 tion requires that compensatory or constructive processes 

 should be set in motion by the same condition that calls 

 forth the destructive or energy-yielding activity. 



The general metabolism of any living system repre- 

 sents an ordered combination of constructive and 

 destructive processes; the living condition always 

 involves metabolic construction; as Bernard expresses 

 it, ''synthesis is life," even during rest. Hence the rate 

 of metabolic construction is to be recognized as under 

 the same kind of control as the rate of destruction; i.e., of 

 energy-production or normal activity. Growth processes 

 are therefore modified by any condition (cold, poisons, 

 H-ion concentration, salts, anaesthetics) which alters the 

 general activity of the living cell. The growth of the 

 embryo can be temporarily arrested by anaesthetization; 

 the same is true of seedlings and dividing cells. ^ Such 



' Claude Bernard, Leqons stir les phenomenes de la vie, I, 127. 



^ Bernard describes the anaesthesia of seedlings and embryos (La 

 Science Experimentale, Paris [1890], p. 224). For a study of anaesthesia 

 of cell-division, see my article in Journal of Biological Chemistry, XVII 

 (1914), 121. 



