Opium and chloral belong to this class of medicines.

The danger is that, after a person has used the medicine a little while, he will continue to use it.

If a person takes a poisonous drug every time he has a little pain, he will soon form the habit of using it, and may never break it off.

There are many thousands of people who use opium all the time, and they are very much injured by it in mind and body.

The mind becomes dull and stupid and the body weak and feeble.