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OF THE OSSIFICATION OF A TOOTH, ETC. 131
one point only; the Bicuspis by two, one external, which is the
first and the highest, and the other internal. The Molares.

its inner surface a layer of epithelium. The two layers of epithelium,
that of the pulp and that of the capsule, are in contact, and together
form, according to Huxley, the so-called enamel organ.) The basement
membrane of the pulp is identical with Nasmyth's "persistent mem-
brane," and with the membrana prceformativa. The dentine is formed
beneath the basement membrane between it and the pulp. He holds
thai the dentine is deposited in the pulp, but that no histological element
of the pulp takes part in its formation. (1)
According to Robin and Magitot, the tissue of the mass of the dental
bulb or pulp is composed of ovoid nuclei sprinkled in great number
through a slightly granular transparent homogeneous substance, and
which are at a later period accompanied by laminated fibres, vessels, and
nerves. These nuclei are analogous to embryo-plastic elements, but
differ from them in several particulars, especially in having no nucleoli.
The nuclei are generally disposed parallelly to each other, and their
longest diameter is usually parallel to the vertical axis of the bulb. At
the heart of the pulp and in the neighbourhood of the base near the
point of continuity with the follicular wall, a certain number of nuclei
become developed into fusiform or star-like fibroplastic bodies, and
eventually into laminated fibres. The amorphous matter which occu-
pies the intervals between the nuclei, extends on the surface of the
bulb about the T l^ of a millimetre beyond the most superficial nuclei.
Before the cells of the dentine originate the surface of this bed of
amorphous matter becomes denser. (This denser layer is the mem-
brana prseformativa of Easchkow. It folds easily and is readily
detached.) The whole bed of superficial amorphous matter ceases to
exist at the point of juncture between the base of the bulb and the
follicular wall. It is pale, very transparent, and destitute alike of
nuclei and molecular granulation. In the depth of this bed the cells
of the dentine originate, beneath that denser superficial layer (mem-
brana prseformativa, Easchkow) which is capable of detachment, and
which continues until the time when the cells change into the con-
dition of ivory. These observers believe that the dentinal cells ori-
ginating in the superficial bed of amorphous matter, grow by indi-
vidual genesis, and are not the product of any other organ. They
are oblong, nucleated, disposed in rows parallel to each other, and in
consequence of their relative approximation, they assume a prismatic
form, with four, five, or six sides. The}- are connected by their central

(1) Vide Huxley on the Development of the Teeth. 'Microscopic Journal,'
1853, p. H9.