eipally inserted into the inner straight margin of the base of the
tooth, from which their glistening fasciculi radiate to be implanted into
the jaw. The rest of the base of the tooth is connected at its circumference
with more lax and yielding fibrous bands, and with the
mucous membrane of the mouth, which covers the alveolar tract in the
interspaces of the teeth. To any attempt to bend these teeth outwards
resistance is offered by the internal ligaments above described,
and by the pressure of the anterior angle of the base of the tooth
against the alveolar process or raised tubercle on which it rests
but the tooth readily yields to a force acting in the opposite direction,
and the largest and most prominent teeth can be bent inwards and backwards
so as to point to the gullet when the hand is pressed over them
in the direction a body would take when drawn into the mouth to be
swallowed : the moment, however, this force ceases to act, the teeth
recoil to their erect position, as if operated on by a spring. If every
thing attached to the base of the tooth,, excepting the internal pyramidal
band of ligamentous fibres, be removed, the tooth, after being
bent down, returns with the same force to the erect position g it is,
therefore, to this band that its resilience is due.
The teeth of the Lophius exhibit, as stated in the first chapter,
the higher type of dental structure: such as characterizes the teeth
of sauroid fishes and of most reptiles and mammals. The fully-
formed teeth are constituted by a single system of calcigerous tubes,
radiating from a single sub-central pulp-cavity : this is widely open
at the base of the tooth, but soon diminishes by the convergence of
its sides, which arch inwards and meet at the basal third of the
tooth, whence the pulp-cavity is continued as a mere line to near its
apex. The course of the calcigerous tubes is unusually uniform,
throughout the entire length of the tooth. On leaving the pulp-
cavity they ascend obliquely and then incline in a graceful curve to
the side of the tooth, to the exterior of which they are continued, in
the greater part of their course in a straight line, and nearly at a right
angle to that surface. This description applies to what I have termed the
primary curvature of the calcigerous tubes ; the secondary curvatures
that each tube exhibits throughout its whole course consist of
undulations, which are coarser, more angular, and less regular than
in ordinary mammalian dentine. The tubes divide and subdivide
dichotomously four or five times in their progress to the perhiphery;
their diminution of diameter is not proportionate to their degree of
subdivision: their diameter at their origin is ^„th of an inch ; at their
terminations it is jp^th of an inch : their interspaces equal three or
four of their diameters. The small lateral branches given off at the
angles or sharp bends of the secondary undulations into the clear
uniting substance are unusually conspicuous. A very small proportion
of the calcigerous tubes proceeds from the apex of the linear
pulp-cavity in the axis of that cavity. The apex of the entire and
newly-developed tooth is coated with a thin, dense, white layer of an
enamel-like substance, which is soon lost. A line of dentinal tissue,
more opake than the rest, runs parallel with the pulp-cavitv through
the dentine about half way between the cavity and the external
surface; this line, analysed with a sufficiently deep power, is
seen to result from an unusual number of lateral branches sent
off from a certain extent of the calcigerous tubes along the same
parallel line, which branches anastomose together and dilate into
small opake cells in the interspaces of the tubes from which they
are given off.
Owing to the extent of the secondary inflections of the calcigerous
tubes, and the difficulty, if not impossibility of obtaining a section
which does not include three or more layers, they exhibit in every
part of the tooth the appearance of an universal plexiform interweaving
; this character, in combination with their general transverse
course and the length of the linear pulp-cavity, might serve to
distinguish the tooth of the Lophius from that of a reptile or mammal
which it otherwise might most nearly resemble in general form and
texture.
The new or successional teeth are found recumbent in different
stages of development, some inclosed in their capsules, others with
their apices projecting more or less from the lax gelatinous mucous
membrane covering the broad alveolar margin of the jaws. When this
membrane is stript off, the successional teeth and their matrices are
brought away with it; their basis being inserted into its substance,
just as the quills of the porcupine are attached to the skin. In the