Tonics

Tonics are medicines which, in cases of want of tone in the system, are employed to restore its strength and vigour. Tonics, to a certain degree, are stimulants; but while the latter produce a rapid but transitory excitement, the former slowly induce a certain degree of excitement, and the effect is permanent. Most tonics, in which category we must place the shower-bath, cold seabathing, open-air exercise, friction, &c., as well as drugs, act primarily through the nervous system, and secondarily produce their effects upon the system at large. It is of course of the greatest importance to ascertain to what defect in the system the loss of tone is due; whether to poorness of blood, to weakness of the heart, to defective digestion or excretion, or to enfeeblement of the nervous system generally. Otherwise the measures employed, while suitable in one of these conditions, may be very harmful if used in another. Amongst the chief medicines of this class are the dilute hydrochloric, nitric, nitro-hydrochloric, and phosphoric acids, various salts of iron, silver, and zinc, the various kinds of cinchona bark, with their alkaloids and their salts, cusparia, calumba, cascarilla, chiretta, gentian, quassia, and taraxacum, and generally most vegetable bitters. Although nux vomica and its alkaloid strychnine are placed by writers on Materia Medica amongst the 'special stimulants,' when given in very small doses they have a well-marked tonic action; and there is probably no tonic medicine of more general utility than the Syrup of Phosphates of Iron, Quinine, and Strychnine (Easton's Syrup), a non-officinal but widely-used preparation, of which every drachm (the ordinary dose) contains $\backslash frac\{3\}\{100\}$ of a grain of strychnine.