From ‘Beiträge über die Anwendung des Cocaïn,’ Weiner Medizinische Wochenschrift, 28, pp. 929–932, July 1887

All reports of addiction to cocaine and deterioration resulting from it refer to morphine addicts, persons who, already in the grip of one demon are so weak in will power, so susceptible, that they would misuse, and indeed have misused, any stimulant held out to them. Cocaine has claimed no other, no victim on its own. I have had broad experience with the regular use of cocaine over long periods of time by persons who were not morphine addicts, and have taken the drug myself for some months without perceiving or experiencing any condition similar to morphinism or any desire for continued use of cocaine. On the contrary, there occurred more frequently than I should have liked, an aversion to the drug, which was sufficient cause for curtailing its use.

To Wilhelm Fliess, from Vienna, 24 November 1887

Esteemed friend and colleague:

My letter of today admittedly is occasioned by business; but I must introduce it by confessing that I enterain hopes of continuing the relationship with you and that you have left a deep impression on me which could easily lead me to tell you outright in what category of men I place you.

To Wilhelm Fliess, from Vienna, 28 December 1887

Your cordial letter and your magnificent gift awakened the most pleasant memories for me, and the sentiment I discern behind both Christmas presents fills me with the expectation of a lively and mutually gratifying relationship between us in the future. I still do not know how I won you; the bit of speculative anatomy of the brain cannot have impressed your rigorous judgment for long. But I am very happy about it.