288 HEREDITY AND DISEASE 



members had all their fingers and toes two-jointed like the thumb 

 and big toe. The normal members had normal children, even 

 in the case of a first-cousin marriage. The abnormal members 

 married normal individuals, and the fourteen families bred in 

 this way contained 33 normals and 36 abnormals — a close 

 approach to equaUty. The abnormals are indicated by capitals. 



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Along with defects of parts we may include imperfections due 

 to an arrest of the normal course of development at certain 

 stages, perhaps through inadequacy of nutrition, perhaps 

 because of what we must vaguely call " deficient developmental 

 vigour." Thus, hare-lip is practically the persistence of a normally 

 transient condition, and cleft palate is in the same category. 

 Hutchinson has recorded hare-lip in ten members of a family of 

 twenty. The interest of some of these cases is considerable, since 

 among animals there are not a few examples of what might 

 be called normal arrests. Thus, every one is familiar with the 

 hare-lip of the hare and its relatives, and the persistent external 

 groove which connects each nostril of the skate with the corner 

 of the mouth is even more striking. 



Inhibitions or disturbances during ante-natal life are believed 

 to result in various other abnormalities, such as cleft-palate, 

 cervical fistulae (persistence of traces of visceral clefts), spina 

 bifida, certain peculiarities of the eyes and teeth, and so on. 



