XXVIII 
ON THE DIFFERENT EFFECTS OF IONS UPON MYO- 
GENIC AND NEUROGENIC RHYTHMICAL CON- 
TRACTIONS AND UPON EMBRYONIC AND MUSCULAR 
TISSUE! 
I, ON THE DIFFERENT EFFECT OF IONS UPON THE MARGIN 
AND THE CENTER OF A HYDROMEDUSA (GONIONEMUS) 
In a preceding paper’® I gave a number of facts which 
force us to assume that not the salts themselves, but their 
ions, are in combination with the proteids, and that the 
physical qualities of the various ion proteids are different. 
This being true, a pure solution of an electrolyte ought to be 
poisonous, and I have been able to prove that a pure NaCl 
solution of the strength in which marine animals live kills 
them in a comparatively short time. The addition of a small 
amount of certain other metal ions (K and Ca) renders the 
solution harmless. This supports the assumption that irri- 
tability depends wpon the various tons, especially the metal 
ions (Na, Ca, K, and Mg) existing in definite proportions 
in the tissues. But as each tissue has its own specific irri- 
tability, it would follow that various tissues must possess the 
various ions in different proportions. This paper contains 
the result of a series of investigations on this subject. 
Gonionemus propels itself by rhythmical contractions of 
its swimming-bell. The swimming-bell, however, does not 
contract continuously, like the heart, but in groups of 
rhythmical contractions, followed by longer pauses. The 
swimming-bell of the Medusa may be divided into two 
regions, a marginal region containing the double nerve ring 
1 American Journal of Physiology, Vol. IIT (1900), p. 383. 
2Part IT, p. 544. 
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