524. But these statements shall be illustrated by comparisons: The sins an impenitent man holds fast to may be compared to various diseases in him, from which, he dies unless remedies are applied and the malignities thereby removed. They may be compared especially to the disease called gangrene, which unless healed in time, spreads, and causes inevitable death; in like manner to boils and abscesses, unless they break out or are opened; for from them empyemata or collections of pus will be diffused into the neighboring parts, from these into adjoining viscera, and finally into the heart, from which comes death.
 These sins may also be compared to tigers, leopards, lions, wolves, and foxes, which unless kept in dens or bound with chains or ropes, would attack the flocks and herds and kill them as the fox does poultry; also to poisonous serpents, which unless held tight with sticks, or deprived of their teeth, would inflict deadly wounds upon man. A whole flock, if left in fields where there are poisonous herbs, instead of being led by the shepherd to safe pastures; would perish. So the silk-worm would perish, and all silk with it, unless other worms were kept from the leaves of its tree.
 These sins may also be compared to grain in granaries or barns, which would be rendered musty and rotten and thus useless, if the air were not permitted to pass freely through it, and remove whatever is injurious. If a fire were not quenched at the very outset, it might lay waste a whole city or forest. Thorns, briars, and thistles would take full possession of a garden unless rooted out. Gardeners know that a tree sprung from a bad seed and root conveys its bad sap to the branch of a good tree budded or engrafted upon it, and that the bad sap which comes up is turned into good sap, and produces useful fruit. And the like takes place in man through the removal of evil by means of repentance; for man is thereby engrafted into the Lord as a branch into a vine, and bears good fruit (John 15:4-6).