88 
FIRST CLASS OF THE VERTEBRATED ANIMALS. 
lead the student to perceive the importance of these or^jans, and the different func- 
tions which they are destined to fulfil. But a much more enlarged view is acquired by 
studying the different forms of the teeth, in their relations to each other, as well as 
to the nature and habits of the animals possessing tliem. It remains for us to give a 
rapid outline of this part of the subject. 
On placing before our view the teeth of all known Mammalia, we soon perceive 
that they admit of being classified under a small number of different forms. With 
some of them, as we have already remarked, there is no (hffercnce between the root, 
or rather, the parts inserted within the bones which bear the teeth, and the crown, 
or part beyond these bones. Teeth of this nature have no real roots, in the proper 
acceptation of the word ; that is to say, the crown is continued inwards as far as the 
dentary capsule, which never produces anything but the crown, as long as it remains 
free and active a circumstance occurring with some animals during the whole course 
of their lives. Among others, on the contrary, the roots are very distinct from the 
crown; they maybe either simple or complex, but do not, in general, exhibit in 
their forms that constancy of character which is always to be recognised in the 
forms of the crown. This circumstance arises naturally from the different manner 
in which each of them is formed. 
Hestricting, therefore, our view of the teeth solely to their crowns, we find that 
there exist three principal forms among them. These may be almost infinitely mo- 
dified, and some transformed into others, in such a manner, that it becomes impossi- 
ble rigorously to determine the precise point where the one form passes into the 
other. This manner of classifying the teeth must be regarded as nothing more than 
a purely artificial method, for enabling us to speak of their forms without too much 
obscurity and confusion, by restrmning, within their proper limits, the observations 
necessary to be made. The crowns of all teeth may be regarded as conical, tren- 
chant, or tuberculous. 
(1.) The Conical Teeth vary in form from the cylinder, more or less compressed, 
terminated by a point, more or less obtuse, to the oval or ellipse. Some are straight, 
some angular, others curved. Those of an elliptical, or oval form, are the least 
common, and are observed among the Cachalots. The conical teeth, which comprise 
, the Canines of the Carnassiers, the tusks of the Elephants, Hippopotamus, &c. are the 
most numerous. Finally, the cylindrical may be seen in the molars of such Edentata 
as are possessed of teeth. Among the Conical teeth, only two kinds of composition 
can be observed. Some are formed only of ivory and cortex, such as the Molars 
of the Cachalots ; for although the external part of these teeth possesses a whiter 
tinge than the central, it is not formed of enamel, as some have thought. Both 
substances arc ivory in reality, and it is the same w'ith the tusks of the Elephant. 
Others are covered with enamel, such as the Canines of the Carnassiers, and many 
others. In this class of conical teeth are found by far the greater number of those 
destitute of roots, such as nearly all tusks ; and of those, wherein the root is distinct 
from the crown, only a small number have been observed with many roots, as the 
Canines of the Moles, for example. 
(2.) The Trenchant or Cutting Teeth may be presented under a simple or com- 
pound form. Among the former may be placed the Incisors of the Rodentia, which 
belong as much to the first division as to the second, the Incisors of the Quadru- 
mana, the Carnassiers, the Ruminantia, and others. In this division we may 
place the false and carnassier molars of the Carnivorous animals. There are, how- 
ever, many among the former vshich approach nearer to conical than to trenchant 
teeth. All teeth of this class are composed of ivory and enamel, though some also 
have cortex. These last are the incisors of the Rodentia, which present the singular 
anomaly of having enamel only on their anterior surface. They are with simple or 
multiple roots ; and those of the Rodentia alone are possessed of the same peculiarity 
as tusks, in having no roots properly so called. 
(3.) The Tuberculous Teeth present the greatest variety of form, and are all 
Molars. The simple tubcrculoiia Molars are those of the Quadrumana, the hind - 
most molars of some Carnassiers, the grinders of Squirrels and Rats, those of 
the Babyroussa, or Indian Hog. The proper tuberculous Molars arc found 
in the Insectivora, &c. The compound tuberculous molars belong to a great num- 
ber of Rodentia, such a* the Beavers, the Pacas (^Ccdogeny.%\ the Agoutis, the 
Hares, the Guinea Pigs, and others. The simple tubcrcnlous molars arc always formed 
of ivory and enamel, while they arc all possessed of several roots. This observatioti 
is equally applicable to the proper tuberculous molars. 
Among the compound tuberculous molars there are perhaps none which do not 
possess the cortex, in addition to the ivory and enamel. Some of these teeth arc 
found with several roots, as in the Beavers, Elephants, Horses, and Ruminantia ; 
and without roots, as in the Hares, the Cabiais, the Lagomys, and other Rodentia. 
