Warren was involved not once but twice in the earliest history of anesthesia. The first incident was a failed demonstration of nitrous-oxide by dentist Horace Wells on January 20, 1845. Although Warren did not believe that the anesthesia would work, he arranged for a demonstration at Massachusetts General Hospital. Warren presented Wells to his students but the patient who had been scheduled that morning, for an amputation, refused to be operated on. Warren then asked his students if anybody needed a tooth extracted and one student agreed. Unfortunately the gas was not properly administered. The student suffered normal levels of pain, thus discrediting Wells and nitrous-oxide as an anesthetic.