20 HEREDITY AND INHERITANCE 



through six generations, and the pathologist Bouchut (cited by 

 Ziegler) refers the origin of the evil to the rage of an ancestor, 

 who terrified his wife during her pregnancy with the wish that 

 the fingers with which she had plucked an apple against his 

 orders might be cut off ! Apart from the story's quaint sugges- 

 tion of a much older episode, it requires but an elementary know- 

 ledge of the facts of heredity and inheritance to convince us that 

 the alleged cause was inadequate to account for the effects. 



In two hundred families tainted with a predisposition to 

 haemophilia an excessive and chronic liability to immoderate 

 haemorrhage Grandidier * found six hundred and nine male 

 " bleeders." It is a problem of inheritance (and partly perhaps 

 of sexual physiology) to discover why the disease should be 

 restricted to males ; and the interest of the problem is enhanced 

 by the fact that the disease rarely passes from father to son, but 

 usually from a male parent, through an apparently unaffected 

 daughter, to a grandson. In short, the female offspring of 

 bleeders hand on the taint to male offspring, without themselves 

 showing the disease, f 



De Candolle J reported from American statistics that thirty 

 per cent, of the children of congenitally deaf-mute parents were 

 deaf-mute, but that the percentage was fifteen when only one 

 parent was congenitally deaf-mute. It is a problem of heredity 

 to interpret the greater frequency of inheritance when both 

 parents were affected. 



While there is much and justifiable uncertainty in regard to 

 the origin of what are called instincts, there is no doubt that an 

 organism's inheritance often includes the power of carrying out 

 a complex series of operations without experience and without 

 education when the appropriate stimuli occur. 



* Grandidier, Die Hamophilie (1876). 



f Bulloch and Fildes, Haemophilia. Treasury of Inheritance, Pt. xiva. 

 (1911). 



J De Candolle, Arch. Sci. Phys. Nat. xv. p. 25, cited by Ziegler (1886). 



