mutual action, afford striking evidence of the lapse of time. Some one
may possibly object, however, to this: "What right have you to assume
that these teeth were worn away at the moment of its creation, admitting
the animal to have been created adult? May they not have been entire?" I
reply, Impossible: the Hippopotamus's teeth would have been perfectly
useless to him, except in the ground-down condition: nay, the unworn
canines would have effectually prevented his jaws from closing,
necessitating the keeping of the mouth wide open until the attrition was
performed; long before which, of course, he would have starved. In a
natural condition the mutual wearing begins as soon as the surface of
the teeth come into contact with each other; that is, as soon as they
have acquired a development which constitutes them fit for use. The
degree of attrition is merely a question of time. There is no period
that can be named, supposing the existence of the perfected teeth at
all, in which the evidence of this action would not be visible. How
distinct an evidence of past action, and yet, in the case of the created
individual, how illusory!
[Illustration: SKULL OF HIPPOPOTAMUS.]
"Trampling his path through wood and brake,
And canes, which, crackling, fall before his way,
And tassel-grass, whose silvery feathers play
O'ertopping the young trees,--
On comes the Elephant, to slake
His thirst at noon, in yon pellucid springs.
Lo! from his trunk upturn'd, aloft he flings
The grateful shower: and now
Plucking the broad-leaf'd bough
Of yonder plane, with waving motion slow,
Fanning the languid air,
He waves it to and fro."
We will not be content with admiring the vast size of the fine
Dauntelah, and the majesty of his air and movement, and the intelligence
manifested in all the actions of the "half-reasoning" beast, as he
explores the amoenities of the young world to which he has but this
morning been introduced. We are out on another sort of scent: let us try
if we can glean any light from him on our present question.
And, first, we cannot fail to notice his fine pair of tusks curving
upwards almost to a semicircle. Each tusk is composed of a vast number
of thin cones of ivory, superimposed one on another; ever increasing by
new ones formed within the interior at the base, and moulded upon the
vascular pulp which fills the cavity, and by which the solid ivory is
constantly secreted and deposited. Each new cone pushes further and
further out those previously deposited, and thus the tusk ever grows in
length as it increases in age.
[Illustration: SKULL OF ELEPHANT.]
How many years have these tusks occupied in attaining their present
diameter and length? We cannot tell: without a transverse section we
cannot determine the number of layers of which each consists: and if we
could, we should yet require to know what ratio exists between the
deposition of a cone of ivory and a fixed period of time. The cones,
however, in a tusk of these dimensions, are very numerous, for they are
but thin; and it is enough for our purpose that they have occupied the
same number of periods of time for their formation, though we cannot
precisely indicate the length of these periods.
Leaving the tusks, which are the upper incisors, let us now examine the
molars. And there is in these a remarkable peculiarity of development,
which will assist us greatly in our chronic inquiries. Before we look at
them it may be as well to consider this peculiarity.
The Elephant has, from first to last, six, or perhaps eight, molars on
each side of each jaw; but there are never more than two partially, or
one wholly, in use at once. They have originally an uneven surface,
produced by the extremities of a number of what may be considered as so
many finger-like constituent teeth, arranged in transverse rows, covered
by hard enamel, and cemented together by a bony substance. These points
are gradually worn down by the process of mastication, and then the
compound tooth appears crossed by narrow cartouches, or long ovals of
enamel, indented at their margins.
"The first set of molars, [_i. e._ the first compound molar] or milk
teeth, begins to cut the jaw eight or ten days after birth, and the
grinders of the upper jaw appear before those of the lower one. These
milk-grinders are not shed, but are gradually worn away during the time
the second set are coming forward; and as soon as the body of the
grinder is nearly worn away, the fangs begin to be absorbed. From the
end of the second to the beginning of the sixth year, the third set come
gradually forward as the jaw lengthens, not only to fill up this
additional space, but also to supply the place of this second set, which
are, during the same period, gradually worn away, and have their fangs
absorbed. From the beginning of the sixth to the end of the ninth year,
the fourth set of grinders come forward to supply the gradual waste of
the third set. In this manner to the end of life, the Elephant obtains a
set of new teeth, as the old ones become unfit for the mastication of
its food.
"The milk-grinders consist each of four teeth, or _laminae_; the second
set of grinders of eight or nine _laminae_; the third set of twelve or
thirteen; the fourth set of fifteen, and so on to the seventh or eighth
set, when each grinder consists of twenty-two or twenty-three: and it
may be added, that each succeeding grinder takes at least a year more
than its predecessor to be completed."[85]
As each tooth advances, only a small portion pierces the gum at once;
one of twelve or fourteen _laminae_, for instance, shows only two or
three of these through the gum, the remainder being as yet imbedded in
the jaw; and in fact the _tooth is complete at its fore part_, where it
is required for mastication, _while behind it is still very incomplete_;
the laminae are successively perfected as they advance. The molar of an
Elephant _can never, therefore, be seen in a perfect state_: for if it
is not worn in front, the back part is not fully formed and is without
fangs; and when the structure of the hinder portion is perfected, _the
front part is already gone_.
