The animal body, we all know, is made up, in a general sense, of a hard bony skeleton, which forms the frame-work that acts as a support to the rest of the body. Bone is found, by chemical analysis, to consist of 65 per cent of mineral matter, chiefly phosphate of lime. Upon and attached to this bone are large masses of fibrous flesh, which constitute the muscles of the body. About 77 per cent of this muscle consists only of water, and the remaining 23 per cent is chiefly composed of fibrin, the characteristic properties of which are supposed to be derived from the large proportion of nitrogen which it contains about 16 per cent. Large quantities of fat are found dispersed over all parts of the animal body. It is found to be composed chiefly of carbon. The intestines, veins, nerves, are composed chiefly of fibrous matter. Of the juices of the body, the largest proportion consists of water; and of the fluids, the blood composes the largest proportion, and the dry part of the blood has much the same composition as fibrin.

1664. Now, you have seen from the composition already given of the several vegetables and grains raised on farms, for the support of the domesticated animals, that they contain principally starch and sugar, which consist of carbon, hydrogen, and oxygen, and the protein compounds, which last comprehend all the substances that contain nitrogen, such as albumen, fibrin, casein, gluten. And the composition of the ash of such of the vegetable substances as has been given, indicates that it is composed principally of lime, phosphoric acid, and the alkalies potash and soda. So that the vegetables and grains raised on the farm contain, in their composition, all the materials necessary to form all the water, bone, fibrin, fat, and fluids, which compose the animal body.

1665. In the application of these substances to the particular state of the animal economy, it should conform with reason to give such of them as contain phosphoric acid and lime most abundantly to young animals, because these are still forming their bones, and will until the skeleton is fully developed. The substances which supply fibrin freely should be given to animals at all ages, as the enlarge

ment of muscle is one of the principal objects of the breeder of live-stock. And those substances which supply fat should chiefly be given when it is desired to fatten the animals for the butcher or domestic use. This seems a very simple view of the rearing and fattening of animals; but in practice it is not so easy as it is simple in theory, for the vital principle often interferes very influentially with the desired results, by creating differences in the constitution of animals reared under exactly similar circumstances, as to give so complete a bias to the results as evidently to place the forming of the condition of any particular animal almost beyond our control. Still, as much of the result accords with expectation as to encourage us to persevere in the improvement of the rearing and fattening of our live-stock.

1666. As no one has done so much of late years to explain the process of digestion, and, in consequence, to establish the practice of feeding animals upon rational and truly scientific principles-a rough sketch of which I have attempted to give in a preceding paragraph, as the now famed Liebig of Giessen in Germany, it is but fair to give his views on the subject, and which I find ably done to my hand by Dr Gregory of Edinburgh, in his edition of a recent work of great merit. "The life of animals," he says, "is distinguished chemically from that of vegetables by the circumstance, that by animals oxygen is constantly absorbed and replaced by carbonic acid, while, by vegetables, carbonic acid is absorbed, its carbon retained, and its oxygen given out. Consciousness, and the power of locomotion, are peculiar to animals. In animals, two processes are constantly carried on-that of respiration, by which the animal heat is kept up; and that of nutrition, by which the matter consumed in the vital functions, and expelled from the body, is restored. Respiration is essentially a combustion of carbon and hydrogen, which, in combining with oxygen, are converted into carbonic acid and water, and at the same time furnish the animal heat. Liebig calculates that the amount of carbon daily burned in the body of an adult man is about 14 ounces, and that the heat given out is fully sufficient to keep up the temperature of the body, and to account for the evapora

tion of all the gaseous matter and water expelled from the lungs. This carbon is derived, in the first place, from the tissues of the body, which undergo a constant waste, but alternately from the food.

The tissues can only be decomposed by the exercise of the vital functions, and the food of the herbivora contains but little of the albuminous compounds, only sufficient to restore the waste of the tissues; while the carbon required for respiration is supplied by the starch, gum, sugar, oil, &c., which form the great mass of their food, and no such amount of muscular motion is required in them as in the carnivora. It is in the form of bile, chiefly, that the carbon undergoes combustion. Hitherto the true function of the bile has been disputed.

