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Art. I. The Philosophy of Natural History. By William Smellie,
Member of the Antiquarian and Royal Societies of Edinburgh.
THE Audy, bf nature is the most delightful that can engage
That beauty, that order, that sym-
But the subject of natural history is locked up in foreign or dead languages, and obscured with a farrago of barbarous names and indelicate illusions. To explore these rich mines, and to extract and refine the coarse ore, is to render an essential service to mankind. The study is easy and attracting, and is equally accommodated to the youth of both sexes. Several works of this kind have been composed; but they have been generally defective in method or elegance. Ray, in the end of last cena tury, and Derham in the beginning of the present, published treatises of this popular nature; but the uncouth manner, the confused arrangement, and the unpolished language, were equally forbidding, and their productions have fallen into oblivion. The Abbé Le Pluche was more successful ; his Spectacle de la Nature is even now read with confiderable pleasure. But the author is limited in his views, and extremely superficial. The only good work of the kind, with which we are acquainted, is the Contemplation de la Nature of Bonnet; and it deserves our higheft commendation. It is at once clear, elegant, and profound. The author takes an ample range, and his views are extenfive, and sometimes sublime. His diction is smooth and perspicuous, and through the whole he breathes an air of beneficence and piety.
We consider the work now before us as a valuable present to the public. It furnishes the most rational entertainment, and mingles, in a remarkable degree, the useful with the pleasant. It contains information that is various, elegant, and important. The method of treating it is clear and natural. The language, though sometimes perhaps diffuse and nerveless, is, upon the whole, simple, correct, and perspicuous. To novelty of facts, or originality of views, Mr. Smellie does not indeed pretend; but, in the selection of his materials, he displays judgment and talte. Like his friend, the late ingenious Lord Kaims, he discovers a fondness for investigating final causes; a disposition which, though hardly consistent with the cautious Spirit of accurate philosophy, gives a favourable turn to the mind, and is peculiarly pleasing to youth. And in an age when a superficial knowledge pervades every rank, we doubt not that this work will be read with avidity.
In the first chapter, Mr. Smellie considers the distinguishing characters of animals, plants, and minerals, and the analogies which subsist between them. The productions of nature ascend by gradual and imperceptible steps. Those classes which, at first fight, appear to be so widely removed, are found, upon a closer examination, to be separated by no precise and determinate boundary. Hence definitions are useless and futile. In every circumstance plants, to a certain degree, resemble animals. The structure and irritability of parts, and the power of performing
certain motions, are in some measure common to both. The delicate shrink of the sensitive plant has long been the subject of wonder and surprise. The moving plant, a native of the EastIndies, is affected by the mere impulse of the solar rays. During the night, or in cold and cloudy weather, it is still and torpid; but when the sun shines it is enlivened, and moves its leaves briskly in all directions. The Venus' Aly-trap, an American plant, is of a very singular kind. Its leaves are furnished with a double row of prickles, with which it feizes and transfixes the small infects that approach it.The sleep of plants is performed variously, and in a manner the best adapted to their particular structure. The leaves of the tamarind-tree contract round the tender fruit, and protect it from the nocturnal cold. The leaves of the chickweed, the swallow-wort, the orach, &c. are disposed in pairs, and during the night they rise, join at the top, and conceal the flowers. The leaves of the Indian mallow, the ayenia, and the tree-primrose, are placed alternately. Though horizontal, or even depending during the day, they rise at the approach of night, and embrace the stem. In the same manner the nightshade, and the Egyptian vetch, erect their leaves during the night. The young buds of the white lupine are protected by the pendulous state of the leaves.--Plants have a fingular power of accommodating themselves to their situation, and of recovering their original pofition. In some instances they seem to be actuated by the principle of choice, and almost capable of reAection :
• When trees grow near a ditch, the roots which proceed in a direction that would necessarily bring them into the open air, instead of continuing this noxious progress, fink below the level of the ditch, then shoot across, and regain the soil on the opposite side. When the root is uncovered, without exposing it to much heat, and a wet sponge is placed near it, but in a different direction from that in which the root is proceeding, in a short time the root turns towards the sponge. In this manner the direction of the roots may be varied at pleasure. All plants make the strongest efforts by inclining, turning, and even twisting, their ftems and branches, to escape from darkness and shade, and to procure the influences of the sun. Place a wet sponge under the leaves of a tree, they soon bend downward, and endeavour to apply their inferior surfaces to the sponge. If a vessel of water be placed within fix inches of a growing cucumber, in twenty-four hours the cucumber alters the direction of its branches, bends either to the right or left, and never stops till it comes in contact with the water. When a pole is placed at a confiderable distance from an unfupported vine, the branches of which are proceeding in a contrary direction from that of the pole, in a short time it alters its course, and stops not till it clings around the pole.' X 2
Mr. Smellie proceeds to trace the analogy between plants and animals in the several points of fructure and organs, growth and nourishment, dissemination and decay.
