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Anatomy and Physiology of the Teeth, 17
a manner peculiar to themselves, which anatomist term gom-
phosis, (to drive a nail) like a nail in a piece of wood.
Every tooth has an internal cavity somewhat of the shape of
the tooth itself, which, gradually diminishes in size towards the
end of the fang or fangs, and terminates in a minute foramen or
hole. This cavity is filled with a pulpy substance, commonly
called the nerve, which is highly vascular and exquisitely sensi-
tive : the nerve and blood-vessels which supply this substance,
enter the foramen at the extremity of the root : the roots are sur-
rounded by a periosteum or membrane which secures the teeth
in their articulation, and nourishes them by means of the
numerous blood-vessels penetrating the fangs : the arteries
which supply both jaws and give off minute branches to the
teeth, are derived from the internal maxillary branch of the
external carotid.
The nerves of the teeth are derived from the fifth pair,
which is distributed to the face and head, and is the grand
medium of sensation to these parts. This nerve, according to
two fore teeth of the lower jaw of the mus maritimus, or African rat,
the largest species of the genus hitherto discovered. The same teeth
are equally moveable in the kangaroo ; and the hollow tusks or poison-
ing fangs of the rattlesnake, and other venomous serpents, are capable
of depression or elevation at the option of the animal. In the lamprey
and myxine, the teeth, which are almost innumerable, are placed on the
surface o f the tongue in the cancer genus, in the stomach ; where we
;
likewise find them in the common earwig. In the cuttle-fish, they are
also placed in the middle or lower part of the body, two in number, and
horny, and in their figure resemble the bill of a parrot. In the echinus,
or sea-hedgehog, they are five in number, arranged around the opening
of the under part of the shell, and being moveable by different mus-
cles, they form a very complete organ of mastication. In the aphrodita
aculeata, or sea-mouse, they are fixed upon the proboscis, four in number,
and are consequently extended or retracted with this organ at pleasure.
The leech has three pointed cartilaginous teeth, which it is able to em-
ploy in the same way, and by means of which it draws blood freely.
The form of the teeth is so different, even in the different genera of
animals that possess them in a true or perfect state, that this diversity has
been laid hold of by many naturalists, as a distinguishing characteristic
of their kinds or orders. Linnaeus, confining himself to the fore-teeth,
has hereby formed seven distinct orders for the class of mammalia
and M. de Blainvillc, carrying the basis of this distinction farther than
to the form and structure of the fore-teeth, has made it a foundation for
the subdivisions of these orders into genera.
1*
Anatomy and Physiology of the Teeth, 17
a manner peculiar to themselves, which anatomist term gom-
phosis, (to drive a nail) like a nail in a piece of wood.
Every tooth has an internal cavity somewhat of the shape of
the tooth itself, which, gradually diminishes in size towards the
end of the fang or fangs, and terminates in a minute foramen or
hole. This cavity is filled with a pulpy substance, commonly
called the nerve, which is highly vascular and exquisitely sensi-
tive : the nerve and blood-vessels which supply this substance,
enter the foramen at the extremity of the root : the roots are sur-
rounded by a periosteum or membrane which secures the teeth
in their articulation, and nourishes them by means of the
numerous blood-vessels penetrating the fangs : the arteries
which supply both jaws and give off minute branches to the
teeth, are derived from the internal maxillary branch of the
external carotid.
The nerves of the teeth are derived from the fifth pair,
which is distributed to the face and head, and is the grand
medium of sensation to these parts. This nerve, according to
two fore teeth of the lower jaw of the mus maritimus, or African rat,
the largest species of the genus hitherto discovered. The same teeth
are equally moveable in the kangaroo ; and the hollow tusks or poison-
ing fangs of the rattlesnake, and other venomous serpents, are capable
of depression or elevation at the option of the animal. In the lamprey
and myxine, the teeth, which are almost innumerable, are placed on the
surface o f the tongue in the cancer genus, in the stomach ; where we
;
likewise find them in the common earwig. In the cuttle-fish, they are
also placed in the middle or lower part of the body, two in number, and
horny, and in their figure resemble the bill of a parrot. In the echinus,
or sea-hedgehog, they are five in number, arranged around the opening
of the under part of the shell, and being moveable by different mus-
cles, they form a very complete organ of mastication. In the aphrodita
aculeata, or sea-mouse, they are fixed upon the proboscis, four in number,
and are consequently extended or retracted with this organ at pleasure.
The leech has three pointed cartilaginous teeth, which it is able to em-
ploy in the same way, and by means of which it draws blood freely.
The form of the teeth is so different, even in the different genera of
animals that possess them in a true or perfect state, that this diversity has
been laid hold of by many naturalists, as a distinguishing characteristic
of their kinds or orders. Linnaeus, confining himself to the fore-teeth,
has hereby formed seven distinct orders for the class of mammalia
and M. de Blainvillc, carrying the basis of this distinction farther than
to the form and structure of the fore-teeth, has made it a foundation for
the subdivisions of these orders into genera.
1*
