Nerve-Conduction in Cassiopea Xamachana. 9 



to another glass vessel which contained 90 per cent sea-water plus 

 10 per cent distilled water, and thus it was tested in more and more 

 dilute solutions down to 50 per cent sea-water plus 50 per cent distilled 

 water, after which it was replaced in natural sea-water. Rings which 

 have been in 50 per cent sea-water recover more than 80 per cent of 

 their normal rate within an hour after being replaced in pure sea-water, 

 and, if replaced from 70 per cent sea-water, recovery is practically- 

 complete at the end of an hour. Even 50 per cent dilution produces, 

 however, little or no permanent injury. 



EXPERIMENTS. 



Studies of recent years have shown the important influence of 

 hydroxyl and hydrogen ions upon the rate of nerve-conduction. The 

 free hydroxyl ion is a stimulant through a considerable range of con- 

 centration, but the free hydrogen ion is a depressant, excepting that in 

 very weak concentration it acts as a moderate stimulant. Thus, if 

 sea-water be diluted with acid distilled water of about Ph 5.5 (H-ion 

 concentration 0.316 X 10"^) the rate of nerve-conduction is augmented 

 in slight dilutions, but it declines more and more rapidly in dilutions 

 of 80 per cent sea-water plus 20 per cent distilled water and over. 

 The muscular activity, as measured by the amplitude of the pulsation 

 wave, usually declines steadily in sea-water diluted with acid distilled 

 water of ?„ 6, while when diluted with alkaline water of ?„ 8 it 

 maintains itself or even augmetits. 



Table 2 shows the effect upon the nmscular activity as measured by 

 the amplitude of the pulsation wave in Cassiopea when taken from 

 natural sea-water and gradually run into diluted sea-water composed 

 of 50 volumes sea-water plus 50 volumes distilled water (50 per cent 

 sea- water), at 30° C. 



Table 2. 



Thus when sea-water is diluted with alkaline distilled water, more 

 than half the rings show augmented muscular activity, whereas if the 

 distilled water be slightly acid the muscles of more than half are 

 depressed, and this depression is much more marked the greater the 

 acidity of the distilled water used in diluting, so that with distilled water 



