I ought to explain why I, being a person without any of the scientific attainments that would fit one for the task, take it on me to write of dreams. It occurred to me that there were certain kinds of dreams common to nearly every one. Every one (using the word in a liberal sense, and not in the grudging spirit of the man who objected to ninety-nine ducks being spoken of as a round hundred) is familiar with the dream of falling over a precipice. A great many people know the dream that they are flying. Few have not dreamed that they have entered a polite assembly in a costume very much more appropriate to a Turkish bath than to their visionary surroundings, and there are many other common, generally familiar, dreams. And this being so, I was struck by the fact that no one seemed to have tried to find the common cause of each kind respectively of familiar dreams. If three-quarters of mankind, say, dream many times in their lives that they are falling over precipices, and half mankind dream nearly as often that they are flying, then it seems only reasonable to think that some tolerably constant cause must produce the one, and some other constant cause the other. There seemed at least a strong probability that this was so.

And seeing that no better qualified person than myself appeared inclined to tackle the problem so suggested, I took upon myself - rushing in where angels seemed fearful of treading - to write an essay in Longman's Magazine, briefly stating the problem and asking for lights. Lights came, in abundance that was rather dazzling and stupifying. I was deluged with letters on the subject. I had rashly asked people to help me by giving me their own experiences and ideas. As a result I was so pelted with experiences as to bewilder my own ideas completely, and make the daily burden of the postman almost too heavy for him to bear. The experiences were interesting, the ideas were illuminating. I can never be sufficiently grateful to those who took the wholly gratuitous pains of communicating them to me. But what came to me as the most striking illumination of all was the discover)' that the subject possessed so much general interest It was quite astonishing. And it is this discovery that has made me so very bold as to attempt this volume, discussing the whole subject of dreams in a more or less comprehensive, though altogether in a popular way.

When I essayed my first essay on the dream problem that I have stated above, I was assailed by one critic (using rather heavy bludgeons for the beating of a butterfly) because I displayed ignorance of the writings of the learned on the subject of dreams generally. It would have needed extraordinary acuteness on my part to conceal such ignorance. More ignorant few men could have been. Since then I have read, with the feeble grasp that a hopelessly unscientific brain has of matters scientific, as much as I could lay hands on of what the learned have written. But my critic need not have bludgeoned so heavily, for I fail to discover that the particular problem, as I stated it, was ever tackled, or, apparently, ever realised by the learned, and certainly at that time it was with no idea of treating the subject of dreams comprehensively, even from the most popular point of view, that I wrote. And now, my grasp on the scientific details being but feeble, I shall not try to explain to anybody else what I have not been able to explain to myself, and shall avoid as far as possible all references to different nerves of the body and cells of the brain that fulfil different functions.

A few words touching on the physiological aspect of the subject are almost inevitable if we are to get any idea of the stuff that dreams are made of. If any one who has not yet studied the physiology of the subject is disposed to do so, he may have fat pasture of the kind for his brain in the works of Maury (Le Sommeil et les Rives), of Macario (Du Sommeil, des Rives, et de la Somnambu-lisme), of Volkhelt and of Wundt Of our own countrymen, Dr. Carpenter and Sir H. Holland have perhaps said most that is to be understood by the general reader, but it is not easy in most points to go behind or beyond Maury's book, which is as interesting and intelligible as it is instructive, although it is doubtful whether the factor which he suggests as the to be said that most people, on being suddenly woken, awake invariably to find that the sudden waking has broken off a dream, and this seems to make it very probable indeed that the mind is unconsciously active all the while that we sleep, but that it is comparatively seldom that a memory of its activity remains with us when we awake.

When we awake gradually, in a normal manner, it is likely that as we regain full use of our sensory apparatus the impressions it conveys to us gradually efface those feeble ones that have come to us during sleep, and so we forget the latter. In case of a sudden awakening, memory and attention become active before any awakening sensory impressions have intervened to obliterate the impressions made in sleep. Incidentally the question arises as to the meaning we are to give the word "dream". It would be far more convenient to restrict it to operation of the mind during sleep that is remembered on awaking; but since, in common parlance, we use it of any operation of the mind during sleep (though forgotten by ourselves on awaking) of which others can take notice (as we say of dogs that they "dream" when they yap and move in their sleep), it is better perhaps to use it, for the present, at least, in its common sense, although, if we adopt the view that the mind is active throughout all the sleeping hours, we must look on "dreaming" in that sense as a constant accident of sleep.

Sleep, so far as we can understand it, is a means of repairing fatigue by rest. Chemically described, it is the repairing of the waste in tissues, nerves and as caused by oxidation. The rate of the circulation is lessened, and the heat of the body is lowered. On the other hand, the heat of the brain is increased, and there is a greater flow of blood into its cells than in the normal waking state. This influx of the blood is found to produce, curiously enough, one of two almost opposite conditions - a comatose congestion that accompanies, perhaps produces, perhaps is, sleep • or a hyper-excitability, such as we are very familiar with when we lie awake with hot head and cold feet. And it also happens, and generally happens (perhaps always) in sleep that some of the cells of the brain, which correspond on the psychical side to certain mental faculties, are in the state of comatose congestion, while others, cells corresponding to other faculties, are in the state of higher excitability. And further it would appear that it is always those faculties of attention, will, judgment, reasoning, which we may call the higher faculties, that become comatose during sleep, while the imaginative faculty becomes hyper-excitable. It may be difficult to see why the influx of blood should produce congestion in the one and this hyper-excitability in the other.