106 EVOLUTION 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 
Fic. =3.—Two geminatea antlers of the moose (Alces ma- 
teeth, illustrating equaland ¢/J/s) in which the broad palm, so 
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 
