Strychnine is a very toxic, colourless crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as rodents. Strychnine causes muscular convulsions and eventually asphyxia or sheer exhaustion. The most common source is from the seeds of the Strychnos nux-vomica tree. Strychnine is one of the most bitter substances in the world. Its taste is detectable in concentrations as low as 1 ppm.

Ten to twenty minutes after exposure, every muscle in the body will start to simultaneously contract, starting with the head and neck. The spasms then spread to every muscle in the body, with nearly continuous convulsions. They get worse at the slightest stimulus. They progress, increasing in intensity and frequency until the backbone arches continually. Death comes from asphyxiation caused by paralysis of the brain's breathing apparatus, or by exhaustion from the convulsions. At that time, the body "freezes," even in the middle of a convulsion. Rigor mortis sets in immediately, with the eyes left wide open.

Formal Chemical Name (IUPAC)

References

http://en.wikipedia.org/wiki/Strychnine