If the infant could express itself it would undoubtedly acknowledge that the act of sucking at its mother’s breast is far and away the most important thing in life. It would not be wrong in this, for by this act it gratifies at the same moment the two greatest needs in life. Then we learn from psycho-analysis, not without astonishment, how much of the mental significance of this act is retained throughout life. Sucking at the mother’s breast (_saugen_) becomes the point of departure from which the whole sexual life develops, the unattainable prototype of every later sexual satisfaction, to which in times of need phantasy often enough reverts. The desire to suck includes within it the desire for the mother’s breast, which is therefore the first _object_ of sexual desire; I cannot convey to you any adequate idea of the importance of this first object in determining every later object adopted, of the profound influence it exerts, through transformation and substitution, upon the most distant fields of mental life. First of all, however, as the infant takes to sucking for its own sake (_lutschen_) this object is given up and is replaced by a part of its own body; it sucks its thumb or its own tongue. For purposes of obtaining pleasure it thus makes itself independent of the concurrence of the outer world and, in addition, it extends the region of excitation to a second area of the body, thus intensifying it. The erotogenic zones are not all equally capable of yielding enjoyment; it is therefore an important experience when, as Dr. Lindner says, the infant in feeling about on its own body discovers the particularly excitable region of its genitalia, and so finds the way from sucking (_lutschen_) to onanism.