Nerve-Conduction in Diluted aiid in Concentrated Sea-Water. 183 



with this potassium-chloride sokition, both at 25° C, the ratio of 

 their electrical conductivities became as 1 to 4.179. 



The salinity of the sea-water was determined by titration with silver 

 nitrate, using potassium chromate as an indicator and titrating against 

 a sample of standard sea-water from Professor Kniidsen's laboratory. 



The fact that the rate of nerve-conduction increases in a straight- 

 hne ratio in comparison with the increase of electrical conductivity 

 suggests a causal relation between the two, as was pointed out by Ralph 

 S. Lillie, 1916,^ but the same ratio exists between the concentration of 

 the dissociated cations Na*, Ca**, Mg", and K*, su'Tounding the nerves 

 and the rate of nerve-conduction ; and thus the rate may be dependent 

 upon the concentration of these electrolytes rather than upon their 

 electrical conductivity as such. Thus, in experiments made m 1917 

 upon Cassiopea, we find that if the electrical conductivity of 0.601 m. 

 NaCl be taken as 1.00, that of an isotonic solution composed of 81. 1 

 c.c. of 0.601 m. NaCl + 14.36 of 0.39 in. MgCL is 0.932; yet if the rate 

 in the pure sodium chloride be 100, that in the NaCl-f-^MgClo is 115. 

 Thus the rate has increased while the electrical conductivity has dimin- 

 ished. This experiment is a striking illustration of Loeb's law that a 

 bivalent cation tends to offset the injurious effects of a univalent cation 

 and even magnesium, a well-known depressant, acts as a stimulant 

 for rate of nerve-conduction in association with sodium. 



Comparing the effects of these solutions with that of normal sea- 

 water, all being practically isotonic one with the other, we find : 



Rate of nerve-conduction is 100 in natural sea-water of 36.24 



0/00 salinity, 8.22 Ph, and 1.00 relative electrical conducti\ity. 



Rate of nerve-conduction is 79.6 in 0.601 m. NaCl of 8.2 P„, 



and 0.996 relative electrical conductivit}^ 

 Rate of nerve-conduction is 92.2 in 81.1 c.c. of 0.601 m. NaCl-f 

 14.36 of 0.39 m. MgCls of 8.2 ?«, and 0.94 relative electrical 

 conducti\'ity. 



It may be of interest to see that diluted sea-water is less depressant 

 for nerve-conduction than abnormally concentrated sea-water. 



The injurious effects of concentrated sea-water upon regeneration 

 and gi'owth have been studied by Loeb- and by Goldfarb,^ and there is 

 a general resemblance between their curves and ours for the rate of 

 nerve-conduction, excepting that for regeneration somewhat dilute 

 sea-water seems to be more favorable than normal sea-water, whereas 

 in nerve-conduction the highest rate is obtained in sUghtly concen- 

 trated sea-water. 



'Lillie, R. S., 1916, American Journal Physiologj', vol. 41, pp. 126-136. 

 *Loeb, J., 1891, Organbildung und Wachsthum, 82 pp., Wurzburg. 



^Goldfarb, A. J., 1914, Papers from the Tortugas Laboraton-, Carnegie lust. Wash. Pub. 

 No. 183, pp. 83-94. 



