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THE DENTAL RIDGE AND DENTAL GROOVE. 61

formations, but form a reticulum and have a stellate appearance
when seen in section.
While the change in form of the central cells of the enamel organ is
tiiking place, the dentin germ is assuming the form of the future tooth-
point. From the base of the dentin germ, connective tissue is being

Section of jaw, embryo of pig, showing fU i(i. lary molar tooth : 1, enamel organ ;
I, dentin germ.

formed around the enamel organ, like the outer walls of a bag, this
laver beino; the wall of the dental sacculus ; and when the enamel
organ is nearly enclosed, the epithelial cord that connects it with the
INIalpighian layer breaks up into epithelial clusters ; some of which
wander toward the INIalpighian layer, while others cluster to the wall
of the sacculus, where it is supposed they become absorbed. In their
origin the sacculus and dentin germ are identical, springing as they do
from the embryonic connective tissue.
At this time there is no evidence of a basement membrane. When
the enamel organ and dentin germ become enclosed in the sacculus, it
and its contents become the dental follicle, at which period calcifica-
tion is about to commence.