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c. If the clear liquor from which the
The soft parts of the body, indeed the starch has subsided be brought to a boil on entire combustible part, consists essentially the fire, white curdy flocks will separate of three substances, or, more correctly, of and fall to the bottom. From its close re- three groups of analogous substances.
albumen of chemists—this white matter has and forms the outline of the whole body. been called vegetable albumen.
When the skins of animals are boiled, a d. If, after the separation of these flocks, jelly is obtained, to which the name of glue the water be evaporated to dryness, a little is usually given ; by chemists it is called sugar and gum will remain behind; while gelatine. When the cartilages of young if the gluten, obtained as above described, bones are boiled, they also yield a jelly, dilbe boiled in ether, a portion of fatty oil fering in some degree from the former, and will be extracted.
to which the name of chondrin is given. In e. If oatmeal or beanmeal be intimately a solid state, these compounds form the mixed with water, and then allowed to substance of the cells and vessels of the ani. stand till the starch settles to the bottom, mal body. the addition of vinegar to the clear liquid b. The muscular fibre, which forms the will throw down a curd, having much re- fleshy parts of the body. If a piece of fresh semblance, in properties and composition, lean mutton or beef be washed for a length to the curd of milk. As its composition of time in a stream of water, the blood will has not as yet been exactly made out, the be removed, and a white fibrous substance provisional names of avenine and legumin will remain, which is the pure fibre of the are given to the substances thus obiained muscle, more or less mixed with fat. The from the oat and the bean respectively. white of the egg, (albumen,) and the pure They serve the same purpose in these seeds curd of milk, called by chemists casein, are as the gluten does in the grain of wheat. analogous to muscular fibre. They are all
Thus the organic part of plants consists analogous, also, to the gluten and legumin essentially of four classes of substances,- of wheat and other grains, and, like them, The cellular substance or woody fibre,
contain fifteen per cent. of nitrogen, and Starch, gum, and sugar,
a little sulphur or phosphorus, or both. Gluten, albumen, avenine, legumin,
c. The fat, which, in an animal in good Oil, or fat.
condition, forms nearly one-third of the The first of these is composed of carbon weight of the soft parts of the body. It is (pure charcoal) and water only, and forms very analogous—in some cases absolutely from a fourth to a half by weight of all our identical—with the fatty matter of the cultivated crops in their dry state. The vegetable food. starch group consists also of carbon and It will be useful now to compare together water only, though in different proportions. the constitution of the organic parts of the It forms from one-half to three-fourths of animal and the vegetable respectively. the weight of all the kinds of vegetable food The plant contains, The animal contains on which we usually live. The gluten 1. Cellular substance, 1. Cellular substances. group is distinguished by containing about or woody fibre. Gelatine, chondrin. fifteen per cent. of nitrogen, with a small 2. Gluten, albumen, &c. 2. Fibrin, albumen,&c. proportion of sulphur or phosphorus, or both. 3. Fatty matters. 3. Fatty matter. In wheat it forms about one-tenth, in oat
4. Starch, gum, sugar. meal nearly a fifth, and in beans often as This comparison shows us, that in both much as a fourth of the whole weight. The animals and vegetables there is a cellular fats contain no nitrogen, and, in our culti- substance performing analogous functions vated grains, vary from one per cent. to ten in each, though of unlike compositionper cent. of the whole; in our oily seeds they that in both there are substances, gluten sometimes amount to one-fourth of their and fibrin, which are almost identical; the weight.
fats, which are often absolutely identicalThe animal eats all these substances and that the only marked difference bemixed together, in its vegetable food; it ween them consists in the large quantity lives upon, and is nourished by them. of starch, &c., which is present in vegetaWhat purposes do they respectively serve in ble food. We can now understand what the animal economy? To understand this, are the functions which the plant has to we must first study the composition of the perform in reference to animal life, and organic part of the body itself.
what purposes are served by the several be built up.
constituents of the vegetable food which we upon animal food; still fewer the diet of eat.
which might not occasionally be improved Thus as to the duty of the plant, we by a judicious admixture of substances of formerly saw, that one of its purposes was animal origin.* to draw from the soil those mineral, saline, The gluten of the plant and the muscular or inorganic substances which are neces- fibre of the animal are almost identical, and sary to form the harder parts of the animal yet they are chemically different. It may body. This work is done by the roots. be interesting to convey to the reader a We now see that it has besides to manufac- general idea of the nature of the agreement ture the materials—the gluten and fat–out and of the minute differences which prevail of which the soft parts of the animal are to between these and the other substances we
This is done in the interior have classed along with them. of its root, stem, and leaves.
