[Sexes separately. M. 350; F. 360 mandibles]
Column Headings
A:
B:
----------+-----------------+--------------+--------------+--------------
|None or | Slight to | |
|indistinguishable| moderate | Medium | Pronounced
----------+--------+--------+------+-------+------+-------+------+-------
| Males |Females | Males|Females| Males|Females| Males|Females
----------+--------+--------+------+-------+------+-------+------+-------
Specimens | 71 | 144 |193 | 163 | 67 | 47 | 19 | 6
Per cent | 20.3 | 40.0 | 55.1 | 45.3 | 19.1 | 13.1 | 5.4 | 1.7
----------+--------+--------+------+-------+------+-------+------+-------
The significance of these hyperostoses is not yet quite clear.
Danielli, who in 1884 reported them[171] in the Ostiaks, Lapps,
a Kirghiz, a Peruvian Indian, and four white skulls, offered no
explanation. For Søren Hansen,[172] who first suggested the resemblance
of these formations to the torus palatinus, "the significance of
this feature, which also occurs in other Arctic races not directly
related to the Eskimos, is not clear." R. Virchow,[173] who reports
"wulstigen und knolligen Hyperostosen" on both the upper and lower jaws
of a Vancouver Island Indian, restricts himself to a brief mention
of the condition with a suggestion as to its causation (see later).
Welcker[174] found them in the skulls of a German (Schiller?), Lett,
and a Chinese, but has nothing to say as to their meaning. Duckworth
and Pain[175] report the "thickening" in 10 out of 32 Eskimo jaws, but
do not discuss the causation; and the same applies to Oetteking,[176]
who reported on a series of Eskimo from Labrador. In 1909
Gorjanovič-Kramberger[177] somewhat indirectly notes the condition,
without a true appreciation of its meaning.
In 1910 I had the opportunity to report on the mandibular hyperostoses
in a rare collection of crania and lower jaws of the central and Smith
Sound Eskimo.[178] Of 25 lower jaws of adults and 5 of children, 18,
or 72 per cent, of the former and 2 of the latter showed distinct to
marked lingual hyperostoses, while in the remaining cases the feature
was either doubtful (absorption of the alveolar process) or absent. Two
of the five children showed the peculiarity in a well-marked degree. A
critical consideration of the condition leads me to the conclusion that
it is not pathological, and my remarks were worded (p. 211) as follows:
"A marked and general feature is a pronounced bony reinforcement of
the alveolar arch extending above the mylohyoid line from the canines
or first bicuspids to or near the last molars. This physiological
hyperostosis presents more or less irregular surface and is undoubtedly
of functional origin, the result of extraordinary pressure along the
line of teeth most concerned in chewing; yet its occurrence in infant
skulls indicates that at least to some extent the feature is already
hereditary in these Eskimo."
In 1912, Kajava[179] reported lingual hyperostotic thickenings on the
lower jaws of 68 adult Lapps, and found the condition in frequent
association with pronounced wear of the teeth. In 1915, finally, Fürst
and C.C. Hansen, in their great volume on "Crania Groenlandica,"
approach this question much more thoroughly. They, as also Kajava,
did not know of the writer's report of 1910. They found the "torus"
(p. 181), "also in the mandibles of some various Siberian races in a
not insignificant percentage * * * and also not infrequently among
European races, especially in the Laplanders (30 to 35 per cent)."
They also report the presence of the condition "in a Chinaman," and
saw indications of a good development of it in 17 per cent of 164
middle ages to prehistoric, and in 12 per cent of later Scandinavian
lower jaws. Their interesting comments on its possible causation,
though at one point seemingly not harmonizing, are as follows (p.
180): "The possibility is not precluded that we have here a formation
which, even though it has at first arisen and been acquired through
mechanical causes, has in the end become a racial character, albeit a
variable one." And page 181: "There seems to be no doubt whatever that
it is a formation connected with Arctic races or Arctic conditions of
life; and, accordingly, it can not safely be assumed to be a racial
character, however difficult it is to regard it as a formation only
acquired individually."
