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.
Nigel de Brulier, who replaced Boris Karloff, gives a suitably ghoulish performance as the 'banshee' like autopsy doctor that hovers about. How Karloff might have brought his calculated, macabre character mannerisms to the role is left to the imagination.
Technical advisor Dr. Harry Martin was married to Hollywood gossip columnist Louella Parsons at the time of this film.
The medical techniques shown are remarkably accurate. Although medical science has advanced considerably, the basics remain the same: scrubbing up, sterilizing instruments, surgical scrubs, anesthesia equipment. A Dr. Harry Martin is listed as the film's medical advisor---and he did a good job.
Lotti states that she will go to her beloved, even (presumably) without marrying him. Her mother is suitably aghast. Although it is never explicitly stated, Lotti planned to live with Karl out of wedlock. A very risque topic, but it slipped past the censors somehow.