APPENDIX A. 



HEREDITARY RESEMBLANCE OF FIRST COUSINS*. 



I. OBJECT OF MEASUREMENTS AND GENERAL INSTRUCTIONS. 



I.— The present state of our knowledge of the laws of inheritance in man may 

 be summed up as follows : — 



We know well for a variety of organs direct inheritance from parent to offspring, 

 and the collateral relationship between brothers and sisters. We have less complete, 

 but still valuable data for the direct line in the case of grandparent and great-grand- 

 parents, and for the collateral line in the case of uncles and aunts. To supplement 

 our knowledge, one of the most urgent problems is the determination of the degree 

 of resemblance between cousins. It is with a view of solving this problem of cousin 

 relationship that I appeal for cooperative observations and issue the present paper 

 and schedules. 



II. — For the purposes of the present investigation we are to understand by the 

 word cousin ; 



(i) Full blood First Cousins, that is children of two whole (not half) brothers, 

 of two whole (not half) sisters, or of a whole (not half) sister and brother. Such 

 cousins are to have one and only one grandparental pair in common, and we term 

 them normal cousins. 



(ii) " Abnormal " first cousins are to be excluded. 



It may happen that two brothers of one family have married to two sisters 

 of another family, or that a sister and brother of one family have married a brother 

 and sister of a second. The issue of such marriages are "doubly" first cousins having 

 all their grandparents in common. Again, a brother and sister in one family might 

 marry an aunt and a nephew in a second family, or again, might marry a woman 

 and a man who are cousins in a second family, or, two brothers may marry two half 

 sisters in a second family. Indeed cases of abnormal cousinship occur in which the 

 abnormal cousins have 1, 2, 3 or 4 common grandparents. All such cases are excluded 

 from the present investigation, which is concerned only with normal cousinship as 

 defined under (i). 



(iii) Normal cousins for the purpose of this investigation must be between 18 

 and 45 years of age. 



* Issued by Professor Pearson, 1902 and onwards. 



