Medicines are used in the solid, liquid, and aeriform states. In the solid state, they arc employed, internally, in the several shapes of powder, electuary, conserve,,pill or bolus, and lozenge; and externally, of cataplasm, ointment, cerate, and plaster. In the liquid state they are either originally liquid, or rendered so by mixture or solution. In the aeriform state they have the form either of gas or of vapour. For ample details upon each of the Solid and liquid forms mentioned, the reader is referred to the U. S. Dispensatory. It will be sufficient, in this place, to make a few general observations, calculated to facilitate to the learner the study of the practical application of medicines which is to follow.