86 THE MENDEL JOURNAL 



ophthalmic surgeon, Mr. Nettleship. It is one of the 

 largest known human pedigrees of its kind, comprising 

 somewhere near a total of two thousand individuals, 

 and it extends back through ten generations to the 

 year 1637, when the individual Jean Nougaret, with 

 whom it commences, was born. The peculiar here- 

 ditary character which affected one hundred and 

 thirty-five persons of this family, and which mani- 

 fested itself in each generation, is one which is known 

 as congenital stationary night-blindness. The real 

 nature of the disease is quite well confirmed, for Mr. 

 Nettleship, with Professor True and M. Capion, have 

 been able to examine fifteen night-bhnd subjects, 

 belonging to the ninth, eighth, seventh, and sixth 

 generations. The affected persons can see as well 

 during the daytime as normal people. But at night 

 time they can see only by candle light and by very 

 bright moonlight. On moonless nights, or in very 

 dark places such as cellars, they are blind. The 

 affection is present from birth, and mothers are able 

 to determine whether their babies are night-blind or 

 normal by the apathy or interest manifested by them 

 when objects likely to attract their attention are held 

 up at night time. In this case of congenital night- 

 blindness it is shown by the facts of the pedigree 

 that the abnormal condition is the dominant one, 

 and the normal one is recessive. The Mendelian 

 expectation therefore is that when two extracted 

 normal persons marry, or when an extracted normal 

 person marries a normal individual, that all the off- 

 spring shall be normal. Is the Mendelian expectation 



