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"302. The glutinous principles contained in food are the most nutritious. "Gluten, albumen, caseine, and lean meat, are all classed together as glutinous principles, in consequence of their being all nearly of the same nature. They all contain nitrogen, are of a highly plastic character, and are converted into organized structure in the living body.

"303. The oily principles contained in food are the most heating.

"They are so, because they are almost exclusively composed of carbon and hydrogen, which are both very combustible elements, and convertible into carbonic acid and water, with the production of free heat, by union with oxygen. The oily principles of the food are chiefly consumed in the system as fuel, and in the heating service of the body, without having first been made into organized structure.

"304. The oily principles of the food are, however, nutritious in a degree.

"The illustrious German chemist, Liebeg, asserts that the plastic nitrogenized principles of the food are exclusively nutritive; and the other principles exclusively combustive, and employed in the heating service. There is no doubt that, in the main, these diverse principles are thus differently used; but it is also known that some heat is set free when the plastic principles or the structures are decomposed, although very much less in amount than that which is procured from the burning of the same quantity of oil; and so, again, that oil is used in some constructive purposes, although generally of much less service plastically than the nitrogenized compounds. The heating power of the plastic principles is instanced in the case of carnivorous animals, which keep up a high temperature within their frames, when they get nothing but lean flesh for their food. The constructive power of oil is shown in the influence of cod-liver oil in restoring the wasted flesh of consumptive people. The fact therefore is, as stated above, that the glutinous or plastic principles of food are the most nutritious, and the oily principles the most heating.

"305. The farinaceous and saccharine principles of the food are chiefly heating, although in a less degree than oil.

"Farina is the Latin name for Starch, and Saccharum the Latin name for Sugar. Hence starch and sugar are termed farinaceous and saccharine principles. Sugar and starch are less combustible than oil, because there is already some oxygen combined with their combustible elements-carbon and hydrogen. They are converted into oil in the system, before they are burned, as will be hereafter seen. "306. The glutinous, oleaginous, and farinaceous principles are all necessary for the sustenance of life.

"When animals are fed for a long time on any one of these principles alone, they die of starvation, just as they would if they were kept from food altogether. "307. The best diet is that which combines these several principles in itself, in the proportion in which they are required by the system.

"In mosto f the substances employed as food, these several principles are naturally combined together, but some foods have more of the one than of the other. Hence, some foods are more nutritious, and others more heating, according to their constitution. Diet means food, viewed in relation to its character and effects on the living body. The word is derived from the Greek term diaita, which signifies 'rule of living." "

"308. All the several principles are contained in milk, in the relative portions required for the formation of a perfect food.

"Milk is nature's own compound, prepared for the support of young animals, before they undertake the business of foraging for themselves. It contains all the principles that are needed for nourishing and warming their frames. It has in itself glutinous matter, oil, and sugar (the representative of the farinaceous principle.) The glutinous principle is caseine, which is separated from the other ingredients in the process of cheese making. The oil is churned out of it as butter. The sugar is held in solution in the whey, and is at once detected by the sweetness of the taste. One hundred ounces of cow's milk consist of ten ounces of solid matter held diffused in ninety ounces of water. Of the ten ounces of solid matter about two and a half are glutinous matter (cheese), and seven and a half butter and sugar (oleaginous saccharine principles.) Human milk contains a larger proportion of oil: there are in it two ounces only of cheese (caseine) to every eight ounces of butter. Hence it may be inferred that four to one are about the proportions in which the combustible and the plastic constituents need to be mingled in the food of man. "309. Wheat flour contains glutinous and farinaceous principles, mingled together in very nearly the same proportions that similar principles are in milk.

"Wheat-flour consists of starch and gluten mixed together, in the proportions of four and a half of the former to one of the latter. It differs from milk chiefly in the solid and crude condition in which these stored-up constitutents are, and in the absence of water. When water is added, it is sufficient for the support of human life for considerable periods of time. Hence, bread is in such general use among mankind, and hence, in strict accuracy, it deserves the name that is commonly given to it, of The Staff of Life.'

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"310. Many of the commonest admixtures of different kinds of food are judicious, on account of their mingling together opposite principles.

"Thus butter is added to bread, because in flour the combustible principle is in the fixed state of starch, which requires to be converted into oil before it can become serviceable. Potatoes and rice (which are principally composed of starch) are eaten with meat because it is deficient in farinaceous matter. The addition of butter to bread augments its sustaining powers. The addition of meat to potatoes increases their nutritive capacities. A mixed diet of bread, butter, meat, and potatoes, furnishes all the ingredients required by the animal frame, and hence possesses the sanction of science as well as of custom.

