toms from the source of masochistic tendencies. The perfect
concurrence with the behavior of the corresponding positive perversions
is certainly very noteworthy. In the picture of the disease, however,
the preponderant role is played by either one or the other of the
opposing tendencies.

Gamma. In a pronounced case of psychoneurosis we seldom find the
development of one single perverted impulse; usually there are many and
regularly there are traces of all perversions. The individual impulse,
however, on account of its intensity, is independent of the development
of the others, but the study of the positive perversions gives us the
accurate counterpart to it.

PARTIAL IMPULSES AND EROGENOUS ZONES

Keeping in mind what we have learned from the examination of the
positive and negative perversions, it becomes quite obvious that they
can be referred to a number of "partial impulses," which are not,
however, primary but are subject to further analysis. By an "impulse" we
can understand in the first place nothing but the psychic representative
of a continually flowing internal somatic source of excitement, in
contradistinction to the "stimulus" which is produced by isolated
excitements coming from without. The impulse is thus one of the concepts
marking the limits between the psychic and the physical. The simplest
and most obvious assumption concerning the nature of the impulses would
be that in themselves they possess no quality but are only taken into
account as a measure of the demand for effort in the psychic life. What
distinguishes the impulses from one another and furnishes them with
specific attributes is their relation to their somatic _sources_ and to
their _aims_. The source of the impulse is an exciting process in an
organ, and the immediate aim of the impulse lies in the elimination of
this organic stimulus.

Another preliminary assumption in the theory of the impulse which we
cannot relinquish, states that the bodily organs furnish two kinds of
excitements which are determined by differences of a chemical nature.
One of these forms of excitement we designate as the specifically sexual
and the concerned organ as the _erogenous zone_, while the sexual
element emanating from it is the partial impulse.[27]

In the perversions which claim sexual significance for the oral cavity
and the anal opening the part played by the erogenous zone is quite
obvious. It behaves in every way like a part of the sexual apparat