leads us only to consider an invisible and unknown being called _excitability_. Hence diseases peculiar to certain constitutions more than others are said to be occasioned only by certain degrees of excitability common to all, or perhaps to consist in these very degrees themselves. Thus a peculiar mode of practice has been introduced, in which almost the whole materia medica is rejected. We have already quoted Dr. Girtanner, saying that _all diseases whatever_ may be _cured_, as well as _produced_, by only _four_ articles; but in the following quotation he goes still farther. “The art of pharmacy and the science of prescription will become useless; a phial of alcohol or laudanum will supply the place of that enormous quantity of drugs which crowd the shops of apothecaries. The trade of the druggist----but hold; if I continue this prophetic language, I shall only expose myself to ridicule,” &c. Reveries of this kind certainly deserve the most severe reproof. People may no doubt amuse themselves with _theories_ as well as any thing else, while these theories continue inoffensive; but when the belief of them leads to a rejection of what has been established by the _experience_ of many ages, they begin to assume a consequence which they originally had not. We have already seen that a disbelief of the doctrine of contagion leads people into a practice accounted dangerous by many, and which cannot be proved to be safe. A total rejection of medicines, the efficacy of which have been attested by thousands, and which never can be proved to have _no_ efficacy, must be attended with still worse consequences, as thus we should be deprived of the means of curing those diseases which our imprudence in rejecting the former doctrine might have brought on. But, to return to the subject of the plague.