I commenced the present translation while pursuing the study of medicine in Paris in the winter of 1813-14. It was then my intention to have completed and published it immediately upon my return to the United States; but I learnt in England in the spring following, that a translation of this work was about to appear from the London press. This information induced me to abandon my undertaking, but after waiting more than six years for the appearance of the English edition, and finding from letters received from London, that there was but little if any expectation of its being published there at all, I was led to pursue my original plan and complete the translation which I now offer to the public. In doing this, I was influenced more by the intrinsic value of Bichat's work than by any and every other motive. I was unwilling that so many of my professional brethren should be any longer denied access to this admirable production, because it was in a foreign language, and though I could have wished that another had undertaken the task, yet I was resolved to go through the labour rather than it should not be performed at all. Some of the writings of Bichat are so well known and so justly appreciated in this country, that it is perhaps unnecessary for me to speak of his merits as an author, or offer an apology for translating the present work. Every thing which he gave to the public bore unequivocal proofs of being the production of a mind of the most original and powerful cast, and it is impossible to estimate what the influence of his labours might have been upon medical science if a longer career had been permitted to him. As it was, he accomplished much, and as his writings are more known, their influence will be more sensibly felt. His manner of investigating physiological subjects was characteristic of his strong and original mind, and it is difficult to determine which is the most admirable, his acute and accurate reasoning, or his ingenious and well conducted experiments. Nor were these experiments the result of preconceived opinions, he seems to have brought his mind perfectly unbiassed to every subject that he investigated, and to have been guided in every instance by the most rigorous laws of induction. To these high qualifications he added great perspicuity in his arrangement, remarkable purity and beauty of style, and an extensive knowledge of disease, which enabled him to enrich his work with much valuable practical information. It is not pretended, but that his experiments upon living animals may have in some few cases led him to erroneous conclusions, but how numerous were the instances in which he obtained from them the most satisfactory and important information. It has, I know, become fashionable of late to undervalue these experiments, and to deny that any useful application can be made of them. It is no doubt true, that the sufferings which animals sometimes undergo in these experiments, are such as to destroy