On knowing the Age of the Horse by his Teeth.

It was in the commencement of the Veterinary College, in the year 1792,
that I composed this Table, apprehending strongly that it would create a
smile among my friends, if, as being a young student, I should be mistaken
in giving the age of a horse, I therefore, for a few months, gave my atten-
tion entirely to this object, procuring an enormous quantity of jaws and
teeth from the neighbouring slaughter-houses for this purpose.

This Table is a collection of all the material circumstances which attend
the teeth from birth to the latest period of life ; for the fact turns out to be,
that it is the history of the teeth which forms the basis of this knowledge,
taking into the account some discrepancies and anomalies which disturb its
nniformity, and to which are to be added certain changes which age pro-
duces in other parts of the body. *

The changes which take place in the teeth at any age are seen in the
Table : if we look down the column perpendicularly for any age, we see the
state of every tooth at that age ; or if we look for any particular tooth, by
carrying the eye along the line horizontally, we see the state of that tooth
at half-yearly periods through all its progress to old age ; so that, with this
Table before him, the tyro may soon acquaint himself with every particular,
and much better than by the vague, unconnected, and often untrue accounts
hitherto given.

We may perhaps advantageously preface our remarks with a short view of
the formation of these Incisor teeth, according to the best information we
have been able to obtain, and from our own reflections; not only on account
of some novelties we introduce into it, but as being one of the most singular
and interesting processes of the animal economy. Their formation appears
to be nearly as follows :�A cavity, by absorption, is first formed in the bone
of the jaw, which, when sufficiently enlarged, receives a deposit of a mass
resembling jelly or gluten, but is more tough, and covered over by a thin
fine vascular membrane; a sac also, or membranous capsule of some thick-

b 2

TABLE OF THE APPEARANCE OF ALL THE TEETH

At Birth 12 Days. 5 Weeks. 2 Months 3 Months 6 Months 1 Year. If Year. 2 Years. 2� Years. 3 Fears. 3i Years

INCIS. 1st pair.
2nd pair.
Corner...

ANT. 1 st pair ..
2nd pair..
Corner...

1 Molar........

2 Molar........

3 Molar........

4 Molar........

5 Molar........

6 Molar........

Not ap.

Appears Advncg.

Level Wearing

Worn

Mk. ob.

Smooth

SHED

H. Tooth I
sharp Level

edged |

Not ap.

Appear

Advncg.

Wearing

Worn

Mk. ob.

Mk.ob.

SHED

Not

ap.

Not

ap.

Not ap. Not ap.

Appear

Level

Wearing

Worn Worn

Worn

Not ap.

Appear Advncg. Level

Wearing Worn

Worn

'Mk. ob.

Smooth SHED

I
H. Tooth I Level

Not ap.

Appear

Advncg.

Wearing

Worn

Worn Mk. ob.

Mk. ob. SHED

Not ap. I Not ap.

Not ap. Not ap.

Appear

Worn

Wearing

Worn

Appear

Advncg.

SHED

Level

Advncg

Appear

Advncg.

Advncg. Advncg.

Advncg.

Advncg. Advncg.

Advncg.

SHED

Appear

Advncg.

Advncg

Advncg.

jAdvncg.

Advncg

Notap.

Not ap.

Notap. Notap. Notap

Not ap.

RISES

Level

Advncg.

Advncg,

Not ap.

Notap.

Not ap.

Notap.

Not ap.

Notap.

RISES

Advncg.

Advncg

Not ap.

Notap.

Notap. ! Notap. | Notap.
I I

Not ap.

Notap.

RISES

ness and strength, and double, is also found to envelope this jelly or pulp;
the fine membrane covering the pulp, is supposed to be an extension of the
periosteum, the usual, and perhaps universal, genetrix of bone. This pulp,
growing and enlarging within the capsule, becomes at length of the figure
and mould of the crown of the future tooth, and assuming next the office of
a gland, begins to secrete upon its surface a thin shell of bone of its own
figure; this shell is not, however, formed in one entire surface at once, but
by a separate deposit on the most projecting and prominent points first,
which uniting, form the shell, and it then becomes general over the whole
pulp, and if examined at this period, it is found but very loosely adhering
to it. A thin shell of bone is no sooner formed by the pulpy gland, than the
capsule, assuming a glandular property also, commences depositing upon its
surface the enamel, first in parallel longitudinal lines and processes, and
then by a reticulated coat, and finally a glossy covering of smoother enamel;
so that by the gland within thickening the shell inwardly, and by the enamel
being deposited without, the crown of the tooth is completed. And while
the thickening process is going on above, an extension of the shell proceeds
below, formed by the same jelly or gland, which, as it elongates, diminishes
in diameter as it proceeds, and the enamelling process follows it, till at
length is formed the crown, the body, and shank or tube of the tooth. The
Horse Incisor in this stage is a mere hollow shell or tube of bone and enamel,
enlarging upwards, and bent to the exterior figure of the jaw. The head
or crown of the tooth being sufficiently consolidated, and provided with a
tube or shank of certain length, is in a state for external protrusion and use.*

The external capsule, or investing double membrane of the tooth, having
completed its office, grows thinner by degrees, and is at last totally wasted
and absorbed. The gums also waste, and the tooth is then in a state for ex-
ternal appearance.

