PHOSPHORUS DERIVED FROM MINERALS.

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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 sulphureted 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 are everywhere spread throughout the earth's surface; so that nothing is easier than to understand, that by the disintegration of these rocks-a process at all times in activity-minute portions of phosphates are continually added to the adjacent soil. Even in sea-water phosphates have been detected. As to the existence of phosphorus in the vegetable kingdom, the ashes of red wheat contain, according to Liebig, 94.44 per cent. of phosphates; the ashes of white wheat, 91.47 per cent. ; the ashes of pease, 85.46 per cent.; the ashes of beans, 97.05 per cent. of the same salts; whence it follows that the ashes of these several substances have phosphorus present in them to the extent of 15 to 20 per cent. And as phosphates are invariable constituents of the seeds, not only of all kinds of grasses and leguminous plants, but also of the seeds of plants in general which are fit for food, it is not too much to say, that phosphorus, in minute proportions, is spread throughout the vegetable kingdom.

In the animal kingdom phosphates make a prominent figure among its saline constituents. It has even been believed of late that uncombined phosphorus exists in the animal body, as in albumen and fibrine.

If the phosphates in the human body amount to about one-fifth part of its weight, as indicated by some calculations, then every human body must contain several pounds of phosphorus. The phosphates, and particularly the phosphate of lime, are the chief hard materials of the bones in vertebrated animals, the carbonate of lime being in very inferior proportion. In the true shells, as in those of the crustaceous molluscs, or testaceous animals, there appear to be no phosphates, the hard substance being almost entirely carbonate of lime; but in the true crustaceous animals, as in the shells of the lobster, crab, and crayfish, there is both phosphate of lime and carbonate of lime, the latter predomi

44

POTASSIUM DERIVED FROM MINERALS.

nating. In egg-shells there is a portion of phosphate of lime, while the predominating constituent is the carbonate of lime. The bone, as it is termed, of the cuttle-fish, contains no phosphate of lime. In the zoophytes the composition of the indurated part varies in different animals. Madrepore consists entirely of carbonate of lime, without phosphate; and the red coral yields a little phosphate of lime. In the higher animals phosphates are found generally throughout the fluids and soft parts, as well as in the skeleton.

Silicon, or Silicium.-Silica, or silicic acid, is found in small proportion throughout the organised kingdoms of nature. In the animal kingdom it is met with, in trifling quantity, chiefly in the bones and in the urine. In the vegetable kingdom it performs the important office of imparting strength to the stem, as in grasses, so as to enable them to support the weight of the grain. In the stem of the equisetacea, or horse-tails, the silica is seen to be disposed in a crystalline arrangement. In the bamboos of the East Indies there occurs a deposit of pure silica in considerable masses, to which the name "Tabashen" is given, and to which various mystical properties are ascribed.

Potassium.-The ashes of trees and of herbaceous plants growing elsewhere than on the sea-shore, contain the carbonate of potassa; and such is the sufficient proof of the existence of potassium generally throughout the vegetable kingdom. The proportion of potassium varies considerably in different plants; and those which contain a large proportion refuse to grow in soils not rich in salts of potassa. The carbonate of potassa was formerly called the vegetable alkali, as if it belonged peculiarly to the vegetable kingdom. But it is now well ascertained, that all the potassa of the vegetable kingdom had its original source in the mineraï kingdom, whence, by the disintegration of the rocks containing it in small proportion, new supplies are continually passing into soils.

In the animal kingdom potassium is not found so extensively diffused. Salts of potassa exist in some of the fluids of the human body, as in the blood, the milk, the urine. The same salts are abundant in the urine of herbivorous animals; that is, the excess of potassa received with vegetable food is thrown off by the urine.

Sodium.-In the ashes of sea-weeds, and of plants growing on the sca-shore within reach of sea-water, the carbonate of soda exists. Kelp and barilla are the names applied respectively to the soda obtained from these two sources. Soda was formerly termed the mineral alkali, and perhaps it is more easily obtained from the mineral kingdom than potassa, owing to its salts existing in a more isolated form in that kingdom; for example, the chloride of sodium in the shape of rock-salt and sea-water, the nitrate of soda, and natron, found in certain districts of the globe. Soda, like potassa, exists also diffused through mountain rocks in minute proportion; for example, the difference between felspar and albite, or natron felspar, is, that in the latter the potassa of the felspar is replaced by soda.

Soda is more particularly the alkali of the animal kingdom. Besides the chloride of sodium, widely diffused, as already mentioned, in the animal kingdom, the sulphate of soda, the phosphate of soda, and various combinations of soda with the organic acids, are met with, particularly in the animal fluids.

Calcium.-Lime, or the oxide of calcium, exists widely spread in organised nature. In the vegetable kingdom the salts of lime everywhere exist in minute proportion, while in the animal kingdom these salts accumulate so as to obtain a particular prominence, as has been already indicated under the head of phosphorus.

