Fig. 116.
Fig.116.—A section of the cranium of a full-grown African Elephant, taken to the left of the middle line, and including the vomer (Vo) and the mesethmoid (ME);an, anterior, andpn, posterior narial aperture. ×1⁄12. (From Flower'sOsteology.)
The skull is large and massive. Its large and heavy character is, as has been stated in the definition of the sub-order, due to the immense development of air cavities in the diploe; the diameter of the wall of the skull is actually greater than that of the cranial cavity. These cavities are not obvious in the young animal. They are most conspicuous in the roofing bones of the skull, but are seen elsewhere, and thicken the basis cranii,the maxillae, and so forth. This state of affairs, together with the presence of the huge tusks, has, as it were, pushed back the nasal orifices to near the top of the skull in a very Whale-like fashion. As in the Cetacea, the nasal bones are limited in size, and the premaxillae send up processes to join the frontals and the nasals. There is a straight and somewhat slender zygomatic arch, but the orbit is not separated from the temporal fossa. The malar bone is small, and, as in Rodents, forms the middle part of the zygoma. This is not the case with most Ungulata. The symphysis of the mandibles forms a spout-like rim. The scapula has a narrow prescapular, but a very wide postscapular region. The spine has a strong process projecting backwards from near its middle; this is a point of likeness to certain Rodents. No Elephant has a clavicle. The most remarkable feature about the fore-limb is the separation and crossing of the radius and ulna. The arms of these animals are permanently fixed in the position of pronation. The foot is short, and the bones of the carpus are serially arranged. There are, however, traces of a commencing interlocking of these bones in many forms. The hind-feet are somewhat smaller than the fore-feet, and the tibia and fibula are both developed.
As to the teeth, this genus is to be distinguished from allied forms by the presence of tusks in the upper jaw only. These tusks have no bands of enamel such as characterise those ofMastodon. They are incisors. There is, however, a trace of the former enamelling in the shape of a patch at the tip, which soon wears away. The molar teeth ofElephasare so large that the jaws cannot accommodate more than at the most two and a part of a third at a time. These are gradually replaced by others to the number of three, the replacement of teeth suggesting that of the Manatee. Each molar is deeply ridged, the interstices between the ridges being filled up with cement. As the tooth wears away, therefore, the surface continues to be flat. Each ridge consists of a core of dentine surrounded by a coat of enamel. The number of these ridges varies greatly from species to species. The Indian Elephant is one of those which have the greatest number of plates in a single tooth, as many as twenty-seven.[130]Of the six molars whicheventually appear, the first three are considered to correspond to premolars. But successional teeth are rare in the genus; that is to say as far as concerns the molars, for the tusks have their milk forerunners. As to the molars it is apparently onlyE. planifronswhich certainly shows a milk dentition. InMastodonand older types a milk dentition is commoner.
The viscera of the Elephant have been examined by many zoologists. The latest paper, dealing chiefly with the African species, but containing facts about its Indian congener also, is quoted below.[131]The Elephant is remarkable in possessing, in addition to the three usual pairs of salivary glands present in mammals, a fourth, situated in the molar region, and opening on to the cheek by many pores. This gland is especially well developed in Rodents. There is a gland which may be mentioned in this connexion, though it opens externally between the eye and ear, known as the temporal gland; its use does not seem clear. The thoracic cavity of the Elephant, as may be inferred from the large number of ribs, is very large as compared with the abdominal.
The stomach is simple in form, and the epithelium of the oesophagus does not extend into it as is the case with the Horse and Rhinoceros. A gland or a collection of smaller glands occurs in the stomach, and recalls the "cardiac gland" of the Wombat and the Beaver, also that of the Giraffe. The large intestine is long, rather more than half the length of the small intestine. The caecum is well developed in these animals. The liver has a very simple form, being but slightly lobulated. It is actually only bilobed, but it is important to notice that this division does not correspond to the two halves of the liver. As shown by the attachment of the suspensory ligament, one half consists of the left lateral lobe alone, the other half embracing the remaining primary lobes. The simplicity of the liver looks like an archaic character. No Elephant has a gall-bladder. The lungs again are simple in form through their slight lobulation. Each half in fact is without subdivisions, and is of a triangular form. In this the Elephants resemble the Whales, as in the simple liver. In both cases probably the likeness is due to the permanence of primitive features of organisation. The brain[132]of the Elephanthas hemispheres which are extremely well convoluted; but they leave the cerebellum entirely uncovered. This suggests a brain which is a great specialisation of a low type. The brain has been particularly compared with that of the Carnivora, with which group the Elephants agree in the characters of the placenta. It is, however, always a matter of the very greatest difficulty to compare the brains of mammals belonging to different orders.
