Fisher — The Effect of Diet on Endurance. 35 



The following table shows that the number of errors committed 

 Avas remarkably constant for most of the men and for the average : 



TABLE XVII. 

 NUMBER OF ERRORS OF ADDITION. 



B E Lq Lw M P R T W Average 



(Jan. 14 10 8 12 4 1 1 2 1 1 4.4 



Errors \ Mar. 28 16 5 8 4 3 8 2 I 4. G 



( June 16 8 13 5 4 2 16 2 4.5 



The adding test Avas too short to be of great value. In future 

 tests a larger number of figures will be employed, and a diiferent 

 method. After the specified amount of adding has been done, it 

 will be at once repeated on another equivalent set of examples. The 

 excess of time required for the second set over that required for the 

 first may be called the " fatigue time," and this fatigue time, taken 

 as a percentage of the total time of adding, may be used as a criterion 

 of endurance— the less it is, the greater the endurance, and vice 

 versa. This j^Ian w^as developed too late to be put into operation at 

 the beginning of the experiment. It Avas, however, employed in the 

 March and June tests, and confirmed the conclusion reached above, 

 that there was little difference between the mental endurance in 

 March and June. Five of the men showed a less "fatigue time " in 

 June than in March, and four a greater. 



The following statements of the men themselves will show that 

 their feelings as to working power were in harmony with the conclu- 

 sion that it had improved : 



Subjective Impressions as to 3Iental Working Poioer. 



B. (March) " Not decreased at any rate, seems to have increased." 

 (June) I did more work during the latter part of year than I 

 ever did before in an equal period of time. But, I had the 

 work to do and compelled myself to do it. However, I was 

 mentally tired at the close of the yeai*, particularly so at the 

 time of the test, for it came after the siege of exams for Avhich 

 I did m}'^ own work besides a couple of days of hard tutoring. 

 This much, at any rate, is positive : There was no decrease 

 of mental power resulting from the experiment. I was no 

 more tired at the close of last year than I was at the close of 

 the year before. After a week's rest I felt quite normal and 

 then did considerable mental Avork all summer. 