This curved figure of the new formed tooth, we may remark, brings the

* It has been formerly supposed that the investing capsule was the secreting agent of the
bony shell of the tooth; but as this would only be so for a moment, or till the thinnest lamen
of bone was formed, since this would effectually cut off all future communication between the
capsule and the gland, so the after-thickening of this bony case inwards must entirely depend
on the gland within it: and we find on examination, that the primitive shell so formed differs
in nothing from the substance afterwards added, and, therefore, it is but reasonable to conclude
the whole is formed by the same agent.

AT ANY AGE OF THE HORSE.

4 Years.

4j Years.

5 Years.

6 Years.

7 Years.

8 Years.

9 Years.

10 Years.

11 Years. | 12 Years.

18 Years.

24 Years.

50 Years.

Wearing

Worn.

Mk. ob.

Round.

Oval.

Oblong.

Triang.

Longit.

Oblong.

Fall?

Level.

Wearing

Mk. ob.

Rounded

Oval
1

Triang.

Mk. ob.

SHED

Level. 1 Wearing Worn.

i I

Mk. ob.

Oval

Triang.

Wearing

Worn.

Mk. ob.

Smooth.

Rounded

Oval

Triang.

Level.

Wearing

Worn.

Mk. ob.

Rounded

Oval

Triang.

Mk. ob.

SHED

Level.

Wearing

Worn.

Mk. ob.

Rounded

Oval

Triang.
)

Advncg.

Adv.

We believe a well-recorded case of a Horse attaining
60 years, has occurred in this country.

Level.

Adv.

The teeth of the famous Eclipse horse are now before
me, and the incisors are getting triangular; his age,
when he died, is well known to have been 26.

Adv.

SHED

Level.

Adv.

Adv. Adv.

Adv.

Level.

Adv.

Adr.

Adv.

Fall?

Risen.

Half inch long, grooved, concave within.

Large, convex without, concave within.

Fully formed.

Rather worn at the point.

More worn, and fuller on the inside.

Considerably worn and rounded.

Wearing shorter and rounder.

Rounded, and conical close to the gums.

It s probable, that life becomes extinct in these animals before the final
destruction of their teeth, that is, if left to a pure state of nature.

Risen.

Much worn.

Very much worn.

crown of it in a position almost perpendicular at its first emerging from the
jaw, and occasions it to meet the teeth of the opposite or upper jaw nearly
perpendicularly; but as the tooth wears away, and, in very advanced age,
after passing through a succession of inclining angles, is at last reduced to the
shank, which being placed nearly in the direction of the jaw itself, will oc-
casion these teeth to meet the opposing teeth of the upper jaw in nearly an
horizontal line, so that their internal lateral surfaces get worn, instead of
their points, into an oblong irregular figure, and the reduced lean jaw bones
approach each other in the same direction, the redundant skinny lips are
seen protruding beyond the teeth; whereas in the youthful jaw these parts
are rounded, plump, and deep in front. Accessions to the fang or posterior
parts of these front teeth are made to almost the latest period of life, which
accessions are flattened in the opposite direction to the compressed flatness
of the crown of the fresh tooth, and thus diminish the lateral extent of the jaws.
And these prolongations are, after a certain age, of solid bone, without enamel,
of a yellowish colour, and very hard.

In the centre of thecrown of the tooth,and externally visible, is aninverted
hollow or funnel of enamel, which we have called the infundibulum; it has
been called the mark by dealers, and is supposed by them to fill and grow
up, but is in reality worn away by the use of the teeth, and obliterated
about the sixth year.

The primitive germs and formation of both sets of teeth, must be sought
in the foetus some months before birth; but the circumstances attending the
growth and progress of the teeth generally, are most beautifully to be
observed by the dissection of the jaw of a horse two years old
previous to their shedding a tooth. On carefully taking the jaw to
pieces, we may observe underneath the two front milk Incisors, and lying
within them, the front pair of the second set, now about one inch and three
quarters long, consisting of hardly anything more than a shell of enamel,
with the small enamel inverted cone coming down the inside of it from the
crown, and tapering to a point; this hollow tube is now of the full size of
the tooth, and requires only to be strengthened with bony matter for being
brought into use. The second pair of Incisors are only one inch long, con-
sisting of a shorter case of enamel, covered with a brown furred matter of
an ochre colour, and the inverted enamel cone within is not closed at the
point, so that you see through it. The enamel in both the cone and the

tooth terminate below in a fine thin edge, which shows that the formation
of this matter commences at the crown of the tooth, and is carried down-
wards, thickening as it proceeds, and not all formed at the same time. The
extreme upper edges of this second pair are just become white, hard, and
glossy with enamel.

