e example also shows that any other region
of skin or mucous membrane may assume the function of an erogenous zone;
it must therefore carry along a certain adaptability. The production of
the sensation of pleasure therefore depends more on the quality of the
stimulus than on the nature of the bodily region. The thumbsucking child
looks around on his body and selects any portion of it for
pleasure-sucking, and becoming accustomed to it, he then prefers it. If
he accidentally strikes upon a predestined region, such as breast,
nipple or genitals, it naturally has the preference. A quite analogous
tendency to displacement is again found in the symptomatology of
hysteria. In this neurosis the repression mostly concerns the genital
zones proper; these in turn transmit their excitation to the other
erogenous zones, usually dormant in mature life, which then behave
exactly like genitals. But besides this, just as in thumbsucking, any
other region of the body may become endowed with the excitation of the
genitals and raised to an erogenous zone. Erogenous and hysterogenous
zones show the same characters.[12]

*The Infantile Sexual Aim.*--The sexual aim of the infantile impulse
consists in the production of gratification through the proper
excitation of this or that selected erogenous zone. In order to leave a
desire for its repetition this gratification must have been previously
experienced, and we may be sure that nature has devised definite means
so as not to leave this occurrence to mere chance. The arrangement which
has fulfilled this purpose for the lip-zone we have already discussed;
it is the simultaneous connection of this part of the body with the
taking of nourishment. We shall also meet other similar mechanisms as
sources of sexuality. The state of desire for repetition of
gratification can be recognized through a peculiar feeling of tension
which in itself is rather of a painful character, and through a
centrally-determined feeling of itching or sensitiveness which is
projected into the peripheral erogenous zone. The sexual aim may
therefore be formulated as follows: the chief object is to substitute
for the projected feeling of sensitiveness in the erogenous zone that
outer stimulus which removes the feeling of sensitiveness by evoking the
feeling of gratification. This external stimulus consists usually in a
manipulation which is analogous to sucking.

It is in full accord with our physiological knowledge if the d