THE MAMMALIA— MAN AND BEASTS. 
87 
its appearance ; finally, the first dentition is terminated by a second Molar, It must 
bo remarked that Molars, and not false Molars, immediately follow tho Canine ; and 
this is contrary to what is observed in the final dentition of the human species. The 
general law, of which this is only a particular case, will come afterwards to be ex- 
plained. 
The formula for the Milk-teeth, or first teeth of the Infant, is therefore 
»| 2 + C + 2 M _ 10 _ 
I 2 + C + 2 M 10 
All ^.he tcela of tne first dentition fall exactly in the same order as they have ap* 
peared. The Incisors and Canines are replaced by Teeth of the same nature as 
themselves, only stronger and larger than the first. On the contrary, the two first 
Molars are replaced by false Alolars oi ly Tliis operation is finished towards the 
twelfth yeai*, and tho first tuberculous molar, being tho third in the order of time, 
shows itself about the sixteenth or eighteenth year. This tooth is larger than any 
which preceded it, or even than those which follow. Finally, tho last of these teeth, 
commonly termed wisdo7n (eeth, and which may not improperly be styled a third 
dentition, make their appearance a few years later, though sometimes they are de- 
layed as long as the tliirtieth year. 
All the teeth of the second dentition are formed, according to the import.ant re- 
searches of M. Serros, by the vessels and nerves of a special dentary canal, developed 
beneath the first, and which replaces it as soon as the first set of teeth begins to fall. 
We may thence conjecture that, at the time when tho other Mammalia change their 
teeth, an analogous phenomenon takes place. 
Wlien the teeth of tho first dentition fall, it is observed that the greater part ot 
them have lost their roots, and that the lower part of the crown is tinged black, 
and covered with asperities which seem to be the effget of a species of corrosion. It 
will be proper, however, to postpone further notice of this curious phenomenon until 
the subject of successive dentition has been concluded. 
The Apes of both continents present nearly the same phenomenon as the human 
H^cmes, in respect to their first and second dentition. Tho Makis and Insectivora 
have not yet been studied in these respects, but some Carnivora have been satisfac- 
torily examined, and especially the Dogs and Cats, in which two dentitions are 
recognised. 
The first dentition of the Cats consists in the upper jaw of three incisors, one 
Canine, one rudimentary false Molar, one carnassier, and one small tuberculous 
Molar ; in the lower jaw of three incisors, one Canine, one false IMolar, and one 
<^arna5sicr. Or, 
3 + C + (F + C'+\) M ^ _I4 ^ 26 
I 3 (J ( b -4“ C IVl 12 
In the second dentition of the Cats, tho incisors and canines are replaced without 
^tiy important changes, by teeth similar to them in nature. It is also the same with 
the first two false JSIolars ; but the carnassiers are replaced by the second false 
Molars, and both are. developed immediately after tho others, so that, from being 
second IMolars in the first dentition, tho carnassiers pass onwards to be third Molars 
‘n the second ; that is to say, in the upper jaw, tho carnassier Molar has taken tlie 
place of the tuberculous Molar, which in the second dentition appears in the fourth 
and last place, while the carnassier of the lower jaw is developed in the place where 
tooth was found in the first dentition. This will he readily under.stood on com- 
paring the following formula of the second and adult dentition of the Cats with the 
preceding. 