The tissues, which are consumed, are resolved first into bile and urate of ammonia. The former is secreted from the liver, reabsorbed, and burned. The latter, in serpents and birds, is expelled unchanged; but in man and quadrupeds, in whom the amount of oxygen inspired is much greater, it also is oxidised, yielding finally carbonic acid, ammonia, and urea.

The urine of the herbivora differs from that of man, in containing, besides urea, much hippuric acid when they are at rest or stall-fed, and beuzoic acid when they are in full exercise, and when, consequently, more oxygen is supplied. The bile of the herbivora is much more abundant than that of the carnivora, -an oX secreting, according to Burdach, 37 lbs. of bile daily. As the waste of matter in the herbivora is but limited, it is obvious that it cannot supply all the bile, and, consequently, a great part must be derived from the starch and other non-azotised constituents of their food, which lose oxygen, and enter into combination with some azotised product of the decomposition of the tissues. Soda is necessary for the formation of bile, and is supplied in the form of common salt: when the supply of soda is defective, the metamorphosis of albuminous compounds can yield only fat and urea. Now, it is worthy of observation that, if we wish to fatten an animal, we must carefully avoid giving it much salt in its food.

In the urine of the herbivora, soda is present in far larger quantity than that of the carnivora, and combined with carbonic,

hippuric, or beuzoic acid. This shows that the herbivora require a far greater amount of soda than is contained in the amount of blood-constituents daily consumed, which in them is small; and this soda is obtained from their food, and employed in producing their abundant bile. The plants in which the herbivora feed cannot grow in a soil destitute of alkalies; but these alkalies are not less necessary for the support of the animals than of the plants. The soda is found in the blood and bile; and the potash is now known to exist in large quantity in the juice of flesh, and to be absolutely essential to the production of casein, that is, the secretion of milk. In like manner the phosphate of lime, which is essential to the growth of grasses, is equally essential to the production of bone in the animals which feed on these plants. It is impossible not to be penetrated with admiration of the wisdom which is shown in these beautiful arrangements.

1667. "Let us now consider the changes which the food undergoes in the process of digestion. When the food has entered the stomach, the gastric juice is poured out, and after a short time the whole is converted into a semi-fluid homogeneous mass, the chyme. Many researches have been made to discover the solvent contained in the gastric juice, but in vain. It contains no substance which has the property of dissolving fibrin, albumen, &c.; and we are compelled to adopt the opinion of Liebig, according to which the food is dissolved in consequence of a metamorphosis analogous to fermentation, by which a new arrangement of the particles is effected. As in fermentation, the change is owing to the presence of a body in a state of decomposition or motion, which is propagated from the ferment to the sugar in contact; so, in digestion, the gastric juice contains a small quantity of a matter derived from the living membrane of the stomach, (1810,) which is in a state of progressive change; and the change or motion is propagated from this to the particles of the food, under certain conditions, such as a certain temperature, and, as it now appears, the presence of a free acid, which is phosphoric or lactic, or both. Besides the gastric juice, the only other substance employed in digestion is the oxygen which is introduced into the sto

mach with the saliva, which, from its viscidity, encloses a large quantity of air. The chyme then leaves the stomach, and gradually passes into the state of chyle, which resembles blood, except in colour, being already alkaline, not acid like the chyme. By means of the circulation, oxygen is conveyed in the arterial blood to every part of the body. This oxygen, acting on the tissues destined to undergo change, produces a metamorphosis by which new soluble compounds are formed. The tissues thus destroyed are replaced by the new matter derived from the food. Mean time, those of the products of metamorphosis which contain the principal part of the carbon are separated from the venous blood in the liver, and yield the bile; while the nitrogen accumulates, and is separated from the arterial blood in the kidneys, in the form of urea or uric acid.

1668. "The blood has another important function to perform, namely, to convey for excretion to the lungs the carbonic acid formed in the extreme vessels or cells in all parts of the body. There is reason to believe that the globules of blood possess the property of absorbing oxygen in the lungs, when they become arterial, and thus convey this oxygen to all parts. The globules then give up the oxygen to the particles of the tissues undergoing change, and in its stead carbonic acid is taken up, and the blood becomes venous. It is not known what chemical compound in blood absorbs and carries the oxygen, but it is by some conjectured to be a compound of iron analogous to the protoxide. It is certain that air is indispensable to the blood, and it is remarkable that sulphuretted hydrogen and hydrocyanic acid both instantly destroy the power of the blood to perform its functions-hence their horrible energy as poisons, when inhaled. Now, these compounds both act on protoxide, protochloride, and other analogous compounds of iron, immediately depriving them of their characteristic power of acting on oxygen.

