PHYSICOCllI■^fICAL FACTORS— P.ROWN 7 



(lc])()hu-i/.;iti()n. 'l^his would permit a i^rcaUT sodium sliift and lead to the creation 

 of a greater actixalion ])otential. Such changes in the intracellular ion concentra- 

 tion would he secondary to the membrane changes accompanying depolarization. 

 The basic problem then is the nature of the reactive process which determines the 

 period of membrane depolarization. 



The purpose of presenting the foregoing somew^hat detailed consideration of heart 

 muscle was to give an example of the type of system which re(|uires intensive 

 physicochemical study and to indicate one way in which it may be investigated. It 

 has been shown that the reactive state of the cell surface can influence the duration 

 of the active state and the size of the contraction, that it is subject to the action of 

 temperature and pressure, and that substances such as (3 strophanthin in very small 

 concentration can give great stability to the system. A concerted attack on the 

 physical chemistry of this interfacial activator system, particularly in the direction 

 of identifying more effective stabilizing agents, would be a worthwhile etTort. From 

 such a program there might come methods of regulating more effectively the activi- 

 ties of cells in hypothermia and other conditions. 



REFERENCES 



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