Of the third pair of Incisors, we have not yet any appearance, but we
may observe the bone is very cellular, and here and there considerable spaces
in it, so that we see a cavity is forming by the absorbents for the reception
of the crown of the tooth. What consciousness leads these vessels to re-
move an old formation for the reception of a new one entirely different ? What
sense should urge these absorbents to provide a space so long before the
want is really experienced? and what power is it that should direct
a mere arterial vessel to become the reflecting architect of so extraordinary
a structure and figure as is one of these horse's teeth! Dr. Darwin, I ob-
serve, calls this power, animal appetency, which is almost or quite synony-
mous to the stimulus of necessity of Hunter: want certainly may lead to
an effort, but what sense directs its issue ? Modern researches, have, how-
ever, much removed this appearance of mystery, by showing us that a por-
tion or off-set from the capsule of the milk tooth is thrown off to form the
second set, passing out by a channel or foramen of the alveolus for this pur-
pose, and it is likely, though too minute for vision, that the germs of both
sets of teeth are given with the foetus, and only wait their evolution : and it
is the stimulus of the presence of these germs that produces these operations.

In noticing the two first Grinders in this two-year old head, which are
deciduous or milk teeth, their lower parts are so absorbed as to resemble
somewhat the fangs of a human grinder. They stand astride the Grinder
beneath, and are ready to fall out on the least application of lateral violence.

We may observe, that at this age the jaws are full of young and grow-
ing teeth, and must be in a particular degree tender and susceptible of in-
jury, therefore great care should be taken that they receive no blows or
violence of any kind at this period on these parts.

The Horse Teeth, on the shedding of the Milk Teeth, appear to rise in
their sockets, for they are so very soon level with the remaining Milk
Teeth, that it appears almost impossible the Milk Teeth can be soon worn
down to them and the jaw absorbed so rapidly; whether it be so, might be
seen by marking the other teeth with a file opposite the crown of the

Horse Tooth. On trying this experiment, it did appear that they really
rose in their sockets to the level; this perhaps may be performed by the
growth of the fang, which, lengthening backwards, forces it up. This, I
since find, has been generally admitted by writers on the teeth.

An Incisor tooth, on first emerging from the socket, presents only two
sharp edges of enamel, the posterior edge much lower than the front edge,
and serrated; from the wear the outside and inside edge are sood reduced to a
level, and proceeding further, four sharp lines of enamel present themselves
from the enamel of the cavity becoming distinct; or we may describe them
as two concentric circles of enamel somewhat elevated: these prominent
edges must make the grasp or. hold of the tooth very firm. After the enamel
cavity is obliterated, for it is a more correct expression to say obliterated
than filled up, (which is the common phrase of the dealers); there is
then left only one circle of enamel, which environs the outside of the
tooth.

The use of this hollow cavity in the Incisors of the horse appears
to be to give sharpness to the upper surface of the tooth; but the very dif-
ferent lengths of this inverted enamel cone or infundihulum in the teeth of
horses, and which is called the mark, occasions its obliteration to be very
irregular, and, therefore, an uncertain criterion in judging of the age. This
mark in the front teeth I have sometimes seen after eight or nine, and in
others, as is generally the case, obliterated at six. The compressed flatness
of the tooth at its early rising should be particularly observed, and also the
length or degree of its exposure.

The Incisor tooth of the horse, when fully formed, is of an oblong
conical figure, very much curved, the curvature obeying the sloping figure
of the front of the jaw; and when young is very hollow in the inside. The
filling up of this hollow gradually takes place from the sides towards the
centre, and a section of the tooth exhibits a very elongated cone, and nar-
row towards the apex, and the actual filling up with solid bone does not
much precede the demand for its use by the wear ; in this way, with suffi-
cient strength, the jaw is kept lighter in weight. The bone successively
filling this hollow appears like a brown mark in the centre of the tooth,
and enlarging as the tooth grows older, presents us with another means of
judging of the age of the horse; and Vegetius appears to have made obscure
mention of this. This brown or black mark, examined with a lens, appears

in a remarkable manner sometimes to have a small circle of enamel, form-
ing a white eye in the centre of it.

If we make a section of the Incisor with a saw in several places down its
body and shank, they will exhibit very much the appearances they present
in the course of wear.

St. Bel used to place much reliance on the upper corner Incisor tooth
being worn to an angle, always declaring the horse nine under these circum-
stances ; we have seen, though rarely, this angle worn at seven, much de-
pending on the distance of the lower Tush, and his manner of using the
Incisors of the lower jaw, by being too much in advance, or not taking
sweep enough, to grind them all to an even surface.

