RESEARCHES 
ON THE 
DEVELOPMENT, STRUCTURE AND DISEASES 
OF 
THE TEETH. 
BY 
ALEXANDER NASMYTH, F. L. S. F.G.S. 
MEMBER OF THE ROYAL COLLEGE OF SURGEONS, LONDON; FELLOW OF THE ROYAL MED1CAI 
ANU CHIRURGICAL SOCIETY. 
BALTIMORE: 
PUBLISHED BY 
THE AMERICAN SOCIETY OE DENTAL SURGEONS. 
WOODS AND CRANE, PRINTERS. 
1842. TO 
ROBERT NASMYTH, ESQ. 
EDINBURGH. 
MY DEAR ROBERT, 
As there is no one more capable than yourself of 
fully appreciating the beauty and importance of the sub- 
jects discussed in the following pages, and none so likely 
to regard their defects with an indulgent eye, it is to 
you that this work is dedicated by 
Your affectionate Brother, 
Alexander Nasmyth. 
London, George-st. Hanover Square, 
May, 1839. PREFACE, 
The teeth may be regarded in the first place as the armory 
of the mouth; and in the second, as the instruments by which the 
process of assimilation is commenced. They assist in seizing, 
dividing, tearing, and masticating the substances which the 
diversified surface of the earth, the fathomless depths of the 
ocean, and the boundless expanse of atmosphere, afford in infinite 
variety as materials for building up the physical frame-work of 
animated existence. They present themselves as appendages to 
the skin, to the products of which in some of their modifications 
they bear a great resemblance, whilst in others they resemble 
true bone. The varieties which they present throughout the 
range of the animal kingdom correspond to the infinite diversities 
in the functions they are required to perform; and wonderful are 
the minute and perfect adaptations which they present in various 
animals to the wants and instincts of the latter. Indeed, from 
their peculiar conformation, they indicate so exactly the type of 
animal to which they belong, that they are found to furnish the 
best characteristic marks by which to classify the members of 
the animal kingdom. Their importance, therefore, in a scientific 
point of view, is very great, the aid which they afford to the 
naturalist being precise and definite ; they have held a prominent 
place in all classifications of animals, and Brisson adopted them 
exclusively as his guide in this department of his labours. Such 
is the beautiful harmony of Nature, that the information acquired 
by means of these organs puts us at once in possession of a 
knowledge of many of the anatomical peculiarities and distin- 
guishing habits of the animals to which they respectively belong. VI 
PREFACE. 
Moreover, the enduring nature of the materials which enter into 
their structure cannot but give them additional value in the eyes 
of the geologist. 
Cuvier, whose scientific research was at once remarkable for 
its elevation, and for the grandeur and breadth of contempla- 
tion which it displayed, has widened by his profound labours the 
field of physical philosophy ; he has lit torches in the abyss of 
time, to guide us in our inquiries into the past, which were they 
zealously prosecuted, "man, to whom only a momentary sojourn 
on earth has been accorded, would have the glory of unfolding 
the history of the thousands of centuries which have preceded 
his existence, and of the millions of beings who were not his 
contemporaries."* 
Profundity and clearness are the characteristic qualities of this 
immortal philosopher, and are alike displayed in his researches 
themselves, and in the deductions which he has drawn from them. 
In the following passage we have, as it were, an outline of the 
system which all his labours tended to establish :-"If the intes- 
tines of an animal are so organised as only to digest flesh, and 
that recently killed, it is necessary also that its jaws should enable 
it to devour its prey; that its claws should be capable of seizing 
and tearing the latter; its teeth of cutting and dividing it; its 
organs of motion of pursuing and reaching it; its organs of sense 
of perceiving it at a distance: it is necessary even that nature 
should have placed in its brain the instinct necessary for teaching 
it to hide itself and entrap its victims." 
From amongst the several links of this harmonious chain of 
organs and properties, all adapted with wonderful fitness to the 
purpose in view, Cuvier has fixed on the organs' of mastication 
as the truest and most comprehensive marks of the respective 
types of the different members of the animal kingdom. Can we 
hesitate to pursue such an inviting path, pointed out to us as it is 
by such an exalted master? 
F. Cuvier mentions "1'emploi des dents comme un des signes 
les plus certains de la nature des animaux, et des rapports qu'ils 
ont entre eux; signes qui sont un des fondemens de la science, 
puisqu'ils sont de sa methode, ou autrement de Ford re des faits 
* Cuvier sur les Ossemens Fossiles. Discours Prelim, p. cxl. PREFACE. 
VII 
ou de leurs liaisons, conditions indispensables a 1'existence de 
toute science." 
In the sequel to the present work it will be shown that, besides 
the general conformation and external appearance of the teeth, 
another distinctive peculiarity by which the Almighty has cha- 
racterised the different members of the animal kingdom exists in 
their beautiful internal, minute, and hitherto hidden organisation, 
which further demonstrates in a most striking manner the har- 
mony of all created existence- 
In man the mouth is as important as in the lower animals, for 
the performance of functions which are common to both, and has 
also other offices corresponding to the intellectual qualities, with 
which he is exclusively endowed. With him, too, it is the porch 
of assimilation, but with him alone it serves for the expression of 
mental operations-the elevated characteristic of his race. He 
not only performs mastication by its means, but accomplishes 
with its aid the emission of articulate sounds; communicates his 
ideas to his fellow-men, receiving information conveyed in the 
same manner in return ; and thus are means furnished for the 
infinite progress and improvement of mankind. By the endow- 
ment of speech man is enabled to command and direct the beings 
around him, and to bring to bear on a single point the will of a 
whole race. The teeth are of essential importance in the exercise 
of this faculty, for the eloquence of the statesman would be 
powerless, and the force of his arguments unavailing, if they were 
deprived of the sonorous utterance imparted to them by these or- 
gans, without which, too, the warrior's exhortation and command 
must lose their electrifying influence. 
The Historical Introduction with which the present work com- 
mences, occupies a much larger space than I at first intended to 
allot to it: its length is owing to the variety and importance of 
recent investigations in this department of science, conducted 
principally by Swedish and German anatomists. It still, however, 
might have been enlarged in that part which treats of old writers; 
but I have been induced to omit many of their statements, as 
being more curious and fantastic than practically valuable : the 
labours of many modern writers of ability might also be added to 
it, but not with much advantage. From the very commencement VIII 
of it the reader will be struck with the conflicting nature of the 
evidence which it contains on even the most elementary points. 
I am inclined to think, however, that these discrepancies have not 
their origin so much in absolute error, or in defect of observation, 
as in the constantly varying condition of the parts which have 
been described, and in the diversity and imperfection of the means 
which have been used for their examination. Without recurring 
to such an explanation as this, it is impossible to conceive how 
such men as Hunter, Cuvier, Bichat, and Blandin, for instance, 
can often flatly contradict each other. Those who have hitherto 
published the results of their experiments in this department of 
anatomy, have, for the most part, omitted to give an account of 
their methods of investigation, and of the species, age, &c. of the 
subjects which have been submitted to examination; thus render- 
ing it impossible to test the accuracy of their facts, and to discover 
the source of fallacy either in the new views, or in those which 
had hitherto been current. 
I have endeavoured to conduct my investigations on a scale 
which I conceived commensurate with the importance of the 
subject; and in detailing the results which I have arrived at, I 
shall give as careful a description as possible of the nature of the 
experiments, dissections, or observations which led me to them. 
The substance of what I have to offer will go to prove, I think, a 
greater degree of simplicity and uniformity, than has hitherto 
been suspected in the organisation of these structures. 
The great advance which has of late years been made in the 
science of optics, has enabled the student of minute anatomy to 
penetrate into new regions,-has unfolded, as it were, new pro- 
vinces of animated existence to the gaze of the zealous and 
delighted inquirer. The urgent demands made by geologists, for 
microscopic sections of different organised structures, have been 
so well responded to by those who prepare them, that various 
structures have lately been brought within the range of our vision, 
of which the nature had hitherto been wrapped in obscurity, from 
our not having possessed the means of ocularly examining them. 
To these two causes united we may trace the splendid contribu- 
tions with which science has lately been enriched; and it is prin- 
cipally on account of the interest excited by the writings of one 
PREFACE. PREFACE. 
IX 
of the labourers with the microscope, whose observations were 
made on the delicate sections above alluded to, that I have been 
induced to collect and publish my researches on this subject. 
In 1837, I learnt that Professor Retzius, of Stockholm, had 
published a very interesting series of microscopic investigations 
on the structure of the teeth, and I then made every exertion to 
obtain his publication, but without success. I first saw it in 
April, 1838, when I was favoured with a loan of it, by my learned 
friend, Dr. Grant. 
The interest excited by the new views of this intelligent and 
industrious Swedish physiologist, induced me to resume a course 
of investigations on all the points connected with the structure of 
those organs, and I immediately announced my intention of pub- 
lishing on the subject, and pursued my investigations with assi- 
duity. Not less than five years ago, I made many observations 
on the structure of the teeth, and saw at that time their striated 
appearance; but being unable satisfactorily to explain this, and 
knowing that it had already been recorded by Cuvier, I did not 
attach sufficient importance to it, as it did not then seem to me to 
be likely to lead to any practical results. My observations were 
shortly afterwards interrupted, owing to the imperfections of the 
microscope which I then used, and to the difficulty I experienced 
in making suitable sections of the teeth- 
I did not at first intend to publish the whole of Retzius' 
account of the tubular system in different animals, but I at length 
determined to do so, as I found that it could not be divided with- 
out injury to the whole, and that, moreover, I should frequently 
be compelled to refer to almost every part of it. 
Those who contemplate the teeth merely as ornaments, or con- 
sider them in no other light than as the active agents at a feeding 
trough, or as the formidable weapons of the wild tenants of the 
forest, will, doubtless, regard the details of Retzius as irksome 
and tedious; but he who with ardour and admiration tracks the 
steps of Nature through the regions of Zoology, will welcome 
with delight a full description of these new researches ; he will 
recognise at once their importance, and cannot fail to be struck 
with the unostentatious manner in which a great mind has opened 
to the world a new field of exertion, foreseeing its value to the X 
PREFACE. 
student of Geology as well as of Natural History. But I have 
been still further induced to publish the researches of Retzius, 
from having myself made numerous observationsand experiments 
on the same subjects, which I hope will be found to illustrate 
some of them, and to carry out others to very interesting and 
original conclusions. 
The importance of the study of Odontology in a zoological and 
geological point of view, has induced me to form as complete a 
collection as possible of microscopic preparations of the teeth of 
the various classes, both living and extinct, of the animal king- 
dom. From these I intend, in the course of the present work, 
when treating of the structure of the teeth, to make a selection 
calculated to serve as an index of the type of any animal. This 
part of the work I think will prove of much use to the geologist, 
in enabling him to state to what class of animal any tooth, or 
fragment of tooth, belongs. 
All must be fully aware of the importance which the study of 
the teeth assumes from a pathological point of view; but, gene- 
rally speaking, many of the maladies incident to them seem to be 
overlooked. I shall therefore attempt, in the course of this work, 
to describe fully their diseases, and to ascertain their source, with 
a view to the alleviation of suffering from symptoms, which often 
appear to be as anomalous as they are distressing. 
{0* The continuation of this work will appear in a short time. The next 
parts will contain an account of the development and structure of the teeth. 
The four plates, C. 1 to C. 4, at the end of the present part, form the com- 
mencement of a series of plates illustrating the structure of the teeth. CONTENTS 
OF 
HISTORICAL INTRODUCTION. 
Mention made by Herodotus of Egyptian dentists-Views of Hippo- 
crates on the structure of the teeth-Opinions of Aristotle, of 
Aretteus, of Pliny-Progress made by Galen, who describes these 
organs as bones-Details on this subject by Aetius, Rhazes and Abul- 
casis-Writings of Vesalius and Eustachius-Doctrines of Ambrose 
Pare, of Scaliger and Kerkring-New views promulgated by Mal- 
pighi, and comments upon them by Retzius-Leeuwenhoek's announce- 
ment of the discovery of tubes in the dental bone-Malpighi on the 
fibres of the enamel-Duverny on the development of the teeth-Wins- 
low on the enamel-Bertin-Herissant's paper on the formation of the 
enamel, and on the organisation of the gums-Jourdain on dental deve- 
lopment-Opinions of Hunter, physiological, pathological, and practical: 
singular resemblance on some points between him and Ambrose Pare. 
Commencement of the modern anatomical era-Bichat on the teeth- 
Blandin. Works which have been published on the teeth in Great 
Britain during the present century-Essay of Dr. Blake-Work of Mr. 
Fox-of Mr. Bell, &c. Consideration of the French school resumed- 
G. Cuvier, "Sur les ossemens fossiles"-Serres' views-F. Cuvier's 
work on the Teeth of the Mammalia-Rousseau's Comparative Anatomy 
of the Dental system. Modern German writers on this subject-Weber 
in Hildebrand's Anatomy-Schreger and Wagner. Views of va- 
rious writers on the structure of the ivory-G. Cuvier on the enamel- 
Hunter, Tenon, and Cuvier on the crustapetrosa. XII 
CONTENTS. 
Recent researches on the structure of the teeth-Purkinje and Muller on 
the tubes in the dental bone and on the fibres of the enamel-Retzius' 
microscopical researches on the structure of the ivory, enamel, and crusta 
petrosa in the teeth of mammalia, reptiles, and fishes-His summary and 
physiological conclusions-Mr. Owen's paper read at the British Asso- 
ciation. 
Recent researches on the development of the teeth-Mr. Goodsir's paper 
in the Edinburgh Medical and Surgical Journal-Arnold on the dental 
follicle-Original and historical details of Valentin-Raschkow on the 
origin of the dental follicle-on the enamel-organ-on the dental germ- 
on the formation of the enamel-on the cement-on the alveolar mem- 
brane-on the development of the gum. 
Retrospective review and summary of the present state of information. 
State of the questions concerning the origin of the dental follicle-concern- 
ing the capsule itself-the osseous nature of the teeth-their vascularity- 
their composition and structure. Reflections on the evidence adduced in 
favour of the existence of a tubular system-Erroneous views of Muller 
on the crusta petrosa-On the admission of a fourth substance as entering 
into the composition of the teeth-Concluding remarks on the methods of 
conducting experiments on these organs. HISTORICAL INTRODUCTION. 
It is at all times instructive and of great utility to trace the 
progress of any branch of science, and as much importance is 
always justly attached to priority of information, as marking in- 
dustry and activity of research, it behooves us, in the first place, 
to give a condensed view of the progress of knowledge respect- 
ing the teeth. This will enable us to judge what departments 
have hitherto been principally defective, and have remained to 
be elucidated by present or future researches.* 
We learn from Herodotus that amongst the Egyptians at a 
very remote period, the care of the teeth was assigned to a par- 
ticular class of persons; but respecting their anatomical know- 
ledge, or proficiency in their art, we have no information. Of 
the views entertained of the physiology and pathology of these 
organs in Greece before the time of Hippocrates, we know but 
little, except that they are embodied in the works of the latter. 
Homer calls the teeth "little barriers opposed by nature to the 
unruliness of the tongue, and to the abuse of speech." He is 
fond of designating them as forming a wall or fence o5o»rw».) 
The views of Hippocrates, who lived between three and 
four hundred years b. c., respecting their origin and formation 
are extremely crude and fantastic. He says, "There is a gluti- 
*In compiling the following Historical Sketch, I have consulted the 
works of original writers on the subject, and have derived much general 
assistance from Blandin's excellent work on the teeth, and from the late 
remarkable publication of Professor Retzius, of Stockholm, whose ingenu- 
ousness in acknowledging the merits of preceding inquirers cannot be too 
much applauded. In collating the different accounts which have appeared 
of his Researches with the original Swedish work of Retzius, entitled 
"Mikroskopiska Undersokningar dfver Tantiemes sardeles Tandbenets, 
struktur: Stockholm, 1837," I have received valuable assistance from my 
learned friends, Dr. Minton and Dr. Bialloblotzky. 14 
HISTORICAL INTRODUCTION. 
nous increment from the bones of the head and jaws, of which the 
fatty part is dried by heat and burnt up, and the teeth are made 
harder than the other bones, because there is nothing cold in 
them." He goes on to say, that in the foetus they are nourished 
by the food of the mother, and after birth by the milk which the 
infant sucks from the breast. He calls the wise teeth avtyviarDfig, 
and holds an opinion, which several authors have maintained 
after him, that to have a great number of teeth is a sign of 
longevity. 
Aristotle was so ignorant of the anatomy of these parts, as 
to assert that man has more teeth than woman, and that this 
difference is observable between the sexes in various classes of 
animals, as for instance in sheep, goats, pigs. All viviparous 
red-blooded animals have, he says, teeth; but all have them not 
in both jaws. Animals with horns, he continues, have no teeth 
in the front of the upper jaw, and in some without horns this 
peculiarity is observed, for example in the camel. He states that 
only the front teeth change in man; that the molars are not shed 
in any known animal; that the pig loses no tooth; that the age 
of animals may be determined by their teeth; and that they be- 
come discoloured in course of time, except in the horse, whose 
teeth are whitened by age. He considers that the difference 
betwixt bone and tooth consists in the circumstance, that the 
teeth increase in length during life, whilst the bones have a 
determinate limit to their growth. 
We may judge of the knowledge of these organs possessed by 
Aret^us, from his assertion that the cause of the tooth-ache is 
only known to God. Pliny, who lived about four hundred years 
after Aristotle, does little more than repeat the doctrines of the 
latter, illustrated and embellished by various fables of his own. 
He mentions, however, the indestructibility of these organs, re- 
marking that every other part of the bodies which were enclosed 
in the sarcophagi was destroyed, except the teeth. 
In the second century after Christ, Galen, who had profited 
by the labours of his predecessors, more particularly of the 
Alexandrians, wrote a better account of the teeth than any 
which had hitherto existed. He teaches that they are formed 
during the period of gestation; but that they remain hidden in 
the alveoli until birth; that the molars of the upper jaw have 
three roots, those of the lower only two; and that the canine 
teeth had also received .the appellation of ocular, (otpdx^xoi,) 
because branches are sent to them of a nerve, which distributes 
others to the eye. He has a long chapter on their forms, their HISTORICAL INTRODUCTION. 
15 
functions, and their evolution, and does not hesitate to pronounce 
them true bones: in ossium numero dentes habendi sunt, etsi se- 
cus nonnulli sophistce arbitrentur. He maintains that the teeth 
feel, and that he has proved this on himself: quare utriusque do- 
loris sensum expertus, alium quidem gingivis, alium ipsius dentis 
substantia esse non dubito. 
Aetius says that the teeth are open at the roots, where they 
admit small nerves coming from the trifacial; and that it is for 
this reason that they are the only bones which can become pain- 
ful of themselves. He adds that they grow till old age by the 
deposition in their interior of a nervous fluid; but that at that 
period the process of nutrition ceases, and they become loose, 
and finally drop out. Rhazes described the process of dentition, 
but in a very incomplete manner. Abulcasis was the first who 
distinctly taught that teeth may be replaced either by other hu- 
man teeth, or by artificial ones, made out of the bones of an ox. 
Vesalius, the restorer of human anatomy, who was born 
about 1512, does not appear to have studied the teeth with the 
same attention which he devoted to the other parts of the body. 
According to him, the milk-teeth are the germs of the permanent 
teeth. The knowledge of these organs was greatly advanced by 
Eustachius, whose description of their number, different forms 
and varieties, leaves nothing to be desired: he compares their 
adhesion to the gums to that of the nails to the skin; (sicut cutis 
extremes unguium parti adhoerescit ita gingivae dentibus adjuncts 
sunt;) and thinks with the ancients that their degree of hardness 
is proportioned to the ferocity of the animal. He made careful 
inquiries into their structure, in which he recognises two con- 
stituent parts, and compares the enamel to the bark of trees (du- 
plici substantia veluti arbores teguntur). In an article on their 
development, he describes the follicles, their vessels and nerves; 
refutes the opinion of those who think that the roots of the milk- 
teeth are employed towards the formation of the permanent ones, 
and says that if the germs of the latter are not seen in the foetus, 
it is not that they do not exist, but that they are still too small to 
be recognised. That the teeth are nourished in a different man- 
ner from bones, he concludes, for this amongst other reasons, 
that their fractures cannot be made to unite. In his writings we 
find some details on their comparative anatomy, and he dwells 
more particularly on the teeth of the monkey. He relates a 
series of curious anomalies in the development of the teeth, and 
speaks of a case of four successive dentitions. 
Ambrose Pare, who wrote in the year 1579, gives a very cor- 
rect account of the teeth, of their number, position, and uses, and 16 
HISTORICAL INTRODUCTION. 
of their attachments to, and connections with, adjacent parts. He 
considers that the adherence of the teeth to the jaw is strengthen- 
ed by a ligament which extends from the root of the tooth to the 
socket. "The teeth,"* he says, "differ from the other bones, be- 
cause they have action whilst they chaw the meat, because being 
lost they may be generated, and for that they grow as long as the 
party lives; for otherwise, by the continual use of chawing, they 
would be worn and wasted away by one another." He adds, 
"You may perceive this by any that have lost one of their teeth, 
for that which is opposite to it becomes longer than the rest, 
because it is not worn by its opposite." Another of this writer's 
curious notions is, "that they have such quick sense, that with the 
tongue they might judge of tastes." 
His cures for the tooth-ache are on a par with his ideas respect- 
ing the structure and functions of the teeth; but they are as 
rational as those of many practitioners of the present day, some 
of whom still firmly believe "that in the most grievous pains of 
rotten teeth, the thrusting of a hot iron into their roots, or stop- 
ping them with cotton dipped in oil of vitriol, or aquavitae, gives 
most certain ease." P. 283. 
His opinion was, that the teeth, "like other bones, suppurated, 
and were subject to inflammation, the breeding of worms," &c. 
In such cases, he directs that a physician should first be consulted, 
and recommends "purging, phlebotomy, application of cupping- 
glasses to the neck and shoulders, scarification, washing the mouth 
with the juice of pomegranates, plantain-water, concocted vine- 
gar, (for which he gives several nostrums,) narcotics to be drop- 
ped into the ear in order to stupify the nerve, leeches to the gums, 
and opening the veins under the tongue or behind the ears." He 
gives directions for the use of other similar remedies, which it is 
unnecessary to enumerate, as I have only given the above exam- 
ples in order to show that this celebrated authority may be quoted 
for many strange practices of the present day. It is curious to 
notice that the peculiar remedies and treatment recommended by 
Hunter seem to have originated with Ambrose Pare, who was 
the first to describe the operation of transplanting, which, strange 
to say, found a strenuous advocate in our great physiologist. 
Ambrose Pare, however, only gives upon hearsay a case in which 
this operation was said to have succeeded. 
In his chapter on operations, his directions are to a certain 
extent admissible, if it were not that he recommends interference 
where it is unnecessary. Within the last ten years I have known 
the very pelican of which Pare gives a drawing, used in London, 
and its propriety and efficacy asserted. His account of the ope- 
* The works of that famous chirurgeon, Ambrose Parey. Translated by 
Johnson. London, 1665, p. 125. 17 
rations of tooth-drawing is as follows:-"For the better plucking 
out of the tooth, the patient shall be placed in a low seat, bending 
back his head between the tooth-drawer's legs; then the tooth- 
drawer shall deeply scarify about the tooth, separating the gums 
therefrom, and then if spoiled, as it were, of the wall of the gums, 
it grow loose, it must be shaken and thrust out by forcing it with 
a three-pointed levatory; but if it stick in too fast, and will not 
stir at all, then must the tooth be taken hold of with some of the 
toothed forcipes, now one, then another, as the greatness, figure 
and site shall seem to require. I would have a tooth-drawer 
expert and diligent in the use of such toothed mullets ; for, unless 
one know readily, and cunningly how to use them, he can scarce 
so carry himself but that he will force out three teeth at once, 
ofttimes leaving that untouched which caused the pain." (p. 416.) 
In the chapter of his work, "Of the placing of teeth artificially 
made instead of those that are lost or wanting," he says, "Teeth 
artificially made of bone or ivory may be put in the place of those 
that are wanting; and they must be joined one fast unto another, 
and also so fastened unto the natural teeth adjoining that are 
whole ; and this must chiefly be done with a thread of gold or 
silver, or for want of either, with a common thread of silk or flax, 
as it is declared at large by Hippocrates, sect. ii. lib. de art. Sent, 
xv."* 
Scaliger calls the teeth bone, sui generis; he denies that they 
have any proper sensation, and compares them in this respect to 
the nails. Kerkring, on the other hand, finds that they are 
perfectly analogous to bones ; but he devotes only a very short 
space to them, and concludes by saying, "De dentibus nihil dicam 
aliud quam nihil esse quod hie peculiariter sit commemorandum!" 
Malpighi says that the teeth consists of two parts, of which 
the interior, a bony lamella, is formed of fibrous, and as it were 
tendinous hair, woven into a kind of net-work. Dentes ^duphei 
excitantur parte, quarum interior ossea lamella fibrosis et quasi 
tendinosis capillamentis, in naturam retis implicitis, constat." 
Anatome plantarum, Lugd. Batav. 1687, p. 37. In another place, 
he says, "Completus et stabilis dens molaris ut plurimum binis 
pollet radicibus, quarum altera latior est et facta per longum 
scissione ejus compages manifestatur; ossea namque substantia 
lubulosa apparel qua dens compaginatus folliculum continet." 
(Opera Posthuma. Amstelod. 1698, p. 72.) On these passages 
Retzius observes, that the words in the former one, "in naturam 
retis" show that Malpighi here alludes to reticular fibres of the 
tooth-bone, and that by the phrase "tubulosa substantia," in the 
HISTORICAL INTRODUCTION. 
' The passage here alluded to 1 have not been able to find. 18 
HISTORICAL INTRODUCTION. 
second one, he means the hollow tubulated roots. At page 71 
1. c. he says of the incisor tooth,-"sensim in cylindrum seufistulam 
desinit, qua intra mandibulam condita loco radicis inservit."- 
"Totus tubulosus est, et folliculum continet." 
The most valuable publication, however, of the seventeenth 
century on the subject of the teeth, is a paper of Leeuwenhoek, 
in the Philosophical Transactions for 1678, in which we find the 
following remarkable passage: -"I have some time since applied 
a glass (esteemed by several gentlemen who had tried it a very 
good one) to observe the structure of the teeth and other bones, 
which both to them and myself also then seemed to consist of 
globules; but since then, having drawn out one of my teeth, and 
for further observation applied better glasses than the former, the 
same gentlemen with myself agreed, from what we plainly saw, 
that the whole tooth was made up of very small, strait, and trans- 
parent pipes. Six or seven hundred of these pipes put together, I 
judge, exceed not the thickness of one hair of a man's beard. In 
the teeth of a cow, the same pipes appear much bigger, and in 
those of a haddock somewhat less." Drawings of the teeth are 
given here, and also in his "Continuatio Epistolarum f yAmch. 
work contains the results of his researches on the teeth of the 
horse and the pig, which he likewise finds to consist of tubes pro- 
ceeding from the cavity to the periphery. He here proves, too, 
that he was acquainted with the cortical substance, for, speaking 
of the teeth of the calf, he says, " Undiquaque alio osse circumducti 
erant-"adeo ut jam vie adhuc magis quam antea certum red- 
dere possem, circum primo confectum dentem os accrevissef (p. 
7.) He further speaks of crystals which he found in the cavities 
of the teeth of horses, and gives drawings of them. Strange to 
say, these statements attracted no attention either from his cotem- 
poraries or successors, though Portal, in his Histoire de l'Anatomie 
et de la Chirurgie, (Paris, 1770, t. iii. p. 460,) cites the letter 
inserted in the Philosophical Transactions, observing: "Leeuwen- 
hoek dit ici que les dents sont composees de tres petits tuyaux 
transparents et droits, dont six ou sept cents egalent a peine un 
poil de la barbe," &c. In the " Anatomia Plantarum" of Mal- 
pighi, (Op. omn. Lugd. Batav. 1687,) the fibres of the enamel are 
mentioned and delineated. In his Op. Posthum. (Amstel. 1698, 
p. 71 et seq.) he calls it a "substantia ossea filamentosaf and a 
"crusta candida filanientosa." Speaking of the teeth of the calf, 
he says, "interior (substantia) ossea est, et obscuram habet com- 
positionem, qua. in piscibus tamen evidenter fibrosa est; in homi- 
nibus vero compacta valde. Ab hac exterius perpendiculariter 
erumpunt pili., ut in holoserico villoso, qui versus dentis apicem 
inclinari videntur." "Ha (stria) intersecantur aliis c^uasi crassis 
lineis, brevibus pilis contextis, qua eleganti ordine horizontuliter 
ducta dcscribi nequeunt." HISTORICAL INTRODUCTION. 
19 
Duverney is the author of a monograph on the teeth, which 
contains much more vague speculation, and much less solid re- 
search, than the writings on this subject by Leeuwenhoek and 
Malpighi. This author compares the membrane which surrounds 
the tooth to that which envelopes the foetus, and calls it the 
"choroid." He says that the follicle has the form of the tooth 
which it is destined to produce; and thinks that the latter is com- 
posed of layers of which the most external are the hardest. Ac- 
cording to him, the choroid abandons the tooth at the period of 
extrusion, and remains in the alveolus, of which it forms the peri- 
osteum. 
Winslow (in his Exposition Anatomique, Paris, 1732, p. 46) 
says of the enamel, "This vitreous matter, or species of enamel, 
when viewed through the microscope, appears to be composed of 
a number of very short fibres, so arranged that at one extremity 
they point inwards, and at the other outwards." Ludwig, in his 
dissertation "De Cortice Dentium" treats particularly of the 
structure of the enamel, which he declares to be fibrous; he sets 
about indicating the direction of the fibres in the different parts of 
the crown, and says that they all leave an impress on the ivory. 
Bertin, in his Treatise on Osteology, gives a complete descrip- 
tion of the teeth, and states "that it has appeared to him that the 
layer of enamel which invests the crown of the tooth is prolonged, 
notwithstanding all that has been said to the contrary, over the 
root, and that it only becomes weaker by degrees from the apex 
to the opposite extremity." (p. 242.) He says that the cavity of 
the tooth is not entirely empty; but is filled, on the contrary, by 
a soft substance, produced by a lymphatic juice, which becomes 
thickened, though still without acquiring the consistence of bone. 
"This," he continues, "is what I call the third substance of the 
tooth, differing from the kernel (le noyau) and the enamel," &c. 
He affirms, moreover, that this substance forms sometimes a hard 
mass, which has scarcely any adherence with the other two, but 
which at length is consolidated with the ivory. 
In the "Memoires de VAcademic des Sciences" there is a re- 
markable paper by Herissant on the formation of the enamel, 
and on the organization of the gums. He admits that there are 
two species of gums, one temporary, the other permanent; the 
former being a tough tissue lining the whole extent of the alveo- 
lar arch, and closing up the alveoli; and thinks that when the 
tooth traverses it, it is exfoliated, as it were, and comes off in 
shreds. According to him, the sac that contains the dental folli- 
cle is a prolongation of the temporary gum; is the organ which 20 
HISTORICAL INTRODUCTION. 
secretes the enamel, and presents on its surface a great number 
of small vesicles filled with a fluid which, by a process of solidifi- 
cation, is converted into the latter. The views of Herissant are 
confirmed by Bourdet. Jourdain, in his essays on the forma- 
tion of the teeth, has described minutely the dental follicle from 
its first appearance till the period of birth ; and he follows it in 
its successive evolutions. He describes also two canals in the 
lower jaw of the foetus-one, which is only a furrow destined for 
the passage of the vessels and nerves of the milk-teeth; the 
other, which is a true canal, transmitting those of the permanent 
teeth. These writings of Jourdain, which are devoted exclusively 
to the subject of the development of the teeth, are of great interest; 
for it is evident that he made numerous experiments on the sub- 
ject, and only describes what he saw. 
John Hunter, in his work on the teeth, printed in London in 
the year 1778, describes with uncommon clearness and precision 
the results of the investigations which had hitherto been made on 
the subject; and adds an account of a number of important 
experiments made by himself. He says that the enamel, which 
he calls lamina vitrea, is composed of striae running from the cir- 
cumference to the centre; he believes that it is quite inorganic, 
because it cannot be converted, by any means whatever, into 
animal mucus: exposed to fire, it separates from the ivory. He 
calls the latter the osseous part of the teeth, and holds that it is 
analogous to bone. He says, however, that madder only reddens 
those layers which are formed whilst the animal is fed with it, 
and does not at all change the colour of those which previously 
existed,-a fact which shows that this substance differs a little 
from bone. A part of the tooth once impregnated with madder 
always retains the colour of the latter; and Hunter concludes 
from his experiments, that the teeth are to be considered as ano- 
malous bodies with respect to their circulation. 
He thinks that the roots are surrounded by a periosteum which 
comes from the alveolus, and which is prolonged into the cavity 
of the tooth ; and that the ivory is formed of concentric laminae. 
He states that the incisors have three centres of ossification; the 
canine only one, and the molars three or four: that the tooth, at 
the moment of its extrusion, is a foreign body in relation to the 
gums; and that the enamel is probably secreted by the capsule 
which surrounds the body of the tooth before it is extruded. The 
milk-teeth he describes as being shed by a law of organizing 
nature, and he denies that their removal is effected by the 
mechanical agency of their permanent successors. Such are his 
leading views-the results of his characteristic industry and 
accurate observation. On many points his work still continues a HISTORICAL INTRODUCTION. 
