These organs may be defined to be closed, transparent, thin-sided membranous sacs, varying in form according to the part of the plant in which they are placed, and the purpose they serve.

If for the conveyance of fluid matter equally in all directions, and for the general purposes of digestion and respira- | tion, they have a spheroidal figure shaped into a polygon by the pressure of the sacs upon each other, and constitute common cellular tissue; if fluid is to be conveyed more in one direction than another the spheroids are lengthened in that direction, and prismatical cellular tissue is the result, or muriform if they are placed horizontally and strongly compressed from the side; sometimes instead of being prismatical they are lengthened into bags acute at each end, the clostres of some French botanists, and the issue thus formed is named prosenchyma, in contradistinction to parenchyma, which is a collective name for all cellular tissue the ends of whose sacs are truncated. Now and then a fibre is generated spirally in the inside of a sac of cellular tissue, but for what purpose is unknown.

If the elementary organs are for the conveyance of air they are lengthened into tubes, the sides of which are protected in the inside by a fibre, or fibres twisted spirally, so that the threads touch each other, thus forming a lining to the membrane and preventing the ingress of fluid through the sides. Such organs are called spiral vessels, and are exclusively (except in a very few cases) stationed around the pith of exogens, in the woody bundles of endogens, and in the veins of the leaves and of all the parts of the flower. They unrol with elasticity when stretched; and even uncoil with the growth of the membranous tube in which they have been generated so as to leave spaces between the threads through which fluid percolates; they then become ducts, and probably cease to convey air, but become passages for fluid.

If they are required to serve the two purposes at once of conveying fluid along the plant and of strengthening and protecting the parts in which they are placed, the sacs become fine tubes, thick-sided, elastic, tough, and collected in bundles so as to bend any way without breaking; this occurs in wood, which is composed principally of them, and which gives them the name of woody tissue, in the liber, and in the veins of the leaves where they are placed around the spiral vessels.

For an explanation of the many varieties of the elementary organs, and for a more particular account of their nature and uses, see Lindley's Introduction to Botany, 2nd edit., book i.

ELENCHUS, the Latin form of the Greek elenchos (EXEYXos), and commonly translated by the words argumentum, inquisitio, confutatio, and demonstratio, is a term of frequent use in the Aristotelian system of logic, and signifies argument, replication, refutation, or the point, subject, or nature, of dispute or demonstration. (See the authorities cited in Valpy's edition of Stephens's Greek Thesaurus under 'EXyxw.) Aristotle defines elenchos as 'a syllogism of contradiction,' that is, an argument alleged in opposition to another; and Mr. Thomas Taylor, in his translation of the Organon, considers the Greek term to be precisely equivalent to Redargutio in Latin. By some of the early English authors the noun elench is used in a similar sense, and also the verb elenchize, meaning to argue with captious or sophistical opposition. (Johnson's Dict.) In the two last books of the Organon, entitled Hepi Tv Zopiotikov 'EXéyxwv, Aristotle minutely classifies and discusses the various kinds of sophistical elenchi, or modes of argument used by contentious sophists. The sophism which, in scholastic phraseology, is designated Ignoratio elenchi, that is, a real ignorance of, a mistaking, or sinister deviation from, the argument, or question under discussion, consists in proving something irrelevant, and which, as it may be true without affecting the truth of the real proposition, with which it has no necessary connexion, does not determine, though it may seem to determine, the question. Aristotle includes under this designation the introduction of anything extraneous to the point in dispte trou páуparoc); the disproving of what is not asserted, as well as the proving of what is not denied. Examples of this species of sophism are of very frequent occurrence in discourses which display the rhetorical artifice of appealing to passions and prejudices, and resort to injurious imputations, or ludicrous and satirical illustration; especially in religious, political, and forensic disputations, which affect individual inP C., No. 574.

