DICHOTOMY. 
fifth metacarpal bone. 
larly affected. 
109 
The opposite hand was _ simi- 
When dichotomy extends beyond the fingers and 
metacarpal bones it may involve the terminal segment 
and lead to reduplication 
of the hand. Accessory 
hands or feet due to dicho-, 
tomy are, in man, of very 
great rarity. An excellent 
specimen of double hand 
has been described by the 
late Dr. Jardine-Murray.' 
A sketch of the hand is 
given on next page (fig. 57). 
It may easily be conceived 
that should dichotomy in- 
volve a greater extent of 
the axis of the limb, we 
should get an accessory 
arm or leg. Accessory 
limbs arising in this way 
are, in man, very rare; 
indeed no such specimen is 
known to me, but it un- 
doubtedly occurs in other 
vertebrata. Supernumerary 
Fic. 56.—The left hand of a Silvery 
Gibbon (Hylobates leuciscus), with 
dichotomy of the fifth finger and dis- 
tal segment of the metacarpal bone. 
legs are met with in the human subject, but, as will 
be seen later, these arise from dichotomy of the trunk 
axis. 
It should be mentioned that all specimens of poly- 
dactyly do not arise from dichotomy. Some are atavistic: 
* “ Medico-Chir. Trans.” vol. xlvi. p. 29. 
