Original (inglés)

Preface In the introductory Chapter the reader will find the aim and object of these studies set forth at length. In view of the importance and complexity of the problems involved it seemed better to incorporate such a statement in the book itself, rather than relegate it to a Preface which all might not trouble to read. Yet I feel that such a general statement does not adequately express my full debt of obligation. Among the many whose labour has been laid under contribution in the