We are indebted to Professor Mulder of Then as to the purposes of the several Utrecht for the observation, that is gluten, constituents of the food—the gluten is car- albumen, casein, fibrin, &c, be dissolved in ried into the stoinach, and thence by the caustic potash, and an acid be then added proper vessel to build up almost unchanged to the solution, a white matter is separated, the muscular parts of the body, The which from every one of these substances fat also is merely transferred from the is the same-which exists in and forms stomach to the parts of the system where from 95 to 99 per cent. of them all—and to its presence is required, or where it is to which he has given the name of protein.f be laid up in store. The plant is thus the In fact, these substances are all compounds brickmaker and hodman, as it were, while of protein, with minute proportions of sulthe animal is the bricklayer, who selects phur and phosphorus, which in many cases the materials brought ready to his hand, have not hitherto been determined. It is dresses them a little, if necessary, with his upon these minute proportions of sulphur trowel, and fits them into their places. and phosphorus that the differences observ
Here, again, we see the beautiful adapta- ed among these several substances as they tion of the plant to the animal-a distinct exist in the animal and the vegetable in a forethought, in obedience to which the plant considerable degree depend. The following prepares beforehand what the future animal table exhibits a simple view of the mutual is to require. The stomach of the animal relations of some of these compounds :is not fitted to manufacture the materials of
Protein. Sulphur. Phosphorus. its own body out of the raw elements which | Glutint of wheat conexist in the atmosphere and the soil. This
10 with 2 labor, therefore, is imposed upon an infe- Fibrin of the muscles
and rior race of living things; but if this inferior Albumen of the blood,
i race from any cause, cease to labor, the Casein or curd of milk, 10
Hair and Wool, animal must cease to live. The life of man has been likened to a flower; but the hum- This fundamental substance, protein, blest flower has, in reality, a more inde- therefore, exists in a great number of those pendent existence than be.
compounds of which ihe parts of our bodies The analogy—the almost absolute iden- consist. It is manufactured by the vegetatity-above shown to exist between the sev- ble out of the elements or more elementary eral parts of the plant and those of the ani- compounds of which it consists-exists, mal, and the way in which the substance of the one is directly converted into the sub- * On his visit to the stud of the Pasha of Egypt, stance of the other, shows how unfounded Colonel E. Napier says,-“ Amongst other things, is that prejudice which many entertain, that tening horses on chopped sheep's heads, and was
I happened to mention the Indian system of fata difference exists between animal and ve- not a little surprised when he said that he could getable food so essential, that the former is the more readily credit it, as to his personal knowwholly unfit to feed and support the herbivor- ledge the Arabs of the Hedjaz often feed their ous races. The starch contained in vegetable milk, and that in some of the districts along the
horses on dried flesh of the camel, as well as its food does constitute an important distinc coast, when barley was scarce, even dried fish tion between the two, and one which is con- was used for them as an article of fuod."- Wild nected, as we shall presently see, with very Sports in Africa, &c., ii., p. 206. beautiful and important purposes in the
t In chemical language, this protein is repre
sented by C40, H3, N5, 012. animal economy ; but there are few ani
Glutin is that part of the Gluten which is solumals, indeed, which may not be kept alive ble in alcohol.
therefore, in the vegetable food we eat, and robs the land of this its special conand through the stomach is conveyed to the stituent. We are informed by Professor several parts of our bodies. In the stomach Johnston, in his Elements, p. 273, that the it may be altered, combined with more or wool which is grown in Great Britain and less sulphur or phosphorus, but cannot be Ireland carries off the land every year upformed from its elements. Thus we see a wards of four millions of pounds of sulphur, little farther into the kind of duty which is to supply which would require the addition imposed upon plants, and into the kind of to the soil of 300,000 tons of gypsum. dependence in which the animal is kept Things that appear trifling to us when upon the labors of the vegetable kingdom. viewed in the small way in which we actu
But even in the plant, while it is prepar- ally see them, become important when ing for the animal, this protein serves im- considered on the large scale in which portant purposes. It is produced from the they take place in nature. The hair on food of the plant in the first root that is the heads of our population carries off formed. It is carried up and deposited nearly half as much as the wool of our along with the young wood. It is necessary sheep: it is not without reason, therefore, in some way to the production of every that the Chinese collect, and employ as a cell. It is first laid down in the solid state manure, the hair shaven every ten days along the walls of the young cells and ves from the heads of their people. sels—it chalks them out as it were. It is We cannot advert to the numerous other afterwards redissolved and shified in the in- practical deductions and applications which terior of the plant, probably to form new How from what has been stated aboveparts-old cells 'containing less of it, and how the kind of soil, the mode of culture, young cells more—till at last it is allowed the condition of the land as to drainage, to accumulate in the seeds, from which man &c., modify the proportions of gluten, and other animals obtain it
. Thus there is starch, and fatly matter in the crop-and a unity of purpose and design throughout how the proportion of these, again, in the all the phenomena of life; and while on the food, determines, in a great degree, the way, as it were, to fulfil some great end, rapidity with which, other things being many minor purposes are served by every equal, the animal we feed lays on muscle particle of living matter.
