When, however, the mode of life in mature age is active and laborious, and the waste matter thrown out of the system is consequently considerable, the appetite for food and the power of digesting it are correspondingly strong; for in general it is only when the mode of life is indolent and inactive, and the waste consequently small, that the appetite and digestion are weak. So natural, indeed, is the connexion between the two conditions, that exercise is proverbially the first thing we think of recommending to improve the appetite and the tone of the digestive organs, when these are observed to be impaired; and where positive disease does not exist, no other remedy is half so effectual. But, as already noticed, exercise to be beneficial must be of a description calculated to increase the activity of the secretions and excretions; otherwise it cannot place the system in a condition to require an abundant supply or excite vigorous digestion.
It is highly important to notice this natural relation between waste and appetite, and between appetite and digestion; because, if it be real, appetite must be the safest guide we can follow in determining when and how much we ought to eat. It is true that in disease, and amidst the factitious calls and wants of civilized life, its suggestions are often perverted, and that hence we may err in blindly following every thing which assumes its semblance. The conclusion to be drawn from this, however, is, not that the sense of hunger will, if trusted to, generally mislead us, but only that we must learn to distinguish its true dictates before we can implicitly rely on its guidance. If, when fairly consulted, its dictates are found to be erroneous, it will constitute the only known instance where the Creator has failed in the attempt to fulfil his own design—an assumption not only repugnant alike to feeling and to reason, but in fact altogether gratuitous. For the apparent discrepancies which occasionally present themselves between the wants of the system and the dictates of appetite, are easily explicable on the more solid ground of our own ignorance and inattention.
Many practical errors arise from overlooking the relation which nutrition ought to bear to waste and growth. Thus, it is no uncommon thing for young men who have experienced all the pleasures of a keen appetite and easy digestion when growing rapidly or leading an active life, to induce severe and protracted indigestion, by continuing, from mere habit, to eat an equal quantity of food either when growth is finished and the system no longer requires the same extensive supply, or after a complete change from active to sedentary habits has greatly diminished that waste which alone renders food necessary. This is, in fact, one of the chief sources of the troublesome dyspeptic complaints often met with among the youthful inhabitants of our larger cities and colleges, and ought not to be lost sight of in the physical education of the young.
The error, however, is unhappily not confined to the young, but extends generally to all whose pursuits are of a sedentary nature. There are numerous persons, especially in towns and among females, who, having their time and employments entirely at their own disposal, carefully avoid every thing which requires an effort of mind or body, and pass their lives in a state of inaction entirely incompatible with the healthy performance of the various animal functions. Having no bodily exertion to excite waste, promote circulation, or stimulate nutrition, they experience little keenness of appetite, have weak powers of digestion, and require but a limited supply of food. If, while inactive and expending little, such persons could be contented to follow nature so far as not to provoke appetite by stimulants and cookery, and to eat and drink only in proportion to the wants of the system, they would fare comparatively well. But having no imperative occupation and no enjoyment from active and useful exertion, their time hangs heavily on their hands, and they are apt to have recourse to eating as the only avenue to pleasure still open to them; and, forgetful or ignorant of the relation subsisting between waste and nutrition, they endeavour to renew, in the present indulgence of appetite, the real enjoyment which its legitimate gratification afforded under different circumstances. Pursuing the pleasures of the table with the same ardour as before, they eat and drink freely and abundantly, and, instead of trying to acquire a healthy desire for food and increased powers of digestion by exercise, they resort to tonics, spices, wine, and other stimuli, which certainly excite for the moment, but eventually aggravate the mischief by obscuring its progress and extent. The natural result of this mode of proceeding is, that the stomach becomes oppressed by excess of exertion—healthy appetite gives way, and morbid craving takes its place—sickness, head-ach, and bilious attacks, become frequent—the bowels are habitually disordered, the feet cold, and the circulation irregular—and a state of bodily weakness and mental irritability is induced, which constitutes a heavy penalty for the previous indulgence. So far, however, is the true cause of all these phenomena from being perceived even then, that a cure is sought, not in a better regulated diet and regimen, but from bitters to strengthen the stomach, laxatives to carry off the redundant materials from the system, wine to overcome the sense of sinking, and heavy lunches to satisfy the morbid craving which they only silence for a little. Some, of course, suffer in a greater and others in a less degree, according to peculiarities of constitution, mode of life, and extent of indulgence; but daily experience will testify, that, in its main features, the foregoing description is not over-charged, and that victims to such dietetic errors are to be met with in every class of society.
