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130 HUNTER ON THE TEETH.
it is generally by three points, the middle one being the highest,
and the first that begins to ossify. The Guspidatus begins by

other underneath them, so that the designation of the layer of cells in
question as the dentinal membrane, membrana eboris, appears to he
warranted, especially as these cells really yield the dentine. The inner
parts of the pulp consist throughout of a mure granular or homogeneous,
but subsequently more fibrous matrix, with numerous cell nuclei of a
roundish or elongated form, which is to be regarded as a kind of
connective tissue. At the period of ossification, vessels are developed in
large numbers in the pulp, and the most numerous, perpendicularly dis-
posed loops of capillaries of about 0-006'" are found principally upon
the border of ossification. The nerves accompany the vessels, but
are developed subsequently to them. Their number is likewise very
considerable, and their distribution in the pulp similar to that in the
fully developed teeth." (1) It is only the outermost epithelial-like cell-
layer of the pulp, which is concerned in the formation of the dentine.
Kolliker believes that the whole of the pulp is not converted from with-
out inwards into dentinal cells and ossified, but that the pulp serves for
the formation of the dentine simply by supporting the vessels which are
necessary for the growth of the dentinal cells. Its decrease in the pro-
cess of ossification, he thinks, is owing to the gradual absorption of its
soft part, and not to its conversion into dentine. He holds that no other
tissue but the dentinal cells contributes to the formation of dentine, and
refers to some observations of Lent as explanatory of the process of trans-
formation. In growing teeth which were macerated to disintegration in
hydrochloric acid, Lent succeeded in isolating the cells in question with
complete dentinal canals prolonged from them. A previous observation
of Kolliker's had also partly led him to form the opinion that the den-
tinal cells became prolonged into the dentinal canals. He therefore con-
cludes with Lent
: 1. That " the dentinal canals are direct processes of the
whole dentinal cells, which processes may send out subordinate branches
and anastomose by means of them. To all appearance a single cell
seems in many cases to be sufficient to forni an entire dentinal canal, or
at least a very large part of one." 2. That " the matrix of the dentine is
not formed of the dentine cells, but is a secretion of these cells and of the
tooth pulp ; in other words, an intercellular substance." (2)
Professor Huxley believes that the tooth pulp is a dermic process
bounded by a basement membrane having on its outer surface a layer of
epithelium. (He also regards the follicular wall or capsule as an invo-
lution of the derm, which is lined with a basement membrane, having on

(1) Kolliker, op. cit., p. 303-304.
(2) Kolliker, op. cit., p. 307.