So on his NIGHTMARE through the evening fog Flits the squab Fiend o'er fen, and lake, and bog; Seeks some love-wilder'd Maid with sleep oppress'd, Alights, and grinning fits upon her breast. 55 --Such as of late amid the murky sky Was mark'd by FUSELI'S poetic eye; Whose daring tints, with SHAKESPEAR'S happiest grace, Gave to the airy phantom form and place.-- Back o'er her pillow sinks her blushing head, 60 Her snow-white limbs hang helpless from the bed; While with quick sighs, and suffocative breath, Her interrupted heart-pulse swims in death. --Then shrieks of captured towns, and widows' tears, Pale lovers stretch'd upon their blood-stain'd biers, 65 The headlong precipice that thwarts her flight, The trackless desert, the cold starless night, And stern-eye'd Murder with his knife behind, In dread succession agonize her mind. O'er her fair limbs convulsive tremors fleet, 70 Start in her hands, and struggle in her feet; In vain to scream with quivering lips she tries, And strains in palsy'd lids her tremulous eyes; In vain she _wills_ to run, fly, swim, walk, creep; The WILL presides not in the bower of SLEEP. 75 --On her fair bosom sits the Demon-Ape Erect, and balances his bloated shape; [_The Will presides not._ 1. 74. Sleep consists in the abolition of all voluntary power, both over our muscular motions and our ideas; for we neither walk nor reason in sleep. But, at the same time, many of our muscular motions, and many of our ideas, continue to be excited into action in consequence of internal irritations and of internal sensations; for the heart and arteries continue to beat, and we experience variety of passions, and even hunger and thirst in our dreams. Hence I conclude, that our nerves of sense are not torpid or inert during sleep; but that they are only precluded from the perception of external objects, by their external organs being rendered unfit to transmit to them the appulses of external bodies, during the suspension of the power of volition; thus the eye-lids are closed in sleep, and I suppose the tympanum of the car is not stretched, because they are deprived of the voluntary exertions of the muscles appropriated to these purposes; and it is probable something similar happens to the external apparatus of our other organs of sense, which may render them unfit for their office of perception during sleep: for milk put into the mouths of sleeping babes occasions them to swallow and suck; and, if the eye-lid is a little opened in the day-light by the exertions of disturbed sleep, the person dreams of being much dazzled. See first Interlude.] Rolls in their marble orbs his Gorgon-eyes, And drinks with leathern ears her tender cries.