(_d_) _Why the Dream is Forgotten after Awakening._—That the dream “fades away” in the morning is proverbial. To be sure, it is capable of recollection. For we know the dream only by recalling it after awakening; but very often we believe that we remember it only incompletely, and that during the night there was more of it; we can observe how the memory of a dream which has been still vivid in the morning vanishes in the course of the day, leaving only a few small fragments; we often know that we have been dreaming, but we do not know what; and we are so well used to the fact that the dream is liable to be forgotten that we do not reject as absurd the possibility that one may have been dreaming even when one knows nothing in the morning of either the contents or the fact of dreaming. On the other hand, it happens that dreams manifest an extraordinary retentiveness in the memory. I have had occasion to analyse with my patients dreams which had occurred to them twenty-five years or more previously, and I can remember a dream of my own which is separated from the present day by at least thirty-seven years, and yet has lost nothing of its freshness in my memory. All this is very remarkable, and for the present incomprehensible. The forgetting of dreams is treated in the most detailed manner by Strümpell.[66] This forgetting is evidently a complex phenomenon; for Strümpell does not explain it by a single reason, but by a considerable number of reasons. In the first place, all those factors which produce forgetfulness in the waking state are also determinant for the forgetting of dreams. When awake we are wont soon to forget a large number of sensations and perceptions because they are too feeble, and because they are connected with a slight amount of emotional feeling. This is also the case with many dream pictures; they are forgotten because they are too weak, while stronger pictures in proximity will be remembered. Moreover, the factor of intensity in itself is not the only determinant for the preservation of the dream pictures; Strümpell, as well as other authors (Calkins), admits that dream pictures are often rapidly forgotten, although they are known to have been vivid, whereas among those that are retained in memory there are many that are very shadowy and hazy. Besides, in the waking state one is wont to forget easily what happened only once, and to note more easily things of repeated occurrence. But most dream pictures are single experiences,[J] and this peculiarity equally contributes towards the forgetting of all dreams. Of greater significance is a third motive for forgetting. In order that feelings, presentations, thoughts and the like, should attain a certain degree of memory, it is important that they should not remain isolated, but that they should enter into connections and associations of a suitable kind. If the words of a short verse are taken and mixed together, it will be very difficult to remember them.