cii.\i'ri':R x\'ii 



MAN 



Though the interest attaching to heredity in man 

 is more widespread than in other animals, it is far 

 more ditVicult to obtain evidence that is both com- 

 plete and accurate. The species is one in whicii 

 the differentiatinjj^ characters separatini; indi\idiial 

 from individual are \'er)' numerous, while the number 

 of the offspring; is comparatively few, and the L^ener- 

 ations are far between. For these reasons, even if 

 it were [)(jssible, direct experimental work with man 

 would be likel)' t(3 prove both tedious and expensive. 

 There is, however, another method besitlcs the direct 

 one from which somethini,^ can be learned. '1 his 

 consists in collectini; all the e\idence possible, ar- 

 raiv^iuL; it in the form of pedi<4rees, and comparin^^ 

 it with standard cases alread)' worked out in animals 

 and plants. In this wa\' it has been possible to 

 demonstrate in man the existence of .several char- 

 acters showin;j^ simple Mendelian inheritance. As 

 few besides medical men have hitherto l)een con- 

 cerned practically with hereilitv, such records as 

 exist are, for the most part, records of deformity or 

 of disea.se. So it happens that most of the pedii,^rccs 



199 