"When the complex molar cuts the gum, the cement is first rubbed off the
digital summits; then their enamel cap is worn away, and the central
dentine comes into play with a prominent enamel ring; the digital
processes are next ground down to their common uniting base, and a
transverse tract of dentine, with its wavy border of enamel, is
exposed; finally, the transverse plates themselves are abraded to their
common base of dentine, and a smooth and polished tract of that
substance is produced. From this basis the roots of the molar are
developed, and increase in length, to keep the worn crown on the
grinding level, until the reproductive force is exhausted. When the
whole extent of a grinder has thus successively come into play, its last
part is reduced to a long fang supporting a smooth and polished field of
dentine, with sometimes a few remnants of the bottom of the enamel folds
at its hinder part. Then, having become useless, it is attacked by the
absorbent action, by which, and the pressure of the succeeding tooth, it
is finally shed."[86]
With these physiological facts ascertained, let us proceed to the
determination of the actual age of our noble Dauntelah. The molar in
present use has a length of about nine inches, and a diameter of three
and a half. Its crown is crossed by about eighteen enamel-plates; of
which the anterior ones are much worn away, while the hinder ones can
scarcely be counted with precision, as they have not wholly cut their
way through the gum. These characters indicate the fifth molar (or set
of molars) of the whole life-series. And the following facts will help
us now to fix the actual age, at least approximately.
The first molar cuts the gum at two weeks old, is in full use at three
months, and is shed in the course of the second year. The second cuts
the gum at about six months, and is shed in the fifth year. The third
appears at two years, is in full use about the fifth year, and finally
disappears about the ninth year. In the sixth year the fourth breaks
from the gum, and lasts till the animal's twenty-fifth year. The fifth
cuts the gum at the twentieth year, is entirely exposed soon after the
fortieth, and is thrust out about the sixtieth year, by the advance of
the sixth molar, which appears at about fifty years old, and probably
lasts for half a century more. If others succeed this,--a seventh and
even an eighth, as some assert,--these would carry on the Elephant's
life to two or three centuries, in accordance with an ancient opinion,
which is in some degree countenanced by modern observations.
To come back, then, to the case before us, since the fifth molar has its
fore part much worn, and the posterior laminae scarcely yet protruded
from the gum, it follows that this Elephant is now not far from the
fortieth year of his life, a deduction which well agrees with the
dimensions of his tusks, and his appearance of mature vigour.
Can you detect a flaw in this reasoning? And yet how baseless the
conclusion, which assigns a past existence of forty years to a creature
called into existence this very day.
X.
PARALLELS AND PRECEDENTS.
(_Man._)
"Once, in the flight of ages past,
There lived a Man,--and who was he?
Mortal, howe'er thy lot be cast,
That man resembled thee."--MONTGOMERY.
We have knocked at the doors of the vegetable world, asking our
questions; then at those of the lower tribes of the brute creation, and
now at those of the higher forms; and we have received but one
answer,--varying, indeed, in terms, but essentially the same in
meaning,--from all. And now we have one more application to make; we
have, still in our ideal peregrination, to seek out the newly-created
form of our first progenitor, the primal Head of the Human Race.
And here we behold him; not like the beasts that perish, but--
"Of far nobler shape, erect and tall,
Godlike erect, with native honour clad,
In naked majesty, as lord of all."
The definitive question before us is this: Does the body of the Man just
created present us with any evidences of a past existence, and if so,
what are they? And that we may rightly judge of the matter, we will, as
on former occasions, call in the aid of a skilful and experienced
physiologist, to whom we will distinctly put the question.
_The Physiologist's Report._
In replying to your inquiry concerning the proofs of a past existence in
the Man before me, I must treat of him as a mere animal,--a creature
having an organic being.
And, first, I find every part of the surface of his body possessing a
nearly uniform temperature, which is higher than that of the surrounding
atmosphere. There is, moreover, on all parts of the body, a tinge of
redness, more or less vivid in certain regions. The heat, and the
carnation tinge, alike indicate the presence of blood, arterial blood,
diffused throughout, and, in particular, occupying the capillaries of
the superficial parts. Every drop of this blood is preceded and
succeeded by other drops, every one of which has been impelled out of
the heart by its constant contractions.