terests and feelings, and in which the predominant desir is not the exhibition of truth, but merely the obtaining of victory; for a disingenuous disputant when excited, and conscious of the superiority of his adversary's argument, strives to elude conviction by the stratagem of deploying, and seeks to gain a sinister advantage and triumph, by proving or disproving, not the real proposition in question, but one or more which in some way are apparently involved or implied, so as to create the assumption of identity. The following instance is given by Dr. Kirwan (Essay on Logic, vol. ii., p. 440): Paschal arguing against atheism insists that it is more dangerous than theism, whereas the point in debate is the truth, and not the prudence of either system. Some Christian sects use similar arguments. Mistake or misrepresentation of the question to be determined, and the consequent proving of what is not to the purpose, are also common in didactic and conversational discussions, and the sophisms of Petitio principii and non causa pro causa are frequently combined with the Ignoratio elenchi. In all cases of irrelevant conclusion, when something is proved which does not in reality contradict the adversary's proposition, the latent fallacy is best exposed by showing that both propositions may be equally true (Archbishop Whateley's Logic, p. 235, 5th ed. 1834); and the best means of preventing sophistical deception of this nature is to keep the attention constantly fixed upon the precise point of dispute, neither wandering ourselves, nor suffering our opponent to wander or make any substitution. (Dr. Watts's Logic.) In dramatical writing the Ignoratio elenchi, or as it is otherwise called, the quid pro quo, is frequently adopted as a very effective expedient for the production of laughter. Numerous and long continued instances of consistent dialogue, displaying the most ingenious and amusing équivoque or cross-purposes, are to be found in the comedies of Molière, the source of amusement being in each party's 'ignorance of the question' about which the other is concerned.

ELEPHANT, in Latin Elephas and Elephantus; in Greek Xipaç; in Spanish Elephante; in Italian Elefante, in French Elephant; in German Olyphant; the name o. the well-known genus which forms the only living type of the family of true Proboscidians or Pachydermatous Mammifers, with a proboscis and tusks, and presents the largest of existing terrestrial animals.

The proboscis or trunk, from which the name of the family is derived, demands some attention previous to our inquiry into the rest of the structure, habits, and history of the elephants.

*

The great size of the alveoli necessary for the lodgment of the tusks renders, as Cuvier observes, the upper jaw sc high and shortens the nasal bones to such a degree, that in the skeleton the nostrils are placed towards the upper part of the face; but in the living animal they are prolonged into a cylindrical trunk or proboscis composed of thousands of small muscles variously interlaced, so as tc bestow on it the most complicated powers of mobility in all the varieties of extension, contraction, and motion in every direction. It is of a tapering subconical form, and has internally two perforations. On the upper side of the extremity, immediately above the partition of the nostrils, is an elongated process, which may be considered as a finger; and on the under edge is a sort of tubercle, which acts as an opposable point; in short, as a thumb. Endowed with exquisite sensibility, nearly 8 ft. in length, and stout in proportion to the massive size of the whole animal, this organ, at the volition of the elephant, will uproot trees of gather grass-raise a piece of artillery or pick up a comfit

kill a man or brush off a fly. It conveys the food to the mouth and pumps up the enormous draughts of water, which by its recurvature are turned into and driven down the capacious throat, or showered over the body. Its length supplies the place of a long neck, which would have been incompatible with the support of the large head and weighty tusks. A glance at the head of an elephant will show the thickness and strength of the trunk at its insertion; and the massy arched bones of the face and thick muscular neck are admirably adapted for supporting and working this powerful and wonderful instrument.

The following cuts will convey some idea of the form and action of the termination of the proboscis:

• Cuvier gives the number of muscles having the power of distinct action as not far short of 40,000. VOL. IX.-Y

appears completely when the animal is two years old; the third consists of twelve or thirteen, and comes at the age of six years; and in the fourth up to the eighth grinder both inclusive, the number of plates varies from fifteen to twenty-three. It would seem that every new tooth takes at least a year more for its formation than its predecessor. As the tooth advances gradually, a comparatively small portion only is through the gum at once. A molar tooth, composed of twelve or fourteen plates, shows only two or three of these through the gum, the others being imbedded in the jaw, and in fact the tooth is complete anteriorly, where it is required for mastication, while, posteriorly it is very incomplete. As the lamina advance, they are successively perfected. An elephant's molar tooth is therefore never to be seen in a perfect state; for if it is not worn at all anteriorly, the posterior part is not formed, and the fangs are wanting; nor is the structure of the back part of the tooth perfected until the anterior portion is gone.

