Page:Popular Science Monthly Volume 55.djvu/534

516 second set of tracings, gained from a girl, E. H., twelve years of age, shows evidences of marked fatigue after a few hours' work; but the effect upon the bodily activities is quite in contrast with that of the case just mentioned. Here there was relaxation of the muscles,



a general letting go of the whole body, revealed in the tracings taking an abrupt downward direction. The third group of tracings was gained from W. R., whose characteristics have already been adverted to, and who indicated here, as in the other tests, that his morning's duties had had no serious effect upon his nervous energies.



It should be said in passing that the principle of healthful mental growth and activity seems to require that in education of any sort cerebral cells should be freely exercised up to the point of fatigue, but never beyond; for after this there is not only no progress, but what has been gained by previous training may even be lost. And, what is more serious, the undue depletion of the nerve cell renders



its recovery extremely slow, and investigation has shown that school children when overtaxed return to their studies day after day in a fatigued condition, their energies not being fully restored until the