1. Stručture and organs. An accurate and distinct account occurs of that singular being the polypus :
• His body consists of a single tube, with long tentacula, or arms, at one extremity, by which it seizes small worms, and conveys them to its mouth. It has no proper head, heart, stomach, or intestines of any kind. This fimplicity of structure gives rise to an equal fimplicity in the economy and functions of the animal. The polypus, though it has not the distinction of sex, is extremely prolific. When about to multiply, a small protuberance or bud appears on the surface of its body. This bud gradually swells and extends. It includes not a young polypus, but is the real animal in miniature, united to the mother as a sucker to the parent-tree. The food taken by the mother passes into the young by means of a communicating aperture. When the footing polypus has acquired a certain growth, this aperture gradually closes, and the young drops off, to multiply its 1pecies in the same manner. As every part of a polypus is capable of sending off shoots, it often happens that the young, before parting from the mother, begin to shoot; and the parent animal carries several generations on her own body. There is another singularity in the history of the polypus. When cut to pieces in every direction fancy can suggest, it not only continues to exist, but each section foon becomes an animal of the same kind. What is still more surprising, when inverted as a man inverts the finger of a glove, the polypus seems to have suffered no material injury. M. Trembley, in the course of his experiments, discovered that different portions of one polypus could be ingrafted on another. He gave scope to his fancy, and, by repeatedly
splitting the head and part of the body, formed hydras more complicated than ever ftruck the imagination of the most romantic fabulists.'
Vegetables are, like animals, composed of a series of vessels. The bark consists of the cortex or exterior covering, the parenchyma, a pulpy substance formed by a variety of folliculi, and the liber or rind, which, towards the end of autumn, coalesces with the wood, and acquires the same consistence. The pith is a congeries of air and fap vefsels, interwoven like gauze. It continually diminishes, because a part dries and incorporates with the general mass. The wood consists of a dense compact ligneous matter, and a porous pulpy parenchyma. The same structure extends through every part of a vegetable; and the roots, the branches, and the leaves, however unlike in appearance, are similar in their texture. The ascension of fap is aflifted by capillary attraction, and the action of the air veffels or trachea; but these causes are not alone adequate to the effect. The great fource of motion is the principle of life inherent in vegetables, and which is excited and stimulated by the application of warmth.
The analogy between the circulation of the blood in animals is not indeed complete ; for the fap rises vigorously in the day, when the plant is cherished by the enlivening rays of the sun, and again descends during the night. The pith of vegetables resembles the spinal marrow and brain, the great seat of life. The leaves are expiratory organs, and supply the place of lungs. The branches, like the arms and tentacula of animals, serve for support and defence. Bones, as well as wood, confist of concentric layers. The grasses differ considerably from other plants in their structure. Their tubular and knotted form gives them strength to resist the violence of the wind. They resemble the polypus and tænia. Succulent vegetables bear an analogy to worms, caterpillars, and soft infects.
2. Growth and nourishment. Animals grow by developement, vegetables by accretion. Water is the principal food of plants; which is absorbed by the fibres of the root, elaborated and converted into sap, and then conducted, by numberlefs vessels, to nourish the various parts. Seeds and embryos grow in the same manner. A part of the grain is converted, by the process of vegetation, into a pulpy faccharine substance, which nourishes the infant plant, and the seminal leaves, by attracting air and moifture, assist the expansion. The age of animals admits of great variety. Plants are annual, biennial, triennial, and perennial. Warmth and moderate moisture are equally favourable to vegetation and animal life. Some plants are confined to particular climates. The arctic bramble is only found in Norway and Canada. Others, as the chickweed, are diffused over the earth. The elephant is the native of warm regions, the reindeer inhabits only cold countries; but man is dispersed through all the varieties of climate. The rush is an amphibious plant, the milletoe a parasite.--Access of air and exercise are necessary to the health and vigour of vegetables as well as of animals. Plants, in confined situations, become weak, dwarfilh, and pallid.
3. Dissemination and decay. The distinction of animals into oviparous and viviparous is not sufficiently marked. Some poffefs the power of generating in both ways; nor is the presence of eggs always necessary to production. One species of polypus multiplies its kind, by sending of ihoots; another, by splitting longitudinally, another by dividing into tranfverfe fections. The dart-millepes discharges its young, by a spontaneous separation. The animalcules which appear in animal and vegetable infufions, multiply ad infinitum, by continual divisions and fubdivisions. The vine-fretter has been discovered to be capable of producing, without the influence of the male; and Bonnet has conducted the experiment through a fucceffion of nine geneX 3