In our climate, hepatic diseases, or those arising from excess of carbon, prevail in summer: in winter, pulmonic diseases, or those arising from excess of oxygen, are more frequent. The cooling of the body, by whatever cause it may be produced, increases the amount of food necessary. The mere exposure to the open air, in a carriage or on the deck of a ship, by increasing radiation and vaporization, increases the loss of heat, and compels us to cat more than usual. The same is true of those who are accustomed to drink large quantities of cold water, which is given off at the temperature of the body, 98.5°. It increases the appetite, and persons of weak constitution find it necessary, by continued exercise, to supply to the system the oxygen required to restore the heat abstracted by the cold water. Loud and long-continued speaking, the crying of infants, moist air, all exert a decided and appreciable influence on the amount of food which is taken.' -pp. 23, 24. When we read, as we lately did, of five substantial meals a day in Calcutta as very common, while four are universal there, can we be surprised at the prevalence of liver complaint? or can we doubt that a much nearer approach to the native diet would insure to our countrymen in India a condition of health much nearer what they 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, 324 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 100 lbs. 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-established 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 whatever 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: 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 atmosphere. 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. 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 support the process of respiration; when the diseased organs are incapable of performing their proper 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 air, protect the system from its influence-then, the substance of the organs themselves, the fat 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 strokes of the pendulum which regulate it. In our ordinary 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 case of a watch.'-p. 29. After effectually disposing of the doctrines which would attribute animal heat to 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 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 organism, 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 brought to the growing organs by means of this fluid. '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. 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 M. Dénis, who has actually succeeded in giving to muscular fibre, by very simple 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 sub stance, stance, 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 + St + salts. is proteine+P+2S+ salts. is proteine + S+ salts. Albumen Fibrine Arterial membrane is proteine + water. is proteine+water+ oxygen. are proteine + ammonia + oxygen. is proteine+ammonia + water + oxygen. Now it is obvious, that if proteine be present in the food, the other necessary elements are all ready at hand. For animal food, of course, contains as much phosphorus, sulphur, and salts as the body to be nourished; while oxygen and water are always present, and ammonia is a constant product of the decomposition of animal matter. Let us now consider the nutrition of herbivorous animals. Whence do they obtain the means of producing their blood? It * 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 compound, the same in every case, and the organic composition of which was the same as that of fibrine and albumen, while it contained no inorganic matter, gave to this compound, which he considered as the original organic product, from which all the others were derived, the name of proteine (from grow, I take the first place). P. and S. do not stand for equivalents, but for certain very small quantities, much under 1 per cent., of phosphorus and sulphur. In the remaining compounds, the water, oxygen, and ammonia are merely expressed generally, without reference here to their actual quantity. 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 nitrogen; an element indispensable to the existence of blood, as well as of every organised animal solid. But in what form does nitrogen exist in these nutritious vegetables? There are found in the vegetable kingdom three nitrogenised compounds, which alone are capable of supporting animal life, and these have been called vegetable fibrine, albumen, and caseine. The truly interesting result of recent investigations is, that these three compounds are, in composition and chemical properties, absolutely identical with the corresponding animal principles. All are compounds of proteine; and while the whole six are identical in the proportion of organic elements, vegetable albumen is found to contain the same mineral elements as animal albumen, vegetable fibrine as animal fibrine, and vegetable caseine as animal caseine (milk, cheese). All such parts of vegetables as can afford nutriment to animals contain certain constituents 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 are commonly called vegetables. They exist, however, in all plants, without exception, and in every part of plants in larger or smaller quantity. These nitrogenised forms of nutriment in the vegetable kingdom may be reduced to three substances, which are easily distinguished by their external characters. Two of them are soluble in water, the third is insoluble. When the newly-expressed juices of vegetables are allowed to stand, a separation takes place in a few minutes. A gelatinous precipitate, commonly of a green tinge, is deposited, 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 nutrition of animals, and has been named vegetable fibrine. The juice of grapes is especially rich in this constituent, but it is most abundant in the seeds of wheat, and of the cerealia generally. It may be obtained from wheat flour by a mechanical operation, and in a state of tolerable purity: it is then called gluten, but the glutinous property belongs not to vegetable fibrine, but to a foreign substance, present in small quantity, which is not found in the other cerealia. The method by which it is obtained sufficiently proves that it is insoluble in water; although we cannot doubt that it was originally dissolved in the vegetable juice, from which it afterwards separated, exactly as fibrine does from blood. 'The |