It is difficult to describe, without the use of technical terms, the structure of the mechanism by which Dream is produced. But as these are at once unintelligible and repulsive to the non-scientific reader, indulgence is entreated for an endeavour to present the subject in shape and language that may be understood by everybody.

It must be premised that this description is partly derived from the recent treatise of Professor Ferrier on “The Functions of the Brain,”[1] in which he details the experiments that have thrown so much light alike upon physiology and psychology.

The spinal cord expands at its upper end into a ganglion or cluster of nerves called the medulla oblongata.

At this point the brain is said to cease and the nerve system to begin. But there is no perceptible beginning nor ending either of the brain or of the nerves. The entire nerve system is, in fact, only an extension of the brain. When a nerve is irritated at the point of the finger the brain as well as the nerve is affected. The nerve transmits the sensation and the brain feels it. Psychologists would venture a step further, and say, “It is not the brain that feels, but the intelligent individual entity, the living soul or self, of whom the brain is only the material transmitting organ.”

It is at the extremity of this ganglion that the cords wrapped within that great bundle of nerve cords which constitutes the spinal cord cross each other and pass into opposite sides of the brain and of the body. The nerves that control the left side of the body pass into the right side of the brain, and those that control the right side of the body pass into the left side of the brain. As the consequence of this exchange, the right side of the brain controls and directs the left side of the body, and the left side of the brain the right side of the body.

Above this basal ganglion, but connected with it, is a ganglion which anatomists have divided into two parts, but which for the present purpose it will be convenient to recognize as one whole lying at the base of the brain and crowned and inclosed by the cerebral hemispheres. From this great basal ganglion small white threads radiate into the two cerebral hemispheres in the form of a hollow cone.

Above the basal ganglion lies another great ganglion (the cerebellum), also divided into lobes, and which is connected with the basal ganglion by two bands (or peduncles). It is connected also with the two cerebral hemispheres by two bands. It is connected with the central ganglion by a thin lamina, which stretches to the other ganglia, thus connecting all the ganglia with the centres of the senses and the centres of motion—that is to say, with the centre that receives the messages of the senses and with the centre that conveys the commands of the Will to the body.

Above and extending in front of these are the cerebrum, the organ of the intelligence, composed of two hemispheres, which crown, inclose, and overlap the ganglia at the base of the brain.

These two great hemispheres are distinct bodies, each complete in itself but united by fibres that pass from one hemisphere to the other and thus secure their united action. These fibres are observed to connect together corresponding regions of the two hemispheres.

At their bases the two hemispheres are in direct contact with the ganglion above described as the central ganglion, but which has been anatomically subdivided into two pairs of ganglia. For the purposes of this treatise, however, minute divisions are not necessary.

This ganglion is the centre upon which all the nerves of the senses converge and each division of it is supposed to be appropriated to a distinct sense. But even if each part has its own work to do, it is not less a whole than is the cerebral hemisphere, which is now proved to have various parts devoted to various mental operations.

The cerebral hemispheres are formed of great bundles of fibres, in the shape of rolls, plainly visible on the outside, but which baffle the attempts of the most dexterous anatomist to sever them below the surface.

And the whole brain is covered with an extremely delicate and highly sensitive membrane, which is now conjectured to be the medium by means of which all the parts of the brain are brought into communication, and the co-ordination and unity of action of the entire organ preserved.

The substance of the brain itself is insensible, although it is the recipient and supposed seat of the pains and pleasures of the body—or rather of the nerves, for what we call the body is only the insensible clothing of the nerves. The nerves feel; the flesh and bones do not feel.

Is not this fact another powerful argument against the doctrine of the Materialists that consciousness and mind are only states of brain or conditions of matter? If the brain is not conscious of injuries done to itself, if it is insensible even to its own destruction, how can it be the “Conscious Self?”

But the enveloping membrane of the brain is exquisitely sensitive. It is the seat of headache, of delirium tremens, of brain fever, of hydrocephalus, and probably of many more diseases which we are wont to refer to the substance of the brain.

We refer—Who refers? What refers? The brain to the brain? Or one part of the brain to another part of the brain? Will the Materialists explain?

It is probable that this envelope of nerves unites all the parts of the brain and by transmitting to each part the condition of all the other parts produces co-ordination of the parts and unity of action. But this membrane of nerve cannot surely be deemed by the most bigoted Materialist to constitute the Conscious Self.

