translation.en: Mood modifiers have been used from time immemorial -- caffeine, alcohol, nicotine, immune system enhancement, vision enhancement, anesthetics -- we take that very much for granted, but just think about how great progress that is -- like, having an operation before anesthetics was not fun.
translation.zh: 自古以来，情绪改善剂就一直为人们所使用—— 咖啡因、酒精、尼古丁、免疫系统增强剂、 视力增强品、麻醉剂。 我们通常认为这些是理所当然的，没什么稀奇， 但想想看这是多么伟大的进步—— 比如，不实施麻醉而进行手术可不是好玩的。