An inquiry of the kind is, from the analytical point of view, tedious and often difficult; for though the analytical chemist can easily and quickly identify the nature of inorganic salts in a mixture or powder, and estimate their amount, most vegetable drugs which exert any appreciable effect on the body owe their power to the presence of an alkaloid or glucoside. The active principle of opium, for instance, is morphine; that of cinchona bark, quinine; that of belladonna, atropine, and so on, and the chemist can recognise any alkaloids present in a mixture or pill. It is otherwise, however, with vegetable extracts and colouring matters, for which pharmaceutical science has not yet been able in all cases to supply easily applicable and conclusive tests, because for the most part they contain no active principle and are used in pharmacy for their agreeable odour or bitter taste, as vanilla or sorrel are used in cookery. Of the accuracy of the analytical data published there can be no question; the investigation has been carried out with great care by a skilled analytical chemist, who has controlled his results in various ways, one being that in every doubtful case the formula obtained by analysis has been tested by making it up and comparing the appearance, taste, and physical properties of the imitative mixture with those of the secret preparation sold to the public. The articles in this volume have not been confined to a mere dry statement of the results of analysis. Care has been taken to reproduce the claims and exuberant boasts of the vendors, and the contrast between them and the list of banal ingredients which follow must strike every reader. This juxtaposition of analytical facts and advertising fancies is instructive and sometimes entertaining, the fancy is so free and the fact so simple. It must not be assumed that the concoctors of these mixtures and powders and ointments show any particular skill in the compounding of drugs. On the contrary, they appear curiously indifferent to taste and appearance, and perhaps count on the belief, common among the poorer classes at least, that the nastier a drug the more effective it is. There is, at any rate, the excuse for this belief that the effort to subdue the repugnance to the draught produces a glow of virtue which may perhaps have a certain stimulating effect on the mind; the patient having not only spent his money but suffered some discomfort, is anxious to justify his faith by assuming himself to be the better for the double sacrifice.