Professor Ferrier has proved, by a multitude of minutely detailed experiments, that not only has each ganglion its function, but that each part of each ganglion is devoted to some special duty, thus completely shattering the theory that holds every mental operation to be an act of the whole brain. He establishes at least the grand basis of modern mental Science, the assumption that the brain is the material organ of the mind; that distinct parts of the brain are devoted to distinct mental operations; that not the whole brain, but only parts of it, are employed in any mental operation. The question is still open for observation and experiment to ascertain what are the parts of the brain so appropriated and what are the precise functions of each part.

Professor Ferrier has made considerable advances towards the determination of this question. His experiments have demonstrated what are the functions of the ganglia at the base of the brain, not being the seat of the Intelligence. His experiments were attended with more cruelty than I could excuse even for the important accessions they have brought to our knowledge. But they are not therefore the less valuable as contributions to Physiology and Psychology. I can but briefly describe the results of such of them as bear immediately upon the subject here treated of.

Let me, however, first confirm, by the authority of Professor Ferrier, the proposition I have ventured to advance as to the various functions of various parts of the brain.

“That the brain is the organ of the mind,” he says, “and that mental operations are possible only in and through the brain, is now so thoroughly well established and recognized that we may, without further question, start from this as an ultimate fact.” He proceeds:

As the object of this treatise is not anatomy but psychology, it will be unnecessary to describe minutely the entire of the brain structure. It will suffice for the present purpose to view the brain, above roughly sketched, as having three well marked divisions, each with definite and distinct functions.

The ganglia at the base of the brain govern the actions of the body. The ganglia in the centre of the brain are the recipients of the impressions made upon the senses and thus connect us with the external world. The two hemispheres at the summit of the brain are the organs of the Intelligence.

Professor Ferrier’s experiments were made with a view to ascertain whether the theory of Dr. Carpenter is true, that the whole brain works in each mental action, or if the phrenological doctrine be the true one, that the several parts of the brain have several and distinct functions. Dr. Carpenter had prematurely boasted that he had killed Phrenology. The boast would have been justified if his assertion (for it was merely a dogma, not a proved fact) had been found to be true. But Professor Ferrier’s experiments have decisively disproved the boast of Dr. Carpenter and killed his theory of mental unity.

The experiments were conducted chiefly with monkeys and dogs. The former were the most valuable, because the brain structure of the monkey is almost identical with that of man. The experiments were certainly cruel and I should object to procure even such valuable knowledge at such a price. But, as it is obtained, we may use it.

The experiments were performed by making the animal insensible by chloroform and then extracting in mass certain portions of the brain, or destroying parts of the brain by the actual cautery. Electrodes were applied to the various parts of the brain to which access had been thus obtained and their effects upon the actions of the animal were carefully observed.

I will not attempt to detail these experiments—but merely state some of the results. For the many important facts that were discovered by them reference must be made to the valuable volume in which they are reported.

He found the entire brain to be connected with the nerve system by the process of interlacing. Excitation of the right brain was shown by the left side of the body; of the left brain by the right side. So it was with the nerves of the senses. Whether the like structure exists in the duplex organ of the intelligence he could not trace, because the mental results were incapable of being expressed by experiment upon animals, who cannot tell us what are their emotions. But he entertains no doubt that the same structural scheme is observed in the action of the two hemispheres also.

The great ganglia at the base of the brain, whether excited by electricity or destroyed by cautery, yielded the same result. They proved beyond doubt that their function is to direct the actions of the body under the peculiar conditions of its duplex structure—that is to say, a formation by two distinct and not wholly similar halves joined together and requiring community of action. This process of separate action for each part combined with motion in co-ordination—that is to say, the regulation of the motions of the limbs, so that the two halves of which the body is builded may act in definite relationship—was found to be the special business of those basal ganglia, any disturbance in those ganglia being attended with imperfect movements of the body, even to the extent of causing the animal to walk in a circle, having lost entirely the power to “walk straight.” The results of this ingenious experiment are extremely curious and throw great light on the physiology of locomotion.

