posed four series of problems in addition and multiplication, the written solution of each of which would require at least ten minutes. He gave them, mostly during the earlier school hours, to pupils of different classes, between eleven and thirteen years of age, so that the pupils would have to make four calculations ten minutes long. Five minutes' pause was given between each problem and the next. The whole experiment thus lasted fifty-five minutes, or about the usual length of a school hour. One hundred and sixty-two pupils took part in the exercises, and the results were so nearly uniform that their trustworthiness can not be doubted. The first result was a notable increase of facility in the several sections of the experiment. The number of numbers counted up was about forty per cent larger in the last section than in the first. It was found, however, that not all the pupils shared equally in this advance, but that about forty-three per cent of them showed an evident sinking of efficiency at the end of the hour. The differences in personal susceptibility to fatigue previously observed among adults was also expressed here. This, however, is only a small part of the real results of the experiment. Prof. Burgerstein took pains to determine the number of mistakes committed by the pupils and the corrections they made, in order to estimate the value of the work accomplished in the several sections. Both appeared to increase from the very first, and much more rapidly than the speed of the work. It follows hence incontestably that the evidences of fatigue in the children under examination make themselves evident with increasing force from the second section of the experiment, and that in the majority of the children it is only outwardly concealed by the likewise increasing skill. The quantity of work rose, but its value underwent a constant depreciation. Similar results were obtained by the Russian Sikorski from dictation exercises, and by Höpfner in Berlin from dictations to boys nine years old.
The general result of these still too limited investigations of the susceptibility of school children to fatigue is the incontestable fact that the demands which the schools make upon the mental capacity of their pupils are far in excess of what they should be.
Yet this work is never continuous, but is interrupted by numerous pauses for rest, which doubtless have considerable influence on the progress of fatigue. The results of Burgerstein and Höpfner's experiments would have been much more unsatisfactory if brief pauses had not been interpolated between the different working spells. The remarkable fact was brought out in my experiments with adults in addition, in which pauses of ten minutes were interposed between the half-hour tasks, that the efficiency immediately after each pause was much higher than at any time before. This result is explained simply by the different velocities
