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OF THE FORMATION OF THE ENAMEL. 137
Capsula, where the Gum is joined to it, and its opposite surface
lies in contact with the basis of the above described Pulp, and

formed, is continued into the membrane prseformativa of the tooth-pulp.
Eolliker observes thai it we assume the correctness of these observa-
tions, the following seem to be the only admissable explanations of the
mode in which the enamel is formed.
1. "The enamel fibres are produced by a secretion of the cells of the
enamel membrane, which penetrates the membrana prceformativa in a
fluid condition, but hardens and ossifies beneath it.
Or 2. That "the enamel fibres are formed by the dentine from an
exudation furnished by the dentinal canals.'' This second supposition,
he adds, leaves the facts of the formation of regular fibres in the enamel,
and its growth in thickness by means of the apposition of new layers
upon its outer surface wholly unexplained. The former assumption
although more probable is also beset with difficulties. (1)
Robin and Magitot distinctly confirm the observations of Huxley and
Lent. They describe the organ of the enamel as consisting of fibro-
plastic bodies and of amorphous matter interposed between the fibro-
plastic bodies. The tissue of the organ of the enamel they assert is
absolutely without blood capillaries and nevous filaments. It is sur-
rounded on all sides by an epithelial layer, consisting of a continuous
single range of cells. On the bulb face of the organ these cells are pris-
matic (membranaadamantinoe, Raschkow) ; these cells, however, are not
transformed into enamel fibres, for the prismatic epithelial cells are
always separated from the enamel fibres by the pellicle styled the mem-
brana prseformativa. The prisms of the enamel, according to these
authors, originate by autogenesis at the surface of the ivory, and from
the first, have individually the density, form, consistency, and brittle-
ness which they always exhibit. " Their development is nothing more
than the molecular phenomenon of which their appearance is the result,
which, continuing to operate at the extremity opposite to the ivory,
causes their progressive elongation/' (2)
Mr. Tomes, however, has found reason to doubt the correctness of Pro-
fessor Huxley's observations. He asserts that proceeding in the mode
of examination adopted by Huxley and Lent, " No difficulty attended
the production of the membrane, but the columns of the enamel pulp
(i. e., the prismatic cells of the enamel membrane) were found at many
points adherent, and their continuity with the (enamel) fibres could be
distinctly traced. Again, the detached columns adhered in bundles to
each other by the ends which approached the enamel, and many of the

(1) Kolliker, op. tit. p. 304-6.
(2) Robin and Magitot, op.cit.