1669. "With regard to the carbonic acid which is produced in all parts of the body in the continual metamorphosis of the tissues, Enderlin has proved that blood contains no carbonates whatever; and Liebig has

since recently pointed out that the required properties exist in a still higher degree in the phosphate of soda, which does exist in the blood, and appears to be altogether indispensable to its existence. No salt known is so well adapted for this function. It is truly remarkable that, while both phosphate of soda and phosphate of potash exist in the food, the former alone should occur in the blood; and this is especially wonderful when we consider that the juice of the flesh, which is only separated from the blood by various thin membranes, permeable to liquids by endosmose and exosmose, contain much phosphate of potash, and little or no phosphate of soda. It is evident that the vessels or cells must possess in their peculiar membranes a power of selection, or of allowing some salts to pass in one direction only, and others in the opposite.. There can be no

doubt that the function of the acid salt, the phosphate of potash, in the juice of the flesh, and apparently also in the gastric juice, is as important as that of phosphate of soda in the blood. Probably a part of that function is to insure the constant acidity of these fluids, as phosphate of soda does the constant and essential alkalinity of the blood, in which the power of absorbing and giving out carbonic acid-in other words, respiration-depends. And we see, too, that if this be so, the phosphate of potash, of the juice of flesh, and of the gastric juice, cannot be replaced, as far as its functions are concerned, by phosphate of soda.

1670. "Another probable function of the substances which give acidity to the juice of the flesh, and alkalinity to the blood, is the production of electric currents. It has been shown by Matteucci that such currents exist in the body; and we can easily see how they may arise, when we observe two fluids, one acid, the other alkaline, separated by a membrane permeable to one or both, and the fluids in contact with muscle and with nervous matter. At the request of Liebig, Buff constructed piles of discs of pasteboard steeped in blood, with slices of muscle and brain, which showed a powerful current from the blood to the muscle.

1671. "Since no blood can be formed without soda, no animal could live if con

fined to such inland plants as contain only potash. It is well known, indeed, that animals in countries far inland, as Bavaria, are habitually supplied with common salt, either in substance or in the form of saltsprings. Of both they are instinctively fond. But fortunately salt is found, in even inland countries, in all soils and in all waters, and consequently in most plants. Were it altogether absent no blood could be formed, unless salt or soda were artificially supplied to every animal. All inland plants contain earthy phosphates, and phosphate of potash, in variable proportion, often with mere traces of the compounds of sodium. When these phosphates act as common salt, (chloride of sodium,) there are formed chloride of potassium and the common alkaline phosphate of soda, which latter salt is absolutely indispensable to the formation of blood. The chloride of potassium is found in the juice of flesh.

1672. "It is truly a spectacle worthy of admiration, to see the essential properties of two of the most important animal fluids -the blood and the juice of flesh-thus secured by the existence of a difference, at first sight altogether insignificant, between the relation of phosphoric acid to two alkalies, which so much resemble one another that they may be mutually replaced, each by the other, in a multitude of cases-nay, do actually replace each other in many plants. The reader will not fail to remark, how emphatically these facts impress on us the necessity of attending carefully to the most minute characters of all the compounds which can be formed among the elements composing the organic kingdom, even when these characters appear, at the time, to have no considerable relation to the vital pro

cesses.

1673. "The researches of Dr R. D. Thomson have demonstrated, that the most favourable proportion between the albuminous or azotised, and the saccharine or non-azotised constituents in the food of animals, is that of 1 part by weight of the azotised to 7 or 8 of the saccharine. This proportion exists naturally in the most nutritious food, such as grain; while in such food as potatoes, the amount of albuminous matter is much too small. Hence

potatoes alone must be regarded as very inferior in nutritive power to wheat, oats, rye, or maize, equal weights being compared.

1674. "There is another constituent of the animal body, namely, fat, the production of which deserves notice. It is not an organised tissue, but is formed and collected in the cellular tissue under certain circumstances. These are, rest and confinement,—that is, a deficiency of oxygen, and an abundance of food containing a considerable proportion of non-azotised matter, such as starch, sugar, &c.

