Pharmacology is the study of the changes produced in living animals by chemical substances. There is a great emphasis on the mechanisms underlying the actions of drugs, and both physicians and patients acknowledge the role of drugs in modern therapy. Drug treatment is recognized as the primary modality in the prevention and alleviation of diseases. For hundreds of years most drugs were impure mixtures of only vaguely known composition, and primarily of plant and animal origin. A physician was required to know only what effects might be anticipated from a particular preparation. How the mixture produced the effects was beyond the scope of knowledge of that period. Over the past 60 years the situation has changed and today the physician should know the overt expected effects of a drug, its precise mechanism of action, its elimination routes, its side effects and its potential toxicity. Systematic investigations contributing to such...