Upon this theory of "mumia," or magnetic force, the sympathetic cure of disease was based. The weapon salve, the sympathetic ointment, and the famous powder of sympathy were the instruments through which it acted. The magnetic cure of wounds became the vogue. Van Helmont adopted these views in his famous treatise "De Magnetica Vulnerum Curatione,"(16) in which he asserted that cures were wrought through magnetic influence. How close they came to modern views of wound infection may be judged from the following: "Upon the solution of Unity in any part the ambient air . . . repleted with various evaporations or aporrhoeas of mixt bodies, especially such as are then suffering the act of putrefaction, violently invadeth the part and thereupon impresseth an exotic miasm or noxious diathesis, which disposeth the blood successively arriving at the wound, to putrefaction, by the intervention of fermentation." With his magnetic sympathy, Van Helmont expressed clearly the doctrine of immunity and the cure of disease by immune sera: "For he who has once recovered from that disease hath not only obtained a pure balsaamical blood, whereby for the future he is rendered free from any recidivation of the same evil, but also infallibly cures the same affection in his neighbour . . . and by the mysterious power of Magnetism transplants that balsaam and conserving quality into the blood of another." He was rash enough to go further and say that the cures effected by the relics of the saints were also due to the same cause--a statement which led to a great discussion with the theologians and to Van Helmont's arrest for heresy, and small wonder, when he makes such bold statements as "Let the Divine enquire only concerning God, the Naturalist concerning Nature," and "God in the production of miracles does for the most part walk hand in hand with Nature." (16) An English translation by Walter Charleton appeared in 1650, entitled "A Ternary of Paradoxes." That wandering genius, Sir Kenelm Digby, did much to popularize this method of treatment by his lecture on the "Powder of Sympathy."(17) His powder was composed of copperas alone or mixed with gum tragacanth. He regarded the cure as effected through the subtle influence of the sympathetic spirits or, as Highmore says, by "atomicall energy wrought at a distance," and the remedy could be applied to the wound itself, or to a cloth soaked in the blood or secretions, or to the weapon that caused the wound. One factor leading to success may have been that in the directions which Digby gave for treating the wound (in the celebrated case of James Howell, for instance), it was to be let alone and kept clean. The practice is alluded to very frequently by the poets. In the "Lay of the Last Minstrel" we find the following: