iQii] Carl L. Aisberg 131 



The Absorption of Inorganic Salts by Living Protoplasm 



W. J. V. OSTERHOUT 



(Department of Botany, Harvard University, Cambridge, Mass.) 



The iisual method of determining osmotic pressure by plasmolyz- 

 ing in salts of Na and K is very erroneous. Salts of Ca give more 

 nearly the true osmotic pressure. 



Since one substance may greatly affect the penetration of another, 

 it is unsafe to use the common method of adding a toxic to a non- 

 toxic substance and judging the penetration of the former by the 

 plasmolytic action of the mixture. 



It is possible to State which salts penetrate and at what rate of 

 speed, and also how various salts affect the permeability of the 

 plasma membrane. 



From the data obtained we have a definite clue to the nature of 

 the plasma membrane. Since all the salts studied penetrate, it seems 

 certain that the membrane cannot be lipoid because these salts are 

 not soluble in lipoid. Its behavior toward balanced Solutions 

 (together with other facts) indicates unmistakably that the mem- 

 brane is protein in nature. 



Antagonistic salts such as NaCl and CaCla hinder or prevent 

 each other from entering. To such an extent is this true that by 

 choosing Solutions of NaCl and of CaClg which are not quite strong 

 enough to plasmolyze, we produce by mixing them together a Solu- 

 tion which plasmolyzes strongly. 



The fact that these salts hinder or prevent each other from enter- 

 ing may explain why they act as antidotes to each other. But since 

 they may eventually penetrate to some extent we must attach im- 

 portance to their effect on the protoplasm within the cell as well as 

 to their effect on the plasma membrane. These two effects may be 

 very similar. (Science: 191 1, xxxiv, p. 189.) 



