Strychnine is a highly toxic ( = c. 16 mg/kg in rats, 1–2 mg/kg orally in humans ), colorless crystalline alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...

 used as a pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

, particularly for killing small vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s such as bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

s. Strychnine causes muscular convulsion
A convulsion is a medical condition where body muscles contract and relax rapidly and repeatedly, resulting in an uncontrolled shaking of the body. Because a convulsion is often a symptom of an epileptic seizure, the term convulsion is sometimes used as a synonym for seizure...

s and eventually death through asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...

 or sheer exhaustion. The most common source is from the seeds of the Strychnos nux vomica
Strychnine tree
The Strychnine tree also known as Nux vomica, Poison Nut, Semen strychnos and Quaker Buttons, is a deciduous tree native to India, southeast Asia, a member of family Loganiaceae. It is a medium-size tree growing in open habitats...

Strychnine was the first alkaloid to be identified in plants of the genus Strychnos
Strychnos is a genus of flowering plants, belonging to family Loganiaceae . The genus includes about 190 species of trees and lianas, distributed around the world's tropics....

, Family Loganiaceae
Loganiaceae are a family of flowering plants classified in order Gentianales. The family includes 13 genera, distributed around the world's tropics.Earlier treatments of the family have included up to 29 genera...