S|3 + C-i- (2F4- 16 _ 
I 3 + U -1- (2 F -f CO M 14 
In the dontitiou of the Dogs we find phenomena very analogous to ihe above. On 
^■’^mpleting their first dentition, they have in the upper jaw three incisors, one Canine, 
falsG Molar, one carnassier, and one large tuberculous Molar; in the lower jaw, 
^Hree incisors, one Canine, two false Molars, and one carnassier. Tlie formula for the 
l**‘st dentition of the Dogs is therefore 
2 . ;^ 4 .C + (F+C^+ 1 )M ^ ii ^ os 
I 3 -j- C -f- F C^) M 14 
^ Iri the same manner as among the Cats, we find that the incisors and canines of the 
are renewed, at the second dentition, in both jaws, without any important change, 
^^ediately after the canine, in the upper jaw, there appears a rudimentary false molar 
^ spot whore no tootli had previously existed. The false molar of the first dentition 
^‘^pUced by a tooth similar to itself ; the carnassier by a third false molar, and tho 
^**’^ulous molar by a carnassier. Finally, a tuberculous molar, v^ith a second or 
^’^allei- one, appears art<’r the carnassier. In the lower jaw, as in the upper, theru 
a rudimentary fa!.so molar .after tho canine. The two false molars of the first 
dion are replaced by teetli which resemble them, and the carnassier by another 
ttjolar. Kext follosvs the new carnassier, ami immediately behind it, one largo 
7^^<=uious mol, 
dui ■ 
mmodiatoly behind it, one largo 
place where no tooth had appeared 
, and one rmlimentary 
^ the first de 
® l^ollowiug formula of tlic adult dentition in the Dogs witii that last given. 
the first dentition. These changes appear obvious to tho sight, on contrasting 
3 -I- C + (3 F + CM- 2^ _ — 
3 -j- C + (4 F + C' + 2) M 
“ ‘22 ~ 
are 
^ t follows from this, that in the second dentition of the Dogs and Cats, the teeth 
^ tiot only more numerous, but the carnassier molars are placed at a muCli greater 
from the eanino teetli than in the first dentition. 
Perc-'^ is equally applicable to all Carnassiers, and it is not difiicult to 
design of Nature, in thus altering the position of these teeth, which are 
Qf , t.o animals feeding almost exclusively on flcah. T6 render the action 
the ■ f^lways powerful, they are'brought nearer to the fulcrum or hinge of 
i„ ^hus the effect which tho jaw would otherwise produce from its growth, 
‘‘"ishitig tlieir ptjwer, is effectually counteracted. 
As the Rodentia do not possess different kinds of molars, they cannot present 
these changes which we observe in the Carnassiers. Excepting the Cabiais (ITydro- 
eharu8)i their teeth of the second dentition are developed immediately under those 
of the first, and the latter entirely resemble the former. The Cabiais, on the con- 
trary, possess a peculiar mode of dentition, in common with the Elephants and Ethio- 
pian Hogs (^Phacochoertts), 
It has not yet been ascertained, whether the incisors of the Rodentia fall, and are 
replaced. The Baron Cuvier has proved, that all species of Rodentia which have 
only three molars, possess only a single dentition ; and that there is a second denti- 
tion only among those species which have more than these throe teeth ; that is to say, 
all molars surpassing three in number, and placed before them in the jaws. He has 
further made the singular observation, that tho teeth of the first dentition fall, in 
the Guinea Pigs, while these animals arc yet in the womb of their mother. In spe- 
cies of the liarc genus (Lepws}, the first teeth fall a few days after birth, and this 
phenomenon is found even in those rudimentary incisors, which are known among all 
animals of this genus to develop themselves behind the principal incisors. 
Wo proceed to the Pachydermata, as the Edentata have not yet oflered any im* 
poitant observation in this branch of the subject. The first dentition of the Hippo-* 
potamus consists of two incisors and one canine in each jaw, of three false molars 
and three tuberculous molars in the upper jaw, and of two false molars and three 
tuberculous molars in the lower. Or, 
»| 2 + C + (3 F + 3) M _ ^ 
]2 -j- (J -J- (^2 F ”1“ 3) M It) 
In the second dentition, the incisors and canines of both jaws experience no change. 
