Part 74 (2/2)
_GENUS ELEPHAS--THE ELEPHANT_.
In the writings of older naturalists this animal, so singular in its construction, will be found grouped with the horse, rhinoceros, hippopotamus, tapir, coney, and pig, under the name of pachydermata, the seventh order of Cuvier, but these are now more appropriately divided, as I have said before, into three different orders--Proboscidea, the elephants; Hyracoidea, the conies; and the rest come under Ungulata.
Apparently singular as is the elephant in its anatomy, it bears traces of affinity to both Rodentia and Ungulata. The composition of its ma.s.sive tusks or incisors, and also of its grinders, resembles that of the Rodents. The tusks grow from a persistent pulp, which forms new ivory coated with enamel, but the grinders are composed of a number of transverse perpendicular plates, or vertical laminae of dentine, enveloped with enamel, cemented together by layers of a substance called _cortical_. The enamel, by its superior hardness, is less liable to attrition, and, standing above the rest, causes an uneven grinding surface. Each of these plates is joined at the base of the tooth, and on the grinding surface the pattern formed by them distinguishes at once the Indian from the African elephant. In the former, the transverse ridges are in narrow, undulating loops, but in the African they form decided lozenges. These teeth, when worn out, are succeeded by others pus.h.i.+ng forward from behind, and not forced up vertically, as in the case of ordinary deciduous teeth, so that it occasionally happens that the elephant has sometimes one and sometimes two grinders on each side, according to age. In the wild state sand and grit, entangled in the roots of plants, help in the work of attrition, and, according to Professor W. Boyd Dawkins, the tame animal, getting cleaner food, and not having such wear and tear of teeth, gets a deformity by the piling over of the plates of which the grinder is composed. An instance of this has come under my notice. An elephant belonging to my brother-in-law, Colonel W. B. Thomson, then Deputy Commissioner of Seonee, suffered from an aggravated type of this malformation. He was relieved by an ingenious mahout, who managed to saw off the projecting portion of the tooth, which now forms a paper-weight. In my account of Seonee I have given a detailed description of the mode in which the operation was effected.
[Ill.u.s.tration: Side view of Grinders of Asiatic Elephant.]
[Ill.u.s.tration: Grinder of Asiatic Elephant.]
[Ill.u.s.tration: Grinder of African Elephant.]
[Ill.u.s.tration: Section of Elephant's Skull.]
The skull of the elephant possesses many striking features quite different from any other animal. The brain in bulk does not greatly exceed that of a man, therefore the rest of the enormous head is formed of cellular bone, affording a large s.p.a.ce for the attachment of the powerful muscles of the trunk, and at the same time combining lightness with strength. This cellular bone grows with the animal, and is in great measure absent at birth. In the young elephant the brain nearly fills the head, and the brain-case increases but little in size during growth, but the cellular portion progresses rapidly with the growth of the animal, and is piled up over the frontals for a considerable height, giving the appearance of a bold forehead, the brain remaining in a small s.p.a.ce at the base of the skull, close to its articulation with the neck. According to Professor Flower, the cranial cavity is elongated and depressed, more so in the African than the Indian elephant. The tentorial plane is nearly vertical, so that the cerebellar fossa is altogether behind the cerebral fossa, or, in plainer terms, the division between the big brain (cerebrum) and the little one (cerebellum) is vertical, the two brains lying on a level plane fore and aft instead of overlapping. The brain itself is highly convoluted. The nasal aperture, or olfactory fossa, is very large, and is placed a little below the brain-case. Few people who are intimate with but the external form of the elephant would suppose that the b.u.mp just above the root of the trunk, at which the hunter takes aim for the ”front shot,” is really the seat of the organ of smell, the channels of which run down the trunk to the orifice at the end. The maxillo-turbinals, or twisted bony laminae within the nasal aperture, which are to be found in most mammals, are but rudimentary in the elephant--the elongated proboscis, according to Professor Flower, probably supplying their place in warming the inspired air. The premaxillary and maxillary bones are largely developed, and contain the socket of the enormous tusks. The narial aperture is thus pushed up, and is short, with an upward direction, as in the Cetacea and Sirenia, with whom the Proboscidea have certain affinities.
There are no lower incisors (except in a fossil species), and only two of the molar teeth are to be seen on each side of the jaw at a time, which are pushed out and replaced by others which grow from behind. During the life-time of the animal, twenty-four of these teeth are produced, six in each side of the upper and lower jaws.
