condensation we have already considered the case where two conceptions
in the dream having something in common, some point of contact, are
replaced in the dream content by a mixed image, where the distinct germ
corresponds to what is common, and the indistinct secondary
modifications to what is distinctive. If displacement is added to
condensation, there is no formation of a mixed image, but a _common
mean_ which bears the same relationship to the individual elements as
does the resultant in the parallelogram of forces to its components. In
one of my dreams, for instance, there is talk of an injection with
_propyl_. On first analysis I discovered an indifferent but true
incident where _amyl_ played a part as the excitant of the dream. I
cannot yet vindicate the exchange of amyl for propyl. To the round of
ideas of the same dream, however, there belongs the recollection of my
first visit to Munich, when the _Propyloea_ struck me. The attendant
circumstances of the analysis render it admissible that the influence of
this second group of conceptions caused the displacement of amyl to
propyl. _Propyl_ is, so to say, the mean idea between _amyl_ and
_propyloea_; it got into the dream as a kind of _compromise_ by
simultaneous condensation and displacement.

The need of discovering some motive for this bewildering work of the
dream is even more called for in the case of displacement than in
condensation.

Although the work of displacement must be held mainly responsible if the
dream thoughts are not refound or recognized in the dream content
(unless the motive of the changes be guessed), it is another and milder
kind of transformation which will be considered with the dream thoughts
which leads to the discovery of a new but readily understood act of the
dream work. The first dream thoughts which are unravelled by analysis