There are three substances in the above It is interesting, however, to observe, table, a moment's attention to which how still higher practical questions arise will give us an idea of the kind of changes out of such investigations. In feeding also which take place within the animal stock for the growth of beef or mutton, or body itself. These are the albumen of the in keeping dairy cows for the production blood, the fibrin, and the hair. It one of milk and cheese, the husbandman is of the functions of the blood to repair and really a manufacturer. He raises certain rebuild the fibre of the muscles. Suppose raw materials in the form of grass, clover, the albumen of the blood to be changed and turnips, and he must convert them into into fibrin, it only loses one equivalent of beef and mution, or into butter and cheese, sulphur. Thus
before he can take them to market. To
the practical man, who has a rent to pay, Protein. Sulphur. Phosphorus. the primary question is, In which of these From one of albumen, 10 Take one of fibrin,
ways can I turn my raw material to the best There remains of sulphur,
account? If the balance of profit, in his
locality, is on the side of beef and mutton, What becomes of this sulphur? It is part- he feeds cattle and sheep; if on the side of ly, at least, expended in the production of the milk, he makes butter and cheese. hair or wool, in which the proportion of both But the country at large puts the question sulphur and phosphorus is large. This hair in another form. When the population is is daily growing, and requires to be daily constantly ahead of the productive powers supplied with new materials.
of the land, the primary question becomes, Such researches as the above are not " In which of these states-of beef or milk curious merely, or physiologically interest. -can the largest quantity of human food ing; they have important bearings also on be manufactured from the same quantity of practical life. Thus the wool and hair to turnips, grass, or clover ?" Professor Johnwhich we have just alluded, as containing ston has stated the amount of our present so much sulphur, necessarily draws upon knowledge to be, that the same herbage will
produce about five times as much human food ly diffused carbonic acid to form so large a in the form of milk as in the form of beef; proportion of its own substance. We are and adds—“Should the population of this alsu tempted to ask, why, if plants depend country ever become so dense as to render so much upon it, so small a quantity of this a rigorous economy of food a national ques- gas is diffused through the air ? The answer tion, butcher meat, if the above data deserve and explanation of all, however, is simple. any reliance, will be almost banished from Animals live in this air as well as plants. our tables, and a milk diet will be the daily It must therefore be adapted to the nature sustenance of nearly all classes of society.” of both. But if the carbonic acid had been Elements, p. 279. This result is very cu- present in much larger quantity, it would rious, and there is an unexpected interest have been injurious to animal life. To in finding chemical research thus connect- compensate, however, for this smallness of ing itself with the highest and most impor- quantity in adaptation to animal life, the tant considerations of our national economy. plant is made to shoot up a long stem, to
thrust out long branches, and to suspend There remains one other important topic thousands of broad leaves in the midst of to which it is necessary to advert, in order, the ever-moving air, and thus, by millions in some measure, to complete our sketch of of mouths at once, to drink in the minute the relations of chemistry to rural economy. particles of aerial sustenance, which togethWe have already seen that the organic part er are to build up the substance of its growof the plant contains much starch or sugar, ing parts. Thus the balance is kept up, while that of the animal contains none. while wisdom and beauty and prevision apWhat is the reason of this difference? We pear in the way in which it is effected. eat starch and sugar in our food,
and yet The carbon thus drawn from the air unites they form no part of our bodies. They are with the water in the interior of the leaf or not, like the gluten and the fat, built into stem, and is changed into starch, or sugar, our substance. What becomes of them, or woody fibre, all of which, as we have therefore ? What purpose do they serve in already seen, consists of carbon and water the animal economy? Why do they exist only. In this way, the starch we eat in our 80 largely in all vegetable substances ? food is formed out of carbonic acid, drawn These inquiries lead us to the discovery of from the air by the leaves, and of water other beautiful contrivances and other wise drawn from the soil by the roots. But what ends.
becomes of the starch after it has been eat. Plants draw their organic food—that food en? What purpose does it serve in the anfrom which their organic part is formed imal economy? in part from the soil, and in part from the Among the necessary functions of animal air. Of that which they draw from the air, life is that of breathing. We breathe that the carbonic acid* is the most important. we may live. During respiration, we draw This carbonic acid consists of carbon (pure into our lungs atmospheric air, containing, charcoal) and oxygen only. It exists in the as we have seen, a very minute proportion atmosphere in exceedingly small quantity, of carbonic acid gas. But when we return five thousand gallons of air containing only the air to the atmosphere from our lungs, it two gallons of this gas.