But the very existence of this blood supposes the pre-existence of chyle
and lymph, out of which it has been constructed. The chyle was formed
out of chyme, changed by the action of the pancreatic and biliary
secretions. Chyme is food, chemically altered by the action of the
gastric juice. So that the blood, now coursing through the arteries and
veins, implies the previous process of the reception of food. And these
pancreatic and biliary secretions, which are essential to the conversion
of chyme into chyle,--and therefore into blood,--do you ask their
origin? They were prepared, the one by the pancreas, the other by the
liver, from blood already existing,--blood _previously formed_ of chyle
with the addition of bile, &c.--and so indefinitely.
Again, the blood in these capillary arteries is of a bright scarlet hue,
which it derives from its being charged with oxygen. This it received in
the _lungs_, parting at the same time with the carbon which it had taken
up in its former course. The lungs then must have existed _before_ the
blood could be where and what it is, viz. arterial blood in the
capillaries of the extremities; before it was driven out of the heart,
since it was transmitted from the lungs through the pulmonary veins
into the heart, thence to be pumped into the arterial system.
But since all the tissues of the body are formed from the blood, the
lungs were dependent on already-existing blood for their existence. And
as the formative and nutrient power is lodged exclusively in _arterial_
blood, the very blood out of which the lungs were organized was
dependent on lungs for oxygenation, without which it would have been
effete and useless.
Here then is a cycle of which I cannot trace the beginning.
But further. On the extremities of the fingers and of the toes, there
are broad horny _nails_. These I trace down to the curved line where
they issue from beneath the skin, and whence every particle of each nail
has issued in succession. They are composed of several strata of
polygonal cells, which have all grown in reduplications of the skin,
forming compressed curved sheaths (_follicles_); stratum after stratum
of cells having been added to the base-line, as the nail perpetually
grew forwards. About three months elapse from the emergence of a given
stratum of cells, before that stratum becomes terminal; and therefore
each of these twenty-four finger- and toe-nails is a witness to three
months' past existence.
[Illustration: GROWTH OF HAIR (_magnified_).]
The head is clothed with luxuriant _hair_, composed of a multitude of
individual fibres, each of which is an epidermic appendage, essentially
similar to the nails. Every hair is contained at its basal extremity in
a delicate follicle, where it terminates around a soft vascular bulb,
made up of blood-vessels and nerves. On the surface of this living bulb
the horny substance is continually secreted and deposited in layers,
each of which in succession pushes forward those previously made, till
the tip extrudes from the follicle of the skin, after which it continues
to grow in the same way, as an external hair. The tip is gradually worn
away; and thus the constant growth cannot, in general, cause it to
exceed a certain given length. Each of the thousands of hairs with which
this majestic head is clothed, bears witness to past time; and as the
increase of hair is about an inch per month, and as this hair is about
four inches in length, we have here thousands of witnesses to at least
four months of previous history.
The bones which make up the firm and stately fabric about which this
human body is built, are no productions of a day. Long before this they
existed in the form of cartilages. In these, minute arteries began to
deposit particles of phosphate of lime, around certain centres of
ossification, doing their work in a determinate order, and in regular
lines, so as to form continuous fibres. These fibres, aggregated, and
connected by others, soon formed a texture of spicula or thin plates.
Now take as an example a cylindrical hollow bone, as that of the thigh.
Here the spicula were arranged longitudinally, parallel to the axis of
the bone: preserving the general form of the cartilage which constituted
its scaffolding.
But the bone required a progressive increase in size. In its early
state, moreover, it was not hollow, but solid. Changes must have taken
place to bring it to its present dimensions and condition. These were
effected by the actual removal of some parts, simultaneously with the
deposition of others.
At a certain stage of ossification, cells were excavated by the action
of the absorbent vessels, which carried away portions of bony matter
lying in the axis of the cylindrical bone. Their place was supplied by
an oily matter, which is the marrow. As the growth proceeded, while new
layers were deposited on the outside of the bone, and at the end of the
long fibres, the internal layers near the centre were removed by the
absorbent vessels, so that the cavity was further enlarged. In this
manner the outermost layer of the young bone gradually changed its
relative situation, becoming more and more deeply buried by the new
layers which were successively deposited, and which covered and
surrounded it; until by the removal of all the layers situated near to
the centre, it became the innermost layer, and was itself destined in
its turn to disappear, leaving the new bone without a single particle
which had entered into the composition of the original structure.[87]
These processes have been the slow and gradual work of years, of the
lapse of which years the bones are themselves eloquent witnesses.
Within the mouth there are many _teeth_. I will not now speak of their
exact number, nor of some other particulars concerning them, because I
mean to return to them presently; but I look only at their general
structure and origin. Each tooth consists of three distinct parts, the
central portion, which is _ivory_; the exceedingly hard, polished,
glassy coat of the crown, which is _enamel_; and a thin layer of bone
around the fang, which is the _cement_.
