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animal obtains in its food the very same princi- , for the process of respiration. Fat conples on the presence of which the nutrition of tains much more carbon, with an excess of the carnivora entirely depends.'-pp. 45–48.
hydrogen, but serves the same purpose.
The chief difference between the carniThe author goes on to show that vegetables alone can produce proteine, which, this :-in the foriner, the carbon consumed
vora and herbivora would seem to be as it is the most complex product of vegan in respiration must be derived from the table life, is the starting-point of the still more complex animal products from the food, which being identical with their boblood, the origin of all the solids, to the dies, we may say that the carbon is suplast and most important product of animal plied by the daily waste of their tissues, life, wamely, the substance of the brain this waste being compensated by their and nerves. Thus we perceive that the
food. But, to furnish enough of carbon to food of herbivorous animals contains the keep up the heat of the body in this way, very same principles (compounds of
the waste must be prodigious: it must be
proteine) which constitute the food of carni- accelerated by motion. Hence the rest
less habits of carnivorous animals ; hence vorous animals. They are mixed, however, in the former case, with a large pro: hunting alone must eat five times as much
the reason why the savage who lives by portion of substances containing no nitro
flesh as if he lived on a mixed diet; hence gen-such as sugar, starch, gum, &c., the uses of which will shortly appear.
the total absence of fat in his body, as well The food of vegetables is invariably in- as in that of all carnivorous animals
the herbivora the waste of matter is far less organic matter, carbonic acid, ammonia, water, and salts. The results of vegeta- rapid, and is fully compensated by the retion are, compounds of proteine, starch, latively small amount of proteine in their sugar. gum, &c., and finally fat or vil: ali food: they eat incessantly; the great mass of sugar. gum, &c., and finally. fat or oil; all their food, (starch, &c.) is consumed in resof which serve to support life in animalsthe compounds of proteine for nutrition; piration; thus rendering needless a rapid the other matters, as we shall see, for res
change of matter in the animal tissiies. piration. The food of animals is always ments are brought out clearly and beauti
The whole of these admirable arrangeorganised matter. Plants form or produce proteine, which in some form is essential fully, in the present work; and nothing to animals, as the latter cannot form pro
can be more satisfactory than ihe author's teine from substances that do not contain array of established facts, with the arguit. Proteine being once given, the animal
ment founded on them. organism forms from it all its peculiar tis • The young animal receives the constituents sues, which are never found in vegetables. of its blood in the caseine of the milk. A meThus, no vegetable can produce nervous tamorphosis of existing organs goes on, for bile
and urine are secreted: the maiter of the metamaiter. It is to the author that we owe the dis- urine, of carbonic acid, and of water ; but the
morphosed parts is given off in the form of covery that vegetables, especially the le- butter and sugar of milk also disappear-they guminous seeds, produce vegetable caseine, cannot be detected in the fæces. a substance absolutely the same with the • The butter and sugar of milk are given out peculiar principle of milk, inasmuch that, in the form of carbonic acid and water, and when curdled, it is not to be distinguished the clearest proof that far more oxygen is ab-from skimmed-milk cheese, either chemi- sorbed than is required to convert the carbon cally or physically. Thus the vegetable and hydrogen of the metamorphosed tissues world produces white of egg, fibrine, and into carbonic acid and water. milk; these are all convertible into blood, • The change and metamorphosis of organized from which any of them may be again pro- tissues going on in the vital process in the duced where it is required. They are all young animal, consequently yield, in a given compounds of proteine, as above stated.
iime, much less carbon and hydrogen in the What, then, is the use of the sugar, corresponds to the oxygen taken up in the lungs.
