EFFECT OF Ions UPON TISSUE 563 
rhythmically in a pure NaCl solution, but beats much more 
rapidly in such a solution than in sea-water, shows that 
neither the Ca nor K ions of the surrounding medium are 
directly necessary for the systole or diastole. If they have 
any effect, they only diminish the rate of contraction (besides 
maintaining the contractility much longer). But the above- 
mentioned erroneous conception concerning the réle of the 
three ions can be disproved in another way. I had solutions 
of cane sugar and glycerin prepared which were isosmotic 
with a $n NaCl solution. The following solutions were 
tried: 
(1) 96 cc, distilled water +2 c.c. §n KCl+2 cc. 42 n CaCl, 
(2) cane sugar + “ e+ “ . 
(8) “ glycerin + “ a “ " 
(4) i £ n LiCl + (73 “ + (73 “re 
(5) “« $n NaCl + ne eo f « 
(6) “ $n NaBr + ws eo “ " 
Tn the first four solutions no rhythmical contractions occurred 
after the first minute. In the fifth and sixth solutions the 
rhythmical contractions continued for several hours. If it 
were true that the NaCl serves only to maintain the osmotic 
pressure, while the Ca produces the contractions, we ought 
to expect that the Gonionemus would contract just as well in 
the glycerin or sugar or LiCl solution as in the NaCl solu- 
tion. I have made, in addition to these, a number of other 
experiments, all of which prove that only in solutions of 
electrolytes (especially Na salts) is the Gonionemus able to 
contract rhythmically. The belief that calcium is the 
stimulus that produces the heart-beat is based upon another 
observation which I think was first made by Howell and his 
pupils.’ When a heart stops beating in Ringer’s solution 
it begins to beat again (for a little while) in a solution which 
contains more Ca. It is easy to confirm this observation for 
1 Ibid. 
Digitized by Microsoft® 
