For millennia, physicians' literature has addressed means of ensuring that purchased medicines are what they are claimed to be. Herbs are much more likely than cultivated vegetables to be accidentally confused: most botanicals are not highly modified in form and may closely resemble related or even unrelated species, and many are collected from the wild, where similar-looking species may also occur. Furthermore, inexpensive botanicals have sometimes been fraudulently substituted for or commingled with rare and costly botanicals. While most botanicals are correctly identified, substitution of the wrong species can cause serious harm. At worst, people have been poisoned after using a toxic species that was confused with an unrelated plant; in a relatively recent case, contamination of cultivated plantain with digitalis resulted in several reported illnesses. More commonly, the substituted plant may provide the consumer lesser benefits than the desired species, or none at all. In modern practice, every marketer of crude botanicals or manufacturer of botanical products should have explicit quality-control procedures to ensure that materials sold are correctly identified and of acceptable purity.