Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
Fritz Lang made several films about Dr. Mabuse, the evil criminal mastermind who has the power to control other people's minds. In this one, Mabuse is in his laboratory where we see two terrariums with snakes in them. He pulls one out grabbing it by the neck with small tongs, and hands it to an assistant who grabs it by the neck. The snake looks like a harmless snake with a non-viper-like head. Then we see a close-up of what is probably the hands of two snake wranglers and a different snake, some kind of a viper, with fangs that are milked of their venom into a glass bowl. Then Mabuse puts the snake back in the terrarium. We never see what he does with the venom, but later some poison is given to a woman who is coerced to take it, and we can deduce that it was made with the snake venom.