The Cuspidati, Laniarii, or Tushes, in the horse, are separated at some
distance from the Incisores, and still greater from the Molares; they are
only given to the males, though rudiments of them are often seen with the
females ; they are formed of harder bone than the teeth, and the part that
rises above the jaw is nearly straight, the part beneath it is generally curved
like the Incisors, but describing the segment of a smaller circle.

The Tush is every where covered with enamel at its first rising, and is
very like a carnivorous tooth, having a sharp lacerating edge on each side,
which forms a sort of arch inside by meeting at the top, the centre lon-
gitudinally projecting and convex, the outside more gibbous, but reaches no
farther than the gums, where it becomes rounded and curved. Horses, in
fighting, would probably make great use of them, or in tearing their own
bodies, as they sometimes do in extreme anguish. For a description of
their rise, change, and decay, we refer to the Table.

In judging of the age of the horse, the thickness and roundness of the
Tush at its base is of consequence to be observed as affording a good cri-
terion in forming an opinion, for though old, it shall often be sharp at its
point and concave on its inside, depending on the accidental contact or its
absence with the other teeth; for we find the wear of this tooth is very
uncertain; in some cases it is liable to receive no friction at all, in others it
is quickly worn, but the base of it, whether its point is worn or not, is
almost uniformly rounded and exposed by advancing age. In ascertaining
the age, it is also well to examine both the Tushes and both corner teeth,
for they sometimes differ very much on the different sides of the mouth,
depending on the manner of using their jaws.

Of the Grinders.�These teeth are almost entirely removed from our
view, and therefore are of small value as indicators of age, but of no secon-
dary importance in the business of the mouth and mastication, and as such
deserving our earnest attention.

The Molares, or Grinders of the horse may be said to be larger in pro-
portion to the size of the head, than the Grinders of most other animals,
and are remarkably square and solid. These teeth are formed in linear
ridges and angular elevated points of enamel. By these irregularities they
grind their corn and crush the hay with much greater ease and effect, and
for this reason the enamel is introduced into the centre of these grinding
teeth, which are gradually filled up with bone as it becomes wanted, by
exposure and wear, and the matter of the bone being softer than the enamel,
is more easily worn away, and so ever leaves these asperities of enamel in
prominent points and lines, to retain and divide the food.

The body of one of these upper Grinders is nearly a square column
throughout, a little diminishing downwards, and slightly curved to the in-
side or lingual aspect, with the grinding surface nearly at right angles to
the direction of the curvature, which causes it to slope inwards and towards
the mouth, and to throw the food upon the tongue. The outside or malar
aspect of this upper Grinder has prominent longitudinal ribs, and two flat
surfaces, one of them more depressed, which, on the inside, is answered by
a flat projecting rib of rather greater width, and the sides resting against
the neighbouring teeth are nearly flat.

A Grinder Tooth of the lower jaw is smaller, thinner, and flatter in figure
than the upper one, and nearly straight, its upper grinding surface obliquely
shelving outwards, or in the contrary direction to the upper grinder; its
inside or lingual aspect is ribbed in four or five longitudinal lines or projec-
tions, and one deep depression; the outside or aspect to the cheek has two
flattened columns, with a depressed narrow line between them, which
receives a process of bone from the jaw to secure it, and of the dental
sides, one is flat and the other obliquely slanting. For this description, we
have taken one of the middle Grinders, the extreme or end ones being
sharpened to their terminating edge. These teeth are left hollow for a consi-
derable time, and do not appear to fill up solid with bone till late, or it is
wanted by exposure and wear.

The Grinders are all pretty much the same; the capsule of the third

foetal grinder is however remarkable in sending off two dental germs or
offsets, one to form the horse tooth immediately beneath, the other to form
the fourth permanent grinder. The fourth again sends off one to form the
fifth grinder, and the fifth one to form the sixth. The tush, it is probable,
is a single primitive formation.

And it appears upon examination, that the fourth Grinder in its structure,
differs from the rest in this, that the columns of enamel are not continued
more than half way down the body of the tooth, and there converge to a
blunt point; indeed this tooth is not so long as any of the rest, and is in
part closed over at the bottom by a process of bone, like a cover, attached
by processes to the sides. We have noticed in the table, that this tooth is
finally shed earlier than the third, and perhaps in some instances, than the
second, and this furnishes us with the reason.

The three farthermost Molar teeth are placed in the jaw, not upright,
as the others, but leaning forwards, and occupying a wider part of the jaw,
are of an extraordinary length.

The Grinders of the horse, with process of age, have at last three fangs,
which to the young teeth are almost wanting, and the sixth with one fang
more than the others. The third Molar is however the largest.

