INCISORS OF OX.
Dentine. Enamel. Cement.
Phosphate of lime with a trace of fluate of lime 59.57 81.86 58.73
Carbonate of lime • . | 7.oo 9.33 7.22
Phosphate of magnesia . 0.99 1.20 0.99
Salts i 0.91 0.93 0.82
Chondrine . 30.71 6.66 31.31
Fat • • • . 0.82 0.02 0-93
100.00 100.00 100.00
CROCODILE.
Dentine. Cement* Phosphate of lime, with a trace of fluate of lime 53.69 53.39
Carbonate of lime 6.30 6.29
Phosphate of magnesia . 10.22 9.99
Salts • • • 1.34 1.42
Chondrine • • . 27.66 28.15
Fat . . 0.79 0.76
100.00 100.00
p i k e (Esox Lucius),
Large teeth of lower jaw.
Phosphate of lime with a trace of fluate of lime . . 63.98
Carbonate of lime . , 2.54
Phosphate of magnesia . . . . . 0.73
Salts . . . . . . . 0.97
Chondrine . . . . . . 30.60
Fat . . . . . . 1.18
100.00
The proportion of mineral or inorganic substance would seem
to vary, within certain limits, in different individuals of the same
species : thus in the molar teeth of one man Bibra found 79.00 of
inorganic matter, and in another 71.99; whilst Berzelius found
72.0. The proportion of inorganic matter in hard dentine will
depend in some degree upon the number of dentinal tubes, from the
areae of which the salts are in part excluded: thus in the modified
dentine (ivory) of the Elephant’s tusks, in which the tubuli are
more numerous, close-set, and extensively undulated, in a given
space, than in ordinary dentine, the organic bears a greater proportion
to the inorganic matter, than in the dentine of the teeth of
most other Mammals. The cement of the composite molar teeth
of the Ruminants and of the Elephant contains a little more organic
matter than the dentine does; but in the cetaceous Dolphin it
contains a rather less proportion, and is consequently harder.
The nerves of the teeth (1) are derived from the trigeminal, or
fifth pair, of which the second division supplies those of the upper
jaw, the third division those of the lower jaw. In the Human
Subject the three dental branches of the infra-orbital nerve intercommunicate
by their primary branches, from which, and from a rich
plexus formed by secondary branches upon the membrane lining the
antrum, two sets of nerves are sent off to the alveolar processes of
the upper jaw ; one set (rami dentales) supplies the teeth, the other
(rami gingivales) the osseous tissue and the gums ; the latter agree
in number with the intervals of the teeth, as the proper dental
nerves do with the teeth themselves. These two sets are not,
however, so distinct but that some intercommunications are established
between the fine branches sent off in their progress to the parts
they are specially destined to supply. The rami dentales take the
more direct course through the middle part of the osseous tissue
to the teeth; penetrate the orifices of the fangs, and form a rich
plexus with rhomboidal meshes upon the coronal surface of the
pulp; the peripheral elementary filaments returning into the plexus
by loops.
In the lower jaw the dental nerve, besides supplying the proper
nerves to the teeth, also forms a rich plexus, in which it is joined
(1) Swan, Demonstration of the Nerves of the Human Body, fol. 1830, pi. xn. Schumacher,
Ueber die Nerven der Kiefer und des Zahnfleisches, 4to. 1839.