564 STUDIES IN GENERAL PHYSIOLOGY 



Gonionemus. If a Gonionemus is thrown into a solution of 

 98 c.c. fw NaCl -\- 2 c.c. l - n CaCl 3 solution or a pure |-. 

 NaCl solution, it stops contracting after a certain time, but 

 beats again for a little if thrown into a solution with more 

 CaCl 3 (for instance, 95 c.c. f ?iNaCl + 5 c.c. y -wCaCl 2 ). This 

 seems to favor the assumption that the Ca ions are the stimulus 

 for the contraction of the swimming-bell of a Medusa. But 

 a simple control experiment shows that this assumption is 

 erroneous. If we throw a Gonionemus first into the stronger 

 solution (for instance of 95 c.c. -f n NaCl + 5 c.c. | n CaCl 3 ), 

 and wait until it stops contracting, it will begin to contract 

 again if we put it back either into the solution with less 

 CaCl 3 (for instance, 98 c.c. fn NaCl + 2 c.c. ^ n CaCl 2 ) 

 or into a pure NaCl solution. The true explanation of this 

 phenomenon is, I believe, as follows : In the pure NaCl 

 solution or the solution with little CaCl 2 , too many Na ions 

 combine with the proteids, and this leads to a loss of irrita- 

 bility. If the Gonionemus be brought into a solution 

 with more Ca and less Na ions, some Ca ions will take the 

 place of Na ions in the tissues, and this restores the irrita- 

 bility. But finally too many Ca ions enter, and the physical 

 qualities are changed again, thus making the Gonionemus 

 inirritable. If the same Gonionemus then be put into a 

 pure NaCl solution or into a NaCl solution with fewer Ca 

 ions, the Na ions will take the place of some of the Ca ions, 

 and this will restore the irritability. 



We thus arrive at the conclusion that the rhythmical 

 contractions of Gonionemus depend upon the presence of 

 Na, Ca, and K ions in definite proportions in the ion pro- 

 teids of the tissues. These proportions evidently differ in 

 various kinds of tissues. Myogenic contractions are pre- 

 vented by a smaller amount of K and Ca ions in the sur- 

 rounding NaCl solutions than neurogenic contractions or 

 contractions originating in parts containing ganglia. 



