1042 
cavity to the gullet. The direction in which the masticatory muscles 
draw the lower jaw against the upper jaw, was in the Wadjak-Man 
from below and outside towards above and inside, in which direction 
the masticatory surfaces of the molars have been ground off against 
each other. For such a jaw is also frequently active alternately left 
and right, in which the half of the mandible which was first somewhat 
abduced when the mouth was opened — in such a way that the 
molar-crowns are directly above each other — is moved obliquely 
from below and outside towards above and inside. Thus between 
the bueeal crown-halves of the upper and lingual crown-halves of 
the lower molars, which have remained unworn for the greater part, 
and form two rows of cusps, pieces of meat and fish are stretched 
in such a way that when the jaws are firmly closed, particles are 
comparatively easily pinched off by the other crown-halves, which 
have been ground off against each other. 
The two sides can also act simultaneously, but 
then more crushing. In any case these jaws are 
almost as unsuited for grinding movement as those 
of the Carnivora among the Mammals. The con- 
verging direction of contraction of the masticatory 
muscles and in connection with this the formation 
of the chin in the type of Homo sapiens-wadjakensis is, therefore, 
to be explained by the more carnivorous masticatory apparatus of 
this type of Man. 
_ Vegetable food, however, on which the men of the type Homo 
neandertalensis-heidelbergensis cbiefly lived, like the Monkeys, is 
generally much poorer in nourishing substances, contains them at 
least in less concentrated condition, or else it is very hard. If suffi- 
cient quantities of nourishing substances were to be absorbed and 
digested, the masticatory apparatus had to be very active and the 
food had first to be ground very fine. This took place through - 
grinding mastication, in which the food was continually pushed 
automatically by the tongue and the not masticating side of the 
lower jaw — the grinding movement is chiefly alternately one-sided — 
under the masticating teeth of the upper jaw of the other side 
(which takes place on opening the mouth in the other type of 
jaws and teeth). The direction of the movement of the lower jaw, 
determined by the direction of contraction of the muscles of masti- 
cation, had therefore to be from below and inside to above and 
outside. And the directions of muscular contraction of the two sides 
thus diverging in this diluvial type of Man, as in the Monkeys, led 
to the formation of a torus mentalis internus, in the latter besides 
