But, taking, for instance, the herb Rue, which was formerly brought into Court to protect a and the Bench from gaol fever, and other infectious disease; no one knew at the time by what particular virtue the Rue could exercise this salutary power. But more recent research has taught, that the essential oil contained in this, and other allied aromatic herbs, such as Elecampane, [xvi] Rosemary, and Cinnamon, serves by its germicidal principles (stearoptens, methyl-ethers, and camphors), to extinguish bacterial life which underlies all contagion. In a parallel way the antiseptic diffusible oils of Pine, Peppermint, and Thyme, are likewise employed with marked success for inhalation into the lungs by consumptive patients. Their volatile vapours reach remote parts of the diseased air-passages, and heal by destroying the morbid germs which perpetuate mischief therein. It need scarcely be said the very existence of these causative microbes, much less any mode of cure by their abolishment, was quite unknown to former Herbal Simplers. Again, in past times a large number of our native, plants acquired a well-deserved, but purely empirical celebrity, for curing scrofula and scurvy. But later discovery has shown that each of these several herbs contains lime, and earthy salts, in a subtle form of high natural sub-division: whilst, at the same time, the law of cure by medicinal similars has established the cognate fact that to those who inherit a strumous taint, infinitesimal doses of these earth salts are incontestably curative. The parents had first undergone a gradual impairment of health because of calcareous matters to excess in their general conditions of sustenance; and the lime proves potent to cure in the offspring what, through the parental surfeit, was entailed as [xvii] a heritage of disease. Just in the same way the mineral waters of Missisquoi, and Bethesda, in America, through containing siliceous qualities so sublimated as almost to defy the analyst, are effective to cure cancer, albuminuria, and other organic complaints. Nor is this by any means a new policy of cure. Its barbaric practice has long since obtained, even in African wilds, where the native snake doctor inoculates with his prepared snake poison to save the life of a victim otherwise fatally bitten by another snake of the same deadly virus. To Ovid, of Roman fame (20 B.C.), the same sanative axiom was also indisputably known as we learn from his lines:-- "Tunc observatas augur descendit in herbas; Usus et auxilio est anguis ab angue dato." "Then searched the Augur low mid grass close scanned For snake to heal a snake-envenomed hand." And with equal cogency other arguments, which are manifold, might be readily adduced, as of congruous force, to vindicate our claim in favour of analytical knowledge over blind experience in the methods of Herbal cure, especially if this be pursued on the broad lines of enlightened practice by similars.