Page 87 - My FlipBook

CALCIFICATION. 85

process of calcification in the enamel has begun, will show, between
the enamel cells and the formed enamel, a thin layer which has been
called, by earlier investigators, the membrana prceformativa. It was
misunderstood then : it is not a membrane. It is the latest deposition
of enamel from the enamel cells, composed of globules or masses of
calco-globulin ; and around these globules there seems to be a fibrous
network. Connecting with this fibrous network, and running to the
formed enamel beneath, are innumerable thread-like processes, in ap-
pearance like fibers. There are indications of fibers which have been
broken on the upper portion of thi^ thin layer ; these appear as
though they had been broken otf in the separation of the layer from
the enamel cells. In a longitudinal section of the tooth of a calf at
birth, when the recently formed layer of enamel is still in contact with
the fully calcified enamel, this younger portion may be teased oif,
exposing to view what appear to be fibrils standing out from the sur-
face. These have apparently been drawn out from the only partially
calcified new tissue. In other sections this appearance is more marked.
Thty may appear so large that it is probable they have been enlarged
either by the action of reagents or by calcific matter clinging to a
fiber, if one is there, and tliey are undoubtedly partially calcified.
They are very much coarser than the fine fibrils seen between the
enamel cells. Deeper within, these processes are seen to surround the
globules or masses which have been deposited by the enamel cells, and
which are forming the rods. In other sections from the tooth of the calf
the younger layer of forming enamel shows a network of fibers ; they
are surrounding the recent deposition of globules. It is only in this
layer that this appearance is clearly shown ; this network in more
fully formed enamel cannot be seen, yet a distinct network is always
visible in the layer first deposited. It is probable that these pro-
cesses have their origin among the cells of the stratum intermedium ;
that they pass either within or between the enamel cells, and thus on,
to form a very fine fibrous substructure, throughout which are deposited
the globules which are to form the future enamel rods. When the cal-
cification of the rod is complete, the calcium salts have been so densely
deposited as to entirely obscure the appearance of any fiber.
To sum u]) : there probably exists in developing enamel, as has
already been found in developing bone and dentin, a fibrous sub-
structure on and throughout which the enamel globules are deposited.
After the enamel is wholly formed, this structure seems to be wholly
blotted out in the dense calcification of the tissue (Figs. 73, 74). In
sections of completely formed enamel the writer has been unable to
trace it, although the methods of those who claim to have seen it
have been faithfully followed. In regard to a protoplasmic reticulum