Page 134 - My FlipBook

118 HUNTER ON THE TEETH.
are the most complete. About this age, too, the ossifications

which it is about to originate becomes more opaque and vascular than
the surrounding gelatiniform tissue. In the middle of the vascu-
larity, which depends on a network of capillaries, a small, obscure,
roundish mass appears. This is the bulb. When the bulb reaches a
certain size, a dark, greyish band is formed round it. This represents
the follicular wall. This band, after circumscribing the bulb, becomes
raised above it, and eventually its free edge unites with itself, so as to
convert the follicle into a closed sac. The cavity of the sac is soon
divided into two equal parts, the upper of which is occupied by the
organ of the enamel, which is formed immediately on the occlusion of
the follicle—the lower by the bulb. At this time the bulb is in con-
tinuity with the surrounding tissue at its base, the rest of its periphery
although immediately contiguous to the surrounding tissue, is easily de-
tached, and has a smooth and very clearly denned surface. The bulb,
from the time of its appearance, is formed of finely-granulated ovoid
nuclei, separated from each other by a small quantity of granulated
amorphous matter. At the time of its origin, the bulb of the incisor, or
canine, is shaped like a cone, or more or less elliptical ; that of the
molar is blunt, more bulged, and broader at the base. The appearance
of the follicular wall is accompanied by an increase of vascularity. The
wall itself is traversed from its base to its summit by a capillary net-
work, having regular polygonal meshes. The vessels and nerves of the
bulbs are not developed until a little later, but always before the moment
of the appearance of the first cells of origin of the dentine. The organ
of the enamel has the appearance of a clear, transparent mass, situated
between the inner surface of the wall and the progressing part of the
bulb. It has no continuity of substance with the wall—it is only in
contact with the surface of the bulb, from which a pale, white line septa-
rates it shortly after its appearance. This line consists of a continuous
range of the cells of the enamel. As the follicle progresses, its wall
becomes better marked, until it forms quite a resisting envelope, corn-
pletely distinct from the neighbouring tissues. The base of the bulb,
which is at first its broadest or almost its broadest part, becomes after-
wards constricted and lengthened out to form the radicular portion of
the bulb, which receives the vessels and nerves. The bulb at first consists
only of ovoid or rounded nuclei with a little intervening amorphous
matter. These nuclei are less transparent than the embryo-plastic nuclei.
The follicular wall includes some embryo-plastic nuclei, a little firmly-
granulated amorphous matter, and some laminated fibres, in the con-
dition ot fusiform bodies, or more completely developed. The organ of
the enamel is a thin, gelatiniform bed, composed of star-studded fibro-
plastic bodies, which are ramified and anastomosed. It soon exhibits, on
its deep or bulbular surface, the continuous range id' the cells of the
enamel. They are prismatic and vertically arranged, and when seen as