and its bearings observed. A week afterward, possibly, the matter would be remembered; and with further thought about it might occur a recognition of some wider application than I had before perceived. . . Again, after an interval, perhaps of a month, perhaps of half a year, something would remind me of that which I had before remarked; and mentally running over the facts might be followed by some further extension of the idea. When accumulation of instances had given body to a generalization, reflection would reduce the vague conception at first framed to a more definite conception; and perhaps difficulties or anomalies passed over for a while but eventually forcing themselves on attention, might cause a needful qualification and a truer shaping of the thought.. And thus, little by little, in unobtrusive ways, without conscious intention or appreciable effort, there would grow up a coherent and organized theory.'

Evidently, the organizing activity of brain and mind, below the level of consciousness, is an ally of no mean worth, provided the mind is supplied with the material upon which to work. Merely loading it with facts, however, does not produce the result. In reading or studying, the subject-matter should be systematized to the best of the learner's ability. Questions and problems must be clearly thought if the mind is to do its share toward furnishing the solution. Whatever thinking one does should be orderly. A clear-cut error may lead to truth, but mental confusion never. Force a conclusion or belief back against the wall, doubt its accuracy, cross-examine it, tear its inferences from it; then leave it to its fate, and before many days its truth or falsity will be revealed; and this subconscious cerebral activity is of inestimable importance for learning so far, at least, as knowledge, experience, prejudices, and "intuitions" bear upon our present opinions or the acquisition of new view-points.

Learning, then, we have found to be largely an uncon

scious process. In acts of manual skill new ways of securing results are happened upon accidentally and adopted. The learner then becomes conscious of their value for the work in hand. It is the trial-and-error method, in which the useless movements are gradually eliminated.

In mental activities the same unconscious adoption of methods of improvement is observable; and in thinking we tend to accept the ideas, beliefs, and opinions which surround us. The conventional views of "our set" are compelling; but "our set" is not altogether local. It includes those of our social standing, respectability, conservatism or radicalism, with whose views we are constantly confronted in the newspapers that we take and the books which we read.

Efficiency requires that the selection of ways and means, as well as of ideas and beliefs, be more conscious and intelligent. Methods of improvement will continue to come accidentally, for this is the nature of the learning process. We should, however, be critical in accepting and adopting them, since only in this way can progress be continuous.

Intervals of cessation of progress are likely to occur in complex acts of manual skill, and at this time practice is especially important. The mind should be active during the practice, in order that errors may be more quickly eliminated and the most effective improvements chosen.

There should be periods of rest in everything-in manual skill that the movements may become "set," and in mental activity to give new ideas a chance to assert themselves. A man who continuously works at white heat will not secure the results that will be obtained by one who stops at times to deliberate. An efficiency expert once told the manager of a large business that his chief defect was lack of leisure moments in which calmly to view his problems. This expert, by observing many men, had discovered one element of efficiency which psychologists have found in their laboratory experiments.

Finally, a man having acquired a degree of efficiency that meets the minimum requirements of his position and enables him to hold it, settles down at that level. He may be capable of much greater achievements, but the situation does not demand more energy. So he does not expend it. We cease to form new habits when no incentives for improvement stir us; and the amount of mental energy expended is as much a habit as is the quantity of physical energy applied to doors with check attachments. There is always adaptation to the needs of situations, but parsimony continually operates. We thus act below our ability unless the conditions force exceptional effort.

CHAPTER V

FATIGUE AND ITS PSYCHOLOGY

MUSCULAR and mental activity are always accompanied by liberation of energy and disintegration of tissue. A man gives out more than three and one-half times as much carbon dioxide per minute when walking at the rate of two miles an hour than when asleep. If his pace is quickened to three miles an hour he discharges more than five times as much, and when working in a treadmill nine times as much is given out as when asleep.

This making and remaking of the tissues of the body is a continuous process during life. "Did we possess some optic aid," says Foster, "which should overcome the grossness of our vision, so that we might watch the dance of atoms in this double process of making and unmaking in the living body, we should see the commonplace, lifeless things which are brought by the blood, and which we call food, caught up into and made part of the muscular whorls of the living muscle, linked together for a while in the intricate figures of the dance of life, giving and taking energy as they dance, and then we should see how, loosing hands, they slipped back into the blood as dead, inert, used-up matter. In every tiny block of muscle there is a part which is really alive, there are parts which are becoming alive, there are parts which have been alive but are now dying or dead; there is an upward rush from the lifeless to the living, a downward rush from the living to the dead.

"This is always going on, whether the muscle be quiet and at rest or whether it be active and moving. Whether the muscle be at rest or be moving, some of the capital of living material is always being spent, changed into dead waste, some of the new food is always being raised into

living capital. But when the muscle is called upon to do work, when it is put into movement, the expenditure is quickened, there is a run upon the living capital, the greater, the more urgent the call for action. Moreover, under ordinary circumstances, the capital is spent so quickly, during the action, that it cannot be renewed at the same rate; the movement leaves the muscle with an impoverished capital of potential stuff, and a period of rest is needed in order that the dance of atoms of which I just now spoke may make good the loss of capital and restore the muscle to its former power." 1

Drawing on the capital of living matter, if the expenditure be in excess of production, brings fatigue. The causes of fatigue are chemical conditions resulting from changes within the organism. Certain substances essential to the activity of the protoplasm have been consumed in this activity, and waste products have accumulated. Oxygen and carbohydrates have been consumed. The chief source of the energy of muscles is carbohydrates. Experimentally, it has been shown that removal of most of the carbohydrates from the body of an animal produces symptoms of fatigue without exercise. Recovery may be brought about by feeding sugar. It is well known that mountaineers, and soldiers on a long march, are greatly strengthened by eating chocolate. Oxidation of carbohydrates results in the production of certain substances which act as poisons to the body. They are spoken of as "fatigue substances." Two of these substances, carbon dioxide and lactic acid, investigation has shown, are hostile to protoplasmic action. When present in considerable quantity they weaken the sensibility of muscle and diminish its response. A muscle so affected requires more prodding for a given piece of work. Indeed, a muscle treated with either of these substances is "fatigued" without having done any work.

1 Michael Foster, Nineteenth Century, vol. 34, P. 337.