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 MgCl 2 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 MgCl 2 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 MgCl 2 . 

 Here the electrical conductivity of the solution is somewhat reduced, 



.. i ........ i . 1 __! 1 & 14 1 1 I 1 1 1 I 1 1 il 



W^^ 



sea wa-ter H-ttm 10-** l^s c. 



. ...... . % ... i i t i ''*'* i i i i i i j > i * . 



J\MMMj^^ 



^5 ' +5 <$ 10-* H a.0 30.^ C. 



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SO 2,0 - Si"/) c - 



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70 - 30 " 3X.3 c, 



50 -. 3!SC, 



i i > i i i > t * . t t * > . t i L_ i i i i :_J i i i I I I I i ) t I i * I > > > 



yXy-sj~>v^^/X^^JX^^^-^^ r N^v'"N^^/ 



t o sea. 



FIG. 11. Showing changes in 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. 



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



