Monsieur, you must let me take a specimen of this woman's blood.
5 seconds sound clip from the Murders in the Rue Morgue (1932) movie soundboard.
You can hear this line at 00:24:18.508 in the Blu-ray version of the movie.
Quote context
[...]
- Monsieur, would you be good enough to show them to me once more?
- If you wish, Monsieur Dupin, I will show you three.
- Three?
- You mean, there's been another one?
- Yes.
- Yes.
- Marks?
- See them? They're on the others, too.
- Monsieur, you must let me take a specimen of this woman's blood.
- It's against all regulations.
- Tomorrow night, huh? Good night, monsieur.
[...]