DOCKERAY : PHYSICAL FATIGUE AND MENTAL EFFICIENCY. 225 



period. At the end of seven and one-half minutes of lift- 

 ing a weight of 51/2 kilograms he was forced to stop from 

 exhaustion. Yet he then lifted 110 kilograms. This method 

 was, therefore, abandoned, and the general habits and physical 

 development of each subject were used as a basis upon which 

 to approximate the value of a given amount of work for the 

 production of fatigue in each individual. 



The form of the ergographic curves obtained with the two 

 spring ergographs may, to some extent, indicate the degree 

 of fatigue, though these curves do not, as a rule, resemble 

 very closely the form of such curves as we find them in the 

 literature. There was always a quite rapid fall in the height 

 of the curve during the first three minutes, and by the end of 

 five minutes it had reached a level that was generally main- 

 tained until the end. The principal exceptions were the curves 

 of W., which decreased rapidly during the first three minutes 

 and then more and more gradually to the end. At the end of the 

 twenty minutes his curves were still decreasing. Whether the 

 knowledge that the work was expected to endure for twenty 

 minutes compelled the subjects unconsciously to conserve their 

 strength, or whether the realization that the curve was falling 

 acted as an incentive (the curves were not screened from the 

 subject) to exert more effort, as Wright (47) found, or 

 whether the employment of a large group of muscles allowed 

 sufficient shifting of the burden to alter the form of the curve, 

 our work furnishes no data to determine. It is quite probable 

 that more than one of these factors had an influence. Both 

 ergographs gave the same form of curves and both were open 

 to these possibilities, though the possibility of shifting with 

 the thumb ergograph was not so great as with the lifting 

 ergograph. 



ADDITION TEST. 



With Ca. speed in adding has always been increased after 

 rest and decreased two out of three times after physical work. 

 Two factors might influence accuracy: an increase (or de- 

 crease) in speed might mean a corresponding decrease (or 

 increase) in attention to accuracy of the processes; or it might 

 mean greater or less mental ability expressed in terms of 

 accuracy of the association processes independently of the 

 association time. The subjects were always instructed to add 

 as rapidly as was consistent with accuracy, and it was ex- 



