Suicide gland
From Memory Alpha, the free Star Trek reference.
The suicide gland is a gland unique to the Xindi-Reptilians, who use it to commit suicide in the event they are captured. This gland, when activated, releases a neurotoxin into the bloodstream, resulting in death. However, the gland did not come naturally to the Xindi-Reptillians, but was rather the result of genetic engineering. (ENT: "Rajiin")
