Omphalos Part 13

See yonder stately bird, nearly of the height of man, marching among the luxuriant musa-groves, and feeding on the succulent fruits. There is nothing very admirable in its coa.r.s.e, black, hair-like plumage; but the rich hues of its naked neck, azure, purple, and scarlet, of the most vivid intensity, attract the gaze. The most remarkable feature in its physiognomy, is the singular, tall ridge of horn on its head, which, like the crested helmet of some mailed warrior, imparts an air of martial prowess to the bird, little in accordance with its peaceful habits.

This protuberance is altogether a development of age. The skull, in the youth of the Ca.s.sowary, was scarcely more elevated than that of a chicken; but in the lapse of years, the bony ridge, encased in horn, has gradually elevated itself to the height which it now possesses.

Here again we have a record of time, which is belied by the fact of the bird's recent creation.

What is the glorious train of the Peac.o.c.k, all filled with eyes, but a false witness of the same kind? It leads us to infer that the bird is three years old at least, since before that period, the covert feathers, which are to form the splendid ornament of maturity, are not developed.

What are the lengthened tail-plumes of most refulgent blue, that adorn the Fork-tailed Humming-bird (_Trochilus forficatus_); what the gorgeously golden tail of the Resplendent Trogon; what the elegant lyre-shaped feathers of the Menura; what the l.u.s.trous plumage of the Birds of Paradise,--all of which have been but this hour created,--but so many testimonies, unworthy of confidence, to a past history?

But, further, every individual feather of this beautiful array of plumage concurs in bearing its unblushing witness to the same untruth.

What says the physiologist, who is able to read off these autographic records?

[Ill.u.s.tration: GROWTH OF A FEATHER.]

"A little while ago, the tips of these feathers were seen each protruding from the extremity of a thick, opaque tube; and a little while before that, the tube itself, was a closed capsule, imbedded in a deep follicle of the skin. If you had then cut open the capsule, you would have found two concentric membranous tubes investing a highly vascular secreting pulp, abundantly supplied with nerves and blood-vessels through an orifice at the bottom of the capsule, and destined to form the substance of the coming feather. Indeed, you would have seen the soft, newly-formed barbs folded round the central organized matrix; and below, the incipient quill, filled with the living pulp-cells, and their blood-vessels, which were destined subsequently to wither up and collapse into the light skinny pith which you see in the perfectly matured feather. These are stages which each of these hundreds of feathers has pa.s.sed through; and these are but a single generation, which have replaced former series that have been lost in the process of moulting, every one of which had in its turn pa.s.sed through exactly corresponding stages, and so on backward, till we reach the first race of feathers, which were already partly developed when the chick burst forth from its imprisoning egg-sh.e.l.l."

So says the physiologist; but is he not most egregiously in error, since this is the day of these lovely beings' creation?

There goes the great Whale, the true Whalebone Whale, rolling and wallowing in the trough of the sea, and exposing his enormous black back like an island amidst the white foam, which he stirs up, "making the deep to be h.o.a.ry." We will use our privilege and take a peep into his mouth, as we did just now into that of the Shark.

What a cavern! and all bristling with long black hair! Why it seems as if the hair grew on the wrong side of his head--on the inside instead of the outside!

Nay, what you call hair is really the Whale's teeth, or what represents teeth. This is the interior free fibrous margin of the _baleen_, which descends in long triangular plates from the upper jaw. There are about two hundred plates on each side, set face to face, with an interval between, and the edges outward. The inward edge runs off into those long hair-like filaments, which also extend from the slender tip. And the whole forms an effective sifting apparatus, by which the volume of sea-water, which the huge creature takes into his mouth in feeding, is drained of the sea-blubbers, the worms, the mollusks, and other small matters, which const.i.tute the subsistence of this vast body.

Now each of these four hundred plates, some twelve feet in length, has grown from a minute sort of bud, in the upper jaw. Its base is hollow, resting on the formative pulp which is developed from the gum. The pulp is understood to be the immediate origin of the hairy fringe, while a dense vascular substance, seated between the bases of the plates, forms the plate itself. When the plate reaches a certain length, its diameter has become greatly attenuated, and its tip is constantly breaking away, leaving the hair projecting. There is therefore a continual disappearance of the substance of the plates at the tips, and a continual growth at the base to supply the deficiency; and even more, at least during the period of adolescence, because the actual dimensions of the plates have to be increased in the ratio of the growth of the whole animal.

Here, again, we read a record of past history. The Whale is known to be a long-lived animal; and a period of many years must have pa.s.sed in bringing these plates of baleen to their present maturity. Yet the vast organism before us has been created in its vastness but to-day.

On the most prominent shelf of yonder precipice, a sharp b.u.t.tress of naked limestone, stands an Ibex, guarding, like a watchful sentinel, the herd in the sheltered valley which own his leadership. The pair of n.o.ble horns, which are at once his defence and his pride, are marked throughout their ample curve with semi-rings, or k.n.o.bs, on their anterior side. These afford us an infallible criterion of the animal's age.

We can count in this Ibex fourteen of such prominent bosses. Now the horn in these animals is not shed during life, but consists of a persistent sheath of h.o.r.n.y substance, enveloping a bony core. Until full adult age, both the core of bone and the sheath of horn are continually growing; and in the spring, when there is an unusual augmentation of vital energy in the system, the increase is more than usually rapid. At this season, the new matter deposited in the corneous sheath acc.u.mulates in the form of one of these bosses, each of which is therefore produced at the interval of a year. As the first boss appears in the second year of the animal's age, we have but to add one to the number of the bosses on each horn, and we have the number of years which it has lived. The Ibex before us is just fifteen years old.

