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enjoyed at home? The attempt to transport an English appetite to a tropical climate is utterly hopeless, and has cost thousands of valuable lives. Let us hope that our author's lucid explanation of the cause of liver disease may have some effect in reforming our habits both in the East and West Indies.

The accuracy of Professor Liebig's views of the action of oxygen on the system is shown by the phenomena of starvation, where the body so rapidly wastes

away.

In the case of a starving man, 32 oz. of oxygen enter the system daily, and are given out again in combination with a part of his body. Currie mentions the case of an individual who was unable to swallow and whose body lost 100lbs. in weight during a month; and, according to Martell, a fat pig, overwhelmed in a slip of earth, lived 160 days without food, and was found to have diminished in weight, in that time, more than 120 lbs. The whole history of hybernating animals, and the well-establishled facts of the periodical accumulation, in various animals, of fat, which, at other periods, entirely disappears, prove that the oxygen, in the respiratory process, consumes, without exception, all such substances as are capable of entering into combination with it. It combines with what

ever is presented to it; and the deficiency of hydrogen is the only reason why carbonic acid is the chief product: for, at the temperature of the body, the affinity of hydrogen for oxygen far surpasses that of carbon for the same element.

In the progress of starvation, however, it is not only the fat which disappears, but also, by degrees, all such of the solids as are capable of being dissolved. In the wasted bodies of those who have suffered starvation, the muscles are shrunk and unnaturally soft, and have lost their contractility: all those parts of the body which were capable of entering into the state of motion have served to protect the remainder of the frame from the destructive influence of the at

mosphere. Towards the end, the particles of the brain begin to undergo the process of oxidation, and delirium, mania, and death close the scene; that is to say, all resistance to the oxidising power of the atmospheric oxygen ceases, and the chemical process of eremacausis, or decay, commences, in which every part of the body, the bones excepted, enters into combination with oxygen.

The time which is required to cause death by starvation depends on the amount of fat in the body, on the degree of exercise, as in labour or exertion of any kind, on the temperature of the air, and, finally, on the presence or absence of water. Through the skin and lungs there escapes a certain quantity of water, and as the presence of water is essential to the continuance of the vital motions, its dissipation hastens death. Cases have occurred in which, a full supply of water being accessible to the sufferer, death has not occurred till after the lapse of twenty days. In one case life was sustained in this way for the period of sixty days.

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In all chronic diseases death is produced by the same cause, namely, the chemical action of the atmosphere. When those substances are wanting, whose function in the organism is to eased organs are incapable of performing their support the process of respiration; when the disproper function of producing these substances: when they have lost the power of transforming the food into that shape in which it may, by entering into combination with the oxygen of the the substance of the organs themselves, the fat air, protect the system from its influence then, of the body, the substance of the muscles, the nerves, and the brain, are unavoidably consumed. The true cause of death in these cases is the respiratory process, that is, the action of the atmosphere. Respiration is the falling weight, the bent spring, which keeps the watch in motion: the inspirations and expirations are the stroke of the pendulum which regulate it. In our or dinary time-pieces, we know with mathematical accuracy the effect produced on their rate of going, by changes in the length of the pendulum, or in the external temperature. Few, however, have a clear conception of the influence of air and temperature on the health of the human body; and yet the research into the conditions necessary to keep it in the normal state is not more difficult than in the cas eof a watch.'-p. 29.

trines which would attribute animal heat After effectually disposing of the docto some mysterious power in the nerves, or to the mechanical contraction of the muscles, the author proceeds to show that the quantity of carbon daily converted into carbonic acid in an adult, which is 13.9 oz., gives out, in combining with oxygen in the body, just as much heat as if burned in a furnace, and more than enough to account for the heat of the body being kept up, for the evaporation of moisture, and for the heat lost by external cooling. The only difference is, that the combustion is very slow, and the heat is extended over a much longer period. Its amount is the same; its intensity is smaller. He comes to the conclusion that there is nothing yet known to justify the opinion that there exists in the body any other unknown source of heat besides the chemical action between the oxygen of the air and the elements of the food. The existence of this cause cannot be denied or doubted, and it is amply sufficient to explain all the phenomena.