form adapted for the respiratory process than starch, &c., in the food of the herbivora ? or The substance of its organized parts would unwhat is the use of the sugar of milk, and dergo a more rapid consumption, and would nefat (butter), in the food of the young car- cessarily yield to the action of the oxygen, were nivora ? This important question is treat- not the deficiency of carbon and hydrogen suped in the most profound and ingenious plied from another source. manner; and the author demonstrates that and the free and unimpeded development of
•The continued increase of mass, or growth, these substances—which may all, except the organs in the young animal, are dependent fat, be considered as compounds of carbon on the presence of foreign substances, which, and water (Prout)-serve to furnish carbon in the nutritive process, have no other function
than to protect the newly-formed organs from It can hardly be doubted that the substance the action of the oxygen. It is the elements of which is present in the gastric juice in a state these substances which unite with the oxygen; of change is a product of the transformation of the organs themselves could not do so without the stomach itself. No substances possess, in being consumed: that is, growth or increase of so high a degree as those arising from the promass in the body, the consumption of oxygen gressive decomposition of the tissues containing remaining the same, would be utierly impossible. gelatine, the properly of exciting a change in
• The preceding considerations leave no doubt ihe arrangement of the elements of other comas to the purpose for which Nature has added pounds. When the lining membrane of the to the food of the young of carnivorous mam- stomach of any animal, as, for example, that of malia substances devoid of nitrogen, which the calf, is cleaned by continued washing with their organism cannot employ for nutrition, water, it produces no effect whatever, it brought strictly so called, that is for the production of into contact with a solution of sugar, with milk, blood; substances which may be entirely dis- or other substances. But if the same mempensed with in their nourishment in the adult brane be exposed for some time to the air, or
In the young of carnivorous birds, the dried, and then placed in contact with such subwant of all motion is an obvious cause of di- stances, the sugar is changed, according to the minished waste in the organized parts; hence, state of decomposition of the animal matter, milk is not provided for them.
either into lactic acid, mannite and mucilage, or • The nutritive process in the carnivora thus into alcohol and carbonic acid; while milk is presents itself in two distinct forms, one of instantly coagulated. An ordinary animal bladwhich we again meet with in the graminivora.' der retains, when dry, all its properties un
changed; but when exposed to air and moisture
it undergoes a change not indicated by any obWe shall now attempt a sketch of the in- vious external signs. If, in this state, it be termediate steps in the processes by wbich placed in a solution of sugar of milk, that subnutrition is accomplished, which will in- stance is quickly changed into lactic acid. clude the chemistry of digestion and of the of a calf, digested with weak muriatic acid,
• The fresh lining membrane of the stomach formation of the bile and urine, with the gives to this fluid no power of dissolving boiled true function of the former fluid. We flesh or coagulated white of egg. But if previconfine ourselves, here, to the carnivora, in ously allowed to dry, or if left for a time in wawhom the vital process is more simple.- ter, it then yields, to water acidulated with muThe food, consisting of compounds of pro- riatic acid, a substance in minute quantity, the teine, is first dissolved into chyme in the decomposition of which is already commenced, stomach. This first process of digestion is and is completed in the solution. If coagulated one of the most interesting, but hitherto decomposition is communicated to it, first at the
albumen be placed in this solution, the state of perhaps the most obscure, of the vital ope- edges, which become translucent, pass into a rations. Solution is effected by means of mucilage, and finally dissolve. The same the gastric juice. But what is the solvent change gradually atfecis the whole mass, and at in that wonderful fluid ? The answer is last it is entirely dissolved, with the exception very simple-the gastric juice contains no of fatty particles, which render the solution solvent; and yet the food is dissolved. If turbid. Oxygen is conveyed to every part of the reader recollects what has been said of rywhere present; and thus we have united the
the body by the arterial blood ; moisture is evefermenta'ion and metamorphosis, he will chief conditions of all transformations in the readily follow our author's explanation. animal body.'-pp. 109–111.
• The clear gastric juice contains a substance In like manner, air is essential to digesin a state of transformation, by the contact of lion in the stomach, and is introduced by which with those constituents of the food means of the saliva. which, by themselves, are insoluble in water, the latter acquire, in virtue of a new grouping During the mastication of the food, there is of their atoms, the property of dissolving in secreted into the mouth, from organs specially that fluid. During digestion, the gasiric juice, destined to this function, a fluid, the saliva, when separated, is found to contain a free mine- which possesses the remarkable property of enral acid, the presence of which checks all further closing air in the shape of froth, in a far change. That the food is rendered soluble higher degree than even soap-suds. This air, quite independently of the vitality of the diges by means of the saliva, reaches the stomach tive organs has been proved by a number of the with the food, and there its oxygen enters into most beautiful experiments. Food, inclosed in combination, while its nitrogen is given out perforated metallic tubes, so that it could not through the skin and lungs. The longer digescome into contact with the stomach, was found tion continues, that is, the greater the resistance to disappear as rapidly, and to be as perfectly offered to the solvent action by the food, the digested, as if the covering had been absent; more saliva, and consequently the more air, enand fresh gastric juice, out of the body, when ters the stomach. Rumination, in certain graboiled white of egg, or muscular fibre, were minivorous animals, has plainly for one object a kept in contact with it for a time at the tem- renewed and repeated introduction of oxyg-u; perature of the body, caused these substances to for a more minute mechanical division of the lose the solid form and to dissolve in the liquid. 'food only shortens the time required for solution.