21 
standard text-book. In every part of it he displays his usual 
originality; but still it is evident on perusing it, that the author 
did not enjoy daily opportunities for close observation on the sub- 
ject, and that consequently he did not duly appreciate some points 
of great interest. Nevertheless, I have been informed, on autho- 
rity which I cannot doubt, that when Mr. Hunter first came to 
London, his brother sent him to attend in the surgery of a dentist 
to give advice on any case which might present itself. His 
description of the anatomy of the jaws, and of the muscles which 
are connected with them, is given with his usual perspicuity. 
Very few of the appearances observable in health or disease 
seem to have escaped his penetration. He has left us many 
valuable hints to be worked out; and it is a reproach to subse- 
quent inquirers that they have remained so long on record with- 
out illustration. His description of the swelling, which he calls 
spina ventosa, of the roots, and of the appearances of anchylosis ; 
his apparently anomalous reasonings on the facts established by 
his beautiful experiments of feeding animals with madder-his 
observations also regarding the periosteum and the capsule, have 
always appeared to me to require accurate examination; nor can 
I help regarding as erroneous his views on the necessity for three 
fangs in the upper teeth of the human subject. His ideas on the 
connection of the gum and tooth are not fully worked out; this 
subject, with that of the functions of the cellular texture of the 
periosteum, is very interesting. It is singular to observe the 
manner in which our great physiologist expresses himself on 
points which he did not settle by actual demonstration ; as, for 
instance, on the nature of the enamel, and on the mode in which 
the teeth are shed. 
That he had no long and careful practice in the diseases of 
these organs is evident from some statements which would 
doubtless have been corrected, had he enjoyed better opportu- 
nities for observation. These statements have given rise to 
unwarrantable practice by superficial collators of information, 
whose respect for authority often leads them to follow it blindly 
without examination. I may instance here as prejudicially erro- 
neous, his assertion that general affections of the system have 
less influence on the teeth than on any other part. On the sub- 
ject of the wearing down of the teeth, he also makes a few 
remarks, which have led to very pernicious practice. He calls 
the extraction of teeth "a weakening cause," and says that "if by 
accident one tooth is lost, the rest will necessarily fail in some 
degree, even though they are sound, and likely to remain so, had 
not this accident happened; and this weakening cause is greatei' 
in proportion to the number that are lost. From this observa- 
tion we see that the teeth support one another." 22 
His practical remarks on the operations of stopping, extrac- 
tion, &c. will not be assented to by the well informed practition- 
er of the present day; yet they still frequently find a place in 
text-books, and are adopted by many as a guide in their daily 
practice. The art of transplanting teeth, which he illustrated by 
some very curious experiments, has been since adopted with 
very injurious and even fatal consequences, but is now, I believe, 
almost entirely abandoned by all practitioners at home and 
abroad. A persuasion, however, seems still to linger in the minds 
of many, that there is a possibility of its being practised without 
any ill effects. The indifference with which many practitioners 
still see dead teeth remaining in the mouths of their patients, as 
well as sundry unwarrantable measures, may be traced to doc- 
trines promulgated by no less an authority than Hunter. But 
sixty years have now elapsed since ha wrote, and the profession 
is surely justified in demanding a vast improvement in the ac- 
quirements of the practitioner who devotes himself to the care of 
these organs. 
From the introduction to the pathological part of Mr. Hunter's 
work, the reader is led to conclude that a very low standard of 
education is necessary to fit the officiers de sante, on whom the 
management of these organs devolves, for the safe treatment of 
the diseases of the teeth, and the adjacent parts. He prefaces 
that portion of his work by stating, that "he purposely avoids 
entering into common surgery, not to lead the dentist beyond his 
depth, and to matters of which it is to be supposed he has not 
acquired a competent knowledge," and states, "that all the dis- 
eases of the teeth which are common to them with the other 
parts of the body, should be put under the management of the 
physician and surgeon; but those which are peculiar to the teeth 
and their connections, belong properly to the dentist," and allows 
at the same time that "diseases in the teeth are apt to produce 
diseases in the neighbouring parts, frequently of serious conse- 
quences." That it is possible distinctly to comprehend the struc- 
ture and diseases of any individual part without the general rudi- 
ments at least of a medical education, is a position which is now 
generally rejected, and it is to be hoped with beneficial results. 
It is much to be regretted, moreover, that such talent as Hunter's 
should have so long sanctioned by its high authority many prac- 
tices which, to the present day, are adhered to, and which tend 
to a direct increase of suffering, and in some cases even to the 
gradual destruction of life. His errors can only be explained by 
the limited field of observation and practice on these organs which 
he enjoyed; a wider range of experience would soon have 
awakened his penetrating mind to a sense of the injurious nature 
of such practices, for instance, as "extracting a decayed tooth," 
HISTORICAL INTRODUCTION. HISTORICAL INTRODUCTION. 
23 
in order to "boil and replace it," as applying the actual or other 
cautery to exposed nerves, where disease is present; burning the 
ear with hot iron to cure the tooth-ache; blistering for decayed 
teeth, &c. With regard to his directions for stopping, extrac- 
tion, and other operations, it is very evident that he never per- 
formed these often himself, or his instructions would have been 
very different. 
His general remarks on diseases of the teeth are replete with 
sound sense, and leave little to be desired. The practical obser- 
vations on the cure of irregularity are good, but appear, in com- 
mon with many other parts of the work, to be rather compila- 
tions from the practice of others than original observations. The 
principles laid down in the chapter on operations do not coincide 
with the notions of the present day, and it is astonishing that such 
a measure as transplanting and replacing teeth should have 
received his sanction, and have been the subject of repeated 
notice and elaborate investigation at his hands. Subsequent 
experience has added scarcely anything to the information on 
dentition contained in his chapter on that subject. 
His details on many of the essential points connected with the 
physiology of the teeth seem to have passed entirely undigested 
through a great proportion of the works on this subject, which 
have been published from his time to this. 
In sketching the progress of surgical information in this par- 
ticular department of science, we find a singular similarity between 
the opinions and even the diction of those two eminent writers, 
Ambrose Pare and John Hunter. Though the latter wrote no 
less than two hundred years after the former, science in this inter- 
vening period had made so little progress, that our great English 
physiologist seems to have had no more recent or better authority 
to refer to as a standard of facts than his antiquated French pre- 
decessor; a circumstance which marks well how stationary the 
healing art must have been during the seventeenth and the greater 
part of the eighteenth century. 
The reader, doubtless, has already observed the similarity here 
alluded to; but as the subject is curious, it may be well to insti- 
tute a more formal comparison. Pare, in the 36th chap, of his 
10th book, in a passage quoted above, (p. 15,) recommends a hot 
iron, or cotton dipped in oil of vitriol to be applied in cases of 
tooth-ache, in order to "burn the nerve which is inserted into their 
roots." This does not much differ from Mr. Hunter's treatment, 
as we learn from the following passage: "The nerve may be 
burned ; that this may have the desired effect, it must be done to 
the very point of the fang." Again, "Either of the concentrated 
acid, such as those of vitriol, nitre, or sea-salt, introduced as far 
as possible, is capable of destroying its soft parts, which most 
probably are the seat of pain." If the reader has any curiosity to 24 
trace further the similarity between the surgery of these two 
writers, he may compare the whole of the 30th chap, of the 17 th 
book of Pare with what Mr. Hunter says, from p. 17 to p. 209 of 
the second part of his work on the teeth. 
In the 26th chap, of the 17th book of Ambrose Pare, we are 
told, amongst other things, that "if the teeth become loose by a 
fall or blow, they must not be taken forth, but restored and 
fastened to the next that remain firm, for in time they will be 
confirmed in their sockets, as I tried in Antonio de la Rue, the 
tailor, who had three of his teeth loosened, which were put in 
their places, and bound to the rest with a double waxed thread." 
He fed his patient with "broths, jellies, and the like, and made 
him astringent gargarisms," and "by these means brought it to 
pass, that he, a little while after, could chew as easily upon those 
teeth as upon the other." Mr. Hunter, after directing that sound 
teeth, extracted by mistake, should be replaced, desires similar 
measures to be adopted in accidents such as the above, and 
relates a case similar to the one narrated by Pare. It is curious 
that the very next paragraph in both these celebrated authors 
treats of the Transplanting of Teeth. Pare gives a case where 
this had been successful, communicated to him by "a credible 
person, concerning a lady of the prime nobility," whilst Hunter, 
I believe, is the only writer who has entered into the minute and 
circumstantial details of the practice. 
In making a selection from the works on the teeth, which have 
appeared since what may be termed the present school of anatomy 
was founded, we cannot do better than begin with Bichat, with 
whom the course of modern improvement may be said to have 
commenced. 
Bichat, in treating of the enamel, was unable to decide whether 
it is an organised substance, or merely a fluid exuding from the 
external surface of the tooth, and hardening round it. His observa- 
tions are more valuable where he comes to treat of the sympathies 
and functions of the teeth. After the eruption of the second teeth, 
he says that they evidently grow both longer and thicker; but 
that they lengthen only at the root; that the crown has always 
the same dimensions, and that its appearing longer in old than in 
young men is owing to the shrinking of the gums, which is also 
observed in persons who become emaciated, in those who have 
been under a course of mercury, &c. He adds, that the teeth only 
increase in substance internally, "the canal of the root and the 
cavity of the body become gradually narrower, and at length 
become obliterated: then, as the vessels and nerves no longer 
penetrate into the tooth, it dies and drops out of its socket; but 
this death seems to be also accelerated by the accumulation 
HISTORICAL INTRODUCTION. 25 
throughout its substance of phosphate of lime, which so predomi- 
nates over its gelatine, that its vitality is entirely extinguished, so 
that, in this respect, the loss of the teeth presents a phenomenon 
similar to that of the falling off of the horns of herbivorous ani- 
mals," &c. The ivory he considers to be of a rocky consistence, 
very different from cellular tissue. Its fibres, he says, are very 
close, run in different directions, but chiefly towards the root, and 
are distinguished with difficulty. He states that the internal 
cavity is lined with a thin membrane, "qui par sa face opposee 
revet la pulpe." 
The pulp he regards as a spongy substance, which appears to 
be formed by the interlacement of vessels and nerves; but the 
nature of which is not well known: its sensibility, however, he 
describes as great, and as equal at least to that of the marrow. 
With regard to the phenomena of dentition, he asserts that, 
previous to the eruption of the teeth, the jaws of the foetus seem 
to be of a uniform continuous texture; but when they are examin- 
ed internally, the dental capsule is found to be a shut sac lining 
the alveolar cavity to which it adheres by prolongations. It 
leaves the alveolus where the vessels enter the pulp, and is reflect- 
ed on the latter, forming an envelope for the vessels. In its general 
character he considers this membrane to be serous, as also from 
the manner in which it is reflected, and from the fluid which it 
secretes. Although the pulp and its vessels are covered by it, 
they are, he says, really without its proper cavity. 
M. Blandin, the intelligent editor of Bichat's "General Anato- 
my," has published a very excellent treatise on the teeth, in which 
are incorporated his observations on these organs, appended to 
the last edition of Bichat. Contrary to the opinion of the latter, 
he holds that the teeth are not bone, but productions of mucous 
membrane, analogous to nails, hair, &c., and differing from bone 
in their external position, connections, form, structure, develop- 
ment, and uses. He considers that "the follicle of these osteides, 
after their eruption, bears a perfect analogy to that of a hair, and 
in fact is continuous near the neck with the common integument 
of the mouth, of which it ought to be regarded as a simple depres- 
sion. Before the extrusion of the tooth this analogy exists posi- 
tively, but is not very clear, and has been mistaken," he adds, 
"by Bichat, who represents the membrane proper to the follicle 
as forming a shut sac; whereas at present, and indeed since the 
work on this subject of M. Delabarre, it is acknowledged that the 
dental follicle is united at the gum to the mucous membrane by a 
canular prolongation, which establishes a positive continuity on 
the one hand between the cavity of the mouth generally and that 
of the follicle, and on the other hand between the mucous mem- 
HISTORICAL INTRODUCTION. 26 
brane of I he gum and the dental membrane. This canal, closed 
at an early stage by the approximation of its walls, but dilated 
at a later period by the tooth which traverses it for the purpose 
of arriving at the surface, represents in reality the neck of this 
particular follicle, but in a very elongated state." 
Blandin states that "the dental follicle is composed of two 
divisions, viz. of the membrane which constitutes its parietes, and 
of the pulp or papilla on which the tooth is formed. The mem- 
brane of the follicle consists," he adds, "of two layers-of an 
external and fibrous one, intended to adhere at a subsequent 
period to the alveolus as the alveolo-dental periosteum, and which 
is le derme of the mucous membrane of the mouth depressed in 
the form of a follicle to a level with the teeth-the other layer is 
situated internally, is villous and vascular in its texture, and forms 
the cavity of the follicle. These two layers united are further 
described as extending to the base of the pulp, near the point at 
which it receives the vessels and nerves which form its pedicle; 
but neither the one nor the other is really reflected on the pulp, 
as Bichat supposed. This eminent physiologist was deceived on 
this point," says Blandin, "by the circumstance that the texture 
of the pulp is continuous with that of the internal layer of the 
follicle, from the bottom of which it is a vascular and nervous 
expansion-a papilla analogous to those found in all parts of the 
tegumentary membrane, (but more extensively developed on 
account of its peculiar functions,) and particularly to those of 
hair and feathers." 
According to our author, the fluid of the follicular cavity 
differs in many respects from that of serous membranes, being 
more consistent and viscid, of a dark yellow colour, and possess- 
ing, moreover, peculiar properties, which Berzelius states to be 
owing to the presence of lactic acid. 
Blandin considers that the relation between the dental papilla 
and the tooth is not analogous to that existing between primitive 
cartilage and bone; since the papilla does not ossify, any more 
than the papilla of a hair or a feather solidifies in order to produce 
those structures. He imagines that the tooth is secreted by the 
external surface of the papilla on which it rests; that it takes the 
exact form of the latter, and increases in length and thickness in 
the same way as hair, feathers, and nails-that is to say, by the 
successive addition of layers internally to those already secreted. 
In regard to the production of the enamel, he allows that its 
origin is involved in great obscurity, and notices the conflicting 
opinions respecting it-Cuvier holding that it is produced by an 
immediate secretion from the internal layer of the follicle, whilst 
Hunter states that it remains for some time dissolved in the fluid 
of the follicle, and afterwards crystallises on the ivory of the 
HISTORICAL INTRODUCTION. 27 
HISTORICAL INTRODUCTION. 
tooth; and whilst others have held that it is also secreted by the 
pulp, and traverses the pores of the ivory in order to arrive at 
the surface. If any of these theories are adopted, it is difficult 
to explain why the root of the tooth, which, like the crown, is 
formed on the papilla in the cavity, and in the midst of the cavity 
of the follicle, should not be also covered with enamel. M. Dela- 
barre has tried to solve this difficulty: he holds that the enamel 
is secreted by the internal layer of the follicle, but that this layer 
does not descend further than the pedicle of the papilla-a theory 
which Blandin does not consider as satisfactory. 
This author maintains that the yellow, calcareous matter, call- 
ed tartar, is secreted by a senes of small sacs which surround 
the mouth of the follicle. 
In Great Britain, the principal works which have been published 
on the teeth during the present century are those of Dr. Blake, 
(8vo. Dublin, 1801,) of Mr. Fox, (4to. London, 1803,) and of 
Mr. Bell, (8vo. London, 1829.) And these I shall notice together, 
although not in chronological order. 
The essay of Dr. Blake must always be regarded as the 
best work on the subject of the period at which it was written, 
and will keep its place as a standard production. He is one of 
the few authors who have taken the trouble to read their lesson 
from nature; and the deductions which he has drawn from his 
observations are practically useful. His ideas respecting the 
"crusta petrosa" were original at the time, and have since been 
generally acquiesced in; but his views on most of the functions 
of the dental capsule are similar to those entertained by other 
writers, and very different from the opinions which 1 shall have 
an opportunity of stating in the course of the present woik. His 
remarks on the succession of the teeth of fishes are very accurate. 
We now come to speak of the justly celebrated work of Jos. 
Fox, which appeared in 1803. He was one of the first members 
of the profession who devoted his practical attention exclusively 
to this particular department of the healing art. As a practition- 
er he was most skilful; and in his lectures at Guy's Hospital he 
laid much valuable information and many excellent rules of 
practice before the students of his time. The opinion he enter- 
tained of his great predecessor, Mr. Hunter, is thus expressed :- 
"Mr. Hunter's publication on the teeth was the first scientific 
book ever published upon this subject; and as an anatomical 
work must ever enjoy great celebrity; but not having practically 
devoted much of his attention to the operations upon the teeth, theie 
can be no reflection upon Mr. Hunter's merit in stating, that in 28 
HISTORICAL INTRODUCTION. 
many essential points he was wholly and unavoidably deficient."* 
Again (at p. 18) he states that "into Mr. Hunter's treatise, for 
want of closer attention, many inaccuracies have been suffered 
to creep." 
The development of the teeth is very accurately described by 
this author, who, in his description of the successive appearance 
of the different teeth, anticipates the remark regarding the more 
early development of the first small grinder, which more than 
twenty years afterwards was claimed as original by M. Serres. 
It ought to be observed, however, that from the cursory manner 
in which Fox mentions this fact, the subject hardly obtains its 
due importance. Serres, I have no doubt, was totally ignorant 
of the existence of Mr. Fox's work or he must have known that 
the excellent plates in it present a correct delineation of this 
phenomenon. 
Fox considers that the teeth differ in their formation from 
bones only in having a covering of enamel, and in being more 
dense, and he is a strenuous advocate of the vascularity of the 
teeth. He notices the intimate union of the capsule to the gums, 
and also the two layers of which the capsule is composed, both 
of which he states are vascular. He holds that the capsule or 
membranes derive vessels from the gums, but the pulp from the 
jaw. This is contrary to the opinions of Hunter and Blake, who 
again differ from each other, inasmuch as the former considers 
that the inner layer only is vascular, whilst the latter maintains 
that vessels are found in the outer layer alone. He mentions, 
(p. 23,) that in a young elephant dissected by Sir A. Cooper, "the 
adhesion of the pulp to the chamber around was strong, and re- 
quired a considerable degree of force to separate." Cuvier 
expressly denies that any such intimacy of union exists in this 
case. 
According to Fox, the enamel is fibrous, and the ivory strati- 
fied; he considers the periosteum of the fang common to both it 
and the alveolar process, and states (p. 2, pt. ii.) that it is a 
reflection on the fang, being firmly attached to the gum at the 
neck of the tooth. 
This writer again differs from Hunter in considering the teeth 
from their vascularity as similar to bone, and as only differing 
from it inasmuch as they are denser, and their exposed surface is 
covered with enamel. They are moreover subject, he says, to 
the same diseases as bone, but cannot exfoliate like the latter. In 
enumerating their diseases, he uses the same nomenclature as for 
those of bones. 
According to him, it is a process of absorption which opens a 
passage for the extrusion of the teeth, this absorption taking place 
first in the membranes, and then in the gum. 
* Preface, p. ix. third edit. 29 
Fox is at issue with Hunter on the subject of the origin of 
decay ; the former expressing himself surprised that the latter 
should not have arrived at its true cause, which, according to 
him, is inflammation terminating in mortification. He considers 
that disease originally attacks the internal membrane or pulp, 
causing suppuration, but not attended with decay in the solid sub- 
stance of the tooth. In cases of this kind, he recommends a hole 
to be drilled in the side of the tooth to allow the escape of the 
matter. Under this head he observes, that the pulp in its diseased 
state is separated from the bone, (thus forming one of the causes 
of external decay,) but in its healthy state adheres firmly to it. 
As other causes of decay, he mentions the faulty organization of 
the ivory or enamel, and many circumstances dependant on the 
constitution of the individual, as also contact with another decay- 
ed tooth, the crowded state of the teeth in general, want of clean- 
liness, disease of the gums, putrefaction from tartar, &c. His 
observations on the diseases of the teeth are excellent, and dis- 
play much judgment and discrimination ; but still an era of inves- 
tigation has since commenced, which has thrown much new light 
upon the pathology of the teeth, and considerably facilitated the 
diagnoses of their diseases. 
The remaining parts of Mr. Fox's work are replete with sound 
and valuable information. In the article on artificial teeth, he 
observes of Mr. Hunter's operation of transplanting, that "he was 
naturally partial to it from its being of his own invention." He 
is not, however, correct in this, as we have seen that Ambrose 
Pare alluded to it two hundred years before Hunter. 
Fox's Operative Surgery was excellent for the time at which 
he wrote, but may now be said to be almost entirely obsolete. 
The next work we have to examine is from the hand of that 
able and intelligent practitioner, Mr. Thomas Bell, the accom- 
plished successor of Mr. Fpx as lecturer on this subject at Guy's 
Hospital. In this work are found incorporated all the facts 
known at the time, and many excellent practical considerations. 
He is of opinion that teeth are true bone. "That they possess 
vitality, and are connected by their organization with the general 
system, having nerves, blood-vessels, and absorbents, and are 
analogous in this respect to true bone," is his expressed opinion.* 
He considers the membrane of the pulp to be a production of the 
periosteum of the alveolus. The adhesion existing between the 
membrane and the bone of the tooth he considers is owing to the 
passage of "numerous vessels, &c. from the one to the other 
and he shows throughout the whole of his work that he is a most 
HISTORICAL INTRODUCTION. 
* Page 9. 30 
strenuous advocate for a degree of vitality in the teeth equal to 
bone, and adduces as a proof of that opinion the red tinge in the 
teeth of persons who have died of strangulation. He considers 
that "the periosteum of the maxillary bones, after covering the 
alveolar processes, dips down into each alveolar cavity, the 
parietes of which it lines. From the bottom of the cavity where 
the vessels and nerve of the internal membrane enter, it appears 
to be reflected over the root of the tooth, which it entirely covers 
as far as the neck, at which part it becomes intimately connected 
with the gum."* The ivory of the tooth, he considers, is a secre- 
tion from the membrane of the pulp, and not from the pulp itself; 
and agrees with Dr. Blake in "conjecturing this membrane to be 
a propagation of the periosteum of the jaw." He agrees with 
Fox regarding the vascularity of both layers of the capsule, and 
that the external layer secretes the crusta petrosa. He divides 
the membranes of the teeth generally into deciduous and persis- 
tent; "the deciduous being the two lamellae of the capsule; and 
the persistent are, 1st, the internal periosteum of the dental 
cavity; 2nd, the periosteum of the root; 3rd, the periosteum of 
the alveolus." He considers that the external layer of the capsule 
does not extend farther than the neck of the tooth, and with the 
internal layer becomes absorbed. The outer layer he considers 
merely rudimentary in man and other animals with simple teeth. 
The shedding of the temporary teeth he calls a process of antici- 
pation. The practical digest of the diseases which occur both in 
the early and adult state of these organs is excellent, and conducts 
to the best rules of practice. 
Since Mr. Bell's work made its appearance, we have had 
several manuals on the teeth displaying talent and industry, by 
Mr. Koecker, Mr. Jobson, Mr. Waite, and others. 
To return to the French school.-In 1812 appeared the Baron 
Cuvier's work on Fossils Remains, every department of which 
displays equal brilliancy of talent. The section in which he treats 
of the structure of the teeth of the elephant, contains much mat- 
ter of great importance. He holds that the ivory and enamel are 
formed by the gradual production of superimposed laminae ; and, 
in direct opposition to the opinion of all his predecessors and con- 
temporaries, he says, "Pour moi,je me suis assure que le cortical 
est produit par la meme lame et par la meme face qui a produit 
PemailP He holds that the different substances which constitute 
the teeth are produced by excretion and in layers; "that the 
internal substance in particular has nothing in common with ordi- 
nary bone but its chemical nature ;" that it consists of equal pro- 
HISTORICAL INTRODUCTION. 
* Page 42. HISTORICAL INTRODUCTION. 
31 
portions of gelatine and of phosphate of lime ; but that it does 
not resemble bone either in its tissue, or in its manner of deposi- 
tion and increase. "Son tissu," he add, "n^offre ni cellulosite, ni 
fibres, mais seulement des lames emboite.es les unes dans les autres." 
He gives at length his reasons for believing that it is entirely non- 
vascular. 
In speaking of the capsule, he remarks, "11 ne produit point 
d'email ni de cortical sur les racines, parceque la lame interne de 
la capsule, qui a seule le pouvoir de secreter ces deux substances, 
ne s'etend pas jusque-la.'"' (p. 43.) The recent researches of 
the German school decidedly prove this observation to be incor- 
rect. 
In treating of the tusks of the elephant, he states from actual 
observation, that there is no connection whatever between the 
pulp and the ivory, and under this head he cites the appearance 
presented by the decomposition of fossil teeth as corroborative of 
his opinion regarding the concentric layers of growth. 
His remarks on the diseases of the teeth are generally fraught 
with sound sense and practical information. 
In 1817, M. Serres published a most interesting little work 
on the Anatomy and Physiology of the Teeth, in which he treats 
particularly of their organization at an early stage. He says,* 
"The rudiments of the head, and of all the organs which it con- 
tains, exist almost as soon as the embryo begins to be distinct in 
the product of conception; the teeth, which are destined to per- 
form the first function in the circle of life, are formed and deve- 
loped in the interior of the maxillary bones. Preceding anato- 
mists have only ascertained the existence of their germs at a late 
period of foetal life ; but I have thought it necessary to examine 
them at as early a period as possible. "In the jaws of an embryo 
of two months, I found the germs of the first incisors and small 
molars ; but I could not find the canine till two months and a half; 
at three months I discovered the germs, not only of the first, but 
also of the second dentition, and even that of the wise tooth. 
These germs are found lodged in membranous folds, which form 
at this period the gum ; those of the first dentition are immediately 
attached to this fold ; those of the second are suspended from it 
by a pedicle of about two lines long, which alone enables them to 
be distinguished, together with the yellow colour which they con- 
tract by exposure to the air, and which contrasts with the dull 
white of the gum. At four months I found fibrous partitions 
separating the incisors ; but all the other germs were contiguous 
to each other. At six months the osseous partition of the incisors 
was very distinct; that of the small molar was also partly ossified ; 
and the two posterior molars were contained in the same division." 
* Essai sur l'Anatomie et la Physiologie des Dents, &c. Paris, 1817. p. 2 32 
HISTORICAL INTRODUCTION. 
He gives a very circumstantial account of the position of these 
germs, and of the mode of demonstrating them, which consists in 
detaching them from the internal portion of the alveolar arch. 
He comes to the conclusion that he has "demonstrated the pre- 
sence of all the germs in the jaws of the foetus." (p. 9.) 
He states that he has insulated all the pulps of the first set in the 
jaws of a foetus without disturbing either the capsule or the gums, 
and concludes that the pulp and the capsule "quoiqu' intime- 
ment unies sont distinctes I'une de 1'autre." (p. 11.) 
He then proceeds to describe the dental membrane, as he calls 
it, or capsule, enclosing the germs of the teeth, and in the interior 
of which these bones are developed. This he states to be com- 
posed of two plates or layers, "one external and the other inter- 
nal, distinct not only in their destination, but also in their 
structure and functions. The external layer, which is fibrous, is 
opaque and whitish; on one side, it lines the interior of the alveo- 
lus, and serves as a periosteum; on the other, it is applied to the 
external surface of the internal layer. Closely adhering at its 
inferior part to the dental nerves and vessels, it unites with the 
cartilage of the gums, and when the tooth has protruded, it em- 
braces its neck. It is endowed with a considerable degree of 
elasticity, and compresses the liquid in which the tooth is plung- 
ed ; this appears," he says, "to be its use; for if a small opening 
is made in it, or if a small portion of it be removed, the internal 
layer, and the liquid which it contains, immediately protrudes 
like a hernial sac through the opening, which proves that com- 
pression must be exercised by the external layer." 
"The internal layer is a very delicate transparent membrane 
sui generis. Bichat affirms that it is serous; but it is entirely 
vascular, and differs in this respect from that class of membranes: 
moreover, the fluid which it secretes is mucous as well as serous. 
It differs from mucous membranes, inasmuch as it has no folli- 
cules, and in its natural position may be regarded as a closed 
sac. I consider it as intermediate between these two orders of 
membranes. Externally it is covered, as we have stated, by the 
external layer, to which it adheres with considerable tenacity, 
particularly superiorly at the place where it corresponds to the 
fibro-cartilage of the gums. At the spot where the vessels and 
nerves penetrate, it detaches itself from the external layer, to 
which it does not henceforth seem to be united, except by means 
of small vessels which pass from one layer to the other. Being 
now isolated from the external layer, it is reflected from below 
upwards, and evelopes the vessels and nerves as far as the base 
and the inferior circumference of the pulp, where it is evidently 
inserted ; whether it is continued over the surface of the pulp or 
not, I cannot say; but I have never been able to follow it fur- HISTORICAL INTRODUCTION. 
33 
ther than the base, though I have made several careful attempts. 
It results from this arrangement, 1st, that the sac formed by this 
layer is closed above by the dental pulp, which forms a kind of 
lid to it; 2dly, that this pulp is not enveloped by the membrane, 
and that it is free in the interior of the sac which it forms, bathed 
by the fluid which it secretes; 3dly, also that the external mem- 
brane is prolonged no further than the place where the vessels 
and nerves pass in order to penetrate the dental germ, and that 
it closely adheres to them." (p. 14.) 
Serres next proceeds to give an account of the dental arteries 
and nerves, and states that although the adult subject possesses 
only one canal, the foetus, and even the infant till its sixth or sev- 
enth year, (or till that age when the removal of the first tooth 
commences,) possess two canals for the transmission of vessels : 
he gives a drawing of this arrangement, which I believe is far 
from having been established as a constant appearance. 
"From whatever trunk," says this author, "are derived the 
vascular branches which penetrate the roots of the teeth, their 
distribution in the germs is always the same. When they reach 
the base of the tooth, they pierce the external layer of the 
membrane, and are continued to the internal layer, on which 
they ramify to such an extent that this portion of it is rendered 
entirely vascular in appearance. Beyond the point where the 
internal layer of the membrane is inserted, several branches pen- 
etrate the substance of the dental bulb. I have followed them to 
the distance of a line from the point where dental ossification 
takes place. It is to be remarked, that all round the point of in- 
sertion of the internal layer into the base of the bulb, the vessels 
are much more numerous than at any other part, and that they 
form a vascular circle similar to the anterior and posterior cir- 
cles of the iris; it is also to be remarked, that this circle, or this 
reddish areola, which they form on the bulb, descends in propor- 
tion as ossification advances, a circumstance which results from 
the mechanism of the formation of the teeth. It is worthy of no- 
tice and admiration, that these vessels in teeth with a single root, 
form only a single bundle; in teeth with double roots, they form 
two bundles; and they are divided into three or four, if the tooth 
is to have three or four roots." (p. 19.) 
In this work of Serres we find a minute account of the dental 
nerves, and of a plexus which, he says, is situated beneath the 
incisors and canines; and this is accompanied by some excellent 
remarks on the sympathetic pains experienced in the teeth and 
adjoining parts. 
He is almost the first who pointed out what he calls the den- 
tal glands, which he describes as small sacs or cysts disposed in 
regular groups spread over the whole cartilaginous substance 34 
which form the gums of the new-born infant. Their function, he 
considers, consists in lubricating the cartilages of the gums ; they 
also, he thinks, assist the infant in the act of sucking, by retaining 
the nipple of the mother. He has succeeded in pressing a fluid 
like serum out of them ; and he says that they resemble the Meibo- 
mian glands. They are numerous, and the largest are situated in 
the internal portion of the gum. In the adult subject, Serres main- 
tains that their function is changed to that of secreting the tartar; 
and he follows up this opinion by observations on that substance 
which it is not necessary here to discuss. We must also pass over 
in silence his ideas on the physiology of the facial angle at the 
different periods of life. 
The second part of his work is devoted to the physiology of the 
teeth; and he commences it by.the general assertion that these 
organs belong to the osseous system, but are still of a different 
"tissue." They are composed, he says, of three different sub- 
stances ; viz. enamel which covers the crown, a bony part which 
constitutes the base and a soft part which fills up the internal 
cavity, adont la nature ne nous estpas encore bien connue." The 
position and texture of the enamel are well described., He con- 
siders that it does not acquire its hardness and polish till it is ex- 
posed to the air; and he combats the opinions of Herissant and 
Cuvier on this subject. He has never been able to see the folli- 
cles of Herissant. This substance has never appeared to him to 
be fibrous; and he asks why its functions are interrupted when it 
reaches the fang. After making observations and conjectures on 
the origin and structure of the enamel, he concludes by confessing 
that "il reste beaucoup de choses afaire sur les dents." 
In regard to the osseous part of the tooth, or ivory as it is 
called, he commences by citing Bichat's opinion that it is fibrous, 
and dismisses the subject by observing that he has never been able 
to demonstrate any fibres in it, though he has treated it with acid 
and submitted it to the action of fire. He concludes by a series 
of observations (p. 45) on the difference which he Considers to exist 
between bones and teeth, and these, in order better to illustrate the 
subject, we will place in parallel columns:- 
HISTORICAL INTRODUCTION. 
