Cannabis and the psychoactive riddle -- Cannabis and the colonial milieu -- The discovery of marijuana in Mexico -- The place of marijuana in Mexico, 1846-1920 -- Explaining the missing counterdiscourse I: the science of drugs and madness -- Explaining the missing counterdiscourse II: people, environments, and degeneration -- Did marijuana really cause "madness" and violence in Mexico? -- National legislation and the birth of Mexico's war on drugs -- Postscript: Mexican ideas move North.