82 DYJVAM/CS OF LIVING MATTER 



facts which Dr. Lingle found is that even the heart stimulants, such as 

 caffeine, cannot cause the strip to beat, except in the presence of NaCl. 

 These experiments give the impression' that the ventricle of the tor- 

 toise does not beat in the blood, because of the fact that the NaCl in 

 the blood is prevented from entering inio the heart cells or from acting 

 upon them through the presence of another salt; namely, CaClj, or 

 MgCl,, or both. 



These experiments show that in order to start the heartbeat, a pure 

 NaCl solution, or a pure solution of an Na-salt, is required; but if 

 the heart remains permanently in a pure NaCl solution, it stops beating. 

 The pure solution of NaCl acts like a poison. If, however, a small 

 amount of CaCl^ be added to the NaCl solution after the heartbeats 

 have once started, the beats can go on for a long time. They can also 

 continue in serum after they are once started in a pure NaCl solution. 

 The addition of Ca therefore acts antagonistically to the injurious 

 action of the pure NaCl solution. Ca cannot start rhythmical con- 

 tractions in the ventricle, but it is necessary to sustain the rhythmical 

 action once started by NaCl. It is possible again that the pure NaCl 

 solution becomes toxic through the fact that in such a solution too 

 many Na-ions take the place of Ca, in the ion-colloids, and that this 

 is prevented by the presence of a trace of Ca. It is possible that the 

 Ca prevents or retards the diffusion of Na into the muscle. In a pure 

 NaCl solution, however, the rhythmical action of the heart strip can 

 also be sustained for a long time without the addition of Ca, if pure O 

 is allowed to bubble through the NaCl solution, or if a trace of HjO^ 

 is added to the solution. I consider these observations of the greatest 

 importance, inasmuch as they show that the processes of oxidation 

 going on in the muscle give the latter equal protection against the NaCl 

 poisoning, just as the addition of CaClj to the NaCl solution. Could 

 it be possible that the increase in oxidations leads to the setting free of 

 Ca inside the muscle, and that the Ca acts in this case? 



When I entered upon the investigation of the effect of salts on the 

 rhythmical contractions of the muscle, I had in mind the solution of 

 the problem of electrical stimulation. Previous experiments on the 

 effects of the galvanic current had led me to the idea that the polar 

 effects of the current are due to the ions which are blocked in their prog- 

 ress by the semipermeable membranes in these organs; and my idea 

 was that experiments with salts would show which ions are responsible 

 for the effects of a galvanic current. If the hypothesis that ions are 

 responsible for the stimulating effects of a current were correct, it was 

 to be expected that in solutions of nonconductors no twitchings would 

 occur. One of the first facts that I ascertained was that this idea was 