There are but two living species of Elephant, of both of which we shall now proceed to give some account. Only a few of the rather numerous fossil forms can be touched upon here.
The African Elephant,E. africanus, has been sometimes referred to a distinct genus or sub-genus,Loxodon, by reason of the lozenge-shaped areas on the worn grinding-teeth. It lives, as its name denotes, in Africa. This species has a number of external features which enable it to be distinguished from the Oriental Elephant. The head slopes back more, and has not the two rounded bosses which give so wise a countenance to the Indian species. The ears are very much larger. The tip of the trunk has a slight triangular projection on both the lower and the upper part of the circumference of the aperture. There are four nails on the fore-feet and three on the hind. As in the Indian form, the toes are all bound together, and do not appear for any part as free digits. A thick pad of fat, etc., makes the animal when alive look as if plantigrade, whereas it is, as a matter of fact, digitigrade. In internal features the most prominent difference fromE. indicusis in the molar teeth, which are ridged by much fewer ridges. The outside number for a single tooth in the present species is 10 or 11. InElephas indicuson the other hand there are as many as 27.
The African Elephant, thinks Sir Samuel Baker, reaches a height of about 12 feet, and it will be remembered that the notorious "Jumbo" was found to be 11 feet high at the shoulder. The tusks are found in both sexes, as in the Indian beast, but are relatively larger in the female in the species now under consideration. It is also a rather more active creature, and is more savage;[133]however it can be tamed, as is shown by severalspecimens which have been and are in the possession of the Zoological Society, and other proprietors. It was apparently used in the past. Certain Carthaginian coins are stamped with a figure of the African Elephant; but in Africa no attempts are now made to utilise this creature except for food and ivory.
Fig. 117.
Fig.117.—African Elephant.Elephas africanus.×1⁄56. (After Sir Samuel Baker.)
The meaning of an Elephant as an emblem. upon a coin appears to be eternity, and there is no question but that theElephant is a long-lived animal. It is said that it hardly reaches proper maturity before forty, and that 150 years is not beyond probability in the way of longevity. Even longer periods have been assigned to it.
The tusks of the Elephant are by no means necessarily sexual adornments, used for fighting purposes only. The African Elephant is a most "industrious digger," and grubs up innumerable roots as food. It appears to be a fact that during these operations the right tusk is mainly used, and in consequence that tusk is shorter as well as thinner than the other. Two average tusks would weigh respectively 75 and 65 lbs., the latter of course being the weight of the more worn right tusk. These weights, it should be observed, by no means indicate the limits to which finely-developed tusks can attain. The very heaviest tusk known to Sir Samuel Baker[134]weighed 188 lbs. This was sold at an ivory sale in London in the year 1874. The pace of the African Elephant, says the same authority, is at most at the rate of fifteen miles an hour at first, and of course in a furious rush. This pace cannot be kept up for more than two or three hundred yards, after which ten miles an hour is a better approximation to the rate which can be kept up for long distances.
The Indian Elephant,Elephas indicus(orEuelephas indicus, if the genusLoxodonis to be accepted), is better known and has been longer known than the African. It occurs in India and Ceylon, and in some of the Malayan islands, the Elephants of which latter parts of the world have been regarded as a distinct form, an apparently unnecessary procedure.
Fig. 118.
Fig.118.—Indian Elephant.Elephas indicus.×1⁄54. (After Sir Samuel Baker.)
This species does not stand so high at the shoulder as the African; its back is more rounded in the middle. The trunk has but one pointed tip; there are five nails on the fore- and four on the hind-feet. As this species comes from India and the East, it has been longer as well as better known than the African form. Thus many of the stories and legends that have congregated round Elephants apply really to this form. As is well known, the Indian Elephant is much used as a beast of burden, and for other purposes where its huge strength renders it invaluable. But its great drawback as a servant of man is its great independability. On the one hand we have furious, vicious, and generally unreliableElephants, and on the other perfectly docile creatures, who obey the slightest hint from their driver. Huge though the Elephant is, it is frequently a timid beast. Sir Samuel Baker relates how one which he was riding fairly bolted at the sight of a Hare. Tobe bolted with by an Elephant is far from pleasing, though a rather exciting event. It makes for the nearest jungle at once, being, much more than the African species, an inhabitant of forest. And in rushing through the dense undergrowth, the occupiers of the Elephant's back are apt to be swept off or cut to pieces by innumerable thorns.
