591. But a dense substance like enamel, acting with force against so hard a substance as bone, would produce a jar which, propagated along the bones of the face and skull to the brain, would severely injure that tender organ, and effectually interfere with the comfort of eating.
592. This evil is guarded against,
1. By the structure of the alveoli (fig. [CLXII].), which are composed not of dense and compact, but of loose and spongy bone (fig. [CLXII].). This cancellated arrangement of the osseous fibres is admirably adapted for absorbing vibrations and preventing their propagation (90).
2. By the membrane which lines the socket.
3. By the membrane which covers the root of the tooth; and,
4. By the gum.
View of the upper and lower teeth in the alveoli; the external alveolar plate being cut away to show the cancellated structure of the alveoli, and the articulation of the teeth.
These membranous substances, even more than the cancellated structure of the alveoli, absorb vibrations and counteract the communication of a shock to the bones of the face and head when the teeth act forcibly on hard materials; so many and such nice adjustments go to secure enjoyment, nay to prevent exquisite pain, in the simple operation of bringing the teeth into contact in the act of eating.