Image: January 17, 1939 Look magazine article from http://www.cartoonbrew.com/classic/hollywood-censors-its-animated-cartoons-1939-2775.html .
See the full magazine article at the link. It shows what animated cartoon images and sounds were acceptable and what were not. Hollywood adhered to the Motion Picture Production Code which was self-censorship adopted as an alternative to possibly more stringent federal government controls. Learn more about it at https://censorshipinfilm.wordpress.com/resources/production-code-1934/ .