86 HEREDITY AND EUGENICS 



of the others owing to the great length of its proximal 

 phalanx. The first and second fingers are also more 

 or less tilted away from the thumb (see Figs. 15 and 

 1 6) . There are thirty-six descendants of the abnormal 

 members of the family, fifteen of whom show the 

 abnormality. The feet in these individuals show 

 ordinary brachydactyly. From a careful study of 

 radiographs the following anatomical interpretation 

 emerges : The index finger has at its base an extra 

 triangular bone which sets the finger obliquely to the 

 hand. The proximal phalanx of the middle finger 

 appears to be divided equally or unequally into two 

 parts; the lower part, however, is probably an extra 

 bone corresponding to that in the index finger, and it 

 also is set somew^hat obliquety. In the adult hand 

 these extra bones become ossified with the proximal 

 phalanx of the corresponding finger. Another 

 peculiarity in this pedigree is the abnormal^ great 

 length of the proximal phalanx of the ring finger. 

 All these anatomical features behave as a unit in 

 inheritance, with remarkably little variation in their 

 development so far as observed. 



Drinkwater (191 7) has described yet another digital 

 abnormality, which is remarkable for the number of 

 generations for w^hich it is known to have been 

 handed down in one family. The peculiarity is as 

 follow^s, as found in the hands of a gentleman, A. T., 

 of the present generation : In the middle finger the 

 joint between the middle and basal phalanges is only 

 very slightly movable, the articular surfaces of the 

 bones being enlarged, while in the ring and little 

 fingers there is no joint between the proximal and 

 middle phalanges, these two being completely fused 

 into one (see Fig. 17). All the fingers are movable 

 at the distal joint, and both hands are alike. All the 

 toes, except the hallux, are affected exactly like the 

 ring and little fingers. This man's father and his 



