In order, then, to have every portion of the body properly developed, it is necessary to take such a variety of food, that from one source or another, every organ of the body shall be sustained by its appropriate nourishment. The experiments which prove this, have been conducted on a great scale, and the method and results are detailed in the work of Dr. Pereira.
This fact exhibits one cause of the craving, sometimes felt for certain kinds of food, which usually is the call of nature for some ingredient, that the daily round of aliment does not supply. The statistics furnished in the work of Dr. Pereira, from various armies, prisons, almshouses, and asylums, show, that, where many hundreds are fed on the same diet, the general health of the multitude is better sustained by a considerable variety and occasional changes, than by a more restricted selection. Experiments on dogs and other animals, also, have been tried on a large scale, which prove that there is no kind of food, which, alone, will preserve full and perfect health; while every kind (except the food containing gluten, which is the chief ingredient of wheat and other bread-stuffs), when given exclusively, eventually destroys life. The exclusive use of wheat bread and potatoes, as found by experiment, will sustain life and health more perfectly, for a great length of time, than any other kinds of food.
The above fact is a striking exhibition of the beneficence of Providence, in providing such an immense variety of articles of food. And no less so is the instinct of appetite, which demands not only a variety, but is wearied with one unchanging round.
Having ascertained that it is needful to health, that a due variety of food should be secured, we next proceed to examine the principles that are to guide us in the selection.
It is found that the articles used for food and drink may be arranged in the following classes:—
First, articles that furnish no other stimulation to the animal functions than is secured by the fresh supply of nutrition. All food that nourishes the body, in one sense, may be called stimulating, inasmuch as it imparts renewed energies to the various bodily functions. In this sense even bread is a stimulant. But the more common idea attached to the word stimulant is, that it is a principle which imparts a speed and energy to the organs of the system above the ordinary point secured by perfect and appropriate nourishment. The first class, then, are those articles that serve to nourish and develop perfectly every animal function, but do not increase the strength and speed of organic action above the point of full nourishment. The bread-stuffs, vegetables, fruits, sugar, salt, acid drinks, and water are of this class.
Secondly, those articles, which serve to nourish perfectly all the animal system, and at the same time increase the strength and speed of all functional action. All animal food is of this class. All physiologists and medical men agree in the fact, that the pulse and all the organs of the body, are not only nourished, but are quickened in action by animal food, while speed and force are reduced by confining the diet to farinaceous, vegetable, and fruit diet.
Thirdly, those articles which impart no nourishment at all to the body, but act solely to stimulate all the organs to preternatural action. Alcoholic drinks, condiments, and aromatic oils are of this description.
Fourthly, articles that are neither nourishing nor stimulating, but pass out of the system entirely undigested and unassimilated. The bran of coarse bread is an example.
Fifthly, articles that, either from their nature or modes of combination and cooking, are difficult of digestion, unhealthful, and, of course, tend to weaken the organic powers by excessive or unnatural action. Animal oils, either cooked or rancid, and many articles badly cooked, are of this kind.