A BONE 
Passes through a cartilaginous stage. 
Has a periosteum. 
Is affected by rachitis and the other 
diseases of the osseous system. 
Is destroyed by concentrated nitric 
acid. 
A TOOTH 
Passes through no cartilaginous stage, 
but is a transudation from the sur- 
face of the pulp. 
Has no periosteum. 
Is not affected by rachitis, or the other 
diseases of the bones. 
Is not affected by concentrated nitric 
acid. 35 
HISTORICAL INTRODUCTION. 
When calcined, leaves a bluish re- 
sidue. 
Remains untouched in extra-uterine 
conception. 
Is not vascular. 
When calcined, leaves a white re- 
sidue. 
Is destroyed in extra-uterine concep- 
tion. 
Is vascular. 
Finally, bones decay much more quickly after interment than 
teeth; and the diseases of bones and teeth offer the least possible 
analogy. Serres relates many curious facts touching the inde- 
structibility of the latter. 
The pulp he considers as especially formed by the nerve; and 
in fact, he regards it as a ''veritable ganglion," (p. 53); and this 
opinion he follows up by speculations on its formative functions, 
and on the fluid which he says surrounds it. 
He is opposed to instituting any analogy between the pulp and 
the cartilage of bone; he regards the tooth as an evident secre- 
tion from the pulp; and, with respect to the structure of the for- 
mer, makes an unfortunate assertion which has been signally 
refuted by the researches of more recent inquirers in this branch 
of science. His words are:-"A quelques epoques qu'on les con- 
sidere, on n'apercoit aucune trace fibreuse, aucune maille cellu- 
leuse, qui aient de la parite avec le systeme osseux." (p. 62.) 
On the eruption of the teeth he makes some very excellent 
remarks; but, together with all who have hitherto written on the 
subject, he hold that the capsule is absorbed, or detached from the 
crown, at the period of extrusion, but that it adheres to the neck, 
and forms by its external layer the periosteum of the socket, 
whilst its internal layer adheres to the fang of the tooth. 
With regard to the order of eruption, he is one of the first who 
pointed out a circumstance of considerable practical importance, 
which is, that the first small grinder succeeds next to the lateral 
incisor, and that the canine appears afterwards, contrary to the 
generally received opinion that the canine succeeds the lateral 
incisor; he gives a summary of reasons why the former must be 
the case. 
His views on the process of shedding, and on the various theo- 
ries extant on this subject, are concisely stated ; but it does not. 
appear to me that his own hypothesis throws much new light on 
this process. His explanation resolves itself to the acknowledg- 
ment of a "loi primordiale, dont on ne peut donner aucune raison 
physique," which destroys the partition between the alveoli of the 
two sets of teeth, and liberates the root of the first tooth, which 
becomes loose, and falls out on the slightest movement. He does 
not consider it as a necessary consequence that the fangs of the 
first set should be absorbed. 
He discusses at considerable length the order and period of 
appearance of the second set of teeth, and the contradictory 36 
HISTORICAL INTRODUCTION. 
accounts which have been given of this phenomenon ; he has 
evidently studied the subject, and his own ideas on it are narrated 
with great perspicuity. He concludes his work by a rather 
lengthy enumeration of supposed examples of third sets of teeth, 
and of other irregularities. 
Generally speaking, his pathological remarks, such as those 
respecting stumps, do not accord with the results of practical 
observation. 
The genius of Baron Cuvier not only displayed itself in his 
own discoveries, but in the facilities which it opened to the 
researches of others. Two works on the teeth have originated 
with his scholars, both of which confer great honour on their 
authors. The first of these appeared in 1825, and is entitled, 
"On the Teeth of the Mammalia considered as zoological charac- 
ters," by F. Cuvier : a work forming a most useful and interest- 
ing accession to our knowledge of natural history. The illustra- 
tions are executed with great care and fidelity, and form a perfect 
text-book of reference. The work is preceded by a most valuable 
dissertation on the development and structure of the teeth, replete 
with sound sense and accurate observation. The author con- 
siders the teeth as appendages to the skin, and as analogous in 
some respects to the other dermal appendages, inasmuch as they 
are secreted by somewhat similar organs; and also, inasmuch as 
they may be said to be dead, being devoid of vessels and nerves, 
and consequently insensible. But, though they resemble dermal 
productions in these respects, he does not think that they ought to 
be included in the same category, seeing that they still differ from 
them in some essential particulars. According to him, the Orni- 
thorynchus possesses the most simple teeth, for in this animal they 
are entirely composed of gelatine. The next in order have a 
gelatinous base with earthy salts deposited in their meshes. These 
two forms, simple as they are, differ essentially from horn or hair; 
and he considers them as true secretions from organs destined for 
the purpose. In common with his brother, he regards them as 
distinct from bone; but at the same time he admits that they are 
more similar to the latter than to either hair or horn. 
To whatever set of appendages they may be considered as 
analogous, the teeth, he says, consists of a secreting and a secreted 
portion, at their origin as well as during their whole life. The 
secreting organ, composed essentially of vessels and nerves, is 
always placed internally, and is composed of three, or at least 
two, other organs. Around this is deposited the secreted portion, 
formed of a certain number of substances entirely non-vascular, 
and removed from all immediate connection with the system at 
large. It can be demonstrated, he continues, by mechanical ana- HISTORICAL INTRODUCTION. 
37 
lysis, that only three substances enter into the composition of all 
the different classes of teeth. One class consists of ivory, enamel, 
and "cortical;" a second, of ivory and enamel; a third, of ivory 
and cortical; a fourth, of ivory alone. The two kinds of fangs 
he designates as real and apparent. 
His views on the capsule are as follows :-"It appears to be a 
production of the maxillary nerves and vessels ; but it is not with- 
out relation to the contiguous parts, being even connected with 
the gum, but to a much less extent than most authors have stated." 
He call this a secondary attachment, but has not had an opportu- 
nity of examining it at an early stage of development. The 
capsule he states, is adapted to the nature of the tooth which is to 
be formed from it. Thus teeth which are composed of three sub- 
stances, have capsules divided into three distinct portions, each of 
which is to be considered a distinct organ. The first of these is 
the central portion or bulb, which produces the ivory; the second 
is in the form of a membrane, and produces the enamel; the third, 
called by our author the external, envelopes all the others, and 
produces the cortical or external ivory. 
The bulb, he says, appears to be entirely composed of nerves 
and vessels, and is surrounded by the "membrane emaillante," 
except at its base, corresponding to the neck of the tooth where 
the membrane terminates. It is deprived of vessels and disap- 
pears entirely when the functions of the external membrane 
commence. The external membrane he describes as highly 
vascular, and as forming an external pulp: he assigns to it the 
formation of the cortical substance, and the protection of all the 
other formative processes of dentition. "Elle est percee," he 
adds, "a son sommet par revolution de la dent, mais ses Lords 
s'attachent aux, gencives, et en deviennent en quelque sorte la 
continuation." (p. xxiv.) 
In the tusks of the elephant, he considers that the ivory is de- 
posited in concentric layers, and refers for proof of this to fossil 
remains: its texture differs, however, in different animals-in 
man, the monkey, and in carnivorous animals, for instance, it ap- 
pears to be fibrous. It is of a uniform contexture in the whale, 
hippotamus, &c., whilst the teeth of the orycteropus seem formed 
of longitudinal and parallel fibres, "qui rappelleut la structure du 
jonc." 
The enamel, F. Cuvier describes as apparently crystalline, and 
as deposited in a direction contrary to that of the ivory. Accord- 
ing to him, the cortical substance is of "absolutely the same" na- 
ture as the ivory-generally speaking, it contains only gelatine 
and phosphate of lime; but in some cases colouring matter in ad- 
dition, as for instance in many ruminants, in the incisors of the 
castor, hedge-hog, &c. 38 
HISTORICAL INTRODUCTION. 
He relates that, amongst herbivorous animals, the vitality of 
the pulp continues for several years, but ceases in carnivorous 
animals at a very early period. 
The two sections which this writer devotes to the consideration 
of the relative development of the teeth are admirable, and con- 
tain a mass of excellent and original matter. 
The second work by a scholar of Cuvier, to which we have 
above alluded, is the ''Comparative Anatomy of the Dental Sys- 
tem in Man, and the principal Animals. Paris, 1827. By AI. 
Rousseau." This author acknowledges that the subject is part 
of the "Baron's great domain;" but he has cultivated it with 
great industry, and has arrived at some very interesting results. 
His description of the anatomy of the jaws and gums is quite 
satisfactory as far as it goes; but he concludes the subject by 
saying, "Il me semble que ce point d' anatomic n'a pas ete jusqu' 
ici aussi bien eclairci qu'il est susceptible de Petre." (p. 45.) 
At the commencement of his general considerations on the de- 
velopment of the teeth in man, he remarks, "that it is probable 
that the embryo contains, from the first moment of its conception, 
the rudiments of all the organs ultimately necessary to the exis- 
tence and perfection of the individual." He gives a very excel- 
lent description of the sacs and pulps, agreeing with Herissant in 
his views concerning their anatomical structure and functions. 
He believes that the formation of the ivory does not commence 
until after the enamel has began to be deposited. Air. Hunter's 
experiment with madder proves, he thinks, the concentric depo- 
sition of the dental substance; but, strange to say, he ascribes 
that experiment to Cuvier, whose work was not published less 
than forty years after Air. Hunter had described it. With re- 
spect to the fibrous structure of the teeth, he compares its appear- 
ance to the rays of a quill. He notices and explains the "osteides," 
which are found occasionally in the internal cavity of the teeth, 
and which Bertin had noticed before him. 
According to Rousseau the second set of teeth are more solid 
than the first, being required for harder aliment. He asserts that 
the first set of teeth exert so strong a pressure on the alveolus, 
that they deprive the milk-teeth of nourishment and vitality by 
compressing the nervesand vessels which are distributed to them. 
In his opinion the order of succession is quite different from that 
which Serres gives with regard to the canine. 
The work under consideration gives a very accurate descrip- 
tion of dentition in many of the lower animals, The porous 
appearance of the teeth of the orycteropus is remarked, which 
has so erroneously been considered as a striking example of the 
tubular structure of the teeth. HISTORICAL INTRODUCTION. 
39 
Rousseau maintains that what has obtained the name of corti- 
cal or cement, is nothing but a dental tartar, and he attempts to 
explain the manner in which this is produced. 
The section which he devotes to the "aberrations and maladies 
of the dental system," is very instructive. He traces the origin 
of the erosin of the teeth to a congenital source, and explains the 
mode in which he conceives that it is effected. "There are 
examples," he says, "where the foetus has been attacked by 
partial or general inflammations, without any morbid affection on 
the part of the mother .... This truth has been confirmed by the 
examination of subjects, in whom some teeth of the first dentition 
were apparent, on the enamel of which were observed points 
similar to those produced by engraving or chiseling; which 
proves that these inflammations having attacked a greater or less 
quantity of the small vesicles which secrete the enamel, at the 
moment when nature was engaged in the formation of the dental 
system, deprived of this substance all the places where they 
caused ulceration and the destruction of these excretory glands, 
leaving there furrows, which are called erosions.', (page 240.) 
In regard to the accidents which the teeth experience, he 
attaches considerable importance to the cracking of the enamel 
by rapid alternations of heat and cold, and cites an old adage, 
"that a glass of wine drunk immediately after soup draws a 
crown from the pocket of the physician, and puts it into that of 
the dentist." 
Caries of the teeth, according to this author, is simply ulcera- 
tion-many causes, both internal and external, predispose to this 
malady, as a scrofulous or scorbutic diathesis, the humidity or 
particular character of the atmosphere, the nature of the water 
which is drunk, &c. &c. The latter causes are supposed to ope- 
rate in the province of Caux in France, and in the neighbourhood 
of Beauvais in Picardy, where the greater part of the inhabitants 
have the two centre incisors of the upper jaw decayed; after 
these the laterals begin to be affected, and so on, so that by the 
time the individual has arrived at the age of thirty, he has in 
general lost almost all his teeth. Rousseau is unable to decide 
whether this results from the air, the water, or from the immense 
quantity of apples which are consumed in these parts. He 
remarks, "that the inhabitants of large cities are most subject to 
decay of the teeth-that the dog, the faithful companion of man, 
in good or bad fortune, is often attacked by it, and that the cat, 
which inhabits our houses, is equally liable to it." Savage tribes, 
on the contrary, appear to retain their teeth in health, although 
worn. 
Carnivorous animals have very healthy teeth: in the savage 
state, indeed, time appears to effect no change in them, except 
that by degrees they become worn down. 40 
Amongst other cases of disease in the teeth, Rousseau mentions 
one of a bony growth internally, and another of exostosis of the 
fang, similar in structure to the latter. 
In the excellent edition of Hilderbrand's "Handbuch der Ana- 
tomic," by Weber, we find the following on the structure of the 
ivory: "Although its fracture in recent teeth is smooth, and 
shows no fibres or leaves, still many facts prove that its sub- 
stance is not quite uniform. The fractured surface has a bright 
silky lustre, which is still more perceptible when it is polished. 
In teeth which have been fractured longitudinally, bright lines are 
seen, curved in much the same manner as is the inner surface of 
the cavity of the tooth on the side which is towards the surface; 
whence we may presume that the osseous substance of the tooth 
consists of several concentric layers, which we have no method 
of separating from each other. Teeth are also more easily bro- 
ken longitudinally than in any other direction ; and Rudolphi ob- 
served that when the osseous substance of the crown was separa- 
ted in very diluted nitric acid from its investment of enamel, the 
crown (but not the roots) divides longitudinally into several 
pieces, of which the number is tolerably definite in the different 
classes of human teeth. In Weber's edition of Rosenmuller's 
"Handbuch der Anatomic" fifth edition, Leipsic, 1833, it is stated 
that the ivory, macerated in diluted muriatic acid, is converted 
into a white, half transparent, smooth, shining cartilage, in which 
no fibres can be distinguished. 
The discovery of the lines or streaks above alluded to has 
been attributed to Schreger, but this is a mistake, they were 
mentioned by Duverney so early as 1639, and have been dis- 
tinctly described by Sommering. In Cuvier's " Recherches sur les 
Ossemens Fossiles," (t. i. p. 31.) he thus speaks of the structure of 
the ivory in the teeth of the elephant: "Its tissue is neither cellu- 
lar nor fibrous, but presents merely laminae encased one within 
another." Wager says of the ivory, that it presents "a hard, 
shining, sometimes foliated or fibrous arrangement." (Verg. Anat. 
Leipsic, 1834, 1835.) Frederick Cuvier says, "that the teeth of 
man, of monkeys, and of carnivorous animals, have an ivory of 
a silky appearance, which seems formed of fibres." (Dents des 
Mammiferes. Discours Prelim, p. 27.) G. Cuvier describes the 
enamel as follows-(Sur les Ossemens Fossiles, tom. i. p. 34)- 
"In the first place, the enamel is deposited on the surface of the 
substance called osseous by the internal membrane of the cap- 
sule, in the form of little fibres, or rather of little crystals, all 
perpendicular to this surface, and forming there at first a sort 
of velvet a brinsfms. When the capsules of the germ of a tooth 
HISTORICAL INTRODUCTION. HISTORICAL INTRODUCTION. 
41 
is opened, the little molecules of the future enamel are found 
adhering, but as yet very slightly, to the internal face of this cap- 
sule, and are easily detached from it. A part of them are even 
found swimming in the liquor interposed between the capsule and 
the germ." 
The "crusta petrosa" has been seldom mentioned by writers 
on the teeth. Hunter only speaks of it in the first stage of its 
formation. Tenon, in his excellent Treatise on the Changes of 
Form in the Teeth of Horses, (Mem. de 1'Institute Nationale des 
Sc. et des Arts, sec. Math, et Phys, pour Pan. 6, p. 568,) is the 
first who gives a good idea of it; he calls it cortical osseux. 
Cuvier (op. cit., p. 35) says, "that the 'cortical' is produced by 
the same lamina and the same face which has produced the 
enamel; which is proved by this lamina remaining externally to 
the 'cortical,' as it was before external to the enamel, and that it 
is soft and loose so long as room is left it by the 'cortical? The 
nature of its tissue, however, changes: so long as it only fur- 
nished enamel, it was thin and transparent; but in order to pro- 
duce the 'cortical' it becomes thick, spongy, opaque, and of a 
reddish colour." 
In tracing the progress of knowledge in this department of 
science, we have now arrived at an era of novel and important 
investigation, highly honorable to the zealous inquirers who have 
commenced it, though more from the results it promises than 
from the practical facts which it has as yet established. 
Researches on the structure of the teeth by Purkinje have lately 
been given to the world in a dissertation by one of his pupils, 
(K Fraenkel de penitiori dentium humanorum structura observa- 
tiones." Purkinje found in the gum of the new-born child the 
small sacs discovered by Serres, and, in the fluid they contained, 
thin quintangular lamellae, enclosing in their centre a round ker- 
nel, which he also found in the saliva and epithelium. He states 
that the substance of the tooth and the enamel have a near simi- 
larity to the structure of bone, but on the outer surface of the 
root, he says, that there is a layer of true osseous substance, in 
which, at any rate, may be seen the osseous corpuscula which 
he has discovered.* This same structure he has discovered in 
the cement of the teeth of several animals. The proper dental 
substance examined in thin polished lamellae consists of a uniform 
structureless (structurlos) substance, and of fibres passing through 
it. These latter run in parallel lines from the outer to the inner 
surface of the tooth, obliquely in some places, straight in others: 
they are in every part nearly of the same size, and communicate 
* Muller states that he has had frequent opportunities of confirming these 
results. 42 
by but few branches with each other. Though they are very 
thickly placed, still the structureless intermediate substance forms 
the greater part of the mass of the tooth: as their diameter he 
gives one-fifth or one-sixth of the space between two of them. 
He has also discovered that these fibres are tubular, and that in 
the teeth of the horse, at any rate, they are capable of absorbing 
ink by capillary attraction-a fact which is also confirmed by 
Muller. As to what these tubuli may contain in their normal 
state, Purkinje is silent; but Muller has instituted researches 
which go to prove that parts of them, at any rate, are filled with 
inorganic, calcareous salts. The latter goes on to say, that when 
the light falls on fine polished lamellae of dental bone, the white 
colour of the tooth is soon seen to be owing to these tubes or 
fibres, and that the intermediate substance is more transparent; 
moreover, that when such sections are submitted to the action of 
an acid, the white colour of the fibres disappears, the remaining 
cartilage still presenting tubes in their interior, which, however, 
when dried, are no longer white. He saw in healthy as well as 
in carious teeth, that in parts of these tubes something was con- 
tained. Linderer, who has long been engaged in researches on 
healthy and decayed teeth, has observed, that the dental substance 
in the latter (even where the enamel only is affected) loses its 
colour in several parts between the carious spot and the internal 
cavity. As this is nearly always the case, it is evident that an 
alteration in the substance of the tooth must be produced by the 
superficial caries. In fine polished sections of such teeth, Muller 
could easily see with the microscope, that where they were be- 
come transparent, a crumbly substance was contained in parts of 
the tubuli, and that this substance was more coherent in the tu- 
buli of the white tracts; by adding diluted acid, he also observed 
under the microscope that this crumbly substance was dissolved. 
He has often performed this experiment with the same result on 
fine polished slices of healthy teeth. In these he found individual 
fibres, frequently in considerable number, on which were dark 
spots following close on each other. 
Inasmuch as the dental fibres have their white colour destroy- 
ed by acids, whilst the intermediate substance remains transpa- 
rent, it follows that either the parietes of the tubes, or their 
interior, must contain calcareous salts. In breaking fine sections 
of teeth perpendicularly to the fibres, Muller has frequently seen 
the latter projecting a little at the fractured edge. In such cases 
they are quite straight and not curved, and seem to be not at all 
flexible. Hence it follows that the tubes have an organised basis, 
a membrane, and that this in the solid tooth is stiff and brittle, 
and probably saturated with calcareous salts, but weak and soft 
in the tooth which has been deprived of the latter. 
HISTORICAL INTRODUCTION. HISTORICAL INTRODUCTION. 
43 
The calcareous salts of the tooth exist not merely in the tubuli, 
but also in the intermediate substance, which contains, at all 
events, the greater part of the calcareous earth, either chemically 
united with the cartilage, or deposited in it in an invisible manner. 
The calcareous earth of the intermediate substance may be ren- 
dered visible, by carefully boiling for several hours fine sections 
of teeth in a solution of potash. The substance between the 
fibres, which was before transparent, then becomes, from the 
solution of a great part of its cartilage, opaque and white; and 
the sections are rendered extremely brittle, and cannot without 
great caution be further polished. The calcareous matter pre- 
sents the appearance of thickset granules. Near the cavity of 
some teeth which had been treated in this way, lines were observ- 
ed running parallel to the surface of the former. 
According to Purkinje's researches the enamel consists of sim- 
ple perpendicularly-placed fibres, increasing somewhat in size 
towards their upper extremity, forming quadrilateral prisms, and 
often making several curves on one and the same level. These 
fibres are adherent to lamellae, which run transversely round the 
tooth, and generally rest obliquely on the surface of the dental 
substance. These observations are fully confirmed by Muller, 
W'ho has examined the last molar tooth of a calf, on which the 
enamel was still soft, and found that even in this state the latter 
consists of separate prisms, as yet uncemented, but held together 
by a transparent fluid matter. These firm but somewhat flexible 
fibres are not easily acted on by acetic acid, but quickly dissolve 
in muriatic acid, without any perceptible escape of air. 
The interior of the roots of old teeth consists, according to 
Purkinje, not of dental substance, but of bone properly so called, 
as does also the deposit on the external surface of the root, and 
this statement is confirmed by Muller. The teeth have been 
reckoned by some amongst the corneous formations; but though 
they grow in layers like the latter, still they contain no horn, as 
Muller has repeatedly satisfied himself, but true cartilage yield- 
ing glue. From the dental cartilage of a horse's tooth, he obtain- 
ed by boiling, a large quantity of beautiful colourless glue. 
Whalebone, and other corneous formations, which supply the 
place of teeth, consist, he has found, of true horn, and furnish no 
glue, however long they may be boiled. It would seem from 
this, that horn supplies the place of dental cartilage when the 
teeth contain no deposition of calcareous earth. This is the case, 
at any rate, with the vertebrata. 44 
HISTORICAL INTRODUCTION. 
We now proceed to give an account of the late researches of 
Professor Retzius, of Stockholm,* which have excited so much 
attention, and thrown so much light on the structure of the teeth. 
He first examined the cartilage in teeth which had been mace- 
rated in diluted muriatic acid, and found, on making sections of 
it, that it appeared to consist of slightly undulating fibres lying 
close together, resting with one extremity against the cavity of 
the pulp, whilst the other terminated near the surface of the tooth. 
It was not till a subsequent period, he says, that he discovered 
that these were hollow ; but in the meantime he observed no 
internal similarity between this cartilage and that of bone. He 
next procured, with the aid of a file, slices of tooth-bone as thin 
as writing-paper ; increased their transparency by means of olive- 
oil and turpentine varnish; and on examining them under the 
microscope, found that they were composed, not merely of hol- 
low fibres, but of ramifying tubes, of which the trunks open into 
the cavity of the tooth, supporting themselves on its pulp, whilst 
their terminations, in the form of extremely fine branches, run 
towards the external surface of the tooth. The branches were 
most distinct, and most easily shown at the external extremities of 
the main tubes; but in the whole course of the canals, both dicho- 
tomous divisions and delicate branches were observed; the latter 
were infinitely minute, and formed, as it were, a peculiar vascular 
system. Under reflected light, and on a dark ground, all these 
tubes seemed to contain a white matter. The enamel he found to 
consist of hexagonal solid prisms,f on which were generally ob- 
served transverse lines or streaks, making them appear as if they 
were formed of several pieces, lying one above the other; they 
rested with one end against the crown of the tooth, and with the 
other formed a part of its surface. Round the roots and necks of 
teeth he found a structure presenting some similarity to osseous 
substance, from the small cavities it contained, which, under 
reflected light, appeared to be filled with white matter, and from 
the number of winding, anastomosing tubes, as well as other 
larger canals opening into these cavities. This is the cortical 
substance which has been described as existing in the teeth of 
elephants, pigs, and oxen, by Tenon, G. Cuvier, and Fr. Cuvier, 
but which plainly forms part also of the teeth of man, and many 
other animals, in which it has not hitherto been remarked.J 
In man the contiguous tubes appear to run parallel to each 
other ;§ but when several distant ones are compared, they are 
*The title of the work of Retzius is quoted above (p. 1); an excellent 
account of his discoveries was also published in Muller's Archives, in 1837, 
and to this I have been greatly indebted in drawing up the following sketch. 
t Plate A. 1. fig. 1. |Plate A. 1. fig. 2. a, a. § Plate A. 1. fig. 2. b. HISTORICAL INTRODUCTION. 
45 
found to radiate, as it were, from the cavity of the tooth. In a 
few' parts only of the fully developed tooth, and not constantly 
even in these parts, do the tubes proceed directly from the cavi- 
tas pulpae to the external surface: these parts are those which 
correspond to the apex or apices in the crown,* and to the com- 
mencement of the inferior third of the root. In the other parts, 
most of the tubes assume more or less the form of a line with 
three curvatures, frequently resembling the Greek zeta. The 
central curvature points inferiorly or internally; the outer ex- 
tremities of the tubes turn inwards towards the axis of the tooth, 
or towards its surface. Where the tubes are the shortest, which 
is the case near the end of the root, the central curve only is seen, 
and it is convex towards the surface. Sometimes a fourth curva- 
ture is observed, which has of course the same direction as the 
second; but he only found it at the inner extremity of the tubes, 
where these were last formed or prolonged, in order to close 
gradually the cavity of the pulp. In some cases, towards the 
root, two curvatures are found; the tube having then the form of 
an/: the external one then points towards the root; still, by 
means of the microscope, another small curvature in the opposite 
direction is generally found at the extreme end, which is neither 
perceptible to the naked eye, nor by means of a 'loupe.' The 
curvatures on both sides appear, in well-formed teeth, to present 
a certain symmetry, so that the cavities on one side correspond 
to those on the other, &c. Hence towards the middle of the 
crown, the central curvatures come to diverge, and those which 
point from within outw'ards to converge. The curvatures are 
found to be most regular in sections of the front teeth, cut from 
before backwards, and parallel to the axis of the tooth. They 
are less regular in the side teeth, which have several apices, and 
particularly in that part of them, which in the crown forms the 
wall of the cavity of the pulp; also in that side of the root which 
in thin preparations is shown to be a continuation of this wall, 
lying close to the longitudinal axis of the tooth: finally, they are 
less regular at the extremity of the roots. In a perpendicular 
section of the front teeth from right to left, or from left to right, 
most of the tubes in the crown are seen to approach a perpen- 
dicular direction, and they are generally straight. As Leeuwen- 
hoek, and also Purkinje and Fraenkel have remarked, the most 
internal tubes in the crown are generally perpendicular; those on 
the sides of the crown, more oblique; and those further down 
towards the root, more transverse: in some roots, the lowest of 
all are again oblique. Besides the larger curves, the tubes, when 
more highly magnified, present an immense number of other short 
curvatures, of which Retzius says he has counted so many as two 
* Plate A. 1. Fig. 2. c. 46 
HISTORICAL INTRODUCTION. 
hundred in the extent of a line. These curvatures, however, are 
very various in different teeth. In the milk-teeth they are gene- 
rally fewer in number, and more lengthy; they are also fainter 
towards the outer extremities of the tubes than at their centres. 
Besides these are seen, particularly in old teeth, other curvatures 
more or less deep, which in a number of contiguous tubes corres- 
pond to each other; and it is these nearly parallel flexions which 
principally form the concentric line, running nearly parallel with 
the inner surface of the tooth, and of which Leeuwenhoek re- 
marked, that they could not be produced by tubes running in a 
longitudinal direction. 
When the tooth is being formed, the outer extremities of the 
tubes are first developed ; these grow inwards of course, and 
become joined with that part which is subsequently produced, and 
a continuous canal is at length completed. This process would 
seem to be effected in stages, in each of which one curvature is 
added to the preceding ones ; and hence we may conclude, that a 
certain undulating motion, takes place on the surface of the pulp 
during the deposition of the dental bone. 
In general, and particularly in the teeth of old persons, it seems 
at first as if these tubes did not divide or give off branches; they 
seem too, under the microscope, to be of the same diameter in 
nearly their whole extent; but this is not the case in reality : they 
all divide and give off branches, and their diameter diminishes 
towards their outer extremities in every case. From their com- 
mencement at the cavitas pulpae, for five-sixths of their course, 
they appear to be of the same diameter in fully-developed teeth ; 
and this diameter Retzius, with the aid of one of Frauenhof's 
micrometers, has ascertained to be^fT Paris line, or about of 
an English line. In their remaining course their diameter dimin- 
ishes considerably, until they, as it were, disappear, or terminate 
in small, irregularly circular, scattered cells. The distance 
between the tubes at their middle equals about the breadth of 
three of them ; but at their commencement at the cavitas pul- 
pse, they are nearer than this to each other. When very thin 
and transparent slices are examined on a clear day under a glass 
of 300-500 times magnifying power, it is found that these canals 
are main tubes, dividing dichotomically, and giving off in their 
entire course an infinite number of smaller subdividing branches, 
which partly help to fill up the spaces between the tubes, and 
partly cross over the latter, and are lost beyond them. These 
branches are almost always easily perceptible in the milk-teeth. 
In the permanent teeth the branches are found almost without 
exception at the outer extremities of the main tubes: those which 
are given off more internally are fewer in number, and often 
appear as nothing more than roughnesses or points on the tubes HISTORICAL INTRODUCTION. 
47 
in the crown and neck of the tooth. On the other hand, they are 
very easily seen in the most recent, and as it appears more imper- 
fect formations, of the tooth, as, for instance, in the wall of the 
crown, which looks down towards the bottom of the alveolus, 
which in the side teeth of the lower jaw is beneath, and in the 
side teeth of the upper jaw above, the coronal portion of the cavi- 
tas pulpae (superficies alveolaris of Frankel;) as also in the roots 
of the side teeth with more than one apex ; and, best of all, in 
that part of the root which, within the cavity of the pulp, lies 
towards the longitudinal axis of the tooth. Retzius could not 
discover that the branches from different tubes communicated 
with each other, except, perhaps, at their extremities. 
Most of the preparations which Retzius examined had been 
moistened with water, or soaked in olive-oil, or turpentine var- 
nish: without which, he considered, they would not have been 
sufficiently clear. He found, however, that if completely pene- 
trated by fluid, they became too transparent; the tubes and their 
branches filled up, disappeared, and left merely indistinct, delicate, 
faint streaks behind. The most delicate branches are first pene- 
trated, and so are the first to vanish, leaving only here and there 
a curved line. On the other hand, when a preparation, either of 
a recent or dried tooth, newly made and fresh dipped into one of 
the above fluids, is examined, the branches are seen in all their 
delicacy and abundance. But in proportion as the water, oil, or 
varnish penetrates them, they fill and disappear. From the same 
cause the main tubes in some parts of different preparations of 
teeth, particularly of their roots, are found to have disappeared 
entirely in some places, and to have broken off, as it were, and 
have run into the faint lines above mentioned in others. Hence 
also teeth which have been long immersed in spirits of wine 
become quite transparent and similar to horn, like dried teeth 
which have been long kept in oil. 
When the wall of the cavitas pulpae is viewed under a glass of 
a sufficiently magnifying power, it is found to be perforated like 
a seive, and to present an immense number of orifices, which are 
the mouths of the main tubes. When a section of tooth-bone is 
made transversely to the latter, which is most easily effected in 
the crown where the tubes run parallel to the axes of the tooth, 
their interior is rendered visible. They appear like rings, and arc 
dark or light, or partially light, according as the light falls into 
them. Under a certain light they are bordered by a definite 
shadow, and when the light falls directly into them, present 
an appearance different from that of the substance of the tooth 
which surrounds them. Frequently these rings are of a darkish 
colour verging towards yellow. From these appearances Retzius 
confidently concludes, that the tubes are not merely hollowed out 
of the substance of the tooth, but that they arc true canals having 48 
HISTORICAL INTRODUCTION. 
their own walls; that the latter are of a structure differing in ap- 
pearance from that of the tooth ; and that the round spot inside the 
ring is the opening of the canal. When the transversely-cut prepa- 
rations are viewed on a dark ground, the round circular spot is 
seen to be white; and white spots only are visible where before 
there were generally transparent tubular orifices. Retzius was 
not able to seethe rings or the walls of the tubes when he viewed 
the preparations on a dark ground. 
With respect to the contents of the canals, he found with Profes- 
sor Muller that they consisted of an inorganic or earthy substance, 
which, when seen on a dark ground, seems white, and which dis- 
appears when the preparation is submitted to the action of diluted 
muriatic acid. When the light falls into the canals, this matter is 
seen to be composed apparently of infinitely fine particles, adher- 
ing together in lumps. The greater or less number and distinct- 
ness of these lumps seem to depend on the degree in which the 
preparation has been penetrated by water, oil, or turpentine. 