Observation shows that the enamel is deposited in longitudinal striae,
on an extremely thin shell of bone ; over these striae a harder matter is laid,
having a reticulated appearance in dense irregular lines and threads; over
this again is applied, or, as it were, floated, in transverse lines, a coating of
the whitest, most compact, and shining enamel, which extends from the
crown and prominent points downwards, covering by degrees the former
structure, so that in fact three different coats unite to form the complete"
body of enamel. Small black points, or pores, are discoverable with a lens
in the terminating edges of the last coating. The first coating of enamel
will, on drying, split into regular lines longitudinally, with intervening
spaces, and is much softer than the thin bony shell on which it is de-
posited.

We may observe, in respect to the molar motion of the Grinders, that
it is not rotatory, or like one millstone upon another, in an horizontal plane,
but is chiefly or wholly lateral, or from side to side, at an oblique angle,
inclining upwards, so that the stroke is from either side successively.
For if we observe the wear of the upper and under Grinders, they are

different; the outer edges of the upper, highest or most projecting, and the
outer edges of the lower or posterior jaw obliquely deficient and worn
away, which with the arched appearance of the upper teeth, makes it pretty
clear that the molar motion is nearly a lateral one, or from side to centre only,
and if we make this motion with the dead jaw, we bring the worn surfaces
of these teeth into contact in the direction in which they are worn.

A Molar tooth of the horse, in its upper grinding surface, presents us with
an almost appalling complexity of construction, where we see labyrinths and
tortuous circles of enamel, winding and meandering about in the solid bone,
and which the most perfect knowledge of the formation of an Incisor tooth,
does not furnish us with any clue to the solution of.

By the researches of Dr. Blake, we have been taught, however, the ex-
planation of these appearances, and we shall attempt in the following brief
description, to convey a notion of the singular manner of the formation of
these complex teeth.

A horse's grinder though, strictly speaking, it consists but of one piece,
is arranged in so tortuous a manner, that it has the appearance of a collec-
tion of variously figured teeth, covered every where outside with enamel, as
the Incisors, and held together and consolidated into one mass by an inter-
mediary deposit, secreted into all those spaces which their irregular forms
do not allow of their coming into contact or apposition of surfaces.

To trace the lines and contortions of enamel in one of these grinders,
would be difficult, or to reduce them to any system; we shall, however, form
some idea of their actual distribution, if we compare them to the lines and

double curve of the open letter |T�0 the semi-circles which are placed next
the tongue, twice repeated; the second smaller, and adhering to the outside
of the arches of the former; the back of the letter also is straight, but in
the tooth tortuous, forming a double zig-zag, or two angular lines, making
together a triple series of shells, the last is however single. On being worn,
two transverse elevations of the bone appear with as many transverse de-
pressions between them; such is the case with the upper jaw. In the lower
jaw, whose teeth are narrower, only two transverse courses of shells are
found; and in the fresh recent tooth, these lines are single, forming one
edge of enamel, but by the wear, a double line is soon presented, as we
see in the letter.

In following the process of their actual formation, we may imagine five

or six of these irregular figured tubes or cases placed together, being formed
by as many pulps, first by points, and then united into one shell; these
shells are quickly covered with enamel, laid on in three coats, as we have
stated : first the striated, next the reticulated, and finally the glossy coat.
The first, however, I consider rather as a foliated coat, being formed of pa-
rallel leaves, somewhat like the inside of the horse's hoof, to hold on the
enamel more securely, and to afford, perhaps, a slight degree of elasticity
and yielding: as an homogeneous, hard, chrystaline body like this, would
be liable to be more easily fractured, without this softer bed to act against.
Each of these may be seen distinctly by looking down the course of the
tooth, from its crown to the shank, being formed in succession, and we ap-
prehend have not been distinctly noticed before.

These shells being strengthened by enamel without, and hard bone
within, are in a state to receive a most extraordinary process for their union
and consolidation into one mass, which is done, according to present know-
ledge and apprehension, by the membranes of the capsule, which had just
covered them with enamel, changing the nature of their secretion, and pour-
ing forth solid bone between these cases, and filling up and obliterating all
the intervening spaces, till the tooth becomes one solid body, and the mem-
branes are excluded by their own secretions.