The elephant has seven cervical vertebrae, the atlas much resembling the human form; of the thoracic and lumbar vertebrae the number is 23, of which 19 or 20 bear ribs; the caudal vertebrae are 31, of a simple character, without chevron bones.
The pelvis is peculiar in some points, such as the form of the ileum and the arrangement of its surfaces, resembling the human pelvis.
The limbs in the skeleton of the elephant are disposed in a manner differing from most other mammalia. The humerus is remarkable for the great development of the supinator ridge. ”The ulna and radius are quite distinct and permanently crossed; the upper end of the latter is small, while the ulna not only contributes the princ.i.p.al part of the articular surface for the humerus, but has its lower end actually larger than that of the radius--a condition almost unique among mammals” (_Prof. Flower_).
On looking at the skeleton of the elephant, one of the first things that strikes the student of comparative anatomy is the perpendicular column of the limbs; in all other animals the bones composing these supports are set at certain angles, by which a direct shock in the action of galloping and leaping is avoided. Take the skeleton of a horse, and you will observe that the scapula and humerus are set almost at right angles to each other. It is so in most other animals, but in the elephant, which requires great solidity and columnar strength, it not being given to bounding about, and having enormous bulk to be supported, the scapula, humerus, ulna and radius are all almost in a perpendicular line. Owing to this rigid formation, the elephant cannot spring. No greater hoax was ever perpetrated on the public than that in one of our ill.u.s.trated papers, which gave a picture of an elephant hurdle-race. Mr. Sanderson, in his most interesting book, says: ”He is physically incapable of making the smallest spring, either in vertical height or horizontal distance.
Thus a trench seven feet wide is impa.s.sable to an elephant, though the step of a large one in full stride is about six and a half feet.”
[Ill.u.s.tration: Skeleton of Elephant.]
The hind-limbs are also peculiarly formed, and bear some resemblance to the arrangement of the human bones, and in these the same perpendicular disposition is to be observed; the pelvis is set nearly vertically to the vertebral column, and the femur and tibia are in an almost direct line. The fibula, or small bone of the leg, which is subject to great variation amongst animals (it being merely rudimentary in the horse, for instance), is distinct in the elephant, and is considerably enlarged at the lower end. The tarsal bones are short, and the digits have the usual number of phalanges, the ungual or nail-bearing ones being small and rounded.
[Ill.u.s.tration: A. Muscles of Elephant's Trunk. B. Cross-section of ditto.]
I have thus briefly summarised the osteology of the elephant, as I think the salient points on which I have touched would interest the general reader; but, in now proceeding to the internal anatomy, I shall restrict myself still more, referring only to certain matters affecting externally visible peculiarities. The trunk of the elephant differs somewhat from other nasal prolongations, such as the snouts of certain insectivora, which are simply development of the nasal cartilages. The nasal cartilages in the Proboscidea serve merely as valves to the entrance of the bony nares, the trunk itself being only a pipe or duct leading to them, composed of powerful muscular and membranous tissue and consisting of two tubes, separated by a septum. The muscles in front (_levatores proboscidis_), starting from the frontal bone, run along a semicircular line, arching upwards above the nasal bones and between the orbits. They are met at the sides by the lateral longitudinal muscles, which blend, and their fibres run the whole length of the proboscis down to the extremity. The depressing muscles (_depressores proboscidis_), or posterior longitudinals, arise from the anterior surface and lower border of the premaxillaries, and form ”two layers of oblique fasciculi along the posterior surface of the proboscis; the fibres of the superficial set are directed downwards and outwards from the middle line. They do not reach the extremity of the trunk, but disappear by curving over the sides a little above the end of the organ. The fibres of the deeper set take the reverse direction, and are attached to a distinct tendinous raphe along the posterior median line” ('Anat. Ind. Elep.,' Miall and Greenwood).
These muscles form the outer sheath of other muscles, which radiate from the nasal ca.n.a.ls outwards, and which consist of numerous distinct fasciculi. Then there are a set of transverse muscles in two parts--one narrow, forming the septum or part.i.tion between the nasal pa.s.sages, and the other broader between the narrow part and the posterior longitudinal muscles.
