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ELEMENTS OF ORGANIC MATTER.

THE ULTIMATE AND PROXIMATE ELEMENTS OF ORGANIC BODIES.

The chemical constitution of Organic Bodies is most readily understood by a reference to what have been named their Ultimate Elements, and their Proximate Elements. The ULTIMATE ELEMENTS are all those substances found in organic matter which rank as simple bodies in modern chemistry; that is, bodies which have hitherto resisted all further analysis. In the whole of nature, chemists admit the existence of no more than sixty-three or sixty-four such simple bodies. Out of these sixty-three or sixty-four elementary substances, seventeen exist in organic nature.

The PROXIMATE ELEMENTS are formed by the union of several of these ultimate elements. Most commonly three or four ultimate elements unite in large proportion, while a few others are present in very minute proportion. The proximate elements, in which there are three principal ultimate constituents, are termed ternary compounds; those containing four are called quaternary compounds. The ultimate elements, which enter in large proportion into the ternary and quaternary proximate elements of organic nature, are the simple constituents of air and water namely, oxygen, nitrogen, carbon, and hydrogen. As examples of the proximate elements formed out of these, united in different proportions, we may enumerate albumen, well known under the form of white of egg, and caseine, the essential constituent of cheese — what, in short, makes up nearly the whole of well-pressed cheese made from skimmed milk; also the starch extracted from the flour of wheat and sugar; and lignine, which constitutes ninety-five per cent. of wood.

As the proximate elements are made up of ultimate elements, so the solid textures and fluids of organic bodies are composed by the union of the proximate elements. By the union of textures, organs are formed; by the union of organs, the body itself is framed. Here, then, we obtain a mixed analysis of the organic frame, in part chemical, and in part mechanical.

The modern idea of the organs being made up of textures, so that each might be conceived as being reducible to its ultimate mechanical elements, was a happy improvement on the ruder notion of ancient times, which represented the animal body as consisting of flesh, blood, bone, skin, hair, nail, gristle, sinew, nerve, brain, &c. What, then, is a texture? This question is more easily answered by examples than by a definition. The muscular flesh - that is, the lean of beef or mutton is the muscular texture or tissue; the substance of the brain and nerves is the nervous texture or tissue; the connecting medium of the several organs of the body is the cellular tissue, called also the filamentous, or areolar tissue; and these three are the

PROPERTIES. OF OXYGEN.

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best distinguished textures or tissues of the animal body. In the vegetable kingdom, the cellular tissue is almost the only texture.

This kind of mechanical analysis does not admit of a rigid exactness; because it is only in idea, for the most part, that the decomposition can be carried out to a complete mechanical simplicity. Hence, in a practical point of view, we do not define a texture as a simple solid, as if the next act of decompounding would bring us to the proximate chemical elements contained in it, but content ourselves with saying, in the plural number, that the textures are the simpler solids which enter into the structure of complete parts and

organs.

This general view being premised, we must now look a little more narrowly 1st, into the ultimate elements; 2ndly, into the proximate elements; and, 3rdly, into the component textures of organic bodies.

The ultimate elements are divisible into two orders: those which are at once in larger proportion and more constantly present; and those which, while they usually exist in small proportion, follow a more variable rule as to their presence or absence in the several textures. In the first order, as before pointed to, stand Oxygen, Hydrogen Carbon, and Nitrogen. In the second order we find Chlorine, Iodine, Bromine, Fluorine, Sulphur, Phosphorus, Potassium, Sodium, Calcium, Magnesium, Silicium, Iron, and Manganese.

In a third order, two or three simple bodies might be placed, which are met with accidentally along with the proper elements of organic matter.

ULTIMATE ELEMENTS OF THE FIRST ORDER.