For the accomplishment of this purpose, processes are sent off from the
investing capsule, which wind among all the convolutions of the shells, and
deposit this bony matter. Now, it has been said, that these membranes
pass down perpendicularly from the capsule, going down between the shells,
and pouring out their secretions, till the spaces are filled ; this view of it,
however, would lead us into embarrassment, and give us an erroneous idea
of the real process : for this matter is not poured out as lead might be sup-
posed to be poured out, among some pipes or tubes stuck in a bed of sand,
where the process of consolidation would commence at the bottom and pro-
ceed upwards: since, if we examine the horse's tooth, we see evidently
enough, that the consolidating process begins at top, near the crown of the
tooth, in order that this part should be early brought into use. Now, if
these membranes dipped down perpendicularly from above, they would, by
the filling up of the tooth at top, be cut off from their sources, and be de-
stroyed, that it would appear necessary, in order to conceive this process
aright, that we should consider these membranes, though standing perpen-
dicularly, in respect to the position of the tubes or shells, to have rather a

lateral communication with the capsule, and, like the wind-screen before the
fire, which, though standing perpendicularly, receives its motion, when
moved, laterally ; or, more familiarly, perhaps, we may compare these mem-
branes to the septa of an orange, which pass into it laterally from the rind,
and are appearing above and also below, perpendicularly between every
quarter of the fruit; so these membranes are entering all the convolu-
tions of the teeth, and depositing upon the shell, enamel first, and then bone,
or supplementary bone; beginning and finishing this process at the crown of
the tooth first, and afterwards passing downwards, fill up the tooth by suc-
cessive vertical layers, meeting in the centre, and obliterating the vacuities,
and rendering it nearly solid; and the tooth so filled up and made solid,
then presents us, as we have already observed, to an enigma of no easy
solution.* The outside of the tooth is also covered over with bone of the
same kind by the investing double capsule, supporting the enamel outside.

This peculiar kind of succedaneous bone is rather softer than the real
bone of the tooth within the enamel, and is more easily marked with the
graver, and is often yellower,, and in its analysis differs nothing from bone. It
has been called by Dr. Blake the crusta petrosa, but not being a shell, which
crusta implies, nor yet petrosa, or rocky, or stony, as petros, would signify,
we have ventured to propose with diffidence, in speaking of this supplemen-
tary material, to call it, till a better name shall be found, Stereodontum, or
Stereodont, from (TTspeoa to strengthen, and oiW-ovrtK a tooth; and in speaking
adjectively of its qualities, we may use stereodontic or stereodontous, while
the two former words would require a tedious circumlocution, especially
when used adjectively.

The term cortex striatus for the enamel, we have hardly thought less
unfortunate, and could not with any pleasure follow, not only on account of
its complexity, but also because it is not the property of bark to be harder
than the wood which it covers, or be at times inside it. That I have preferred
the use of the simple term enamel, though in some respects objectionable.

The term striatus seems also not well chosen, as the striae are not visi-
ble externally, but by a transverse section of the tooth, when they appear
as short radiating lines, having a direction towards the centre of the tooth,

* The enamel, by chemical analysis, is not found to differ very much from bone, being phos-
phat of lime, with a small portion of carbonate of lime, and without any cellular fibre.

and being in reality the processes of the foliated first coat we have described
of the enamel.

I have seen in the possession of my worthy friend Thomas Bell, Fellow
of the Linnean Society, and Lecturer on the Teeth at Thomas's and Guy's
Hospitals, whose kindness in assisting me with information, and use of his
elegant museum, deserves my public acknowledgements, a preparation of
a foetal molar tooth of the horse, covered with its membranes, both equally
injected, which shows that both the membranes of the capsule are nearly
equally vascular; John Hunter having asserted, that the inner, and Dr.
Blake, that the outer, was chiefly possessed of vascularity. This prepara-
tion, my friend informs me, was made by that excellent man and philanthro-
pist Joseph Fox,* and exhibits an arched stylus or petiolus, proceeding from
near the top of it, and conveying away the embryo of its future successor.
This petiolus seems somewhat thin in the middle by its extension, aud is
about half an inch long, of the thickness of a crow quill, and holding at
its extremity the germ of the tooth, being a portion of the capsule, with,
probably, the modelling gland within it. This mass is about the size of a
small horse-bean, and outwardly somewhat angular: it seems to have
escaped like the cicatricula of an egg, conveying a portion of the membrane
with it.

In the foetus we have only three Grinders, which appear as fully to
occupy the whole of this part of the jaw as the six do afterwards, the jaw
therefore lengthens behind principally, and not in the same degree anteri-
orly, as the three horse Molar teeth are formed directly under these fetal
teeth. The three posterior Grinders at this age, are to be sought in the
wide part of the jaw, which posterior part is covered by the masseter
muscle. It may be remarked also, that the space without teeth, called the
bars, extending from the first Molar to the Incisors, is nearly wanting in
the foal, or at least bears no proportion to the rest of the jaw when com-
pared with the same space of the jaw when the mouth is complete.

We may remark, that the symphysis of the upper jaw, or where the two

* This benevolent character, in the early difficulties and attempts of Lancaster to form
Schools of mutual instruction, seeing a danger of their failing for want of funds, gave to Lan-
caster, in a private donation, more than two thousand pounds, and kept the expiring cause
upon its legs. He has also left behind him a most valuable Treatise on the Teeth, and especi-
ally of their Diseases.

halves unite, is singular in possessing projecting lamellae of great length,
and terminating in toothed points to render the connexion more firm.

