WOOD-CUTS.

PREFACE.

The present volume is essentially a continuation of the work first published about two years ago, under the title of “The Principles of Physiology applied to the Preservation of Health and to the Improvement of Physical and Mental Education;” and its object is the same—namely, to lay before the public a plain and intelligible description of the structure and uses of some of the more important organs of the human body, and to shew how information of this kind may be usefully applied, not only in the prevention of suffering, but in improving the physical, moral, and intellectual condition of man.

In “The Principles of Physiology,” the structure and functions of the skin, muscles, bones, lungs, and nervous system, the laws or conditions of their healthy action, and the unsuspected origin of many of their diseases in infringements of these laws, were explained in succession at considerable length; and the means by which their health and efficiency might best be secured were pointed out. It was stated that, in selecting these organs as subjects for discussion, I had been guided by the desire to notice in preference those functions which are most influential in their operation on the general system, and at the same time least familiarly known; and that, if the attempt to convey the requisite information in a manner suited to the general reader should prove successful, I would afterwards prepare a similar account of others, in the right understanding and management of which our interest is not less deeply involved, but in regard to which much ignorance continues nevertheless to prevail, even among the most liberally educated classes of society.

The numerous proofs which I received of the utility of my former work, not only from professional and literary journals, but also from individuals previously unknown to me,—many of them guardians and instructors of youth, speaking from personal experience,—together with the rapid sale of four large editions in little more than two years, soon completely satisfied me that I had neither been deceived as to the real importance of physiological knowledge to the general public, nor been altogether unsuccessful in the method of conveying it. Thus encouraged, accordingly, I cheerfully resumed my labours, and, from materials which had been long accumulating, began the preparation of the treatise now submitted to the indulgent consideration of the reader.

The matters discussed on the present occasion relate chiefly to the function of Digestion and the principles of Dietetics; and in selecting them I have been guided by the same principle as before. It may, at first sight, be doubted whether I have not exceeded proper bounds in thus dedicating a whole volume to the consideration of a single subject; but the more we consider the real complication of the function of Digestion,—the extensive influence which it exercises at every period of life over the whole of the bodily organization,—the degree to which its morbid derangements undermine health, happiness, and social usefulness,—and especially the share which they have in the production of scrofulous and consumptive as well as of nervous and mental affections,—we shall become more and more convinced of the deep practical interest which attaches to a minute acquaintance with the laws by which it is regulated. In infancy, errors in diet, and derangement of the digestive organs, are admitted to be among the principal causes of the striking mortality which occurs in that period of life. In youth and maturity, the same influence is recognised, not only in the numerous forms of disease directly traceable to that origin, but also in the universal practice of referring every obscure or anomalous disorder to derangement of the stomach or bowels. Hence, too, the interest which has always been felt by the public in the perusal of books on Dietetics and Indigestion; and hence the prevailing custom of using purgatives as remedies for every disorder, very often with good, but not unfrequently with most injurious effects.

Numerous and popular, however, as writings on Dietetics have been, and excellent as are many of the precepts which have been handed down by them from the earliest ages, sanctioned by the warm approval of every successive generation, it is singular how very trifling their influence has been, and continues to be, in altering the habits of those to whom they are addressed. In a general way, we all acknowledge that diet is a powerful agent in modifying the animal economy; yet, from our conduct, it might justly be inferred, that we either regarded it as totally devoid of influence, or remained in utter ignorance of its mode of operation, being left to the guidance of chance alone, or of notions picked up at random, often at variance with reason, and, it may be, in contradiction even with our own daily experience.

It has been alleged by a friendly critic of the first edition, that the author is too sanguine in expecting that the mere communication of knowledge will suffice to alter the habits of the race, and that, although the information conveyed in the present volume may be turned to account by third parties—by mothers and nurses, for example—“yet with respect to the direct effect upon eaters,” slender results must be anticipated. “The world,” it is wittily added, “will read, admire, and applaud Dr Combe on Digestion and Dietetics, and then go on in its usual way eating what it likes, and digesting what it can.” The Author, however, never entertained the hope that his work would immediately produce the slightest perceptible change in the general practices of society, or that many healthy men of mature age and confirmed habits would forsake their accustomed regimen merely because it was shewn to be at variance with the laws of Nature. But as human conduct is in some measure influenced by knowledge, he is still confident enough to believe, that, among valetudinarians and the young of both sexes, whose habits are not formed, and numbers of whom err as much from ignorance as from the force of passion, many may be found who will be glad to obtain the guidance of knowledge and principle in the regulation of their mode of life; and that even many parents, who may not have resolution enough to forsake mischievous indulgences to which they have long been accustomed, may nevertheless be anxious to avail themselves of any assistance on which they can depend for the better bringing up of their children. If in these expectations he is not too sanguine, the future advantage to the race from the present diffusion of dietetic knowledge is as certain, and almost as encouraging, as if its effects were instantaneous on both old and young. In the march of human improvement, months and years count but as moments. The men of to-day will soon have acted their part, and give place to those who are now with youthful energy adding to their knowledge, and throwing off a portion of the prejudices of their fathers. They in their turn will speedily be succeeded by their children, and the discoveries of the one generation will thus become the established and influential truths of the next. Each individual change in the habits of society may be so slow and minute as at the moment to escape our notice, but it is not on that account the less real. Nobody who compares the coarse feeding and riotous convivialities of our forefathers, at the beginning of last century, with the more refined and temperate habits of the present day, will think of denying that a prodigious step has been made in the interval even with respect to eating and drinking, which the critic seems to consider as so much beyond the influence of reason. And yet, if we take any single year of the whole century, we shall be unable to particularize any marked reformation which took place within its limits. This being the case, then, can we, their descendants, maintain that we are arrived so nearly at perfection as to leave no room for corresponding improvement in our day? My conviction is so much the reverse, that it seems to me certain that our onward progress will continue through generations yet unborn, with the same steadiness as it has done through generations long since gathered to their fathers; and that every attempt made to render man better acquainted with the laws of his own constitution, and thereby provide him with fixed and better principles of action, will exert a positive and decided influence on the progress of the race, proportioned in extent to the truth, clearness, and general applicability of the views which are unfolded. On such considerations do I ground my hope that the present volume, notwithstanding its numerous defects, will (in so far as it really embodies truths of practical importance) contribute in its own limited sphere to the general end.

The real cause of the little regard paid to dietetic rules—and it is of consequence to remark it—is not so much indifference to their influence, or even the absolute want of valuable information, as the faulty manner in which the subject is usually considered. In many of our best works, the relation subsisting between the human body on the one hand, and the qualities of alimentary substances on the other, is altogether lost sight of, although it is the only solid principle on which their proper adaptation to each other can be based. In this manner, while the attention is carefully directed to the consideration of the abstract qualities of the different kinds of aliment, little or no regard is paid to the relation in which they stand to the individual constitution, as modified by age, sex, season, and circumstances, or to the observance of the fundamental laws of digestion. And hence, although these conditions are not unfrequently of much greater importance to the general health than even the right selection of food, yet, when indigestion arises from neglecting them, the food alone is blamed, and erroneous conclusions are drawn, by relying on which, upon future occasions, we may easily be led into still more serious mistakes.