FOOD:

ITS ADULTERATIONS

AND

THE METHODS OF THEIR DETECTION.

CHAPTER I.

ON FOOD, ITS FUNCTIONS AND QUANTITY.

Ir will facilitate the comprehension of much that is to follow, and enable us to answer questions which will be often put to us as to the quality, genuineness, wholesomeness, and quantity of the various kinds of food consumed, if we first bestow a few observations upon the functions performed by the several classes and kinds of food, and the amounts necessary to the growth, sustenance, and maintenance of the body in a state of health.

The bodies of men and animals are built up of several substances; some of these, from the fact of their containing nitrogen, are called nitrogenous; others, being destitute of that principle, are termed nonnitrogenous, or carbonaceous, mineral constituents, and water.

The principal nitrogenous substances of the animal body are fibrin, found in the blood and muscles; albumen and globulin, abounding in the blood; gelatine, in the bones, tendons, and ligaments; and casein, in milk; while the chief non-nitrogenous constituent is fat; they are identical in their ultimate composition, and contain carbon, hydrogen, nitrogen, oxygen, and sulphur, in the following proportions::

Now, the vegetable has a composition resembling, in the main, that of the animal, it containing analogous nitrogenous substances, though usually in smaller amounts; while the fat is represented chiefly by

B

sugar and starch, though in some exceptional cases fat or oil is met with, as in the seeds of various plants. All the nitrogenous substances entering into the composition of the human and other animal bodies are derived, either directly or indirectly, from the vegetable kingdom, the vegetable being constructive and the animal destructive.

The nitrogenous elements are capable, under some circumstances, of furnishing both fat and sugar; thus, there is evidence to show that the fatty matter of milk and the sugar of diabetes are thence derived, at least to some extent. Again, starch and sugar are sometimes transformed into fat, but the greater part of the fat of the body is derived from that contained in the food.

Notwithstanding this partial and occasional formation of fat from the nitrogenous, starchy, and saccharine elements of the food, each separate class is needed to sustain the body in a state of health. Thus, perfect health cannot be maintained for any length of time on nitrogenous food alone, even with water and the mineral constituents; and although it may be supported for a longer period on such food combined with fat, yet, for perfect health, the albuminates, fat, and the carbo-hydrates, as sugar and starch, are all necessary, though how the latter act in nutrition is not yet fully understood, since they do not enter into the composition of the tissues like the others. Further, it should be clearly understood that excess of lean meat increases the oxidation of the fat, thus tending to the reduction of obesity; excess of the carbo-hydrates acts in the same way.

Now, these several nitrogenous and non-nitrogenous constituents of the food are constantly undergoing change and destruction in ministering to the several necessities of the living animal organization, as the growth, sustenance, and waste of the body, its heat, electricity, and muscular force; and hence the necessity for a frequent supply of food. The various constituents of the food, having served the several purposes in the animal economy which have been already noticed, are eliminated from the system, the nitrogenous chiefly as urea, uric and hippuric acids, creatine and creatinine, and the non-nitrogenous in the forms of carbonic acid and water.

While starch and sugar only want as much oxygen for complete combustion as is required to combine with their carbon, fat needs a larger proportion, for it contains an excess of hydrogen, which consumes a proportionate amount of oxygen to form water. By the combustion of fat, therefore, more heat-2-4 times as much—is developed, than by an equal quantity of starch or sugar.

Now, the process of respiration is merely an act of combustion; the air carried to the lungs by inspiration is there deprived of much of its oxygen, while, in place of this gas, the expired air contains a proportionate quantity of carbonic acid, which is derived from the food introduced into the blood, and especially from its non-nitrogenous constituents, which may be termed heat producers,' for by their oxidation the heat of the body is chiefly obtained.