The broad triple series of enamel shells in the upper jaw to grind
against, makes quick dispatch ; nor need we be so much surprised when we
see the apparatus, that a horse on his journey should so soon remove his
half peck of corn. The points of the lower grinders appear to be more irre-
gular than the upper, and fall into their depressions, and these undulations
in the teeth increase their quantity of surface, and their effect also. The
transverse channels across the Molar teeth, we may observe, are perfectly
straight, which would seem to show that the grinding motion must be
nearly or quite so.

Having considered the teeth themselves, we shall make some remarks of
a general nature in respect to judging of the age, which it may be necessary
to notice in order to form an accurate judgment; for instance,�if we ex-
amine a horse in May, and find his mouth denote neither 5 nor 6, we do not
say that he is between 5 and 6, though the marks denote it, but exactly
5 or 6, as most colts are foaled in this month ; and this we are led to do, as
the appearances predominate in the mouth for 5 or for 6, though it is true
there are some Autumn colts, but such are of rare occurrence, and after
May we should say that he had just passed 5 or 6, though the appearances
of the mouth may hardly indicate that he had attained it; for it is necessary
that we should be guided by these considerations, as the teeth themselves
are subject to almost endless variations in every different subject, and this
is the only correcting rule that can be applied, for irreconcilable difficulties
occur but too frequently; sometimes a young Tush with old Incisors, and
sometimes young Incisors with a worn Tush, and very convex and full
in the inside ; in these cases we must, after considering all the circum-
stances, take the more predominating, and make our decision, recollecting
the season of the year. The age of the mare is more uncertain and dubious
for the want of the Tush; in judging by the Incisors, it is particularly ne-
cessary to be recollected, that in the fresh tooth rising from the jaw, it is
very wide and fiat, with two nearly parallel cutting edges of enamel; by
wear, these are soon reduced to a level, and the lateral width diminishing
and increasing in the opposite direction, the tooth produces a sort of ellipse
or oval, and next a rounded figure, and finally a triangle, all of which may
be seen by making a series of transverse sections of an incisor tooth down the

shank. Dealers are often led to feel the Tush only, and if they find it
pointed and hollow, they are sure of a young horse ; but when this part is
made very full on the inside, as it sometimes is, and convex, or has been
rapidly worn away by the bitts or otherwise, they will be very likely, if
guided by this circumstance alone, to be led into error in believing the
horse to be older than he really is. The upper Tush is latest in appearing, but
is by much the soonest worn away, beginning to wear about 9, or generally
earlier. I am uncertain whether this wear is done by the mouth-piece or
bitt, which is usually placed posteriorly to the lower Tush, and nearly oppo-
site the upper Tush, or whether it is the lower Grinders that do this, though
they appear too remote for this effect. The wear of these upper tushes, if
we examine them attentively, is in a sort of waving line, almost confined to
the inside of the tooth, and is extremely smooth and highly polished, as
though it had been worn by some soft body, and would lead one to conjec-
ture whether it was not done by the tongue, or by occasional contact with
grit or rough particles received with their food.

It would dilate this account too much, to enter upon all the varieties and
singularities which occur in different mouths, yet some of the most remark-
able may here be noted; thus I have seen the four-year old milk tooth re-
maining in and unshed till after six, the corner Incisor horse tooth being up
and in parallel line with it and the rest of the teeth, so as to make seven
Incisors in the upper jaw ; this one should suppose, must have arisen from
an unusually long shank or fang to the milk tooth. Sometimes we have
seen the front Incisor horse tooth with its cavity obliterated, before the
four-year old corner milk tooth was shed, so that the one was indicating six
and the other four years old. This early detrition, or obliteration, of the
cavity, must have arisen from an unusually short enamel cavity, or infundi-
hulum and long fang, as we have stated, to the milk tooth.

I onee remember to have seen an error of the mouth which deceived
an able judge; the near side corner tooth of the lower jaw was perfectly
fresh and sharp as at its first appearance, consequently indicating four years
and a half; the corresponding tooth on the opposite side indicated by its
wear seven or eight. On examining the upper jaw on the near side, the
corner tooth, by some accident, was found to have been knocked out, so that
the opposing tooth in the lower jaw receiving no friction, had conse-
quently retained its perfect freshness.

When the front surface of the Incisors is worn, it is generally done by
rubbing against the manger, and may indicate a suspicion of crib biting,
though not always so, for irritation of the stomach, from foul or too high
feeding, often induce them to lick, gnaw, or rub the manger.

