excitement abundantly supplied with blood taken from organs of less importance in critical moments." It also tones up the muscles that have become fatigued through continued activity. Emotional excitement, of course, always accompanies stress and danger. Consequently, the relation of excitement to adrenal secretion is important.

Adrenal secretion is known to be increased during strong emotions. This has clearly been demonstrated in a cat placed near a barking dog, and Elliott1 observed that no greater excitement is needed in animals than the strangeness of new quarters to induce a greater discharge of adrenalin into the blood.

Have we not here, then, a possible explanation for the failure to observe fatigue in school children? The youngsters know that they are to be tested for something. The conditions of class routine are changed. Perhaps a stranger comes into the school to give the tests. The situation is surely as "exciting" as the new quarters for the animals that Elliott tested. One who has given unusual tests of any sort knows well how alert and animated the children become. It is also a matter of common experience that the fatigue of adults often vanishes in even mild excitement. We know that under excitement the adrenal glands secrete and as a result physical fatigue disappears. To be sure, this has been proven only for muscular fatigue, but as Gruber has said: "Its effect upon nervous elements . . . cannot be denied." If the blood circulation of the brain is controlled by the autonomic system, and there is some evidence for this, then the tonic effect of adrenalin, already demonstrated in muscular fatigue, is also operative in mental activity. Further, there is no doubt that the increased arterial pressure flushes the nerve-cells of the higher centres as well as the muscular tissue, removing the fatigue products, and this is itself invigorating.

IT. R. Elliott, Journal of Physiology, vol. 44, p. 409.

There are, then, two physiological reasons why fatigue in its early stages may not be discovered by the tests usually given; the first is that fatigue substances in small quantities are stimulating, and the second is that adrenalin secreted under excitement and passed into the blood dissipates fatigue by increasing arterial pressure and by acting directly upon muscles, and perhaps upon nervous elements. Thus the condition that is sought disappears by reason of its very presence or because of the animation aroused by the attempts to find it. One may seriously doubt, however, whether fatigue is present in many cases. Children fortunately are endowed with an indifference to the demands of their teachers. If they did all that they are told to do and did it as well as they are told they should, every school must needs be equipped with an adrenalin laboratory-like Weichardt's antifatigue-toxin factory. Happily, native indolence comes to the aid of children, and they refuse to be overworked. Undoubtedly, they could do much more without fatigue than they actually accomplish if the things at which they are set appealed to them as worth while. Subjects of study should not be made easy, but their value and significance should be evident to those working in them. And, after all, this is a very human demand.

As one looks through the voluminous literature on fatigue1 one is impressed by the fact that "fatigue," as ordinarily investigated and measured, is exceedingly complex and that many times it is not fatigue that is tested but inattention and the inability to ignore sensations, feelings, and thoughts of one sort or another which have no definite relation to fatigue. Sleepiness, discomfort from the hard, straight-backed chair, temporary ennui for the

1 The investigations are too numerous to cite, but excellent bibliographies are given by C. S. Yoakum in Psychological Review Monograph Supplement, no. 46, 1909, and by F. C. Dockeray in the Kansas University Science Bulletin, vol. 9, 1915.

task in hand, and staleness on account of the ennui, as well as thoughts of pleasanter activities, are a few illustrations from the many that might be mentioned. "I was constantly surprised," says Thorndike,1 in his analysis of this condition, "to find myself when feeling, as I would certainly have said, 'mentally tired,' unable to demonstrate in the feeling anything more than emotional repugnance to the idea of doing mental work. On at least half the occasions this seemed to be all there was."

The feeling of lassitude, again, is quite commonly the result of lack of physical exercise. It has been observed that adults who engage in vigorous out-of-door work or sports, without overdoing, require less sleep and accomplish more mental work without fatigue. The sensations of strain and the feeling of effort may be due, also, to the disagreeable monotony of the task. As a relief from ennui, mere change is recuperative, and this is probably another reason why experiments and tests so frequently reveal little fatigue. The student may be weary from his previous work, but not fatigued.

Curves showing the progress of work, aside from the practice effect, are curves of a good many more things than fatigue. Pleasure and displeasure are important factors in postponing or hastening fatigue. Wright noticed 2 in his investigations that "the fatigue accompanying work is not so great when the person is working under the direct stimulus of a definite aim, notwithstanding the fact that he has at the same time produced an increase in the amount of work." The aim gives point and zest to what would otherwise be a disagreeable task, and it prevents the sensations, feelings, and thoughts mentioned above from arising in the mind. This is always the effect of a purpose in which one is interested. Aimless work is soon reduced to drudgery, and few activities are more fatiguing. The more

1 Psychological Review, vol. 7, p. 547.

2 W. R. Wright, Psychological Review, vol. 13, p. 23.

immediate and direct the aim and the more it concerns the present interests of the worker, the less likely is the mental condition commonly regarded as fatigue to appear. Since we may suppose that toxic products are always produced by continuous physical or mental activity, the difference in the effect of pleasant and dreary work would seem to lie in the rapidity with which they are disposed of or eliminated. It is not unlikely that the freer blood-circulation and the buoyant feeling attending the exhilaration of pleasure carries away these toxic products more rapidly than in the more sluggish condition of ennui. At all events, it is clear that disagreeable, monotonous work fatigues and wears one out more quickly than pleasant occupations. Perhaps this is one reason for the prodigious and at the same time unimpairing work of von Humboldt, Mommsen, and Edison. Such men are fortunate enough to have found work in which they could engage with unmitigated joy.

CHAPTER VI

CURIOSITIES OF MEMORY

NOT long ago one of our leading monthly magazines exhibited a tragic scene. A man with wild despair pictured in his face was tearing his dishevelled hair in a most indiscreet manner, and under the picture were emblazoned the portentous words, "I forgot." The advertisement then went on to inform the readers where they might purchase a memory system with which they could remember five thousand facts.

The success of such advertisements in selling the lessons indicates that remembering is, to a large extent, a "lost art," and that people commonly regard information as the most important factor in memory and intelligence. But what should we do with five thousand isolated facts if we had them? We all have many more now than we are able to use.

The first problem in connection with memory, therefore, is to learn how to make use of facts. Memory of so much information as can be used will then take care of itself, for facts that are applied are retained. Information is of value only to the extent to which it enters into one's thinking. It is the raw material out of which thoughts are made. But thinking, we have seen, is not a mechanical process. It does not come from merely piling up facts. Not even when the facts are put together in some sort of order, after the manner of the bricks that make a house, does thinking occur. An artistic arrangement of facts may produce day-dreams, but thinking is directed toward a definite end, like solving a problem or reaching a conclusion.

At its lowest terms thinking requires selection of mate