Nerve-Conduction in Cassiopea Xamachana. 15 



recovery of excitation is also completed and thus the two mechanisms 

 may be identical and conduction may be merely the spread of a local 

 exciting process. 



Contrary to Lillie's hypothesis, we have direct evidence that the rate 

 of nerve-conduction may be independent of the electrical conductivity 

 of the electrolytic solution surrounding the nerves, for I have found 

 (1915)* that if sea-water be diluted with 0.415 molecular MgCU the rate 

 of nerve-conduction is only slightly more depressed than if the sea-water 

 be diluted with distilled water, or with dextrose; yet the MgCl2 main- 

 tains a nearly normal electrical conductivity, while with distilled water 

 or dextrose it declines in nearly the same ratio as the dilution. Nor do 

 the experiments I have made with solutions containing some but not 

 all the cations of sea-water support Lillie's view. Thus if the rate of 

 nerve-conduction in 0.647 molecular NaCl be 55, it becomes 100 in 

 85.3 c.c. of 0.6 molecular NaCl + 14.69 c.c. of 0.39 molecular MgCl2. 

 Here the electrical conductivity of the solution is somewhat reduced, 



■ ■ ■ ' I l_l I I I l-_l l—l 1 I .1 1— I 1 « I ■ L— i « » I 



sea wa-ter H-lo^-i \o-*i 2.<f*.*^5 C. 



>■« ■'■■■■■■■'■■■ l__S I II III I I I I I I I I I I I- I I 



^'Wwvr#J\Jww\j\Ai\/w\^^ivm^J^)WJWW\^^ 



''lO.- i- .• 10 •• •. .. 3i«% c. 



\m\m\jmwm\N\N^^ 



so •• •• ■• 20 ■• •■ " 3l*'.'f C, 



»■■ I 1 ■ ■■'■■■'« ' I ■ ■ > I »__| »__i I — 1_— I 1 I I I I I I I I ' > 



\AA(V\AAJ\J\j\AAAf\j\f\r\AAj\Af\J\jyV^^ 



10 30 •• •• " 3X.^ C. 



■ ■ ■ . ■ t l_| ■ ■ ' ■ t . ■ ,__, , 1 1 i_j 1 ! 1 1 1 1 I I I I I I 1 i 1 1 1 1 1 



Tletu.rrjecl to Sea. NA/a'tor- 



Fig. 11. — Showing changes hi rate of nerve-conduction in a ring of Cassiopea in successive 

 dilutions of sea-water, and the recovery of rate on being returned to natural sea-water 

 from .50 per cent. 



*Proceedinga National Acad. Sciences, vol. 1, p. 270. 



