138 



W. J. V. OSTERHOUT 



After remaining five minutes in NaCl the resistance had 

 dropped to 1000 ohms; after ten minutes to 890 ohms; after fif- 

 teen minutes to 780 ohms; after sixty minutes to 420 ohms. It 

 continued to fall steadily until it reached 320 ohms, at which 

 point it remained stationary; it then had practically the conduc- 

 tivity of sea water. On replacing in sea water it did not recover 

 any of its resistance, even after standing for several days. It 

 should be noted that the solution of NaCl employed is nearly 

 isotonic with sea water and that none of the observed effects 

 could be due to osmotic action. 



A very striking contrast is obtained by placing living tissue in 

 a solution of CaCL having the same conductivity as sea water. 

 The resistance then rises rapidly to a maximum (very often in 

 the first fifteen minutes from 1100 ohms to 1750 ohms). After 

 this it slowly sinks and finally reaches about 320 ohms, which 

 is the resistance of an equal amount of sea water. 



What is the effect of combining NaCl and CaCL in the pro- 

 portions in which they exist in sea water? This question has 

 great theoretical and practical interest in view of the fact that 

 CaCl2 is known to antagonize the toxic action of NaCl in the 

 most striking way. To answer this question the following exper- 

 iment was performed. To 1000 cc. NaCl 1 M there was added 

 15 cc. CaCU 1 M; the mixture was then diluted until it had the 

 same conductivity as sea water. On placing living tissue in this 

 mixture it neither gained nor lost in resistance and even after 

 twenty-four hours had the same resistance as at the start. 



It is therefore evident that the entrance of the ions of NaCl is 

 greatly hindered by the presence of very small amounts of CaCl2 

 and that this may explain the antagonistic action of CaCl2 on 

 NaCl. 



Further experiments showed that such salts as KCl, MgCl2, 

 CsCl, RbCl, LiCl, NH4CI, NaBr. Nal, NaNOa, KNO3, Na2S04 and 

 Na-acetate act in general like NaCl (though with different degrees 

 of rapidity) while BaCl2 and SrCl2 act like CaCL. 



It might be supposed that some of these effects are due to expan- 

 sion or contraction of the cells under the influence of the salts, 

 but microscopic observation showed that this was not the case 



