What could be the reason for this sloping wall?

Once again, I know Fluther jellies would come out with the answer to this. Because Fluther jellies are awesome. Everyone knows that.

My friend and I are puzzled why this wall, in a scene from a classic Frankenstein movie, was made to slope from the window.

Was it for engineering reasons or artistic expression-? Could it be historically, there were real prison chambers like this one where people could throw something at a prisoner-?

Thanks jellies-!

Ok, I was hoping when you click on the link, it will show you that particular photo right away. But sadly, no. It is the 3rd pic from the right….3rd line from below. Please click to enlarge that picture where Frankenstein is strapped to a chair.

http://www.filmweb.pl/film/Narzeczona+Frankensteina-1935-97229/photos/313945