f we attempt to interest a cultured layman in the problems of dreams, and if, with this end in view, we ask him what he believes to be the source of dreams, we shall generally find that he feels quite sure he knows at least this part of the solution. He thinks immediately of the influence exercised on the formation of drams by a disturbed or impeded digestion, an accidental position of the body, a trifling occurrence during sleep. He does not seem to suspect that even after all these factors have been duly considered something still remains to be explained. Earlier we examined at length the opinion of scientific writers on the role of somatic stimuli in the formation of drams, so that here we need only r4ecall the results of this inquiry. We have seen that three kinds of somatic stimuli will be distinguished: the objective sensory stimuli which proceed from external objects, the inner states of excitation of the sensory organs, having only a subjective reality, and the bodily stimuli arising within the body; and we have also noticed that the writers on dreams are inclined to thrust into the background any psychic sources of dreams which may operate simultaneously with the somatic stimuli, or to exclude them altogether. In testing the claims made on behalf of these somatic stimuli we have learned that the significance of the objective excitation of the sensory organs - whether accidental stimuli operating during sleep, or such as cannot be excluded from the dormant relation of these dream-images  and ideas to the internal bodily stimuli and confirmed by experiment; that the part played by the subjective sensory stimuli appears to be demonstrated by the recurrence of hypnagogic sensory images in drams; and that, although the broadly accepted relation of these dram-images and ideas to the internal bodily stimuli cannot be exhaustively demonstrated, it is at all events confirmed by the well-known influence which an excited state of the digestive, urinary and sexual organs exercises upon the content of our dreams. "Nerve stimulus" and "bodily stimulus" would thus be the anatomical sources of dreams; that is, according to many writers, the sole and exclusive sources of dreams. But we have already considered a number of doubtful points, which seem to question not so much correctness of the somatic theory as its adequacy. However confident the representatives of this theory may be of its factual basis - especially in respect of the accidental and external nerve-stimuli, which may without difficulty be recognized in the dram-content - nevertheless they have all come near to admitting that the rich content of ideas found in drams cannot be derived from the external nerve-stimuli alone. In this connection Miss Mary Whiton Calkins tested her own dreams, and those of a second person, for a period of six weeks, and found that the element of external sensory perception was demonstrable in only 13.2 per cent and 6.7 per cent of these dreams respectively. Only two dreams in the whole collection could be referred to organic sensations. These statistics confirm what a cursory survey of our own experience would already have led us to suspect. A distinction has often been made between "nerve-stimulus dreams" which have already been thoroughly investigated and others forms of dreams. Spitta, for example, divided dreams into nerve-stimulus dreams and associated-dreams. But it was obvious that this solution remained unsatisfactory unless the link between somatic sources of dreams and their ideational content could be indicated. In addition to the first objection, that of the insufficient frequency of the external sources of stimulus, a second objection presents itself, namely the inadequacy of the explanations of dreams afforded by this category of dream-sources. There are two things which the representatives of this theory have failed to explain: firstly, the true nature of the external stimulus is not recognized in the dream, but is constantly mistaken for Something else; and secondly, why the result of the reaction of the perceiving mind to this misconceived stimulus should be so indeterminate and variable. Strumpell, in answer to these questions, asserts that the mind, since it turns away from the outer world during sleep, is not in a position to give the correct interpretation of the objective sensory stimulus, but is forced to construct illusions on the basis of the indefinite stimulation arriving from many directions.
Q.1. One of the reason why the author believes that the external stimuli alone cannot be a source of dreams is because,