Elephants have no canine teeth; but in the upper jaw there are two incisors better known by the name of tusks. These enormous weapons are round, arched, and terminating in a point, and their capsule is always free, so that the tusk continues to grow as long as the animal lives. The structure of the ivory of which it is composed differs from other tusks; and a transverse section presents strim forming the arc of a circle from the centre to the circumference, and, in crossing each other, curvilinear lozenges which occupy the whole surface. The tusk is hollow within for a great part of its length, and the cavity contains a vascular pulp, which supplies successive layers internally as the tusk is worn down externally. Blumenbach, in his 'Comparative Anatomy,' observes, that not to mention other peculiarities of ivory, which have induced some modern naturalists to consider it as a species of horn, the difference between its structure and that of the bone of teeth is evinced in the remarkable pathological phenomenon resulting from balls, with which the animal has been shot when young, being found, on sawing through the tooth, imbedded in its substance in a peculiar manner. Haller employed this fact, both to refute Duhamel's opinion of the formation of bones by the periosteum, like that of wood by the bark of a tree, as well as to prove the constant renovation of the hard parts of the animal machine. It is still more important in explanation of that ' nutritio ultra vasa,' which is particularly known through the Petersburgh prize dissertation. Blumenbach further states that the fact above mentioned may be seen in Buffon (4to. ed., tom. xi., p. 161); in Galandat over de Olyphants Tanden; in the Verhandelingen der Genootsch, te Vlissingen, p. 352, tom, ix.; and in Bonn. descr. thesauri Hoviani, p. 146. In all these cases, according to Blumenbach, the balls were of iron; and he adds that he possesses a similar specimen. In the cases we have seen the balls were also of iron. But,' continues Blumenbach, there is a still more curious example in my collection, of a leaden bullet contained in the tusk of an East Indian elephant, which must have been equal in size to a man's thigh, without having been flattened. It lies close to the cavity of the tooth; its entrance from without is closed, as it were, by means of a cicatrix; and the ball itself is surrounded apparently by a peculiar covering. The bony matter has been poured out on the side of the cavity in a stalactitic form. Upon this Lawrence well remarks that the facts here recounted have been sometimes brought forward in order to prove the vascularity of the teeth; a doctrine which is refuted by every circumstance in the formation, structure, and diseases of these organs. When a bullet has entered the substance of the body, the surrounding lacerated and contused parts do not grow to the metal and become firmly attached to its surface, but they inflame and suppurate in order to get rid of the offending matter. If the ivory be vascular, asks Mr. Lawrence, why do not the same processes take place in it? We can explain very satisfactorily,' writes Mr. Lawrence in continuation, 'how a bullet may enter the tusk of an elephant, and become imbedded in the ivory without any opening for its admission being perceptible. These tusks are constantly growing during the animal's life by a deposition of successive lamina within the cavity, while the outer surface and the point are gradually worn away; and the cavity is filled for this purpose with a vascular pulp, similar to that on which teeth are originally formed. If a ball penetrate the side of a tusk, cross its cavity, and lodge in the slightest way on the opposite side, it will become covered towards the cavity by

the newly-deposited layers of ivory, while no opening will exist between it and the surface to account for its entrance. If it have only sufficient force to enter, it will probably sink by its own weight between the pulp and the tooth, until it rests at the bottom of the cavity, It there becomes surrounded by new layers of ivory; and as the tusk is gradually worn away and supplied by new depositions, it will soon be found in the centre of the solid part of the tooth. Lastly, a foreign body may enter the tusk from above, as the plate of bone which forms its socket is thin: if this descends to the lower part of the cavity, it may become imbedded by the subsequent formations of ivory. This must have happened in a case where a spear-head was found in an elephant's tooth. The long axis of the foreign body corresponded to that of the cavity. No opening for its admission could be discovered, and it is very clear that no human strength could drive such a body through the side of a tusk.' 'Phil. Trans.' 1801, part 1.

The great size to which these tusks grow may be judged of by examining the table published by Cuvier in his Ossemens Fossiles,' tome i., p. 57. It is generally considered that the tusks of the African elephant are the largest; but with regard to the table, Cuvier observes that the African tusks could not be distinguished from those of the Indies, and that there is not the certainty that could be wished in the measures employed. According to Mr. Corse, the tusks of the Indian elephant seldom exceed 72 lbs. in weight, and do not weigh beyond 50 lbs. in the province of Tiperah, which produces thousands of elephants. There are however, in London, tusks which weigh 150 lbs., probably from Pgue; for it is from Pegu and Cochin China that the largest Indian elephants and tusks are brought. The largest recorded in Cuvier's table was a tusk sold at Amsterdam, according to Klokner, which weighed 350 lbs.: this is stated on the authority of Camper; and one possessed by a merchant of Venice, which was 14 feet in length, and resting on the authority of Hartenfels, in his Elephantographia. The largest in the Paris Museum is nearly 7 feet long, and about 5 inches in diameter at the large end. These tusks have different degrees of curvature.

