Amygdalin is a glycoside. It consists of a molecule that combined glucose with cyanide. As discussed earlier, cancer cells must have glucose to survive. Thus, when the molecule of amygdalin enters a cancer cell, the molecule breaks apart and releases the cyanide. The cyanide then kills the cancer cell. The cyanide is not released in a healthy normally functioning cell, because a cancer cell contains a special enzyme, which must be present to release the cyanide. Thus amygdalin is harmless to a normal cell.
Another well know spice in the kitchen cinnamon is also known for it's medicinal properties. While not really an herb I still think it's important to list it in our list of herbs and their uses. Cinnamon actually comes from the inner bark of a tree in the laurel family. It's been used for centuries and was a hot commodity for trade in ancient times. In fact during the first century A.D. in Rome cinnamon was 15 times more expensive than silver. The Chinese were probably the first to use cinnamon as a medicinal herb and used it to treat fevers, and diarrhea. In more modern times cinnamon has been found to stabilize blood sugar levels in diabetics, as it has an insulin kind of effect.