114 
its position in the series of disks which com- 
posed the cylinder. The mere act of rinsing 
the disks in this way and then reclamping the 
electrodes made only slight changes in the 
reading. 
After remaining five minutes in NaCl .52 MW 
the resistance had dropped to 1,000 ohms; after 
ten minutes to 890 ohms; after fifteen 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 sta- 
tionary; 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. 
Further experiments showed that if the 
material was removed from NaCl solution and 
placed in sea water as soon as its resistance 
had fallen about one hundred ohms below the 
original resistance it quickly regained its 
original resistance and remained unchanged 
for a long time. 
It is therefore evident that pure NaCl pro- 
duces a very rapid decrease in resistance 
which, up to a certain point, is reversible. 
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 maxi- 
mum (very often in the first fifteen minutes 
from 1,100 ohms to 1,750 ohms) and remains 
practically stationary for some hours. After 
this it slowly sinks and finally reaches about 
820 ohms, which is the resistance of an equal 
amount of sea water. If, however, it be re- 
turned to sea water shortly after it has reached 
its Maximum it soon regains its original re- 
sistance and remains for a long time (in sea 
water) practically unchanged. The rise in 
resistance caused by CaCl, is in no way due 
to its action on the cell walls, for dead tissue 
shows no rise. 
It is therefore evident that CaCl, produces 
a very rapid increase in resistance, which is 
reversible. 
SCIENCE 
[N.S. Vou. XXXV. No. 890: 
What is the effect of combining NaCl and 
CaCl, in the proportions in which they exist. 
in sea water? This question has great the- 
oretical and practical interest in view of the 
fact that CaCl, is known to antagonize the 
toxie action of NaCl in the most striking way. 
To answer this question the following experi- 
ment was performed. To 1,000 c.c. NaCl 1 
there was added 15 ¢.c. CaCl, 1 M; the mix- 
ture 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 CaCl, and 
that this may explain the antagonistic action 
of CaCl, on NaCl. 
Further experiments showed that such salts 
as KCl, MgCl, CsCl, RbCl, LiCl, NH,Cl, 
NaBr, Nal, NaNo,, Na,So, and Na-acetate act 
in general like NaCl (though with different 
degrees of rapidity) while BaCl, and SrCl, act 
like CaCl,. 
It might be supposed that some of these 
effects are due to expansion or contraction of 
the cells under the influence of the salts, but 
microscopic observation showed that this was 
not the case except only that when a cell is 
injured by the salt a contraction (which I 
have elsewhere called false plasmolysis) may 
take place. But as the fall in resistance is 
already great before any such contraction 
begins and as the contraction is in any case 
too small to account for more than a small per 
cent. of the decrease in resistance it may be 
regarded as at best a secondary factor which 
is absent until the resistance has reached a 
low point and which is almost negligible be- 
yond that point. 
It might be supposed that the change in 
resistance is due to causes which operate in 
the interior of the cell rather than in the 
plasma membrane, but this is opposed to a 
variety of evidence which can not be discussed 
here. 
Two hypotheses may be formed regarding 
