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184 THIRD PERIOD—MODERN TIMES

difficulties that are encountered in dissecting dental bloodvessels and
nerves, and reproves those who, by inaccurate illustrative figures, convey
the erroneous idea that these parts are very clearly and easily observable.
In Chapter XXI the author goes on to speak of the best mode of
proceeding in order to make successful observation of the small nerves
and vessels going to the roots of the teeth. These researches are much
more easily made in large animals than in man; and therefore such things
as cannot be observed well in the latter must be studied in the former.
In the first place, it is necessary to dissect the lower jaw; and after
having done so several times, with all the accuracy required in making
researches of this kind, one may proceed to study the dental nerves and
vessels of the upper jaw, which is much more difficult. Having opened
up the inside of the lower jaw, one observes a cavity full of marrow, and
within this a nerve enclosed entirely in its own sheath. Having removed
the marrow, and opened the sheath lengthwise, one perceives that the
nerve therein enclosed is constituted (analogous to what may be observed
in the large nerves of the limbs) by several nervous strings, and that among
these runs a comparatively large artery, besides small vascular branches
of minor importance. If one then removes the sheath from the bone,
together with the nerve and the vessels contained in it, raising it very
gently, one sees, issuing therefrom, some very slender fibers, on the nature
ot which it is, however, difficult to pronounce; and, considering their
thinness, one can hardly conceive that they are composed of three different
elements, that is, of small nervous, arterial, and venous twigs. At any
rate, the author admits that this may be so. On arriving at the lesser
teeth, the nerve and the artery that accompanies it divide into two branches,
one of which traverses the opening presented by the bone at that point
(mental foramen), and is destined to the lower lip; the other directs its
course toward the roots of the incisors. The small twigs which penetrate
into the roots of the incisor and canine teeth are less slender than those
which enter the roots of the molars, and are easily to be seen not only in
large animals, but also in man. If the tooth of an ox or that of a ram
be split through the middle, the mucous substance contained in the
interior is seen to be traversed by small bloodvessels; and one perceives,
besides, certain fibers, which are probably nerves. All these things, says
Eustachius, I have observed many times in different animals, in some
cases more, in others less distinctly. But it is an exceedingly difficult
thing to follow the single twigs, of which we have spoken, from their
origin to their insertion, or, vice versa, from their insertion to their origin.
And so, adds the great anatomist, being able to observe but a small
part of the things I should like to see, I find myself compelled, in my
perplexity, to supply by the aid of ratiocination the deficiency of the
senses. I therefore maintain that the interior part of a tooth is susceptible