Magnesium.-Magnesia, or the oxide of magnesium, exists much more sparingly than lime in organic nature. Phosphate of magnesia is a salt of continual recurrence in

the chemical analysis of the parts of vegetables. Thus, in the ashes of wheat, rye, beans, and pease, the phosphate of magnesia exists to a considerable extent. It also occurs in the human blood, and in the bones.

Iron.-Iron appears to possess important offices in organic nature. Its oxide exists, combined with phosphoric acid, in such seeds as wheat, rye, and pease; and the oxide is discoverable in the ashes of various kinds of wood,-for example, in the ashes of fir-wood the oxide has been found to the extent of 22.3 per cent. In the animal kingdom iron is a universal constituent of the blood.

Manganese.—Manganese is found in the analysis of various woods, and also in the human hair.

THE PROXIMATE ELEMENTS OF ORGANIC NATURE.

The proximate elements of organic nature are divisible into the azotised and nonazotised proximate elements; that is, into those which contain nitrogen, and those destitute of nitrogen.

Albumen, fibrine, and caseine are proximate elements, common to both kingdoms. According to a view which has excited much attention, these three proximate elements are merely slightly modified forms of the one proximate element, proteine. Mülder, the author of this view, conceived that the compound to which he gave the name of proteine was the basis of these several substances, and that the difference in their properties depended on the circumstance that the proteine in each was united with a different proportion of sulphur, or, in some cases, of sulphur and phosphorus and salts. A degree of doubt still envelopes this view; but certain it is, that the three proximate elements just enumerated, differing as they do very materially in properties, agree very closely in ultimate composition. All the three, whether obtained from the vegetable or from the animal kingdom, consist of oxygen, hydrogen, carbon, and nitrogen, with a proportion of sulphur and phosphates; the proportion of nitrogen being about fifteen or sixteen per cent.

Albumen. This proximate element is most conveniently represented by the white of eggs. It is soluble in water, and exists dissolved in the serum, or watery part, of the blood, and in vegetable juices. It is coagulated by heat; that is to say, after having been exposed to the heat indicated by the 160th degree of Fahrenheit's thermometer, it ceases to be soluble in water, and several chemical agents produce the same effect as heat upon it. Albumen exists in the serum of the blood; in the secretions poured into what are termed the shut cavities of the animal body, such as the thorax and abdomen; in the humours of the eye; in the bile; in the muscular tissue; and, more or less modified, in many of the animal solids. It is met with, also, in many vegetable juices, and in seeds, such as nuts, almonds, &c.

Fibrine.-Like albumen, fibrine is known under two forms-the coagulated and the non-coagulated. The latter is found in fresh-drawn blood and in fresh-drawn vegetable juices; but, on standing, each coagulates. In the coagulated state it exists naturally in muscular flesh, in the gluten of wheat flour, and in the seeds of the grasses.

Caseine.-In milk caseine is found. It does not coagulate spontaneously, like fibrine, nor by heat, like albumen, but by the action of acids it coagulates. Cheese made from skimmed milk, and well pressed, is nearly pure caseine. The name legumine was formerly applied to a substance quite identical with caseine, found in the seeds of leguminous plants. The ashes of caseine are rich in phosphate of lime and in potass. Coagulated caseine is a compound of caseine with the acid employed in the coagulation.

When milk, by long standing, seems to coagulate spontaneously, the effect is produced by the previous generation of lactic acid, a portion of which has combined with the caseine. In the oily seeds, such as almonds, nuts, &c., caseine is present, together with albumen.

Gelatine.-Isinglass represents the chemical body termed gelatine, which consists of carbon, hydrogen, nitrogen, oxygen, and sulphur. To speak strictly, it does not exist in the animal tissues, but is formed out of certain of these by the action of boiling water. Gelatine is soluble in hot water, and by cooling forms a jelly. It is precipitated by tannic acid, and upon this property depends the formation of leather. The gelatinous tissues, as they are termed, are the bones, the tendons and ligaments, the cellular tissue, or filamentous tissue, and the membranes in general. Glue and size are formed from such tissues by long boiling. Gelatine is found to be more closely allied to albumen, fibrine, and caseine, than was at first supposed. It is believed, however, that it cannot be transformed within the animal body into albumen, fibrine, or caseine; and that is the reason why animals fed exclusively on gelatine die with symptoms of starvation.

Chondrine.-Between gelatine and chondrine, which forms the tissue of cartilage, there is a close resemblance; with this difference, however, that chondrine is not precipitated by tannic acid.

Horny Matter.- Of horny matter there are two varieties, the membranous and the compact. The membranous constitutes the epidermis and the epithelium, or lining membrane of the vessels, the intestines, the pulmonary cells, &c. The compact forms hair, horn, nails, &c. Feathers are allied to horny matter.

