MEASURE OF RESEMBLANCE OF FIRST COUSINS 5 



may be of great relevance. The existing state of doubt as to the quantitative value 

 of cousinship may be illustrated from such a vital problem as that of the hereditary 

 predisposition to mental disease where some medical authorities would exclude entirely 

 evidence drawn from the cousinship*, while they retain the inquiry as to the direct 

 line and as to collaterals in the first degree. As the cousinship often combines many 

 lines, it requires of course careful handling, but its size and relative accessibility may 

 be factors which give it equal importance with the grandparentage or the parental 

 sibships. 



2. With the object of throwing light on the value of the record of cousinship, an 

 inquiry as to the physical and psychological resemblance of first cousins was set on foot 

 by Karl Pearson some five years ago and a grant obtained from the Government 

 Grant Committee to assist the investigation. The assistance derived from this source 

 is here gratefully acknowledged. The plan followed was twofold. Two independent 

 collections were started. The first part of the investigation was based upon very 

 general inquiries as to the physical and psychical characteristics of families. At 

 present about 300 families have supplied very full particulars of ancestors and 

 collaterals as far as the personal knowledge of the recorders extend. These Family 

 Records supply the material upon which the bulk of the present paper is based, and 

 provide sufficient pairs of cousins to give a fair idea of the general intensity of re- 

 semblance in cousins. The family schedules asked for the following information: 



(1) Present Age or Age at Death of each individual. 



(2) Ailments in Life. 



(3) Cause of Death, if dead. 



(4) General Health under the Categories : Very Robust, Robust, Normally 

 Healthy, Delicate, and Very Delicate. 



(5) Ability under the categories : 



A. — Mentally Defective. — Capable of holding in the mind only the simplest 



facts, and incapable of perceiving or reasoning about the relationship 



between facts. 

 B. — Slow Dull. — Capable of perceiving relationship between facts in some 



few fields with long and continuous effort ; but not generally or without 



much assistance. 

 C. — Slow. — Very slow in thought generally, but with time understanding is 



reached. 

 D. — Slow Intelligent. — Slow generally, although possibly more rapid in 



certain fields ; quite sure of knowledge when once acquired. 

 E x . — Fairly Intelligent. — Ready to grasp, and capable of perceiving facts in 



most fields ; capable of understanding without much effort. 



* Bucknill and Tuke : Psychological Medicine, 2nd edn. p. 266. 



