Page 528 - My FlipBook

538 DENTAL EMBRYOLOGY AND HISTOLOGY.
Ciliated cells are also found in the nasal passages of man, an illustra-
tion of which may be seen in Fig. 273.
The middle or older layer of cells of the buccal epithelia are more or
less polyhedral in shape, and have an imbricated border : they are some-
times called "prickle cells," and generally extend beyond the oral cavity
into the pharynx.
The deepest or infant layer of the epithelium of the mouth is com-
posed of spheroidal or slightly cylindrical cells placed vertically upon
the dividing-line between the epithelium and the dermal layers. It is
in this layer of the rete Malpighii that cell-multiplication occurs ; the
Fig. 279.

Articular Cartilage from Head of ^Metatarsal Bone of Man (osraic-acid preparation) : the cell-bodies
entirely fill the spaces in the matrix CilO dianieter.s) : a, group of two cells; 6, group of four cells;
h, protoplasm of cell, with ;/, fatty granules; >i, nucleus.
changes "whereby tiie cells undergo division appear first in the nucleus
(see Fig. 274, after Fleming, from Schaefer's Histology), afterward
extending to the cell-body in adult tissues.
The method of cell-growth in embryonal tissues will be considered
later on, in the section on the development of the mucous membrane of
the mouth.
Connective-tissue cells of the dermal layer of the mouth are of two
kinds, jxxed and imnderinfi cells. The first are fibrillated, and have a
definite relationship to the basement-substance, although varying in
form and number in different positions. The second are spheroidal,
and have been considered in our study of the white blood-corpuscles.
The fixed cells may have one or more processes, and when infiltrated
with fat, constitute fat-tissue.