Gi APE REX. 
ANATOMICAL PECULIARITIES OF THE TEETH IN 
RELATION TO INJURY AND DISEASE. 
MANY troubles and disasters arise in animals in conse- 
quence of injuries to their teeth, and injuries, trivial in 
one mammal, may in another be fraught with serious 
results, due to variations in the use and specialization of 
the dental organs. 
We may commence this subject with the kangaroo. 
This mammal has three incisors in the upper jaw, but 
only one in the mandible. This lower incisor is procum- 
bent and flattened from side to side; the outer surface 
is slightly convex, the inner flat, but has a median ridge ; 
the margins of the tooth are sharp. The lower incisor, 
instead of antagonizing the upper teeth by means of its 
tip, or crown, meets them along its sharp outer margin 
(fig. 107). The lower incisor is provided with a large 
persistent pulp ; the pulp chamber, contrary to what is 
usual in teeth, extends nearly to the tip. The points of 
these teeth, shaped something like a lancet, are exceed- 
ingly thin and brittle. As a consequence, the tips are 
easily broken, and if only a small piece is detached, the 
pulp is exposed (fig. 108). Kangaroos, like mammals of 
even high moral pretensions, have domestic differences, 
which occasionally lead to unpleasant consequences. In 