With respect to the fatty substances which enter into the composition of our food, we would remark that they are not merely heat producers, but that they play a very important part in the process of digestion, not only increasing and accelerating greatly the digestibility of nitrogenous articles of food, but also aiding in the formation of bile. Again, the starch is converted in the system into glucose, which is carried by the blood to the lungs, where it is split up into carbonic acid and water, as already described. Another product of the oxidation of starch and sugar is lactic acid, an important constituent of the gastric juice.

Starch, sugar, and fat have the following formulæ and percentage composition:

The mineral constituents of the body are not less necessary than the albuminates, fat, and the carbo-hydrates, and equally require to be renewed in the food consumed. Thus, sulphur and phosphorus are constantly present, combined chiefly with the albuminates. Phosphate of lime is found principally in the bones, teeth, and growing cells and tissues; phosphate of potash in the tissues, cells, and blood-the latter fluid is particularly rich in basic phosphate of potash, which forms by far the largest portion of its mineral constituents; chloride of sodium in the liquids, iron in the blood, and, lastly, carbonic, lactic, tartaric, acetic, and some other acids, which are converted in the system into carbonic acid, are requisite to maintain the alkalinity of the body, the absence of which gives rise to scurvy.

The function of chloride of sodium, or common salt, is but ill understood. It has been asserted that it is necessary for the assimilation of the food, but this seems not to be the case. Salt, in fact, is considered by some to be quite a superfluous addition to most of our articles of food, and nothing more than a condiment. It does not enter into the composition of any of the tissues, but is thrown out of the system in the excretions; and it has been repeatedly shown that some tribes of natives of Africa do not know the use of salt at all, and consider it a luxury and delicacy.

Iron is a most important constituent of the blood; the colouring matter of the red corpuscles contains it in chemical combination. It is said to assist in the oxygenation of the blood.

Again, the imbibition of a large quantity of water daily is likewise

a necessity, in order to endow many of the constituents of the foodespecially the albuminates—with certain physical properties, to render them plastic, soluble, or the more readily reducible to a state of solution; thus aiding absorption, nutrition, and elimination.

To sum up then, there is between the composition of the body and the food consumed, whether animal or vegetable, the closest possible resemblance.

Having thus enumerated the various kinds of food required to sustain the body in health, we have to consider the quantities needed. It will be obvious from what has already been advanced, that the quantities will vary, being dependent upon age, weight, muscular exertion, climate, &c.; but it has been determined by numerous independent inquiries, that the food daily consumed by an adult man of average weight-140 lb.-and in moderate work, should contain about the following quantities of the several classes of food, the figures given being those of Moleschott, quoted by Parkes in his admirable work on "Practical Hygiene,' and which figures should be generally adopted, in order to save the multiplication of sums and calculations::

One ounce of dry albuminate contains 69 grains of nitrogen and 234 of carbon; 1 ounce of dry fat, 3360 grains of carbon, and the same weight of either of the carbo-hydrates, starch or sugar, 194.2 grains; or 100 grains of albuminates contain 15.8 of nitrogen and 53.5 of carbon; fat, 76-8 grains of carbon, and starch and sugar 444 grains. But water to the extent of between 50 and 60 per cent. is contained in the food consumed, raising the amount to about 40 ounces.

Now, nearly the whole of the nitrogen and carbon contained in the chief articles of our food may be thus divided and distributed :—

Having thus arrived approximately at the quality and quantity of the several kinds of food required by an adult man of average size and weight, and in moderate work, it next becomes important to explain how each person may calculate for himself, and so ascertain the nutritive quality of his own, or any other, dietary. This important object may be accomplished by the help of the following table, taken, with one exception, from the work of Dr. Parkes, before quoted:Table for calculating Diets.

The use of the above table is exceedingly simple. Thus, the quantity by weight of any of the articles enumerated being known, the amounts of the albuminates, fats, and carbo-hydrates are easily calculated by a simple rule-of-three sum. Thus, supposing the allowance is 12 oz. of meat, one-fifth must be deducted for bone; the water in remain75 × 9.6 100

ing 9.6 oz. will be ascertained as follows: the other constituents.

=

7.2; and so on for