The second division of the brain, lying in its centre, overlapped behind by the cerebrum, resting on the centres that direct bodily actions and dominated by the hemispheres that are the organs of the intelligence, is shown by these experiments to be the centre upon which the senses converge. To this common centre the impressions made upon the senses by the external world are conveyed. The experiments seem to indicate that a distinct ganglion is devoted to each sense, although all are united in one mass for the common purpose of reception of the information they bring. The destruction of different parts of this brain centre is found to be followed by the loss or impairment of different senses. It was found, also, that this part of the brain was duplex, like the other parts, for destruction of the right side of the ganglion caused paralysis of the senses on the left side of the body and vice versâ.

A question of much interest arises here. What is the precise function of this sense-receiving portion of the brain? Is itself perceptive of the sense-impressions brought to it, or is it merely the medium for transmitting those impressions to the hemispheres above? That in health it does communicate to the intelligence the same impressions that it receives there can be no doubt, for we take cognisance of them in almost every mental act. We know also that when the brain is diseased false impressions are conveyed to the Intelligence. But in exploring the psychology of Sleep and Dream, it would be of great advantage to ascertain if the same receiving portion of the brain is an active or merely a passive agent.

The experiments of Professor Ferrier are almost conclusive upon this most important point. He removed the two brain hemispheres of a monkey and of a dog. The animals lived and appeared to enjoy health, but they had lost intelligence. They had not, however, lost the use of the senses and they were manifestly conscious of the impressions brought by the nerves of sense. The external world continued to exist for them and was perceived by them as before the organs of the intelligence were removed. But when this central division of the brain was taken away and nothing left but the lower lobes that govern muscular motion, all the senses ceased to act, or consciousness of action had ceased. Nevertheless the power of locomotion and the co-ordinate action of the limbs was preserved with very little loss of power.

Above the central sense-organ tower two hemispheres—two brains, each distinct and complete in itself and each capable to act without the other. The function of these hemispheres is that we term mental. They are the organs of the intellect and of the sentiments. Through them we think, reason and feel. Injury to parts of these injures more or less, not the whole mind, but parts of the mind—certain mental faculties only. Destruction of the entire of these hemispheres is not death but idiotcy.

Let it then be clear in the mind of the reader, when surveying the phenomena of sleep and dream and inquiring into their causes, that for the purpose of such an outline of the Physiology of the Mind as this, the brain is to be viewed by him as having three marked divisions—the organ of the intelligence at the summit, of the senses in the centre, of bodily motion at the base.

There are many sub-divisions of the brain known to anatomists and necessary to be known by the Student of Physiology. But these will suffice for the Student of Psychology. They are easily understood and readily remembered.

In the waking and normal state, the whole brain is awake, all its parts acting in concert and preserving strict co-ordination. The reasoning faculties correct the senses; the senses correct the imagination; the intelligence controls the emotions; the emotions give vigour to the Will; the Will commands the entire mechanism of the body and expresses upon the external world the results of that combination of intelligent actions and emotions which we term “the mind.”

In sleep this relationship is changed. The reasoning faculties cease to correct the senses; the senses no longer correct the imagination; the emotions are unable to influence the Will; the Will loses its command of body and mind alike.

However it may be in dreamless sleep, in the condition of dream the entire mechanism certainly does not sleep. Some part of it is awake and active. What is that waking part?

It is undoubted that the cerebral hemispheres are wholly or partially awake in the process of dream. In deep sleep the sense-ganglia are wholly asleep. In all sleep the senses sleep, only sometimes not so profoundly as completely to exclude cognizance, by the Conscious Self, of the sense-borne impressions. Sleep affects also the ganglia at the base of the brain that control the actions of the body. This, indeed, would appear to be the primary purpose of sleep. Sleep is obviously designed to give rest to the material structure—time for growth and renovation. It is for this reason that the Will, which in the waking state directs the motions of the structure, ceases to control it during sleep. The Will itself wakes—for we are self-conscious in dream—but in sleep the material mechanism does not obey the command of the Will, because itself is sleeping.

The central and basal portions of the brain are, therefore, the seat of sleep. Unless they sleep we do not sleep. If they sleep we sleep, even although both brain hemispheres are at the same time wide awake.

And this raises the question, so important in the Psychology of Dream; do the brain hemispheres, that duplex organ of the intelligence, sleep wholly or partially, or do they continue to be awake while the sense-brain and the body-moving brain are sleeping?

