No process or transaction of the mind has engaged so much attention for so many centuries as our dreaming when we sleep. Long before there was any thinking about thought, there was thinking about dreams. - F. Greenwood.

From the earliest dawn of history and legend we know that men have dreamed and have told their dreams. From as remote a past interpreters were found ready to explain the significance of dreams; but it is only within the last quarter of a century that the light of modern research has been turned fully on to their study, and that, in place of the soothsayers of old, men of science of all nations have began to analyse the frail stuff of which our dreams are made.

During the lifetime of a generation the way in which the subject is regarded has totally changed. To have ventured fifty years ago to write a book about dreams would have required moral courage, for the subject was looked upon as unworthy the consideration of serious people. To write on it to-day also requires courage, but of a wholly different kind.

It is formidable now only because of the number and the learning of the books that are already written about it. This change of attitude is very noticeable if the literature of dreams in the nineteenth century is considered. Scientific men were still absorbed in the triumphs of that wonderful age of discovery in the physical world, and had hardly begun to find out how great was the work awaiting science in the field of psychology. Many of them still regarded psychology with a certain suspicion, and had not recognised that any purpose useful to science could be served by the study of the unconscious or semi-conscious mind. In every generation the fields of knowledge have had to be widened and extended so as to cover new investigations, and only too often the mandarins of science have tried to bar the way of the explorer, and have condemned the impulse to push out into new regions of thought. It was not until recent years that investigation of certain secrets of man's personality, by means of the revelation of the mind in sleep, began to attract the attention of men of science, and that this new study began to throw light upon some of the difficult problems that confront the physician in dealing with the human nerves and brain.

It is no longer true, as it was when people began to study and to write about dreams in the last century, that the science of medicine approaches such an enquiry as this in a spirit of simple materialism. The interest of medical science is no longer "narrowed down into a predetermination to believe in the dissecting knife, the microscope, and the galvanic battery, as the only interpreters of man to himself." No one would rest content to-day with the explanation given by Dr. Benjamin Richardson in a coarse of health lectures delivered in the "eighties," when he told his hearers to banish from their minds the idea that there was anything in dreams that was not to be explained by purely physical causes. He showed how dreams arose from disturbances com-municated to the brain by the system of nerves, acting much as a telegraph wire acts, which inform the brain of the existence of local trouble or distress in some part of the body. Such perturbations of the brain, when they occur during sleep, occasion our dreams; but the lecturer went no further and would allow no other explanation of the mystery of dreaming than the purely bodily one.

There entered into his definition of dreams nothing that could throw any light upon the working of the imagination, the memory, or any of the other faculties of the mind in sleep - he did not, it would seem, even see how much his explanation left unexplained. Scientific thought has moved very far from this standpoint. Some of the great physicians are devoting themselves to special branches of medical psychology; they have come to realise the immense, the almost incalculable, power of the human mind over the body, and are therefore ready to study every manifestation of the mind and its subtle processes; and a wise physician writing to-day tells us frankly that the medicine of the future will have to take ever fuller and fuller account of aspects of human nature which the medicine of yesterday would have dismissed as mere emotionalism and as wholly outside its province. If it is true, as M. Bergson believes, "that the principal task of psychology in this century will be to explore the secret depths of the unconscious, and that in this science discoveries will be made rivalling in importance the discoveries made in the preceding century in the physical and natural sciences," then it is probable that the observations of each one of us, useless as these would be if they simply remained individual notes, may have a real value when they form part of the accumulating sum of the recorded facts of man's experience, from which science will at last be able to formulate laws that are at present unknown.

We may need for this purpose a "Clearing House of Dreams," where there may be collected the experiences of many men and women trained to record as accurately as possible their observations of dreams and of other subtle processes of the mind and of the subconscious mind. If science is ever to make real progress in understanding much that is now inexplicable with regard to these uncharted regions, it must be furnished with ample materials, and materials drawn from widely different sources and embodying the experiences of very many people. It seems important that these records, upon which science may have eventually to base its conclusions, should not be drawn exclusively, or even in a large proportion, from the records of the physician's consulting-room. Much as we owe to the work of physicians who have faithfully pursued this study, who have seen in it the possible means of solving some of the hardest problems that a doctor has to meet, and who carry forward the science of mind-healing hand in hand with that of the healing of the body, yet the physician starts at a disadvantage in the stndy of dreams or of other little-understood mental processes.