Elephants, no doubt of the Indian species, were used by the Persians in battle, and from fifteen which were captured at the battle of Arbela some notes were drawn up by Aristotle. In stating that the animal reaches an age of 200 years, the naturalist and philosopher was probably not very far out. The mode of Elephant-catching as related by Aristotle is that pursued at the present day. Then, as now, tame Elephants were made use of as decoys. Pliny,[135]who was apt to confound fact and fiction in a somewhat inseparable tangle, had something to say about Elephants, both Indian and African. Serpents, he thought, were their chief enemies, which slew them by coiling round them and thrusting their heads into the trunk, and so stopping respiration. In Europe Elephants were first seen in the yearB.C.280. Pyrrhus used them in his invasion, and copying his example the Romans themselves learnt to use Elephants. The first Elephant seen in England arrived in the year 1257, presented by the King of France to Henry III. It was kept in the Tower (for long afterwards a menagerie), and died at twelve years of age. Much use of the Elephant has been made in symbols. We have spoken of the African Elephant on Carthaginian coins as an emblem of eternity. The Oriental Elephant resting on the back of a tortoise and supporting the world is the same idea; and it is instructive to note that remains have been found in the Siwalik Hills of a tortoise which would have been actually big enough to support the creature, even "Jumbo," who weighed 6½ tons. Another symbol is that of an Elephant upon whose back is a child with arrows; this occurs on a medal of the Emperor Philip. It can perhaps hardly signify the eternity of a strong human feeling!
The intelligence of the Elephant has been both exaggerated and minimised. Perhaps the most elaborate attempt to endow the beast with unusual mental perceptions is that of Aelian, who related that an Elephant carefully watching his keeper, wrote after him with his trunk letters upon a board. That the animal doespossess a good deal of brains, seems to be shown by the way in which a well-trained animal will obey the slightest sign of the mahout in India. According to Sir Samuel Baker, localities which produce in abundance particular kinds of fruit are remembered, as well as the time at which the fruit will be at its best. Stories of revenge, which are numerous enough, attest, so far as their data are to be accepted as accurate, the power of memory possessed by the Elephant.
In spite of their longevity, however, Elephants, unlike Rome, have not been built for eternity. We can only find two living species; but in past times Elephants were very numerous. They commenced, so far as we know, in the Miocene.
The existing forms are known in a fossil, or at least sub-fossil state, from diluvial deposits; and it is interesting to note that the African Elephant had formerly a wider range than now. Its bones (described asE. priscus) have been met with in Spain and Sicily.
One of the best known of completely-extinct Elephants is the Mammoth,E. primigenius. This great Elephant in most respects more nearly approached the existing Indian Elephant. The teeth have quite as numerous plates. The tusks were enormous, reaching a maximum length of 15 feet; they were much curved upwards as well as outwards. A large tusk weighs as much as 250 lbs. The Mammoth was of exceedingly wide range. Not only was it found in various parts of Europe, but it was especially abundant in Siberia, as is exemplified by the fact that for the last two hundred years as many or more than 100 pairs of tusks annually have been sold from that region. It also occurred in America together with forms at least not far removed from it, such asE. columbianus. Mammoths have been more than once found as entire carcases in the frozen soil of Siberia. The first was discovered in the year 1799, and rescued some years later for the St. Petersburg Museum. This example showed that the Mammoth, unlike existing Elephants, was covered with thick wool mingled with long and more bristly hairs of some 10 inches in length. The softer wool formed a kind of mane beneath the neck, which hung down as far as the knees. Another carcase was discovered later by Lieut. Benkendorf, who did not save it, but was nearly swept along with it into the sea by a flood. These creatures died in the position in which they were found by being bogged when in search of vegetation or water.
How primeval man, with his inferior weapons, slew the Mammoth is not easy to understand; but that they were contemporaneous is clearly shown by associated remains, and by the notorious sketch of the Mammoth on a piece of its own ivory, in which curved tusks and a forehead like that of an Indian Elephant are plainly to be seen. Although it was only so recently as the year 1799 that an example of this great creature was actually studied on the spot, and removed to St. Petersburg, the existence of Mammoths and of ivory is a matter of much more ancient knowledge. M. Trouessart relates[136]that fossil ivory was known to the Greeks. Theophrastus spoke of ivory imbedded in the soil, and the tusks were recovered by the Chinese. It is a curious fact that the Chinese described and figured the Mammoth as a kind of gigantic Rat. The likeness between the elephantine molar and that of Rodents has been commented upon; but the existence of its tusks below the level of the ground led the Chinese Natural Historians to consider that the ways of life of the Mammoth were those of the Mole. As to the carcases themselves, the Chinese said that the flesh was cold, but very healthy to eat. This expression can hardly be explained, except upon the view that fresh carcases were known to that people long before they were known to us of the Western world. The value of the Mammoth ivory was known to antiquity; the famous Haroun-al-Raschid gave to King Charlemagne not only a pair of living Elephants, but a "horn of Licorne," which seems undoubtedly to have been a name for the tusks of the Mammoth. For in an account of the sacred treasures of Saint Denis, published in the year 1646, the author states this to be the fact.
