THE BRADSHAW LECTURE 33 



TENACITY OF DEVELOPMENT OF DEFORMITY. 



With regard to the first point, the tenacity 

 with which a defect or deformity once developed 

 persistently clings to a stock, and is repeated 

 generation after generation, in spite of new blood 

 being infused, there are pedigrees innumerable 

 now to prove. Cannot a defect ever be washed 

 out in its early beginnings by normal blood ? My 

 own small studies in search of hidden deformities 

 appear to show their tendency is rather to increase 

 than decline. The normal appears powerless to 

 overcome the abnormal, or, as. the Mendelians 

 say, the deformity is dominant, and the normal 

 recessive. The pedigrees of spade hands or 

 brachydactyly recorded by Farabee and Drink- 

 water are claimed as clearly illustrating these 

 features, the abnormal only giving origin to ab- 

 normals and the recessive normals yielding only 

 normals. Nettleship's pedigree of congenital 

 cataract is also claimed as following this law, but 

 in some cases the defect was apparently trans- 

 mitted through a normal. In future the closest 

 attention should be applied to those exceptions, 

 as from them new facts will probably be gathered. 

 The best illustration we have of tenacity of descent 

 of an abnormal condition is Cunier's ten genera- 

 tions of night-blindness. The descent appears to 



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