The uses which animals make of these different forms of teeth are exceedingly 
various. To some they are powerful arms, by means of which they attack their prey, 
or any enemy that threatens them, or else defend themselves when attack<*d. In 
others they seem rather to he intended to retain a prey, which has already been seized. 
Some kinds are used for dividing the food like pincers ; others for cutting it like 
scissors. Again, we find another class of teeth which grind like the stones of a rail), 
or which triturate their food, like jagged pestles fitting into mortars as jugged as them- 
selves. Sometimes they crush by a single jerk, or pressure. All these forms and 
different modes of action find their final object in the ever-varied substances, which 
may serve for the nourishment of animals. The kind of food which each animal re- 
quires is determined by iU nature ; this again regulates the influence which it exer- 
cises upon other beings, and determines its station in the scale of creation. 
The different kinds of teeth are found combined together in different manners. In 
many Carnassiers, wo find conical, trenchant, and tuberculous teeth, all united in the 
same individual. Among the greater number of the Ruminantia, we can discover 
only the trenchant and tuberculous teeth. The conical teeth alone are found in some 
Edentata, and in the Cachalots and Dolphins, while only the trenchant and conical 
teeth arc found in the common Seal. 
In fact, wo find in almost all Mammalia at least some of these forms — simple teeth, 
semi-compound, or compound, with one or more roots— conical, compressed, pointed, 
with fiat crowns, tuberculous or trenchant. At present it is unnecessary further to 
enumerate the different possible combinations of teeth, A general idea of the sub- 
ject may be obtained from the following 
SYNOPSIS OF THE MAMMALIA, EXHIBITING AN OUTLINE OF THE NATURE. FORM, AND POSITION 
OF THEIR TEETH. 
Instances. 
[■ of va- 
rious 
forms 
Teotli 
Calcareous 
in both 
jaws 
of one 
form 
only 
|_in one jaw only 
■completely lin- 
ing the mar- 
gins of both 
jaws 
not completely 
lining the mar- 
gins of both 
jaws, leaving a 
. vacant space 
'of three kinds 
not very strong- ^ 
ly defined 
(Anomalous) 
r 
in the middle, both above and below 
[ 
f tubercles blunt Man, Orang-Outang. 
molars simple J pointed Lemurs, Flying-Cats. 
I very sharp ...Hedgehogs, Shrews, Moles. 
.molars compound Aiioplotherium (fossil). 
f Apes generally, the Ouistitis. 
f .u 1 • j 11 1 c j ^xT IS 1 nearly all C.vbnassieus, HiP' 
of three kinds, well denned (Normal) ■<! ,, 
I popotamus. Hog, lap"> 
L Opossums. 
C really Rodentia, Asiatic Rhinoceros- 
(apparently ...Horse, Kangaroo-Rat. 
r both above and below Sloths, Morse. 
r Elephants, Mastodon (fossil)- 
the front ...•<; below, and in the middle above i Diigong (adult), Manatus 
I ( (young). 
(above, and in the middle below Ruminantia. 
c Armadilloes, Oryctcropus, 
1 Megatherium (fossil), Afr**-*'*'’ 
( Rhinoceros, Manatus (adult)- 
all Conical or Canines Dolphins generally. 
f the upper Narwhal, some Dolphins. 
I the lower Cachalots? 
all Molars 
Iloriiv 
Wanting 
■ in both jaws Ornithorhynchus. 
in the upper jaw only Whales. 
f Manis, Ant-eaters, Echidna, 
I some Dolphins ? 
These varied forms and positions, and even the number of the several kinds of teeth, 
often afford the best speciffo characters for determining the Mammalia ; in all cases 
they offer the surest characteristics of the genera, and oven of other divisions of a higher 
order. In this way. one of the Mammalia may be immediately recognised by a simple 
inspection of its teetli ; and, reciprocally, wo may determine the nature of the animal 
to which a single isolated tooth has belonged. The importance of this study towards 
the knowledge of fossil animals, as well as for establishing the generic groups of fos- 
sils, has been forcibly illustrated in the celebrated work of the Baron Cuvier, on the 
Fossil Bonos of Quadrupeds t^Sur les Ossemens Fossiles), and liy MJI- Fr*^ 
Cuvier and llligor. The teeth may, indeed, be regarded as one of the most 
ant subjects in Zoology, and one of the most certain marks for ascertaining the 
ture of animals, and the relations established among them. They are, in 
foundations of the science ; and, hence, should occupy an important place in 
system of classification, as they serve as an index to the order of facts and 
lations ; and, hence, may be considered as indispensable to the existence of tb“ 