The causes of the disappearance of the Mammoth are not easy to understand. Some held that it was a naked animal like the existing Elephants, and that the lowering of the temperature in Siberia proved fatal; it is, of course, now certain that it was clothed with dense woolly hair. Along with the bogged corpses of the great pachyderm, numerous trunks of pine-trees have been found, together with associated remains of other animals now extinct in that neighbourhood. Thus it is plain that Siberia was once covered by mighty forests, through which the Mammoth roamed. The decay of these forests, upon whose branches the Elephant fed, as is attested by the remains of pine leaves foundin the interstices of its teeth, was the signal for the disappearance of their most colossal inhabitant.
The large number of remains of this and of other extinct species ofElephasin this country gave rise to the supposition that they were Elephants brought over by Caesar to aid in the subjugation of these islands. The Rev. J. Coleridge (father of the poet) pointed out that though Caesar in hisCommentariesmade no mention of any such importation of Elephants, a passage in theStratagemsof Polyaenus expressly mentions that Cassivelaunus was confronted by the Romans with an Elephant clad in a coat of mail, by whose aid the crossing of the Thames was effected. At the time that attention was called to this (1757) it was not popular to hint at the possibility of fossils. So that fact, conveniently historical, served to explain away a difficulty. It is remarkable that the Elephant, common enough of course in Asiatic monuments, actually occurs in English architecture. Mr. Watkins, from whose interesting work (Natural History of the Ancients) a good many of the facts detailed here are drawn, tells us that the church of Ottery St. Mary has an Elephant's head sculptured on one of its pillars. The same ornament appears in Gosberton Church, Lincolnshire. Whether this has anything to do with a reminiscence of formerly existing Elephants is a hard question to answer. In this figure of an Elephant the trunk has a spiral representation, and the trunk of an Elephant is believed by some to be intended by the common "so-called Pictish ornamentation" in Scotland; this spiral alone is to be seen constantly. If it is a reduction of an Elephant to its simplest terms, it is highly interesting as an almost undoubted survival of remembrance of Elephants. For at such a period we cannot use the memories of Crusaders or others who may have visited the East to explain the facts. The sculptured Elephants' heads might conceivably be so explained.
The name Mammoth, thinks Mr. Watkins, may be derivable from the Arabic word Behemoth. He quotes a writer, who first described the beast in 1694, as using the two words indifferently. The Arabs, moreover, were then as they are now great ivory traders; and in the ninth and the two succeeding centuries explored the confines of Siberia, as they now do the forests of Africa, for ivory. The "Behemoth" of Job "eateth grass as an ox.... He moveth his tail like a cedar" (the Hippopotamus has a much morestumpy appendage). "Behold, he drinketh up a river, and hasteth not" is surely much more suggestive of the copious draughts of an Elephant than the possibly equally copious but not so visible libations of a Hippopotamus.
The most ancient of the true Elephants (genusElephas) isE. meridionalis. It is of the African type,i.e.the plates of the molar teeth are not abundant, and are not so many as in the existingE. africanus. It seems to have been one of the largest of Elephants, standing 4 metres high. Its remains are abundant in Europe, and are known also from England. Like this speciesE. antiquusis also of the African type. It was contemporary with man. Certain dwarf or "pony" races found in caves in Malta, and calledElephas melitensisorE. falconeri, are believed to belong to this species. Mr. Leith Adams, who described these[137]remains, placed them in two dwarf species called by the names used above, and found associated with them a larger form, which he referred toE. antiquus. The existence of these animals in Malta seems to argue at least its former larger dimensions, and the presence of more abundant fresh water. The remarkable swimming capabilities of the Elephant do not necessarily imply either a former absence of land connexion or, on the other hand, its existence. Nor as a third possibility can it be suggested that the dwarf size argues an island of limited dimensions, when we bear in mind the huge tortoises of the Galapagos and some other islands. It is important to notice that Elephants of the African type (Loxodon) were not formerly absent from India.E. planifronswas one of these.
The genusStegodonis so called from the fact that the molar teeth, seen in longitudinal section, present a series of roof-shaped folds, the interstices between which are not, or are, imperfectly filled up with the cement which inElephasreduces the surface of the teeth to a level plane. This genus is exclusively Asiatic, and is Miocene to Pleistocene in time range. The number of ridges on the molars is small, not more than two. The incisors (tusks) have no enamel; the skeleton generally is like that ofElephas, between which andMastodonthe present genus is intermediate. Among the four or five species isS. ganesa(called after the Indian Elephant-headed divinity), with tusks 10 feet long, to be seen at the British Museum of Natural History.
