PREFACE. IN offering to the British public the present translation of the latest work of Baron Liebig, T may be permitted to say, that I feel highly honoured in being intrusted with the duty of conveying to my countrymen a knowledge of one of the most interesting and valuable investigatioiis which has yet been made in Animal Chemistry. The researches into the nature of the soluble constituents of nluscle or flesh, which constitute the chief part of the present work, are preceded by considerations on the true Method of Research in Animal Chemistry, which are worthy of the most earnest attention on the part of those who intend to devote themselves to investigations in this most important and at the same time most difficult department of science. A careful study of this section will convince the reader that much more might have been done of late years in Physiological Chemistry, but for the wrong direction u lfortunately given to recent researclles, ant1 will 1 owerfully contribute to direct into the right channel the energies of those rising chemists to whom Britain must look to sustain her scientific reputation in the present age of rapidly advancing discovery in the most recondite parts of Organic Chemistry and of Physiology. The physiologist will also find in this introductory section, the most convincihg reasons to show that, henceforth, it is indispensable that Anatomy, structural Physiology, and Chemistry should unite their forces with n view to the solution of the great questions which it is the common object of these sciences to solve. With regard to the chemical researches contained in the present work, it is most emphatically to be stated, that they constitute only the first steps in an almost new career that they are very far from exhausting even the single subject here investigated, namely, the nature of the soluble constituents of the muscles and that, consequently, they are chiefly valuable as indicating the true pat11 at present to be pursued by chemists. It would be contrary to the principles as well as to the wishes of their author, if physiologists were to regard them as completed, or as in any one point exhausting the subject and how many more subjects does the animal organism present, which must reniain obscure and impe netrable. till they shall be studied on principles analogous to those which have guided the author Nevertheless, these researches have already thrown much light on many important but obscure questions and independeiltly of the interest which, in a purely chemical view, they must always have for the chemist, they will be found, by the physiologist and the medical man, both interesting and valuable in a very high degree. I n connection with previous researches, they serve to demonstrate, that the more me know of the processes going on in the organism, the more do we find these to involve strictly chemical changes, and to be capable of a chemical interpretation. It would indeed appear as if every change in the organism were attended by a definite chemical or physical action and although we shall probably never succeed in uiiveiling the nature of the peculiar influence, called vitality, under which these changes occur, yet the present as well as previous investigations render it certain that we have still a great deal more to discover concerning the share taken by chemical action in the vital processes... --This text refers to an alternate Paperback edition.