THE ALIMENTARY CANAL AND ITS APPENDAGES 157 
Mammals generally, but little specialised. The molars in parti- 
cular are comparatively simple cuspidate teeth, such as are found 
among the oldest Mammals. Judged from the form of their 
teeth, the Primates would appear to have branched off very 
early from the common Mammalian stem. If we can draw 
conclusions from the fossils as yet found, the Apes were not very 
widely distributed in earlier periods. They probably lived, as 
they now do, as climbing animals in tropical climates. In con- 
sequence partly of their frugivorous manner of life, and partly of 
the higher development of their intelligence, their teeth, of no 
great service for warfare in the struggle for existence, appear to 
have remained comparatively simple. 
The dentition of Man agrees with that of the Old World 
Apes in number and shape of the teeth. The dental formula is: 
eee Al. Ze 
ig OF P.M M5 = 32. The New World Apes, on the other 
hand, have one more premolar in each set, their formula being 
Zak..3.-d 
Del, 33 
the nearly related Anthropoids, it is found that their respective 
milk teeth agree in form and size more nearly than do their 
permanent or successional dentitions. In the Anthropoids [with 
the exception of the Gibbon (Hylobates)| the teeth of the second 
series are larger and stronger than in Man, the contrast being 
most marked in the size of the canines. The latter serve, in the 
Ape, as powerful weapons in the struggle for existence,’ and the 
premolars of the Apes are also, in consequence of the greater 
development of their outer cusps, more caniniform than in Man. 
The molars, on the contrary, are remarkably similar throughout, 
although they are larger in Anthropoids than in Man; and in 
Aylobates, both in form and size, they can hardly be distinguished 
from those of the human subject. 
[Since, among Mammals generally], the milk teeth, 7.e. those 
= 36. If the teeth of Man are compared with those of 
1 We have abundant evidence that teeth were once used by Man or by his 
ancestors as weapons of defence ; traces of such a use have not altogether disappeared 
in human beings of the present day, and I cannot refrain from quoting in this connec- 
tion a comment of Darwin which occurs in his book on the Origin of Man. 
‘“He who rejects with scorn the belief that the shape of his own canines, and 
their occasional great development in other men, are due to our early forefathers 
having been provided with these formidable weapons, will probably reveal by sneer- 
ing the line of his descent. For though he no longer intends, nor has the power, to 
use these teeth as weapons, he will unconsciously retract his ‘snarling muscles’ (thus 
named by Sir C. Bell) so as to expose them ready for action, like a dog prepared 
to fight.” 
