10 Papers from the Department of Marine Biology. 



of about 5.5 P H the amplitude of muscular movement is hardly 

 perceptible in 50 per cent sea-water. As the average temperature of 

 the sea-water was about 30 C., the neutral point was about 6.86 P H 

 and thus it appears that even very slightly acid distilled water is 

 usually a muscular depressant, whereas alkaline distilled water is a 

 correspondingly efficient stimulant; this is the more remarkable when 

 we consider that the hydrogen-ion concentration of the sea-water is 

 very slightly augmented by dilution even with its own volume of 

 distilled water of 6 P H . Thus McClendon found that such a dilution 

 of sea-water of 8.1 P H changed the P H of the solution to 8.09; in 

 other words, the relative concentration of the hydrogen ions was 

 increased only from 1 to 1.02, such is the efficiency of the buffer 

 carbonates in preserving the normal alkalinity of the sea-water. 



It will be recalled that Osterhout (1914)* finds that a slight concen- 

 tration of HC1 is at first stimulating to plants, but later (after the 

 plasma membranes have been penetrated by the acid) it becomes 

 depressant. It would seem that in Cassiopea a very slight relative 

 increase of the H ion can not penetrate the cells, but acts only on the 

 cell surfaces or membranes and in so doing becomes a stimulant; but 

 in stronger concentration the cell membranes are penetrated and the H 

 ion then exerts its well-known depressant effect. 



The muscles are much more sensitive to changes of concentration in 

 H' or OH' ions than are the nerves. 



The stimulating effect of a very slight increase of acidity or of alka- 

 linity upon the rate of nerve-conduction is well shown if we place the 

 pulsating ring hi natural sea-water and then add about 5 per cent of 

 acid distilled water of P H about 5.5, for the rate suddenly augments 

 about 5 per cent. Similarly, if we take the pulsating ring from nor- 

 mal sea-water and place it in sea-water which has been condensed 

 by evaporation at normal temperature in the sun to about 90 per 

 cent of its original volume, the rate augments on account of the high 

 alkalinity of the evaporated sea-water. 



Professor McClendon made up a series of acid and alkaline sea- 

 waters. He added 23 c.c. of n/10 NaHC0 3 to each 1,000 c.c. of natural 

 sea- water and after bubbling air through the solution for 12 hours the 

 P H was 8.26, and a film of calcium carbonate was precipitated upon 

 the sides of the glass flask containing the solution. Similarly, he made 

 acid sea-waters of P H 7 by adding to each liter 24 c.c. of n/10 HC1 

 and then aerating for 12 hours; and a sea- water of P H 5.6 was obtained 

 in the same manner by aerating for only half an hour. 



The rates of nerve-conduction are nearly normal in all these solu- 

 tions; but although the differences in rate are slight, they are such as 

 we expected , the alkaline sea-water and the weakly acid sea-water are 

 both slightly stimulating, while the more acid sea-water is depressant, 



*Journ. Biol. Chemistry, vol. 19, p. 518. 