The last genus of the family Elephantidae isMastodon, so called from the structure of the molar teeth. These are provided with but few transverse ridges, not more than five, so that their structure is intermediate between those ofDinotheriumand those ofStegodon. Between the ridges are sometimes isolated, boss-like protuberances (whence the name ofMastodon), produced by a subdivision of the ridges. There is either but little or no cement between the ridges. This genus differs from nearly all other Elephantidae by the possession of milk molars, which occasionally persist throughout life, the permanent dentition in those cases being a mixture of milk and permanent teeth, as has been (erroneously) stated of the Hedgehog.[138]
The tusks (incisors) are sometimes present in both jaws, and as they have, during youth at any rate, a coating of enamel, the likeness to the chisel-shaped incisors of Rodents is patent. In connexion with the implantation of incisors in the lower jaw, many species have a prolongation of the bones of that part of the skeleton. In the bones, generally, there is not very much difference fromElephas, but the forehead is a little less pronounced. The genus existed from the Miocene and became extinct in the Pleistocene. It was nearly world-wide in range, being known from all four continents. Naturally with this very wide range was associated a large number of species. Zittel enumerates no less than thirty-two.
This genus is the only one of the Elephantidae which extended its range into South America, where the remains of two species occur. The bones of these great Elephants have attracted attention for some centuries. They were often held to be the bones of giants (as they actually were!), and in one case were ascribed to a deceased monarch, Teutobochus. The American Indians considered that equally gigantic men lived who were able to combat these great Proboscideans. There are legends of the Mastodons as living animals, which is quite probable, considering their geological age. There is a curious parallelism between the legends of two such widely-separated localities as North America and Greece. Buffon relates how among the Indians of Canada there was a belief that the Great Being destroyed both Mastodons and men of equal proportions, with thunderbolts. With this we may perhaps compare the story of the destruction of Typhoeus by Zeus, whoalso used thunderbolts. One of the giants was not slain, but was compelled to stand and bear up the heavens. Atlas holds thus the position of the Elephant supporting the globe of Indian mythology.
Fig. 119.
Fig.119.—Dinotherium giganteum.Side view of skull,1⁄15th natural size. Miocene, Germany. (After Kaup.)
The genusDinotherium, sole representative of the familyDinotheriidae, differs in a number of important particulars from the true Elephants. In the Elephants, if there is but a single pair of incisors, these are found in the upper jaw; inDinotheriumthere is apparently but a single pair, but these are implanted in the lower jaw, the symphysis of which is much prolonged and greatly bent downwards, so that the tusks emerge at right angles to the long axis of the head, and are even bent backwards. The molar teeth are five in number on each side of each jaw and are bi- or tri-lophodont, not unlike those of the Tapir. There is no cement in the valleys between the ridges of these teeth, and there is a regular succession, the premolars being two and the molars three.[139]All the teeth are in use at the same time,their small size enabling them to be accommodated in the jaw together. The skull ofDinotheriumis lower than that ofElephasorMastodon. The bones of the skeleton generally are like those ofElephas.
Though a suggestion of marsupial bones attached to the pelvis has been discredited, there is no doubt thatDinotheriumoccupies the most primitive position among the Proboscidea; but at the same time it cannot be regarded as the ancestor of Elephants, as it is so much specialised in various ways. The incisors for one thing forbid this way of looking at the creature. It is an ancient genus found in beds of Miocene age in Europe and Asia. It is not known from America. The creature was larger than any Elephant. Eighteen feet in length has been assigned to it. The enormous weight of the lower jaw and tusks seems to argue that it was at least partially aquatic in habit, and that it may have used these tusks for grubbing up aquatic roots or for mooring itself to the bank. At first there were naturalists who considered it as an ally of the Manatee, and the skull is not unsuggestive of that of the Sirenia.
Pyrotheriumhas been referred to the Proboscidea; but our knowledge of that form is limited to a few teeth from Patagonian rocks of an uncertain age.[140]They are simple bilophodont molars, very like those ofDinotherium. A tusk has been found in the neighbourhood of these teeth which may possibly belong to the same animal; but it is uncertain.
