Consanguineous Marriages in the American Population

This monograph does not claim to treat exhaustively, nor to offer a final solution of all the problems which have been connected with the marriage of kin. The time has not yet come for a final work on the subject, for the systematic collection of the necessary statistics, which can only be done by governmental authority, has never been attempted. The statistics which have been gathered, and which are presented in the following pages, are fragmentary, and usually bear upon single phases of the subject, but taken together they enable us better to understand many points which have long been in dispute.
The stock illustrations from isolated communities have been omitted as too difficult to verify, and little space has been given to the results of the inbreeding of domestic animals, for although such results are of great value to Biology, they are not necessarily applicable to the human race.
The writer regrets that it is impossible here to acknowledge all his obligations to those who have assisted him in the preparation of this work. Such acknowledgement is due to the many genealogists and other friends who have kindly furnished detailed cases of consanguineous marriage. For more general data the writer is especially indebted to Dr. Alexander Graham Bell, to Dr. Martin W. Barr, to Professor William H. Brewer of Yale University, and to Dr. Lee W. Dean of the University of Iowa. In the preparation of the manuscript the suggestions and criticisms of Professors Franklin H. Giddings and Henry L. Moore have been invaluable.
G.B.L.A.
MARCH, 1908.

INTRODUCTION
Problems to be Treated—Degrees of Consanguinity—Literature of the Subject—Noah Webster—Bemiss—Dally—G.H. Darwin—Huth—Bell—Legal Status in the United States—Methods of Investigation—Genealogical—Personal—Isolated Communities
RATIO OF THE CONSANGUINEOUS TO ALL MARRIAGES
Previous Estimates—Mayo-Smith—Mulhall—Darwin—Application of Darwin's Method to American Data—Direct Method—Consanguineal Attraction—Same-name and Different-name Cousin Marriages—Summary