Medicines which are supposed to be capable of facilitating the excretion of mucus from the breast, _ex pectore_, that is, from the trachea, and cells and passages of the lungs. If the term _Expectorant_ be intended to express a medicinal substance which has the power of promoting the expulsion of fluid from the lungs, by some _specific action_ on the parts concerned, we can have no hesitation in at once rejecting the word, and denying the existence of such remedies: if, however the term be received, conventionally, as comprehending all those substances which are capable, according to the state of the system in each particular case, of producing expectoration, it will be extremely proper to recognise, and practically useful to retain, such a class of medicinal agents. In order that their _modus operandi_ may be correctly understood, the following classification is submitted to the reader. * * * * * A CLASSIFICATION OF EXPECTORANTS, According to their supposed Modes of Operation. CL: I—MEDICINES WHICH INCREASE PULMONARY EXHALATION, AND THEREBY DILUTE THE MUCUS IN THE FOLLICLES OF THE LUNGS. _a._ By removing constriction of the Pulmonary Exhalant vessels. _Blisters._ _Venesection._ _Nauseants._ _b._ By stimulating these vessels by the _actual contact_ of a medicinal substance. _Allium._ _Scilla?_ _The different Balsams._ _fœtid Gums._ _c._ By stimulating the top of the trachea, and thereby increasing the action of the exhalant vessels of the lungs, by a species of _Contiguous Sympathy_. _Stimulating Lozenges_, _Linctusses_, _The Inhalation of certain vapours_, _&c._ CL: II.—MEDICINES WHICH DIMINISH THE INORDINATE FLOW OF FLUID INTO THE LUNGS, AND RENDER THE EXPECTORATION OF THE REMAINDER MORE EASY. _a._ By removing the debility of the Exhalants. _Sulphate of Zinc._ _Bitter Tonics._ _b._ By increasing the power of the Absorbents. _Digitalis._ _Nicotiana._ _c._ By determining to the skin by gentle diaphoresis. _Tartarized Antimony._ _d._ By exciting serous discharges from the bowels. _Saline Purgatives._ CL: III.—MEDICINES WHICH OPERATE, MECHANICALLY, IN PROMOTING THE REJECTION OF ACCUMULATED MUCUS. _a._ By stimulating the muscles of Respiration. _Ammonia._ _b._ By exciting vomiting, and thereby compressing the thoracic viscera. _Emetics._ I. OF MEDICINES WHICH INCREASE PULMONARY EXHALATION. _a._ _By removing constriction of the Pulmonary Exhalant vessels._