All of rich summer smacked, of autumn all: Pears at our feet, and apples at our side Rolled in luxuriance; branches on the ground Sprawled, overweighed with damsons; while we brushed From the cask's head the crust of four long years.

It is due to an overweighing of the pituitary, controller of good brain tone, and alive wakefulness, by the demands of the organism.