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PROFESSOR C. R. MARSHALL ON THE 



it was applied. The irritability then gradually diminishes, but, as already mentioned, 

 it is still considerable after twenty-four hours' immersion (fig. 8). The diminished 

 irritability of the muscle seen during and after relaxation does not seem to be due 



Fig. 7. — Effect of - 3 per cent, tetra-ammonium chloride on gastrocnemii of same frog after previous immersion in one part 

 calcium chloride and three parts 0'6 per cent, sodium chloride (upper tracing) and in normal saline alone (lower tracing). 

 Weight 5 g. Time in ten seconds, x f . 



to fatigue following the contracture, although this may be a contributory cause, since 

 it is obtained to almost as great an extent when the contracture induced is much 

 less than the maximal. This is seen in fig. 9. The sartorius was immersed in 

 Ringer's solution for twenty-three minutes, towards the end of which time a series 



Flo. 8. — Effect of 0'4 per cent, tetraniethyl-ammonium chloride on irritability of sartorius of frog. Larger arrow indicates 

 addition of solution, the smaller arrow the commencement of electrical stimulation of the muscle (secondary coil at 14 cm.). 

 A control stimulation in '6 sodium chloride is shown before the contracture. Contractions x 9. The small crosses show 

 intervals of five minutes, the double cross an interval of nineteen hours. Time in ten seconds, x $, 



of break contractions (secondary coil at 14 cm.) were taken. Isotonic tetra-methyl- 

 ammonium chloride diluted five times with Ringer was then applied, and the same 

 stimuli continued at intervals of ten seconds. The first stimulus increased the 



lV 



