CHAPTER XXXIV 



THE INHERITANCE OF HUMAN CHARACTERS, 

 PHYSICAL AND MENTAL 1 



ELLIOT R. DOWNING 



Anyone who undertakes to trace the ancestry of an individual is 

 soon impressed with the fact that it is a difficult task even to find the 

 names of the persons involved three or four generations back; it is 

 much more difficult to determine with certainty their physical and 

 mental characteristics. One can more surely find the pedigree of a 

 horse or hog that he may own than he can of a child in whom he is 

 interested, for we do have registry books for good stock, but none 

 ordinarily for human family relations (in Illinois not even compulsory 

 birth registrations until very recently), so that a child born in this 

 state may not even legally prove his existence or parentage by official 

 records. It is not an easy matter, therefore, to find human data that 

 illustrate the various phases of heredity concerning which we are 

 reasonably sure in dealing with animals and plants. 



Fortunately, there are some studies of the inheritance of physical 

 characters that are quite satisfactory. There is an increasing number 

 of studies of the inheritance of insanity, feeble-mindedness, epilepsy, 

 and alcoholism by the scientific staff of institutions dealing with such 

 cases, and we do have a fairly good mass of material in the lines of 

 descent of the royal families of Europe, where the matings and the 

 characters of the individuals are more or less matters of history. 

 Thanks to the generosity of some men of wealth and foresight, appre- 

 ciative of the importance of a better knowledge of the laws of human 

 heredity, we have in several countries well-endowed laboratories with 

 expert staffs founded on purpose to study this topic; such as the 

 Galton Laboratory of Eugenics in England and the Eugenics Labora- 

 tory of the Carnegie Institution, Cold Springs Harbor, New York. 



Occasionally a family is found in which one or more members have 

 five fingers instead of four; such a condition is known as polydactyl- 

 ism. Sometimes a case is recorded in which a person has fingers with 



1 From E. R. Downing, TJie Third and Fourth Generation (The University of 

 Chicago Press, copyright 1920). 



459 



