1229 



exactly anived at. The average of tlie stimulation-intervals was for 



9° 

 10° 

 11° 

 12° 

 13° 

 14° 

 18° 

 20° 

 21° 

 22° 

 23° 

 25° 

 26° 



0.006" 



0.0047" 



0.0039" 



0.0047" 



0.0034" 



0.0033" 



0.0045" 



0.003" 



0.0029" 



0.0036" 



0.003" 



0.0032" 



0.0036" 



in which, thougi» somewhat irregular because 

 of the relatively small number of experiments, 

 it is evident that this, and consequently 

 also the refractory stage, is greater at a 

 low temperature. After refrigeration or 

 heating to a certain temperature, the values 

 found become respectively greater and 

 smaller than those above. 



The average of the values is somewhat 

 less than 0.004", so ihat the average value 

 of the refractory stage of the frog's gastroc- 

 nemius must also be somewhat less than 

 0.004", which is 0.001" less than the value 

 found by Tigerstedt for the latent period. 



The figure represents the contraction 

 curves of a muscle after it had been cooled 

 down from 14° to 4°. At 14° the stimulation- 

 interval still showing summatioji was found 

 to be 0.003". At 4° stimulation with the 

 same interval produces no summation : the 

 contraction-curve caused by two stimulations 

 (II) coincides with the contraction-curve 

 after one stimulation (I). The interval was 

 lengthened to 0.0075", then to 0.017" without summation following 

 (curves 11' and 11"). Lengthening to 0.028 gives curve IT", in which 



the summation is plainly visible. 



85 



Proceedings Royal Acad. Amsterdam, Vol. XX 