The enamel, according to Berzelius, "after its solution in acids, 
leaves no cartilage, but only an extremely slight, brown, mem- 
branous tissue, which had adhered to its inner surface. On being 
submitted to fire, it is not at all blackened externally, and but very 
little internally; has a slight ammoniacal odour; and it loses, 
after having been xyell dried, less than two per cent, of its weight 
by burning. Hence we see that it essentially contains no ammo- 
niacal matter." After quoting this passage, Retzius states that 
the enamel is adherent internally to a thin membrane, which, he 
continues, is probably the remains of that surrounding the organ 
for the production of the enamel, which has been described in 
such a masterly manner by Purkinje. This membrane resists, 
for a long time, the action of water. In teeth which had been 
macerated for several months in water, he has found it remain- 
ing on his separating and dissolving the enamel in acids. To his 
great astonishment, when he once dissolved in diluted muriatic 
acid a large slice of enamel from the fossil tooth of a horse, 
(which had been dug out of a turf moor,) he found, after the 
solution had been effected, this membrane floating at the top of 
the fluid. He examined it under a glass of considerable magni- 
fying power, and found it perforated in every part, but it showed 
no trace of fibres. 
In the fossil teeth of this horse, Retzius had an opportunity of 
observing the different degrees of durability of the different parts 
of the tooth. The cortical substance of the external side of the 
teeth had fallen off altogether: in the recesses its texture was so 
loose that it crumbled away as soon as it was touched. The 
dental bone was also, for the most part, destroyed: that which 
remained was very friable, and resembled brown velvet. It was HISTORICAL INTRODUCTION. 
49 
separated, as it were, into fibres of a loose texture, which ran in 
the same direction as the tubes. The greatest part of the residue 
of the tooth consisted consequently of the enamel, and this had 
the same crystalline appearance, and the same hardness as in a 
dried, recent tooth. This fact again tends to prove that the 
enamel is very slightly organised, and that it contains very little 
organic matter. When very recent, however, it seems to present 
an exception to this rule; for if the loose enamel, which has as 
yet only attained a slight degree of consistence, be separated from 
the tooth whilst the latter is still in its sac, or, better still, from 
the root of a young horse-tooth, it can be easily dissolved, and 
falls partly into irregular pieces, and partly into extremely delicate 
prisms. 
When recently-formed enamel is submitted to the action of 
diluted muriatic acid, every delicate prism leaves behind on its 
solution a small portion of organic matter: but as this cannot be 
found at a later period, it is probably only a deposit from the 
moisture, which in the first place surrounded the enamel fibres. 
These latter are still invested by this organic deposit when they 
are first arranged together; but as they become closer pressed, 
and new ones are wedged in between them to form the hard 
enamel of the adult tooth, this deposit, Retzius imagines, is, as it 
were, dislodged, or pushed away, or remains in such a small 
proportion that it cannot be recognised in an isolated state. 
The enamel-fibres appear under the microscope as small angu- 
lar needles, about one-five-hundredth of a line p. m. in diameter. 
On many of them are small, crowded, transverse streaks, of 
which some run round the entire fibre, some round only a part of 
it. The fibres are seen in connection with each other when thin 
slices of enamel cut longitudinally through the cavitas pulpse, and 
near its central line, are examined under the microscope. Under 
a sufficiently magnifying power, the transverse lines are also 
visible in several parts of such a preparation. In some places 
they are close together ; in others, at a distance from each other; 
some are continued across several fibres ; others have an irregu- 
lar course somewhat like that of a line of mortar in a brick- 
wall.* Retzius has not succeeded in ascertaining how these 
lines are produced, but presumes, that if the enamel-fibre itself be 
an inorganic mass which is surrounded by an organic capsule, 
they belong to the latter and not to the former. 
The enamel-fibres rest with one extremity on the membrane 
mentioned above, which is pressed closely on the surface of the 
dental bone. In human teeth Retzius saw distinctly, that this 
surface formed a number of small points, and between these were 
small, slight, but tolerably regular indentations, in which the 
enamel-fibres terminated. In man, the fibres support themselves 50 
on this surface at different angles; the lowest are generally trans- 
verse, and those which form the masticating surface of the tooth 
more perpendicular. In some parts of several teeth they are 
curved in various ways. They are somewhat larger at the outer 
than at the inner extremities, but in a degree which is not per- 
ceptible without the aid of the micrometer. In the crown of the 
human molar tooth, a number of fibres are wedged into the outer 
part of the enamel, but do not penetrate to the surface of the den- 
tal bone. Retzius has also seen a similar arrangement in other 
teeth, as for instance in the long, straight sides of the molars of 
the horse, and of the ruminating animals. In some of the mam- 
malia the enamel-fibres are extremely indistinct. Retzius could 
seldom find them in amphibious animalsand fishes; but where 
they presented themselves distinctly, they were but slightly dis- 
similar to those in the human tooth. 
A glass which magnifies three hundred times is necessary in 
order that the enamel-fibres may be distinctly observed : they are 
then seen ranged, side by side, like the wax tubes in the honey- 
comb, and like these they are hexagonal.* 
If the enamel of a well-formed human tooth, which has not 
been worn away by attrition, be examined under a good glass, a 
number of elevated, undulating lines are observed on it running 
parallel from side to side, which are so delicate and so close 
together, that Retzius says he counted not less than twenty-four 
of them on an incisor, in the space of a Parisian line. They are 
most beautiful and closest together on the outside of the incisor, 
canine, and single molar teeth; and are less distinct and more 
apart in the tricuspides. They do not run merely on the outer 
side of all these teeth, but are continued round their crowns, 
though internally they are less distinct and less regular. Leeu- 
wenhoek was acquainted with these lines, and believed that they 
marked the stages of the progress of the teeth through the gums. 
From examining a fossil horse-tooth, in which they were very 
large and plain, Retzius comes to the conclusion that they are 
formed from the enamel-fibres having united into belts, of which 
the inner rests on the tooth-bone, whilst the outer projects beyond 
that next to it. The enamel is first deposited on the extremity of 
the crown, oi' on the apices of the masticating surface; round 
this first deposit the next succeeding one forms a conical belt, 
which is again in its turn surrounded by another, and so on till 
the enamel is completed. In milk-teeth Retzius could not suc- 
ceed in ascertaining that any of these rings existed. 
In the interior of longitudinal fractures, or of polished longitu- 
dinal sections of enamel, two other appearances are observable. 
One consists of a sort of generally brownish parallel lines, which 
HISTORICAL INTRODUCTION. 
* Plate A. I. fig. 4. HISTORICAL INTRODUCTION. 
51 
in teeth with their crowns not yet worn down, curve round the 
coronal apices of the dental bone; but which towards the sides, 
particularly in teeth with wedge-formed crowns, run nearly 
parallel with the axis of the tooth. Some of the coarser of these 
lines are perceptible to the naked eye. They appear to be the 
traces of different stages in the formation of enamel, and are 
analogous to the lines running round the cavity of the pulp in the 
dental bone. Schreger found that horizontal transverse sections 
of enamel presented three different belts or layers-an external 
gray one, a milk-white middle one, and a third gray like the first, 
in contact with the dental bone. These layers, says Retzius, are 
obviously the coarse lines mentioned above, or several fine ones 
in conjunction. 
The second set of appearances above alluded to, is that of 
short, white, generally curved streaks, broad in proportion to 
their length, which are hardly perceptible to the naked eye, but 
which may be easily seen with the aid of a lens: at the end of 
the enamel, towards the neck of the tooth, they strongly incline 
outwards, and in the crown are turned towards each other, as it 
w?ere, in an upright position. They are only visible under a 
slight magnifying power on a dark ground, and run sometimes in 
the same direction as the enamel-fibres, and sometimes in a dif- 
ferent one. Under a full light they disappear, and in their place, 
by the aid of a glass of considerable power, is seen a sort of very 
faint broad streaks, formed by the meeting of the parallel sha- 
dows of the transverse lines of the enamel-fibres. Retzius found 
them in the enamel of most of the mammalia which he examined, 
and in greater quantity than elsewhere in the rings on its surface. 
At its junction with the dental bone, and also in some other 
parts, the enamel almost always presents a number of delicate 
chinks, which appear to arise from its fibres shrinking from each 
other. Where this has taken place, they often present a dentated 
appearance like the fibres in the crystalline lens. When thin 
sections of a tooth are left for some hours in a solution of caustic 
potash, groups of these chinks are observed in different parts of 
them. This fact confirms Retzius in the opinion that the enamel- 
fihres are surrounded by delicate capsules of organic matter. 
The chinks were particularly remarkable in the enamel of the 
teeth of the Batistes Vetula and Sparus Rondeletii: they were 
here very numerous, almost regular in their course, and some- 
what similar to the tubes in dental bone. 
The Cortical Substance, like dental and other bone, consists of 
cartilage and osseous earth. From the cartilage of human teeth, 
of which the osseous earth has been dissolved in acid, the carti- 
lage of the cortical substance may be separated in the form of a 
membrane, which is thickest at the end of the root: in human 52 
HISTORICAL INTRODUCTION. 
teeth it appears to have less consistence than the cartilage of den- 
tal bone. Viewed under the microscope, it presents the same 
cellules or so called corpuscula as the proper osseous substance, 
dental bone, and most cartilaginous structures. It was less easily 
dissolved in boiling water than that of dental bone, and retained 
several earthy granules after those of the latter had all disap- 
peared. When either recent or dried cortical substance, polished 
or in fine slices, is examined with a good lens, a number of white, 
crowded points, almost invisible to the naked eye, are discovered 
in it, which, on being further magnified, show themselves to be 
the cells above-mentioned, deriving their white colour from the 
osseous matter they contain. As in dental and common bone, 
numerous tubes pass into and from them, widening as they enter, 
and giving them the appearance of irregular stars. These tubes 
have numerous communications with each other, partly direct, 
and partly by means of branches to of a line p. m. in 
diameter: some of them pass immediately from one cell to an- 
other, precisely as in the dental bone. The osseous cells are of 
various forms and sizes; some are elongated, so as to look al- 
most like tubes; some are nearly round: their average size Ret- 
zius found to be line p. m. In sections made transversely to 
the axis of the tooth, it is plainly seen that the osseous cells are 
arranged in parallel lines or concentric rings, some fainter than 
others, or that the cortical substance is deposited in delicate, co- 
herent layers. 
In the human tooth the cortical substance is an extremely thin 
stratum, taking its origin in most teeth with a complete root at 
the neck where the enamel terminates, and increasing in size as 
it descends towards the extremity of the root, where it is gene- 
rally thickest. In young teeth, of which the roots are not yet 
fully developed, it is so thin that the osseous cells in it are not 
perceptible ; and it has merely the appearance of a delicate mem- 
brane. On the other hand, the older a tooth is, and the more the 
cavitas pulpce is closed, the thicker is the cortical substance at 
the end of the root, where it sometimes forms a considerable en- 
largement, or what is commonly called an exostosis. Retzius 
has seen a case where this increment was of the length of three 
lines at the root; and has also examined a wise tooth, where the 
cortical substance was so plentiful at the neck, that it formed a 
sharp projecting border turned towards the crown, and gave to 
the whole tooth an uncouth appearance. In teeth projecting con- 
siderably from the alveolus, and which have not been worn away, 
Retzius found it sometimes thicker than the dental bone itself, and 
this he thinks is particularly the case in those teeth which have 
been loosened by the scurvy, or by the use of mercury. HISTORICAL INTRODUCTION'. 
53 
Retzius has not only examined the teeth of the human subject, 
but also those of the Cercopithecus cynomolgus, Felix lynx, Canis 
fa miliar is, Erinaceus eur opacus, Sorex fodiens, Castor fiber, Le- 
pus borealis, Bradypus tridactylus, Dasypus tricinctus, Ovis Aries, 
Bos taurus, Equus caballus, Elephas indicus, Hippopotamus am- 
phibius, Rhinoceros indicus, Sus scrofa, Phoca annellata, Tri- 
chechus rosmarus, Delphinus delphis, Crocodilus sclerops, Python 
bivittatus, Squalus cornubicus, Sparus rondeletii, Anarrhichas 
lupus, Cyprinus idus, Esox lucius, Gadus molva, and Batistes 
vetula. 
Cercopithecus Cynomolgus.-In the monkey the main tubes 
are of about the same size as in the human subject. Retzius only 
saw branches at the extremities of the tubes which belong to the 
crowns of the molar teeth. Here and there in the neck a larger 
branch is given off; and down at the root all the main tubes are 
surrounded by extremely delicate, subdividing, and thick-set 
branches, given off in almost opposite directions, of which those 
which run towards the crown are the largest. They are for the 
most part curved like a bow, and in such a way that the con- 
cavity of the arch is turned towards the cavitas pulpce. The un- 
dulating curvatures of the main tubes themselves seemed to be 
longer drawn out and less numerous than in man. 
In the monkey, the cortical substance begins where the enamel 
terminates. The cells are somewhat larger and closer together 
than in man ; but are also of several different forms, as triangular, 
circular, oblong, with pointed extremities, &c. The majority of 
the tubes which terminated in them came from without, and the 
greater number opened into that side of the cells which looked 
from the axis of the tooth. Most of the fine calcareous tubes 
opened into the cells without any particular widening at the basis. 
Felis Lynx.-1Of the lynx he examined two canine teeth, and 
two of the most posterior molar teeth : they had all been kept for 
some time in alcohol. In both kinds of teeth, the tubes appeared 
of the same size as in man. In the canine teeth, which, although 
the animal was very young, were nearly closed at the end of the 
root, the tubes, towards the external part of the whole tooth, pre- 
sented numerous and beautiful branches: these braches divided 
and subdivided, forming at length a net-work like down. In ma- 
ny parts lay, as it were in scattered rows, oblong cells filled with 
osseous earth, and branches from the tubes wound round about 
them. When the preparation was laid for some time in turpen- 
tine-varnish, it became nearly transparent; the branches of the 
tubes were then rendered very incomplete, and were only appa- 
rent in some few places: in the other parts, the main tubes 
appeared to terminate abruptly, and to give off no branches, or 
there were only visible the dull streaks which they had left be- 
hind them. 54 
HISTORICAL INTRODUCTION. 
In the lynx, the dog, and the hedge-hog, the cortical substance 
existed only as a thin layer at that part of the tooth which was 
not invested with enamel, and it gradually diminished, and then 
terminated towards the border of the enamel. In an incisor tooth 
of an old dog, which had been much worn away, it was very 
thick round the extremity of the root, but could only be traced to 
a very short distance. In the canine tooth of a full-grown lynx 
the cells were on the whole somewhat smaller, and also rounder 
than in the human subject. The fine calcareous tubes had gene- 
rally almost straight trunks, which ran tolerably parallel to each 
other, and horizontally towards the sides of the teeth. The corti- 
cal substance was thickest at the end of the root, and closed the 
cavitas pulpce. Nevertheless, this cavity still existed, end con- 
tained a red pulp, which was continued as far as the apex of the 
tooth. In connection with this, the cortical substance at the root 
was perforated by several canals, which in a converging direction 
were prolonged towards the end of the cavitas pulpse. The 
diameter of these canals was about line, p. m. In a rugged 
molar tooth from the upper jaw of the same animal, the small os- 
seous tubes presented in several places similar parallel prolonga- 
tions to those in the canine tooth ; in other places they were ab- 
sent. On the sides and between the roots the cells were the same 
as in the canine tooth ; but round the ends of the short roots they 
were in the highest degree irregular. Several were two or three 
times larger than those just mentioned ; they ran into each other, 
and intruded as it were into the region of the dental bone. Here 
also were found similar but larger canals, running to the end of 
the cavitas pulpce: these canals contain probably the blood-vessels, 
which furnish nourishment to the pulp. 
Canis familiar is.-The teeth of the dog were found to be like 
those of the lynx. In the roots of the incisor teeth the tubes were 
very angularly curved, curled as it were, and splitting into lengthy 
branches. 
Erinaceus Europceus.-In the hedge-hog the main tubes are of 
the same thickness as in the preceding, but shorter in conse- 
quence of the smallness of the teeth. In the incisor teeth they 
are, as it were, drawn out, and faintly undulating, with only a 
few larger curvatures; on the other hand, the branches here are 
extremely evident; they curve very beautifully in almost all 
directions, more particularly towards the crown and the root; 
but in the crown itself the curves are generally turned towards 
the surface. The branches are probably so particularly evident 
in these teeth, because they continue thicker for a longer dis- 
tance than in different other teeth. 
Whoever wishes to convince himself of the ramification of the 
tubes in dental bone, cannot better or more easily do so than by HISTORICAL INTRODUCTION. 
55 
examining a thinly filed longitudinal slice of the incisor tooth of 
a hedge-hog. In the crowns of the molar teeth, the main tubes 
are straighter, in the roots curled and undulating ; the particularly 
short trunks terminate immediately after their commencement 
in long, thick branches, running towards the surface of the tooth, 
and giving off'in their course other curved branches above and 
below, which cross the contiguous tubes. 
Sorex Fodiens.-In the shrew, in which the teeth are still 
smaller, (the dental substance in the incisor teeth near the root 
being in some parts only p. m. thick from the cavitas pulpse 
to the surface,) the tubes are in the same proportion very short. 
Still their diameter at their commencement is equal to that in the 
human subject; and their outer extremities lose themselves in 
equally fine points or branches. They accordingly diminish very 
rapidly, and in these places present no longer the appearance of 
cylindric tubes, but of small, sharply-pointed cones, which give 
off a number of proportionally thick branches, which again sub- 
divides several times. In the apices, too, of the incisor teeth, 
which are so peculiarly formed in this animal, the ramifications 
of the main tubes are particularly well seen-some of the branches 
being small, short, and their direction transverse; others being 
extended, longer, and longitudinal in their course. 
Castor Fiber and Lepus Borealis.-In the beaver, as well as in 
the hare, the main tubes are of the same diameter as in the pre- 
ceding, and present the most remarkable and extensive ramifica- 
tion in the whole length of the tooth. In the incisor, as well as 
in the molar teeth, most of the tubes present a curve like the letter 
f. In the incisor teeth most of the branches are given off from 
that side of the main tube which is turned towards the crown: 
in the molar teeth, on the other hand, the most numerous and the 
largest bundles of branches appear to have their origin on the 
side towards the root, and along the root of the tube. The main 
tubes lie very close together, particularly in the crown, so that 
the intermediate spaces are scarcely wider than the diameter of a 
single tube; but towards the root they are further apart, and the 
branches are seen here more particularly to turn towards the 
root. In the roots only is the direction of the main tubes trans- 
verse; near the masticating surface, they approach the direction 
of the axis of the tooth. Of the ramifying tubes near the root, in 
a dens incisivus major of a hare, a drawing is given, plate A. 2. 
fig. 2. a. The most inferior tube, fig. 2. b, is isolated from the 
rest in order that it may be represented more clearly. In the 
longitudinal streaks running in the direction of the axis of the 
tooth, which give to some of these teeth an appearance as if they 
were composed of cones contained one within another, (See 
Heusinger Histologie, part i. Fasciculus 2nd, p. 200,) no certain 56 
HISTORICAL INTRODUCTION. 
curvature of the tubes could be discerned, nor any evident cor- 
puscules, or osseous cells, but only thin layers of a connected, 
whiter, more opaque substance. In the singularly constructed 
molar teeth of the beaver and of several other rodentia, the tubes 
in the proper dental bone are just as regular, and present the same 
forms, and the same ramifications, as in the incisor teeth. 
In the beaver and hare the cortical substance was only found on 
the molar teeth, where it exists principally in the furrows which 
the enamel and the dental bone internally make towards the cavity 
of the pulp. The cells in this cortical substance were extremely 
irregular in the beaver; some held line p. m.; some were five 
or six times larger : some of the fine tubes radiated from a centre, 
others were parallel; but the parallel ones ran in more various 
directions. On the external side of the molar teeth of the beaver 
an extremely fine layer of cortical substance was recognised ; on 
the other hand, the part of the tooth which was enclosed in the 
alveolus was completely covered with enamel. In the incisor 
teeth of the beaver, as also in those of the hare, the cortical sub- 
stance was wanting. 
In the beaver and hare, and probably in all the rodentia, the 
teeth are invested with enamel in their entire extent. It is well 
known that these teeth, particularly the incisors, continue to grow 
during the whole life of the animal without closing at the alveolar 
extremity; so that one of them which has not been worn away, 
owing to its having grown in a wrong direction, becomes much 
longer than it was when it first projected from the alveolus. The 
enamel in these animals continues to be formed as long as the 
teeth continue to grow; (Oudet, Experiences sur Vaccroissement 
continu et la reproduction des dents chez les lapins, 2. mem.,) 
whence we may come to the certain conclusion, that it is not 
formed alone within the proper folliculus dentis, but that an organ 
for its production may continue to exist at the bottom of the 
alveolus itself during the whole life of the animal. The attention 
of Retzius was first called to this fact on his examining a longitu- 
dinal section of the third molar tooth (three inches and a half 
long, p. m.) out of the lower jaw of an old horse :-he found that 
even here the coating of enamel proceeded to terminate at the 
extreme border of the roots; two roots of four lines in length, but 
open at the end, were already formed ; but even these were 
covered, as above described, with enamel. In order to ascertain 
more exactly whether the enamel in this case had actually been 
formed after the tooth had burst through the dental sac, Retzius 
instituted a comparison between this and the same tooth in ano- 
ther horse, whose third milk-molar in the lower jaw was about to 
be shed, and to be succeeded by its lengthy substitute, and he 
found that the latter was the shorter by nearly an inch, and did HISTORICAL INTRODUCTION. 
57 
not display the slightest trace of the formation of a root. If we 
assume that it might still have grown a quarter of an inch before 
bursting through the dental sac,) which, however, round the crown 
was already absorbed,) three quarters of an inch of the enamel 
investment still remains, which had been formed after the dental 
sac had been burst through in the alveolus. But though, as we 
have seen, the enamel in certain horses' teeth may be deposited 
as far as the divided roots, this is not universally the case in this 
class of animals. In the molar teeth of very old horses, with 
long roots, the latter are only covered with enamel at the com- 
mencement; and in the milk-molar of the new-born foal, which 
have already divided roots, the enamel terminates at the com- 
mencement of the latter. 
The red colour in the incisor teeth of the beaver is derived 
from the enamel. Retzius cannot understand how that excellent 
writer, F. Cuvier, was so far deceived on this point, as to believe 
that it belonged to the cortical substance, seeing that these teeth 
present no cortical coat whatever. Cuvier's words are : "In fact, 
the colour of the anterior part of these teeth depends on a very 
delicate layer of true cortical matter, as I have assured myself by 
repeated particular experiments ; and it only becomes brown on 
that part of the tooth which is not covered by the gums." The 
incisor teeth of the beaver, and probably of all "glires," are in- 
vested with enamel. In the beaver, Retzius observed this pecu- 
liarity, that the above-described transverse lines on the enamel- 
fibres here run with particular regularity in straight parallel lines, 
which, at equal distances from each other, intersected the streaks 
between the enamel-fibres at oblique angles, forming oblique, 
equilateral squares. The red colour has its seat in this enamel, 
but in only a very thin layer of it. Just beyond the border of the 
gum the thickness of this layer was line p. m.; nevertheless, 
in an extremely thin slice, and magnified several hundred times, 
it was strongly marked, and had a well-defined border towards 
the white part of the enamel. 
Bradypus Tridactylus.-In the Bradypus, the tubes are very 
different from those in the preceding animals. The substance 
which properly corresponds to the solid dental bone consists here 
of merely a thin cylindric shell, which in newly-formed teeth is 
probably closed in the crown, but which was wanting there in all 
the teeth of these animals examined by Retzius. The cylindrical 
shell, which is consequently formed from the proper solid white 
dental substance, is filled towards the crown with a yellowish or 
brown, half-transparent, softer, almost horn-like substance, which 
terminates internally towards the end of the pulp.* In young 
* Of the shell here mentioned, F. Cuvier observes, "Toutes les machelieres 
ont la meme forme, sont cylindriques et leur partie centrale se compose (Pune 
substance plus tendre que celle qui Venvironne, et qui est analogue a Pemail, 
quoique moins dur que lui." 58 
HISTORICAL INTRODUCTION. 
subjects this plug, if it may so be called, is very short; in older 
ones, it is longer, and is continued through half or two-thirds of 
the whole tooth. In this internal, yellowish, horn-like substance, 
a sort of coarse tubes are generally seen of | to p- in 
thickness, which proceed from the surface contiguous to the pulp, 
rise towards the crown, and are curved outwards in such a man- 
ner that the middle ones are generally parallel to the axis of the 
tooth, whilst the external ones turn more towards the sides, just 
as in certain teeth of fishes, or somewhat as the jets of a fountain. 
These tubes are not uniform: some are dilated in one place, and 
immediately afterwards contracted, or are large in one part and 
small in another. They give off several larger and less irregu- 
larly winding branches: between them is here and there a cavity, 
into which delicate winding passages open, just as the small 
winding passages terminate in the calcareous cavities in the more 
delicate structure of bone. Finer tubes, similar to those usually 
found in dental bone, are given off from the larger ones, and are 
continued as far as the shell which is composed of the firmer 
white dental substance. The larger tubes, too, terminate in the 
more regularly arranged tubes which belong to that substance; 
but precisely at this junction they become minute nearly of a sud- 
den, make at the same time two particularly definite curvatures, 
and then nearly straight run in an oblique direction; some to- 
wards the crown, and some towards the sides of the tooth. That 
portion of the tubes situated in the above-named white substance, 
may be regarded as analogous to the tubes in the dental bone of 
other teeth, and have the same diameter as the corresponding 
tubes in the human subject. The most perceptible branches are 
seen in the white substance near the junction above alluded to: 
they run nearly at right angles to the axis of the tooth: a part of 
the branches turn towards the crown, others towards the root of 
the tooth to which they belong. In the crown they appear, at 
their outer extremities too, as plainly ramifying; but besides, un- 
der a three hundred to a four hundred times magnifying power, 
these main tubes, so to call them, which belong to the white sub- 
stance, are as it were covered with a downy net-work, composed 
of extremely minute tubuli, of which the further course could not 
be traced by the eye. When we have got beyond that part of 
the dental cylinder, which towards the crown is filled with the 
above-mentioned plug of horny substance, we find that the tooth 
is hollow for a considerable distance. In this hollow part, the 
main tubes towards the cavitas pulpae internally appear to be as 
it were distended at their extremities. In this part of the tooth, 
these same trunks have some of them the form of an f, and are 
also more scattered, and more evidently provided with large 
branches than those nearer the crown. 59 
HISTORICAL INTRODUCTION. 
The teeth of the Bradypus are covered with cortical substance 
as far upwards as towards the masticating surface, and it seemed 
to Retzius as if the ends of the tubes in the proper osseous sub- 
stance passed in many places into the cortical substance, and 
united with the tubes of the latter; he thought, too, that he per- 
ceived that several of the tubular branches passing from the dental 
bone into the cortical substance, opened into the small calcareous 
cavities of the latter. This arrangement was frequently investi- 
gated, and appeared clearly to be as just described, although 
Retzius was at first as much inclined as possible to doubt its 
reality. 
It results then from the above facts, that the teeth of the Bra- 
dypus present a very low degree of development, and approach, 
in their internal construction, as comparison will show, a type of 
formation which seems properly to belong to certain fish, particu- 
larly to the pike. It is also probable that the dental tissue in the 
orycteropus is analogous to the internal soft dental substance in 
the Bradypus. That direct communications exist between the 
tubular systems in the two constituent formations, developed at 
different periods, that is to say, in the dental bone and cortical 
substance, seems to lead to the conclusion that certain canals 
open into the former after it has been fully formed, and that hence 
it is not altogether impossible that a formative action may go on 
in it after its first production. On the teeth of this animal there 
is no enamel. 
They are invested in their whole length with cortical substance. 
The cells nearest the dental bone are nearly round and about T|T 
line p. m. wide; those lying more externally are generally oblong, 
line p. m. long, and broad. The fine tubes which opened into 
them seemed to form large bundles running from them in an 
external direction. They were extremely delicate; were not 
dilated at their opening into the cells, on the external sides of 
which they were nearly parallel; and for each cell they were so 
numerous that Retzius could not count them with any degree of 
certainty. The cells themselves lie very close together. 
Dasypus Tricinctus.-In the small, cylindric, hollow teeth of 
the dasypus tricinctus, which are open towards the root, the 
main tubes were not more than half as thick as in the human 
subject: those occupying the internal part of the crown were 
more winding, more diverging, and less parallel than those at the 
sides; the latter ran nearly straight, with a single faint curva- 
ture, of which the convexity was turned towards the crown and 
the axis of the tooth. The inner tubes of the crown did not dis- 
play any ramification ; but all had branches towards their outer 
extremities. In the teeth of the dasypus, Retzius only found one 
dental substance; neither enamel nor cortical substance were 
present. 60 
HISTORICAL INTRODUCTION. 
Dasypus Novemcinctus.-On the teeth of this animal no trace 
of cortical substance, or of enamel, could be found. 
Oms dries.-In the incisor teeth, as well as in the thin folded 
plates of the osseous substance of the molar teeth of the Sheep, 
the main tubes present delicate undulating curlings. In a section 
of an incisor tooth, which was cut from before backwards with 
the axis of the tooth, these main tubes presented three more 
considerable curvatures; and between these were ramifications, 
differing in extent, which indicated different stages in the forma- 
tion of the tooth. To the naked eye, too, the substance appeared 
as consisting of three layers, one lying before another. In the 
external layer the main tubes were straightest and most regular; 
in the middle one, more curved, and in the internal one, most so. 
At the border, between the external and inner one, that is to say, 
immediately within the external large layer of tubes, was situated 
in the whole length of the tooth, except at the crown, a row of 
oval bodies which, on closer examination, were found to be small 
cavities filled with osseous earth, of which the largest was 
par. m. wide, and long. The tubes wound close round the 
parietes of these cells, giving off several branches which also sur- 
rounded them, and some of which communicated with them. At 
the outer border of the preparation, or on the external surface of 
the tooth, appeared a number of thickset calcareous, scale-like 
corpuscules, between and in which the minute terminations of the 
tubular* branches seemed to be lost. These corpuscules, as well 
as the small calcigerous cavities just mentioned, presented a white 
appearance when viewed on a dark ground. 
The tubes in the incisor teeth had evidently large branches 
from their commencement in the cavitas pulpoe; and, moreover, 
in the whole course of the main trunks, and of the principal 
branches, minute ramifications were observable. The main tubes 
in the external third of their course were not half so thick as at 
their commencement in the cavitas pulpa, and the concavity of 
their curvatures was in this part generally turned towards the 
crown. More internally, several branches ran in a vertical direc- 
tion towards the main tubes. 
In the dental substance of the molar teeth the tubes present no 
large curvatures; but at the outer wall one was observable, of 
which the convexity was turned towards the crown and the axis 
of the tooth. In the tubes lying next to the crown this curvature 
was nearer to the external enamel; in those more in the neigh- 
bourhood of the root, it was nearer the middle of the tube. The 
tubes belonging to the alveolar part of the tooth were, for the 
most part, of the form of an/ All these tubes gave off branches 
in their entire course; but those were the most conspicuous and 
most numerous which formed the termination of the main tubes 61 
towards the enamel. Most of the ramusculi proceeding from the 
outer extremities of the main tubes, appeared to be given off by 
the concave sides of the latter, which are turned towards the root; 
and they were themselves curved towards the root. 
In the Sheep, Retzius found only a thin layer of cortical sub- 
stance on that part of the teeth which is covered with enamel; it 
was more plentifully deposited round the ends of the roots which 
were nearly closed, and also in the indentations of the crown. 
The cells as well as the tubes were rudely and very irregularly 
formed. In the thin lamella which invested the enamel, the cells 
seemed more to resemble large, reticular, vascular glands than 
proper cavities: the tubes were large, and their course irregular. 
In the cortical substance round the roots, some cells were oblong, 
very angular, and drawn out to a considerable length; and, 
moreover, a number of rude canals tolerably parallel, but very 
wide apart, were found running from within outwards. The 
above-mentioned gland-like cells were about -fa line p. m. in 
diameter: the thickness of the large tubes was J less. It was 
particularly remarkable that there were frequent and conside- 
rable communications between the cortical cells and the cells in 
the outer part of the dental bone. The cortical substance in the 
dental furrows was porous in the highest degree, and consisted of 
still more irregular tubes and cells, than in the above-mentioned 
places. 
Bos Taurus.-In an incisor and in a molar tooth of the Ox, 
Retzius found the organisation to be very similar to that in the 
sheep. The molar tooth being an old one, the small cavities for 
the foliform prolongations of the pulp were found to be nearly 
closed by the dental substance. In this last-formed dental sub- 
stance the tubes were very undulating, and in different directions; 
in the midst of it were several yellow bodies lying longitudinally 
in rows, and the tubes wound spirally round about these. In the 
incisor as well as in the molar tooth, the main tubes displayed a 
plentiful ramification ; some of the branches being long and gene- 
rally parallel; others short, transversely-running, curved, delicate, 
and forming, as it were, a downy net-work. The extreme ends 
of the tubes in the neighbourhood of the enamel showed the same 
mixture of extremely fine osseous corpuscules as in the sheep. 
