As the salt was found to have undergone no change in the small guts, it appears, that it is not prevented from entering the lacteals by its being decomposed or precipitated, as has been imagined; but, on the contrary, that what renders it incapable of being received by these vessels, is its _astringency_: for the lacteals seem to be endowed with that admirable faculty of admitting such particles of pure chyle as they happen to be in contact with, and of accommodating their diameters to them, at the same time that by their natural irritability, and power of constriction they obstinately exclude such as are astringent; which, were they to enter the lacteals, would either produce dangerous obstructions in these vessels, or, if they got into the blood, would occasion polypous concretions in the larger vessels, or coagulations incapable of being transmitted thro’ the minute vessels of the lungs; the effects of which would be either sudden death, or at least inflammations and suppurations from obstructions in the pulmonary vessels; inconveniences, which nature, by precluding astringents from entering the lacteals, has carefully and wisely avoided. Salt of steel, taken internally, must retain its astringency until it be precipitated; which can scarce ever fail to happen in the great guts, from the putrid _fæces_ they contain, which are always observed to be tinged of a black colour from the metallic basis of the salt, part of which, as it has little or no astringency, may, no doubt, enter the blood, as Signor Menghini observed of the _crocus_, which is the same substance; and we know, from the experiments of Lister and Musgrave[35], that particles much grosser than those of the white chyle, provided they be not astringent, or very acrid, are conveyed by the lacteals. But the metallic basis being separated from its acid, and thus reduced to a mere calx or earth, can scarce be supposed to have any medicinal quality whatsoever, or at least to have any share in the virtues justly attributed to salt of steel. As this salt is not only astringent, and consequently a strengthener, but at the same time acts with a gentle _stimulus_, all its virtues (which are known to be very great in diseases, where the fluids are either viscid, cold, and phlegmatic, or dissolved and watery, from a laxity of the solids) may be accounted for from its immediate effects on the stomach and _primæ viæ_, and on the system of the solids in general by consent; which it would be needless to illustrate by similar examples, because well known to every one the least versed in medical studies. I shall therefore only beg leave, from the obvious qualities of this medicine, and from what has been observed above, to deduce the following corollaries.