when he laid his hand on the delicate material of the paranoic psychology, was forced to doubt the applicability of the conception of libido held by him at that time. The sexual definition of this did not permit me to understand those disurbances of function, which affect the vague territory of the hunger instinct just as much as that of the sexual instinct. For a long time the theory of libido seemed to me inapplicable to dementia præcox. With increasing experience in analytical work, however, I became aware of a gradual change in my conception of libido. In place of the descriptive definition of the "Three Contributions" there gradually grew up a genetic definition of the libido, which rendered it possible for me to replace the expression "psychic energy" by the term "libido." I was forced to ask myself whether indeed the function of reality to-day does not consist only in its smaller part of libido sexualis and in the greater part of other impulses? It is still a very important question whether phylogenetically the function of reality is not, at least in great part, of sexual origin. To answer this question directly in regard to the function of reality is not possible, but we shall attempt to come to an understanding indirectly.
A fleeting glance at the history of evolution is sufficient to teach us that countless complicated functions to which to-day must be denied any sexual character were originally pure derivations from the general impulse of propagation. During the ascent through the animal kingdom an important displacement in the fundamentals of the procreative instinct has taken place. The mass of
