546 
is only a slight attempt at splitting of the metacarpal, as shown by 
the indentation at the distal end. (Fig. 2.) 
The two cases differ in the extent to which the metacarpal has 
been split. In the first case the metacarpal seems to have been split 
slightly more than half way down, and the external subdivision then 
to have become separated from the metacarpal. This explanation 
would account for the fact that there are only two phalanges in the 
second case, as here the splitting has not gone far enough to split off 
part of the metacarpal. 
The Etiology of the condition of Polydactyly is somewhat obscure, 
and the condition seems naturally to divide itself into two classes, 
Fig. 2. 
namely: those with a distinct family history, and those without. In 
the former case one finds that the condition is symmetrical, very often 
involving all four extremities and at the same time associated with 
syndactyly and other congenital defects and malformations. 
In both these cases of pre-hallux none of these features existed, 
therefore one may conclude that their origin is probably quite different 
from the heredity type and must either be classed as sporadic or 
what might be hetter termed, a “developmental accident”. 
Various theories have been put forward to explain the above 
condition. 
1) The evolution theory namely, that in a very early stage of 
evolution mammals had seven digits namely, an extra one on each side 
of the hand. Thus the pisiform has been regarded not so much as a 
