CONTENTS

PREFACE

CONTENTS

CHAPTER I

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

CHAPTER II

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

CHAPTER III

MASCULINITY

Constancy of the Sex-ratio—Consanguinity and Masculinity—Theory of Westermarck and Thomas—Duesing—Gache—Negroes in the United States—Genealogical Material—Other Compilations—Summary

CHAPTER IV

CONSANGUINITY AND REPRODUCTION

Theories of the Effect of Consanguinity upon Offspring—Comparative Fertility—Statistics from Darwin and Bemiss—Genealogical Statistics—Youthful Death-rate—Degeneracy—Fallacies in the Work of Bemiss—Isolated Communities—The Jukes—Other Degenerate Families—Scrofula

CHAPTER V

CONSANGUINITY AND MENTAL DEFECT

Idiocy and Insanity—Inheritability of Mental Defect—Intensified Heredity—Barr's Investigations—Other American and English Data—Mayet's Prussian Statistics—Genealogical Data

CHAPTER VI

CONSANGUINITY AND THE SPECIAL SENSES

United States Census Data—The Blind—Consanguinity of Parents—Blind Relatives—Degree of Blindness—Causes of Blindness—Retinitis Pigmentosa—European Data—Probability of Blind Offspring of Consanguineous Marriages—The Deaf—Irish Census—Scotland and Norway—United States Census—Consanguinity of Parents—Deaf Relatives—Causes of Deafness—Degree of Deafness—Direct Inheritance of Deafness—Intensification through Consanguinity—Dr. Fay's Statistics—Personal Data—Probability of Deaf Offspring from Consanguineous Marriages—Opinion of Dr. Bell

CHAPTER VII

SUMMARY AND CONCLUSION

Summary of Results—Inbreeding and Evolution—Effects of Close Inbreeding—Crossing and Variation—"Difference of Potential"—Resemblance and Intensification—Coefficient of Correlation between Husband and Wife—Between Cousins—Between Brothers and Sisters—Consanguinity and Eugenics—Consanguinity and Social Evolution—Conclusion

BIBLIOGRAPHY.

GENEALOGIES CONSULTED.

FOOTNOTES