Oxygen. This chemical element, when in the isolated state at common temperatures, exists in the form of a gas, with the properties of common atmospheric air, which is indeed oxygen gas diluted, and thereby rendered less energetic in its effects. Oxygen gas is essential to the life of plants and animals; but unless diluted, it destroys both by its excessive stimulus. It supports the combustion of combustible bodies, such as phosphorus, much more vividly than atmospheric air. In combination with other bodies, oxygen exists, diffused extensively throughout the three kingdoms of nature. Besides nearly making a fourth part, by weight, of the atmosphere, it constitutes eight-ninths of the whole weight of the waters of the globe, and not far from one-half of the weight of the common crust of the earth. In the animal kingdom, it forms something less than the fourth part of the weight of dried muscular flesh, and one-half of the weight of lignine, which, as we have seen, is nearly identical with wood. There are, indeed, but few natural bodies at the earth's surface which do not contain oxygen. These are easily

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FIRST ORDER OF ULTIMATE ELEMENTS.

enumerated, the few bodies which exist in a simple form; carbon as in the state of diamond; sulphur in some of its states; such metals as are found in the virgin state; the combinations of metallic bodies with chlorine, iodine, and sulphur,- for example, the beds of rocksalt, and the sulphurets of iron, copper, and zinc.

The process of combustion, in which oxygen plays so important a part, is not altogether foreign to the subject of Physiology. Combustion is a chemical action, in which the union of one body with another is attended with development of heat, and, under ordinary circumstances, with an evolution of light. When a bit of phosphorus is introduced into a jar of pure oxygen gas at an elevated temperature, the phosphorus unites so rapidly with the oxygen, that vivid combustion is exhibited. What, then, is the source of the heat? To resort to the common explanation, the compound formed has a much less capacity for heat than the oxygen and phosphorus taken together; hence the excess becomes developed or sensible, having been before latent. Or, the explanation may as usefully be drawn from the rule, that when a body passes from a rarer to a denser state of aggregation, as from the gaseous to the liquid or the solid state, heat is uniformly evolved. In the case under consideration, the phosphorus, by uniting with the gaseous oxygen, rapidly condenses it into a solid, in which state the compound exists; and so, in obedience to that rule, much heat is evolved. In most cases of combustion, the temperature of the combustible body must be raised considerably above the common temperature of the atmosphere, by some means independently of the combustion; but as soon as the union between the combustible and the supporter of combustion commences, as between the wick of a lamp charged with oil and the atmosphere, then new heat is developed.

The product of the union of the two bodies in combustion is not always solid, as in the case of phosphorus and pure oxygen gas, more frequently the product is gaseous; thus, when charcoal, a form of carbon, burns, whether in oxygen gas or in atmospheric air, the product is carbonic acid gas-the same gas which is continually discharged from the lungs of animals with the expired air. Nevertheless, heat is evolved in this case, the oxygen becoming considerably denser by the addition of the carbon. Of late, in the chemistry of the animal kingdom, the term combustion has been extended to include those processes of oxidation which take place slowly within the bodies of animals, accompanied by an evolution of heat; the distinctive name eremacausis, or slow combustion, being employed in this sense. By this eremacausis, not only do the simpler forms of carbon within the animal body become changed by combination with oxygen into carbonic acid, but the salts which contain a vegetable acid, as the acetates, the tartrates, and citrates, pass into carbon

FIRST ORDER OF ULTIMATE ELEMENTS.

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ates of the same base, just as the tartar of wine (the impure bitartrate of potassa) is changed by a destructive heat into carbonate of potassa, so long known, as derived from this source, by the name of salt of tartar.

Nitrogen. Nitrogen, like oxygen, exists, at the ordinary temperature of the earth's surface, in the gaseous state, and possesses the common physical properties of atmospheric air. Unlike oxygen, however, it can support neither combustion nor life. It forms nearly four-fifths of the atmosphere by weight, it exists but sparingly in the mineral kingdom, and is not contained, like oxygen, in the common rocks of the crust of the earth. Its chief source in mineral nature, besides the atmosphere, is in two orders of salts, the nitrates and the salts having ammonia for their base. It exists also in the compound mineral inflammables, such as coal, justly regarded as being of vegetable origin. It exists in both the organised kingdoms of nature, yet is much more extensively diffused in the animal than in the vegetable kingdom. Under the head of the nutrition of plants, nitrogen must come in for a large share of attention.

