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ELEMENTS OF MATERIA MEDICA.

masticatories might be resorted to, but we And that acrids of variouskinds have always been preferred. Masticatories, as therapeutic agents,have been principally used either as topical applications, in affections ofthe gums, tongue, tonsils, salivary glands, &c., or as counter-irritants incomplaints of neighbouring organs, as in ear-ache, rheumatism of thepericranium, affections of the nose, &c. The stronger masticatories, asmustard and horse-radish, excite an increased discharge of nasal mucusand tears, as well as of saliva and mucus of the mouth.

ft. Remote sialogogues. —Several substances have had the reputation ofp oducing salivation or ptyalism by internal use. Of these, the pre-parations of mercury are the only ones on which much reliance can beplaced, and even they sometimes disappoint us. The preparations ofgold, of antimony, and of iodine, occasionally have this effect. Thecontinued use of the hydrocyanic or nitric acid has, in several instances,produced salivation. In poisoning by foxglove this has been observed.Lastly, nauseants increase the secretion of saliva.

Mercurials are given in certain diseases to excite ptyalism, and in somecases it is necessary to keep up this effect for several weeks. It is notsupposed that the salivation is the cause of the benefit derived, but it isproduced in order that we may be satisfied that the constitution is suffi-ciently influenced by the medicine.

4. Expectorants {expectorantia) are agents which promote the expul-sion of mucus and other secreted or exhaled fluids from the bronchia,trachea, and larynx In the healthy state, the liquids secreted ot exhaledby the aerian membrane are got rid of by evaporation and absorption.But when from any circumstance the balance between the two processesof production and removal is destroyed, and an accumulation of mucustakes place, nature endeavours to get rid of it by coughing. Hence somehave applied the term expectorant to irritating substances (as chlorinegas, the vapour of acetic or of benzoic acid, &c.), which, when inhaled,produce coughing. “We provoke cough,” says Schwilgub {Traiti deMatiere Medicate, tom. ii. p. 296), “ to favour the expulsion of foreignbodies introduced from without into the aerian tube, and especially ofliquids; we have recourse to it to favour the expectoration of mucus,of mucosities, of membranil'orm concretions, and of pus, which haveaccumulated in the aerian passages, whenever the local irritation is notsufficiently great.”

It has been thought by some that the mucus secreted may be tootough and viscid to admit of its being easily brought up by coughing, andthe term expectorant has been applied to those medicines which havebeen supposed to render it thinner and less viscid. But as Mr. Moore{An Essay on the Materia Medica, 1792) has justly observed, thickphlegm is sometimes more easily expectorated than thin: and if thiswere not the case, we have no specific means of rendering the phlegmeither thicker or thinner. Frequently the tenn expectorant is applied tosubstances supposed to increase or promote the secretion of bronchialmucus, and in pharmacological works a long list of medicines, thought tohave this effect, is usually given. Most of the agents employed with thisview act relatively,—that is, they obviate the causes which checked thehealthy secretion. Some are topical agents, as various gases andvapours. There are others, however, which, when taken internally, aresupposed to affect the aerian membrane in a specific manner, and are