[Homage to Kraepelin, honouring his 150th birthday--"Zerfahrenheit", Kraepelin's specific symptom for schizophrenia]

Kraepelin described but one single specific sign for all forms of dementia praecox (later: schizophrenia) and coined a new word for it, "Zerfahrenheit" (various translations: distraction, dilapidation, incoherence, among others). What he meant by it, clearly results from Kraepelin's description even now. The origin of the idea could been found in German philosophy of the times of enlightenment, when it had been described already in a distinct way. That time coined the word "Verrücktheit" for it (usual translation: mental derangement; better translations would be the same as for "Zerfahrenheit"). Because of the influence of French psychiatry with its quite different background and the hurly burly about paranoia (Heinroth's Greek translation for "Verrücktheit") the knowledge of the sign got lost. Kraepelin restored the original meaning, without referring however to the sources directly. In spite of having been acknowledged as a specific sign for dementia praecox by all German psychiatrists, only one decade after the first description a new process of unclearing recommenced. This bow curved from Eugen Bleuler via Kurt Schneider and others to DSM III/IV and ICD-10. In the current paper we follow Kraepelin's process of clearing via all 9 editions of his textbook of psychiatry. Since the German original of Kraepelin's first extended description currently can be found only in larger libraries, the integral text of it is being reprinted (in English a recent translation by Jacques M. Quen is available). No corrections or changes are necessary. Kraepelin's 150th birthday is the best occasion for reminding of what remains unique in the clinical unity of schizophrenia, which for ever is linked to his name. It still is a solid sign for schizophrenia, for all its various forms.