PREFACE. VU copiousness of facts and illustrations which constitutes so distinguish¬ ing a merit in the larger work, has been retained in the abridge¬ ment. In the latter, as in the former, the student will find those wonderful revelations in histogeny which make an era in the his¬ tory of physiology, and which, although the last discovered, must, henceforth, be regarded as essential preliminaries to future descrip¬ tions of tissues and organic functions. In these pages, the student will become acquainted with the results of the discoveries and ob¬ servations of Schleiden, Schwann and Valentin on the formation of the most different elementary tissues of plants and animals, by the development of primitive or nucleated cells out of structureless or unformed gummy and mucous substances,—and of Barry and others on embryology, showing a similar development of various tissues and organs from the ovum, quickened into vital activity by the stimulus of spermatozoa, and growing by the evolution from and addition to its own primitive one, of fresh cells. Similar nucleated cells are found to exist in or rather to make up the globules of the blood, and are readily evolved from Coagulated fibrin; proving this fluid to be, conformably with long observation, the formative and vitalizing one. From these facts, in perfect harmony with each other, we are able at last to deduce a general theory of vegetation and organisation. So important are the new views of histogeny, that it has been thought advisable to transfer the chapter containing them from the end of the large work, where it was placed, to the beginning of Special Phy¬ siology in the present volume. In natural relation to the subject of the original formation of the tissues, is that of their regeneration or repro¬ duction, with or without inflammation, and, on this account, the descrip¬ tion of the latter is removed from the place which it occupied to that immediately following histogeny. Another deviation from the arrange¬ ment of the author will be found in bringing in the chapters on Diges¬ tion immediately after those on Respiration, in place of letting them remain after Nutrition and Secretion; and in making the chapters on Secretion precede those on Nutrition and Growth, rather than allow them to follow, as they do in the original. The progressive order of the changes to which aliment is subjected, from its introduction into the stomach to its conversion into blood, and the consequent metamor¬ phosis of this fluid into secretions and matters for nutritive deposit and the growth of the tissues, are exhibited better in the modified than in the original arrangement. A few notes at the foot, and some paragraphs in the body, of the page, have been added by the editor, who did not feel himself free to do much in this way, when his office was to abbreviate and arrange.