The chief points that remain to be determined are the relation
of the dentinal pulp to the transitional cells between it
and the dentine ; the nature of the transition, | and the relation
of the Cells to the dentinal tubes and the intertubular tissue.
From the expression used by Purkinje and Raschkow in the
passage already quoted;—“ After a stratum of dental fibres
has been deposited between the parenchyme of the pulp and the
preformative membrane the same process is continued from the external
to the internal region, the pulp supplying the ma t e r i a l i t
may be inferred that they considered the formation of the dentine
to be a process of deposition from the formative surface of the
pulp, like' a secretion from a gland. If such were not the
idea of thele authors of the relation of the formative pulp to the
dentine they nowhere clearly express the contrary opinion, and
the; foriinftipn of the dentine by its deposition in successive strata
from The phlp continued to be taught in the best works on physiology
subsequently published. (1) 1
(1) Muller’s Physiology, by Baly, part i, 2nd ed. p. 429.
Mr. Beil who appears to have clearly recognized,, long before the publication of the
Thesis of Raschkow, the S preformative ’ or external membrane of the pulp, supposed that it was
persistent' and that it was the true formative organ of the dentine. (See Anatomy, Physiology and
Diseases^ the Teeth, 8vo. 1829). In his valuable edition of Hunter’s Natural History of the
Human T-eeth, in reference to Hunter’s statement that the teeth are formed from the pulp, Mr.
Bell observes: “ The statement that the bone of a tooth is produced from the pulp is erroneous.
This substance constitutes only the mould upon which the ossification is formed, between which
and theipulp is placed a membrane of extreme tenuity, which I have termed the proper membrane
of'the pulp. It is slightly attached to the surface of the pulp, which it completely covers,
and it is from the outer surface of this membrane that the bone is secreted. As the pulp recedes
on the deposit of the successive laminae of bone, the ossific membrane continues to cover it,
and ultimately forms the well-known membrane lining the internal cavity of the perfect tooth.”
—Bell’s * Hunter on the Teeth,’ 8vo. 1835, p. 38.
Dr. Schwann was the first to express his leaning to the ancient
doctrine that ‘ the dentine is the ossified pulp.’ But the nature of
the subjects selected by him for his observations left him in a state
of doubt and indecision on this point: and the author by whom
Dr. Schwann’s observations were communicated to the British Asso^-
ciation in August, 1839, although he adopted the doctrine of the
formation of ivory by the ossific transition of cells, rejected the idqa
that the dental substance was the ossified pulp, and declared ‘ the cels
of the ivory to be altogether a distinct formation.’(1)
In fact, the subjects chosen by both Dr. Schwann and his contradictor,
for the examination of the development of the dentine, were
inadequate to the exhibition of the relations of that substance to the'
formative pulp during any part of the process of its formation, ;
The shape of the teeth of the mammalia selected by them for examination
will not yield a view of the cap of new-formed ivory and the sub- |§
jacent pulp, in undisturbed connection, by transmitted light with the V
requisite magnifying power; and, if placed under the microscope as |
an opake object, the light is reflected from the cap of ivory, and displays
only the characters of its surface and not its relations to the |
surface of the pulp in contact with it. To examine this surface micrcf-
scopically in either a human tooth or that of any of our domestic
quadrupeds the cap of dentine must be removed, and the exposed sup-
face of the pulp and the corresponding surface of the dentine be
examined as opake objects by reflected light. Or, if the layer of the
dentine be thin enough to allow the transmission of sufficient light, it
must be removed from the subjacent pulp before it can be so examined.
(!) Report of the Papers read at the Medical Section of the British Association-at Birmingham,
Literary Gazette, Sept. 21, 1839, p. 598.