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CHAPTER I.

OF DIET.

DR. ARNOTT gives the following amusing summary of the powers of the steam-engine, and of the objects upon which they have been employed.

"In its present perfect state, the steam-engine appears a thing almost endowed with intelligence. It regulates with perfect accuracy and uniformity the number of its strokes in a given time, and counts and records them moreover, to tell how much work it has done, as a clock records the beats of its pendulum; it regulates the quantity of steam admitted to work, the briskness of the fire, the supply of water to the boiler, the supply of coals to the fire; it opens and shuts its valves with absolute precision as to time and manner;-it oils its joints; it takes out any air that may accidentally enter any part that should be vacuous; and when anything goes wrong, which it cannot of itself rectify, it warns its attendants by ringing a bell; yet, with all these talents, and even when possessing the power of a hundred horses, it is obedient to the hand of a child :-it never tires, and wants no sleep; it is not subject to malady, when originally well made; and only refuses to work, when worn out with age; it is equally active in all climates, and will do work of any kind;—it is a water-pumper, a miner, a sailor, a cotton-spinner, a weaver, a blacksmith, a

miller, &c.; and a small engine in the character of a steam-pony may be seen dragging after it on a railroad a hundred tons of merchandise, or a regiment of soldiers, with greater speed than that of our fleetest coaches. It is the king of machines, and a permanent realization of the genii of eastern fable, whose supernatural powers were occasionally at the command of man.”

In order, however, that the steam-engine may perform these wonders, and work in any of the capacities which have been enumerated, two things are necessary. The engine must be fed; and as its parts become worn by use, they must be repaired. It must be supplied with coal, wood, charcoal, or other combustible matter, and water, which it converts into power; and when the machinery is injured, what is imperfect must be changed and replaced.

The machinery of the animal frame works under the same conditions. In order that it may energize, it must have food, and that it may not sensibly be deteriorated by use, it must undergo constant repairs. But there is this difference in the two cases. In the animal frame, the source both of its energies and of its structural restoration is one and the same. Its food furnishes both. The blood, which is formed from our food, flowing to the brain, and the muscles, and the stomach, not merely maintains their power, but in addition carries to the same parts, and to all the rest, the materials of their growth and renovation.

The supply of food to the steam-engine, has one

purpose only to effect. It is, again, administered with absolute precision as to time and quantity: for it is meted out by those who understand the construction and working of the machinery, who know its wants exactly, and have no bias from prejudice or inclination to supply them otherwise than with rigorous exactness.

The food of human beings, more complicated in its objects, is meted out under much less favourable circumstances. The party who apportions it, for the most part, does not understand the action or the wants of the machine which he undertakes to supply; and what is more, for a long period is not only incurious on the subject, but often disposed to repel any information which may fall in his way. His motive for conveying aliment into his inside is of a totally different complexion to a calculated forethought of the needs of his economy; his exclusive object is to please two senses, and to gratify two appetites ;-perhaps he besides takes delight in the whirl into which the machinery is thrown by excess, that fills him with giddy transport, while it endangers and undermines his existence. Well, indeed, may Dr. Beaumont say, "In the present state of civilized society, with the provocatives of the culinary art, and the incentives of highly-seasoned food, brandy, and wines, the temptations to excess in the indulgence of the table are rather too strong to be resisted by poor human nature."

I shall endeavour, in the present chapter, to explain the principles by which our diet should be regulated. Accordingly, I shall treat-of the nature of digestion;

-of the nature of the various substances used as food; -of the qualities which render food wholesome and nutritive;-of the circumstances which strengthen or weaken digestion ;-of rules for the frequency, quality, and quantity of our meals, adapted to different periods of life.

It is not the young and the healthy who will profit by these remarks. But every one who has reached the middle of life must have had occasion to observe how much his comfort and his powers of exertion depend upon the state of his stomach, and will have lost some of his original indifference to rules of diet. Such rules must especially interest those, who have the care of others,-of children with delicate health,-of the aged who have ceased to exert their former care and observation of themselves. And if the principles have already been laid down by many writers, no one, it is probable, can attentively reconsider this subject, without seeing some of its bearings more justly and usefully than his predecessors have done.

I. DIGESTION.

DIGESTION is the commencement of assimilation, or of that process by which, in animals, their food is by successive mutations converted into a liquid, that is to circulate as a living and vitalizing agent through their frame.

In human beings, assimilation comprises the following steps. The solid food is bruised in the mouth,

and mixed with the saliva; it is then swallowed, and conveyed along the oesophagus into the stomach, where it is altered into an uniform pulpy mass, termed chyme*; from the stomach it passes into the small intestines, where it is mixed with the bile and other fluids, which cause the chylet or recrementitious part to separate from it: the chyle is absorbed by the lacteals, and transmitted by them to the veins; mingling with the blood in the veins, the chyle is then passed through the vessels of the lungs, and aërated. The process of assimilation is then complete, and the blood so obtained from the food is fit to sustain life.

Of these changes, there is one, which in a popular treatise like the present, exclusively merits attention. This is the alteration which the food undergoes in the stomach :-its conversion into chyme. Mr. Abernethy emphatically called this DIGESTION; that is to say, he restricted the term digestion to this function. What precedes this change is mechanical, and a mechanical substitute may be found for it. The steps in assimilation which follow this change, if it has been perfectly executed, and the meal converted into proper chyme, are unfelt by us, executed independently of volition, and certain, if the system is in health, to be accomplished properly.

The stomach is the seat of hunger; we take food to allay its cravings, which are found to be equally appeased, whether the food is swallowed in the ordi

Chyme, xvei, fundere, a fusion.

† Chyle, xuλos, a juice, or liquid.