by some branches from the division of the nerve that afterwards
escapes by the foramen mentale, and from this plexus the cancellous
tissue of the bone and the vascular gums are supplied.
In the Dog and other Carnivora the nerve of the laniary tooth
is conspicuous from its size; that which supplies the still more
developed analogous tooth or tusk of the Boar, is still larger having
relation also to the continual reproduction of the matrix at the
base of the tusk.(l)
In the lower jaw of the Porcupine the nerve of the great incisor
is given off from the dental nerve near the middle of its course
through the osseous canal, and returns at an acute angle to penetrate
the cavity at the base of the scalpriform tooth, and supply its
persistent pulp. (2) This recurrent course indicates the progressive
change in the relative position of the pulp to the origin of its nerve.
Besides the branches for the molar teeth, many smaller filaments
penetrate the spongy texture of the bone, and form a rich plexus
from which the gum derives its filaments.
The maxillary plexus is most developed, in the Horse,
above and between the alveoli of the three premolar teeth ; it is
less complex where it supplies the molar teeth, their alveoli and the
gums. In the lower jaw of the Horse a very rich plexus begins
to be formed in the cancellous substance of the bone by branches
of the dental nerve, soon after its entry into the canal.
The intercommunications between the dental and gingival
nerves, and those supplied to the osseous tissue from the supra-
maxillary and infra-maxillary plexuses explain the sympathies
manifested in neuralgy and rheumatic pains between the teeth and
the osseous cavities in which they are implanted. I
I have been represented as having arrived at the conclusion
(1) PL 140, fig. 2. (2) PI. 104, fig. 1, 1*.
■“ that the structure of the teeth, as manifested by means of the
microscope, forms a new, distinct, and specific guide for classifying
the different members of the animal kingdom, and determining their
respective types :”<1) the absurdity of which will he obvious to the
youngest student of Zoology, who knows that true teeth are developed
only in one of the primary divisions of the animal kingdom. What
I have stated is, that the teeth, by their microscopic structure, as
well as their more obvious characters, form important, if not
essential aids to the classification of existing, and the determination
of extinct species of Vertebrated animals : but in this comparatively
restricted sphere the teeth have different degrees of value,
as zoological characters, in different classes ; the lowest degree
being in the Class of Fishes, and the highest in that of
Mammals. Numerous rows of teeth, for example, gradually succeeding
and displacing each other, characterise the higher organized
or Plagiostomous Fishes, and particular modifications of the form and
(1) “ The labours of Purkinje, Muller, and Retzius on the structure of the teeth have now
been recorded, and the views entertained by these physiologists have been most ably investigated
and confirmed by Mr. Owen, who has submitted to microscopical examination the
teeth of several other animals, both recent and fossil. From an excellent Report of these
Researches read at the last Meeting of the British Association, I have great satisfaction
in finding that he has arrived at the same conclusion which I had previously embodied in
the first announcement of this work, viz., that the structure of the teeth, as manifested by
means of the microscope, forms a new, distinct, and specific guide for classifying the different
members of the animal kingdom, and determining their respective types. From the enduring
nature of these organs, the characteristic modifications which they present, will form, as Mr.
Owen has admirably pointed out, a most valuable accession to geological science.” Mr.
Nasmyth, f Researches on the Teeth/ 8vo. 1839, p. 123. Where this Author obtained the
idea, “ which he had previously embodied” to the best of his comprehension, is of little
moment. The paragraph is cited to show that when Mr. Nasmyth penned and printed his
eulogy on my “ Report” of 1838, he seemed not to feel it as “ a strange and unlooked for
opposition” as he has represented it since the exposure, in 1840, of the nature of his * Papers’
read at Birmingham.