Mr. Corse, speaking of the Asiatic elephant, states that the first or milk tusks of an elephant never grow to any size, but are shed between the first and second year. These, as well as the first grinders, are named by the natives dood-kau-daunt, which literally signifies milk teeth. The tusks which are shed have a considerable part of the root or fang absorbed before this happens. The time at which the tusk cuts the gum seems to vary. Mr. Corse knew a young one which had his tusks when about five months old, while those of another did not cut the gum till he was seven months old. Those tusks, which are deciduous, observes the same author, are perfect and without any hollow at the root, in a foetus which is come to its full time, and at this period the socket of the permanent tusk begins to be formed on the inner side of the deciduous tusk: he gives the following examples of the progress of this part of the dentition, A young elephant shed one of his milk tusks on the 6th of November, 1790, when near thirteen months old, and the other on the 27th of December, when about fourteen months old: they were merely two blackcoloured stumps, when shed; but, two months afterwards, the permanent tusks cut the gum, and on the 19th of April, 1791, they were an inch long, but black and ragged at the ends. When they became longer and projected beyond the lip, they soon were worn smooth by the motion and friction of the trunk. Another young elephant did not shed his milk tusks till he was sixteen months old. The permanent tusks of the female are very small in comparison with those of the male, and do not take their rise so deep in the jaw; but they use them as weapons of offence in the same manner as the male named Moaknah, that is by putting their head above another elephant, and pressing their tusks down into the animal,

In the lower jaw there are neither incisors nor canines, and the molar teeth resemble those to which they are opposed.

Cuvier comes to the conclusion that the females of the African species have large tusks, and that the difference between the sexes in this respect is much less than in the Indian elephants; but Burchell attributes the want of success of the elephant hunters whom he met with to their having only fallen in with females whose tusks were small.

the case in the skeleton of the Asiatic elephant at Cassel Blair, he remarks, found the same number in the individuals of which he has given an account; and a manuscript Italian description of the elephant which died at Florence in 1657 confirms this statement. Allen Moulins, on the contrary (Anatomical Account of the Elephant burned in Dublin, London, 1682, 4to.), and Daubenton, represent the number of pairs as 20. The elephant in the Museum of the Royal College of Surgeons (Chunee, formerly of Exeter Change) has 19 pairs of ribs; and that in the British Museum has the same number, 14 true and 5 false; but Mr. Gray informs us that, in a second specimen of a young one, the bones of which have not been separated, there are 20 pairs, 15 true and 5 false. There are only three lumbar vertebræ. The margin of the seapula, which is turned towards the spine, and is shortest in most of the proper quadrupeds, is the longest in the elephant, as it is in the Cheiroptera, most of the Quadrumana, and especially in man. There is no ligamentum teres, and consequently no impression on the head of the femur or thighbone.

Structure of internal soft parts.-The following internal soft parts are more particularly worthy of remark in the elephant. Brain, &c.-A portion of the dura mater from an Asiatic elephant may be seen in the Museum of the Royal College of Surgeons, in London (Gallery No. 1346), where the termination of the falx and the commencement of the tentorium or process which separates the cerebrum from the cerebellum are shown. The two fibrous layers of the dura mater are separated by a softer cellular substance, in which the vessels ramify; and it may be observed that the thickness of the dura mater is in proportion to the size of the skull, and of the entire animal, but not to the size of the brain, which does not much exceed that of the human brain, as will be seen in the preparation of the brain of a young Asiatic elephant (No. 1331). For though the absolute size of the organ exceeds that of man, the proportion which the cerebrum bears to the rest of the brain, and especially that part of the hemisphere which forms the roof and sides of the lateral ventricle, is much less. The hemispheres are broad and short, with a considerable development of the natiform protuberance. The convolutions are comparatively small and numerous. A lateral section has been removed from the left hemisphere, which shows that the anfractuosities are also deep, extending in some cases more than two-thirds of an inch into the substance of the brain. The hippocampus is comparatively

smaller than in the ass, and the corpus striatum larger The ventricle is seen to be continued into the olfactory bulb. The cerebellum is of considerable width, and its surface, as shown by the lateral section, is increased by numerous and complex anfractuosities. The tuber annulare corresponds in size to the development of the lateral lobes of the cerebellum. The corpora olivaria are remarkably prominent. The origins of all the cerebral nerves are shown, among which the olfactory nerves of the fifth pair, which supplies the proboscis, are remarkable for their prodigious size; whilst the optic nerves, and those which supply the muscles of the eye, are remarkable for their small size. The pia mater is left on with the vessels at the base of the brain. A bristle is placed in the infundibulum. (Cat. Gallery, vol. iii.) The brain in man is from

to of the body, that of the elephant The stomach is simple, the intestines are very voluminous, and the cæcum enormous. In the sanguiferous system the heart is worthy of note, and a section of the right auricle and ventricle of that of an Asiatic elephant may be seen in the museum last mentioned (Gallery, No. 924). In this animal, which, in some other respects, singularly resembles the Rodentia, three vena cava terminate in the right auricle. Besides the Eustachian valve, which projects between the orifices of the inferior and left superior cave, there is also, as in the Porcupine, a rudiment of a superior valve, ex