Tropolisine was a psychotropic compound known for its hallucinogenic effects. Normally found in certain flowering plants, each tropolisine atom contained a stray neutron. Once it started to break down in a humanoid's bloodstream it released an undetectable toxin. By the early 23rd century, a permanent cure for the hallucinogenic effects of tropolisine had been found, allowing Humans to settle the planet. ("In a Mirror, Darkly, Part II" , personnel file)