Literary quotations and time-worn stereotypes exert a deplorable influence on our thinking. They lead us to consider certain open questions as settled, certain puzzling problems as solved.

From time immemorial, the unthinking and thinking alike, have accepted the idea of a kinship between sleep and death. Expressions like “eternal sleep” show by the frequency with which they recur, how constantly associated the two ideas are in the average mind.

Not only is that association absurd but its consequences are regrettable, at least from one point of view: if sleep is a form of death, the psychic phenomena connected with it are bound to be misinterpreted and either granted a dignity they do not deserve or scornfully ignored.

The superstitious may loose all critical sense and see in sleep and sleep thinking something mysterious and mystical. The scientist, on the other hand, may consider such phenomena as beneath his notice.

No sober appreciation of sleep and dreams can be expected from any one who associates in any way the idea of sleep and the idea of death.Respiration seems to be the essential feature of life, and its lack, the essential feature of death. As long as respiration takes place, the two ferments of the body, pepsin and trypsin, break up insoluble food molecules into soluble acid molecules which are then absorbed by the blood and carried to the cells of the body where they are utilized to build up new solid cell matter.

When respiration ceases, a degree of acidity is reached which enables the two ferments to digest the body of disintegrating each cell. This is according to Jacques Loeb the meaning of death.

No such chemical action is observable in any form of sleep.

From that point of view, sleep is a form of life.

Sleep is even a more normal form of life than the average waking states.

In the normal waking states, the vagotonic nerves of the autonomic system which upbuild the body and insure the continuance of the race should dominate the organism, being checked in emergencies only by the sympathetic nerves which constitute the human safety system.

The vagotonic nerves contract the pupil, make saliva and gastric juice flow, slow down the heart beats, decrease the blood pressure, promote sexual activities, etc.The sympathetic nerves on the contrary, dilate the pupil, dry the mouth, stop the gastric activities, increase the heart beats, raise the blood pressure, decrease or arrest the sexual activities, etc.

In peaceful sleep, we observe that the vagotonic functions hold full sway. In sleep, our pupils are contracted. Even when they have been dilated by atropine, they become contracted again in sleep.

In sleep, the digestive organs continue to perform their specific work, all the popular beliefs to the contrary notwithstanding. Infants and animals generally go to sleep as soon as they finish feeding. Animals digest infinitely better if allowed to sleep after being fed, than if compelled to stay awake, walk or run.

The activity of the sexual organs is as great in sleep as in waking life; in certain cases, it is even greater.

At certain times, during sleep, the pressure of the blood in the brain is greatly reduced, and certain authors have concluded that sleep was characterized by brain anaemia, which some of them consider as the cause of sleep.

Indeed, unconsciousness can be induced by producing a temporary brain anaemia, for instance by compressing the carotid arteries of the neck for a minute or so. Sleepiness almost always appears then and lasts as long as the pressure is exerted.

Special manometers show that the fall in the blood pressure invariably precedes the appearance of sleep. In dogs whose skulls have been trephined for purposes of observation, the brain can be seen to turn pale as soon as the animals fall asleep.

But we have here simply one of the vagotonic activities mentioned previously. In the normal organism, the blood pressure should be low, rising only in emergencies, when the organism is facing some danger and must be prepared for fight or flight.

And in fact, the slightest light, noise, pain or smell stimulus, is sufficient to bring the blood back to the brain during sleep. Our sympathetic nerves are on the watch and even if the subject does not wake up, they rush the blood whenever it is needed for emergency action, in this case, to the general switchboard of the organism, the brain.

But this so-called brain anaemia is not constant during the entire period of sleep. The pressure falls gradually before sleep sets in and only reaches its minimum an hour after sleep has begun. Then it increases gradually and becomes normal again about the usual waking time. We shall see later that attention follows an identical curve.

It has been pointed out that in sleep the respiration becomes slower and that the amount of air inspired and consequently of oxygen assimilated is lowered. But inaction in the waking states will show exactly the same results.

A smaller quantity of carbonic acid is eliminated in sleep, the decrease being about sixteen per cent. But that condition is not due to sleep. It is due to many other factors such as the absence of light, etc.

The nature of the food taken before retiring has also a notable influence on the quantity of carbonic acid eliminated by the sleeper; the quantity varies from seventy five per cent after a meat supper to ninety per cent after a diet of starches.

The sweat glands of the skin secrete more actively in sleep than in waking life, which is also a vagotonic symptom and is also due to the fact that the sweat centre is easily affected by carbonic acid.

This increase in the activity of the skin accounts for the decrease we notice in the activity of the kidneys. (More urine is produced on cold days when the perspiration is scanty than on hot summer days.)

The lowering of the temperature in sleep is simply a result of inactivity, not of sleep.

We know that many pains, especially neuralgias, disappear in sleep. Many of those ailments, however, are of a neurotic origin and constitute a form of escape from reality. When reality has been practically abolished by unconsciousness, they are no longer “needed.”

Experiments made on instructors of the University of Iowa who were kept awake for ninety hours showed that the weight of the subjects increased during the experiments, decreasing later when the subjects were allowed to resume their natural life and to sleep. The increase was solely due to the fact that during the experiments, the subjects were relieved of their duties, remained idle in the psychological laboratory and hence consumed less organic matter than if they had led an active life, preparing their courses and teaching several hours a day.

It has been stated many times that a form of motor paralysis sets in during sleep. Yet we all know of the many motions performed by every sleeper, turning from side to side, drawing or pushing away the bed clothes, removing stimuli applied to the face, talking, not to mention, of course, sleep walking.

Sleep does not even mean complete muscular relaxation, for sentinels have been observed who could sleep standing; some people sleep sitting up in their chairs. Many animals, birds, bats, horses, sleep in positions which make muscular relaxation impossible; when their balance is disturbed by an observer, they re-establish it without awaking. Sleeping ducks keep on paddling in circles to avoid drifting against dangerous shores, etc.

In other words, there is not a part of our body which ceases in sleep to perform its specific work. Our lungs continue to breathe, our heart to send blood to all parts of the body, our glands secrete various chemicals; we hear, smell and to a certain extent, see. The lowering of our eyelids is simply a half-conscious effort to remove sight stimuli. Our nails and hair continue to grow, although, for that matter, they do so for some time even after death.

Finally our mental activity does not cease during sleep. Wake up a sleeper at any time and he will awaken from a dream. He may not be able to tell that dream but he will know for sure that, not only was he dreaming, but had been dreaming for a long while before awaking.

Wherein, then, does sleep differ from waking life?

Solely in the form of our mental activities.

Sleep is not as ManacÉine, the author of the most complete book on sleep, stated: the resting time of consciousness. We do not withdraw our attention completely from the environment in sleep.When we make up our minds, for instance, to wake up at a certain time, we seldom fail to carry out our purpose. Which does not mean that we are suddenly aroused out of our unconsciousness by something within ourselves, but more probably that our attention has been concentrated all night on certain stimuli indicating time, distant chimes, activities taking place at a definite hour, and which we had noticed unconsciously, 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.