The contact of objects with the tactual organ is one of the best recognized causes of dreams.  M. Maury found that when his lips were tickled, his dream-fancy interpreted the impression as of a pitch plaster being torn off his face.  An unusual pressure on any part of the body, as, for example, from contact with a fellow-sleeper, is known to give rise to a well-marked variety of dream.  Our own limbs may even appear as foreign bodies to our dream-imagination, when through pressure they become partly paralyzed.  Thus, on one occasion, I awoke from a miserable dream, in which I felt sure I was grasping somebody’s hand in bed, and I was racked by terrifying conjectures as to who it might be.  When fully awake, I discovered that I had been lying on my right side, and clasping the wrist of the right arm (which had been rendered insensible by the pressure of the body) with the left hand.

In close connection with these stimuli of pressure are those of muscular movement, whether unimpeded or impeded.  We need not enter into the difficult question how far the “muscular sense” is connected with the activity of the motor nerves, and how far with sensory fibres attached to the muscular or the adjacent tissues.  Suffice it to say that an actual movement, a resistance to an attempted movement, or a mere disposition to movement, whether consequent on a surplus of motor energy or on a sensation of discomfort or fatigue in the part to be moved, somehow or other makes itself known to our minds, even when we are deprived of the assistance of vision.  And these feelings of movement, impeded or unimpeded, are common initial impulses in our dream-experiences.  It is quite a mistake to suppose that dreams are built up out of the purely passive sensations of sight and hearing.  A close observation will show that in nearly every dream we imagine ourselves either moving among the objects we perceive or striving to move when some weighty obstacle obstructs us.  All of us are familiar with the common forms of nightmare, in which we strive hopelessly to flee from some menacing evil, and this dream-experience, it may be presumed, frequently comes from a feeling of strain in the muscles, due to an awkward disposition of the limbs during sleep.  The common dream-illusion of falling down a vast abyss is plausibly referred by Wundt to an involuntary extension of the foot of the sleeper.

Action of Internal Stimuli.

Let us now pass from the action of stimuli lying outside the organism, to that of stimuli lying within the peripheral regions of the sense-organs.  I have already spoken of the influence of subjective sensations of sight, hearing, etc., on the illusions of waking life, and it is now to be added that these sensations play an important part in our dream-life.  Johannes Mueller lays great prominence on the part taken by ocular spectra in the production of dreams.  As he observes, the apparent rays of light, light-patches,