Catarrh, adenoids, enlarged tonsils may suggest dreams of suffocation. Cardiac and respiratory disturbances aid in suggesting dreams of falling and flying. Poisoning, whether the result of diseased gums, diseased tonsils, defective kidney action, etc., or from excessive ingestion of alcohol, coffee, tea, drugs, is sometimes referred to as a cause of unpleasant dreams. Opium is reputed as causing pleasant dreams; this is a fallacy. Often the dreams of its habitues are very unpleasant; others have no memory of their dreams. Fevers are said to cause dreams of fire but this happens rarely. As a rule, the dreams of a person in good health are pleasant in nature; the reverse holds good as a rule of those in poor health. Unpleasant dreams which are more or less habitual are best considered as indicating some disturbance of health, which disturbance may be physical or mental.

Among mental impressions inciting dreams may be mentioned a vivid experience of some kind. For example, a doctor friend says that at the age of sixteen he witnessed the drowning of a chum; for a long time afterwards the incident figured in his dreams. A lady states that after the death of a brother she dreamt of every detail of the funeral for weeks. Plutarch once said: "When sorrow takes me sleeping I am disturbed by dreams." As a rule, ordinary troubles do not figure prominently in dreams; generally one does not dream of his sorrows until these have lost much of their painful content. Wrong-doers are supposed to dream of their crimes. This may happen occasionally in persons who have a good conscience, but the confirmed criminal rarely dreams of his delinquencies; even when awake his errors fail to trouble him. Scholz1 tells us that "King Henry II of France attended the burning of a heretic where the unhappy victim was drawn up and down in iron chains above a slow fire. The man in torture cast a look of agony at the window where the king sat. The king turned away in horror, but in dreams the poor victim appeared to him with the same look of agonizing appeal upon his face." Among other inciters of dreams ghost, murder, and similar stories might be mentioned; these are apt to particularly apply in young persons. The works of Poe are potent inciters for many. Usually when one has been much impressed just prior to going to sleep by something weird, a very slight physical or external stimulus will be sufficient for the impression to become acted out in dreams.

If dreams depended entirely on such stimuli as have been mentioned, we would dream little or none. A great percentage of the dreams recorded as showing the influence of somatic and peripheral instigators in sleep were experimentally produced, and, of course, natural sleep is free from these stimuli. As before stated, very few dreams can be definitely traced to external or physical instigators. Many of us regard indigestion as a very potent inciter, but that it is overemphasized is shown by the fact that most of our remembered dreams occur in the morning, when the stomach is practically empty. Again, very many vivid dreamers are free from indigestion and other discoverable physical impairments.

It is true, however, that dreams may be influenced by external and physical stimuli. When these act, the dream may be explained in the following way: The stimulus reaches the brain through the sensory organs, making an impression sufficient to obtain recognition. The brain then attempts to account for this impression, and in order to do so calls forth an image, or images, which seems to be most suitable. Any one stimulus may have a resemblance to a number of memories, which memories may be new or old, familiar or unfamiliar to waking consciousness. Sleep relaxes the mental tension, thus permitting a number of memories to rush forth, some of which may have only a slight relation to the stimulus, and which would in waking thought be dismissed. Will power is abeyant, asleep; we are unable to discard memories which are not to our liking, or memories which are absurd, considering the stimulus. We must take the memory offered; sometimes, a number of memories will crowd into consciousness, fuse with one another, and thus produce a more or less fantastic picture. In general, sleeping consciousness will seize the first memory offered it, and this memory will be likely to be one which is the nearest related to the stimulus, and which is at the same time of more importance in the psychic life than other possible memories which the same stimulus might evoke. This memory will give rise to other memories by association. Slight resemblances which the first memory has to other memories will be seized, and owing to the fact that the mind is in a state of disinterest, is not busy keeping back material which seems to have no relation to the image first presented to sleeping consciousness - in fact, is unable to exercise will-power, there will be a swift change of scenes and incidents. For example, a mosquito might bite me while I slept. Of many possible ideas, this stimulus might give rise to the idea of being prodded by a savage who was using a long spear. Then my dream thoughts might concern themselves with jungles, various animals, and so on. This would be because the thought of savages gave rise to memories with which savages were associated. Thus savages live in jungles, jungles contain animals, etc. One thing suggests another and from a simple suggestion enough material may be derived to promote an indefinite amount of, and varied dreaming.

1 Sleep and Dreams, 1893, p. 61, English Translation, Funk & Wagnalls Co.

If dreams traceable to sources outside the mind should strike one as absurd, we should not cast reproaches on the mind's interpretation of the stimuli. For instance, one may think that to interpret the sting of a mosquito as due to the prodding of a savage with a long spear exemplifies feeble reasoning powers. However, the fact that the mind interpreted the stimulus shows that a certain attention,1 judgment, and reasoning were applied to the stimulus. The reasoning was, of course, poor, contrasted with waking reason. But considering the difference between the faculties available for dream activity, the interpretation was not so very illogical. In sleep the mind has not actual sight to aid it. Again, stimuli reaching the brain in sleep appear magnified, just as the pains of the day seem worse, or magnified, when the distractions of the day are removed. Moreover, if we reasoned in sleep as we do when awake we would not rest. Sleep is intended to rest the higher mental faculties particularly, which have been much employed in the waking state; sometimes dreams make use of these higher faculties to some degree, but in such cases the sleep is not the usual sleep, and the individual is not refreshed by it. In sleep the will is quiescent; the relaxed state of the mind permits many images to appear which waking consciousness could dismiss; the criticism, the reasoning, is below par. The mind in sleep has feebler faculties at its disposal but it makes good use of them. And considering the great power sleep has in opening the door to forgotten memories, its imaginative flights, etc., we have good reason to credit it with more ability than it ordinarily receives.