I found via TYWKIWDBI. This is a clip from a 1924 movie about the story of Siegfried, who slew a dragon and "[f]rom bathing in the dragon's blood, he is invulnerable except for a spot on his back where a leaf adhered to his skin" (Wikipedia). He then goes on to have many other adventures.
The interesting part is how well-articulated the dragon is, particularly for this era of film-making. The movie is by Fritz Lang, who also made one of my favorite movies, "M."