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455. The chemical or elementary principles vegetables, are carbon, water, and air; or hydrogen (15,) and oxygen (85,) for the constituent parts of (100) water; and azote or nitrogen (72,) and oxygen (28,) as the constituent parts of (100) atmospheric air; and carbon.
Obs. 1.-Wood burnt in a close vessel till it has neither smell nor taste, will produce the basis of all vegetable matter called charcoal; or, when purified, called carbon, which is the most indestructible substance in nature. The diamond approaches the nearest to pure carbon of any substance at present known.
2. It is found that water is nothing but a composition of two airs or gasses, one the inflammable or light gas called hydrogen, and the other the vital gas called oxygen ; and water may be made by combining these; or, it may also be separated into these ; one hundred parts water are composed of fifteen of hydrogen, and eighty-five of oxygen.
3. In like manner, the air or Auid in which we live, is found to be composed of 28 parts of oxygen, or pure vital air ; and 72 parts of nitrogen, or azotic gas; but the due mixture of both, forms a salutary daid or atmospheric air in which we breathe.
4. I have explained the meaning of these easy terms in this place, in order to illustrate the beautiful provisions of vegetables which follow. There is no mystery in them; and they may be understood now as well as when I treat of Chemistry.
456. Vegetables generate, or give out oxygen or vital air, in the light or sunshine, by a natural process of their own.
Air, which has been breathed by animals, is deprived of its 28 parts of oxygen, and will no longer sustain life.
In like manner, a body while burning, deprives air of its 28 parts of oxygen, and the fame will go out.
An animal would die, or a flame go out, when put into air so deprived of its oxygen; but a vegetable will then thrive in it, and will restore it to its original power of sustaining animal life.
Obs.-Hence, the oxygen of the whole atmosphere would, in due time, be consumed by the breathing of animals and by flame, but for this provision of nature. The leaves of vegetables give out oxygen in the day time, and keep up the due proportion which is necessary to the support of animal life : the leaves of aquatic and herbaceous plants produce it however, in the greatest quantity.
457. The saccharine and oily productions of vegetables are parts of their sap or juices; but the turpentine, the bitter, and the acid principles, are considered as the effect of preparation or secretion.
The green colour of vegetables arises from the oil they contain ; the rays of the sun extracting the oxygen from the outer surface, and leaving the carbon and hydrogen, which are known to be the constituent parts of oil.
458. Healthy vegetables perspire water, by the under part of their leaves, equal to one third of their weight every twenty-four hours; by which part they also give out oxygen.
459. Nor do they derive their substance in a prineipal degree from the matter of the soil in which they
grow; but they are created by a vital principle of their own, out of air and water, and of the imperceptible matters combined with air and water, from which all their distinctions of smell, taste, and substance, are derived!
Hail Source of BEING! Universal Soul
All this innumerous colour'd scene of things.-THOMSON. 460. Some plants exhibit signs of great sensibility, besides the effects in nearly all arising from the presence or absence of the rays of the sun : these are the sensitive plant, whose leaves fold together on being touched by the hand; and Venus's mouse trap, which closes on any insect that goes into it, and stings it to death.
Obs. Throughout universal nature, a gradation of beings may be traced ; and yet their particular differences elude the observation, like the various colours of the rainbow, blending and mixing with each other. Where vegetation ceases, or seems to cease, perception begins; and we trace some of the first rudiments, or sparks of it, in the actinia, or sea-anemone, the oyster, and the snail. The polypus ranks as the first of plants, and the last of animals; if its propagation, as some naturalists affirm, can be effected by cuttings, similar to the multiplication of plants by slips and suckers. Then it ascends through various gradations of beings, distinguished hy more enlarged and active faculties, more perfect and more numerous organs, to those creatures which approach to the na. ture of man. We behold the distant resemblauce of his sagacity in the elephant; of his social attachments in the bee and the beaver; and the rude traces of his form in the ourang outang.
XX. Of Animated Nature. 461. Animals are a class of beings differently ore ganized from vegetables ; because they have different destinations, have different habits, and have the power of moving from place to place, called the faculty of loco-motion.
See, thro' this air, this ocean, and this earth,
From thee to nothing. Obs.—The principal object of the study of natural history, is to teach us the characteristics, or distinctive marks of each individual natural object, called classification. To distinguish a species from all others that exist in nature, it is necessary to express in its characters almost the whole of its properties. A number of species brought together, constitutes a genus or tribe. Those properties which are common to all genera, compose a character that distinguishes this assem. blage or group from all other groups. Such an assemblage is oalled an order. By bringing together such orders as are niore nearly allied, we form a more general assemblage, called a class; and by the union of several classes, we obtain a higher division, to which naturalists have given the name of king, dom.
462. When the all wise CREATOR determined on making beings which should be able to move from place to place, he contrived for them a different organization from that of beings which were fixed.
As moveable beings could not have their roots in the ground, he provided them with the cavity of the stomach, in which they were to carry about what should be equivalent to the soil for plants; and the suckers of their nutriment centering in that cavity, were destined to act like the roots of plants in the soil.
463. Hence, in all animals, exists the necessity of
eating frequently, to fill the cavity of the stomach; hence the folly and mischief of filling it with heterogeneous and unnatural substances; it being the object of nature simply to extract from the matter in the stomach a single uniform milky substance called chyle; no other juice but chyle being admitted into the animal system, the rest being rejected and expelled.
464. As animals were intended to move about, the perfect are therefore provided with eyes, to see objects which might endanger their existence; with ears to hear, for a similar reason; with a voice to warn others or to obtain assistance in danger.
Hence, also, they were provided with the senses of smelling and tasting, to discriminate the food which was proper for the stomach; and with the sense of feeling, or irritability, to secure their identities, and excite them to action.
And though things sensible be numberless,
And in those five all things their forms express, Which we can touch, taste, smell, or bear or see. 465. The organs of sense and the powers of volition proceed from the head and brain, by the nerves, which direct the muscles and tendons ; but the functions of animal life are sustained by a simple, yet wonderful arrangement in the stomach and cavities of the body.
The heart is the centre of a thousand tubes, called arteries; and by its never-ceasing contractions, it carries the blood through them, to all parts of the frame, diffusing every where warmth and life.
466. The blood of a man, thus driven by the contraction of the heart (a force like that by which water is driven out of a syringe or bladder,) weighs thirty pounds; and, as this is the stock of the precious fluid possessed by each of us, and our lives depend on its constant circulation, it is not allowed to remain at the extremity of the arteries, but is there taken up by