Now the chief source of fat is sugar, the composition of which is such, that when deprived of oxygen fat remains.

It is obvious, therefore, that fat can only be formed by a process of deoxidation. But it is produced when oxygen is deficient; and it appears, as Liebig has pointed out, that, when there is a deficient supply of oxygen, the production of fat, which is the consequence of the deficiency, yields a supply of that element, and thus serves to keep up the animal heat and the vital functions, which would otherwise be arrested. This is another beautiful instance of contrivance equally simple and wonderful. That fat must be formed by the deoxidising process is proved by the phenomena of the fattening of animals. A goose tied up, and fed with farinaceous food, altogether destitute of fat, acquires in a short time an increase of weight of several pounds, the whole of which is fat. Again, the bee produces wax, a species of fat, from pure sugar.

1675. "With regard to the production of nervous matter, which animals alone can form, we see, from its composition, intermediate between that of albumen and fat, that it may be formed, either by depriving albuminous matter of some azotised product, or by adding to fat an azotised compound. Where it is formed we do not know, but it must be formed in the animal body; and Liebig has suggested, that the power of the vegetable alkalies to affect the nervous system may be owing to their composition, which approaches nearer to that of nervous matter than any other compounds. These alkalies may promote or check the formation

of nervous matter, and thus produce their peculiar effects."*

1676. These observations tend to show, that we may expect in progress of time to explain a large class of phenomena connected with animal life on chemical principles. We cannot do so yet, notwithstanding the plainness of the views propounded by Liebig. He may have opened up the true path, but it is for experimenters to pursue it with research and perseverance, in order to confirm or refute his views. As yet, philosophers are by no means agreed as to the circumstances which regulate the process of digestion some would ascribe our ignorance of it on account of the intricacy of the subject, the obscurity which attends it, and the deficiency of observation as to the true nature of the process; whilst others regard the process as simple, referring the preparation of the food in the stomach to the presence of an acid in that organ, which dissolves the food, and enables it to enter as a constituent of the circulating fluids of the animal system. The acid which effects this important object is the hydrochloric acid, which they consider to have been satisfactorily proved to be present during the period when food exists in the stomach; and they conceive they can imitate the process of animal digestion in glass, or other vessels out of the body, simply by exposing animal and vegetable food to the influence of dilute acids. The subject is not so very simple in nature as it would seem to be when conducted in a glass vessel. There are indications, no doubt, of the direction in which we are to search for a solution of the difficulties of the subject, but we are still at a great distance from the elucidation of the precise manner in which animals digest their food.

1677. "There cannot be a doubt," as Dr R. D. Thomson observes, "that if we understood the nature of the process by which the food which we swallow is converted into living flesh, important results would follow in reference to the preservation of the health of animals, and the treatment of diseases. If

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we were properly acquainted with every transformation through which the constituents of the food pass, after it has been masticated, until it is finally removed from the system, it is clear that, in cases where the stomach is unable to perform its accustomed functions, the assistance of art might be called in to minister to digestion." If Dr Thomson, who has experimented so largely on the subject, feels any difficulty in it, it must indeed be difficult. His own researches were conducted with a view to arriving at a practical resultnamely, the comparative effects of certain given articles of food on the fattening or secreting powers of animals; and these seem to demonstrate, that the fat of animals cannot be produced from the oil of the food, but must be evolved from the calorifiant or heat-forming portion of the animal, essentially assisted by its nitrogenous materials. By following out this principle, he has been enabled to detect an important relation existing between the nutritive and calorifiant portion of the food, upon the determination of which, for the various conditions of animals, he considers the laws of animal dieting depend. He endeavoured to apply the law to various articles of human food; and he trusts that the basis has been laid for future researches, which may be directed to administer to the health and comfort of mankind, and of the domesticated animals. In conducting the experiments upon cattle, he found not only his habitual acquaintance with animals, but also his medical knowledge, in continual requisition, in consequence of the tendency of the varied condition of the animal system, from the sudden and frequent changes of diet, to induce symptoms of disease. These were carefully watched and overcome, by such precautions as clearly follow from a close consideration of the principles announced in his work."+ This work I would recommend for perusal by every student of agriculture.

ON THE ACCOMMODATION OF THE GRAIN CROPS IN THE STEADING.

1678. On looking at the plan of the stead