494 



PROFESSOR C. R. MARSHALL ON THE 



produced by this solution after previous immersion of a sartorius in normal saline 

 solution for ten minutes or more is 40 mm. 



It was further found that when Ringer's solution was employed as the normal 

 immersion fluid, the contracture obtained was less and generally somewhat more 

 prolonged than when a pure sodium chloride saline solution was employed. These 

 observations led to some experiments on the influence of different concentra- 

 tions of calcium chloride on the contracture produced by tetra-methyl-ammonium 



Fig. 5 — Effect of 0"4 per cent, telra methyl-ammonium 

 chloride on sartorius of frog. Upper tracing = right 

 sartorius after immersion in - 65 per cent, sodium 

 chloride. Lower tracing = left sartorius after immersion 

 in equal parts of same saline and isotonic calcium 

 chloride solution. Time in ten seconds. 



Fig. 6.— Comparative action of 0"3 per cent, 

 tetra-methyl-ammonium chloride, with(lower 

 tracing) and without (upper tracing) addi- 

 tion of calcium chloride, on sartorii of same 

 frog. Addition of solution indicated by 

 arrow. Time in ten seconds. 



chloride. It was found that previous immersion in an isotonic solution of calcium 

 chloride prevented the appearance of the contracture, but that a mixture of equal 

 parts of isotonic solution of calcium chloride and 0'6 per cent, sodium chloride 

 did not completely inhibit it (fig. 5). # With isotonic solutions containing smaller 

 concentrations of calcium chloride correspondingly greater contracture was obtained. 

 It is questionable, however, if the calcium ion exerts any specific antagonism. There 

 is no association of calcium chloride with tetra-methyl-ammonium chloride, since 



* When comparative experiments are mentioned they refer to experiments on the two muscles of the same frog. 



