Now I shall ask you to consider the fact that the waking dreams offer by far the best chances for determining the influence of external sleep-disturbing stimuli. In most of the other cases it will be more difficult. One does not wake up in all dreams, and in the morning, when one remembers the dream of the night, how can one discover the disturbing stimulus which was perhaps in operation at night? I did succeed once in subsequently establishing such a sound stimulus, though naturally only in consequence of special circumstances. I woke up one morning in a place in the Tyrolese Mountains, with the certainty that I had dreamt the Pope had died. I could not explain the dream, but then my wife asked me: "Did you hear the terrible bell ringing that broke out early this morning from all the churches and chapels?" No, I had heard nothing, my sleep is a sound one, but thanks to this information I understood my dream. How often may such stimuli incite the sleeper to dream without his knowing of them afterward? Perhaps often, perhaps infrequently; when the stimulus can no longer be traced, one cannot be convinced of its existence. Even without this fact we have given up evaluating the sleep disturbing stimuli, since we know that they can explain only a little bit of the dream, and not the whole dream reaction. But we need not give up this whole theory for that reason. In fact, it can be extended. It is clearly immaterial through what cause the sleep was disturbed and the psyche incited to dream. If the sensory stimulus is not always externally induced, it may be instead a stimulus proceeding from the internal organs, a so-called somatic stimulus. This conjecture is obvious, and it corresponds to the most popular conception of the origin of dreams. Dreams come from the stomach, one often hears it said. Unfortunately it may be assumed here again that the cases are frequent in which the somatic stimulus which operated during the night can no longer be traced after waking, and has thus become unverifiable. But let us not overlook the fact that many recognized experiences testify to the derivation of dreams from the somatic stimulus. It is in general indubitable that the condition of the internal organs can influence the dream. The relation of many a dream content to a distention of the bladder or to an excited condition of the genital organs, is so clear that it cannot be mistaken. From these transparent cases one can proceed to others in which, from the content of the dream, at least a justifiable conjecture may be made that such somatic stimuli have been operative, inasmuch as there is something in this content which may be conceived as elaboration, representation, interpretation of the stimuli. The dream investigator Schirmer (1861) insisted with particular emphasis on the derivation of the dream from organic stimuli, and cited several splendid examples in proof. For example, in a dream he sees "two rows of beautiful boys with blonde hair and delicate