the true nature and mode of development of a class of organs by
tracing the modifications of such through the entire range of the
series of animals to which it is peculiar, is, that, from the length
of time required to complete and arrange the extended series of
observations, partial glimpses and illustrations of the main conclusions
sought to be established are published by authors who
are excited to pursue some limited branch of the subject, and
have leisure for following it out. The right of priority of original
observation thus affected, is, however, a matter only of personal
interest, and of small moment in comparison with the benefit which
science derives not only from the collateral and independent evidence
thus adduced, but also from the stimulus to further research emanating
from the discussion of such right. Where the concurrent
investigations are liberally pursued in the spirit of truth, they ought
to produce no other feeling than that of friendly emulation. It is
with unalloyed pleasure that I have seen the investigations commenced
in the first Part of the present Work, extended by the
beautiful illustrations of the microscopic structure of the Teeth of
Fishes in the later Numbers of the ‘ Poissons Fossiles,’ of M. A g a s s iz ,
in which most of my descriptions are verified,* and my indications
of the lahyrinthic structure of the teeth of certain Fishes have
received direct illustration by the figures of the microscopic structure
of those of the Lepidosteus. In like manner the Memoirs of M.M.
E r d l , B ib r a , and D u v e r n o y ,! have confirmed and extended my
* With regard to the Psammodus and allied extinct Fishes, in which the medullary canals
are affirmed by M. Agassiz to open directly upon the grinding surface of the tooth, it would
be as reasonable to suppose that the long vascular and sensitive pulp should'be exposed upon
the working surface of the perpetually growing incisor of a Rodent. But apart from any
physiological objection to the opinion of the learned Ichthyologist of Neuchâtel, I have made
new sections of the teeth of different species of Psammodonts, and have demonstrated their
perfect agreement with my descriptions, and with Plate 20, in the first Part of this Work,
to the satisfaction of Sir Philip Egerton, Mr. Stokes, Mr. Broderip, and other scientific
friends. All these specimens show that, as the grinding surface is worn down, the vascular
contents of the medullary canals have become calcified within a short distance from that
surface, and thus, in the existing Fish, were the cavities of the canals defended from the
effects of friction.
■f- I regret that the pages in Part III, descriptive of the Teeth of the Insectivora were
printed off before I received the last memoir of M. Duvernoy containing his observations and
beautiful figures of the microscopic structure of the teeth of the Shrews.
earlier observations on the microscopic structure of the teeth of
Mammals.
The published Parts of the great Work by Prof. Db B l a in v il l e ,
entitled 1 Ostéographie, ou Description Iconographique Comparée du
Squelette et du Système Dentaire des cinq Classes d’Animaux
Vertébrés,’ contain accurate and beautiful figures of the external
forms of the teeth of various genera of Mammalia. These Fasciculi,
the immortal ‘ Ossemens Fossiles’ of Baron C u v ie r , and the express
Treatises on the Comparative Anatomy of the Teeth of .Mammalia
by M. Fr. C u v ie r , and Dr. R o u s s e a u , the able assistant in
the Museum of Comparative Anatomy in the Garden of Plants,
have supplied the third Part of the present Treatise with figures of
some of the instructive and valuable specimens of the dental organs
in that rich Collection ; but my descriptions have been taken, in
every instance, from the specimens themselves, or from the teeth
of the same species, which, when not present in the Collections
of this country, I have examined in the Parisian Museum, or in the
Anatomical and Zoological Collections at Leyden and Frankfort.
My best acknowledgments are due to Prof. Temminck, Dr. Riippell,
and M. Laurillard, for the facilities which they kindly afforded me
in studying those valuable Foreign Collections, which impart essential
aid to all who would treat systematically of the dental or
osteological characters of the Vertebrate Animals.
The present Work would, however, have been very incomplete,
if I had not been privately aided by the liberal contributions of
teeth of rare fossil and recent animals, which were not available
for the purpose of microscopic examinations when present in public
collections.
The Earl of Enniskillen and Sir Philip Egerton have supplied
me with the requisite specimens of Cochliodus, Saurichthys, the
Chimæroids, and other fossil Fishes. To Charles Darwin, Esq., I
owed the opportunity, at an early period of my investigations of
dental structures, of examining microscopically the fossil teeth of
the Megatherium, Mylodon, Scelidotherium, and Toxodon. Through
Sir Woodbine Parish and M. Falconett, I have been able to examine
the teeth of the Glyptodon. Prof. Pflieninger, of Stuttgard, most