Page 129 - My FlipBook

OF THE FORMATION OF THE ALVEOLAR TROCESS. 113
chiefly in the outer plate of the bone, which occasions the con-
tracted orifices of the cells to be nearer the inner edge of the
Jaw. The reason, perhaps, why the bone shoots overj and
almost covers the Tooth, is that the Gum may be firmly sup-
ported before the Teeth have come through, (t)

originate. Those of the molars are, however, the only ones that
originate here, for the canal belongs only to the maxillary, and not to
the incisive bone, and because it is already separated from the groove in
front when the follicle of the canine makes its appearance." From the
third month, the posterior half of the groove, which was confounded
with the suborbital canal, becomes closed, and separates the dental
follicles placed at the level of the vessels and nerves." The external
and internal plates which bound the groove are thin, fragile, and slightly
undulated. The plates sink in a little opposite the intervals between
the dental follicles. About the beginning of the fourth month, the
rudiments of partitions begin to form as in the lower jaw, but they arc
produced from the bottom as well as the sides of the groove. " After
the seventh month, the partitions reach in height nearly but not quite
the level of the edges of the groove between the first molar and the
canine, as well as between the incisors ; the rest of the groove remains
undivided and common to the two molars. At this period, the nerve
and suborbital vessels, which start at first at the level of the line of
contact between the canine and the second incisor, show their orifice of
egress at the level of the rudimental partition interposed hetween the
first molar and the canine. That part of the upper maxillary, which
separates the canal of the bottom from the follicles is, at this time, only
in the condition of a thin osseous plate, not thicker at most than from
a quarter to half a millimetre, and perforated by one or two very small
orifices intended for the passage of the vessels destined for these
organs." (1) ]
(t) [Mr. Tomes, who has given a very minute and accurate description
of the changes which take place in the child's jaw from the time of birth
to the fifth year, states that the partial closure of the alveoli commences
between the second and third month after birth. He says that, when
the third month has been attained, " the alveoli exhibits a considerable
change in character, their depth has increased, and the free edges which
were before open, so that in a macerated preparation the teeth readily
fall out, are now turned inwards towards the median line of the alveolar
ridge, thereby contracting the orifices, and affording protection to the

(1) Robin and Magitot in the ' Journal de la Thysiologie de l'Honime et
des Animaux.' Edited by Dr. E. Brown-Sequard, 1860. Translated in the
' Dental Cosmos.'