Tobacco

For centuries the leaves of the tobacco plant have been used for making smoking tobacco and chewing tobacco. Tobacco contains small amounts of nicotine, a stimulant that acts on the heart and other organs and the nervous system when tobacco is inhaled, ingested, or absorbed. Nicotine's effect on the nervous system causes people to become addicted to it, and the stimulating effects make smoking and chewing tobacco pleasurable. Concentrated amounts of nicotine are poisonous, however. Although the use of tobacco was condemned on occasion in the past, not until the latter half of the twentieth century were concerted efforts made to curb tobacco use in the United States.