The first of the three false molars in the upper jaw falls, and is not replaced; the 
two others arc replaced by teeth the same as themselves, and a false molar succeeds 
to the first real molar. But, at the same time, another molar is developed at the 
extremity, so that the number of these real molars remains always the same, not- 
withstanding the fall of the first real molar. In the lower Jaw, the first false molar 
falls without re-appearing ; the two following arc replaced by teeth of the same kind,' 
and then, as in the other jaw, the last molar appears. The second dentary system 
of the Hippopotamus may, therefore, be represented thus ; 
^12 + C + C-t F + 3) M ^ ^ _ 38 
I 2 + C + (2 F + 4) M 18 
We may apply the same observation which has already heoii made regarding the 
Carnassiers to the Hippopotamus ; and it is, probably, for a similar rc.oson, that the 
first real mo^ar of the first dentition is replaced by a false molar in the second. 
The Ethiopian Hogs ( P/mcocAfiTtts) exhibit a new mode of change, which they 
possess in common with the Cabiais (^JIi/drocha.Tuii). Their last molar possesses a 
movement from behind towards tlie front, so that, when entirely grown, the two 
small teetli which preceded it have disappeared, and it alone occupies the ji»vs. 
The Elephants have a mode of dentition resembling the Cabiais and Phacocha'ru?. 
Their molars begin to show themselves by the fore part, and continue to advance 
from behind forwards ; from which it follows, that these animals liave at first only 
one molar in each jaw, afterwards two, then only one, then two again, and so on. It 
appears that this movement is the consequence of the growth of eight teeth. The 
first, which occurs soon after birth, has not fallen when the second makes its appear- 
ance. At the age of two years, the latter remains alone; and this continues until 
the appearance of the thiri’, which remains alone until the sixth year. At nine years 
of age, it also disappears to give place to the fourth, and so on. It should be noticed, 
that these teetli always appear at first by their fore part, which, on that account, is 
much sooner worn out than the hinder. 
Passin‘» to tho Horses, we return to the mode of dentition first described. The 
teeth of the second dentition develop themselves immediately under such of the first 
as are intended to fall; that is to say, under all the incisors, the canines, and the 
first three molars. The only particulars requiring notice at present are, tliat the first 
teeth arc narrower than those which succeed, and that the last molars appear as soon 
as the first have fallen. 
The Ruminantia present analogous phenomena. All the incisors and canines of 
the first dentition give place to teeth of the same nature as themselves; and of the 
six nu>lars found in each jaw, the first three are replaced by the same kind of teeth, 
being only less complicated. It is then, also, that the last molars, which are very 
complicated, present themselves ; and wc may thus perceive the same design of Na- 
ture, already noticed, in respect to the Carnassiers and others. 
Among nil these animals, the greater part of the teeth, at the time of falling, )»rc- 
sent nearly the same appearance as those of Man. Their roots have disappeared; 
and from the ii regularities in these teeth at their innermosl surface, it might be im- 
agined that they had been corroded ; and further, that being composLul of different 
substances, some of them were less accessible than others to the action of the corrosive 
substance. As spots or black stains arc perceived on the whole extent of this surface, 
they might appear to exhibit manifest traces of a kind of corrosion, and forcibly recall 
the appearance of caries, or decay of the teeth, as has often been remarked. 
Many hypotheses have been proposed to explain this singular phenomenon. Vet 
it is not easy to perceive how a corrosive lluid, if it really existed, could spare the 
adjoining parts, and especially the teetli of the second dentition. I'lie mechanical 
action of the second teeth upon tho first has also been supposed, and of all attempts 
to explain the phenomena, this is undoubtedly the most unfortunate. One tooth can- 
not wear out another without wearing itself out likev\ise; and the second teeth arc 
always in their most unblemished state at the time when the first have fiillen : finally, 
this has been attributed to a power of absorption ; and the last opinion is most gciu*- 
rally adopted. It is not unUkely that caries, or decay ot the teeth, tuny be produced 
by a similar cause. 
From the observations which have already been made, on the complication of ilie 
dentary cajisules, on the variety of substances of which tho teeth are composed, on 
tho care which Nature takes in supplying the places of those teeth destined to fall, 
on the different situations which they occupy, and the names they h.ave received, will 