Hydrogen. Hydrogen is a gaseous body, and the lightest of known ponderable substances. The great source of hydrogen is the waters of the globe, of which it forms one-ninth part by weight. It does not exist in the rocks of the crust of the earth, unless in so far as they contain water. Combined with nitrogen, it is present in ammonia. It makes up about one-sixteenth part of the whole weight in the tissue of wood, and nearly the same in starch and sugar; and of dried muscular flesh it forms about one-thirteenth by weight. In such proportions, then, does the hydrogen of water contribute to the substance of animal and vegetable tissues.

Carbon. At ordinary temperatures carbon is a solid body; and its most familiar form is the charcoal of wood. Uncombined, it exists very sparingly in the mineral kingdom; but combined with oxygen, in the form of carbonic acid gas, it exists abundantly, as in combination with earthy and metallic bases, such as the carbonate of lime, the carbonate of magnesia, the carbonate of zinc. The carbonate of lime, as chalk, marble, limestone, marl, is one of the most abundant substances in mineral nature; and of this substance carbon forms one-seventh part by weight. In the atmosphere carbonic acid is uniformly present, but in variable proportion. It exists also in waters. The respiration of animals and the combustion by common fires are continually adding to the carbonic acid of the atmosphere; while the process of vegetation is as constantly decomposing it, appropriating to itself the carbon, and setting free the oxygen. In dried muscular flesh the proportion of carbon by weight is not far from one-half; and in the tissue of wood the weight of carbon is nearly three-sevenths.

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SECOND ORDER OF ULTIMATE ELEMENTS.

ULTIMATE ELEMENTS OF THE SECOND ORDER.

Chlorine.-Chlorine does not exist free in organic nature, but only in combination with metallic bases, or with hydrogen. The chloride of sodium, or common salt, is a constituent of the animal fluids, and in certain classes of animals must be regarded as essential to life, because it is the source of muriatic or hydrochloric acid, the presence of which is one of the conditions of their digestion.

Iodine. Iodine exists in sea-water, in some mineral waters, and in a few minerals. Its chief source, however, is the oceanic algæ or sea-weeds; it exists also in sponges; and has been detected in the oyster and other marine molluscs.

Bromine.

- Bromine exists also in sea-water, and in some mineral waters. It has been found in marine plants, and in the ashes of at least one animal, the janthina violacea, one of the testaceous molluscs.

Fluorine. Fluorine exists, combined with lime, in the bones and teeth of animals. It has been found also in the vegetable kingdom to a sufficient extent to account for its existence in the animal kingdom. In the mineral kingdom it exists in great abundance.

Sulphur. Sulphur exists as widely diffused in the mineral kingdom as in volcanic products, also combined with metallic bodies, and in mineral waters; and to these sources in the mineral kingdom should be added the sulphates, such as the sulphates of lime, as selenite, alabaster, and plaster of Paris; the sulphate of magnesia, or Epsom salts; and the sulphate of baryta, or heavy spar. In the vegetable kingdom sulphur does not exist in much profusion; the sulphates are among the salts met with in the analysis of vegetable tissues; and sulphur is particularly found in some orders of plants, as the cruciferous family and the lichens. In the cruciferous plants such as the coleworts-the presence of sulphur is indicated by the smell of sulphuretted hydrogen, given off during their decomposition.

Phosphorus. Phosphorus hardly exists free in any part of nature. The salts which its acid combinations with oxygen form, are widely spread through the three kingdoms of nature, and appear to have important offices assigned to them in the economy of organic life. Phosphorus exists diffused through all fertile soils. The source from which these important constituents of vegetable and animal substances originally reach the soil, is now proved to be the mineral kingdom. The phosphate of lime exists in the mineral kingdom under two forms-namely, apatite and phosphorite-which, though in some districts they constitute even mountain masses, yet are not widely spread over the earth's surface. But recent chemical analysis has satisfactorily shown that minute portions of phosphates