42 THE MENDEL JOURNAL 



Now, in the abnormal child this middle bone 

 (the second) consists of one bony piece only instead of 

 two, and this one is much smaller than normal (Plate 5). 

 Instead of remaining separate, it unites later on with 

 the third bone, and thus we eventually have two 

 bones in the finger instead of three. Though all the 

 bones of the finger are shorter than normal,the marked 

 shortening of the fingers is due chiefly to the imperfect 

 development of the middle (second) one. 



Union of the third bone with the imperfectly- 

 developed second is the rule, but there are a few 

 exceptions to it. 



This union invariably occurs in the -first and fourth 

 fingers, but sometimes in the middle and ring finger 

 it does not do so, and the middle bone can then be 

 seen even in the adult as a separate though very 

 short bone (middle finger, Plate 4). Thus the second 

 hone is never absent, hut it is ahvays imperfect and 

 generally joined to the terminal one. When present as 

 a separate bone, it has only about one-quarter the 

 normal length. 



The first bone of the thumh is very much shortened 

 (Plates 4 and 5), sometimes so much so that its 

 length is exceeded by its breadth, but it is never 

 united to the terminal one. It is imperfectly developed 

 similarly to the middle bone of the fingers. 



This description of the fingers and thumb applies 

 equally well to the toes (Plate 6). 



It is thus clear that the fingers of these people are 

 reduced to the condition of thumbs, for, as a rule, 



