38 
PHYSIOLOGY: A. G. MAYER 
Prof. G. A. Hulett, the distilled water was freed in so far as possible 
from CO2 by bubbling through it for 60 hours air which had passed 
through glass tubes containing granulated soda-Hme. As the water 
still appeared sHghtly acid to phenolpthalein it was rendered alkaline 
by adding NaOH until the concentration of the OH ion was about 
0.75 n. X 10-^ 
Although this water was kept in a glass carboy carefully protected 
from contact with air containing CO2 it nevertheless became slowly 
less and less alkaline, probably due to decomposition of traces of organic 
matter, so that in the course of 11 days the distilled water became nearly 
neutral, both the H and OH ion concentration approaching lO-*^. 
The use of this nearly neutral distilled water in diluting the sea-water 
should enable one to determine the true effects of the sodium, calcium, 
and potassium cations of the sea-water without serious disturbances due 
to H or to OH ions, both of which in weak concentration accelerate and 
in strong concentration depress the rate of nerve conduction. 
Thus we find that a concentration of about 6 X 10~^ OH in sea-water 
is a maximal stimulant for nerve conduction, but becomes a depressant 
if its concentration be still further increased. 
Experiments were made upon 71 Cassiopea xamachana medusae be- 
tween July 5 and 16, 1915; the OH ion concentration in the distilled 
water declining during the course of the experiments from about 10 ~^ 
to about 10~^. Thus for the first 25 medusae, when the OH ion concen- 
tration was at the start about 10"^ and was approaching 10"^, the curve 
for the decHne in rate is fairly well represented by the formula 
y = 103. 37-0. 541 {9S.2-xy-^S 
wherein y is the rate of nerve conduction, the rate in undiluted sea- 
water being 100 and x the concentration of the sodium, potassium, and 
calcium cations, their concentration in natural undiluted sea-water being 
100. 
Later as the OH ion concentration continued to decline the formula 
became 
y= 100-0. 2 (100-x)i-3^ 
and finally for the last 14 medusae when the distilled water was still 
alkaline but nearly neutral, the rate is given by the formula 
y = 2.Snx^'\ 
This is also equally well represented by the formula 
3; = 100-0. 778 {m-xY'^'K 
