undergo when they are improperly combined by the ignorant practitioner, are not as some have supposed imaginary, the mere _deliramenta doctrinæ_, or the whimsical suggestions of theoretical refinement, but they are really such as to render their powers unavailing, or to impart a dangerous violence to their operation. “_Unda dabit flammas et dabit ignis aquas._” In the history of the different medicinal preparations, the pharmacopœia of the London College is the standard to which I have always referred, although it will be perceived that I have frequently availed myself of the resources with which the pharmacopœias of Edinburgh and Dublin abound. To a knowledge of the numerous adulterations to which each article is so shamefully exposed, too much importance can be scarcely attached; and under this palpable source of medicinal fallacy and failure, may be fairly included those secret and illegitimate deviations from the acknowledged modes of preparation, as laid down in the pharmacopœia, whether practised as expedients to obtain a lucrative notoriety, or from a conceit of their being improvements upon the ordinary processes; for instance, we have lately heard of a wholesale chemist who professes to supply a syrup of roses of very superior beauty, and who, for this purpose, substitutes the petals of the _red_ (rosa gallica) for those of the _damask_ rose (rosa centifolia); we need not be told, that a preparation of a more exquisite colour may be thus afforded, but allow me to ask if this _underhanded_ substitution be not a manifest act of injustice to the medical practitioner, who, instead of a laxative syrup, receives one which is marked by the opposite character of astringency. These observations will not apply, of course, to those articles which are _avowedly_ prepared by a new process; for in that case the practitioner is enabled to make his election, and either to adopt or refuse them at his discretion. Thus has Mr. Barry applied his ingenious patent apparatus for boiling _in vacuo_, to the purpose of making Extracts; we might almost say _a priori_, that the results must be more active than those obtained in the ordinary way, but they must pass the ordeal of experience before they can be admitted into practice. As a brief notice of the most notorious _Quack Medicines_ may be acceptable, the formulæ for their preparation have been appended in notes, each being placed at the foot of the particular article which constitutes its prominent ingredient; indeed it is essential that the practitioner should be acquainted with their composition, for although he would refuse to superintend the operation of a boasted _panacea_, it is but too probable that he may be called upon to counteract its baleful influence.