But it is much more difficult to account for the infection of the houses. For it seems hardly possible in nature, that the leprous spots should grow and spread on dry walls, made of solid materials. But upon a serious consideration of the different substances employed in building the walls of houses, such as stones, lime, bituminous earth, hair of animals, and other such things mix’d together; I thought it probable, that they may by a kind of fermentation, produce those _hollow greenish or reddish strokes in sight lower than the wall_ (or within the surface)[59] which, as they in some measure resembled the leprous scabs on the human body, were named the _Leprosy in a house_. For bodies of different natures, very easily effervesce upon being blended together. Wherefore we may reasonably suppose that this moisture or mouldiness, gradually coming forth and spreading on the walls, might prove very prejudicial to the inhabitants, by its stinking and unwholesome smell, without having recourse to any contagious quality in it. And somewhat analogous to this is pretty frequently observable in our own houses; where, when the walls are plaistered with bad mortar, the calcarious and nitrose salts sweat out upon their surface, of a colour almost as white as snow. The power of inspecting their houses was invested in the priests; who, when they observed this foulness, gave orders first to have the walls of the house scraped all around; and afterwards, if it continued to break out, to pull down the house, and carry the materials out of the city into an unclean place. [59] _Levit. Chap. xiv. v. 37._ I am well aware, that all this is related, as if God himself had struck the house with this plague. But it is well known, that that way of speaking is not uncommon in the jewish history; as in unexpected evils and dreadful calamities, which are sometimes said to be done by the hand of God, tho’ they may be produced by natural causes. Nor can I be easily induced to believe, with some divines, that God, who commanded his people to be always free from every sort of uncleanness, would vouchsafe to work a miracle, in order to inflict this most filthy punishment on any person. Thus much is indubitable, that the precepts of the mosaic law were constituted particularly, to avert the people from idolatry and false religion, and at the same time to keep them clear of all uncleanness.[60] To this end conspired the prohibition of eating blood, carrion, or animals that died spontaneously, swines flesh, and that of several other creatures.[61] For all these meats yield a gross nutriment, which is improper and prejudicial in diseases of the skin. [60] _Mos. Maimonid. More Navochim, Part. iii. Cap. xxxiii. et xlviii._ [61] _Levit. Chap. xi. et xvii._