H. Drinkwater 333 



What is the nature of this cubical basal portion of the teiTninal 

 phalanx ? and what has become of the second phalanx ? 



In the middle finger of every abnormal adult member of this family, 

 the second phalanx is always present as a separate bone, but invariably 

 it is so far reduced in length as to become a cube ; and the terminal 

 (third) phalanx is of the normal pyramidal shape. The ring-finger 

 also, in certain individuals, resembles the middle finger in these 

 particulars, having a normal-looking third phalanx, and a separate, 

 short, cubical middle j)halanx. Whenever the terminal phalanx has a 

 cubical base, this base corresponds in shaf)e with the second phalanx 

 present as a separate bone in the middle finger. In fact " this 

 cubical basal portion is the second (middle) phalanx that has become 

 ankylosed' to the terminal phalanx. The pyramidal distal portion of 

 these bones corresponds to the ungual phalanx and the basal cubical 

 portion to the middle phalanx." 



" It does not exist as a separate bone in either the index or little 

 finger in a single adult." 



" What, then, has happened to the middle phalanx ? It varies in 

 two respects from the normal : 



1. It is always very short. 



2. It generally becomes ankylosed to the base of the terminal 



phalanx. 



The fact that the middle phalanx is abortive, but not completely 

 absent, is proved conclusively by an examination of the radiogi-aphs 

 of the hands of young children, before ankylosis has occurred, and in 

 whom the middle phalanx is seen to be invariably present, but at the 

 same time abnormal. Each phalanx, in the ordinaiy (normal) hand, 

 consists at first of cartilage (gristle) and is gradually transformed into 

 bone, or, as it is termed, becomes ossified, such transformation being 

 limited for some time to two parts, one forming the great bulk or shaft 

 of the phalanx, and the other a thin plate or disc at the base. This 

 disc is termed the Epiphysis of the phalanx. 



That narrow strip of the cartilage which is situated between the 

 bony shaft and the bony epiphysis usually remains unossified until 

 about the twentieth year in each phalanx. The epiphysis of each 

 phalanx is seen to be situated at its base ; but the epiphysis of 

 each metacarpal (palmar) bone is at the distal extremity. So long 

 as the strip of cartilage between the shaft and the epiphysis remains 



^ Joined by bony union. 