The tubes also resembled those in the sheep with respect to their 
undulations, curvatures, and gradual diminution. The diameter 
of the main tubes, near the cavitas pulpce, varied from to 
The cortical substance in the ox is much thicker than in the 
sheep: the large tubes were here found to ramify, and ran in an 
almost horizontal direction towards the sides of the tooth. The 
cells were smaller and more irregular than in the sheep. They 
HISTORICAL INTRODUCTION. 62 
HISTORICAL INTRODUCTION. 
lay very close together; approached the circular form ; and were 
about line p. m. in diameter. It has been customary to con- 
sider the so called cement or cortical substance as only belonging 
to the crown of the teeth of ruminating animals, or to that portion 
which is invested with enamel. That this view is erroneous 
results from what has been stated respecting the cortical invest- 
ment of the teeth of sheep ; but it is still further refuted by an ex- 
amination of the shapeless, tuberous roots of certain ox-teeth. 
The deformity in these cases arises, as Retzius has found, from a 
too great deposit of cortical substance from the alveolus. Some 
teeth of this kind are preserved in the collections of the Carolinian 
Institution, and of one of these Retzius has given a drawing to 
illustrate the subject (Plate A. 1. fig. 10.) 
Equus Caballus.-In sections of fully-developed, permanent, 
incisor teeth of the Horse, cut from before backwards, longitudi- 
nally to the cavitas pulpae, the tubes nearest the masticating sur- 
face, which were generally parallel with the axis of the tooth, 
were of the form of the letter/.- more inferiorly in the crown the 
succeeding ones resembled ane; and those which belonged to 
the extreme part of the root, a C, of which the convexity is turned 
towards the crown. In younger teeth which were not yet filled 
up in the crown, one or two curvatures were wanting. The un- 
dulations of the tubes were, so to say, more stretched out than in 
the human subject. At their inner extremity the diameter of the 
tubes varied between sis'" and sis'" P-M- Their diameter dimin- 
ishes considerably before they terminate in branches at the outer 
part of the tooth. In the middle of their course, their diameter 
appeared to be $ less than at its commencement. In the first or 
inner half of their course the tubes lie so close together, that the 
space between two of them is no larger than the width of one of 
them: here Retzius could discover no branches; but about the 
middle of the course of the tubes, which at the sides of the tooth 
correspond to the central curve resembling an e, branches begin 
to be seen, some presenting the appearance of small, transversely- 
running streaks, which are bent inwards; others being longer, 
and, as it were stretched out. As the tubes proceed towards the 
surface, the branches become more and more numerous, are most 
plentiful on the convex sides of the main tubes, though in several 
places they are equally numerous on both sides, and frequently 
form very acute angles with the main tubes. Hence most of the 
branches lie closer, as it were, to the main tubes, than in the 
above-mentioned animals. On the external side of the tooth the 
branches ran in almost opposite directions. Under a three-hun- 
dred-and-fifty-times magnifying power, the most delicate branches 
appeared to be as close together as the filaments in down. In 
several places the minuter branches seemed to terminate in small 63 
angular cells, similar in appearance to the small calcareous cells 
in bones. These cells were particularly numerous in the external 
part of the tooth, and most so immediately beneath the enamel, 
where the greatest number of minute branches terminate. These 
minute branches wind between the calcareous cells, and terminate 
partly in them. There were also found here a number of ex- 
tremely minute passages, running from cell to cell, and forming 
an anastomosing net-work, between the branches as well as be- 
tween the calcareous cells. (See plate A. 3. fig. 6.) 
These calcareous cells are much more minute than those which 
are found in bone. 
In the incisor teeth of the horse, too, are found several some- 
what opaque streaks, running parallel to the cavitas pulpae, which 
resemble the annual circles in a tree. These did not result, how- 
ever, here alone from certain parallel curvatures of the main 
tubes, but principally from similar calcareous cellules, which pre- 
sented themselves in the same track in the greatest part of the 
length of the tooth. (See plate A. 3. fig. 6.) 
Round these cellules wound also numerous ramusculi, and 
seemed to terminate in them. In the dental substance, which 
fills the cavity of the pulp from above, similar cells are found, but 
much larger. 
In a milk incisor-tooth the tubes wrere much more conspicuous 
than in the permanent ones. The trunks here evidently divided 
in many places in a furcated manner The small branches were 
given off from the trunks at very short intervals from each other. 
Where they gave off branches the trunks were in many places 
dilated, as it were, and thus presented an unequal appearance. 
The branches ran partly stretched out, and inclining at an acute 
angle towards the external ends of the main tubes, and in part 
transversely towards these in short arches. Osseous cells were 
everywhere scattered throughout the intermediate spaces; but 
here, too, they were most numerous in the surface of the tooth, 
and under the enamel. 
The main tubes were most undulating near the cavity of the 
pulp; as they advanced towards the surface the undulating cur- 
vatures gradually diminished. 
On the posterior side of the neck of the tooth were found, along 
the axis of the tooth, longitudinal streaks, which arose from pa- 
rallel curvatures and furcated divisions of the tubes. The streaks 
did not here owe their origin to any accumulated cells. The 
calcareous cells were larger than in the permanent teeth. 
In the permanent molar teeth of the full-grown horse, the main 
tubes in the dental substance were not so close as in the incisor 
teeth, and maintained exactly the same diameter till very near the 
enamel, which here, singularly enough, invests the whole extent of 
HISTORICAL INTRODUCTION. 64 
the dental bone as far as the ends of the roots. The branches were 
thicker on leaving the trunks, and did not run so close to these as 
in the incisor teeth. The undulations were better marked,though 
drawn out and irregular. Most of the main tubes were con- 
siderably extended towards the crown, assuming the form of an 
in verted/, with a considerable prolongation of the lower extremity. 
The outer or coronal extremity of the main tubes was curved 
away from the axis of the tooth in an almost transverse direction. 
In this transverse part several of the tubes seemed near their ter- 
mination to make one or two larger curvatures. In the neigh- 
bourhood of the root, most of the lubes assumed a more trans- 
verse position, as in most other teeth. The greatest part of the 
cavities of these teeth was closed, in the neighbourhood of the 
masticating surface, by dental bone, and the cavity of the pulp 
was very narrow as far as the commencement of the root. It 
was filled with a more yellowish, brown, osseous substance, which 
nearer the masticating surface was dark brown, probably from 
colouring matter which had penetrated from the food without. 
As the tubes in this more recent dental structure ran almost di- 
rectly towards the masticating surface, where their ends were 
worn away by attrition, and were denuded of all covering, it is 
easily conceivable, that during mastication, colouring matters of 
different kinds penetrate this substance more easily than any other. 
The cortical substance in the horse presents more large tubes 
than that of the ox ; they are about ?rr line p. m. in width, run hori- 
zontally from without inwards, and divide into branches. From 
these tubes, which may be compared, to a certain extent, with 
the medullary canals in osseous substance, innumerable minute 
branches are given off, which are as thick as the hairs in the 
finest nap. Between these are situated small, short, oval cells of 
about line p. m. in length. The tubes which leave the latter 
are so minute and so close together, that here, as in the sheep, 
such a group assumes the appearance of a vascular gland several 
times larger than the cell itself; Retzius succeeding in seeing 
these knots of tubes whilst the preparation was being varnished 
with turpentine. After having been thus steeped, the preparation 
was almost opaque. Immediately after it had been penetrated by 
the turpentine, the above-mentioned knots of tubes presented an 
appearance almost similar to that of the balls of the Conferva 
Aegagropila, but still one ran into the other. This appearance, 
however, was not long kept up: the minute tubes were shortly 
filled with varnish, and then they disappeared altogether. A few 
minutes afterwards the large tubes and the cells (filled for the 
most part with varnish) were all that was to be seen. It was not 
till now that the small cells could be properly seen, and, from the 
appearance which they presented, no one would have supposed 
that any tubes or vessels opened into them. The corticle invest- 
HISTORICAL INTRODUCTION. 65 
ment was very thin round the roots of the molar teeth; on the 
other hand, it was almost a line thick in some places round that 
part of the crown which is not surrounded by the gum. In young 
molar teeth, just before the period of extrusion, the enamel fur- 
rows were quite filled with cortical substance, and a thi k layer 
was already deposited on the sides of the masticating surface, 
whilst on the other hand this same substance was nearly altogether 
wanting on two-thirds of the length of the tooth, nearer the root. 
The outer surface of this recent cortical substance was already 
porous, and on the border, towards the root, it was deposited in 
small, separate, undulating rings. 
Elephas Indicus.-Of the elephant, Retzius only examined 
sections of the tusks. For the investigation of their tubular struc- 
ture, slices were taken out of the hollow alveolar end, because in 
them the whole extent of the tubes from their commencement in 
the cavitas pul pee to their termination towards the cortical sub- 
stance can be surveyed in a small compass. From the examina- 
tion of the concentric rings, he used more transversely cut sections, 
which were taken from nearer the apex of thetu.sk. 
The main tubes at their commencement at the cavitas pulpoe, 
and afterwards in their entire course, are much smaller than in 
the human subject; on an average they present a diameter of 
to?" p- m. Their distance from each other scarcely amounts 
to the breadth of a single tube. They are undulating, though to 
an almost imperceptible degree, but, on the other hand, they pre- 
sent a number of nearly angular parallel curvatures, of which 
some follow each other at a distance ofJis" p- m. some at rather 
a greater interval. These curvatures point in different directions 
-some upwards, others downwards; some to the right, others to 
the left: or, to express it more properly, they appear to run on 
two planes which cross, or are at right angles to each other. In 
these curvatures the concentric rings are formed, of which more 
will be stated below. 
In these, as in most other teeth, the calibre of the tubes dimin- 
ished as they approached the external parietes, and formed fur- 
cated divisions at very acute angles, thus filling the larger space 
which they had to occupy the further they were removed from 
the axis of the tooth. Besides these grand divisions, they gave 
off smaller branches following close on each other, of which 
Retzius could not trace the course, because they filled so rapidly 
with the fluid in which the preparation was immersed, that they 
became as clear as the spaces between them. Besides these 
short tubes which fill up, in a greater measure, the intermediate 
spaces, the latter were occupied, more than in any teeth which 
have previously been described, by small, white, angular points, 
or calcareous cells of different sizes, which lay strewn about like 
HISTORICAL INTRODUCTION. 66 
HISTORICAL INTRODUCTION. 
grains of white sand. Then again, as well as these scattered and 
less thick-set calcareous cells, there were also other larger ones, 
more crowded and connected together, which lay in the above- 
mentioned parallel curvatures. In transverse sections of the 
canine teeth of the elephant, they form beautiful, regular rings 
round the cavity of the pulp, or the axis of the tooth, of which 
some stand about p> m. from each other, and which are so 
minute that they could not be seen with the naked eye. In longi- 
tudinal sections they form whiter, longitudinal, parallel streaks. 
These streaks and rings are not, however, those which Cuvier 
and others have described, for the latter are visible to the naked 
eye, and they shew themselves as broad, darker or lighter con- 
centric osseous layers; they are also not to be confounded with 
the streaks in ivory, which appear in a transverse section running 
in arches from the centre to the periphery, which cross each 
other, and in longitudinal sections appear as unequal, but generally 
parallel stripes, which here and there are cut into rhomboid figures, 
as it were, opliquely, and which partly run into each other. The 
latter streaks corresponding to the arched ones which cross each 
other obliquely in the transverse section, arise, like these from the 
refraction of the rays of light, by the parallel curvatures of the 
main tubes. They appear in longitudinal as well as in transverse 
sections from this cause, that the parallel curvatures, as has been 
already remarked, run in two planes, which intersect each other, 
or, as it does not seem improbable, they run spirally. 
In the elephant, Retzius only examined the corlicle substance 
which invests the canine teeth. The cells varied little in size or 
form; some were oval, but the most were almost round : their 
size was about line p. m. The small vessels terminating in 
them were so minute, that they could not well be distinguished. 
What principally characterises the organisation of this substance 
is the almost parallel and horizontal running, undulating tubes, 
which evidently approach the appearance of the tubes in the den- 
tal bone. The larger of the tubes were line p. m. broad ; the 
smaller line. Although, when cursorily examined, they 
appeared to be continued from the surface of the tooth to that of 
the dental bone itself, Retzius found, on closer investigation, that 
this was not the case. They appeared to be continued partly 
because they had the same direction, and partly because the 
minuter terminations projected, as it were, beyond each other. As 
well in the outer as in the inner surface of this substance, they 
terminated in ends which became gradually finer, and which 
most internally were curved towards the wall of the dental bone. 
They gave oft from their sides a number of larger and smaller 
branches, which entered into numerous communications with the 
contiguous ones: the larger branches were given oil'generally at HISTORICAL INTRODUCTION. 
67 
an acute angle. It would have been doubtless interesting to have 
examined this substance in other parts, and particularly on the 
molar teeth; but Retzius could not procure any preparation of 
these. 
Hippopotamus amphibius.-Of the hippopotamus, Retzius only 
examined the incisors, and for the investigation of their tubular 
structure, he chose here also slices which were taken from the 
border of the hollow alveolar extremity. 
The main tubes did not lie so close here as in the elephant, but 
are of about the same calibre. As in the latter animal, they are 
scarcely preceptibly undulating, but make on the other hand a 
number of parallel curvatures, which, however, are not so close 
together as in the elephant. The branches were somewhat more 
distinct than in the teeth of the latter. The small calcareous cells 
which occupy the greatest part of the intermediate spaces, are 
much more thinly scattered than in ivory : they are partly larger, 
and partly smaller. In fewer parallel curvatures appear such de- 
posits of calcareous earth as contribute to form the concentric 
rings in the tooth of the hippopotamus; on the other hand they 
formed a thick and constant layer on the entire surface of the 
tooth between the most external, minute branches, in which the 
ends of the main tubes terminate. 
The concentric rings in the tooth of the hippopotamus are not 
so regular as in ivory: they are more abrupt, are undulating, as 
it were, and arise principally from the refraction of the rays of 
light in the parallel curvatures. 
Rhinoceros Indicus.-In the rhinoceros, Retzius had only the 
opportunity of examining pieces cut longitudinally from the edge 
of the roots of a molar tooth. In these the tubular structure was 
admirably demonstrated. He found the main tubes at their widest 
end 4 } r"' p. m. broad. Although they were somewhat unequal, 
and showed here and there an extremely faint curve, they still 
could not be regarded as undulating. Like the main tubes in the 
alveolar ends of most teeth, they had an almost horizontal direc- 
tion from the cavity of the pulp to the periphery of the root. As 
they proceeded in their course towards the periphery, their furcat- 
ed divisions were very apparent, and they gave off moreover a 
great abundance of branches, of which many appeared distinctly 
to terminate in large calcareous cells. These lay thinly scattered 
in the interstices between the main tubes, which interstices, 
bordering on the cavity of the pulp, were of about the width of 
two tubes. A thick and compact layer of larger and smaller cal- 
careous cells had its seat at the outer surface of the root, imme- 
diately under the cortical substance which invested it. Between 
these closely-situated, communicating cells, the extreme ends of 
the tubes wound in particular abundance, and seemed partly to 68 
terminate in these calcareous cells themselves, and partly to 
anastomose with branches from contiguous tubes. These anasto- 
moses appeared in many places to form beautiful arches. In one 
or two places were larger groups of calcareous cells in the midst 
of the dental bone, which had, as it were, supplanted the main 
tubes. Round these cellular groups wound a number of beautifully- 
arched branches from the most contiguous main tubes, which 
themselves inclined somewhat towards them : these branches ran 
also straight to the cells, and terminated in them. 
Besides the branches which are visible in great abundance, 
Retzius could see from thick-set, nearly alternately situated 
unevennesses on both sides of the main tubes, that these uneven- 
nesses were derived from branches, which in these places were 
given off from the main tubes, but which were filled and rendered 
invisible by the varnish by which the preparation had been pene- 
trated. 
Retzius only examined the cortical substance in a molar tooth 
of the rhinoceros. The thin shell of this which covered the crown, 
as also the thicker one round the roots, presented thinly-strewn, 
large cells of various, and, as it seemed to him, irregular forms. 
Some were round, line p. m. broad; others were drawn out 
longitudinally, partly in the shape of tubes, partly as irregular 
figures; a number of tubes opened into all of them from every 
side. Round the circular cells the tubes which opened into them 
lay very close, and presented a radiated appearance. 
Sus Scrofa.-In the pig, of which Retzius examined a small 
molar and two canines, he found the greatest diameter of the tubes 
to be p. m. They diminish only gradually towards the outer 
extremities, and do not become very minute until they reach the 
outer part of the tooth, where they are distributed into an irregular 
net-work of tubes and calcareous cells, and form the outer wall 
of the dental bone. They are but slightly curved, and are 
scarcely to be called undulating. Most inferiorly, towards the 
alveolar border, they are of the form of the letter C; near the 
middle of the crown they are almost straight and parallel with the 
axis of the tooth ; and towards the masticating extremity, they 
present the form of an S. Their distance from each other is about 
the width of from one and a half to two tubes. Their divisions 
in an external direction arc furcated and acutely angular. The 
branches thus formed run immediately after the division again 
parallel with each other. Moreover, along the whole course of 
the main tubes, short branches arc given ofi*, of which Retzius 
traced some to dilated extremities which resembled calcareous 
cells. These short branches, lying on both sides of the main tubes, 
proceed in part almost transversely and curved over the nearest 
interstices, and run partly as serpentine or winding lines towards 
HISTORIC IL INTRODUCTION. the outer wall of the tooth. Only a few calcareous cells were 
found in the interstices, and Retzius could discover no concentric 
rings. On the other hand, there were a number of very large, 
many-cornered cells, giving off numerous branches in the yellow- 
ish substance, which at the top of the tusk filled up the narrow 
cavity of the pulp. 
In the pig, the cortical substance presented nearly the same 
structure as in the elephant. The cells were of the same size 
and appearance, but the parallel, stretched-out tubes were some- 
what larger. In the pig, this substance proceeds a little beyond 
the border of the enamel; but on the remaining surface of the 
latter it could not be discovered. Here, as in the human subject, 
it only forms an investment of the roots of the teeth. 
Phoca Annellata.-Of the seal, Retzius examined longitudinal 
and transverse sections, both of the incisor and molar teeth. On 
no part of them could he discover an enamel; but, on the other 
hand, he found considerable layers of cortical substance, particu- 
larly round the roots. The greatest breadth of the main tubes 
was p- M- 1° these teeth, although they were taken from 
young animals, the cavity of the pulp was almost closed. The 
continuations of the main tubes, which occupied the most internal 
and most recently formed part of the dental bone, were winding, 
only slightly parallel to each other, and very irregularly curved. 
On the other hand, the more externally situated portions of the 
same tubes were faintly undulating, and ran parallel to each other, 
the interstices between them being of somewhat more than the 
width of a single tube. They gave off a great abundance of fur- 
cated branches at acute angles, stretched out in an external direc- 
tion, as well as of other short, almost oppositely situated ones, 
which ran transversely over the interstices. Although a number 
of different, alternate layers of darker and whiter substances can 
be distinguished in these teeth with the naked eye, as well as with 
the aid of a glass, still Retzius could only perceive in a few places 
under the microscope definite parallel curvatures, or rings of 
osseous cells. The appearance of these rings seemed partly to 
depend on the more aggregated or scanty exit of small lateral 
branches from the main tubes. Immediately within the external 
surface of the tooth lay a beautiful layer of osseous cells, inter- 
woven with incredibly minute and abundant bundles of the extreme 
terminal branches of the main tubes. In some places these extreme 
branches seemed to terminate in contiguous tubes and cells of the 
cortical substance. In the yellowish, osseous substance, which in 
the middle of the canine teeth had filled up that part of the cavity 
of the pulp which was prolonged towards the apex, a number of 
large cells were found, which, however, appeared to contain only 
very little osseous earth. 
HISTORICAL INTRODUCTION. 
69 70 
Trichecus Rosmarus.-Of the walrus, Retzius examined the 
canine and molar teeth. In both, the covering of enamel was 
wanting; but to make up for this, they were provided with a 
larger investment of cortical substance. The tubes bore the 
greatest similarity to those in the seal; they were of the same 
breadth, displayed the same degree of undulation, and the same 
relation to each other. Their ramification, however, was much 
more distinctly evident. Both the long, bifurcated di visions of the 
tubes and the small lateral branches ran in acute angles towards 
the periphery of the tooth: a few only of the small lateral 
branches proceeded in short curves across the interstices and the 
most contiguous tubes. 
In the singular teeth of this animal, the dental bone is particu- 
larly remarkable from the numerous, large, calcareous cells which, 
except at the extreme end of the alveolar part, lie scattered every 
where between the tubes. These calcareous cells appeared, nearer 
to the apex of the tooth, to be larger and oblong, and their length 
to be about p. m. Besides these, there was situated in the 
entire circumference of the teeth, between the extremities of the 
tubes in the dental bone, a thick, delicate, compact layer also of 
calcareous cells. The incisors of this animal are also remarkable 
from the more recent irregularly formed, and almost preponde- 
rating dental substance, which constitutes a great part of the 
internal mass of the tooth, and, so to say, fills its cavity from the 
apex to the alveolar end, with the exception of a short space 
where it is hollow for the reception of the short pulp. To the 
naked eye, this substance seems clearer, and presents in its trans- 
verse sections a number of rings-of eyelets, as it were, as also 
various darker patches. This is the appearance which G. Cuvier 
has compared with that of pudding-stone, (Lecons d'Anatomic 
Comparee.) This substance with which the interior is, so to say, 
stuffed, plays a very important part both in the canine and molar 
teeth, and is the cause why only the outer shell of the canine 
teeth of the walrus is applicable for finer bone-work. If an entire 
transverse section of a canine tooth of a walrus be examined, this 
spurious dental bone will be found to occupy a third of its extent 
from before backwards, and half of its width from side to side. 
It fills up the greater part of the dental cavity, even in teeth 
which are not old. An incisor tooth, which Retzius examined 
shortly before publishing his work, was only hollow for the recep- 
tion of the pulp for two inches and a half from the alveolar 
extremity. In this hollow portion are found a number of connect- 
ed and generally cylindrical projections, resembling those of sta- 
lactites : of these the most central ones arc the longest; the more 
external ones are shorter, and the most external are shortest of 
all. These projections leave between them a number of interstices 
HISTORICAL INTRODUCTION. HISTORICAL INTRODUCTION. 
71 
which were tilled with pulp, so that it would be more proper to say 
that the whole group of projections lie embedded in the pulp of the 
tooth. If we examine these remarkable contents of the incisor 
tooth of the walrus with the aid of the microscope, we shall find 
that their structure bears great similarity to the internal structure 
of the substance of some cylindric bones. 
In a thin, transversely-cut, polished, and transparent section, it 
is found that every eyelet (of which the surface presents a number, 
from the size of a grain of mustard to that of a pea) represents, 
as it were, a peculiar dental corpuscule, with a hole in its centre, 
which is analogous to the cavity of the pulp, or to the medullary 
canal in a transversely-cut section of a cylindrical bone. These 
holes are in many places full of a yellowish or reddish matter, 
different from the dental substance, and which is probably nothing 
else than the dried residue of a thready pulp. From the border 
of these orifices tubes run in all directions, as in a small tooth, but 
inasmuch as they are immediately surrounded by other similar 
formations, they shortly become, as it w'ere, pressed together. 
Hence they cannot develope themselves equally in their entire 
circumference, but creep in bundles, forming beautiful parallel 
curvatures, between the contiguous substances. A great part of 
them proceed into the externa], regularly formed, dental bone, 
and are even continued into the main tubes which belong to it. 
These tubes of the dental bone, too, are abundantly and beautifully 
ramified, and present numerous concentric rings, which apparently 
owe their origin to parallel curvatures. In the lesser rings this 
arrangement is found to be less complete, and in the smallest there 
is often only a round, transparent spot, which now contains irregu- 
lar scattered tubes, now congregated or isolated calcareous cells, 
&c. Calcareous cells are also scattered in almost every direc- 
tion, and in great number, throughout this substance, as well be- 
tween the more regular radiating bundles of tubes, as between the 
scattered ones, and they form everywhere frequent communica- 
tions with the contiguous tubes. 
Similar contents, but of less solidity, are found in the molar 
teeth, where they close up the cavity of the pulp as far as the ex- 
tremity of the root, which has been remarked by G. Cuvier. 
This celebrated philosopher states that the teeth of the walrus are 
provided with enamel. His words are: "In some animals, for 
instance in the walrus, the enamel surrounds the tooth on all sides. 
In this animal the enamel is even thicker under the root of the 
molar teeth than on their crown." F. Cuvier speaks of only one 
substance in the tooth of the walrus: he says of the molars, "all 
these teeth have but one very short root, and they are entirely 
formed of one single substance, which is very hard, very compact, 
and analogous to that of the tusks." 72 
HISTORICAL INTRODUCTION. 
That which G. Cuvier calls enamel in the walrus, is in fact 
cortical substance, which is always much softer than enamel, and 
has indeed none of its peculiar properties. The cortical substance 
in the tooth of the walrus and in all other teeth contains calca- 
reous cells and calcareous tubes, which, when viewed here in a 
transverse section, show themselves arranged in beautiful rings, 
one external to the other. In the canine teeth, the cortical sub- 
stance forms only a thin layer of from to 1'" in diameter; but 
in many parts of the small molar tooth the diameter is 2"'. ft 
surrounds the tooth on all sides, except at the masticating surface 
which has been worn away, where the denial bone itself is expo- 
sed. It is this thick cortical investment which gives to the molars 
of the walrus their peculiar clumsy appearance, and causes them 
to lose, as it were, their normal shape. If such a tooth be split 
along its axis, that part which is formed by the pulp is found to 
be deeply bedded in the above-mentioned shapeless cortical mass, 
which, as has been said, surrounds the root itself. The tooth 
whilst whole is thicker towards the crown than towards the root; 
but on its being sawn open, it is found that the dental bone, pro- 
perly so called, is narrower towards the crown and thicker near 
the root. There is a well-defined boundary between the dental 
bone and the cortical substance, in the shape of a clear, yellowish 
streak: nevertheless, it is found by means of the microscope that 
the outer extremities of the tubes, or the outer cells in the dental 
bone, communicate with the internal cells of the cortical substance. 
These communications are particularly distinct in the root. Be- 
sides them, there were also found here tolerably large tubes, 
w'hich run upwards into the substance in the centre of the tooth 
above described, and which contained a red matter, probably 
dried blood. These broader tubes are very similar to the medul- 
lary canals in deer-horns which have been shed. Retzius pre- 
sumes that they are here the small and scattered remains of the 
cavity of the pulp, since it is very evident that the closing of the 
cavity of the pulp in the walrus is connected with a division of 
the pulp itself, which seems to be separated into a number of long 
threads, and round these the above-described, small, dental cor- 
puscules, constituting the central substance, begin to form in the 
shape of projections, which, when they are cut transversely, are 
found to have a central cavity, from which main tubes radiate in 
all directions. 
The cortical substance in the walrus invests the canine as well 
as the molar teeth, and is deposited in such immense quantity 
round the latter, that the small teeth lose through it their proper 
form, as has been above described. The internal structure of 
this substance is remarkable, from the abundance of almost paral- 
lel, ramifying, thick-set tubes which it presents, and between HISTORICAL INTRODUCTION. 
73 
which the cells lie scattered. These tubes run, too, perpendicu- 
larly, so to say, towards the surface of the dental bone, and seem, 
as it were, to commence and terminate in the different layers in 
which this substance was formed. They are, however, by far 
less regular and parallel than the tubes in the dental bone. Be- 
sides the cells themselves, the interstices are also filled in a great 
measure by a net-work of minute tubes. The tubes which enter 
the cells form thick bundles round them, which seem to be lar- 
gest on the external side of the cells. In longitudinally-cut slices 
the cells were of the form of an almond : they were about -2 
line p. m. in length, and about half that in width. The tubes of 
the cortical substance entered into numerous connexions with the 
finer terminations of the tubes of the dental bone, particularly at 
the end of the roots of the molar teeth: at the same place were 
seen a number of larger canals which entered into the cavity of 
the pulp, and probably belonged to blood-vessels. 
Delphinis Delphis.-The teeth of the Dolphin have a covering 
of enamel on that part which projects from the alveolus, and of 
cortical substance on that which the alveolus embraces. The 
cavity of the pulp was so filled with dental bone as to be reduced 
to a small canal, which was only present in that fourth of the 
length of the tooth nearest the root. This remaining portion of 
the cavity of the pulp was of little more than the thickness of a 
human hair, although the tooth examined was that of a young 
animal. In some teeth it was somewhat wider, but closed at both 
extremities : in others, it was altogether closed in its entire length. 
The tubes in the dental bone of this animal are somewhat 
smaller in their w'idest parts than those of the phoca and trichechus. 
The interstices were from three to four times broader than the 
diameter of a single tube. In the three-fourths of the tooth near- 
est the crown, they were parallel to each other; but in the fourth, 
nearest the root, they were almost irregularly winding. Some 
of the main tubes were extremely faintly undulating, in lengthy 
w7aves; others wzere not. In the coronal half of the tooth seen 
from both sides, they lay like S's placed against each other, with 
their upper ends converging towards the crown; but nearer the 
root they were almost straight and transverse; and more infe- 
riorly still, in the root itself, their direction was the same as in the 
crown. Owing to their minuteness, and to the comparatively 
large interstices between them, the division of the main tubes, as 
also the giving off of the lateral branches, were seen w'ith par- 
ticular distinctness. The former is best seen nearer the root, 
inasmuch as at every division of the main tube the new branches 
curve somewhat away from each other, whilst those in the part 
nearer the crown part straighter and at more acute angles. 74 
HISTORICAL INTRODUCTION. 
The small lateral branches run in the greatest abundance from 
both sides of the main tubes and their divisions, generally in 
transverse arches, of which a part cross over the nearest tubes 
and interstices beyond. The outer extremities of the main tubes 
are distributed in bundles into the surface of the dental bone, next 
to the enamel and cortical substance, in extreme minuteness and 
abundance, and also into the thick layer which is there situated, 
of minute, angular, calcareous cells. Such cells were found al- 
most everywhere in the dental bone of the dolphin. In the teeth 
which Retzius examined were found, immediately within the ex- 
ternal surface of the dental bone, several white streaks, which 
were present in the entire circumference of the tooth, and which 
were entirely formed by such closer, partly very large and angu- 
lar calcareous cells, some of which ran into each other, whilst 
others were in communication with the minute extremities of the 
tubes. 
Round the medullary canal there were here, as well as in many 
of the above-described teeth, oval tracts where the main tubes 
had been supplanted by peculiar and, as it were, more independent 
tubular structures. The main tubes round about these clear, oval 
tracts surrounded them in curves, and gave off thinly scattered 
branches which wound amongst them from all sides: a part of 
the tubes were at their terminations, as it were, pyriformally 
dilated into calcareous cells, which by intermediate tubes again 
communicated with other cells of triangular and various other 
forms. The tubes themselves formed here also numerous and 
direct communications with each other, in the form of loops, net- 
work, &c., (Plate A. 3. fig. 4.) On some of the larger cells Ret- 
zius counted from eight to ten larger tubes, which were given off 
from them, or opened into them. In the teeth, of which the roots 
were pointed, the cells were so predominant that scarcely any reg- 
ular tubes were found ; but nevertheless a definite border was ob- 
servable between the dental bone thus constituted and the cortical 
substance, in which the cells lay in nearly regular rows. The 
external cells in the dental bone formed, however, connexions with 
the cells in the cortical substance. 
The teeth of the dolphin, like those of the walrus and seal, 
appear to be closed at an early period, and to be deprived, as it 
were, of their pulp, which peculiarity may perhaps have its origin 
in the circumstance that the teeth of this animal have generally 
only to work on soft substances, are hence less exposed to be 
worn away, and so have less occasion for additional growth than 
those of most of the land mammalia. On the other hand, they 
appear to be provided better than other teeth with a strong cover- 
ing of cortical substance, secreted by the internal membrane of 
the alveolus, which is doubtless a residue of the dental sac. If 75 
HISTORICAL INTRODUCTION. 
we suppose that the tooth must keep up a continual communica- 
tion with the rest of the organism, it is probable that when this 
ceases to be kept up by means of the pulp, from the disappear- 
ance of the latter, it is effected through the cortical substance, 
and the tubes which pass from it into the cells of the dental bone: 
moreover, such an alteration may in some measure promote the 
extrusion of the tooth from the alveolus after the cavity of the 
pulp has closed. 
In an old tooth of the dolphin, Retzius found cortical substance 
only in that part which is wedged into the alveolus, and there 
only in a rather thin layer. It displayed here also a great abun- 
dance of similar, almost parallel tubes, running from without to 
the surface of the dental bone, between which the cells were 
situated. The latter were for the most part drawn out into irreg- 
ular shapes: some were very large; but most were oval and 
round. The round ones were of the size of line p. m. ; the 
oval ones line broad, and double as long. They lay in beau- 
tiful rows, running towards the periphery of the tooth, and the 
tubes opened into them in almost equal quantities at every angle. 