When we consider the bulk of these well-knit muscles we can no longer wonder at the power of which this organ is capable, although, according to Mr. Sanderson, its capabilities are much exaggerated; and he explodes various popular delusions concerning it. He doubts the possibility of the animal picking up a needle, the common old story which I also disbelieve, having often seen the difficulty with which a coin is picked up, or rather sc.r.a.ped up; but he quite scouts the idea of an elephant being able to lift a heavy weight with his trunk, giving an instance recorded of one of these creatures lifting with his trunk the axle of a field-piece as the wheel was about to pa.s.s over a fallen gunner, which he declares to be a physical impossibility. Certainly the story has many elements of improbability about it, and his comments on it are caustic and amusing: _par exemple_, when he asks: ”How did the elephant know that a wheel going over the man would not be agreeable to him?” That is the weak point in the story--but, however intelligent the animal might be, Mr. Sanderson says it is physically impossible.
Another thing that strikes every one is the noiseless tread of this huge beast. To describe the mechanism of the foot of the elephant concisely and simply I am going to give a few extracts from the observations of Professor W. Boyd Dawkins and Messrs. Oakley, Miall, and Greenwood: ”It stands on the ends of its five toes, each of which is terminated by comparatively small hoofs, and the heel-bone is a little distance from the ground. Beneath comes the wonderful cus.h.i.+on composed, of membranes, fat, nerves, and blood-vessels, besides muscles, which const.i.tutes the sole of the foot” (_W. B. D. and H.
O._). ”Of the foot as a whole--and this remark apples to both fore and hind extremities--the separate mobility of the parts is greater than would be suspected from an external inspection, and much greater than in most Ungulates. The palmar and plantar soles, though thick and tough, are not rigid boxes like hoofs, but may be made to bend even by human fingers. The large development of muscles acting upon the carpus and tarsus, and the separate existence of flexors and extensors of individual digits, is further proof that the elephant's foot is far from being a solid unalterable ma.s.s. There are, as has been pointed out, tendinous or ligamentous attachments which restrain the independent action of some of these muscles, but anatomical examinations would lead us to suppose that the living animal could at all events accurately direct any part of the circ.u.mference of the foot by itself to the ground. The metacarpal and metatarsal bones form a considerable angle with the surface of the sole, while the digits, when supporting the weight of the body, are nearly horizontal” (_M. and G._). This formation would naturally give elasticity to the foot, and, with the soft cus.h.i.+on spoken of by Professor Dawkins, would account for the noiselessness of the elephant's tread. On one occasion a friend and myself marched our elephant up to a sleeping tiger without disturbing the latter's slumbers.
It is a curious fact that twice round an elephant's foot is his height; it may be an inch one way or the other, but still sufficiently near to take as an estimate.
Now we come to a third peculiarity in this interesting animal, and that is the power of withdrawing water or a similar fluid from apparently the stomach by the insertion of its trunk into the mouth, which it sprinkles over its body when heated. The operation and the _modus operandi_ are familiar to all who have made much use of elephants, but the internal economy by which the water is supplied is as yet a mystery to be solved, although various anatomists have given the subject serious attention. It is generally supposed that the receptacle for the liquid is the stomach, from the quant.i.ty that is ejected. An elephant distressed by a long march in the heat of the sun withdraws several quarts of water, but that it is water, and not a secretion produced by salivatory glands, is not I think sufficiently evident. In talking over the matter with Mr. Sanderson, he informed me that an elephant that has drunk a short time before taking an arduous march has a more plentiful supply of liquid at his disposal. Therefore we might conclude that it is water which is regurgitated, and in such quant.i.ty as to preclude the idea of its being stored anywhere but in the stomach; but the question is, how it is so stored there without a.s.simulating with the food in the process of digestion. Sir Emerson Tennent, in his popular and well-known, but in some respects incorrect, account of the elephant, has adopted the theory that the cardiac end of the stomach is the receptacle for the water; and he figures a section of it showing a number of transverse circular folds; and he accepts the conclusion arrived at by Camper and Sir Everard Home that this portion can be shut off as a water chamber by the action of the fold nearest to the oesophagus; but these folds are too shallow to serve as water-cells, and it has not been demonstrated that the broadest fold near the oesophagus can be contracted to such an extent as to form a complete diaphragm bisecting the stomach. Messrs. Miall and Greenwood say: ”The stomach is smooth, externally elongate, and nearly straight.
The cardiac end is much prolonged and tapering. A number of transverse, nearly circular, folds project inwards from the cardiac wall; they almost disappear when the stomach is greatly distended, and are at all times too shallow to serve as water-cells, though they have been figured and described as such.”
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