81 
and the Man’s, a similar constant difference of the same 
order (that is to say, consisting in excess or defect of the 
same quality) may be found between the Gorilla’s skull and 
that of some other ape. So that, for the skull, no less than 
for the skeleton in general, the proposition holds good, that 
the differences between Man and the Gorilla are of smaller — 
value than those between the Gorilla and some other Apes. 
In connection with the skull, I may speak of the téeth, 
—organs which have a peculiar classificatory value, and 
whose resemblances and differences of number, form, and 
succession, taken as a whole, are usually regarded as more 
trustworthy indicators of affinity than any others. 
Man is provided with two sets of teeth—milk teeth and 
permanent teeth. The former consist of four incisors, or 
cutting teeth ; two canines, or eye-teeth ; and four molars, or 
grinders, in each jaw, making twenty in all. The latter 
(Fig. 18) comprise four incisors, two canines, four small 
grinders, called premolars or false molars, and six large 
grinders, or true molars in each jaw—making thirty-two in 
all. The internal incisors are larger than the external pair, 
in the upper jaw, smaller than the external pair, in the lower 
jaw. -The crowns of the upper molars exhibit four cusps, or 
blunt-pointed elevations, and a ridge crosses the crown ob- 
liquely, from the inner, anterior, cusp to the outer, posterior 
cusp (Fig. 18 m2). The anterior lower molars have five cusps, 
three external and two internal. The premolars have two 
cusps, one internal and one external, of which the outer is 
the higher. 
In all these respects the dentition of the Gorilla may be 
described in the same terms as that of Man; but in other 
matters it exhibits many and important differences (Fig. 18). 
Thus the teeth of man constitute a regular and even 
series—without any break and without any marked projec- 
tion of one tooth above the level of the rest ; a peculiarity 
which, as Cuvier long ago showed, is shared by no other 
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