The process will be found not a mere speculative theory, but one based upon the great laws of Nature, as manifested throughout the whole of the animal kingdom. AUTHOR'S PREFACE TO THE THIRD EDITION. Can corpulence be reduced without injuriously affecting the general health? This is the grand question, and it is suggestive of another, which is:--an inordinate amount of fat once having been deposited in and among the living tissues, is its presence necessary for the preservation of the health and life of the individual? My answer is,--most assuredly no! Every one knows that an undue degree of corpulence is not only accompanied with great inconvenience to the individual, but is, in most instances productive of ill health, and too frequently of positive disease. Having answered this question, another occurs:--are there any substances generally known to the profession which have the power either to destroy fat or to cause its disappearance, and which, at the same time, will have no action upon the other tissues of the body? My reply is most assuredly there are such; and I will prove my assertion in this respect to be correct, without resorting to the use of subtle reasonings or invoking the aid of learned theories, but will be content to rest it upon the sure foundation of chemical science,--on that science which teaches the action of one body with another, which shews us that in some cases no change whatever is effected by the mechanical combination of two or more indifferent substances; and that in other instances, the chemical union of two bodies will be productive of a third, having properties wholly dissimilar from either of the two original substances:--thus, that one or more elementary substances or chemical compounds may enter into combination with a fatty body to produce a third, and yet have no power of action whatsoever upon the muscles, the bones, the nerves, or any other than the fatty tissues of the living organism. Knowing, therefore, the chemical constituents of fat, and also those entering into the composition of the several articles of diet which are principally made use of in the civilized world, we are enabled to say of a certain class of alimentary substances, that such contain the elementary ingredients of fat; and that if you desire to escape the inconveniences and evils attendant on corpulency, it will be well to abstain from them; and that, on the other hand, by making use of such and such alimentary substances, and that too in any quantity the appetite may prompt, there will be no danger of suffering the inconveniences alluded to, because such substances contain but a minute portion of those elements which enter into the composition of fat.