Heredity — Genetics 715 



Inheritance of Human Traits — Cont'd 



health, etc., has prevented our study of them in heredity. In other 

 words, definite unit characters must be w^orked out so that we know^ 

 their limits, variations, normalities, and abnormalities. 



Human Pedigrees or Family Trees: Much of our information regard- 

 ing human inheritance has been secured by the accurate collection of 

 data and their proper evaluation and interpretation. A most desirable 

 method of recording such data is in the form of a family tree or pedigree, 

 several of which are shown in Figs. 352 to 356. In order for such a study 

 to be of value, there must be a rather large number of individuals in the 

 families, and there must be several generations. Every member of each 

 family must be recorded accurately and none can be omitted, because 

 if one is omitted it may be just the one who would throw most light upon 

 the inheritance of that particular trait. The investigator must not guess 

 in any case, since the guess may be wrong and consequently the final 

 result inaccurate. 



20. Eugenics and the Future. — Eugenics (u-jen'iks) (Gr. eu well; 

 genos, birth) attempts to impro\e the human race through scientific 

 genetic measures. Race improvement may be brought about by attempt- 

 ing to prevent the hereditary transmission of undesirable traits or causing 

 the transmission of desirable traits from generation to generation. Im- 

 provement of certain environmental conditions whereby that which is 

 inherited may develop to the maximum of its inherent abilities may also 

 prove beneficial, although this does not alter the genie composition of 

 the individuals involved. No matter what the approach may be, there 