[Ill.u.s.tration: HORNS OF STAG;

In their successive developments.]

Yon Stag that is rubbing his branchy honours against a tree in the glade,--can we apply the same criterion to him? Not exactly: for the horns of all the Deer-tribe are of a different structure from those of the _Capradae_. They are bones of great solidity, not invested with any corneous sheath, but clothed for a certain portion of their duration with a living vascular skin, and are shed every year during life and as constantly renewed.

Yet the bony horns of the Stag are no less sure a criterion of age, at least up to a certain period--than are those of the hollow-horned Ibex.

In the spring of the second year of the Fawn, the horns first appear, seated on bony footstalks that spring from the frontal bone. The skin that covers these k.n.o.bs begins to swell and to become turgid with blood supplied by enlarging arteries. Layers of bone are now deposited, particle by particle, on the footstalks, with surprising rapidity, producing the budding horns, which grow day by day, still covered by the skin, which grows also in a corresponding ratio. This goes on till a simple rod of bone is formed, without any branches. When this is complete, the course of the arteries that supplied the skin is cut off by fresh osseous particles deposited in a thick ring around the base.

The enveloping skin then dies, and is soon rubbed off.

After a few months, the connexion of the now dead bone with the living is dissolved by absorption, and the horns fall off.

The next spring they are renewed again, but now with a branch or antler; and the whole falls again in autumn. Every spring sees them renewed, but always with an increase of development; and this increase is definite and well-known; so that the age of a Stag, at least of one in the vigour of life, can be readily and certainly stated.

For example, the individual Stag before us, now browsing so peacefully, has each horn composed of the following elements:--the beam, or main stem; two brow-antlers; one stem-antler, and a coronet of four snags, or royal-antlers, at the summit. This condition is peculiar to the seventh development, to which if we add one year for the hornless stage of fawnhood, we obtain eight years, as, beyond all doubt, the age of this Stag.

Both of these examples, however, the Ibex and the Stag, though so conclusive, and seemingly so irrefragable, are rendered nugatory by the opposing fact of a just recent creation.

See this Horse, a newly created, really wild Horse,

"Wild as the wild deer, and untaught, With spur and bridle undefiled,"--

his sleek coat of a dun mouse-colour, with a black stripe running down his back, and with a full black mane and tail. He has a wild spiteful glance; and his eye, and his lips now and then drawn back displaying his teeth, indicate no very amiable temper. Still, we want to look at those teeth of his. Please to moderate your rancour, generous Dobbin, and let us make an inspection of their condition!

Now notice these peculiarities. The third pair of permanent incisors have appeared, and have attained the same level as their fellows; all are marked with a central hollow on the crown, the middle pair faintly: the canines have acquired considerable size; they present a regularly-convex surface outwardly, without any marks of grooving on the sides; their inner side is concave; their edges sharp; the third permanent molar has displaced its predecessor of the milk set, and the sixth is developed.[83]

This condition of the teeth infallibly marks the fifth year of the Horse's age. A year ago the third incisor was only just rising; the canines were small, and strongly grooved, and the third milk grinder was yet existing. A year hence, the central incisors will be worn quite flat, and their marks obliterated; the canines will be fully grown tusks, the second molar will have reached its full height, and all the teeth will be of the same level. We can then with perfect confidence a.s.sert this to be a five-year old Horse. And yet, if we do so, we shall a.s.sert a palpable untruth, for the young and vigorous stallion has been created to-day.

[Ill.u.s.tration: SKULL OF BABIROUSSA.]

In the thickets of this nutmeg grove beside us there is a Babiroussa; let us examine him. Here he is, almost submerged in this tepid pool.

Gentle swine with the circular tusk, please to open your pretty mouth!

Here are four incisors in the upper jaw; _at one time there were six_.

The canines of the same jaw having pierced through the flesh and skin of the face, have grown upward and curved backward like horns; nay, they have nearly completed a circle, and are threatening to re-enter the skull; _once these tusks had not broken from the gums_. There are two pre-molars: _once there were four_. There are three molars, of which the first is worn quite smooth: _once this surface was crowned with four cones; but the third molar had not then appeared_.

Away to a broader river. Here wallows and riots the huge Hippopotamus.

What can we make of his dent.i.tion? A strange array of teeth, indeed, is here; as uncouth and hideous a set as you may hope to see. Yes, but the group is instructive. We will take them in detail.

Look at the lower jaw first. Here are two large projecting incisors in the middle, with their tips worn away obliquely on the outer side, by the action of their opponents in the upper jaw, which are also worn inwardly. The outer incisors, both above and below, are also mutually worn in like manner. The lower canines form ma.s.sive tusks, curved in the arc of a circle, ground away obliquely by the upper pair; which are short and similarly worn on their front edges. There are three pre-molars on each side, below and above, much worn: once there was a fourth, but it was shed early. Lastly, we find three molars, whose crowns are ground down so as to expose two polished areas of a four-lobed figure. A little while ago, these double areas were trilobate, but at first there were no smooth areas at all; for these are but sections, more or less advanced, of the conical k.n.o.bs, with which the crown of the molar was originally armed.[84]

In both these examples, the polished surfaces of the teeth, worn away by mutual action, afford striking evidence of the lapse of time. Some one may possibly object, however, to this: "What right have you to a.s.sume 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 const.i.tutes 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!

[Ill.u.s.tration: SKULL OF HIPPOPOTAMUS.]

"Trampling his path through wood and brake, And canes, which, crackling, fall before his way, And ta.s.sel-gra.s.s, 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.

[Ill.u.s.tration: 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 a.s.sist 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 const.i.tuent 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 s.p.a.ce, 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]