I am a fan of Herzog so I'll cut to the chase---- There is a scene in the film where a cat is thrown out of a second story window--- right into the arms of Kinski--- after he catches the cat I believe he becomes hypnotized. Kinski starts to shake and convulse (granted he is an excellent actor) but the fact that Herzog is always dealing with hypnotizing people and chickens (Heart of Glass, Even Dwarfs Started Small) i believe that he knew something about Kinski and his love for animals--- or maybe his hate for animals--- in any case he has strong feelings attached to these innocent creatures--- and I believe that Herzog exploits this to hypnotize Kinski.
When I watched it (again) I did so without the subtitles, I wanted to concentrate on the imagery and the shots. I came to realize how much Herzog's movies are like theater. The sets are made and there is usually just one shot in a scene and from a direction that makes me feel like part of a theater audience--- granted some of these sets are on a location where there is little that needs to be done to get the imagery across.
It also contains one of the best death scenes in film history.