are conditioned by the fact that a nerve-stimulus produces its psychical effect in the life of the mind in accordance with the laws of reproduction."

In all essential points identical with this doctrine is Wundt's statement that the concepts of dreams proceed, at all events for the most part, from sensory stimuli, and especially from the stimuli of general sensation, and are therefore mostly phantastic illusions- probably only to a small extent pure memoryconceptions raised to the condition of hallucinations. To illustrate the relation between dream-content and dream- stimuli which follows from this theory, Strumpell makes use of an excellent simile. It is "as though ten fingers of a person ignorant of music were to stray over the keyboard of an instrument." The implication is that the dream is not a psychic phenomenon, originating from psychic motives, but the result of a physiological stimulus, which expresses itself in psychic symptomatology because the apparatus affected by the stimulus is not capable of any other mode of expression. Upon a similar assumption is based the explanation of obsessions which Meynert attempted in his famous simile of the dial on which individual figures are most deeply embossed.

Popular though this theory of the somatic dream-stimuli has become, and seductive though it may seem, it is none the less easy to detect its weak point. Every somatic dream-stimulus which provokes the psychic apparatus in sleep to interpretation by the formation of illusions may evoke an incalculable number of such attempts at interpretation. It may consequently be represented in the dream- content by an extraordinary number of different concepts. * But the theory of Strumpell and Wundt cannot point to any sort of motive which controls the relation between the external stimulus and the dream-concept chosen to interpret it, and therefore it cannot explain the "peculiar choice" which the stimuli "often enough make in the course of their productive activity" (Lipps, Grundtatsachen des Seelen-lebens, p. 170). Other objections may be raised against the fundamental assumption behind the theory of illusions- the assumption that during sleep the mind is not in a condition to recognize the real nature of the objective sensory stimuli. The old physiologist Burdach shows us that the mind is quite capable even during sleep of a correct interpretation of the sensory impressions which reach it, and of reacting in accordance with this correct interpretation, inasmuch as he demonstrates that certain sensory impressions which seem important to the individual may be excepted from the general neglect of the sleeping mind (as in the example of nurse and child), and that one is more surely awakened by one's own name than by an indifferent auditory impression; all of which presupposes, of course, that the mind discriminates between sensations, even in sleep. Burdach infers from these observations that we must not assume that the mind is incapable of interpreting sensory stimuli in the sleeping state, but rather that it is not sufficiently interested in them. The arguments which Burdach employed in 1830 reappear unchanged in the works of Lipps (in the year 1883), where they are employed for the purpose of attacking the theory of somatic stimuli. According to these arguments the mind seems to be like the sleeper in the anecdote, who, on being asked, "Are you asleep?" answers "No," and on being again addressed with the words: "Then lend me ten florins," takes refuge in the excuse: "I am asleep."

* I would advise everyone to read the exact and detailed records (collected in two volumes) of the dreams experimentally produced by Mourly Vold in order to convince himself how little the conditions of the experiments help to explain the content of the individual dream, and how little such experiments help us towards an understanding of the problems of dreams.

The inadequacy of the theory of somatic dream-stimuli may be further demonstrated in another way. Observation shows that external stimuli do not oblige me to dream, even though these stimuli appear in the dream-content as soon as I begin to dream- supposing that I do dream. In response to a touch or pressure stimulus experienced while I am asleep, a variety of reactions are at my disposal. I may overlook it, and find on waking that my leg has become uncovered, or that I have been lying on an arm; indeed, pathology offers me a host of examples of powerfully exciting sensory and motor stimuli of different kinds which remain ineffective during sleep. I may perceive the sensation during sleep, and through my sleep, as it were, as constantly happens in the case of pain stimuli, but without weaving the pain into the texture of a dream. And thirdly, I may wake up in response to the stimulus, simply in order to avoid it. Still another, fourth, reaction is possible: namely, that the nervestimulus may cause me to dream; but the other possible