116 heredity in relation to eugenics 



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Fig. 82. — Pedigree of a family, every affected member of which (black 

 symbols) has drooping eyelids, a fold over the inner corner of the eye, and nar- 

 row eye opening. Vignes, 1889. 



One family pedigree is reproduced in Fig. 82. This is 

 remarkable because every affected person showed the same 

 combination of characters, namely, drop of upper eyelid, 

 epicanthus, and ophthalmoplegia. 



In Cutler's case (Fig. 83) the parents are first cousins; all 

 affected persons have strabismus. Expectation in this group 

 of cases is that an affected person will have affected off- 

 spring but that two normal parents will rarely have off- 

 spring with the defect, even though one 

 belongs to the defective strain. 



•^ 



1. Pigmentary degeneration of the ret- 

 ina (retinitis pigmentosa). — This degen- 

 erative process is accompanied by an 

 Fig. 83.— Pedigree atrophy of the optic nerve and leads to 

 the%Ss 'are'^fiS eventual blindness. It is frequently as- 

 cousins and both have sociated with consanguineous marriage, 



strabismus (squint). ^^ j. j j_i ■ i • i . t i 



Three of their 6 chil- ^^ P^r cent of the marriages which yield 

 dren are similarly af- it being (according to Feer's list, 1907, 



fected. Cutler. . . 



p. 14) consanguineous. The method of 

 inheritance is well illustrated by Fig. 84 which is a portion 

 of a chart prepared by Nettleship. This figure illustrates 

 the general law of this disease; namely, that two normal 



