This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
The parts to which medicines are applied, in order to affect the system, are chiefly 1. the alimentary canal, 2. the skin, 3. the bronchial tubes and pulmonary air-cells, and 4. the subcutaneous areolar tissue. When applied to other surfaces, it is generally with a view to local effect.