Hematosine.-The colour of the blood is due to a peculiar albuminous principle, termed hematosine.

Globuline. In the blood-globules, besides hematosine, there is another albuminous principle, on which the name globuline has been bestowed.

Kreatine. There has been obtained of late, from the juice of flesh, a remarkable substance, to which the name kreatine has been given. It is a crystalline compound, consisting of oxygen, hydrogen, carbon, and nitrogen. It has neither acid nor basic properties. It is very soluble in hot water, and cold water retains a minute portion of it in solution. By the action of strong acids it is resolved into a new body, named kreatinine. Kreatine has been found, in minute quantity, in the muscular flesh of the common domestic quadrupeds, and also in that of birds and fishes.

Urea. The chief peculiar constituent of the urine is urca, which consists of oxygen, hydrogen, carbon, and nitrogen, the last being the predominant element. Although, then, the constituents of urea are the same as those of albumen, fibrine, and caseine, the proportions are very different. In those albuminous bodies the proportion of nitrogen is only about 15 per cent., while in urea it is 47 per cent. In those so-called forms of proteine the carbon amounts to 52 or 53 per cent.; while in urea it is no more than 20 per cent. In the former, the hydrogen is very much the same per cent. as in the latter; but the oxygen in urea is 27 per cent., while in the forms of proteine it is about 22 per cent.

Uric Acid. In uric acid the proportion of nitrogen is also great, while that of carbon is also considerable. The nitrogen is present to the extent of 32 per cent., while the carbon amounts to 37 per cent. Uric acid is secreted, not only by animals and birds, but also by serpents and many insects. Guano consists chiefly of uric acid combined with ammonia.

Hippuric Acid.-In the urine of graminivorous animals another acid has been discovered, to which the name hippuric has been given. In this acid there is no more than 8 per cent. of nitrogen.

THE NON-AZOTISED PROXIMATE ELEMENTS OF ORGANIC BODIES.

Oil, or Fat.-For sake of convenience, we still speak of the oily constituents of organic bodies as proximate elements, though, strictly speaking, the oily acids, of which these oils consist, are the true proximate elements. The term fixed oil, or fat, denotes a compound of oxide of glyceryle with certain organic acids, chiefly compounds of that oxide, with stearic, margaric, and oleic acids,—two of these, and often all three, being present. In animals, fat occurs chiefly in the cellular membrane, or in a tissue connected with it. Among plants, oils occur in the seeds, capsules, or pulp surrounding the seeds, and very seldom in the root.

Starch.-Fecula, or starch, as already stated, has only lately been recorded as existing in the animal kingdom. In vegetable nature it is everywhere met with. It occurs abundantly in the seeds of the cercalia; in the tubers of tuberiferous roots, as in the potato; in the stems of palms; and in lichens. Starch, by its ready convertibility into soluble forms-such as dextrine and sugar-is well fitted to act important parts in the economy of vegetable nature. It appears to be stored up in the seeds, roots, and pith of plants, to supply materials for some of the most essential vegetable products.

Gum.—The mucilaginous compound, gum, is widely spread throughout the vegetable kingdom. It is soluble in water, and insoluble in spirit. Its precise uses in the vegetable economy have hardly yet been made known.

Lignine.-The basis of wood, and of the stems and leaves of herbaceous plants, is termed lignine, or woody fibre. It is a fibrous matter, insoluble in all ordinary solvents, and is left after vegetables have been successively exposed to the effects of ether, alcohol, water, diluted acids, and diluted alakalies. Lignine forms about 95 per cent. of baked wood, and is the chief constituent of linen, paper, and cotton. Lignine, together with starch and gum, constitutes the principal mass of the vegetable kingdom.

Such are the chief proximate elements of the organised kingdoms of nature; as to the rest, it would be tedious to enter upon any allusion to them at present, while such of them as deserve particular attention, will meet with the necessary mention in the further course of this treatise.

THE CHIEF COMPONENT TEXTURES OF ORGANIC BODIES.

It will be sufficient to exhibit a few distinct examples of the character and properties of the component textures of organic bodies, without attempting, at this stage of our undertaking, to exhaust the whole of the details which might come under this section.

In the animal kingdom, as before hinted at, there are three well-distinguished textures, namely, the muscular, the nervous, and the filamentous. In the vegetable kingdom there is only one distinct texture, namely, the cellular.

The muscular tissue-to confine our attention to a single fibre-has the property of shortening and elongating itself by a molecular movement of its minute constituent parts, so as to impart a mechanical impulse to the adjacent solids, or fluids. In the meantime the cilia, as they are termed, or the minute bodies observed in motion on membranous surfaces, may be ranked with the muscular texture, though it be still uncertain to what extent the molecular action in each is different. The nervous texture has the property of being so influenced from without, as to execute and regulate the