Plants have been used as medicinals since time immemorial. Man must have soon realized that the beneficial effects of the plants concerned were dose related. If one consumed too much of a medicinal herb at any one time the "cure" might be worse than the original malady, even resulting in death. The deliberate use of plants as ritual poisons is well documented by the ancient Greeks and the deleterious effects of certain plants, even when eaten in very small quantities, to both man and animals well known. Many oxygenated sesqui-and diterpenes are as toxic as the steroidal alkaloids. Fortunately these compounds appear to be rather rarely found in plants in sufficient quantity to cause dire effects on man or livestock. The glucosinolates are a group of sulfur-containing glycosides which also yield toxic constituents on hydrolysis. These are the mustard oils or isothiocyanates, which if ingested in quantity, are toxic to animals.