Tobacco (Nicotiana tabacum) originates from tropical America and is now cultivated worldwide, in particular, the United States, China, Turkey, Greece, Holland, France, Germany, and most subtropical countries. There are several species of tobacco although Nicotiana tabacum is the most widely grown. The dried leaves can be used for medicinal purposes. Tobacco contains pyridine alkaloids, the chief one being nicotine. In a small dose, tobacco increases blood pressure and the activity of the gastric mucous membrance. In a large dose, it reduces blood pressure and lowers muscle tone of the gastrointestinal tract. Tobacco is a stimulant to the respiratory and central nervous system.