waste products from this process, than to a loss of interest in school work, with its lack of vital and varied appeal, and its monotony of instruction and environment. The bored child, unconsciously or consciously, rebels and does a less correct amount of work. Continued work produces boredom and continued boredom decreases efficiency, on account of the close mutual relation between physiological and mental attitudes. With sound bodies, a hygienic school, proper classification, frequent relaxation, a vital and varied curriculum, and live teachers, most children will show no problem of fatigue in relation to the daily school programme."

Heck also tested 573 children in the Lynchburg, Virginia, schools.1 As before, two periods were taken in the morning and two in the afternoon. The length of the test was increased from ten to twenty-five minutes to determine whether a longer period would reveal fatigue. The results strengthened the former conclusions.

2

Still another test was made by Heck, this time with 467 boys and girls in the Roanoke, Virginia, schools. "The final conclusion to be drawn from this experiment in Roanoke with reasoning-tests in arithmetic, as well as from those in Lynchburg and New York with the fundamental operations, is that normal, healthy children in the grammar grades, in a hygienic school environment, can meet the requirements of the usual daily school programme without injury to themselves or their work."

Short tests of ten minutes and also those involving continuous effort extending through an hour or more have been made recently in the grades of the Winthrop Training School. The short tests consisted of examples in addition and subtraction, while the longer ones were drawn from algebra, history, and Latin. The results indicate that "in

3

1 Psychological Clinic, vol. 7, p. 29.

2 Op. cit., vol. 7, p. 258.

L. A. Robinson, Bulletin no. 2, Winthrop Normal and Industrial College.

general there is more weariness than fatigue in the children; and mental activities are more necessary than complete idleness. Here, then, is the teacher's problem: How to provide the proper mental stimulations for keeping up the interest in school. .. If a boy sees no purpose in

learning he will not learn."

"A fair claim to make on the basis of the results obtained," says Thorndike,1 in summing up his investigation of fatigue in school children, "is that a regular day's work in the grammar school does not decrease the ability of the child to do mental work. . . .. The chief responsibility for mental exhaustion in scholars falls, I should be inclined to think, not on a Creator who made our minds so that work hurts them, nor on the public opinion which demands that children shall do a given amount of work, but upon the unwise choice of material for study, the unwise direction of effort, the unwise inhibition of pleasurable activities, the unwise abuse of sense-organs, and unattractiveness of teachers and teaching."

We have quoted from these experiments in some detail because the information is needed as an antidote to the sentimentality regarding fatigue. Maudlin emotions threaten to deprive children of the advantages of a busy, thoughtful life during a small part of the day. As a matter of fact, if children are as fresh after two hours in school as when they entered, they have missed something worth while. Moderate fatigue, if caused by work and not by foul air or nervous irritation, is not bad, provided school is forgotten on the playground and sleep is abundant and undisturbed. Probably one of the chief causes of injurious fatigue in children is the constant nagging to which they are so commonly subjected. A shrill, penetrating voice, exploding with "don'ts," has little efficiency beyond nervous irritation.

Experiments on fatigue presuppose that it will always Psychological Review, vol. 7, p. 547.

1

reveal itself in the quantity or quality of work accomplished. Yet there are two physiological facts which seem to deny this assumption. And this contribution from physiology has not received sufficient attention from investigators of mental fatigue. The first of these two facts is the stimulating effect of small quantities of fatigue-substances.

"If present in small quantity, or moderate quantity, for a brief time, each substance," says Lee, "causes an augmentation of activity of the muscle, which is characterized by an increase in irritability and working power, an increase in the height to which the load is lifted, and an increase in the total amount of work performed." 1 And again, as Bayliss says: "It appears that the presence of a small quantity of products of activity is favorable." 2 This has been demonstrated only for muscle, but the assumption that it is also true of mental activity is a possibility which cannot, at any rate, be denied. If this stimulating effect of a moderate amount of fatigue-substances shall be found true also of mental activity, we may then expect, for a brief time, an improvement in the quantity and quality of work; and one investigator3 thinks that there is such a period when fatigue acts as a stimulant in mental as well as in muscular work.

