In 1922, Hirt obtained his doctorate in medicine with "Der Grenzstrang des Sympathicus bei einigen Sauriern" (English: The Ganglions in the Sympathetic Nervous System of Some Dinosaurs). He then worked at the Anatomical Institute in Heidelberg and in 1925 he was authorized to teach thanks to a thesis on nerve cells. In 1930 he became professor at Heidelberg University.