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DENTAL RIDGE. 625

elements thus described are immersed in a translucid amorphous mass
coagulable in acids and having the consistence and appearance of the
white of an egg. These starred bodies—or stellate cells, as they are
usually termed—are formed directly at the expense of the polygonal
elements composing the internal mass of the enamel organ. The pro-
cess is as follows : The substance mentioned above interposes itself
little by little between these originally small polyhedral cells, and thus
their walls lose their mutual contact except at certain points where they
still cohere. As a direct result of this phenomenon the primitive polyg-
onal cells exhibit a number of depressions extending from their exterior
surface toward the centre, giving them their stellate appearance. From
this transformation the primitive cells would become entirely insulated
by the intervention of this new mucous formation were it not for these
connecting processes, which give to this organ, as a whole, its peculiar
reticulated appearance and to each cell its stellate form. It is a remark-
able fact that no line of juncture can be discovered where these cells
are connected with each other, the various reagents failing to disclose
the least trace of it, so effectually have these parts been cemented
together. According to this theory, the stellate arrangement of the
' pulp ' of the enamel organ (the intimate composition of which we do
not propose to describe in this memoir) results from a mmple viodifica-
tion of the form of the primitive polygonal cells—a change which they
have undergone passively, as it were. These elements of the enamel
organ, notwithstanding their stellate form, must be regarded, therefore,
as absohiteli/ epithelial in their nature. The mechanism of this trans-
formation, however, differs materially from that given by Kolliker, and
after him bv several other anatomists, who contend that these prim-
itive cells might take this stellate form spontaneously. Our opinion,
however, is in conformity with that of Walcleyer, who was the first to
properly examine and describe this phenomenon, though Huxley at a
much earlier day had advanced the idea (hypothetically, it is true) that
the enamel organ had an epithelial origin ; but he did not indicate
the mode whereby the transformation of its elements was affected."
The stratum intermedium of Hanover consists of those cells which
lie nearest the infant layer of tlie inner tunic. They have not become
stellate, as have the cells found nearer the central portion of the enamel
organ. They are younger than are the stellate cells. They have no
particular signification other than that which we assigned to them" when
discussing the formation of the cuticula dentis. Nearer the central por-
tion of the enamel organ a more marked reticulation is seen in most
specimens.
The vacuoled appearance of the interior of the enamel organs begins
in the central portion in the oldest layer of cells ; the cells which lie
nearest the infant layer are the last to become affected. The change
does not occur uniformly, but in places here and there. This is shown
very nicely in the accompanying figure (354). The part from which
the cut was taken comprises that portion, including the inner tunic and
the overlving cells, situated immediately above the apex of the dentinal
papilla. The infant cells of the inner tunic are of the character before
described, no attempt having as yet been made upon the part of Nature
Vol. I.—40.