The fact of Nature having meant the inactive and indolent to eat and drink less than the busy and laborious, is established not only by the diminished appetite and impaired digestion of human beings who lead a sedentary life, as contrasted with the keen relish and rapid digestion usually attendant on active exertion in the open air, but on a yet broader scale by the analogy of all other animals. In noticing this relation, Dr Roget remarks that “the greater the energy with which the more peculiarly animal functions of sensation and muscular action are exercised, the greater must be the demand for nourishment, in order to supply the expenditure of vital force created by these exertions. Compared with the torpid and sluggish reptile, the active and vivacious bird or quadruped requires and consumes a much larger quantity of nutriment. The tortoise, the turtle, the toad, the frog, and the chameleon, will indeed live for months without taking any food.” “The rapidity of development,” he continues, “has also great influence on the quantity of food which an animal requires. Thus the caterpillar, which grows very quickly, and must repeatedly throw off its integuments, during its continuance in the larva state, consumes a vast quantity of food compared with the size of its body; and hence we find it provided with a digestive apparatus of considerable size.”[9] Hence, too, the greater demand for food in infancy and youth when growth and activity are both at their height.
In thus insisting on regular bodily and mental activity as indispensable to the enjoyment of a good appetite and sound digestion, the attentive reader will not, I trust, be disposed to accuse me of inconsistency because, when treating of muscular exercise in the former volume,[10] I explained the bad effects, and inculcated the impropriety, of indulging in any considerable exertion immediately before or after a full meal. It is true, as there mentioned, that exercise, either in excess or at an improper time, impairs the tone of the stomach; but it is not on that account the less true that bodily exertion when seasonably and properly practised, is the best promoter of appetite and digestion which we possess; and it is only under the latter conditions that I now speak of it as beneficial and even indispensable to health.
In a work like the present, it is obviously impossible to fence round every general proposition with the numerous limitations which an unusual combination of circumstances, or a departure from the state of health, might demand. And, even if possible, it would not be necessary, as the laws of exercise have been so fully explained in the volume alluded to, that their re-discussion here would unavoidably involve much repetition from its pages. At the same time, some warning remark may be required to prevent any risk of misconception, as it might otherwise be plausibly argued, for example, that there can be no such relation as I have alleged between waste and appetite, because a European perspiring under a tropical sun incurs great waste, and yet loses both appetite and digestive power. To render this a valid exception, it must be shewn that the European is intended by Nature to live in a tropical climate, and that the diet to which he accustoms himself is that sanctioned by experience as the best adapted for his constitution; because, if neither is the case, his condition under such influences must necessarily be more or less closely allied to the state of disease, and therefore beyond the sphere to which alone my remarks are meant to apply. But even in that instance there is less contradiction than might be imagined, for the waste of the system being chiefly fluid, excites—not appetite, but its kindred sensation—thirst, to repair the loss by an unusual demand for refreshing liquids.
So true is it that the Creator has established a relation between action and nutrition, that when we attempt for any length of time to combine a full and nutritious diet with systematic inactivity, the derangement of health which generally ensues gives ample proof of the futility of struggling against His laws. Individuals, indeed, may be met with, who, from some peculiarity of constitution, suffer less than the generality of mankind from making the experiment; but even those among them who escape best, generally owe their safety to the constant use of medicine, or to a natural excess in some of the excretory functions, such as perspiration or the urinary or alvine discharges, by means of which the system is relieved much in the same way as by active exercise; and hence the remark made by Hippocrates, that severe perspirations arising during sleep without any other apparent cause are a sure sign that too much nourishment is made use of. In others, again, the day of reckoning is merely delayed, and there is habitually present a state of repletion, which clogs the bodily functions, and may lead to sudden death by some acute disease when the individual is apparently in the highest health. I am acquainted with several individuals of this description, who, in the absence of all bodily exercise, are accustomed to live very fully,—to eat in the morning a hearty breakfast, with eggs, fish, or flesh,—a good solid luncheon, with wine or malt liquor, in the forenoon,—a most substantial dinner, with dessert and several glasses of wine, and afterwards tea and wine and water, in the evening,—and who nevertheless enjoy tolerably good digestion. But this advantage is generally only temporary, and even when permanent can scarcely be considered as a boon; because it is gained at the direct expense either of a very full habit of body and an unusual liability to abdominal congestion and all its attendant evils, or of frequent and profuse perspirations, and severe attacks of bowel complaint, endangering life; so that strictly considered such cases are no exceptions to the general rule.
It is, then, no idle whim of the physician to insist on active exercise as the best promoter of appetite and digestion. Exercise is, in fact, the condition without which exhalation and excretion cannot go on sufficiently fast to clear the system of materials previously taken in; and where no waste is incurred, no need of a fresh supply, and consequently, in a healthy state of the system, no natural appetite, can exist. It is therefore not less unreasonable than vain for any one to insist on possessing, at the same time, the incompatible enjoyments of luxurious indolence and a vigorous appetite,—sound digestion of a hearty meal, and general health of body; and no one who is aware of the relation subsisting between waste and appetite can fail to perceive the fact, and to wonder at the contrary notion having ever been entertained.