although they may have escaped our conscious attention. It has even been suggested that as respiration and pulse are more or less constant in rest, they are used by the organism as unconscious time-registers. This is possibly one of the phenomena due to the activity of the pituitary body in which may reside the “sense of time” and which controls all the rhythms of the body.

Jouffroy, Manacéine and Kempf have remarked that nursing mothers may sleep soundly in spite of the disturbances which take place about them, but that the slightest motion of their infant will awaken them. Many nurses not only can wake up at regular intervals to administer a drug to their patients, but, besides, can be aroused out of a sound sleep by a change in the patient’s breathing foreboding some danger.

Our withdrawal of attention from reality follows the same curve as that followed by the withdrawal of blood from the brain.

Many experiments have been made to determine that curve and to sound the depth of sleep. In one case a metallic ball was allowed to fall from varying heights until the noise awakened the sleeper; in another case electric currents of varying voltage were used to stimulate the subject, etc. All experiments have yielded the same results: Sleep reaches its lowest depth during the first two or three hours, the average time being shorter during the day than at night. In the majority of subjects, the greatest depth is reached about the end of the first hour. After the third hour, sleep is easily disturbed, the more so as the usual awakening time approaches.

To conclude, we will say that sleep partakes of all the characteristics of normal life, the only essential difference we can establish scientifically being a greater withdrawal of attention from reality in normal sleep than in normal waking life.

We insist on using the terms normal waking life, for there are forms of abnormal waking life in which attention is withdrawn as completely from reality as it is in normal sleep.

In the disease designated by psychiatrists as dementia praecox, the patient may become entirely negative, some time regressing to the level of the unborn child, and withdraw even more entirely from reality than the sleeper who, without awaking, is conscious of certain stimuli and performs certain actions showing a comprehension of their nature.

CHAPTER II: FATIGUE AND REST

What causes sleep? What causes us to withdraw partly our attention from our environment? The answer: brain anaemia, is unsatisfactory for we may ask in turn: what causes brain anaemia?

A study of brain anaemia leads one to conclude that it coincides with the usual sleeping period and that it is produced by sleep instead of producing sleep.

The large majority of laymen and scientists, however, give a much simpler answer: we go to sleep because we are tired and need rest.

Even as sleep and death have been coupled in the literature of all nations, fatigue and sleepiness, rest and sleep have come to be generally considered as synonymous.

Fatigue, however, is as difficult to define scientifically as sleep. Drawing a line between physical fatigue and mental fatigue does not simplify the problem; on the contrary, it complicates it by positing it wrongly.

We know that there is no purely physical fatigue. Fatigue is only caused in a very restricted measure by the accumulation of “fatigue” products or the depletion of repair stocks.

Under certain “mental” influences, our muscles can perform much more than their usual “stint” without showing fatigue. Hypnotize a man and he will do things he could not attempt in the waking state. He can lie rigid, reposing on nothing but his neck and heels; he can even support in that position the weight of a full-sized man. Men on the march can show wonderful endurance provided their “spirits” are kept up by some form of cheer, band music, etc. Ergograph observations show that signs of muscular fatigue appear and disappear without any obvious “physical” reason. Standardized motions which have been made almost automatic, tire us less than conscious activity.

We shall not deny that in certain cases fatigue may appear purely “physical.” When a continued expenditure of energy, walking, carrying heavy burdens, has induced muscular soreness, the organism must cease exerting itself for a while and recuperate.

But relatively few people perform physical activities which actually wear out the organism.

Even then, if that form of exhaustion was conducive to sleep, the more complete the exhaustion was, the deeper the sleep should be.

Yet we know that people can be “too tired to sleep.”

This is easily explained through a consideration of a phenomenon known as the “second wind” and which, before Cannon’s observations on the chemistry of the emotions, was rather mysterious.

Athletes competing on the running track are often seen to falter and fall back, apparently exhausted; after which, they suddenly seem to breathe more freely, they overcome their limpness and start out on a fresh spurt which may cause them to head off steadier runners.

What happens in such a case is this: great physical exertion causes a form of asphyxiation. Asphyxiation and the concomitant fear, liberate adrenin which restores the tone of tired muscles and also glycogen (sugar) which supplies the body with new fuel.

If the exertion continues long enough to use up all these emergency chemicals, the muscular relaxation necessary for sleep may be obtained. Otherwise, the organism prepared for a struggle with reality, will not lend itself to a flight from it. Although we are “worn out” we toss about in our bed, try all possible sleeping positions and only sleep when the energy which was supplied for a long struggle has been entirely burnt up.

The majority of people, after all, busy themselves with tasks which do not really deplete their stores of energy, but which prove monotonous. That monotony is then interpreted as fatigue.

In such cases, rest seems to be more easily attained through a change of activity than through mere cessation of activity.

A business man has been closeted in his office attending to many tedious details, reading letters and answering them, etc., and by five o’clock he feels “tired.” He will then go home, change his day suit for evening wear, attend a dinner at which he will do perhaps much talking, then watch actors for three hours and feel “rested.”

Or at the end of a “heavy” week, he will gather up his golf outfit and walk miles in the wake of a rubber ball. He returns to his work “rested,” although he has only exchanged one form of activity for other forms of activity. Of actual “rest” he has had none.

Children “tired” of sitting in a class room will romp wildly, shout at the tops of their lungs, jostle and fight one another and return to meet their teacher “rested.”

Undirected activity in the young, pleasurable activity in the adult do not seem to make rest necessary, and in fact are a form of “rest.”

Egotistical gratification easily takes the place of rest. Heads of large businesses have sometimes mentioned to me that they worked much harder than some of their employés. Some of them kept on revolving commercial schemes in their heads or attending business meetings long after their office workers had left. “And yet,” they added, “we are not complaining about being tired.” Nor were they as tired, after