20 



The Journal of Heredity 



should give a 1:1 ratio, because in 

 every instance an abnormal individual 

 was mated with a normal. Thus 

 every abnormal person was hetero- 

 zygous (xA.a) and every normal homo- 

 zygous (aa). 



Table 1 further shows that matings 

 of heterozygous (Aa) individuals with 

 normal persons (aa) gave as a total 

 9 who died in infancy, 12 abnormal 

 children and 15 normal. Of those 

 who died as infants some at least 

 might have had the abnormal char- 

 acter linked with the mortality ; how- 

 ever, if this interpretation is not cor- 

 rect, the law of probability would 

 lead us to expect that half of those 

 individuals who died in infancy would 

 be normal and the others abnormal. 

 It therefore seems desirable to omit 

 those who died as infants from any 

 further consideration. 



Following this suggestion the au- 

 thor tabulated in Table 4 the Observed 

 Data, Observed Ratio, Theoretical 

 Ratio, and Probable Error. The con- 

 clusion is that the observed ratio is 

 a good fit because the number of 

 normals and abnormals give a 1:1 

 ratio, which proves that in this fam- 

 ily all almormals are heterozygous, 

 while the normals are homozygous re- 



Other Abnormalities of the Skeleton 



The many human pedigrees which 

 have been published show that the 

 majority of hereditary abnormalities 

 found in the skeleton are inherited as 

 ]\lendelian dominants. Davenport' 



enumerates several in this connection. 

 One of the most common is polydactyl- 

 ism, by which is meant supernumerary 

 fingers and toes ; another abnormality 

 is syndactylism, which means that the 

 bones and tissues of two or more 



fingers are fused or webbed into one 

 mass; while another is brachydactyl- 

 ism, which may be defined as an ab- 

 normality having digits and limbs ex- 

 ceedingly short. Gushing" has added 

 another to this list of dominants, sym- 

 phalangism, which means that the prox- 

 imal phalangeal joints become fused. 

 Another dominant is that of achondro- 

 plasism, described by Davenport' as a 

 condition in man characterized by ab- 

 normally short limbs, as is osteopsath- 

 rosis or hereditary fragility of bones as 

 shown by Davenport and Conard^ 

 Lastly, hereditary shortness of thumbs 

 as described in this paper is another 

 abnormality of the skeleton which is 

 dominant. 



Summary 



The character is neither sex-limited 

 nor sex-linked, because it is found in 

 both sexes, and is not transmitted 

 from a man through his daughters to 

 one-half of their sons. The evidence 

 presented indicates that it is an auto- 

 somal jMendelian dominant. 



Table 1. The character of the offspring of 

 the eight abnormal parents. The matings 

 were in every instance between an abnor- 

 mal (Aa) and a normal (aa) . 



Parents 



Progeny 



Abnormal 

 No. 



Died in | Adults 



infancy | Abnormal | Normal 



No. 



' Davenport, Charles B. Heredity in Relation to Eugenics. 298 pps. Henry Holt and 

 Company, New York. 191 1. 



'^ CusHiNG, Harvey. Hereditary Anchylosis of the Proximal Phalangeal Joints (Sym- 

 phalangism). Genetics I: 90-107. 1916. 



^ Davenport, Charles B. and H. S. Conard. Hereditary Fragility of Bone (Fragility 

 Osseus, Osteopsathyrosis). Eugenics Record Office Bulletin 14. 31 pps. 1015. 



