DICHOTOMY. 



109 



fifth metacarpal bone. The opposite hand was simi- 

 larly affected. 



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. 1 

 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 



FIG. 56. The left hand of a Silvery 

 Gibbon (Hylobates leuciscus], with 

 dichotomy of the fifth finger and dis- 

 tal segment of the metacarpal bone. 



vertebrata. Supernumerary 

 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 : 

 1 " Medico-Chir. Trans." vol. xlvi. p. 