"311. Different kinds of diet are required by different habits of life.

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"Under some circumstances, men need a more than usually nutritious food; under others, they need a more than usually heating diet.

312. Great exertion calls for very nutritious food.

"Since all activity is attended by waste of structure, it is clear that the more exertion there is made, the more nourishing material must be furnished to keep the organs in a working state; but this nourishing material must be of a plastic, rather than of a heating kind. If large quantities of oily matter were taken under these circumstances, the system would become either oppressed with combustible matter, or

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with the heat resulting from its burning, instead of being strengthened for the increased labour. The best addition that can be made to the ordinary diet to meet this requirement is lean meat. One pound of meat contains as much plastic matter as two pounds of bread or four pounds of potatoes. Lean meat is the most nutritive and the least heating of all the substances employed as food. A plentiful meat diet has the same effect upon a hard-working man that a corn diet has upon a hard-working horse; it fits him to bear the constant strain made upon his muscular structures, and it does this without overloading his body with combustible matter at the same time. "313. Absolute repose necessitates the employment of a chiefly farinaceous and a very sparing diet.

"When very little exertion of either body or mind is made, the waste of the organized structures is proportionally slow; and hence very little plastic food is called for. The farinaceous materials of the nature of rice, potatoes, and tapioca, then, contain as much direct nourishment as the inert system requires for its sustenance; and they have the further recommendation, that they are at the same time not of a very heating nature, because their starch needs to be converted into oil in the system before it can be burned or produce heat.

"314. Exposure to great degrees of cold is best borne when a very oleaginous diet is used.

"The Esquimaux, who habitually brave the extreme cold of the arctic winter, live almost exclusively upon seal oil. Two ounces of oil produce as much effect in heating the body, when consumed as food, as an entire pound of lean meat.

"315. Farinaceous foods are most suitable for hot climates and seasons.

"In the hottest regions of the earth, the mean temperature of the air is not sufficiently high for the purposes of the animal body; hence the internal furnace is kept burning in them as well as in the colder climates. But less fuel, of course, needs to be consumed. Under such circumstances, starch forms a better fuel than oil, because it is less combustible and burns more slowly. Oil differs from starch principally in containing ten times less oxygen: it therefore has a greater attraction or thirst for the corrosive element, in this degree, and of necessity gives out more heat when burned. Two ounces of oil produce as much heat in the body as five ounces of starch; but the heat produced by the burning of the starch is also set free more gradually, because this principle has to undergo a preliminary process of conversion into oil before it is ready for use. It is on this account that the natives of India and China find rice so suitable an article to form the chief bulk of their food.

"316. In temperate climates the diet is best varied with the seasons.

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"The remarks made in relation to the various heating and nourishing powers of different kinds of food apply as much with regard to seasons as they do with regard to climates. More oleaginous principles are required in winter than in summer. frequently happens that persons who take cod-liver oil through the winter, in England, get so oppressed by it in summer that they are constrained then to refrain from

its use.

"317. Animal food is not absolutely essential for the support of life.

"This may be inferred from the fact that there are many animals which feed exclusively upon vegetable matters. The ox, that supplies beef to man, eats only grass and

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turnips. Many individuals of the human species take nothing but vegetables as food, and yet preserve vigorous health for long periods of time. There is no nutritious principle in meat that is not also found, although in a more sparing and less condensed form, in vegetable substances.

"318. A mixed animal and vegetable diet is the best adapted to the general wants of man.

