Wilhelm Fliess

Wilhelm Fliess (German: Wilhelm Fließ; 24 October 1858 – 13 October 1928) was a German Jewish otolaryngologist who practised in Berlin. On Josef Breuer's suggestion, Fliess attended several "conferences" with Sigmund Freud beginning in 1887 in Vienna, and the two soon formed a strong friendship. Through their extensive correspondence and the series of personal meetings, Fliess came to play an important part in the development of psychoanalysis.

Fliess developed several idiosyncratic theories, such as reflex nasal neuroses, postulating a connection between the nose and the genitals, and vital periodicity, forerunner of the popular concepts of biorhythms that never found scientific favor, though others, such as the idea of innate bisexuality, were incorporated into Freud's theories. Fliess believed men and women went through mathematically fixed sexual cycles of 23 and 28 days, respectively. Freud referred occasional patients to him for treatment of their neurosis through anaesthetization of the nasal mucosa with cocaine, and through nasal surgery. Together, Fliess and Freud developed a Project for a Scientific Psychology, which was later abandoned. Fliess was also an author and wrote Der Ablauf Des Lebens a book about his biorythmic theories.

Emma Eckstein (1865–1924) had a particularly disastrous experience when Freud referred the then 27-year-old patient to Fliess for surgery to remove the turbinate bone from her nose, ostensibly to cure her of premenstrual depression. Eckstein haemorrhaged profusely in the weeks following the procedure, almost to the point of death as infection set in. Freud consulted with another surgeon, who removed a piece of surgical gauze that Fliess had left behind. Eckstein was left permanently disfigured, with the left side of her face caved in. Despite this, she remained on very good terms with Freud for many years, becoming a psychoanalyst herself.

Fliess also remained close friends with Freud. He even predicted Freud's death would be around the age of 51, through one of his complicated bio-numerological theories ("critical period calculations"). Their friendship, however, did not last to see that prediction out: in 1904 their friendship disintegrated due to Fliess's belief that Freud had given details of a periodicity theory Fliess was developing to a plagiarist. Freud died at 83 years of age.

Freud ordered that his correspondence with Fliess be destroyed. It is only known today because Marie Bonaparte purchased Freud's letters to Fliess and refused to permit their destruction.

Fliess's son Robert (1895–1970) was also a psychoanalyst and a prolific writer in that field. He devised the phrase ambulatory psychosis. Jeffrey Masson claimed that Fliess sexually molested his son Robert and that this caused Fliess to undermine Freud's investigation of the seduction theory because of its implications for his life Though Fliess' ideas are often ridiculed today, modern science has in fact revealed that the nose has more than one connection with sexual behaviour and the genitals. The nose is now known to contain erectile tissue, and this may also become engorged during sexual arousal as a side-effect of the signals fired off by the autonomic nervous system to trigger changes in the genitals of both men and women. A condition exists known as honeymoon rhinitis, in which men and women experience nasal stuffiness during sex, and a small number of people are known to sneeze, sometimes uncontrollably, when engaging in or even thinking about sexual activity. The existence of evolutionary relics within the autonomic nervous system has been hypothesised as a cause. Even more remarkably, a study on mice has suggested that the difference between male and female sexual behaviour may be explained by a tiny organ in the nose rather than gender-specific brain circuitry.

He appears as a character in Joseph Skibell's 2010 novel, A Curable Romantic.