Suicide gland
The suicide gland was a gland unique to the Xindi-Reptilians, who used it to commit suicide in the event they were captured. This gland, when activated, released a neurotoxin into the bloodstream, resulting in death.The gland did not occur naturally in the Xindi-Reptilians; rather, they were a surgical "enhancement". 

In 2153, the last member of a Xindi-Reptilian boarding party left aboard  activated his suicide gland rather than be captured alive. Upon learning of the gland,  questioned, "What kind of species is born with a suicide gland?" ()

See also 
 Neuro-depolarizing device
 Termination implant

nl:Zelfmoordklier
Glands
Death