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Scientific Proceedings (36). 



that is, on stimulation of the nerve plexus there was no response 

 while on stimulating the muscle directly there was a good con- 

 traction. Such a result was seen by many observers and was 

 spoken of as curare-like action. In a previous paper we have 

 called attention to the fact that similar results can be obtained also 

 by perfusion of the leg with solutions of sodium chloride and even 

 with calcium chloride. The magnesium effect, however, is some- 

 what more pronounced. The second result is that the subsequent 

 infusion of the muscles through the abdominal aorta, with calcium 

 chloride, restores rapidly the abolished indirect irritability. This 

 is similar to the observation of Auer and Meltzer on the antago- 

 nistic action of calcium to magnesium in mammals and is also 

 similar to the antagonistic action of calcium to the curare-like 

 action of sodium chloride. 



In another series of experiments the muscles of the leg of 

 completely curarized frogs were perfused with magnesium chloride. 

 There was, of course, on account of the curare, no indirect irrita- 

 bility from the start. In these experiments it was found as an 

 invariable result that magnesium definitely abolished or reduced 

 the direct irritability. There was then a definite difference with 

 regard to the direct irritability between the action of magnesium 

 and that of curare and the problem presented itself as to how to 

 reconcile this experience with that of the first series of experiments 

 in which the lymph sac injection of magnesium chloride had prac- 

 tically no effect upon the direct irritability of the muscle. 



In the following series of experiments, however, facts came to 

 light which are capable of explaining this apparent contradiction. 

 In this series, legs of normal frogs were perfused with magnesium 

 chloride through the aorta and were later perfused with calcium 

 chloride and sodium chloride in various orders. The following re- 

 sults were obtained. In the first place, in all cases magnesium 

 chloride reduced definitely or even completely abolished also the 

 direct muscle irritability ; but this effect was somewhat slower and 

 not as pronounced as the effect of the magnesium upon the indirect 

 irritability. Furthermore, when after the depression caused by 

 magnesium, calcium chloride was perfused, it caused no recovery 

 either of the indirect or direct irritability. When instead of the 

 calcium the perfusion of sodium chloride followed that of mag- 



