PREFACE. He who engages in the labour of abridgement ought to feel that it is a self-imposed task, for the successful performance even of which he will not always be requited by the gratitude of those for whose benefit it was undertaken. It is not enough that he is faithful to his original, and that, while preserving its continuity of narrative and description, he retains all that is relevant in facts and valuable in doctrines; thus giving, in reduced dimensions, the characteristic features which were spread out with fatiguing amplification in the large work. Expectation will still go beyond ability; and, after all his conscientious pains-taking, he must be prepared to hear of omissions charitably imputed to him as negligences, and of compression complained of as obscurity. Many who never read the original, and who would have been repelled by its length and perplexing details, some who knew nothing at all antecedently of its character, will affect a sudden critical illumination, and with an oracular shrug whisper a wish that it had been spread out before them entire. If from timidity, or want of entire conviction of the propriety of undertaking to abridge Muller’s great work on Physiology, it were deemed necessary to invoke the sanction of authority, the editor of the present volume might refer to one eminent teacher,* who advised the measure, and to anothert who gave it his ready approval. The editor, himself, felt assured, from an experience of many years teaching Phy¬ siology, as part of and in connection with the Institutes of Medicine, that the work of Müller in its entireness, however admirably calculated it may be to, furnish information to the writer and lecturer, is not adapted to the wants, nor can it come within the requirements of the student of medicine. It is a vast repertory of facts and opinions in physiological science, but it bewilders the inexperienced votary by its very extent; and he who has gone over it without halt or pause, or, indeed, at all, may well speak, as even the indefatigable German student himself is said to do, of his having performed a feat. * Dr. Horner. f Dr. Jackson.