I20 PROTOPLASMIC ACTION AND NERVOUS ACTION 



Ca salts is thus explained; when the two salts are 

 present in appropriate proportions (20 NaCl+i CaCla) 

 conductivity is unaltered, and the tissue remains living 

 for days, while in the pure solution of either salt toxic 

 action and death soon result. The changes of permea- 

 bility accompanying normal physiological processes have 

 also been measured by the conductivity method in cer- 

 tain cases, especially by McClendon and Gray in the 

 fertilization of sea-urchin eggs.^ 



The question of the condition of the salts in the living 

 protoplasm arises here; and this question is of consider- 

 able general importance, since it has been held by certain 

 investigators that these salts are present chiefly or 

 entirely in a combined or adsorbed state and are hence 

 not free to act as conductors. As we shall see later in 

 dealing with the phenomena of stimulation and trans- 

 mission, the electrical conductivity of the internal 

 protoplasm appears to be a necessary factor in its 

 normal activity; and any evidence that this conductivity 

 is what we should expect it to be from the known salt- 

 content of protoplasm is of interest. The contention 

 that the salts in protoplasm are non-ionized, or that the 

 ions are in some manner rendered immobile, is incon- 

 sistent with the physico-chemical observations relating 

 to the behavior of salts in the presence of proteins, lipoids, 

 or other colloids. According to Bugarszky and Lieber- 

 mann, the addition of even large quantities of protein 

 to salt solutions affects the ionic concentration only 

 slightly;^ Michaelis and Rona^ have shown by '^com- 



^ McClendon, American Journal of Physiology, XXVII (19 lo), 240J 

 J. Gray, Journal of the Marine Biological Association, X (1913), 50. 



* Bugarszky and Liebermann, Arch. ges. Physiol., LXXII (1898), 51. 

 5 Michaelis and Rona, Biochem. Zeitschrift, XIV (1908), 476. 



