Not all children suck their thumbs.  It may be assumed that it is found only in children in whom the erogenous significance of the lip-zone is constitutionally reenforced.  Children in whom this is retained are habitual kissers as adults and show a tendency to perverse kissing, or as men they have a marked desire for drinking and smoking.  But if repression comes into play they experience disgust for eating and evince hysterical vomiting.  By virtue of the community of the lip-zone the repression encroaches upon the impulse of nourishment.  Many of my female patients showing disturbances in eating, such as hysterical globus, choking sensations, and vomiting, have been energetic thumbsuckers during infancy.

In the thumbsucking or pleasure-sucking we have already been able to observe the three essential characters of an infantile sexual manifestation.  The latter has its origin in conjunction with a bodily function which is very important for life, it does not yet know any sexual object, it is autoerotic and its sexual aim is under the control of an erogenous zone.  Let us assume for the present that these characters also hold true for most of the other activities of the infantile sexual impulse.

THE SEXUAL AIM OF THE INFANTILE SEXUALITY

The Characters of the Erogenous Zones.—­From the example of thumbsucking we may gather a great many points useful for the distinguishing of an erogenous zone.  It is a portion of skin or mucous membrane in which the stimuli produce a feeling of pleasure of definite quality.  There is no doubt that the pleasure-producing stimuli are governed by special determinants which we do not know.  The rhythmic characters must play some part in them and this strongly suggests an analogy to tickling.  It does not, however, appear so certain whether the character of the pleasurable feeling evoked by the stimulus can be designated as “peculiar,” and in what part of this peculiarity the sexual factor exists.  Psychology is still groping in the dark when it concerns matters of pleasure and pain, and the most cautious assumption is therefore the most advisable.  We may perhaps later come upon reasons which seem to support the peculiar quality of the sensation of pleasure.

The erogenous quality may adhere most notably to definite regions of the body.  As is shown by the example of thumbsucking, there are predestined erogenous zones.  But the same 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,