When we turn to the important subject of growth or nutrition, the first point that arrests attention is the function of the blood, that wonderful fluid out of which all the tissues of the body are formed.

All the parts of the animal body are produced from a peculiar fluid, circulating in its or ganism, by virtue of an influence residing in every cell, in every organ, or part of an organ. Physiology teaches that all parts of the body

were originally blood; or that at least they were] M. Dénis, who has actually succeeded in brought to the growing organs by means of this giving to muscular fibre, by very simple

fluid.

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The most ordinary experience further shows, that at each moment of life, in the animal organism, a continued change of matter, more or less accelerated, is going on; that a part of the structure is transformed into unorganised matter, loses its condition of life, and must be again renewed. Physiology has sufficiently decisive grounds for the opinion, that every motion, every manifestation of force, is the result of a transformation of the structure or of its substance; that every conception, every mental affection, is followed by changes in the chemical nature of the secreted fluids; that every thought, every sensation, is accompanied by a change in the composition of the substance of the brain.

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In order to keep up the phenomena of life in animals, certain matters are required, parts of organisms, which we call nourishment. In consequence of a series of alterations, they serve either for the increase of the mass (nutrition), or for the supply of the matter consumed (reproduction), or, finally, for the production of force.'pp. 8, 9.

Now, the blood contains two principal constituents: fibrine, which forms the clot, and albumen, which is dissolved in the serum the former is identical with pure muscular fibre, the latter with white of eggs. Here chemistry steps in, and shows that, as far as regards their organic elements (carbon, nitrogen, hydrogen, and oxygen), these two bodies are identical in composition; and that they differ only in the proportions, absolutely very small, of sulphur, phosphorus, and saline matters | which they contain.

This important and unexpected fact, first observed by Mulder, has been very recently established beyond all doubt by

Albumen
Fibrine

Caseine

Arterial membrane
Chondrine

means, all the characters of albumen, out of the body. On the other hand, Mulder has proved that fibrine and albumen may be viewed as compounds of a peculiar substance, proteine* (which contains only the four organic elements), with minute quantities of sulphur, phosphorus, and salts. This explains at once the ready conversion of muscle into blood, in the process of digestion, and the reconversion of blood into muscle, in that of growth. Albumen is converted into blood or muscle with the same facility; and all these transformations occur without the addition or the removal

of any organic element: for the composition of proteine is the same as that of fibrine and albumen, excluding the mineral ingredients, which form a small fraction of the two latter.

The author proceeds to show that this very remarkable identity in composition. enables us to understand very easily the process of nutrition in the carnivora: for their food consists of muscle, of albuminous tissues, of blood-in short, of compounds of proteine. These animals may be said to devour themselves, for their food has the same composition as their bodies. By the very recent researches of Mulder, Scherer, and Bence Jones, it has been shown that all the tissues of the body, the composition of which differs from that of fibrine or albumen, are yet closely related to proteine. Thus we may express the composition of the chief animal solids as follows (P represents phosphorus, S sulphur):—

is proteine P+S+ salts.
is proteine + P+2S+ salts.
is proteine +

is proteine water.

S+ salts.

is proteine+water+oxygen.

are proteine + ammonia + oxygen.

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is proteine+ammonia + water + oxygen.

Now it is obvious, that if proteine be product of the decomposition of animal present in the food, the other necessary matter.

elements are all ready at hand. For ani- Let us now consider the nutrition of mal food, of course, contains as much phos-herbivorous animals. Whence do they obphorus, sulphur, and salts as the body to be nourished; while oxygen and water are always present, and ammonia is a constant

tain the means of producing their blood? It is here that chemistry again comes to our aid, and points to the remarkable fact, that all vegetable matters capable of supporting animal life contain more or less all the others were derived, the name of proteine (from preve, I take the first place).

