By posology (posos-how much) is meant the science of dosage. By doses are meant the quantities of drugs that are required to produce effects on the body whether the body is in a state of disease or normal health. In order to produce the direct effects of drugs, a definite quantity within a certain range is requisite. This can only be determined by experiment and experience, and differs according to the age, temperament and state of health of the subject. It is known as the physiological dose. This use of drugs by means of a definite physiological dosage has nothing to do with their homoeopathic use.