44 Thaddeus L. Bolton and Eleonora T. Miller 



tion would incline us to this point of view. Furthermore, the 

 amount of increase after the pauses in the "not exhaustion" curves 

 seems to be greater than the amount of loss, which is sustained 

 by the fact that the curve is not carried to the exhaustion point. 

 Our figures are scarcely sufficient to give an unequivocal answer. 

 Undoubtedly these accessory movements are energy-consuming 

 and may, therefore, by exhausting a greater number of nerve cen- 

 ters and creating a larger accumulation of waste products, actu- 

 ally prevent the most rapid and full recovery of those centers 

 who^e activities we are trying to study. The question can be 

 answered finally only by further investigations. 



The general growth of practice during these "exhaustion" and 

 "not exhaustion" observations was evident and surprisingly 

 great. The limitations of the apparatus were reached by both 

 hands of both reagents, and it was thus impossible to trace it 

 completely. It seemed at the beginning of the experiment that 

 with the weight which we used the limits of practice effects must 

 certainly be reached before those of the apparatus had been ex- 

 ceeded. The weight was for M. increased by almost a kilogram. 

 The observations with this weight, which is now about 4.5 kilos, 

 are included in a later table. The results seem to confirm those 

 for the smaller weights. The percentages of increase for "ex- 

 haustion" and "not exhaustion" are greater than for the other 

 weights. The first fatigue curve is therefore shorter than when 

 the smaller weight is used, but the larger percentages represent- 

 ing the second and third curves seem to indicate that the recu- 

 peration after a one-minute pause was greater proportionately 

 than when the smaller weight was used. This presents the inter- 

 esting point of the way a heavier weight affects respectively the 

 endurance and skill acquired in using a lighter weight. With 

 the smaller weight a greater number of contractions was neces- 

 sary to exhaust the finger, that is, greater endurance was re- 

 quired. Endurance is dependent upon the number of successive 

 explosions of which the nerve centers are capable before they 

 cease to respond, and hence recuperation after endurance will 

 mean, in a measure, cell reconstruction. In the longer period of 

 work the removal of waste can more nearly keep pace with the 



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