[Illustration: BUREAU OF AMERICAN ETHNOLOGY FORTY-SIXTH ANNUAL REPORT
PLATE 61
WESTERN ESKIMO AND ALEUT (MIDDLE) LOWER JAWS, SHOWING LINGUAL
HYPEROSTOSES. (U.S.N.M.)]
With both the previously published and the present data, I believe the
subject of these bony formations may now be approached with some hope
of definite conclusions.
These hyperostoses give no indication of being pathological. They are
formed largely, if not entirely, by compact bone tissues of evidently
normal construction. They never show a trace of attending inflammation
or of ulceration or of breaking down. They resemble occasionally the
osteomae of the vault of the skull, and more distantly the osteomae
of the auditory meatus, but in those cases where the bony swelling
is uniform and in many others they show to be of quite a different
category. (Pl. 61.)
As a rule these bony protuberances in the Eskimo are not connected
with evidence of pyorrhoea, root abscesses, or any other pathological
condition of the teeth, for those conditions are practically absent
in the older Eskimo skulls; therefore they can not be ascribed to any
irritation due to such conditions, and the Eskimo have no habits that
could possibly be imagined as favoring, through mechanical irritation,
the development of these bony swellings. Wear of the teeth, which
has been thought to stand possibly in a causative relation to these
developments, is common in many races and even in animals (primates,
etc.), without being accompanied by any such formations.
The development of such overgrowths is not wholly limited, as already
indicated from the cases reported by Danielli (1884) and Virchow
(1889), to the lower jaw, but somewhat similar growths may also be
observed, though much more rarely, both lingually and on the outer
border of the alveolar process of the upper jaw in the molar region.
When present in the latter position they interfere with the measurement
of the external breadth of the dental arch.
But, if neither pathological themselves nor due to any pathological or
mechanical irritation, then these hyperostoses can only be, it would
seem, of a physiological, ontogenic nature; and if so, then they must
be brought about through a definite need and for a definite purpose or
function.
These views are supported by their marked symmetry, which is very
apparent even where they are irregular; by the fact that in general
they are not found in the weakest jaws (weak individuals), or again in
the largest and stoutest mandibles (jaws that are strong enough, as it
is); and by the history of their development.
Our rather extensive present data on children show that these
formations are absent in infancy. They begin to develop in older
childhood, in adolescence, or even during the earlier adult life; they
stop developing at different stages in different individuals, and they
never lead to any deformity of the body of the mandible.
These overgrowths are further seen to be more common and to more
frequently reach a pronounced development in the males than in the
females.
What is the effect of these hyperostoses? They strengthen the dental
arch. With them the arch is stronger; without them it would be weaker.
The view is therefore justified that they augment the effectiveness
of the dental arch; which is just what is needed or would be useful
in such people as the Eskimo where the demands on the jaws exceed in
general those in any other people.
All these appear to be facts of incontrovertible nature; but if so
then we are led to practically the same conclusion that I have reached
in the study of the central and Smith Sound Eskimo, which is that the
lingual mandibular hyperostoses are physiological formations, developed
in answer to the needs of the alveolar portions of the lower jaw. They
could be termed synergetic hyperostoses.
The process of the development of these strengthening deposits of
bone is probably still largely individual; yet the tendency toward
such developments appears to be already hereditary in the Eskimo, as
indicated by their beginning here and there in childhood. But their
absence in nearly one-third of the Eskimo mandibles, their marked
differences of occurrence and development in the two sexes, and their
occasional presence in the jaws of various other peoples, including
even the whites, speak against the notion of these hyperostoses being
as yet true racial features.
Taking everything into consideration, the writer is more than ever
convinced that the lingual hyperostoses of the normal lower (as well
as the upper) jaw, in the Eskimo as elsewhere, are physiological,
ontogenic developments, whose object and function is the strengthening
of the lower alveolar process in its lateral portions. Only when
excessively developed, which is very rare, they may, mechanically,
perhaps cause discomfort and thereby approach a pathological condition.