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PEEIDEyTAL MEMBRA NE. 139

attached at their other extremity to the bone, cementum, or fibrous
tissue.
To arrive at an understanding of the arrangement of the fibers of
the peridental membrane, they must be studied in both longitudinal and
transverse sections. In longitudinal sections of the membrane, in the
gingival portion (Fig. 120), the fibers springing from the cementum at
the gingival line pass out for a short distance at right angles to the
long axis of the tooth and then bend sharply to the occlusal,^ passing

Fig. 121.

Transverse section of the peridental menihrane in tlio giny^ival portion (from sheep): K. epi-
theliuui ; /'fibrous tissue of gum ; B, point where peridental membrane fibers are lost in fibrous
mat of the gum ; P, pulp ; F', fibers extending from tooth to tooth. (About 30 X.)
into the gingivus to support it and hold it closely against the neck of
the tooth. These fibers are most numerous on the lingual side, where
food is brouo;ht against the giufjivus with force in mastication and tends
to crush it down. In the middle of the gingival portion the fibers pass
out at right angles to the axis and are blended with the fibrous mat of
the gum on the labial and Ungual sides, or are attached to the cementum
of the adjoining teeth on the approximal sides. A little farther from the
^ In describing the direction nnd inclination of peridental membrane fibers they are
always traced from the cementum to the bone, the angle with tlie horizontal plane being
formed at tlie surface of the cementum.