302 THE ANIMALS AND MAN 



In small amounts, then, alcohol may be considered as a 

 kind of food but should be administered, like other medicines, 

 under a physician's order. In large amounts it is recognized 

 as a poison and dangerous. The direct action of alcohol 

 upon certain organs will be considered later. 



Narcotics. — Narcotics are substances which blunt the 

 sensibilities and induce sleep. Tobacco, alcohol (in large 

 quantities), opium, morphine and cocaine, are the most 

 common. All narcotics are deadly poison when taken in 

 large quantities. Some of them, like tobacco and alcohol 

 may stimulate in small doses and narcotize in large doses. 



Tobacco, like alcohol, affects the nervous system. It 

 leads to weakness of the heart and irregular pulse by inter- 

 fering with nerve regulation. The poisonous ingredient 

 of tobacco is nicotine. It is this that makes boys sick and 

 sleepy when they first begin to use tobacco. The constant 

 use of tobacco impairs the digestion through its action on 

 the salivary secretions. It produces hoarseness and catarrh 

 through irritation of the mucous lining of the mouth. 