• The fact that nitrogen is given out by the The blood, now charged with fresh fiskin and lungs is explained by the property brine and albumen, is sent to the lungs, which animal membranes possess of allowing whence it returns saiurated with oxygen. all gases to permeate them, a property which This oxygen is conveyed, chiefly by the glocan be shown to exist by the most simple expe bules of the blood, to the minutest capillariments. A bladder, filled with carbonic acid, nitrogen, or hydrogen gas, if tightly closed and ries, where it contributes to the metamorsuspended in the air, loses in twenty-four hours phosis of existing tissues in other words, the whole of the enclosed gas; by a kind of ex- to the change of matter. By this metamorchange, it passes outwards into the atmosphere, phosis, certain parts of the living tissues while its place is occupied by atmospherical air. lose the condition of vitality, and are resolA portion of intestine, a stomach, or a piece of skin or membrane, acts precisely as the bladder, ved into new and lifeless, unorganised comif filled with any gas." This permeability to pounds, while a corresponding quantity of gases is a mechanical property, common to all the fibrine and albumen of the blood supanimal tissues; and it is found in the same de- plies their place, assuming the structure of gree in the living as in the dead tissue.
living tissues. To prevent the accumulaIt is known that in cases of wounds of the tion of the lifeless products, the blood is lungs a peculiar condition is produced, in which, by the act of inspiration, not only oxygen, but subjected to two processes, as it were, of atmospherical air, with its whole amount (four- filtration. In the kidneys the arterial blood fifths) of nitrogen, penetrates into the cells of gives up those new products in which nitrothe lungs. This air is carried by the circulation gen predominates. These are uric acid, to every part of the body, so that every part is urea, and carbonate of ammonia. In the inflated or puffed up with the air, as with water liver the venous blood is purified from those in dropsy. This state ceases, without pain, as products in which the carbon prevails, and wound is stopped. There can be no doubt that these may be represented by choleic acid, the oxygen of the air, thus accumulated in the the chief constituent of bile. The matters cellular tissue, enters into combination, while secreted by the kidney. being no longer its nitrogen is expired through the skin and available for any purpose in the body, are lungs.
at once expelled. But with the bile it is Finally, if we consider the fatal accidents far otherwise. which so frequently occur in wine countries from the drinking of what is called feather-white function of the bile recognized as ascertain
In no previous work on physiology is the wine (der federweisse Wein), we can no longer doubt ihai gases of every kind, whether soluble ed. It is viewed by some as an excretion; or insoluble in water, possess the property of by others as assisting in digestion. But our permeating animal tissues, as water penetrates author shows that it is no excretion, for in unsized paper. This poisonous wine is wine the carnivora the whole solid excrements still in a state of fermeniation, which is increased do not contain a trace of bile, being comby the heat of the stomach. The carbonic acid posed entirely of inorganic matter, earth of gas which is disengaged penetrates through the parietes of the stomach, through the diaphragm, bones, &c., while no bile can be found in and through all the intervening membranes, the urine. Neither can the bile, owing to into the air-cells of the lungs, out of which it its composition, serve for the nutrition of displaces the atmospherical air. The patient the tissues. In fact, the whole of it returns dies with all the symptoms of asphyxia caused into the circulation, and disappears entirely. by an irrespirable gas; and the surest proof of It is consumed in the respiratory process, the presence of the carbonic acid in the lungs and is merely the vehicle of the carbon and is the fact, that the inhalation of ammonia (which combines with it) is recognized as the hydrogen, which in that process unite with best antidote against this kind of poisoning. '- oxygen, and are given out from the lungs pp. 113–116.
and skin as carbonic acid and water. Even in the carnivora, the quantity of bile daily
secreted is very large-in a large dog, for Lactic acid has no share in digestion. example, 24 lbs.-yet not a trace is to be Professor Liebig has shown that it never detected, as bile, in the excretions. occurs in the healthy gastric juice, and that Such is a brief sketch of the process of even the artificial gastric juice does not con- nutrition in the carnivora, and, were it only tain it when fresh. But starch or sugar, that the function of the bile is satisfactorily when animal membrane is present, are rap- ascertained—that we now see in the bile the idly converted into lactic acid out of the chief part of the fuel which serves for respibody; so that experimenters, not aware of ration and for producing the animal heatthis fact, have concluded that the lactic acid were it only on this account, the volume which they found had existed in the fresh before us would be full of interest to every gastric juice, which never happens in a state physiologist. of health.
