458 DREAM in ancient and modern systems of medicine has already been referred to. States of the stomach, lungs, heart, secretory organs, teeth and gums, &c.. are, as we all know, powerful provocatives of dreams. Owing to the close con nection of dreams with these organic conditions they may serve as important elements in the diagnosis of bodily disease. Thus M. Macario (Du Sommeil, des Revcs, et da Somnambulisme) recognizes among the morbid class of dreams those which are " prodromic, or premonitory (e.g., a dream of sanguinary conflict before hemorrhage), as well as those which are symptomatic of existing bodily and mental disorders. (II.) We pass to internal or cerebral excitations. Under (a), the direct excitations, are to bs included all dream -ideas which do not arise from bodily stimuli, or through associa tion with preceding feelings and ideas. It seems fairly certain that many of our dream-images are thus occasioned by a kind of " automatic excitation " of the cerebral regions. The dreams which clearly arise from an after-effect in the brain of recent perceptions, especially those of the previous day, appear to illustrate this process. Also, many of the images which correspond to persons and scenes supposed to be long since forgotten may be due to some such local automatic cerebral " sub- excitation." Maury distinctly recognizes this factor in dream-stimulation. It appears from experiences recorded by him that by means of these automatic central excitations images may sometimes be called up of objects which have never been distinctly perceived, and which yet have left a trace of their action on the cerebral substance. (ft) The indirect central stimulations include, no doubt> a large number of our dream-fancies. When once a starting-point is reached, whether through a peripheral or a central automatic (direct) excitation, the nervous connections which answer to mental associations provide a vast range of new cere bration. It is to be added that the very same causes which excite particular cerebral regions. to automatic action must affect other and connected parts in a less degree, producing a powerful predisposition to activity. Hence it is to be supposed that links of association which are insufficient to restore an idea to consciousness in the wak ing^ state may suffice to do so in sleep. (B) The Order of Dream-Combinations. Dreams are i commonly said to be incoherent, and this is no doubt fre quently the case. On the other hand many dreams appear to simulate orderly arrangements of objects and successions of events. It must follow that on simple theory, such as that the mind has lost the forms of thought as space, time, and causation (which, as we have seen, is contradicted by Schopenhauer) will cover all the facts. The absence of volition and voluntary attention goes far to throw light on dream-combinations. In dreaming, as Maury observes, attention, instead of dominating the images which present themselves, is itself dominated by these. At the same time, as we shall see presently, the action of attention, though no longer controlled by the will and directed to some practical end, plays an important part in dream- construction. In order, if possible, to get at the laws of dream-structure, we may roughly divide dreams into two classes : (a) the disconnected and incoherent, and (ft) the coherent. (a) The want of coherence in disorderly dreams appears to arise from the play of association acting on all the heterogeneous and disconnected elements supplied by peripheral and central (direct) stimulation at the time, there being no volitional control (dominating attention) to inter fere with the process. Supposing that these two primary sources are continually sending forth new and disconnected images to the dream-consciousness, and that owing to the extreme excitability of the brain during sleep numerous paths of association open themselves up in connection with every such image, we may see how it is that objects group Ihemselves, and events succeed one another in such a chaotic manner. It is not correct to say that we here dispense with the " forms " of space and time ; objects are viewed in space, and events " intuited " in time, it is only that the particular positions of things in space and time are overlooked. On the other hand, it is true that there is in these loosely-threaded dreams, if not in all dreams, a suspension of the reasoning process by which objects are intuited in a causal relation. In these dreams, then, the mind is passive, and consciousness is made up of a flu^ of images and feelings which is not analyzed and rationalized as it is in the normal processes of waking perception. (ft) Let us now consider the more coherent class of dreams. These, as we have seen, have by some been accounted for as the products of some occult power of the soul, as the " phantastical power " of Cud worth and the symbolic plastic phantasy of Schemer. There is no doubt that in many of the more elaborate and pictorial of our dreams a result is reached very similar to the products of the waking imagination. Can this operation be analyzed into simple processes ? First of all, the images, however disconnected their corresponding objects may be, group themselves in a certain arrangement. This process would be -described by psychologists of the Kantian school as the superposition on the dream-materials of certain mental forms. On the other hand, it may perhaps be explained as a result of association. When two orders of impression for example, the sight of the human form and the sound of a human voice have been habitually associated, there arises what may be called a general associative disposition to con nect some variety of one order of impression with any par ticular variety of the order which happens to present itself to the mind ; and so, when dreaming, the mind is disposed to add to images of colour certain relations of space, posi tion, magnitude, &c., to images of human beings some form of the appropriate human actions, relations. &c. By this means the intuitive clearness and completeness of our dream-imaginations may largely be accounted for. It is to -be added that these general associative tendencies do not determine what particular relations or actions are to be attributed to the images of sleep. These latter depend on the particular circumstances of the moment, as, for example, the locality of the optis fibres involved, the varying excitability of the central regions, &c. In this- factor of our dream-constructions the mind seems to be wholly passive. We have now to turn to a second influence, which involves to some extent the active side of the mind, namely, the play of attention under the influence, not of the will, but of certain vaguo emotional impulses. The chief of these are the feeling for unity, and the instinct of emotional harmony. First of all, there seems to bo a tendency in the more orderly dreams to bring new images into some intelligible connection or relation of unity with the pre-existing ones. This vague im pulse, acting through the processes of expectation and attention, becomes selective, leading to a detention of those members of the ever-renewed flux of images which are fitted to enter into the dream-scene as con sistent factors. In certain cases, indeed, this process seems to rise to something like a conscious voluntary exertion. We occasionally remember that we strove in our dream to discover a consistency in the variegated and confused scene presented to consciousness. Secondly, the unity of dream-structure is largely determined by the need of emotional harmony. A large part, if not all, of our dream-fancies are attended with a feeling of pleasure or of pain. Now, when a certain state of emotion has been
excited ia the mind, there is a tendency to reject all ideas