* Mulder, having discovered that fibrine, albumen, and almost all the animal tissues, when acted on by potash, which dissolves them, and the solutions precipitated by acetic acid, yield a peculiar + P. and S. do not stand for equivalents, but for compound, the same in every case, and the organic certain very small quantities, much under 1 per composition of which was the same as that of cent., of phosphorus and sulphur. In the remaining fibrine and albumen, while it contained no inor-compounds, the water, oxygen, and ammonia are ganic matter, gave to this compound, which he con- merely expressed generally, without reference here to sidered as the original organic product, from which their actual quantity.

from blood.

nitrogen; an element indispensable to the afterwards separated, exactly as fibrine does existence of blood, as well as of every organised animal solid. But in what form The second nitrogenised compound remains does nitrogen exist in these nutritious fibrine. It does not separate from the juice at dissolved in the juice after the separation of the vegetables? the ordinary temperature, but is instantly coagThere are found in the vegetable king-ulated when the liquid containing it is heated to dom three nitrogenised compounds, which the boiling point. When the clarified juice of alone are capable of supporting animal life, nutritious vegetables, such as cauliflower, and these have been called vegetable asparagus, mangel-wurzel, or turnips, is made fibrine, albumen, and caseine. The truly to boil, a coagulum is formed, which it is absolutely impossible to distinguish from the subinteresting result of recent investigations stance which separates as a coagulum, when the is, that these three compounds are, in serum of blood or the white of an egg, diluted composition and chemical properties, ab- with water, are heated to the boiling-point. solutely identical with the corresponding This is vegetable albumen. It is found in the animal principles. All are compounds of greatest abundance in certain seeds, in nuts, alproteine; and while the whole six are monds, and others, in which the starch of the identical in the proportion of organic ele- graminea is replaced by oil. "The third nitrogenised constituent of the ve ments, vegetable albumen is found to con-getable food of animals is vegetable caseine. It tain the same mineral elements as animal is chiefly found in the seeds of peas, beans, lenalbumen, vegetable fibrine as animal tils, and similar leguminous seeds. Like vegefibrine, and vegetable caseine as animal table albumen, it is soluble in water, but differs caseine (milk, cheese).

'These three compounds are the true nitrogenised constituents of the food of graminivorous animals; all other nitrogenised compounds occurring in plants are either rejected by animals, as in the case of the characteristic principles of poisonous and medicinal plants, or else they occur in the food in such very small proportion, that they cannot possibly contribute to the increase of mass in the animal body.

from it in this, that its solution is not coagulated by heat. When the solution is heated or evaporated, a skin forms on its surface, and the ad All such parts of vegetables as can afford nu-dition of an acid causes a coagulum, just as in triment to animals contain certain constituents animal milk. which are rich in nitrogen; and the most ordinary experience proves that animals require for their support and nutrition less of these parts of plants in proportion as they abound in the nitrogenised constituents. Animals cannot be fed on matters destitute of these nitrogenised constituents. These important products of vegetation are especially abundant in the seeds of the different kinds of grain, and of peas, beans, and lentils; in the roots and the juices of what 'The chemical analysis of these three subare commonly called vegetables. They exist, stances has led to the very interesting result that however, in all plants, without exception, and they contain the same organic elements, united in every part of plants in larger or smaller quan- in the same proportion by weight; and, what is tity. These nitrogenised forms of nutriment in still more remarkable, that they are identical in the vegetable kingdom may be reduced to three composition with the chief constituents of blood, substances, which are easily distinguished by animal fibrine and albumen. They all three their external characters. Two of them are dissolve in concentrated muriatic acid with the soluble in water, the third is insoluble. same deep purple colour; and even in their When the newly-expressed juices of vegeta-physical characters, animal fibrine and albumen bles are allowed to stand, a separation takes are in no respect different from vegetable fibrine place in a few minutes. A gelatinous precipi- and albumen. It is especially to be noticed, tate, commonly of a green tinge, is deposited, that by the phrase-identity of composition— and this, when acted on by liquids which remove the colouring-matter, leaves a greyish white substance, well known to druggists as the deposit from vegetable juices. This is one of the nitrogenised compounds which serves for the How beautifully and admirably simple, with nutrition of animals, and has been named vege- the aid of these discoveries, appears the process table fibrine. The juice of grapes is especially of nutrition in animals, the formation of their rich in this constituent, but it is most abundant organs, in which vitality chiefly resides! Those in the seeds of wheat, and of the cerealia ge- vegetable principles, which in animals are used nerally. It may be obtained from wheat flour to form blood, contain the chief constituents of by a mechanical operation, and in a state of blood, fibrine and albumen, ready formed, as far tolerable purity: it is then called gluten, but as regards their composition. All plants, bethe glutinous property belongs not to vegetable sides, contain a certain quantity of iron, which fibrine, but to a foreign substance, present in re-appears in the colouring-matter of the blood. small quantity, which is not found in the other Vegetable fibrine and animal fibrine, vegetable cerealia. The method by which it is obtained albumen and animal albumen, hardly differ, sufficiently proves that it is insoluble in water; even in form: if these principles be wanting in although we cannot doubt that it was originally the food, the nutrition of the animal is arrested; dissolved in the vegetable juice, from which it and when they are present, the graminivorous