in the herbivora the process of the for
mation of bile takes a somewhat different Here, then, we have the chemical explaform. Here the change of matter could not nation of the process by which living tisyield more than a small fraction of the vast sue is converted into dead compounds. quantity of bile they secrete. A horse, for The blood, or rather the muscular fibre, example, secretes 37 lbs. of bile daily (Bur- which, having performed its functions, is to dach); and even in man, whose diet is mix- be removed, undergoes, with the aid of oxyed, from 17 to 24 ounces of bile are daily gen and water, a metamorphosis, the prosecreted. The products of the metamor- ducts of which are the chief constituents of phosis of the tissues, entering into new bile and urine. The latter is at once expellchanges along with the elements of starch, ed; the former returns into the circulation, sugar, &c, contribute to yield this enormous and, being consumed or burned in the requantity of respiratory fuel; and here, also, spiratory process, furnishes the animal heat. the whole disappears, and is not to be tra In carnivorous quadrupeds and in man ced in the excretions. The excrements of the urate of ammonia disappears, its place the horse contain, in one day, only a few being occupied by urea. Now, the proounces of matter which might be bile, but found researches of Liebig and Wöbler on which, on examination, appears not to be uric acid have shown that by simple oxida
Horse-dung is chiefly composed of un- tion uric acid passes in urea and ca: bonic digested woody fibre, and of saline mat- acid. This beautifully explains the differters.
ence between the urine of serpents and Professor Liebig very justly observes, that of quadrupeds or man. In the latter, that
respiration is far more active, and hence
their urine contains, at most, a trace of • The experience of all those who have occu- uric acid, while urea abounds in it. In serpied themselves with researches into natural pents, with their sluggish respiration, the phenomena leads to this general result, that uric acid, or urate of ammonia, once formthese phenomena are caused, or produced, by ed, remains unchanged. A deficiency of means far more simple than was previously supposed, or than we even now imagine ; and it is oxygen, or, what amounts to the same precisely their simplicity which should most thing, an excess of carbon, in the food of powerfully excite our wonder and admiration. man, disturbs this arrangement; and the
“Gelatinous tissue is formed from blood, from consequence is, that a portion of the uric compounds of proteine. It may be produced by acid is not changed into urea, and calcuthe addition, to the elements of proteine, of al
lous disease ensues. Phthisical patients lantoine and water, or of water, urea, and uric acid; or by the separation from the elements of never suffer from calculus, because in them proteine of a compound containing no nitrogen. there is an excess of
paThe solution of such problems becomes less dif- tients who, from a sedentary town-life, ficult, when the problem to be solved, the ques- have become affected with calculi of uric tion to be answered, is matured and clearly put. acid, no sooner go to the country and take Every experimental decision of any such ques- more exercise, than mulberry calculus (oxtion in the negative forms the starting point of alate of lime) supervenes-oxalic acid bea new question, the solution of which, when obtained, is the necessary consequence of our hav- ing, as Liebig and Wöhler have shown, an ing put the first question.'—pp. 143-144. intermediate product of the oxidation of
uric acid along with urea; wbile that oxiTurning now to the chemical part of the dation, if complete, would yield nothing above process, he proceeds to investigate, but carbonic acid and urea.
In wild carby the help of recent and most accurate nivorous animals calculi are quite unknown, analyses, what relations can be traced in owing to their active habits. Fat food, regard to composition, between the blood which contains 70 or 80 per cent. of caron the one hand, and the secretions and ex- bon, favours the production of uric acid cretions on the other. Having first caused calculus. Those animals which drink blood and muscle to be carefully analysed, much water have no calculi, because a sufhe finds, as might now be expected, that ficient supply of water dissolves and rethey agree in composition. He then goes moves the uric acid as fast as it is formed ; on to compare the formula thus obtained and, finally, calculus, except as an imwith that of choleic acid (bile) and with ported disease, is unknown on the Rbine, that of urate of ammonia (the solid urine of because the Rhenish wines contain so serpents and carnivorous birds.) It is sure- much potash that the uric acid is kept disly very striking to find that the elements of solved by the alkali; while the wines of the two latter, representing the bile and the south, which are deficient in potash, urine, when added together, exactly cor- promote by their alcohol, acting in the same respond to those of blood, with the addi- way as fat, the formation of uric acid. How tion of a little oxygen and water,
important are these views in reference to
50 common and so dangerous a disease : , they agree with observation in many cases, and how probable is it that a rational ap- and in all are founded on very careful explication of them may serve greatly to as- periments. We would again remind the sist in its prevention, or even in its cure ! reader of the analogy between these sup
Another remarkable illustration of the posed transformations and the metamorphoinfluence of respiration, or of the supply sis of sugar into carbonic acid and alcubol. of oxygen, on the urine, is found in our The author terminates this section with the author's discovery, that the urine of stall- following conclusion, drawn from a compafed catile contains hippuric acid—an acid rison of all the facts known in regard to with 18 equivalents of carbon ; while the the food, the secretions, and the excretions urine of the same animals, when living in of the herbivora, namely:the fields, or compelled to labour, does not
• That if the elements of proteine and starch, yield a trace of hippuric acid, but only oxygen and water being present, undergo metabenzoic acid, with only 14 equivalents of morphosis, and mutually affect each other, we carbon. The difference is consumed in may obtain, in certain circumstances, as the prorespiration.
