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DEVELOPMENT OF CORD FOB PERMANENT TEETH. 635
the temporary cords present certain buddings which gather themselves
into whorls of epithelial cells ; to these have been attributed the origin
of supernumerary teeth. I have no opinion to advance in the matter,
never having seen any developing enamel organs in such position as to
connect this supposed source with these abnormalities. The cord for the
permanent teeth arises, as a rule, from the lingual aspect of the tempo-
rary follicle or the cord for the same. With the severance of the tempo-
rary enamel organ from its cord, the cord for the permanent enamel organ
appears as a continuation of the former, and passes down upon the
lingual aspect of the temporary tooth. This is shown in the preced-
ing figure (358). The direct continuation of the temporary cord into
Fig. 359.

Vertical Transverse Section cm. Bovine Embryo (^C -oO) : ep, ei)ithelium il, infant layer ; cp, cord of
;
permanent tooth, still united at c with outer tunic (o/) of temporary tooth; it, inner tunic; nl,
older layer of cells, known as stratum intermedium; , dental papilla; reticulum.
the permanent is nicely shown in the accompanying cut from a 9 cm,
bovine embryo, where the connection is not yet entirely severed between
the cord and the temporary tooth-follicle.
The time for the origin of the cord for the permanent teeth varies
considerably. In the human embryo the cord for the jiermanent cen-
tral incisor first makes its appearance about the fifth month. In the
porcine and bovine embryos the cords for the permanent central incisors
arise when the fcetus has attained about 8 cm. in length. Those of the
premolars in porcine embryos arise as we have seen in the 1 cm. fcetus
(Fig, 358). The length of the cords for the permanent teeth varies
noticeably in different sjiecies and in different teeth of the same species.
The course of the cords for the permanent teeth also assumes a more
spiral direction than do the cords for the temporary teeth. I have
never been able to satisfy myself as to the special signification, if any,