Several actors are in studio records/casting call lists as cast members, but do not appear in the movie. These are (with their character names): Boris Karloff (autopsy surgeon), Claire Dodd (Mrs. Beverly) and Reginald Barlow (professor of the university). Karloff was replaced by Nigel De Brulier when he was not available for retakes and the British censors objected to the gruesomeness of his scenes.