Review of Dental Literature and Art. [Volume: 2, Issue: 6, January, 1861, pp. 334-344]

342

THE DENTAL COSMOS.

single. In the Gorilla, the opening is placed a little nearer the lower
than the upper border of the mandible. The outer walls of the incisor
and canine alveoli are slightly protuberant, as is also that occupied by
the anterior root of the first premolar; corresponding depressions mark
the interspaces. The external surface of the horizontal ramus is flat, but
becomes slightly convex near the lower border; along the outer margin
of the molar sockets is a thin ridge of bone, and beneath it a shallow
longitudinal depression; but the external oblique ridge is absent in the
Gorilla, and although there is a slight protuberance below the outer
anterior commencement of the vertical ramus, the degree of elevation is
less than in the human subject. The vertical extent of the horizontal
ramus, instead of diminishing as it approaches the ascending portion of
the bone, increases in the Gorilla. The vertical ramus commences anteriorly, as in Man, by two ridges; the outer one forms a platform of bone,
which extends outward beyond the last molar alveolus: the strong inner
ridge commences from behind that socket, but in its upward course it presents an angular deflection, which is not present in Man; this ridge joins
the outer one after it has formed the anterior boundary of the well-marked
crotaphite fossa. The anterior border of the ascending ramus is vertical
for two-thirds of its extent; it then gently curves backward, so that the
point of the coronoid process is considerably posterior to the fore part of
the base of the ramus-not on the same vertical line with it, as in Man.
The concavity dividing the coracoid from the condyloid process is proportionately deeper than in Man. The inner end of the articulating condyle
is the larger; it also differs from human structure in the want of definition in the posterior portion of the articulating surface, which is insensibly
lost on the neck of the process. The angle of the jaw may be said to be
absent in the Gorilla; for the lower border of the horizontal ramus passes,
by a regular convex curve, into the posterior border of the ascending.
On the inner surface of the latter are four or five tuberosities, with intermediate depressions for the attachment of the pterygoid. The internal
surface of the symphysis is marked in its lower fourth by a rough, oval,
shallow depression, divided by a median vertical ridge, which terminates
below in a broad transverse ridge extending backward, and limiting the
extent of the bone in this direction. In one jaw of an aged Gorilla we
have had an opportunity of examining this ridge was produced backward,
in the form of a large triangular process. The spinae mentales on the inner
surface of the symphysis are absent in the Gorilla. The inner surface of
the horizontal ramus is smooth; it is not abruptly overhung by the inner
margin of the molar alveoli; as in Man, neither does it exhibit the internal oblique ridge which is so characteristic of human structure-a slightly
roughened longitudinal tract beneath the last two molar sockets takes its
place in the jaw under consideration. The inner surface of the ascending
ramus commences by a sudden but slight sinking of the surface. It is
divided into two portions by a ridge which leads from the anterior internal ridge before described to the condyle; the upper and smaller surface
is deeply depressed for the insertion of the great crotaphite muscle, (crotaphite fossa;) the lower presents about the middle of the ramus the
opening of the dental canal. This is smaller than in Man, and its internal margin is not produced backward. We have already alluded to the
more numerous projections for the insertion of the pterygoid muscle on
the inner surface of the posterior boundary of the ascending ramus in the
mandible of the Gorilla."
(To be continued.)