The present edition considerably extended - Popular interest of the subject - Works on Dietetics numerous, but not satisfactory - Contrariety of opinion begets Scepticism - The Fate of a Patient who consults too many Physicians - Quackery - The Quantity of Food, and the circumstances under which it is taken, more important than its Quality - Dietetic Precepts should not savour of ascetic austerities - Absurdity of the supposition that Nature can direct us in the selection of Food - Man has no natural food- - The qualities of Vegetables completely changed by Cultivation - Cookery - The folly of denying the influence of regimen in the cure and prevention of disease - Digestion - Comprehensive meaning of the term.

1. Several years have passed away since this work was first given to the public, and from events to which it is not necessary to allude it has remained out of print for a considerable period; so far, however, from this being a subject of regret, I rejoice at the opportunity it now affords me of collecting from the stores of a wider experience, such facts as may tend to confirm and extend the doctrines, or to illustrate more clearly those general views which were submitted to the profession in the first edition of the Treatise. I must here beg to repeat, that I did not entertain the idea of writing an Essay on Diet, without having been duly impressed with the high importance of the subject, and with the numerous difficulties by which it was encompassed.

In venturing to add a new work on a branch of medical science, which had already animated such a host of writers, and which for reasons to be hereafter stated, had retained only a dubious claim to the attention of the practitioner, I well knew that I should expose myself to a very severe ordeal, unless prepared either to increase the general fund of information by the addition of new facts, and the consequent developement of new views, or to render the often-repeated tale more simple and intelligible, by divesting the subject of the various fallacies with which wild theory on the one hand, and vulgar prejudice on the other, might have contaminated and disfigured it. I did not, indeed, despair of rendering the work acceptable on the former of these grounds, but I certainly relied with more confidence on pretensions founded on the latter; for, let it be remembered, although many valuable works on dietetics have descended to us, that since their publication, the views as well as language of medical and physiological science have undergone many and considerable revolutions.

It is true that facts are immutable, but if buried amidst the ruins of fallen systems, they remain unknown and without value until rescued from the confused mass, and re-arranged in conformity with the acknowledged theories of the day.

Since the publication of the first edition of the present treatise, a fresh impulse has been given to the enquiry, and some valuable productions have been the result; and I must be permitted to remark, that the little reserve with which several of their authors have appropriated my own peculiar views and precepts affords, at least, some indication of their estimated, though not acknowledged, value.

2. It will be readily admitted that few subjects, connected with the medical art, have excited greater interest, or occasioned more sedulous inquiry, than that of which I propose to treat in the following pages; and yet, were the popular works on dietetics subjected to a healthy digestion, how meagre would be the proportion of real aliment extracted from their bulky materials. Upon this occasion, at least, we may, with Diderot, ridicule the popular adage, "the more heads the better counsel - because nothing is more common than heads, and nothing so unusual as good advice." Suppose an unprejudiced reader (my assumption I admit is violent) were to wade through the discordant mass to which I allude, would he not inevitably arrive at the mortifying conclusion that nothing is known upon the subject in question; or rather, that there does not exist any necessity for such knowledge? Nothing cherishes the public scepticism, with regard to the efficacy of the medical art, so much as the publication of the adverse and contradictory opinions of its professors, upon points so apparently simple and obvious, that every superficially informed person constitutes himself a judge of their merits.

If a reader is informed by one class of authors, that a weak stomach is unable to convert liquid food into aliment, and by another, that solid food is injurious to feeble stomachs, he at once infers that the question is one of perfect indifference; and ultimately arrives, by a very simple process of reasoning, at the sweeping conclusion, that the stomach, ever kind and accommodating, indiscriminately converts every species of food into nourishment, and that he has therefore only to consult his own inclination in its selection. And let me here observe that a conclusion, when in accordance with our wishes and prejudices, is not only very readily adopted, but most pertinaciously maintained. If the truth were told, a large portion of dyspeptics seek the advice of a physician not so much for the adjustment and better regulation of their diet, as for the means by which they may counteract the ill effects of their indulgences - hence the popularity of those " antibilious" remedies, which promise to take the sting out of their excesses, and to enable the unhappy dupes to fondle and play with vice as with a charmed serpent.

On the valetudinarian, however, incapable of healthy reflection, and ever seeking for causes of fear and anxiety when they do not choose to come uncalled, such adverse and conflicting opinions may have a contrary tendency, and lead him to suspect the seeds of disease in every dish, and poison in every cup.

3. To make the case still stronger, let us suppose that the unprejudiced person whom we have chosen to represent on this occasion, instead of a reader becomes a patient, and submits his complaints to the judgment of these discordant authors; might he not, like the Emperor Adrian, prepare an inscription1 for his tombstone? This is not an imaginary case, but one of daily occurrence in this metropolis. A dyspeptic invalid, restless and impatient from the nature of his complaints, wanders from physician to physician, and from surgeon to surgeon, in the eager expectation of procuring some relief from his sufferings: under the direction of one, he takes the blue pill, and, like Sanctorius, measures with scrupulous accuracy the prescribed quantity of his ingesta; but, disappointed in the promised benefit, he solicits other advice, and is mortified by hearing that mercury, in every form of combination, must aggravate the evils he seeks to cure, and that a generous diet, and bitter stomachics, are alone calculated to meet the exigencies of his case; a trial is given to the plan, but with no better success: the unhappy patient at length determines to leave his case to nature; but at this critical juncture he meets a sympathizing friend, by whom he is earnestly entreated to apply to a skilful physician, who had succeeded in curing a similar complaint, under which he had himself severely laboured: the anxious sufferer, with renewed confidence, sends for this long-sought-for doctor, and he hears with a mixture of horror and astonishment, that his disorder has been entirely mistaken, and that he must submit to the mortifications of a hermit, or his cure is hopeless.