The practice of causing patients to inhale various volatilized substances appears to have been of very ancient date. It has been already stated in this work (p. 39) that the fumes of Orpiment were directed to be breathed by Galen, and that the practice has been adopted by practitioners of later date.[306] Few attempts of this kind however were made, until the time of our countryman Bennet, the author of “_Theatrum Tabidorum_,” who arranges volatilized substances into the two classes which have been announced at the head of the present section, _viz._ _Suffitus_, and _Halitus_. The numerous trials which have been since made with the different gases must be in the remembrance of every reader, but unfortunately, the injudicious and empirical spirit with which these inquiries have hitherto been conducted, has thrown such discredit upon the subject, that the practitioner who should resume the investigation, must be prepared to hear his understanding, or his integrity, questioned. SUFFITUS. _Fumes of Burning Substances._ The particular forms of pulmonary disease in which Tar fumes appear to be most serviceable, are of the chronic kind; where an inflammatory diathesis prevails, or any tendency to hæmopthysis exists, the practice cannot be said to be free from danger. In treatment of hooping cough the inhalation of tar fumes have been also said to be beneficial. For the mode of applying this remedy, see _Pix Liquida_. The practice of smoking the roots of _Stramonium_, _Tobacco_, &c. might with propriety be noticed under this head. With the respect to the former of these remedies, much has been said and written, and asthmatic patients have occasionally expressed a belief in its palliative powers; in my own practice however, I have never met with any success that has inspired my confidence. See _Stramonii Herba_. HALITUS. _Aqueous Vapours._ In certain catarrhal affections, when accompanied with painful and difficult expectoration, benefit may be occasionally obtained from the inhalation of the steam of hot water, or of vinegar and water, the acid in this case assisting the expectoration, while the whole acts as an emollient and soothing application to the tender and inflamed vessels of the internal surface of the bronchial tubes. The same practice is also highly serviceable in Cynanche Trachealis, and Tonsillaris. In Pneumonia, after the violence of the arterial excitement has been reduced by depletory measures, the inhalation of the steam of hot water, or decoctions of emollient herbs, will often contribute to the support of an easy expectoration. It has been already stated under the history of Expectorants (_page 106_), that in certain dry states of the air, the evaporation of water in an artificially warmed apartment, is frequently attended with considerable relief to the pulmonary patient.