THE RELATION BETWEEN THE DEGREE OF CONCENTRATION OF THE 



ELECTROLYTES OF SEA-WATER AND THE RATE OF 



NERVE-CONDUCTION IN CASSIOPEA. 



By Alfred Goldsborough Mayer. 



CONCLUSIONS. 



If sea-water be diluted with distilled water, or with a 0.9 molecular 

 solution of dextrose, thus preserving its normal osmotic pressure but 

 reducing the concentration of the cations of sodium, magnesium, calcium, 

 and potassium, the rate of nerve-conduction increases as dilution proceeds, 

 becoming most rapid in 90 per cent sea-water +10 per cent distilled water 

 or dextrose. In 80 per cent sea-water it is again about normal in rate, and 

 in successively lowered concentrations it declines in a right-line ratio. The 

 curve for rate of nerve-conduction in sea-water diluted with distilled water 

 is practically identical with that for sea-water diluted with 0.9 molecular 

 dextrose, thus showing that the changes in rate are due to changes in concen- 

 tration of the electrolytes and not to osmotic pressure. (See fig. 6, page 40.) 



If sea-water be diluted with a solution of 0.487 molecular sodium 

 chloride dissolved in 0.075 molecular dextrose, thus preserving the normal 

 concentration of sodium in sea-water and the normal osmotic pressure of 

 the sea-water, the rate of nerve-conduction is most rapid in about 90 per 

 cent sea-water -f- 10 per cent of this solution and then declines becoming 

 about normal in rate in 80 per cent sea-water -f- 20 per cent of the (NaCl -f- 

 dextrose) solution, after which it declines in a right-line ratio upon further 

 dilution, but more slowly than if the sea-water had been diluted with dis- 

 tilled water or dextrose. Thus the sodium cation is an active stimulant 

 for nerve-conduction. (See fig. 7, page 43.) 



Similar experiments with the magnesium cation show that it is not a 

 stimulant for nerve-conduction, being no more effective in this respect than 

 is distilled water. Thus it is inert and nontoxic, and exhibits only neg- 

 ative properties and probably it should not be classed as an active inhibitor. 

 Speaking crudely, its role in respect to sodium in sea-water is comparable 

 to that of the nitrogen of the air in relation to oxygen. (See fig. 9, page 47.) 



In very slight excess the potassium cation produces a permanently 

 stimulating effect, as does sodium, but in denser concentration it produces 

 momentary stimulation of the rate of nerve-conduction followed by de- 

 pression. In all essential respects the effects of potassium are similar in 

 kind, but more marked in degree, to those of its close chemical ally, 



sodium. 



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