658 



SCIENCE 



[N. S. Vol. XXXEV. No. 881 



by a combined action of two salts, whereby 

 the membrane becomes less permeable for 

 both salts. 



V 



It is not easy to find examples of experi- 

 ments in the literature which are equally 

 unequivocal in regard to the character of 

 antagonistic salt action; but I think that 

 some recent experiments by Osterhout sat- 

 isfy this demand. 



It has long been a question whether or 

 not cells are at all permeable for salts. 

 Nobody denies that salts diffuse much more 

 slowly into the cells than water; but some 

 authors, especially Overton and Hoeber, 

 deny categorically that salts can diffuse at 

 all into the cells. Overton's view is based 

 partly on experiments on plasmolysis in 

 the cells of plants. If the cells of plants, 

 for example, those of Spirogyra, are put 

 into a solution of NaCl or some other salt 

 of sufficiently high osmotic pressure, the 

 volume of the contents of the cell decreases 

 through loss of water and the protoplasm 

 retracts, especially from corners of the 

 rigid cellulose walls. Overton maintains 

 that this plasmolysis is permanent, and con- 

 cludes from this that only water but no 

 salt, can diffuse through the cell-wall ; since 

 otherwise salts should gradually diffuse 

 from the solution into the cell, and through 

 this increase in the osmotic pressure of the 

 cell the water should finally diffuse back 

 into the cell and restitute the normal vol- 

 ume of the cell. According to Overton this 

 does not happen. 



Osterhout has recently shown that Over- 

 ton's observations were incomplete in a 

 very essential point and that in reality the 

 plasmolysis, which occurs in this case when 

 the cell is put into the hypertonic solution, 

 disappears again in a time which varies 

 with the nature of the salt in solution. 

 This stage of reversion of plasmolysis had 

 been overlooked by Overton. If the cell, 



however, remains permanently in the hy- 

 pertonic sodium chloride solution, after- 

 wards again a shrinking of the contents of 

 the cell takes place, which superficially re- 

 sembles plasmolysis, but which in reality 

 has nothing to do with plasmolysis, but is a 

 phenomenon of death. That this second 

 "false plasmolysis," as Osterhout calls it, 

 has nothing to do with the hypertonic char- 

 acter of the solution was proved by the fact 

 that hypotonic solutions of toxic substances 

 may produce the same phenomenon. 



In one experiment which Osterhout de- 

 scribes, "a portion of a Spirogyra filament 

 was plasmolyzed in .2 m. CaCl,, but not in 

 .195 m. CaCL. A .29 m. NaCl solution has 

 approximately the same osmotic pressure as 

 a .2 m. CaCla solution. But on placing 

 another portion of the same Spirogyra fila- 

 ment in a .29 m. NaCl solution the expected 

 plasmolysis does not occur and it is impos- 

 sible to plasmolyze the cells until they are 

 placed in .4 m. NaCl. ' ' Osterhout explains 

 this difference in the concentration of the 

 two salts required for plasmolysis by the 

 assumption that NaCl diffuses more rapidly 

 into the cell than CaClj, a conclusion which 

 I reached also on the basis of my earlier 

 experiments on animals. 



Osterhout 's experiments also show that 

 the antagonism of NaCl and CaClj depends 

 partly on the facts that the two salts in- 

 hibit each other from diffusing into the 

 cells, and this conclusion is based among 

 others upon the following experiment. 

 "By dividing a Spirogyra filament into 

 several portions it was found that it was 

 plasmolyzed in .2 m. CaCL and in .38 m. 

 NaCl, but neither in .195 m. CaClj nor in 

 .375 m. NaCl. On mixing 100 c.c. .375 m. 

 NaCl with 10 c.c. .195 m. CaCL and placing 

 other portions of the same filament in it, 

 prompt and very marked plasmolysis oc- 

 curred. ' ' 



The explanation for this observation lies 



