214 ~~ ~Proceedings of the Royal Physical Society. 
but also because they are more closely pa together, especially towards 
the front. 
In man the symphysis is short, and is not carried far back behind the 
incisor teeth, the curve of the front of the symphysis is concave except in the 
single case of the Heidleberg jaw. A vertical section, through the symphysis, 
shows an unmistakable difference between the jaw of every variety of human 
being and that of any ape. This difference in the symphysis is accompanied - 
by a difference in the lower border of the body, in the human jaw it is rounded 
and in line generally with the upper part of the bone and the alveolar border. 
In the ape jaw, e.g. the chimpanzee, the lower border curves inwards towards 
the floor of the mouth, and forms a wide flange. 
Correlation of Jaw and Skull.—The size and the form of the lower j jaw 
stand in intimate correlation with the upper jaw, and through it with the 
whole skeleton of the face, and it in turn is correlated with the shape and 
form of the cranium. The length of the palate is, ¢g., correlated with the 
length of the skull. There is a further correlation, in that the width between 
the condyles of the mandible is that between the glenoid fossz, which 
corresponds with the width of the skull. There is also a muscular correlation, 
since the muscles of mastication are attached at one end to the skull, and at 
the other to the jaw, and hence the strength or the weakness of such muscles 
will be shown at each attachment. A muscle with a large area of origin must 
have a correspondingly powerful insertion. | 
Comparison of the human jaw and skull with that of the ape shows that 
with the ape’s long jaw there is of necessity a long palate. The implied 
maxillary protrusion causes an obliquity of the anterior opening of the nose, 
and thus the nasal bones do not project forwards, but lie comparatively flat. 
The further correlations of jaw and skull in the associated changes in the 
basi cranial axis, in the position of the foramen magnum, the characters 
of the mastoid processes, and such like, are morphological features well 
established, but not demanding further elaboration here. 
In the half mandible of the Piltdown find, we find a reproduction of all 
the features of the chimpanzee jaw which are usually considered distinctive ; 
in its absolute measurements as well as in its proportions there is a similarity. 
The injury which the jaw has sustained has obliterated the more obvious ~ 
features. To quote Mr Miller, “ Deliberate malice could hardly have been 
more successful than the hazard of deposition in so breaking the fossils, as — 
to give free scope to individual judgment in fitting the parts together,” but 
the jaw fragment in its size, proportions, and in its structural characters 
displays features which render it indistinguishable from the jaw of a 
chimpanzee. One, therefore, believes that it must have articulated with a — 
