CHAPTER XXXIV 
THE INHERITANCE OF HUMAN CHARACTERS, 
PHYSICAL AND MENTAL 
ELLIOT R. DOWNING 
Anyone who undertakes to trace the ancestry of an individual is 
soon impressed with the fact that it isa 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 
t From E. R. Downing, The Third and Fourth Generation (The University of 
Chicago Press, copyright 1920). 
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