Preface.

The preceding dedication is intended as an expression of the fact that the name it bears should, according to the nature of the matter and my own personal wish, have appeared alongside my own on the title page of this work. In June 1899, Miss M. Radaković first drew my attention to the facts that I have designated in the present work as assumptions and subjected to an initial investigation. The aforementioned lady kindly agreed to assist in conducting this investigation; she truly undertook the monographic study of the areas in which the new fact had first become apparent to her, primarily play and art, and carried them almost to the point of publication. However, an illness as severe as it was protracted, against which it required the courage and strength of a hero to assert oneself not only physically but also mentally, forced my dear collaborator to temporarily forgo the continuation of her research. Since it is to be hoped that she will be able to make her unusual talent useful to science again in the not-too-distant future, I have had to forgo her help for the execution of the present work, at least as far as that would have involved the independent drafting of several sections of this book that have now been omitted.