This problem can be solved only by careful examination of the phenomena of dream. Suppose that Professor Ferrier could do with us as he did with the monkeys and dogs—take out a portion of the brain—and it were possible to remove altogether the middle and basal sections, leaving the hemispheres alone in the skull, would they sleep wholly or in part or, if awake, would they exhibit the phenomena of dream as they are now experienced?

Contemplate, then, if you can, a duplex intelligent brain, in a state of activity, but cut off from all communication with the external world through the media of the senses and from all control over the body;—in fact, an isolated, self-acting, self-contained mechanism, the organ of intelligence and emotion.

How would it work?

First, it must be set in motion. Thus we are brought directly to the problem “What moves the mind?” Why does this particular thought or feeling come into the mind at this moment rather than some other?

The solution commonly accepted is that ideas come by suggestion. This means that ideas are, as it were, linked together and consequently that when one idea comes it is followed by certain other ideas which at some former time were connected with it. Probably the greater portion of the ideas that come to us apparently without such association are suggested by some impression brought by the senses, but received by the sensorium unconsciously to ourselves and that thus the “train of thought” is started.

If it be so in one waking time, when the mind is busy with a multitude of impressions flowing in upon it from every sense—much more is it likely so to be when the impressions made by the senses are few, as is proved by the experience of every reader. In sleep, a slight sound falling upon the ear will suggest a dream of roaring cannon or rattling thunder.

But the idea, once suggested, draws after it whole trains of associated ideas, and these ideas excite the emotions precisely as they would have done had they been brought by the senses in the waking state. Thus far, then, we learn that the faculties which produce what we call ideas and sentiments and passions are not asleep. Some, if not all, of them are certainly awake and as active as in waking life.

The Will, too, is not asleep, although powerless to command. In dream we will to speak and do, but the body does not obey the Will. The efforts of the Will to command the limbs to move—as to escape from dreamed-of danger—and the failure of the limbs to obey, are often attended with consciousness of painful efforts made in vain.

So far the phenomena of dream are consistent with the entire of the duplex brain organ of the intelligence being awake while the lower portion of the brain is sleeping. Certainly it is difficult to conceive of parts of such an organ as the two hemispheres sleeping, relaxed, and insensible, while other parts of it are awake and active.

For, if Professor Ferrier is right, and distinct functions belong, not only to each ganglion but to various parts of each ganglion, the brain hemispheres, which are the material mechanism of the intelligence, must consist of many parts having different duties. We know that anatomically these parts, if they exist, are in intimate connection, lying closely packed together if not actually interlacing, and it is difficult to suppose that one part can be sleeping while its neighbour is awake, especially as sleep is attended, if not caused, by a depletion of blood from the fibres of the brain, retreating from the entire hemisphere and not from parts of it.

Nevertheless, there are characteristics of Dream which appear to indicate a suspension of activity in some parts of the intellectual mechanism. Although perfectly conscious of the presence of the dream, we are unable to discover that it is not real; we cannot discern incongruities, nor recognize impossibilities. The dead of long ago come to us and we are not amazed. We walk the waters and float in the air and are not astonished. Nothing is too impossible to be done and nothing too monstrous to be implicitly believed. We are, in fact, insane in dream.

What is the solution of this problem? Some faculty that corrects the action of the mind when we are awake is certainly absent or paralysed during dream. Something must come to us from without or operate upon the mind within that restores us to sanity when we wake, enabling us then to discern the false from the true, the shadow from the substance, the impossible from the possible.

What is this absent faculty?

The solution most favoured by psychologists is that in sleep we lack the correcting influence of the senses. The mind, they say, having nothing wherewith to compare its own creations, necessarily accepts them as realities; it puts implicit faith in them, however monstrous, simply because they are presented to it as facts and in the same manner as facts are presented when it is awake.

I confess to great doubt if this explanation be adequate. True, that we believe the impossibilities of our dreams to be because they appear to the mind to be. But that does not explain the strange absence of perplexity and wonder when we witness (as we then verily believe) the dead alive, the distant near, and impossible things performed with ease. In our waking state, if the like dreams come into the mind at some moment of idleness, they are never mistaken for realities. Reason rejects them, and if entertained for awhile it is only as a pleasant vision. Nor is the problem solved by the suggested slumber of the reasoning faculties. These are not always asleep in dream, for often we dream that we are exercising them readily and effectively. The power of reasoning employed in dream is, however, very limited. It can exercise itself on the subject of the dream, but not upon its surroundings. It is not uncommon for the sleeper to dream that he is making a speech or preaching a sermon. The discourse is argumentative and logical. It is not merely that he dreams he is logical; he is so in fact, for the dream is often remembered after waking and no flaw is found in the argument. Nevertheless, at the moment that our reasoning faculties are constructing a strictly logical and perfectly rational discourse, they are unable to inform us—as when we are awake they would have done—that the place where we suppose the speech to be spoken, the occurrence and the occasion, are not merely fictitious but attended with the most palpable absurdities.