This group of small mammals contains only one well-marked genus which is usually namedHyrax, althoughProcaviaseems to be the accurate term. Popularly these creatures are known as Coneys. They have a singular resemblance to Rodents, the short ears and much reduced tail, besides the squatting attitude adopted, contributing to this merely skin-deep likeness. They agree with other Ungulates in the structure of the molar teeth, which are much like those ofRhinoceros; in the absence of a clavicle; in the absence of an acromion; in the reduction of the digits of the limbs to four digits in the manus and three in the pes. On theother hand they differ from most Ungulates in the incisors growing from persistent pulps, a point in which they resemble the Rodentia. The muffle also is split as in those animals. The Hyracoidea are peculiar in the fact that in addition to the caecum at the junction of the small and large intestines, there are a pair of caeca (bird-like in being paired) some way down the large intestine. The dorsal vertebrae are unusually numerous, 22. The adult dentition according to Woodward,[141]who has recently examined the matter, is I 1/2 C (1/0) Pm 4/4 M 3/3, while the milk dentition is I 3/2 C 1/1 Pm 4/4.
Fig. 120.
Fig.120.—Cape Hyrax.Hyrax capensis.× ⅛.
The inclusion of the canine of the permanent set of teeth in brackets signifies that it is the milk canine which occasionally persists. It should further be remarked about the teeth that they are both hypselodont and brachyodont, the extremes being connected by intermediate forms. Another peculiarity of the genus is the dorsal gland, which is covered with hair of a different colour to that covering the body generally. This is present in all species.
The genusHyrax(the most recent authority on the subject, Mr. Oldfield Thomas,[142]only allows one genus) is limited in its range to Ethiopian Africa and to Arabia, including Palestine, It does not reach Madagascar. Mr. Thomas allows fourteen species with two or three sub-species.
Some of the Coneys live in rocky ground, while others, formerly placed in the genusDendrohyrax, frequent trees, in holes in which they sleep. The Coney of the Scriptures is familiar, who is "exceeding wise," though a "feeble folk." But the further observation that he "cheweth the cud but divided not the hoof," is obviously entirely wrong. As to the wisdom, it is said that this beast is too wary to be taken in traps; while the suggestion of chewing the cud is, according to Canon Tristram, to be interpreted in the light of a habit of working and moving its jaws which the animal has. The traveller Bruce kept one in captivity to see if it did really chew the cud, and found that it did!
Fig. 121.
Fig.121.—Bones of the manusA, of Tapir (Tapirus indicus). ×1⁄5.B, of Rhinoceros (Rhinoceros sumatrensis). ×1⁄5.C, of Horse (Equus caballus). × ⅛.c, Cuneiform;l, lunar;m, magnum;p, pisiform;R, radius;s, scaphoid;td, trapezoid;tm, trapezium;u, unciform;U, ulna;II-V, second to fifth digits;VinB, andIIandIVinC, represented by rudimentary metacarpals. (From Flower'sOsteology.)
These Ungulates derive their name, which is that given by the late Sir Richard Owen, from the fact that the middle digit of the hand and foot is pre-eminent. As will be seen from Fig. 121, the axis ofthe limb passes through the third finger, which is larger than any of the others, and is symmetrical in itself. In this the present group contrasts with the Artiodactyla, where the axis is not "mesaxonic," but where there are two digits, on either side of the axis, which are symmetrical with each other. This arrangement of the limbs is highly characteristic, but appears to be not quite universal. In the Titanotheres, which form a group of the Perissodactyles, the fore-limbs are not quite accurately mesaxonic. Nor on the other hand can all Ungulates which show the Perissodactyle condition be safely included in the present group. The ancient Condylarthra and the Litopterna show precisely the same state of affairs. But other features in their organisation lead to their separation from the Perissodactyles, of which, however, the Condylarthra are probably ancestors. The Litopterna on the other hand, which possess even one-toed members likeEquus, are believed to represent a case of parallelism in development. The number of functional toes varies from four to one. In the ankle joint the astragalus either does not, or does only to a comparatively slight extent, articulate with the cuboid as well as with the navicular bone. Moreover the fibula when present does not as a rule articulate with the calcaneum. In the opposed group of Artiodactyles the precise reverse of these conditions obtains. It is usually stated as part of the definition of this group that they do not possess horns of the type of those met with in the Cervicornia and Cavicornia. But the strong bony bosses on the skull of many Titanotheres, so curiously reminiscent of those of the not nearly relatedDinocerasandProtoceras, may well have supported horns of the Ox and Antelope pattern.
Fig. 122.
Fig.122.—Bones of the manus of Camel (Camelus bactrianus). × ⅛.c, Cuneiform;l, lunar;m, magnum;R, radius;s, scaphoid;td, trapezoid;u, unciform. (From Flower'sOsteology.)
The teeth of the Perissodactyles are lophodont, more rarely bunodont. The selenodont Artiodactyle form of molar is not met with. The dental formula, moreover, is at least near thecomplete one, the more modern forms as usual being the more deficient in numbers of teeth.
