a poisonous alkaloid that is obtained from seeds of the nux vomica tree (S. nux-vomica) and related plants of the genus Strychnos. It was discovered by the French chemists Joseph-Bienaimé Caventou and Pierre-Joseph Pelletier (Pelletier, Pierre-Joseph) in 1818 in Saint-Ignatius'-beans (S. ignatii), a woody vine of the Philippines. The nux vomica tree of India is the chief commercial source. Strychnine has a molecular formula of C₂₁H₂₂N₂O₂. It is practically insoluble in water and is soluble only with difficulty in alcohol and other common organic solvents. It has an exceptionally bitter taste.

Strychnine has been used in rodent poisons and in smaller doses as a stimulant in veterinary practice. It increases the reflex irritability of the spinal cord, which results in a loss of normal inhibition of the body's motor cells, causing severe contractions of the muscles; arching of the back is a common symptom of poisoning. Strychnine rapidly enters the blood, whether taken orally or by injection, and symptoms of poisoning usually appear within 20 minutes. The symptoms begin with cramps and soon culminate in powerful and agonizing convulsions that subside after a minute but recur at a touch, a noise, or some other minor stimulus. Death is usually due to asphyxiation resulting from continuous spasms of the respiratory muscles.