Of the other indications of advancing age in horses, we may remark that the
upper Incisor teeth become arched in front like a parrot's beak, projecting
over the inferior ones, and meeting these almost in front, for the upper teeth
are ever larger and stronger than the lower ones, and receive their action
chiefly laterally, which occasions the formation of this arch, and so much do
the upper teeth sometimes project over the lower ones,as to wear them in
front to a considerable angle; whereas, at setting out, or at four or five
years old, this surface is highest in front, and the back of the tooth is
lowest.

The teeth of horses are found sometimes subject to decay, of which I
possess various specimens; it is known by the difficulty of chewing the
food, and the inflammation and swelling of the adjacent parts; in this case
they have been drawn out, but are more easily punched out; this is how-
ever an extremely severe operation, and we may perhaps find a better sub-
stitute in the application of the actual cautery or acids to the nerve, or by
dividing the nerve itself going to the tooth ; though anti-phlogistic reme-
dies are generally sufficient, and in the course of a long practice with horses,
I never found it necessary to extract a tooth.

The sunken eye and prominent orbit, the hollow eye-pits, the grey eye-
brow, the rugged temple, the lean thin muzzle, the over-hanging thin lips,
the rising points of bone every where, the dry hard skin and disfigured
hoofs, indicate sufficiently the advancing age, without any appeal to the
mouth. The grey horse becomes flea-bitten, the chesnut dark, and the bay
horse more dull.

I purchased a young chesnut mare in Suffolk for experiments on the
feet, and also to observe the changes and shedding of the teeth. She shed
her front Incisor tooth October 12, 1808, within a month after I bought her,
which proved her to be two years and a half old; for, as we have remarked,
they are foaled in the Spring, but shed their teeth in Autumn, successively
at two and a half, three and a half, and four and a half, years old. The gap
or space where the tooth came away was soon covered with red gum,
very irregular, broken in the middle, and rising higher on the sides, but
there was a view of the horse Incisor that was to emerge. She did not shed

her second pair till Christmas day of the next year; the Horse tooth was
much below the rest of the teeth, and a long period elapsed before they
were even. On February 9th, 1810, one tooth of the second Incisors still
remained, and this was in the upper jaw, which seems to show that they
shed them rather later than the posterior jaw ; perhaps the fangs in these
are also longer.

My bay blood stallion (Heathfield) did not shed his first pair Milk Teeth
till the end of November, and the upper pair on this occasion were shed
before the lower; the shank of the tooth was for some days projecting out
before it fell, and the body of the tooth appeared to be held by the new
tooth and the gums within, and the shedding of the teeth I thought was at-
tended with a slight fever, which caused him to look hagged, and to be
rather feebler than at other times. The four front teeth, from the first to
the last shed, took about three weeks, that is, from December the 1st to
about the 21st; when shed, the difference of elevation between the surfaces
of the old and the sharp edges of the new was about a quarter of an inch;
ten days after there was no sensible elevation, or the unevenness percepti-
bly restored. January loth, the level was not near restored. This length
of time would make one almost suppose that they did not sometimes rise in
their sockets, but depended more upon the wear of the other teeth for re-
storing the level among them. The second pair of Incisors were shed not
a year, as might have been expected, but in little more than half a year, so
that there is considerable irregularity in the periods of this process.

It is a singular fact that the lower jaw of horses, where the masseter
muscle is inserted, is sometimes in old horses worn through into a hole.
Is this simply from the extreme tenuity of the bone with age, or the muscles
being inserted on both sides the bone. The perforation is mostly as large
as a crown piece.

Fig. 1. Lower jaw, with incisors and tush.

2. Section of an incisor, shewing the

cavity and infundibulum, which
sometimes at the point is found
to contain stereodont.

3. A shed incisor, having the shank

absorbed half away, to make
room for the advaucing horse-
tooth.

4. Crown of an incisor horse-tooth in

the shell, the infundibulum not

Fig. 5. Incisor horse-tooth ready for pro-
trusion.

6. The tush seen internally.

7. Section of the tush.

8. View of the windings of the enamel

in the third upper grinder�a, the
bone, b b, the stereodont.

i). The capsule covering a fetal grinder,
and sending off the germ for the
horse-tooth.�See p. 12.

closed.



	ON

	THE KNOWLEDGE OF THE AGE OF THE

	HORSE BY HIS TEETH.

	WITH REMARKS.

	BY BRACY CLARK, F.L.S. Member of Acad, of Sciences of Paris, of the Nat Hist. Soc. of Berlin and of Copenhagen, Honorary Member of the Lyceum of Nat. Hist. New York, and of the Royal Agricultural Society of Stutgard, Sfc.

	LONDON, PRINTED FOR THE AUTHOR, BY C. RICHARDS, loo, ST. MARTIN'S LANE: SOLD BY UNDERWOOD & Co., FLEET STREET; AND THE AUTHOR, No. 7, TAUNTON PLACE, REGENT'S PARK.

	1826.