HUMAN DEGENERACIES 171 



But so far only one individual, No. 15, manifests any 

 impairment of vision. Her father. No. 19, C, suffers 

 from the defect, but not her mother. She is only eighteen 

 years of age, and for some years back has progressively 

 been becoming blind ; her relations recognise the con- 

 dition as being the same as their own. No opportunity 

 for examination of this particular member presented 

 itself. 



General Considerations. 



This clanship illustrates what Nettleship and others 

 have called " anticipation " in the appearance of the 

 cataract. The period at which it first becomes evident 

 is progressivel}^ earlier in the more recent generations. 

 Thus in the A generation it seems to have appeared 

 when the patient was over eighty years of age. In the 

 B generation it manifested itself at about seventy-six 

 years of age. In the C generation it showed itself at 

 ages varying from childhood up to the age of eighteen. 

 In the latest generation the symptoms have also put in 

 their appearance during adolescence. 



No deductions wiU here be drawn from the frequency 

 of the condition either in the entire stock or in the 

 family where both parents were affected (seven unaffected 

 to five affected, and one doubtful), but it is noteworthy 

 that in the instance recorded by Nettleship,* of a 

 cataractigenous family where the condition was evident 

 in both parents, there was a similar occurrence of several 

 individuals free from the organic defect among the 

 offspring. 



* Loco citato. 