we do not here imply mere similarity, but that even in regard to the presence and relative amount of sulphur, phosphorus, and phosphate of lime, no difference can be observed.

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 carnivora and herbivora would seem to be

this:-in the former, the carbon consumed

The author goes on to show that vegetables alone can produce proteine, which, as it is the most complex product of vege-in respiration must be derived from the table life, is the starting-point of the still food, which being identical with their bomore complex animal products-from the dies, we may say that the carbon is supblood, the origin of all the solids, to the last and most important product of animal plied by the daily waste of their tissues, life, namely, the substance of the brain food. But, to furnish enough of carbon to this waste being compensated by their and nerves. Thus we perceive that the food of herbivorous animals contains the keep up the heat of the body in this way, very same principles (compounds of pro-accelerated by motion. Hence the restthe waste must be prodigious: it must be teine) which constitute the food of carniless 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 nitroflesh 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. In organic matter, carbonic acid, ammonia,

the herbivora the waste of matter is far less

their food, (starch, &c.) is consumed in respiration; thus rendering needless a rapid The whole of these admirable arrangechange of matter in the animal tissues. ments are brought out clearly and beautifully in the present work; and nothing can be more satisfactory than the author's array of established facts, with the argu

water, and salts. The results of vegeta- rapid, and is fully compensated by the rewater, and salts. The results of vegeta-latively small amount of proteine in their tion are, compounds of proteine, starch, sugar. gum, &c., and finally. fat or oil: all food: they eat incessantly; the great mass of of which serve to support life in animals the compounds of proteine for nutrition; the other matters, as we shall see, for respiration. The food of animals is always. organised matter. Plants form or produce proteine, which in some form is essential to animals, as the latter cannot form proteine from substances that do not contain it. Proteine being once given, the animal organism forms from it all its peculiar tissues, which are never found in vegetables. Thus, no vegetable can produce nervous

matter.

ment founded on them.

The young animal receives the constituents A meof its blood in the cascine of the milk. and urine are secreted: the matter of the metatamorphosis of existing organs goes on, for bile urine, of carbonic acid, and of water; but the morphosed parts is given off in the form of butter and sugar of milk also disappear-they cannot be detected in the fæces.

It is to the author that we owe the discovery that vegetables, especially the leguminous seeds, produce vegetable caseine, 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 abtheir conversion into oxidized products furnishes 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, from which any of them may be again produced where it is required. They are all compounds of proteine, as above stated.

What, then, is the use of the sugar, starch, &c., in the food of the herbivora ? or what is the use of the sugar of milk, and fat (butter), in the food of the young carnivora? This important question is treated in the most profound and ingenious manner; and the author demonstrates that these substances-which may all, except fat, be considered as compounds of carbon and water (Prout)-serve to furnish carbon

The change and metamorphosis of organized tissues going on in the vital process in the young animal, consequently yield, in a given time, much less carbon and hydrogen in the corresponds to the oxygen taken up in the lungs. form adapted for the respiratory process than The substance of its organized parts would undergo a more rapid consumption, and would necessarily yield to the action of the oxygen, were not the deficiency of carbon and hydrogen supplied from another source.