Crocodilus Sclerops and Esox Lucius.-The teeth of the cro- 
codile and of the pike have a covering of enamel on the crown, 
and a tolerably thick coat of cortical substance on that part 
which is situated within the alveolus. The breadth of the largest 
tubes of the dental bone is p. m. They are in lengthy 
curves, are considerably apart, and faintly undulating. In seve- 
ral places they present parallel curves; but still run without 
definite arched curves, and (when slightly magnified) seem to 
course almost straight from the internal cavity to the external 
surface of the tooth. Their distance from each other was equal 
to the breadth of four or five of them. The trunks of the tubes 
divide distinctly immediately after their commencement at the 
internal cavity: the branches of the divisions curve immediately 
away from each other, and wind particularly in the neighbour- 
hood of the root nearly irregularly. Numerous minute branches 
of various lengths are given off on all sides, of which, however, 
most seem to turn towards the root. These ramusculi seem in 
many places to terminate with dilated extremities in osseous cells. 
Numerous layers of osseous cells are found in the whole length 
of the tooth, some of which are of larger size than others. They 
curve beautifully round in the crown, and follow most exactly 
the contour of the dental cavity. The largest layer of these cells 
is situated here, as in the teeth of most mammalia, in the external 
layer of the dental bone. It is partly these layers of osseous cells 
and partly parallel curvatures which form the numerous, delicate, 
parallel streaks which, under a simple magnifiying glass are visi- 
ble in the transverse sections of the teeth of the crocodile. The 76 
HISTORICAL INTRODUCTION. 
inner side of the dental bone, or its cavity, appeared to be lined 
with a thin membrane, which protected it from contact with the 
reserve teeth, which this cavity also contains. 
In the crocodile also the cortical substance, only coated the 
roots. Its cells were about line p. m. broad, and for the most 
part circular and stellated, every stellated point being constituted 
by the entrance of a tube into a cell. The tubes scattered in 
every direction were so minute, and formed such dark groups, 
that they could not be very evidently distinguished. Still Retzius 
could see that they did not run so parallel or regular as in the 
cortical substance of the animals whose teeth have been last 
described. 
Python Bivittatus.-In the teeth of the python Retzius could 
discover neither enamel nor cortical substance: the tubes of the 
dental bone are a little thicker than in the crocodile, and have an 
extremely faint curvature externally and towards the root. Only 
in a few places, and after longer intervals, do they present a 
slight curve. Their distance from each other appears to be equal 
to the width of four or five of them. They do not divide, as in 
the above described, into branches, which in their turn are trunks ; 
all branches in the the crown of the tooth run outwards towards 
the periphery; and in the remaining part they are given off by 
that side of the main tubes which is nearest the root. These 
branches are given off almost parallel, and at very acute angles. 
Some of them are thicker than others, and they correspond to the 
main divisions in other teeth. They also give off numerous 
branches, which, however, run parallel with the others. This 
parallelism gives to the dental bone of the python, seen through 
the microscope, a very peculiar appearance. (Plate A. 3. fig. 6.) 
In the surface alone appeared a faint trace of osseous cells. 
Sparus Rondeletii and Balistes Vetula.-In the limited number 
of fish teeth, examined by Retzius, he found the dental bone of the 
sparus rondeletii and balistes vetula to resemble most in point of 
internal structure that of the mammalia and amphibia, inasmuch 
as in these fish it is white and hard like ivory, and displays, when 
viewed under the microscope, beautiful, regular, minute, and pa- 
rallel main tubes. 
In the Sparus Rondeletii the diameter of the tubes in the inci- 
sor teeth, near their commencement, is p. m. They are 
tolerably regular and closely undulating, with several larger and 
smaller parallel curvatures. Internally towards the cavity of the 
pulp in the crown, they were very and irregularly winding. They 
divide at acute angles, and the branches lie so close to the trunks 
from which they have been given oft', that their divisions are scarce- 
ly visible, with the exception of those which rise nearest their 
outer extremities, in the neighbourhood of the external surface of 77 
HISTORICAL INTRODUCTION. 
the tooth. The osseous cells were very indistinct. The coating 
of enamel was thick, light brownish, and traversed by innumera- 
ble minute furrows, running in an external direction, partly cross- 
ing each other, and nearly resembling tubes. 
In the Batistes Vetula, the tubes are more minute than in the 
sparus, being p. m. broad; they are beautifully parallel, 
with the exception of their more recent parts in the coronal end 
of the cavity of the pulp. Their undulations were very faint, and 
very lengthy. Their distance from each was scarcely equal to 
the breadth of a single tube. The larger branches lie close to the 
trunks, whilst the smaller ones, for the most part, curve away 
from them in a transverse direction. Near the surface of the 
tooth the ends of the main tubes themselves presented considerable 
parallel curvatures. 
The greater part of the tooth of this animal is covered by a 
thick, hard and strong enamel, which looks, in many places as if 
the tubes of the dental bone were continued into it, and which, 
like that of the sparus, is full of furrows, coursing in an external 
direction. Round the root-end of the tooth there appeared to be 
also a sort of cortical substance. 
The rest of the fish-teeth which Retzius examined, consisted, 
for the most part, of a more imperfect dental bone, with a number 
of larger tubes forming rude anastomoses, and nearly resembling 
the soft imperfectly developed dental bone, which fills up the in- 
terior of the teeth of the bradypus 
The cells in the above-mentioned cortical substance were large, 
extremely irregular, terminating immediately in each other, or 
being, as it were, confounded together. The course of the minute 
bundles of tubes was also in the highest degree irregular. The 
cortical covering was very thin, and terminated immediately un- 
der the border of the enamel. 
In other fish-teeth which Retzius examined, he found no other 
substance which could be considered as analogous to the cortical 
covering, except the proper osseous substance, which united the 
tooth with the jaw. In the Shark, whose teeth are bound to the 
jaw by ligaments, this substance formed a rounded basilary part 
on the free extremity, the organization of which part is scarcely 
to be distinguished from that of a more perfect structure of real 
bone. 
Squalus Cornubicus.-In the lamna most of the teeth, though 
flat, were still somewhat hollow, and were provided with a thick 
coating of enamel. The largest diameter of the tubes of the den- 
tal bone is p. m. At the top of the tooth they run in an 
upward direction; on the sides, transversely towards the external 
surface; and nearer the root, (which is fastened on a basis of real 
bone), they radiate in a downward direction. The proper trunks 78 
of the tubes lie at a tolerable distance from each other, and their 
divisions, which in many cases commence very near to the origin 
of the main tubes from the internal wall which is turned towards 
the cavity of the pulp, recede considerably from each other- 
(Plate A. 2. fig. 3) ; whilst their diameter diminishes more rapidly 
than in more perfect teeth of the same size. In the entire course of 
the divisions, as well as of the trunks, numerous minuter lateral 
branches arc given off in a direction which is exactly transverse to 
that of the tubes from which they rise. In the neighbourhood of 
the external surface, these minuter branches become completely 
parallel, and terminate under the enamel in large, irregular calca- 
reous cells. These calcareous cells give off other irregular tubes, 
which partly unite with each other, and partly terminate in other 
cells. The outer part of the dental bone forms, as it were, a pe- 
culiar layer, which is darker than the internal one; precisely at the 
border between these two layers are situated a number of large 
calcareous cells. Besides these, other calcareous cells of diffe- 
rent sizes are found throughout the dental bone. The cavity of 
the pulp in most of the teeth of the shark, which Retzius examined, 
though they were in different stages of developement, was very 
small. Towards the root some larger tubes opened into it, which 
contained a red matter, bearing some resemblance to desiccated 
blood. These tubes ran longitudinally into the osseous basis on 
which the root is fastened, and terminated in its medullary canals. 
Esox Lucius.-In the common pike, as in most fishes, are found 
a number of unequally developed teeth-from the smallest loose 
points, to the teeth immovably fixed to the jaw by a solid osseous 
base. On none of them could Retzius, by means of the micro- 
scope, perceive any covering of enamel: on the contrary, the 
dental bone was found to be so soft, that it could almost as easily 
be cut with a knife as a common quill. In the neighbourhood of 
the apex only, and on the sharp edges, did it feel somewhat hard- 
er at the surface. The bone by which the older teeth were fast- 
ened by their base to the maxilla, constitutes, though of a different 
appearance, a continuation of the inner or more recent dental 
bone itself, and wants the whiteness and lustre of the remaining 
tooth, inasmuch as it is traversed by large tubes even to the sur- 
face. The dental bone itself in the pike is properly divided, as 
it seems to Retzius, into an internal kernel provided with large 
tubes, and into an external thinner part, which latter forms the 
covering of the first, and contains minute and parallel tubes. The 
larger main tubes which occupy the internal more imperfect part 
of the dental bone, are in their widest parts about p. m. in 
diameter. They run almost parallel with each other, and with 
the axis of the tooth, and form with each other numerous larger 
and smaller anastomoses. 
HISTORICAL INTRODUCTION. 79 
Near the base of the firmly-fixed teeth, the larger transverse 
anastomoses are so near to each other, that the interstices are 
scarcely as wide as the diameter of the larger tubes. In some 
few recent teeth these tubes contained here and there a blood-red 
substance, and may hence be regarded as divisions of a cavity 
of the pulp. Remarkably beautiful and very-short tubes of 
to p. m. in breadth, are given off from the large main trunks, 
generally in a transverse direction: most divide immediately after 
their origin into extremely minute bundles, of which the ramifica- 
tions enter into innumerable reticular communications with each 
other, filling up also the interstices between the larger tubes. In 
the passage from this internal dental substance with large tubes 
to the outer one in which the tubes are minute, a particular sim- 
ple extension of the tubular structure is observable, formed by the 
anastomoses of the terminations of the main tubes, which are 
straight at their extremities, but arched previously, and which 
constitute, as it were, the boundary between the external and 
internal dental substance. From these larger border-tubes are 
given off more minute, short, tubular trunks, which follow nearly 
the direction from the above-mentioned boundary outwards, as 
the small tubes in the more recent, thin-walled, hollow shells of 
the crown in more perfect teeth, which run from their large cav- 
ity of the pulp externally towards the surface. Here too those 
which are next to the apex run almost parallel with the axis of 
the tooth; but those which are nearest the root transversely to it, 
and so on. They divide at their commencement into bundles of 
larger and smaller branches, which enter into numerous reticular 
anastomoses with each other, but which most externally give off 
very beautiful, close, parallel, generally straight tubes of about 
from to p. m. in breadth: amongst the latter Retzius 
could discover neither branches, anastomoses, nor cells. This 
most external stratum of dental bone gives to the transverse sec- 
tions of the tooth of the pike a peculiar and pretty appearance, 
and resembles, slightly magnified, a layer of enamel. It begins 
with an acutely angular attenuated border, near to the base of the 
tooth, where the basilary part of the dental bone terminates, 
which, in recent teeth, is of a greyish, in dried of a yellowish 
colour; it increases somewhat in thickness nearer the apex, in 
which the minute tubular ramifications form, as it were, with the 
main trunks, the most beautiful dendritic figures. This minutely 
tubular, external portion of the dental substance is of the purest 
white, and is also much harder and more compact than the interior 
of the dental bone. To judge by the hardness of its surface in dried 
teeth, Retzius would have concluded that it was invested with an 
extremely thin membrane of enamel; but he could not detect any 
with the microscope, although accurate authors have asserted 
that it is present on the teeth of the shark. 
HISTORICAL INTRODUCTION. 80 
HISTORICAL INTRODUCTION. 
Gadus Molva.-In the ling the fixed teeth sit like epiphyses on 
small processes, formed by a peculiarly modified dental substance, 
which presents, as it were, a transition from the osseous substance 
of the maxilla to that of the tooth. The teeth themselves are short, 
conical, and half transparent, and have at their apices alone, when 
those are not worn away, a coating of enamel. This latter is 
here placed like the iron projection (jernskoningen) on some 
wooden spades, runs before and behind as into a transverse edge, 
and in some into a short lancet-formed point: it gives to the apex 
of the tooth its white appearance, and is found, it seems, on all 
teeth from their commencement. The fixed teeth also have a 
cavity of the pulp, which in some is larger, in others smaller, and 
which unites with a corresponding excavation in the osseous 
base on which the tooth is fixed. 
In some teeth the cavity of the pulp is very small, being nearly 
reduced to a conical tube running in the direction of the axis of 
the tooth. 
In the dental bone itself of the ling there was a great paucity 
of tubes. Along the wall of the cavity of the pulp, which ran 
longitudinally, and was in part tubiform, the main tubes opened 
with short trunks of from Tw to p. m. in thickness, which ran 
towards the apex, and in an outward direction, (rami patentes, 
Botanic:') and gave off branches on both sides, between which 
there were considerable intervals: these branches formed, with 
others of the contiguous tubes, large loop-formed anastomoses, 
and their outer extremities entered also into closed anastomoses, 
almost like the more minute blood-vessels in the villi of the ab- 
dominal canal. This most external arrangement of anastomoses 
forms here, as in the pike, a sort of boundary, beyond which no 
larger tubes are found. 
The more minute lateral branches of the tubes of the dental 
bone in the ling were not easily discovered; they appeared to be 
less regular, and generally ran in a direction transverse to the 
tubes from which they rose, or parallel to the axis of the tooth. 
Anarrhichas Lupus.-The teeth of the wolf fish resembled in 
many respects very much the solid teeth of the ling. Like these 
they contain a small cavity; like them they are placed as 
epiphyses on elevations of the maxilla; they have all only a small 
patch of enamel on the apex, and their tubular structure is almost 
the same, with the exception of the difference which arises from 
the more limited extent of the cavity of the pulp. The processes 
on which the teeth are fastened have particularly attracted the 
attention of Cuvier. In his lectures on comparative anatomy, he 
says of the anarrhichas, "Its jaws are covered with elevations 
which are composed of fibres or tubes alone. ...In the full-grown 
animal nothing is found besides these, and one feels inclined to regard them as teeth.... The sea-wolf is the only animal with 
which I am acquainted in which, besides the teeth, a part also of 
the bone (viz. the osseous elevations of which I have spoken 
above) falls out. The shedding of these is conformable, as I have 
already mentioned, with the shedding of the horns of deer; and 
their separation is doubtless effected in the same manner, with 
this only difference, that the new elevation on which the tooth is 
fixed does not lake precisely the place of the former one, but is 
developed by the side of it, and only through its enlargement 
does the hollow left by the falling out of the old one become fill- 
ed up." 
Retzius has examined several heads of the anarrhichas, and, 
from what he has found, cannot but conclude that the views of 
Cuvier on this point are completely false. The processes descri- 
bed on which the-teeth are said to be situated do not, he says, 
exist in reality. Their appearance is a mere deception, which 
originates in the following manner:-At a little distance from the 
place where the teeth are fixed, runs a border which resembles 
the border of the alveolus. The osseous substance which lies 
between it and the teeth, is peculiarly porous, and has on both 
sides small furrows which correspond to the interstices of the 
teeth, and which give to this basilary substance as it may be 
called, an appearance as if it were divided into as many pro- 
cesses as there are teeth fixed upon it. This appearance is also 
strengthened by the circumstance, that at the end of each of the 
above-mentioned furrows, next to the boundary of the dentigerous 
bone which resembles the border of the alveolus, the round ori- 
fices of small cavities are found, which contain sacks for the 
reserve-teeth, and some of them also reserve-teeth themselves 
nearly fuliy developed. These alveolar orifices, of which one is 
situated near the end of each interdental furrow, and consequently 
before each dental interstice, chiefly contribute to give an appear- 
ance to the above-mentioned basilary part of the dentigerous bone, 
as if it were divided into as many processes as there are teeth. 
Whence Cuvier derived the idea that these portions of bone 
supplied the place of the teeth after the latter had been shed, and 
that they themselves are finally changed-this, says Retzius, I 
am not at all able to explain, for in the numerous heads of the 
anarrhichas which I have examined, I never found any teeth 
wanting, though I have seen them very much worn away. The 
longest and most anterior teeth in the inter-maxillary bones, and 
those which correspond to them in the inferior maxilla, have most 
the appearance of being situated on peculiar osseous processes, 
which, in connexion with their teeth, have a distant resemblance 
to the place where the horns of the deer are fastened on the bone 
beneath, and this similarity has been noticed both by Cuvier and 
HISTORICAL INTRODUCTION. 
81 82 
HISTORICAL INTRODUCTION. 
Von Born. The latter has given a faithful drawing of the beau- 
tiful circle of folds, which is seen on the spot where the tooth is 
situated, after the latter has been removed. (See Heusinger, 
Zeitschr. f. d. organ. Physik, Bd. 1. Taf. vi. fig. 2.) The same 
author incorrectly asserts that the teeth of both the anarrhichas 
and the pike are invested with enamel; whilst Andre on the other 
hand says, (Phil. Trans. ofwe Royal Society, vol. Ixxiv. p. 277,) 
"The teeth are formed of a hard bony matter, not covered with 
enamel as in some animals." Retzius has never found a trace of 
enamel on any protruded tooth of the anarrhichas, which had 
grown fast at its base. Having, however, always without ex- 
ception seen the teeth of this animal worn away at the apex, he 
examined the small dental germs enclosed in the above-mentioned 
reserve-alveoli, and found that all these had at their apex, or at 
the point which corresponded to it, a small portion of enamel. 
The germs of the conical, pointed, front teeth had only the ex- 
treme summit coated with enamel; the lenticular germs of the 
obtuse teeth indhe vomer had in the centre of their almost flat 
and radiated coronal surface a small white elevation of enamel, 
of which the breadth at the base was not quite I"' p. m. That a 
fish which uses its teeth for crushing large muscles, snails, lob- 
sters, &c., must soon wear off these small tips of enamel, and that 
the latter indeed can scarcely be of any use here, seems to be 
quite evident. 
The main tubes in the dental bone are somewhat larger than 
in the ling; the inner ones run parallel with the axis of the tooth; 
the external ones incline somewhat outwards. This direction of 
the main tubes in the anarrhichas has its origin in the circum- 
stance that the formation of the tooth is in a great measure finish- 
ed before the cavity of the pulp has begun to be formed, as may 
be learnt from the dental germs; hence the cavity of the pulp 
does not attain, as in the ling, the extended form of a main tube, 
from the sides of which the other tubes rise. These main tubes 
subsequently divide into beautiful, parallel, minuter branches, 
which form numerous reticular anastomoses with each other, and 
which partly occupy the interstices: they terminate externally in 
the same way as in the ling. 
The larger trunks of these tubes were in a great measure filled 
with a red matter, which was doubtless a production of the pulp. 
The more minute calcigerous tubes were very indistinct. 
Cyprinus Idus.-In the carp, which has only teeth in its pha- 
rynx, the structure of these organs is very similar to that in the 
balistes. They contain a considerable cavity of the pulp, which 
extends through almost the entire length of the tooth, and partly 
also laterally into the bone beneath the fastening of the tooth, 
where there is an orifice for the entrance of vessels from within. 83 
When these teeth are viewed with the naked eye, and also with 
the lens, their points are seen to be tipped with a white, transpa- 
rent substance, resembling enamel, but Retzius could not render 
himself certain that it was such by the aid of the microscope. 
The tubes of the dental bone are tolerably regular and parallel; 
their thickness near their commencement at the cavity of the pulp 
is p. m. They bifurcate, and the divisions run parallel 
with each other; but the more minute branches, particularly 
those towards the outer part of the tooth, diverge more, and run, 
as in the balistes, in a direction towards the base of the tooth. 
Hence the branches are most beautiful, most abundant, and most 
distinct towards the external part of the tooth. 
Cuvier, as well as Von Born, was acquainted with the tubular 
structure in different fish-teeth; but both seem to have considered 
the tubes, or fibres as they call them, as undivided, and as running 
parallel from the cavity of the pulp to the end of the dental bone. 
Von Born says, expressly, that some fish-teeth consist of fibrous 
substance with a coaling of enamel, others of osseous substance 
with the same. In the former class, he places the teeth of the 
anarrhichas, in which the tubes have a considerable diameter, so 
that they may easily be seen when slightly magnified : in the lat- 
ter class he numbers such teeth as have a harder and more com- 
pact dental bone, in which the tubes escaped his view. Both 
Cuvier and Von Born maintain that nerves and nutritive vessels 
enter the hollow tubes. Retzius has found that the larger of these 
in the shark, pike, ling, and anarrhichas, often contain a red sub- 
stance quite similar to the pulp, in the same way as do the larger 
tubes in the inner mass of the tooth of the walrus, (whence they 
may rightly be pronounced to be ramifying prolongations of the 
cavity of the pulp, analogous to the proper medullary canals in 
the substantia ossea,) and believes that the more minute tubes are 
alone properly calcigerous. 
HISTORICAL INTRODUCTION. 
"These inquiries into the Microscopical Structure of the Teeth," 
says Retzius, in conclusion, "have been made with the greatest 
care, and have cost me a great deal of trouble: they refute the 
observations and views of many of my predecessors; but 1 never- 
theless clearly see, that the results to which I have arrived can 
make no pretensions to completeness. Whoever considers, for 
an instant, the variety of forms presented by the teeth of mammalia, 
amphibia, and fishes, as also their diversity corresponding to the 
diversity of the parts to which they are fixed, and, further, the 
different milk-teeth and permanent teeth, must instantly see that 
a complete investigation of this department of science would be a 
labour of several years, and would fill a large volume. I confess, 84 
too, that my observations can make no pretensions to infallibility, 
which can only be attained in proportion as experiments are made 
with exactness and repeatedly varied. According to my expe- 
rience, it is by varying experiments continually, that light is most 
easily thrown upon obscure phenomena. Hence, as long as I 
confined my observations to the teeth of the human subject, I 
overlooked the osseous cells which are so important towards ob- 
taining a knowledge of the dental bone ; the divisions of the tubes 
also escaped me for a long time, as did also their highly interest- 
ing ramifications, &c. I cannot therefore regard the present 
communication as anything more than a foundation for future 
inquiries, and I submit it to the eye of the public, in order that it 
may be strictly examined and brought to perfection. I have 
found the subject so important, and its examination has given me 
so much satisfaction, that I ardently hope to find a future oppor- 
tunity to correct a portion of the defects which I have already 
discovered. In the meantime some general results may be 
drawn from the facts which I have related, and the comparison 
of them with observations on similar structures. These results 
are as follows :- 
"The teeth of mammalia consist in general of three substances, 
the dental bone, the enamel, and the cortical substance. These 
three substances form also the teeth in certain amphibia and fishes. 
The dental bone contains tubes and cells which are in communi- 
cation with each other, and which are analogous to the minute 
tubes and cells forming an important part of the organization of 
bone. 
"The minute tubes in the osseous substance I demonstrated, to- 
gether with those of the dental bone, by making slices of teeth 
which were still fixed in the alveoli. Preparations made in this 
manner contained of course a portion of the alveolar bone, which, 
when it was filed as thin as the sections of the tooth, illustrated the 
internal structure of the dental bone. These tubes in bone itself 
had been shortly before found by Muller and Miescher, as also by 
Purkinje and Valentin. Muller was the first who showed that 
they contained calcareous matter. They are still more minute in 
bone than in the tooth, and are many times smaller than the most 
minute blood-vessels, their thickness, according to Muller, being 
7 line p. m. (J.. Mulleri Observationes de canaliculis corpuscu- 
lorum ossium, atque de modo quo lerrea materia in ossibus contine- 
tur.) They radiate from the minute medullary canals, which 
were first more carefully examined by Purkinje, give off an abun- 
dance of branches which form reticular communications, and ter- 
minate in Purkinje's corpuscula, or cells. I call them by the lat- 
ter name, because I am convinced that they are excavations in 
the substance of cartilage as well as in that of bone, which partly 
HISTORICAL INTRODUCTION. contain a clear fluid, and partly deposits of calcareous salts. The 
horns of deer are organized in nearly the same manner, with this 
difference only, that in them the minute medullary threads appear 
to be really blood-vessels, which view is most strongly confirmed 
by Berthold in his work, "Ueber das Wachsthum, den Abfall, und 
die Wiedererzeugung der Hirschgeweihe, in dessen Beitragen zur 
Anatomie, ^cA Gottingen, 1831. 
"The tubes in the dental bone open into the cavitas pulpae, and 
give off branches in their course, which form a net-work of com- 
munication between each other, and which terminate in cells. 
These cells, together with the branches from the main tubes, 
nearly fill up the interstices between the latter. The breadth of 
the main tubes varies from to °f a line, p- M-> an^ di- 
minishes as they divide into branches: the most minute subdivi- 
sions are many times smaller than of a p. line. It is very 
likely that the tubes and cells which are seen under the micro- 
scope form but a small portion of those which really exist. 
"The dental bone, as Cuviei' and several others have described, 
is deposited layer by layer round the surface of the pulp, and the 
most external layer is that which is first deposited. During this 
process the most external closely contiguous cells have their 
origin, and also the peripheral extremities of the main tubes. 
During the formation of successive layers, the latter are also con- 
tinued inwards; and it would seem as if their parallel curvatures 
were produced during their continuation from one layer into an- 
other. In this case we have grounds for presuming that there is 
a periodical motion of the pulp, by means of which the tubes, 
whilst in process of formation, are at one time pushed towards the 
apex of the tooth, and at another' drawn down and in the direction 
of its root. We may also imagine the periodical motion to be of 
various kinds. The most delicate and most numerous undulating 
curvatures must be the work of very short periods. The longer, 
shallower curves, of which every fully developed tube presents 
only a few, may be regarded as marks of other and slower peri- 
odical changes in the formation of the pulp, during which those 
producing the short tubular undulations are carried on uninter- 
ruptedly. 
"These processes, however, are only carried on with complete 
regularity before the tooth protrudes through the gums. In the 
extremities of the roots, and in the osseous mass filling up the 
centre of the cavitas pulpae, which are subsequently formed, the 
tubes are less regular and uniform than in other parts. In this 
last formed osseous mass, the branches of the tubes are best 
shown, because both the former and the latter have no longer 
their parallel arrangement. In this irregular form of dental bone 
the largest cells are found, and the entrance of the tubes into the 
HISTORICAL INTRODUCTION. 
85 86 
latter is admirably well seen, as also the reticular meshes formed 
by the tubes themselves. In many places this substance presents 
so great a similarity to other osseous formations, that it appears 
rather to belong to ordinary bone than to dental bone; it differs, 
however, from the former in the larger size of its main tubes. 
"In many animals the pulp is divided after the outer shell of the 
dental bone has been formed (e. g. in the bradypus, trichechus, 
esox, gadus, anarrhichas, &c.) After this has taken place, par- 
ticular layers are formed round the division of the pulp. The 
osseous substance which thus arises has a still greater similarity 
to ordinary osseous structure. The divisions of the pulp prolonged 
into fibres then show the strongest similarity to the medullary 
fibres in bones, and form in many cases, like the latter, lateral 
communications, (for instance, in the pristis, gadus, anarrhichas, 
&c.) In several animals, particularly in the trichechus, this form 
of dental bone presents the most evident similarity to proper bone. 
There are found in it medullary tubes, (canals of the pulp,) and 
medullary fibres, (fibres of the pulp,) round which groups of con- 
centric layers have formed; from these the minute tubes radiate, 
which in the different layers are as it were pieced together, and 
in these layers concentric rows or rings of cells are again found 
just as in bones. 
"The similarity between dental bone and real bone is hence 
greater than one is inclined to believe after making the first 
microscopical researches. The greatest difference between them 
consists, as I believe, in the manner of their-formation. In dental 
bone the most external layer is first formed, in bone it is last 
formed, round each small medullary fibre. 
"In bone every medullary fibre has the same size at its com- 
mencement which it afterwards retains. The small osseous cylin- 
ders, or layers, are formed by the veins, which lie externally 
round the medullary fibres, or out of the mass plentifully supplied 
with veins, in which the scattered, so called osseous fibres lie 
imbedded. In order that the hollow fibrous structure in bones 
may be connected, the individual fibres and the small medullary 
canals enclosed within them form numerous communications, 
which give to a bone, during the process of formation, its well- 
known reticular appearance. Hence the medullary organ in the 
osseous fibres is not, in my opinion, like the pulpa dentis, the for- 
mative organ in bone; but, on the other hand, it is probably of so 
much the greater importance for the preservation of the bone. 
The pulpa dentis, however, is the organ of formation as well as of 
preservation in the dental bone. In this diversity may probably 
have its origin the great difference between bone and the tooth, 
that the substance of the former is subject to 'resorption' and con- 
siderable change, which is not the case in the latter. The horns 
HISTORICAL INTRODUCTION. 87 
HISTORICAL INTRODUCTION. 
of deer remain for a considerable time without additional growth, 
and without 'resorption.' It is well known that they are only shed 
in those animals in which the organs of propagation are uninjured; 
in castrated deer the growth goes uniformly forwards. 
"Many of the cylindrical bones are surrounded externally by 
concentric rings, which encircle the whole in the same manner as 
the regular, external, dental bone in the walrus surrounds the sub- 
stance which is similar to pudding-stone. It might hence be said 
that a tooth with a simple pulp is analogous to an osseous fibre 
from the interior of bone, or to the most external, concentric lay- 
ers of a bone which surround the whole. 
"It can scarcely be doubted that the minute tubes in dental bone, 
in the cortical substance, in common bone, and in the horns of 
deer, as well as the cells which are united with them, are a pecu- 
liar kind of vessels, containing a nourishing and supporting fluid, 
of which probably the composition differs at different periods. 
This fluid is most likely secreted by the capillary vessels which 
clothe the surface of the pulp. In common bone in which the 
minute tubes open into the medullary canals, this secretion proba- 
bly takes place after the hollow osseous fibres have been formed, 
in a great part from the surface of the medullary fibres enclosed 
in the cavity of the osseous fibres, whilst the minute tubes collect 
round them in a radiating manner. 
"In the horns of deer, in which the blood-vessels occupy in a 
great measure the place of the medullary fibres and of the minute 
medullary tubes, the same minute osseous vessels are seen radia- 
ting from the parietes of the minute canals which contain these 
blood-vessels. 
"That the small osseous tubes and cells contain osseous earth 
is seen from their whiteness, which disappears when the prepara- 
tion is laid in diluted muriatic acid, in which afterwards the cal- 
careous salts are precipitated, the previously white and dark 
osseous tubes and cells being rendered quite colourless and clear, 
after having been submitted to the action of the acid. These 
calcareous salts were probably left behind in the tubes from the 
first formation of the dental bone, and deposited themselves round 
the parietes of the tubes and cells. In common bone, probably, 
the peculiar vessels in question take a part in the continual, or 
apparently continual, exchange of substance: this cannot in the 
same degree be the case in dental bone, inasmuch as in this no 
such exchange appears to take place. What end then is served 
by this beautiful organization of the dental bone ? We have 
many examples that nature organises structures which have a 
close affinity to each other according to one and the same plan, 
and hence we have, in different parts or organisms, formations, 
which in some are of the greatest importance, whilst in others 88 
HISTORICAL INTRODUCTION. 
they are of much less functional significance, or of none whatever. 
If we hence assume, what is highly probable, that in bone the 
peculiar vessels in question give passage to fluids during the entire 
life of the animal (or a great part of it)-which fluids contain the 
solid as well as the liquid materials of the osseous substance-it 
does not necessarily follow, that the same process must be carried 
on in the teeth during the whole of life. On the contrary, I am 
inclined to believe that these vessels in dental bone are at their 
height during the first period of the formation of the tooth, and 
exercise then their more perfect action. At the same time, the 
existence of a continual vital process in the tooth as well as in the 
crystalline lens cannot be denied, which, however, appears to be 
carried on without any constant exchange of solid matter, and 
must hence consist in a renovating circulation of the dental fluids. 
I refer here to an observation of G. H. Weber, published several 
years ago, and before the existence of the peculiar vessels in ques- 
tion was suspected:-'The tooth appears then to be penetrated 
by fluids secreted by the dental germ, and by the membrane sur- 
rounding the root externally,) both of which are abundantly sup- 
plied with vessels.) These fluids, without circulating in organic 
canals, may operate much towards the preservation of the tooth, 
as also towards the decay of the dental substance when their 
composition is morbid.' 
"When milk-teeth are examined just before they are about to 
be shed, they are found to present an appearance as if, from pres- 
sure of their permanent successors, they had wasted or been 
absorbed at the root. The crown of the advancing tooth appears 
to have pressed itself into the extremity of the deciduous one. I 
have carefully examined how this appearance is produced, and 
have come to the decided conviction that neither tabescence, 
absorption, nor erosion, has anything to do with it. 
"In the milk-teeth which presented it, I found the radical 
extremity quite entire, as also the small cavitas pulp® and the 
deep enamel furrows which, in the horse, descend from the crown, 
and are filled with cortical substance. I found moreover, on 
making transverse sections of them, that their roots assumed a 
form corresponding to that of the crown of the advancing tooth, 
by growing round and closely shutting in the latter. 
"In the teeth a greater degree of hardness is required than in 
any other part of the organism, and a hardness moreover com- 
bined with the same tenacity which exists in bone. They are 
destined to be subject to almost constant pressure; and that pro- 
perty in which they differ from bone, of not disappearing under 
or being affected by pressure, must hence be a necessary condi- 
tion for the fulfilment of their function. This property, which is 
only found besides in the corneous structures ot the skin, is owing, HISTORICAL INTRODUCTION. 
89 
in the teeth, to the circumstance that the solid parts once formed 
are not changed, but are constantly preserved by the circulation 
of a fluid in their minute tubes and cells. 
