DEPARTMENT OF MARINE BIOLOGY. 



213 



electrical conductivity and various physiological reactions has been pointed 

 out by Pfeffer, Bernstein, Hober, and many others. 



Table 7. — Rates of nerve-conduction when Tortugas sea-water is diluted with aerated, alkaline, 

 distilled water having a hydrogen-ion concentration of about 10~^. 



As the rate of nerve-conduction in diluted sea-water declines in the same 

 ratio as does the electrical conductivity, we might seem justified in assuming 

 that it would also change in the same ratio as the conductivity when the 

 sea-water was cooled or heated from the normal 29° C. This, however, is 

 not the case, as is shown in table 8, the change in rate of nerve-conduction 

 being about 2.5 times as great as that of the electrical conductivity of the 

 sea-water. 



Table 8. 



*Mean of Harvey, Mayer, and Gary's observations. 

 ^Determined by Kohlrausch's method. 



Nerve-conduction is due to a chemical reaction involving the cations of 

 sodium, calcium, and potassium; magnesium being non essential. 



The sodium and calcium cations together combine with some proteid ele- 

 ment to form a sodium-calcium-ion proteid (see especially Osterhout, 1916). 

 The high-temperature coefficient of ionization of this ion-proteid may account 

 in some measure for the high-temperature coefficient of the rate of nerve- 

 conduction, which is 2.5 as great as that of the electrical conductivity of the 

 sea-water surrounding the nerve. 



