CHAPTER IX 



THE INHERITANCE OF HUMAN CHARAC- 

 TERS, PHYSICAL AND MENTAL 



Anyone who undertakes to trace the ances- 

 try 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 compul- 

 sory 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 



