102 HEREDITY IN RELATION TO EUGENICS 



female. II, 1 became affected with chorea ''8 years before 

 his death"; II, 2 ''has been affected for many years"; II, 

 3 became ill with chorea at 35 and suffered until her death 

 at 46. These look like cases of Huntington's chorea. Ill, 2 

 suffers from migraine; III, 3 has chorea, IV, 1-3 died at 

 birth of convulsions; IV, 4 at 9 years began to show chorei- 

 fonn movements. These have continued for two years 

 until the present time. This girl also has epilepsy; but 

 her chorea has appeared at the age for St. Vitus's dance. 



i. Huntington's Chorea. — This is said to be a "rare" 

 disease in Europe, but not so in the United States. It is 

 characterized by appearing typically first in middle hfe 

 and progressing with ever increasing disorder of move- 

 ments until dementia and death occur. It affects both sexes 

 about equally. Two pedigrees are given in Figures 67 and 68. 



The method of the inheritance of this disease was recog- 

 nized by its original describer. Dr. George Huntington. 

 He states that those exempt from it cannot transmit it. 

 An examination of the extensive pedigrees shows only one 

 exception to his rule and this a doubtful case. Hunting- 

 ton's chorea is, consequently, a typical dominant trait, the 

 normal condition is recessive; or, the disease is due to some 

 positive factor. The eugenic lesson is that persons with 

 this dire disease should not have children. But the members 

 of normal branches derived from the affected strain are 

 immune from the disease. 



This disease forms a most striking illustration of the 

 principle that many of the rarer diseases of this country 

 can be traced back to a few foci, possibly even to a single 

 focus; certainly in this case many of the older families | 

 with Huntington's chorea trace back to the New Haven ^ 

 Colony and its dependencies and subsequent offshoots. 

 The subject of foci of origin of traits will be discussed more 

 fully later (page 181) 



