I saw, moreover, that the morbid lesions which previous authors had observed to result from medicinal substances when taken into the stomach of healthy persons, either in large doses given by mistake or in order to produce death in themselves or others, or under other circumstances, accorded very much with my own observations when experimenting with the same substances on myself and other healthy individuals. These authors give details of what occurred as histories of poisoning and as proofs of the pernicious effects of these powerful substances, chiefly in order to warn others from their use; partly also for the sake of exalting their own skill, when, under the use of the remedies they employed to combat these dangerous accidents, health gradually returned; but partly also, when the persons so affected died under their treatment, in order to seek their own justification in the dangerous character of these substances, which they then termed poisons. None of these observers ever dreamed that the symptoms they recorded merely as proofs of the noxious and poisonous character of these substances were sure revelations of the power of these drugs to extinguish curatively similar symptoms occurring in natural disease, that these their pathogenetic phenomena were intimations of their homoeopathic curative action, and that the only possible way to ascertain their medicinal powers is to observe those changes of health medicines are capable of producing in the healthy organism; for the pure, peculiar powers of medicines available for the cure of disease are to be learned neither by any ingenious a priori speculations, nor by the smell, taste or appearance of the drugs, nor by their chemical analysis, nor yet by the employment of several of them at one time in a mixture (prescription) in diseases; it was never suspected that these histories of medicinal diseases would one day furnish the first rudiments of the true, pure materia medica, which from the earliest times until now has consisted solely of false conjectures and fictions of the imagination – that is to say, did not exist at all.1
1 See what I have said on this subject in the Examination of the Sources of the Ordinary Materia Medica, prefixed to the third part of my Reine Arzneimittellebre (translated in the Materia Medica Pura, vol. ii).