CHEMICAL CHARACTER AND PHYSIOLOGICAL ACTION 

 OF THE POTASSIUM ION. 



By JACQUES LOEB. 



{From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, August 18, 1920.) 

 I. INTRODUCTION. 



Zwaardemaker^ has recently made the interesting suggestion that 

 the role of potassium in physiologically balanced salt solutions — e.g. 

 the blood or the sea water — is due to the very slight radioactivity of 

 this element and not to its chemical character as determined by its 

 position in the series of elements. It has been pointed out by R. F. 

 Loeb^ in another paper in this Journal that K cannot be replaced by 

 Th and U as far as the development of the sea urchin egg is concerned, 

 that the non-radioactive element Cs is capable of replacing potassium 

 to some extent in this case, and thatZwaardemaker's observations on 

 the influence of radioactive substances on the heart beat might be 

 explained without the assumption that the physiological action of K 

 is due to its radioactivity. 



This then suggests that the physiological action of potassium is due 

 to its chemical character. We know through the work of Sir Ernest 

 Rutherford that radioactivity is caused by an explosive charge in the 

 nucleus of the atom while the chemical and most of the physical prop- 

 erties of the atom depend upon its external ring or shell of electrons. 

 These latter properties are repeated periodically in the series of 

 elements arranged by their atomic numbers and if we can show that 

 the physiological action of an element corresponds to its position in 

 the periodic table we know that we are dealing with purely chemical 

 effects and not with radioactive effects. We intend to show in an 

 indirect way that the action of K in physiologically balanced salt 



^ Zwaardemaker, H., /. Physiol, 1919-20, liii, 273 

 2 Loeb, R. F., /. Gen. Physiol., 1920-21, iii, 229. 



237 