Looking, then, at one hemisphere only of the brain, it is difficult to infer that one or more parts of it are sleeping while the other parts are awake. May the solution of the problem be found in the fact that we have two brains? Can it be that in the condition of dream one hemisphere—that is, one mind—is awake while the other is asleep?

To answer this it is necessary to inquire what is the action of two brains working, like the two eyes, together or separately?

For the common purposes of life the two brains act in complete accord. Like the two nerves of vision, they co-ordinate. Either can act alone for the ordinary uses of existence, just as one eye will do the usual work of sight. But as we see more perfectly, extensively, and roundly with two eyes than with one—so it may be reasonably concluded that we think more truly and clearly, and feel more strongly, when the two brains act together than when one is working alone. The faculty of comparison is one of the most important of the mental powers, for it is the basis of accurate knowledge. But it is doubtful if this faculty can do its work in one brain unless co-ordinated with the same faculty in the other brain. Unlike the other mental faculties, “comparison” can exercise itself only upon two ideas. Its very purpose is to make us conscious of the resemblances and differences between any two ideas presented to it. All mental processes are successive—that is to say, no two mental actions are performed by the same mental faculty at the same instant of time. Consequently, the faculty of comparison cannot exercise itself without having before it two ideas to contrast. As one brain can present only one idea at any one moment, one brain cannot provide the materials wherewith comparison can work. The process of comparison cannot therefore be effected without the aid of the other brain. This, in healthy waking life, is done instantly, perfectly and unconsciously, by means of the power of co-ordination possessed by the two hemispheres.

Such being the action of the waking brain, does sleep present any conditions that might be explained in like manner? Suppose the state of dream to be the slumber of one hemisphere only, the other being awake. May not this solve the problem?

In dream we believe shadows to be substances, ideas to be things, incongruities to be natural, and impossibilities to be realities; and so believing, we have no sense of surprise and reason is not shocked.

Nothing of these results presents itself when we are awake. Why?

Waking, the faculty of Comparison is enabled to do its work. It compares the idea with the reality, the shadow with the substance, the dream within with the impression without, the present picture of the mind with the stored knowledge of the past. The differences being thus discovered, the mind dismisses them as being the mere visions that they are.

The mental operation is performed somewhat in this manner. Two ideas are present in the mind, which compares them and traces their resemblances and differences. The sense-borne idea being thus brought face to face, as it were, with the brain-born idea, the distinction is discovered, and the latter is relegated to the limbo of visions, the former is accepted as a reality and made the basis of action.

But inasmuch as two ideas cannot be presented at the same instant of time by one brain hemisphere, the presence of the two ideas requisite to the process of comparison can be had only by the combined action of both hemispheres. Hence the usual inability of persons afflicted with hemiplegia to compare or reason accurately.

If the action of the faculty of comparison were paralysed, we should dream when awake. The suspension of the action of this faculty in dream would suffice to account for the accepted incongruities of dream, without assuming the sleep of the entire hemisphere.

But, as observed above, it is difficult to assume the slumber of one mental faculty alone, packed as all are among many with which they are intimately united. It is more probable that in dream the entire of one hemisphere sleeps. The facts are in accordance with such a suggestion.

But, however this may be, it does not disturb the conclusion, that the seat of sleep is in the ganglia at the base of the brain. That portion of the brain which directs the motions of the body sleeps always. Sleep reigns more or less perfectly in the portions of the brain that receive the impressions of the senses. Sleep is very partial in the cerebrum, the duplex organ of the intelligence, and probably—(for it is as yet only conjectural)—partial sleep prevails there, if at all, by the contrivance of slumber by one hemisphere while the other is awake.

Such being the Physiology of Dream—so far as science has yet succeeded in tracing it—we proceed now to investigate its Psychology.