CHAPTER II 



THE GENERAL ASPECTS OF HEREDITY 



Many vague conceptions of heredity were formerly 

 held, and much ink was unprofitably spilled in an effort 

 to explain or elucidate inheritance in the absence 

 of adequate experiment. Human inheritance par- 

 ticularly has been the subject of innumerable crude, 

 unscientific conceptions such as " failure " of 

 inheritance when a particular trait does not appear 

 in every generation, a belief in maternal impressions, 

 or scepticism regarding the inheritance of mental 

 traits. The scientific investigation of heredity may 

 almost be said to have begun with Mendel's studies 

 of single characters in garden peas, since the results 

 of the early hybridisers were so contradictory and 

 confused — owing partly to an unfortunate choice of 

 material for crossing and partly to an unsuitable 

 method of experiment — that they never led to a 

 consistent point of view on which future progress 

 could build. The rediscovery of Mendel's principle 

 of segregation in 1900 therefore marked the beginning 

 of an era in the study of heredity. It has become 

 progressively clearer that while mass statistics of 

 resemblances may furnish useful information where 

 no other is available, yet such data cannot furnish 

 a basis for an understanding of the hereditary 

 process. The experimental analytical method is 

 necessary here, as in other fields of biology. The 

 results of the experimental method, however, can 

 be and have been applied to genealogical pedigrees 



of inheritance in man with illuminating results. 



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nOFERTY LIBRARY 



