1 06 E VOL UTION AND DISEASE. 



termed by odontologists, gemination (fig. 53). This 

 abnormality is not confined to the teeth of man, but 

 has been detected in those of other mammals, wild 

 and domesticated. 



Typical cases of gemination may be considered as 

 examples of equal dichotomy. Should the process 

 only involve a part of the papilla, we should then 

 have only an extra crown to the tooth if it affect 

 the incisors or a canine ; but in unequal dichotomy 

 affecting the germ of a molar we should probably 

 find it increase the number of the cusps. 



Antlers of deer occasionally fur- 

 nish instructive specimens. Dicho- 

 tomy may affect the beam or the 

 tine producing puzzling deviations. 

 The museum of the Royal College 

 of Surgeons contains a pair of 

 FIG. 53. TWO geminated an tiers of the moose (A Ices ma- 



teeth, illustrating equal and M ^ j n which the broad pa l m SQ 

 unequal dichotomy. 



characteristic of this deer, is redu- 



plicated in each antler (fig. 54). The specimen is 

 Hunterian, and said to come from America. 



Dichotomy occurs in the limbs of many vertebrata 

 from the lowest to the highest, and is the chief cause of 

 supernumerary fingers and toes, and many examples 

 of reduplicated limbs. Many simple and uncomplicated 

 cases of dichotomy are presented by the digits : the 

 simplest are those in which children are born with a 

 small fleshy nodule hanging from the finger, usually 

 the fifth. As a rule the corresponding digit of each 

 hand is affected. The nodule consists usually of a 



