151. As dietetic regulations are intended for the use of those who are either suffering under disease, or are compelled, from the precarious state of their health, to attend to every circumstance which may be likely to preserve it, it is scarcely necessary, in a professional work, to apologize for the introduction of advice, which, to the robust and healthy, may appear frivolous and unnecessary. It is admitted, that nature never contemplated the necessity of confining men to a certain routine of habits; nor did she contemplate, as far as we can learn, the existence of those diseases which may render such discipline necessary. We have in this place only to inquire into the habits which are most favourable or hostile to the process of digestion, and then to form a code for the direction of those who stand in need of such artificial assistance.

152. Exercise in the open air is essential to the well-being of every person; but its degree must be regulated by the circumstances under which the individual is placed. The interval between breakfast and dinner is the period for active exertion; and the enjoyment of it, when not attended with severe fatigue, will strengthen and invigorate all the functions of the body. This, too, is the period when the mind may direct its energies with the greatest chance of success; but it is important to remark, that the valetudinarian and dyspeptic ought never to take his principal meal in a state of fatigue; and yet I would ask, whether there is a habit more generally pursued, or more tenaciously defended? Aye, and defended too upon principle; - the invalid merchant, the banker, the attorney, the government clerk, are all impressed with the same belief, that after the sedentary occupations of the day, to walk several miles to their villas, or to fatigue themselves with exercise before their dinner, or rather early supper, will sharpen their tardy stomachs, and invigorate their feeblo organs of digestion; as if bodily fatigue were an antidote to mental exhaustion.

The consequence is obvious: instead of curing, such a practice is calculated to perpetuate, and even aggravate the malady under which they may suffer, by calling upon the powers of digestion at a period when the body is in a state of exhaustion from fatigue. Often have I, in the course of my practice in this town, cured the dyspeptic invalid, by merely pointing out the error of this prevailing opinion, and inducing him to abandon the mischievous habit which has been founded upon it. Do not let me be understood as decrying the use of moderate exercise before dinner; it is the abuse of it that I am anxious to prevent. No person should sit down to a full meal, unless he has had the opportunity of previously inhaling the open air, and taken a quantity of exercise, proportionate to his power of sustaining it without fatigue. Upon this point I agree with Mr. Abernethy, who says, "I do not allow the state of the weather to be urged as an objection to the prosecution of measures so essential to health, since it is in the power of every one to protect himself from cold by clothing: and the exercise may be taken in a chamber with the windows thrown open, by walking actively backwards and forwards, as sailors do on shipboard." Horse exercise is undoubtedly salutary, but it should not supersede the necessity of walking; where the two modes can be conveniently combined, the greatest advantage will arise.

I have heard that a physician of eminence has declared, that "equitation is more beneficial to the horse than to his rider;" my own experience on this subject will not allow me to concede to such a proposition; nor to that which maintains, that "riding is the best exercise for regaining health, and walking for retaining it." It must be admitted, that the shaking which attends horse exercise, is salutary to the stomach and intestines; it is also less fatiguing to the inferior limbs; so that persons in a weak state can use it with less pain or difficulty; they can, moreover, better regulate the quantity of exercise, and bring their excursions to a close without fatigue, as soon as they discover the propriety of so doing, winch is not so easy in the case of walking. There is also another circumstance connected with this subject, upon which I am inclined to think that sufficient stress has not been laid, the rapidity with which we change the air. I am not aware that any theory has been proposed to explain the fact; but I am perfectly well satisfied, that rapid motion through the air is highly beneficial. As this is a gymnastic age, I may be allowed to offer some further observations upon the importance of exercising the body.

The occupation of digging is more beneficial than is usually supposed; and to dyspeptic persons it proves useful, by the agitation thus occasioned in the abdominal region. Patients who have suffered from visceral congestion have experienced the greatest benefit from it. I am induced to believe, that the general discontinuance of those manly exercises, which were so commonly resorted to by our ancestors in the metropolis, has contributed to multiply our catalogue of dyspeptic diseases; and I cannot but express my satisfaction at the prospect of the establishment of a society for their reintroduction. Stow, in his Survey of London, laments the retrenchments of the grounds appropriated for pastimes, which had begun to take place even in his day: what would he say, could he now revisit the metropolis? It has been truly observed, that had it not been for the effect of bodily exercise, Cicero1 would never have triumphed at the bar, nor Julius Caesar in the field.

153. One of the great evils arising from too sedentary habits, is constipation of the bowels. This, however, may to a certain degree be remedied, by standing for a certain period; and I have repeatedly known the greatest benefit to arise from the student or clerk introducing a high desk into his office, by which he is enabled to pursue his occupation in an erect posture.