Feind im Blut (English: Enemy in the Blood) is a 1931 Swiss-German drama film directed by Walter Ruttmann.
The film was co-produced with several organisations focused on combatting sexually transmitted infections.
His wife gives birth to a child infected with the disease and commits suicide.
The film was made to inform and warn the public about syphilis.
It was produced by Praesens-Film [de] in collaboration with the Swiss Society to Combat Sexually Transmitted Diseases, the German Association for the Fight Against Sexually Transmitted Diseases and the Main Health Department of the City of Berlin.