218

SKULL OF ELEPHANT

CHAP.

Elephas alone survives. This genus also includes many extinct forms, both American and European, as well as Asiatic and African. The entirely extinct genera are Stegodon and Mastodon. The group is clearly one dwindling towards extermination. From the Middle Miocene downwards these great "pachyderms" have existed; and from the Miocene up to Pleistocene times they were almost world-wide in range and numerous in species.

The genus Elephas comprises usually large, but occasionally (the pygmy Elephant of Malta) quite small forms. The external features of the genus differ slightly in different species, and will therefore be described in relation to those species which we shall notice here. The vertebral formula is C 7, D 19-20, L 3-5, Sa 4-5, Ca 24-30, or even more.

The bodies of the vertebrae are remarkable for their shortness and for the very flattened articular surfaces.

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

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, and pn, posterior narial aperture. X. (From Flower's Osteology.)

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,

IX

TUSKS AND MOLARS

219

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. Νο 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 of Mastodon. 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 of Elephas are 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. Of the six molars which eventu

It must be borne in mind that the teeth increase in complexity, those first pushed up having the fewest plates. The first has only four transverse plates.

220

STOMACH AND BRAIN

CHAP.

ally 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 only E. planifrons which certainly shows a milk dentition. In Mastodon and 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. 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 of the Elephant

1 Forbes, Proc. Zool. Soc. 1879, p. 420.

2

2 See Krueg, Zeitschr. wiss. Zool. xxxiii. 1881, p. 652, and Beddard, Proc. Zool. Soc. 1893, p. 311.

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THE AFRICAN ELEPHANT

221

convoluted; but they This suggests a brain. The brain has

has hemispheres which are extremely well leave the cerebellum entirely uncovered. which is a great specialisation of a low type. 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 from E. indicus is 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. In Elephas indicus on 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; however it can be tamed, as is shown by several

1

1 So convinced are some persons of the untameable character of the African Elephant, that it has even been suggested that the animals with which Hannibal crossed the Alps were not E. africanus, but a now extinct species!

222

THE ELEPHANT AS AN EMBLEM

CHAP.

specimens 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.

The meaning of an Elephant as an emblem upon a coin appears to be eternity, and there is no question but that the

FIG. 117. African Elephant. Elephas africanus. × (After Sir Samuel Baker.)