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3. Food, and its Influence on Health and Disease, or an Account of the
Effects of different kinds of Aliment on the Human Body. With
Dietetic Rules for the Preservation of the Health. By MATTHEW
TRUMAN, M.D.— - London, 1842. 12mo, pp. 240.

THE works placed at the head of this article, taken collectively, profess
to comprise the entire subject of diet. While examining them, we shall
endeavour to ascertain the progress that has been made in the attainment
of correct principles of dietetics; for it may be affirmed that such prin-
ciples are still a great desideratum in medical practice. As a collateral
object, we have it in view to illustrate the importance to mankind of every
step gained in this inquiry, not only in a physical and hygienic, but in an
intellectual, moral, and religious point of view.

Dr. Pereira's treatise is unquestionably the earliest attempt that has
been made, in this country at least, to place the general subject of die-
tetics upon a strictly scientific basis. Accordingly, in the present
article we shall follow his arrangement, and avail ourselves of many of
his valuable suggestions as we proceed. Chemistry in its present state,
and especially the organic chemistry of Prout and Liebig, is made by far
more available in elucidating the question of diet by this physician than
by any writer who has preceded him. He abandons the ordinary method



of arranging foods according to the proximate principle which happens to predominate in their composition, and adopts one of a more scientific character, partly from Tiedemann, and partly original. Under the term "Food" Dr. Pereira comprises not only solids, to which the word " Aliment" has frequently been restricted, but also Fluids and Condiments. The work is divided into two parts, the first treating of "the substances employed by man as food;" the second of "the adaptation of aliment to the different wants and conditions of human existence.'


This part is divided into three chapters, and comprises an account of the chemical elements of food; of alimentary principles, as oil, sugar, protein or fibrin, which are compounds of two, three, four, or more undecompounded bodies; and of compound aliments, as the flesh of animals, vegetables, wheat flour, &c., which are frequently composed of many alimentary principles: each of these divisions requires a special exposition.

1. ELEMENTS OF FOOD. This chapter contains numerous chemical details of the highest importance, introduced by Dr. Pereira for the first time into a systematic treatise on diet. They are chiefly derived from the recent productions of Boussingault, Liebig, Payen, and Dumas. Physiologists variously estimate the number of elements which enter into the human body as essential constituents; with Dr. Prout, the author assumes it to be thirteen. These are all derived from the food.

1. Carbon. This is an essential constituent of every living tissue, and it ultimately serves as fuel for combustion, and the production of animal heat. More or less appears to be required by the system, not so much for the purposes of nutrition, but, according to the varying circumstances of the production of heat, in states of exertion or rest for instance; or according to external temperature as determined by season, climate, the state of the atmosphere, and we may add clothing. It is derived from the food, as a component part of the different alimentary principles, in proportions varying from about 34 to 78 per cent., the smaller proportions being contained in certain vegetables, and the largest quantity in oils and fats. Dr. Pereira shows by calculation that the chemical changes effected upon the carbon received into the system are nearly, if not quite, sufficient to explain the animal temperature.

2. Hydrogen. This also, as an element of the organized tissues, is an essential constituent of food. Where it occurs in the relative proportion to oxygen, which is necessary to constitute water, as in starch and sugar, the substances are regarded as hydrates of carbon, and they yield the latter element only, to combine with oxygen in the system. For this reason the quantity of oxygen inspired by graminivorous animals, is equivalent to the carbonic acid expired, no oxygen being required for the combustion of hydrogen. When the hydrogen is in excess, as in fat, alcohol, protein, and gelatin, whatever intermediate forms the food may assume in the animal solids or fluids, not only is its carbon converted by combustion into carbonic acid, but its excess of hydrogen is converted into water. So that in carnivorous animals, which consume a large quantity of super-hydrogenous food, a larger quantity of oxygen is inspired than of carbonic acid expired, this being an additional source of animal heat. When the hydrogen is deficient in an alimentary substance,

as in citric and tartaric acid, all the hydrogen and part of the carbon being already in combination with oxygen, none of the first element, and probably a part only of the second, can be available as fuel for animal combustion.

3. Oxygen. This element is a constituent of the more essential parts of the vital tissues, and accordingly of food. In the latter it bears a proportion varying from 10 to 140 parts, combined with 120 parts of carbon. Those foods-as fat and proteinized substances-which contain a small proportion of oxygen, must require a larger quantity of respired air for their combustion, than those-as sugar and starch-which contain a larger proportion of oxygen. The latter produce less heat than the former. Hence the quality of the food as respects its elements, and the activity of respiration, reciprocally influence each other; theory in this instance confirming and explaining the results of experience. Oxygen has an interest of the highest importance, distinct from that of food. As vital air it is the supporter of combustion, and of that degree of heat without which no vital action can continue; its ultimate effects being at the same time destructive, consuming the greater number of the products of vital action; but it does not appear that the oxygen of the food is employed in the system for these purposes. The consumption of atmospheric oxygen, and the heat produced, is greater from a diet of animal principles than from an equal quantity of vegetable matter; it is increased by the use of spirituous liquors, the alcohol of which contains no oxygen.

4. Nitrogen. This is also an essential constituent of every vital tissue. Many of the most important alimentary substances are destitute of it; hence the distinction of food, so much insisted upon by Liebig, into nitrogenized, as fibrin and albumen, and non-nitrogenized, as sugar and starch; and it being held that the former only can nourish the vital tissues, while the latter are wholly or in part burned; the former have been called "plastic elements of nutrition," and the latter "elements of respiration." Nitrogen is a constituent of the food of the embryo chick and of the young mammal. The various nitrogenized substances in vegetable as well as animal food contain from 14 to 18 per cent., or proportions nearly identical with those of the tissues which they serve to nourish. Food in its complicated state contains from about 13, as in rice, to 15 or 18 per cent. as in albumen or gelatin. It has been assumed that the quantity of nitrogen is a measure of the nutritive value of food, and Dr. Pereira gives Boussingault's scale of nutritive equivalents constructed upon this principle.

5. Phosphorus is a component part of bones, nerves, muscles, and other parts of the living body, and of course a necessary element of the food of animals. It is a constituent of the yelk of eggs and of milk, and of the greater part of the animal food employed by man. It is also abundant in vegetable food, in the forms of phosphates of ammonia, lime, or magnesia. More phosphorus is supplied to the body under ordinary diet than its wants require, the excess being eliminated in the urine or solid excrements; but some vegetable aliments, as beans and peas, are remarkably deficient in this element.

6. Sulphur is again an essential constituent of various tissues, as of fibrine, hair, and bones, and must be received into the system with the food. The nitrogenized alimentary principles of vegetables, also eggs and milk, water (in the form of sulphate of lime), and numerous compound

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