the ear recede more towards the back of the head. To make room
for the full set of teeth, the jaws are also elongated. It is by the
growth of the teeth, and of those processes of the jaw-bone which
are necessary to support and fix them, that the face is deepened,
or made longer; and by the lengthening of the jaw, and particularly
the receding of the angle of the lower jaw, a manly squareness is
given to the chin, instead of the fulness and roundness of the child.
In attending to the forms of the lower jaw-bone, we may observe
several peculiarities distinguishing the face in different ages.
The cause of the smallness and roundness of a child’s face is
apparent, from the little projection of the point of the jaw at the
chin, and from the obtuseness of the angle behind. In the adult
we observe a greater depth in the body of the jaw-bone, and the
teeth béing added, the base of the jaws must necessarily be more
separated, and of course the face lengthened. We see further, that
as the teeth shoot up in succession backwards, the jaw must be
lengthened to accommodate them; the chin therefore projects,
while the angle of the jaw recedes as in the first outline. Lastly,
when the teeth fall out, in old age, the processes (or alveoli as they
are called) which grew up with them and supported them, waste
away; and there remains nothing but the narrow base of the jaw,
while the length of bone from the hinge of the jaw to the angla
is undiminished. The effect is perceived in the second outline of
the last page, where the teeth of the lower jaw are lost. The jaws
are allowed to approach nearer to each other at the fore part; the
angle comes of course more forward, and resembles that of the
child, were it not that the chin projects; the teeth and adventitious
part of the jaws being gone, the chin and nose approach, and
the mouth is too small for the tongue, the lips fall in, and the
speech is inarticulate.