Geography of Man in Relation to Eugenics 291 



Second, the real units may be isolated by the simple 

 process of preventing the random hybridization and ensuing 

 breeding within the t}'pe. This result has been nearly 

 realized in small oceanic islands, and in other isolated 

 communities. It will be interesting to look at some of 

 these isolated places and learn what has been produced in 

 them. 



At Swans' Island, Maine, much consanguinity in mar- 

 riage occurs; cousin marriages are the rule. A consequence 

 has been that the defect of feeble-mindedness is unusually 

 common and, were the process to continue for many more 

 generations, a race with this trait, among others, would 

 doubtless become established. 



At Western Martha's Vineyard a careful genealogical 

 study has been made by Dr. Alexander Graham Bell and 

 much consanguineous marriage has been found. Here is, 

 or was, being formed a deaf-mute colony; one out of every 

 twenty-five was already a deaf mute. 



At Block Island, with a population of fifteen hundred, 

 much consanguineous marriage has occurred, and a non- 

 fecund strain has been isolated. On the Banks off Palmico 

 Sound consanguineous marriage occurs with extraordinary 

 frequency; and a strain characterized by suspicion, insan- 

 ity, and mental dulness is being formed. At George Island 

 near Eleuthera Island, one of the Bahamas, long inbreed- 

 ing has produced a race that tends toward dwarf stature 

 and eye defects, including cataracts. 



What is true of islands holds for other isolated situations. 

 A physician at an extreme point of the peninsula of Dor- 

 chester Count)', Maryland, writes that marriages there are 

 usually consanguineous and a race of dwarfs and cripples 

 is being formed. Mountain valleys of the Ramapo, Cats- 



