Strychnine is a poisonous substance which is naturally produced by the plant "Strychnos nux-vomica". Together with brucine, another poison, strychnine is found in the leaves and seeds of this plant. They are a rather extreme example of the way some plants protect themselves against herbivores. The substances were discovered early in the 19th century, but it took about 150 years before Robert Robinson worked out their structure.