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"It is a debated question whether man is designed by nature to feed on vegetable or animal substances. It is not difficult, however, to find a satisfactory answer to this. He is intended by nature to live on both. He is omnivorous (" devouring all things") in the widest sense of the term. He eats and thrives upon all kinds of food, and may be restricted to an exclusively animal or vegetable diet with impunity, provided only a due proportion of plastic and combustible principles are supplied, in the condition in which they are available for use. In tropical lands, man luxuriates in delicious, sugary fruits, and in other productions of the ground; in temperate climates he mingles bread and meat in various proportions; on the wide prairies, he can get nothing but buffalo beef and venison; and in the dreary arctic waste, fish and seal oil are his sole resources; yet under all these variety of circumstances he still manages to keep his frame in healthy vigour, and fit for its work. Man, in reality, is enabled to exist upon a great diversity of food, in order that he may dwell in great diversity of conditions; his omnivorous capacities have been conferred upon him, in order that he may "subdue the earth" and cover its surface, from the luxuriant tropics to the desolate poles, with his race. In civilized and densely peopled lands, where mouths multiply much faster than the natural productiveness of the soil, a mixed diet of animal and vegetable substances is invariably adopted, because in practice it is found more economical and convenient. It proves to be easier to make the land yield an augmented produce under the application of science to its culture, when that produce is taken out in mutton, beef, and grain, than when it is procured in the form of grain alone. Every possible advantage has then to be sought out and seized upon, in order that the rapidly increasing numbers of the people may be comfortably and sufficiently fed. But the employment of the mixed diet by highly civilized races of mankind has another very important advantage. It enables a larger quantity of plastic substances to be thrown into the system at any time, to answer a special purpose, without increasing, in the same proportion, the quantity of fuel present in the frame. It furnishes a means for strengthening the body of the hard-working man for extraordinary exertion, without its being heated in a corresponding degree. The natural food of the horse is grass, but so soon as the horse is taken from the pasture and set to drag heavy loads, it is found that its muscular powers must be sustained by the addition of a certain quantity of corn to its daily fare; for the corn has much more plastic nourishment in it than an equal quantity of grass. Meat is added, for the same reason, to the toiling man's daily fare; that is, in order that the excessive waste of plastic substance, entailed by his labour, may be promptly and easily repaired. These remarks apply as much in the case of mental as of bodily exertion. The best physiologists are of opinion that, although there can be no doubt an exclusively vegetable diet is sufficient for the production of a full and perfect development of the bodily frame of many, it is equally clear that the addition to it of some animal food favours the formation of the highest power of mind.

"319. The food of man becomes more easily digestible by being cooked.

"Man may be distinguished as the cooking animal. The savage, in his rudest state,

makes a fire, and prepares his food, by roasting or baking it, before he eats it. No other species of animal performs this operation. All the diversified processes of the cook's art have one object in view (so long as they are confined to their lawful province) the reduction of the various nourishing principles of the food to their most soluble condition. Cooking, indeed, imitates many of the actions that are naturally brought about in the digestive canal, and may be viewed as a preliminary stage of digestion. It breaks the films of the starch grains, and converts them into a sort of sugar or gum; it softens and opens out the texture of the glutinous and albuminous matters, and it changes the oily principles into bland milk-like emulsions. It is best that no uncooked food, excepting ripe fruits, should be eaten, and they can hardly be viewed in the light of an exception, for they have really undergone a sort of cooking in the heat of the sun.

"320. Savoury admixtures of food are addressed more to tempting the appetite than to rendering the food easy of digestion.

"On this account, the refinements which modern luxury has introduced into the cooking art, are evils rather than benefits. The mingling of savoury foods into varied dishes that gratify the palate, replaces natural and healthy appetite by unnatural and disordered craving. All the appetites are given to animals to insure the fulfilment of certain actions that are essential to the well-being of the body. Eating, in common with many of the other ordinary operations of life, has been made pleasurable, in order that the creature may be induced to take the food that is necessary for its sustenance, for the sake of the enjoyment that is attendant upon the act. When, however, numerous different kinds of food are offered to the palate in succession, and when highlyseasoned and richly-flavoured dishes are presented in the place of simple fare, men are apt to continue eating, for the prolonged gratification of the sense of taste, long after the real wants of the system have been satisfied; and so the stomach is oppressed with a load that is far beyond its power of management, instead of being only fairly tasked with the work it is easily able to accomplish. Persons who value the blessings of uninterrupted health, should always train themselves to make their meals consist of at most one or two dishes of simple and plainly-cooked food. All indulgence in the pleasures of the table beyond this is playing with temptation, and planting seeds that are almost sure to ripen into future suffering and evil.”

THIRD DAY AT THE ROYAL POLYTECHNIC
INSTITUTION.

We resume our diary of this well-conducted place of amusing instruction with a few notes culled from Dr. Rae's original and admirable lecture, with special reference to the probable fate of Sir John Franklin and his party. The brave Doctor commenced by referring to the lectures delivered on the beautiful collection of arctic curiosities made by Mr. Barrow, which formed the ornament and attraction of the room he now lectured in, and apologized (as it proved, unnecessarily) for any want of fluency on his part. He had made notes of journeys anterior to his own performed by others, and referred chiefly to those undertaken by boat and sledge parties.

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