contains a much larger proportion of this During the day, all the green parts of our gas. It is constantly produced in the blood, cultivated plants are continually sucking in and given off from the surface of the lungs this gas from the air, and giving off oxygen, into the air. A full grown man throws off adding, in fact, to the proportion of carbon as much carbonic acid every day as contains they contain.
eight or ten ounces of carbon; a cow or a We are surprised at first to learn that up- borse about five times as much. This carwards of three-fourths of the bulk of vast bon the animal derives in great part from forests, as well as of the crops we reap from the starch or sugar which ii eats, and thus our fields, are in this way drawn from the the purpose or function of all the parts of air. We are astonished that the growing the food is explained. The gluten repairs plant should be able, by all its diligence in the waste of the muscles, the oil lays on fat, working, to draw in enough of this sparing the saline matters yield their necessary in
gredients to the bones and the blood, and
the starch feeds the respiration. * Carbonic acid is the kind of
which escapes from soda water, ginger beer, or champagne, and
The carbonic acid, 'it thus appears, is causes them to effervesce.
sucked out of the air by the plant, and its
carbon combined with water into the new by which the other motions of the machine form of slarch. The animal eats this starch, are kept alive. and after a while throws the carbon off again Nor are these explanations simple and into the air in its old form of carbonic acid, beautiful only. The practical man learns ready to be taken up a second time by oth- from them that his stock ought to have a er plants, and to be reconverted into starch. certain quantity of starch in their food, but
This is no doubt a very beautiful little that they can by no means live on starch cycle of operations, by which a compara- alone. We say ought, because economy tively small quantity of carbon is made to prescribes it. Animals will live-herbivoperform a large amount of work; but if it rous animals that is—though there be no be true to nature, the carbon must serve starch or sugar in their food. Fat may supsome useful purpose, while it is undergoing ply its place, or even beef and gluten in certhese successive transformations. The al- tain circumstances. But in our climate ternate production of starch and carbonic these are neither suited to the habits of our acid must have some connection with the stock, nor are they economical to the seedwell being of vegetable and animal exist- er. The use of beef or gluten, indeed, in
We shall for the present, pass over the place of starch, involves an absolute its use to the plant, and consider only the loss of most valuable nourishment. purpose it serves in reference to animal life. But the animal dies. The body is con
When starch or sugar is kindled in the signed to the dust. Its organic and inorair, it burns; its carbon combines with the ganic parts there undergo numerous chemoxygen of the atmosphere, and forms car. ical changes, all of which are intended to bonic acid. Much heat is given off, and adapt the dead matter for entering into the the starch entirely disappears in the form of walls of new superstructures. To follow carbonic acid and water.
these changes would show us further beauA similar change takes place in the body tiful contrivances and happy adjustments of the animal. The starch which is con- connected also with reflections as high, with veyed into the stomach is burned indirectly, practical results as important, and with pracby means of the oxygen which is taken in iical suggestions as useful as any of those by the lungs. Heat is thus produced, while we have already considered. carbonic acid and watery vapors are given We must, however, hold our pen ; we off in the breath.
have given instances enough to show how In our atmosphere, all sensibly warm sub-rich in instruction this whole subject isstances have a tendency to become cooler. how full of instruction especially to the The bodies of warm-blooded animals are improving agriculturist.
How importhus constantly losing heat. Were there tant, therefore, in the present state of our no source of heat within the living body it- national agriculture, that these enlarged self, therefore, it would soon become cold means of good which the Deity offers us, and stiff as those of dead animals so quick- should be placed within the reach of our ly do. The burning of the food in the sys- practical men, and that these men should tem—for so it may be called—is this source be induced to employ them with a view to of heat; hence the coldness and the shiver- their individual as well as to the general ing of the half-sed, and the cheerful warmth welfare. of those who live well; hence also the lar. Had our limits permitted us, we could ger consumption of food where much exer- have wished now to advert to the origin cise is taken and much warmth expended, and progress of this knowledge,—to have and the smaller appetite of those whose lives inquired how, when, and by whom these are sedentary, or who live in comfortable applications of science to agriculture have houses.
been successively made. We should have Thus the purpose of the starch is to keep liked to explain how Lord Dundonald first up the heat of the living animal. This pur- drew together the scattered fragments of pose attained, its duty is performed. It is such knowledge in our own country-how necessary to the working of the animal ma- Davy built upon and added much to this chine, that its temperature should be kept foundation-how De Saussure, meanwhile, up to a certain point. To effect this an ad- was enlarging by important facts and deditional movement, as it were, is attached ductions our knowledge of the chemical to it, by means of which starch is manufac-physiology of plants—how, following in the tured into carbonic acid and water, which footsteps of these men, Sprengel almost escape while a supply of heat is left behind, I alone during a lapse of twenty years, grad
VOL. VI.-No. II. 18