PHARMACOLOGY is that science which treats of medicines.
Materia Medica is that branch of Pharmacology concerned with the origin and composition of drugs, together with their physical and chemical properties, and their dosage. Some brief reference to their therapeutic application is advisedly included.
Pharmacopaedics is that branch of Pharmacology concerned with "the science of medicinal drugs and the art of their preparation." It is quite distinct from Pharmacy, which includes the collection, preservation, identification, compounding, and dispensing of drugs. Pharmacopaedics deals with the various forms under which medicines are dispensed, together with their relative strengths, ingredients of compounds, relative availability and desirability. It is of much importance to the physician that he know the nature of the powerful tools he will later be called upon to use.
Pharmacodynamics is that branch of Pharmacology concerned with the manner in, and degree to which, living tissue reacts to drugs.