"The enamel presents a much more simple structure, being 
without sanguiferous or any especial vessels: its structure most 
resembles that of the crystalline lens. It also probably requires 
an organic fluid for its preservation, which, as I presume, is con- 
ducted to it by the tubes of the dental bone, permeating afterwards 
the membranous parietes which probably clothe the individual 
fibres. This substance is not found in all teeth, but appears in 
many cases in a rudimentary state, so to say, inasmuch as it is 
missed in the teeth which have not yet or have only just pro- 
truded-as in the anarrhichas lupus, gadus molva, and phoca 
annellata. Though I found no enamel on the teeth of the triche- 
chus rosmarus, I still presume that a trace of it may be discovered 
on the crowns before they have been worn away. (In the haly- 
chaerus griscus a complete though thin covering of enamel is 
found) 
"In some animals the enamel is formed not only within the folli- 
culus dentis, but is also secreted during the whole of life by a small 
ring-like organ, which, near the bottom of the alveolus, surrounds 
the root of the tooth (in the hare, beaver, &c.) 
"The cortical substance is found on the teeth of most mammalia, 
and is also met with on those of amphibia and fishes. It is every- 
where distinguished by a predominant abundance of osseous cells, 
and by less extended, in general more minute, and often altogether 
irregular osseous tubes. It is formed in some animals (in the 
elephant, the horse, the ox, &c.) as the outer covering of the 
enamel, particularly within the folliculus dentis before it is closed; 
but in these animals also it is secreted during the whole of life 
from the membrane surrounding that part of the tooth which is 
concealed in the alveolus. In most animals with simple teeth, as 
also in man, it only invests that part of the tooth which is not 
covered with enamel. In the bradypus, in which no enamel is 
found, it covers the whole tooth. 
"Its deposition round the root of the tooth increases as the 
cavitas pulpae closes, and as the pulp itself correspondingly di- 
minishes. The minute osseous tubes in the cortical substance 
then form immediate communications with the osseous cells and 
osseous'Hikes in the dental bone, so that the latter can now, when 
the pulp has as good as ceased to exist, receive the necessary 
supply of fluids from without. In certain animals the cortical 
substance presents also larger canals, which are of about the 
same thickness as the medullary canals in bone. In the cortical 
substance closing in some teeth the end of the cavity of the pulp 
which would else be open, those lubes open into the said cavity, 90 
HISTORICAL INTRODUCTION. 
and contain the blood-vessels which belong to the pulp itself. The 
larger tubes which are found in that portion of the cortical sub- 
stance lying exposed beyond the gum, appeared empty, and are 
probably only the remains of the blood-vessels which were en- 
gaged in its formation. It is, however, still probable that even in 
this substance a circulation is kept up of peculiar fluids secreted 
from the blood, which fluids rise into the peculiar minute tubes 
and cells, in much the same manner as the sap rises in a plant. 
"The layers of dental bone are deposited, as above described, 
from without inwards, the most external being thus always the 
first formed : in the cortical substance the reverse obtains,-its 
inner layers contiguous to the surface of ihe tooth are first formed, 
and afterwards the outer ones. 
"The cortical substance presents no similarity to tartar; and 
one of the best proofs that the latter is a mere deposit from the 
saliva, is the fact that we find thick crusts of it round artificial 
teeth." 
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 con- 
firmed by Mr. Owen, who has submitted to microscopical exam- 
ination the teeth of several other animals both recent and fossil. 
From an excellent report of these researches read at the last 
meeeting of the British Association, I have great satisfaction in 
finding, that he has arrived at the same conclusion, which I had 
pceviously 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 valua- 
ble accession to geological science. 
I have now to give an account of a series of investigations in 
a different department of the subject, viz. on the Development of 
the Teeth. Here we must not expect the brilliant display of beau- 
tiful construction and diversified forms with which the above de- 
tails present us; but on the other hand wc may hope to arrive at 
more practically useful results; for on a correct knowledge of 
their development must the pathology of these organs be founded. 
The authors of whom I have now to treat are more especially 
Arnold, Raschkow, and Goodsir. The first and last of these 
gentlemen have devoted their attention exclusively to the early, 
or, as it is called, follicular stage in the development of these HISTORICAL INTRODUCTION. 
91 
organs. They consider that the process of dentition ought to be 
divided into three separate stages or sub-processes, and that this 
division is not arbitrary, but well marked and defined by obvious 
transitions in the progress of development from the embryonic to 
the adult state-these transitions moreover being indicated by 
phenomena attendant on the position of the pulp in relation to the 
cavity in which it is contained. The first of these stages Mr. 
Goodsir denominates the follicular-the second, the saccular-the 
third, the eruptive. He further thinks that there may be said to 
be another stage, anterior to all these, the papillary-designating 
that state of the pulp when it is a mere papilla on the free surface 
of the mucous membrane; but he finally prefers to include this in 
the follicular stage, on account of its very brief duration. 
Mr. Goodsir commences his paper* by an excellent account of 
the appearances presented on the dissection of fifteen human em- 
bryos, at different periods of development after the sixth week. 
He found at the fourth month bodies which he describes as gela- 
tinous and granular, situated between the pulp and the sac-the 
same bodies which a few years previously had forcibly attracted 
the attention of Purkinje and Raschkow, as we shall presently 
relate. 
On the extrusion of the tooth Goodsir speaks as follows:- 
"At the moment, however, that the tooth passes through the gum, 
(when the non-adherent portion of the sac resumes its primitive 
follicular condition, its inner membrane becoming continuous 
with the mucous membrane of the mouth,) the non-adherent por- 
tion of the sac shortens more rapidly than the fang lengthens, in 
consequence of which, the adherent portion with the fang itself 
separates from the fundus of the alveolus, and the body of the 
tooth advances through the gum." (p. 27.) He at the same time 
considers it to be a law in the development of animal bodies, 
"that pans or organs which have once acted an important part, 
however atrophied they may afterwards become, yet never alto- 
gether disappear so long as they .do not interfere with other parts 
or functions." (p. 28.) 
"The first or follicular stage," he says, "comprehends all the 
phenomena which present themselves from the first appearance 
of the dental groove and papillae, till the latter become completely 
hid by the closure of the mouths of their follicles, and of the 
groove itself. It is upon this hitherto unknown stage of dentition 
that I have insisted so much in the former sections of this paper. 
"The second or saccular stage is the one with which anato- 
mists have been so long familiar, during which the papillae are 
pulps, and the open follicles which contain them are shut sacs, 
* In the Edinburgh Med. and Sur. Journal for January. 1839. 92 
when the tooth-substance and the enamel, constituting the teeth 
themselves, are deposited. It is during this stage also that some 
of the most interesting phenomena in the formation of the alveo- 
lar processes present themselves. 
"The third or eruptive stage includes the completion of the 
teeth, the eruption and shedding of the temporary set, the erup- 
tion of the permanent, and the necessary changes in the alveolar 
processes. 
"When viewed in reference to an individual tooth, these three 
stages are distinct; but when viewed in reference to both sets, 
and to the whole process of dentition, they become somewhat 
intermingled. 
"When considered in the latter point of view, we may state 
that the follicular stage commences at the sixth or seventh week, 
and terminates at the fourth or fifth month of intra-uterine exis- 
tence; that the saccular commences at the termination of the 
first, and lasts for certain of the teeth till the sixth or eighth 
month, and for others till the twentieth or twenty-fifth year of 
extra-uterine existence; and that the third, or eruptive, com- 
mences at the sixth or eighth month, and lasts till the twentieth 
or twenty-fifth year." (p. 31.) 
"Careful observation of the whole process of dentition in man, 
leads," says Mr. Goodsir, "to the following conclusions;- 
"Milk-teeth.-1. The milk-teeth are formed on both sides of 
either jaw, in three divisions, a molar, a canine and an incisive, 
in each of which dentition proceeds in an independent manner. 
2. The dentition of the whole arch proceeds from behind for- 
wards-the molar division commencing before the canine, and 
the latter before the incisive. 
3. The dentition of each of the divisions proceeds in a contrary 
direction, the anterior molar appearing before the posterior, the 
central incisive before the lateral. 
4. Two of the subordinate phenomena of dentition also obey 
this inverse law, the follicles closing by commencing at the me- 
dian line, and proceeding backwards, and the dental groove dis- 
appearing in the same direction. 
5. Dentition commences in the upper jaw, and continues in 
advance during the most important period of its progress. 
The first tooth-germ which appears is that of the superior 
anterior molar, which precedes that of the inferior anterior molar. 
The apparent exception to this law in the case of the inferior 
incisive has already been explained. 
Permanent Teeth.-G. The germs of the permanent teeth, with 
the exception of that of the anterior molar, appear in a direction 
from the median line backwards. 
7. The milk-teeth originate, or are developed, from the mucous 
membrane. 
HISTORICAL INTRODUCTION. 93 
8. The permanent teeth, also originating from mucous mem- 
brane, are of independent origin, and have no connexion with 
the milk-teeth. 
9. A tooth pulp and its sac must be referred to the same class 
of organs as the combined papilla and follicle, from which a hair 
or feather is developed, viz. bulbs." (p. 35.) 
Mr Goodsir, it is true, was anticipated in some of his observa- 
tions by Arnold, in the Salzburg Med. Chir. Zeitung, 1831, p. 
236; but he has treated his subject so much more fully than the 
latter gentleman, that I have thought proper to commence this 
portion of the subject with an account of his researches. Mr. 
Goodsir himself quotes the substance of Arnold's statement, which 
is as follows:-"In an embryo of the ninth week we may per- 
ceive in both jaws, on the projecting edges of the gums, a pro- 
portionally pretty deep furrow, with ten depressions in it; a little 
later we may see a flat surface, on which there are many open- 
ings, communicating with small sacs, into which fine bristles may 
be passed. At the third month, the sacs of the second molars 
may be be seen communicating with the cavity of the mouth by 
small holes. The openings of the remaining sacs are soon closed 
by the mucous membrane of the mouth. 
"The sacs of the permanent teeth are also formed immediately 
from the mucous membrane of the mouth, partly at the fourth 
month of foetal existence, partly toward the end of that period, 
partly at birth. Once only, in a new-born child, I observed be- 
hind the most prominent edge of the gums several openings, 
which led to the sacs of the incisives and canines, and which are 
usually already obliterated before birth." 
Valentin* says, "The dental border of the upper and lower 
jaw thickens at a very early period in the ruminantia and in pigs, 
when the embryo is more than an inch long; in man, in the first 
half of the third month. In this border arise a series of oval, 
fibrous vesicles, which at first lie close together, and are separa- 
ted from each other by a compact granular substance. This 
increases and is separated more and more, and runs through the 
above-mentioned stages to ossify in the form of alveoli, where the 
vesicles come into close contact with it. Within every vesicle 
is formed, probably somewhat later than this, the sac of the tooth, 
which, according to the general opinion, is in no way connected 
with the mucous membrane of the mouth. But according to Ar- 
nold, on the other hand, the entire sac is formed from this mucous 
membrane dipping into the groove in the upper and lower jaw." 
The subsequent details on this subject given by Valentin are so 
interesting that I cannot abstain from quoting them. 
HISTORICAL INTRODUCTION. 
* Entwwkelungsgeschichte des Menschen, p. 482. 94 
"The dental sacculus itself consists of two membranes; of 
which, according to Hunter, only the inner one, according to 
Blake only the outer one is vascular: Fox, Meckel, and E. H. 
Weber, on the other hand, state that both are vascular. Into 
this sacculus the vessels and nerves enter through an orifice op- 
posite to the external side. Between the two membranes there 
is a fluid, which, according to Meckel, has at first a reddish and 
then a whitish yellow colour, but which Meissner says is as clear 
as water, or only turbid from a few flakes swimming in it, ino- 
dorous, tasting like mucus, easily drawn into strings or threads, 
containing a free acid, (probably lactic acid,) mucus, (but this 
is doubtful according to E. H. Weber,) a little albumen, phosphate 
of lime (more in that of the permanent than in that of the milk- 
teeth,) and muriatic and sulphatic salts. On analysing this fluid 
in a young calf, its components were found to be essentially the 
same. It contained, however, more mucus, and a free alkali 
was found in the place of the free acid. Within the sacculus is 
developed the germ of the tooth as a small, soft, compact, round- 
ish corpuscle, in which the shape of the crown is soon manifest, 
and subsequently the form of the neck. 
"The teeth consist in general, as Purkinje and 1 shall demon- 
strate at length in our dissertation on the structure of bone, of 
fibres or tubes lying one above the other, and running like radii 
towards the central axis, and which are either straight or uni- 
formly curved superiorly or inferiorly. Not a trace of osseous 
corpuscles is found between them in the fully-developed state. 
The first formative mass of the tooth consists likewise of a granu- 
lar substance, which, however, is transparent where it is not 
granular. Here the globules arrange themselves in the same 
direction as is taken by the subsequent fibres : it almost seemed 
to me as if the globules themselves dissolved and ran into the 
fibres, the intermediate jelly playing here a more subordinate 
part. 
"According to Meckel, the commencement of ossification is 
marked about the middle of pregnancy by the appearance of thin, 
delicate, elastic bodies (scherbchen,} which become gradually 
thicker and firmer. They correspond at first to the apices of the 
future teeth, and soon become thicker and harder on the masti- 
cating surface, whilst the tooth is still short, (being without a 
neck,) and hollow internally. As the tooth grows thicker, its 
cavity diminishes, and the dental germ disappears. The enamel 
is formed from the inner surface of the internal membrane (or 
leaf,) and is deposited on the osseous substance of the tooth. Its 
connexion with the tooth is tolerably loose in the foetus. The 
period of its formation is the same as that of the tooth itself. 
HISTORICAL INTRODUCTION. 95 
"With respect to the individual teeth, those of the lower jaw 
are formed earlier than those of the upper. First appear the two 
incisor teeth, then two molar teeth, and after them the canine 
in each half of the jaw, which collectively belong to the milk-teeth. 
Near them are shortly developed the sacs for the permanent teeth, 
which at first are seated on the sacs of the milk-teeth, are after- 
wards removed from these, and only connected with them by a 
thread, whilst they penetrate deeper into the jaw. (See Burdach's 
Phys. ii. 8, 475.) Hunter describes three centres of ossification 
in the incisor teeth, in the small molars two or three, in the large 
molars four or five, and in the canine one. Rudolphi describes 
two in the canine, whilst .Cloquet states that there is only one in 
all the teeth; and Albinus, Blake, and Serres, assert that there is 
only one in the incisors. According to Meckel, the incisors and 
canines have only one germ, the molars, on the other hand, seve- 
ral. According to Burdach, the crowns of the incisors are quite 
formed towards the end of pregnancy, and the root begins to be 
developed. In the canines a third part of the crown is formed, 
and in the first molar its upper part with its apices. On the 
second molar the four apices are still separated. In the perma- 
nent teeth the ossification of the crown of the third molar has 
sometimes commenced." 
The last work on this subject which we have to examine is 
another of the valuable productions of the present industrious and 
intelligent German school, which was published under the auspices 
of Purkinje, and which presents a striking proof of the efficiency 
and excellence of the system of medical education in operation in 
Germany. I allude to the "Meletemata circa Mammalium Den- 
tium Evolutionem,"-an inaugural dissertation by Raschkow. 
This publication first saw the light in 1835, four years after 
Arnold had written on the follicular stage of development. The 
department of anatomy under consideration has shared the fate 
common to almost every branch of the subject,-that is to say, 
what has been affirmed in it by one inquirer has been systemati- 
cally denied by the next. Raschkow and Purkinje directly and 
positively contradict the opinions of Arnold and Goodsir. 
"Arnold," says Raschkow, "has very recently brought forward 
an opinion upon the origin of the dental follicle, differing widely 
from the views of most writers. According to him, the dental 
follicles take their primal origin from the mucous membrane of 
the cavity of the mouth, the membrane in question being inflected 
into the alveolar groove of the upper and lower jaw." (p. 19.) 
And in the following page he adds, "Our own investigations by no 
means allow us to adopt the opinion of Arnold; for we have never 
been able to see, either in the human foetus, or in other animals, 
HISTORICAL INTRODUCTION. 96 
HISTORICAL INTRODUCTION. 
any such apertures. We have examined with this object the 
foetuses of calves and sheep ; but we never saw the mucous mem- 
brane of the mouth dip into the alveolar groove; and in the 
grooves themselves we never discovered the deeper recesses 
which Arnold describes. It was always, on the contrary, clear 
to us, that the dental follicle at its origin is altogether separate 
from the gum, and is not closely attached to it by any interme- 
diate connexion. Serres and Burdach were also in error when 
they said that the dental germ is a continuation of the nerve; for 
we have shown above, that at its commencement neither nerves 
nor vessels are to be seen in it." (p. 20.) 
I have commenced with this portion of Raschkow's thesis, 
from its immediate connexion with the subject of which we have 
just been treating. 
The new doctrines promulgated by Raschkow relate principally 
to the existence of what he calls the adamantine organ or pulp, 
situated between the follicle and germ, and destined for the pro- 
duction of enamel. He considers that this organ is very different 
from the internal layer of the capsule, and requires a separate and 
distinct consideration. He gives a very circumstantial account 
of his manner of proceeding in these investigations. 
"The dental follicle," he says, "which contains the other for- 
mative parts of the tooth, is, as it were, its common chorion. It 
is surrounded by a dense net-work of vessels, which, distributed 
over it from the neighbouring blood-vessels, take their origin 
principally in that part where the root of the tooth is situated. 
In the same manner the dental nerves send no small quantity of 
branches to this surface. 
"The membrane itself of the follicle of the tooth is not to be 
considered as altogether fibrous, because its fibres are extremely 
soft, and are intermixed with much granular parenchyma. In 
the first weeks of the life of the foetus (in the calf till about the 
eighth week), the follicle of the tooth has not yet grown into 
union with the gum; for both the epithelium of the latter, which 
then, compared with its state at subsequent periods, is found of a 
considerable size, and a certain peculiar stratum of its parenchy- 
ma, are easily separated from the denial follicle, so that in the 
coronal part it appears altogether free, and is only in the region 
of the dental arteries and nerves closely adherent to them. 
"The interna] plane of the dental follicle is smooth, and exhibits 
the appearance of a serous membrane. The membrane is every- 
where free, except in that place where the dental germ proceeds 
from it. For the dental germ appears to proceed from nowhere 
else except from the internal plane of the follicle of the tooth, and 
from that part of it where the principal vessels and nerves enter 97 
into it, since between its substance and the membrane of the fol- 
licle there is a very close and uninterrupted connexion. 
"In the internal chamber of the follicle or capsule, between its 
internal surface and the dental germ, another organ is also found, 
which at first, almost before the first stage of the growth of the 
dental germ, forms a nearly globular nucleus, of which the exter- 
nal surface appears in some slight degree to bulge out, and of 
which the internal substance presents a singular parenchyma, 
consisting probably at first, before evolution has been further car- 
ried out, of the usual granular formative mass, similar to that of 
all the other organs of the foetus; subsequently, however, by de- 
grees it exhibits more clearly granulations of an angular form, 
which, connected together in various ways by filaments of cellular 
tissue, present the appearance of a kind of actinenchyma, such as 
may be seen in plants. 
"This globular nucleus, which the capsular membrane sur- 
rounds, leaves a small interval between the latter, itself, and the 
dental germ, in which a peculiar fluid is found effused, which, 
when the capsular membrane is ruptured by continued pressure, 
flows freely out, and has the appearance of pure lymph, present- 
ing no granules of any kind. This globular nucleus we have 
called by anticipation the organ of the enamel, because, from 
subsequent contemplation of the evolution of this organ, it will be 
rendered clear, that it is intended for the formation of the enamel 
substance, inasmuch as it is gradually transformed into the mem- 
brane which produces that substance. 
"This takes place in the following manner.-The dental germ, 
in advancing further and further into the interior of the dental 
follicle, makes first only a slight impression on the globular mass 
of the enamel organ, but this impression is rendered gradually 
deeper as the growth of the germ proceeds. When the dental 
germ has penetrated further into the hollow thus made, it appears 
narrower towards the base, and thicker under the apex, and so 
is enclosed around on every side by the parenchyma of the 
enamel-organ, which thus assumes the appearance of a hood, 
covering the dental germ when advanced in its development, and 
capable of being separated from it without difficulty, and without 
any injury, either by the compressor, or in another manner by 
being placed under water. This enamel-hood, so to call it, pre- 
sents, towards the basilary part of the dental germ, a margin 
which is at first obtuse, afterwards sharp, but which is always 
free at every part: moreover, it still appears to be altogether as 
freely situated between the capsular membrane and the dental 
germ as previously when it existed under the form of a globular 
nucleus, and is probably everywhere surrounded by the lymph 
above-mentioned. The inquiries respecting the connexion of the 
HISTORICAL INTRODUCTION. 98 
HISTORICAL INTRODUCTION. 
enamel-organ with the capsule have not yet been completed. At 
first it appears to be altogether free in the capsular fluid ; subse- 
quently, however, at the extremity of the capsule, that is to say, 
in the coronal region, some connexion exists by means of loose 
vessels; moreover, the parenchyma of the organ itself is seen to 
be pervaded by numerous capillaries, and these facts prove that 
from the commencement this organ is connected with the cap- 
sule. If this is the case, we may assume that the dental germ 
takes its origin from that extremity of the capsule which is 
towards the root, the enamel-organ from the coronal extremity, 
since both these organs, arising at opposite points, approach each 
other, are adapted together, and contribute together towards the 
formation of the tooth. 
"When the enamel-organ has assumed the form of a hood, a 
peculiar organ is perceived on the surface of that cavity in which 
the dental germ is lodged, consisting all of it of short uniform 
fibres placed perpendicularly to the surface of the cavity, and 
forming, as it were, a silky lining to the whole of the latter. In 
a transverse section of the enamel-organ, this stratum of perpen- 
dicular fibres is clearly seen, and can be accurately distinguished 
from the other stellated parenchyma of the substance which we 
may here call the pulp of the enamel. 
"This stratum of fibres is at first strictly connected with the 
pulp of the enamel, and seems to originate in the immediate 
transformation of the latter. Afterwards it separates itself from 
it more and more, and only adheres to it by some few filaments 
of cellular tissue. After it has freed itself in this manner, and 
become, as it were, independent, it may justly be considered as a 
genuine membrane, and, on account of its function presently to 
be noticed, we have already termed it the membrane of the ena- 
mel. The greatest part of it can then easily be separated from 
the circumjacent pulp of the enamel, only a thin stratum of the 
latter remaining adherent, except in the hollows of the molar teeth 
where the parenchyma of the enamel-pulp remains aggregated 
till the period of eruption ; but neither then, nor at any preceding 
period, does it present any distinct traces either of vessels or 
nerves. 
"When we examine more closely the membrane of the enamel, 
its interna] surface is seen to consist of hexangular, nearly uni- 
form corpusculcs, visible only through a magnifying glass, towards 
the centre of each of which is a round eminence. These corpus- 
cules are nothing more than the ends of short fibres, of which the 
whole membrane is composed, and which, being pressed together, 
assume freely the hexangular form. The same hexangular cor- 
puscules are disposed in regular series,-from which arrangement 
it follows that they correspond exactly to the rows of enamel 
fibres formed from them. "At the inferior extremity of the enamel-organ, the enamel- 
membrane is never so evidently separate from the parenchyma 
as in the other parts; and it may hence be rightly concluded, as 
the enamel-substance is formed there at a later period, that the 
enamel-organ continues to grow anew there, till the enamel-sub- 
stance has been perfectly formed. In the molar teeth of the 
ruminantia, this organ appears, in part at least, to be connected 
with the capsule in such a manner that it seems to receive thence 
continually by proper vessels a sufficient supply of nourishment 
and of material for its increase, whilst, on the other hand, it dis- 
appears in other parts where its functions have been performed. 
This appears to obtain much more in those teeth, which (like 
those of swine and the rodentia) never cease to grow. 
"Hitherto we have only treated of the dental germ in so far 
as was necessary towards the description of the dental follicle 
and enamel-organ : we now proceed to examine more closely its 
organic structure and development. 
"The dental germ is doubtless a product of the internal wall of 
the dental capsule, seeing that the substance of its parenchyma is 
indissolubly connected with the capsular membrane, and there 
being the same origin, moreover, for the vessels and nerves of 
both. The doctrine which some have promulgated, that the den- 
tal germ is a continuation of the dental nerve itself, evidently 
cannot be maintained; although it cannot be denied that from the 
very commencement there exists an organic connexion with the 
nerves, as is the case in all parts in the interior development of 
which nerves are formed 
"At first the dental germ presents a parenchyma consisting of 
almost uniform globular granules, in which neither nerves nor 
vessels can be discovered. Subsequently vessels appear in it ; 
but a long period must still elapse before any trace of nerves is 
visible in it. When the development of the tooth is much more 
advanced, and its vascularity has long been evident, true nervous 
filaments are also discovered. The same rule obtains here which 
is manifest in all the parts of the foetus during development. First 
is seen the formative parenchyma, which has no specific charac- 
ter, (indifferenti qua. sic dicitur indole?) and which, though it 
contains the germs and seeds of nerves, presents as yet no true 
nerves themselves. 
"Perhaps no part of the body exists where the extremities of 
the nerves present so evident and beautiful an appearance as in 
the dental pulp. For displaying this, it is best to select the pulp 
of an adult tooth. We have examined it in the human subject, 
and in several of the rodentia and ruminantia. The nerves, after 
they have severally, or in bundles of several branches, entered the 
pulp of the tooth, recede more or less from each other; and so in 
HISTORICAL INTRODUCTION. 
99 100 
HISTORICAL INTRODUCTION'. 
simple filaments, partly separated and partly combined, proceed 
to the extreme apex of the crown, where again they divide by 
degrees into their simplest filaments, which, swelling like rows of 
beads, constitute the primitive series of variously interrupted 
nervous articuli, being accompanied in their course by a delicate 
cellular tissue, in order that they may not deviate from a right 
line. At length, under the apex, they again form a plexus, from 
which filaments are given off, terminating like 'penicilli' at the 
extremity of the apex, where they are surrounded by a net-work 
of vessels. In the incisors of a man of about thirty, we found a 
great abundance of filaments in comparison with other parts of 
the body, and also with the teeth of other animals which we have 
examined; and hence may be deduced the great sensibility of the 
tooth, especially in man. 
"It is worthy of mention, also, that in the teeth of the hare, the 
sow, and the stag, especially in the molars, we constantly found 
stony masses. They were semi-transparent, for the most part 
oval, and rounded bodies, which were situated in the axis of the 
dental pulp towards its apex in irregular rows, never extending 
the whole length of the dental pulp, but only to a greater or less 
distance from the coronal extremity. Such examinations of the 
dental pulp are facilitated by the use of the compressor; but 
without its assistance the same results may be obtained, though 
with more trouble. 
"In the dental germ, from the very first period of its formation, 
we invariably find the dental pulp together with a peculiar pellu- 
cid membrane without any characteristic organization, which 
covers the surface of the pulp from the base to the apex. This 
we have denominated the prae-formative membrane, seeing that in 
it the formation of the dental substance commences, and that it 
always precedes the latter. 
"The parenchyma of the dental substance is composed, as we 
have already mentioned, of uniform, globular granules, with no 
evident filaments of cellular tissue; by which circumstance it is 
best distinguished from the filamento-granular parenchyma of the 
enamel-pulp. Afterwards an abundance of nerves and vessels 
make their appearance. Vessels with several small stems com- 
municating with each other enter into the interior of the pulp, 
partly proceed to the other surface, and there, principally in that 
part where the dental substance has begun to be formed, their 
branches are distributed, constituting a net-work of capillary ves- 
sels. But where the formation of the proper dental substance has 
not commenced, and the praeformative membrane alone is found, 
no evident net-work of vessels is yet perceived. This fact offers a 
certain analogy to what takes place in osseous substance, where 
also net-works of sanguiferous vessels are not rendered evident till 
the proper earthy substance of the bones is found deposited. 101 
HISTORICAL INTRODUCTION. 
"The prseformative membrane belongs so peculiarly to the 
dental germ, that it uniformly exists from its first commencement, 
so that by its presence, should there be any doubt, the dental 
germ may be distinguished from every other organ ; for example, 
from the capsular membrane, or the enamel-organ. With respect 
to its consistence, (if I may use the expression,) it displays a re- 
markable tenacity, for under the compressor, even when continued 
pressure is exercised, it is only ruptured with difficulty, and before 
being ruptured it not unfrequently swells into a considerable vesicle. 
Immediately under this membrane are found granules of the pa- 
renchyma of the dental germ, more regularly arranged, and more 
longitudinally extended, placed uniformly on the membrane, partly 
at right angles, and partly at somewhat acute angles. 
"When the development of the dental germ has made conside- 
rable progress, and the time for the formation of the denial sub- 
stance approaches, a number of elevations (tumidorum instar) are 
found in the praaformative membrane, at the apex and its vicinity, 
which are probably afterwards transformed into the undulating 
ridges of the extreme surface of the dental substance, in which 
the enamel fibres are firmly placed. At this period also, imme- 
diately under the membrane, the proper dental substance is formed, 
the process commencing always at the coronal apex, and thence 
uniformly advancing on the one hand towards the coronal fossae, 
and on the other towards the root of the tooth. 
"At first the dental substance appears to be composed of fibres 
variously curved, contiguous, and adherent at their convex sides, 
and is already hard and osseous (ostoidea.) In the apex itself 
these fibres spread equally in all directions, but towards the lateral 
parietes the longitudinal direction prevails ; whilst fibres whose 
course is sinuous, which are arranged contiguously in an uniform 
manner, and which leave at their concavities interstices between 
each other, proceed everywhere from the coronal apex to the 
root. Only the extremities of these are still soft; the remaining 
parts harden in a very short time, unlike the substance of the 
enamel, in which the fibres, long after they have been deposited, 
appear soft and easily to be broken up. Whilst these are being 
formed, the prseformative membrane also becomes of a stony 
hardness, except at the margin of the recently-formed dental sub- 
stance, where it is soft and easily rent. The substance of the 
enamel begins to be formed at the same time with the dental sub- 
stance. 
"We have now to consider in a similar manner from its first 
commencement, the process of formation of the dental substance, 
with regard to its thickness. After a stratum of dental fibres has 
been deposited between the parenchyma of the dental germ and 
the praeformative membrane, which is now also ossified, the same 102 
process is continually going on from the external region towards 
the internal, the parenchyma of the dental germ supplying the 
material. This parenchyma decreases in proportion as the dental 
substance increases, and is withdrawn as it were into the dental 
cavity, which is gradually contracted. The convex curvatures 
of the dental fibres, which increase in breadth as they proceed 
from without inwards, and which in mutual apposition form con- 
tinuous canals, rise at the periphery of the dental substance, pro- 
ceed with many delicate windings to the pulp of the tooth, and its 
cavity, where their mouths open, and serve there, as long as the 
formation of the dental substance lasts, towards gathering new 
fibres, until at length these apertures also, in the last stage of the 
development of the tooth, are closed by a somewhat different 
substance, which is yellow and semi-transparent, and which has 
been compared by Blumenbach to corneous tissue. 
"Whilst the growth of the dental substance is thus advancing, 
the dental germ increases in the same manner at the radical 
extremity. Although at first it only formed the extreme apex of 
the crown, by degrees its growth extends into the body of the 
tooth, and as the development proceeds it is narrowed into one or 
more dental roots, which, after the dental substance has made still 
further progress, stretch into the dental cavity, like broad canals 
filled with a considerable quantity of dental pulp. These canals, 
however, when the formation of the dental substance is further 
advanced, become narrower by degrees, and when it is completed, 
give entrance to nerves and vessels only by one or more very small 
foraminula. We say by more than one aperture advisedly; for 
in the incisors of the stag, and in some rare cases of the human 
subject, we saw several canals, which in a transverse direction 
penetrated into the substance of the root of the tooth, so that in 
this respect it presented considerable similarity to true osseous 
substance. We were not able to decide whether that layer of 
osseous substance which, commencing at the neck of the tooth, 
invests the surface of the roots, is produced by the dental pulp 
like the other dental substance, or whether it has not its origin at 
a later period in the transformation of the capsular and enamel- 
membranes into true osseous membrane, and belongs thus to true 
bone. This perhaps takes place also in the cement of horses and 
of ruminantia, where the whole is similar to true osseous sub- 
stance-but on this point we have had no experience to instruct us. 
"We proceed now to explain the formation of the substance of 
the enamel. This is not, as previous writers have erroneously 
maintained, a deposition (like that observed in the formation of 
minerals, or as if it were a crystalline sediment) from the lymph 
surrounding the dental germ, but its formation also is effected by 
a true organic process. We have already accurately determined 
HISTORICAL INTRODUCTION. 103 
the origin, structure, and form of the organ by which the enamel- 
substance is formed. It still remains to explain more closely the 
nature of its function, as it appears to us. The organ from which 
the substance of the enamel is immediately formed is the enamel- 
membrane which we have described above. Each of its short 
perpendicular fibres is to be regarded as an excretory organ or 
gland, destined for the secretion of the enamel-fibre corresponding 
to it. At the same time with the first formation of the dental sub- 
stance and pari gressu from the coronal apex to the root, each 
one also of these fibrillae, whilst it places itself on the now harden- 
ed praeformative membrane, begins to deposit in due order the 
primitive part of each enamel-fibre, so that each one of these 
enamel-fibres, carefully examined under a microscope, shows that 
it is composed of layers disposed in a transverse direction. At 
the period when these fibres are being formed, an organic lymph 
seems to be secreted from the parenchyma of the enamel-mem- 
brane, which is found between its glands, and this penetrates 
between the individual fibres, and renders their whole substance 
soft. Subsequently, however, the latter, probably by some chemi- 
co-organic process, enters into an intimate combination with 
earthy substances, and so forms the animal base of the enamel- 
substance, which (after they have been dissolved by acids) again 
presents itself under the form of a mucous tissue; this, however, 
on account of its extreme delicacy, cannot be easily discerned by 
the naked eye, nor without the aid of a magnifying glass. 
