I began to guess why the formula for trimethylamin had been so prominent in the dream. So many important subjects converged upon that one word. Trimethylamin was an allusion not only to the immensely powerful factor of sexuality, but also to a person whose agreement I recalled with satisfaction whenever I felt isolated in my opinions. Surely this friend who played so large a part in my life must appear again elsewhere in these trains of thought. (2.1.40)
The unnamed friend Freud mentions here is Wilhelm Fliess. James Strachey notes that Fliess "exercised a great influence on Freud during the years immediately preceding the publication of this book," and "figures frequently, though as a rule anonymously, in its pages" (source).
Chapter 6, Section A
In my embarrassment I sought help from the physician whom I, like many other people, respect more than any as a man and before whose authority I am readiest to bow. (6.2.56)
In Sigmund Freud's Dreams, Alexander Grinstein identifies this friend as Josef Breuer, a senior colleague of Freud's and the man with whom Freud collaborated on his first published book, Studies on Hysteria (source). As Grinstein also notes, by the time Freud dreamed his Dream of Irma's Injection (to which this passage refers), relations between Freud and Breuer had started to turn sour (source).
The first reader and critic of this book—and his successors are likely to follow his example—protested that "the dreamer seems to be too ingenious and amusing." This is quite true so long as it refers only to the dreamer; it would only be an objection if it were to be extended to the dream-interpreter. (6.2.51)
As editor James Strachey notes, the "first reader" that Freud speaks of here is his good friend Wilhelm Fliess. As this passage suggests, not only does Fliess appear frequently in Freud's dreams, but his influence can also be felt in the ways that Freud frames his arguments.
Chapter 6, Section B
On the one hand we see the group of ideas attached to my friend Otto, who did not understand me, who sided against me, and who made me a present of liqueur with an aroma of amyl. On the other hand we see—linked to the former group by its very contrast—the group of ideas attached to my friend in Berlin, who did understand me, who would take my side, and to whom I owed so much valuable information, dealing, amongst other things, with the chemistry of the sexual process. (6.2.44)
Here again, Freud's "friend in Berlin" is Wilhelm Fliess. Fliess is mentioned throughout The Interpretation of Dreams as a trusted friend and adviser, and he often appears in Freud's dreams. Sometimes those appearances are explicit, and sometimes his presence is felt in obscure ways that only become clear when Freud gets on with his interpretations.
Chapter 6, Section F
I once acted in the scene between Brutus and Caesar from Schiller before an audience of children. I was fourteen years old at the time and was acting with a nephew who was a year my senior. He had come to us on a visit from England; and he, too, was a revenant, for it was the playmate of my earliest years who had returned in him. Until the end of my third year we had been inseparable. We had loved each other and fought with each other; and this childhood relationship, as I have already hinted above, had a determining influence on all my subsequent relations with contemporaries. (6.7.55)
Having realized that he has unconsciously represented himself as Shakespeare's Brutus in his Non Vixit Dream, Freud realizes that the "P." who appears in the dream is not only his junior colleague Joseph Paneth, but also a representation of a beloved childhood playmate—his nephew John.
It then struck me as noticeable that in the scene in the dream there was a convergence of a hostile and an affectionate current of feeling towards my friend P., the former being on the surface and the latter concealed, but both of them being represented in the single phrase Non vixit. As he had deserved well of science I built him a memorial; but as he was guilty of an evil wish (which was expressed at the end of the dream) I annihilated him. (6.7.54)
During his interpretation of this dream, Freud asks himself why he has phrased things as he has here. Focusing on two of the lines that he has written—"As he had deserved well of science I built him a memorial; but as he was guilty of an evil wish I annihilated him"—Freud realizes that he has unconsciously echoed lines from Shakespeare's Julius Caesar: "As Caesar loved me, I weep for him; as he was fortunate, I rejoice at it; as he was valiant, I honour him; but, as he was ambitious, I slew him" (6.7.54).
Chapter 6, Section H
I have already shown how my warm friendships as well as my enmities with contemporaries went back to my relations in childhood with a nephew who was a year my senior; how he was my superior, how I early learned to defend myself against him, how we were inseparable friends, and how, according to the testimony of our elders, we sometimes fought with each other […]. All my friends have in a certain sense been re-incarnations of this first figure who "früh sich einst dem trüben Blick gezeight": they have been revenants. (6.9.50)
As editor James Strachey notes, the passage in German that Freud quotes here is from the Dedication to Goethe's Faust (source). If we weave Strachey's translation into Freud's sentence, we get this: "All my friends have in a certain sense been re-incarnations of this first figure who 'long since appeared before my troubled gaze'" (source). What do you make of that, Shmoopers? Is Freud suggesting that the lifelong repetition of this pattern is a good thing or a bad thing?
Otto had in fact told me that during his short stay with Irma's family he had been called in to a neighbouring hotel to give an injection to someone who had suddenly felt unwell. These injections reminded me once more of my unfortunate friend who had poisoned himself with cocaine. I had advised him to use the drug internally [i.e., orally] only, while morphia was being withdrawn; but he had at once given himself cocaine injections. (P.1.23)
The medical use of cocaine was very new in the Europe of Freud's day, and Freud himself had done some of the exploratory research that led to its use as a painkiller. But with so little known about the drug, tragedies were bound to happen. The friend Freud's talking about is Ernst Fleischl von Marxow. As Alexander Grinstein notes in Sigmund Freud's Dreams, Fleischl was Freud's senior colleague at the Physiological Institute where he trained—a young man "whom Freud took as a model and almost worshipped" (source).
In another stratum of my thoughts, during the ceremonial unveiling of the memorial, I had reflected thus: "What a number of valued friends I have lost, some through death, some through a breach of our friendship! How fortunate that I have found a substitute for them and that I have gained one who means more to me than ever the others could, and that, at a time of life when new friendships cannot easily be formed, I shall never lose his!" (6.9.55)
Unfortunately, Freud did lose the friendship of Wilhelm Fliess, the man he is alluding to here. As the editors of the Oxford World's Classics edition of The Interpretation of Dreams explain, by 1902, just a few years after the first edition of the book was published, Freud and Fliess's once intense friendship had "cooled" (source).