As set out in the Comprehensive Drug Abuse Prevention and Control Act of 1970, any of the following drugs, whether produced directly or indirectly by extraction from substances of vegetable origin, or independently by means of chemical synthesis, or by a combination of extraction and chemical synthesis: opium, coca leaves, and opiates; a compound, manufacture, salt, derivative or preparation of opium, coca leaves, or opiates; and a substance (and any compound, manufacture, salt, derivative, or preparation thereof) which is chemically identical with any of the substances referred to above. The term is very irregularly used, sometimes being any drug which dulls the senses and reduces pain, sometimes being any drug whose use is subject to special governmental control. Narcotics include heroin, morphine, demerol, and methadone. They do not, by the first definition, include marihuana, hallucinogens, amphetamines or barbiturates. The narcotics are among the most common causes of drug, dependence.