38 THE MENDEL JOURNAL 



They are numbered 1st (the nearest), 2nd (the middle), 

 and 3rd (the terminal one which supports the nail). 

 The first is the longest bone, and the third is the 

 shortest. 



Each finger or toe has two joints, one between 

 the first and second bone, and one between the 

 second and third. Each joint in a finger causes a 

 crease on the palmar surface, and a knuckle on the 

 back. A normal finger shows these two palmar 

 creases very clearly. 



The thumb and big toe have each only two bones, 

 one joint and one crease. 



Now, how do the hands and feet of the abnor- 

 mals differ from the common type ? 



Abnormalities ot the fingers and toes are not by any 

 means rare occurrences, and many people are familiar 

 with them ; but the precise peculiarity is seldom accu- 

 rately reproduced in successive generations. One 

 member of a family may have four fingers, another 

 three, another two. 



Now, the remarkable fact about this family is 

 the accurate reproduction of the deformity in all 

 the abnormal members. 



Whenever the deformity appears at all, it affects 

 every finger and every toe of both hands and both feet. 

 The deformity consists in the absence (or apparent 

 absence) of the middle bone, so that each finger and 

 toe has only two bones instead of three, and one joint 

 and one crease instead of two. The fingers are thus 

 reduced to the condition of thumbs (Plates 2 and 3). 



