PHYSICAL CHARACTERS IN MAN iii 



and polar. Details are given of a number of pedigrees 

 of inheritance, but no attempt is made to draw con- 

 clusions regarding the manner of inheritance. In 

 another paper, however, the same author (Harman, 

 1909) cites a pedigree of live generations showing 

 the condition to be a Mendelian dominant. Parents 

 who are normal have only normal children. Of 

 fifty-five persons, nineteen were known to be affected. 

 Others who w^ere not examined probably had the 

 defect slightly. Among forty-one persons personally 

 examined or certified, nineteen were cataractous. 

 This is very close to the expected 50 per cent. 



The indications of the de novo origin of hereditar}' 

 congenital cataract are clearly substantiated by the 

 pedigree of a family whose history is described by 

 Danforth (191 4). That congenital cataract is a 

 dominant character has been disputed by Jones and 

 Mason {ig\6a), who, from a discussion of Harman's 

 data in the Treasury of Human Inheritance, conclude 

 that it is a simple Mendelian recessive. This con- 

 clusion was criticised by Danforth (191 6), who, how- 

 ever, did not hold that a single Mendelian factor was 

 involved. In their reply Jones and Mason (1916^^) 

 conclude that it is impossible to arrive at a satis- 

 factory view of cataract inheritance, but that the 

 hypothesis of a single Mendelian recessive is the one 

 that is best supported by the facts in hand. Detlefsen 

 and Yapp (1920) describe a case of congenital cataract 

 in cattle, which they conclude behaves as a simple 

 Mendelian recessive. A registered Holstein-Friesian 

 bull inbred with his own stock gave a number of 

 cataractous offspring. There is no record of cataract 

 in any of the ascendants. To unrelated cows this 

 bull produced only normal calves. But thirty-two 

 Fj daughters mated to an Fj son gave sixt^'-three 

 calves, fifty-five of which were normal and eight had 

 congenital cataract of the stellate t3'pe. 



