The document discusses various preanaesthetic agents used to prepare animals for anesthesia. It describes different classes of preanaesthetics including anticholinergics, tranquilizers, sedatives, and alpha-2 agonists. It provides examples of specific drugs from each class and discusses their mechanisms of action, effects, dosages, and cautions. The purpose of preanaesthetics is to sedate the animal, reduce stress, and facilitate safe and effective induction and recovery from anesthesia.