Many people think of the word “drug” as meaning a habit-forming sum stance that is taken to relieve pain or to produce sleep. Actually, a drug is any substance or mixture of substances used as a medicine.

The mixing of such substances, the art of healing with “drugs,” is a very ancient one. In fact, the first step forward in the treatment of diseases came about through the knowledge that priests and teachers had of plant products and their healing power. The ancient Greeks used plant products as drugs thousands of years ago.