Moreover, if we study the literature of dreams it becomes quite evident that some writers (Maury, Weygandt) have been led to the study of dream- problems by the influence their own pathological state has had on the content of their dreams.

The enlargement of the number of dream-sources by such undeniably established facts is, however, not so important as one might be led to suppose; for dreams are, after all, phenomena which occur in healthy persons- perhaps in all persons, and every night- and a pathological state of the organs is evidently not one of the indispensable conditions. For us, however, the question is not whence particular dreams originate, but rather: what is the exciting cause of ordinary dreams in normal people?

But we have only to go a step farther to find a source of dreams which is more prolific than any of those mentioned above, and which promises indeed to be inexhaustible. If it is established that the bodily organs become, in sickness, an exciting source of dreams, and if we admit that the mind, when diverted during sleep from the outer world, can devote more of its attention to the interior of the body, we may readily assume that the organs need not necessarily become diseased in order to permit stimuli, which in one way or another grow into dream-images, to reach the sleeping mind. What in the waking state we vaguely perceive as a general sensation, perceptible by its quality alone- a sensation to which, in the opinion of physicians, all the organic systems contribute their share- this general sensation would at night attain a greater potency, and, acting through its individual components, would constitute the most prolific as well as the most usual source of dream-representations. We should then have to discover the laws by which organic stimuli are translated into dream- representations.

This theory of the origin of dreams is the one most favoured by all medical writers. The obscurity which conceals the essence of our being- the "moi splanchnique" as Tissie terms it- from our knowledge, and the obscurity of the origin of dreams, correspond so closely that it was inevitable that they should be brought into relation with one another. The theory according to which the organic sensations are responsible for dreams has, moreover, another attraction for the physician, inasmuch as it favours the aetiological union of the dream with mental derangement, both of which reveal so many points of agreement in their manifestations, since changes in the general organic massive sensation and in the stimuli emanating from the internal organs are also considered to have a far-reaching significance as regards the origin of the psychoses. It is therefore not surprising that the organic stimulus theory can be traced to several writers who have propounded this theory independently.

A number of writers have followed the train of thought developed by Schopenhauer in 1851. Our conception of the universe has its origin in the recasting by the intellect of the impressions which reach it from without in the moulds of time, space and causality. During the day the stimuli proceeding from the interior of the organism, from the sympathetic nervous system, exert at most an unconscious influence on our mood. At night, however, when the overwhelming effect of the impressions of the day is no longer operative, the impressions that surge upward from within are able to force themselves on our attention- just as in the night we hear the rippling of the brook that was drowned in the clamour of the day. But how else can the intellect react to these stimuli than by transforming them in accordance with its own function into things which occupy space and time and follow the lines of causality?- and so a dream originates. Thus Scherner, and after him Volkelt, endeavoured to discover the more intimate relations between physical sensations and dream-pictures; but we shall reserve the discussion of this point for our chapter on the theory of dreams.

As a result of a singularly logical analysis, the psychiatrist Krauss referred the origin of dreams, and also of deliria and delusions, to the same element, namely, to organically determined sensations. According to him, there is hardly any part of the organism which might not become the starting-point of a dream or a delusion. Organically determined sensations, he says, "may be divided into two classes: (1) general sensations- those affecting the whole system; (2) specific sensations- those that are immanent in the principal systems of the vegetative organism, and which may in turn be subdivided into five groups: (a) the muscular, (b) the pneumatic, (c) the gastric, (d) the sexual, (e) the peripheral sensations (p. 33 of the second article)."