HEREDITARY LEFTHANDEDNESS, WITH A NOTE 



ON TWINNING. 



(STUDY III.) 



By H. E. JORDAN, 



University uf Virginia. 



This study is based chiefly on data collected by Dr Albert Ernest 

 Jenks, Professor of Anthropology, University of Minnesota, in the form 

 of questionnaire blanks and filed at the Eugenics Record Office, Cold 

 Spring Harbor Long Island. My best thanks are due to Professor Jenks 

 for his generous contribution, and to Dr Charles B. Davenport for 

 kindly placing the blanks at iny disposal for examination and record 

 in the form of charts. The material includes also six pedigrees from 

 various other sources. Respecting this body of data the primary 

 objects here sought are to make it more widely accessible by putting 

 it into more available form, and to analyze it with a view to testing 

 my earlier conclusions, namely, that lefthandedness is hereditary and 

 closely follows the behaviour of a Mendelian recessive character. The 

 questions of the cause and anatomical basis of this trait will not be 

 touched upon' ; these are similar to those involved in physiologic 

 "unit characters" generally. Scarcity of data respecting ambidexterity 

 precludes effective discussion of this character from a hereditary view- 

 point. The pedigrees include a considerable number of twins ; this 

 circumstan3e invites a consideration also of hereditary twinning; and 

 explains the inclusion of pedigree chart Fig. 80. 



^ This matter is discussed in my earlier papers. 



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