" 1215 



Fatigne. 



The gastrocnemius of a frog which had been poisoned with 

 cuiai-ine was prepared in the usual way, and fastened to a lever 

 with a counter-weight of 5 grammes; the whole weight acting on 

 the muscle amounted to 10 grammes. The electrodes were fastened 

 to the femur and to the tendon. The curves were written on the 

 rooty paper of a fall-rotatorium as indicated by Schenck. For tiie 

 untired muscle the minimum distance was found at which two 

 stimuli still gave a summation of the contractions, and then after 

 the fatigue caused by a number of induction-shocks (100 in 1'), 

 the stimuli were applied at the same distance from each other. If 

 the refractory stage was lengthened by fatigue of the muscle, which 

 might with some ground be expected, then it would appear in a 

 simple and conclusive way from the fact that a stimulus-interval 

 only just causing summation before the fatigue, would give no 

 summation if the muscle was fatigued, whilst by lengthening the 

 interval so much that summation only just set in, the new length 

 of the refractory stage might be arrived at. I succeeded, however, 

 but seldom in finding quickly the stimulus-interval which differed 

 so little from the refractory stage, that an increase of the latter 

 must be the cause of the entire disappearance of the summation. 

 In most cases I had to content myself with investigating tiie changes 

 which underwent the degree of summation i.e. the difference between 

 the contraction-heights caused by one and by two stimulations, 

 expressed in the contraction-height after one stimulation. 



As an example of one experiment first number 4. 



At an interval of 0.002" summation sets in amounting to 0.1 ; after 

 fatigue by meaiis of 400 break shocks the summation is reduced 

 to 0. Lengthening of the stimulation-interval to 0.005" scarcely 

 causes the summation to return: it becomes 0.043; at a stimulation- 

 distance of 0.015" the degree of summation has become 01 2. 



In experiment 64 fatigue caused by a great many break and 

 make shocks changes a degree of summation of 0.066 successively 

 to 0.069, 0.08, 0.07, 0.07, 0.109, 0.14, 0.13, 0.08, and 0.09. The 

 stimulation-interval is always 0.0053". 



The following is experiment N". 20. 



After 25 break and make-shocks the degree of summation, which 

 was at first 0.14 has become 0. Lengthening of the stimulation- 

 interval from 0.0025" to 0.004' raises it again to 0.04. After 125 

 shocks the summation has disappeared again, whilst an increase of 

 the stimulus-interval to 0.0063' still gi\es a summation of 0.12. 



30 experiments gave the following results. 



84* 