"In order to explain the various curvatures of the enamel- 
fibres, wre must suppose that the enamel-membrane also, during 
the progress of formation of the enamel-substance, changes the 
situation of its fibres by certain brief movements, while it partly 
retires from the internal region, and is dilated by the increase of 
the enamel-substance in thickness, and partly by following the 
curvatures of the individual enamel-fibres along the sides and 
longitudinal direction of the tooth, experiences slight changes in 
its situation either in single or successive portions. In those teeth 
of which the crowns only are covered with enamel-substance, 
the enamel-membrane also does not extend beyond the crown it- 
self, and there principally the enamel-organ, like a hood, evidently 
unattached, can be separated from the dental germ. But in those 
teeth of which the growth has no fixed limit, as in the rodentia, 
in the tusks of the sow, in the pachyderms, &c., the extent of the 
enamel is not so contracted; and for this reason we are led to 
conclude, that from the beginning there are no such bounds of 
the enamel-membrane, nor any formation of a hood. Nay, in 
this case the enamel-membrane, especially after the eruption of 
the tooth, always assumes the form of a girdle of greater or less 
breadth, which, surrounding the basilary part of the tooth, is con- 
HISTORICAL INTRODUCTION. 104 
tinually being changed towards the crown into an osseous mem- 
brane, which is always arising anew about the root, and in the 
middle always depositing fresh enamel-substance. If, however, 
we regard the different distribution of the enamel substance, in 
respect to quantity, over the surface of the dental substance in 
the different kinds of teeth, and in the different classes of animals, 
we shall perceive that another peculiar circumstance also con- 
tributes to the especial formation of the enamel-organ ; respecting 
this, however, no accurate investigations have yet been made. 
There are two principal directions observable in the motions of 
the teeth with regard to each other, in grinding and breaking 
down food; the one perpendicular, in carnivorous, frugivorous, 
and insect-eating animals-the other horizontal, in the ruminan- 
tia, rodentia, and most of the pachyderms. To these directions 
in which the teeth are worn down, the distribution of the enamel 
on the dental substance corresponds. Where the tooth is worn 
in a perpendicular direction, the greatest quantity of enamel is 
deposited on the coronal plane, and also on the apex; but where 
it is worn in a horizontal direction, there exists, even at first, only 
a thin and easily pulverized layer of enamel on the apex of the 
crown, but it is found in great abundance on the dental parietes, 
which are in various apposition to each other. This obtains 
principally with regard to the molar teeth; the incisors and ca- 
nines exhibiting but little difference, and their function being in all 
cases almost the same. To this distribution of the enamel-sub- 
stance, the first formation of the enamel-organ ought to corres- 
pond. In the first kind of direction of the teeth, the principal 
mass of the parenchyma ought to be found at the coronal apex; 
but in the other kind, partly on the parietes of the tooth, partly 
in the coronal fossae, (in the ruminantia and in horses,) partly 
also in the lateral recesses of the tooth (in the rodentia)-but on 
this point no accurate investigations have yet been made. 
"We see from the foregoing that the dental substance is form- 
ed in an opposite direction to the enamel. For in the one case 
the pulp of the dental germ is covered with the fibres of the dental 
substance, and, after it has deposited a layer, recedes from the 
external to the internal region : this substance, therefore, increases 
from the circumference towards the centre; but the contrary 
takes place in the deposition of the enamel. Its first layer which 
touches the dental substance is most internal, whilst each subse- 
quent one approaches nearer the periphery, towards which the 
enamel membrane recedes. The direction of this, therefore, is 
from the centre to the circumference. The formation of the den- 
tal substance has a more organic character; and in some respects 
reminds us of the formation of osseous substance, from which, 
however, it still greatly differs. The formation of the enamel, on 
HISTORICAL INTRODUCTION. 105 
the other hand, is of a more mineral character. It may best be 
compared to the secretion of the calcareous shell in the duct of 
the egg of the bird, which Hunter has already touched upon. It 
would be altogether false, however, to regard it as a true process 
of crystallisation, for its fibres are curved in various ways, and are 
arranged »with an organic object: moreover, no small quantity of 
organic matter is contained in its substance ; and the absence of 
all the strict lines of crystallisation, as well as the mode in which 
the fibres are severally secreted, sufficiently show the peculiar 
difference between these processes. We have already mentioned 
the law of polarity which obtains in the whole course of dental 
development, and we leave to the reader more closely to study 
the point which is called indifferential, because it is contained in 
the contact of both substances, the dental and the enamel; fur- 
ther, the polaric opposition between the enamel-membrane and 
the prseformative membrane, between the enamel-parenchyma 
and the dental germ, and, finally, between the region of the gum 
and that of the nerves of the capsule of the tooth. 
"This would be the most fitting place to treat more at large of 
the formation of the cement, of which we have already made 
mention. As, however, we ourselves are deficient in experience 
with regard to many points belonging to this subject, and the 
opinions of authors respecting it are vague, we have only ven- 
tured here to form our own opinion derived partly from the 
examination of the substance of the tooth with the microscope, 
in reference to its structure and development. 
"The cement is always placed externally to the enamel. It is 
consequently formed at a later period, and after, indeed, the for- 
mation of the latter is completed, and the enamel-membrane has 
disappeared, or been in some way transformed. At first the 
enamel-pulp is situated close to the enamel-membrane ; and if it 
does not disappear together with the latter, it is perhaps that 
which serves to deposit the cement. But if it does vanish with 
this membrane, there then remains only the capsular membrane to 
answer this purpose, which, however, at the advanced period 
when the cement begins to be formed, doubtless coalesces with 
the periosteum of the alveolar parietes. The following fact 
greatly supports the opinion that the enamel-pulp is transformed 
into the organ which secretes the cement, viz. that in the deep 
fossae and lateral recesses of the teeth of ruminantia, of horses, 
and of rodentia, after the formation of the enamel-substance has 
been completed, the simple enamel-pulp remains without any con- 
tact with the alveolar parietes, and it is here, therefore, the only 
organ there can be for the production of the enamel. Finally, 
the enamel pulp on the external surface of the tooth, where it 
comes into contact with the alveolar parietes,- may, together with 
HISTORICAL INTRODUCTION. 106 
HISTORICAL INTRODUCTION. 
the capsule, be combined with the periosteum,-and this supposi- 
tion is favoured by the circumstance, that the granular and tubu- 
lar structure of the cement presents the greatest similarity to that 
of true bone. 
"This observation, too, ought not to be omitted, that that mem- 
brane which clothes the alveolus, and corresponds to the perios- 
teum, displays even at the first glance, but principally where it is 
joined to the external parts, a loose texture, similar to the pul- 
monary tissue, and which, when examined under a glass, displays, 
besides a large quantity of sanguiferous vessels, a number of air- 
canals of considerable diameter, to the presence of which the soft 
and elastic nature of this tissue is owing: their object, perhaps, 
is to afford greater mobility to the advancing tooth. We have 
mentioned this subject in order that the attention of the reader 
may be directed to the air-vessels which are met with in the 
animal-body, and to correct rather than confirm the belief respect- 
ing them. It ought, moreover, to be mentioned, that on the inte- 
rior. surface of the lobes of the gum which surround the protruding 
molars of Uie young ruminantia, similar rows of perpendicular 
fibres are found to those which we described in the enamel-mem- 
brane. it is a question how far they have the same function, 
and whether it is not probable that the enamel-fibres do not con- 
tinually derive fresh materials of increase from this quarter. 
"The development of the gum is connected in the most intimate 
manner with the history of that of the teeth, the maxillary bones, 
and the alveoli. In treating of the development of the teeth, we 
were unwillingly compelled to devote some attention to observa- 
tions respecting the development of these parts. Thus, for ex- 
ample, we are struck with the great firmness of the inferior maxil- 
lary bone at an early period, compared with that of other bones 
of the foetus, and also with the comparative perfection of its 
nerves and vessels. 
"With respect to the gum, the dental cartilage, as it is called, 
in man and other mammalia, is chiefly worthy of mention. It is 
not true cartilage, for the peculiar granules which principally 
characterize that substance are wanting in its parenchyma, which, 
however, is otherwise firm. In the first place, there is found in 
this dental cartilage a tolerably thick stratum of the epithelium of 
the mucous membrane, which corresponds to the epidermis of the 
external skin, and like it, but in a much more perfect manner, 
consists of various polyedric scales placed one above the other, 
several of which presents an orbicular spot in their centre. Under 
this epithelium is situated the hard parenchyma of the dental car- 
tilage, which, in my opinion, corresponds to the chorion of the 
skin, inasmuch as it is granular, abundantly supplied with vessels, 
and interwoven with numerous firm and fibrous filaments. In HISTORICAL INTRODUCTION. 
107 
this tissue, in the new-born infant, closed cavities are constantly 
found dispersed here and there which are filled with scales similar 
to those of which the epithelium is composed. These, without any 
doubt, are those glands which Serres has already described, and 
which, he most erroneously stales, contribute afterwards to deposit 
the tartar of the teeth. That they are connected with the forma- 
tion of the epithelium is proved by the scales; but in what man- 
ner has not yet been ascertained. Perhaps, also, they are the 
same follicles which Arnold describes in a new-born infant as 
apertures, situated near the most prominent margin of the gum, 
and which, in his opinion, lead to the sacs of the incisors and the 
canine. (See Frankel, Dissert, de Dent. Human. Struct, p. 4.) 
"In the first stages of development, (as far as we are able to 
judge in certain animals (the calf, the sow, and the dog.) the stra- 
tum of epithelium is much thicker than afterwards. The confor- 
mation of its scales is not yet such as in the period which precedes 
birth; but they present a parenchyma very similar to the cellules 
of plants-every scale which afterwards appears as such present- 
ing itself then as a polyedric cellule, consisting of very tenacious 
membrane, and containing a globular drop of fluid. These cel- 
lules were ruptured by pressure, and lymphatic fluid was poured 
out. In the course of development they are probably flattened 
and changed into the polyedric scales. At first, the stratum of 
cpithelum is most easily Separated from the subjacent parenchyma 
of the mucous membrane. It presented, in a calf of nine weeks, 
above the molars, in the surface separated from the teeth, a double 
series of processes like epistomia, which, although lodged in the 
corresponding cavities of the parenchyma of the gum, still did not, 
as it at first seemed, penetrate into the cavities themselves of the 
molars, being evidently separated from these by the capsular 
membrane and enamel-pulp." • . 
It will be interesting, now that, we have brought down our. 
Historical Sketch to the present time, to inquire what at present 
is the real amount of our knowledge in the science of Odontology. 
The result of such an inquiry is unfortunately far less satisfactory 
than we might at first be led to anticipate from the number of 
works which have been published on this subject, and from the 
number of eminent men who have devoted their attention to it. 
The statements of writers are very much at variance, and not 
only do opinions differ, but the facts on which those opinions are 
based, we find everywhere described in a different manner. How 
such discrepancies, as we here find in abundance, can have arisen 
in the simple field of anatomical description, it requires no little 
diligence and perseverance to explain. They have partly their 108 
HISTORICAL INTRODUCTION. 
origin, doubtless, in the infinite variety of aspects presented by the 
teeth in their constantly varying condition, and in the numerous 
stages of development through which they pass. At one period, 
a particular membrane is highly vascular, and at another, in such 
a state of atrophy as to induce the observer to consider it as absent 
altogether. The arrangement of the parts appears at one time so 
confused, as at a superficial glance to seem destructive of the 
vital functions. Hence the anatomists, whose observations have 
been confined to the state of these organs at particular periods, 
have come to conclusions of a correspondingly limited character. 
It is no easy matter to accomplish a complete investigation of the 
development of the teeth, and more particularly in man, from the 
great difficulty in obtaining an adequate supply of subjects at a 
sufficiently early stage; in short, it cannot be denied that no de- 
partment of anatomy is more complicated, and that none presents 
more difficulties to the investigator than the anatomy and physi- 
ology of the teeth: none, however, on the other hand, is more 
fraught with interest to the investigator of minute, organic 
structure. 
Let us now attempt to test the value of our present information, 
by inquiring what assistance it is able to afford us in practice.- 
In treating the urgent symptoms attendant on dentition, a know- 
ledge of the true nature of the capsule, the pulp, and the surround- 
ing parts, is required. On these points one of the latest inquirers 
is Arnold, whose observations tend to prove that the early stage 
of dental development presents an open follicle of the mucous 
membrane, which afterwards closes and becomes the capsule. 
The observations of Arnold have been contradicted by Raschkow 
and Valentin, and again corroborated with many circumstantial 
details by Mr. Goodsir, published in the Edinb. Med. Journ. for 
Jan. 1839. This subject may therefore be considered to be still 
sub judice. 
With respect to the capsule itself, some writers contend that it 
consists of two layers; others, that it is composed of one layer 
only. Some maintain that both its layers are vascular; others 
that vessels are exclusively found in the external layer; and others, 
again, that they are discovered only in the internal one. Many 
authors assert that the capsule has also the office of a periosteum; 
whilst in several works we find it stated, that the latter consists 
of two distinct laminae. There are writers who hold that the pulp 
is covered by a proper membrane, which they conjecture is a con- 
tinuation of the periosteum of the jaw; but the very existence of 
this membrane is denied by others: a third opinion is, that a pro- 
per membrane exists, but fhat it only partially covers the pulp. 
The observation of only a limited number of subjects must be the 
cause of this diversity of opinion, as there can be no doubt that HISTORICAL INTRODUCTION. 
109 
the capsule consists of two layers, that both these layers are vas- 
cular at certain periods of their development, and also that a pro- 
per membrane exists on the surface of the pulp. 
Anatomists are far from being agreed as to the source whence 
the capsular vessels are derived: they have their origin exclu- 
sively in the gum, according to some, and in the dental trunks, 
according to others. My own opinion is, that they derive their 
origin from both these sources 
There is one opinion which has been uniformly maintained by 
all writers on this subject, viz. that when the teeth of man, or 
other analogous simple teeth, are extruded, the enamel is divested 
of all external covering, and exposed immediately to the atmos- 
phere, denuded of both the envelopes of capsule and mucous 
membrane which it possessed during what has been called the 
sacular stage; and this denudation has always been supposed to 
be effected by the disruption of these coverings. My own views, 
however, on this point, which are contained in a paper read some 
time ago before the Medical and Chirurgical Society, are different 
from those generally received ; and 1 have no doubt that I shall 
be able to prove that it is a process of absorption, and not of dis- 
ruption, by means of which the tooth is emancipated, and that 
when perfected and extruded it is still invested with a capsular 
covering. This covering, as it is seen to be continuous with the 
crusta petrosa, I consider to be analogous to it, as the latter has 
been found to invest the whole tooth in an enlarged state in many 
animals, and in a particularly interesting form in the orycteropus,* 
bradypus, walrus,f &c. In my collection are numerous prepa- 
rations of this covering on the teeth of man, on the incisor of the 
calf, and on the simple teeth of many other animals. I have de- 
tected it, indeed, on the tfeeth of so many animals, that I presume 
it will be found universal. By means of acid, I have rempved 
it in the shape of a membrane from the surface of these teeth ; 
and in delicate dry sections prepared in a peculiar manner, I have 
been enabled, with the microscope, to examine its structure. In 
man it forms a thin layer, of a darker colour than the enamel; it 
is continuous with the crusta petrosa which covers the fang, but 
differs from it in not always containing corpuscules. On the in- 
cisor of the calf this covering is very distinct, and generally 
presents corpuscules. The extreme difficulty which is experienced1 
in getting a fine section of a tooth without this membrane being 
removed in the process of reduction, is, probably, the cause of its 
having been overlooked by previous observers. 
It has been left to the sagacity of Raschkow, one of the most 
recent writers in this department, to explain what Herissant calls 
* Plate C. 1, Fig. 4, a a. 
f Plate C. 3, Fig. 1, a. 110 
HISTORICAL INTRODUCTION. 
the temporary gum. Other writers have presumed that the tooth, 
before its extrusion, has a cartilaginous investment, forming of 
course a considerable obstacle to its progress; but the truth is, 
that this covering, instead of being cartilaginous, is merely com- 
posed of thickened epithelium. The details of the development 
and structure of this latter substance will be given in an early 
chapter of the present work. 
The minute and interesting bodies first noticed by Cloquet and 
Serres, and denominated by them the dental glands, have been 
denied to exist by some inquirers, and one writer has gone so far 
as to assert that they are "too manifestly a mistake to require 
any particular refutation." They certainly, however, do exist, 
though probably they are neither entitled to the appellation of 
glands, nor endowed with the permanent functions assigned to 
them by Serres and Blandin-and in my opinion they merit very 
attentive consideration. ■ 
A knowledge of what may be called the periosteal functions of 
the capsule, in connexion with 'those of the true periosteum of the 
socket, is also of great practical importance; for many sound 
teeth are lost from suppuration of the membranes connected with 
their sockets and roots: but on this subject, also, the opinions of 
writers on the teeth are contradictory in the extreme. Monro 
maintains that the teeth have no periosteum of their own, "but 
that it is supplied by the reflected membrane of the gums."* Hun- 
ter considers that the periosteum of the alveolus "is common to 
the tooth and socket."! Blake says, that "the external periosteum 
of the jaw seems lost in the gum;" but that the teeth are ^attach- 
ed to the alveolar cavity by a strong periosteum.Fox con- 
siders that the periosteum "is reflected from the alveolar process 
on the root of the tooth."§ Delabarre considers that the socket 
and the root of the tooth have each a periosteum of their own ; 
but 'that both are very intimately connected. Meckel describes 
the "root and neck to be covered by a thin membrane, and the 
alveolar cavity to be lined with a thick, fibrous membrane," which 
is "continuous with the gum."|| On this subject Mr. Bell ex- 
presses himself as follows:-"The periosteum of the maxillary 
bones, after covering the alveolar process, dips down into each 
alveolar cavity, the parietes of which it lines. From the bottom 
>of the cavity, where the vessels and nerves of the internal mem- 
brane enter, it appears to be reflected over the root of the tooth, 
which it entirely coveYs as far as the neck, at which part it be- 
* Monro on the Bones, p. 114. 
t Hunter's Natural History of the Teeth, p. 43. 
| Blake, p. 169 and 33. § Fox, p. 11. 
|| Meckel, Man. d'An, vol. iii. p. 325. HISTORICAL INTRODUCTION. 
111 
comes intimately connected with the gum."* "At this stage," 
says Blandin, "we can recognise perfectly the continuity of the 
capsule with the mucous membrane of the mouth." "The cap- 
sule," he adds, " is formed of two layers,-an external one, of a 
fibrous nature, confounded with the proper periosteum of the al- 
veolus; and an internal one more vascular than the other, and 
adherent to the root of the tooth."j- Thus Blandin allows the 
existence of not less than three distinct layers of membrane inter- 
posed between the root of the tooth and the bony socket. 
From these numerous discrepancies, to which I need add no 
more, it ip evident that the above inquirers cannot all have pur- 
sued the simple method of investigation which M. Delabarre tells 
us he had determined to adopt:-"Le scalpel,le burin, et la loupe 
en main," says he, "je promenerai mes regards sur la nature 
comme etant la seul livre qui ne peut pas nous egarer." In the 
want of a proper "loupe" is probably to be sought the origin of 
many of the above discrepancies. The hitherto unsettled state of 
our ideas on the development of these parts is such, that we must 
not be surprised that some of their diseases are not well under- 
stood, are often found very untfactable, and run frequently into 
a malignant state. 
It appears to me to be certain, that the external periosteum 
sends a continuation to line the cavity of the alveolus simply, and 
that the fang of the tooth continues invested by the original cap- 
sule. 
We have seen that all writers on the Anatomy and Physiology 
of the Teeth have discussed the question, whether these organs 
are to be regarded as positively belonging to the osseous system, 
or whether they are to be considered as productions of the tegu- 
mentary membrane. The explanation of many of the peculiarities 
connected with the diseases of infancy, depends on a proper solu- 
tion of this difficult question. The origin and nature of decay in 
the teeth, and its treatment, as well as many other points, cannot 
be satisfactorily discussed before this subject is settled. Authori- 
ties here again are almost equally divided, and indeed no depart- 
ment of the science of odontology has given rise to a greater 
number of conflicting statements than we here encounter at its 
very commencement. 
Ambrose Pare considered the teeth to be vascular, and liable 
like other bones to inflammation and suppuration. Leeuwenhoek, 
in 1678, suspected them to be vascular or endowed with vitality, 
as he considered them to be composed of "small, straight, and 
transparent pipes." Monro, Hunter, Blake, and Fox regard them 
as bone. Monro, however, is undecided as to their vitality. 
* Bell on the Teeth, p. 42. 
t Blandin sur le Systeme Dentaire, p. 76. 112 
HISTORICAL INTRODUCTION. 
Hunter thinks that they have "no circulation, but a vital principle." 
Blake believes it to be "incontestable" that vessels, both "circu- 
latory" and others, are present in the tooth, and that there are 
vessels passing from the pulp to the ivory. Fox dilates largely 
on their great analogy to bone, which he regards as perfect 
except as to their density. He considers that their diseases also 
are similar to those of bone, and thinks, with Ambrose Pare, that 
they "have their origin in inflammation." G. Cuvier and Serres 
deny both the vitality of the teeth, and that their structure is 
strictly speaking osseous. Serres, who also perfectly expresses 
the opinion of Cuvier, speaks on this subject as follows:-"Tout 
me porte a croire que le tissu propre des dents n'est pas le meme 
que le tissu propre du systeme osseuxand at p. 52 of his work 
he further says, "N'y a point de nerf qui se distribue dans son 
tissu, puisqu'il est exhale, et, pour ainsi dire, inorganique (anato- 
miquement parlant.)" 
M. Delabarre is the next author in chronological order, and we 
find him in direct opposition on these points to Cuvier and Serres. 
He is here a follower of Bichat, whose testimony is directly in 
favour of the vitality and osseous character of the teeth. Meckel 
is not to be classed on this subject with any of the preceding: his 
views resemble in some respects those of Cuvier, and in others 
those of Bichat. 
F. Cuvier inclines to think the analogy between the teeth, and 
hair or horn, more perfect than that between the former and bone. 
He describes the tooth as "depourvue de vaisseaux et de nerfs, et 
privee de tout raport immediate et necessaire avec les autres 
organes." On the points under consideration, Rousseau is very 
undecided; but he still states distinctly that vessels pass from the 
pulp into the ivory. Bell regards the teeth as osseous and vascu- 
lar; and states that there is a vascular communication kept up 
between the pulp and the ivory. But all that is flatly contradicted 
by the next writer, Blandin, who maintains that all that has been 
advanced on the other side of the question is marked "au coin de 
la plus pure hypothese." 
Mr. Tomes, the latest labourer in this field of inquiry-the 
author of an excellent paper in the Medical Gazette, No. 585- 
adopts the conclusion, that "of the several parts which have been 
treated of, all, save the enamel, are vascular, and he would not 
deny even to this all connexion with the circulating fluids." 
Thus on each side we have writers of equal authority; and the 
points at issue remain altogether unsettled by any positive ana- 
tomical demonstration, although they are of great practical im- 
portance, and so prominent as to demand the active scrutiny of 
the student of nature. 
In short, the impression left on the mind of the student, after 
having perused the works which have been published in this HISTORICAL INTRODUCTION. 
113 
department of science is, that almost every point requires to be 
investigated anew. 
How various and contradictory are the opinions of writers on 
the composition and structure of the teeth ! Hippocrates taught 
that they were composed of hardened fat. Leeuwenhoek was 
the first who stated that their structure is tubular, and this doc- 
trine, after having been forgotten for one hundred and sixty years, 
has lately reappeared in a most attractive garb. Monro believed 
that these organs are longitudinally fibrous: Fox, that they were 
deposited in layers. G. Cuvier says, "that they are neither cellu- 
lar nor fibrous, but composed of laminae. Bichat held that they 
were analogous to rock, and fibrous; Serres, on the other hand, 
sees nothing like fibres in them. Rousseau describes their struc- 
ture as being longitudinally striated. Blandin, who wrote so late 
as 1836, tells us, that they are composed of plates, situated paral- 
lel to their external surface; and this statement was made a year 
after Purkinje, and others, in Germany, had so beautifully demon- 
strated their fibrous texture. This latter subject has been further 
elucidated in the most complete manner by Professor Retzius; and 
that the structure of the ivory is at any rate fibrous, could not now 
be denied even by M. Serres, or by those who have stood up for 
its rocky or simply stratified character. 
The labours of Retzius and his contemporaries must be consid- 
ered as a most splendid contribution to minute anatomy; but I 
still think that the evidence in favour of the existence of a system 
of ramifying tubes in dental bone or ivory, requires much further 
examination and corroboration, before we can be justified in 
adopting a theory tending to overthrow many received opinions, 
results of ordinary experience. The difficulty in arriving at just 
views of this subject is partly owing, I think, to the circumstance 
that writers have comprehended very different structures under 
the same term. All the diversified textures entering into the 
composition of the bodies of different teeth have been described as 
dental bone or ivory ; and it is unfortunate that the advocates of 
a tubular system have not been much more precise than their 
predecessors in defining the specific nature of the various dental 
structures, in which they state that they have traced hollow fibres. 
Like all newly-propounded doctrines, the theory of a tubular 
system, as laid down in the preceding pages, will be found to pre- 
sent some internal contradictions. "It can scarcely be doubted," 
says Retzius, "that the minute tubes in dental bone, in the cortical 
substance, in common bone, and in the horns of deer, as well as 
the cells with which they are in connexion, are a peculiar kind of 
vessels containing a nourishing and supporting fluid." In another 
part of his work, however, he says, "with respect to the contents 
of the canals, I, as well as Professor Muller, have found that they 114 
consist of an inorganic or earthy substance, which appears white 
when viewed on a dark ground, but which disappears when the 
preparation is placed in diluted muriatic acid. When the light 
falls into these canals, this matter is seen to be composed appa- 
rently of infinitely fine particles, adhering together in lumps. The 
greater or less number and distinctness of these lumps seem to 
depend on the degree in w'hich the preparation has been penetra- 
ted by water, oil, or turpentine." "That the small osseous tubes 
and cells," he afterwards adds, "contain osseous earth, is seen 
from their whiteness." And one of his followers states, that 
"these tubes are chiefly rendered visible by means of their con- 
tents." How a tube can be filled with osseous matter, and at the 
same time allow of the circulation of a "nourishing and support- 
ing fluid," I cannot understand. It must not be forgotten, too, 
that Retzius allows "that, in the tooth, no renovation of the 
material appears to take place." 
Nor is it with respect to the more direct inductions drawn from 
the tubular system alone, that I must avow myself in some respects 
at issue with the ingenious and industrious Professor of Stockholm. 
"When the milk-teeth," he says, "are examined just before they 
are about to be shed, they are found to present an appearance as 
if, from pressure of their permanent successors, they had wasted 
or been absorbed at their roots. The crown of the advancing 
tooth appears to have pressed itself into the extremity of the de- 
ciduous one. I have carefully examined how this appearance is 
produced, and have come to the decided conviction that neither 
tabescence, absorption, nor erosion has anything to do with it." 
This is a statement which may be so easily refuted by the sim- 
plest observation, that I need not here waste the time of the reader 
by entering into a formal demonstration of its fallacy. 
With a candour which cannot be too highly praised, Retzius 
allows that he is ignorant of the specific functions of the tubes in 
the dental bone of the adult tooth. His ideas on this subject, as 
might be expected at this early stage of the inquiry, are far from 
definite. "In common bone, probably," says he, "the peculiar 
vessels in question take a part in the continual, or apparently con- 
tinual, exchange of substance; this cannot in the same degree be 
the case in dental bone, inasmuch as in this no such exchange 
appears to take place. What end then is served by this beautiful 
organization of dental bone? We have many examples that 
nature organizes structures w7hich have a close affinity to each 
other according to one and the same plan, and hence we have, in 
different parts or organisms, formations, which in some are of the 
greatest importance, whilst in others they are of much less func- 
tional significance, or of none whatever. If we hence assume, 
what is highly probable, that in bone the peculiar vessels in ques- 
HISTORICAL INTRODUCTION. HISTORICAL INTRODUCTION. 
115 
tion give passage to fluids during the entire life of the animal, (or 
a great part of it,) which fluids contain the solid as well as the 
liquid materials of the osseous substance; it does not necessarily 
follow that the same process must be carried on in the teeth during 
the whole of life. On the contrary, I am inclined to believe that 
these vessels in dental bone, are at their height during the first 
period of the formation of the tooth, and exercise then their more 
perfect action At the same time, the existence of a continual 
vital process in the tooth, as well as in the crystalline lens, cannot 
be denied, which, however, appears to be carried on without any 
constant exchange of solid matter, and must hence consist in a 
renovating circulation." I have quoted this sentence again, be- 
cause it characterises, more justly than any objections I could 
make, the imperfect state of the inquiry. 
The theory of the tubular system assumed to be true, has been 
with considerable ingenuity employed by a very eminent natural- 
ist to explain that which takes place when teeth are stopped; it 
has been said that the mouths of the vessels which have been cut 
across in this operation deposit a layer of calcareous matter under 
the stopping; but I believe that no facts bearingout this assertion 
have yet been observed ; and I cannot but think that the general 
character of the tooth, and the nature of the functions which it 
has to perform, are altogether incompatible with the existence of 
a system of open-mouthed vessels ready to pour out fluid of any 
kind to a greater or less extent. It is well known that even the 
least increment, or change of the material of the tooth under the 
stopping, renders that operation quite ineffectual, either by displac- 
ing the stopping, or by admitting the fluids of the mouth, and thus 
promoting decomposition beneath it. 
I may here remark, that the intelligent professor of Stockholm 
states that the crusta petrosa ceases at the neck of the tooth in 
many animals in which it is in fact continued over the whole 
'extent of the enamel. The views of Muller on the crusta petrosa 
are very erroneous. "This new substance, the cement, or crusta 
petrosa," he says, "seems to be merely a deposit from the salts of 
the saliva, and to be essentially the same as what is called the 
tartar of the human teeth." (Muller's Phys, translated by Dr. 
Baly.) A simple examination of the organized structure of the 
cement by means of the microscope is sufficient to convince any 
one of the fallacy of this statement. 
Retzius states that only three substances enter into the compo- 
sition of the teeth in their various forms, viz. ivory, enamel, and 
cement; but I think that a fourth ought to be added to this list, 
viz. a structure having the appearance of ossified pulp, in which 
the vessels seem to retain their original position, but are found in 
a state of atrophy, intermingled occasionally with irregularly- 116 
HISTORICAL INTRODUCTION. 
formed ivory. This substance may be considered as constant as 
any of the other three: it constitutes almost exclusively the sim- 
plest teeth, as those of the ornithorynchus, anarrhichas lupus, 
&c.; and it is occasionally found to enter into the composition of 
the teeth of almost every animal, either normally, as in the wal- 
rus, bradypus, orycteropus, ptychodus poly gyrus, &c., or ab- 
normally, as in some human teeth. It also often presents itself 
in the diseased tusks of the elephant. 
A detailed account of my own opinions and researches on the 
structure of the teeth, the reader will find in the body of the work. 
The above remarks I offer more to justify myself for not fully 
and at once agreeing with all the positions laid down by those 
who have writtenon the dental tubes, than with the intention of 
directly refuting or denying them. All that I wish to do at pre- 
sent is, to show that further research, more varied experiments, 
and a more rigid examination of the subject in all its departments 
and bearings, are absolutely required before the doctrine of a 
tubular system can be considered as immutably established. 
The sketch which I have given of the progress of information 
in this department of science shows that many interesting branches 
of the subject are still uncultivated, and that, though many re- 
markable points connected with the structure have recently been 
started, mehanical analysis alone has been resorted to for their 
elucidation, and that, too, as I have already mentioned, without 
sufficient attention to the nature of the structures submitted to ob- 
servation, or to the kind of manipulations adopted for their prepa- 
ration. I feel confident that even the method of mechanical 
analysis hitherto pursued is still capable of great improvement, 
and that it would have been considerably modified by Professor 
Retzius, had he been able to devote further attention to the sub- 
ject. Having commenced my experiments where his terminate, 
I think I may say that a year and a half's constant attention to 
the subject has much improved and facilitated my means of ob- 
servation, and has led me to new and important results. One of 
the greatest chemists of the present day has promised me an 
analysis of the structures entering into the composition of the 
teeth throughout the range of the animal kingdom, which when 
completed will furnish a valuable accession to our knowledge of 
these organs. I have also myself had recourse to chemical de- 
composition, which has yielded me no little assistance in unravel- 
ing the texture of these organs. MISSING PLATES 1-5