Before either of these appeared, a minute papillary process of vascular
pulp was formed in a cavity of the jaw. Over the pulp was spread an
excessively thin membrane, which secreted from the blood, and deposited,
a thin shell of bony matter, or ivory, moulded on the form of the pulp.
Successive layers of ivory were then added, from within; the pulp
diminishing in a corresponding ratio. The cavity of the jaw at the same
time deepened, and the pulp lengthened downward into the space thus
provided; layers of bony substance being gradually deposited upon it, as
above.
[Illustration: SECTION OF HUMAN TOOTH (_magnified_).]
The cavity itself was lined with a thick vascular membrane, united to
the papilla at its base. Within the space lying between this membrane
and the pulp, there was deposited from the wall of the former a soft,
granular, non-vascular substance, known as the enamel organ. The cells
on the inner surface of this substance then took the form of long,
sub-parallel prisms, set in close array, perpendicular to the surface of
the tooth. Earthy matter was progressively deposited in them, by which
they became the exceedingly dense and hard enamel of the crown. The
cement of the fang was then formed by a slight modification of the
process which had produced the enamel.
Here, then, are several distinct and important processes, effected in
regular and immutable succession, each requiring time for its
performance, and all undeniably witnessed-to by the structure of every
tooth here seen.
As I have thus proved the _fact_ of life existing in this human body for
some time previous to the present moment, I now proceed to inquire how
far its structure may throw light on the _actual duration_ of that past
life. How far can we ascertain its chronology?
The stature of the Man before me is about six feet. An infant at birth
is from eighteen to twenty-one inches in length. At ten years old the
average stature is about four feet. Six feet may be taken as the full
adult height of man; and this is attained from the twenty-first to the
twenty-fifth year. The stature of this individual would therefore
indicate an age not less than twenty-one years.
On the front of the throat I perceive a strongly-marked, angular
prominence, formed by the union of the two plates of the thyroid
cartilage. The prominence of this angle is due to the enlargement of the
larynx; and it is accompanied by a deepening of the pitch of the voice,
producing the full rich sounds that we have this instant heard, as the
Man chanted his song of praise. These tones, and this projection of the
thyroid cartilage, are equally distinctive marks of puberty, and do not
appear till about the sixteenth or seventeenth year.
The chin, and sides of the face, are clothed with a dense bush of crisp
hair,--the beard. This is a distinctive mark of the adolescent period,
and may be taken as indicating an age not less than twenty years.
On again examining the mouth, I find the teeth are thirty-two in
number; viz., four incisors, two canines, four pre-molars, and six true
molars, in each jaw. None of these existed (at least visibly) during the
first seven years of life; in that period they were represented by the
milk-teeth of infancy. The appearance of the middle pair of incisors
occurred at about the eighth year; the lateral incisors at nine; the
first pre-molars at ten; the second at eleven; the canines at about
twelve; the second molars at thirteen or fourteen; and the third molars,
or _dentes sapientiae_, at about seventeen or eighteen.
The state of the dentition, then, points to an age certainly not less
than the period just named. How much more it may be, we must gather from
other sources.
I come now to certain phenomena which are not appreciable to us on mere
external examination; but which I am able with certainty to predicate.
And the first of these is the proportion of arterial to venous blood in
the capillaries. In infancy, the arterial capillaries contain far more
blood than the capillary veins; in old age, the proportion is exactly
reversed; whereas, in maturity, the ratio is just equal. Now, here there
is a very small preponderance of arterial blood, indicating a period
but slightly remote from maturity on the side of youth; well agreeing
with the conclusion arrived at from previous premises, of some twenty to
five-and-twenty years.
Other and more marked manifestations occur in the condition of the
skeleton. In the spine, I find _the spinous and transverse processes_ of
the several vertebrae are completed by separate _epiphyses_, the
ossification of which does not commence till after puberty, and the
final union of which with the body of the bone does not occur till about
the age of twenty-five years.
Each _vertebra_, moreover, has attained a smooth annular _plate_ of
solid bone, covering a surface that was previously rough and fissured,
which is invariably added at the same period.
The _ossification of the sacrum_ also has reached its culminating point.
At the age of puberty, the component vertebrae began to unite from below
upwards, and the two highest have now coalesced; which also marks a
period of life not earlier than the twenty-fifth year. The whole united
mass, moreover, is furnished on each side with thin bony plates, the
appearance of which is no less characteristic of the same age.
Each of the _ribs_ is here furnished with two _epiphyses_, one for the
head and the other for the tubercle; the ossification of these began
soon after puberty; but their union with the body of the bone, as
presented here, has taken several years to accomplish.