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OF THE OSSIFICATION OF A TOOTH, ETC. 129
When the Tooth cuts the gum, this membrane likewise is per-
forated ; after which it begins to waste, and entirely gone by
the time the Tooth is fully formed, for the lower part of the
membrane continues to adhere to the neck of the Tooth, which
has now risen as high as the edge of the gum. (h)
OF THE OSSIFICATION OF A TOOTH UPON THE PULP.(/)
The beginning of the ossification upon the pulp is by one
point, or more, according to the kind of Tooth. In the Incisores

tissue, containing, in its interspaces a large quantity of fluid, rich in
albumen and mucus. Robin and Magitot describe minutely the change
in the enamel organ produced by putrefaction. They say that tin;
enamel organ acquires the condition of a viscous fluid, which ropes like
synovia, and is yellowish or reddish in colour. This matter consists of
a finely-granulated fluid, containing some cells of enamel, and star-
studded fibro-plastic bodies, with their fibrils broken off more or less
near the nuclei. (1)]
(h) [The upper part of the tooth-sac is firmly united with the gum, and
is spontaneously absorbed before the growing tooth. The remaining por-
tion becomes closely applied to the fangs, and is converted into the
dental periosteum.
(i) [Although since Hunter's time the microscope has been assiduously
used to explain the method in which the earthy and animal substance of
the tooth is deposited, the subject is confessedly so difficult that even at
present observers are anything but unanimous in the opinions they hold
as to the process. Kblliker describes the dental pulp as consisting of an
" inner part rich in vessels, and subsequently also in nerves, and of an
outer non-vascular portion. The latter is bounded by a delicate struc-
tureless membrane, the membrana prceformativa of Raschkow, which is
of no significance in the formation of the tooth ; and beneath the mem-
brane are cells, the dentinal cells, 0-016'" to 0-024'" long, and 0-002"' to
0-0045'" broad, with beautiful vesicular nuclei, and one or more distinct
nucleoli, which are placed close to one another, like an epithelium upon
the whole surface of the pulp ; they are not, however, so sharply limi-
ted internally as an epithelium, and there is at least apparently a
gradual transition by means of smaller cells between them and the
parenchyma of the pulp. Nevertheless, in more vascular tooth pulps, a
certain limitation arises from this, that the capillary loops of the vessels
do not pass in between the cylindrical cells, but terminate close to each

0) Kblliker, Op. ciL, p. 304. Robin and Magitot, Op. cit.