and the free and unimpeded development of The continued increase of mass, or growth, the organs in the young animal, are dependent on the presence of foreign substances, which, in the nutritive process, have no other function

than to protect the newly-formed organs from the action of the oxygen. It is the elements of these substances which unite with the oxygen; the organs themselves could not do so without being consumed: that is, growth or increase of mass in the body, the consumption of oxygen remaining the same, would be utterly impossible. The preceding considerations leave no doubt as to the purpose for which Nature has added to the food of the young of carnivorous mammalia substances devoid of nitrogen, which their organism cannot employ for nutrition, strictly so called, that is for the production of blood; substances which may be entirely dispensed with in their nourishment in the adult state. In the young of carnivorous birds, the want of all motion is an obvious cause of diminished waste in the organized parts; hence, milk is not provided for them.

The nutritive process in the carnivora thus presents itself in two distinct forms, one of which we again meet with in the graminivora.' -pp. 68-70.

'It can hardly be doubted that the substance which is present in the gastric juice in a state of change is a product of the transformation of the stomach itself. No substances possess, in so high a degree as those arising from the progressive decomposition of the tissues containing gelatine, the property of exciting a change in the arrangement of the elements of other compounds. When the lining membrane of the stomach of any animal, as, for example, that of the calf, is cleaned by continued washing with water, it produces no effect whatever, if brought into contact with a solution of sugar, with milk, or other substances. But if the same membrane be exposed for some time to the air, or dried, and then placed in contact with such substances, the sugar is changed, according to the state of decomposition of the animal matter, either into lactic acid, mannite and mucilage, or into alcohol and carbonic acid; while milk is instantly coagulated. An ordinary animal bladder retains, when dry, all its properties unchanged; 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 which 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 proteine, is first dissolved into chyme in the This first process of digestion is one of the most interesting, but hitherto perhaps the most obscure, of the vital operations. Solution is effected by means of the gastric juice. But what is the solvent in that wonderful fluid? The answer is very simple-the gastric juice contains no solvent; and yet the food is dissolved. If the reader recollects what has been said of fermentation and metamorphosis, he will readily follow our author's explanation.

stomach.

'The clear gastric juice contains a substance

in a state of transformation, by the contact of

riatic acid, a substance in minute quantity, the decomposition of which is already commenced, and is completed in the solution. If coagulated decomposition is communicated to it, first at the albumen be placed in this solution, the state of edges, which become translucent, pass into a mucilage, and finally dissolve. The same change gradually affects the whole mass, and at last it is entirely dissolved, with the exception of fatty particles, which render the solution turbid. Oxygen is conveyed to every part of . the body by the arterial blood; moisture is everywhere present; and thus we have united the chief conditions of all transformations in the animal body.'-pp. 109-111.

In like manner, air is essential to digestion 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
of their atoms, the property of dissolving in
that fluid. During digestion, the gastric juice,
when separated, is found to contain a free mine-
ral acid, the presence of which checks all further
change. That the food is rendered soluble
quite independently of the vitality of the diges-
tive organs has been proved by a number of the
most beautiful experiments. Food, inclosed in
perforated metallic tubes, so that it could not
come into contact with the stomach, was found
to disappear as rapidly, and to be as perfectly
digested, as if the covering had been absent;
and fresh gastric juice, out of the body, when
boiled white of egg, or muscular fibre, were
kept in contact with it for a time at the tem-
perature of the body, caused these substances to
lose the solid form and to dissolve in the liquid.

'During the mastication of the food, there is secreted into the mouth, from organs specially destined to this function, a fluid, the saliva, which possesses the remarkable property of enclosing air in the shape of froth, in a far higher degree than even soap-suds. This air, by means of the saliva, reaches the stomach with the food, and there its oxygen enters into combination, while its nitrogen is given out through the skin and lungs. The longer digestion continues, that is, the greater the resistance offered to the solvent action by the food, the more saliva, and consequently the more air, enters the stomach. Rumination, in certain graminivorous animals, has plainly for one object a renewed and repeated introduction of oxygen; for a more minute mechanical division of the food only shortens the time required for solution.

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