The stimulus which reaches a brain-cell gives rise, as we have seen, to an expansion of this stimulus to the neighbouring cells, to a wave of stimulus proceeding in all directions. And since every stimulus is connected with the rise of conscious presentations, it proves that every stimulus calls a large number of presentations into consciousness, and not only such presentations as are related to the immediate external cause of the stimulation perceived, but also such as are only aroused by the cells that elaborate them happening to lie in the vicinity of that cell, or group of cells, which the external stimulus has immediately reached. The wave of stimulus, like every other wave-motion, is strongest at its inception; it subsides in direct ratio to the widening of its circle, till at last it vanishes into the imperceptible. Corresponding to this, the presentations, having their seat in cells which are in the immediate neighbourhood of those first reached by the stimulus, are the most lively, while those arising from the more distant cells are somewhat less distinct, and this distinctness continues to decrease until consciousness can no longer perceive them--until they, as science expresses it, sink beneath the threshold of consciousness. Each particular stimulus arouses, therefore, not only in the cell to which it was directly led, but also in countless other contiguous and connected cells, the activity which is bound up with presentation. Thus arise simultaneously, or, more accurately, following each other in an immeasurably short interval of time, thousands of impressions of regularly decreasing distinctness; and since unnumbered thousands of external and internal organic stimuli are carried to the brain, so continually thousands of stimulus-waves are coursing through it, crossing and intersecting each other with the greatest diversity, and in their course arousing millions of emerging, waning, and vanishing impressions. It is this that Goethe means when he depicts in such splendid language how ‘...ein Tritt tausend Fäden regt, Die Schifflein herüber, hinüber schiessen, Die Fäden ungesehen fliessen, Ein Schlag tausend Verbindungen schlägt.’[71]