The dorso-lumbar vertebrae are as a rule twenty-three; but the extinct Titanotheres are again an exception; for, at least inTitanotherium, there are but twenty of these vertebrae—an Artiodactyle character. The femur has a third trochanter. There are so few recent Perissodactyles that an enumeration of the distinguishing characters of the viscera may very probably be useless for purposes of classification. But the living genera at any rate are to be separated from the living Artiodactyles by the invariable simplicity of the stomach coupled with a very large and sacculated caecum. The liver is simple and not much broken up into lobes, and the gall-bladder is always absent. The brain is well convoluted. The teats are in the inguinal region. The placenta in this group is of the diffused kind.
Fig. 123.
Fig.123.—Anterior aspect of right femur of Rhinoceros (Rhinoceros indicus). × ½.h, Head;t, great trochanter;t′, third trochanter. (From Flower'sOsteology.)
The living Perissodactyles belong to three types only, indeed to three genera only (in the estimation of most), which are the Horses, Tapirs, and Rhinoceroses. But taking into account the extinct forms, they may be divided primarily (according to Professor Osborn) into the four following groups:—(1) Titanotherioidea, including but one family, Titanotheriidae; (2) Hippoidea, including the families Equidae and Palaeotheriidae; (3) Tapiroidea, with two families, Tapiridae and Lophiodontidae; and (4) Rhinocerotoidea with families Hyracodontidae, Amynodontidae, and Rhinocerotidae. It is conceivable, according to the same writer, that the Chalicotheres (here treated of as a separate sub-order, Ancylopoda) should be added to the Perissodactyle series.
Fig. 124.
Fig.124.—Side view of skull of Horse with the bone removed so as to expose the whole of the teeth.c, Canine;Fr, frontal;i1,i2,i3, incisors;L, lachrymal;m1,m2,m3, molars;Ma, malar or jugal;Mx, maxilla;Na, nasal;oc, occipital condyle;Pa, parietal;pm1, situation of the vestigial first premolar, which has been lost in the lower, but is present in the upper jaw;pm2,pm3,pm4, remaining premolars;PMx, premaxilla;pp, paroccipital process;Sq, squamosal. (After Flower and Lydekker.)
Fam. 1. Equidae.—This family, which includes the living Horse, Zebras, and Asses, as well as a number of extinct genera agreeing with those types in structure, may be defined by the possession of but one functional toe, the two lateral ones being mere splints, or but little more. The molar teeth are hypselodont, andthe premolars, with the exception of the first, resemble the molars in their pattern. The orbit is completely surrounded by bone. The incisors are chisel-shaped, with a pit on the free surface. The canines are rudimentary if present. The radius and ulna are fused, as are the tibia and fibula. Although for the sake of uniformity a family, Equidae, is here separated from its allies, it is quite impossible owing to the full state of our knowledge of this group to draw a really hard-and-fast line between this family and the Palaeotheriidae. We shall deal presently with the conjectured pedigree of the Horse, which naturally involves that family, and which presents an unbroken series from four-toed Perissodactyles to the present one-toed Horse, the various bones and teeth becoming modified in the course of the descent "with the regularity of clockwork." We are compelled to draw the line at functional second and third toes; directly these are no longer used the animal is a Horse in the strict sense! This is irrational and regrettable, but necessary for practical purposes, ifwe are to continue the plan of defining the various families of Mammalia.
The genusEquus[143]contains not only the Horse, but the Asses and Zebras. The genus is to be distinguished as regards external characters by the following features:—The body is thickly clothed with hair; there is a more or less bushy tail and mane; the colours are apt to be disposed in stripes of black or blackish upon a yellowish brown ground; this is of course best seen in the Zebras, but the wild Asses also have some traces of it, if only in the single cross-bar of the African Wild Ass, and it is even "reversionary" in the domestic Horse at times. There are no horns upon the forehead or elsewhere; the fore-limbs or both pairs have a callous pad upon the inside, which is possibly to be looked upon as an aborted gland, possibly originally of use as secreting some odorous substance calculated to enable strayed members of the herd to regain their companions. The terminal phalanx of each of the (functionally) single digits is enclosed in a large horny hoof.
