case of the suckling mother and her infant. The mother is indebted to the
child for the pleasurable relief of her distended breasts; and, while in
civilization more subtle pleasures and intelligent reflection render this
massive physical satisfaction comparatively unessential to the act of
suckling, in more primitive conditions and among animals the need of this
pleasurable physical satisfaction is a real bond between the mother and
her offspring. The analogy is indeed very close: the erectile nipple
corresponds to the erectile penis, the eager watery mouth of the infant to
the moist and throbbing vagina, the vitally albuminous milk to the vitally
albuminous semen.[17] The complete mutual satisfaction, physical and
psychic, of mother and child, in the transfer from one to the other of a
precious organized fluid, is the one true physiological analogy to the
relationship of a man and a woman at the climax of the sexual act. Even
this close analogy, however, fails to cover all the facts of the sexual
life.

A very different view is presented to us in the definition of the sexual
instinct as a reproductive impulse, a desire for offspring. Hegar,
Eulenburg, Näcke, and Löwenfeld have accepted this as, at all events, a
partial definition.[18] No one, indeed, would argue that it is a complete
definition, although a few writers appear to have asserted that it is so
sometimes as regards the sexual impulse in women. There is, however,
considerable mental confusion in the attempt to set up such a definition.
If we define an instinct as an action adapted to an end which is not
present to consciousness, then it is quite true that the sexual instinct
is an instinct of reproduction. But we do not adequately define the sexual
instinct by merely stating its ultimate object. We might as well say that
the impulse by which young animals seize food is "an instinct of
nutrition." The object of reproduction certainly constitutes no part of
the sexual impulse whatever in any animal apart from man, and it reveals a