EFFECT OF IONS UPON TISSUE 573 



The problem is the same as for Gonionemus. In the latter it 

 >B certain that under ordinary circumstances (/. e., in the 

 presence of the K and Ca ions of the sea-water), the impulses 

 for the rhythmical contractions originate in the nervous 

 system, or at least in the margin. It is, however, not the 

 histological or morphological structure of the ganglia which 

 allows them to be so important, but their chemical constitution. 

 The center of Gonionemus is able to beat rhythmically in a 

 pure NaCl or NaBr solution. It is true that the center of 

 Gonionemus (and the apex of the heart) contain single scat- 

 tered ganglion cells. One might think that these latter are 

 responsible for the rhythmical contractions of the center 

 which occur in pure NaCl or NaBr solutions. But the mus- 

 cles of the skeleton (even if curarized) show rhythmical con- 

 tractions in the same pure NaCl or NaBr solutions, provided 

 the latter do not contain any K or Ca ions. 



2. It would be unwarranted to say that Ca or any other 

 ions are the cause of, or the stimulus for, the rhythmical con- 

 tractions in Gonionemus, or the heart, or any other organ. It 

 would be much nearer the truth to assume that for the possi- 

 bility of rhythmical contractions the Na, Ca, and Kions must 

 exist in definite proportions in the tissue which is expected to 

 show rhythmical activity. Only so long as these propor- 

 tions are preserved does the tissue possess such physical 

 properties and such labile equilibrium as to be capable of 

 rhythmical processes or contractions. If the tissue has per- 

 manently or temporarily more Ca and fewer Na ions than 

 are required for the above-mentioned physical properties 

 and condition of equilibrium, an increase of Na ions in the 

 tissue will cause rhythmical contraction. In such a case the 

 tissue will begin to contract rhythmically or beat at an 

 increased rate in a pure NaCl solution. If the tissue, how- 

 ever, contains too many Na and too few Ca ions, a further 

 increase of the latter in the tissue will cause the beginning 



