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PROFESSOR C. R. MARSHALL ON THE 



of an isotonic solution of the drug, continued until stimulation of the nerve no longer 

 produced contraction with this strength of stimulus. Afterwards the effect of 

 continued stimulation of the nerve and muscle was generally tried. From the 

 figure it will be seen that the nervous mechanism was paralysed in about the 

 same time as was required in the case of an isotonic solution of tetra-methyl- 

 ammonium chloride. 



Di-methyl-di-ethyl-ammonium Chloride. — This substance in isotonic solution 

 does not produce contracture of the isolated sartorius, even when this has been 

 immersed for some time in a normal saline solution, but it may induce contracture 

 in an isolated gastrocnemius. An instance of this is seen in the rise occurring 

 previous to the first stimulation after the application of the solution in fig. 15. If, 

 however, a small quantity of ethyl alcohol is added to the isotonic di-methyl-di- 



FlG. 15. — Effect of 1 - 4 per cent, di-methyl-di-ethyl-ammoiiium chloride on the irritability of the gastrocnemius of the frog to 

 direct and indirect stimulation. Description as fig. 14. An interval of eight minutes occurred between the two parts 

 of the tracing, x S. 



ethyl-ammonium chloride solution some degree of contracture is obtained in the 

 sartorius, and is greater the greater the concentration of alcohol up to ten per cent., 

 the largest concentration of alcohol used. 



The action of di-methyl-di-ethyl-ammonium chloride on the irritability of the 

 nerve-endings was found to be less powerful than that of tri-methyl-ethyl-ammonium 

 chloride. Thus while isotonic solutions of tri-methyl-ethyl-ammonium chloride, like 

 isotonic solutions of tetra-methyl-ammonium chloride, paralyse the nerve-endings in 

 the gastrocnemius in six minutes, an isotonic solution of di-methyl-di-ethyl-ammonium 

 chloride requires about fourteen minutes (fig. 15). The effect on the irritability of 

 the muscle was very similar to but somewhat less powerful than that of the two 

 preceding substances. This is seen in fig. 15. It has also been obtained in 

 experiments on the sartorius. The effect of an isotonic solution of di-methyl-di- 

 ethyl-ammonium chloride on this muscle is shown in fig. 16, which further shows 

 that a small terminal irritability may occur with this substance as with many other 

 muscle poisons. The tracing also shows that a notable increase in the strength of 

 the stimulus produces at first well-marked contractions with some residual 



