Although I profess to offer merely a few illustrations of those doctrines, whose perverted applications have influenced the history of the Materia Medica, I cannot pass over in silence that of John Brown, “the child of genius and misfortune.” As he generalized diseases, and brought all within the compass of two grand classes, those of _increased_ and _diminished_ excitement, so did he abridge our remedies, maintaining, that every agent which could operate on the human body was a _Stimulant_, having an identity of action, and differing only in the degree of its force; so that, according to his views, the lancet and the brandy bottle were but the opposite extremes of one and the same class: the mischievous tendency of such a doctrine is too obvious to require a comment. But the most absurd and preposterous hypothesis that has disgraced the annals of medicine, and bestowed medicinal reputation upon substances of no intrinsic worth, is that of the DOCTRINE OF SIGNATURES, as it has been called, which is no less than a belief that _every natural substance which possesses any medicinal virtue, indicates by an obvious and well-marked external character, the disease for which it is a remedy, or the object for which it should be employed_![47] This extraordinary monster of the fancy has been principally adopted and cherished by Paracelsus, Baptista Porta, and Crollius, although traces of its existence may be certainly discovered in very ancient authors. The root of the _Mandrake_, from its supposed resemblance to the human form, was esteemed as a remedy for Sterility: thus did Rachael demand from her sister the Mandrakes (_Dudaim_) which Reuben had gathered in the field; impressed, as it would appear, with a belief in the efficacy of that plant against barrenness.[48] There would moreover appear in this case to have been some idea of additional virtue arising from the person who gathered it, for great stress was laid upon this circumstance, “_my son’s_ Mandrakes:” such a notion is by no means uncommon in the history of charms. The supposed virtues of the _Lapis Ætites_, or _Eagle stone_,[49] described by Dioscorides, Ætius and Pliny, who assert that if tied to the arm it will prevent abortion, and if fixed to the thigh forward delivery, were, as we learn from ancient authority, solely suggested by the manner in which the nodule contained within the stone moves and rattles, whenever it is shaken. “_Ætites lapis agitatus, sonitum edit, velut ex altero lapide prægnans._” The conceit however did not assume the importance of a theory until the end of the fourteenth century, at which period we find several authors engaged in the support of its truth, and it will not be unamusing to offer a specimen of their sophistry; they affirm, that since man is the lord of the creation, all other creatures are designed for his use, and _therefore_, that their beneficial qualities and excellencies must be