PETERS. — METABOLISM AND DIVISION IX rUOTOZOA. 485 



influence ? It is not. For while the abstraction of water was greater 

 in milk siiuar than in the salts, the mean results show that milk suijar 

 was, in comparison with the salts, practically harmless. It is true tliat 

 abstraction of water by sufficiently high concentration of sugar, or of 

 inactive salt, if such there be, may be at least a prominent factor in the 

 destruction of the cell. But at present we are describing lower, though 

 still hyperisotonic, concentrations, where there is the possibility that both 

 osmosis and a metabolic activity of the same substance are present. The 

 demonstration of these two modes of action, and especially their separate 

 estimation, is the first important step toward a physico-chemical analysis 

 of the action of physiological salts upon cells. We have now carried the 

 analysis far enough to be able to exclude abstraction of water as the deter- 

 mining factor in the destruction -produced by these salts at the higher ends 

 of the curves. Wliere, then, shall we look for the efficient factor? 



I now return to the process of equilibration which takes place when 

 the cell is more or less permeable to the salt. With the outward move- 

 ment of water there is also, because of unequal salt pressure already 

 described, a concurrent inward movement of the single salt applied (or 

 of its ions). There results an introduction into the cell of an excess of 

 that salt in proportion to other salts present in normal amount. We 

 have to deal, then, with the physiological effect of an excess of one salt 

 within the cell, a normal proportion of which would not interfere, in the 

 case of physiological salts, with its usual metabolism. The ruin of the 

 cells in the given hyperisotonic solutions was due to an excessive proportion 

 of a single salt. 



In the next section I shall present experimental evidence that there is 

 an increased division-reaction with Stentor under the influence of several 

 salts together, as compared with that under the action of one, and espe- 

 cially of the adjustment of Stentor to limited proportions oi different salts. 



From the experiments with distilled water it might be suggested 

 here that an objective determination should be made — either by elec- 

 trical conductivity or by quantitative chemical estimation — to prove 

 that water has increased or that salt has proportionately diminished in 

 the external medium. This was not done because the above described 

 conditions of concentration are made sufficiently certain by the ascer- 

 tained osmotic concentration of the native mass-culture medium of the 

 Stentors and the purposely prepared higher concentration of the reagents 

 used. Granted a certain degree of permeability, of which the experi- 

 ments themselves furnish evidence, the above described processes tending 

 to equilibration of pressure follow as a physical necessity. Furthermore 