Let us now turn to the second physiological fact to which reference has been made. Gruber fatigued a musIcle with an hour's work and then allowed it to rest for an hour and a half. The result of this rest was a gradual but steady recovery of vigor. Then adrenalin was injected, and the effect, five minutes after the injection, was a further, but at the same time abrupt, recovery of 61 per cent. Subsequent rest for an hour and a half produced no further recovery. In another experiment the effect of 1 American Journal of Physiology, vol. 20, p. 170, and Columbia University Studies in Psychology, reprints, 1907–1909.

2 Op. cit., p. 451.

3 May Smith, British Journal of Psychology, vol. 8, p. 327.

4 Charles M. Gruber, American Journal of Physiology, vol. 33, p. 335.

adrenalin, after an hour's work, was substantially the same, showing a recovery of 62 per cent. Gruber proved that the effect of adrenalin is a counteraction of fatigue by determining the threshold stimulus for muscle and nerve-muscle in non-fatigued animals before and after injecting adrenalin. He found that in the case of nonfatigued muscle there was no lowering of the threshold, “a result in marked contrast with the pronounced and prompt lowering in fatigued muscle by this agent."

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"It is quite conclusive," says Gruber, "that adrenalin, in some way, causes a rapid recovery of normal irritability of muscle after fatigue. The question whether this is done by neutralizing, transforming, or destroying the fatigue toxins is still obscure. That the action may be on the muscle itself has been definitely shown in this" [Gruber's] paper; its effect, however, upon the nervous elements or on the region of the neuromuscular union cannot be denied. . . . Adrenalin acts quickly, requiring five minutes or less to produce its effect on the threshold" [of fatigue]. “In that length of time, in some cases, it reduces the threshold to normal, whereas rest would require fifteen minutes to two hours." 1

The experiments just quoted show that adrenalin injected into fatigued muscle has a remarkable recuperative effect. The inquiry arises at once then, Is there any arrangement in the body by which adrenalin is supplied and made to serve the same purpose during life? Experiments have answered this question in the affirmative. The suprarenal capsules are glands, situated above the kidneys, which secrete a substance, to which the name adrenalin has been given. This secretion passes into the blood. Investigations2 have demonstrated that artificial 1 Op. cit., p. 354.

2 T. R. Elliott, Journal of Physiology, vol. 44, p. 400; Otto Folin, W. B. Cannon, and W. Denis, Journal of Biological Chemistry, vol. 13, p. 477; W. B. Cannon and Henry Lyman, American Journal of Physiology, vol. 31, p. 376.

stimulation of the splanchnic nerves increases this secretory activity, and as a result the adrenalin in the blood is increased. Here, then, is a mechanism by which the adrenal glands can be made to discharge their secretion into the blood.

Several years ago, it was observed1 that, with artificial stimulation of the splanchnic nerve, a muscle did "for a short period 80 per cent more work than before splanchnic stimulation, and for a considerably longer period exhibited an intermediate betterment of its efficiency." At that time a considerable part of this improvement was ascribed to the increased blood-flow resulting from splanchnic stimulation. The investigators raised the question, however, as to whether this explanation was sufficient. Later investigation2 verified this effect of increased blood-flow through excitation of the splanchnic nerve, but it proved, in addition, that the recovery of muscle and its strengthened action was due in part to a specific action of adrenalin itself. Splanchnic stimulation is thus seen to promote recovery of muscle from fatigue and increase its action in two ways, first, by increasing the arterial blood-pressure and so cleansing the working muscles with fresh blood, and second, by liberating adrenalin, which acts specifically upon muscles, restoring their working power.

How, then, does this work out in life? It is clear, as Cannon has indicated, that increased arterial pressure would be highly serviceable to animals in times of stress. It would clear away the waste and fatigue products. Now adrenalin, secreted by the adrenal glands and passed into the blood, does this and more. "The heart, the lungs, and the brain, as well as the skeletal muscles, are in times of

1 W. B. Cannon and L. B. Nice, American Journal of Physiology, vol. 32, P. 44.

2 Charles M. Gruber, American Journal of Physiology, vol. 32, p. 221, vol. 33, p. 335, and vol. 34, p. 89.

Walter B. Cannon, Bodily Changes in Pain, Hunger, Fear, and Rage, 1915, pp. 132 f.