As was set forth above, the cerebral cortex receives its stimuli, not only from the external nerves, but also from the interior of the organism, from the nerves of separate organs, and the nerve-centres of the spinal cord and the sympathetic system. Every excitement in these centres affects the brain-cells, and arouses in them more or less distinct presentations, which are necessarily related to the activity of the centres from which the stimulus proceeds. A few examples will make this clear, even to the uninitiated. If the organism feels the need of nourishment, and we are hungry, we shall not only be generally conscious of an indeterminate desire for food, but there will also arise in our minds definite representations of dishes, of served repasts, and of all the accessories of eating. If we, from some cause, maybe an affection of the heart or lungs, cannot breathe freely, we have not only a hunger for air, but also accompanying ideas of an uneasy nature, presentiments of unknown dangers, melancholy memories, etc., _i.e._, representations of circumstances which tend to deprive us of breath or affect us oppressively. During sleep also organic stimuli exert this influence on the cerebral cortex, and to them we owe the so-called somatic dreams (_Leibesträume_), _i.e._, dream-images about the functioning of any organs which happen not to be in a normal condition. Now, it is known that certain organic nerve-centres, the sexual centres, namely, in the spinal cord and the medulla oblongata, are frequently malformed, or morbidly irritated among the degenerate. The stimuli proceeding from them therefore awaken, in the brain of patients of this sort, presentations which are more or less remotely connected with the sexual activity. In the consciousness, therefore, of such a subject there always exist, among the other presentations which are aroused by the varying stimuli of the external world, presentations of a sexual character, erotic thoughts being associated with every impression of beings and things. In this way he attains to a state of mind in which he divines mysterious relations among all possible objective phenomena, _e.g._, a railway-train, the title of his newspaper, a piano on the one hand, and woman on the other; and feels emotions of an erotic nature at sights, words, odours, which would produce no such impression on the mind of a sound person, emotions which he refers to unknown qualities in those sights, words, etc. Hence it comes that in most cases mysticism distinctly takes on a decidedly erotic colouring, and the mystic, if he interprets his inchoate liminal presentations, always tends to ascribe to them an erotic import. The mixture of super-sensuousness and sensuality, of religious and amorous rapture, which characterizes mystic thought, has been noticed even by those observers who do not understand in what way it is brought about.