The main internal features of structure which divide this genus of Perissodactyles from the Rhinoceros or the Tapir, or from both, are: the existence of strong incisors, three on each side of each jaw; there are canines, but these are small and do not always persist in the full-grown mare. They are popularly known as "tusks" or "tushes." The first of the four premolars (the "wolf tooth") is small and quite rudimentary; it is often absent. As there are three molars, the present genus has the "typical" number of the Eutherian dentition,i.e.forty-four. In the skull the orbit is—as it is not in Tapirs and Rhinoceroses—completely encircled by bone. There is but one functional finger and toe on each hand (Fig. 121 C) and foot; the second and third digits are represented by mere splints, one of which may as an abnormality be enlarged, and reach nearly as far as the well-developed digit. There are even occasionally traces of digit number two.
The Horse,E. caballus, is to be distinguished from its congeners by the small callosities on the hind-limbs which it possesses in addition to the larger ones on the fore-limbs. The hairy covering of the tail is more abundant, as is also the mane. The head too is proportionately smaller, and the general contourmore graceful. Though Zebra markings are not usual uponE. caballus, there are plenty of examples of—what we may perhaps in this case term—a "reversion" to a striped state. The celebrated "Lord Morton's mare,"[144]whose portrait hangs in the Royal College of Surgeons, is an interesting case of this. It was as a matter of fact thought to be an example of that rather doubtfully-occurring phenomenon, "telegony." Its history is briefly this. The animal was the offspring of a mare that had previously produced to a male Quagga a hybrid foal. Afterwards a second foal was produced by the same mare to an Arab sire. This foal, the one in question, was striped, and hence was thought to be an example of male prepotency. But instances are known of unquestioned Horses which show the same stripes, such as a Norway pony which had not evenseena Zebra!
A last remnant of the naked palm of the hand and sole of the foot is left in the shape of a small bare area, smaller in the Horse than in the Asses, known technically as the "ergot," the term being that of the French veterinarians. As already mentioned, the Horse differs from the Asses and Zebras in the fact that the hind-limbs have callosities on the inner side. They are known as "chestnuts," and their nature has been much disputed. It has been suggested that they are the last rudiment of a vanished toe; but in all probability they are, as already suggested, traces of glandular structures, which are common, upon the limbs in many animals (see above, p.12).
It is a singular fact that there are apparently no wild Horses of this species. The case is curiously analogous to that of the Camel, which also is only known as feral or domesticated. Why the Horse should have become extinct as a wild animal, considering that when it does run wild it can thrive abundantly, is impossible to understand. Sir W. Flower thinks[145]that "the nearest approach to truly wild horses existing at present are the so-called Tarpans, which occur in the Steppe country north of the sea of Azov between the river Dnieper and the Caspian. They are described as being of small size, dun colour, with short mane and rounded obtuse nose." But he adds that there is no evidence to prove whether they are really wild. In favour, however, of their possibly being wild and indigenous European Horses, may bementioned the fact that their general build and appearance is highly suggestive of the wild Horses sketched by primitive man upon ivory.
A really wild Horse, and possibly the ancestor of the European domestic Horse, isE. przewalskiiof the sandy deserts of Central Asia. This animal has been believed to be a mule between the Wild Ass and a feral Horse; but if a distinct form, and probability seems to urge that view, it is interesting as breaking down the distinctions between Horses and Asses. The species possesses the four callosities of the Horse, but has a poorer mane and an asinine tail.
There is no question that the Horse has been a domestic animal for very many centuries. Hieroglyphics appear to show that the Egyptians had not originally domesticated the Horse; it seems to have been first introduced among them by the Hyksos or Shepherd Kings.[146]Whatever the date may be, it is certain that considerably anterior to the Egyptians the Assyrians and Phoenicians possessed Horses. In Western Europe the date of the introduction of the Horse seems to have been during the bronze epoch. Lord Avebury[147]has pointed out that out of eighteen cases of graves in which the remains of Horse were found, twelve contained metal implements,i.e.66 per cent. This does not of course prove that the Horse was domesticated at that period, but it throws doubt upon the earlier occurrence of the Horse in abundance. The Horse, however, does occur on the Continent associated with the remains of man during the Quaternary period.[148]
Messrs. Cuyer and Alix enumerate between fifty and sixty domesticated races of Horse, not counting the supposed wild varieties which have been already referred to. These may be further subdivided; for instance, under the race "pony" we may distinguish the Irish, Scotch, and Shetland varieties, all of which, however, according to Sanson, have originated in Ireland. They are used, remark the authors above quoted, "par les jeunes filles des lords pour leurs promenades." The Arab, the Barb, the Suffolk Punch, etc., are among the numerous races of domestic Horses, into which to enter properly would require another volume, and that of large size.
The Asses and Zebras differ from the Horse in the characters mentioned under the description ofEquus caballus. In addition to these may be pointed out a feature to which attention has been directed by Mr. Tegetmeier.[149]According to him the period of gestation in the Horse is only eleven months; in the others more than twelve.