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656. DENTAL EMBRYOLOGY AND HISTOLOGY.

stellate layer of cells, which may be seen lying underneath and con-
nected with the odontoblastic layers.
I am unable to make any statement regarding the termination of the
nerves of the pulp. I am very skeptical regarding their having any
direct connection with the fibrils of the odontoblasts, and have never
been able to demonstrate any such relationship. Tlien, again, as no
nerves can be demonstrated until after calcification has progressed to
a very considerable extent, the proof is conclusive that they are not an
essential element to the process. I am more inclined to the view held
by Magitot—that the terminal fibrils unite with the odontoblasts, and
that sensation is thus transmitted by the dentinal fibrils to the terminal
branches of the nerves. As there exists a very considerable degree of
ignorance regarding the termination of nerves in other parts of the
body where the conditions are favorable for their demonstration, I do
not think it strange that we should be unable to state authoritatively
just how they terminate in the pulp, seeing that the technique for their
demonstration in that organ is so difficult.
The calcification of the crown being completed and the time for erup-
tion having arrived, the process of eruption begins as the tooth makes
its appearance above the gum. The root is gradually developed; the
jaw is also growing rapidly and gives a firmer setting for the erupting
tooth. The attachment of the tooth to the jaw is fibrous in character
and surrounds the root as a membrane, being united to the root on one
side by many fine prolongations, which penetrate and anastomose with
the processes of the bone-cells which occupy the lacunae of the cemen-
tum. A similar attachment exists with the alveolar wall upon the
outer periphery. The development of the cement, as we have seen
when discussing that subject, is accomplished in a manner identical with
subperiosteal formation of bone. The formative membrane remains as
the pericementum and persistent cement organ. The deposits of sec-
ondary cement known as exostoses are due to this membrane. The pro-
cess of calcification is not always a continuous, harmonious effi^rt upon
the part of Nature, but is subject to many interruptions ; these leave
their indications upon the cement, enamel, and dentine. Interglobular
spaces are seen in both dentine and enamel. These ^ve have discussed
to a considerable extent. The pits seen upon the surface of the enamel
are no doubt, in some instances, caused by these spaces. The serrations
seen upon the edges of newly-erupted teeth—so long known as '' Hutch-
inson teeth"—have now pretty generally come to be attributed not alto-
gether to congenital syphilis, but to lack of nourishment or inherited
conditions which may be other than sy]>hilitic.
Besides the markings seen upon the individual prisms, there are other
lines which run transversely across the prisms. These have been called
the "broken strise of Retzius." The lines of stratification have a more
or less decided brownish tint, but just what gives rise to the appearance
I am unable to conjecture. It is held by some to be the result of an
arrest in the process of calcification, each line marking such a period;
others hold that it is due to the varying character of food taken by the
mother during gestation, some being rich in lime salts of one kind,
while another salt predominates in another kind of food. If this is the