The reasons which have induced me to reprint the present work from the American original, are, Ist, A strong sense of its inherent importance and of the numerous applications which may be made of the facts and principles developed in it to the pre vention and cure of disease; ly, Its comparative inaccessibility to the European physiologist from the difficulty which still exists of procuring it on this Side of the Atlantic; and, lastly, An earnest desire that the author should obtain that credit which is unquestionably due to his disinterested and indefa tigable labours.