But the prohibition goes much farther than that. It enshrines a tremendous principle, a principle that is nowhere else so clearly stated. Sir Walter Scott evidently saw that; and no exposition could be clearer than his. The circumstances were, briefly, these. The Countess of Leicester was a prisoner. Just outside her room at the castle was a trapdoor. It was supported by iron bolts; but it was so arranged that even if the bolts were drawn, the trapdoor would still be held in its place by springs. Yet the weight of a mouse would cause it to yield and to precipitate its burden into the vault below. Varney and Foster decided to draw these bolts so that, if the Countess attempted to escape, the trap would destroy her. Later on, Foster heard the tread of a horse in the court-yard, and then a whistle similar to that which was the Earl's usual signal. The next moment the Countess's chamber opened, and instantly the trapdoor gave way. There was a rushing sound, a heavy fall, a faint groan, and all was over! At the same instant Varney called in at the window, 'Is the bird caught? Is the deed done?' Deep down in the vault Foster could see a heap of white clothes, like a snowdrift. It flashed upon him that the noise that he had heard was not the Earl's signal at all, but merely Varney's imitation, designed to deceive the Countess and lure her to her doom. She had rushed out to welcome her husband, and had miserably perished. In his indignation, Foster turned upon Varney. 'Oh, if there be judgement in heaven, thou hast deserved it,' he said, 'and wilt meet it! Thou hast destroyed her by means of her best affections. _It is a seething of the kid in the mother's milk!_'
At that touchstone the inner meaning of the interdict stands revealed. The mother's milk is Nature's beautiful provision for the life and sustenance of the kid. Thou shalt not pervert that which was intended to be a ministry of life into an instrument of destruction. The wifely instinct that led the Countess to rush forth to welcome her lord was one of the loveliest things in her womanhood, and Varney used it as the agency by which he destroyed her. She was lured to her doom by means of her best affections. Charles Lamb points out, in his _Tales from Shakespeare_, that Iago compassed the death of the fair Desdemona in precisely the same way. 'So mischievously did this artful villain lay his plots to turn the gentle qualities of this innocent lady into her destruction and make a net for her out of her own goodness to entrap her!' It is this that the prohibition forbids. Thou shalt not take the most sacred things in life and apply them to base and ignoble ends. _Thou shalt not seethe a kid in his mother's milk._