Conversation so far:
Who is Sigmund Freud's friend Wilhelm Fliess?
During this formative period of his work, Sigmund Freud valued on the intellectual and emotional support of his friend Wilhelm Fliess, a Berlin-based ear, nose and throat specialist.
What was Sigmund Freud and Wilhelm Fliess' relationship?
Sigmund Freud and Wilhelm Fliess saw themselves as isolated from the prevailing clinical and theoretical mainstream because of their ambitions to develop radical new theories of sexuality.
Did Sigmund Freud and Wilhelm Fliess collaborate?
They maintained an extensive correspondence from which Sigmund Freud drew on Wilhelm Fliess's speculations on infantile sexuality and bisexuality to elaborate and revise his own ideas.

Question: How else did Fliess influence him?
Self-contained rewrite: How else did Wilhelm Fliess influence Sigmund Freud besides maintaining an extensive correspondence?