In this letter, Huxley answers a request for information about the clinical availability of hallucinogenic drugs for experimentation. The drugs include mescaline, LSD-25, and psilocybin, and the letters lists the pharmaceutical companies that were producing them at the time. The letter closes with a note about his own experimentation: "My own acquaintance with mescaline and LSD-25 has been mediated by research workers here and at Harvard." (Description provided by Bromer Booksellers.)