Influenza has long been recognized as a precipitating factor in the production of mental disease. Although a few authorities maintain that it may be the sole cause of certain psychoses, probably no one today believes that influenza is ever the sole cause of general paresis. It has been observed, however, that neurosyphilis has sometimes appeared clinically for the first time after attacks of influenza, and this evidence makes the influence of influenza in the etiology of neurosyphilis a legitimate point of inquiry.
Even in the pre-Wassermann days influenza was, strangely enough, not generally considered as among the possible causes of general paresis. After the epidemic of 1890 a number of instances of the precipitation of neurosyphilis by influenza were reported, and these, along with analogous cases of epilepsy, chorea, etc., were styled by Kalischer,1 Kirn2 and others, "Pseudoinfluenza psychoses." The implication was that the influenza acted merely as an incidental