ducts of this complex metamorphosis, choleic The section of the work now under con- acid, urea, ammonia, and carbonic acid, and be sideration contains many other beautiful sides these no other product whatever.' examples of the close chemical relation be
Soda is essential to the formation of bile tween the tissues of the body and the secretions or excretions. Thus, it is ex. immense quantity of bile, tliey require a
in the herbivora; and as they secrete an plained that proteine, by very simple chemical reactions with other compounds large supply of salt. If there be a defipresent in the body, may be made to yield ciency of soda, proteine, with water and bippuric acid, gelatine, or allantoine (the oxygen, will yield no bile, but only fat, peculiar principle of the urine in the fetal urea, and carbonic acid. This is the reacalf); that the blood, with a certain amount
son why an animal cannot be fattened if ed, urate of ammonia and choleic acid, but, bile amounts to five or six times the quanof oxygen, may yield not only, as above stat- too abur dantly supplied with salt.
In this class of animals the carbon of the as occurs in the herbivora, hippuric acid,cho. leic acid, urea, ammonia, and water-or, in- tity of that contained in the daily amount creasing the supply of oxygen benzoic acid, of metamorphosed tissue, or what is the choleic acid, urea, carbonic acid, and water:
same thing, five or six times the carbon of and that proteine with a little water may the daily waste of matter.
the proteine in their food, which supplies
Hence the yield gelatine and choloidic acid (one of the acids of the bile); while again proteine, starch, &c., of their food must necessarily added to uric acid, urea, and water, may ther, in consequence of the large amount
contribute to the formation of bile. Furyield gelatine.* tails ; but although professedly hypotheti- of soda required for their bile, the urine of cal, and intended chiefly as a means of pro- the herbivora is loaded with soda, while
that of the carnivora contains but little. moting the study of this curious subject, we cannot help thinking that there is much On the other hand, the urine of the latter actual truth in these chemical statements :
is rich in phosphates, which occur in very
small proportion in that of the former; the Such of our readers as are familiar with the phosphoric acid in their food, which is not chemical works of the day will understand that abundant, being retained to assist in the these relations are best expressed in the form of equations, in which chemical symbols or abbrevia- formation of the bones and of the substance tions are employed. The system of notation adope of the brain and nerves. ed by the author is extremely simple and clear, but we do not quote his equations, because the explana- tened, and that only when they are stall
It is only the herbivora that can be fattions necessary for understunding them may not be within the reach of many readers, and woulů, if give fed. In the wild state, they become full and en here, occupy too much space. We have preti-r- plump, but uut fat, as is seen in the deer red, therefore, attempting to describe these interest and hare, while the carnivora have always ing coincidences of composition in as few words as possible. The principle to be borne in mind is, that
lean and sinewy muscles. Caitle, when any given number of atoms or equivalents if cer- confined, and fud on food containing much tain elements admits of many different arrange starch, &c., are in the best circumstances ments, each of which may yield a new compound, for becoming both fleshy and fat.
Their or a new group of compounds, the sum of the elements in each group or arrangement remaining the organism possesses the power of assimilatsame. This principle has been long known and ing, or converting into animal tissue, all the occur in inorganic chemistry: it is here extended; the starch, &c., respiration being checked, constantly applied in explaining the changes which compounds of proteine in their food; while with the aid of exact analyses, to the more complex changes in the animal body.
cannot be entirely converted into bile, or