At first, I experimented only with dead animals and then a human heart, which I kept beating for three weeks.

10 seconds sound clip from the Frankenstein (1931) movie soundboard.

You can hear this line at 00:21:48 in the Blu-ray version of the movie.

Quote context

[...]

- Dr. Waldman, I learned a great deal from you at the university about the violet ray, the ultraviolet ray, which you said was the highest color in the spectrum. You were wrong.

- Here in this machinery, I have gone beyond that.

- I have discovered the great ray that first brought life into the world.

- Oh. And your proof?

- Tonight you shall have your proof.

- At first, I experimented only with dead animals and then a human heart, which I kept beating for three weeks.

- But now, I'm going to turn that ray on that body and endow it with life.

- And you really believe that you can bring life to the dead?

- That body is not dead. It has never lived.

- I created it. I made it with my own hands from the bodies I took from graves, from the gallows, anywhere!

[...]