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70 EMBRYOLOGY OF THE DENTAL TISSUES.
have bc't'ii spoken of in describing' the growth oi" tiie temporary enamel
organ. Dr. 8udduth says that as a rnh; the cords ibr the permanent
molars arise directly from the epithelium of the mouth, that is, the
Malpighian layer. Other authorities state that the first permanent molar
only is from the Malpighian layer, as is the enamel organ of the tem-
porary tooth. Bodecker is the author of the statement that all the
permanent molar teeth are an offspring of the enamel organs of the
second temporary molar tooth. The enamel organ of the second per-
manent molar is an outgrowth from the first permanent molar ; the
enamel organ of the third permanent molar being an outgrowth from
that of the second. Von Brunn holds that the primary function of
the enamel organ is that of determining the form of the future tooth.
He goes so far as to assert that its calcification into enamel in some
animals is a secondary function taken on later. In support of this
o])inion, he says that enamel organs are universal, even where no
enamel is found. He holds that wherever dentin is to be found, there
is an antecedent " form-building" investment of enamel organ.

The Dentinal Papilla.
The dentinal papilla, or, preferably, the dentin germ, has its
origin in the embryonic connective tissue of the jaw. Sometime about
the second month of foetal life, as the enamel organ of the first-forming
teeth assumes its flask-like shape, and the cells within its central portion
are seen to be differentiating, just under it is noticed an area of dense
tissue, in shape somewhat like a crescent. It is distinctly outlined by
its dense and active cell-multiplication. This is the first indication of
the commencing growth of the dentin germ. As the enamel organ
enlarges, and assumes the shape of a surrounding cap, a papilla-like
growth takes place coincidently with it. About the ninth week it
assumes the pointed form of the future incisor. With these changes the
outer layer of the connective-tissue cells next the enamel cells will be
found to have changed their form, and to have assumed a very distinct
columnar appearance, forming a layer somewhat like the enamel cells,
but broader. This layer has been falsely called a membrane, " mem-
brana eboris" or membrane of the ivory. It is not a membrane, and
all recent authorities ignore it as such. If the tissue has been carefully
prepared, minute glistening bodies are seen, under the higher powers
of the microscope, within the substance of the germ. These are calco-
^pherites, and are seen everywhere near the odontoblastic layer in the
dentin germ, as well as in the enamel organ, near the enamel cells.
They are mostly minute globules. Some are larger than others, caused
undoubtedly by several merging together. They indicate that the