198 KANSAS UNIVERSITY SCIENCE BULLETIN. 



thus increase the efficiency; or, (c) it may have no appre- 

 ciable effect in either direction. Furthermore, it might be 

 assumed that all these effects might be manifested in the 

 same individual under different physical conditions, or that, 

 given a definite amount of physical fatigue, individuals might 

 be divided into groups according to the effects produced. It 

 might also be supposed that the immediate effects would not 

 necessarily be the same as those to be noted later, say in a 

 half hour, or even after a longer time. The immediate effects 

 of physical fatigue on mental efficiency are all with which 

 we are directly concerned in this paper. Though the later 

 effects may be of even greater importance, the amount of time 

 involved in such tests has made it impossible to collect suffi- 

 cient data to warrant their incorporation here. 



HISTORICAL. 



As Max Offner (31) has reviewed the literature dealing 

 with the various phases of fatigue as they affect the problem 

 of school hygiene, and as C. D. Yoakum (50) gives a very 

 thorough review of the general field, it is not deemed advis- 

 able to attempt a discussion of the subject here, except those 

 phases which bear more directly upon the relation between 

 physical and mental fatigue. 



Mosso (30) seems to be the first to call attention to the 

 possible relation of physical and mental fatigue. He found 

 with the ergograph which he invented that after voluntary 

 contraction of the finger was no longer possible the finger 

 could still be made to lift the weight if an electric stimulus 

 was applied to the flexor muscle. If the subject was mentally 

 fatigued by lecturing, or by a two-hour examination, the 

 amount of voluntary work he could do on the ergograph was 

 decreased, and the muscle failed to respond to the same ex- 

 tent to the electric stimulus that it did before mental fatigue. 

 It would appear, therefore, that mental fatigue had a direct 

 influence upon the voluntary muscles. However, not all of 

 Mosso's subjects were in complete agreement. Under normal 

 conditions part of the subjects produced convex curves and 

 part concave curves. Only those with concave curves showed 

 reduced muscular ability immediately after mental work. 

 Those with convex curves showed an increase immediately 

 after the mental work, followed an hour later by a decrease. 



