Victorian readers were very familiar with hypnotism. Scottish surgeon James Braid introduced the concept of neuro-hypnotism (neural sleep) in 1841, and by the 1890s it was being used to treat the widespread disorder of hysteria. While Stoker was writing Dracula, Sigmund Freud was developing the practice of regression hypnotherapy.
At the same time, hypnosis was already in demand on the stage. Indeed James Braid took his inspiration from a "mesmerism" show.